Formation of Isoparaffins through Pd/β Zeolite Application in Fischer−Tropsch Synthesis

The direct synthesis of isoparaffins from synthesis gas (H2/CO = 2) was carried out in a consecutive dual reactor system under the conditions of P = 1.0 MPa and W/F = 4.97 g·h·mol-1. In the upper reactor, Co/SiO2 was used for Fischer−Tropsch (FT) reaction. To primarily decompose the heavy FT hydrocarbons, zeolite β (4:1 weight ratio) was physically mixed with Co/SiO2. The Pd/β catalyst with a Pd loading of 0.5 wt % and different Si/Al ratios in zeolites β was loaded in the lower reactor for hydroconverting the products from the upper reactor. Irrespective of the Si/Al ratio of zeolite β, the results indicate that the final products showed a sharp carbon number distribution in the range of C4−C6 and very high selectivity to branched isomers of C4−C6 alkanes. An apparent change of selectivity to isoparaffins was observed with the variation of the Si/Al ratio in Pd/β catalyst. Moreover, the stability of the catalyst was also influenced by the Si/Al ratios. The effect of the Si/Al ratio on the selectivity of ...

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