Luận Án tiến sĩ study on the sio2 supported ionic liquid phase silp catalysts for the hydroformylation of ethylene

243 Calculation of vatalytic aclivities CIIAPTER 3: RESULTS AND DISCUSSION 31 Catalyst characterization 311 The density of ionic liquid 31.2 NMR spectra of ligand TPPTS-Cs; 313 TPD

FOR THE HYDROFORMY LATION OF ETHYLENE

Speciality: Petrochemistry and catalysis for organic synthesis

Code: 62.44.35.01

CHEMISTRY DISSERTATION

A thesis submitted to Ilanoi University of Science and Technology

lor the degree of Doctur of Philusophy in Chemistry

By

Nguyen Thi Ha {anh

SUPERVISORS : Assoc.Prof Dr Vu Dao Thang

Assoc.Prof Dr Le Minh Thang

INVITED SUPERVISOR: Prot Rasmus Fehrmann

TIANOI - 2011

ACKNOWLEDGMENTS

1 would like to thank my supervisors, Assoc Prof Vu Dao ‘Thang, Assoc

Prof Le Minh Thang, Prof Rasmus l’erhmann, and Assoc Prof Anders Rissager

for their guidance, encouragement, and the academic and fmancial support in accomplishing this work

Many thanks to Dr Olivior Nguyen Van Buu for introducing me to the air- sensitive synthetic techniques, the hydroformylation reactor unit

T also would like to thank my college - Mse Truong Due Due lor all his help in the characterization of calalysL structures presented in this dissertation

Very special thanks to my husband Quach and my daughter Minh Khue for

their love, support, and encouragement And ta my mom, and my dad— thanks for

being always there for me

1 would like to thank to my teachers at Department of Organic and Petrochemical Technology, my colleges at the Laboratory of Petrochemical Refining and Catalysis Materials for their supports, their commendation and their

discussions

Acknowledgments are also extended to Danida |’oundation for funding this research.

CONTENTS TNTRODUCTION

CHAPTER 1: LITERATURE REVIEW

Catalysts for hydroformylation reaction Recent trends in the heterogeneous hydroformylation

Composition of SILP catalysts

Synthesis of SILP catalysts

Catalytic aclivily of STLP catalysis

323 ‘Thermal analysis

324 SEM- TEM Iechnichque

335 Nuclear magnetic resonance spectroscopy NMR

23 Measurement of density of ionic liquid

34 Moasuarcmctt of eatalylic aclivity

241 Tiydroformylation of ethane

342 Hydroformylation of penten

243 Calculation of vatalytic aclivities

CIIAPTER 3: RESULTS AND DISCUSSION

31 Catalyst characterization

311 The density of ionic liquid

31.2 NMR spectra of ligand TPPTS-Cs;

313 TPD NHy of SiO, support

314 Thermal analysis of IL, ligand and SILP catalyst

315 Surface arca and physical adsorption properties of

321 Catalytic activity of the catalysis using ligand TPPTS-

Cs; for the hydroformylation of ethylene

32.11 Tufluence of ioniv liquid loading content on acitivity

of SILP

3.2.1.2 Influence of Rhodium content on activity of SILP

3213 — Influence of ligan@/Rh ratios on activity of SILP

catalyst 3.2.1.4 Deactivation of catalytic performance

CONCLUSION References

Classification of immobilised metal complex catalysts Supported ionic liquid phase hydroformylation in ionic liquids Supports used for SILP-catalysed hydroformylation of propene Summary of synthesized catalysts

Retention times of reactants and products in the hydroformylation of

ethylene

Retention times of reactants and products in the hydroformylation of

penlerie

Densily of monic liquid {BMIM ]|n- CsH,;OS03],- at different temp

Weight loss due to the decomposition of IL in the samples with different

LL loadings, before and after use

Influence of TL loading on the Surface properties of STLPs

Surlace properties of STLPs with dilTeront ligand and 1./Rh ralios

Surface properties of SLLP catalysts with different LL loading before and after hydroformy] reaction (used)

Element compositions of different points indicated in figure 3.23

65

66

68

" a

LIST OF FIGURES

1.1 Global consumption of 2-ethylhexanol for various applications (wt %)

1.2 Global consumption of n-butanol and iso-butanol (wt %)

13 Worldwide growth in the production of oxo produets

1.1 Region wise production statistics for oxo products (2008)

1.5 Statistics of oxo products for Asia region (2003)

16 Worldwide oxo product derivatives distribution

1.7 Production capacities for oxo produets by worldwide known

industries

18 Hydroformylation reaction in biphasic medium

1.9 Coordiaative anchoring of a metal complex to the support surface

1.10 Aschlenk line and schlenk tube

21 The Schlenk system to synthesize catalysts

22 BET plot

2.3 Ways to obtain vibrational spectroscopy: ‘lransmission infrared

2.4 A themal Analysis Deviee

25 — Biflects produced by electron bombardment of a material

2.6 Transmission electron microscope will alt of iis componens

2.7 Spin state of a mulear

28 A description of the transition energy for a*“P mucleus

‘TPD NH3 profiles of uncalcined and caleinated S102

TG-DSC profiles of [BMIM][n-CgH17OS03] (nitrogen atmosphere,

heating rate: 5°C/min)

TG-DSC profile of ligand TPPTS-Cs; (nitrogen atmosphere, heating

rate: 5°C/min)

TG-DSC profile of SLLP -Cs-L/Rb10-I1L10- RhO.2 (mitrogen

atmosphere, heating rate: 5°C/min)

TG-DSC profile of SILP -Cs-L/RhI10-IL50- RhO.2 (nitrogen

almosphere, heating rate: S°CAnir1)

TG-DSC profile of STP -Cs-T/Rh10-11.30- RhO.2 Gutrogen

atmosphere, heating rate: S°C/min)

TG-DSC profile of SLLP -SX-L/Rh10-1L10- RhO.2 (nitrogen

atmosphere, heating rate: 5"C/min)

BIH desorption profiles of samples with different IL loading content before (a) and after the reaction (used) (b)

