JP2008525624A - Oxidative desulfurization process - Google Patents

Abstract

  The disclosure discloses a process for producing refined transportation fuels or blended components for refined transportation fuels in the presence of an oxidation catalyst comprising a titanium-containing composition under oxidizing conditions. Is a process of reducing the sulfur and / or nitrogen content of the distillation feedstock by converting sulfur species to sulfones and / or sulfoxides adsorbed on the titanium-containing composition.

Description

  The present invention relates to natural petroleum-derived transportation fuels, and more particularly to a method for producing refinery blending components of transportation fuels that are liquid at ambient conditions. More particularly, the present invention relates to contacting a petroleum distillate with an oxygen-containing gas under oxidizing conditions in the presence of a heterogeneous catalyst to oxidize nitrogen and / or sulfur containing organic impurities contained in the petroleum distillate. It relates to a process for the production of such fuels, including the oxidation of petroleum distillates by

  It is well known that internal combustion engines have reformed transportation in connection with the invention of internal combustion engines in the last decade of the 19th century. Among them, Benz and Gottleib Wilhelm Daimler invented and developed an engine that uses electric ignition of fuel such as gasoline, and Rudolf CK Diesel developed a diesel engine that uses compression for fuel auto-ignition to use low-cost organic fuel. Invented and assembled. Development of improved diesel engines for use in transportation is advancing with improvements in diesel fuel compositions. Modern high-performance diesel engines seek improved specifications for fuel compositions, but cost remains an important consideration.

  Currently, most transportation fuels are derived from natural petroleum. In fact, petroleum is still the world's leading source of hydrocarbons used as fuel and petrochemical feedstock. Although the composition of natural petroleum or crude oil varies widely, all crude oils contain sulfur compounds and most contain nitrogen compounds. Although it may contain oxygen, the oxygen content of most crude oils is low. Generally, the sulfur concentration in crude oil is less than about 8%, but most crude oils have a sulfur concentration of about 0.5 to about 1.5%. The nitrogen concentration is usually less than 0.2% but can be as high as 1.6%.

  Crude oil is rarely used as it is produced in oil wells and is converted into a wide range of fuels and petrochemical feedstocks at refineries. Typically, transportation fuels are produced by processing and blending distillates from crude oil to meet specific end-use specifications. Today, most crude oils available in large quantities are high in sulfur, so the distillate must be desulfurized in order to obtain a product that meets performance and / or environmental standards. Sulfur-containing organic compounds in fuels remain a major source of environmental pollution. During combustion, they are converted to sulfur oxides, which then generate sulfur oxyacids and further contribute to particulate matter release.

  Even in modern high-performance diesel engines, conventional fuel combustion generates soot in the exhaust. Oxygenated compounds and compounds with little or no carbon-carbon chemical bonds, such as methanol and dimethyl ether, are known to reduce soot and engine exhaust emissions. However, most of such compounds have a high vapor pressure and / or are almost insoluble in diesel fuel and have low ignition quality as indicated by their cetane number. In addition, other methods of improving diesel fuel that reduce sulfur content and aromatic content by chemical hydrogenation also reduce fuel lubricity. Low lubricity diesel fuel may cause excessive wear of fuel pumps, injectors and other moving parts that come into contact with the fuel under high pressure.

  The distillate used as a fuel or fuel blend component for use in compression ignition internal combustion engines (diesel engines) is typically a middle distillate containing about 1-3 wt% sulfur. In the past, typical specifications for diesel fuel were up to 0.5 wt%. By 1993, regulations in Europe and the United States limited sulfur in diesel fuel to 0.3 wt%. In Europe and the United States by 1996 and in Japan by 1997, the maximum sulfur content in diesel fuel was reduced to less than 0.05 wt%. This global trend is expected to continue to lower levels for sulfur.

  The US Environmental Protection Agency is targeting a sulfur level of less than 15 ppm for on-road diesel vehicles during 2006. The European Union (EU) standard will be less than 50 ppm during 2005. In addition, the World Wide Fuels Charter, supported by all global automobile manufacturers, has a 5-10 ppm level of IV fuels for developed countries. Recommend strict sulfur requirements. In order to meet these standards for ultra-low sulfur content fuels, refiners will have to produce fuels with lower levels of sulfur at the refinery gate. Thus, refiners are faced with the challenge of reducing fuel sulfur levels, particularly diesel fuel sulfur levels, within the time frame prescribed by regulatory agencies.

  In one aspect, the new emission regulations being discussed for introduction in California and other states have generated great interest in catalytic exhaust treatment. The challenge of applying catalytic exhaust gas control to diesel engines, particularly heavy-duty diesel engines, differs greatly from spark ignition internal combustion engines (gasoline engines) in two respects. First, conventional three-way catalysts (TWC) are not effective for removing NOx emissions from diesel engines, and secondly, the need for particulate matter control is much higher than for gasoline engines.

  Several exhaust gas treatment technologies have emerged to control emissions from diesel engines, and in all sectors, fuel sulfur levels affect the efficiency of the technology. Sulfur is a catalyst poison that reduces catalyst activity. In addition, in the catalytically controlled flow of emissions from diesel engines, high sulfur fuels also cause secondary problems of particulate matter release due to the catalytic oxidation of sulfur and reaction with water forming sulfate mist. This mist is collected as part of the particulate matter release.

  Emissions from compression ignition engines are different from emissions from spark ignition engines because of the different methods used to initiate combustion. Compression ignition requires the combustion of fuel droplets in a very lean air / fuel mixture. The combustion process leaves very small carbon particles and causes a significantly higher particulate emission than in gasoline engines. Because of lean operation, CO and gaseous hydrocarbon emissions are significantly lower than in gasoline engines. However, a very large amount of unburned hydrocarbon is adsorbed on the carbon particulate matter. These hydrocarbons are called SOF (soluble organic fraction).

