Effect of synthesizing conditions on the activity of zinc-copper aluminate nanocatalyst prepared by microwave combustion method used in the esterification reaction

The effect of microwave radiation power and fuel type as two important parameters on the morphology, properties, and activities of the zinc-copper aluminate spinel fabricated was assessed by microwave combustion method (MCM). Characterization results of the catalysts fabricated at different microwave irradiation power showed faster evaporation of remained water in the precursor gel that can lead to the formation of the sample with better crystalline form and structure. These properties enhance the activity of the nanocatalyst in the esterification reaction. The effect of fuel type (e.g., urea, ammonium acetate, and their mixture) on properties of the nanocatalyst synthesized at the maximum microwave power was also examined. Due to different levels of thermogenesis, the nanocatalyst properties were modified using fuel mixtures a result of increasing the pore diameter of the nanocatalyst from 2.1 to 9.5 nm for the sample with the highest activity. In addition, the nanocatalyst structure such as particle-size distribution and the agglomerated particles was noticeably improved. The best spinel zinc-copper aluminate nanocatalyst was prepared at maximum microwave power and ammonium acetate to urea ratio of 1:3. Also, the yield of 99.1% was obtained at the operating conditions of 180 degrees C, 9:1 M ratio of methanol to oleic acid, and 3 wt% of catalyst. The catalyst presented high stability such that it can be reused at least for nine cycles. Owing to catalysts activity and reusability, this catalyst can be recommended for a variety of catalyst systems.