The hydroformylation of olefins using supported film catalysts


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The hydroformylation of olefins using supported film catalysts
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viii, 149 leaves : ill. ; 29 cm.
Naughton, Michael J., 1963-
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Thesis (Ph. D.)--University of Florida, 1993.
Includes bibliographical references (leaves 143-148).
Statement of Responsibility:
by Michael J. Naughton.
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For my family because their love and support are never ending.


There are numerous people to whom I would like to express my gratitude.

It is through their support and encouragement that I was able to finish this phase of

my career. First I would like to thank my research director Dr. Russell S. Drago.

He has a unique relationship with his students which allows him to be both a mentor

and friend. I would also like to thank his wife Ruth for her hospitality. It is very

comforting to arrive in a new town and be greeted by people such as the Dragos who

make you feel that you are part of their family.

My family has been an important influence through out my graduate career.

I would like to thank them for their support throughout this undertaking.

I would also like to thank the members of my graduate committee, Drs. David

Richardson, Jim Boncella, Eric Enholm and David Silverman for the help they have

offered throughout my career. In addition, thanks go to Dr. Jerry Unruh (Hoechst

Celanese) and Dr. Tambra Dunams (Tennessee Valley Authority) for many

informative and enlightening discussions.

While attending Plattsburgh State, during the early portion of my academic

career, I was unsure what field to pursue. If it wasn't for the guidance and

encouragement of Dr. Rudolph J. Bobka I may not have found what wonders

chemistry has to offer. In addition, I would like to thank my graduate advisor at

Plattsburgh, Dr. Edward J. Miller, who encouraged me to strive for more, never give

up the pursuit, and to "hang in there."

Of course no one could do work without the help of his peers. The Drago

group, past and present, has always been there to help and harass me when I needed

it. I would particularly like to acknowledge the guys that joined the group in the

same year as I, Don Ferris, Steve Petrosius and Steve Showalter. Although we had

some lean and rugged times, we all weathered the storm and made it relatively

unscathed. I would also like to recognize some specific members of the group for

their advice and encouragement: Chris Chronister, Jerry Grunewald, Bobby Taylor,

Alan Goldstein, Tom Cundari, Robert Beer, Doug Patton, John Hage, Todd LaFrenz,

Mike Robbins, Phil Kaufman, David Singh, Karen Frank and Rich Reily.

I have made many friends while attending UF. It is impossible to list them all,

but there are a few that need to be singled out. Matt Ryan, long time roommate and

friend (even though the IGNATS won), was always a source of consistency in a world

of changing scenery at both home and work. John New, Linda Casazza and Don

Berhinger were my roommates. Some of the things that I'll never forget are Ben and

Jerry's Yogurt, John Madden Football, and the seemingly endless supply of chickens.

I would also like to thank the guys of the now defunct Idylwilde Basketball

Association (IBA) for many stress releasing, fat burning mornings and afternoons.

During my time at UF I have been blessed with a special person in my life,

Donna Robie. She has been the source of love and support that has carried me

through many difficult times. We have had many memorable times and I shall

cherish them forever.


ACKNOWLEDGEMENTS ..................................... iii

ABSTRA CT ................................................ vii

INTRODUCTION .................................. .......... 1

HYDROFORMYLATION OF OLEFINS .......................... 3
Introduction ............................................. 3
Background ........................................ 3
Phosphine Modified Rhodium Catalysts ................... 8

Introduction .................................
Supported Liquid Phase Catalysts (SLPC) .....
Other Heterogeneous Catalysts .............
Experim ental ................................
Chem icals .............................
Synthesis of Reagents ................
Preparation of Supported Film Catalysts ......
Results and Discussion ............. ..........
Calculations ............................
Hydroformylation in Thin Films .............
Polymers and Triphenylphosphine/Polymer Films
Alternative Films ........................
Other Vapor Phase Substrates ..............
Hydroformylation of Propylene with Supported
Catalysts .........................
Conclusions ............................







Introduction ......................
Supported Transition Metal Catalysts
Supported Aqueous Phase Catalysts .
Experimental .......................
Chem icals ....................
Apparatus and Instrumentation ...
Synthesis .....................
Catalytic Run .................
Results and Discussion ................
Statement of the Problem ........
Choice of Catalyst, Ligand and Film .
Calculations ...................
Hydroformylation of Olefins with
Catalysts ................
Conclusions ...................



. ......




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. . .
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.. .... ....

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.. ... .... .
.. ... ... ..
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. ... ... ...

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.. .
. .. .

SUMMARY ...................

REFERENCES .................




........... .. ... ... ... .. 149

Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy



Michael J. Naughton

May 1993

Chairperson: Russell S. Drago
Major Department: Chemistry

The conversion of homogeneous to heterogenous catalytic systems is an

intriguing and a formidable endeavor. Novel approaches to the hybridization of

heterogenous and homogeneous catalysts are described and their effectiveness is

illustrated with the hydroformylation of gaseous and liquid olefins to their

corresponding aldehydes. Supported film catalysts (SFC) utilize a non-volatile film

consisting of a soluble catalytically active complex supported on silica gel. The use

of polymers and other non-volatile films as reaction mediums for SFC's has not been

well established. We have chosen rhodium (I) aryl phosphine complexes in the

presence of excess phosphine for our catalyst due their acute sensitivity to the

reaction environment towards hydroformylation. Supported film catalysts have been

used to hydroformylate propylene, 1-butene and 1,3 butadiene in a gas flow reactor.

The hydroformylation of propylene shows selectivities greater than 99% to n-

butyraldehyde under mild conditions.

Extending SFC's to liquid substrates, such as 1-hexene, presents the added

problem of leaching the active catalyst and/or film phase into the solvent during

catalysis. We have developed a system which uses hydrophilic polymers (ie.

polyethylene glycol) and catalysts supported on silica gel to inhibit leaching during the

reaction. The rhodium complex HRh(CO)(TPPTS), (TPPTS = triphenylphosphine

trisulfonate sodium salt) has been selected as the catalyst due to its hydrophilic

nature. Comparisons of the SFC's to supported aqueous phase catalysts (SAPC) and

to biphasic aqueous systems are made. Unusually high activities and moderate

selectivities are observed at temperatures ranging between 75C and 125C and

pressures of 50 psig syn gas.


The focus of this dissertation is the development of a new class of supported

liquid phase catalysts (SLPC). Suppored liquid phase catalysts are heterogeneous

catalysts in which a liquid film containing a soluble catalyst coats a support (generally

inorganic oxides). To date the majority of the liquid phases have consisted of high

boiling liquids. These liquids have some volatility and may evaporate from the

support with time. The catalysts presented herein utilize non-volatile films such as

polymers and molten salts as replacements for the high boiling liquids and will be

given the general term supported Film catalysts (SFC).

The hydroformylation of olefins with rhodium catalysts has been chosen as the

test system for the new catalysts. There are several reasons for this selection. 1.

Rhodium catalysts are the most active catalyst for hydroformylation. This high

activity makes for easy analysis and evaluation of the catalysts. 2. The environment

of the rhodium catalyst influences both the activity and selectivity of the catalyst. 3.

Catalytic conversion of olefins to aldehydes is a vital chemical industry. It is the

largest commercial homogeneous catalytic process.

This study is divided into two areas. The first concerns the hydroformylation

of gaseous substrates such as propylene. The second studies the hydroformylation


of liquid substrates (e.g. 1-hexene) with a subclass of SFC's, supported hydrophilic

film catalysts (SHFC).




Hydroformylation or the "oxo" process is the reaction of hydrogen and carbon

monoxide with olefins in the presence of a catalyst to form aldehydes. Although the

reaction is energetically favorable (-28 Kcal/mol) it does not occur to a measurable

extent in the absence of a catalyst.' Generally, with low molecular weight olefins two

major products are formed, the linear and branched aldehydes; economically the

linear aldehyde is preferred. The reaction is depicted in Figure 2-1. Side reactions

such as isomerization and hydrogenation also occur. These will be discussed in

greater detail later.

Hydroformylation was discovered by Otto Roelen in 1938 in Germany while

studying the activity of ethylene under Fischer-Tropsch reaction conditions." Since

that time, this process has found its place in the petrochemicals industry.

Approximately 10 billion pounds of products are made annually via the

hydroformylation process, making it the largest homogeneous catalytic process.45

The largest classification of substrates for this process are gaseous olefins (C,-C4).

Table 2-1 shows some commercial catalytic systems.6

RCH2CH26H Linear
Catalyst O
RCH2CH8H Branched

Figure 2-1. Hydroformylation reaction of olefis to aldehydes.


S 2

o 0o \C O
00 00 0i O\




L. -





0 0
u u 8

^ ^03

0 0





It should be noted that aldehydes themselves are not very useful but are

precursors to other more economically attractive chemicals. Aldehydes can be

hydrogenated to alcohols or oxidized to carboxylic acids. These in turn can be further

processed to plasticizers, metal working fluids, alkyd resins, specialty greases and




Several transition metal carbonyls are known hydroformylation catalysts. In

order of decreasing activities they are Rh, Co, Ru, Mn, Fe, Cr, Mo, W, Ni, Pt and

Cu.8 Rhodium and cobalt carbonyls are the most commonly studied and are the only

catalysts active enough for use as commercial catalysts. Rhodium catalysts are

approximately 3500 times more active than cobalt. In addition, the rhodium catalysts

modified with phosphine ligands are more selective than cobalt catalysts. The

principal disadvantage of rhodium catalysts is cost, currently RhCI,- 3H0O is $145/gr.9

Table 2-2 lists several substrates that can be hydroformylated with rhodium

complexes and their relative rates of reaction. Linear olefins such as 1-hexene and

1-octene are more readily hydroformylated than the branched or internal alkenes,

such as 2-methyl 1-pentene and 2-hexene.1

Hydroformylation Rates of Various Olefins Using
HRh(CO)(PPh,), as the Catalyst at 250C.


