Study On Preparation Of Phosphotungstic Hrteropoly Acid Composite Catalytic And Its Application In Degradation Of Waste Mulberry Branches

Traditional liquid catalysts（H₂SO₄,H₃PO₄,HF,etc.）are often used as acid catalysts in the fields of petrochemical and chemical industry.Environmental pollution caused by strong acid corrosion of production equipment and waste acid liquid has caused people to pay attention to the research of environmentally friendly acid catalysts that replace traditional acids.The solid acid heteropoly acid has the advantages of strong acidity,oxidation-reduction properties,thermal stability,and low environmental pollution.The unique‘quasi-liquid phase’behavior is often used in the fields of environmental pollution treatment and chemical productio n.This article replaces sulfuric acid with solid acid heteropoly acid,introduces the synthesis of Tert-Butyl Hydroperoxide（TBHP）,and utilizes the resources to prepare the remaining phosphoric acid.The research of heteropoly acid compound acid degradation of waste mulberry branches to extract natural products is carried out to improve the acid catalytic performance,reducing traditional acid environment pollution,realizing reduced disposal and high value utilization of waste mulberry branches.In order to obtain solid phosphotungstic heteropoly acid（HPA）with increased specific surface area and reduced water solubility,sodium tungstate and phosphoric acid were used as raw materials to prepare HPA_CAA by one-step directcitric a cid（CA）modification.Using FTIR,XRD,SEM,BET to analyze the phase structure of HPA_CAA and detect water solubility.In order to verify the acid-catalytic per formance of HPA_CAA instead of sulfuric acid,HPA_CAA catalyzed the synthesis of T BHP and DTBP,and analyzed the influencing factors of HPA_CAA acid catalytic an d energy efficiency,the research of HPA_CAA and the remaining phosphoric acid compounded acid（compound acid）in the preparation process for acid hydrolysis of mulberry branch to extract isoquercetin was carried out,and the amount and reaction of compound acid were optimized by uniform design method.The appropriate parameters such as temperature,reaction time,and molar ratio of P were analyzed,and the interactions between the factors were analyzed tireveal the acid-catalyzed effect of compound acid catalyzed acid-catalyzed dissolution of mulberry isoquercetin,the kinetics and thermodynamics of isoquercitruin and compound acid hydrolysis to produce polysaccharides were obatined,and the rate constants k,Ea and other parameters were obtained,combined with FTIR,SEM and BET,the phase structure of the mulberry substrate and the change of the surface energy groups were analyzed;the particle diffusion of isoquercetin.The man results are as follows:（1）The yield of HPA_CAA modified by CA was 80.57%,and the water solubility was less than 0.01g·100g^-1,FTIR clearly shows the characteristic diffraction peaks of P-O,W-Oa-W,W-Ob-W and W=O of HPA;XRD shows that HPA_CAA has a keggin structure diffraction peak and was sharper;SEM showed thatc was a hexagonal cage with a smaller particle size;BET analysis showed that the specific surface area of HPA_CAA was 81.16m²·g^-1,which was 6.12%more than HPA.The acid activity sequence of catalyzed synthesis of TBHP is HPA_CA＞HPA＞H₂SO₄＞H Cl＞H₃PO₄.（2）Catalytic synthesis of TBHP by HPA_CAA instead of sulfuric acid shows th at:at a reaction temperature of 80℃,reaction time of 6 hours,the amount of HPA_CAA added is 20%of the mass of TBA,and the molar ratio of TBA to 30%of H₂O₂ is 1:2,3.0000g of TBA synthesized TBHP yield was 78.86%,which was21.13%higher than HPA;the yield of DTBP was 7.35%,which was 97.71%hi gher than HPA.The recovery rate of HPA_CAA after three times of use can reach41%,and the yields of TBHP and DTBP are only reduced by 4.01%and 0.21%,showing good acid catalysis,catalytic stability and water insolubility.（3）The catalytic activity of the complex acid in different organic solvents is propanol＞ethanol＞methanol,and the catalytic activity of the complex acid is significantly better than that of phosphoric acid in a 60%ethanol solution by volume.FTIR showed that it was beneficial to degrade mulberry plant tissues-COO-,C=C,CO.SEM showed that the mulberry branch substrate eroded degree and specific surface area were increased.Compared with HPA,it increased by 183.83%;the compound acid improved the ability of HPA to catalyze the degradation of mulberry plant tissue.（4）The optimum conditions of isoquercetin dissolving from waste mulberry branches by compound acid hydrolysis were as follows:the molar ratio of P was 0.42:1,the dosage of compound acid was 335.09mg,the reaction temperature was 165℃,the reaction time was 100min,the isoquercetin dissolving from 0.5000g mulberry branches was 5.962mg·g^-1,and the yield of polysaccharide was 0.430g·g^-1,which was 3.17 times and 12.3 times of that without compound acid.The fitting model R²=0.989,F=44.394＞F（4,2）=19.3,the model is available,the reaction time and temperature have significant effect on isoquercetin dissolution.（5）Compound acid hydrolysis of polysaccharides from mulberry conforms to the first-order kinetic model,and the hydrolysis rate constant K increases with increasing reaction temperature.Compound acid hydrolysis of isoquercetin is a spontaneous endothermic process of temperature rise,which meets Fick’s second The first-order kinetic model of the law,the leaching rate constant K_b increases as the reaction temperature increases.Thermodynamics showed that the dissolution of isoquercetin was a spontaneous endothermic process at elevated temperature;the index model calculated that the isoquercetin raffinate ratio was 10.62%at 165℃,and the dissolution rate constant K_C increased with increasing temperature,second to Fick The laws agree.The internal diffusion of isoquercetin is divided into a rapid dissolution stage and an equilibrium stage,and the diffusion rate constant K_t becomes smaller as the thickness of the boundary layer increases.