JP2009517499A - Selective naphtha hydrodesulfurization with high-temperature mercaptan decomposition - Google Patents

Abstract

A process for the selective hydrodesulfurization of olefinic naphtha streams containing substantial amounts of organically bound sulfur and olefins. The olefinic naphtha stream is selectively desulfurized in the first hydrodesulfurization reaction stage. This effluent stream is then contacted with a stripping agent, such as steam or an amine solution, in the H ₂ S removal zone to remove H ₂ S from the effluent stream, thereby the H ₂ S partial pressure of the process stream. Is reduced. The process stream is then subjected to a second desulfurization reaction stage. This reduces the mercaptan sulfur content in the final product stream following the mercaptan decomposition step. In a second embodiment, the effluent stream from the first hydrodesulfurization reaction stage is subjected to an H ₂ S removal zone and then fed directly to the mercaptan cracking stage where the total sulfur content and mercaptan are Sulfur content is reduced in the final product stream.
[Selection] Figure 1

Description

  The present invention relates to a multi-stage process for selectively hydrodesulfurizing and removing mercaptans of olefinic naphtha streams containing substantial amounts of organically bound sulfur and olefins.

  Environmentally driven regulatory pressures on sulfur levels in motor gasoline (“Morgas”) have led to extensive production of moxa with less than 50 wppm sulfur in 2004. Levels below 10 wppm are considered in later years. In general, this will require deep desulfurization of refinery naphtha streams. The greatest goal of naphtha streams for these processes is that obtained from cracking operations, particularly from fluid catalytic cracking units. This constitutes a generally higher sulfur content than the large quantities of refinery formulations available, as well as “non-degradable” refinery naphtha streams. Naphtha ("cat naphtha") from a fluid catalytic cracker typically contains substantial amounts of both sulfur and olefins. Cat naphtha deep desulfurization requires improved techniques to reduce sulfur levels without severe octane loss. This involves an undesired hydrogenation of the olefin.

  Hydrodesulfurization is one of the basic hydroprocessing processes in the refining and petrochemical industries. Removal of the raw organically bound sulfur by conversion to hydrogen sulfide typically involves hydrogenation with non-noble metal sulfide supported and unsupported catalysts, particularly those containing Co / Mo or Ni / Mo. Achieved by reacting with. This is usually accomplished at fairly severe temperatures and pressures in order to achieve product quality specifications or to feed the desulfurization stream to a subsequent sulfur sensitive process.

  Olefinic naphthas (such as cracked naphtha and coker naphtha) typically contain greater than about 20% by weight of olefins. Conventional new hydrodesulfurization catalysts have both hydrogenation and desulfurization activities. Hydrodesulfurization of cracked naphtha using conventional naphtha desulfurization catalysts under conventional start-up procedures and conventional conditions required for sulfur removal typically results in undesirable olefin loss due to hydrogenation. Because olefins are high octane components, it is desirable to retain olefins rather than hydrogenate saturated compounds (typically lower octane). This results in a lower grade fuel product. This requires further purification, such as isomerization, mixing, etc. to produce higher octane fuels. These further purifications, of course, substantially increase manufacturing costs.

Selective hydrodesulfurization is a technique for removing organically bound sulfur while minimizing olefin hydrogenation and octane reduction by various techniques (such as selective catalysts and / or process conditions). Has been described. For example, a process called SCANfining was developed by ExxonMobil Corporation. In doing so, the olefinic naphtha is selectively desulfurized with little octane loss. Patent Document 1, Patent Document 2 and Patent Document 3 (all of which are incorporated herein by reference) disclose various aspects of SCANfining. A selective hydrodesulfurization process has been developed to avoid substantial olefin saturation and octane loss. These processes have a tendency to liberate H ₂ S. This reacts with the retained olefin and forms mercaptan sulfur upon return.

Since these refinery hydrodesulfurization catalyst processes are operated at harsher conditions to meet the lower sulfur specifications of the product, the H ₂ S content in the process stream is increased. This results in a higher olefin saturation and return to the mercaptan sulfur compound. Therefore, there is a need in the industry for a method to increase the desulfurization efficiency of the process while reducing or eliminating the return of mercaptan sulfur compounds in the final product.

  Many refiners are considering combinations of available sulfur removal techniques to optimize economic objectives. Technology providers have devised a variety of strategies, as refiners want to minimize capital investment and meet the objectives of low sulfur mogas. This includes distilling cracked naphtha into various fractions. This is most suitable for individual sulfur removal techniques. While the economics of these strategies may be considered favorable compared to a single processing technology, the complexity of total refinery operation has increased, and successful mogas production has many critical By sulfur removal operation. Economically competitive sulfur removal strategies that would minimize olefin saturation, minimize the production of mercaptan sulfur compounds in the product, and also reduce the required capital investment and operational complexity would be advantageous to refiners .

