Research on double template agents to regulate the grain growth behavior of SAPO-34

The effects of different template ratios on the physicochemical properties of SAPO-34 molecular sieve and the catalytic performance of methanol to olefin (MTO) were investigated using tetraethylammonium hydroxide (TEAOH) and morpholine (Mor) as mixed templates. It was found that when the amount of Mor was more, the grains were smooth and regular cubes, and the acidity was stronger, and the mesoporous content was more. With the increase of TEAOH, the grain surface gradually changed into a multi-grain stacking structure, the acidity decreased slightly, and the large-sized mesopores slowly disappeared, replaced by small-sized mesopores with a diameter of 3-4 nm. It can be seen from the MTO reaction that the molecular sieve with stronger acidity de-activates faster, and the mesoporous size is too large to affect the shape-selective catalytic ability of the catalyst, which is not conducive to the formation of light olefins. Combined with the reaction and characterization, when the template ratio R = 4, the acidity distribution in the molecular sieve is moderate, and the average pore size is small, which improves the selectivity of low olefins.