Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G21/00—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents
  • C10G21/06—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents characterised by the solvent used
  • C10G21/12—Organic compounds only
  • C10G21/24—Phosphorus-containing compounds
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G29/00—Refining of hydrocarbon oils, in the absence of hydrogen, with other chemicals
  • C10G29/06—Metal salts, or metal salts deposited on a carrier
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C7/00—Purification; Separation; Use of additives
  • C07C7/10—Purification; Separation; Use of additives by extraction, i.e. purification or separation of liquid hydrocarbons with the aid of liquids
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G21/00—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents
  • C10G21/02—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents with two or more solvents, which are introduced or withdrawn separately
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G21/00—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents
  • C10G21/06—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents characterised by the solvent used
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G21/00—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents
  • C10G21/06—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents characterised by the solvent used
  • C10G21/08—Inorganic compounds only
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G21/00—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents
  • C10G21/28—Recovery of used solvent
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G31/00—Refining of hydrocarbon oils, in the absence of hydrogen, by methods not otherwise provided for
  • C10G31/08—Refining of hydrocarbon oils, in the absence of hydrogen, by methods not otherwise provided for by treating with water
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G67/00—Treatment of hydrocarbon oils by at least one hydrotreatment process and at least one process for refining in the absence of hydrogen only
  • C10G67/02—Treatment of hydrocarbon oils by at least one hydrotreatment process and at least one process for refining in the absence of hydrogen only plural serial stages only
  • C10G67/04—Treatment of hydrocarbon oils by at least one hydrotreatment process and at least one process for refining in the absence of hydrogen only plural serial stages only including solvent extraction as the refining step in the absence of hydrogen
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
  • C10G2300/10—Feedstock materials
  • C10G2300/1074—Vacuum distillates
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
  • C10G2300/20—Characteristics of the feedstock or the products
  • C10G2300/201—Impurities
  • C10G2300/202—Heteroatoms content, i.e. S, N, O, P

Definitions

• This invention relates to processes for reducing the sulfur compound content of vacuum gas oils (VGO). More particularly, the invention relates to removing sulfur compounds from VGO using an ionic liquid that are contaminants in downstream processes.
• VGO vacuum gas oils
• VGO is a hydrocarbon fraction that may be converted into higher value hydrocarbon fractions such as diesel fuel, jet fuel, naphtha, gasoline, and other lower boiling fractions in refining processes such as hydrocracking and fluid catalytic cracking (FCC).
• the contaminants in VGO such as sulfur, nitrogen, metals and Conradson Carbon cause deactivation of catalysts. Total sulfur removal from feeds down to low ppm-wt levels is an attainable goal. A significant portion of the contaminants are present as highly aromatic polar compounds. Certain phosphonium based ionic liquids have been found to selectively extract these compounds from VGO. Removal of the contaminants from the VGO will have a beneficial impact on downstream processing conditions and have an environmental impact by reducing the NOx and sulfur emissions from the regenerator.
• Desulfurized feeds can be further processed using noble metal catalysts.
• the contaminant content of VGO feeds are reduced by hydrotreating the feed to remove nitrogen, metals and sulfur prior to further processing.
• this process uses hydrogen, in a costly process step.
• hydroprocessing of feeds reduced in contaminants is significantly easier than processing highly contaminated feeds. It can be envisioned that similar aromatic compounds could be extracted from other hydrocarbon streams as well.However, VGO feed streams having higher amounts of sulfur compounds are more difficult to convert. It is the objective of the current invention to improve the ionic liquid extraction of sulfur compounds by first removing the more highly aromatic polar nitrogen species from VGO. Experiments have shown that deep de-nitrogenation of VGO can lead to increased selectivity to sulfur removal.
• Hydroprocessing includes processes which convert hydrocarbons in the presence of hydroprocessing catalyst and hydrogen to more valuable products.
• Hydrocracking is a hydroprocessing process in which hydrocarbons crack in the presence of hydrogen and hydrocracking catalyst to lower molecular weight hydrocarbons.
• a hydrocracking unit may contain one or more beds of the same or different catalyst.
• Slurry hydrocracking is a slurried catalytic process used to crack residue feeds to gas oils and fuels.
• Hydrotreating is a hydroprocessing process used to remove heteroatoms such as sulfur and nitrogen from hydrocarbon streams to meet fuel specifications and to saturate olefmic compounds. Hydrotreating can be performed at high or low pressures, but is typically operated at lower pressure than hydrocracking.
