Study On The Reaction Process Of The Direct Conversion Of Natural Gas To The Preparation Of Liquid Hydrocarbons

Benzene and other aromatic hydrocarbon products are important basic chemical raw materials.Annual growth rate of global benzene demand will reach 3.9%.Benzene production growth may be only 2%.Supply gap leads to high prices of benzene.The methane（main component of natural gas）dehyroaromatization in high temperature without oxygen can be directly converted into aromatic products having been widely used and generate a large amount of hydrogen.HZSM-5 is considered to be one of the most effective catalysts for methane aromatization with its unique microporous structure and acid properties,but the micro structure of ZSM-5 restricted the diffusion of benzene and other large molecules.A recent study shows that with the development of micro-mesoporous composite structure molecular sieve,It provides a new direction and possibility to solve the diffusion limitation of material in micro pores.Therefore,it is significant to study the ZSM-5 molecular sieve of the multi stage pore structure.Methane（CH₄）is the main component of natural gas.In this paper,methane instead of natural gas was used as a reaction gas.This paper researched the synthesis of ZSM-5 under hydrothermal conditions.It was characterized by XRD、IR、TG、NH₃-TPD、BET、SEM and so on.The results indicate the optimum condition of ZSM-5 mesoporous zeolite compose is: the synthetic material ratio is n（SiO₂）:n（Al₂O₃）:n（TPABr）:n（NaCl）:n（H₂O）:n（NaOH）=60:1:10:40:1800:9,the dynamic crystallize at the temperature of 150℃ for 48 h and Thin layer structure of ZSM-5 zeolite compose is: the synthetic material ratio is n（SiO₂）:n（Al₂O₃）:n（Na₂O）:n（TPABr）:n（H₂O）n:（Triton-X-100）:n（urea）=50:1:10:10:1800:3.5:1.25,the dynamic crystallize at the temperature of 150℃ for 48 h.The characterization of the results show that,the synthesis of samples having dual pore structure.Surface area were 420m²/g and 392m²/g.In addition,the thermal stability of the synthesized samples is better and the particle size distribution is more uniform.The Mo-ZSM-5 molecular sieve modified by a new type of molybdenum loading method was used as catalyst.The catalytic performance of methane aromatization was investigated in the fixed bed micro reactor.The experimental results show that when the Mo load of the catalyst is6wt%,the reaction temperature being 700 ℃,the pressure being under the condition of atmospheric pressure,the conversion rate of methane is 10.97%.activity of the catalyst was thehighest.6Mo/ZSM-5 was modified by adding a second metal component（Mg）and the B acid sites have obviously reduced.reduced B acid avoided catalyst deactivation,which is beneficial to the reaction.when the mass fraction of Mg is 0.75wt%,reaction temperature being 973 k,reaction pressure being atmospheric,the feed rate of methane for the 1500 mL/gcal?h,the activity of the catalyst reached the maximum.At this time,the conversion of methane reached to 11.41%and the yield of benzene reached to 10.34%.