The present invention relates to a process for the production of a recycled catalyst comprising at least one metal M1 from group VI B, and/or at least one metal M2 from group VIII, optionally phosphorus and/or sulfur, and a support based on oxide(s). The process comprises the recycling of at least a part of the metal or metals of a source catalyst comprising the metal M1 and/or the metal M2 common with the recycled catalyst to be produced, with: an extraction by an extraction solution of the metal M1 and/or of the metal M2 from said source catalyst, in order to obtain a solution of extracted metal/metals, thenan impregnation of the support with an impregnation solution resulting from said solution of extracted metal/metals, in order to obtain an impregnated substrate, said extracted metal(s) remaining in the liquid phase from the extraction until the impregnation.

The invention relates to 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 two OH groups bonded as substituents 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.

A process for separating a catalyst component from a catalyst-containing slurry by centrifugation including separating the catalyst component from the mother liquor of the catalyst-containing slurry using a stacked disc centrifuge equipped with an auto-discharging functionality. The solids discharge from the stacked disc centrifuge is enhanced by adding a washing solution to the bowl and the solids discharge chute of the stacked disc centrifuge.

A process for separating a catalyst component from a catalyst-containing slurry by centrifugation including separating the catalyst component from the mother liquor of the catalyst-containing slurry using a stacked disc centrifuge equipped with an auto-discharging functionality. The solids discharge from the stacked disc centrifuge is enhanced by adding a washing solution to the bowl and the solids discharge chute of the stacked disc centrifuge.

The invention relates to a process for the rejuvenation of an at least partially spent catalyst resulting from a hydrotreating process, said at least partially spent catalyst resulting from a fresh catalyst comprising a metal from group VIII, a metal from group VIb, an oxide support, and optionally phosphorus, said at least partially spent catalyst additionally comprising carbon in a content of between 2% and 20% by weight, with respect to the total weight of the at least partially spent catalyst, and sulfur in a content of between 1% and 8% by weight, with respect to the total weight of the at least partially spent catalyst, said process comprising the following stages: a) said spent catalyst is brought into contact with an impregnation solution containing a compound comprising a metal from group VIb, b) a drying stage is carried out at a temperature of less than 200 C.

The invention relates to a process for rejuvenating an at least partially spent hydrotreating and/or hydrocracking catalyst, said catalyst comprising a group VIII metal, a group VIB metal and an oxide support, said process comprising the following steps: a) the catalyst is regenerated, b) said regenerated catalyst is then brought into contact with an impregnation solution consisting of a mixture of water, at least one precursor of a group VIB metal, at least one precursor of a group VIII metal and at least one organic compound, the amount of organic compound introduced into the regenerated catalyst being optimized with respect to the metals already present in the regenerated catalyst and with respect to the amount of metals introduced via the impregnation solution, c) a drying step is then carried out without subsequently calcining it.

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 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).

The invention has as its object a catalyst that comprises a substrate based on alumina or silica or silica-alumina, at least one element from group VIII, at least one element from group VIB, and at least one additive that is selected from among 2-acetylbutyrolactone and/or its hydrolysis products, 2-(2-hydroxyethyl)-3-oxobutanoic acid, and 3-hydroxy-2-(2-hydroxyethyl)-2-butenoic acid. The invention also relates to the method for preparation of said catalyst and its use in a method for hydrotreatment and/or hydrocracking.

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.