Preparation And Catalytic Performance Of Cobalt-based Catalysts For Fischer-Tropsch Synthesis

This topic is about Fischer-Tropsch synthesis which is an important part of the 863 technology projects. Fischer-Tropsch synthesis is a promising catalysis process for synthesis gas (CO+H2) conversion to environmentally clean fuels and other chemicals. With the growing shortage of oil resources, the increasingly serious environmental pollution and the development of biomass technology, Fischer-Tropsch synthesis has once again attracted worldwide researchers'attention. The preparation of catalyst for Fischer-Tropsch synthesis is one of the key technologies, so it has been a research focus all the time. Cobalt-based catalysts are considered to the most promising catalysts for Fischer-Tropsch synthesis due to its high catalytic activity and chain growth capacity, difficult to carbon deposition and deactivation, low activity for water-gas shift reaction.In this paper, the cobalt-based catalysts for Fischer-Tropsch synthesis were prepared by wetness impregnation. At the same time, the catalytic performances of Co/γ-Al2O3 catalysts for Fischer-Tropsch synthesis were evaluated in a small fixed-bed reactor. The influences of prepatation and reaction conditions on catalyst activity and performances of Fischer-Tropsch reaction were investigated and optimized.This paper includes the following aspects:(1) The influences of cobalt precursors, solvent, calcination temperature, cobalt loading, pretreatment. catalyst molding and preparation methods in the preparation process were investigated and optimized. It shows that the optimal preparation conditions are cobalt precursors of cobalt nitrate, solvent of ethanol. calcination temperature of 400℃,cobalt loading of 10%and three-steps impregnation.(2) The influences of reduction temperature, reduction pressure, reduction time, reaction temperature, reaction pressure, feed gas space velocity and catalyst usage on the catalytic activity and product selectivity in the Fischer-Tropsch synthesis process were studied and optimized. It finds that the best reaction conditions are reduction temperature of 400℃reduction pressure of 2.0 MPa. reduction time of 10 h, reaction temperature of 230℃reaction pressure of 2.0 MPa, feed gas space velocity of 900 ml/g.h, catalyst amount of 2.0 g.(3) According to above test, the 60 hours stability test of Co/γ-Al2O3 catalyst for Fischer-Tropsch synthesis were also measured. The results show that CO conversion and the yield of C5+hydrocarbon, respectively, are maintained at 69%and 73%in 60 h. Thus, the synthesized cobalt-based catalysts are ideal Fischer-Tropsch synthesis catalysts due to their high activity, selectivity and performance stability.