  Increasing combustion temperature can reduce particulate emissions, but leads to increased NOx emissions by the well-known Zeldovitch mechanism. Therefore, there is a need for a process that matches the emission of particulate matter and NOx to emission regulations.

  Available evidence strongly suggests that ultra-low sulfur fuel is a key and prominent technology for the catalytic treatment of diesel exhaust to control emissions. Fuel sulfur levels below 15 ppm are likewise necessary to achieve particulate levels below 0.01 g / bhp-hr. Such a level would be very compatible with existing exhaust gas treatment catalyst combinations that have demonstrated the ability to achieve NOx emissions near 0.5 g / bhp-hr. In addition, NOx trap systems are extremely sensitive to fuel sulfur and available evidence suggests that sulfur levels below 10 ppm may need to remain active.

In the face of stricter sulfur standards in transportation fuels, sulfur removal from petroleum feedstocks and products will become increasingly important over the next few years.
Conventional hydrodesulfurization (HDS) catalysts can be used to remove most of the sulfur from petroleum distillates for refinery transportation fuel blends, but the sulfur atoms as in polycyclic aromatic sulfur compounds are steric. It is not effective for removing sulfur from the hindered compound. This is especially true when the sulfur heteroatom is doubly hindered (eg, 4,6-dimethyldibenzothiophene). These hindered dibenzothiophenes dominate at low sulfur levels, such as 50-100 ppm, and will require stringent processing conditions to be desulfurized. The use of conventional hydrodesulfurization catalysts at high temperatures will cause yield loss, fast catalyst coking and product quality degradation (eg, color). Using high pressure requires a large capital investment.

  In the future, such hindered sulfur compounds will also have to be removed from distillation feeds and products to meet stricter standards. There is an urgent need for economical removal of sulfur from distillates and other hydrocarbon products.

  In the art, processes for removing sulfur from distillation feeds and products are substantial. One known method is an oil containing at least a major amount of material boiling at a higher temperature than a very high boiling hydrocarbon material (a petroleum fraction containing at least a major amount of material boiling above about 550 ° F.). Oxidation of the fraction and subsequent treatment of the effluent containing the oxidized compound at elevated temperature to form hydrogen sulfide (500 ° F. to 1350 ° F.) and / or hydrotreatment to hydrocarbons Including reducing the sulfur content of the material. See, for example, US Pat. No. 3,847,798 (Jin Sun Yoo, et al) and US Pat. No. 5,288,390 (Vincent A. Durante). Such a method has only been demonstrated with limited equipment. Rather, only a low degree of desulfurization is achieved. In addition, there may be a substantial loss of value product due to cracking and / or coke formation during the implementation of these methods. Therefore, it would be beneficial to develop a process that improves the degree of desulfurization while reducing cracking or coke formation.

  US Pat. No. 6,087,544 (Robert J. Wittenbrink et al.) Relates to a distillation feed stream process for producing a distillate fuel having a lower level of sulfur than the distillation feed stream. Such fuels are produced by dividing the distillation feed stream into a light fraction (containing only about 50-100 ppm sulfur) and a heavy fraction. The light fraction is hydrotreated to remove substantially all of the sulfur in the light fraction. The desulfurized light fraction is then blended with 1/2 of the heavy fraction to produce a low sulfur distillate fuel. For example, 85 wt% desulfurized light fraction and 15 wt% untreated heavy fraction reduced sulfur levels from 663 ppm to 310 ppm. However, to obtain this low sulfur level, only about 85% of the distillation feed stream is recovered as a low sulfur distillate fuel product.

  US 2002/0035306 A1 (Gore et al.) Discloses a multi-stage process for desulfurizing liquid petroleum fuels that also remove nitrogen-containing compounds and aromatics. The process steps are thiophene extraction; thiophene oxidation; thiophene-oxide and dioxide extraction; raffinate solvent recovery and polishing; extraction solvent recovery; and recycle solvent purification.

The Gore et al. Process attempts to remove 5-65% of the thiophenic and nitrogen-containing compounds and some aromatics in the feed stream prior to the oxidation step. While the presence of aromatics in diesel engine fuels tends to reduce cetane number, the Gore et al. Process requires end use for extracted aromatics. Furthermore, the presence of an effective amount of aromatic compounds increases fuel density (Btu / gal) and enhances the cold flow characteristics of diesel engine fuel. Therefore, it is not wise to extract excessive amounts of aromatic compounds. For the oxidation step, the oxidant is prepared in situ or preformed. The operating conditions included a molar ratio of H ₂ O ₂ : S between about 1: 1 and 2.2: 1; an acetic acid content between about 5% and 45% of the feed; 10% and 25% of the feed There may be mentioned a solvent content between; and a catalyst volume of less than about 5,000 ppm sulfuric acid, preferably less than 1,000 ppm. Gore et al. Further discloses the use of an acid catalyst, preferably sulfuric acid, in the oxidation process. The use of sulfuric acid as the oxidizing acid is problematic in that corrosion is a concern in the presence of water and hydrocarbons can be sulfonated in the absence of water.

  According to Gore et al., The purpose of the thiophene-oxide and dioxide extraction process is to include more than 90% of the various substituted benzothiophene and dibenzothiophene oxides and N-oxide compounds in addition to one or more. Is to remove the fraction of the aromatic compound in the extraction solvent which is an aqueous acetic acid having a co-solvent.

  US Pat. No. 6,368,495 B1 (Kocal et al.) Further discloses a multi-step process for the removal of thiophenes and thiophene derivatives from petroleum fractions. This process involves contacting the hydrocarbon feed stream with an oxidant, followed by cracking the oxidized sulfur-containing compound to produce a heated liquid stream and a volatile sulfur compound, resulting in solid cracking of the oxidization process effluent. A step of contacting with a catalyst. This patent discloses the use of oxidizing agents such as alkyl hydroperoxides, peroxides, percarboxylic acids and oxygen.

