The Butanone Gas Phase Catalytic Oxidation System Butanedione

Diacetyl (DA) is a kind of important food perfumer and intermediate of fine chemicals. Commonly, DA is prepared by the reaction of methyl ethyl ketone (MEK) with ethyl nitrite prepared from sodium nitrite and hydrochloric acid, which costs high and brings serious pollution. Furthermore, the purity of DA prepared by this method can not satisfy the requirement of food perfumers. It is reported that DA synthesized by vapor-phase air-oxidating MEK in the presence of V2O5-P2O5 catalyst can overcome the above shortcoming. Apparently, DA prepared by this method is of great importance for green chemistry. However, the reported results were obtained from micro reactors, which is not much interested in the industrial.At the present work, the oxidation process of MEK over a series of supported V2O5-P2O5 catalysts have been investigated in an integral fixed-bed reactor firstly. The components of products have been analyzed by gas chromatography (GC) with FFAP packed column. The catalysts have been characterized by X-ray diffraction (XRD) and infrared (IR) techniques. The influence of P/V atomic ratio and metal oxide promoters in the preparation of V2O5-P2O5 /kieselguhr catalysts, and the reaction conditions on the catalytic performances have been studied. The reaction mechanism has also been proposed. The obtained results are as follows:1. XRD results indicate that the catalytic active composition of V2O5-P2O5 is amorphous and highly dispersed on the surface of kieselguhr. FT- IR results prove that in addition to P2O5 into V2O5 causes the formation of V-P-O complex through the bonding interaction between V2O5 and P2O52. The P/V atomic ratio in the preparation of catalysts has obvious effects on the catalytic properties. The conversion of MEK and the selectivity of DA are enhanced with an increase of P/V atomic ratio when it is lower than 3.2, but which decrease if the P/V atomic ratio keeps on increasing after that. The conversion of MEK is 61.8% and the selectivity of DA is 32.7% when the atomic ratio of P/V is around 3.2.3. The addition of metal oxides can change obviously the V2O5-P2O5 /kieselguhr catalyst performances. The addition of bases can prompt the conversion of MEK and decrease the selectivity of DA. The addition of the oxides of Cr, Cu, Mo, or Co causes a decrease of the selectivity of DA, and the addition of the oxides of La or Ce has no much influence on the catalytic activity. The addition of Zr, Mo, Zn can apparently enhance DA selectivity (about 43%), but the conversion of MEK decreases (only40%). On the optimum V1.0P3.2Zr.05Mo.05Zn.05La.15catalyst, the conversion of MEK attains to 54%, and the selectivity of DA is 40%.4. A Ha of MEK and DA have been measured by the absorption of MEK and DA on a series of V2O5 catalysts by GC method. The results show A Ha of MEK and DA are -27.1KJ/mol and -24.2KJ/mol respectively, on the typical V1.0P3.2Zr.05Mo.05Zn.05La.15 catalyst. The conversing experiments using DA and HAC as reactants have been also studied. The reaction mechanism is then concluded that both the lattice oxygen in the catalyst and molecular oxygen take part in the reactions, but the oxygen of products mainly comes from molecular oxygen.