US Pat. No. 5,985,136 US Pat. No. 6,013,598 US Pat. No. 6,126,814 S. J. et al. Tauster et al. “Structure and Properties of Molybdenum Sulfide: Correlation between O 2 Chemisorption and Hydrodesulfurization Activity” (Journal of Catalysis, Vol. 63, 515-519, 1980).

  Thus, reducing the cost and complexity of hydrotreating olefinic naphtha to low levels of sulfur content, while reducing the amount of mercaptans formed or formed as a result of a hydrotreating process There is a need in the art for technology that would either be by providing an economic process that destroys. There is an industrial need for a process to reduce these product mercaptan levels while meeting higher sulfur reduction specifications, minimizing olefin saturation and reducing octane loss in the final product.

In accordance with the present invention, a process is provided for hydrodesulfurizing an olefinic naphtha feed stream and retaining a substantial amount of olefin, wherein the feed stream is about 50 ° F. (10 ° C.) to about 450 ° F. ( 232 ° C.) and contains organically bound sulfur and at least about 5% by weight of olefin content. This method
a) Olefinic naphtha feed stream in the first reaction stage in the presence of a hydrogen-containing process gas and hydrodesulfurization catalyst at a temperature of about 450 ° F. (232 ° C.) to about 800 ° F. (427 ° C.), pressure Organically combined in an olefinic naphtha feed stream by hydrodesulfurization at first hydrodesulfurization reaction conditions comprising about 60 to about 800 psig and a hydrogen-containing process gas ratio of about 1000 to about 6000 standard cubic feet / barrel A portion of the converted elemental sulfur is converted to hydrogen sulfide to produce a first reactor effluent stream having a reduced total sulfur content;
b) The first reactor effluent stream is directed to the H ₂ S removal zone where a stripping agent such as steam or amine solution is used so that substantially all of the H ₂ S is in the first reaction. Removing a stripped effluent stream to produce a stripped effluent stream;
c) The stripped effluent stream is passed to the second reaction stage in the presence of a hydrogen-containing process gas and hydrodesulfurization catalyst at a temperature of about 450 ° F. (232 ° C.) to about 800 ° F. (427 ° C.). Organics remaining in the stripped effluent stream, conducted at a second hydrodesulfurization reaction condition comprising a pressure of about 60 to about 800 psig, and a hydrogen-containing process gas ratio of about 1000 to about 6000 standard cubic feet / barrel At least a portion of the chemically bound elemental sulfur is converted to hydrogen sulfide to produce a second reactor effluent stream having a reduced total sulfur content, and d) a second reaction The reactor effluent stream is passed to a mercaptan cracking reaction stage in the presence of a mercaptan cracking catalyst at a temperature of about 500 ° F. (260 ° C.) to about 800 ° F. (427 ° C.) and a pressure of about Leading at reaction conditions comprising 60 to about 800 psig, at least a portion of the mercaptan is cracked to produce a mercaptan cracking reactor product having a lower mercaptan sulfur content than that of the second reactor effluent stream. Including a process.

In a second embodiment of the present invention, a process is provided for hydrodesulfurizing an olefinic naphtha feed stream and retaining a substantial amount of olefin, wherein the feed stream is about 50 ° F. (10 ° C.). ) To about 450 ° F. (232 ° C.) and contains organically bound sulfur and at least about 5% by weight of the olefin content. This method
a) Olefinic naphtha feed stream in the first reaction stage in the presence of a hydrogen-containing process gas and hydrodesulfurization catalyst at a temperature of about 450 ° F. (232 ° C.) to about 800 ° F. (427 ° C.), pressure Hydrodesulfurization at a first hydrodesulfurization reaction condition comprising about 60 to about 800 psig and a hydrogen-containing process gas ratio of about 1000 to about 6000 standard cubic feet / barrel provides a portion of the organically bound sulfur. A first reactor effluent stream converted to hydrogen sulfide and having a reduced total sulfur content is produced;
b) The first reactor effluent stream is directed to the H ₂ S removal zone where a stripping agent such as steam or amine solution is used so that substantially all of the H ₂ S is in the first reaction. Removing from the reactor effluent stream to produce a stripped effluent stream; and c) presence of the hydrogen-containing process gas and mercaptan cracking catalyst into the mercaptan cracking reaction stage. Reaction conditions comprising a temperature of about 500 ° F. (260 ° C.) to about 800 ° F. (427 ° C.), a pressure of about 60 to about 80 psig, and a hydrogen-containing process gas ratio of about 1000 to about 6000 standard cubic feet / barrel And at least a portion of the non-mercaptan organic and elemental sulfur compound is converted and at least a portion of the mercaptan is separated. By comprising the step of mercaptan decomposition reactor product with a lower mercaptan sulfur content than that of the effluent stream of the first reactor is manufactured.

  In a preferred embodiment, the feed stream to the hydrodesulfurization reactor and mercaptan cracking stage will be in the vapor phase.

