Direct synthesis of middle isoparaffins from synthesis gas 2003-01-1941
Branched paraffins with 4 to 7 carbon number shows high octane number as well as high reactivity for steam reforming, which suggest the binary fuel for both internal combustion engine and fuel cell engine as well.
It was tried to make iso-paraffin rich hydrocarbons by Fischer-Tropsch Synthesis (F-T-S) over Co/SiO2 catalyst. The basic concept is to secondarily isomerize or hydrocrack the F-T-S products.
Small amount of added zeolite to Co/SiO2 catalyst, enhanced the formation of C4-C10 isoparaffins while suppressing the formation of longer hydrocarbons probably because of the selective cracking of higher hydrocarbons by zeolite. The three-component catalyst (Co/SiO2-Pd/SiO2-ZSM-5) promoted the formation of paraffins, whereas the yield of isomerized products was not high enugh.
For 2-steps reaction, the first step catalyst is the zeolite modified Co/SiO2 catalyst and the second catalyst is Pd/SiO2+ZMS-5 catalyst where additional hydrogen was added. The selectivity of isoparaffins was markedly promoted and the molecular weight of the product decread while the syngas conversion was kept constant.
The hydrocracking of n-octane (which is the model compound of FTS reaction) over hybrid catalyst composed of Pd/SiO2-zeolite and showed high and stable activity giving iso-paraffin rich hydrocarbons. The isomerization was favored for Pd rich catalyst. The role of Pd is the port hole of hydrogen spill-over to zeolite.