The Preparation And Modification Study Of Mesoporous MCM-48 Molecular Sieve And Membrane

The route that synthesis of dimethyl carbonate by methanol and carbon dioxide accords with the atom economy and the concept of green chemistry,which used carbon dioxide and solved the problem of methanol overcapacity.Because of thermodynamic limitations,the main research focus on seeking a highly efficient catalyst and breaking the chemical balance limitation.The mesoporous MCM-48 with Ia3 d cubic structure and higher molecular diffusion has a promising prospect in catalysts,but is catalytic inert,in this paper,the author synthesized MCM-48 molecular sieve membrane and doped the active component of the above reaction into membrane,used as catalytic membrane reactor to achieve separation-catalytic conversion integrate.In this paper,MCM-48 mesoporous molecular sieves was synthesized by the directly hydrothermal method under the condition of lower template? fluorine ion,the effects of template agent?ethanol adding agent?crystallization temperatures?varying-temperatures crystallization on synthesis molecular sieves were investigated.The samples were characterized by XRD?SEM and so on,the results showed that the high quality MCM-48 mesoporous molecular was synthesized at 423 K for 12 h with CTAB/Si=0.09.Under the condition of low temperature,the smaller molecular sieve particles can be synthesized at 100? for 14 h.The MCM-48 membranes were synthesized on the ?-Al2O3 support with pore size of 2-3?m by in-situ hydrothermal synthesis and two-seeding method.The effects of support surface pretreatment ?seeding method?crystallization temperatures and times?varyingtemperatures crystal-lization on as-synthesis membrane were investigated.The membranes were characterized by XRD,SEM,IR and single gas permeation test,the results showed that the impermeable MCM-48 membrane can be synthesized once by varying-temperatures crystallization(120?2h+150?12h).The.Solvent extraction to remove surfactant template,is more effective to synthesize high quality MCM-48 membranes than calcination.The separation factor of H2 and N2 was about 3.5.Based on the MCM-48 membrane preparation,the membrane was modified by doping metal active components were successfully synthesized,the catalytic membranes were characterized XRD,SEM,ICP,single gas permeation test.The results show that the catalytic membranes can be successfully synthesized in the range of n(Cu)/n(Ni): n(Si)=(0.005-0.02),the membrane after activation,that the nitrogen gas permeation rate was in the order of magnitude of 10-8,the permeation rate of hydrogen gas was in the order of 10-7,in the Cu-Ni-MCM-48-0.0075-0.0075 membrane showed the best performance,the H2/N2 separation factor is about 4.1,the ICP test results showed Cu,Ni metal successfully doped into the MCM-48 membrane.