The problem of chemical safety and sanitary air protection is particularly relevant due to the increase of harmful emissions of industrial enterprises, which have a strong toxic effect. Toluene, xylene and ethyl-benzene are major part of the solvents used in various industries, which are present in gaseous emissions. Results of the development of catalysts based on Ni, Cu, and Cr supported on 2 % Ce/θ-Al2O3 with addition of natural clays and waste mixtures of metallurgical production are presented. It was found that the highest degree of toluene conversion (up to 98.8 %) is observed on the three-component Ni-Cu-Cr/2 % Ce/θ-Al2O3 catalyst with optimal metal ratio Ni : Cu : Cr = 1.0 : 3.0 : 0.1 at GHSV = 5×103 h-1 and a temperature of 723 - 773 K. The presence of CeO2 crystals, X-ray amorphous clusters (d = 20 – 100 Å) of variable valence metal oxides NiO and CuO as well as solid metal solutions CuO (NiO) was detected on the surface of optimum catalyst calcined at 873 K using XRD and transition electron microscopy methods. Interaction of oxygen with Ni-Cu-Cr catalyst were studied by temperature-programmed desorption, temperature-programmed reduction and temperature-programmed oxidation methods. It was shown that thermal desorption curve has bends at 773 K and 923 K as well as maximum at 1,023 K, which is caused by desorption of the adsorbed oxygen (670 – 870 K, Edes = 88 - 89 kJ mol-1) and decomposition of Ni and Cu oxides (870 – 1,070 K, Edes = 100 - 128 kJ mol-1) to Cu2O, Ni2O, and then mixed oxides of aluminates (> 1,070 K, Edes = 140 - 144 kJ mol-1), the content of which is sharply reduced when heating at 1,473 K. By IR spectroscopy and thermal desorption has been shown that SO2 chemisorption (a.b. 1165 cm-1, Tmdes = 673 K) and its oxidation to sulfate structures (a.b. 1,235, 1,140, 1,100, 985 and 615 cm-1, Tmdes = 973 K) is the result of reacting a mixture of SO2 + O2 with 9 % Ni-Cu-Cr/2 % Ce/-Al2O3 catalyst at 673 K. These structures are decomposed to SO2 and O2 and destroyed by reduction with hydrogen at T = 973 K.
This research was funded by Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (grant number AP08855562, AP08052090).
|Publication||IOP Conference Series: Earth and Environmental Science|
|Position of speaker||Prof.|
|Affiliation of speaker||D.V. Sokolsky Institute of Fuel, Catalysis and Electrochemistry|