In other preferred embodiments, a portion of the hydrogen-containing process gas to the first, second, and mercaptan cracking reaction stages is removed from the first reactor effluent stream in the H ₂ S removal zone. Consists of a part of gas.

  In yet another preferred embodiment, the heat from at least a portion of the first reactor effluent heats at least a portion of the olefinic naphtha feed stream prior to contacting the first reaction stage. Used for.

  In yet another preferred embodiment, the heat from at least a portion of the product of the mercaptan cracking reactor is used to heat at least a portion of the olefinic naphtha feed stream prior to contacting the first reaction stage. Used.

  In yet another preferred embodiment, the total sulfur content of the product stream of the mercaptan cracking reactor is less than about 1% by weight of the total sulfur content of the olefinic naphtha feed stream.

  In yet another preferred embodiment, the mercaptan sulfur content of the product stream of the mercaptan cracking reactor is less than about 10% by weight of the mercaptan sulfur content of the first reactor effluent stream.

  A suitable feedstock for use in the present invention is a refinery stream in the olefinic naphtha boiling range. This typically boils in the range of about 50 ° F. (10 ° C.) to about 450 ° F. (232 ° C.). The term “olefinic naphtha stream” as used herein is a naphtha stream having at least about 5% by weight of olefin content. Non-limiting examples of olefinic naphtha streams include fluid catalytic cracker naphtha (FCC catalytic naphtha or cat naphtha), steam cracked naphtha, and coker naphtha. Mixtures of olefinic and non-olefinic naphthas are also included as long as the mixture has at least about 5% by weight of olefin content.

  Olefinic naphtha refinery streams generally contain not only paraffins, naphthenes, and aromatics, but also unsaturateds (such as cyclic and cyclic olefins, dienes, and cyclic hydrocarbons having olefinic side chains). The olefinic naphtha feedstock can include a total olefin concentration of about 60% by weight, more typically about 50% by weight, and most typically about 5% to about 40% by weight. The olefinic naphtha feedstock can also have a diene concentration of about 15 wt% or less, but more typically less than about 5 wt%, based on the total weight of the feedstock. High diene concentrations are undesirable because they can result in gasoline products with poor stability and hue. The sulfur content of the olefinic naphtha will generally range from about 300 wppm to about 7000 wppm, more typically from about 1000 wppm to about 6000 wppm, and most typically from about 1500 to about 5000 wppm. Sulfur will typically exist as organically bound sulfur. That is, as simple aliphatic, naphthenic, and sulfur compounds such as aromatic mercaptans, sulfides, di- and polysulfides. Other organically bound sulfur compounds include a class of heterocyclic sulfur compounds such as thiophene and its higher homologues and analogs. Nitrogen will also be present. This will usually range from about 5 wppm to about 500 wppm.

  As previously mentioned, it is highly desirable to remove sulfur from an olefinic naphtha with as little olefin saturation as possible. It is also highly desirable to convert as much of the naphtha organic sulfur species as possible to hydrogen sulfide with as little mercaptan return as possible. It has been found that the level of mercaptan in the product stream is directly proportional to both the hydrogen sulfide and olefinic species concentrations at the hydroconversion reactor outlet and inversely proportional to the temperature at the reactor outlet.

  FIG. 1 is a schematic flow diagram of a first preferred embodiment for carrying out the present invention. Various accessory devices (such as compressors, pumps, heat exchangers, and valves) are not shown for simplicity.

In this first embodiment, the olefinic naphtha feed (1) and the hydrogen-containing process gas stream (2) are preferably operated at selective hydrodesulfurization conditions, a first hydrodesulfurization reaction stage (3). In contact with the catalyst. This will vary as a function of the concentration and type of organically bound sulfur species in the feed stream. “Selective hydrodesulfurization” means that the hydrodesulfurization reaction stage is operated to achieve the highest possible level of sulfur removal with the lowest possible olefin saturation level. It is also driven to avoid as many mercaptan returns as possible. Generally, the hydrodesulfurization conditions for both hydrodesulfurization reaction stages include a temperature of about 450 ° F. (232 ° C.) to about 800 ° F. (427 ° C.), preferably about 500 ° F. (260 ° C.) to about 675 °. F (357 ° C.); pressure of about 60 to about 800 psig, preferably about 200 to about 500 psig, more preferably about 250 to about 400 psig; hydrogen feed rate of about 1000 to about 6000 standard cubic feet / barrel (scf / b), preferably and liquid hourly space velocity from about 0.5 hr ^-1 to about 15 hr ^-1, preferably from about 0.5 hr ^-1 to about 10 hr ^-1, more preferably at about 1 ^-; about 1000 to about 3000scf / b is ¹ to about 5 o'clock ^-1 is included. The feed stream to the first and second reaction stages, as well as the mercaptan destruction reaction stage, is preferably a vapor stage when contacting the catalyst. The terms “hydrotreating” and “hydrodesulfurization” are often used interchangeably herein.

