KR20070091297A - Oxidative desulfurization process - Google Patents

Abstract

Disclosed is a process which reduces the sulfur and/or nitrogen content of a distillate feedstock to produce a refinery transportation fuel or blending components for refinery transportation fuel, by contacting the feedstock with an oxygen-containing gas in an 5 oxidation/adsorption zone at oxidation conditions in the presence of an oxidation catalyst comprising a titanium-containing composition whereby the sulfur species are converted to sulfones and/or sulfoxides which are adsorbed onto the titanium-containing composition.

Description

Oxidative Desulfurization Method {OXIDATIVE DESULFURIZATION PROCESS}

The present invention relates to a process for the production of components for refinery blending of natural petroleum derived vehicle fuels, in particular vehicle fuels which are liquid at ambient conditions. More specifically, oxidizing the petroleum distillate by contacting the petroleum distillate with an oxygen-containing gas in the presence of a heterogeneous catalyst under oxidizing conditions to oxidize the nitrogen and / or sulfur-containing organic impurities therein. It is related with the manufacturing method of the said fuel.

It is well known that internal combustion engines have revolutionized transportation in the last decades of their inventions. While people like Benz and Gottleib Wilhelm Daimler invented and developed engines that use electrical ignition of fuels such as gasoline, Rudolf CK Dissel applies compression to the auto-ignition of fuels to use low-cost organic fuels. Invented and made diesel enzymes. Developing improved diesel engines for use in vehicles has been in progress with improvements in diesel fuel compositions. Modern high performance diesel engines require further improvements in the specification of the fuel composition, but cost remains an important issue.

Currently, most of the fuel for transportation comes from natural petroleum. Indeed, up to now, petroleum is the world's major source of hydrocarbons used as feedstock for fuels and petrochemicals. Although the composition of natural petroleum or crude oil varies considerably, all crude oils contain sulfur compounds, most contain nitrogen compounds, which may also contain minor amounts, but the oxygen content in most crude oils is low. Generally, the sulfur concentration in crude oil is less than about 8%, and in most crude oil the sulfur concentration is in the range of about 0.5 to about 1.5%. Nitrogen concentrations are typically less than 0.2%, but can be as high as 1.6%.

Crude oil is rarely used in the form of oil wells, and is converted from refineries to feedstock for a wide range of fuels and petrochemicals. Typically fuels for vehicles are prepared by processing and blending distillation fractions from crude oil to meet the requirements of a particular end use. Since most crude oils available today in large quantities contain high amounts of sulfur, the distillation fraction must be desulfurized to obtain products that meet performance specifications and / or environmental standards. Sulfur-containing organic compounds in fuels continue to be a major source of environmental pollution. During combustion they are converted to sulfur oxides, which then generate sulfur oxyacids and also contribute to particle emissions.

Even in new, high performance diesel engines, combustion of conventional fuel produces smoke in the exhaust. Oxygenated compounds, and compounds with little or no carbon-to-carbon chemical bonds, such as methanol and dimethyl ether, are known to reduce smoke and engine exhaust emissions. However, most such compounds have high vapor pressures and / or are almost insoluble in diesel fuel and, as their cetane number indicates, are poor in ignition. Moreover, other methods of improving diesel fuels by chemical hydrogenation to reduce their sulfur and aromatics content also result in reduced fuel lubricity. Low lubrication diesel fuel can cause excessive wear to fuel pumps, injectors and other moving parts that come into contact with the fuel under high pressure.

The fuel for use in a compression ignition internal combustion engine (diesel engine), or the distillation fraction used in the blending component of the fuel, is usually a middle distillate containing about 1 to 3% by weight of sulfur. In the past, typical requirements for diesel fuel were up to 0.5% by weight. The 1993 legislation has limited sulfur in diesel fuel to 0.3% by weight in Europe and the United States. In 1996, in Europe and the United States, and in 1997, the maximum amount of sulfur in diesel fuel was reduced to 0.05% by weight or less. This global trend is expected to continue to lower sulfur levels.

The US Environmental Protection Agency targets sulfur levels in on-road diesel below 15 ppm. In 2005, the European Union's requirements will be less than 50 ppm. In addition, the World Fuel Charter, supported by all of the world's leading automakers, proposes even more powerful sulfur regulations of 5 to 10 ppm for Category IV fuels in "developed countries". In order to comply with the above regulations for ultra-low sulfur content fuels, refineries will have to produce fuels with lower sulfur levels at refinery gates. Thus, the company faces the challenge of reducing sulfur levels in fuels, especially diesel fuels, within the terms of the agreement set forth by the refinery regulators.

In one phase, the introduction of new emissions regulations in California and other jurisdictions has called for considerable attention to catalytic exhaust gas treatment. The challenge of applying catalytic emission control to diesel engines, in particular large diesel engines, differed significantly from that of spark-ignition internal combustion engines (gasoline engines) for two reasons. The first is that conventional three-way catalysts (TWCs) are not effective at removing NO _x emissions from diesel engines, and the second is that the demand for particle control is considerably higher than in gasoline engines.

Many exhaust gas treatment technologies are emerging for the control of diesel engine emissions, and sulfur levels in fuels affect the efficiency of the technology in all sectors. Sulfur is a catalyst poison that reduces catalytic activity. Moreover, in the context of catalytic control of diesel emissions, high fuel sulfur also creates secondary problems of particle emissions, due to the catalytic oxidation of sulfur and the formation of sulfate mists by reaction with water. This mist is collected as part of the particle emissions.

