Hydrocracked bottoms fractions are treated to separate HPNA compounds and/or HPNA precursor compounds and produce a reduced-HPNA hydrocracked bottoms fraction effective for recycle, in a configuration of a single-stage hydrocracking reactor, series-flow once through hydrocracking operation, or two-stage hydrocracking operation. A process for separation of HPNA and/or HPNA precursor compounds from a hydrocracked bottoms fraction of a hydroprocessing reaction effluent comprises contacting the hydrocracked bottoms fraction with an effective quantity of a oxidizing agent to produce corresponding oxidized HPNA compounds and/or oxidized HPNA precursor compounds, and to form an oxidized hydrocracked bottoms fraction. The oxidized hydrocracked bottoms fraction is separated into an HPNA-reduced hydrocracked bottoms portion and an oxidized HPNA portion. All or a portion of the HPNA-reduced hydrocracked bottoms portion is recycled within the hydrocracking operation.

A light naphtha feedstock containing olefins is introduced with hydrogen sulfide into a mercaptanization zone for conversion of the olefins into a mercaptan stream that is substantially free of olefins, after which the mercaptans are sent with an alkali caustic solution into a mercaptan oxidation treatment unit (MEROX) to produce a spent caustic stream and sweet light naphtha product stream that is substantially free of olefins and of mercaptans. Disulfide oils are produced from the wet air oxidation of the spent caustic, and the disulfide oils can be further processed to provide high purity olefin building blocks.

We disclose a process for purification of hydrocarbons, suitable for a wide range of contexts such as refining bunker fuels to yield low-sulphur fuels, cleaning of waste engine oil (etc) to yield a usable hydrocarbon product, recovery of hydrocarbons from used tyres, recovery of hydrocarbons from thermoplastics etc, as well as the treatment of crude oils, shale oils, and the tailings remaining after fractionation and like processes. The method comprises the steps of heating the hydrocarbon thereby to release a gas phase, contacting the gas with an aqueous persulphate electrolyte within a reaction chamber, and condensing the gas to a liquid or a liquid/gas mixture and removing its aqueous component. It also comprises subjecting the reaction product to an electrical field generated by at least two opposing electrode plates between which the reaction product flows; this electrolytic step regenerates the persulphate electrolyte which can be recirculated within the process. The process is ideally applied in an environment at lower than atmospheric pressure, such as less than 1500 Pa. A wide range of hydrocarbons can be treated in this way. Used hydrocarbons such as engine oils and sulphur-contaminated fuels are prime examples, but there are a wide range of others such as hydrocarbons derived from the pyrolysis of a material having a hydrocarbon content. One such example is a mix of used rubber (such as end-of-life tyres) and used oils (such as engine oils, waste marine oils), which can be pyrolysed together to yield a hydrocarbon liquid which can be treated as above, and a residue that provides a useful solid fuel.

We disclose a process for purification of hydrocarbons, suitable for a wide range of contexts such as refining bunker fuels to yield low-sulphur fuels, cleaning of waste engine oil (etc) to yield a usable hydrocarbon product, recovery of hydrocarbons from used tyres, recovery of hydrocarbons from thermoplastics etc, as well as the treatment of crude oils, shale oils, and the tailings remaining after fractionation and like processes. The method comprises the steps of heating the hydrocarbon thereby to release a gas phase, contacting the gas with an aqueous persulphate electrolyte within a reaction chamber, and condensing the gas to a liquid or a liquid/gas mixture and removing its aqueous component. It also comprises subjecting the reaction product to an electrical field generated by at least two opposing electrode plates between which the reaction product flows; this electrolytic step regenerates the persulphate electrolyte which can be recirculated within the process. The process is ideally applied in an environment at lower than atmospheric pressure, such as less than 1500 Pa. A wide range of hydrocarbons can be treated in this way. Used hydrocarbons such as engine oils and sulphur-contaminated fuels are prime examples, but there are a wide range of others such as hydrocarbons derived from the pyrolysis of a material having a hydrocarbon content. One such example is a mix of used rubber (such as end-of-life tyres) and used oils (such as engine oils, waste marine oils), which can be pyrolysed together to yield a hydrocarbon liquid which can be treated as above, and a residue that provides a useful solid fuel.