  This first hydrodesulfurization reaction stage can consist of one or more fixed bed reactors. Each can include one or more catalyst beds of the same or different hydrodesulfurization catalysts. A fixed bed is preferred, although other types of catalyst beds can be used. Non-limiting examples of these other types of catalyst beds that may be used in practicing the present invention include fluidized beds, ebullated beds, slurry beds, and moving beds. Interstage cooling between reactors or between catalyst beds in the same reactor can be used. This is because some olefin saturation can occur and olefin saturation as well as desulfurization reactions are generally exothermic. Some of the heat generated during hydrodesulfurization can be recovered by conventional techniques. If this heat recovery option is not available, conventional cooling may be performed by a cooling facility such as cooling water or air, or by using a hydrogen quench stream. In this way, the optimal reaction temperature can be more easily maintained. The first hydrodesulfurization stage is so configured and a total target sulfur removal of about 40% to 100%, more preferably about 60% to about 95% is reached in the first hydrodesulfurization stage. It is preferable to operate under such hydrodesulfurization conditions.

  Preferred hydrotreating catalysts for use in both the first and second hydrodesulfurization reaction stages are at least one Group VIII metal oxide (preferably selected from Fe, Co, and Ni, more preferably Co and And / or selected from Ni, most preferably Co metal oxides), and at least one Group VI metal oxide (preferably selected from Mo and W, more preferably Mo metal oxides). Is supported on a high surface area carrier material (preferably alumina). Other suitable hydrotreating catalysts include zeolite catalysts as well as noble metal catalysts, wherein the noble metal catalyst is selected from Pd and Pt. It is within the scope of the present invention that more than one type of hydroprocessing catalyst is used in the same reactor. The Group VIII metal oxide of the first hydrodesulfurization catalyst is typically present in an amount ranging from about 0.1 to about 20% by weight, preferably from about 1 to about 12% by weight. The Group VI metal oxide will typically be present in an amount ranging from about 1 to about 50% by weight, preferably from about 2 to about 20% by weight. The weight percent of total metal oxide is on the support. “On carrier” means that the percentage is based on the weight of the carrier. For example, if the support weighs 100 g, 20% by weight Group VIII metal oxide means that 20 g of Group VIII metal oxide is on the support.

Preferred catalysts for both the first and second hydrodesulfurization stages will also have a high degree of metal sulfide edgeplane area. This is measured by the oxygen chemisorption test described in Non-Patent Document 1 (incorporated herein by reference). The oxygen chemisorption test involves measuring the edge plane area, where a pulse of oxygen is applied to the carrier gas stream, which thus rapidly traverses the catalyst bed. For example, the oxygen chemisorption will be about 800-2,800, preferably about 1,000-2,200, more preferably about 1,200-2,000 μmol oxygen / gMoO ₃ .

The most preferred catalysts of the first and second hydrodesulfurization zones can be characterized by the following characteristics: That is, (a) the MoO ₃ concentration is about 1-25% by weight, preferably about 2-18% by weight, more preferably about 4-10% by weight, and most preferably 4-8%, based on the total weight of the catalyst. (B) the CoO concentration is also about 0.1-6 wt.%, Preferably about 0.5-5.5 wt.%, More preferably about 1-5, based on the total weight of the catalyst. (C) the Co / Mo atomic ratio is about 0.1 to about 1.0, preferably about 0.20 to about 0.80, more preferably about 0.25 to about 0.72. And (d) the median pore diameter is from about 60 to about 200, preferably from about 75 to about 175, more preferably from about 80 to about 150, and (e) the MoO ₃ surface concentration is about 0.5 × 10 ^-4 to about ^{_{3 × 10 -4 gMoO 3 / m}} 2, preferably from about 0.75 × 10 ^- To about ^{_{2.5 × 10 -4 gMoO 3 / m}} 2, more preferably about ^{1 × 10 -4 ~2 × 10 -4} gMoO 3 / m 2, (f) an average particle size diameter, 2.0 mm Less, preferably less than about 1.6 mm, more preferably less than about 1.4 mm, and most preferably as small as practical for commercial hydrodesulfurization process equipment.

  The hydrodesulfurization catalyst used in the practice of the present invention is preferably a supported catalyst. Any suitable refractory catalyst support material (preferably an inorganic oxide support material) can be used as the support for the catalyst of the present invention. Non-limiting examples of suitable support materials include zeolite, alumina, silica, titania, calcium oxide, strontium oxide, barium oxide, carbon, zirconia, diatomaceous earth, lanthanide oxides (cerium oxide, lanthanum oxide, neodymium oxide, yttrium oxide, And include praseodymium oxide); chromia, thorium oxide, urania, niobia, tantala, tin oxide, zinc oxide, and aluminum phosphate. Alumina, silica, and silica-alumina are preferred. More preferably, it is alumina. Magnesia can also be used in the catalyst having a high metal sulfide edge plane area of the present invention. It should be understood that the carrier material can also contain small amounts of contaminants. Fe, sulfate, silica, and various metal oxides that can be introduced during the preparation of the support material. These contaminants will be present in the raw material used to prepare the carrier and preferably will be present in an amount of less than about 1% by weight, based on the total weight of the carrier. More preferably, the carrier material is substantially free of these contaminants. It is an embodiment of the present invention that about 0-5% by weight of additive, preferably about 0.5-4% by weight, more preferably about 1-3% by weight, is present in the support. In that case, the additive is selected from the group consisting of phosphorus and metals or metal oxides from Group IA (alkali metals) of the Periodic Table of Elements.

