Abstract: A process for the preparation of calcium fluoride from industrial waste waters which comprises treatment of the waste waters with potassium hydroxide, followed by lime precipitation, neutralization with carbon dioxide and filtration to provide the calcium fluoride product.

Abstract: A process for producing maleic anhydride which comprises partially oxidizing a hydrocarbon feed at a temperature in the range 300.degree.-600.degree. C by contacting said feed and an oxygen-containing gas with a catalyst comprising vanadium, phosphorus and silicon oxides prepared by steps comprising coprecipitating vanadium oxide and silica or a silica precursor. Preferably an organic silicon compound, especially an alkyl orthosilicate, is used to form the silica precipitate. Preferably the organic silicon compound is added so as to coprecipitate both during the reduction of the vanadium from a +5 oxidation state to a 3.5-4.6 oxidation state and also is added or is present so as to precipitate silica or a silica precursor simultaneously with the reaction of phosphoric acid with the reduced vanadium.

Abstract: A process for producing maleic anhydride which comprises partially oxidizing a hydrocarbon feed at a temperature in the range 300.degree.-600.degree. C by contacting said feed and an oxygen-containing gas with a catalyst comprising vanadium, phosphorus and silicon oxides prepared by steps comprising coprecipitating vanadium oxide and silica or a silica precursor. Preferably an organic silicon compound, especially an alkyl orthosilicate, is used to form the silica precipitate. Preferably the organic silicon compound is added so as to coprecipitate both during the reduction of the vanadium from a +5 oxidation state to a 3.5-4.6 oxidation state and also is added or is present so as to precipitate silica or a silica precursor simultaneously with the reaction of phosphoric acid with the reduced vanadium.

Abstract: A high-activity vanadium-phosphorus mixed-oxide catalyst is prepared by a method requiring heating the catalyst precursor at about 350.degree.-410.degree.C. to drive off at least a portion of the water of hydration, and then at a higher temperature. The catalyst is especially useful for oxidation of n-butane to maleic anhydride.

Abstract: A process for producing citraconic anhydride from isoprene which comprises contacting the isoprene feed and oxygen-containing gas in vapor phase in a pretreatment zone at a temperature between 150.degree. and 430.degree.C with a solid base composition, said base composition comprising an alkali or alkaline earth metal, and then contacting the effluent from the pretreatment zone at a temperature between 180.degree. and 500.degree.C with a hydrocarbon oxidation catalyst effective for catalyzing the reaction of isoprene with oxygen to obtain citraconic anhydride.