Intra-gallery Templating Synthesis Of Pillared Montmorillonites And Their Structure&Performance

Pillared interlayered clays (coded as PILCs), a family of porous materials withzeolite-like structure, could be used as catalysts and adsorbents in many fields, such aspetrochemistry, enviromental protection and so on. However, the microporous structureand relatively low thermal stabilty (300~400℃) restrict their development and application.Recently, a new type of PILCs called silica pillared clays (coded as SPCs) was sucessfullysynthesized, which provides some enlightenment on solving above problems. SPCs haveordered porous structure, pore size distribution between super-micropore and mesopore,bigger special surface area, good thermal stabilty and designable structure, and thus havereceived more and more attentions. But the intra-gallery pillar of SPCs is pure silica, whichhas weak surface acidity and low catalytic performance. As a young branch of PILCs, thestudy on modification of SPCs is very limited. Therefore, functionalization of SPCs is oneissue with great importance in both theory and application.According to the development of present PILCs, the synthesis characteristics of SPCs,and the new requirements of catalysts, this thesis focuses on the study of mesoporousPILCs synthesized by an intra-gallery templating method (coded as IGT) and their catalyticperformances. Here, a series of new PILCs were designed and prepared by IGT, and theinfluence facors, such as basic clay, pillaring agent, modification with metal or non-metalelement, on the structure and properties of these PILCs were investigated Finally, it isexpected to obtain new types of PILCs with ordered gallery mesoporous structure,excellent thermal stabilty and hydrothermal stability as well as good catalytic performancein some reactions. The specific researeches included five aspects as follows.First, two kinds of montmorillonites from Inner Mongolia Province and ZhejiangProvince, were used to synthesize SPC-NM and SPC-ZJ by IGT. The effect of the natureof basic clays on their structure and properties were systematically investigated. Resultsindicate that two SPCs have order gallery mesoporous structure and open slit-shaped pore. Both of them have excellent thermal stability, but SPC-ZJ shows worse hydrothermalstability than SPC-NM because there are part of montmorillonite delamination and theformation of some mesoporous SiO2formed out of gallery regions in the structure ofSPC-ZJ. Compared with SPC-NM, SPC-ZJ shows higher conversion in catalysis crackingof heavy oil, but lower selectivion of gasoline and worse reusability.Second, a facile method was developed to synthesize Fe-doped SPC (deneted asFe-SPC) with various content of Fe2O3. A mixture of ethanol and water was used as thesolvent, which improves the dispersion of Fe3+in silica sol and high content of Fe2O3(upto27.03wt.%). Then, the effects of additive amount of Fe3+on their structure andproperties were systematically investigated. The results indicate that, Fe-SPC has orderedmesoporous structure, which is related to the usage of Fe(NO3)3. Fe ions were incorporatedinto the SiO2framework as tetrahedral coordination, meanwhile octahedral Fe species orFe2O3were formed out of the framework. Fe-SPC has good hydrothermal stability but badthermal stability. All Fe-SPCs show excellent catalytic performance and reusability inoxidative desulfurizations of coking benzene and model oil, especially in the former.Third, as octahedral Fe species in Fe-SPC trend to agglomerate, a new method was setup to synthesize Fe-incorpated SPC (deneted as (Fe,Si)-PILC) with high concentration ofFe. Moreover, their structure and properties were systematically investigated. The resultsshow that all iron species are tetrahedrally coordinated with the gallery silica nano-pillarsand no octahedral Fe species or Fe2O3are formed out of the framework.(Fe,Si)-PILC has asimilar structure as SPC, but the porous structure of the former is different from the laterowing to the incorporation of Fe. However this change is less than that in above Fe-SPC.(Fe,Si)-PILC has outstanding hydrothermal stability (better than Fe-SPC) and thermalstability. They also show good catalytic performance and reuseablity in phenolhydroxylation, which is supposed to be very sensitive to the framework iron species.Forth, a new kind of TiO2pillared monmorillonite (denoted as Ti-PILC) wassynthesized under a non-acidic condition by the IGT method, which was different fromtraditonal method. Furthermore, the effect of surfactants on their structure and propertieswere systematically investigated. Ti-PILC has ordered gallery mesoporous structure, whichis similar as SPC. The used surfactant will affect the porous structure, especially foraverage pore size. Because intra-gallery TiO2pillar belongs to anatase, Ti-PILC showsgood catalytic performance and reuseablity in the photolysis of methylene blue. The reactivity is influenced by the usage of catalyst and porous structure.Finally, to overcome the bad catalytic activity under visable light of Ti-PILC, a newkind of N-doped Ti-PILC (denoted as (Ti,N)-PILC) was synthesized, and the effects ofnitrogen atom on their structure and properties were also investigated. The nitrogen dopingdoes not obviously change the structure of Ti-PILC, but the absorption of gallery TiO2tovisable light is enhanced, which makes (Ti,N)-PILC show some catalytic performance inthe photolysis of methylene blue under visable light.