Returning now to FIG. 1 herein, the total effluent product (4) from the first hydrodesulfurization reaction stage is directed to the H ₂ S removal zone (6). In this zone, a stripping agent (5) such as steam or an amine solution is contacted with the first reactor effluent to remove substantially all of the H ₂ S from the effluent stream (7 ). This H ₂ S removal zone operates at substantially the same pressure as that of the first hydrodesulfurization reaction stage. The product stream (8) stripped of H ₂ S from the H ₂ S removal zone and the hydrogen-containing process gas (9) are then contacted with the catalyst in a second hydrodesulfurization reaction stage (10). . This is also preferably operated at selective hydrodesulfurization conditions. In general, hydrodesulfurization conditions for the second stage reaction include similar temperature range, pressure range, process gas range, liquid space velocity range, catalyst properties, catalyst characteristics and catalyst composition, reactor configuration, As well as forms of heat recovery. This is described above for the first reaction stage. The reactor effluent (11) from the second reaction stage is then contacted with the catalyst in a mercaptan cracking reaction stage (12).

This mercaptan cracking reaction stage may consist of one or more fixed bed reactors. Each can include one or more catalyst beds of the same or different mercaptan cracking catalysts. A fixed bed is preferred, although other types of catalyst beds can be used. Non-limiting examples of these other types of catalyst beds that may be used in practicing the present invention include fluidized beds, ebullated beds, slurry beds, and moving beds. Suitable mercaptan decomposition catalyst for use in the present invention, the mercaptan return, is intended to include substances that catalyze back to H 2 _S and olefins. Suitable mercaptan decomposition catalyst materials for this process include refractory metal oxides that are resistant to sulfur and hydrogen at elevated temperatures. This has virtually no hydrogenation activity. The catalyst material having substantially no hydrogenation activity is obtained from the saturation or partial saturation of any unsaturated hydrocarbon molecules (such as aromatics and olefins) in the feed stream as disclosed in this invention. It is a substance that has virtually no tendency to promote under the conditions of the cracking reaction stage. These catalytic materials specifically exclude catalysts containing metals, metal oxides, or metal sulfides of Group V, VI, or VIII elements. This includes, but is not limited to, V, Nb, Ta, Cr, Mo, W, Fe, Ru, Co, Rh, Ir, Ni, Pd, and Pt. Non-limiting exemplary non-limiting examples of catalytic materials suitable for the mercaptan decomposition reaction process of this invention include alumina, silica, both crystalline and amorphous silica-alumina, aluminum phosphate, titania, magnesium oxide Alkali and alkaline earth metal oxides, alkali metal oxides, magnesium oxide supported on alumina, faujasite ion-exchanged with sodium to remove acidity, and aluminum phosphate treated with ammonium ions, etc. Substances are included.

In general, the conditions for the mercaptan decomposition reaction stage include a temperature of about 500 ° F. (260 ° C.) to about 800 ° F. (427 ° C.), preferably about 550 ° F. (288 ° C.) to about 700 ° F. (371 ° C.); A pressure of about 60 to about 800 psig, preferably about 150 to about 500 psig; a hydrogen feed rate of about 1000 to about 6000 standard cubic feet per barrel (scf / b), preferably about 1000 to about 3000 scf / b; and a liquid space velocity of about 0 5 hour ^-1 to about 15 hour ^-1 , preferably about 0.5 hour ^-1 to about 10 hour ^-1 , more preferably about 1 hour ^-1 to about 5 hour ^-1 . In this mercaptan decomposition reaction stage, organic and elemental sulfur compounds, and mercaptan sulfur compounds are converted with a minimum amount of olefin saturation. This results in a final product stream (13) having the characteristics of reduced organic and elemental sulfur content, reduced mercaptan content, and minimal octane reduction.

  FIG. 2 is a simplified flow diagram illustrating a second preferred embodiment for practicing the present invention. Again, various accessory devices (such as compression devices, pumps, heat exchangers, and valves) are not shown for simplicity.

