Title : Advances in heterogeneous catalysis for green conversion of propene to aldehydes and alcohols
Abstract:
Conversion of propene to aldehydes and alcohols are industrially important reactions and are carried out by hydroformylation of propene using syn gas, a mixture of carbon monoxide and hydrogen gases. Propene hydroformylation to n- butanal had a great commercial importance, because from the total hydroformylation production capacity (8.8 million tons/year), ~86% is based on propene hydroformylation. The industrial application of n- butanal is to use it as a vital chemical intermediate to produce plastics, resins, solvents and rubber accelerators. Propene hydroformylation is industrially practiced under homogeneous conditions using Cobalt and Rhodium metal based catalysts. Homogeneous catalysis has limitations of the separation of the cost effective metal based catalysts and products. Heterogeneous catalysis has the potential benefit of easy separation and recycling of the catalyst as well as easy purification of the products. About 60% of world consumption of n-butanal, obtained from propene hydroformylation, is converted to 2-ethylhexanol. 2-ethylhexanol is a valuable intermediate for the chemical industry in the production of dioctyl phthalate, other plasticizers, coatings, adhesives, lubricants, fine and specialty chemicals. In the existing commercial process, the synthesis of 2-ethylhexanol from propene is carried out in three steps (with three different catalysts): hydroformylation (Rh/Co), aldol condensation (NaOH/KOH) and hydrogenation (Ni/Cu) which has drawbacks: (i) three steps process is uneconomical from industrial and energy perspectives (ii) use of hazardous reagents liquid KOH/NaOH in large amount for the aldol condensation step, and problem of their effluent in disposal and (iii) Handling of liquid base and post synthesis work-up in separation of spent KOH/NaOH from reactants/products increases the capital as well production cost of 2-ethylhexanol. In this existing commercial homogeneous catalytic process the spent liquid base generated after the reaction is in the range of 1.0 to1.5 ton, for every 10 tons of product. This causes a huge cost of 30%, spending for cleaning and recycling the liquid base. To overcome these drawbacks, a novel multi-functional catalyst, [HF/HT], synthesized by impregnation of inorganic metal complex, HRh(CO)(PPh3)3 [HF] on a solid soft base hydrotalcite; (Mg1-xAlx(OH2))x+(CO32-)x/n·m H2O) [HT] is developed by us, and this had effectively performed the effective heterogeneous catalysis of hydroformylation, aldol condensation and hydrogenation in a single pot. In the heterogeneous catalyst [HF/HT], the soft solid base hydrotalcite [HT] effectively afforded to play duel role as support as well as base, thereby potentially avoiding the use of strong liquid base NaOH/KOH, during the synthesis of 2-ethylhexanol form propene. The heterogeneous catalyst [HF/HT] had potentially made the synthesis of aldehydes and alcohols from propene, green, economic and environment friendly. Present key talk will account the detailed investigations performed for the said multifunctional catalyst system involving the synthesis, characterization of the catalyst, catalysis, kinetic and future aspects of the reactions of propene with synthesis gas.
