Preparation Of Cobalt-Based Catalysts And Their Catalytic Performance In CO₂ Hydrogenation

CO₂ hydrogenation to CH4 or C₂⁺ hydrocarbons with renewable energy is a promising research direction to produce chemicals and fuels,which not only reduces the CO₂ concentration in the atmosphere,but also covers the shortage of fossil fuels.Herein,we focus on the Co-based catalysts to clarify the influence of metal-support interaction on the catalytic mechanism and catalytic performance using various research methods?e.g.,series in situ techniques and DFT calculation method?.In addition,we also provide some versatile ways to synthesis highly dispersed Co-based catalysts for CO₂ hydrogenation with good prospects.The main contents and conclusions are as follows:?1?Co/ZrO₂ catalyst was prepared by impregnation method with high activity and stability in CO₂ methanation.Re-dispersion of Co species on the ZrO₂ support was observed after the reduction by hydrogen.New Co-Zr phase formed on the Co-Zr02 interface benefits the adsorption and activation of CO₂.An energetically more favorable H2 dissociative adsorption,faster H*surface migration,and easier Co-O bond breaking on the Co/ZrO₂ surface than on the Co/Al₂O₃ surface were revealed by DFT analysis.?2?Highly dispersed Co/Zr02 catalysts were prepared through organic acid-assisted method.The universal conclusions of the organic acid-assisted strategy for highly dispersed Co/ZrO₂ catalysts are proposed.The organic acid-assisted strategy can lead to increased metal dispersion and higher TOF for Co/ZrO₂ catalysts.It is noteworthy that,among the numerous organic acids,citric acid-assisted Co/ZrO₂ catalyst exhibited the superior catalytic activity with 1116 h^-1 turnover frequency.?3?Highly dispersed Co-based catalysts were prepared through ZIF-67 carbonation in N2.The ZIF-67 crystal morphology can be controlled from cubic to rhombic dodecahedron and the original particle size can be regulated from 150 nm to 1 ?m using cetyltrimethylammonium bromide?CTAB?.When the CTAB amount is 0.01 wt.%,the Co-based porous carbon catalyst exhibited superior CO₂ methanation activity with 1300 h^-1 turnover frequency at 400?.?4?Cobalt supported on TiO₂ with different crystal forms?anatase and rutile?differs sharply on CO₂ conversion and products selectivity for CO₂ hydrogenation.The formate species is identified and suggested to be the key intermediate for CH4 formation on Co/TiO₂ catalyst.Zr,K and Cs addition further improved the CO,CO₂ and H2 adsorption both in the capacity and strength over anatase-and rutile-supported catalysts.In addition,the increased surface C/H ratio leaded to a highest C₂⁺ selectivity of 17%with 70%CO₂ conversion over K-Zr-Co/anatase-TiO₂ catalyst.