Compression ignition engine emissions are different from those of spark ignition engines because of the different methods applied to initiation of combustion. Compression ignition requires fuel droplets to be burned in a very thin air / fuel mixture. The combustion process leaves fine particles of carbon and results in significantly more particle emissions than are present in gasoline engines. Due to the lean operation, CO and gaseous hydrocarbon emissions are significantly lower than in gasoline engines. However, significant amounts of unburned hydrocarbons are adsorbed on the carbon particles. These hydrocarbons are called SOF (soluble organic fraction).

Increasing the combustion temperature can reduce particle emissions, but this leads to an increase in NO _x emissions by the well-known Zeldovitch mechanism. Therefore, in order to meet emission regulations, particles and NO _x There is a tradeoff between emissions.

Extremely low sulfur fuels have been strongly proposed on the right grounds to be important technical assistants in the catalytic treatment of diesel exhaust for emission control. Fuel sulfur levels below 15 ppm will be required to achieve particle levels below 0.01 g / bhp-hr. This level can be very well matched with the catalyst formulations for the currently emerging flue gas treatment, showing the ability to achieve NO _x emissions of about 0.5 g / bhp-hr. Moreover, NO _x trap systems are extremely susceptible to fuel sulfur, and it is suggested on an appropriate basis that they will require sulfur levels below 10 ppm in order to remain active.

As sulfur requirements in vehicle fuels continue to strengthen, the removal of sulfur from petroleum feedstocks and products will become even more important every year.

Conventional hydrodesulfurization (HDS) catalysts can be used to remove large amounts of sulfur from petroleum distillates for blending of refinery vehicle fuels, but they are compounds when sulfur atoms are steric hindrance, such as in polycyclic aromatic sulfur compounds. Not efficient at removing sulfur from This is especially true where sulfur heteroatoms are double interrupted (eg 4,6-dimethyldibenzothiophene). These hindered dibenzo thiophenes are mainly present at low sulfur levels, such as 50 to 100 ppm, and harsh process conditions will be required for desulfurization. Using conventional hydrodesulfurization catalysts at elevated temperatures will result in yield loss, faster catalyst coking and product quality degradation (eg, color). Using high pressures requires high capital expenditures.

In order to meet further stringent requirements in the future, such hindered sulfur compounds will also have to be removed from the distillate feedstock and products. There is an urgent need for economic removal of sulfur from distillates and other hydrocarbon products.

There are many processes known in the art to remove sulfur from distillate feedstocks and products. One known process involves oxidizing a petroleum fraction containing at least a large amount of material boiling at a higher temperature than a very high boiling hydrocarbon material (petroleum fraction containing at least a large amount of material boiling above about 550 ° F.). Emissions containing oxidizing compounds are treated at elevated temperatures to form hydrogen sulfide (500 ° F. to 1350 ° F.) and / or hydroprocessed to reduce the sulfur content of the hydrocarbon material. For example, U.S. Patent 3,847,798 (Jin Sun Yoo et al.) And U.S. See Patent 5,288,390 to Vincent A. Durante. Such a method has been found to be only useful on a limited basis because it only achieves relatively low levels of desulfurization. In addition, during the execution of these methods, due to cracking and / or coke formation, substantial loss of valuable products may occur. Therefore, it would be advantageous to develop a process that reduces cracking or coke formation, while improving desulfurization levels.

U.S. Patent 6,087,544 (Robert J. Wittenbrink et al.) Relates to processing a distillate feedstream to produce a distillate fuel having a lower sulfur level than the distillate feedstream. Such fuels are prepared by fractionating a distillate feedstream into light fractions (containing only about 50-100 ppm sulfur) and heavy fractions. The light fraction is hydromodified to substantially remove all sulfur therein. The desulfurized light fraction is then blended with half of the heavy fraction, such as 15% by weight untreated heavy fraction and 85% by weight desulfurized light fraction with reduced sulfur sulfuric distillate fuel, eg, sulfur levels from 663 ppm to 310 ppm. Is manufactured. However, to achieve this low sulfur level, only about 85% of the distillate feed stream is recovered as the low sulfur distillate fuel product.

U.S. Published patent application 2002/0035306 A1 (Gore et al.) Discloses a multi-stage desulfurization process of liquid petroleum fuel that also removes nitrogen-containing compounds and aromatics. The process steps are as follows: thiophene extraction; Thiophene oxidation; Thiophene-oxide and dioxide extraction; Extract residue solvent recovery and polishing; Extractive solvent recovery; And recycle solvent purification.

Gore et al. Seek to remove some of the aromatics and 5 to 65% of the nitrogen-containing compounds and thiophene-based materials from the feed stream before the oxidation step. The presence of aromatics in diesel fuels tends to inhibit cetane, but processes such as Gore require the final use of the extracted aromatics. In addition, the presence of an effective amount of aromatics increases fuel density (Btu / gal) and serves to enhance the cold flow characteristics of diesel fuel. Therefore, it is not good to extract excessive amounts of aromatics.

In the oxidation step, the oxidant is prepared in situ or is formed in advance. The operating conditions were a molar ratio of H ₂ O ₂ to S of about 1: 1 to 2.2: 1; Acetic acid content of about 5 to 45% of the feed, solvent content of 10 to 25% of the feed, and a catalyst volume of less than about 5,000 ppm sulfuric acid, preferably less than 1,000 ppm. Gore et al. Also disclose the use of acid catalysts, preferably sulfuric acid, in the oxidation step. When sulfuric acid is used as the oxidative acid, there is a concern that corrosion is present when water is present, and hydrocarbons can be sulfonated when only a small amount of water is present.