  International patent application WO 02/18518 A1 (Rappas et al) discloses a two-stage desulfurization process utilized downstream of a hydrotreater. This process involves distillate aqueous formic acid-based hydrogen peroxide biphasic oxidation to convert thiophene sulfur to the corresponding sulfones. During the oxidation process, some sulfones are extracted into the oxidation solution. These sulfones are removed from the hydrocarbon phase by a subsequent phase separation step. The hydrocarbon phase containing the remaining sulfones is then subjected to a liquid-liquid extraction or solid adsorption process.

  The use of formic acid in the oxidation process is undesirable. Formic acid is relatively higher than acetic acid. In addition, formic acid is considered to be a “reducing” solvent and hydrogenates certain metals to weaken them. Therefore, a special alloy for handling formic acid is required. These expensive alloys should be used in solvent recovery areas and storage containers. The use of formic acid requires the use of high temperatures to prevent the appearance of a third precipitated solid phase and also for the separation of the hydrocarbon phase from the aqueous oxidant phase. It is believed that this undesirable phase can be formed due to the poor lipophilicity of formic acid. Thus, at lower temperatures, formic acid cannot maintain some of the extracted sulfones in solution.

  US Pat. No. 6,171,478 B1 (Cabrera et al.) Discloses another complex multi-step desulfurization process. In particular, the process includes a hydrodesulfurization step, an oxidation step, a cracking step, and a separation step, where a portion of the sulfur-oxidized compound is separated from the cracked step effluent stream. The aqueous oxidation solution used in the oxidation step preferably contains acetic acid and hydrogen peroxide. Any residual hydrogen peroxide in the oxidation process effluent is decomposed by contacting the effluent with a cracking catalyst.

  The separation step is performed with a selective solvent to extract the sulfur-oxidized compound. According to the teachings of Cabrera et al., Preferred selective solvents are acetonitrile, dimethylformamide and sulfolane.

  A number of solvents have been proposed to remove oxidized sulfur compounds. For example, US Pat. No. 6,160,193 (Gore) teaches the use of a wide range of solvents suitable for use in the extraction of sulfones. A preferred solvent is dimethyl sulfoxide (DMSO).

Notsuki, T .; Takashima, N .; Qian, W .; Ishihara, A .; Imai, T .; Kabe, T "Oxidative Desulfurization of Light Gas Oil and Vacuum Gas Oil by Oxidation and Solvent Extract", published in Energy & Fuels 2000, 14, 1232. The list is shown below.
N, N-dimethylformamide (DMF)
Methanol acetonitrile sulfolane
Gore states that there is a relationship between solvent polarity and solvent extraction efficiency. All of the solvents listed in the patent and paper are desirably immiscible with diesel fuel. All of these are characterized as either polar protic or aprotic solvents.

  International patent application WO 01/32809 discloses a process for selectively oxidizing distillate fuel or middle distillate. This reference describes an oxidized distillate fuel in which hydroxyl groups and / or carbonyl groups are chemically bonded to paraffinic molecules in the fuel, resulting in unburned fuel during combustion of the fuel. That result in a reduction in particulate matter. This reference describes saturated aliphatic or cyclic compounds in fuels with peroxide, ozone or hydrogen peroxide in the presence of various titanium-containing silicon-based zeolites so that hydroxyl or carbonyl groups are formed. A process for selective oxidation of is disclosed.

  US Pat. No. 6,402,939 B1 (Yen et al.) Discloses an oxidative desulfurization process for fossil fuels using ultrasound. Briefly, liquid fossil fuels are combined with an acidic aqueous solution containing water and hydroperoxide to produce a multiphase reaction mixture, followed by ultrasound for a time sufficient to cause oxidation of sulfides to sulfones. Apply to multiphase reaction medium. The sulfones are subsequently extracted.

  U.S. Patent Application Publication 2001/0015339 A1 (Sherman) discloses that an oxidizing gas is formed into submicron sized bubbles and these bubbles are dispersed in flowing diesel fuel to convert sulfur compounds into sulfoxides and / or sulfones. Disclosed is a method for removing sulfur compounds from diesel fuel, including oxidizing.

  In view of the above, it does not use costly hydroprocessing techniques involving the use of large amounts of hydrogen, or uses expensive chemical oxidants, avoids the complex handling and corrosion problems associated with it, and is less complicated It is clear that there is a need for an economical distillation or diesel fuel desulfurization process.

  The present invention involves contacting a distillation feed with an oxygen-containing gas under oxidizing conditions in the presence of a heterogeneous catalyst comprising a titanium-containing composition to convert the sulfur-containing compounds in the distillation feed to the corresponding sulfones or sulfoxides. And then a relatively simple selective desulfurization process that adsorbs a portion of sulfones or sulfoxides to the titanium-containing composition.

  The process of the present invention involves contacting a feedstock with an oxygen-containing gas in the presence of a heterogeneous oxidation catalyst comprising a titanium-containing composition at oxidation conditions in an oxidation / adsorption zone and converting sulfur-containing compounds to sulfones and / or sulfoxides. By reducing the sulfur content of the distillation feed containing sulfur-containing organic impurities and by refining it into a hydrocarbon, and subsequently adsorbing a portion of the sulfones and / or sulfoxides onto the titanium-containing composition. Producing a blend component for a transportation fuel. The fuel or blending component having a reduced sulfur content is then recovered from the oxidation zone. The sulfones and / or sulfoxides may be further removed from the catalyst for further processing and the catalyst regenerated for reuse in the process.

