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

PP-III-33PRODUCTION OF METHYLETHYLKETONE BY OXIDATION OFn-BUTENES WITH DIOXYGEN IN THE PRESENCE OFHOMOGENEOUS CATALYST (Pd + HETEROPOLY ACID)E.G. Zhizhina, V.F. Odyakov, M.V. Simonova and K.I. MatveevBoreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences,Prosp. Akad. Lavrentieva, 5, Novosibirsk 630090, RussiaFax: +7(383) 330 8056. E- mail: zhizh@catalysis.ruMethylethylketone (MEK) is used as solvent for dyes, enamels, polyurethane and otherresins as well as for deparaffination of lubricating oils with the aim of security of their frostresistance.MEK is a raw material for production of fine chemicals too.In yearly 1970s we suggested a method of direct catalytic oxidation of n-butenes withdioxygen to MEK via reaction (1) [1].Pd + HPA -xn-C 4 H 8 + O 2 CH 3 COC 2 H 5 (1)Aqueous solutions containing Pd(II) complex and Keggin-type Mo-V-phosphoricheteropoly acids H 3+x PV x Mo 12-x O 40 (ГПК-x, 2 ≤ x ≤ 6) were used as catalysts for this process.To secure explosion-safety and maximal selectivity (> 97%), process (1) was carried intwo stages. Interaction of n-C 4 H 8 with the catalyst solution via reaction (2) took place at 60°Cin a reactor 1 to yield MEK and reduced form of HPA-x (H m HPA-x). Regeneration of HPA-xby dioxygen was realized via reaction (3) at 130–140°C in a reactor 2. When this scheme isused, the liquid catalyst continuously moves in a closed loop. In the course of reactions (2)and (3), vanadium atoms undergo redox transformations: V(V)V(IV).n-C 4 H 8 + HPA-x + Н 2 О Pd IICH 3 COC 2 H 5 + Н m HPA-x (2)Н m HPA-x + 1 / 2 O 2 ⎯⎯⎯→ HPA-x + H 2 O (3)MEK prepared in the reactor 1 was separated from the reduced catalyst by distillation in alayer evaporator. Degree of the catalyst reduction, m red = [V IV ] / [H m HPA-x], was maximal atthe output from reactor 1, and minimal at the output from reactor 2. Inasmuch as productivityof the catalyst in process (1) is determined by its oxidative capacity, OC = C HPA-x·(m red(2) -m red(3) ), solutions of HPA-x with high vanadium content (x) must be used as catalysts.Study of kinetics of reaction (2) allowed us to conclude that its mechanism is describedby two stages (4) and (5). At stage (4), Pd II complex oxidizes n-C 4 H 8 into MEK. At stage (5),HPA-x does Pd 0 into Pd II [2]:n-C 4 H 8 + Pd II fast+ Н 2 О CH 3 COC 2 H 5 + Pd 0 + 2 H + (4)365