Design Of Pr-SO₃H-PMO/H₃PW₁₂O₄₀ Composite Catalysts And Their Acid Catalytic Performance

Acid-catalyzed reaction is one of the most important reactions in catalytic chemistry. At present, carbon-carbon coupling reaction and transesterification reaction have attracted widespread attention due to their functionality in fundamental research and application-oriented demands. Among them, the carbon-carbon coupling reaction has developed into an indispensable method for the form of the carbon-carbon bond. And its coupling products are extensively used in the fields of organic chemistry, polymer chemistry, and among others. Biodiesel is a kind of economical and sustainable energy. To date, transesterification become important methods for the production of biodiesel. This paper is dedicated to design and prepare a series of mesoporous pr-SO₃H-PMO, PW₁₂/PMO and pr-SO₃H-PMO/H₃PW₁₂O₄₀ composite catalysts. Those heterogeneous catalysts were studied in acid catalytic performance and the concrete research contents are as follows.1. One-pot hydrolysis and co-condensation method for the preparation of ordered periodic mesoporous ethylenesilica functionalized in-situ with sulfonic groups was successfully developed. The functionalized composition and structure of as synthesized pr-SO₃H–PMO material was characterized by FT-IR, Low angle XRD, Nitrogen gas porosimetry measurement, TEM and XPS to confirm the structure integrities and investigate the morphology and surface textural properties of the composite catalysts. These materials were subsequently utilized as catalysts in the reaction of carbon-carbon coupling of α-nitro ketenedithioacetals and benzhydrol under mild reaction conditions. Finally, the reusability of the catalysts was evaluated over three catalytic runs.2. A series of mesostructured H₃PW₁₂O₄₀/PMO materials with different phosphotungstic acid loading amount（10.07%-33.36%） were developed by one-step co-condensation technique combined with hydrothermal treatment. The composition, structure, surface morphology characterization and physicochemical properties of the prepared composite materials were characterizied by XRD, FT-IR, TEM and N₂ adsorption methods. The results indicated that the H₃PW₁₂O₄₀/PMO catalysts presented larger BET specific surface area, and the Keggin unit evenly dispersed in the organic silicon material. These materials were subsequently utilized as catalysts in the reaction of carbon-carbon coupling of α-nitro ketenedithioacetals and benzhydrol under mild reaction conditions. Finally, the reusability of the catalysts was evaluated over three catalytic runs, which lay a foundation for its practical application.3. A series of sulfonic acid functionalized and based on different phosphotungstic acid loading（9.35%-23.14%） periodic mesoporous materials by alkyl-bridged organosilica moieties, pr-SO₃H-PMO/H₃PW₁₂O₄₀, were developed. The structure, composition, surface morphology, acid properties, and physicochemical properties of the materials were well characterized by XRD, FT-IR, TEM, Raman, solid-state NMR measurements and N₂ adsorption. The catalytic performance of the resulting bifunctionalized organic-inorganic hybrid materials was evaluated by the transesterification of tripalmitin with methanol for biodiesel production under the mild conditions and the influences of the factors including functional component loadings and molar ratios of oil to methanol on the yields of fatty acid monoalkyl esters were studied. Additionally, the excellent catalytic activity was discussed in detail. Finally, deactivation and significant loss of activity for the catalyst were not observed through five consecutive transesterification cycles, which lay a foundation for its practical application.