CO2 hydrogenation to light olefins using In2O3 and SSZ-13 catalyst − Understanding the role of zeolite acidity in olefin production

• Published in: Journal of CO2 utilization Vol. 72; p. 102512
• Main Authors: Di, Wei, Ho, Phuoc Hoang, Achour, Abdenour, Pajalic, Oleg, Josefsson, Lars, Olsson, Louise, Creaser, Derek
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2023
• Subjects: Al distribution; CO2 hydrogenation; In2O3; Light olefins; SSZ-13; SSZ-13; Al distribution; Light olefins; In2O3; CO2 hydrogenation
• ISSN: 2212-9820; 2212-9839
• DOI: 10.1016/j.jcou.2023.102512

With the aim to explore the effect of acidic properties of zeolites in tandem catalysts on their performance for CO2 hydrogenation, two types of SSZ-13 zeolites with similar bulk composition, but different arrangements of framework Al, were prepared. Their morphology, pore structure, distribution of framework Al, surface acid strength and density, were explored. The results showed that SSZ-13 zeolites with isolated aluminum distribution could be successfully synthesized, however, they contained structural defects. During calcination, the framework underwent dealumination, resulting in weaker Brønsted acidity and lower crystallinity. The morphologies were, however, well preserved. Compared with the SSZ-13 zeolites, synthesized conventionally, these low acidity SSZ-13 zeolites with isolated aluminum were good zeolite components in bifunctional catalysts for CO2 hydrogenation to light olefins. By combining with In2O3, they exhibited better catalytic performance for light olefin production during CO2 hydrogenation at low temperatures. Na+ cation exchange was used to adjust the Brønsted acid site (BAS) density with only minor changes to the cavity structure. Comparative experiments established that the BAS density of the zeolite, rather than the framework Al distribution (BAS distribution), overwhelmingly affected catalyst stability and product selectivity. A higher acid density reduced the selectivity for light olefins, while lower acid density tended to form inert coke species leading to rapid deactivation. The ideal amount of BAS density in the bifunctional catalyst was approximately 0.25 mmol/g, which exhibited 70% selectivity for light olefins among hydrocarbons, and 74% selectivity for CO without deactivation, after 12 h reaction at 325 ℃ and 10 bar. [Display omitted] •Na+ in SDA affects Al distribution and defect formation in zeolite crystallization.•SSZ-13 with isolated Al distribution has defects and lower BAS densities.•BAS density of zeolite is decisive for olefins production and stability of catalyst.•Higher BAS density promotes hydrogenation of olefins to paraffins.•Lower BAS density slows MTO reaction and hydrogenation leading to deactivation.