The Alkenylation Of P-xylene With Phenylacetylene Via A Novel Solid Acid Catalyst

The alkenylated arenes are a kind of important fine chemical intermediate, and the alkenylation of arenes with alkynes is a simple and green pathway to synthesize desired products with the high atom economy. Although the liquid acids have been exploited in the alkenylation, many problems still exist,such as the corrosion of equipments, serious pollution, low catalytic efficiency, not satisfied yield, the obvious limited scope of substrates, complexity in the isolation and cyclic utilization. It is of important academic significance and realistic value to study the eco-friendly solid acids. In this paper, the alkenylation of p-xylene with phenylacetylene as model reaction to cleanly synthesize alkenylated arenes in the presence of a novel solid acid catalyst in a fixed bed reactor is studied in detail. The characterization techniques of GC, GC/MS, HNMR are adopted to analyze the products formed in the reaction, the results demonstrate that the produced compound is the desired product1-phenyl-1-(p-xylyl)ethane. The effect of phosphotungstic acid (PTA) loading, calcination temperature (Tc) in the process of catalyst preparation and reaction parameters on the alkenylation is studied.The results show that the solid acid H3PW12O40/MCM-4I with an intermediate H3PW12O40content (25wt.%) by adopting the method of incipient wetness impregnation technique in a vacuum has a satisfactory catalytic activity. At the same time, it is found that the calcination temperature has a significant influence on the reaction and the proper calcination temperature is300℃.The desired product1-phenyl-l-(p-xylyl)ethane is selectively (90%selectivity) obtained with an almost full conversion (99%) under the optimum reaction conditions, i.e. reaction temperature150℃, system pressure1.0MPa, volume hourly space velocity (VHSV)6ml-h-1·g-1cat., the byproducts mainly focus on the oligomers with a small amount of acetophenone and hydrogenated products. Besides, in comparison with Y-type zeolite HSZ-360, the H3PW12O40/MCM-41samples exhibit absolutely higher catalytic activity in the fixed bed reactor system and nearly eliminate the produce of acetophenone with a bright prospect. By the use of XRD, NH3-TPD techniques to characterize the catalyst, it’s found that the loading of H3PW12O40and calcination temperature have a remarkable impact on the nature of acidic centers and the dispersity of H3PW12O40and the proper acidic sites and larger pores can boost the process of alkenylation.