Allyl Alcohol
1,5 Hexadiene
Allyl cyanide

Turnover Rate

Turnover Rate

Table 2-2.

Phosphine Modified Rhodium Catalysts

Rhodium is by far the most active metal for the hydroformylation of olefins.

Reaction rates and product distributions depend on a number of reaction variables.

These include the substrate and ligand type, the concentrations of the reactants

(hydrogen, carbon monoxide and olefin), the concentration of the catalyst and ligand,

and the reaction temperature. The difficulties with these catalysts are the undesirable

isomerization of olefins and the instability of the catalysts. The addition of phosphine

ligands to these systems not only improves the selectivity and activity of the catalysts

but also increases catalyst lifetimes and reduces the amount of isomerization in the


Effects of equilibrium positions and mechanisms

It has been shown that in the presence of hydrogen, carbon monoxide and

excess phosphine, most any rhodium(I) complex is converted to the form HRh(CO),Py

(P=phosphine).'1 Depending on the concentration of the reactants, several

carbonyl/phosphine species exist in solution (see Figure 2-2).14.15,16 These

intermediates are thought to be the active catalytic species for hydroformylation.

Both the selectivity and rate of reaction are influenced by the position of the

equilibria that are established with reactant variation.

HRh(C O)(PP h3)3


-PPh3+ 3




PPh1 +PPh3

HRh(C O)2(PPh)2








Figure 2-2. Equilibrium species of hydrido rhodium carbonyl phosphine

The predominant species for hydroformylation under standard conditions

(HJCO of 1:1 and no excess phosphine) is the 18 electron species HRh(CO);(P), (A).

From this intermediate either the associative or dissociative mechanism can be

followed as proposed by Wilkinson (see Figure 2-3)..11'23.l117.l19,M21L2223

The associative route starts when HRh(CO)(PR,)(L)2 (L = PR3 or CO)

dissociates a phosphine to form the 16 electron species HRh(L), (1). This complex

then can add CO rapidly to form the active catalytic species, HRh(CO)(L)3 (2), which

corresponds to A B, and C in Figure 2-2. Olefin can then bind to the rhodium

complex to form HRh(CO)(L)3(RCH=CH,) (3) and then rearranges rapidly to the

18 electron species Rh(CO)(L)3(CHCH2R) (4). It is this rearrangement where the

selectivity takes place. Anti-Markovnikov addition leads to the linear alkyl species

and hence a linear product, while Markovnikov to a branched metal alkyl which

produces branched aldehydes (see Figure 2-4). Bulky phosphines promote anti-

Markovnikov addition. From here CO insertion/alkyl migration yields the acyl

complex 5. Formation of linear products is favored by the associative route. This is

attributed to the more sterically hindered olefin coordination.

Dissociative mechanism occurs when another phosphine dissociates from 2 to

give HRh(CO)(L)2 (2) which then binds the olefin to form 8 and rearrangement

occurs to form 9. Due to the loss of phosphine there is a lack of steric influence and

Markovnikov addition occurs more readily than in the associative path, hence

favoring branched products. Addition of the phosphine and CO insertion/alkyl

migration gives 4, the common intermediate in both pathways.








L. I

H2 1










L i I

L= PR3 or CO




Figure 2-3. Mechanisms for the hydroformylation of olefins.

Anti-Markovnikov Addition

L.,Rh .. R
L' I 'CO

S-* Linear Aldehydes

Markovnikov Addition



- Branched Aldehydes

L=PR3 or CO

Figure 2-4. Anti-Markovnikov and Markovnikov addition
to the rhodium catalyst.

In both mechanisms oxidative addition of H2 to the acyl complex gives the six

coordinate intermediate 6. This is the rate determining step. Alternatively CO could

add to the acyl complex to give Rh(L)3(CO)-acyl which is catalytically inactive.

Reductive elimination then yields an aldehyde and the square planar complex

HRh(L), (1).

Phosphine concentration effects the rate of reaction as well as the n/b ratio.

Figure 2-5 shows the effect of the change in phosphine using a 1-hexene feed. As the

concentration of phosphine increases the rate initially increases until the phosphine

to rhodium ratio (P/Rh) is in the 20:1 50:1 and then decreases. The n/b ratio

increases with the P/Rh ratio.7 If the concentration of phosphine is high, the resultant

rhodium catalyst has a high degree of substitution by phosphines and the active

catalyst exists as the 18 electron species HRh(CO)(P), (B), refer back to Figure 2-2.

This follows the associative pathway which allows a high selectivity towards linear

aldehydes but slow rates of reaction. In the case of low phosphine concentrations a

phosphine dissociates from A to form the 16 electron species HRh(CO),(P) (D).

Hence the dissociative route predominates. The result is an increase in the reaction

rate but a loss in selectivity."

At low carbon monoxide concentrations A can dissociate a carbonyl to form

the 16 electron complex, HRh(CO)(P), (E). This intermediate allows for high rates

of reactions but also the less selective dissociative mechanism to predominate. At

high carbon monoxide concentrations the reaction is inhibited.

0.4 0.8 1.2 1.6
PPh3 Concentration, M

Figure 2-5.

Effects of phosphine concentration on the activity
and product distribution of rhodium catalyzed
hydroformylation of 1-hexene.

6 -





The changes in reaction rates and product distribution can be explained by the

steric influence of the ligands. Phosphine ligands are more sterically hindering than

carbon monoxide. Upon coordination of a phosphine ligand there is relatively less

area about the metal for olefin coordination. This causes the olefin to favor anti-

Markovnikov addition to the metal, resulting in a higher selectivity towards linear


An undesirable side reaction of hydroformylation is the isomerization of

a-olefins to internal olefins (see Figure 2-6). The undesirability is derived from the

fact that internal olefins are much less reactive than their alpha counterparts (see

Table 2-2), and the resultant aldehydes usually are of no economic importance.

Isomerization is thought to come about by olefin coordination to HRh(CO)(L), (1)

prior to CO addition (see Figure 2-3). Isomerization can be repressed by the

addition of excess phosphine ligand.2z4'

In addition to the degree of substitution, the size and basicity of the ligand

effects catalyst performance (see Table 2-3). Bulkier ligands yield a more selective

catalyst, and as the basicity of the ligand decreases the activity and selectivity

increases." In the same vein less bulky phosphines are more susceptible to

substitution by CO resulting in decreased in selectivity. As L is substituted by CO

poor selectivity is realized.

In addition to ligand effects many variables control the activity and product

distribution of hydroformylation catalysts. These include the concentration of the

substrate, hydrogen, carbon monoxide, rhodium, and ligand as well as temperature,


L, I

L ., I

Figure 2-6. Mechanism for the isomerization of olefins.

Dependence of Product Distribution
Hydroformylation of 1-Octene.

on Phosphine Ligands in the

Ligand Percent Reaction Cone Angle v(cm )b
Linear Time (min) (0)
P(OCHp-C1), 93 55 128 33.2
P(OPh), 86 50 128 29.2
P(OC.H44pPh), 85 70 128 28.9
P(OC.HpOMe), 83 270 128 28.0
PPh, 82 35 145 12.8
P(OBu), 81 60 107 20.2
P(OC,H,Ph), 78 52 141 28.0
PBu, 71 225 132 4.2
P(OC,H,o-Ph), 52 95 132 28.9
P(O-2,6-Me,CH,), 47 80 190 27.1

" 112 g 1-octene. 10 g 5% Rh/C, and 0.05 mol L
1:1 HJCO at 90"C. Adapted from reference 1.
b v = m-2056.1 cm'.

(L:Rh = 10:1) with 80-100 psig of

Table 2-3.

pressure and solvent polarity. Table 2-4 shows intrinsically how the increase of a

variable influences the reaction rate and product distribution of rhodium catalysts.

Solvent polarity and basicity contribute to the reaction selectivity. As a general rule,

selectivity increases as solvent polarity and basicity increase.1?

Table 2-4. Effects of Reaction Variables on the Rate
Rhodium Hvdroformylation Catalysts.

and Selectivities of

Variables Rate n/b Ratio Isomerization

[H,] + + +
[CO] -
[olefin] + 0
Increasing + + +

[Rh] + +
[L] + -

Based on the hydroformylation of 1-hexene in benzene using
HRh(CO)(TPP) as the rhodium source. + indicates an increase and a
decrease. Abbreviations: [H], [CO] olefinn], [Rh] and [L] are the
concentration of hydrogen, carbon monoxide, olefin rhodium, and ligand.
respectively. Adapted from reference 1.
Not reported.



Homogeneous hydroformylation of olefins has matured into a finely tuned art.

Rhodium catalysts are optimal catalysts for hydroformylation yielding systems which

are unusually active and showing selectivities as high as 10:1 to the linear aldehyde.

