The Study Of Catalyst For Methanol Synthesis From CO₂ Hydrogenation

The concentration of CO₂ in atmosphere gradually increased with the acceleration of human industrialization and overusing of fossil energy.How to reduce CO₂concentration and convert it into high-value energy attracted researchers'attention recently.The hydrogenation of CO₂ into methonal is one of the effective ways.Methanol is a basic chemical raw material and high-quality fuel.But there still many difficulties and challenges in this reaction,for example,the activation of CO₂,the low selectivity of methanol.Developing an efficient catalyst for the hydrogenation of CO₂to methanol is a problem that should be solved quickly.The catalysts for CO₂ hydrogenation into methanol can be divided into copper-based catalysts,noble metal catalysts and other non-copper-based?metal carbides,etc.?catalysts.Noble metal catalysts have excellent activity for CO₂ hydrogenation,but they are expensive and scarce resources.Molybdenum carbide is called platinum-like catalysts due to its unique electronic structure.It is a good catalyst for CO₂hydrogenation to methanol due to its H₂ dissociation and C=O sheared ability.Spinel structure catalyst has unique structure.The zinc oxide dissolves in the spinel structure in the nonmetroscopic spinel structure and produces oxygen vacancy defect,which promotes the adsorption and dissociation of CO₂,and catalyzes CO₂ conversion in mild condition.In this paper,platinum-like catalyst MoC@C and Cu-based catalyst Cu/ZnCr were studied.The specific research work shows below:?1?Molybdenum carbide catalyst MoC@C was prepared by one-step melting method using molybdate as molybdenum source,glucose and urea as carbon source.The MoC@C exhibited higher catalytic activity compared with the pure molybdenum carbide prepared by the traditional synthesis route.The CO₂ conversion of MoC@C catalyst was 18.5%and the yield of methanol was 1.7 mmol·g^-1·h^-11 at 300?.It was found that the addition of Co slightly reduced the activity of MoC@C catalyst,the selectivity of CO almost remained the same,the selectivity of alkanes decreased,and the selectivity of alcohols increased.After hydrogen pretreatment,methanol selectivity obviously increased.The CO₂ conversion was 20.2%,and the yield of methanol was3.0 mmol·g^-1·h^-11 at 300?.?2?ZnCr support with different ratio of Zn/Cr was synthesized by coprecipitation method,Cu/ZnCr series catalysts were prepared by impregnation method.The results showed that the CO₂ conversion rates of the three catalysts were almost the same,and remained about 11%during 50 h.Only CO and methanol were detected in the products,The best yield of methanol(3.2 mmol·g^-1·h^-1)and the conversion of CO₂?10.9%?was obtained for Cu/ZnCr-3.5 at 250?after reduction at 300?.In order to reduce the selectivity of CO in the product,Co was introduced into Cu/ZnCr-3.5 catalyst.The results showed that the selectivity of CO significantly reduced after the addition of Co.However,due to its strong hydrogenation ability,methane and other alkane products generated.The best yield of methanol(4.7 mmol·g^-1·h^-1)and the conversion of CO₂?25.1%?was obtained for Cu/ZnCr-3.5 at 300?.