The invention refers to a process for rejuvenating a hydrotreating catalyst comprising a group VIB hydrogenation metal and/or a group VIII hydrogenation metal, which comprises the steps of: (a) regenerating the catalyst by contacting said catalyst with an oxygen containing gas at a temperature from about 300 C. to 550 C., (b) impregnating the regenerated carbon-reduced catalyst with an impregnation solution which comprises a mixture of water and a combination of MoO.sub.3 and H.sub.3PO.sub.4, (c) aging the impregnated catalyst and (d) drying the aged catalyst. The invention also refers to the rejuvenated catalyst obtained and its use for hydro-treating hydrocarbon feedstocks.

A process for regenerating a silica-supported depleted alkali metal catalyst is described. The level of alkali metal on the depleted catalyst is at least 0.5 mol % and the silica support is a zero-gel. The process comprises the steps of contacting the silica supported depleted alkali metal catalyst with a solution of a salt of the alkali metal in a solvent system that has a polar organic solvent as the majority component. A re-impregnated catalyst prepared by the process of the invention any comprising a silica zero-gel support and a catalytic metal selected from an alkali metal in the range 0.5-5 mol % on the catalyst, wherein the surface area of the silica support is <180 m.sup.2/g is also described. The invention is applicable to a process for preparing an ethylenically unsaturated acid or ester comprising contacting an alkanoic acid or ester of the formula R.sup.1CH.sub.2COOR.sup.3, with formaldehyde or a suitable source of formaldehyde.

A process involves sequentially treating a plurality of lipid feedstocks comprising a set of lipid feedstocks each having a chloride content of at least about 2 ppm with a metal oxide catalyst on an oxide support under first treating conditions to produce respective treated streams of the set of lipid feedstocks having a chloride content less than 1 ppm until a given one of the respective treated streams has a chloride content greater than 1 ppm and the metal oxide catalyst is converted to a spent metal oxide catalyst, converting the spent metal oxide catalyst to a rejuvenated metal oxide catalyst, and treating one or more additional lipid feedstocks each having a chloride content of at least about 2 ppm with the rejuvenated metal oxide catalyst under second treating conditions to produce one or more respective treated streams each having a chloride content less than 1 ppm.

Disclosed is a method for regenerating a SCR denitration catalyst assisted by microwaves. The method comprises: (1) a poisoned SCR denitration catalyst is immersed in deionized water, and the SCR denitration catalyst is cleaned by a bubbling method; (2) the SCR denitration catalyst is transferred to a container containing a pore-expanding solution for a soaking treatment; (3) the SCR denitration catalyst is transferred to a microwave device and treated for 1-10 minutes; (4) the SCR denitration catalyst is transferred to a container with an activating liquid and impregnated for 1-4 hours; (5) the SCR denitration catalyst is dried with microwaves for 1-20 minutes; and (6) the SCR denitration catalyst is calcined under conditions of 500-600 C. for 4-7 hours. The present invention has readily available raw materials, is simple and energy-saving in device and process, and is suitable for industrial scale regeneration. The catalyst treated by the method of the present invention has the advantages of loose pore channels, obviously optimized pore structures, significantly improved catalyst surface conditions, high activity, and good economic benefits.

Methods for the operation of membrane reactors (MRs) are disclosed for the efficient production of hydrogen-enriched fuel blends with tunable composition and high hydrogen recovery at both elevated and isobaric pressure operation. These methods enable use of greatly reduced operating temperatures relative to packed bed reactors (PBRs) and elimination of the need for a secondary separation unit operation. These methods provide greater productivity and hydrogen recovery while relaxing membrane selectivity constraints relative to conventional MR operation.

Catalytic activity of a spent precious metal-iron catalyst is restored by combining the spent catalyst with an iron (III) compound. This can be performed by adding the iron (III) compound into a chemical reaction that contains the spent precious metal-iron catalyst. It is unnecessary to add more of the precious metal. The process is especially useful in a continuous process for converting a nitro compound such as nitrobenzene to the corresponding amine.

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.