Low-silica RHO zeolites have been recognized as efficient catalysts for synthesizing industrial intermediates monomethylamine (MMA) and dimethylamine (DMA) through the reaction of methanol (MeOH) with ammonia. However, they typically suffer from rapid deactivation. Herein, we report the synthesis of high-silica RHO zeolite with small crystal sizes (1–2 μm) via interzeolite conversion of SSZ-13, utilizing a reduced amount of organic structure-directing agent (OSDA) and without the use of fluoride. It was demonstrated that the double eight-membered rings of RHO zeolite can be formed using the single eight-membered ring of SSZ-13, resulting in a reduction of OSDA dosage by approximately 30% and Cs⁺ by about 38%. The resulting high-silica RHO zeolites exhibit an excellent methanol conversion of ∼93%, a high MMA and DMA yield of ∼90%, and good reaction durability under conditions more severe than those of industrial manufacture conditions, at 350 °C with a liquid hourly space velocity at 11.7 h⁻¹. Compared to directly synthesized high-silica RHO zeolites with larger crystal sizes (3–8 μm), interzeolite-converted high-silica RHO zeolites with smaller crystal sizes show a 10–16% higher yield of MMA and DMA. These findings highlight the significant potential of high-silica RHO zeolites for the industrial manufacturing of MMA and DMA.

中文翻译：

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无氟合成高硅RHO沸石用于高选择性合成甲胺


低硅RHO沸石被认为是通过甲醇（MeOH）与氨反应合成工业中间体一甲胺（MMA）和二甲胺（DMA）的有效催化剂。然而，它们通常会遭受快速失活的困扰。在此，我们报道了通过 SSZ-13 的沸石间转化合成了小晶体尺寸 (1-2 μm) 的高硅 RHO 沸石，使用减少量的有机结构导向剂 (OSDA)，并且不使用氟化物。结果表明，用SSZ-13的单八元环可以形成RHO沸石的双八元环，从而使OSDA用量减少约30%，Cs ⁺ 减少约30%。 38%。所得高硅 RHO 沸石表现出出色的甲醇转化率（约 93%）、高 MMA 和 DMA 产率（约 90%），以及在比工业制造条件更严酷的条件下（350 °C 液体）具有良好的反应耐久性。 11.7 h 时的每小时空速 ⁻¹ 。与直接合成的较大晶体尺寸（3-8μm）的高硅RHO沸石相比，分子筛间转化的具有较小晶体尺寸的高硅RHO沸石的MMA和DMA产率高出10-16%。这些发现凸显了高硅 RHO 沸石在 MMA 和 DMA 工业制造中的巨大潜力。