第316回触媒化学研究センターコロキウム
Isobutane selective oxidation to methacrylic acid:
Still a challenge after 25 years!
Professor Sébastien Paul (Ecole Centrale de Lille)
2012年12月10日（月）14：20—15：00（創成科学研究棟4階セミナー室B・C）
http://www.cat.hokudai.ac.jp/access.html
The development of a catalytic process for the selective oxidation of isobutane intomethacrylic acid has been representing for more than 25 years a difficult but fascinating challenge. As a matter offact such a process coupled to the esterification of the methacrylic acid obtained by methanol would give an accessto a very competitive shortcut for producing methyl methacrylate - the monomer of poly(methyl methacrylate) better
known under its commercial names Plexiglas® or Altuglas®. Actually, the current industrial process - the so-calledacetone-cyanohydrin (ACH) route - suffers from serious environmental and economic drawbacks which need to beaddressed. During the oxidation of isobutane into methacrylic acid, a double C=C bond has to be formed and one
methyl group has to be converted into a carboxyl group. Therefore, a bifunctional catalyst presenting both acid andredox properties – which are responsible for the oxidative dehydrogenation and the insertion of oxygen,
respectively – is necessary. In this context Keggin-type heteropolyacid such as H4PMo11VO40 and its salts like Cs+
and NH4+ have proved to be interesting candidates because of their simultaneous strong acidity and redox
properties which are moreover easily tunable. In this seminar I will describe our work aiming at developing anefficient catalyst for the reaction and at understanding the role of each element present in the catalytic formulation.
In a first step the kinetics of the reaction was studied, using a mixed cesium-ammonium salt of 11-molybdo-1vanadophosphoric acid. It shown that the reaction obeys the Mars and van Krevelen redox mechanism and that therate-limiting step was the reaction between isobutane and the oxidized sites of the catalyst. Moreover, the influenceof the relative amounts of NH4+ and Cs+ cations was demonstrated, the ammonium ions being essential to get highselectivity to MAA by helping to maintain a partially reduced active phase at the steady state. On one hand, thecesium cations proved to be essential to form a cesium salt on which the active phase is dispersed while, on theother hand, the presence of vanadium is necessary to improve the redox process. From this basis Cs3PMo12O40and HCs3PMo11VO40 heteropolysalts, that could be obtained by a controlled synthesis, were used as carriers todisperse firstly the simple H4PVMo11O40 active phase and then the more efficient protonated ammonium salt of 11molybdo-1-vanadophosphoric acid, (NH4)3HPMo11VO40 (APMV). The influence of the nature of the support (i.e.
SiO2, SBA-15, ZrO2/SBA-15 and Cs3PMo12O40 (CPM)) on the catalytic properties and the catalytic reaction
performances has also been investigated. Compared with silica-supported catalysts which were poorly stable, twomain effects were observed upon supporting APMV on CPM support: (i) the resulting multilayer dispersion limited
the thermal decomposition of the active phases, and (ii) the acidity of surface species was much stronger. To
confirm these findings and optimize the properties of APMV/CPM catalyst, a series of catalysts with 10-50 wt.%
loading of APMV on CPM was prepared. Their physicochemical properties, their reactivity in reducing atmosphere,and, of course, catalytic performances in the isobutane oxidation were studied. As a result one of the best
conversion of isobutane (15.3%) and yield of the desired products (MAC+MAA, 8.0%) reported up to now in the
open literature were achieved.
問合せ先： 触媒化学研究センター・福岡淳（fukuoka@cat.hokudai.ac.jp/011-706-9140）
Sébastien Paul is Professor at the Ecole Centrale de Lille, a Generalist Engineer School in the North of France, where he is thehead of the Sciences of the Matter department since 2009. After his PhD in Chemical Engineering at the University ofTechnology of Compiègne, France (1996), he was hired by the Ecole Centrale de Lille as an Assistant Professor (1998). From2004 to 2009 he was at the head of the “Chemical Engineering” Department which then became the “Sciences of the Matter”
Department. In 2009 he was nominated Associate Professor and in 2011 Full Professor. He is involved in the development of alarge variety of catalytic processes starting from compounds issued from the biomass or hydrocarbons. Finally, he is supervisingor co-supervising 11 PhD, 10 post-docs, is co-author of 30 scientific articles, 3 patents, and 65 communications (oral and poster)in national and international congresses.

316th Catalysis Research Center (CRC) Colloquium