A multi-phase process involves physical and chemical methods to recover the oil bases of used oils. The resulting oil base meets the standards and technical specifications necessary for reuse in the formulation of lube oils, greases and alike. The process includes classifying the used oil according to its physicochemical characteristics in order to optimize the subsequent phases. Next, the used oil is subject to physical pre-treatment to remove the solids of about 20 microns, dehydrate them and extinguish the remains of light hydrocarbons. Afterwards, the used oil undergoes extraction with organic chemical solvents on specific proportions within certain pressure and temperature ranges. The output is an extract composed of the oil base, the solvents and a semi-solid precipitate containing the used oil pollutants. Next, the extract is separated from the precipitate by physical methods. Subsequently, the extract passes through another physical procedure that separates the solvents from the oil base.

A multi-phase process involves physical and chemical methods to recover the oil bases of used oils. The resulting oil base meets the standards and technical specifications necessary for reuse in the formulation of lube oils, greases and alike. The process includes classifying the used oil according to its physicochemical characteristics in order to optimize the subsequent phases. Next, the used oil is subject to physical pre-treatment to remove the solids of about 20 microns, dehydrate them and extinguish the remains of light hydrocarbons. Afterwards, the used oil undergoes extraction with organic chemical solvents on specific proportions within certain pressure and temperature ranges. The output is an extract composed of the oil base, the solvents and a semi-solid precipitate containing the used oil pollutants. Next, the extract is separated from the precipitate by physical methods. Subsequently, the extract passes through another physical procedure that separates the solvents from the oil base.

A light naphtha feedstock containing olefins is introduced with hydrogen sulfide into a mercaptanization zone for conversion of the olefins into a mercaptan stream that is substantially free of olefins, after which the mercaptans are sent with an alkali caustic solution into a mercaptan oxidation treatment unit (MEROX) to produce a spent caustic stream and sweet light naphtha product stream that is substantially free of olefins and of mercaptans. Disulfide oils are produced from the wet air oxidation of the spent caustic, and the disulfide oils can be further processed to provide high purity olefin building blocks.

An integrated mercaptan extraction and/or sweetening and thermal oxidation and flue gas treatment process for a wide variety of sulfur, naphthenic, phenolic/cresylic contaminated waste streams is described. It provides comprehensive treatment for the safe disposal of sulfidic, naphthenic, phenolic/cresylic spent caustic streams, disulfide streams, spent air streams, spent mixed amine and caustic streams (also known as COS solvent streams) from sulfur treating processes. It allows the use of regenerated spent caustic in the sulfur oxide removal section of the thermal oxidation system reducing the need for fresh NaOH. It may also contain an integrated make-up water system. The integration allows the use of the liquefied petroleum gas or other hydrocarbon feeds to the respective extraction or sweetening process to offset external fuel gas requirements for the thermal oxidation system and for the push/pull system of the spent caustic surge drum and optional hydrocarbon surge drum.

A method of desulfurizing a liquid hydrocarbon having the steps of: adding a liquid hydrocarbon to a vessel, the hydrocarbon having a sulfur content; adding a catalyst and an oxidizer to create a mixture; oxidizing at least some of the sulfur content of the liquid hydrocarbon to form oxidized sulfur in the liquid hydrocarbon; separating the liquid hydrocarbon from the mixture; and removing at least some of the oxidized sulfur from the liquid hydrocarbon. Such methods can be carried out by batch or continuously. Systems for undertaking such methods are likewise disclosed.

A method of desulfurizing a liquid hydrocarbon having the steps of: adding a liquid hydrocarbon to a vessel, the hydrocarbon having a sulfur content; adding a catalyst and an oxidizer to create a mixture; oxidizing at least some of the sulfur content of the liquid hydrocarbon to form oxidized sulfur in the liquid hydrocarbon; separating the liquid hydrocarbon from the mixture; and removing at least some of the oxidized sulfur from the liquid hydrocarbon. Such methods can be carried out by batch or continuously. Systems for undertaking such methods are likewise disclosed.