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

KINETICS OF METHANE OXIDATION OVER NIOBIUM(V)OXIDE CATALYSTSJ. Ziebro, B. MichalkiewiczPP-I-10Szczecin University of Technology, Institute of Chemical and Environment Engineering,ul. Pulaskiego 10, 70-322 Szczecin, Poland,phone: +48914494096, fax:+48914494686, e-mail: janusz.ziebro@ps.plThe selective methane oxidation to oxygenates is very attractive as it would eliminate anenergy-consuming process of methane to synthesis gas steam reforming, the former of whichis nowadays the basic raw material used to produce methanol and later formaldehyde. Thiswould lead to a considerable reduction of cost production of both these compounds and otherones, which are produced from them. This is one of the most fundamental problems ofcontemporary technology, which until now has not yet been solved. Despite the fact thatmethane to formaldehyde and methanol oxidation using both O 2 and N 2 O isthermodynamically possible, carbon oxides are much more privileged products. Theactivation of only one of the four equivalent C-H bonds is interesting also from the scientificpoint of view. The process of direct methane to formaldehyde synthesis should be carried outin conditions which exclude deep methane oxidation and which prevent secondary oxidationreactions of the desirable product. This is possible by means of heterogeneous catalysts.The selective methane to formaldehyde oxidation was examined over various catalysts,which mainly contained oxides of transition elements, such as molybdenum [1], iron [2] andvanadium [3] antimony [4], as well as ZSM-5 [5] and MCM-41 [6].The work is continuation of former investigations [7] of methane one-step oxidation toformaldehyde and/or methanol using as catalysts various compounds. As catalyst niobium(V)oxide and Nb 2 O 5 on silica support. were used.The experiments were carried out at the range of temperatures between 420 and 750°C.The contact time differed from 0.7 to 1.8 s (5150-2000h –1 space velocity at NTP) whilekeeping a constant ratio of methane to oxygen. The substrates and products were analyzed bymeans of the chromatograph SRI 8610C equipped with a TCD.The kinetic studies were run in the differential reactor. Two series of measurements wereconducted. In the first one the temperature was kept constant while the contact time waschanged. In the other one, the process was carried out at different temperatures, with the samecontact time.229