Preparation Of Gallium Supported Catalyst Based On Silica Carrier And Its Application In Propane Dehydrogenation

As an important organic chemical raw material,propylene is not only the main raw material of polypropylene in production,but also the main raw material of phenol,acetone,propylene glycol,acrylonitrile,propylene oxide,acrylic acid,butanol,octanol and isopropanol and other related products.Under the influence of market demand at the present stage,the consumption of propylene increases significantly while the production of propylene lags behind.At present,propylene is mainly produced from naphtha through cracking to ethylene,and from liquefied gas produced by catalytic cracking unit of refinery through separation to propylene,from coal to methanol and then to propylene.With the gradual shortage of petroleum resources,the traditional propylene production technology has been unable to meet the growing demand for propylene,and the search for new propylene production technology has become the main development trend of the petrochemical industry.Propane dehydrogenation to propylene production technology in the early development process because propane value is relatively high,in the process of engineering investment will be affected by various factors.At present,direct dehydrogenation of propane to propylene(PDH)has been industrialized.The research on propane dehydrogenation catalysts focuses on the preparation of catalysts with high conversion and selectivity.The traditional catalysts often take vanadium or platinum as the catalytic center or are modified by other metals to achieve better catalytic effect.However,vanadium or platinum as a catalytic center has its own disadvantages.It has been found that gallium can be used as a catalyst in the dehydrogenation of propane to propylene.In this paper,hydrothermal synthesis method and equal volume impregnation method were used to prepare catalysts.The effects of two synthesis methods,calcination temperature and gallium load on catalyst performance were investigated.The results showed that the calcination temperature are500 ℃ and 600 ℃ when the catalyst of catalytic activity is superior to the roasting of 700 ℃.In order to study the influence of gallium load on the catalytic activity of the catalyst,five different gallium load catalysts were synthesized during the preparation of the catalyst.The galliumload was 1%,3%,5%,7% and 9%,respectively.It was found that the catalyst had the best catalytic performance when the gallium load reached 7% and 9%,and the active component gallium oxide could be more evenly distributed on the surface of the carrier.The effects of two synthesis methods on catalysts were studied.Firstly,a three-dimensional dendritic mesoporous silica spherical carrier was prepared by the equal volume impregnation method.Then,the amount of gallium nitrate solution needed was calculated according to the gallium load capacity.Then,equal volume impregnation was carried out.Hydrothermal synthesis method is to first calculate the amount of gallium nitrate solution required according to the gallium load,in the process of synthesis of silicon dioxide carrier add gallium nitrate solution,step preparation of catalyst.The catalysts prepared by the two methods were characterized and tested,and the results showed that: the structure and properties of the catalysts prepared by the two methods are different;however,the catalyst prepared by volume impregnation method has better catalytic performance than that prepared by hydrothermal synthesis method;both catalysts have good stability.