Abstract An efficient and simple method was proposed to synthesize hierarchical and phosphorous-modified HZSM-5 zeolites by sequential alkaline and acid treatment. In the first NaOH alkaline treatment, intracrystalline mesoporosity was introduced into the zeolites by the crystal defect formation and growth of crystal defects due to desilication. The excessive defect growth caused amorphization of the zeolites, dramatically decreasing their surface area and micropore volume. The aluminum-related debris resulting from the desilication deposited on the extra-framework positions and had a dramatic influence on the crystallinity and microporosity of the zeolites. In the subsequent H3PO4 treatment for the alkaline-treated HZSM-5, the deposited extra-framework aluminum species were selectively removed, thus increasing the micropore volume and surface area of the zeolites. Along with the dealumination, the phosphorous species were introduced into the framework to occupy the silicon sites, leading to a crystalline structure repair. The post-treatments could modify the structural and acidic properties of the HZSM-5 zeolite. Catalytic tests showed that the hierarchical and phosphorous-modified HZSM-5 zeolite exhibited higher methanol conversion and propylene selectivity in methanol-to-olefins reactions over a longer period compared with the parent HZSM-5.

中文翻译：

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通过连续碱/酸处理开发分级和磷改性 HZSM-5 沸石及其对甲醇制烯烃的催化性能

摘要 提出了一种高效、简便的方法，通过连续碱酸处理合成多级磷改性HZSM-5沸石。在第一次 NaOH 碱处理中，由于脱硅作用导致晶体缺陷的形成和晶体缺陷的生长，晶内介孔被引入到沸石中。过度的缺陷生长导致沸石的非晶化，显着降低其表面积和微孔体积。脱硅产生的铝相关碎屑沉积在骨架外位置，对沸石的结晶度和微孔率产生显着影响。在碱处理的 HZSM-5 的后续 H3PO4 处理中，沉积的框架外铝物种被选择性去除，从而增加沸石的微孔体积和表面积。随着脱铝，磷物质被引入框架以占据硅位点，导致晶体结构修复。后处理可以改变 HZSM-5 沸石的结构和酸性性质。催化试验表明，与母体 HZSM-5 相比，分级和磷改性的 HZSM-5 沸石在更长的时间内在甲醇到烯烃的反应中表现出更高的甲醇转化率和丙烯选择性。