Construction and eva‎luation of copper, chromium, and manganese nanostructure catalysts for carbon monoxide oxidation at low temperatures

9/10/2024 12:00:00 AM

Catalytic oxidation of carbon monoxide to carbon dioxide is one of the most significant environmental and industrial processes, as well as one of the primary methods for removing polluting and toxic carbon monoxide gas. CO is released into the atmosphere as a result of the partial oxidation of carbon-containing substances. Copper-chromium oxide and copper-manganese oxide catalysts are the most promising transition metal oxides, with comparable activity for CO oxidation with precious metals. The research was conducted in three stages in order to obtain an active and stable catalyst in this process. In the first stage, catalysts based on a copper-chromium oxide mixture were synthesized and eva‎luated using the mechanochemical method with molar ratios of Cu: Cr=1:0, 1:0.5, 1:1, 1:2, 0:1. In the second phase, catalysts based on copper-manganese oxide combination with molar ratios of Cu: Mn=1:0, 1:0.5, 1:1, 1:2, and 0:1 were synthesized using the mechanochemical technique. The first stage findings revealed that the activity of the sample with a molar ratio of Cu: Cr=1:1 calcined at 500 °C temperature was more than other samples, reaching around 90% CO conversion at 133 °C temperature. The formation of the CuCr2O4 spinel phase and the large surface area of this sample (23.9 m2/g) in comparison to other catalysts were the factors of high activity of this sample. According to the results of the second stage, the activity of the sample with a molar ratio of Cu:Mn=1:0.5 calcined at 400℃ was higher than other samples. So, in the temperature range of 113-150 ℃, the conversion of CO is more than 90%, and it also exhibits 100% conversion from 175 ℃ up. In addition, this sample was chosen as the selected catalyst due to its higher BET level (27.73 m2/g) and lower crystal size of 8.7 nm compared to other samples, as well as the creation of CuMn2O4 spinel structure compared to the Cu: Cr=1:1 catalyst. In the third step, in order to compare the synthesis method, the Cu:Mn=1:0.5 catalyst (as the best sample from the perspective of stability and conversion rate) was compared with wet impregnation, sol-gel and hydrothermal synthesis methods. The results showed although the CuMn-H sample (prepared by hydrothermal method) had the highest specific surface area (43.29 m2/g) and the lowest crystal size (4.8 nm) among the mentioned synthesis methods, it showed the lowest activity due to its amorphous structure. Compared to the CuMn-M sample, which completely converted CO at 150 ℃, the CuMn-H sample only achieved a 25% conversion rate at the same temperature. Finally, the copper-manganese oxide catalyst with a favorable crystal structure, crystal size, and suitable specific surface area showed a much better performance than other synthesis methods with using mechanochemical synthesis method.

اكسيداسيون CO , مكانيكي-شيميايي , مخلوط اكسيدي مس-كروم , مخلوط اكسيدي مس-منگنز , ساختار اسپينلي

CO oxidation , Mechanical-chemical , Copper-chromium oxide mixture , Copper-manganese oxide mixture , Spinel structure

zahra fekri

mehran rezaei-seyed mahdi alavi