FT-IR spectrum of SiO), TPPTS-Cs; ligand, 1L, and SILP-Cs-L/Rh10-

Positions for 1X measurement and HDX spectra of SILP-Cs- 1/Rh10-IL10-Rb0.2 catalyst:

2) position for EDX measurement, b) EDX spectrum at $1, ¢) EDX spectrum at $2, d) EDX spectrum at $3

SEM images of SILP-Cs-L/Rhl 0-1L5-Rh0.2 before and afer exposed

to high temperatures of the reactions

SIIM images of SILP-Cs-L/Rhl 0-IL10-Rh0.2 before and afer

exposed to high temperatures of the reactions

SEM images of SIT.P-Cs-1./Rh1 0-11.50-Rh0.2 before and afer

exposed to high temperatures of the reactions

3.29

3.36

3.37

TEM images of Si02 support

TEM images of SILP-Cs-L/Rh10-IL5-Rh0.2 botore and afer exposed

to high temperatures of the reactions

TEM images of SILP-Cs-L/Rh10-IL10-Rh0O.? before and afer

exposed to high temperatures of the reactions

TEM images of SIT-P-Cs-1/Rh10-11.10-RhO.2 before and afer

exposed to high temperatures of the reactions TEM images of SILP catalysts with different Rh loading Catalytic activity of SLLP catalysts with different LL loading

Influence of IL loading contents on the maximum temperature which the catalysts still work stably

Influence of IL loading content on the catalytic activity of SILP

catalysts

Influence of Rh content on the activity of SILP catalysts

Tafluence of hgand/Rh ralios on the catalytic activity of STLP

catalysts

Influence of ligand/Rh ratios on the maxinrum temperature which the catalysts still work stably

TOF at 90°C (except for the sample with 50%IL, which TOF is at

80°C since the catalyst start to loose activity from 900 already) of the catalysts with different IL loading, contents before and after the

exposition to high temperatures

TOF al 90°C of the catalysts with different Rh loading contents

belore and afler the exposition to high temperatures

Activily al 90°C of the catalyst ST.P-Cs-L/Rh10-11.10-Rh0.2 before

and afer cofeed 10%V propanal in the feed stock Influence of evacuation on the activity of deactivated catalysts Arthenius plots of the samples with different TI loading content

Arhonius plots of the samples wilh differ (Rh loading content Azthenius plots of the samples with different L/Rh ratios

Influence of ethylene partial pressure on the TOF of the catalyst Influence of ethylene partial presure on the ethylene conversion Influence of cthylene partial pressure on propanal selectivity

Catalytic activity on stream of the catalyst SILP-SX-L/Rhl0-IL10- RhO.2 at different ethylene pressures

Influence of residence time on ethylene conversion Influence of residence time on propanal selectivity Influence of residence time on tum over frequency

Aathenius plots to calculate activation energy of the catalyst SILP- SX-L/Rh10-1L10-RH0.2 at different cthylone pressures

Yield and selectivity at temperature of 1250C

Yield and selectivity at temperature of 1160C Arrhenius plot for Rh-SIL.P-catalyzed hydroformylation

Selectivity (n/iso ratio) at different temperatures

Anhenius plot for hydroformylation of ponlene on the catalyst STLP- SX-L/Rh1@1L10-RH0.2 10bar syngas (alkene:CO:H; — 1:1:1),

Hydroformylation of ethylene and propylene

Dissociative mechanism for hydroformylation cycle

Associative mechanism for hydroformylation cycle

Mechanism for ethylene hydroformylation, 1 PPhy

‘he formation of heavy products (by-product)

Illustration of supported ionic liquid phase catalyst

Page 13

LIST OF SYMBOLS AND ABBREVIATIONS

Nuclear magnetic resonance

phenyl

Scanmung electron microscopy

Supported ionic liquid phase

‘Transmittance electron microscopy

1,1,3,3-tetramethylguanidinium lactate

Tum-over-frequency

‘Iri-cesium tris(m-sulfonatopheny!)phosphine

Yield, mol-%

INTRODUCTION:

Hydroformylation is one of the oldest and largest homogeneously catalyzed reactions of olefins

Hydroformylation is conducted in a mixture of reactants and products, and

as of 1984 in biphasic aqueous media to allow dissolution of Rh catalyst and reactants in a homogeneous liquid phase ‘he catalysts used are homogeneous in nature, dissolved into the solvent or reactant/product mixture This poses significant challenges related to separation, which is simplified in the biphasic RCILRP oxo-process This process is based on aqueous biphasic catalysis and uses tri(m-sulfonyl) tiphenylphosphine (TPPTS), as the ligand and a water soluble Rh metal as the catalyst

Rhodium is more active than cobalt, but is also more expensive Rhodium

is the catalyst of choice for conversion of low molecular weight alkenes, while cobalt based catalysts are used for conversion of high molecular weight alkenes For example, Ruhrchemie/Rhone-Poulenc (RCH/RP) process has been applied for hydroformylation of propene by Rh based catalysts

Though, homogencous catalysts give higher conversion and selectivity for desired product in short reaction time as compared to helerogencons catalyst system, this have disadvantage in the separation of catalyst from the product

mixture [hus, efforts are directed towards the heterogenization of rhodium

complex on the inorganic solid supports for hydroformylation of alkenes In this concem, more attention in the present thesis has been paid on literature review related to the recent developments in the heterogenizaton of homogeneous catalysts on the inorganic solid supports for hydroformylation of alkenes

On the other hand, ethylene, propene, butene are light alkene, but only the hydroformylation of propene, butene reaction in biphasic medium very successfully

The main product - propanal derived from the hydroformylation of ethylene, however, bears a significant miscibility with water If the reaction could happen in aqueous- biphasic like propene reaction, there would be some problems:

- Water in the aldshyde cannot be removed by distillation, duc to the

formation of azcotropic mixtures,

- Together with the water dissolved in the propanal, a significant amount of catalyst is transported out of the reactor, a recovery of this portion of the catalyst

is difficult

Athough, the hydroformylation of ethylene itself in the water-based RLTPPTS system is quite fast, ethylene can soluble in the water phase, is counterbalanced by the unfavorably high solubility of water in propanal Vor this reason the hydroformylation of ethylene is performed in homogeneous Rh/TPP

systems

‘Thus, if the hydroformyltion of ethylene reaction can be done by using SILP catalyst as heterogenous way, it will be a promising way to apply in industry scale

The goal of this research was to develop a solid catalyst for heterogeneous hydroformylation of ethylene Rhodium is the most active transition metal for hydroformylation and it was obvious choice for the catalytic metals in the preparation of the solid catalysts Silica was chosen, because it is an inert,

available support material widely applied in catalysis

Ligands change the electronic and steric properties of the catalyst complex Two ligands (TPPTS-Cs; and sulfoxantphos) were chosen to evaluate their

activity in ethylene hydroformylation

The thesis includes Ilsee chapters The first chapter surmmarizes the aspects

aboul the hydrofermytation process, synthesis, the structure, the calalylic

properly of STLP catalyst im the Hieralure The second chapter describes (he

calalysis synthesis and introduces basic principles of the physico-chemical

methods used im the thesis

The chapler TT is focused on the characterization of STLP, the calalylic

activily of STP with twe above mentioned ligands

Finat is the general conclusions of the performed work

CHAPTER 1: LITERATURE REVIEW

Development of green calalyfic routes for the synthesis of commercially

important chemicals is a rewarding crdeavor [rom enviroment and ceonoric

point of view Green chemistry comprises designing, development and

es 1o Teduce or eliminate the

implementation of chemical products and proce

use and generation of subslanecs hazardous to the human health and

environment It is an imnovative, nontegulatory, economically driven approach loward sustainability Groon technology is receiving significant attention as the awareness about environmental issues has increased ‘The concept for the design

of environmentally benign products and processes is embodied in the 12 Principles of Green Chemistry as follow [11]

1 Waste prevention instead of remediation

2 Atom efficiency

3 Use of less hazardous/toxic chemicals

4, Design safer chemicals and products

5 Use innocuous solvents and reaction conditions

6 Design energy efficient processes

7 Preferably renewable raw materials

8 Shorter synthesis route and avoid derivatization

9 Use catalyst instead of stoichiometric reagents

10 Design products for degradation after use

11 Real time analytical methodologies for pollution prevention

12 Tnherently safer processes lo minimize the potentials for accidents

Catalysis plays a vital role in production of wide variety of products, which are having applications in drugs, plastics, agrochemicals, perfumery, detergents, food, clothing, fuels etc [90] In addition to, it plays an important role in the balance of ecology and environment by providing cleaner alternative routes to stoichiometric technologies Green catalytic process efficiently utilize all the

atoms of raw materials, eliminates waste and avoids the use of toxic and/or

3

hazardous reagents and solvents in the manufacture and application of chemical products

Llydroformylation is an important commercial process for the conversion of alkenes, carbon monoxide and hydrogen into aldehydes to be further used in the

production of various chemicals The industrial processes operate in a

homogeneous mode Therefore, the development of a solid catalyst would solve problems related to catalyst separation and thus, contribute to decrease waste

from these chemical processes This section summarizes the basic knowledge in

the field of hydroformylation of alkenes in liquid phase and especially in the gas

phase condition

1.1 Hydroformylation of alkencs (Oxo Reaction}

Hydroformmylation is one of the oldest and largest homogencously catalyzed reactions of olefins The reaction was furst discovered in 1938 by Roclen while working for Rulrehemic in Germany Rolo investigated ihe olfect, of added olefins to cobalt catalysts and identified aldehydes as one of the oxygen containing components Hz and CO can add across the double bond of olefins to form aldehydes in the presence of a Co (or Rh) catalyst [42, 93]

The process is Frequently referred to as the “Oxe” process, with Oxa beiug short for Oxonation, i.e the addition of oxygen to a molecule However, the term

hydroformylalion is descriptively more avcurale and more useful in

characlerizing this type of reaclion catalyzed by various transition melal

complexes beeause during the reaction a hydrogen alom and a formyl group are

added to the olclimie double bord

RCH, CH; +CO+ H,2RCH,CH,CHO + RCH(CH,)CHO (Fq.1.1)

“normal” “branched”

‘The relative amounts of normal- and branched-chain aldehydes produced depend on the identity of R and other constituents of the reaction mixture Normal-chain aldehydes, the more desirable products, usually are hydrogenated, affording straight-chain alcohols, or self-condensed, affording more complex aldehydes With a terminal alkene as substrate, the normaV/branched ratio is an important parameter in the industrial hydroformylation process; generally speaking, the better catalytic

developed for the branched aldehydes In addition to linear terminal olefins,

a wide variety of different olefins have been successfully hydroformylated,

e.g linear internal olefins, unsaturated alcohols, phenols, ethers, and amides

Hydroformylation, the reaction of an alkene with syngas (carbon

monoxide and hydrogen) to form aldehydes and alcohols, is an homogeneously catalyzed reaction performed industrially on a large scale Rhodium and cobalt carbonyls have been used for a long time, but such a homogeneous process includes a difficult and expensive step of catalyst recovery Consequently it has been attempted to avoid this step by using heterogeneous catalysts

The first generation of hydroformylation catalysts was based on cobalt

carbonyl without phosphine ligand [26, 42, 93] The conditions were harsh,

as activity of cobalt is low The process was used both for lower as for higher alkenes, and notably also internal alkenes give mainly linear product

aldehyde Initially rhodium catalyzed reaction seemed slow, because the

formation of rhodium hydrides requires high pressures of hydrogen

A nearly commercial application of phosphine-free rhodium was by Mitsubishifor the hydroformylation of higher l-alkenes in 1970, Since Shell's report on the use of phosphines in this process [93], many industries started applying phosphine ligands in the rhodium process as well While

alkylphosphines are the ligands of choice for cobalt, they lead to slow

catalysis when applied in rhodium catalysis In the mid-sixties the work of

Wilkinson showed that arylphosphines should be used for rhodium and that even at very mild conditions very active catalysts can be obtained [37, 114]