However, the drawbacks of these systems, namely the recovery of valuable rhodium

catalysts and the convenient separation of products from the reaction solution, merit


Heterogeneous catalysts have been designed to circumvent the shortcomings

of homogenous systems. Several methods have been used to immobilize homogenous

catalysts. These include 1. chemisorption of the metal complex on a solid support;

2. physical adsorption of a catalytic complex; 3. entrapment of complexes in zeolites;

4. coordination of the metal complex to functionalized polymers or inorganic oxides;

and 5. supported liquid phase catalysts. These techniques have yet to produce a

commercially viable catalyst for hydroformylation. The lack of success can be

attributed to leaching of the metal from the support to the surrounding environment

and to the loss in activity and selectivity associated with immobilization of

homogenous catalysts. This chapter will concentrate on heterogeneous catalysts as

they pertain to the hydroformylation of gaseous substrates, such as propylene and


Supported Liquid Phase Catalysts (SLPC)

Of all the types of heterogenous catalysts, supported liquid phase catalysts

(SLPC) seem to have the most promise in the commercialization of a catalytic

process. SLPCs are true hybrids of homogeneous and heterogeneous catalysts in that

a support is coated with a catalytic film that consists of a homogeneous catalyst and

a high boiling liquid.''7 Several applications of supported liquid phase catalysts

exist, these include the oxidation of SO,,' dimerization of alkenes,2 and Wacker

oxidation.3 However, the largest application of SLPC has come in the field of


A multitude of catalytic supports are known. Some supports (e.g. porous glass

and macroreticular polymer resins) are inert, while others (e.g. silica and alumina)

possess acid/base properties.1" These sites may synergistically enhance the activity

of the catalyst or may act to anchor the catalyst to the support.2 The chemical

alteration of organic polymers and inorganic oxides creates ligands to coordinate

active metal species but they can also change the activity of a catalyst.

The interactions of the metal complexes and/or additives with the support are

important." If the support deactivates a complex or competes for the ligands

rendering them unavailable for coordination, then that material may be a poor

support for SLPC. As previously stated, triphenylphosphine is an important additive


for most rhodium based hydroformylation catalysts. Triphenylphosphine can

chemisorb on alumina (see Figure 3-1). In addition, triphenylphosphine can also

hydrogen bond to the inorganic oxide surface (see Figure 3-2). These phosphines are

bound tightly and are not available for coordination to the rhodium complexes.

Rhodium complexes are known to chemisorb to the surface of alumina (see

Figure 3-3). In the presence of excess phosphine the chemisorption of the rhodium

is eliminated.

SLPC for the hydrformylation of gaseous substrates

Supported liquid phase catalysts are active for the hydroformylation of gaseous

alkene substrates and realize long term stability in gas flow reactors.'" Generally,

conditions for reaction range from 80-1250C and 250-1000 psig. Table 3-1 shows the

activity and selectivity of some selected catalysts. Activities varied with the change

in support, liquid phase and transition metal complex. Most systems studied used

phosphine modified rhodium catalysts and high boiling liquids as the catalytic liquid

phase. Catalysts which possess a liquid phase have been shown to be more active

than their surface bound counterparts consisting of the same rhodium sources and

supports.3 It has been observed that in these systems the reaction rate is

diffusionally retarded.

A crucial requirement for an efficient catalyst in a gas flow reactor is that

reactants and products must be gases at reaction temperatures. This minimizes

condensation of the substrates and/or products in the pores of the support.

a OH 0

PPh3 OH 0

t 11

Figure 3-1. Adsorption of triphenylphosphine on alumina.
O anion vacancy


OH oh
i i

Figure 3-2. Adsorption of triphenylphosphine on silica.



Figure 3-3. Adsorption of rhodium phosphine complex on an oxide
surface site. L= triphenylphosphine

SIn v0 in ir, Ir,

\O C -I ell e


0 r

C 1

-C -
c e rsM r


o u
~ U
g s -

vi/ vi" v/i T -T -T -

N r -
- (-1 3N '- C]

*^- u- i r-~

2* ^ tr N:

ur-> >< c!-r' r^r"

'^ ^ >D m 3C -
r^ .r, s ~

3~~ ~~ 3 r <



OO. c
O 0 C..
_ o a- a-

U U '
g- ^ S =-

.c .c c e c
r2 .cM

0 0 0 e~ 0 r
C C u V Cu
e~ c c ^ ~

a a
.E E .E -

- Cu
C U U U Cu u '9








-. N

0: U.
m C



A catalyst with a liquid phase of butylbenzylphthalate and (PPh,),Rh(CO)Cl

and excess phosphine on an alumina support exhibits an optimal activity at a liquid

loading of 0.5 cm3 per gram of catalyst.

Aldehydes, the products of hydroformylation are soluble in many of the liquid

phases. Three possible scenarios may develop: 1. As the reaction proceeds, the

amount of alkanals condensed in the pores fill the pores so that the degree of pore

filling, 6, is greater than one, this leads to leaching of the transition metal catalyst.'

2. The amount of rhodium complex adsorbed to the surface is influenced. 3. The

amount of alkanals in the liquid phase influences the equilibria between various

dissolved rhodium complexes.

A study of SLPCs which utilize molten triphenylphosphine as the liquid phase

showed that condensed aldehydes are discernibly soluble in the liquid phase of the

catalyst, but the solubility of hydrogen and carbon monoxide in this medium is not

appreciably effected. However, the solubility of the alkene is strongly influenced.3'

A SLPC in which aldehyde was added to the film led to a lowering of the linear to

branched ratio from 20 to 15 but an increase in activity by 10%."7

Degree of pore filling and its relation to activity and selectivity

The degree of pore filling, 6, greatly effects the activity of most SLPCs for the

hydroformylation of olefins.3"9 In an ideal system, the liquid phase covers the

entire surface uniformly then preferentially fills the smallest pores (see Figure 3-4).0

Due to the complexity and non-uniform nature of the pore structure of many

V=x V=O

Figure 3-4.

Diagram of an ideal liquid filled macropore. The fraction of total pore
length that is occupied by a liquid plug is denoted by x. Adapted from
reference 42.

supports the description of SLPCs can only be done with statistical parameters. Rony

et al.41 utilized these parameters to describe the optimal loading for an alumina

support with a butylbenzylphthalate liquid phase, they found that the optimal value

of 8 was 0.5 cm3 liquid/cm3 pore (see Figure 3-5). The activity decreases as the pores

become filled. It has been claimed that it is rarely beneficial to pore fill over this

value. This is due to the long liquid diffusion paths as S approaches 1.

Generally for a given system, the activity reaches a maximum and then

decreases with increasing 6. Most of the catalysis occurs at the gas/liquid interface,

and it follows that the increase in activity is due to the increase of the gas/liquid

interface. Low or no pore filling leads to catalysts which bound to the support. On

the other hand, SLPCs with a large 6 contain liquid plugs or pools of solution in the

pores. In these areas the majority of the rhodium catalyst exists in the bulk solution,

which'possesses a high concentration of phosphine and a low concentration of carbon

monoxide and substrate. This gives rise to highly substituted rhodium phosphine

species which favors selectivity to linear products. However, due to the decrease in

the gas/liquid interface, the activity of these systems are greatly reduced.

Other Heterogeneous Catalysts

Hydroformylation in polymer matrices

The deposition of rhodium catalysts in thin polymer films provide marginally

active hydroformylation catalysts for ethylene and propylene. A film of cellulose

acetate and HRh(CO)(PPh,)3 gives an activity of 0.41 TON/min under atmospheric


0. 06 -



0. 00 0.20 .. I I
0.00 0.20

de l ta

0.60 0.80 1.00
( 1 Lq)

Figure 3-5. Conversion curves for the hydroformylation of propylene as a function
of liquid loading. The liquid phase is butylbenzylphthalate. Adapted
from refence 42.



1 : i ; ; r_ ~ l i ~_ _~_ _

pressures and 80CC.4 Active catalysts for hydroformylation also are formed in

polystyrene and polybutylmethacrylate films.

Chemisorbed catalysts

Silica supports. A strong affinity between silica and HRh(CO)(PPh,), exists

and is evidenced by the decolorization of a HRh(CO)(PPh,), benzene solution in the

presence of silica." Phosphine modified rhodium complexes impregnated on

alumina or carbon have activities >30% and n/b ratios of 2. Good long term stability

over a 300 hour period are seen for these catalysts.

Functionalized supports

Inorganic oxide supports. Coordinating homogenous catalytic complexes to

functionalized organic polymers or inorganic oxides with ligand derivatives is a

common method of heteroginizing homogenous catalysts. Functionalized silica with

phosphorous, nitrogen and oxygen donor ligands have been prepared.5" In the case

of hydroformylation, rhodium is commonly used as a catalyst. Figure 3-6 shows the

preparation of an immobilized rhodium catalyst on a functionalized silica support.

Functionalized polymers. Polystyrene and divinylbenzene based polymers are

by far the most common choice for functionalized supports." This is because the

aromatic side chains are easily modified to contain phosphine side chains, which are

good ligands for rhodium hydroformylation catalysts (see Figure 3-7). Copolymers

have been designed by cross-linking to create supports which are porous, insoluble

and swellable8.



tinctionalied silica


- Rh(acac)CO),

iCH CH ,CHPPh, Rh(acacX)CO)

heterogeneous catalyst

Figure 3-6.

