Direct conversion of synthesis gas to aromatic hydrocarbons: Variation of product distribution with time‐on‐stream

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Abstract
The synthesis of hydrocarbons from syngas was studied over a zirconia‐based cobalt‐nickel catalyst (FT catalyst) alone as well as mixed with zeolite HZSM‐5 at 101.3 kPa in a 12.7 mm i.d. down flow reactor. The product distribution was recorded as a function of time‐on‐stream for several days of continuous operation under fixed operating conditions of 250°C and H2/CO = 1. For the FT + HZSM‐5 system, a dramatic variation in the product distribution takes place during the first 24 h of operation. A comparison of time‐on‐stream results obtained using FT catalyst alone and mixed with HZSM‐5 suggests that the reactions leading to the build‐up of overall product distribution are slower over HZSM‐5 compared to those taking place over FT catalyst. These differences have been attributed to the different nature of reactions taking place over the two components of the mixed catalyst system. Analyses of the coke on the deactivated catalysts are also reported.