Silicoaluminophosphate with AEI structure has been modified by silica coating using polydimethylsiloxane (PDMS) and tetraethoxysilane (TEOS) as silica sources. The single step procedure including deposition of 0.5, 1.0, 1.5 and 2.0 wt.% of silicon in one step and the multistep procedure including stepwise deposition of silica source by small portions corresponding to 0.5 wt.% of silicon with intermediate calcination steps have been applied. The modified materials have been characterized by X-ray fluorescence spectroscopy, X-ray diffraction analysis, low temperature nitrogen adsorption, ²⁹Si MAS NMR, thermoprogrammed desorption of ammonia and FTIR spectroscopy of adsorbed 2,6-ditertbutylpyridine (2,6-DTBPy). The results show that multistep procedure leads to the gradual increase of silicon content and results in the deposition of 2 wt.% of Si in 4 steps, whereas single step procedure does not lead to the desired result. Coating with silicon leads to poisoning of Brønsted acid sites located on the external surface of SAPO-18 crystal. This effect is more pronounced in the case of PDMS due to more uniform silica deposition in this case. Coated materials show higher stability of catalytic activity with time on stream in methanol to olefins conversion (MTO) and higher selectivity to light olefins. The mechanism of silica coating with PDMS and TEOS is discussed.

具有AEI结构的硅铝磷酸盐已通过使用聚二甲基硅氧烷（PDMS）和四乙氧基硅烷（TEOS）作为二氧化硅源的二氧化硅涂层进行了改性。已经应用了包括一步沉积0.5％，1.0％，1.5％和2.0％重量的硅的单步程序和包括通过中间煅烧步骤按相当于0.5wt％的硅的小部分逐步沉积二氧化硅源的多步程序。 。通过X射线荧光光谱，X射线衍射分析，低温氮吸附对改性材料进行了表征²⁹Si MAS NMR，氨的热程序解吸和吸​​附的2,6-二叔丁基吡啶（2,6-DTBPy）的FTIR光谱。结果表明，多步法导致硅含量的逐渐增加，并导致在4步中沉积2 wt％的Si，而单步法则无法获得所需的结果。硅涂层会导致位于SAPO-18晶体外表面的布朗斯台德酸性位中毒。由于在这种情况下更均匀的二氧化硅沉积，因此在PDMS情况下，这种效果更为明显。涂层材料在甲醇转化为烯烃的过程中，随着时间的流逝显示出更高的催化活性稳定性，并且对轻质烯烃的选择性更高。讨论了用PDMS和TEOS进行二氧化硅涂层的机理。