The invention concerns a synthesis process of a compound of the following formula (I) or one of the salts thereof, ##STR00001## wherein R represents a COOH, CH.sub.2OH or CHO group, comprising the step according to which the but-3-ene-1,2-diol (BDO) is subjected to an oxidation in the presence of a catalyst, said catalyst comprising an active phase based on at least one noble metal selected from palladium, gold, silver, platinum, rhodium, osmium, ruthenium and iridium, and a support containing alkaline sites. The invention also concerns the application of this reaction to the preparation of bioavailable compounds of methionine used, in particular, in animal nutrition.

The invention relates to a method for catalytically producing formic acid and regenerating the catalyst used in the process. A vanadyl ion, vandate ion, or polyoxometallate ion, which is used as the catalyst, of the general formula [PMo.sub.xV.sub.yO.sub.40].sup.n is brought into contact with an alpha hydroxyl aldehyde, an alpha hydroxy carboxylic acid, a carbohydrate, a glycoside, or a polymer, which contains a carbon chain and which comprises at least one OH group that is bound to the carbon chain as a substituent in a repeating manner and/or an O, N, or S atom contained in the carbon chain in a repeating manner, in a liquid solution (12) in a vessel (10) at a temperature above 70 C. and below 160 C., wherein 6x11, 1y6, 3<n<10, and x+y=12, where n, x, and y is each a whole number. The catalyst reduced in the process is returned to its starting state by oxidation. For this purpose, the solution (12) is brought into contact with a gas (18) which contains a volume percent of oxygen of at least 18% at a pressure of at least 2 bar and maximally 16 bar by means of a mixing device or via a liquid-non-permeable gas-permeable membrane. CO and/or CO.sub.2 resulting during the reaction and merging with the gas (18) is discharged in such a quantity that the volume percent of CO and CO.sub.2 combined does not exceed 80% in the gas (18).

A process for regenerating a deactivated vanadium-titanium-phosphorous catalyst which has been used in the production of unsaturated carboxylic acid is disclosed. The process comprises contacting the deactivated vanadium-titanium-phosphorous catalyst with a regeneration stream comprising steam as a regeneration agent at a temperature which is the same or similar to that used in the production of the unsaturated carboxylic acid.

The present invention relates to a synthesis method of N-substituted maleimides using a non-homogeneous solid acid catalyst, and particularly, a synthesis method of N-substituted maleimides with high synthesis yield by using a zirconium(IV) hydrogen phosphate as a catalyst, by which, the loss of the catalyst is minimized, the separation and recovering processes of the catalyst are simplified, in case when the activity of the separated and recovered catalyst is decreased, the complete regeneration of the catalyst is possible via washing or firing, and solvents that could be used during a washing process of the catalyst are not limited.

The present invention aims to provide a regeneration method capable of sufficiently restoring the catalytic performance of a solid catalyst used in a dehydration reaction of lactic acid and derivatives thereof. The present invention relates to a method for regenerating a solid catalyst used in a dehydration reaction of lactic acid and derivatives of lactic acid, the method including a contacting step of bringing a solid catalyst containing a component that forms a molten salt in the presence of steam into contact with oxygen and steam under pressure.

A oxygen transfer agent useful for the oxidative dehydrogenation of saturated hydrocarbons includes at least one mixed oxide derived from manganese or compounds thereof, as well as a promoter, such as tungsten and/or phosphorus. The oxygen transfer agent may also include an alkali metal or compounds thereof, boron or compounds thereof, an oxide of an alkaline earth metal, and an oxide containing one or more of one or more of manganese, lithium, boron, and magnesium. A reactor is at least partially filled with the oxygen transfer agent in the form of a fixed or circulating bed and provides an unsaturated hydrocarbon product, such as ethylene and/or propylene. The oxygen transfer agent may be regenerated using oxygen.

Provided is a method of reactivating a used titania catalyst for hydrogenation treatment, capable of improving the catalytic activity of the used titania catalyst for hydrogenation treatment that is obtained by supporting a catalyst component on a titania support and exhibits reduced catalytic activity after having been used for hydrogenation treatment of a hydrocarbon oil, to a level comparable to that of a newly prepared fresh titania catalyst before use. The method of reactivating a used titania catalyst for hydrogenation treatment, the used titania catalyst for hydrogenation treatment being obtained by supporting a catalyst component on a titania support and exhibiting reduced catalytic activity after having been used for hydrogenation treatment of a hydrocarbon oil, includes: a coke removal step of removing a carbonaceous component on a surface of the used catalyst by heating the catalyst in an oxygen-containing gas atmosphere; an impregnation step of impregnating the carbonaceous component-removed catalyst obtained by the coke removal step with a saccharide-containing solution; and a drying step of drying the saccharide-impregnated catalyst obtained by the impregnation step, to obtain a catalyst in which a saccharide is supported.

A method for separation of at least one catalyst or adsorbent from a homogeneous mixture of catalysts or adsorbents, used in a method for treatment of gas or hydrocarbon feedstock, in which the grains of catalysts or adsorbents are separated according to a sorting threshold corresponding to a content of the constituent element that is sought and defined by the user.

A regenerated spent hydroprocessing catalyst treated with a chelating agent and having incorporated therein a polar additive.

Process for the rejuvenation of a catalyst comprising a metal from group VIII, a metal from group VIb and an oxide support not comprising zeolite, comprising the following stages: a) said catalyst is regenerated at a temperature of between 360 C. and less than 420 C. so as to obtain a regenerated catalyst comprising a certain content of carbon and sulfur and a proportion of crystalline phase determined by X-ray diffraction and characterized by a ratio of less than 0.6, b) said regenerated catalyst is brought into contact with an aqueous solution consisting of water, of phosphoric acid and of an organic acid having each acidity constant pK.sub.a greater than 1.5, c) drying is carried out at a temperature of less than 200 C.