Tuning the catalytic performance of Rh/FePO4 catalyst by reduction temperature for quinoline selective hydrogenation
1,2,3,4-tetrahydroquinoline derived from selective hydrogenation of quinoline has vital applications in the fields of pharmaceutical,alkaloid,agrochemical and so on,where tuning the interaction between quinoline molecules and active sites plays an important role in improving the catalytic performance.Herein,the effect of reduction temperature was explored with Rh/FePO4 catalyst employed for the hydrogenation of quinoline.The results showed that the hydrogenation performance decreased along with increasing the reduction temperature,in which the catalyst reduced at 75℃gave the best performance,yielding 98.5%conversion and＞99%selectivity of 1,2,3,4-tetrahydroquinoline,as well as high reaction rate of 353mol/(mol·h).Various characterizations indicated that the catalyst structure changed from FePO4 to amorphous crystal and Fe2P2O7 phase at increased reduction temperature.Meanwhile,the high reduction temperature led to more metallic Rh species and the absent of acidic sites.Combining with the experimental results,we demonstrated that the decline in catalyst performance at high temperature is due to the formation of more metallic Rh species,which strongly coordinated with quinoline molecule and poisoned the active sites.And the catalyst reduced at a low temperature of 50℃cannot form the metallic Rh species.Comparatively,the catalyst reduced at 75℃had the suitable electronic property and acidic sites,both of which promoted the hydrogenation of quinoline under mild conditions.
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