Characterization of precursors of methanol synthesis catalysts, copper zinc aluminum oxides, precipitated at different pHs and temperatures
Characterization of precursors of methanol synthesis catalysts, copper zinc aluminum oxides, precipitated at different pHs and temperatures
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DOI：
10.1016/0926-860x(95)00284-7
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发表时间：
1996-03-28
影响因子：
5.5
通讯作者：
Inui, T
中科院分区：
文献类型：
--
作者：
Li, JL;Inui, T
采用并流沉淀法在不同pH值和不同温度下制备了原子比为6/3/1的铜/锌铝混合氧化物催化剂的催化剂前体。采用红外光谱、X射线衍射、热分析、程序升温氧化和BET比表面测试等手段对前驱体、催化剂和还原后的催化剂进行了表征。还测试了催化剂在含有少量二氧化碳的合成气中的甲醇合成活性。当沉淀在pH = 7.0下进行时，沉淀物主要由孔雀石样相组成，并且由此得到的催化剂更有活性。在pH小于或等于6的沉淀有利于羟基硝酸盐的形成，这导致活性较低的催化剂。虽然在pH = 7.0和低于50 ℃的温度下获得的前体的组成与在pH = 7.0和T = 70 ℃下获得的那些相同，但催化剂的活性低得多。老化温度是影响最终催化剂分散性和活性的重要因素。虽然pH值和温度对催化剂活性的影响可以归因于类似的原因，即，铜和锌的分散性不同，pH值的影响可能是通过改变前驱体的相组成来实现的，而温度的影响则是通过改变相同组成的前驱体的沉淀动力学来实现的。
Catalyst precursors for copper/zinc aluminum mixed oxide catalysts with an atomic ratio of 6/3/1 were prepared by co-current precipitation at different pH levels and different temperatures. The precursors, catalysts and reduced catalysts were characterized by means of infrared spectroscopy, X-ray diffraction, thermal analysis, temperature-programmed oxidation and BET surface measurements. The catalysts were also tested for methanol synthesis activity in a synthesis gas containing a small amount of carbon dioxide. When the precipitation was conducted at pH = 7.0, the precipitates mainly consisted of the malachite-like phase and the catalysts therefrom were more active. Precipitation at pH less than or equal to 6 favored the formation of hydroxynitrate, which led to less active catalysts. Although the composition of the precursors obtained at pH = 7.0 and temperatures lower than 50 degrees C was the same as those at pH = 7.0 and T = 70 degrees C, the activity of the catalysts was much lower. It was also found that the aging temperature was an important factor in determining the interdispersion and activity of the final catalysts. Although the effects of both the pH value and the temperature on activity of the catalysts can be ascribed to a similar reason, i.e., the different interdispersion of copper and zinc, it seems that the pH value exerts its effect through altering the phase composition of the precursors, while the temperature functions through the precipitation kinetics of the precursors with a same composition.