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Hydroformylation of Higher Olefins Using Radium Phosphite Complex Catalyst

SHAHARUN, MAIZATUL SHIMA (2009) Hydroformylation of Higher Olefins Using Radium Phosphite Complex Catalyst. PhD thesis, Universiti Teknologi PETRONAS.

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Hydroformylation of olefins with CO and Hz at total pressure of IS to 50 bar and temperature of 80 to l20°C, in presence of rhodium (Rh)-based homogeneous catalysts for production of aldehydes has demonstrated high yields and selectivity. Rh-based catalysts are expensive and the commercial viability of a process that uses such catalysts substantially depends on the efficiency of catalyst recovery and product separation. In this work, a novel temperature dependent multi-component solvent (TMS) or 'thermomorphic solvent' system has been used as the reaction medium to investigate hydroformylation of two higher olefins - 1-octene and 1-dodecene - to synthesize the corresponding aldehydes at a lower pressure of 15-25 bar and temperature of 80 to 100°C. Such a solvent mixture changes thermally from biphasic to monophasic with distribution of the products and of the catalyst in the non-polar and polar phases thus simplifying the process of separation and recycling of the catalyst. A TMS- system consisting of three components - propylene carbonate (PC), ndodecane and 1,4-dioxane was used in this study. The presence of 1,4-dioxane imparts the thermomorphic character to the solvent mixture. For a gas-liquid reaction, the solubility of the reactant gas in the liquid medium is an important parameter required for the interpretation of reaction kinetics. Therefore experimental measurement of solubility of the gaseous reactants - CO and Hz - in the individual components of the solvent as well as in their mixtures was performed up to a pressure of 1.5 MPa and temperature range of 298-343 K. The effects of solvent composition, partial pressures of the gaseous reactants - CO and Hz, reaction temperature and catalyst loading on the rate, yield and selectivity of the linear aldehydes were also investigated. At a reaction temperature of 363 K and total pressure of 1.5 MPa and 0.68 mM HRh(CO)(PPh3)3, the conversion of 1- octene and the yield of aldehyde were 97 % and 95 %, respectively. The aldehyde product was recovered in the non polar phase whereas the catalyst remained in the polar phase with low catalyst loss of 3 %. With a reaction-time of 2 h and a selectivity of 89 %, this catalytic system can be considered as highly reactive and selective. The rate was found to be first order with respect to catalyst, 1-octene and PH, . The rate vs. Pco resembled a typical case of substrate inhibited kinetics.The solubility data have been correlated using three models - an empirical model based on the Henry's law, the regular solution theory with Yen and McKetta modification and the modified UNIF AC model. The accuracy of prediction with the second model without any adjustable constant was within 11.0 % whereas the UNIF AC model offered a better accuracy of 8.5 %. In the kinetic study a mechanistic rate model for the hydroformylation of higher olefins using Rh-based catalyst in a homogeneous system was developed by using ab initio technique of quantum chemical computation to identifY the rate-controlling steps in the reaction pathways. Computations were done for three olefins- 1-decene, 1-dodecene and styrene- by the restricted Hartree-Fock method at the second order Moller-Plesset level of perturbation theory and basis set of 6-31++G(d,p) using the GAMESS Pro 11.0 program package. Three generalized mechanistic rate models were developed on the basis of the reaction path analysis and experimental findings available in the literature. The rate model with oxidative H2-addition as the controlling step predicted the conversion of the three alkenes quite satisfactorily with an average deviation of±7.6 %. The UNIQUAC and UNIFAC models were used to model the catalyst and product recovery (at 298 K) of the hydroformylation of 1-octene. The average deviation of the calculated mole fractions from the experimental values for the UNIQUAC and UNIF AC method was ±6.5 % and ±8.2 %, respectively. The work done has established the potential of the thermomorphic solvent system and the rhodium phosphite complex catalyst for the hydrofonnylation of 1-octene and 1- dodecene. In the range of conditions employed, the rate and selectivity calculated using the developed mechanistic rate model and selectivity model were in good agreement with experimental result. The work also concluded that the novel TMS system can be used to produce valuable fine chemicals from syngas and olefin at a lower operating cost. ix

Item Type: Thesis (PhD)
Academic Subject : Academic Department - Chemical Engineering - Separation Process
Subject: T Technology > TP Chemical technology
Divisions: Engineering > Chemical
Depositing User: Users 2053 not found.
Date Deposited: 30 Sep 2013 16:55
Last Modified: 25 Jan 2017 09:43
URI: http://utpedia.utp.edu.my/id/eprint/7987

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