The Process of PDH to propylene

Our country is rich in propane reserves.And the development of shale gas in recent years has further increased the production of propane. At present, most of the utilization of propane in our country adopts the method of burning energy. It is even consumed in the form of "sky lanterns", which greatly reduces its use value.Converting propane into products with high added value is one of the key technologies to improve the utilization efficiency of propane and realize the efficient utilization of carbon-based energy. It has broad practical prospects and huge economic benefits.Among the downstream products of propane, propylene is a very important chemical raw material, which can be used to produce high value-added products such as polypropylene, acrylonitrile, propylene oxide, ethylene propylene rubber, nylon 66 and ABS resin.Among them, polypropylene is widely used in people's daily life, making propylene the second largest chemical raw material after ethylene.From 2012 to 2016, the output of propylene in our country continued to rise, but it still could not meet the demand for propylene in downstream industries.It is estimated that in 2020, our country's propylene production will reach 33 million tons/year, while the equivalent demand for propylene will reach 37 million tons/year.It can be seen that my country's downstream demand for propylene is very large in the future.The rising demand for propylene and the large amount of propane by-product of the shale gas revolution have brought opportunities for the development of propane dehydrogenation technology.

In the process of propane dehydrogenation to propylene, although the direct dehydrogenation of propane has been industrialized.However, this reaction is a strong endothermic process with limited thermodynamic equilibrium, which requires a higher temperature (>600°C) to obtain a higher conversion rate, and high temperature will also bring problems such as catalyst carbon deposition.In contrast, propane oxidative dehydrogenation (OPDH) is an exothermic reaction that is not limited by thermodynamics,Theoretically, a high conversion rate can be achieved at a lower temperature, and there is no carbon deposition problem, so it has aroused extensive research interest of scholars.However, the weakest C-H bond energy of propylene (360.7kJ/mol) is smaller than that of propane (401.3kJ/mol).In the presence of oxygen, propylene is prone to deep oxidation to form COx.This results in low propylene selectivity and yield in the propane oxidative dehydrogenation system, and the OPDH process also fails to meet the requirements of industrialization.

At present, the industrialized propylene production routes mainly include naphtha steam cracking, oil refining by-products, heavy olefins (C4~C8) conversion, methanol to propylene (MTP) and propane dehydrogenation (PDH). Among them, the first two are the traditional processes and main ways to obtain propylene at present, and the others are some emerging processes.