  Suitable feedstocks are generally in the range of about 50 ° C to about 650 ° C at atmospheric pressure, preferably in the range of 150 ° C to about 400 ° C, more preferably about 175 ° C and about 375 ° C for best results. Includes refinery streams boiling at temperatures between. These streams include virgin light middle distillate, virgin heavy middle distillate, fluid contact cracking process light contact cycle oil, coker distillation chamber distillate, hydrocracker distillate, jet fuel, vacuum distillate and these streams. There may be, but is not limited to, collective or individual hydroprocessing embodiments. Preferred streams are collective or individual hydroprocessing embodiments of fluid contact cracking process light contact cycle oil, coker distillation chamber distillation and hydrocracker distillation.

  It is also understood that one or more of the above distillate diverts may be combined for use as a feed for the process of the present invention. In many cases, the performance of refined transport fuel or blended components for refined transport fuel obtained from a variety of different feedstocks is comparable. In these cases, logistics management such as flow volume effectiveness, closest connection location and short-term economics may determine which flow to use.

  In one aspect, the present invention provides the manufacture of refined transportation fuel or blend components for refined transportation fuel from hydrotreated petroleum distillates. Such a hydrotreated distillate is obtained by reacting a petroleum distillate with a hydrogen source under hydrogenation conditions in the presence of a hydrogenation catalyst to remove hydrogen and sulfur from the hydrotreated petroleum distillate. Assisting; in some cases, at least one low-boiling blend component comprising a poor sulfur-rich monoaromatic fraction and a high-boiling feedstock comprising a sulfur-rich, poor monoaromatic fraction, hydrotreated petroleum distillation Prepared by hydrotreating a petroleum distillate boiling between about 50 ° C. and about 650 ° C. by a process involving fractional distillation. According to one embodiment of the process of the present invention, a hydrotreated distillate or low boiling component can be used as a suitable feedstock for the process of the present invention.

  In general, useful hydrogenation catalysts have at least one activity selected from the group consisting of d-transition elements in the periodic table supported on an inert support in an amount of about 0.1% to about 30 wt% of the total catalyst. Contains metal. Suitable active metals include d-transition elements with atomic numbers 21-30, 39-48 and 72-78 in the periodic table elements.

  The catalytic hydrogenation process can be carried out under relatively mild conditions in a fixed bed, moving fluidized bed or boiling bed of catalyst. Under conditions such that a relatively long time elapses before regeneration is required, e.g. about 200 ° C to about 45O ° C, preferably about 250 ° C to about 400 ° C, most preferably about 275 ° C for best results A solid bed of one or more catalysts is preferably used at an average reaction zone temperature of about 350 ° C. and a pressure in the range of about 6 to about 160 atmospheres.

  A particularly preferred pressure range in which hydrogenation provides very good sulfur removal while minimizing the pressure and amount of hydrogen required for the hydrodesulfurization process is in the range of 20-60 atmospheres, more preferably about 25-40 atmospheres. The pressure is within the range.

  The hydrogen circulation rate is generally about 500 SCF / Bbl to about 20,000 SCF / Bbl, preferably about 2,000 SCF / Bbl to about 15,000 SCF / Bbl, and most preferably about 3,000 to about 13,000 SCF / Bbl for best results. Range. Reaction pressures and hydrogen circulation rates below these ranges can result in faster catalyst deactivation rates that result in less effective desulfurization, denitrification and dearomatization. An excessively high reaction pressure increases energy and equipment costs and reduces marginal profit.

The hydrogenation process is typically about 0.2 hr ^-1 to about 10.0 hr ^-1 , preferably about 0.5 hr ^-1 to about 3.0 hr ^-1 , and most preferably about 1.0 hr ^-1 to best results. Operate at a space velocity per liquid hour of approximately 2.0 hr ^-1 . An excessively high space velocity will reduce the overall hydrogenation.

The further reduction of heteroaromatic sulfides from hydrotreating from such distilled petroleum fractions will result in very severe catalytic hydrogenation of the stream to convert these compounds to hydrocarbons and hydrogen sulfide (H ₂ S). Would need to be served. Typically, the larger any hydrocarbon site, the more difficult it is to hydrogenate sulfides. Thus, the residual organosulfur compound remaining after hydrotreating is the larger and most structurally disturbed heteroaromatic compound.

  Where the feedstock is a high-boiling distillate derived from refinery stream hydrogenation, the refinery stream may be a substance that boils between about 200 ° C and about 425 ° C. Preferably, the refinery stream may be a material that boils between about 250 ° C and about 400 ° C, more preferably between about 275 ° C and about 375 ° C.

  Distillation fractions useful for hydrogenation boil at atmospheric pressure in the range of about 50 ° C to about 650 ° C, preferably in the range of 150 ° C to about 400 ° C, more preferably between about 175 ° C to about 375 ° C. Any one, several or all refinery streams may be used. Lighter hydrocarbon components in the distillate product are generally advantageously recovered by gasoline, and the presence of these lower boiling substances in distillate fuel is often constrained by distillate fuel flash point specifications. The heavier hydrocarbon components boiling above 400 ° C. are generally more advantageously treated as a fluid contact cracker feed and converted to gasoline, but are compliant for use in the process of the present invention. The presence of heavier hydrocarbon components in the distillate fuel is further constrained by the distillate fuel end point specification.

