CaO–Al₂O₃ mixed oxides were prepared by different preparation methods–such as sol–gel, co-precipitation, impregnation, and MW-assisted solution combustion synthesis (M-SCS)–and then impregnated with KOH to examine their activity in transesterification of canola oil to biodiesel. Synthesized nanocomposites were characterized by XRD, FTIR, BET/BJH, and SEM/EDX. The mixed oxides, except those prepared by M-SCS method, exhibited a nearly amorphous structure with some diffraction peaks of calcium oxide. Due to high combustion temperature during the M-SCS process, Ca ions could diffuse into the alumina lattice to form CaAl₂O₄. But upon impregnation with KOH, the former transformed to Ca₁₂Al₁₄O₃₃. The KOH/Ca₁₂Al₁₄O₃₃ nanocatalyst prepared by M-SCS method exhibited better basicity, mean pore size, and activity, as well as highest Ca/Al and K/Al ratios. In the presence of this catalyst, around 86% of canola oil were converted to biodiesel in the transesterification reaction carried out at 65°C, methanol/oil molar ratio 12: 1, 4 wt% catalyst, 4 h. Such parameters seem appropriate for industrial application. The M-SCS method is technically simple, cost effective, time/energy saving and requires no further thermal treatment.

中文翻译：

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KOH–CaO–Al 2 O 3纳米复合材料在生物柴油生产中的催化活性：制备方法的影响

CaO-Al ₂ O ₃混合氧化物的制备方法不同，例如溶胶-凝胶，共沉淀，浸渍和MW辅助溶液燃烧合成（M-SCS），然后用KOH浸渍以检查其活性。低芥酸菜子油向生物柴油的酯交换反应。通过XRD，FTIR，BET / BJH和SEM / EDX对合成的纳米复合材料进行了表征。除了通过M-SCS方法制备的那些以外，混合氧化物表现出几乎无定形的结构，具有一些氧化钙的衍射峰。由于在M-SCS过程中燃烧温度高，Ca离子可能扩散到氧化铝晶格中形成CaAl ₂ O ₄。但是用KOH浸渍后，前者转化为Ca ₁₂ Al ₁₄O ₃₃。M-SCS法制备的KOH / Ca ₁₂ Al ₁₄ O ₃₃纳米催化剂具有较好的碱度，平均孔径和活性，并且具有最高的Ca / Al和K / Al比。在该催化剂的存在下，在65℃，甲醇/油摩尔比为12：1、4重量％的催化剂，4小时进行的酯交换反应中，约86％的低芥酸菜子油转化为生物柴油。这样的参数似乎适合工业应用。M-SCS方法在技术上简单，经济高效，节省时间/能源，并且无需进一步热处理。