Research For Benzylation Of Benzene With Benzyl Chloride On Fe-Based Catalyst

Benzylation of benzene with benzyl chloride is a very important reaction commonly used in organic chemistry. It is an important method for the preparation of alkyl substituted benzene, and the product of this reaction is diphenylmethane which is important high-value-added products or intermediates widely used in medical, dye and plastics industries. The benzylation of benzene is still challenge in organic synthesis because benzene lacks electron-donating group for activating aromatic ring, and the key for achieving this process is the use of efficient catalysts. However, due to some defect, such as, low efficiency, difficult recovery, pollution and corrosion ect, catalysts used in industry are no longer meet the requirements of "green synthetic chemistry". Therefore, the exploration of new catalysts and structure-activity relationships of the catalysts are of great significance.In this thesis, the catalytic performance and structure-activity relationships of FeOx/HZMS-5 (SiO/Al2O3=25) and Fe-P-0 catalysts were evaluated by the benzylation of benzene with benzyl chloride.(1) First, variety of carriers and load components were combined by the method of impregnation and ion exchange. Catalyst performance was evalued under the same conditions, and the results showed that activity of the FeOx/HZMS-5 (SiO2/Al2O3=25, Fe loaded was 2.5 wt%) catalyst was the best. Then, reaction conditions of this catalyst were optimized, and the results showed that:increasing the load of Fe on the catalyst, higher temperature, longer reaction time and an appropriate increase in the rate of benzene/benzyl chloride ratio helped to improve the conversion of benzyl chloride and the yield of diphenyl methane. The kinetic data for the reaction over this catalyst could be fitted well to a pseudo-first-order rate law. Finally, characterization results of the catalyst showed that activities of catalyst were closely related with the separated Fe3+ on the catalyst. Increasing the amount of Fe3+ helped to improve the conversion rate, and a small amount of nano-Fe2O3 on the catalyst helped to activate benzene. Activity, especially reusability of FeOx/HZMS-5 (SiO2/Al2O3=25) zeolite catalyst were to be further improved, thus, benzylation of benzene with benzyl chloride on the Fe-P-O catalysts was studied.(2) First, Fe-P-0 catalysts were prepared by mixture wetness method, and evaluated the effects of reaction conditions on activities of the catalysts. Evaluation results of the catalysts showed that Fe-P-O were excellent catalysts for benzylation of benzene with benzyl chloride. Conversions of benzyl chloride were all above 99% and the selectivities to diphenyl methane were all 100% on those catalysts (Fe/P mole rate is 1:1-1:0.12). Since the reaction rate was too fast, the time required for achieving the same conversion rate (>99%) with different catalysts was the standard for comparing the differences among catalyst's performances. Catalyst (mole rate of Fe/P is 1:0.25) was prepared by mixture wetness method, the whole reaction needed 20 min under the conditions of 60℃, molar ratio of benzene/benzyl chloride=14.4:1 and 0.2 g catalyst.In addiion, a series of characterizations were performanced, and the effects of properties and structures of the catalysts on their catalytic activities were studied. Characterization results of the catalysts showed that these catalysts showed different properties and reactivity as a function of P/Fe ratio in these catalyst. The obtained catalyst (Fe/P=l:0.25) had high reactivity and good reusability, which most reported catalysts could not achieved. P/Fe ratio modified the properties of these catalysts, which affected the reactivity of these catalysts. The interaction of Fe(PO3)2 and Fe2O3 occured in these catalysts, including the changes of the Lewis acidity and the electron transfer. The medium Lewis acid sites were closely relative to the reactivity of these catalysts in the benzylation of benzene with benzyl chloride. The high concentration of Lewis acid sites favored the benzylation of benzene with benzyl chloride on the Fe-P-O catalysts.These studies may provide theoretical guidance for the preparing modified zeolite catalysts and Fe-P-0 catalyst, and also have important reference values for exploring of the structure-activity relationships of catalysts with iron species, applying Fe-P-O catalyst and developing of new catalyst for benzylation of benzene with benzyl chlonde...