  Distillation fractions for hydrogenation are derived from high and low sulfur virgin distillates derived from high and low sulfur crudes, coke oven distillates, catalytic cracker lights and heavy contact cycle oils, hydrocracking units and residual hydrotreating units. The distillation boiling range product may be included. In general, coke oven distillate, light and heavy contact cycle oils are the highest content aromatic feedstock components in the high range of 80 wt%. The main part of the coke oven distillate and cycle oil aromatics is present as monoaromatics and diaromatics, with small amounts of triaromatics. Virgin stocks, such as high and low sulfur virgin distillates, range in the order of 20 wt% aromatics and have less aromatic content. In general, the aromatic content of the combined hydrogenation facility feedstock is in the range of about 5 wt% to about 80 wt%, more typically in the range of about 10 wt% to about 70 wt%, most typically. It will range from about 20 wt% to about 60 wt%.

  The sulfur concentration in the distillate useful in the present invention is generally a function of high and low sulfur crude oil mixtures, hydrogenation capacity per barrel of refinery crude capacity and other properties of the distilled hydrogenation feedstock components. Higher concentration sulfur distillation feed components are generally contact cycle oils from fluid contact cracking units that process virgin distillates derived from high sulfur crude oil, coke oven distillates and relatively high concentrations of sulfur feedstock. . These distillation feed components may range as high as 2 wt% elemental sulfur, but generally range from about 0.1 wt% to about 0.9 wt% elemental sulfur.

  The nitrogen content of the distillate useful in the present invention is also generally a function of the nitrogen content of the crude oil, the hydrogenation capacity per barrel of refinery crude oil, and other properties of the distilled hydrogenation feedstock components. Higher concentrations of nitrogen distillation feed are generally coke oven distillate and contact cycle oil. These distillation feed components may have a total nitrogen concentration as high as 2000 ppm, but generally range from about 5 ppm to about 900 ppm.

  Typically, sulfur compounds in petroleum fractions are relatively nonpolar heteroaromatic sulfides such as substituted benzothiophenes and dibenzothiophenes. At first blush, the heteroaromatic sulfur compounds may appear to be selectively extracted based on several properties that originate solely from these heteroaromatic compounds. Even though the sulfur atom in these compounds has two non-bonding pairs of electrons that are classified as Lewis bases, this property is extracted by Lewis acid. It is still not enough. In other words, selective extraction of heteroaromatic sulfur compounds to achieve lower levels of sulfur requires that the polarities between sulfides and hydrocarbons be significantly different.

  By means of the heterogeneous catalytic oxidation according to the present invention, it is possible to selectively convert these sulfides directly into more polar Lewis basic oxygenated sulfur compounds such as sulfoxides and sulfones. This oxygenated sulfur compound is then adsorbed onto titania-silica. Subsequently, the desulfurized feedstock is recovered from the oxidation / adsorption zone. The process of the present invention is also believed to result in the oxidation and adsorption of any nitrogen-containing species that can be separated simultaneously with the sulfur-containing species.

  Examples of other compounds having a non-bonded electron pair include amines. Heteroaromatic amines are also found in the same stream where the sulfides are found. Amines are more basic than sulfides. The lone pair of electrons functions as a Bronsted-Lowry base (proton acceptor) as well as a Lewis base (electron donor). This pair of electrons on the atom makes the atom susceptible to oxidation in a manner similar to sulfide.

  In one aspect, the present invention provides a method for producing a refined transportation fuel or a blended component for a refined transportation fuel. The method comprises the steps of providing a distillation feed comprising a mixture of hydrocarbons and sulfur-containing organic impurities; and in the presence of an oxidation catalyst comprising titania-silica that acts as an adsorbent within the oxidation zone. Contacting with an oxygen-containing gas such as oxygen-depleted air. Since oxygen-depleted air can be used in the present invention, the oxygen concentration may be less than about 21 vol%. The oxygen-containing stream should preferably have an oxygen content of at least 0.01 vol%. The effective concentration is 0.5 to 10 vol%. The gas may be supplied from an inert diluent such as air and nitrogen as required. One skilled in the art will readily recognize that certain compositions are explosive and that the composition of the oxygen-containing stream should be selected to avoid explosive regions. The oxygen-containing gas may be circulated in an amount ranging from 200 to 20,000 standard cubic feet per barrel.

The pressure in the oxidation / adsorption zone may range from atmospheric to 3000 psig, preferably from about 100 psig to about 400 psig, more preferably from about 100 psig to about 300 psig.
The temperature within the oxidation / adsorption zone may range from about 100 ° F to about 600 °, preferably from about 200 ° F to about 500 ° F, and most preferably from about 300 ° F to about 400 ° F.

The oxidation / adsorption process of the present invention is performed at about 0.1 hr ⁻¹ to about 100 hr ⁻¹ , preferably about 0.2 hr ⁻¹ to about 50 hr ⁻¹ , most preferably about 0.5 hr ⁻¹ to about 0.5 hr ⁻¹ . Operate at a space velocity per liquid hour of about 10 hr ^-1 . An excessively high space velocity will reduce the overall oxidation and adsorption.

  In general, the oxidation / adsorption process of the present invention begins with a distillation feed preheating step. The distillation feed is preheated in the feed / effluent heat exchanger to the target reaction zone temperature before entering the final preheating furnace. The distillation feed may be contacted with the oxygen-containing stream before, during and / or after preheating.

  Since the oxidation reaction is generally exothermic, interstage cooling consisting of heat transfer devices between fixed bed reactors or between catalyst beds in the same reactor shell can be used. At least a portion of the heat generated from the oxidation process can often be advantageously recovered for use in the oxidation process. If this heat recovery is not possible, cooling may be done through a cooling utility such as cooling water or air, or using a quench stream injected directly into the reactor. The two stage process can reduce the exothermic temperature per reactor shell and provide better oxidation reactor temperature control.

  The oxidation / adsorption zone effluent is generally cooled and the effluent stream is sent to a separator device to remove oxygen-containing gas. The oxygen containing gas may be returned to the process. The oxygen containing gas purge rate is often controlled in order to maintain a minimum or maximum oxygen content in the gas that has passed through the reaction zone. The recirculated oxygen-containing gas is generally compressed and supplemented with “make-up” oxygen or oxygen-containing gas (preferably air) as necessary and injected into a process for further oxidation.

