TY - JOUR ID - 2069 TI - Sturctural flexibility under oxidative coupling of methane; main chemical role of alkali ion in [Mn+(Li, Na, K or Cs)+W]/SiO2 catalysts JO - Iranian Journal of Science JA - ISTT LA - en SN - 2731-8095 AU - Gholipour, Z. AU - Malekzadeh, A. AU - Ghiasi, M. AU - Mortazavi, Y. AU - Khodadadi, A. AD - School of Chemistry, Damghan University (DU), Damghan, Iran AD - School of Chemical Engineering, University of Tehran, Tehran, Iran Y1 - 2012 PY - 2012 VL - 36 IS - 2 SP - 189 EP - 211 KW - Oxidative coupling of methane (OCM) KW - manganes oxide KW - alkali ion KW - electrical conductivity KW - TPR DO - 10.22099/ijsts.2012.2069 N2 - Oxidative coupling of methane has been studied over (Mn+A+W)/SiO2 catalysts in a continuous–flow microreactor, where A represents an alkali ion of Li, Na, K or Cs having different weight percents. The main aim of this study is to find the role of alkali ions in interaction between Mn and W species with SiO2 to make a proper structure for catalyzing oxidative coupling of methane (OCM) reaction. The catalysts were characterized by XRD, SEM, FTIR, TPR and also the electrical conductivity was measured in air and under OCM reaction. It was found that for the formation of crystallized catalyst, the amount of alkali ion should be such that the catalyst containing tungsten transforms into A2WO4. Using a smaller amount of alkali ions does not result in crystalline catalyst by calcination under the same condition of temperature and atmosphere. However, under the OCM reaction condition the catalyst gradually turns into a crystalline structure and its catalytic performance, i.e. conversion and selectivity, for the OCM reaction is almost similar to the (Mn+A2WO4)/SiO2 catalyst. The transformation of the catalyst containing alkali ions from amorphous to crystalline one indicates a kind of structural flexibility of the catalyst under OCM atmosphere. The structural flexibility of the catalyst under the OCM reaction is considered to be the main chemical role of the alkali ions. UR - https://ijsts.shirazu.ac.ir/article_2069.html L1 - https://ijsts.shirazu.ac.ir/article_2069_cb1ae425b9e0cacb6303fa6f611c2d7d.pdf ER -