1.1.1 The Importance of Hydroformylation Products

World production and consumption of hydroformylation (oxo) chemicals is

more than 8.8 million metric tons per year finding use in the manufacture of

solvents, soaps, detergents, plasticizers and various intermediates for fine and

perfumery chemical industry n-propanol and n-propyl acetate produced from ethylene hydroformylation are used in flexographic and gravure inks, which

require volatile solvents to prevent spreading and ink accumulation on printing processes [32,59,104] n-propanol is also used as a solvent, pesticide

intermediate, precursor for glycol ether, surface coating applications, grain and

5

food preservatives, herbicides, etc

Over 90% of world consumption of n-butanal, which is produced by

hydroformylation of propylene, is for the production of 2-ethylhexanol (2-EH)

and n-butanol The butanal is mainly applied as an intermediate for the production of plasticizers, rubber accelerators, synthetic resins, solvents and high

molecular weight polymers The reason for high production and demand of Cy aldehydes is due to its use in the production of 2-ethylhexanol (2-EH) About

60% of the total C, aldehydes production amount (or about 70% of the n-butanal production capacity) is consumed for the synthesis of 2-ethylhexanol 2- Ethylhexanol is used for the production of dioctyl phthalate and other

plasticizers, coatings, adhesives, stabilizers, low volatility solvent, perfumery and specialty chemicals (Figure 1.1) 2-ethylhexanol derivatives are used as an additive for diesel fuel to reduce engine emissions and for lube and mining oils

to improve their performance

n-Butanol is a versatile intermediate for chemical industry It reacts with

acids to yield esters and with oxides to yield glycol ethers n—Butanol is an

intermediate chemical for the synthesis of esters like butyl acetate, butyl acrylate,

butyl methacrylate, etc and these esters are used as solvents for coating Other

applications of n-butanol are solvent, cleaning fluids, herbicides, dyes, printing

inks, personal care products, pharmaceuticals, plasticizers, textiles and lube additives The global consumption of the butanol is shown in Figure 1.2.

Figure 1.2, Global consumption of n-butanol and iso-butanol (wt %)[32]

Cs valeraldehyde derivatives are used predominantly to make lube oil

additives, automotive anti-wear applications, aeromotive synthetic lube formulation and refrigerant lubricants n-valerie acid, which is prepared from the hydroformylation of butene followed by oxidation, is used for the synthesis of lubricants, biodegradable solvents, plasticizers, perfumery and pharmaceutical

chemicals Cøa¿ oxo alcohols are used in the fine chemicals and perfumery industry, for the synthesis of neopolyol esters plasticizers and detergent applications [105]

1.1.2 The role of Hydroformylation Reaction in Industry

The fast growing market for the oxo products plays an important role in the hydroformylation processes Figure 1.3 shows the growth in the production of oxo products around the world [32]

As seen from Figure 1.3 and 1.4, Asia, North America and Western Europe

are contributing 32%, 23% and 30%, respectively to the world production

capacity of oxo products and are major oxo producers today USA and Germany

with 23% and 21% of world’s production are also leading producers Within Asia, Japan, South Korea and China are the major manufacturers with as many

as five other countries engaged in the production of oxo products (Figure 1.5)

Vietnam is still an imported country, production of oxo products has not been

started yet, most of chemicals are imported Between 1998 and 2002,

approximatcly 1.8 million metic tons of oxo chemical capacity was added, mainly in Southeast Asia

Demand for oxo chemicals in the United States is expected to grow moderately, at an average annual rate of almost 2% during 2008-2013 The long- tenm prospects for oxo chemicals m Western Europe improved considerably during 2005-2008, as consolidations and capacity reductions resulted in improved efficiencies and capacity utilization The commissioning of plants for 2-PH and additional isononyl alechol (INA) capacity helped reduce the former reliance on 2-EII Western Buropean consumption of oxo chemicals is forecast

to grow at an average annual rate of 2.0% during 2008-2013 Japanese

consumption is forecast to experience 0.9% average annual growth during 2008—

2013 Other Asian corsumplion, excluding Tapan, is expected 1n grow al 5.0%

annually during the same period, China India and Taiwan are the main growth

markets in this region Middle Easter consumption of oxo chemicals is forecast

to grow significantly at an average anual rate of 4.8% during 2008-2013, albeit

from a smail base, largely as a result of increased n-butanol demand for n-butyl

acrylate by fale 2010

These data show that Asia has been the main growth center for these

chemicals during last five year with North America and Western Europe showing stagnancy It is estimated that in the coming five years too, Asia will

witness the growth in oxo products with ouly a small increase im production

capacities in other countries

Africa South and Middle East Asia North ‘Western

America Figure 1.3 Worldwide growth in the production of oxo products [32]

‘World Consumption of Oxo Chemicals—2008

aero Aion: Indonesia

dapen

United States

Figure 1.4 World concumption of oxo products (2008)[106]

‘The worldwide oxo product derivatives distribution is shown in Figure 1.6

The production rate of 2-ethylhexanol is high among all oxo derivatives, which

is mostly consumed by the plastic industry, followed by production of butanol

Cả-13 Afeshol

zso-Decanol

&o-Nonanol iso-Buzmol n-Buzanol

ọ 30) I00 1500) 2000 2500 5000 3500 4000

Production Rate, kilometric tons‘year

Figure 1.5 Productions of oxo products in Asia region (2003) |32]

Oxo Prodnetion, kilometrie fons/year

Figure 1.6, Worldwide oxo product derivatives distribution [32]

The detergent grade alcohols also have significant contribution im the world

market, which are produced by oxo reaction Figure 1.7 gives the ostimated

production vapacitics for the oxo products via hydroformylation rea on by

worldwide known industries It is observed from these data that around 57% of

the oxo products are produced by seven big companies namely BASF, Exxon,

BON, Celanese, Dow, Kastman and Kyowo Hakko [32]