  The process of the present invention can be carried out in any gas-liquid-solid reaction zone known to those skilled in the art. For example, the reaction zone may consist of one or more fixed bed reactors. The fixed bed reactor may comprise a plurality of catalyst beds. Further, the reaction zone may be a fluidized bed reactor, a slurry or a trickle bed reactor. The simplification afforded by the use of a heterogeneous catalyst facilitates an unconventional scope for the process of the present invention. For example, the process of the present invention is skid-mounted in terminals or pipeline garage fore courts, and in fuel cell-equipped vehicles where sulfur sensitive hydrocarbon reformers and fuel cells are used. It is intended to be able to be done in the design unit.

  It is believed that the heterogeneous catalytic oxidation according to the present invention directly oxidizes some of the sulfur-containing organic impurities to the corresponding sulfones and / or sulfoxides. These sulfones and / or sulfoxides are then adsorbed onto the catalyst.

For purposes of this disclosure, the term “oxidation catalyst” refers to the following titanium-containing materials.
1. Amorphous titania-silica material. These materials are described in a review article by Gao and Wachs in Catalysis Today, 51, 1999, 233-254. Ti concentration: 0.001% to 50% atom. 1. Any surface area, any pore volume Titanosilicate zeolite material. Several of these materials are known in the literature; TS-1, Ti-β, Ti-ZSM-12, Ti-MCM-41, Ti-HMS, Ti-ZSM-48, TS-2, Ti- MCM-48, Ti-MSU, Ti-SBA-15, Ti-MMM, Ti-MWW, Ti-TUD-1 and Ti-HSM are some of these. These materials were described in "Active sites and reactive intermediates in titanium silicate molecular sieves", Ratnasamy and Srinivas, Advances in Catalysis 48 (2004) 1-169.
3. A titania-silica mixed oxide containing 50% or less of titania.
4). All of the above-mentioned catalyst materials that have been subjected to a silylation treatment as described in Schoebrechts et al. International Patent Application Publication WO 02/090468.

Preferred effective titanium-containing materials can be selected from the group consisting of titanium silicate, Ti-MCM and Ti-HMS. .
The process of the present invention can achieve desulfurization to a level of about 10 ppmw or less, and can achieve denitrification to a level of about 10 ppmw or less.

  In general, the oxygen-containing gas is until the oxidation / adsorption zone effluent reaches a predetermined sulfur content or breakthrough indicating that the catalyst has reached the desired capacity or loading of a sulfur species, such as sulfones or sulfoxides. In contact with the feedstock in the presence of an oxidation catalyst in the oxidation / adsorption zone.

  The oxidation / adsorption zone is then regenerated with the operation stopped. The oxidation catalyst can then be regenerated by a number of procedures. These methods include high temperature oxidation at conditions including a temperature of about 500 to about 1000 ° C. and a pressure of about 0 to about 100 psia in the presence of an oxygen-containing gas; a temperature of about 500 to about 1000 ° C. and about 0 High temperature pyrolysis under conditions including a pressure of about 100 psia; high temperature hydrotreatment under conditions including a temperature of about 500 to about 700 ° C. and a pressure of about 25 to about 40 atmospheres in the presence of a hydrogen-containing gas; and There may be mentioned solvent regeneration.

  An effective solvent is methanol. It is believed that other polar solvents such as acetonitrile, dimethyl sulfoxide, sulfolane, acetic acid may have similar effects that restore the oxidation catalyst to essentially initial activity. Solvent regeneration is performed at a temperature of about 50 to about 400 ° F. so that the space velocity per liquid hour of solvent is maintained until the sulfur concentration in the effluent extract stream indicating that regeneration is essentially complete is constant. And a pressure of about 0 to about 300 psig, and conditions including contact time with the catalyst.

  In addition, pressure swing operation can be performed to regenerate the catalyst at conditions including a temperature of about 100 to about 500 ° F. and a pressure of 0 to about 50 psia. Ideally, one oxidation / adsorption zone is used to desulfurize the feedstock and another oxidation / adsorption zone is regenerated after the desulfurization operation.

  In order to better understand the present invention, another preferred aspect of the present invention is schematically illustrated in FIG. Referring to the schematic flow diagram shown in FIG. 1, the liquid feedstock from the feed tank 10 passes through the conduit 15. In conduit 15, the liquid feed is preheated and mixed with the diluted air stream 16. This air stream contains about 7 mol% oxygen, preferably 3 mol% oxygen.

The diluted air and feed preheated mixture then passes to the oxidation / adsorption zone 20. Oxidation / adsorption zone 20 is 325 ° F, 200 psig pressure and a liquid hourly space velocity 0.7 hr ^-1 or preferably may be operated at 1.0 hr ^-1. The zone may be a fixed bed downflow reactor, the fixed bed comprising titania-silica. In the reactor, the sulfur-containing organic species in the feed is oxidized to the corresponding sulfones and / or sulfoxides. These sulfones and / or sulfoxides are then adsorbed to titania-silica in the oxidation / adsorption zone. The reaction is exothermic and the oxidation / adsorption zone is operated in such a way that the temperature rise across the oxidation / adsorption zone preferably does not exceed 25 ° F. The oxidation / adsorption zone may be sized to cycle for 24 hours with a feedstock containing up to 500 ppmw sulfur and product sulfur species not exceeding 10 ppmw. After a 24-hour cycle operation, the oxidation / adsorption zone 20 is switched off-line to regenerate the oxidation catalyst. The effluent stream 21 from the oxidation / adsorption zone 20 then passes to the reactor effluent separator 30 where the low sulfur product or blend components are recovered in the stream 31. The recycle gas stream 32 passes to a Knockout Drum 50 where additional low sulfur product is recovered in stream 53 and the gas recycle stream 52 is dried and recompressed in dryer 60 ( The compressor 70) is recycled to the oxidation / adsorption zone after appropriate addition of makeup oxygen.

