Combining Fischer-Tropsch (FT) and Hydrocarbon Reactions under FT Reaction Conditions: Model Compound and Combined-Catalyst Studies

The main objectives of the further downstream operations (product upgrading) of Fischer-Tropsch products are to i) improve yields and selectivities of the desired fractions, and ii) improve fuel properties to meet the fuel product specifications. The present study addresses the combination of low-temperature Fischer-Tropsch (FT) synthesis (with Co or Fe catalysts) and hydrocarbon modification reactions (hydroprocessing) in one reactor.In addition to earlier results with Pt/ZSM-5 in a dual-layer configuration in a fixed-bed reactor (Mena et al. 2007), the objective of the present investigation was to study the influence of CO during hydroprocessing and oligomerisation reactions of hydrocarbon model compounds (1-octene, ethene/propene) on two different bifunctional catalysts (Pt/ZSM-5, Pt/Beta). In addition, the influence of the catalyst-bed configuration for the combination FT synthesis and hydrocarbon reactions was investigated (dual layer/physical mixture).The achieved results indicate a potential of combining FT and hydrocarbons reactions in one reactor. Hydrogenation, isomerisation, cracking and oligomerisation reactions take place on a Pt/zeolite catalyst at FTS temperatures and in the presence of CO and H2O. The most critical point of this combination seems to be the deleterious effect of CO on the cracking reactions of isomers. For that reason, the wax fraction (C21+) was only partially cracked. The experimental results also indicate that the type of zeolite and the catalyst-bed configuration have an influence on the diesel/gasoline ratio obtained. It seems that the final fuel products will be a mixture of gasoline and diesel fuel and C1 to C5 compounds, as long as no diesel-selective hydroprocessing catalyst is found.