Homogeneous
Catalysis
Overview
Mission
& Goals
Homogeneous catalysis research at NCL is aimed at the development of innovative catalysts consisting of soluble metal complexes, supported metal catalysts and methods of hydrogenizing soluble catalysts. The focus of research programs is on integrated approach to develop catalysts and process routes involving catalysis, organometallic chemistry, surface science and chemical reactor engineering. The research activities cover basic research on new concepts, catalyst design, reaction mechanism, catalyst performance enhancement, kinetic modeling, novel catalyst-product separation techniques as well as analysis of multiphase catalytic reaction systems. The applied research is oriented towards developing industrially relevant process route and contract research on specific topics of interest to industry.
Competencies
- Design and development of catalysts (synthesis of new ligands, heterogenization of homogeneous catalysts - biphasic catalysis, encapsulation and ossification)
- Isolation and characterization of catalytic intermediates
- Kinetic modeling, analysis of multiphase catalytic systems and development of reactor performance models
- Development of laboratory scale processes
- Extensive experience in handling gases like oxygen, hydrogen and carbon monoxide under high pressure high temperature conditions.
Facilities
The homogeneous catalysis laboratory is well equipped with a variety of micro to macro scale (50 ml to 2 lit capacity) stirred pressure reactors for operation up to 15 Mpa pressure and 250° C; fixed bed catalytic reactors (30 and 120 ml catalyst capacity); trickle bed reactor with switchable up flow and down flow modes, CSTR and reactors with hastalloy C-276 material of construction. The analytical facilities include several GCs with auto-sampling, HPLCs, GC-MS, FT-IR and UV-spectrophotometer.
Glimpses
of current research
Carbonylation of olefins/alcohols/halides
Carbonylation of olefins/alcohols and halides using homogeneous catalysis provides a promising and environmentally cleaner route for the synthesis of carboxylic acids with wide ranging applications. The recent research is focused on:
(a) Carbonylation of aryl-ethanols and aryl olefins to aryl propionic acids with particular interest in Ibuprofen and Naproxen,
(b) Carbonylation of vinyl acetate to methylacetoxypropionate, a precursor for -lactic acid, and,
(c) Carbonylation of methanol to acetic acid using Ni based catalyst.
Oxidative carbonylation
reactions
Oxidative carbonylation of:
(a) Amines, diamines and polyamines to carbamates and urethanes, and,
(b) Phenol to DPC/ bis-phenol to polycarbonate oligomers
Hydroformylation of functionalised olefins
A low-pressure synthesis of vitamin-A intermediate via hydroformylation of 1,4-diacetoxy-2-butene has been developed. The hydroformylation and deacetoxylation steps can be carried out in a single step (tandem synthesis) using novel heterogenized Rh-complex catalyst in mesoporous supports. A new route for propanediols via hydroformylation of vinyl acetate under low pressures has been developed. The research programmes are also focused on new concepts for separation and recycle of the catalysts, as biphasic, reverse biphasic and interfacial hydroformylation techniques and also for lower alkenes (< C ) using tethered, anchored and encapsulated Rh-complex catalysts in porous matrices.
Amination of aryl halides
The role of bidentate chelating ligands in improving activity and selectivity to triarylamines (95% yield) was established. With “heterogenized” Cu-catalysts, a high selectivity for di- or triaryl mines could be realized by appropriate choice of support and heterogenizing methodology.
Liquid phase oxidation of hydrocarbons
The group has explored the liquid phase oxidation of organic compounds and has been actively involved in research programs on catalysis, kinetic modeling and reaction engineering of these processes. Experimental facilities for oxidation under high-pressure conditions, safety aspects and analysis of mass transfer effects, gas liquid reactors with precipitation of products, modeling of impurity removal from precipitating products and oxidation reactor performance.
Hydrogenation of functionalised organic compounds
The focus in the area of liquid phase hydrogenation is towards the development of new active, selective and stable mono- and bimetallic catalysts for hydrogenation of nitro-aromatics, ketones, acetylenes, carboxylic acids and other unsaturated organic compounds. Synthesis and characterization of catalysts, performance testing in high pressure slurry and trickle bed reactors, kinetic modeling and multiphase reaction engineering of hydrogenation processes are the key strengths.
Heterogenization of homogeneous catalysts
(a)
Biphasic catalysis
The biphasic catalysis using water-soluble metal complex catalysts is believed to be the most practical approach for separation of homogeneous catalysts from the products. We were the first to introduce a concept of promoting using catalyst binding ligands and demonstrated its role in enhancing the rate of hydroformylation reactions by 50-100 fold (Nature, 1995, 373, 501). Currently, a variety of new water-soluble catalysts are being synthesized to investigate their catalytic chemistry, nature of active species, catalytic cycle and activity/ selectivity/ stability profiles.
(b)
Encapsulation
Techniques for encapsulation of Pd, Rh, Cu complex catalysts in zeolites and mesoporous supports like Zeolite Y, MCM-41, MCM-48, etc., have been developed. Highly stable catalysts for carbonylation, hydroformylation and amination reactions have been explored.
A novel approach to heterogeneous hydrocarboxylation catalyst applicable for a variety of aryl olefins and alcohols has been recently explored. Further, the metal complex remains anchored to the support and these catalysts can be recycled a number of times without the metal catalyst leaching out of the silicate. This anchoring disrupts neither the geometry nor oxidation state of the catalyst (J. Am. Chem. Soc., 2002, 124, 9692).
Homogeneous catalytic reaction engineering
The catalysis by soluble metal complexes involves gas liquid, gas-liquid-liquid, gas-liquid-solid reactions or even more complex systems requiring a careful understanding of the coupled effect of interfacial mass transfer, hydrodynamics and catalytic reactions. In this field, the group has contributed to the kinetic modeling and reaction engineering aspects of a variety of homogeneous catalytic reactions.
Contact
Dr. RV Chaudhari
National Chemical Laboratory ,
Pune 411 008
Email
:rvc@ems.ncl.res.in
Phone
:+91-20-2589 3163
Fax
:+91-20-2589 3260