Preparation of an immobilized catalyst by coordination
to a functionalized silica support.


PPh-RhCI(PPh )

(PPh ) RhCl

Figure 3-7. Preparation of an immobilized catalyst by coordination to
a functionalized polymer.

The rigidity of the polymer also plays an important role in activity.49 If the

polymer chain has low flexibility the access of reactants to the metal center decreases,

hence a decrease in activity.5'" On the other hand, if the chains are too mobile,

deactivation of the rhodium may occur by the formation of rhodium clusters.""

Due to preferred conformations within the polymer some of the phosphines

may be unavailable for coordination to the metal center. If the number of

coordinated ligands to a rhodium center is considerably lower than in homogeneous

systems depends, it follows that the selectivity for the polymer system is lower.52


Rhodium catalysts have been incorporated into zeolites and used in the vapor

phase hydroformylation of olefins.455 The hydroformylation of substrates shows

activity towards ethylene, propylene and 1-butene at 150C and at a n/b ratio of

2:1.56 These catalyst have demonstrated stability for up to one month.



The following were used without any further purification: RhCl- 3HO (Strem

Chemical Inc.); triphenylphosphine (Aldrich); potassium hydroxide (Fisher); absolute

ethyl alcohol (Florida Distilleries); hexanes (Fisher); chloroform (Fisher); polybutyl-

methacrcrylate (Aldrich); silicon gum rubber (Varian); polybutadiene (Aldrich);

Aliquat 336 (Aldrich); tetrabutylphosphonium chloride (Aldrich); formaldehyde

(Aldrich); propylene carbonate (Fisher); 1-octanol (Fisher); silica gel (Davison, pore

volume 1.1 mL/g); hydrogen (Matheson); carbon monoxide (Matheson); propylene

(Matheson); 1-butene (Matheson); 1,3 butadiene (Matheson).

Synthesis of Reagents

Preparation of Hydridocarbonvltris(triphenvlphosphine)rhodium, HRh(CO)(PPh,,

Synthesis of HRh(CO)(PPh3), was carried out as reported.57 Under an

atmosphere of nitrogen, triphenylphosphine (2.64g, 10 mmol) was added to refluxing

ethyl alcohol (100mL, absolute). To this RhCl,.3H,O (0.26g, 1.0 mmol) in hot ethyl

alcohol (20mL) was added. After a 15 second delay, formaldehyde (lOmL, 37% in

water) followed immediately by potassium hydroxide (0.8g) in hot ethyl alcohol

(20mL) were added. It should be noted that the addition of the reactants in the

indicated order is critical in this synthesis. Upon addition of potassium hydroxide the

solution turns yellow and the formation of a precipitate is evident. The yellow

mixture was allowed to reflux an addition 10 minutes then cool with stirring to room

temperature. The yellow solid was filtered, washed with ethanol (2xlOmL), followed

by H,O (2xl0mL), then again with ethanol (2xlOmL) and finally by hexanes (10ml).

The yellow solid is dried under vacuum at 400C for 18 hours. Infra red bands

vco=1919 (lit. 1918), vRh,.H2037 (lit. 2041).

Preparation of Supported Film Catalysts

The following is a description of the preparation of a typical catalyst.

A solution of chloroform (25mL) and polybutyl-methacrcrylate (0.06g) was

added to a solid mixture containing HRh[P(C6H,)]3(CO) (0.10g), 0.262gm of

triphenylphosphine (0.262g) and silica gel (0.60g). After 2 minutes of stirring the

solvent was removed under reduced pressure at room temperature. The yellow

powder was dried under vacuum overnight with the temperature not to exceed 450C.

A 0.50 g sample of this product was placed in a stainless steel column of a

gas flow reactor (Figure 3-8) which was placed in an preheated constant temperature

oil bath at the specified reaction temperature. A premixed gas of HJCO/propylene,

also at specified pressures and flow rates was fed through the reactor. Analysis was

performed by an on-line gas chromatograph. Table 3-2 is a compilation of the

experiments presented in the Results and Discussion section.

Carrier Gas


Lecture Bottle

Flow Meter

Reactor Tube

Schematic for a gas flow reactor with an on-line gas chromatograph.

Figure 3-8.

S- r C = = = 1- C l-. = ^ -
^ j1 -~ l i M f



- r -^ -* C4 n k C'A t C4

-88-8--cc -"- -


L A -- c- Q- CL -----------------a- ----L-----

5- *-'

=- =- r-~ 'p = = = = -'"- r- = c- r N- "x -, r

- -- Cl(-

. .x x. ..s. .
aqaacico^^0 0^ ^ ^^0;^^00

- 7 --
~- ~-- ---

'Cl C4 C( C1 Cl C Z c '

! ---- ----X- -- --- -

00000c QQ

t- -U

u u u u
.G a. a.C



-- 4.

-t --r =




= --

c "



E E 'i- 5
i ,

.. .
S0- -

|= .- .

2c., tS
2 = ^ ^ E



Results and Discussion

The system described herein demonstrates the activity of previously reported

SLPC but uses a non-volatile "liquid" phase such as a polymer or molten salt.

Polymer or molten salt films are non-volatile and should retard the sublimation of the

transition metal catalyst or phosphines in the film.

Several polymers and molten salts were chosen as reaction media for the

supported catalysts, these include polybutylmethacrylate (PBMA), polybutadiene

(PBD), silicone gum rubber (SGR), aliquat 366 and tetrabutylphosphonium bromide.

The transition metal complex, hydridocarbonyltristriphenylphosphine rhodium(I), was

chosen as the catalyst, for its high activity, selectivity, and stability in homogenous

catalytic systems. Silica gel was chosen as the support for its porosity, and high

surface area.


The activities (a) were calculated in units of TON/min, where TON is the

turnover number defined as the number of moles of products formed (n,) per mole

of catalyst (n,), eq. 3-1. The value of n, can be calculated by multiplying the

a(TON/min)- n (eq. 3-1)

conversion to products, ap, by the moles of substrate, ns, (np and n. are in units of

moles/min). The moles of substrate, n,, can be calculated via the ideal gas law

np-aopn (eq. 3-2)

(equation 3-3.). The pressure of the substrate, P,, is measured at the gas outlet. The

value Vf, is the flow rate, R is the gas law constant and T is the temperature at the

sample loop. It should be noted that the flow rate is incorporated into the activity.

n~ (eq. 3-2)

In hydroformylation the selectivity is the percentage of the products which are

aldehydes. Included in this term is the ratio of normal to branched aldehydes (n/b

ratio). Occasionally the equivalent term linear to branched or 1/b is used. This value

is calculated from the calibration corrected area for the two aldehyde products. In

this work many of the catalysts gave only one isomer product, the linear aldehyde.

Hydroformylation in Thin Films

The question of activity in thin polymeric films was addressed in our labs by

utilization of hydroformylation catalysts immobilized in polymer films.5 In previous

work, the rhodium complexes HRh(CO)(PPh,), and (tfa)Rh(PPh,),

(tfa=trifluroacetylacetonate) were placed in a polymer membrane and tested for the

hydroformylation of propylene at 850C and 15 psig. These systems were moderately

active and the activities and selectivities could be influenced by altering the polymer

media. A polystyrene membrane catalyst yielded a system which produced 1x109 mol


of butyraldehyde in 3 days with a n/b of 0.71. Changing the polymer matrix to the

rubbery polymer polybutylmethacrylate produced a system that increased in activity

to 2.2x10"mol in one day and the selectivity was an amazing 500:1. Figure 3.9 is a

schematic of the reactor used in these experiments.

It was suspected that diffusion of the reactant gases (syn gas and propylene,

1:1:1 gas mixture) through the polymer matrix was the limiting effect in the

membrane reactor. In order to increase the surface area of the catalytic film we

supported these films on inorganic oxides. This forms a thin catalytic film over the

support which should decrease the diffusion time of the reactants through the

polymer. In addition, the resultant catalyst is a dry powder that can be easily handled

in the air for a short period of time.

Polymers and Triphenylphosphine/Polymer Films

Polybutvlmethacrylate films

A catalyst containing HRh(CO)[P(CH,),],, and polybutylmethacrylate (PBMA)

was dispersed on silica gel. The catalysis was carried out in a gas flow reactor, using

premixed gases of hydrogen, carbon monoxide and propylene. This catalyst was

considerably more active than the unsupported membrane reactor systems. The

supported polymer film catalyst had an activity of 0.016 TON/min (conditions 100C,

20 psig, flow rate 10mL/min, 6 = 0.25) and a n/b of 2.6:1, while the membrane

reactor showed an activity of 4.17x105 TON/min under similar conditions.

IIe Volve


Sinlered S.S. Plolt
0-12 cm Ihick
|mlcron port llat

Figure 3-9. Thin film membrane reactor.

A PBMA catalyst, with a degree of pore filling, 6, of 0.59 showed an activity

of 6x10-4 TON/min. The selectivity could not be determined due to the low activity.

This film represents a relatively thick coating on the support surface. The activity is

considerably lower than the other catalyst. Figure 3-10 depicts the activity curves for

these experiments. This effect can be attributed to the rigid nature of PBMA films.

Although the polymer is above its glass transition temperature (Tg=80C) at a

reaction temperature of 100C, the polymer is not liquid, but solid. This restricts free

movement of the catalyst and makes diffusion of the reactant gases rate limiting.