In this second embodiment, the olefinic naphtha feed (1) and the hydrogen-containing process gas stream (2) are preferably operated at a selective hydrodesulfurization condition in a first hydrodesulfurization reaction stage (3). In contact with the catalyst. This will vary as a function of the concentration and type of organically bound sulfur species in the feed stream. In general, the hydrodesulfurization conditions of the first reaction stage of FIG. 2 are similar temperature ranges, pressure ranges, process gas ranges, liquid space velocity ranges, catalyst properties, catalyst characteristics and catalyst composition, reactor conditions, Use the form as well as the form of heat recovery. This is described above with respect to the first reaction stage of FIG. The total effluent product (4) from the first hydrodesulfurization reaction stage is directed to the H ₂ S removal zone (6). In this zone, compound (5), such as steam or amine solution, is contacted with the first reactor effluent to remove substantially all of the H ₂ S from the effluent stream (7). . This H ₂ S removal zone operates at substantially the same pressure as that of the first hydrodesulfurization reaction stage. The product stream (8) stripped of H ₂ S from the H ₂ S removal zone and the hydrogen-containing process gas (9) are then contacted with the catalyst in a mercaptan cracking reaction stage (10).

  The mercaptan decomposition conditions in this form (see FIG. 2) of the mercaptan decomposition reaction stage are the same as described above for the mercaptan decomposition reaction stage in the first embodiment (FIG. 1 and accompanying details). See the description). Mercaptan decomposition reaction conditions include similar temperature ranges, pressure ranges, process gas ranges, liquid space velocity ranges, catalyst properties, catalyst characteristics and catalyst composition, reactor configurations, and heat recovery configurations. . This is described above with respect to the mercaptan decomposition reaction conditions described in the first embodiment (see FIG. 1 and the accompanying detailed description). In this mercaptan decomposition reaction stage, organic and elemental sulfur compounds, and mercaptan sulfur compounds are converted with a minimum amount of olefin saturation. This results in a final product stream (11) having the characteristics of reduced organic and elemental sulfur content, reduced mercaptan content, and minimal octane reduction.

  The following examples are presented to illustrate the present invention.

Example 1
In this example, the process configuration used is shown in FIG. The hydroprocessing gas ratio (shown in FIG. 1 as streams (2) and (9)) is 2,000 standard cubic feet / barrel (scf / b). The amount of H ₂ S removal in the H ₂ S reaction zone (6) is determined using a H ₂ S removal step that removes free or dissolved H ₂ S from the process stream at a first hydrodesulfurization reaction pressure (327 psig). Modeled. H 2 _S remove any stripping agent used technically to promote (steam or an amine solution, etc.) can be used. This is shown as stream (5). The H ₂ S or H ₂ S rich compound is then removed from the process via stream (7). Conditions and resulting product quality are predicted based on a kinetic model developed from a pilot plant database. This is shown in Tables 1 and 2 below.

  This process will result in 99.5% total hydrodesulfurization, with an overall RON loss of 4.3 and a MON loss of 1.5. In contrast, a similar design using two HDS reactors and no mercaptan removal would result in RON loss 5.0 and MON loss 1.8.

Example 2
In this example, the process configuration used is shown in FIG. The hydroprocessing gas ratio (shown in FIG. 2 as streams (2) and (9)) is 2,000 standard cubic feet / barrel (scf / b). The amount of H ₂ S removal in the H ₂ S reaction zone (6) is modeled using a H ₂ S removal step that removes free or dissolved H ₂ S from the process stream at hydrodesulfurization reaction pressure (327 psig). The H 2 _S remove any stripping agent used technically to promote (steam or an amine solution, etc.) can be used. This is shown as stream (5). The H ₂ S or H ₂ S rich compound is then removed from the process via stream (7). Conditions and resulting product quality are predicted based on a kinetic model developed from a pilot plant database. This is shown in Tables 3 and 4 below.

  This process will yield 99.5% total hydrodesulfurization with an overall RON loss of 3.7 and MON loss of 1.3. In contrast, a similar design using two HDS reactors and no mercaptan removal would result in RON loss 5.0 and MON loss 1.8.

1 shows a first preferred process diagram for practicing the present invention. The olefinic naphtha feed stream is subjected to two hydrodesulfurization reaction stages having an intermediate H ₂ S removal step. This then follows the final mercaptan decomposition reaction stage. 2 represents a second preferred process diagram for practicing the present invention. The olefinic naphtha feed stream is subjected to one hydrodesulfurization reaction stage. This follows the H ₂ S removal step and then the final mercaptan decomposition reaction stage.