According to Gore et al., The purpose of the thiophene-oxide and dioxide extraction step is to use an extraction solvent (which is an aqueous acetic acid with one or more co-solvents) plus an aliquot of aromatics plus variously substituted benzo- and dibenzo thiophene-oxides and Removing more than 90% of the N-oxide compound.

U.S. Patent 6,368,495 B1 (Kocal et al.) Also discloses a multi-step process for removing thiophene and thiophene derivatives from petroleum fractions. The process of this challenge involves contacting the hydrocarbon feed stream with an oxidant and then contacting the effluent of the oxidation step with a solid decomposition catalyst to decompose the oxidized sulfur-containing compound to obtain a heated liquid stream and volatile sulfur compounds. It includes. Current patents disclose the use of oxidizing agents such as alkyl hydroperoxides, peroxides, percarboxylic acids and oxygen.

WO 02/18518 A1 (Rappas et al.) Initiated a two-stage desulfurization process, which used downstream of the hydroreformer. The process involves oxidizing the distillate over an aqueous formic acid, hydrogen peroxide ideal, to convert thiophene-based sulfur into the corresponding sulfone. During the oxidation process, some sulfones are extracted into the oxidizing solution. These sulfones are removed from the hydrocarbon phase by a subsequent phase separation step. The hydrocarbon phase containing the remaining sulfone is then subjected to a liquid-liquid extraction or solid adsorption step.

It is not suitable to use formic acid for the oxidation step. Formic acid is relatively more expensive than acetic acid. In addition, formic acids are considered “reducing” solvents and can be attenuated by hydrogenating certain metals. Therefore, a rare alloy is needed to handle formic acid. These expensive alloys will have to be used in the solvent recovery portion and storage vessel. With formic acid it is also necessary to use high temperatures to separate the hydrocarbon phase from the oxidant aqueous phase in order to prevent the appearance of a third precipitated solid phase. This unwanted phase is believed to be formed due to the poor fat affinity of formic acid. Thus, at lower temperatures, formic acid cannot keep some of the extraction sulfones in solution.

U.S. Patent 6,171,478 B1 (Cabrera et al.) Discloses another complex multi-stage desulfurization process. Specifically, the process includes a hydrodesulfurization step, an oxidation step, a decomposition step and a separation step, wherein a portion of the sulfur-oxidized compound is removed from the effluent stream of the decomposition step. The aqueous oxidation solution used in the oxidation step preferably contains acetic acid and hydrogen peroxide. Any residual hydrogen peroxide in the oxidation stage effluent is decomposed by contacting the effluent with a cracking catalyst.

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

Many solvents have been proposed for the removal of oxidized sulfur compounds. For example, U.S. Patent 6,160,193 (Gore) teaches using a wide variety of solvents suitable for use in the extraction of sulfones. Preferred solvent is dimethyl sulfoxide (DMSO).

A similar list of solvents used to extract sulfur compounds is described in Otsuki, S .; Nonaka, 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 Extraction" Energy & Fuels 2000, 14, 1232. The list is shown below:

N, N-dimethylformamide (DMF)

Methanol

Acetonitrile

Sulfolane

Gore noted that there is a relationship between solvent polarity and solvent extraction efficiency. All solvents listed in the patents and articles are preferably not mixed with diesel. They are all characterized as being polar protic or aprotic solvents.

WO 01/32809 discloses another process for selectively oxidizing distillate fuels or intermediate distillates. The reference document of the present challenges is that distillate fuels oxidized such that hydroxyl and / or carbonyl groups are chemically bonded to paraffinic molecules in the fuel reduces particles produced as the fuel burns, compared to non-oxidized fuels. It is starting. This reference discloses a process for selectively oxidizing saturated aliphatic or cyclic compounds in a fuel with peroxide, ozone or hydrogen peroxide in the presence of various titanium containing silicon based zeolites to form hydroxyl or carbonyl groups.

U.S. Patent 6,402,939 B1 (Yen et al.) Discloses a process for the oxidative desulfurization of fossil fuels using ultrasonic waves. In brief, the liquid fossil fuel is combined with an acidic aqueous solution containing water and hydroperoxide to form a multiphase reaction mixture, followed by a multiphase reaction medium for a time sufficient to oxidize the sulfide to sulfone (which is subsequently extracted). Apply ultrasonic to

U.S. Published patent application 2001/0015339 A1 (Sherman) discloses a method for removing sulfur compounds from diesel fuel, which forms oxidizing gas into bubbles having a size of less than micron and disperses these bubbles in a flowing diesel fuel, Oxidizing the sulfur compound to sulfoxide and / or sulfone.

In view of the above, less complex, economical distillates, which avoid additional and complex handling and corrosion problems, without the use of oxidation techniques using expensive chemical oxidants or expensive hydrogenation techniques that require the use of large amounts of hydrogen, or It is clear that there is a need for a diesel desulfurization process.

The present invention provides a relatively simple selective desulfurization process wherein the distillate feedstock is contacted with an oxygen-containing gas in the presence of a hybrid catalyst containing a titanium-containing composition under oxidizing conditions, thereby sulphur-containing in the distillate feedstock. The compounds are converted to their corresponding sulfones or sulfoxides, and then a portion thereof is adsorbed to the titanium-containing composition.