10

‘San Company Incerchimprom-Omsincez China Pebscuemial CosgaiaEeia

lierzyn Nitrmgen Works Sslavrarna-llesrp xmsez zdaursya Xiasgen W ni

China National Petralern Formosa Pasur Gromp Chins Mutional Pelioleeu

Te Geen Eyowe Haiko Hasan Chenival Company

1.1.3 Catalysts for Hydroformylation Reaction

The hydroformylation catalysts, typically, consist of a transition metal atom

(MD, especially from the platinum group metals These transition metal

complexes interact with carbanmonoxide and hydrogen to form metal carbonyi

hydride species, which is an active bydroformylation catalyst Typically,

complexes containing carbonyl ligands are known as unmodified catalysts On

the other hand, the introduction of tailor-made ligand to the transition metals are known as the modified catalysts

Three developmental stages for hydroformylation catalysts are reported in the literature The first stage of hydroformylation was exchisively based on cobalt (Co) containing catalysL The catalytic active species for hydrofenuylation reaction was the cobalt carbonyl hydrides in the pressure range of 240 300 bar at 150-200 °C tomperaturc Separation of products from the reaction mixturc,

severe reaction conditions and low activities of catalysts were the main limitations of this stage’s processes The research efforts fed phosphine replacing

11

carbonyl complexes as an clectron donating ligand and this cmerged as a fundamental step in metal carbonyl catalyzed reaction, which imparted ability to the scientists to tailor make catalyst by modifying the electronic and steric properties of the ligand

The second stage of hydroformylation reaction was the combined

development in ligand modification and replacement of cobalt rhodium (Rh)

metal It took almost a decade of research before first rhodium catalyst based

commercial pracess was launched in 1974 and the process was termed as Low

Pressure Oxo (LPO) process Compared to cobalt based processes, many

advances were made in the second developmental stage of hydroformylatian,

especially with respect to material and energy utilization Thus, second stage of

hydroformylalion was concluded with development of mare effective Rh-

phosphine catalyst However, the industrial problems of first stage such as, separation of producis from reaction mixture, calalyst recovery, loss of costly metals, use of corrosive solvents, ete continued in the second stage too

The third stage, can be called a break-through in bydroformylation

process - two-phase catalysis (biphasic or liquid multi-phasc sysicms

hydreformylation), because of finding a way of separating the catalyst and the reaction products under mild conditions that is ecologically as well as economically efficient he fundamental idea consisted in applying water

soluble catalysts by ligand modification and thus transferring the

hydroformylation into aqueous phase With the help of such catalysts, separations of desired products have become an easy task, ‘Ihe idea of applying water-soluble Rb-complex as a catalyst for the hydroformylation of propylene and 1 butene was taken up and commercialized by Rubrohemie AG [29] The first plant was commissioned in 1984, only two years after the development on laboratory scale, followed by rapid further increases in capacity to more than 3x

5

10 tons/year An additional unit for the production of m-pentanal (m- valeraldehyde) from 1-kutene [95] has heen brought on stream in 1995 The developments of bydroformylalion processes im different stages are shown in

Table 1.1 and the catalysts used are presented in Scherne 1.1

‘Table 1.1 Developments in hydroformylation processes [26]

Products aldehyde 2lenhale aldehydes aldehyden

4 = Union Carbide process (LPO),

5 = Rubrchemie-Rhone—Poulene process, LUISV = Liquid hourly space

Cabaltmoditicd ppn;—Trinhzmyiphesphine TPPzS=Triphenyiphosphie

Prosently, most of the industrial plants arc running succossflly with rhodium and cobalt based catalysts Attempts had been made to compare the catalytic activity of group VII and IX metals for hydroformylation of alkenes to understand the role of metal atom in hydroformylation reaction [38, 84] Ruthenium is attracting the attention of the researchers after rhodium and cobalt; nevertheless, it is yet to move from laboratory to pilot plant scale ‘The ligand plays a significant role in the hydroforylation reaction from the catalytic activity, selectivity and regio-selectivity point of view Phosphines and phosphite based monodentate and bidentate ligands are most commonly used and accepted ligands for the hydroformylation reaction [38, 84] Nitrogen containing ligands showed lower reaction rates than phosphines due to their stronger coordination to the metal centers A comparative study of PhR (where R=

elements of main group V) were made for the hydroformylation of 1—dodecane

[84] and showed following order, Ph;P > PhyN > PhjAs > Ph;Sb > Ph;Bi In

another study, the activity of the tiphenylphosphine, triphenylarsine aud

triphenylantimony ligands were compared for hydroformylation of ethylene and

1-hexene usirys tramsilion metal catalysis [58, 59, 84] Today, most of work in

the homogencous catalysis for hydroformylation is focused on the developments

of the bulky phosphorous/phosphite ligands, which include both monodentate,

and more bulky bidentate ligands

1s there a forth stage of the catalyst development for the hydroformylation reaction? Rh-catalyzed hydroformylation can be carried using a wide variety of ligands, allowing for extensive ligand variation and optimization A ligand design has been being, done with several objectives in mind; besides the nommal wish list of activity, selectivity, and stability (of Rh catalyst and free ligand) Besides, the successful applicability of supported ionic liquid phase catalyst (SILP) as heterogenous catalysts for hydroformylation of alkenes has recently appeared in the literature (thus will be discussed in the next section) Llopefully, the combination of the ligand design and applied SLIP catalyts can be realiable and soon become the forth of stage

