Comparative Study of Short-Chain Olefins Synthesis via CO₂ Hydrogenation over Iron-Containing Double Metal Cyanide-Derived Catalysts

Abstract

In this article, we prepared a series of K-promoted double metal cyanide (DMC) catalysts consisting of iron with a late 3d transition metal (Mn, Co, Cu, and Zn) using a single-step conventional precipitation method and examined them for CO2 value addition to short-chain olefins via modified Fischer–Tropsch route. Several ex situ/in situ combined with temperature-programmed desorption (TPD) experiments were carried out to identify the species in the catalysts and evaluate the adsorption/desorption characteristics of the reduced catalysts. The CO2 conversion for bimetallic catalysts increases in the following order: Fe–Mn (R): 24.85% < Fe–Zn (R): 28.60 < Fe–Cu (R): 29.40% < Fe–Co (R): 39.10% whereas selectivity of the short-chain olefins (C2–C4 =) in hydrocarbons decreases in the following order: Fe–Mn (R): 56.1% > Fe–Cu (R): 55.4% > Fe–Zn (R): 50.8% > Fe–Co (R): 44.3%, at 20 bar pressure, 320 °C temperature, and a gas hour space velocity (GHSV) of 3600 mL·gcat –1·h–1. Remarkably, during the optimization of the reaction conditions, short-chain olefins selectivity over the Fe–Mn (R) catalyst unprecedently reached up to 63.8% in hydrocarbons with 30.56% CO2 conversion. The TPD results and reaction performance reveal that the Fe–Co (R) catalyst has higher adsorption for weakly adsorbed CO2, H2, and CO, which results in higher CO2 conversion, lower CO, and higher hydrocarbon selectivity with a lower O/P ratio. Contrarily, the Fe–Mn (R) catalyst exhibits opposite reaction outcomes to the Fe–Co (R) catalyst owing to its lower adsorption for weakly adsorbed CO2, H2, and CO. These findings shed light on how the conversion of reactant and product distribution is affected by the adsorption/desorption characteristics of the catalysts for the reactant and important intermediates.

Preparation of Well-Defined Double-Metal Cyanide Catalysts for Propylene Oxide Polymerization and CO2 Copolymerization

“…Notwithstanding its six-decade-long history and industrial significance, the composition, structure, and working mechanism of the heterogeneous DMC catalyst are still elusive and require further elucidation to continue its progress and improvement. − Furthermore, DMC complexes hold promise beyond polyol production and have displayed potential applications in various fields of catalysis and materials science. − In this study, we have successfully synthesized well-defined DMC catalysts, shedding light on their chemical structure and establishing a correlation between structure and performance, ultimately, leading to the discovery of efficient catalysts for both PO polymerization and CO 2 copolymerization.…”

Polyoxometalate-HKUST-1 composite derived nanostructured Na–Cu–Mo2C catalyst for efficient reverse water gas shift reaction

“…16 The MOF-assisted synthesis can endow the active metals in the derived materials with greater stability than the original MOFs. [17][18][19][20] Moreover, the organic linker-coordinated metal clusters may partially or completely prevent the pyrolysisinduced agglomeration of the resulting metal nanoparticles. 33 Moreover, the large surface area of the materials ensures the efficient diffusion of reactants and products from active sites.…”