TiO.sub.2-supported catalysts include at least molybdenum or tungsten as active components for hydrotreating processes, in particular for the removal of sulfur and nitrogen compounds as well as metals out of crude oil fractions and for the hydrogenation of sulfur oxides.

A method of generating electricity in a body of water includes providing a colony of sulfur-reducing bacteria, a colony of sulfur-oxidizing bacteria, and a colony of denitrifying bacteria submerged in the body of water. The colony of sulfur-reducing bacteria can be used to convert at least a portion of sulfates present in the body of water to hydrogen sulfide. The colony of sulfur-oxidizing bacteria can be used to convert the hydrogen sulfide to sulfuric acid, which can react with manganese to produce hydrogen gas. The colony of denitrifying bacteria can be used to convert at least a portion of nitrogen oxides in the body of water to nitrogen gas, which can be bubbled through a portion of water from the body of water to remove dissolved oxygen gas. The hydrogen gas and oxygen gas can be combined in a fuel cell generator to generate electricity.

A composite material is used for desulfurization. The composite material contains activated carbon, alkali metal oxides, silicon oxides, iron oxides, and rare earth element oxides. The weight ratio among the activated carbon, iron oxides and rare earth element oxides is 100:(0.5-5):(1-10). The composite material, used as a sulfur adsorbent, has a higher sulfur breakthrough capacity and desulfurization rate.

Methods and systems are provided for treating the tail gas stream of a sulfur recovery plant. The methods including generating a tail gas stream from a sulfur recovery plant, treating the tail gas stream with a hydrogen sulfide removal unit and a hydrogen selective membrane unit, generating a stream low in hydrogen sulfide and a stream rich in hydrogen. The hydrogen sulfide rich stream is recycled to the sulfur recovery unit. The hydrogen selective membrane unit includes a glassy polymer membrane selective for hydrogen over hydrogen sulfide and carbon dioxide.

A method of generating hydrogen gas includes providing a colony of sulfur-reducing bacteria and a colony of sulfur-oxidizing bacteria. The colonies can be submerged in a body of water. The colony of sulfur-reducing bacteria can be used to convert at least a portion of sulfates present in the body of water to hydrogen sulfide. The colony of sulfur-oxidizing bacteria can be used to convert the hydrogen sulfide to sulfuric acid. The sulfuric acid can react with manganese to produce hydrogen gas and manganese sulfate.

A method of separating oxygen from a body of water includes providing a colony of denitrifying bacteria submerged in the body of water. The colony of denitrifying bacteria can be used to convert at least a portion of nitrogen oxides present in the body of water to nitrogen gas. The method can also include collecting the nitrogen gas and bubbling the nitrogen gas through a portion of water from the body of water to remove dissolved oxygen from the portion of water. This can form a mixture of the nitrogen gas and oxygen gas.

Methods and systems are provided for treating the tail gas stream of a sulfur recovery plant. The methods including generating a tail gas stream from a sulfur recovery plant, treating the tail gas stream with a hydrogen sulfide removal unit and a hydrogen selective membrane unit, generating a stream low in hydrogen sulfide and a stream rich in hydrogen. The hydrogen sulfide rich stream is recycled to the sulfur recovery unit. The hydrogen selective membrane unit includes a glassy polymer membrane selective for hydrogen over hydrogen sulfide and carbon dioxide.

A biogas cleaning method for purifying a biogas waste stream to form a combustible clean biofuel uses a biogas cleaning system that includes a gas control system, a deoxidizer catalyst bed, a hydrosulfurization catalyst bed, a hydrogen sulfide adsorption bed and a thermal sensor controller. The biogas cleaning method includes using a biogas source to introduce a biogas waste stream into the biogas cleaning system, blending hydrogen with the biogas waste stream, combusting the blended hydrogen and biogas stream to remove oxygen, hydrogenating the heated biogas waste stream to convert sulfur species to hydrogen sulfide and adsorbing the hydrogen sulfide from the biogas stream. In some embodiments, a biogas cleaning system also includes a sulfur polisher adsorption bed, a chlorine removal adsorption bed, a siloxane removal adsorption bed, a heat exchanger loop and a biogas precooler. Some embodiments of a biogas cleaning method can also include precooling the biogas waste stream, adsorbing siloxanes from the biogas waste stream and adsorbing hydrogen chloride from the biogas stream.

A biogas cleaning method for purifying a biogas waste stream to form a combustible clean biofuel uses a biogas cleaning system that includes a gas control system, a deoxidizer catalyst bed, a hydrosulfurization catalyst bed, a hydrogen sulfide adsorption bed and a thermal sensor controller. The biogas cleaning method includes using a biogas source to introduce a biogas waste stream into the biogas cleaning system, blending hydrogen with the biogas waste stream, combusting the blended hydrogen and biogas stream to remove oxygen, hydrogenating the heated biogas waste stream to convert sulfur species to hydrogen sulfide and adsorbing the hydrogen sulfide from the biogas stream. In some embodiments, a biogas cleaning system also includes a sulfur polisher adsorption bed, a chlorine removal adsorption bed, a siloxane removal adsorption bed, a heat exchanger loop and a biogas precooler. Some embodiments of a biogas cleaning method can also include precooling the biogas waste stream, adsorbing siloxanes from the biogas waste stream and adsorbing hydrogen chloride from the biogas stream.

Embodiments provide a method including: supplying the hydrocarbon feedstock to an oxidation reactor, where the hydrocarbon feedstock is oxidized in the presence of a catalyst to selectively oxidize sulfur compounds present in the hydrocarbon feedstock; separating the hydrocarbons and the oxidized sulfur compounds by solvent extraction; collecting a residue stream that includes oxidized sulfur compounds; supplying the residue stream to a gasifier to produce a syngas stream and a hydrogen sulfide stream; supplying the extracted hydrocarbon stream to a stripper to produce a stripped oil stream, which is then supplied to an adsorption column, such that the adsorption column can produce a high purity hydrocarbon product stream, a second residue stream, and a spent adsorbent stream, the spent adsorbent stream containing another portion of the oxidized compounds; and supplying the spent adsorbent stream to the gasifier to produce additional syngas for the syngas stream, thereby disposing of the adsorbent.