Catalytic hydrogenation of carbon dioxide into light olefins

Name: Thanapha Numpilai

LCSH: Kasetsart University -- Dissertations. Ph.D. (Chemical Engineering) 2019

Classification :.LCCS: TP248.A554

LCSH: Kasetsart University. -- Department of Chemical Engineering -- Dissertations

LCSH: Alkenes

LCSH: Hydrogenation

LCSH: Carbon dioxide

Abstract: Recycling of CO2 into light olefins offers opportunity to mitigate CO2 emissions, while alleviating dependence on fossil fuels for their production. In this research, the direct conversion of CO2 -to-light olefins via two effective routes including a modified Fischer-Tropsch synthesis (FTS) and methanol-mediated process are compared in terms of reactivity performance. Regarding the modified FTS, the pore size effects and the influence of K contents on physicochemical properties of Fe-Co/KAl2O3 catalysts are systematically studied to identify the crucial factors affecting the catalytic performance. It is found that the larger pore sizes of support provide the larger Fe2O3 crystallite sizes with the greater degree of reduction which results in a high metallic Fe content, leading to a high CO2 conversion and hydrocarbon selectivity. Eliminating diffusion limitation by increasing the pore sizes can suppress the hydrogenation of olefins to paraffins and thus the largest pore catalyst (152.3 nm) gives the highest O/P ratio. The maximum light olefins yield (14.38%) is obtained over the catalyst having appropriated pore size (49.7 nm) owing to the suppression of the olefins hydrogenation and chain growth reaction. Meanwhile, the modifications of relative strengths of metal-C and metal-H bounds by adjusting K content play a vital role on the light olefins production. A lower surface coverage of weakly adsorbed H species over K-promoted catalyst can suppress the hydrogenation ability of the catalyst, leading to a decrease in CH4 formation and increase in the proportion of olefins and C5+ hydrocarbons. Over-doping of K favors the carbon deposition due to the higher strength of metal-C, leading to an eventual blockage of active sites. The highest light olefins yield (16.04%) is achieved over the catalyst with an optimum K loading (K/Fe=0.5). In methanol-mediated pathway, the interplay of active sites for CO2 hydrogenation (In2O3 ) and methanol transformation (SAPO-34), and operating conditions are key factors determining the catalytic behaviors. The best yield of light olefins (7.31%) with a CO2 conversion of 34.6% is achieved over the In2O3 /SAPO-34 catalyst with a mass ratio of 2:1 at 360 °C, 25 bar and 1,500 mL gcat -1 h -1 . Overall, the modified FTS route gives higher catalytic performance while exhibits lower selectivity to C2 -C4 olefins than methanol-mediated route.

Kasetsart University. Office of the University Library

Address: Bangkok

Email: tdckulib@ku.ac.th

Name: Thongthai Witoon

Role: Thesis Advisor

Name: Metta Chareonpanich

Role: Thesis CO-Advisor

Created: 2019

Modified: 2025-06-27

Issued: 2025-06-27

วิทยานิพนธ์/Thesis

application/pdf

URL: https://www.lib.ku.ac.th/KUthesis/2562/thanapha-num-all.pdf

CallNumber: TP248.A554 .T43

eng

DegreeName: Doctor of Philosophy

Level: Doctoral Degraee

Descipline: Chemical Engineering

Grantor: Kasetsart University

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