Preparation Of Non-precious Metal Oxide Catalysts And Their Catalytic Performance For The Oxidation Of Ethylbenzene

Ethylbenzene is a typical aromatic organic compound,and its catalytic reaction process is also a key process technology in the fine chemical industry.Acetophenone,the main product of selective oxidation of ethylbenzene,is an important chemical intermediate and is widely used in synthetic resins,plasticizers and pharmaceutical intermediates.However,because the C-H bond energy on the side chain of ethylbenzene is relatively large,it has high thermodynamic stability and chemical inertness,and can produce a resonance effect with the benzene ring,resulting in low oxidation reaction activity.In order to improve the reaction activity,harsh reaction conditions must be adopted,but this increases the energy consumption of the reaction.In addition,the product of ethylbenzene oxidation is more likely to cause excessive oxidation because it is rich in more oxygen-containing groups,thereby reducing the selectivity of the target product.Therefore,how to develop a catalyst for the catalytic oxidation of ethylbenzene with high efficiency and mild reaction conditions is a big challenge.In this paper,non-noble metal oxides are used as catalyst precursors.After high-temperature roasting,nano-scale non-noble metal oxide catalysts are prepared,using XRD,SEM,TEM,N₂ physical adsorption and desorption,XPS,H₂-TPR,and FT-IR.Characterization means,research and analysis of the structure-activity relationship between the physicochemical properties of the catalyst and the catalytic performance.The main research contents of this paper are as follows:（1）The CoAlO_x,NiAlO_x and MnAlO_x catalysts were prepared by co-precipitation method,and the catalytic performance of three non-noble metal oxide catalysts for the selective oxidation of ethylbenzene was studied.The experimental results show that MnAlO_x has the best ethylbenzene oxidation performance.Under the optimal reaction conditions,the conversion rate of ethylbenzene is 63.9%,and the selectivity of acetophenone is 87.2%.（2）Mn-based catalysts of MnAlO_x-CO₃^2-and MnAlO_x-Urea were prepared by co-precipitation method and urea precipitation method,respectively.The urea precipitation method with the best catalytic performance of ethylbenzene was selected,and the manganese-aluminum composite oxide MnAlO_x@HZSM-5 catalyst with molecular sieve as the carrier was prepared.The advantage of the MnAlO_x@HZSM-5catalyst is that it reduces the loading of Mn and increases the conversion rate of ethylbenzene while keeping the selectivity of acetophenone unchanged.Under the optimal reaction conditions,the conversion of ethylbenzene was 67.5%,and the selectivity of acetophenone was 95.2%.（3）The mesoporous hydrotalcite-based bimetallic nanocatalyst with Co₂Ni₁-LDHs as the precursor was successfully prepared by the co-precipitation method.By introducing an appropriate amount of Ni as the weak active center,the high efficiency synergistic effect of the bimetallic catalyst greatly improves the ethylbenzene oxidation performance of the Co₂Ni₁Al O_x catalyst.In addition,the catalyst has good cycle stability and can be recycled for many times without significant deactivation.Under the optimal reaction conditions,the conversion rate of ethylbenzene reached 80.0%,and the selectivity of acetophenone was as high as 88.9%.