Preparation Of Pt-based Supported Catalyst And Study On Dehydrogenation Of Methylcyclohexane

With the gradual reduction of fossil energy reserves and environmental pollution in the process of use,it is urgent to seek new renewable and green energy.Hydrogen energy,which is abundant and pollution-free,is a good alternative energy.However,how to achieve efficient and safe hydrogen storage and long-distance transportation is the key to the development of hydrogen energy.Organic liquid hydrogen storage technology,which uses the reversibility of hydrogenation and dehydrogenation reaction to store hydrogen energy into liquid state and ensure the safety of transportation,is regarded as a very potential hydrogen storage method.Common hydrogen storage carriers are mainly unsaturated liquid hydrides（such as benzene,naphthalene,pyridine,alkenes,alkynes,etc.）.Methylcyclohexane（MCH）is the best hydrogen storage carrier considering the harm of dehydrogenation products to human body and the high hydrogen storage density.Based on the previous research,this paper focused on the modification of Pt-supported catalysts.Ce-Al and La-Mg-Al carriers were prepared by co-precipitation method under the condition of constant p H value,then Pt/Ce-Al-O and Pt/La-Mg-Al-O catalysts were prepared by ultrasonic-assisted impregnation with Pt,and then by calcination and H₂ reduction.At the same time,the active component Pt was directly introduced into the Ce-Mg-Al hydrotalcite-like support,and then the auxiliary agent K was supported by the impregnation method.Finally,the Pt-K/Ce-Mg-Al-O catalyst was prepared by calcination and H₂ reduction.XRD,BET,TG,H₂-TPR,H₂-TPD,NH₃-TPD,CO₂-TPD,TEM,Raman and CO-Chemisorption were used to study the internal physical structures and chemical properties of the three catalysts.The effects of preparation method,Ce/Al molar ratio,La content,K content,reduction temperature and reaction temperature on the reaction were investigated with MCH as the substrate.The main contents are as follows:（1）The Ce/Al molar ratio of Pt/Ce-Al-O catalyst has a great influence on the dispersion of Pt.Appropriate molar ratio can increase the dispersion of surface metal Pt and reduce Pt at lower temperature.For Pt/La-Mg-Al-O catalyst,La modification increased the pore volume and pore size of the support,promoted the re-dispersion of Pt,and then reduced the particle size of Pt.However,the addition of a small amount of K in Pt-K/Ce-Mg-Al-O catalyst not only promoted the dispersion of active component Pt,but also stabilized Pt through the interaction between metals and increased the anti-sintering ability of Pt.（2）All the three catalysts showed good dehydrogenation activity.The selectivity of MCH dehydrogenation to toluene was greater than 99%,and no other products were detected.The average conversion rate of MCH was 96.8%when the dosage of Pt/3Ce-Al-350 catalyst was 0.5 g at the reaction temperature of 325℃and the feeding rate of MCH was 0.1m L/min.The hydrogen release rate was 934.1 mmol/g_Pt/min.The average conversion rate of MCH and hydrogen release rate of Pt/8-La-Mg-Al-O catalyst were 98.6%and 951.8 mmol/g_Pt/min at 320℃under the same reaction conditions.For Pt-K-0.1/Ce-Mg-Al-O catalyst,the average conversion rate of MCH was 98.5%and the hydrogen release rate was 951.0 mmol/g_Pt/min.