Summary of the Invention

The process of the present invention involves reducing the sulfur content in a distillate feedstock containing sulfur-containing organic impurities to produce a refinery vehicle fuel, or blending component for the refinery vehicle fuel, which oxidizes the feedstock. Converting the sulfur-containing compound into sulfones and / or sulfoxides by contacting with an oxygen-containing gas in the presence of a hybrid oxidation catalyst containing a titanium-containing composition at oxidation conditions in the adsorption zone, and then part of the titanium-containing composition By adsorbing on. The fuel or blending component with 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 regenerated for reuse in the process.

Detailed description of the invention

Suitable feedstocks generally include a refinery stream boiling at a temperature of from about 50 ° C. to about 650 ° C., preferably from 150 ° C. to about 400 ° C., more preferably from about 175 ° C. to about 375 ° C. at atmospheric pressure for best results. do. These streams include virgin light middle distillates, virgin heavy middle distillates, fluid catalytic catalytic cracking processes, light catalytic cycle oils, coker steel distillates, hydrogenated cracker distillates, jet fuels, vacuum distillates, and collective and individual streams of these streams. Hydrogenated modifications include, but are not limited to. Preferred streams are the collective and individual hydroreformation embodiments of the flow catalytic catalytic cracking process light catalytic cycle oil, coker steel distillate and hydrocracker distillate.

It is also envisaged that one or more of the distillate streams may be combined for use as feedstock to the process of the present invention. In many cases, it can be seen that the performance of refinery vehicle fuels, or blending components for refinery vehicle fuels, obtained from various alternative feedstocks is comparable. In such cases, details such as the volume availability of the stream, the nearest connection location, and the short-term economics can determine which stream to use.

In one aspect, the present invention provides for the preparation of a refinery vehicle fuel, or blending component for a refinery vehicle fuel, from a hydrogenated petroleum distillate. This hydrolyzed distillate reacts the petroleum distillate with a source of hydrogen under hydrogenation conditions in the presence of a hydrogenation catalyst (helping to remove sulfur and / or nitrogen from the hydrolyzed petroleum distillate by hydrogenation); Optionally, the hydrogenated petroleum distillate is distilled to at least one of a high-boiling feedstock consisting of a sulfur-rich, single-aromatic-lean fraction and a low-boiling blending component consisting of a sulfur-lean, single-aromatic-rich fraction. By process comprising fractionation, it is prepared by hydroforming the petroleum distillate material boiling at about 50 ° C. to about 650 ° C. According to one embodiment of the process of the present invention, a hydrogenated distillate or low boiling point component may be used as a suitable feedstock for the process of the present invention.

In general, useful hydrogenation catalysts contain one or more active metals selected from the group consisting of d-transition elements in the periodic table, each of which is incorporated in an amount from about 0.1% to about 30% by weight of the total catalyst on the inert support. Suitable active metals include d-transition elements in the periodic table with atomic numbers 21-30, 39-48, and 72-78.

The catalytic hydrogenation process can be carried out under relatively mild conditions in a fixed fluidized bed, a moving fluidized bed or an ebullient bed of the catalyst. Preferably one fixed bed or a plurality of fixed beds of catalyst are subjected to a relatively long period of time before regeneration is necessary, for example about 200 ° C. for best results within a range of about 6 to about 160 atmospheres. To an average reaction zone temperature of about 45 ° C., preferably about 250 ° C. to about 400 ° C., and most preferably about 275 ° C. to about 350 ° C.

A particularly preferred pressure range, ie, a pressure range that minimizes the amount of hydrogen and pressure required for hydrodesulfurization, while hydrogenation provides extremely good sulfur removal, is between 20 and 60 atmospheres, more preferably between about 25 and 25. 40 The pressure in the range of atmospheric pressure.

The hydrogen circulation rate is generally from about 500 SCF / Bbl to about 20,000 SCF / Bbl, preferably from about 2,000 SCF / Bbl to about 15,000 SCF / Bbl, most preferably from about 3,000 to about 13,000 SCF / Bbl Range. Hydrogen circulation rates and reaction pressures below this range can lead to increased catalyst deactivation rates, leading to less economical desulfurization, denitrogenation and dearomatization. Excessively high reaction pressures raise energy and plant costs and reduce marginal benefits.

The hydrogenation process is typically from about 0.2 hours ^-1 to about 10.0 hours ^-1 , preferably from about 0.5 hours ^-1 to about 3.0 hours ^-1 , most preferably from about 1.0 hours ^-1 to about 2.0 hours for best results. ^It is operated at a liquid hourly space velocity of ^-1 . Excessively high space velocities will cause a reduction in overall hydrogenation.

To further reduce such heteroaromatic sulfides from the distillate petroleum fraction by hydroforming, it will be required to apply the stream to very harsh catalytic hydrogenation to convert these compounds to hydrocarbons and hydrogen sulfide (H ₂ S). Typically, the more any hydrocarbon moiety, the more difficult to hydrogenate the sulfide. Therefore, there are more residual organo-sulfur compounds remaining after hydroreforming, which are structurally the most disturbed heteroaromatics.

If the feedstock is a high-boiling distillate fraction derived from hydrogenation of the refinery stream, the refinery stream may be a boiling material 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.

