Development Of Catalysts For Synthesis Of Higher Alcohols From Syngas

Conversion of syngas to alcohols has been known since the 1930's,but the study of fuel alternatives attracted attention only until the North American oil crisis of the late 1970's.From the 1980's to the present,researchers have made breakthroughs in the production of higher alcohols,however the selectivity of the products of is still low and methanol and hydrocarbons account for a high proportion of hydrogenation products.Development of high activity,high selectivity catalyst has become the bottlenecks of industrial application.In this paper,starting from multi-walled carbon nanotubes?CNTs?supported Ni-Mo-K oxide based catalysts,a new multi-functional catalyst was developed.The obtained progress in the present study was briefly described as follow.1.Development of CNTs promoted Ni-Mo-K oxide-based catalysts for higher alcohols from syngasWith home-made "Herringbone-type" CNTs as support,a type of CNTs-supported Ni-Mo-K oxide-based catalysts for the preparation of higher alcohols from syngas were prepared by co-precipitation-impregnation method.The performance of CO hydrogenation of higher alcohols was evaluated on a pressurized fixed-bed continuous flow reaction system.The results show that Ni1Mo1K0.1-5%CNTs prepared at pH 6.7?7.0 have the best performance.Under the reaction conditions of 4.0 MPa,563 K,GHSV_outlet=6000 mL/?g·h?,the catalyst has a CO conversion of 11.3%and the selectivity of total oxygen-containing product was up to 61.6%?excluding CO2?,where ethanol is the predominant oxygen-containing product with a selectivity of 21.6%?excluding CO2?.2.Study on bi-functional catalyst for CO hydrogenation to dimethyl ether via methanolThe bi-functional catalyst for the hydrogenation of CO to dimethyl ether is composed of hydrogenated and dehydrated component,wherein the different zeolites and the dosage of the used zeolite have marked effect on the performanee of the corresponding bi-functional catalyst for CO hydrogenation to dimethyl ether via methanol.The experimental results show that the performance of CuZnAl/40%HY catalyst is the best.Because the addition of HY increases the difficulty of reduction of copper on the catalyst,the reduced Cu retains smaller particles,which is favorable for the dispersion of Cu particles and then resulted in large specific surface area.This is helpful to improve the hydrogenation activity of the catalyst.In addition,the acid strength of the strong acid sites on the catalyst surface is lower and the suitable acid concentration can inhibit the formation of by-products?hydrocarbons and CO2?.3.Study on multi-functional catalysts for CO hydrogenation to higher alcoholsOn the basis of the bi-functional catalyst,the second?mordenite,MOR?and the third?CuZnAl?catalyst were added successively.Over the 0.05gCZA-2.0gMORM24-0.2gCZA/HY catalyst,under the reaction conditions of 2 MPa,483 K,GHSV_outlet=10000 mL/?g·h??with bi-functional catalyst CZA as the standard?,the CO conversion of the catalyst was 8.2%,and the selectivity of ethanol in the hydrogenation product was 38.5%.The characterization of home-made MOR molecular sieves with different Si/Al ratios shows that we successfully constructed the required framework of the molecular sieve.The suitable molecular sieve surface area is favorable for the catalyst activity,the moderate Bronsted acid and the strong Bronsted acid is also benefit to the catalytic reactions.