Solvent-free Synthesis Of Zeolites At High Temperatures

Zeolites as promising adsorbents,ion-exchangers,and catalysts have been widely applied in industrial processes.Right now,there are more than 200 different microporous framework structure types,comprising thousands of different materials with a diverse selection of compositions.Most of the synthetic zeolites were obtained from hydrothermal synthesis.Notably,crystallization of zeolites from conventional hydrothermal route,is generally suffered from comparable low space-time yields(STYs),which is a key factor for industrial manufacturing.Recently,we developed a solvent-free zeolite synthesis route,where addition of solvents like water is completely avoided.The absence of water solvent in the synthesis effectively reduces the decomposition of the organic template,which could remarkably increase the crystallization temperatures to higher than 200 ℃.In chapter two,it is reported a highly efficient synthesis of zeolite catalysts by means of fast crystallization at temperatures higher than 200 ℃ under solvent-free conditions.For example,MFI could be fully crystallized within 0.5 h at 240 ℃,while conventional hydrothermal synthesis of MFI takes for 12-24 h until full crystallization,respectively.The STY yield of MFI is as high as 11000 kg/m3 per day,In chapter three,it is shown high-temperature synthesis of high silica CHA zeolites(S-CHA)at the temperatures from 160 ℃ to 240 ℃ in absence of water-solvent using TMAdaOH as a template.The S-CHA exhibits high STYs(as high as 4738 kg/m3 per day),good crystallinity,and high SAR.Interestingly,catalytic tests in NH3-SCR show that the catalytic performance of S-CHA sample is effectively enhanced,compared with the CHA zeolite from hydrothermal synthesis.In chapter four,it is shown the synthesis of Ce-CHA.Conventional ion-exchange can’t get the Ce-CHA because Ce ion diameter is bigger than the CHA pore size.In this chapter,it is successful for the preparation of Ce-CHA zeolite from Ce-Y zeolite in the absence of water solvent.The addition of Ce ion is favorable for the hydrothermal stability of CHA zeolite in the NH3-SCR reaction.In chapter five,it is performed the interlayer expansion of COK-5 using dichlorodimethylsilane(DCDMS)at 180 ℃,yielding a new and crystalline microporous framework with methyl groups in the as-made form,which is designated as COE-5.After calcination,sample is designated now as calcined COE-5.Interestingly,calcined COE-5 shows much better catalytic activity in acetalisation of glycerol with acetone than its precursor of COK-5 and conventional zeolites of ZSM-5 and Beta zeolites.Similarly,it is also used bis(2,4-pentanedionate)-dichlorotin[Sn(acac)2Cl2]to replace of silylating agent for interlayer expansion,yielding a new and crystalline microporous framework with tin species(Sn-COE-5).