Direct Conversion of Syngas to Olefins over a Hybrid CrZn Mixed Oxide/SAPO-34 Catalyst: Incorporation of Dopants for Increased Olefin Yield Stability

Abstract

A bifunctional catalyst was developed utilizing a physical mixture of a CrZn-based mixed metal oxide and zeotype SAPO-34 for the direct conversion of syngas to short-chain olefins. A series of promoted CrZn-M (M = Fe, Ga, Al) mixed oxide catalysts were synthesized by coprecipitation and calcined at different temperatures. CrZn-Fe-SAPO-34 catalysts calcined at 400 °C selectively converted syngas to C 2 −C 4 olefins, while maintaining high CO conversion and olefin stability over time. The high olefin yield is ascribed to the stabilization effect of iron on inversed spinel phase ZnCr 2 O 4 and to reduction of the detrimental ZnO phase formed during syngas conditions. At a higher calcination temperature of 600 °C, the stabilization effect is less pronounced. Ga and Al-doped CrZn oxides enabled high and stable olefin selectivity of the hybrid catalysts CrZn-Ga-SAPO-34 and CrZn-Al-SAPO-34, regardless the applied calcination temperature. Spectroscopy analysis demonstrated that these promoters are able to scavenge free ZnO formed on the catalyst, thus stabilizing the inversed spinel. This work demonstrates that a rational design of mixed metal oxide components of the hybrid catalyst process is required to maximize olefin yield and catalyst stability. The selection of dopants capable of stabilizing an inversed spinel phase and scavenging detrimental ZnO is a critical step in successful catalyst design.

Introducing the I&ECR Virtual Collection of Industrial and Industrially Relevant Research (2022–2023)

“…Due to the importance of catalysis within industry, the Kinetics, Catalysis and Reaction Engineering topic area has historically been one of the largest areas within I&ECR . In the present collection, industrial researchers performed studies ranging from the post-synthesis modification of polyethylene terephthalate (PET), to hydrogenation of CO 2 to light olefins (recognized with a May 2023 cover), studies on the kinetics of H 2 S adsorption in monoethanolamine (MEA), the regeneration of Pd/Al 2 O 3 electrochemical catalysts, production of diacrylate monomers by transesterification (recognized with a December 2022 cover), the evolution of coke within beta zeolite catalysts during catalytic cracking, the relationship of fluoropolymer product quality and production efficiency, novel catalysts for polyisobutenyl succinic anhydride synthesis, a new activation procedure for Ziegler–Natta catalysts, a kinetics study related to safety regarding the decomposition of H 2 O 2 , and a study from Dow highlighting the conversion of syngas to olefins, featuring two researchers from the 2022 Class of Influential Researchers …”

“…In the present collection, industrial researchers performed studies ranging from the post-synthesis modification of polyethylene terephthalate (PET), 13 to hydrogenation of CO 2 to light olefins (recognized with a May 2023 cover), 14 studies on the kinetics of H 2 S adsorption in monoethanolamine (MEA), 15 the regeneration of Pd/Al 2 O 3 electrochemical catalysts, 16 production of diacrylate monomers by transesterification (recognized with a December 2022 cover), 17 the evolution of coke within beta zeolite catalysts during catalytic cracking, 18 the relationship of fluoropolymer product quality and production efficiency, 19 novel catalysts for polyisobutenyl succinic anhydride synthesis, 20 a new activation procedure for Ziegler−Natta catalysts, 21 a kinetics study related to safety regarding the decomposition of H 2 O 2 , 22 and a study from Dow highlighting the conversion of syngas to olefins, featuring two researchers from the 2022 Class of Influential Researchers. 23 Engineering chemistry related to Materials and Interfaces is another strong topic area for I&ECR. Here, studies in the collection include a novel methodology of improving polyphenyl sulfide (PPS)-based membranes selected as ACS Editors' Choice in June 2023, 24 an improvement of lubricant oil properties using carbon nanomaterials, 25 synthetic strategies to prepare γ-alumina by coprecipitation (a cover article in January 2023) and FeNi particles by spray pyrolysis, 26,27 the impact of pressure and temperature on sorption of gases by fluoroelastomers, 28 methodologies to improve polymer/clay composite design, 29 novel carbonaceous materials for Li batteries, 30 ripening from a third member of the 2022 Class of Influential Researchers.…”