Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-IV-12The comparative analysis of the catalystsactivity was carried out with pure perovskites inpowder. All catalysts guarantee much lower T 50values than the one related to non catalyticcombustion (816 °C). By inducing a partialsubstitution with 10% of Pd at the B site animprovement of the activity was observed for allFig. 1. SEM view of LaMn 0.9 Pd 0.1 O 3 obtained catalysts. This should entail a reduction of theby Solution Combustion Synthesis.overall catalyst costs compared to conventional Pdonlycatalysts currently employed characterized by high Pd loads. More in detail the methanehalf conversion temperature (T 50 ) of Pd substituted perovskites was lowered of about 5, 40and 60 °C for LaCrO 3 (T 50 = 607 °C), LaFeO 3 (T 50 = 535 °C) and LaMnO 3 (T 50 = 485 °C),respectively; the best catalyst was found to be LaMn 0.9 Pd 0.1 O 3 (T 50 = 425 °C) and therefore itwas selected to be deposited and tested on a cordierite monolith. The catalytic converters(cylindrical cordierite honeycombs by Chauger; cell density: 200 cpsi; length: 25 mm;diameter: 34 mm) were prepared by a preliminary deposition of a layer of γ-alumina by in situSCS (10 wt% referred to the monolith weight) and then 15 wt% (referred to the γ-aluminaweight) of LaMn 0.9 Pd 0.1 O 3 . The adhesion properties between the catalyst and ceramic surfacewas checked by means of an ultrasonic bath test: a piece of the catalytic monolith wasweighted before and after a standard ultrasonic treatment to quantify the catalyst loss. Theadhesion between the deposited catalyst and the channel walls of the traps was excellent, asthe loss of catalyst by ultrasonic treatment was lower than 1%. Catalytic combustionexperiments were performed in a stainless steel reactor heated in a horizontal split tubefurnace with a heating length of 60 cm. The catalyzed monolith was sandwiched between twomullite foams to optimize flow distribution. For the temperature control a thermocouple,inserted along one of the central monolith channel, was used to measure the inlet temperature.Lean inlet conditions (0.4% vol.% CH 4 , 10% vol.% O 2 , N 2 balance) were ensured via massflow controllers. The methane conversion of the LaMn 0.9 Pd 0.1 O 3 cordierite monolith atdifferent GHSVs shows that the conversion shifted to lower temperature at lower spacevelocity. The T 50 values are 570 °C, 455 °C and 385 °C at the space velocity of 80000 h –1 ,40000 h –1 and 10000 h –1 , respectively.References1. Mowery D.L., Graboski M.S., Ohno T.R., McCormick R.L., Appl. Catal. B: Env., 21 (1999) 157.2. Fino D., Russo., Saracco G., Specchia V., Progress in Solid State Chemistry, 35 (2007) 501.163