Side-chain alkylation of toluene with methanol is a potential route for producing styrene. However, there are several challenges that prevent its industrialization, comprising the decomposition of methanol to CO and H 2 , and unavoidable by-products of ethylbenzene. Herein, we disclose that X zeolite after ion exchange of ammonium have an interesting and unexpected feature. It can modulate the Lewis acid-base pairs, via in situ ammonia production from ammonia pools, meanwhile, lead to more Cs + species left in the zeolite, thereby constructing a superior catalyst for toluene side-chain alkylation. Especially for CsX-ex-AP catalyst, the ammonia pools effect (APE) in CsX-ex can achieve both higher toluene conversion and styrene selectivity. Furthermore, the methanol utilization efficiency increases significantly after APE reduction, indicating the selective catalysis for non-oxidative methanol dehydrogenation by in situ NH 3 production from ammonia pools. In addition, the APE reduction contributes to the formation of the active intermediates of m -HCOO* species, which is another reason responsible for the superior performance.
Ultra-deep desulfurization for the generation of clean petrol, diesel, and benzene remains a significant and challenging goal globally. Cu-containing materials have emerged as a promising desulfurization strategy due to their high adsorption capabilities. However, existing reduction technologies often lead to over-reduction. In this study, we reveal an intriguing and unexpected property of Y zeolite following ammonium ion exchange. The in situ generation of ammonia from ammonia pools may alter the location of copper species and modify their acid characteristics. We encapsulated various amounts of Cu into CuY zeolite, labelled as H-Cu X -Y(APE), using a facile self-reduction strategy. Notably, H-Cu 5.71 -Y(APE) exhibits an exceptional breakthrough sulfur capacity for thiophene, achieving 4.17 mg/g, nearly double that of traditional Cu-HY(H 2 ). XPS analysis following APE reduction indicates a high proportion of Cu + species in H-Cu 5.71 -Y(APE). In situ calcination FT-IR provided detailed insights into the chemical transformation of Cu 2+ species during APE reduction. Furthermore, CO-FTIR analysis shows that the Cu + content in the supercages of H-Cu 5.71 -Y(APE) reaches a maximum of 62.3 %. Py-FT-IR reveals the strong Brønsted acid content in H-Cu X -Y(APE) significantly increases. The desulfurization mechanism of H-Cu X -Y(APE) was thoroughly investigated using in situ FT-IR, demonstrating that the protonation and copolymerization of thiophene occurred on HCuY(APE) and could be effectively suppressed by adjusting the amount of copper. This work presents a promising solution for efficient ultra-deep desulfurization using an in situ NH 3 reduction method from ammonia pools.
Reduction process is a key step to fabricate metal-zeolite catalysts in catalytic synthesis. However, because of the strong interaction force, metal oxides in zeolites are very difficult to be reduced. Existing reduction technologies are always energy-intensive, and inevitably cause the agglomeration of metallic particles in metal-zeolite catalysts or destroy zeolite structure in severe cases. Herein, we disclose that zeolites after ion exchange of ammonium have an interesting and unexpected self-reducing feature. It can accurately control the reduction of metal-zeolite catalysts, via in situ ammonia production from ‘ammonia pools’, meanwhile, restrains the growth of the size of metals. Such new and reliable ammonia pool effect is not influenced by topological structures of zeolites, and works well on reducible metals. The ammonia pool effect is ultimately attributed to an atmosphere-confined self-regulation mechanism. This methodology will significantly promote the fabrication for metal-zeolite catalysts, and further facilitate design and development of low-cost and high-activity catalysts.
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