Effect of alumina binder on catalytic performance of PtSnNa/ZSM-5 catalyst for propane dehydrogenation

The influence of alumina binder on the catalytic performance of PtSnNa/ZSM-5 catalyst for propane dehydrogenation was studied. Solid-state Al-27 MAS NMR spectroscopy, temperature-programmed desorption of ammonia (TPDA), temperature-programmed oxidation (TPO), catalytic grain intensity, hydrogen chemisorption, BET surface area, and pore size distribution measurements were used to characterize the catalysts. It was found that the addition of binder results in a decrease in the surface area of the catalyst but an obvious improvement in its particle intensity. Some soluble Al species from the binder might migrate into the ZSM-5 zeolite framework during calcination so as to produce some acid sites of moderate intensity, which consequently increases the acid amount of the catalyst. When propane dehydrogenation is carried out under the same space velocity by changing the weight of the corresponding catalyst, the acid amount is the dominant factor influencing the catalytic properties. When this reaction is performed under the same catalyst weight, a small amount of binder is seen to have a positive effect, increasing the catalytic activity as a result of the enhanced metal dispersion and acid amount. However, a negative effect is observed when the binder amount continues to increase. The function of stabilizing the tin species can be strengthened by alumina addition, which might facilitate the transport of the carbon deposits from the active sites to the carrier. TPO profiles of the corresponding catalysts under different reaction conditions represent dissimilar behaviors, which is attributed to an increase in acid amount and change in metal dispersion in the presence of binder. Finally, a model for the influence of the alumina binder on the catalytic performance of PtSnNa/ZSM-5 catalyst for propane dehydrogenation is proposed.