摘要
A series of Cu-based catalysts were developed for alkylation of benzene with syngas. The catalyst samples were prepared by the impregnation method, and were characterized by XRD, XRF, NH3-TPD, and TEM and evaluated in a fixed bed reactor. The optimized reaction temperature of Cu/Al2O3/ZSM-5 catalyst was 350 ℃, while higher contents of copper were conducive to alkylation of benzene with syngas. The new medium strength acid centers in the catalyst created by Cu were beneficial to alkylation. Hydrogenation reaction of CO was executed on the metal centers without dissociation, Dimethyl ether(DME) was the major intermediate over Cu-based catalysts. Higher selectivity of methylation and lower selectivity of heavy aromatics were confirmed after the second metal(Zn, Mn, or V) was added to the copper catalyst. Cu was partly covered by Zn in the Cu-Zn/Al2O3/ZSM-5 catalyst leading to low dispersion and low activity of copper. Cu-Mn/Al2O3/ZSM-5 catalyst possessed the best yield of methylation product. Cu-Mn composite oxides were probably formed in fresh catalyst, which blocked the sintering of Cu in the reaction process. The loading of Cu decreased dramatically after the introduction of V, while causing an increase of the amount of medium strength acid centers at the same time. V prevented the sintering of copper particles during the reducing process and had a promoting effect on the activity of Cu.
A series of Cu-based catalysts were developed for alkylation of benzene with syngas. The catalyst samples wereprepared by the impregnation method, and were characterized by XRD, XRF, NH3-TPD, and TEM and evaluated in a fixedbed reactor. The optimized reaction temperature of Cu/Al2O3/ZSM-5 catalyst was 350 ℃, while higher contents of copperwere conducive to alkylation of benzene with syngas. The new medium strength acid centers in the catalyst created byCu were beneficial to alkylation. Hydrogenation reaction of CO was executed on the metal centers without dissociation,Dimethyl ether （DME） was the major intermediate over Cu-based catalysts. Higher selectivity of methylation and lowerselectivity of heavy aromatics were confirmed after the second metal （Zn, Mn, or V） was added to the copper catalyst. Cuwas partly covered by Zn in the Cu-Zn/Al2O3/ZSM-5 catalyst leading to low dispersion and low activity of copper. Cu-Mn/Al2O3/ZSM-5 catalyst possessed the best yield of methylation product. Cu-Mn composite oxides were probably formed infresh catalyst, which blocked the sintering of Cu in the reaction process. The loading of Cu decreased dramatically after theintroduction of V, while causing an increase of the amount of medium strength acid centers at the same time. V preventedthe sintering of copper particles during the reducing process and had a promoting effect on the activity of Cu.