Distillate fractions useful for hydrogenation can be any one, multiple, boiling at atmospheric pressure ranging from about 50 ° C. to about 650 ° C., preferably from 150 ° C. to about 400 ° C., more preferably from about 175 ° C. to about 375 ° C. Or all refinery streams. Light hydrocarbon components in the distillate product are generally recovered to gasoline, which is beneficial, and the presence of these low boilers in the distillate fuel is often limited by the distillate fuel flash point requirements. The heavy hydrocarbon components boiling above 400 ° C. are generally processed as a more advantageous catalytic catalytic cracker feed and converted to gasoline, but are compatible for use in the process of the present invention. The presence of heavy hydrocarbon components in the distillate fuel is further limited by the final requirements of the distillate fuel.

Distillate fractions for hydrogenation include high and low sulfur virgin distillates from high- and low-sulfur crude oils, coker distillates, catalytic and cracker light and heavy catalytic cycle oils, and boiling distillates from hydrogenated crackers and residual hydrocracker plants. It may contain a range product. Generally, coker distillates and light and heavy catalytic cycle oils are the most highly aromatic feedstock components and range in the range of about 80% by weight. Most coker distillate and cycle oil aromatics are present as mono-aromatic and bi-aromatics, with minor amounts as tri-aromatics. Virgin raw materials, such as high and low sulfur virgin distillates, are low in aromatic content and range in the range of about 20% by weight aromatics. Generally, the aromatic content of the blended hydrogenation plant feedstock ranges from about 5% to about 80% by weight, more typically from about 10% to about 70% by weight, most typically from about 20% to about 60% by weight. would.

Sulfur concentrations in distillate fractions useful in the present invention are generally a function of high and low sulfur crude oil mixtures, the hydrogenation volume of refined water per barrel of crude oil volume, and alternative treatments of the distillate hydrogenation feedstock components. The high sulfur distillate feedstock component is generally a catalytic cycle oil, coker distillate, and virgin distillate derived from high sulfur crude oil from processing a fluid catalytic contact cracking plant that processes relatively high sulfur feedstocks. These distillate feedstock components may range from about 2% by weight of elemental sulfur, but generally range from about 0.1% to about 0.9% by weight of elemental sulfur.

The nitrogen content of the distillate fractions useful in the present invention is also generally a function of the nitrogen content of the crude oil, the hydrogenation volume of the refinery per barrel of crude oil volume, and alternative treatment of the distillate hydrogenation feedstock component. High nitrogen distillate feedstocks are generally coker distillates and catalytic cycle oils. These distillate feedstock components may have a total nitrogen concentration in the range of about 2,000 ppm, but generally range from about 5 ppm to about 900 ppm.

Typically, sulfur compounds in the petroleum fraction are relatively non-polar, heteroaromatic sulfides such as chlorinated benzothiophenes and dibenzothiophenes. At first glance, it will appear that heteroaromatic sulfur compounds can be selectively extracted based on some characteristics attributed only to these heteroaromatics. Although the sulfur atoms in these compounds have two, non-bonded electron pairs to classify them as Lewis bases, this feature is still not sufficient for them to be extracted by Lewis acids. In other words, selective extraction of heteroaromatic sulfur compounds to lower the level of sulfur requires a greater polarity difference between sulfide and hydrocarbons.

It is possible through the hybrid catalyzed oxidation according to the invention to directly convert these sulfides into more polar, Lewis basic, oxygenated sulfur compounds such as sulfoxides and sulfones which are subsequently adsorbed onto titania-silica. . The desulfurized feedstock is then recovered from the oxidation / adsorption zone. The process of the present invention is also believed to cause oxidation and adsorption of any nitrogen-containing species that can be separated simultaneously with the sulfur-containing species.

Amine is also included in other compounds having non-bonded electron pairs. Heteroaromatic amines are also found in the same stream in which the sulfides are found. Amines are more basic than sulfides. Isolated electron pairs act as Bronsted-Lowry base (proton acceptor) and Lewis base (electron donor). These electron pairs on atoms make them susceptible to oxidation in a manner similar to sulfides.

In one aspect, the invention provides a process for preparing a refinery vehicle fuel, or blending component for a refinery vehicle fuel, comprising: providing a distillate feedstock containing a mixture of hydrocarbons and sulfur-containing organic impurities step; Contacting said feedstock with an oxygen-containing gas such as oxygen depleted air in the oxidation zone in the presence of an oxidation catalyst comprising titania-silica that also acts as an adsorbent. Since oxygen reducing air may be used in the present invention, the concentration of oxygen may be less than about 21 volume percent. The oxygen-containing stream should preferably have an oxygen content of at least 0.01% by volume. Effective concentrations are from 0.5 to 10% by volume. If desired, gas may be provided from air and an inert diluent such as nitrogen. As will be readily appreciated by those skilled in the art, certain compositions are explosive, so the composition of the oxygen containing stream should be chosen to avoid explosive areas. 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 normal pressure to 3,000 psig, preferably from about 100 psig to about 400 psig, more preferably from about 100 psig to about 300 psig.

The temperature in the oxidation / adsorption zone may range from about 100 ° F. to about 600 ° F., 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 has a liquid hourly space velocity of about 0.1 hour ⁻¹ to about 100 hour ⁻¹ , preferably about 0.2 hour ⁻¹ to about 50 hour ⁻¹ , and most preferably about From 0.5 hour ^-1 to about 10 hours ^{- 1} . An excessively high space velocity will reduce overall oxidation and adsorption.

