Design And Synthesis Of Supported Ru-substituted Polyoxometalates Catalysts And Their Application In N-Tetradecane Oxidation

As one class of nano-sized inorganic metal clusters,polyoxometalates（POMs）could be used as efficient bifunctional catalysts because of their acidity and oxidation-reduction quality.Moreover,they have other merits,such as diversiform dimension,tunable structure,rich composition and so on,enabling it to adapt different catalytic reaction system.According to not complete count,the research results in catalysis accounted for more than 80% of all research areas of POMs.Thus it can be seen that POMs as catalysts with great application prospect are worthy of attention.Past research of POMs more focused on homogeneous catalytic system,various disadvantages such as poor dispersion,small surface area and difficult recovery were discovered along with the deepened study.To a certain extent,those disadvantages have restricted their application in catalysis and violated green chemistry theory.Many researchers have made massive exploration to seek solutions.It’s discovered that the most effective way is loading POMs on appropriate substrates to prepared heterogeneous catalyst.The advantages of high specific surface area,high dispersion and easy recovery of heterogeneous catalyst can overcome those disadvantages and achieve green catalytic chemistry process of POMs.Through this idea,several different Ru-substituted polyoxometalates were selected and loaded on different substrates to prepared POMs supported catalysts.Those catalysts were used for the experiments of n-tetradecane oxidation.High pure air was used as the source of oxygen.It’s trying to facilitate the reaction in mild conditions without adding strong oxidizers and any another solvents.The process focuses on the effect of type of appropriate substrates and different reaction conditions to the catalytic experiments.Subject involves the following three main parts:Firstly,tetraruthenium（Ⅳ）-polyoxometalates Rb₁₀[{Ru₄O₄（OH）₂（H₂O）₄}(γ-GeW₁₀O₃₆)₂]·21H₂O(GeW₁₀Ru₂)and NH₄[{Ru₄O₆（H₂O）₉}₂{Fe（H₂O）₂}₂{β-TeW₉O₃₃}₂H]·3 6H₂O（NH₄-2）were synthesized and loaded on different supports to prepare heterogenous catalysts.The mesoporous molecular sieve SBA-15 was chosen as catalyst support and modified with amino-groups.The designed and synthesized GeW₁₀Ru₂ was loaded on mesoporous molecular sieve to prepared POMs supported catalyst SBA-15-Apts-GeW₁₀Ru₂.Many kinds of haracterizations were used to prove the feasibility of this preparation plan.Then,three kinds of mesoporous molecular sieves SBA-15,KIT-6 and FDU-12 with different pore structure were chosen as catalyst supports.They were also modified with amino-groups firstly.The synthesized Ru-substituted polyoxometalate NH₄-2 was loaded on those mesoporous molecular sieves to prepared catalysts X-Apts-NH₄-2（X=SBA-15,KIT-6,FDU-12）.Several kinds of characterizations were used to explore the loading of POMs on different type of supports.Secondly,the catalyst SBA-15-Apts-GeW₁₀Ru₂ was used for catalytic oxidation of n-tetradecane.On the one hand,the effect of different reactions such as catalyst loading amount,reaction time,reaction temperature and catalyst amount on catalytic efficiency was ressarched to achieve the optimal reaction conditions.Results showed the optimal conditons as follow: catalyst loading amount 3.21%,reaction time 7 h,reaction temperature 150 oC,catalyst amount 4mg.The conversion of n-tetradecane reached 50.97% under this reaction conditions.On the other hand,the derivation process of catalytic mechanism was also investigated trough a series of contrast experiments and proven to be process of free radical initiation.Finally,the catalysts X-Apts-NH₄-2 were used for catalytic oxidation of n-tetradecane.On the one hand,the process focused on the influence of the type of support to catalytic activity of X-Apts-NH₄-2 in n-tetradecane oxidation experiments.FDU-12 was selected as the best fit support and the catalyst FDU-12-Apts-NH₄-2 showed a good performance in n-tetradecane oxidation.On the other hand,the effect of different reactions such as catalyst loading amount,reaction time,reaction temperature and catalyst amount on catalytic efficiency was researched.Results showed the optimal conditons as follow: catalyst loading amount 2.55%,reaction time 7h,reaction temperature 150 oC,catalyst amount 4mg.The conversion of n-tetradecane reached 52.84% under the optimal conditions.