Catalytic oligomerization of light olefins is an important CC coupling strategy that can be used to produce high-value transportation fuels and chemicals from shale gas and biomass feedstocks. In this work, vapor-phase propylene oligomerization was studied over a series of overcoated SiO2-MOx materials, whose acid site densities and strengths are tunable by the amount of SiO2 deposition and the nature of the core oxide. These materials contain acid sites only on particle external surfaces, limiting pore diffusion artifacts. SiO2-MOx materials were prepared by depositing stoichiometric amounts of tetraethyl orthosilicate (TEOS) onto Al2O3, anatase TiO2, Nb2O5, and ZrO2. Compared to the unmodified oxides, which are poor propylene oligomerization catalysts, the SiO2-MOx materials exhibit moderate activity with Al2O3, TiO2, and Nb2O5 core materials performing better than commercial amorphous silica alumina (ASA) on a surface area basis. The activity of the materials appears to be primarily driven by their Brønsted acid strength as measured by 31P TMPO MAS NMR with the rates ranked in order SiO2/Al2O3 > SiO2/TiO2 ≈ SiO2/Nb2O5 > SiO2/ZrO2. This study shows that SiO2-overcoated materials are a tunable class of materials that are active for vapor-phase propylene oligomerization.

中文翻译：

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SiO2 包覆氧化物上的丙烯低聚反应


轻质烯烃的催化低聚化是一种重要的 CC 偶联策略，可用于从页岩气和生物质原料中生产高价值的运输燃料和化学品。在这项工作中，研究了一系列包覆 SiO2-MOx 材料的气相丙烯低聚化，其酸位密度和强度可通过 SiO2 沉积量和核心氧化物的性质进行调整。这些材料仅在颗粒外表面包含酸位点，从而限制了孔隙扩散伪影。通过将化学计量量的正硅酸四乙酯 （TEOS） 沉积到 Al2O3、锐钛矿 TiO2、Nb2O5 和 ZrO2 上来制备 SiO2-MOx 材料。与作为不良丙烯低聚化催化剂的未改性氧化物相比，SiO2-MOx 材料表现出中等活性，Al2O3、TiO2 和 Nb2O5 核心材料在表面积上优于商用无定形二氧化铝 （ASA）。这些材料的活性似乎主要由其 Brønsted 酸强度驱动，通过 31P TMPO MAS NMR 测量，速率顺序为 SiO2/Al2O3 > SiO2/TiO2 ≈ SiO2/Nb2O5 > SiO2/ZrO2。这项研究表明，SiO2 包覆材料是一类可调材料，对气相丙烯低聚化具有活性。