A process and system for treating a hydroprocessing unit effluent gas stream for recycling includes introducing the effluent gas stream into a hydrogen purification zone and recovering a hydrogen-rich gas stream and a liquid stream containing a mixture that includes C1 to C4 hydrocarbons and H.sub.2S which is then mixed with an oxidant and fed to an oxidation unit containing catalyst for conversion of the H.sub.2S to elemental sulfur vapors that is separated for recovery of the elemental sulfur, and recovering a sweetened mixture that includes C1 to C4 hydrocarbons. Alternatively, the hydroprocessing unit effluent gas stream containing H.sub.2S is cooled, contacted with a solvent to absorb the C1 to C4 hydrocarbons and H.sub.2S, with the hydrogen-rich stream being recovered for recycling to the hydroprocessing unit, and the rich liquid solvent being flashed to produce a lean solvent stream for recycling to the adsorption zone and a mixed gas stream that includes the C1 to C4 hydrocarbons and H.sub.2S that is passed to an oxidation zone and is reacted with an oxidant in the presence of a catalyst to complete the process as described above for the recovery of elemental sulfur and a mixture that includes the sweetened C1 to C4 hydrocarbons.

Methods for producing cyclododecasulfur are disclosed that include the steps of: reacting a bromide with molecular chlorine to obtain molecular bromine and a chloride; oxidizing the chloride in aqueous solution with removal of electrons to obtain molecular chlorine; reducing water with electrons to obtain hydrogen and a hydroxide; and reacting a metallasulfur derivative with the molecular bromine, to produce cyclododecasulfur and a metallabromide derivative.

A process and system for treating a hydroprocessing unit effluent gas stream for recycling includes introducing the effluent gas stream into a hydrogen purification zone and recovering a hydrogen-rich gas stream and a liquid stream containing a mixture that includes C1 to C4 hydrocarbons and H.sub.2S which is then mixed with an oxidant and fed to an oxidation unit containing catalyst for conversion of the H.sub.2S to elemental sulfur vapors that is separated for recovery of the elemental sulfur, and recovering a sweetened mixture that includes C1 to C4 hydrocarbons. Alternatively, the hydroprocessing unit effluent gas stream containing H.sub.2S is cooled, contacted with a solvent to absorb the C1 to C4 hydrocarbons and H.sub.2S, with the hydrogen-rich stream being recovered for recycling to the hydroprocessing unit, and the rich liquid solvent being flashed to produce a lean solvent stream for recycling to the adsorption zone and a mixed gas stream that includes the C1 to C4 hydrocarbons and H.sub.2S that is passed to an oxidation zone and is reacted with an oxidant in the presence of a catalyst to complete the process as described above for the recovery of elemental sulfur and a mixture that includes the sweetened C1 to C4 hydrocarbons.

A method for heat integration in a sulfur recovery unit, the method comprising the steps of reacting the acid gas stream and the air stream in the reaction furnace to produce a reaction effluent, where the reaction effluent comprises elemental sulfur, reducing the temperature of the reaction effluent in the heating extension to produce an effluent stream, reducing the temperature of the reaction effluent in the waste heat boiler to produce a cooled effluent stream, reducing the temperature of the cooled effluent in the sulfur condenser to produce a liquid sulfur stream and a cooled gases stream, where the liquid sulfur stream comprises the elemental sulfur, and increasing a temperature of the cooled gases stream to produce a hot gases stream, where the heating extension is configured to capture heat from the reaction effluent and release the heat to the cooled gases stream.

Disclosed is a catalyst suitable for the catalytic oxidative cracking of a H.sub.2S-containing gas stream, particularly in the event that the stream also contains methane and/or ammonia. The catalyst comprises iron and molybdenum supported by a carrier comprising aluminum. The carrier preferably is alumina. The iron and molybdenum preferably are in the form of sulphides. Also disclosed is a method for the production of hydrogen from a H.sub.2S-containing gas stream, comprising subjecting the gas stream to catalytic oxidative cracking so as to form H.sub.2 and S.sub.2, using a catalyst in accordance with any one of the preceding claims.

A quench system for sulfur recovery including a quench line for delivering a CO.sub.2 rich off gas into a feed line of the sulfur recovery unit converter system, an oxidation air inlet for feeding an oxidation air to an oxidation air preheater, a feed preheater for receiving the heated oxidation air, the CO.sub.2 rich off gas, the process gas, or a combination thereof, a selective oxidation converter disposed downstream of the feed preheater for producing a converter effluent, an off gas control valve disposed in the quench line for controlling the CO.sub.2 rich off gas to the selective oxidation converter, wherein the CO.sub.2 rich off gas is used for quenching a potential fire, and cooling preheaters and a selective oxidation converter when temperature exceeds normal operating limits or fire is suspected.

Disclosed is a catalyst suitable for the catalytic oxidative cracking of a H.sub.2S-containing gas stream, particularly in the event that the stream also contains methane and/or ammonia. The catalyst comprises iron and molybdenum supported by a carrier comprising aluminium. The carrier preferably is alumina. The iron and molybdenum preferably are in the form of sulphides. Also disclosed is a method for the production of hydrogen from a H.sub.2S-containing gas stream, comprising subjecting the gas stream to catalytic oxidative cracking so as to form H.sub.2 and S.sub.2, using a catalyst in accordance with any one of the preceding claims.

A feed stream including hydrogen sulfide is heated to a preheat temperature. At least a portion of the hydrogen sulfide in the feed stream is converted into hydrogen and sulfur to form a mixed product stream including the hydrogen, the sulfur, and a remaining, unconverted portion of the hydrogen sulfide. The preheat temperature is a temperature that is sufficiently hot to maintain a desired reaction temperature while converting at least the portion of the hydrogen sulfide in the feed stream into hydrogen and sulfur. At least a portion of the mixed product stream is cooled to a specified temperature at which recombination of the hydrogen and the sulfur into hydrogen sulfide is prevented. Cooling at least the portion of the mixed product stream includes condensing at least a portion of the sulfur to form a sulfur stream.

Disclosed is a catalyst suitable for the catalytic oxidative cracking of a H.sub.2S-containing gas stream, particularly in the event that the stream also contains methane and/or ammonia. The catalyst comprises iron and molybdenum supported by a carrier comprising aluminum. The carrier preferably is alumina. The iron and molybdenum preferably are in the form of sulphides. Also disclosed is a method for the production of hydrogen from a H.sub.2S-containing gas stream, comprising subjecting the gas stream to catalytic oxidative cracking so as to form H.sub.2 and S.sub.2, using a catalyst in accordance with any one of the preceding claims.