Structural sensitivity of NO decomposition over a V-O-W/Ti(Sn)O2 catalyst

NOx selective catalytic reduction at high temperatures with mixed oxides derived from layered double hydroxides

“…This indicates that this material is not adequate for the removal of NO x at high temperature. These results agree with those previously described in literature showing that V-catalysts are quite active at temperatures between 250-450ºC [9,10] The influence of the catalyst synthesis method on the catalyst activity was studied by preparing different Co-Al and Ni-Cr catalysts by the different methods described in the experimental part and testing their activity. As it was discussed, the different synthesis methods lead to the formation of LDHs with different crystallinity.…”

“…Nevertheless these additives must be able to operate at the high temperatures found in the FCC regenerator (around 700-750ºC), and in the presence of other gases such as CO, SO 2 , CO 2 , hydrocarbons, O 2 and H 2 O [5][6]. In these conditions, the common catalysts used for the NO x selective catalytic reduction or decomposition such as metal exchanged zeolites [7], modified pillared clays [8] or promoted V catalysts [9][10][11] are not stable enough and other alternatives should be explored.…”

Surface species structure and activity in NO decomposition of an anatase-supported V–O–Mo catalyst

“…Structures of the vanadia surface species of European industrial catalysts -V 2 O 5 /TiO 2 for selective toluene oxidation to maleic anhydride and V 2 O 5 -WO 3 /TiO 2 one for NH 3 -SCR of NO x -were widely discussed in special issues of Catalysis Today [9,10]. It has recently been found that surface species of V-O-W/rutile catalyst with a vanadia structure show relatively high activity in direct NO decomposition to dinitrogen and dioxygen in oxygen presence at 423-453 K [11][12][13]. Such species are formed as a result of an vanadium segregation on the surfaces of the nanocrystallites of rutile and tungsten oxides during the thermal treatment of the catalyst in oxygen [14].…”

“…It was scheduled to obtain an anatase-supported V-O-Mo catalyst by preparing a solid solutions of molybdena and vanadia in anatase and possibly vanadia in some molybdenum oxide and next forming vanadia surface species via oxidation-induced surface V segregation. To obtain such species on the catalyst surface the same procedure as in the case of V-O-W/rutile catalyst [12,13] was applied. It consists of a mild reduction of the freshly prepared catalyst by ammonia to cause dissolution of adventitious vanadium surface species and next oxidation-induced surface V segregation resulting in the gradual formation of the species active in NO decomposition.…”

“…Experimental 2.1. Catalyst preparation A precursor of an anatase-supported V-O-Mo catalyst with the ratio V:Mo:Ti = 1:9:90, analogous to that in the V-O-W/rutile catalyst [12,13], was prepared by the sol-gel method from water solutions of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O and VO(NO 3 ) 2 as well as a 6% TiO 2 sol solution. The details of the synthesis were presented elsewhere [21].…”