1.4.4, Recent Trends in the Heterogeneous Hydroformylation Reaction

Commercial processes are using triphenylphosphine modified Rh complex [IIRhCO(PPha)a] as a catalyst for the hydroformylation of Jower carbon chain

length alkenes (Cz — C5) under milder reaction conditions, This catalyst is

limited upto the hydroformylation of lower carbon chain alkenes such as, ethylene and propylene due to separation problems of Rh-complex from the product mixture after completion of the reaction Conventionally, homogeneous catalyst is separated from the product mixture by stripping the products in

vacum (vacuum distillation) The thermal stress caused by the vacuum

distillation process decomposes the expensive metal complex which is used as a catalyst for hydroformylation reaction Most homogenous hydroformylation catalysts are thermally sensitive and decompose below 150 °C This is the main reason, which limits the applicability of Rh-complex for hydroformylation of

lower carbon chain length alkenes because in case of higher carbon chain length

alkenes, decomposition of rhodium complex occured during, the separation of

catalyst from higher boiling point product mixture As far as hydroformylation reaction is concerned, Rh-complexes as catalysts typically work under mild

conditions (80-100 °C, 20-40 atin), giving good aclivily & selectivity (95-99%)

to the desired linear (n—} aldehyde

For the hydrofommylation of higher alkenes, cobalt catalysts are widely

used, which

quire drastic reaclion conditions (200 °C, 200-250 atm) and yield

poor selectivity for linear aldehyde ‘The cobalt catalyst is recycled after vacuum distillation of the product mixture by the “dooobalung” procedure In the decobalting process, regeneration of cobalt catalyst after reaction is carried out

by changing the oxidation state of cobalt either by hydrothermal treatment or by oxygen treatment in acidic medium ‘Iypically, cobalt is recovered in the form of cobalt formate or acetate by addition of the oxygen and formic or acetic acid [38], Although, cobalt catalyst is recycled for hydroformylation of alkenes, but still has drawbacks of higher temperature, pressure, longer reaction time and lower selectivity of the desired aldehyde as compared to rhodium based catalysts Solving the product separation problem for the thodum catalyzed hydroformylation in an effective and economically acceptable way, would present a major step forward in homogeneous catalysis Therefore, development

of a heterogeneous catalyst for hydroformylation in today’s research scenario can

be broadly classified into two categories

of solid inorganic material, which is uscd as helcrogencous catalyst cither in

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+ In the first category, catalyst is anchored or supported on the surface

continuous reactor (fixed bed) or in the high pressure batch reactor (autoclave),

‘This type of process is often referred to as hetcrogenization of homogencous catalysts

+ Second category is the designing of a water soluble ligand, which is insoluble in the product mixture, is often referred to as biphasic systems One of the most important developments in 1980-2000 im the area of homogeneous catalysis is the successful development of water-stable as well as highly water- soluble catalyst systems and the consecutive introduction of the aqueous two- phase technology ‘Ihe reaction in biphasic system involves aqueous and organic phases (igure 1.8)

With the hydroformylation reaction in biphasic medium; reaction takes place at the interphase Catalyst is separated from the reaction mixture using phase separator [87] There are some reports presented in the literature on the development of cobalt and ruthenium biphasic systems for hydrofonnylation of alkenes [87] Application of biphasic catalyst is limited to hydrofonmylation of

propene and butene due to lower solubility of higher carbon chain length alkenes

in aqueous medium (water)

Though, homogeneons catalysts give higher conversion and selectivity for desired product in short reaction time as compared to heterogeneous catalyst

system The homogeneous catalysis has disadvantage im the separalion of

calalyst from the product mixture Thus, clTorls are directed iowards the

hetcrogenization of thodium complex on the inorganic solid supports for

hydroformylation of alkenes In this concern, more allenion in the present thesis

has been paid on literature reviow relaled to the recent developments in the

heterogenivation of homogeneous catalysts on the iorgartic solid supports for

hydroformylalion of alkenes

Impregnation is the common method for heterogenizaton of homogeneous catalyst In this method, inorganic solid support is mixed with the solution of homogeneous complex prepared by dissolving the complex in suitable solvent,

‘Then, the suspension is stirred for long time either at room temperature or at a paiticular desired temperature Ligands can also be anchored or impregnated onto solid inorganic materials, generally silica, zeolites or polymers The ligand

or complex anchored covalently to the solid support of high surface area ensures the reusability of the catalyst

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Gas Phase (CO and Hy)

Figure 1.8 Hydroformylation reaction in biphasic medium

Main problem in the heterogenization of homogeneous complex is the

breaking of bonds between metal and ligand during the course of catalytic

reaction and this is the cause of leaching of the active metal species responsible for the reaction This “leaching” process leads to the loss of catalytic activity in

the reusability experiments The leaching problems can be solved upto certain

extent by anchoring the homogeneous complex using some tethering agent or encapsulation inside the pores of the solid support used

1.1.5 Heterogeneous Catalysts for Vapor Phase Hydroformylation of

Alkenes

Homogeneous catalysts are highly active and selective, but they have

several disadvantages: problems with separation of the catalyst from reaction products, expensive metal losses, solubility limitations and corrosivity of catalytic solutions For rhodium catalysis, economical operation requires

recovery at ppb level due to the high cost of rhodium Therefore, several

17

attempts have bơen made to hetcrogenise homogeneous catalysts on a solid

support

The heterogenised catalysts can be divided into two groups: immobilised metal complexcatalysts and supported metal catalysts [95] ‘he immobilised metal complex catalysts canbe further divided into supported and anchared metal complex catalysts, as summarised in ‘able 1.2 as below,

Table 1.2 Classification of immobilised metal complex catalysts [62]

LSupported metal complex catalysts

Catalysts containing a dispersed phase of complex an a support

Supported liquid phase Catalysts (ST.PC)

Supported Aquesous Phase catalysts (SAPC)

2 Anchored Metal complex catalysts (Chemical bonding)

Coordinalive anchoring: Metal complex anchored on a chemically modified

supporl containing furclional groups of donor- aceeplor type

The coordinatively anchored metal complex catalysts, where metal complexes are chemically bonded (o the functional groups of the support, are the most promising option for immobilised catalysts (Figure 1.9) ‘The strong bonding, of the complex to the support through the funetional groups, and the possibility for modification of the support properties at the same time, are the obvious advantages compared to other types of immobilised metal complex catalysts ‘The most commonly used fimetional groups are phosphine ligands that are bonded via a methylene chain to an oxide surface or an organic

macromolecule

The supported metal catalysts are prepared by impregnating metal salts and

oxides on the support followed by reduction, or by decomposition of

organometallic compounds on the support For instance, active carbon, silica,

alumina or zeolites can be used as supports onto which e.g the metal nitrates are

impregnated

Both rhodium and cobalt (in inorganic form), separately and together, in

combination with other metals on various supports have been studied in the

hydroformylation of ethene [22, 23] and higher alkenes [24-27]

