Preparation Of Aryl Formaldehyde And Carbon Materials In Its Preparation

Aryl formaldehyde is an important chemical raw material and organic intermediate, which is extensively applied in food, medicine, cosmetic, perfumery, etc. However, the current synthetic methods of aryl formaldehyde in industry are mainly the halide hydrolysis of methyl arenes. These techniques not only contaminate the environment, but also limit their applications as aryl formaldehyde produced by these processes contains halides. In recent years, green catalytic processes of halide-free aryl formaldehyde have been paid increasing attention, and the dominating development trends as follows:preferred to the mild reaction conditions instead of demanding reaction conditions; turned to the catalytic means which have less pollutants; used the supported catalysts with the characteristics of easy separation and recycling; replaced the stoichiometric metal oxides such as chromates and manganese oxides with ozone, oxygen, hydrogen peroxide or air as the terminal oxidant. Therefore, the synthesis of arly formaldehyde was studied in this paper in light of the social needs and technological development.This thesis involves several aspects as follows:1. The current research status of benzaldehyde and the research advances of heteropoly acid were reviewed. Based on the above background, the chief research contents of this thesis were brought up.2. A series of catalysts, comprised of 16-43 wt.% phosphorus tungsten acid (PTA) supported on mesoporous carbons (MC), were prepared through classical backflow adsorption method and characterized by Fourier Transform Infrared Spectroscopy, X-Ray Diffraction, N2 Adsorption-desorption Isotherm Tests and Transmission Electron Microscope. The characterization data reveal that the retention of intact Keggin ion of PTA on the support, and PTA is located inside the mesopores of MC. The catalytic activities of these catalysts were tested for selective oxidation of benzyl alcohol. Under the optimal reaction conditions,82.6% conversion of benzyl alcohol and 94% selectivity of benzaldehyde were obtained after 3.5 hours using 5 mmol 30% hydrogen peroxide as the oxidant and 0.080 g 28% PTA/MC as catalyst. The catalyst could be recycled at least three times without obviously decrease in catalytic activity.3. Active carbon/H2O2/HNO3 system was applied in the selective oxidation of benzyl alcohol. Orthogonal experiment was designed to study the influence of reaction conditions such as the amounts of HNO3, H2O2, and reaction temperature. Under the optimal reaction conditions,94.2% conversion of benzyl alcohol and 81.4% yield of benzaldehyde were acquired within 5 hours at 100 ℃. In addition, the satisfied results of large scale experiment (enlarge 100 times) which benzyl alcohol was nearly consumed up within 1.5 h and the isolated yield of benzaldehyde was up to 81.2%, indicated that this system has benign catalytic activity for oxidation of benzyl alcohol.4.2,6-pyridine dicarbaldehyde was prepared through oxidation of 2,6-distyryl pyridine synthesized from the condensation of 2,6-dimethyl pyridine and benzaldehyde by ozone. Compared with the traditional routes, this process has the advantages of environmental friendly and simplicity.