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Ind. Eng. Chem. Prod. Res. Dev. 1983, 22, 565-570 565 Oil Company for aging the catalyst on an engine dynamometer.Registry NO. Pd, 7440-05-3; Pt, 7440-06-4; Rh, CO, 630-08-0; NO,, 11104-93-1. Literature CitedEngh, 0. T.; Wallman, S. SA€ (Society of Automotive Engineers) 1977, Falk, C. D.; Mooney. J. J. SA€ 1980, 800462. Fed. Regist. 1977, 42(124), 32906. Gandhl, H. S.; Steplen, H. K.; Shelef, M. Meter. Res. Bull. 1975, IO, 837. Gandhl, H. S.; Plken, A. G.; Shelef, M.; Delosh, R. G. SA€ Trans. 1978, 85, 770295. 901; SA€ 1978, 760201. Gandhi, H. S.; Plken, A. G.; Shelef, M.; Delosh, R. G.; Steplen, H. K.; Heyde, M. E. SA€ 1977, 770196. Patent 4 172047, 1979. Gandhi, H. S.; Shelef, M.; Yao, H. C.; Kummer, J. T.; Steplen, H. K. US. Gandhl, H. S.; Yao, H. C.; Steplen, H. K. ACS Symp. Ser. 1982, 178. 143. Hammerle, R. H.; Wu, C. H. Submitted to SAE International Congress, 1984. Hammerle, R. H.; Wu, C. H. SA€ 1981, 810275. Hegedus, L. L. Am. Chem. SOC. Div. fat. Chem. frepr. 1973, 18, 487. Jones, J. H.; Kummer, J. T.; Otto, K.; Shelef, M.; Weaver, E. E. Envfron. Sci. Technol. 1971, 5 , 790. Kummer, J. T.; Yao, Y.. McKee, D. SA€ 1978, 760143. Lachman, I. M.; McNelly. R. N. Preprints of Papers, 83rd Annual Meeting of American Ceramic Society, Washington, DC, 1981. Lester, G. R.; Marlnangell, R. E. SA€ 1980, 800844. Mooney. J. J.; Thompson, C. E.; Dettllng, J. C. SA€ 1977, 770365. National Fuel Survey, Motor Vehlcle Manufacturers Assoc., Detroit, 1982. Oda, I.; Matsuhlsa. T. Preprints of Papers, 83rd Annual Meeting of American Ceramic Society, Washington, DC, 1981. Oser, P. SA€ 1979, 790306. Seler, R. E.; Clark. R. J. SA€ 1978, 780203. Shelef, M.; Koester, D. W.; Mlchel, M. M., Jr., Adv. Chem. Ser. 1975, No. Steplen, H. K.; Wllllamson, W. B.; Gandhi. H. S. SA€ 1980, 800843. Weaver, E. E.; Shlller, J.; Plken. A. 0. AIChE Symp. Ser. 1976, 72(156), Yao, H. C.; Shelef, M. J . Catal. 1978, 43, 393. Yao, H. C.; Japar, S.; Shelef, M. J . M a l . 1977, 5 0 , 407. Yao, H. C.; Wynblatt, P.; Sleg, M.; Plummer, B. K., Jr. In "Sintering Processes"; Kuczynskl, G. C., Ed.; Plenum: New York, 1980; p 561.The oxidation of 1-butene and butadiene to maleic anhydride was tested with an integral reactor with vanadiumphosphorus mixed oxides prepared by different methods and presenting different activities and selectivities. The data were analyzed by utilizing a Langmuir-Hinshelwood type rate expression derived under differential conditions. At high partial pressure, competition between 1-butene and butadiene for the same active centers leads to a decrease in the rate of formatlon of maleic anhydride. This competitlon does not affect the rates of formation of methyl vinyl ketone, acetaldehyde, and carbon oxides. Emphasis is made on the necessity of operating with oxygen-nriched air in order to avoid the negative effect of the reactant on the rate of maleic anhydride formation.

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The interaction of methanol with zinc-chromium mixed oxides has been studied by temperature-programmed desorption (t.p.d.) in the range 430-770 K. Both the amount of methanol adsorbed and the amount of desorbed species in t.p.d. experiments, which can be taken as an indicator of the number of active sites responsible for methanol adsorption, are maximum for the sample with a Zn/Cr ratio of 1 .OOO. The number of active sites increases for some catalysts after pretreatment in hydrogen. The stoichiometric spinel, ZnCr,O,, shows oxidizing properties only for the adsorbed methanol. Non-stoichiometric spinels have some properties typical of ZnO and others typical of the stoichiometric spinel, depending on the Zn/Cr ratio and the thermal treatment. For a spinel with Zn/Cr between 1.500 and 4.000 (the range of composition of industrial catalysts) the reducing treatment increases the adsorption power for methanol. The F.t.i.r. experiments showed that in the case of the stoichiometric spinel after adsorption of methanol, methoxy, formate and carbonate groups are present at the surface, but on the non-stoichiometric spinels only methoxy and formate groups are present. The desorption of CO, and H, at 590 K are attributed to the decomposition of surface formates and the desorption of CO and H, at the same temperature either to formates or to methoxy species. The desorption of CO, at 720 K is attributed to surface oxidation of formates to carbonates. Very likely the excess of zinc in the spinel, localized essentially in octahedral positions, is responsible for methanol adsorption on the surface of zinc-chromium mixed oxides.