• US 7,001,504 B2 discloses a process for the removal of organosulfur compounds from hydrocarbon materials which includes contacting an ionic liquid with a hydrocarbon material to extract sulfur containing compounds into the ionic liquid.
• US 7,553,406 B2 discloses a process for removing polarizable impurities from hydrocarbons and mixtures of hydrocarbons using ionic liquids as an extraction medium.
• US 7,553,406 B2 also discloses that different ionic liquids show different extractive properties for different polarizable compounds.
• US 20110155637 discloses the removal of nitrogen compounds from vacuum gas oil by use of a VGO-immiscible phosphonium ionic liquid, but there remains a need for improved processes that enable the removal of sulfur compounds in addition to other impurities from vacuum gas oil (VGO).
• VGO vacuum gas oil
• the present invention is a process for removing sulfur compounds from a vacuum gas oil comprising contacting the vacuum gas oil with a VGO-immiscible phosphonium ionic liquid to produce a processed vacuum gas oil and VGO-immiscible phosphonium ionic liquid mixture, and separating the mixture to produce a processed vacuum gas oil effluent and a VGO- immiscible phosphonium ionic liquid effluent comprising the sulfur compounds.
• the vacuum gas oil is subjected to additional treatment such as hydroprocessing before or after the contact with the VGO-immiscible phosphonium ionic liquid or between two periods of contact with the VGO-immiscible phosphonium ionic liquid.
• the vacuum gas oil that is treated in the process of the present invention has a low nitrogen content (below 500 ppm-wt). If the VGO feed has a level of nitrogen above this level, then it is treated by ionic liquids, hydroprocessing or other process to reduce the nitrogen level below 500 ppm-wt. In particular, it has been found that by first extracting the more highly aromatic polar nitrogen species, the extraction of sulfur species becomes more efficient.
• the VGO-immiscible phosphonium ionic liquid comprises at least one ionic liquid from at least one of the following ionic liquids: tetraalkylphosphonium dialkylphosphates, tetraalkylphosphonium dialkyl phosphinates, tetraalkylphosphonium phosphates,
• the VGO-immiscible phosphonium ionic liquid comprises at least one of trihexyl(tetradecyl)phosphonium chloride,
• tributyl(decyl)phosphonium chloride tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, triisobutyl(methyl)phosphonium tosylate, tributyl(methyl)phosphonium methylsulfate, tributyl(ethyl)phosphonium diethylphosphate, and tetrabutylphosphonium methanesulfonate.
• FIGURE shows a comparison of the percent desulfurization vs. nitrogen content level for three different ionic liquid compositions.
• the invention may be used to remove a sulfur compound from a hydroprocessed vacuum gas oil (VGO) hydrocarbon fraction through use of a VGO-immiscible phosphonium ionic liquid.
• VGO hydroprocessed vacuum gas oil
• the invention may also be used to remove a sulfur compound from a vacuum gas oil prior to hydroprocessing of the vacuum gas oil. More than one type of sulfur compound may be removed.
• vacuum gas oil VGO
• VGO phase VGO phase
• similar terms relating to vacuum gas oil as used herein are to be interpreted broadly to receive not only their ordinary meanings as used by those skilled in the art of producing and converting such hydrocarbon fractions, but also in a broad manner to account for the application of our processes to hydrocarbon fractions exhibiting VGO-like characteristics.
• the terms encompass straight run VGO, as may be produced in a crude fractionation section of an oil refinery, as well as VGO product cuts, fractions, or streams that may be produced, for example, by coker, deasphalting, and visbreaking processing units, or which may be produced by blending various hydrocarbons.
• the vacuum gas oil that is treated with ionic liquids to remove sulfur compounds has a low nitrogen content.
• the low nitrogen content may be the result of some previous treatment or because the VGO is a product from a low nitrogen feedstock. If necessary, the VGO is treated by hydroprocessing, ionic liquid extraction or other process so that the VGO has a low nitrogen content before being treated with the ionic liquid to remove the sulfur compounds.
• low nitrogen content means less than 500 total ppm-wt nitrogen. In some circumstances, the low nitrogen content may be less than 400 ppm-wt total nitrogen, less than 300 ppm-wt total nitrogen or less than 200 ppm-wt total nitrogen.
