Study The Catalytic Performance Of Cobalt Based Metal-organic Frameworks In The Oxidation Of Benzyl Alcohol

Benzaldehyde is an important chemical raw material and intermediate in organic synthesis,which plays very important role in the field of industrial applications.The traditional benzaldehyde preparation method is a process trival,with low yield,and not in conformity with the green chemical reaction process,thus looking for preparation of green environmental protection and high utilization rate of atoms is becoming a hot spot of modern scientific research.The oxidation reaction of benzyl alcohol is an important chemical reaction which is one of the most commonly method for the preparation of benzaldehyde.In benzyl alcohol oxidation reaction,oxygen is used as oxidant,and the only by-product is water,thus can reduce the pollution to the environment consequently.Due to excellent properties of MOFs with large specific surface area,porosity,adjustable pore size and structural diversity,it has become a hot topic in the field of catalysis.The MOFs were composed of metal nodes and organic ligands,both of them can be used as for catalytic active center,besides,MOFs can introduce other active center according to the needs of the reaction.In this thesis,a variety of MOFs materials with different metals and appropriate organic ligands were synthesized.These materials were used to catalyze the oxidation of benzyl alcohol to benzaldehyde with oxygen as oxidant.The research results are as follows:1.Preparation of metal organic frameworks M?bdc??ted?_0.5?M = Co,Zn,Ni,Cu?and their application in oxidation of benzyl alcohol.The metal organic frameworks M?bdc??ted?_0.5?M = Cu,Zn,Ni,Co,bdc = 1,4-benzenedicarboxylate,ted = triethylenediamine?were synthesized by solvothermal method and the materials were characterized by XRD,FI-IR,N₂ adsorption-desorption,XPS,TG and SEM.The final catalysts were denoted as M?bdc??ted?_0.5.The catalytic oxidation of benzyl alcohol was used as a probe reaction to investigate the effect of MOFs on the oxidation of benzyl alcohol under the same reaction conditions.The experimental results showed that the catalytic activity was the best when Co metal was used as the active center compared to the others,Co?bdc??ted?_0.5 catalyst showed 81.8% benzyl alcohol conversion and ¹00% benzaldehyde selectivity with oxygen as oxidant after reaction for 8 h.Besides,it showed that catalysts in DMF showed better benzyl alcohol conversion and benzaldehyde selectivity than other solvents due to solvent effect.The phenomenon can be attributed to the coordination interaction between DMF and Co²⁺,which affected the coordination ability of the active center of the catalyst.The interrupt and recycled experiments results show that the conversion of benzyl alcohol was not significantly increased and reused three times without significant degradation in activity.The results show that the catalyst had good cycle stability.2.Preparation of metal organic frameworks M-BTC,?M = Co,Cu,Fe?and their properties to catalyze oxidation of benzyl alcoholMetal organic framework materials M-BTC?M = Co,Cu,Fe?was synthesized using 1,3,5-benzenetricarboxylic acid as ligand and transition metal?Co,Cu,Fe?.The results demonstrated that the structure and morphology of MOFs with different transition metals were not exactly same by a series of characterization techniques including XRD,FI-IR,N₂ adsorption-desorption,XPS,TG and SEM.It was found that the catalytic activity of Co-BTC was higher than others under the same reaction conditions.Besides,the catalytic behavior was investigated under different reaction conditions,and the results showed that the catalytic activity of the catalyst Co-BTC in DMF solvent was the best,and the conversion of benzyl alcohol can reach to 92.9%,the selectivity to benzaldehyde can reach to 97.1% after reaction for 10 h with air as oxidant.Leaching and recycled experiments demonstrated that the conversion of benzyl alcohol was not significantly increased and reused three times without significant degradation in activity,the Co-BTC had good stability in the catalytic reaction.What's more,the present reaction process may contribute to the development of green chemistry owing to the present reaction utilizing air as the only oxidant.