Effect of Si/Al Ratio on Physicochemical Properties of Nanostructured LaAPSO-34 for Conversion of Methanol to Light Olefins

The Si/Al ratio is one of the effective parameters on the physicochemical properties of nanostructured LaAPSO-34 catalysts. Utilization of optimum ratio of Si/Al could significantly enhance the efficiency of these molecular sieves in the methanol to olefins conversion. To this aim, a series of nanostructured LaAPSO-34 catalysts with different Si/Al ratios were synthesized via hydrothermal method and characterized by XRD, FESEM, EDX, BET and FTIR techniques. XRD results showed that the growth of crystalline network is not considerable in the low Si/Al ratio, while the crystallinity has increased by increasing of this ratio. FESEM images revealed that by increasing Si/Al ratio, cube-shaped chabazite particles completely were formed. However, rough on the surface of the catalyst particles was observed in the high ratio of Si/Al. EDX analysis confirmed the presence of elements of this zeolite and also showed a uniform distribution of components. BET results showed that by increasing of Si/Al ratio from 0.1 to 0.3, specific surface area of the nanostructured LaAPSO-34 catalysts increased. FTIR spectrums confirmed framework vibrations of chabazite in different Si/Al ratios. Catalytic performance tests showed that by increasing of reaction temperature, methanol conversion increased. Increasing the Si/Al ratio from 0.1 to 0.3 led to the enhancement of the LaAPSO-34 performance and catalyst stability.