• hydroprocessing includes both hydrocracking and hydrotreating.
• Hydrocracking refers to a process in which hydrocarbons crack in the presence of hydrogen to lower molecular weight hydrocarbons.
• Hydrocracking also includes slurry hydrocracking in which resid feed is mixed with catalyst and hydrogen to make a slurry and cracked to lower boiling products. VGO in the products may be recycled to manage coke precursors referred to as mesophase.
• Hydrotreating is a process wherein hydrogen is contacted with hydrocarbon in the presence of suitable catalysts which are primarily active for the removal of heteroatoms, such as sulfur, nitrogen and metals from the hydrocarbon feedstock. In hydrotreating, hydrocarbons with double and triple bonds may be saturated. Aromatics may also be saturated. However, it has been found that hydrotreating is ineffective in removal of certain refractory heteroatoms.
• VGO comprises petroleum hydrocarbon components boiling in the range of from 100° to 720°C.
• the VGO boils from 250° to 650°C and has a density in the range of from 0.87 to 0.95 g/cm 3 .
• the VGO boils from 95° to 580°C; and in a further embodiment, the VGO boils from 300° to 720°C.
• VGO may contain from 100 to 40,000 ppm-wt sulfur.
• the sulfur content of the VGO ranges from 100 to 25,000 ppm-wt. The sulfur content may be determined using ASTM method D5453.
• VGO may contain from 100 to 30,000 ppm-wt nitrogen.
• the nitrogen content of the VGO ranges from 10 to 20000 ppm-wt.
• the nitrogen content may be determined using ASTM method D4629-02, Trace Nitrogen in Liquid Petroleum Hydrocarbons by Syringe/ Inlet Oxidative Combustion and Chemiluminescence Detection. Unless otherwise noted, the analytical methods used herein such as ASTM D4629-02 are available from ASTM International, 100 Barr Harbor Drive, West Conshohocken, Pennsylvania, USA.
• Processes according to the invention remove sulfur compounds from vacuum gas oil. That is, the invention removes at least one sulfur compound. It is understood that vacuum gas oil will usually comprise a plurality of sulfur compounds of different types in various amounts. The invention may remove the same or different amounts of each type of sulfur compound, and some types of sulfur compounds may not be removed.
• the sulfur content of the low nitrogen content vacuum gas oil is reduced by at least 13 wt% and in some instances at least 20 wt%.
• the sulfur content of the low nitrogen content vacuum gas oil may be reduced by at least 25 wt% and in some instances by greater than 30 wt%.
• the sulfur content may be reduced by at least 40 wt% and in some instances more than 50 wt%.
• processes according to the invention may also remove nitrogen compounds. It is understood that vacuum gas oil will usually comprise a plurality of sulfur compounds and nitrogen compounds of different types in various amounts. The invention may remove the same or different amounts of each type of sulfur compound and nitrogen compound, and some types of nitrogen compounds may not be removed. In an embodiment, nitrogen compounds may be reduced by at least 50 wt% and in some instances at least 75 wt% when sulfur content is reduced by at least 15 wt%.
• ionic liquids are used to extract one or more sulfur compounds from VGO.
• ionic liquids are non-aqueous, organic salts composed of ions where the positive ion is charge balanced with negative ion. These materials have low melting points, often below 100°C, undetectable vapor pressure and good chemical and thermal stability.
• the cationic charge of the salt is localized over hetero atoms such as nitrogen, phosphorous, sulfur, arsenic, boron, antimony, and aluminum, and the anions may be any inorganic, organic, or
• organometallic species are organometallic species.
• VGO-immiscible phosphonium ionic liquids suitable for use in the instant invention are VGO-immiscible phosphonium ionic liquids.
• VGO-immiscible phosphonium ionic liquid means an ionic liquid having a cation comprising at least one phosphorous atom and which is capable of forming a separate phase from VGO under operating conditions of the process.
• Ionic liquids that are miscible with VGO at the process conditions will be completely soluble with the VGO; therefore, no phase separation will be feasible.
• VGO-immiscible phosphonium ionic liquids may be insoluble with or partially soluble with VGO under operating conditions.
• a phosphonium ionic liquid capable of forming a separate phase from the vacuum gas oil under the operating conditions is considered to be VGO-immiscible.
• Ionic liquids according to the invention may be insoluble, partially soluble, or completely soluble (miscible) with water.
