Dagle et al. (2014)studied
the activity of a bifunctional catalyst (Pd/ZnO/Al2O3-ZSM-5) as
catalyst for this reaction. Syngas was used directly for conversion to
gasoline hydrocarbons. The mechanism of action of the catalyst
proceeds by sequential methanol production from syngas, its
dehydration over the acidic sites of ZSM-5 to form dimethyl ether
and the subsequent ether conversion to gasoline range hydrocarbon species. Role of parameters such as temperature and pressure
were investigated. At a temperature of 375
C, increasing the reaction temperature had a positive effect on syngas conversion. For
example, raising the pressure from 300 to 500 psi produced an
increased in conversion from 75 to 85%. The higher pressures were
therefore very critical for initial methanol production with this
catalyst. However, the distribution of hydrocarbon products had
been only slightly affected by change in pressure. Lighter hydrocarbons (C1 to C4) dominated the reaction products at all pressures,
with selectivity close to 90%. Gasoline range hydrocarbons were
only detected to low concentration of 6e10%, with significant
amount of aromatics. On the other hand, increasing the reaction
temperature at 300 psi, shifted the conversion until an equilibrium
was established, beyond which the conversion declined. Unfortunately, the selectivity to lighter species was more pronounced at
higher temperatures, limiting any selectivity to gasoline range
products. The overall reaction results indicated the composite
catalyst as more selective to the production of lighter hydrocarbons
(C1 to C4) and polymethylbenzenes than gasoline range paraffins.