Even though the heterogenisation of the homogeneous precursors often

results in a decrease in activity, it has also resulted in improved performance

In liquid-phase applications, leaching of the active metal into the liquid

phase [16, 29, 86] has prevented the commercial use of heterogenised catalysts

In gas-phase hydroformylation, the use of supported metal catalysts is more

feasible, since the operating conditions are mild: the reaction can be carried out

at low pressures (and below 150°C) where the competing Fischer-Tropsch

reaction ceases,

Most of the developments for rhodium based catalysts supported on various

inorganic materials were studied for vapor phase hydroformylation of ethylene

and propylene in a continuous flow (fixed bed) reactor Since, the lower carbon

number alkenes (ethylene and propylene) exist in gaseous form, it seems

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appropriate to produce aldchydes under continuous flow conditions over batch mode In the 1980s, heterogenization of rhodium complex was performed by taking zeolites as solid supports The series of highly active catalysts were synthesized by rhodium entrapping in the framework of zeolite X and Y and used as catalysts for vapor phase hydroformylation of propylene and ethylene (Scheme 1.3) [56 58]

Scheme 1.2 Hydroformylation of ethylene and propylene

Detailed comparative study for hydroformylation of ethylene and propylene were made by Davis ef al using Rh—-Y and RI-X as catalysts in the continuous flow reactor at an atmospheric pressure [85] Activity of catalysts for the formation of propanal and butanal did nolull for a period of one amonth’s continuous experimental run ‘The results coucluded that the active sites were formed cither at the cntrance of pore or external surtace can cffectively catalyze the hydroformylation of ethylene and propylene In another study, hydroformylation of propylene was investigated using palladium (Pd) trimethylphosphine carbonyl chasters entrapped in the cage of zeolite Na Y ‘The rate of reaction was reported to depend on calcination and reduction temperatures as well as concentration of trimethylphosphine LUxcess concentration of trimethylphosphine results into the drop of catalytic activity of the catalyst [59]

Due lo large surface area of silica as compared la zeolites, the Rh-complex was also heterogenized on the surface of silica for hydroformylation Naito et al

found the shodiumn supported sihea lo be the most scleclive eatalyst for the formation of bulanal via hydroformylation of propylene in fixed bed reactor [60]

Thore are some reports in which Tr-situ reduotion of rhodium impregnated calalyst was claimed to convert il into nanocrystalline or amorphous metallic phase which was very active for hydroformylation reaction, Lenarda ot al

reduced the impregnated Rh on silica in a solution of tetrahydrofuran (HK) and

20

1 M lithium aluminum hydnde at low temporahue and øbtained rhodium nanoerystals was used as a catalyst for propylene hydrofonnylation [69] Apparent activation energy for the propylene hydroformylation was found to be

26 ki/mol Catalytic activity and selectivity of aldehyde could be improved by the addition of promoters or use of the bimetallic catalysts The bimetallic nanocrystalline Rh Co based catalysts with varied Rh/Co ratio were synthesized

by the reduction of metal salts impregnated an silica with NaBH, in the nitrogen atmosphere [72] The obtained catalyst showed high regio and chemo- selectivity for aldehyde and catalytic activity was observed to increase with inorease in the Rh/Co ratio Effect of triphenylphosphine (FPh,) on the rhodium

impregnated silica (Rh/SiO,) was also studied for hydroformylation of propylene using fixed bed reactor [74] and baloh shary reactor for hydroformylation of cthylene, 1-hexene and 1—octene [73] The obtained results were compared with

The HRhCO(PPh;)/SIO; and PPh -RWSIO, sysiems The coordination of PPh,

3 was retained in Rb/SiO, catalyst that was confirmed by solid state P-nuclear magnetic resonance (NMR) and in-situ Fourier transform infrared (FT-IR)

spectroscopic arlysis Excellent conversion of propylene with higher néiso ratio

of aldehydes was obtained using PPh,-Rh/SiO, as a catalyst and deactivation of

calalysL was nol obscrved over a perind of 1000 h reaction Line on stream The correlation of homogeneous and heterogeneous catalyst (Rh/SiO ) for

hydroformylation of clhylene was wade based on the resulls oblaied frem the

FT-IR spectroscopic study [65] Later on infrared spectroscopic studies were

conlinued for the hydroformylation of ethylene and propylene and developed the reaction mechanism and kinetic models Chuang et al, using immobilized thodium catalysts studicd the coordination and formation of the intermediate

species during hydroformylation of ethylene, mainly Kh/SiO, and manganese modified Mn-Rh/SiO, Progress of ethylene and propylene hydroformylation,

formation of intermediate active species, mechanistic aspects and reaction

kinetics were sluched from the analysis of transient response of the formed

product obtained by isotopic methods combined with in-situ infrared

spectroscopy [31,76,108,109]

Applicability of the supported ionic liquid phase (SLLP) catalysts, prepared

by impregnation of the partly dehydroxylated silica support with an anhydrous

21

MGOH soluien of xenie lgud [BMTMila-C.H OSO | contaimine cotalyst precursor [Rh(acae)(CO),] and bisphosphine ligand, was used as a effective catalyst for hydroformylation of propylene in a fixed bed reactor [13, 14, 16] Review articles for the applicability of supported ionic liquid as catalysts for hydroformylation of alkenes have recently appeared in the literature [15, 106]

Excopl the applicability of Rh metal for hydroformylalion of alkenes, the

researchers also performed the experiments on the aclivity of ruthernun (Ra)

exchanged pillared clay «

propyl

of 100 — 220°C, The Ru-eatalyst showed constant rate of reaction even at the

a catalyst for bydroformylation of olhylene and

¢ ita fixed bed reavior al, almospheric pressure in the temperalure range cud of 1week experimental run [88]

