Preparation Of Silicalite-1 Membrane And The Application In Dehydrogenation Of Ethylbenzene To Styrene

Zeolite membrane has become an interesting subject because of its excellent properties. The MFI(Silicalite-1 and ZSM-5) membrane was a particularly active research field mainly because of its crystal channel systems with pore diameter(about 0.55nm) near the sizes of many industrially important organic molecules.Due to the absence of A1 atom,Silicalite-1 membrane is highly hydrophobic and can extensively apply in dealcoholizing from the water and also used in membrane reactor.In this dissertation,the Silicalite-1 crystals with different sizes were synthesized with the traditional hydrothermal method and the effect of temperature and the type of template on the growth of the Silicalite-1 were studied.The Silicalite-1 membranes with different thickness were synthesized on theα-Al₂O₃ and porous stainless steel tubular support,respectively.The low-template method was proposed to synthesize Silicalite-1 membrane to reduce the cost of the zeolite membrane and the effect of concentration of the template on the growth of zeolite membrane was researched.To the question that the prepared precedure for the high-quality Silicalite-1 membrane was complicated,the limited-growth method(or the modified secondary growth method) was proposed to prepare the high-permeance MFI membrane on cheap macroporousα-Al₂O₃ tubular support.The Silicalite-1 membranes with different thickness were easily prepared by tuning the thickness of the seed layer.The Silicalite-1 membrane was applied in the dehydrogenation of ethylbenzene to styrene and the good results were obtained.The main results and conclusion obtained in this dissertation were as follows:(1) The effects of the temperature and different template on the growth of zeolite were studied.The growth speed of zeolite was accelerated when the temperature increased and the crystal with the size of 1μm,21μm and 41μm were successfully synthesized at the temperature of 373K,403K and 443K,respectively.At the same synthesis conditions,the crystal was larger with TPABr as template than TPAOH as template.The Silicalite-1 membranes synthesized with the in-situ method and traditional secondary growth method have good single-gas permeation properties.(2) The low-template method was proposed to synthesize the Silicalite-1 membrane to reduce the dosage of the expensive template which adds the cost of the zeolite membrane.The dosage of template in this method was only one-tenth of that in the usual secondary growth method,which effectively decreased the cost of the zeolite membrane.The Silicalite-1 membrane synthesize with the low-template method at the TPA⁺/H₂O ratio of 6×10^-5 has a H₂/SF₆ ideal separation factor of 44 at room temperature,which was higher its corresponding Knudsen ratio of 8.54.(3) The limited-growth method was proposed to synthesize high-permeance Silicalite-1 membrane.The H₂ permeance of as-synthesized Siliclaite-1 membrane reached at 1.64×106mol.m^-2s^-1.pa^-1.The Silicalite-1 membranes with different thickness were easily synthesized with the limited-growth method associated with the rub-coatng,in-situ nucleation and dip-coating method,respectively.(4) The Silicalite-1 membrane supported on the porous stainless steel was used in the reaction of dehydrogenation of ethylbenzene to styrene and the effect of the speed of the sweep gas on the conversion and selectivity of the styrene were studied.Under the optimal conditions,the conversion of styrene increase 7%as compared with the fixed-bed reaction and the anticipated results were obtained.