Concentration effects. The effects of rhodium concentration within the

supported film was tested. It was found that increasing the concentration of rhodium

in the film increased the activity and the selectivity of the catalysts despite the

increased degree of pore filling (the effects of pore filling on this system will be

discussed in greater detail vida infra) (see Table 3-3 and Figures 3-11 and 3-12). The

activity increased with increasing rhodium concentration.

Polvbutvlmethacrylate/triphenylphosphine films

It has been long realized that the addition of excess phosphine ligands to the

rhodium catalyst increases the lifetimes and stability of the catalysts. We decided to

add triphenylphosphine to the PBMA film to stabilize the rhodium complex. With

this addition we observed an unexpected increase in activity to 0.0373 TON/min, this

is approximately twice that of the previous catalyst. In addition, the system produced

only n-butyraldehyde, the desired linear product. This increase in activity was

0.018 i










Figure 3-10.




a I


Time (min)
Activity of the PBMA film catalyst for the hydroformylation of
propylene. .-6 = 0.25. + 6 + 0.59.
Catalyst: Rhodium source-HRh(CO)(PPh,),; P/Rh 10:1; Polymer-
PBMA.Conditions: 80C, 15 psig (1:1:1 H,/CO/propylene).

Table 3-3.

Effects of Change in Concetration of the Rhodium Source.

[Rh]xlO0 Activity (TON/min) n/b
(mmol Rh/mi film)
0.25 .0090 1
1.00 0.023 2.5
2.60 0.058 7.0

Catalyst: HRh(CO)(TPP),; Polymer: PBMA; Additive: None. Conditions: 1000C,
15 psig (1:1:1 H/CO/propylene); Flow rate: l0mL/min.





0.01 -



Figure 3-11.

[Rh] (mol/mL)
Effects of changing rhodium concentration on the activity for the
hydroformyaltion of propylene.
Catalyst: Rhodium source-HRh(CO)(PPh,)3; Polymer-PBMA.
Conditions: 80C, 15 psig (1:1:1 H/CO/propylene).







0- I --I
0.OOE+00 1.00E-04 2.00E-04 3.00E-04
[Rh] (mol/mL)
Figure 3-12. Effects of changing rhodium concentration on n/b ratio for the
hydroformylation of propylene.
Catalyst: Rhodium source-HRh(CO)(PPh,),; Polymer-PBMA.
Conditions: 80C. 15 psig (1:1:1 HjCO/propylene).


attributed to the loosening of the film by molten triphenylphosphine (melting point

810C). This the film should be more mobile than one consisting of PBMA alone.

Table 3-4 shows the activity and selectivity of several catalysts involving PBMA.

The concentration of rhodium within the film was varied while holding both

6 and the percentage of PBMA relative to triphenylphosphine constant. Increasing

the rhodium concentration from 0.040 gRh/g of film to 0.090 gRh/g of film

considerably increased the activity, while not significantly influencing the selectivity

(see Table 3-5).

Effects of temperature and pressure. As expected, the activity of PBMA/PPh,

systems increase with increasing temperature (see Table 3-6). For systems at 50 psig

of reactant gas (1:1:1 HJCO/propylene) an increase of activity was observed from

0.060 TON/min at 800C to 0.14 TON/min at 1000C. At 20 psig similar effects were

observed (0.0064 TON/min, 80C; 0.024 TON/min, 100C). The energy of activation

for this system was calculated to be 52.1 + 11 kJ/mol at 50 psig and 68.15 + 11

KJ/mol at 20 psig (see Figures 3-13 and 3-14). These values are the same with in the

error limits.

Similar increases in activity are seen with pressure. At 80C and 20 psig the

activity is 0.0064 TON/min and is totally selective to n-butyraldehyde. Increasing the

pressure to 50 psig increases the activity to 0.055 TON/min, while the selectivity drops

to 24. A further increase to 100C and 100 psig brings the activity to 0.309 TON/min

and a n/b of 11.

Table 3-4. Selected Catalysts for the Hydroformylation of Propylene.

Support Film Activity Selectivity
silica PBMA 1.60x102 2.62
none PBMA 1.1x10-to a
silica PBMA/TPP 3.73x102 b
silica TPP 3.29x10' b

a- Trace amounts of isobutyradehyde were formed.
b- n-Butyradehyde was the only product detected.
Rhodium source: HRh(CO)(TPP),. Conditions:
H,/CO/propylene), Flow rate 10 mL/min.

1000C. 15

psig (1:1:1

Table 3-5.

Effect of Concentration of the Rhodium Source in the
PBMA/Triphenylphosphine Film.

[Rh] 5 Activity' (TON/min)
(g Rh/g film)
0.090 0.64 0.0064
0.040 0.64 0.0023
Both catalyst produced n-butyradehyde exclusively.
Catalyst: HRh(CO)(PPh,),; Polymer: PBMA; P/Rh = 10:1. Conditions: 800C,
20 psig (1:1:0.1 H./CO/propylene), flow rate of 4.8 mL/min.

Table 3-6.

Effects of Temperature and Pressure on the Hydroformylation of
Propylene using the PBMA/Triphenylphosphine Film Catalyst.

Temperature Pressure Activity n/b Ratio
(C) (psig) (TON/min)
80 20 0.006
80 50 0.055 24
90 20 0.014 55
90 50 0.096 16
100 20 0.024 35
100 50 0.140 15
100 100 0.309 11
115 20 0.009 70
120 20 0.005

a n-Butyraldehyde was the only product detected.
Gas mixture 1/1/0.1 HCO/propylene; Flow rate 4.8 mL/min.
Catalyst: Rhodium source HRh(CO)(P03)3; P/Rh = 10:1;
[Rh] = 0.10 g Rh/g catalyst; 6 = 0.64.














Figure 3-13.

Arrhenius plots for the PBMA catalyst at 20 psig. Temperature range
800C to 1000C.

slope= -8200 1300
Ea= 68 11 klJ/nole
A= 8.58x10^ 7













Figure 3-14.

Arrhenius plots for the PBMA catalyst at 50 psig. Temperature range
800C to 100(C.

slope= -6300 + 1300
Ea= 52 l kJ/niole
A= 2.87x10 ^ 6



-3 -.



Influence of phosphine to rhodium ratio

Dependence of activity and selectivity on the ratio of free phosphine to

rhodium complex was studied. A trend developed that showed selectivity increasing

with increasing P/Rh ratio. This is expected from similar results in homogeneous

systems with these catalysts. The role of excess triphenylphosphine in homogeneous

systems is to enhance the stability and lifetime of the catalyst. With only

triphenylphosphine as the film, the selectivity increases with increasing P/Rh ratio

(Figure 3-15). The addition of PBMA to the film increases the n/b ratio dramatically

at lower P/Rh ratios.

Effects of pore filling

The effect of the degree of pore filling of film was studied. Table 3-7 and

Figure 3-16 shows a drop in catalyst activity with increasing 6, while the n/b ratio

increased. The loss in activity can be easily explained by the decrease in surface area.

Since the film is a solid most of the active species are at the gas/film interface, and

any rhodium complex in the interior of the film would be inactive. Hence a reduction

in surface area equates to fewer active species and a decrease in the overall activity.

Effects of propylene feed

It was noticed that varying the composition of the gas feed greatly effects the

activity of the catalyst (see Table 3-8). In several cases, an increase in propylene feed

increased the overall activity. At a gas mixture of 1/1/4 (HJCO/propylene) the


180.0 -



120.0 .

z 100.0-





0 2.5 5 10

w/o polymer polymer

Figure 3-15. Change in selectivity with variing P\Rh ratio.
Catalyst: Rhodium source-HRh(CO)(PPh,),; 6 = 0.64.
Conditions: 80C, 15 psig (1:1:1 Hi/CO/propylene).

Table 3-7.

Effects of Pore Filling (6) on the
Catalytic System.

Activity of the PBMA Film

6 Activity n/b Ratio
1.64 5.0x10'
0.98 0.012
0.64 0.024 35
0.54 0.033
0.22 0.022 21

-n-Butyraldehyde was the only product detected.
S-Activity was below the detection limit for isobutyraldehyde.
Catalyst: HRh(CO)(TPP),; Polymer: PBMA:
P/Rh = 10; [Rh] = 0.1 g of Rh per g of catalyst.
Conditions: 100C, 22 psig (1:1:0.1 HCO/propylene),
flow rate of 10mL/min.







0.4 0.6 0.8 1
0.4 0.6 0.8 1

1.2 1.4 1.6


Figure 3-16.

Effects of filling the pores with catalytic film on the activity of
propylene hydroformylation. Catalyst: Rhodium source -
HRh(CO)(PPh,),; P/Rh=10:1; [Rh] = 0.11; Polymer-PBMA.
Conditions: 800C, 15 psig (1:1:1 HJCO/propylene).




Table 3-8.

Effect of Pregas Mix/Propylene Concentration on the Activity and
Selectivity of the Hydroformylation of Propylene.

Gas mixture Activity (TON/min) Selectivity
1/1/4 0.450 a
1/1/2 0.057 67
1/1/1 0.033 14
1/1/0.1 0.018 a

a. n-Butyradehyde was the only product detected.
Catalyst: Rhodium source HRh(CO)(PPh,),; Polymer PBMA;
P/Rh = 10:1; 6 = 0.64: [Rh] = 0.11.
Conditions: 100C, 20 psig (l:l:x HJCO/propylene),
flow rate = 4.8 mL.min.


activity was 0.45 TON/min. Mixtures of 1/1/1 gave 0.0325 TON/min. At low

propylene concentration (1/1/0.1) the activity was 0.0175 TON/min. This would

indicate that at low propylene feeds the polymer phosphine films are not being

saturated with enough propylene to get optimal conversion.

