Coconut Shell Columnar Activated Carbon Molding And Its Application In The Synthesis Of Ammonia

The novel ruthenium catalysts have been regarded as a second-generation catalysts for ammonia synthesis followed with the iron catalyst,which perform high activity in the reaction of low temperature and pressure.Activated carbon has been used to be the ideal carrier for ruthenium catalyst industrialization,its pore structure,material,porosity,surface properties have a greater impact on the performance of the catalyst,Meanwhile,the activated carbon must also have sufficient strength and regular shape to meet the needs of catalyst in a fixed bed reactor.Therefore,Columnar activated carbon have been prepared from coconut shell by chemical activation with phosphoric acid,Coconut shell columnar activated carbon with high purity,high surface area,large pore volume,reasonable pore size distribution and high strength were prepared by regulating of preparation process,as carriers,ruthenium catalysts for ammonia synthesis were prepared by co-impregnation method.and activated carbon prepared with the activator of phosphoric acid characterized by physical absorption,TG,FT-IR,XPS,XRD.At the same time,activated carbon carries and Ru/AC catalysts were characterized by Raman,MS,CO pulse adsorption,chemical adsorption,TEM to study the catalytic properties influenced by the physical structure of carries to prepare a highly active ruthenium catalysts for ammonia synthesis,The main conclusions are as follows:Coconut shell activated carbon were prepared with the activator of phosphoric acid,of which surface area,pore volume,pore structure could be regulated by controlling the impregnation ratio,activation temperature,activation time and other factors.In the activation process,phosphoric acid accelerates the course of pyrolysis of raw carbonaceous and plays a role of pore forming as well as a catalyst by promoting a series of complex reactions.At higher activation temperature,phosphoric acid begins to dehydrate and polymerize to react with carbonaceous,form a stable compound-phosphocarbonaceous.when the activation temperature is higher than 700 ?,the phosphocarbonaceous begin to decompose gradually.The studies of molding coconut shell activated carbon show that the activation temperature,the type of the binder,the binder amount,impregnation ratio and other factors play a significant effect on the strength of the activated carbon.As the activation temperature increasing,the intensity gradually improves.when activation temperature is up to 700 ?,the strength begin to decline,due to the gradual decomposition of skeleton of phosphocarbonaceous.Suitable binders can improve the strength of pre-cured molding material,which helps to enhance the strength of activated carbon.A series of columnar activated carbon with different physical structure have been prepared by regulating the process of impregnation ratio,graphitized at high temperature and restored structure by oxidation treatment,then as carries,the Ru/AC catalysts were prepared.Catalytic activity comes along with the carrier surface area and pore volume increasing,then shows a downward trend.However,higher surface area and the pore volume might cause the support structure instability,resulting in decreasing of activity.Activated carbon pore structure could be effective regulated by adding the expanding agent K2HPO4 in the activator,as the result of bigger average pore size,higher mesoporous rate and more concentrated mesoporous distribution.while an inert atmosphere at 900-1500 ? for activated carbon was processed again,pore structure could be further optimized,and surface-labile groups were gradually reduced,the degree of graphitization could be increasing,which contributed to more stable structure.The Ru/AC catalyst has high activity and stability with carries treated by 1500 ? because of the further optimization of the structure and the reduction of carrier surface functional groups and impurities.