Synthesis And Catalytic Properties Of Porous Metal Silicate Materials Templated By Metal-organic Moieties

With the rapid development of the human economy and the continuous progress of society,the chemical industry is playing an increasingly important role in human society.Every progress of the chemical industry means a forward step towards a better world.The chemical industry benefits human society,but it brings a series of problems to mankind,such as energy shortages,ecological pollution,which severely restrict the rapid development of human society and the world economy.In the field of catalysis,green chemistry advocates the concepts of environmental protection,energy saving,and emission reduction.Heterogeneous catalysts overcome the shortcomings of traditional homogeneous catalysts that can not be recycled.They can reduce energy and material consumption,catalyst production costs,and replace traditional catalysts that possibly pollute the environment.Therefore,constracting green,efficient and stable heterogeneous catalyst has become a long-term research focus.In the 1950s,the preparation and use of molecular sieves greatly promoted the development process of modern industry and became a superior carrier of many active metals.In 2005,metal-organic framework compounds were used to catalyze the reaction,which highlighted the joint construction of frameworks and active sites.Both molecular sieves and metal-organic framework compounds have their unique methods to constract pore and active site.After summarizing the construction methods for molecular sieves and metal-organic framework compounds to induce the pore channel and active site,and then analyzing the advantages and disadvantages of the two materials as heterogeneous catalysts,we propose propose a novel synthesis method to rationally in-situ construct pore channel and active in a stable silica framwork.First,in the Chapter 3,the Co-2-methylimidazole complex is used as a bifunctional template and silicate is used as the framework to synthesize a cobalt-porous silicate material(PMS-1).The Co-2-methylimidazole complex interacts with the silicate framework to form a catalyst with specific pores and active sites.The Co-2-methylimidazole complex not only determines the size of the pores,but also in-situ introduces Co active sites to make them highly dispersed in the pores of the material.The silicate framework not only dynamically limits the size of the Co-2-methylimidazole complex,but also provides a high specific surface area,porous and stable framework.The synthesized PMS-1 has a narrow pore distribution of～3.5 nm and a high Co3+ in CoOx active site.In the reaction of cyclohexane oxidation,PMS-1 exhibits very high catalytic performance,with a TOF of 25.7 h-1 at 120℃.In-situ infrared and first-principles studies have shown that PMS-1 contains more active oxygen atoms,which plays a vital role in the activation of the C-H bond of cyclohexane.In Chapter 4,porous Cu-Co silicate(PMS-2)is synthesized by employing Cu/Co-benzoic acid small molecule complex as a bifunctional template and silicate as a framework.The dual-functional template not only cast～1.5 nm pores in the silicate framework,making the material porous,but also in-situ introduce Cu and Co metals into the pores.By changing Si/metal ratio,Cu/Co ratio,ligand/metal ratio,and the treating temperature,the PMS-2 can be regulated at reaqirement for the specific surface size,pore volume,metal dispersion degree,and alloy formation degree.By employing the PMS-2 as catalyst,furfural hydrogenation reaction can be driven at 50℃,and the TOF at 110℃ reaches 24.9 h-1.First-principles studies have shown that Co-substituted Cu surface strengthens the electron aggregation among the H and carboxylic acid O atom regions,and reduces the activation energy required for the reaction.In Chapter 5,we synthesized porous Al silicate materials using different Al-carboxylic acid ligand complexes as bifunctional templates and silicate as the framework.By changing the types of monocarboxylic acid ligands,the size of the pores and the surface area of the material can be tuned,and the Al active sites can be highly dispersed in the pores of the material.Replacing the monocarboxylic acid ligands with tricarboxylic acid ligands can locally agglomerate Al active sites,and increase the pore size,and change the ratio of B/L acid.The synthesized PMS-3 has highly dispersed acidic active centers and exhibits extremely high activity as a catalyst for the alkylation of p-xylene and benzyl alcohol.The TOF reaches 26.0 h-1 at 100℃,whihe the selectivity reaches 91%,suppressing the formation of by-products.Due to the large and uniform pore size,the by-products are well suppressed.