• the VGO-immiscible phosphonium ionic liquid comprises at least one ionic liquid from at least one of the following groups of ionic liquids: tetraalkylphosphonium
• dialkylphosphates tetraalkylphosphonium dialkyl phosphinates, tetraalkylphosphonium phosphates, tetraalkylphosphonium tosylates, tetraalkylphosphonium sulfates,
• the VGO-immiscible phosphonium ionic liquid comprises at least one of trihexyl(tetradecyl)phosphonium chloride, trihexyl(tetradecyl)phosphonium bromide, tributyl(methyl)phosphonium bromide,
• tributyl(decyl)phosphonium chloride tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, triisobutyl(methyl)phosphonium tosylate, tributyl(methyl)phosphonium methylsulfate, tributyl(ethyl)phosphonium diethylphosphate, and tetrabutylphosphonium methanesulfonate.
• the VGO-immiscible phosphonium ionic liquid is selected from the group consisting of trihexyl(tetradecyl)phosphonium chloride, trihexyl(tetradecyl)phosphonium bromide, tributyl(methyl)phosphonium bromide, tributyl(methyl)phosphonium chloride, tributyl(hexyl)phosphonium bromide, tributyl(hexyl)phosphonium chloride,
• the VGO-immiscible phosphonium ionic liquid may be selected from the group consisting of trihexyl(tetradecyl)phosphonium halides, tetraalkylphosphonium
• the VGO-immiscible phosphonium ionic liquid may comprise at least one ionic liquid from at least one of the following groups of ionic liquids trihexyl(tetradecyl)phosphonium halides, tetraalkylphosphonium
• dialkylphosphates tetraalkylphosphonium tosylates, tetraalkylphosphonium sulfonates, and tetraalkylphosphonium halides.
• the invention is a process for removing sulfur compounds from a low nitrogen content vacuum gas oil (VGO) comprising a contacting step and a separating step.
• VGO low nitrogen content vacuum gas oil
• the contacting step vacuum gas oil comprising one or more sulfur compounds and a VGO- immiscible phosphonium ionic liquid are contacted or mixed.
• the contacting may facilitate transfer or extraction of the one or more sulfur compounds from the VGO to the ionic liquid.
• a VGO-immiscible phosphonium ionic liquid that is partially soluble in VGO may facilitate transfer of the one or more sulfur compounds from the VGO to the ionic liquid, partial solubility is not required.
• Insoluble vacuum gas oil / ionic liquid mixtures may have sufficient interfacial surface area between the VGO and ionic liquid to be useful.
• the mixture of vacuum gas oil and ionic liquid settles or forms two phases, a VGO phase and an ionic liquid phase, which is separated to produce a VGO-immiscible phosphonium ionic liquid effluent and a vacuum gas oil effluent.
• nitrogen compounds are removed from the VGO to produce a low nitrogen content VGO that can then be treated with ionic liquids to remove sulfur compounds.
• the removal of nitrogen compounds may be done by treating the VGO with an ionic liquid, hydrotreating or a combination of treating the VGO with ionic liquids preceded or followed by hydrotreating to produce a low nitrogen content VGO. It was found that when a low nitrogen content VGO was processed in accordance with the present invention, it was possible to produce a greater reduction in sulfur content of the VGO with a lower sulfur content than was possible when a higher nitrogen content VGO was treated.
• the process may be conducted in equipment which are well known in the art and are suitable for batch or continuous operation.
• VGO and a VGO- immiscible phosphonium ionic liquid were mixed in a beaker, flask, or other vessel, e.g., by stirring, shaking, use of a mixer, or a magnetic stirrer.
• the mixing or agitation is stopped and the mixture forms a VGO phase and an ionic liquid phase which can be separated, for example, by decanting, centrifugation, or use of a pipette to produce a vacuum gas oil effluent having lower sulfur compound content relative to the vacuum gas oil.
• the process also produces a VGO- immiscible phosphonium ionic liquid effluent comprising the one or more sulfur compounds.
• the contacting and separating steps may be repeated for example when the sulfur content of the vacuum gas oil effluent is to be reduced further to obtain a desired sulfur level in the ultimate VGO product stream from the process. These desired levels of desulfurization may be referred to as predetermined levels.
• Each set, group, or pair of contacting and separating steps may be referred to as a sulfur compound removal step.
