Study On Aluminum Zinc Alloy Hydrolysis And In-situ CO₂ Hydrogenation Conversion By Cu Catalysis

CO2 conversion technologies reduce CO2 to valuable small molecular compounds(such as methane,methanol,formic acid,etc.),which can effectively alleviate the current climate and environmental pressure and dependence on fossil fuels.As a basic chemical raw material,methanol has a wide range of uses in the field of chemical industry.Cu/ZnO/Al2O3 catalyst has been successfully used in industrial production of methanol.The preparation of Cu/ZnO/Al2O3 catalyst was carried out by co-precipitation of metal nitrate and NaOH,washing,high temperature calcination and hydrogen pre reduction.Research results showed that the residual sodium ion,nitrate and nitrogen oxide in the catalyst were the main reason for the chronic poisoning and deactivation of the catalyst in the process of CO2 hydrogenation to methanol.In addition,a large amount of CO2 was produced in the industrial process of hydrogen production by coal gasification or methane catalytic reforming,and the safety of hydrogen transportation and storage has not been well solved.Therefore,the current industrial production process of CO2 hydrogenation to methanol over Cu/ZnO/Al2O3 catalyst didn’t conform to the concept of sustainable development of green and clean production.In this paper,a new concept of hydrogen production by hydrolysis of aluminum zinc alloy and in-situ hydrogenation of CO2 catalyzed by copper was proposed.The effect factors(composition of aluminum zinc alloy,NaOH concentration,reaction temperature and copper source)and different carbon sources(KHCO3,NaHCO3 and CO2),copper sources(Cu,Cu2O,CuO,CuCO3·Cu(OH)2 and CuSO4),copper source composition(single,mixed)and copper source material particle size(nano-level and micron-level)were studied.X-ray diffraction(XRD),scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS)and other characterization methods were used to analyze the microstructure,chemical composition and element distribution of catalytic materials and solid products before and after the reaction.The results showed that the hydrogen production rate of aluminum zinc alloys increased with the increasement of NaOH concentration and reaction temperature.The zinc content in the alloy could inhibit the hydrolysis of hydrogen,while the addition of copper ion promoted the hydrolysis reaction.At 30℃,particle size of 200 mesh and the solid-liquid ratio of 1:252,the hydrogen production rate of aluminum zinc alloy with 5%zinc content during the rapid hydrogen evolution stage(0-7.5 min)was 57.07 mL/min.The average hydrogen production rate of the alloy with a zinc content of 70%during the rapid hydrogen evolution stage was 22.27 mL/min.At 210 ℃,the liquid product of the CO2 conversion reaction catalyzed by Cu,CuO and CuCO3·Cu(OH)2 was HCOOH,while the liquid product catalyzed by Cu2O,in addition to the HCOOH single-carbon product,produced the two-carbon product CH3COOH and CH3CH(OH)2.Different copper sources had a significant effect on the conversion rate of in situ CO2 hydrogenation reaction of aluminum zinc alloy.The catalytic conversion rate of CuSO4 was less than 0.01%,while the catalytic conversion rate of Cu2O was greater than 10%.The solid phase products were mainly Cu/ZnO/ZnAl2O4.The formation of CO2 hydrogenation products was the result of the synergistic effect of Cu and ZnO/ZnAl2O4 carrier:Cu(111)crystal surface transformed the adsorbed H2 into active hydrogen and combined with the adsorbed and activated intermediate products on the surface of the carrier.This study provides new ideas for the preparation of Na-free and N-free Cu/ZnO/Al2O3 catalysts and green CO2 hydroconversion.