Direct Synthesis Of Pyridine And Phenol From Benzene Under Low Temperature Discharge

Pyridine and phenol are very important chemical raw materials and organic synthetic intermediates,widely used in medicine,pesticides,plastics,dyes,synthetic resin and other fields,in addition to being used as solvents,reagents and disinfectants.Originally,pyridine and phenol were extracted from coal tar.With the continuous development of science and technology,pyridine and phenol are more and more widely used,while the traditional pyridine and phenol from natural products are gradually replaced by synthetic methods due to their low yield and many impurities.Among the currently developed synthesis methods of pyridine and phenol,the aldehyde ammonia condensation method and cumene process are the most important industrial processes for the production of pyridine and phenol,respectively.However,the production of pyridine and phenol still can't meet the market demand due to the cumbersome process equipment,harsh reaction conditions,severe environmental pollution and low yield of the products.In addition,there are few reports on the direct production of pyridine from benzene.Although the direct oxidation of benzene to phenol is a simple process,friendly environmentally and broad application prospect,most reports use precious metals as catalysts,with high reaction cost and low phenol yield,which is not conducive to industrial mass production.In order to overcome these challenges,in this thesis,the following works were mainly carried out as described below:First of all,the paper spray ionization mass spectrometry technique was used to investigate the factors and process of direct production of pyridine from benzene.The technology uses the inexpensive filter paper as a substrate,and uses mass spectrometer to perform real-time on-line detection of the reaction process and products,and pyridine can be obtained under the discharge of the paper tip.Since the structure of the benzene ring is very stable and it is difficult to be ionized,the exp eriment was carried out by mixing benzene with an easily ionizable solvent during the experiment.The result showed that the generated pyridine increased first and then decreased with the increase of spray solvent polarity,methanol content in benzene,transfer tube temperature and spray voltage.It is found that pyridine is easier to be obtained when methanol,a polar solvent,is used as the spray solvent When the ratio of raw material benzene to spray solvent methanol was 7:3,the transmission tube temperature was 270 ?,and the spray voltage was 4.5 kV,the formation of pyridine was most favorable.The yield and selectivity of phenol from benzene through dielectric barrier discharge plasma were investigated.During the experiment,a dielectric barrier discharge plasma device was designed and constructed,which was applied to the direct oxidation of benzene to phenol.Finally,the product was qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry.The result showed that the yield of phenol increased first and then decreased with the increase of plasma radiation time,plasma discharge distance and plasma discharge power.It was found that under the conditions of the distance between the electrode and the reaction solution being 2 cm,the plasma radiation time being 150 min,and the discharge power being 10W,when the electrode was coated with silica,the phenol yield reached the maximum 19.5%,and the selectivity was 83%.