Hydroxylation Of Benzene To Phenol Catalytic By Heteropoly Acid (Heteropolyacid Salts)

Phenol commonly known as carbolic acid, is a kind of important organic chemical intermediates, it was used in the manufacture of phenolic resin and bisphenol A and caprolactam etc, in addition, it was important in some aspects, for example synthetic fiber, pesticide, medicine, spices and dyes. It’s dilute solution can be directly used as a preservative and disinfectan.Before the first war, phenol is mainly extracted from coal tar. With the increase of market requirement of phenol, it was produced by chemical method and the methods mainly includes benzene sulfonic acid salt melting method、chlorobenzene、toluene oxidation 、 cumene peroxidation and one-step hydroxylation of benzene. Cumene peroxidation was the main method, which limited by multi- step process、complicated procedure and serious environmental polution. So the one-step direct hydroxylation of benzene,which with the characteristics of simple process, high yield, high selectivity, mild reaction condition, less environment pollution etc,has drawn wide attention of many researchers, with the deepening of the concept of green chemistry.Seeking high activity and economy catalyst is the key for one-step direct hydroxylation of benzene, in recent years, direct hydroxylation of benzene has recived varying degrees of progress under the effect of catalysts such as some oxide(especially the vanadium oxide), molecular sieve, heteropoly acid. Heteropoly acid catalysts have caught much attention for it’s environmentally friendly, high catalytic activity, noncorrosive to equipment, high selectivity, reusable etc, especially vanadium heteropoly acid as a series of new type and high efficient oxidation catalyst is highly valued.A series of solid heteropoly acids and heteropoly acid salts were prepared by ether anti-extraction method and checked by XRD, FT-IR, SEM, TG and ICP-AES methods. The catalytic activity of these catalysts was evaluated in the hydroxylation of benzene to phenol with H2O2 as oxidant. The effects of various parameters on hydroxylation were also tested, which included reaction time, catalyst amount, reaction temperature, different solvents and reactants ratio. The main contributions of the thesis are as follows:1. A serials of heteropoly acids catalyst H3+nPMo12-nVnO40(n=0~5) were prepared by ether anti-extraction method and characterized by XRD, FT-IR, SEM and ICP-AES methods. It shows the catalysts still keep Keggin-structure without obviously change. The catalytic activity of these catalysts was evaluated in the hydroxylation of benzene to phenol with H2O2 as oxidant. The effects of various parameters on hydroxylation were also tested, which included reaction time, catalyst amount and reaction temperature. The yield of phenol could reach 31.0% at optimal reaction conditions.2. Heteropoly acid H7PMo8V4O40 with Keggin structure was prepared by ether anti-extraction method and then the cesium salts Cs4H3PMo8V4O40 were prepared. The cesium salts ware characterized by XRD FT-IR SEM and BET methods. The catalytic activity of these catalysts was evaluated in the hydroxylation of benzene to phenol with H2O2 as oxidant. The effects of various parameters on hydroxylation were also tested, which included reaction time, catalyst amount reaction temperature and reactants ratio.3. Heteropoly acids H5 Si Mo11V1O40 was prepared by ether anti-extraction method and then the cesium salts CsnH5-nSi Mo11VO40(n=1~5)were prepared and characterized by IR, XRD, SEM and BET methods. The catalytic activity of these catalysts was evaluated in the hydroxylation of benzene to phenol with H2O2 as oxidant. The effects of various parameters on hydroxylation were also tested, which included reaction time, catalyst amount, reaction temperature and reactants ratio. Cs H4 Si Mo11VO40 also has excellent stability in the hydroxylation of benzene, and the Keggin-type structure still retained after reused several times.4. Heteropoly acid H8P2Mo16V2O62 with Dawson structure was prepared by ether anti-extraction method and then Si O2-H8P2Mo16V2O62, triethylamine-H8P2Mo16V2O62 and the cesium salts CsnH8-nP2Mo16V2O62(n=1~5)were prepared. These cesium salts ware characterized by IR, XRD, SEM, BET and TG methods. The catalytic activity of these catalysts was evaluated in the hydroxylation of benzene to phenol with H2O2 as oxidant. The effects of various parameters on hydroxylation were also tested, which included reaction time, catalyst amount, reaction temperature, different solvents and reactants ratio. The yield of phenol could reach 31.0% at optimal reaction conditions. The salts also has excellent stability in the hydroxylation of benzene, and the Dawson-type structure still retained after reused several times.