Aromatic ketones are important chemical intermediates used in the synthesis of various perfumes, drugs, and pharmaceuticals. The production of these ketones by Friedel–Crafts acylation of aromatic compounds along with the acyl halide or acid anhydride, leads to the formation of a high volume of toxic and corrosive waste. Nowadays, due to economic and ecologic reasons, heterogeneous catalysts are of considerable importance. The use of metalloporphyrins substituted with electron-withdrawing groups and the immobilization on inorganic supports has resulted in efficient and selective catalysts for the oxidation of hydrocarbon. Oxidation of alkylbenzenes is an important transformation in chemical synthesis generally performed with corrosive, toxic or carcinogenic materials. The desired products are usually obtained with low selectivity accompanied by ecologically dangerous by-products. In recent researches, the possibility of using of metalloporphyrins as a catalyst in oxidation of such substrates has been proposed by several groups. These products strongly dependent on conditions used (catalyst, co-catalyst, oxidising agent, and solvent). The central objective of this research is to carry out oxidation reaction of ethylbenzene and produce acetophenone as the main product, using heterogeneous catalyst. Thus, this projects aims to design a heterogeneous catalyst based on the immobilization of porphyrin on silica gel. In order to do this, the porphyrin containing steric functional group, entitled 5, 10, 15, 20- tetrakis (4-methoxycarbonyl phenyl) porphyrin, was synthesized and immobilized using amidation reaction on modified silica gel (containing amino functional group). Ultimately, immobilized porphyrin was transformed into Mn(III) complex. Different techniques such as UV-Vis, FT-IR, CHN, TG, and BET were used for the characterization of the catalysts called SF-ATPS-Mn(III)TMCPP. Eventually, this catalyst was used for oxidation of ethylbenzene. In order to raise the conversion percentage of ethylbenzene and selectivity of acetophenone as the main product, various reaction conditions such as temperature, solvent, reaction time, oxidant, and a molar ratio of ethylbenzene: oxidant, were optimized.