Synthesis Of TAPO-5Molecular Sieves And Membranes

Aluminophosphate molecular sieves have uniform and regular channels atmolecular scale showing molecule-sieving effect, as well as good chemical,mechanical, and thermal stabilities, showing great application potential in the fields ofseparation and catalysis. Molecular sieve membranes on inorganic porous substrates,when used in industrial process, can greatly improve the separation rate and selectivityof products, having a bright application prospect in continuous separation, membranereactor, chemical sensor, and so on. TAPO-5molecular sieve not only has thoseproperties mentioned above, but also has excellent catalytic properties in series ofoxidation reactions in which hydrogen peroxide presents, due to the variety in valenceof Ti. There are many literatures related to AlPO4-5membrane, but no public studyabout TAPO-5membrane is reported.In this thesis, TAPO-5molecular sieves and membranes have been investigatedusing in situ hydrothermal synthesis method and steam-assisted gel conversion method.Using in situ hydrothermal method, the effects of synthesis conditions, such as pHvalue, crystallization temperature and model, on synthesis of molecular sieves arestudied. The substrates are modified by TiO₂, MnO₂, and SiO₂respectively, to studythe effect of substrate-modification on synthesis of molecular sieve membranes. Usingsteam-assisted gel conversion method, the effects of synthesis conditions, such asgel-aging model, crystallization model and time, and addition of HF, on synthesis ofmolecular sieves are studied. TAPO-5membranes are synthesized on substratesmodified by SiO₂, and compared with those by in situ hydrothermal method. Also,effects of aging model, crystallization time and addition of HF on synthesizingTAPO-5membranes are investigated. All of the synthesized samlaes are characterizedby XRD, SEM and UV-Vis DRS. It can be concluded that when using in situhydrothermal method, the pH value and crystallization temperature affect the morphology of TAPO-5molecular sieves and existing state of Ti, while dynamiccrystallization only influences the morphology and has no effect on the existing stateof Ti. The substrates modified by Ti are not suitable for the formation of membranes.The membranes are a certain c-oriented on substrates modified by Mn and arecontinuous on substrates by Si. Gel conversion method, compared with in situhydrothermal method, can shorten the crystallization time and crystal size of TAPO-5,and are favorable to generate framework Ti. Aging gel and dynamic crystallizationaffect the morphology of TAPO-5but not the existing state of Ti. The addition of HF isunfavorable to generate framework Ti. Using steam-assisted gel conversion methodand aged-gel are favorable to synthesize intergrowth TAPO-5molecular sievemembranes.