Preparation Of Mesoporous Carbon Materials And Their Applications In Organic Catalysis

CMK-1,a porous carbon,was first reported in 1999 and since then,mesoporous carbon materials have been of great interest owing to their high surface area,large pore volume,well-tailored pore size,chemical inertness,high stability,and electroconductibility.Preparation and modification of the carbon materials have been studied more and more intensely in order to meet the demands of various practical applications.This thesis mainly studies the preparation and catalytic performance of mesoporous carbons using hydroxypropyl-β-cyclodextrin as the structure directing agent or carbon source.It includes two major parts.In the first part,a series of mesoporous carbons have been prepared with hydroxypropyl-β-cyclodextrin as the structure directing agent,tetraethoxysilane or aluminophosphate as the inorganic source by using different methods;besides,the catalytic performance of these carbon materials has been evaluated by the reduction of p-nitrotoluene using hydrazine hydrate as a reducing agent.In the second part,some copper-supported mesoporous carbons have been synthesized with hydroxypropyl-β-cyclodextrin,tetraethoxysilane and copper nitrate,and their catalytic properties have been measured through the hydroxylation of arene using hydrogen peroxide as oxidizer.Concretely,it involves several aspects as follows:(1)A series of mesoporous carbons have been prepared from organic-inorganic composites obtained by employing hydroxypropyl-β-cyclodextrin and tetraethoxysilane as precursors via different methods.Mesoporous carbons prepared from the composites synthesized under room temperature display amorphous pore walls,and large pore volume.However,mesoporous carbons prepared from the composites synthesized under hydrothermal conditions display part of graphitic pore walls.Moreover,mesoporous carbons prepared with soft-template method have higher surface area and pore volume,and narrower pore size distribution than those of carbons synthesized with traditional hard-template method.In addition,mesoporous carbons prepared by using sucrose as the carbon source and silicas as the templates which have been obtained by using ammonium perchlorate oxidation at different temperatures to remove the organic matter from composites synthesized under room temperature,have higher surface area and pore volume,and narrower pore size distribution than those of carbons synthesized with calcination method.(2)Eight kinds of mesoporous carbons have been prepared with hydroxypropyl-β-cyclodextrin and aluminophosphate by usig different synthetic routes.With increasing of mole ratio of hydroxypropyl-β-cyclodextrin to aluminophosphate,surface area and pore volume of carbons obtained by soft-template method show a trend of significant decrease,while those of products prepared with conventional hard-template method increase gradually.(3)A series of copper-supported mesoporous carbons have been prepared with hydroxypropyl-β-cyclodextrin,tetraethoxysilane and copper nitrate by different synthetic routes,such as impregnation,nanocasting and soft-template.The Cu-carbon hybrid from the impregnation method exhibits lower the dispersion of copper than that from nanocasting technology.Cu(0)is major form,and a few of copper oxide is also found in the hybrid from impregnation method by XRD analysis.But copper oxide is major form with lesser particle size in the Cu-carbon hybrid from nanocasting technology.However the best dispersion of copper with lesser particle size was found in the copper-supported mesoporous carbon from soft-template method.Moreover,with increases of content of copper,surface area and pore volume of all hybrids decrease gradually,which may be caused by pore blockage because of too much copper.(4)The reduction of p-nitrotoluene with hydrazine hydrate was used as a model reaction for evaluation of catalytic properties of synthesized mesoporous carbons.The results showed that mesoporous carbon materials prepared from hydroxypropyl-β-cyclodextrin-based silicas as inorganic templates synthesized by using ammonium perchlorate oxidation under room temperature have highest catalytic activity,the yield of p-methylaniline is 88.1%,and the catalyst still keeps higher activity after being reused for 4 times through a simple filtration,washed with ethanol and dried.The mesoporous carbon serves as an adsorbent and electrical conductor to enable the reaction to occur.This novel nonmetal catalytic system will attract considerable attention because of its low cost,high efficiency and low environmental impact.(5)Copper-supported mesoporous carbons as the catalysts for the hydroxylation of phenol to dihydroxybenzene with hydrogen peroxide are studied in this paper.The results showed that copper-supported mesoporous carbon prepared by using nanocasting technology has highest catalytic activity,the conversion of phenol is 58.2%and the selectivity of catechol is 65.1%after the reaction for 4 hours.Copper oxide maybe is one of the main active components for this reaction.Activity of the catalyst gradually decreases after being reused for 8 times under the same experimental conditions.In addition,too much content of copper in the mesoporous carbon is less favorable for the catalytic activity.(6)The research about the direct hydroxylation of benzene to phenol is academic and applicable significance.For the high bond energy of the C-H bond,benzene is difficult to be activated;in addition,it is easy to stimulate the deep oxidation because phenol is more active than benzene.Therefore,the direct hydroxylation of benzene to phenol is one of the most challenging topics.The object of this study is to research and develop copper-sopperted mesoporous carbons as the catalyst for hydroxylation of benzene to phenol with hydrogen peroxide in liquid-phase.The results showed that the catalyst prepared by using soft-template method has highest catalytic activity,the conversion of benzene is 48.9%and the selectivity of phenol is 84.1%after the reaction for 10 hours.Pure copper maybe is one of the main active components for the hydroxylation of benzene.Activity of the catalyst gradually decreases after being reused for 4 times under the same experimental conditions.