Selectivity is also affected by the amount of propylene in the gas mixture. It

was evident that the higher the concentration of propylene in the feed the higher the


Effects of flow rates

Since the concentration of propylene plays an important role in the activity of

a catalyst, the flow rate of the reactant gases should also effect the rates. At a flow

rate of 10 mL/min (800C, 50psig) the activity was 0.257 TON/min, while the selectivity

was 2.2. Upon reduction of the flow rate to 4.8 mL/min the activity drops to 0.055

TON/min and the selectivity increases to 24:1. It should be noted that calculation of

the activity includes flow rate as one of the terms. Table 3-9 and Figure 3-17 shows

the steady increase of activity with flow rate at 1000C and 20 psig.

Other polymer films

Silicone gum rubber (SGR) and polybutadiene (PBD) were tested as films

for STFC. These rubbery polymers will produce a more mobile film than PBMA.

Under similar conditions, the SGR catalyst was less active than its PBMA counterpart

[at 20 psig and 800C (0.006 TON/min and 0.015 TON/min respectively)] (see

Activities of PBMA Film Catalyst for the Hydroformylation of
Propylene at Various Flow Rates.

Flow Rate (mL/min)

Activity (TON/min)

0.96 0.007
4.80 0.018
7.20 0.032
9.60 0.031
17.76 0.071
19.20 0.062


1000C. 20 psig.
1/1/0.1 H2/CO/propylene
Rhodium source HRh(CO)(P<3)3; P/Rh 10:1;
[Rh] = 0.10 g Rh per g catalyst.

Table 3-9.

0.08 1








1- I I I r I I I
0 2 4 6 8 10 12 14 16 1
Flow Rate (mL/min)

Figure 3-17. Effects of flow rates on the activity of the PBMA film catalyst on the
hydroformylation of propylene.


Table 3-10 and Figure 3-18), and was very selective producing only n-butyraldehyde.

Two possibilities exist for the decrease in activity: 1) The non-polar nature of the

SGR may decrease the solubility of hydrogen, carbon monoxide and propylene; 2)

The silicon polymer may simply poison the catalyst.

The PBD system was considerably more active (0.81 TON/min) than either

SGR or PBMA, with no apparent loss in activity over a two hour period. The

catalyst produced predominately n-butyraldehyde in a 17:1 n/b ratio. Polybutadiene

is very rubbery under reaction conditions and possesses no functionalities which

would poison the catalyst. Polybutadiene does, however, posses olefinic

functionalities which may be hydroformylated. Analysis of the film was not done but

if this reaction is occurring the film does not deactivate the catalyst. Reactions at

these internal olefinic sites on the polymer is expected to be much slower than the

rate of reaction for the hydroformylation of propylene. This lower activity coupled

with the large excess of propylene used in the reaction should minimize the possibility

of hydroformylation of the polymer alkene units.

Comparisons of activity with temperature and pressure. Figure 3-18

demonstrates the differences in activity of the three polymer systems at 800C. The

polybutadiene film catalyst was the most active followed by PBMA and SGR.

Table 3-11 and Figure 3-19 shows that at 1000C all the polymers are equivalent in

activity. This could be due to loosening of the films by molten triphenylphosphine.

Triphenylphosphine has a melting point of 800C. At 100C triphenylphosphine will

be molten and contribute significantly to the film. Table 3-12 shows the expected

Table 3-10.

Comparison of Polymers as Films for the Hydroformylation of
Propylene with SLPC's at 800C.

Film Activity (TON/min) n/b Ratio
PBMA 0.015
SGR 0.006
PBD 0.085 17
None 0.019

SThe only product detected was n-butyraldehyde.
Conditions: 80C, 15 psig (1:1:1 HJCO/propylene).
Catatalyst: Rhodium source HRh(CO)(P0P),; P/Rh ratio 10:1;
[Rh] = 1.0 x 10' mol Rh per gram catalyst; 6 = 0.64;
mass of catalyst = 0.50 g.










n nnnj

* 0

0 10 20 30 40 50
Time (min)




L No Polyme

Figure 3-18. Activity curves of several supported polymer film catalysts for he
hydroformylation of propylene at 80C. Catalyst: Rhodium source-
HRh(CO)(PPh,),;P/Rh = 10:1: 6 = 0.64.
Conditions: 800C, 15 psig (1:1:1 HjCO/propylene).

60 70

80 90


i I


Table 3-11.

Comparison of Polymers as Films for the Hydroformylation of
Propylene with SLPC's at 1000C.

Film Activity (TON/min) n/b Ratio
PBMA 0.037
SGR 0.029
PBD 0.034
None 0.033

a The only product detected was n-butyraldehyde.
Conditions: 1000C, 15 psig (1:1:1 HJ/CO/propylene).
Catatalyst: Rhodium source HRh(CO)(P0,),; P/Rh ratio 10:1:
[Rh] = 1.0 x 10-4 mol Rh per gram catalyst; 6 = 0.70;
mass of catalyst = 0.50 g.









* E

+ U

20 30 40
Time (min

50 60 70




] PBDNo Po

Figure 3-19. Activity curves of several supported polymer film catalysts for he
hydroformylation of propylene at 1000C. Catalyst: Rhodium source-
HRh(CO)(PPh,),;P/Rh = 10:1; 6 = 0.64.
Conditions: 100C, 15 psig (1:1:1 H./CO/propylene).

+ +


0 10


Table 3-12. Effects of Varired Pressure with a SGR Film Catalyst.

Temperature Pressure Activity n/b Ratio
(C) (psig) (TON/min)
80 15 0.006
80 60 0.061 44
80 80 0.670 27

n-Butyraldehyde was the only product.
Gas mixture: 1/1/1 H/CO/propylene; Flow rate = 10 mL/min.
Catalyst: Rhodium Source HRh(CO)(PPh,),; P/Rh = 10:1;
[Rh] = 0.10 g Rh per g CAtalyst; 6 = 0.64.

increase in activity and decrease in n/b ratio for the SGR film catalyst with the

increase in pressure.

Alternative Films

Molten salts

Molten salts are candidates as liquid phase media", both aliquat 336 (tri-n-

octyl methyl ammonium chloride) and tetrabutylphosphonium bromide demonstrate

similar activity to their polymer counter parts at loadings and conditions comparable

to the polymer systems (see Table 3-13). These systems produced only n-

butyraldehyde and showed no loss in activity over a three hour period. Both Aliquat

336 and tetrabutylphosphonium chloride are molten at room temperature.

As in the case of polymer films, an increase in reaction temperature does

increase the overall activity of the system. At 800C the activity of the aliquat 366

catalyst is 0.010 TON/min and increases at 1000C to 0.044 TON/min. Both catalysts

only produce n-butyraldehyde.

Liquid films

Supported liquid phase catalysts were tested as control catalysts for

hydroformylation of propylene. The liquids examined were 2-octanol, diethylene

phthalate, and propylene carbonate. These catalysts were run as simulants to Rony's

SLPC and to test if the totally selective systems found with rubbery polymers and

molten salts were real phenomena or a product of the flow rates and pressures of the

Table 3-13. Hydroformylation of Propylene with Molten Salt Film Catalysts.

Film Conditions Activity n/b Ratio
(C/psig) (TON/min)
Aliquat 336 80/15 0.010
Aliquat 336' 80/15 0.046
Aliquat 336 100/15 0.044
TBPC1 100/15 0.010
PBMA 100/15 0.038

n-Butyraldehyde was the only product detected.
6 = 1.31, [Rh] = 0.06 g Rh per g catalyst.
Reactant gas 1:1:1 H,/CO/propylene, flow rate = 10 mL/min.
Catalyst: Rhodium source HRh(CO)(PPH,),; P/Rh 10:1; [Rh] = 0.1 g Rh per
g catalyst.

gas flow reactor used in the experiment. As expected, all the high boiling liquid

catalysts showed slightly higher catalytic activity toward aldehydes than their

polymeric counterparts. In addition to higher activity, the production of iso-

butyraldehyde was appreciable (see Table 3-14).

Several experiments were carried out with propylene carbonate under our

relatively mild conditions for the purpose of comparison with the polymer systems.

It was determined that increasing temperature and pressure generally increase the

activity while lowering the selectivity (see Table 3-15).

Other Vapor Phase Substrates

In addition to propylene, 1-butene and 1,3 butadiene are of interest as

substrates. We have tested these substrates with the

HRh(CO)(PPh3)'/PPh3/PBMA/SG catalyst at 1000C and 20 psig. But-1-ene shows

both the linear and branched products in a 15.7:1 ratio, and a activity of 0.084

TON/min. Buta-1,3-diene produced four products with conversions approaching

0.173 TON/min.

Hydroformylation of Propylene with Supported Hydrophilic Catalysts

The hydroformylation of liquid alkenes such as 1-hexene will be described in

the following chapter. In this section we will describe the hydroformylation of

propylene with the catalyst used for liquid alkenes. The catalyst consists of a water

soluble rhodium catalyst (HRh(CO)(TPPTS),) (TPPTS = P(C,6HSO,Na),) and excess

Table 3-14. Hydroformylation of Propylene with Various SLPC's.


