Positive Role of Synthesis Method and Hard Template on the Catalytic Performance of SAPO-34 in Methanol to Olefin Reaction.

In the present study, SAPO-34 particles were synthesized using hydrothermal (HT) and dry gel (DG) conversion methods in the presence of diethyl amine (DEA) as an organic structure directing agent (SDA). Carbon nanotubes (CNT) were used as a hard template in the synthesis procedure to introduce transport pores into the structures of the synthesized samples. The synthesized samples were characterized with different methods to reveal the effects of synthesis method and using hard template on their structure and catalytic performance in methanol to olefin reaction (MTO). DG conversion method results in smaller particle size in comparison with hydrothermal method, resulting in enhancing catalytic performance. On the other side, using CNT in the synthesis procedure with DG method results in more reduction in particle size and formation of hierarchical structure, which drastically improves catalytic performance.

Synthesis of hierarchal SAPO-34 nano catalyst with dry gel conversion method in the presence of carbon nanotubes as a hard template.

In this study, the silicoaluminophosphate (SAPO) particles were synthesized based on dry gel conversion method using diethyl amine (DEA) as an organic structure directing agent (SDA). Transport pores were introduced into the crystalline structure of the catalyst using carbon nanotubes (CNT) as a hard template. The significance of molar ratio of CNT in the starting gel and the other synthesis parameters such as crystallization time, gel drying temperature and water content added in the crystallization stage, on crystallinity of SAPO-34, crystal phase, particle size and morphology were studied. The products were characterized by XRD, SEM, TEM, BET and EDX. D-optimal experimental design with four numeric factors including gel drying temperature, crystallization time, water/dry gel mass ratio and mole of CNT in the precursor gel each at three levels was implemented to optimize the experimental parameters by analysis of variance (ANOVA). The Fischer test results showed that, all the parameters have significant effect on the crystallinity of the synthesized samples.