Claims (38)

A substantial amount of an olefinic naphtha feed stream boiling in the range of 50 ° F. (10 ° C.) to 450 ° F. (232 ° C.) and containing organically bound sulfur and having an olefin content of at least 5% by weight. In which hydrodesulfurization is carried out while retaining the olefin,
a) The olefinic naphtha feed stream is heated in the first reaction stage in the presence of a hydrogen-containing process gas and a hydrodesulfurization catalyst at a temperature of 450 ° F. (232 ° C.) to 800 ° F. (427 ° C.) and a pressure of 60 Elemental sulfur and organically combined in the olefinic naphtha feed stream is hydrodesulfurized at first hydrodesulfurization reaction conditions including -800 psig and hydrogen-containing process gas ratio of 1000-6000 standard cubic feet / barrel. Converting a portion of the sulfur to hydrogen sulfide to produce a first reactor effluent stream having a total sulfur content lower than that of the olefinic naphtha feed stream;
b) directing the first reactor effluent stream to an H ₂ S removal zone where stripping agent is used to remove substantially all of the H ₂ S from the first reactor effluent stream. And producing a stripped effluent stream;
c) directing the stripped effluent stream to a second reaction stage in the presence of a hydrogen-containing process gas and hydrodesulfurization catalyst at a temperature of 450 ° F. (232 ° C.) to 800 ° F. (427 ° C.); Elementary sulfur and organically bound sulfur in the olefinic naphtha feed stream at a second hydrodesulfurization reaction condition comprising a pressure of 60-800 psig and a hydrogen-containing process gas ratio of 1000-6000 standard cubic feet / barrel. Converting at least a portion to hydrogen sulfide to produce a second reactor effluent stream having a lower total sulfur content and some amount of mercaptan sulfur than that of the stripped effluent stream; and d. ) Directing the second reactor effluent stream to a mercaptan cracking reaction stage, in the presence of a mercaptan cracking catalyst, Mercaptan cracking reaction conditions comprising 500 ° F. (260 ° C.) to 800 ° F. (427 ° C.) and a pressure of 60 to 800 psig decompose at least a portion of the mercaptan sulfur to produce a second reactor effluent stream Producing a product stream of a mercaptan cracking reactor having a lower mercaptan sulfur content.   The method of claim 1, wherein the olefinic naphtha feed stream and the stripped effluent stream are in the vapor phase prior to contacting the first and second reaction stages.   The method of claim 2, wherein the second reactor effluent stream is in the vapor phase prior to contacting the mercaptan cracking reaction stage.   The method of claim 3, wherein the stripping agent is selected from the group consisting of steam and amine solutions.   The process of claim 1, wherein the total sulfur content of the product stream of the mercaptan cracking reactor is less than 1 wt% of the total sulfur content of the olefinic naphtha feed stream.   6. The process of claim 5, wherein the mercaptan sulfur content of the product stream of the mercaptan cracking reactor is less than 10% by weight of the mercaptan sulfur content of the effluent stream of the first reactor. .   The hydrodesulfurization catalyst used in the first and second reaction stages comprises at least one Group VIII metal oxide and at least one Group VI metal oxide. the method of.   The hydrodesulfurization catalyst used in the first and second reaction stages is selected from at least one Group VIII metal oxide selected from the group consisting of Fe, Co and Ni, and a group consisting of Mo and W 8. The method of claim 7, comprising at least one Group VI metal oxide.   The method of claim 8, wherein the metal oxide is deposited on a high surface area support material.   The method of claim 9, wherein the high surface area support material is alumina. Said mercaptan decomposition catalyst The method of claim 1, the decomposition of the mercaptan sulfur, characterized by comprising the effective amount of the refractory metal oxide to catalyze against the H 2 _S .   The mercaptan decomposition catalyst removes acidity by ion exchange with alumina, silica, silica-alumina, aluminum phosphate, titania, magnesium oxide, alkali and alkaline earth metal oxides, alkali metal oxides, magnesium oxide and sodium. 12. The method of claim 11, wherein the method comprises a material selected from the group consisting of: faujasite and ammonium ion treated aluminum phosphate.   The method of claim 12, wherein the mercaptan decomposition catalyst comprises a material selected from the group consisting of alumina, silica and silica-alumina.   14. The method of claim 13, wherein the mercaptan decomposition catalyst has substantially no hydrogenation activity.   The first and second hydrodesulfurization reaction conditions include a temperature of 500 ° F. (260 ° C.) to 675 ° F. (375 ° C.), a pressure of 200 to 500 psig and a hydrogen-containing process gas ratio of 1000 to 3000 standard cubic feet / barrel. The method of claim 1, comprising:   The method of claim 15, wherein the first and second hydrodesulfurization reaction conditions include a pressure of 250 to 400 psig.   The method of claim 16, wherein the mercaptan decomposition reaction conditions comprise a temperature of 550 ° F (288 ° C) to 700 ° F (371 ° C) and a pressure of 150 to 500 psig.   The process of claim 17, wherein the total sulfur content of the product stream of the third reactor is less than 1 wt% of the total sulfur content of the olefinic naphtha feed stream.   The process of claim 18, wherein the mercaptan sulfur content of the product stream of the mercaptan cracking reactor is less than 10% by weight of the mercaptan sulfur content of the effluent stream of the first reactor. . A substantial amount of an olefinic naphtha feed stream boiling in the range of 50 ° F. (10 ° C.) to 450 ° F. (232 ° C.) and containing organically bound sulfur and having an olefin content of at least 5% by weight. In which hydrodesulfurization is carried out while retaining the olefin,
