负载铂催化剂中沸石载体酸性对甲烷两步转化的影响

The platinum catalysts supported on two series of supports (NaY, HNaY, HY and NaBeta, HBeta) were prepared to study the influence of electronic properties of platinum particles on two-step, isothermal conversion of methane to higher hydrocarbons after correcting the effect of particle size. The activity of catalysts, that is, the total amount of methane converted to C2+ hydrocarbons and the distribution of C2～C6 products were investigated in the catalytic reaction for methane conversion over platinum catalysts supported on Y and Beta zeolites with different acidity. The results showed that the activity of catalyst increased with increasing support acidity and the selectivity to C2～C6 products varied with support acidity. Moreover, the distribution and reactivity of surface carbonaceous species (CHx) chemisorbed on the catalysts, generating from the methane decomposition at first step were characterized by temperature-programmed hydrogenation (TPH). The total amounts of CHx (Cα+Cβ) and the Cα species, most of which is known to give C2+ hydrocarbons on hydrogenation and which is main resource of C2+ hydrocarbon products increased when the acidity of support increased; The reactivity of surface carbon was enhanced on acidic support compared to neutral support. The changes of catalytic properties are due to electron deficient nature of platinum particles on acidic support from the interaction of metal and support.