Direct alkenylation of aromatics with phenylacetylene over supported H _3PW _(12)O _(40) catalysts as a clean and highly efficient approach to producing α-arylstyrenes

摘要

Phosphotungstic acid (PTA) catalysts supported on MCM-41 prepared via a wet impregnation method assisted by vacuum with heating (IMPVH) were first employed for direct alkenylation of different aromatics with phenylacetylene to synthesize α-arylstyrenes. N _2 adsorption-desorption, FT-IR, X-ray diffraction (XRD), and NH _3 temperature-programmed desorption (NH _3 TPD) characterization techniques were used to reveal the relationship between the catalyst's nature and properties. The results demonstrate that the fabricated 25 wt.% PTA/MCM-41 catalyst exhibits outstanding catalytic performance, remarkably better than that on HY zeolite. It is also found that the catalytic properties of the catalysts are strongly dependent on PTA dispersity, the nature of the acid sites, the preservability of PTA Keggin structure, and the mesopore architecture, notably affected by PTA loading and calcination temperature. The results for catalytic stability illustrate that more than 99% of maximum conversion can be obtained, and more than 92% conversion can be maintained for up to 540 min time on stream. We find that the decrease in catalytic activity, along with the long reaction time, is mainly ascribable to deactivation by coke deposition. The spent catalyst can be refreshed, and 97.1% conversion can be obtained over the regenerated catalyst. This approach is also highly efficient for extra-substituted benzene, polycyclic aromatics, and even heteroaromatics, suggesting that the method presented in this paper can be a green and highly efficient synthesis protocol for α-arylstyrenes.