Study On Alkylation Of Benzene And Methanol To Toluene Catalyzed By Modified HMCM-22 Molecular Sieve

The aromatics industry represented by toluene is the upstream of the manufacturing industry,and its chemical raw materials are used in a large amount and have a wide range of influence.In recent years,the new capacity of benzene in China has increased year by year,while the demand for methanol has shown a downward trend.It is extremely urgent to find a way to effectively allocate resources.The alkylation of benzene with methanol to produce toluene provides a new way to increase the yield of toluene,which has great value in further research and industrial application.In this paper,HMCM-22 molecular sieve was effectively modified by adding acid/alkali,loading metal oxide,adding acid/alkali and loading metal oxide together.Characterization methods such as XRD,SEM,BET,NH₃-TPD,and Py-IR were greatly used to analyze the acidity and pore structure changes of HMCM-22 molecular sieve before and after modification.Those molecular sieves were applied to the alkylation of benzene with methanol to study their catalytic properties,which revealed the correlation between the physicochemical properties and reaction characteristics.Meanwhile,the effect mechanism of each modification on the catalytic performance could be determined.The main contents of this paper are as follows:?1?The modified HMCM-22 molecular sieves were treated with different concentrations of acid/alkali?HCl/NaOH?in order to investigate the effects on the physicochemical and catalytic properties of the molecular sieves.The best acid/alkali concentration was 0.1 mol/L.?2?Using the equal volume impregnation method,the HMCM-22 molecular sieves were modified with different amounts of metal oxides including magnesium oxide,nickel oxide and lanthanum oxide,and analyzed the effects on the physicochemical and catalytic properties of the molecular sieves.The optimum amounts for each metal oxide were 5%MgO,3%NiO and 7%La₂O₃.?3?Based on the previous work,the HMCM-22 molecular sieve was modified by5%La₂O₃ and 3%NiO,or the HMCM-22 molecular sieve was firstly treated with0.1mol/L acid/base?HCl/NaOH??denoted as AMCM-22/BMCM-22?.Then AMCM-22and BMCM-22 were secondly continued to load 5%5%La₂O₃ and 3%NiO respectively.So,three catalysts of 5%La₂O₃-3%NiO/HMCM-22,5%La₂O₃-3%NiO/AMCM-22 and5%La₂O₃-3%NiO/BMCM-22 were obtained.These three different modifications had different impacts on this molecular sieve and would further affect the alkylation of benzene with methanol.The result was that the best composite modified catalyst was5%La₂O₃-3%NiO/BMCM-22.?4?The process conditions of alkylation of benzene with methanol were optimized using 5%La₂O₃-3%NiO/BMCM-22.For example,the optimum reaction temperature was 500?,and the optimum material mass space velocity was 30h^-1.The research in this paper provides a new idea for widening the utilization of benzene and methanol and solving the huge demand for toluene,which is conducive to the rational allocation of resources and upgrading of the overall industrial structure of petrochemical enterprises.It is to be of great significance to study the technological progress in this field.