Propylene carbonate


SThe only product was n-butyraldehyde.
Conditions: 80C, 15 psig 1:1:1 HJCO/propylene. Flow rate = 10 mL/min.
Catalyst: Rhodium source HRh(CO)(PPh,),; P/Rh = 10:1;
[Rh] = 0.10 g Rh per g catalyst.

n/b Ratio


Table 3-15.

Hydrotormylation of Propylene with Various Propylene Carbonate
Film Catalysts.

Temperature Pressure Gas Mixture Activity n/b Ratio
(C) (psig) (H/CO/CH,) (TON/min)
80 15 1/1/1 0.007
80 15 1/1/0.1 0.013
100 15 1/1/1 0.197 41
100 60 1/1/1 0.342 11

" The only product detected was n-butyraldehyde.
Conditions: Flow rate = 10mL/min.
Catalyst: Rhodiun source HRh(CO)(PPh,),; P/Rh = 10:1:
[Rh] = 0.10 gRh per g catalyst; 6 = 0.64.

ligand (TPPTS) in a water soluble polymer (PEG 600) coating silica gel (see

Table 3.16). The degree of pore filling for this catalyst was 1.40. At 100C and 20

psig of 1:1:0.1 H/CO/propylene this catalyst showed a conversion of 0.114 TON/min

and a selectivity of 14.3. An increase in pressure to 40 psig increased the activity to

0.461 TON/min but lowered the n/b ratio to 6.69. A further increase in pressure

raised the activity to 0.519 and a n/b of 5.83. Increasing the temperature to 120C

decrease the activity to 0.196 and increased the selectivity to 8.74.

This demonstrate the feasibility of the water soluble rhodium catalyst in a

hydrophilic film coating silica for the hydroformylation of vapor phase substrates such

as propylene. The activity of this system is high for the degree pore filling (6=1.4).

Further experiments with lower S's should be done.


We developed a novel approach to supported liquid phase catalyst which uses

a polymer or molten salt as the film phase. These catalysts consist of a rhodium

source (HRh(CO)(PPh,)3 in a polymer or molten salt film supported on silica gel.

Previously reported SLPC used high boiling liquids as the liquid phase, leading to

films that evaporate with time, leaving a surface supported rhodium catalyst. We

have seen that the addition of excess phosphine ligand (triphenylphosphine) to the

catalytic film enhances the activity and the selectivity of the overall catalyst. This

enhancement can be attributed to the loosening of the film by molten

triphenylphosphine in the film, at temperatures above 80C.

Table 3-16. Hydroformylation of Propylene with a Supported Hydrophilic

Temperature Pressure Conversion Activity n/b Ratio
(C) (psig) (%) (TON/min)
100 20 3.1 0.114 14.3
100 40 12.5 0.461 6.69
100 60 14.1 0.519 5.83
120 60 5.3 0.196 8.74

Catalyst: Rhodium source HRh(CO)(TPPTS),; Additive: TPPTS;
Polymer: PEG 600; Support: Silica gel: 6= 1.4.
Pregas mixture: 1/1/0.1 H,/CO/propylene, flow rate 4.8 mL/min.

We have varied a number of the conditions and film properties of the catalytic

system and found that even a slight modification of any of the variables affects the

activity of the system dramatically. They include temperature, pressure, degree of

pore filling and concentration of rhodium in the film. It was shown that increased

temperature and pressure increased activity but decreased selectivity of the catalyst,

while the activity decreased significantly with the increase in pore filling. The

concentration of rhodium in the film also had an effect on the activity; as the

concentration increased so did the activity and the selectivity.

We also varied the film material by using different polymers and molten salts.

All of the films tested were active for the hydroformylation of propylene. The molten

salts tested showed extraordinary selectivity by producing only the linear aldehyde.

Liquid films such as propylene carbonate, 1-octanol and diethylene phthalate

demonstrated higher activities than their polymer counterparts but much lower


The catalyst system described herein has shown to be an effective system for

the hydroformylation of vapor phase substrates under mild conditions. The following

chapter will describe a system for the hydroformylation of liquid substrates in a batch




The goal of heterogenizing homogenous catalysts is to design a catalyst that

would have many of the advantages inherent in both heterogeneous and homogenous

catalytic systems. Homogeneous catalysts offer high activity and selectivity along with

the ease of modification of the system. Heterogeneous catalysts offer the ease of

separation of the catalyst from the reactants and products along with the easy

recovery of expensive transition metals.

Many heterogeneous catalysts have been developed for hydroformylation.

Most include the coordination of rhodium or cobalt to functionalized organic

polymers or inorganic oxides. The functionalized groups are usually phosphines. In

addition, catalysts have been trapped in zeolites and several biphasic systems have

been developed.

Supported Transition Metal Catalysts

Organic polymers. Numerous polymer-supported transition metal systems

have been developed and studied for catalysis."6 Organic polymers which

contain pendant phosphines have been prepared. The major drawback to these


catalysts is the elution of rhodium from the polymer surface.`' Pittman et al. have

chemically linked rhodium, cobalt, ruthenium and nickel complexes to polymers via

phosphine coordination. The polymer-bound transition metal catalysts were efficient

catalysts for cyclooligomerization, hydrogenation, and hydroformylation."*5' The

catalysts are depicted in Figure 4-1.

The rhodium phosphine polymer hydroformylated 1-pentene at 250-1000 psi

and 40-60C yielding a n/i ratio of 2.5:1.'" Comparison of the rhodium catalyst to

the homogeneous catalyst, HRh(CO)[P(C6H,)3]3, under similar conditions gave

interesting results. At low temperatures, 400C, the activity of the polymer catalyst was

significantly lower than the homogeneous catalyst. However, when the temperature

was increased to 600C, the activity of the two catalysts were nearly identical. This

phenomena was explained by diffusion of the reactants through the polymer matrix.

At lower temperatures the chains are restricted and immobile. The increase in

temperature decreased the viscosity of the resin which in turn greatly reduced the

diffusion time of the reactants to the rhodium centers.

After extended reaction time the activity of the catalyst decreased but time

while the n/b ratio increased. As the reaction is allowed to proceed the rhodium

center becomes more highly coordinated by anchored phosphines leading to low

activities and high n/b ratios. A later study showed that in catalysts with high loadings

of anchored phosphines a high degree of substitution results and n/b ratios of 12:1

are observed. Low loadings of anchored phosphines gave n/b ratios similar to those

of homogeneous catalysts.

Figure 4-1. Coordination of rhodium to a polymer support via pendant phosphine


Allum et al. developed similar polymer supports shown in Figure 4-2.*

Rhodium catalysts can be made by the addition of Rh(acac)(CO), to the polymer.

These copolymers are efficient hydroformylation catalysts for 1-hexene at 900C and

42 atm (1:1 HCO) but n/b ratios are low (0.81). Treatment of these polymers with

tri-n-butylphosphine increases the ratio to 2.3:1. In a continuous flow reactor (pilot

plant conditions) the activity of this catalyst drops dramatically from 86% to 36%

within 10 hours, but selectivity remains unchanged at 2.5:1. Leaching of the catalyst

into the reaction feed occurs. Trace amounts of oxygen facilitates metal leaching

from the support.

Non-phosphine containing polymer supports coordinate rhodium to produce

active hydroformylation catalysts. The polymer contains a organic sulfide group for

the linkage to the transition metal.70 This catalyst converts 100% of the 1-hexene

over an 8 hour period and has a n:i ratio of 1.

Inorganic oxides. Numerous inorganic oxides can be used as supports for

hydroformylation catalysts (e.g. silica gel, alumina, and porous glass)." Direct

deposition of RhCl3 or (PPh3),Rh(CO)Cl lead to catalysts which show negligible

activity for the hydroformylation of 1-hexene at 1000C and 300 psig.7 At low

pressures these catalysts are efficient isomerization catalysts for the formation of 2-

hexene. Increasing pressure and temperature gives an active catalyst for the

hydroformylation of propylene.

Allum et al supported metal complexes on silica by reacting

HRh(CO)[(EtO),SiCHSiCH2CH,PPh,], with functionalized silica.7 Under pilot plant

Preparation via substituted polystyrenes

,--- *w

- -

Prepation via unsubstituted polystyrenes




Figure 4-2. Preparation of functionalized polymers.






conditions the catalyst leaches into the feed initially but after the first few hours no

further leaching occurs. The leaching can be attributed to the presence of trace

amounts of oxygen in the reaction solution.

Zeolites. Various rhodium complexes can be incorporated into zeolites."73'7

Only a few are useful as heterogeneous catalysts for liquid substrates.75 The main

drawback to zeolite supported catalysts is the leaching of the rhodium complex into

the reaction solution. Never the less, there have been a few catalyst which are active

for the hydroformylation of 1-hexene and do not elute rhodium into the solution.76

Davis and coworkers have described the various types of zeolite catalysts for

hydroformylation in which the rhodium source is cation exchanged into the zeolite.77

There are three fashions in which the rhodium can be bound to the support. For

type I the rhodium species is weakly bound to the surface of the support and easily

elutes into solution. For type II the active species is tightly bound to the zeolite

support. The activities of these sites are low, because the rate is diffusion limited.

