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Preparation and catalytic application of a new solid acid catalyst

Author: LiuKe
Tutor: LeYingHong
School: Fudan University
Course: Physical and chemical
Keywords: carbon-based solid acid sulfonation carbon nanotubes grafting layered zirconium phosphate alkylation of hydroquinone transesterification esterification heterogeneous catalysis stability
CLC: O643.32
Type: Master's thesis
Year: 2011
Downloads: 496
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Abstract

As the core of technology of chemical industry and petro-industry, catalyst is no doubt to be very important. Among all kinds of chemical reactions, acid catalyzed reactions are of the most importance. Traditional acid catalysts are almost liquid, such as sulfuric acid, nitric acid and so on, which are frequently used in homogenous reactions. Deficiencies of liquid acid are found such as difficulty to separation, unreusability, and pollutions to environment, and the solutions of those problems focus on solid acid. As a matter of fact, how to use solid acid instead of liquid acid has been developed to be the hotspot in researches of catalysts. Two different kinds of solid acid catalysts and there applications were specifically studied in our work as followed.(Ⅰ) So far, attentions are mostly put on inorganic solid acid, among which metal oxide, metal sulfate and noble metal compounds are main direction. Although catalysts are indeed good in catalytical activity, problems still exist such as weak applicability, especially in liquid reactions. Recently developed Carbonaceous Solid Acid(CSA) has solved those problems on some scale. They are commonly simple in preparation, cheap and environmentally friendly, and the waste of reaction is very easy to be dealt with. In my thesis, a series of CSA are studied, they are mainly carbonaceous materials dealt with condensed sulfuric acid. For instance, Carbon Nanotubes(CNT), activated carbons, sucrose heated under 400℃are dipped in concentrated sulfuric acid, mesoporous carbons and starbon. Finally, we put most emphasis on sucrose derived carbon based solid acid (C-SO3H-48h). The catalytic activity was tested by alkylation of hydroquinone and a high conversion above 90% and TBHQ selectivity above 70% was obtained. However, some deactivation was observed, and the reasons were carefully studied, according which we introduced this kind of carbon-based catalyst into other reactions with milder conditions, such as esterifications and transesterifications, to lessen deactivation.Carbon nanotubes is another kind of carbon-base material which is difficult to be sulfonated via direct sulfonation. Therefore, we employed in-situ polymerization and thus Poly(styrene sulfonic acid) grafted carbon nanotube (PSA-CNT) was prepared and used as a solid acid catalyst in the alkylation of hydroquinone. The TBHQ yield reached 53% and selectivity of TBHQ was specifically high, as a matter of fact, PSA-CNT was more proper for this reaction. Some deactivation was observed, which was smaller than that of C-SO3H-48h. Similarly, the reasons of deactivation were discussed. At the end, PSA-CNT was compared carefully with C-SO;H-48h.(Ⅱ) Layered zirconium phosphate(ZrP), for its high water-heat tolerance, stability of layered structure and designable surface, has drawn a lot of attention. Another part of this thesis is about this kind of catalyst:ZrP with different organic groups were synthesized by introduction organic group bearing silicon ester into their laminates during the hydrolyzing process by co-condensation. With that method, a series of organic group functionalized pillared zirconium phosphates were prepared, and applied into reactions of hydroquinone alkylation and esterification of lauric acid with methanol. ZrP functionalized by methyl-(ZrP-Me) was better than other materials in catalytic activity, which is close to traditional solid super acid. Reasons of catalytic differences were studied, and proved by experimental method. For ZrP with different organic groups, their catalytic activities related to their acidity, quantity approachable acid site and molecular polarity.

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