Direct Synthesis of Isoparaffin-rich Gasolinefrom Syngas

Isoparaffins are preferred components of high-qualitygasoline because they are much more environmentally friendly as octanenumber contributors than olefins or aromatics. We report here anunprecedentedly high ratio of isoparaffins/normal paraffins (iso/n-paraffin ratio) of 48 in the one-step synthesis of gasoline-rangehydrocarbons from syngas, enabled by a ZnAlOx-SAPO-11 compositecatalyst. Infrared characterization of SAPO-11 upon the adsorption of2,6-DTBPy and a cracking reaction of 1,3,5-TIPB demonstrate that theiso/n-paraffin ratio is almost linearly correlated with the concentration ofexternal acid sites and the sites located near the pore mouths. Inparticular, the formation of multi-branched isomers, which generallyexhibit a higher octane number, is significantly facilitated. A 150 h time-on-stream test indicates rather stable activity in syngas-to-gasoline. Thesefindings provide a general approach for tuning the gasoline quality bymodulating the acid site distribution of zeolites (zeotypes), that is, the concentration of external acid sites.

Automated summary

This study reports a new catalyst with a high ratio of isoparaffins/normal paraffins for the synthesis of gasoline-range hydrocarbons from syngas. The gasoline quality can be adjusted by modulating the concentration of external acid sites, leading to the formation of multi-branched isomers with higher octane numbers.