Type III has the rhodium complex entrapped within the zeolite cage. The n/b ratio

for type III sites are reported to be 2.6:1.

Biphasic catalysts

A variety of water soluble ligands and complexes are used for biphasic

catalysis.7'79 These systems employ the use of immiscible solvents to achieve the

desired separation characteristics of heterogeneous catalysts8" and rely heavily on

the solubility of the substrates in the phase in which the catalyst resides. Sulphonate

phosphines are commonly used as ligands for rhodium complexes in biphasic catalytic

systems." Rhone-Poulenc utilizes the water soluble catalyst, HRh(CO)(TPPTS)3

(TPPTS=trisodium tris(m-sufonatophenyl)phosphine), and the water soluble ligand,

TPPTS, for the hydroformylation of propylene.8"'8' The metal complex and

excess ligand resides in the aqueous phase while the majority of the substrates

(propylene) and products (n-butyraldehyde and isobutyraldehyde) are in the organic

phase. Efficient conversions of the olefin are made with a n:i ratio of 3:1. A similar

system uses a chelating sulfonated phosphine as a ligand for rhodium catalysts. These

systems yield high activities at low P/Rh ratios.87

Other biphasic hydroformylation systems have appeared. Taqui Khan et al.

report a system which exclusively produces n-heptaldehyde from 1-hexene using Ru-

EDTA in a 80/20 ethanol-water mixture at 1300C and 50 atm.8 A rate of 11.8

TON/hr is achieved and the catalyst can be recycled with out loss of activity.

Baird et al have developed a rhodium water soluble catalyst with using the

ammonium phosphine ligand Ph2PCH2CHNMe*NO."9 An active catalyst for

hydroformylation can be made with [(norbornadiene)RhCl]2 in the presence of the

phosphine, (at least a 3:1 P/Rh ratio). The active catalyst is

[(norbornadiene)Rh(Ph,PCH,CHNMe),]3" and hydroformylates 1-hexene which is

dissolved in hydrophobic organic solvents. An n:i ration as high as 4:1 is observed,

the selectivity is dependant upon the choice of solvent. Small amounts of

hydrogenation and isomerization products were observed, and leaching of a small

amount of rhodium into the organic media occurred.

The addition of surfactants such as CTAB or quantinary ammonium salts

increases the efficiency of the biphasic rhodium catalyst (see Table 4-1).'" A

biphasic system that consists of PPh,C6H,COH, and a rhodium source in water

converts 2'% d the 1-hexene substrate in three hours. With the addition of a

surfactant, the conversion increases to 44% in one hour. It was also noticed that

high selectivity occurs with poor mixing.

Supported Aqgeous Phase Catalysts

Recent. supported aqueous phase catalysts (SAPC) have been developed by

Davis et al."91 This system covers an inert porous support, such as porous glass,

with a thin aqueous film containing a water soluble catalyst, HRh(CO)(TPPTS),, and

a water solubk phosphine, TPPTS. Hydroformylation of higher olefins such as 1-

octene and oikyl alcohol can be done at moderate rates and a selectivity of 2.3:1

(conditions:7:7C, 700 psig). It is claimed that the rhodium complex is mobile within

the aqueous fIm and the catalysis occurs at the water/organic interface where the

organic phasecontains the reactants and products.

The rale of hydroformylation is unaffected by the size of the olefin in the

SAPC catalyst, whereas in biphasic systems the rate is highly dependent on this

variable.' Ttis indicates that water evaporates from the surface and leaves a

phosphine-rhetium complex bound to the support via hydrogen bonding of the

hydrated sodint-sulphonate groups to the surface (see Figure 4-3).

Table 4-1.

Effects of Surfactants on the Biphasic Hydroformylation of Olefins.

Surfactant Substrate Time % Conversion n/i
None 1-Hexene 3 2 7
C1H.,N'Me,Br 1-Hexene 1 44 73
None 1-Dodecene 3 2 6
C,2H,N'MeBr 1-Dodecene 1 78 20
none 1-hexadecene 3 0.5
C,_H,N'Me,Br 1-hexadecene 1 73 22

P:Rh= 10:1,
5.5 atms 1:1 H,:CO

Conditions: [Rh],,=300 ppm, 4-Ph,PC.H,COOH,
C,,H,NMe,Br:Rh=20:1 in pH 10 buffer at 800C,



Figure 4-3. Immobilized TPPTS on a hydrophilic support by
hydrogen bonding of the hydrated sodium-sulphonate
groups to the surface.



Water was purified by nanopore filtration and stored under nitrogen. The

premixed syn gas were prepared using a manifold system. A lecture bottle was

pressurized to 500 psig with carbon monoxide and then pressurized to 1000 psig with

hydrogen. The substrates 1-hexene, 1-octadecene, and 1-octene were purchased from

Aldrich Chemical and filtered through acidic alumina before use. Valeraldehyde was

filtered through acidic alumina and freshly distilled before use. Silica gel (grade 62,

mesh 60-200, surface area 700 m g', pore volume 1.1 mL/g) was purchased from

Davison and was dried at 100C overnight, and sealed under nitrogen. The following

were used without any further purification: Rh(acac)(CO), (Strem Chemical);

RhCL,63HO (Strem Chemical); 2-octanone (Fluka); polyvinyl alcohol (Fluka);

absolute ethanol (Florida Distillery Co.); formamide (Aldrich Chemical); polyethylene

glycol (Aldrich Chemical) polyvinyl pyrrolidinone (Polysciences Inc.).

Apparatus and Instrumentation

Catalysis was run in either a 300 mL Parr mini reactor or in glass pressure

bottles equipped with a pressure head (see Figures 4-4 and 4-5). Nuclear magnetic

resonance spectra were obtained by using a Varian VXR 300MHz or a General

Electric QE300 nuclear magnetic resonance (nmr) spectrometer. Infrared spectra

were obtained from a Nicolet 5PC FTIR spectrometer. Gas chromatographs were

obtained by using a Varian 3300, a Perkin-Elmer 900 and a Hewlett Packard 5890

using a DEGS packed column. GC-MS were obtained by using a Varian 3400

equipped with a Finnagan MAT ion trap detector.


Premixed gas cylinder

- psig )

Stirred autoclave

Figure 4-4. Parr High Pressure Reactor.

premixed gas cylinder

Figure 4-5. Parr pressure bottle batch reactor.


All manipulations were carried out under an atmosphere of nitrogen.

Preparation of TPPTS

'The preparation of TPPTS was carried out similarly to the preparation

reported by Arhancet." Oleum (50 mL, 20%) was added dropwise to

triphenylphosphine (8.0g) in a three neck round bottom flask cooled by an ice bath.

After the addition and complete dissolution of the phosphine, the ice bath was

allowed to warm to room temperature and stirring was continued for at least 18

hours (the longer the phosphine solution is allowed to stir the higher the degree of

sulfonation). The solution was then cooled to 0-100C. Cooled deaerated water (200

mL) was added dropwise to the solution to quench the reaction. The acidic

phosphine was extracted from the aqueous solution by the addition of tri-n-

butylphosphate (50 mL, two times). The organic layers (top) were combined and

placed in an ih bath. Concentrated sodium hydroxide (50g, 100 mL) was added

dropwise to tie acidic phosphine solution until neutral. This resulted in the

formation of a white precipitate, from this a white solid forms. The solid was filtered,

washed with ditthylether (50 mL, 5 times) and air dried. The solid was then taken

up in water (75 mL) and methanol was added to precipitate a white solid (mostly

Na2SO,). The solid was removed by filtration and the filtrate was evaporated under

reduced pressure. Phosphorous ("P) nmr of the solid indicated the presence of

TPPTS (-5.50 plpm, 82%), HTPPTS (1.69 ppm, 16%) and OTPPTS (36.11 ppm, 3%).

Barium nitrate test of the solid was positive for the presence of NaSO,. The solid

was taken up in water (50 mL) and the NaSO, was precipitated by the addition of

absolute ethanol (80 mL). Recrystalization from methanol with ethanol removed all

of the phosphine impurities. If any HTPPTS remains it can be removed by washing

the solid with methanol.

Preparation of HRh(CO)(TPPTS),

A. The ligand TPPTS (2.30g, 4.05 mmol) was added to hot water (40mL).

To this RhCl3*3H,O in water (2mL) was added. After 15 seconds formaldehyde

(4mL, 27% in H,O) immediately followed by KOH (0.35g, 6.24 mmol) in water

(5mL) were added. A yellow solution formed almost immediately. The reaction

solution was allowed to stir for 10 minutes and cool to room temperature. Water was

evaporated under reduced pressure. The resultant yellow solid was taken up with

minimal water and the yellow solid was precipitated with ethanol.

B. The ligand TPPTS (0.52g, 0.92 mmol) was added to water (10mL) and

stirred under nitrogen until completely dissolved. Rh(acac)(CO), (0.050g, 0.19 mmol)

was added to the TPPTS solution. Upon complete dissolution an atmosphere of

HJCO (1:1) was introduced and allowed to flow slowly for 18 hours. The yellow

solution was filtered and evaporated to 1 ml. Ethanol was added to precipitate a

dark yellow solid. The solid (I) was filtered, washed with hexanes, and dried under

vacuum. Additional ethanol was added to the filtrate to precipitate additional solid

(II). The mixture was centrifuged and (II) was dried in the vacuum oven. The liquid