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以共沉 淀法合 成的铬镁 铝类水滑 石为前 体,制备 了一系 列不 同原 子比 的铬 镁铝 复合 氧化物,研 究了其对 二氧化 碳 氧 化 丙 烷制 丙 烯 反 应 的 催 化 性 能. 采用 微 量 吸 附 量 热 技 术, 以 C O2 和 N H3 为探 针分子 定量地表 征了样 品表面酸 碱中心的 强度 和数 量, 并与 其催 化性 能进 行了 关联. 结果表 明, Cr ∶ Mg ∶ Al 原 子 比 为 1 ∶1 ∶1 的 催 化 剂 具 有 较 大 的 比 表 面 积( 945 m 2/g) , 样 品 中 Mg( Al1 .5 Cr0 .5) O4 物相的含 量最多 . 样品 表面存在 数量 较 多强 度较 强 的酸 性中 心 和数 量最 少 强度较弱 的碱性中 心,对 N H3 吸附,它 的吸附热 为1 45 k J/ m ol , 吸 附覆盖度 为3 55 μm ol/ m 2 ; 对 C O2 吸附,它 的吸附热 为115 k J/ m ol , 吸附覆 盖度 为0063 μm ol/ m 2 . 该 样品 的 催化 活性 最 高,在 温 度为650 ℃ , C O2/ C3 H8 摩尔比为 36 , G H S V( C3 H8) 为3 00 0 h - 1 时, C3 H8 的 转 化率 为 228 % , C3 H6的选择 性为835 % , 收率为 1
A series of chromium-magnesium-aluminum composite oxides with different atomic ratios were prepared by coprecipitation synthesis of chromium-magnesium aluminate hydrotalcite, and its catalytic performance for propylene oxidation from carbon dioxide and propane was studied. The intensity and amount of acid-base centers on the sample surface were quantified using C O2 and N H3 as probes, and their catalytic properties were correlated with each other. The results show that the catalyst with a Cr: Mg: Al atomic ratio of 1: 1: 1 has a large specific surface area (945 m 2 / g) and the content of Mg (Al 1.5 Cr 0.5) O 4 in the sample most. There are a large number of strong acidic sites on the surface of the sample and a weakly alkaline basic site. The adsorption heat of N H3 is 1 45 kJ / mol and the adsorption coverage is 3 55 μm ol / M 2; for C 2 O adsorption, the adsorption heat is 115 kJ / m ol and the adsorption coverage is 0063 μm ol / m 2. The catalytic activity of this sample was the highest. The conversion of C3H8 was 22 at the temperature of 650 ℃, the molar ratio of C O2 / C3H8 to 3.6 and G H S V (C3 H8) to 300 h "1. 8%, C3 H6 selectivity of 83 5%, the yield was 1