Direct Conversion of Syngas-to-Hydrocarbons over Higher Alcohols Synthesis Catalysts Mixed with HZSM-5

Direct syngas conversion to hydrocarbons was investigated with HZSM-5 physically mixed with either a methanol synthesis catalyst (5Pd/ZnO/Al2O3) or a higher alcohols synthesis (HAS) catalyst. Reactivity measurements show a definitive advantage in using HAS catalysts. Undesired durene formation is negligible with HAS catalysts but it represents 50% of the C-5(+) fraction for 5Pd/ZnO/Al2O3. Furthermore, the desired C-5(+) hydrocarbons yield is twice higher with selected HAS catalysts. The 0.5Pd/FeCoCu (HAS) catalyst was found the most promising due to higher C-5(+) fraction and lower durene formation. When 0.5Pd/FeCoCu and HZSM-5 are operated sequentially (two-step process), the CO conversion and the C-5(+) hydrocarbons fraction are lower. The C-5(+) hydrocarbons yield is thus twice higher for the one-step process. The main advantage of the one-step process is that higher syngas conversion is achieved as the equilibrium-driven conversion limitations for methanol and dimethyl ether are removed since they are intermediates to the final hydrocarbons product