  FIG. 2 shows the oxidation / adsorption zone 40 in regeneration mode. In this case, methanol passes to the regeneration oxidation reactor 40 through stream 71 from fresh methanol tank 70 to desorb the adsorbed sulfones and / or sulfoxides. This regeneration process can remove over 99% of the adsorbed sulfones and / or sulfoxides and can essentially restore the oxidation activity and adsorption capacity of the catalyst. The methanol-containing and sulfones-containing and / or sulfoxide-containing stream 41 then passes to a spent methanol tank before passing to column 90. In column 90, methanol is recovered from waste sulfone and / or sulfoxide methanol stream 91 into stream 92. This waste stream is of relatively low volume and may be sent offsite for hydrocracking equipment, coke oven or distilled hydroprocessing equipment or further processing. Desorption regeneration may be performed at the same pressure as oxidation / adsorption. Preferably, desorption regeneration is performed at a low pressure equal to the pressure in the distillation step. The methanol feed rate may be the same feed rate as the hydrocarbon feedstock is sent to the oxidation / adsorption zone. It is believed that a volume of at least 10 times the catalyst volume in the solvent will be required to perform the desorption / regeneration process. Following the desorption step, the oxidation / adsorption zone may be dried to remove any remaining free methanol. After the drying step, the catalyst in the oxidation / adsorption zone may be calcined at 800 ° F. using a 3% oxygen stream and finally returned to start operation.

  For a more complete understanding of the present invention, reference is made to the embodiments detailed in the following examples.

  A titanium silicate used as an oxidation catalyst and a sulfone / sulfoxide adsorbent in the present invention was prepared as follows. 350 g of tetraethylorthosilicate was added to 500 g of water. Tetraethylorthosilicate does not mix with water and forms two layers with the upper layer being tetraethylorthosilicate. 139 g of 10% HCI, which is soluble in the aqueous layer, was added. The two layers were heated to about 70 ° C. with stirring. The initial reaction with tetraethylorthosilicate formed a monolayer that was further heated to form a clear purple gel. The gel was dried at room temperature to a solid. The solid was washed with 3 liters of water to reduce the amount of Cl. The catalyst was then dried overnight at 100 ° C. In some cases, the solid may be calcined at 500 ° C. for 4 hours. The catalyst yield was 82 g.

The three titania-silica catalysts prepared as described above were analyzed and were mostly amorphous, but as shown in Table 1, Catalyst A and Catalyst C contain a small amount of anatase polymorph of TiO _2. It was out.

  Three types of catalyst were ground with a mortar and pestle. X-ray powder patterns were measured with a Rigaku diffractometer using a standard configuration. Catalyst A was blended with a known concentration of quartz internal standard in a Spex 8000 mixer / mill and the pattern remeasured. Quantitative phase analysis was performed by the Rietveld method using GSAS.

[Experimental equipment]
A pilot scale unit was used to evaluate the catalyst performance with a 350 ppm sulfur-containing diesel oil feed. The pilot scale reactor consists of a 10.5 inch long, 0.75 OD x 0.438 inch ID x 0.065 inch wall 316 stainless steel tube. The reactor temperature was maintained by three electric heating zones on the reactor wall inside the insulated furnace box. The temperature in these zones was controlled by a programmable computer using a single point thermocouple for each of the reactor wall zones. In addition, a 0.125 inch OD stainless steel thermowell, extending from the top through the midpoint of the reactor, was connected to a multipoint thermocouple (three multipoint thermocouples spaced 2 inches apart) to monitor the internal reaction temperature. ).

The pilot plant reactor consists of a preheating zone filled with alumina chips sieved with a Tyler sieve size of -20 +40 (USA Standard Testing Sieve by WS Tyler). The second and third heated zones were loaded with 10 cc catalyst crushed to Tyler sieve size -20 +40 (USA Standard Testing Sieve by WS Tyler). The remainder of the reactor (temperature zone 4) was filled with alumina chips that had been sieved with a Tyler sieve size of -20 +40 (USA Standard Testing Sieve by WS Tyler) and used as a cool-down zone to support the catalyst. The reactor was operated primarily in downflow mode, but also in an upflow configuration. .
Using a Brooks flow controller, 7% oxygen diluted in nitrogen feed gas at 250 ml min ⁻¹ was sent to the reactor. The oxygen content of the offgas at atmospheric pressure was measured with an oxygen analyzer installed downstream of the reactor.

  An accurate syringe metering pump (ISCO) sent the liquid feed to the reactor. The feed was preheated to the reaction temperature in the reactor preheat zone, and the temperature was measured along the centerline by thermocouples at various locations. The liquid product from the reactor entered a cooled high pressure separator / receiver where 7% oxygen in nitrogen was used to maintain the reactor outlet pressure at the operating pressure. The reactor pressure was maintained at 200 psig by a GO back pressure regulator on off-gas from the separator / receiver. A liquid sample was withdrawn from the high pressure receiver / separator and analyzed for sulfur content by Spectra XEPOS XRF analyzer Model XEP01. Nitrogen was determined by chemiluminescence. Sulfur speciation was determined by capillary GC with a sulfur specific detector.

