The kinetic study of light alkene syntheses by CO2 hydrogenation over Fe-Ni catalysts

Abstract

A kinetics model of CO 2 hydrogenation over iron-nickel catalysts was developed based on the detailed mechanism of alkenes re-adsorption and secondary reaction. The corresponding kinetical experiments are conducted in a continuous fixed bed reactor. The effect of reaction conditions on catalyst performance was analyzed according to the results of orthogonal experiments. The results of the experiments show that more methane in products can be obtained with iron-nickel catalysts, the trend of which is consistent with the thermodynamic analysis. However, the content of alkenes in products is equivalent with that of alkanes. This shows that the reaction is controlled by kinetics. In all, the results of the experiments also substantiate that the model can give a good representation of the reaction mechanism of CO 2 hydrogenation over iron-nickel catalysts. The parameters of this model give a better explanation for the question why the iron-nickel catalysts have a higher selectivity toward alkenes compared with other iron-based catalysts.

Can We Afford to Waste Carbon Dioxide? Carbon Dioxide as a Valuable Source of Carbon for the Production of Light Olefins

“…Zhao et al studied the kinetics of light alkene syntheses by CO 2 hydrogenation over Fe-Ni catalysts. [26] When using a Co/g-Al 2 O 3 FT catalyst, but more typical FT reaction conditions (P = 20 bar, T = 220 8C), heavier hydrocarbons were observed (> 70 % in C5+). [27] The presence of CO 2 in the feed stream had a negative effect on catalyst stability and on the formation of heavy hydrocarbons.…”

Catalysis for CO2 conversion: a key technology for rapid introduction of renewable energy in the value chain of chemical industries

“…About 85% selectivity to alkene in the C2-C4 fraction (about 40% of the whole hydrocarbon fraction) was observed. Zhao et al 133 studied the kinetics of short-chain alkene syntheses by CO 2 hydrogenation over Fe-Ni catalysts, observing that the presence of CO 2 in the feed stream has a negative effect on catalyst stability and on the formation of heavy hydrocarbons. The data cannot be extrapolated to the case of the conversion of CO 2 to short-chain olens and used to optimize this reaction.…”

CO2 Hydrogenation to Hydrocarbons over Fe‐Based Catalysts: Status and Recent Developments

“…[38] Since then, CO 2 -FTS models have been continuously improved to encompass a broader spectrum of reaction products and catalysts. Zhao et al [39] first applied Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetics to model CO 2 -FTS over a Fe-Ni-K catalyst, achieving reasonable accuracy in CO 2 conversion and olefin formation rate prediction. However, the prediction is limited to C 1 -C 4 products.…”