1.1.6 Mechanism of hydroformylation reaction

In the carly 1960s Heck and Breslow [46-49] formulated the generally

accepted hydroformylation cvele for cobalt catalysis that is also valid for unmodified rhodium catalysts, The hydroformylation mechanism for phosphine-

modified rhodium catalysts follows, with minor modifications, the Heck-

Breslow vycle According to Wilkinson [34], two possible pathways are imaginable: the associative and the dissociative mechanisms (as depicted in

Scheme 1.3 and Scheme 1.4)

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co 2H

Scheme 1.3, Dissociative mechanism for hydroformylation cycle [95]

‘The associative route begins with coordination of the alkene to the dicarbonyl species (Scheme 1.4, 1B) ‘the dissociative route involves dissociation of one of the ligands (PPh; or CO) and is similar to Lleck-Breslow cycle After the initial steps, the following steps in the associative and dissociative mechanisms are similar, following alkene coordination, an alkyl species (Scheme 1.4, 1D, Scheme 1.3, 2D) is formed Alkyl migration to CO leads to acyl formation (Scheme 1.4, 1B, Scheme 1.3, 2F) Iydrogen addition produces dihydrido acyl species (Scheme 1.4, 1F, Scheme 1.3, 2G) Finally, elimination of the aldehyde and addition of CO regenerates the active catalytic species HRH(CO}T.2

Scheme 1.4 Associative mechanism for bydroformytation [95,117]

The associative mechamsm involves 20-clectron intermediates and is often rejected on the grounds that Rh should form 16 or 18 electron complexes It is accepted today that Wilkinson's dissocialive mechanism is the likely kinetic path for hydroformylation [95] In order to avoid referring, to two figures depicting mechanism as the subsequent, literature reviow discussion will refer to scheme 1.5 as Ít is much simpler to follow

24

Scheme 1.5 Mechanism for cthylene hydroformylation, L=PPh3 [95,117]

The active species are 16-electron hydrides of the general formula HRh(CO),(PPhy)s.z (x = 1, 2) formed by the dissociation of CO from the 18- electron carbonyl hydride The basic steps in the hydroformylation reaction after the initial formation of the hydride metal carbonyl are: (1) dissociation af CO to form the unsaturated 16-electron species, (2) coordination of alkene, (3) formation of the alkylmetal carbony! species, (4) coordination of CO, (5) insertion of CO to form the acylmetal carbonyl, (6) oxidative addition of hydrogen, and (7) cleavage of the avyhnelal species by hydrogen to form the aldchyde and regeneration of the hydridometal carbonyl It is generally belicved that the oxidative addition of hydrogen lo the rhodium-acy! complex (step 6 in Scheme 1.5) is the rate determining step Leeuwen [95] has proposed that, roughly speaking, in phosphine catalyst systems the migratory inscrtion of the alkene into Rh-H (step 3 in Scheme 1.5) is the rate-determining, step under standard industrial process conditions

‘The reaction mechanism on supported catalysts follows a similar mechanism Lenrici- and Olivé [50] have suggested that the decisive difference between the homogeneous and the heterogeneous process is the availability of a

25

free, mobile, very reactive hydrido-motal species in solution According to them, the last step (steps 6 and 7 in Scheme 1.5), the transformation of the acyl-metal species to the aldehyde, proceeds through reaction with a second catalyst species

in homogeneous media, but in heterogeneous media the oxidative addition of molecular hydrogen to an acyl-metal species is the only means of formation of the aldehyde ‘The hydrogenation of the acyl intermediate was identified as the

rate determining step at 0.1 MPa on Rh/SiQ, [21]

In some studies, the CO insertion selectivity on supported unmodified metal catalysts, is related exclusively to the linearly adsorbed CO on isolated Rh sites [59], whereas other studies show that reaction rate and selectivity for hydroformylation increases im the presence of Rh+ sites [28] ‘thus, the dispersion of the catalytic metal and the extent of reduction are the main factors determining the CO insertion activity, and thereby, the selectivity towards aldehyde formation According to Sachtler and Ichikawa [102], two types of active sites are responsible for aldehyde formation: isolated, partially oxidised

metal crystallites for the migratory CO insertion into metal alkyl bonds, and

fairly large metal ensembles for the dissociation of hydrogen Hedrick et al [102,

104] noticed that on a Mn- Rh/SiO2 catalyst, spill-over hydrogen from the metal

to the silica surface plays a role in the hydrogenation of the acyl intermediate

Thus, the hydrogenation of ethyl species to form ethane, and the hydrogetalion

of adsorbed acyl species to [orm propanal, arc involved with two dilTerent types

hydrogen: motal adsorbed hydrogen and hydrogen from Si-O

Besides Ihe maim reaction (bydroformylation reaction), the hydrogenalion,

and aldol condensation are unexpected reactions By-products can be aldehyde

isomers, low — reactive alkene isomers, alcohols, aldkenes, and heavy ends

[Scheme 1.6) ‘The formation of heavy ends constitutes the biggest proplem Heavy-ends accumulation can cause serious process problems such as Rh leaching, difuted ionic liquid (in case catalyst is SLLP)

1.2.1 Composition of SILP catalysts

‘A supported ionic liquid phase catalyst — SILP was a new concept, which was led by the pioneers are Mehneit and co-workers in 2002, they extended this methodology to support Rh(I) complexes for hydroformylation of hex-l-ene to heptanal in both IL and molecular solvents [85]

In these SILP systems, a thin film of ionic liquid containing the homogeneous catalyst is immobilised on the surface of a high-area, porous support material, as depicted in scheme 1.7 SILP catalysts appear as solids, the active species dissolved in the liquid phase on the support, maintaining the attractive properties of ionic liquid homogeneous catalysts such as good dispersion of molecular reactant, and high activity Thus, STLP belonged to the

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