Study On The Design And Synthesis Of Polyoxometalates And Their Properties In The Oxidation Of Aromatic Alcohol

Aromatic alcohol is a very promising molecule in organic chemistry,and a large amount of conversion can occur in organic reactions.In recent years,a large number of applications of alcohols have increased the interest in the catalytic oxidation of aromatic compounds by acid catalysis,and the synthesis of various aldehydes,ketones and acids by selective catalytic oxidation.Direct oxidation of aromatic alcohol to carboxylic acid is a very important reaction in both organic chemistry and industry,and will play an important role in developing sustainable pathways of biomass added-value chemicals.Traditional oxidation processes,most of which use stoichiometric excess precious metals and corrosive strong oxidants,have many drawbacks,such as the lack of selectivity of products,the extensive use of organic solvents,actual toxicity and waste generation.Therefore,there is an urgent need for an environmentally sound alternatiThe ideal green oxidation system is to use molecular oxygen or hydrogen peroxide as the main oxidant and the catalyst that can be recycled.The significant advantage of this method is that the main by-product is water,thus avoiding the production of high organic residues.The development of a bifunctional catalyst for the oxidation of aromatic alcohol will be more beneficial from the requirements and significance of acid and oxidation reactions.In recent years,polyoxometalates（POMs）as economic and environmentally friendly catalysts have attracted wide attention due to their unique acidity,solubility and oxidation,as well as their many advantages compared with traditional catalysts.Based on this,the paper designs polyoxometallate catalyst with acidic and strong redox properties was synthesized and used to catalyze the oxidation of aromatic alcohol in O₂ system to explore its catalytic activity.The main research work is as follows:1.The H₅PMo₁₀V₂O₄₀（HPMoV₂）catalyst with strong oxidizing activity was synthesized and characterized by infrared spectroscopy（IR）,ultraviolet-visible spectroscopy（UV-Vis）and X-ray diffraction powder（XRD）.HPMoV₂ was used as catalyst in oxidation and acidizing reaction with oxygen as oxidant and phenylbutanol as substrate,which showed high activity and selectivity.The effects of acid amount,reaction temperature,reaction time and amount of catalyst on the reaction were also investigated.The optimum reaction conditions are:24 mg phenylbutanol,the catalyst dosage is 0.056 mmol,the oxygen pressure is 1.0 MPa,and the conversion of phenylbutanol can reach 96%after the reaction at 120°C for 8 h,and the yield of phenylbutyric acid can reach 33%.2.A series of HPMoV₂/H₂TPP(H₂TPP=C₄₄N₄H₃₀)complexes with catalytic oxidation properties were synthesized by using polyoxometalate HPMoV₂ as precursor and applied to the oxidation of aromatic alcohol with oxygen.The reaction conditions were optimized by controlling the reaction temperature,reaction time,oxygen intake,different molar ratios of catalysts and catalyst dosage.The experimental results show that the conversion of phenylbutanol can reach 89%and the yield of phenylbutyric acid is 45%under the condition of 0.020 mmol[HPMoV₂][H₂TPP]catalyst and 100 ^oC for 7 h in the oxidation of phenylbutanol by O₂.Compared with the pure polyoxometalate,the improved selectivity is due to the increase of the oxidation ability of the catalyst supported on porphyrin.[HPMoV₂][H₂TPP]shows heterogeneous characteristics and is easy to be separated and reused after reaction.After six times of reuse,it still shows good catalytic activity.3.A series of POM-based ionic liquid catalysts Ch_xH_5-xPMo₁₀V₂O₄₀（x=1,2,3,4,5,Ch=（CH3）3NCH2CH2OH）were prepared by the reaction of choline chloride with polyoxometalate HPMoV₂.Catalytic oxidation of phenylbutanol with Ch_xH_5-xPMo₁₀V₂O₄₀(Ch_xH_5-xPMoV₂)as catalyst,it was found that it exhibited good activity and selectivity in the oxidation of phenylbutanol,and it can directly oxidize aromatic alcohol to carboxylic acid,which has great practical value.The optimum reaction conditions were determined by optimizing the different ratios of catalysts,catalyst dosage,reaction time and temperature.The results showed that the best oxidation effect was obtained by using ChH4PMoV2 as a heterogeneous catalyst under the conditions of 90 ^oC,6 h,6 mL n-hexane,24 mg phenylbutanol,0.018 mmol catalyst,among which the conversion of phenylbutanol is 89%and the yield of phenylbutyric acid can reach 33.8%,the catalyst exhibits heterogeneous characteristics,is easy to recycle,and can be recycled.During the recycling process,the activity of the catalyst remained good and had good stability.