a) The olefinic naphtha feed stream is heated in the first reaction stage in the presence of a hydrogen-containing process gas and a hydrodesulfurization catalyst at a temperature of 450 ° F. (232 ° C.) to 800 ° F. (427 ° C.) and a pressure of 60 Elemental sulfur and organically combined in the olefinic naphtha feed stream is hydrodesulfurized at first hydrodesulfurization reaction conditions including -800 psig and hydrogen-containing process gas ratio of 1000-6000 standard cubic feet / barrel. Converting a portion of the sulfur to hydrogen sulfide to produce a first reactor effluent stream having a total sulfur content lower than that of the olefinic naphtha feed stream;
b) directing the first reactor effluent stream to an H ₂ S removal zone where stripping agent is used to remove substantially all of the H ₂ S from the first reactor effluent stream. Producing a stripped effluent stream; and c) directing said stripped effluent stream to a mercaptan cracking reaction stage in the presence of a hydrogen-containing process gas and a mercaptan cracking catalyst at a temperature of 500 ° F. Decomposes at least a portion of the mercaptan sulfur under mercaptan decomposition reaction conditions including (260 ° C.) to 800 ° F. (427 ° C.), a pressure of 60 to 800 psig and a hydrogen-containing process gas ratio of 1000 to 6000 standard cubic feet / barrel; Converting at least a portion of the elemental sulfur and organically bound sulfur to produce a first reactor effluent stream. Method characterized by comprising the step of producing a product stream of the mercaptan decomposition reactor having a lower mercaptan sulfur content than that of the over arm.   21. The method of claim 20, wherein the olefinic naphtha feed stream is in the vapor phase prior to contacting the first reaction stage.   The method of claim 21, wherein the stripped effluent stream is in the vapor phase prior to contacting the mercaptan cracking stage.   23. The method of claim 22, wherein the stripping agent is selected from the group consisting of steam and amine solutions.   21. The process of claim 20, wherein the total sulfur content of the product stream of the mercaptan cracking reactor is less than 1% by weight of the total sulfur content of the olefinic naphtha feed stream.   25. The process of claim 24, wherein the mercaptan sulfur content of the product stream of the mercaptan cracking reactor is less than 10% by weight of the mercaptan sulfur content of the effluent stream of the first reactor. .   21. The method of claim 20, wherein the hydrodesulfurization catalyst used in the first reaction stage comprises at least one Group VIII metal oxide and at least one Group VI metal oxide.   The hydrodesulfurization catalyst used in the first reaction stage is at least one Group VIII metal oxide selected from the group consisting of Fe, Co and Ni, and at least selected from the group consisting of Mo and W 27. The method of claim 26, comprising a group VI metal oxide.   28. The method of claim 27, wherein the metal oxide is deposited on a high surface area support material.   30. The method of claim 28, wherein the high surface area support material is alumina. Said mercaptan decomposition catalyst, method of claim 20, the degradation of the mercaptan sulfur, characterized by comprising the effective amount of the refractory metal oxide to catalyze against the H 2 _S .   The mercaptan decomposition catalyst removes acidity by ion exchange with alumina, silica, silica-alumina, aluminum phosphate, titania, magnesium oxide, alkali and alkaline earth metal oxides, alkali metal oxides, magnesium oxide and sodium. 31. The method of claim 30, comprising a material selected from the group consisting of: faujasite and ammonium ion treated aluminum phosphate.   32. The method of claim 31, wherein the mercaptan decomposition catalyst comprises a material selected from the group consisting of alumina, silica and silica-alumina.   The method according to claim 32, wherein the mercaptan decomposition catalyst has substantially no hydrogenation activity.   The first hydrodesulfurization reaction conditions include a temperature of 500 ° F. (260 ° C.) to 675 ° F. (375 ° C.), a pressure of 200 to 500 psig, and a hydrogen-containing process gas ratio of 1000 to 3000 standard cubic feet / barrel. 21. A method according to claim 20 characterized in that   35. The method of claim 34, wherein the first hydrodesulfurization reaction conditions include a pressure of 250-400 psig.   36. The method of claim 35, wherein the mercaptan decomposition reaction conditions comprise a temperature of 550 [deg.] F. (288 [deg.] C.) to 700 [deg.] F. (371 [deg.] C.) and a pressure of 150 to 500 psig.   The process of claim 36, wherein the total sulfur content of the product stream of the mercaptan cracking reactor is less than 1 wt% of the total sulfur content of the olefinic naphtha feed stream.   38. The method of claim 37, wherein the mercaptan sulfur content of the product stream of the mercaptan cracking reactor is less than 10% by weight of the mercaptan sulfur content of the effluent stream of the first reactor. .

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