Imperial Chemical Industries Limited

Raymond Higgins

Graham John Hutchings

John R Bamforth

Philip E Starkey

Deborah A Trebilco

Maleic anhydride is produced by oxidizing a straight chain C.sub.4 hydrocarbon with oxygen in a stream comprising 25 to 60% by volume of the C.sub.4 hydrocarbon, 20 to 45% by volume of oxygen and optionally inert gases to produce a stream containing at least 21/2% by volume of maleic anhydride and condensing maleic anhydride substantially free from water from this stream.

Production of maleic anhydride

Hydrocarbons, particularly n-butane, are oxidized to acid anhydrides, especially maleic anhydride, by contacting them at concentrations above the flammable limit with oxygen in the presence of a vanadium/phosphorus mixed oxide catalyst having a surface area of at least 10 m.sup.2 /g. The concentration of inert gas is more than 70 molar percent and the oxygen concentration is greater than 13 molar percent.

Production of maleic acid and anhydride

Catalysts for the oxidation of hydrocarbons to acid anhydrides, for example maleic and phthalic anhydrides, are prepared from a vanadium/phosphorus mixed oxide precursor by conditioning it by contact with a strong acid of concentration at least 3N and solvent extraction to remove unwanted phases. The treated precursor is converted to a catalytically active form by heating. Novel catalysts containing phase X are produced. The catalysts may contain rare earth metal promoters.

Hydrocarbons, particularly n-butane, are oxidized to acid anhydrides, especially maleic anhydride, by contacting them at concentrations above the flammable limit with oxygen in the presence of a vanadium/phosphorus mixed oxide catalyst having a surface area of at least 10 m.sup.2 /g. The oxygen concentration is greater than 13 molar percent and/or the concentration of inert gas is less than 70 molar percent.

Catalysts for the oxidation of hydrocarbons to acid anhydrides, for example maleic and phthalic anhydrides, are prepared from a vanadium/phosphorus mixed oxide precursor by conditioning it by contact with a strong acid of concentration at least 3 N and solvent extraction to remove unwanted phases. The treated precursor is converted to a catalytically active form by heating. Novel catalysts containing phase X are produced. The catalysts may contain rare earth metal promoters.

Production of acid anhydrides and catalysts therefor

A process for the dimerization and cyclization of isobutene to form, as preferred product, paraxylene in which the whole of the product of isobutene dimerization (including unreacted feedstock) is contacted with a catalyst for the cyclization of the isobutene dimer. The process is operable in a single dimerization/cyclization stage or in separate dimerization and cyclization stages with no intermediate separation of products. Optionally, the isobutene feedstock is provided by dehydrogenation of isobutane, unreacted isobutane in the resulting feedstock being carried through the dimerization/cyclization and eventually recycled.

Production of aromatic hydrocarbons

Catalysts for the oxidation of hydrocarbons to maleic anhydride comprise a phosphorus/vanadium mixed oxide promoted by tungsten antimony, niobium, and/or molybdenum, having a surface area of at least 10m.sup.2 /g.

Production of maleic anhydride and catalysts therefor

Compounds of formula R.sub.1 R.sub.2 C .dbd. CR.sub.3 CHR.sub.4 R.sub.5 wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are selected individually from hydrogen, akyl, aryl, cyano, cyclohexyl, halide groups and substituted derivatives of these groups are oxidatively dimerized in the presence of a partially reduced bismuth oxide catalyst, the average degree of reduction of bismuth oxide being 1 to 70%, and in the presence of oxygen, the oxygen conversion being in the range 90 to 99%.

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Middlesbrough, United Kingdom

Raymond Higgins