In general, the oxidation / adsorption process of the present invention begins with a distillate feedstock preheating step. The distillate feedstock is preheated in the feed / exhaust heat exchanger before being put into the furnace for final preheating to the target reaction zone temperature. The distillate feedstock may be contacted with an oxygen-containing stream before, during and / or after preheating.

Since the oxidation reaction is generally exothermic, it is possible to use interstage cooling consisting of a heat transfer device between fixed bed reactors or between catalyst beds in the same reactor shell. At least a portion of the heat generated from the oxidation process can often be recovered for use in the oxidation process to benefit. If this choice of heat recovery is not possible, cooling can be effected through cooling utilities, such as cooling water or air, or by using quench streams injected directly into the reactor. The two-step process can reduce temperature exotherm per reactor shell and improve oxidation reactor temperature control.

Oxidation / adsorption zone emissions are generally cooled and the effluent stream is sent to a separation device for removal of the oxygen-containing gas, which may be recycled back to the process. The oxygen-containing gas purge rate is often controlled to maintain the minimum or maximum oxygen content in the gas passing through the reaction zone. The recycled oxygen-containing gas is generally compressed, supplemented with "supplement" oxygen or oxygen-containing gas (preferably air) if necessary, and injected into the process for further oxidation.

The process of the present invention can be carried out in any kind of 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 also include a plurality of catalyst beds. In addition, the reaction zone may be a fluidized bed reactor, slurry or trickle bed reactor. The simplifications involved by using hybrid catalysts will facilitate a series of less common applications for the process of the present invention. For example, it is contemplated that the terminal may be performed in an on-board fuel cell comprising a small mounted unit or pipeline hanger fore court, and a sulfur sensitive hydrocarbon modifier and a carrier in which the fuel cell is used. do.

Hybrid catalyzed oxidation according to the present invention is thought to directly oxidize some of the sulfur-containing organic impurities into their corresponding sulfones and / or sulfoxides. These sulfones and / or sulfoxides are then adsorbed onto the catalyst.

For the purposes of the present disclosure, the term "oxidation catalyst" denotes a titanium-containing material such as:

1. Amorphous titania-silica material. These materials are described in the review article, Gao and Wachs, Catalysis Today, 51, 1999, 233-254. Ti concentration is 0.001% to 50% atoms. Any surface area, any pore volume.

2. Titanosilicate Zeolite Material. Several kinds of these materials are known in the literature as follows; Some of these are TS-1, Ti-beta, 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. These materials are described in a review article entitled "Active sites and reactive intermediates in titanium silicate molecular sieves", Ratnasamy and Srinivas, Advances in Catalysis 48 (2004) 1-169.

3. Titania-silica mixed oxides containing less than 50% titania.

4. All of the above catalytic material subjected to siliconization as described in Schöbrechts et al., WO 02/090468.

Preferred effective titanium-containing materials can be selected from the group consisting of titanium silicates, Ti-MCM and Ti-HMS.

The process of the present invention can achieve desulfurization at levels of less than about 10 ppmw and denitrification at levels of less than about 10 ppmw.

In general, the oxygen-containing gas is such that when the oxidation / adsorption zone emissions reach a predetermined sulfur content or breakthrough level, which indicates that the catalyst has reached the desired capacity or loading of sulfur species, for example sulfone or sulfoxide. Contact with the feedstock in the presence of the oxidation catalyst in the oxidation / adsorption zone.

The work in the oxidation / adsorption zone is then stopped and regenerated. The oxidation catalyst can then be regenerated by a number of procedures. These methods include the following: high temperature oxidation at conditions including a temperature of about 500 to about 1,000 ° C. and a pressure of about 0 to about 100 psia in the presence of an oxygen-containing gas; High temperature pyrolysis at conditions including temperatures of about 500 to about 1,000 ° C. and pressures of about 0 to about 100 psia; Hot hydrogenation at conditions including temperatures of about 500 to about 700 ° C. and pressures of about 25 to about 40 atmospheres in the presence of a hydrogen-containing gas; And solvent regeneration.

An effective solvent is methanol. Other polar solvents such as acetonitrile, dimethyl sulfoxide, sulfolane, acetic acid are believed to have a similar effect in recovering the oxidation catalyst essentially back to its initial activity. Solvent regeneration is generally a liquid hourly space of solvent until a temperature of about 50 to about 400 ° F. and a pressure of about 0 to about 300 psig, and a constant sulfur concentration in the effluent extract stream (which indicates that the regeneration is essentially complete). It is carried out under conditions that include catalyst contact time such that the rate is maintained.

In addition, a pressure rotation operation can be performed for regeneration of the catalyst at conditions including temperatures of about 100 to about 500 ° F. and pressures of 0 to about 50 psia. Ideally, one oxidation / adsorption zone would be used for desulfurization of the feedstock while another oxidation / adsorption zone is regenerated after the desulfurization service.

In order to better convey the present invention, another preferred embodiment of the present invention is shown schematically in FIG. 1. In the schematic flow diagram shown in FIG. 1, the liquid feedstock from feed tank 10 passes through conduit 15, where it is preheated and diluted air stream 16 (which is about 7 mol% oxygen or Preferably an air stream containing 3 mol% oxygen).

