Comparative Study on the Effect of Ethylene Cofeeding in CO<sub>2</sub> and CO Hydrogenation to Olefins over FeZnNa Catalyst
Kaiyu Zhu, Xingwu Liu, Haoyi Tang, Shuheng Tian, Junzhong Xie, Lingzhen Zeng, Tianye Wang, Hongwei Li, Meng Wang, Ding Ma
Abstract
The hydrogenation of CO and CO 2 to long-chain olefins presents a promising route for chemical production, but optimizing the reaction process requires a thorough understanding of the tail gas recycling process. The effects of cofeeding ethylene on the hydrogenation of CO and CO 2 using a zinc- and sodium-promoted iron catalyst (FeZnNa catalyst) are carefully investigated in this work. For CO 2 hydrogenation, ethylene showed negligible impact on CO 2 conversion, CO selectivity, or CH 4 selectivity but primarily served as a feedstock for the production of ethane and higher carbon number olefins. In contrast, during CO hydrogenation, CO conversion improved with ethylene cofeeding. Ethylene also contributed to chain growth, although a higher fraction was converted to ethane via hydrogenation compared to CO 2 hydrogenation. Structural analysis using XRD and Mössbauer spectroscopy revealed that the catalyst in CO 2 hydrogenation consisted exclusively of the Fe 5 C 2 phase, whereas CO hydrogenation resulted in the formation of both Fe 5 C 2 and Fe 2 C phases. XPS and TPO analyses indicated significantly lower carbon deposition on the catalyst during CO 2 hydrogenation compared to that during CO hydrogenation.