OP-II-3

PP-III-79All the prepared spinel-oxide catalysts showed high NO conversion rates with agood selectivity to N 2 (higher than 90%). The Mn 0,95 Ca 0,05 Cr 2 O 4 , despite the nothighest specific surface area, provided the best performance with a 96% of NOconversion at 125°C and a 97% of selectivity to N 2 .Substitutions at the B site increased the reducibility of chromium, as evidenced bythe amount of hydrogen consumed during TPR runs and a general increase of theselectivity could be observed. Studies are now in progress to better correlate thecatalytic performances with the substitution effects and to evaluate the operativeparameters effect (NH 3 /NO x ratio, amount of O 2 , GHSV, etc) on the catalyticperformance of the best performing catalyst when supported on a ceramichoneycomb.Table 1. Collection of the results of the catalyst characterization tests concerning the BETspecific surface area, catalytic activity and hydrogen temperature programmed reduction.CatalystBET[m 2 /g]Max. NOConversion %Selectivity toN 2 %Consumed H 2in TPR run[mmol/g]MnCr 2 O 4 31.9 90 (at 125°C) 91% 3.0Mn 0.9 Mg 0.1 Cr 2 O 4 41.7 97 (at 150°C) 90% 11.9Mn 0.9 Ca 0.1 Cr 2 O 4 49.9 84 (at 125°C) 97% 10.2Mn 0.95 Mg 0.05 Cr 2 O 4 26.9 99 (at 150°C) 93% 4.3Mn 0.95 Ca 0.05 Cr 2 O 4 36.5 96 (at 125°C) 97% 11.9A B C1 µm1 µm1 µmReferences:Figure 1. FESEM views of the spinel-oxide catalysts:A) Mn 0.9 Mg 0.1 Cr 2 O 4 ; B) Mn 0.95 Mg 0.05 Cr 2 O 4 ; C) Mn 0.95 Ca 0.05 Cr 2 O 4 .[1]. H. Bosch, F. Janssen, Catalysis Today (1988) 2, 369.[2]. M. Kang, ED. Park, Kim J M, Yie J E, Applied Catalysis A, (2007) 327(2), 261.[3]. G. Qi, R. Yang, R. Chang, Applied Catalysis B, (2004) 51, 93.[4]. Li J, Chen J, Ke R, Luo C, Hao J, Catalysis Communications, (2007), 8(12), 1896.589