甲醛对HZSM-5分子筛催化甲苯和苯转化反应积炭失活的影响OA

Methanol-to-hydrocarbons(MTH)reaction serves as a"bridge"connecting coal chemical industry with petrochemical and natural gas chemical industries.HZSM-5 zeolite exhibits excellent catalytic performance in MTH reaction due to its unique pore structure and moderate to strong acidity.Formaldehyde can accelerate the MTH reaction process via the Prins reaction and also promote the cross-linking and condensation of poly-methyl benzenes to form polyaromatic hydrocarbons(PAH).However,the mechanism has not been thoroughly investigated.By designing a co-feeding experiment of toluene,benzene with formaldehyde on HZSM-5 zeolite,respectively,with combining gas chromatography-mass spectrometry and TGA,it is found that the key intermediate in the co-transformation of toluene and formaldehyde is diphenylmethane,which reveals the key interaction pathway between formaldehyde and toluene:Toluene and formaldehyde react at acid sites to form benzyl alcohol derivatives,which then dehydrate to form diphenylmethane.Diphenylmethane can not only accelerate the toluene conversion process but also act as a"bridge molecule"to significantly promote the cross-linking reaction of toluene.