Preparation Of Bimetallic/hydrotalcite Supported Catalysts And Their Dehydrogenation Properties

Energy consumption and pollution are the key issues to be resolved in the harmonious development of human society.Finding alternative energy sources such as hydrogen energy is a practical solution.Hydrogen energy has the advantages of being clean,efficient,convenient to store and transport,and its source is very extensive and can be recycled.However,due to the small volume density of hydrogen,there are many obstacles and safety problems to physical hydrogen storage.Chemical hydrogen storage technology of organic liquids can solve this problem well,now the key to the research of this technology is the dehydrogenation step.It is necessary to prepare a suitable dehydrogenation catalyst to make it have a higher reaction activity,selectivity and a considerable hydrogen release rate at a lower temperature.A co-precipitation method was used to control the pH to prepare a Mg-Al hydrotalcite carrier with a layered structure under weak alkaline conditions.The carrier contained almost no acid sites,and the deactivation of coking of the catalyst was suppressed to some extent.Pt-Ir and Pt-Sn were supported on the hydrotalcite carrier by equal volume impregnation method,followed by calcination and reduction.After these treatments,Pt-Ir/Mg-Al and Pt-Sn/Mg-Al catalysts were prepared.Ultrasonic dispersion technology is used in the preparation of the catalyst to reduce the preparation time and increase the pore size.XRD,BET,H2TPR,TG,TEM,CO-Chemisorption,XPS and other characterization tests were performed to analyze the physical and chemical properties of the catalyst prepared under different conditions.The continuous dehydrogenation reaction of methylcyclohexane under different catalysts was tested using a micro-reactor,to study the effect of different component content,reaction temperature,calcination temperature,reduction temperature,and feed rate on the catalytic activity.The results show that the addition of Ir and Sn promotes the dehydrogenation activity,carbon deposition resistance and stability of the catalyst in different degrees.When the contents were different,the interactions between the active components were different,showing different catalytic properties.The increase of reaction temperature can promote the dehydrogenation reaction to proceed in the positive direction and increase the dehydrogenation conversion rate.Changing the calcination temperature and the reduction temperature also changes the structure of the support and the composition of the active component.Increasing the feed rate reduces the residence time of the reactants and results in a significant decrease in conversion.The average MCH dehydrogenation conversion rate of PtIr-5/Mg-Al-275 under the condition of feeding rate=0.2 mL/min,catalyst mass= 0.5 g,mixed with an equal volume of quartz sand,LHSV=18.0 h-1,T=350° C is 99.9%.The selectivity to toluene was 99.9%and the hydrogen evolution rate was 578.7 mmol·gcat-1·h-1.The average MCH dehydrogenation conversion rate of PtSn-5/Mg-Al-350 catalyst under the condition of feeding rate=0.2 mL/min,catalyst mass=0.5 g,LHSV=18.4 h-1,T=300° C is 66.3%.The selectivity to toluene was 99.9%and the hydrogen evolution rate was 384.1 mmol-gcat-1·h-1.