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

2 shows the oxidation / adsorption region 40 in the regeneration mode. In this case, methanol passes from the fresh methanol tank 70 through the stream 71 to the oxidation reactor vessel 40 of the regeneration 40 so that the adsorbed sulfones and / or sulfoxides are desorbed. This regeneration process can remove more than 99% of the adsorbed sulfones and / or sulfoxides and essentially restores the oxidation activity and adsorption capacity of the catalyst. The methanol- and sulfone and / or sulfoxide-containing stream 41 then passes through the methanol tank used, and then passes through column 90, where methanol is a waste sulfone and / or sulfoxide methanol. Recovered from stream 91 to stream 92. Such waste streams are relatively small in volume and can be sent to a hydrocracker, coker or distillate hydroreformer, or to another location for further processing. Desorption regeneration can be carried out as oxidation / adsorption at the same pressure. Preferably the desorption regeneration is carried out at low pressure equivalent to the pressure in the distillation step. The methanol feed rate may be the same feed rate as the hydrocarbon feedstock is fed to the oxidation / adsorption zone. It is believed that at least 10 times the volume of catalyst in the solvent is required for the desorption / regeneration process to be performed. Following the desorption step, the oxidation / adsorption zone can be dried to remove any free residual methanol. After the drying step, the catalyst in the oxidation / adsorption zone is calcined using a 3% oxygen stream at 800 ° F. and can eventually be used again.

For a more complete understanding of the present invention, reference will now be made to embodiments in which more details are set forth in the examples which follow.

1 shows a schematic flow diagram of an embodiment of the invention.

2 shows a schematic flow diagram of another embodiment of the invention.

3 shows the coordinates of desulfurization percentage vs. hours on stream and reflects the effect of adding oxygen containing gas to the process according to the invention.

4 shows the desulfurization activity of fresh titanium silicate catalyst versus the performance of regenerated titanium silicate as a function of uptime.

5 shows the desulfurization activity of two oxidation catalysts regenerated according to the present invention.

6 shows the effect of oxygen content on the desulfurization carried out according to the invention.

Example 1

Titanium silicates used in the present invention as oxidation catalysts and sulfone / sulfoxide adsorbents were prepared as follows: 350 grams of tetraethylorthosilicate were added to 500 grams of water. Tetraethylorthosilicate did not mix with water, forming a bilayer with a top layer of tetraethylorthosilicate: 139 grams of 10% in HCl was added, which was soluble in the water layer. Both layers were heated to about 70 ° C with stirring. Initial reaction with tetraethylorthosilicate formed a monolayer, which upon further heating formed a clear violet-gel. The gel was dried at room temperature, yielding a solid. The solid was washed with 3 liters of water to reduce the amount of Cl. The catalyst was then dried at 100 ° C. overnight. The solid can optionally be calcined at 500 ° C. for 4 hours. The yield of the catalyst was 82 grams.

Three titania-silica catalysts prepared as described above were analyzed, which were mainly amorphous, but Catalyst A and Catalyst C contained small amounts of anatase polymorphs of TiO ₂ as shown in Table 1.

catalyst Anatase weight% Average crystal size, Å A 1.4 (1) 85 B - - C 1.7 (1) 98

The three limb catalysts were ground in a mortar and pestle. X-ray powder pattern was measured on a Rigaku diffractometer using a standard arrangement. Catalyst A was blended with a known concentration of quartz internal standard in a Spex 8000 mixer / crusher and the pattern was remeasured. Quantitative phase analysis was performed using the Rietveld method using GSAS.

Example 2

Experimental equipment

A pilot-scale facility was used to evaluate the performance of the catalyst and 350 ppm-sulfur-containing diesel feed. Pilot-scale reactors are 10.5 inches long and 0.75 O.D. × 0.438 inch I.D. The wall consisted of 316 stainless steel tubes. The reactor temperature was maintained by three electrically heated zones of the reactor wall inside the insulated furnace box. The temperature of these zones was controlled in each of the reactor wall zones by a programmable computer using a single point thermocouple. In addition, a 0.125 inch O.D. stainless steel temperature sensor thermowell, which penetrated the middle of the reactor from the multi-point thermocouple (3 "spaced 2" apart) housed on top, observed the internal reaction temperature.

The pilot plant reactor consisted of a preheating zone filled with alumina chips sieved with a Tyler screen (USA Standard Testing Sieve, W.S. Tyler) of mesh size -20 +40. The second and third heated zones were loaded with 10 cc catalyst ground with a Tyler screen (USA Standard Testing Sieve, W.S. Tyler) of mesh size -20 +40. The remainder of the reactor (temperature zone 4) was charged with alumina chips sieved with a Tyler screen (USA Standard Testing Sieve, W.S. Tyler) of mesh size -20 +40, used as a cooling zone, and supported with a catalyst. The reactor was operated primarily in downflow mode, but also in upflow arrangement.

Using a Brooks flow controller, 7% oxygen diluted in nitrogen feed gas was delivered to the reactor at 250 ml · min ^{− 1} . The oxygen content in the off-singer was measured at atmospheric pressure with an oxygen analyzer installed along the flow of the reactor.

A high precision syringe-measuring pump (ISCO) delivered the liquid feed to the reactor. The feed was preheated to the reaction temperature in the reactor preheating zone and the temperature was measured along the center with thermocouples at various locations. Liquid product from the reactor was allowed to flow into a cooled high pressure separator / receiver, where 7% oxygen in nitrogen was used to maintain the outlet pressure of the reactor at the operating pressure. The reactor pressure was maintained at 200 psig by the GO back pressure regulator for off-gas from the separator / container. The liquid sample was discharged from the high pressure receiver / separator and the sulfur content was analyzed by Spectro XEPOS XRF Analyzer, Model XEP01. Nitrogen was measured by chemiluminescence. The details of sulfur were measured using a capillary column GC with sulfur specific detector.

