| Titanium silicalite-1?TS-1?,a type of heteroatom zeolite containing titanium,has high hydrothermal stability and good catalytic activity.Especialy,it has been widely used in many reactions using H2O2 as oxidant due to high product selectivity,mild reaction conditions and non-pollution in the reaction process.However,the micropores of TS-1limit the application.Furthermore,the recycling process is complicated and the catalytic activity in the gas phase reaction needs to be improved.According to the above problems,this paper investigated the synthesis conditions of TS-1 zeolite with different particle sizes and TSH zeolite with hollow-structure.The catalytic performance was investigated through phenol hydroxylation.TS-1 membranes were prepared on the inner and outer surfaces of alumina support,thus sloving the problems of recycling.In order to improve the material efficiency and phenol selectivity,the advantages of TS-1 zeolite and Pd membrane were combined to construct TS-1/Pd/TS-1 and Pd/TS-1 composite membrane.The composite membranes was characterized and the performance of gas permeation as well as the reaction performance in the benzene hydroxylation to phenol was tested.The main contents and results are as follows:1.TS-1 zeolite with different particle sizes were prepared by changing the synthesis conditions.The zeolites were characterized and applied in the phenol hydroxylation reaction.The results showed that the particle size became smaller with decreasing the crystallization temperature,crystallization time and H2O/TPAOH ratio.The phenol conversion and selectivity could reach up to 12.68%and 98.24%using the small TS-1with the particle size 130 nm.The TS-1 zeolite with particle size 300 nm was treated by tetrapropylammonium hydroxide?TPAOH?.The effects of alkali treatment time,alkali treatment temperature and the ratio of H2O:TPAOH on the hollow structure were investigated.The results showed that the hollow inside the crystal gradually increased and tended to stabilize with increasing the treatment time,the alkali treatment temperature and the decreasing the ratio of H2O:TPAOH.The maxium of phenol conversion could reach 21.01%when the treatment time was 24 h at 170?and the equimolar of H2O-TPAOH.2.The TS-1 zeolite membrane supported on the outer and inner surface of alumina ceramic tube was prepared by secondary seeding growth method and the performance was tested.The results showed that the outer surface was more conducive to the growth of membrane due to the smaller average pore size.The N2 permeation flux of TS-1 was obtained.3.Based on the previous work,TS-1/Pd/TS-1 and Pd/TS-1 composite membranes were constructed.First,TS-1 zeolite membrane was prepared on an alumina support,followed preparing a layer of palladium membrane by electroless plating,and then a continuous TS-1 membrane was deposited on the surface of the palladium membrane under hydrothermal conditions to form TS-1/Pd/TS-1 composite structure.The results showed that the permeation flux of H2 increased with the temperature and the was obtained with the trans-membrane pressure of 0.15 MPa and the temperature of500?.In order to reduce the mass transfer resistance of the TS-1 zeolite membrane and better utilize the zeolite catalyst,a Pd/TS-1 composite membrane was prepared by depositing a loose layer of nanosized titanium silicalite zeolite on the surface of Pd membrane with a 4?m thickness through covalently bonding method using alkoxysilane mol·m-2·s-1·Pa-1 and the ideal selectivity of H2/N2 with?500 were obtained at 500?.The highest benzene conversion and phenol yield were 23.4%and 22.3%,respectively.The H2 flux was kept at?0.02 mol·m-2·s-1 and the benzene conversion and the phenol selectivity were maintained at 22%and 94%during the 110 h run. |
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