Preparation Of Pt-In Bimetallic Catalysts Supported On Multilevel Structure Hydrotalcite Derivatives For Propane Dehydrogenation

Propylene,as one of the important raw materials in modern life products,demand is increasing along with the development of the economy.Propane dehydrogenation to propylene has developed rapidly and realized industrialization due to the advantages of availability of raw materials,easy operation and high yield of propylene.The high efficiency of Pt catalyst makes it stand out from many propane dehydrogenation catalysts,but it still has serious problems of high temperature sintering and carbon deposition.Increase the activity and life of the catalyst on propane dehydrogenation is still the key point of the present study.In this paper,a systematic study was conducted on the application of the hierarchical Pt In/Mg（Al）O/Zn O catalyst prepared by our group in propane dehydrogenation,including the effect of the reduction and preparation conditions of the catalyst on its structure,chemical state of surface metal elements and catalytic performance.By changing the reduction conditions to obtain the catalyst system of varying degrees of reduction.The study found that the increase of reduction time and temperature was accompanied by the consumption of H₂O or-OH in the catalyst,which caused the increase of specific surface area,pore size and pore volume of the catalyst.The particle size of active metal particles tended to decrease with the increase of reduction time and temperature but accumulate at high temperatures or over long time.The results showed that the catalyst could obtain the highest propane conversion（51%）and propylene selectivity（97%）,the best stability（30 h）and the minimum carbon deposition（27wt%）with reduction time of 6.0 h and reduction temperature of 600°C,respectively.Different reduction atmospheres have different inducing ability to active metal.The minimum active metal particle size,the strongest Pt-In interaction,the maximum Pt dispersion（48%）,the maximum In⁰/In³⁺molar ratio and the best catalytic activity（45%of propane conversion and 92%propylene selectivity for 30 h reaction）were obtained by reducing in the atmosphere containing H₂.The formation of meixnerite is influenced by the degree of reduction,and the suitable formation of meixnerite is helpful to adjust the surface acid and base property of the catalyst and improve the carbon resistance effectively.The samples with different physical structure can be obtained by changing the recovery time of the calcined support.The results show that prolong the recovery time can make the surface and physical structure of catalyst increase and complex.But a longer recovery time will cause the destruction of the catalyst structure.For the first recovery time of 6 h,the sample showed the best catalytic activity and carbon resistance.