乙苯脱氢与二氧化碳转化氧化铝催化剂吸附量热的研究

• 作 者: 葛欣 王文月 邹琥 沈俭一
• 机 构: 南京大学化学系! 南京 210093,南京大学化学系! 南京 210093,南京大学化学系! 南京 210093,南京大学化学系! 南京 210093
• 出 处: 燃料化学学报
• 发表日期: 1999年04期
• 关键词: 催化活性 乙苯脱氢 二氧化碳转化 微分吸附量热 吸附饱和 吸附质 酸位 吸附量 耦合反应 转化反应

研究了负载Ｎａ２Ｏ、Ｋ２Ｏ的γ－Ａｌ２Ｏ３催化剂在乙苯（ＥＢ）脱氢与二氧化碳转化耦合反应（ＥＢ＋ＣＯ２ＳＴＹ＋ＣＯ＋Ｈ２Ｏ）的催化活性及生成苯乙烯（ＳＴＹ）的选择性，考察了各种反应条件对催化活性的影响，并以ＮＨ３和ＣＯ２为吸附质运用微分吸附量热法表征了催化剂的表面酸碱性质。结果表明，γ－Ａｌ２Ｏ３具有较多的强酸位和较少的碱位，其对ＮＨ３的起始吸附热为１３５ｋＪｍｏｌ，吸附饱和覆盖度为２５μｍｏｌｍ２；对ＣＯ２的吸附热为１２５ｋＪｍｏｌ，吸附饱和覆盖度为０３μｍｏｌｍ２，γ－Ａｌ２Ｏ３对反应的催化活性较低。而Ｋ２Ｏ／γ－Ａｌ２Ｏ３具有较多的强碱位和较少的酸位，催化活性较好，其对ＮＨ３的起始吸附热为３０ｋＪｍｏｌ，吸附饱和覆盖度为１５０μｍｏｌｍ２；对ＣＯ２的吸附热为１４５ｋＪｍｏｌ，吸附饱和覆盖度为２７μｍｏｌｍ２。因此表明催化剂表面存在的酸、碱中心对反应具有协同作用，强碱中心对ＣＯ２的活化，有利于催化活性和选择性的提高

The catalytic activities and the selectivity to styrene (STY) of the γ-Al2O3 catalysts loaded with Na2O and K2O were investigated in the coupling reaction between the dehydrogenation and carbon dioxide conversion of EB (EB + CO2STY + CO + H2O). The effects of various reaction conditions on the catalytic activity The surface acid-base properties of the catalysts were characterized by differential adsorption calorimetry with NH3 and CO2 as adsorbates. The results show that γ-Al2O3 has more strong acid sites and fewer base sites, the initial adsorption heat of NH3 is 135kJmol, the saturation adsorption coverage is 25μmolm2, and the adsorption heat to CO2 is 125kJ mol, saturated adsorption coverage of 0  3μmolm2, γ-Al2O3 lower catalytic activity of the reaction. However, K2O / γ-Al2O3 has more base sites and fewer acid sites, and has better catalytic activity. The initial adsorption heat of NH3 is 30kJmol, and the adsorption saturation coverage is 150μmolm2. The adsorption heat of CO2 is 145kJmol and the saturated adsorption coverage is 27μmolm2. Therefore, it is indicated that the presence of acid and alkali centers on the surface of the catalyst has a synergistic effect on the reaction. The activation of CO2 by the strong alkali center is favorable for the improvement of the catalytic activity and selectivity