For these experiments, 10 cc of catalyst was charged to the reactor. The feed flow rate was operated such that the liquid hydraulic space velocity (feed standard volume cc / hour divided by catalyst charge volume cc) was in the range between 1.0 and 2.0 hr ⁻¹ . The reaction zone temperature was maintained at 320 ° F. +/− 5 ° F.
[Experimental procedure]
After the catalyst was charged to the reactor, it was pressurized to 200 psig with 7% oxygen diluted in nitrogen gas and a gas flow of 250 ml min ⁻¹ was established. The catalyst bed was saturated with about 50 ml feed. Then started with a feed rate of 10-50 ml hour ^-1 . The reactor with an established gas and liquid feed was slowly heated to an operating temperature of 300-400 ° F. After the desired operating temperature was achieved, the test was started and the liquid product was collected at hourly intervals. The liquid product was then analyzed for sulfur content with a Spectro XEPOS model XEP01 XRF analyzer. The reaction was continued until catalyst deactivation or breakthrough occurred.
[Spent catalyst evaluation procedure]
1-2 microliters of methanol extract of spent catalyst was injected via a split injection port into a 30 mx 0.32 mm id fused quartz column with a 0.1 micron membrane of polydimethylsilicone (DB1) at 300C. The column temperature was held at 40 ° C. for 2 minutes and then programmed to increase to 300 ° C. at 10 ° C./min intervals. The transfer line from the end of the column to the mass spectrometer ion source was maintained at 300 ° C. Mass spectra were acquired at a scan rate of 0.7 seconds / mass decade at either 3000 mass resolution or 1000 mass resolution.
[Results and discussion]
Experiments were conducted with titanium silicate catalysts using diesel fuel as a feed having the properties shown in Table 2 below. Diesel fuel feed was flowing through the catalyst bed, but at the beginning of the experiment, only pure nitrogen gas was fed into the reactor. The results in Table 4 below show that in the absence of oxygen in the system, the sulfur concentration in the reactor effluent decreases to 12.92%. After several hours, in the flow, the gas flow was switched to a gas flow consisting of no more than 7 vol% oxygen in nitrogen. As is apparent from the results, gaseous molecular oxygen was effectively utilized by the catalyst, reducing the sulfur content in the reactor effluent by 74.72%. These experimental results clearly show that the titanium silicate catalyst is effective in removing sulfur from the feed stream when gaseous oxygen is present in the feed gas. FIG. 3 is a graph showing the experimental results.

  In addition, Table 3 below shows that the same sulfur compounds present in the feed are present at lower concentrations. However, GC-MS analysis of methanol extracted hydrocarbons from spent catalyst revealed the presence of sulfoxides and sulfones in addition to unreacted C1-C4 dibenzothiophenes. As acid washing is expected to selectively remove sulfones and sulfoxides from the product, essentially nothing has been removed, so that the sulfoxides or sulfones are not present in the product and the catalyst It can be concluded that it was adsorbed on.

  Two different methods were tried to regenerate the deactivated Ti-silicate catalyst. The first regeneration (A) shows that the spent catalyst was heat treated under a stream of nitrogen (572 ° F) followed by air (950 ° F) for at least several hours; see Table 5 below. The second regeneration (B) method involves immersing the catalyst in methanol for at least several hours at 310 ° F in a sealed reactor, followed by calcination at 800 ° F for at least several hours with flowing 7% oxygen in nitrogen. did. Subsequently, the process of this invention was performed using these regenerated catalysts. The results are shown as a graph in FIG. 4 and also in Table 6 below.

  The results show that it is possible to regenerate the catalyst after deactivation in the oxidation / adsorption zone. At this time, the oxidized sulfur compound strongly adsorbed on the catalyst surface is considered to correspond to catalyst deactivation. It is believed that nitrogen compounds and oxidized nitrogen compounds (in the catalyst assisted oxidation reaction) present in the feed oil can also play a role in catalyst deactivation.

In this example, three separate deactivation experiments were performed.
Table 7 shows that essentially all of the sulfur has been deposited on the catalyst or recovered in the liquid product.

  Additional experiments were performed using amorphous titanium silicate and a mixture of Ti / MCM and Ti / HMS molecular sieves. Table 8 below and FIG. 5 show the results of these experiments.

  FIG. 6 shows the results of various experiments with varying oxygen levels and varying temperatures performed in accordance with the present invention.

FIG. 1 shows a schematic flow sheet of an embodiment of the present invention. FIG. 2 shows a schematic flow sheet of another embodiment of the present invention. FIG. 3 shows a plot of% desulfurization versus time in the stream including the effect of addition of oxygen-containing gas on the process according to the invention. FIG. 4 shows the desulfurization activity of fresh titanium silicate catalyst versus regenerated titanium silicate performance as a function of time in steam. FIG. 5 shows the desulfurization activity of two oxidation catalysts regenerated according to the present invention. FIG. 6 shows the effect of oxygen content on desulfurization carried out according to the present invention.

Claims (4)

A method of desulfurizing a distillation feed for producing a refined transport fuel or a blended component for a refined transport fuel, the feed comprising sulfur-containing organic impurities,
(A) in the presence of an oxidation catalyst comprising a titanium-containing composition that converts at least some of the sulfur-containing organic impurities into sulfones and / or sulfoxides under oxidation conditions in an oxidation / adsorption zone; Contacting with an oxygen-containing gas;
(B) adsorbing sulfones and / or sulfoxides to the oxidation catalyst; and (c) recovering oxidation / adsorption zone effluent with reduced amounts of sulfur-containing impurities.   The process according to claim 1, wherein the oxidation catalyst is regenerated to produce an oxidation catalyst comprising a small amount of adsorbed sulfones and / or sulfoxides.   The process according to claim 2, wherein the regeneration is carried out by contacting the catalyst with methanol under conditions that desorb adsorbed sulfones and / or sulfoxides.   The method of claim 1, wherein the titanium-containing composition is selected from the group consisting of titanium silicate, Ti-MCM, and Ti-HMS.

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