For this experiment, 10 cc of catalyst was charged to the reactor. The feed flow rate was manipulated so that the liquid hydraulic space velocity (time divided by the standard volume of the feed (cc) / packed volume of the catalyst (cc)) was in the range of 1.0 to 2.0 hours ^{- 1} . The reaction zone temperature was maintained at 32O <0> F +/- 5 ° F.

Experiment process:

After charging the reactor with the catalyst, the pressure as 200 psig with a 7% oxygen diluted in nitrogen gas to a gas flow 250 ml · ^min-1 was established to. The catalyst layer was saturated with about 50 ml of feed. After, 10 ~ 50 ml · hour ^- was initiated by the feed rate of the ^first. After the gas and liquid feeds were established, the reactor was slowly heated to an operating temperature of 300 to 400 ° F. After reaching the desired operating temperature, the test was started and the liquid product was collected at time intervals. The sulfur content of the liquid product was then analyzed by Spectro XEPOS Model XEP01 XRF Analyzer. The reaction was continued until deactivation or a breakthrough level of catalyst occurred.

Evaluation process of the catalyst used:

One to two microliters of methanol extract of the catalyst used was prepared with 0.32 mm i.d. with 0.1 micron film (DB1) of polydimethylsilicone. Injection was carried out at 300 ° C. through a split inlet on 30 meters of the fused silica column. The column temperature was maintained at 40 ° C. for 2 minutes and then programmed to warm up to 300 ° C. with a width of 10 ° C./min. The transfer line from the end of the column to the mass spectrometer ion source was maintained at 300 ° C. Mass spectra were obtained at a scan rate of 0.7 seconds per mass decade at 3,000 mass resolution or 1,000 mass resolution.

Results and discussion:

Experiments were carried out with titanium-silicate catalysts using diesel raw materials as feed having the properties disclosed in Table 2. While the diesel feed was flowing through the catalyst bed, only pure nitrogen gas was fed to the reactor at the beginning of the experiment. The results in Table 4 below show no oxygen in the system, and the sulfur concentration in the reactor effluent was reduced by 12.92%. After several hours of operation, the gas flow was changed to a gas flow consisting of 7% by volume of oxygen in nitrogen. As is apparent from this result, gaseous oxygen molecules have been effectively used by the catalyst to reduce the sulfur content in the reactor effluent by 74.72%. These experimental results clearly demonstrate that the titanium-silicate catalyst is effective in removing sulfur from the feed stream when gaseous oxygen is present in the feed gas. 3 graphically shows the results of the trial run.

In addition, Table 3 below shows that the same sulfur compounds present in the product were present in the product, but the concentration was reduced. However, GC-MS analysis of the methanol extracted hydrocarbons from the catalyst used revealed the presence of unreacted C ₁ -C ₄ dibenzothiophene in addition to sulfoxide and sulfone. The acid wash is expected to selectively remove sulfones and sulfoxides from the product, which essentially concludes that nothing has been removed, so that it can be concluded that no sulfoxides or sulfones were present in the product and they were already adsorbed onto the catalyst. .

Example 3

Two different methods have been tried for the regeneration of deactivated Ti-silicate catalysts. The first regeneration (“A”) involved heat treating the catalyst used in a stream of nitrogen (572 ° F.) and then air (950 ° F.) for at least several hours; See Table 5 below. The second regeneration (“B”) method involves soaking the catalyst for at least several hours at 310 ° F. in methanol in a sealed reactor and then calcining at 800 ° F. for at least several hours in a flow of 7% oxygen in nitrogen. The process of the present invention was then carried out using these regenerated catalysts. The results were shown schematically in FIG. 4 and disclosed in Table 6 below.

The results indicate that the catalyst can be regenerated after deactivation in the oxidation / adsorption zone. At this time, it is believed that the sulfur oxide compound strongly adsorbed on the surface of the catalyst contributes to the catalyst deactivation. It is believed that the nitrogen compounds present in the feed oil and the nitrogen oxide compounds (in the catalyst assisted oxidation reaction) can also affect catalyst deactivation.

Example 3

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

Example 4

Further runs were performed using amorphous titanium silicates and mixtures of Ti / MCM and Ti / HMS molecular sieves. Table 8 and Figure 5 below show the results of this trial.

Example 5

6 shows the results of various runs (different oxygen levels and temperatures) performed in accordance with the present invention.

Claims (4)

A process for desulfurizing a distillate feedstock containing sulfur-containing organic impurities to produce a refinery vehicle fuel, or blending component for a refinery vehicle fuel, comprising the following steps (a) to (c): (a) oxygen-containing in the presence of an oxidation catalyst comprising a titanium-containing composition at oxidation conditions in the oxidation / adsorption zone, in order to convert at least some of the sulfur-containing organic impurities into sulfones and / or sulfoxides. Contacting the gas; (b) adsorbing sulfones and / or sulfoxides on an oxidation catalyst; And (c) recovering the oxidation / adsorption zone effluent with reduced amount of sulfur-containing impurities. The process of claim 1, wherein the oxidation catalyst is regenerated to produce an oxidation catalyst containing less 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 for desorbing the 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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