• the invention encompasses single and multiple sulfur removal steps.
• the term "zone" can refer to one or more equipment items and/or one or more sub-zones.
• Equipment items may include, for example, one or more vessels, heaters, separators, exchangers, conduits, pumps, compressors, and controllers.
• an equipment item can further include one or more zones or sub-zones.
• the sulfur compound removal process or step may be conducted in a similar manner and with similar equipment as is used to conduct other liquid-liquid wash and extraction operations.
• Suitable equipment includes, for example, columns with: trays, packing, rotating discs or plates, and static mixers. Pulse columns and mixing / settling tanks may also be used.
• the equipment may be of an appropriate size or scale to treat the volumes of feed that are to be treated.
• At least one type of sulfur compound is removed in an extraction zone that comprises a multi-stage, counter-current extraction column wherein vacuum gas oil and VGO-immiscible phosphonium ionic liquid are contacted and separated.
• the ionic liquid introduced to the sulfur removal step may be referred to as a "lean ionic liquid” generally meaning a VGO-immiscible phosphonium ionic liquid that is not saturated with one or more extracted nitrogen compounds or sulfur compounds.
• Lean ionic liquid may include one or both of fresh and regenerated ionic liquid and is suitable for accepting or extracting sulfur compounds from the VGO feed.
• the ionic liquid effluent may be referred to as "rich ionic liquid", which generally means a VGO-immiscible phosphonium ionic liquid effluent produced by a sulfur compound removal step or process or otherwise including a greater amount of extracted sulfur compounds than the amount of extracted sulfur compounds included in the lean ionic liquid.
• a rich ionic liquid may require regeneration or dilution, e.g. with fresh ionic liquid, before recycling the rich ionic liquid to the same or another nitrogen removal step of the process. Methods for regenerating a rich ionic liquid are well known and for example are described in US20110155637 or US2010024352.
• the sulfur compound removal steps may be conducted under conditions including temperatures and pressures sufficient to keep the VGO-immiscible phosphonium ionic liquid and VGO feeds and effluents as liquids.
• sulfur compound removal steps will be at a temperature that may range between 10°C and less than the decomposition temperature of the phosphonium ionic liquid; and the pressure may range between atmospheric pressure and 700 kPa(g).
• the decomposition temperature of the ionic liquid is the lowest temperature at which any of the ionic liquid components decompose.
• the sulfur compound removal steps may be conducted at a uniform temperature and pressure or the contacting and separating steps may be operated at different temperatures and/or pressures.
• the contacting step is conducted at a first temperature
• the separating step is conducted at a temperature at least 5°C lower than the first temperature.
• the first temperature is 80°C. Such temperature differences may facilitate separation of the VGO and ionic liquid phases.
• the sulfur compound removal step conditions such as the contacting or mixing time, the separation or settling time, and the ratio of VGO feed to VGO-immiscible phosphonium ionic liquid (lean ionic liquid) may vary greatly based, for example, on the specific ionic liquid or liquids employed, the nature of the VGO feed (straight run or previously processed), the sulfur content of the VGO feed, the degree of sulfur compound removal required, the number of steps employed, and the specific equipment used. In general it is expected that contacting time may range from less than one minute to two hours; settling time may range from one minute to eight hours; and the weight ratio of VGO feed to lean ionic liquid introduced to the sulfur removal steps may range from 1 : 1,000 to 1,000:1.
• the weight ratio of VGO feed to lean ionic liquid may range from 1 : 100 to 100: 1 ; and the weight ratio of VGO feed to lean ionic liquid may range from 1 : 10 to 10 : 1. In an embodiment the weight of VGO feed is greater than the weight of ionic liquid introduced to the sulfur removal steps.
• the amount of water present in the vacuum gas oil / VGO-immiscible phosphonium ionic liquid mixture during the nitrogen compound and sulfur compound removal steps may also affect the amount of sulfur compounds removed and/or the degree of phase separation, i.e., recovery of the VGO and ionic liquid.
• the VGO / VGO-immiscible phosphonium ionic liquid mixture has a water content of less than 10% relative to the weight of the ionic liquid.
• the water content of the VGO / VGO-immiscible phosphonium ionic liquid mixture is less than 5% relative to the weight of the ionic liquid; and the water content of the VGO / VGO-immiscible phosphonium ionic liquid mixture may be less than 2% relative to the weight of the ionic liquid.
