A research team led by Prof. Pan Xiulian and Prof. Bao Xinhe from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences has achieved the direct synthesis of isoparaffin-rich gasoline from syngas using ZnAlO_x-SAPO-11 oxide-zeolite (OXZEO) catalysts. Isoparaffins are preferred components of high-quality gasoline because they are more environmentally friendly as octane number contributors than olefins or aromatics.

The researchers elucidated the active sites of isoparaffin formation, which provided guidance for the one-step synthesis of high-quality gasoline from syngas. Their study is published in ACS Energy Letters.

Previously, the DICP team proposed a new catalyst concept based on metal oxide-zeolite (OXZEO) bi-functional catalysts. This catalyst enabled the direct conversion of syngas to a variety of chemicals and fuels with high selectivity, such as light olefins, ethylene, gasoline, aromatics and oxygenates. The OXZEO concept provided a new technology platform for the highly efficient utilization of coal and other carbon resources.

Direct syngas conversion to isoparaffin-rich gasoline over OXZEO catalyst. Credit: Feng Jingyao

In this study, they achieved 34% CO conversion and 82% gasoline selectivity by modulating the distribution of the zeolite acid sites, in which the iso/n-paraffins ratio was as high as 38.

By optimizing the reaction conditions, they increased the ratio of iso/n-paraffins as high as 48—the highest value of the iso/n-paraffins ratio reported so far.

Moreover, a 150-hour on stream test of the catalyst indicated rather stable activity in the syngas-to-gasoline process.

Further studies showed that the external acid sites of the zeolite could be the active sites for the formation of branched—especially multi-branched—isoparaffins.

Resources

• Jingyao Feng, Dengyun Miao, Yilun Ding, Feng Jiao, Xiulian Pan, and Xinhe Bao (2022) “Direct Synthesis of Isoparaffin-rich Gasoline from Syngas,” ACS Energy Letters 7 (4), 1462-1468 doi: 10.1021/acsenergylett.2c00467