“…Several different bulk and supported oxide catalysts have been tested in this reaction. Different oxides (Ga, Cr, V, Fe, Zr and Zn) were used as active components [1][2][3][4][5][6][7][8][9][10] and potassium oxide was introduced as promoter [7,8]. Inorganic oxides (SiO 2 , Al 2 O 3 ) [1][2][3], mesoporous materials (MCM-41) [4] and carbonaceous materials (diamond, active carbon) [1,5] were used as the supports.…”