• the VGO / VGO- immiscible phosphonium ionic liquid mixture is water free, i.e., the mixture does not contain water.
• connection point of various inlet and effluent streams within the zones is not essential to the invention.
• a stream to a distillation zone may be sent directly to the column, or the stream may first be sent to other equipment within the zone such as heat exchangers, to adjust temperature, and/or pumps to adjust the pressure.
• streams entering and leaving sulfur compound removal, washing, and regeneration zones may pass through ancillary equipment such as heat exchanges within the zones.
• Streams, including recycle streams, introduced to washing or extraction zones may be introduced individually or combined prior to or within such zones.
• the invention encompasses a variety of flow scheme embodiments including optional destinations of streams, splitting streams to send the same composition, i.e. aliquot portions, to more than one destination, and recycling various streams within the process.
• Examples include: various streams comprising ionic liquid and water may be dried and/or passed to other zones to provide all or a portion of the water and/or ionic liquid required by the destination zone.
• the various process steps may be operated continuously and/or intermittently as needed for a given embodiment e.g. based on the quantities and properties of the streams to be processed in such steps.
• the invention encompasses multiple sulfur compound removal steps, which may be performed in parallel, sequentially, or a combination thereof. Multiple sulfur compound removal steps may be performed within the same sulfur compound removal zone and/or multiple sulfur compound removal zones may be employed with or without intervening washing, regeneration and/or drying zones.
• a digitally controlled Optichem hot plate magnetic stirrer with 17 individual sample wells was used to screen ionic liquids for VGO de-sulfurization.
• the experiments were conducted in 6 dram vials with 1.9 cm (0.75 inch) cross shaped magnetic stir bars for mixing.
• 3 grams of ionic liquid were combined in a vial with 6 grams of VGO, heated to 80°C and mixed at 300 rpm for 30 minutes. After 30 minutes, the mixing was stopped and the samples were held static at 80°C in successful experiments in which separation occurred and the extracted VGO was suctioned off with a glass pipette.
• a VGO sample that had been hydrotreated to four different nitrogen levels provided feeds for the de- sulfurization experiments. The hydrotreatmg process reduced the sulfur and nitrogen, but did not completely remove either species. Analysis of the starting VGO and the 4 hydrotreated samples is shown in Table 1.
• tributyl(decyl)phosphonium chloride and 8g of each hydrotreated VGO (HTVGO) sample were combined in 6 dram vials with a stir bar. The vials were placed onto a heated stir plate and stirred at 80°C for 30 minutes. After 30 minutes, the stirring was stopped and the ionic liquid/HTVGO mixtures were allowed to settle for 30 minutes. The HTVGO material was then separated from the ionic liquid and analyzed for sulfur content. Desulfurization ranged from 20.7 to 28.7% depending on the amount of nitrogen remaining in the HTVGO. Results are shown in Table 2. TABLE 2
• tributylethylphosphonium diethylphosphate and 8g of each HTVGO were combined in 6 dram vials with a stir bar.
• the vials were placed onto a heated stir plate and stirred at 80°C for 30 minutes. After 30 minutes, the stirring was stopped and the ionic liquid/HTVGO mixtures were allowed to settle for 30 minutes.
• the HTVGO material was then separated from the ionic liquid and analyzed for S content. Desulfurization ranged from 13.4 to 16.8 wt% depending on the amount of nitrogen remaining in the HTVGO. Results are shown in Table 3.
• a mixture of ionic liquids was prepared that contained 80%
• tributyl(ethyl)phosphonium diethylphosphate and 20% trihexyl (tetradecyl )phosphonium bromide 5 grams of the ionic liquid mixture and 5 grams of HTVGO were combined in 6 dram vials. The vials were placed onto a heated stir plate and stirred at 80°C for 30 minutes. After 30 minutes, the stirring was stopped and the ionic liquid/HTVGO mixtures were allowed to settle for 30 minutes. The HTVGO material was then separated from the ionic liquid and analyzed for S content. Desulfurization ranged from 22.7 to 31.3 % depending on the amount of nitrogen remaining in the HTVGO. Results are shown in Table 4. TABLE 4
• a plot comparing the amount of nitrogen in the feed to the desulfurization attained is shown in the Figure.
• the lower line shows the results with a tributylethylphosphonium diethylphosphate ionic liquid (diamonds) from Example 1.
• the squares are for a

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