A study on the structure and catalytic performance of ZnxCu1−xAl2O4 catalysts synthesized by the solution combustion method for the esterification reaction

Abstract

a b s t r a c tA Zn x Cu 1Àx Al 2 O 4 catalyst was prepared via the microwave-assisted solution combustion method (MSC). This method presents a fast procedure for industrial scale catalyst preparation. The physicochemical properties of the fabricated catalyst were characterized using XRD, FTIR, BET, SEM and TEM analyses. The catalytic performance through the esterification reaction was examined under the following conditions: reaction temperature ¼ 180 C, catalyst concentration ¼ 3% (w/w), molar ratio of oleic acid to methanol ¼ 9 and reaction time ¼ 6 h. XRD results showed that loading both zinc and copper oxides on alumina at a ratio of amounts that were nearly the same resulted in decreased crystalline size and well-dispersed copper-alumina and zinc-alumina crystals. Moreover, the mean pore diameter of the sample was increased by simultaneous loading of zinc and copper oxides on alumina that enhanced permeation of the reactants within pores and increased the interaction of the reactant with the catalyst active sites. The catalyst showed minimum tendency towards adsorbing moisture from air, which was attributed to it having less atoms on the surface through which binding with H 2 O molecules takes place. The highest level of activity in the esterification reaction (96.9%) was obtained at the optimum ratio of the Zn:Cu molar ratio, identified to be 2:3. The sample particles ranged from 10 to 30 nm in size, without agglomeration.

Application of microwave irradiation for fabrication of sulfated ZrO2–Al2O3 nanocomposite via combustion method for esterification reaction: process condition evaluation

“…The ZA-2 nanocatalyst demonstrates only α-Al 2 O 3 due to the increase of the temperature during the preparation of the catalyst. In addition, the bands at 486, 510, 583, and 630 cm −1 correspond to the stretching and bending vibrations of AlO 6 , and the band at 857 cm −1 corresponds to the stretching vibration of Al-O in AlO 4 [5,38]. An identical spectrum in the range of 400-800 cm −1 was also observed for F/O ratios greater than 1.…”

“…From among the solid acid catalysts, alumina and zirconia have been found to be exceptional super-catalysts for various organic transformations due to their high chemical corrosion resistance and thermal stability [5]. Moreover, researchers have reported that sulfate ions are an attractive group for the improvement of the acidity and activity of the catalysts.…”

Application of Microwave Irradiation for Preparation of a KOH/Calcium Aluminate Nanocatalyst and Biodiesel

“…. The Al 2 O 3 bands containing the vibrations of AlO 6 and AlO 4 were observed in the regions of 500–700 cm −1 and 700–850 cm −1 , respectively . The peak below 500 cm −1 is related to the vibration modes of Ca–O.…”

Review of Recent Studies on Solution Combustion Synthesis of Nanostructured Catalysts

“…Highest esterification activity (96.9%) was exhibited at the 2:3 molar ratio of the Zn:Cu, which was proved to be optimum. Nevertheless, further loading of copper oxide (i.e., over a molar ratio of 0.6) on alumina, acidity was severely lessened as a result of the agglomeration of CuO on the zinc aluminate spinel surface that coated the zinc aluminate acid sites, which has a critical role in the esterification reaction …”