Patent Grant
7956227
The present invention relates generally to processing hydrocarbon-containing streams. In one aspect, the invention concerns processes for the oligomerization of hydrocarbon-containing streams.
Much of the refinery related research over the past 5-10 years has been directed at converting light naphtha streams that are too high in Reid Vapor Pressure (RVP) for large volume use in gasoline, to higher molecular weight gasoline and diesel range compounds with lower RVP values. The desire for such capabilities continues to grow with downward pressure on gasoline RVP to reduce fugitive emissions into the atmosphere and as the use of ethanol in the gasoline pool increases.
The Reid Vapor Pressure is a measure of the vapor pressure of gasoline, volatile crude oils, and other volatile petroleum products determined at approximately 38° C. In the past decades, the Environmental Protection Agency (EPA) imposed regulations controlling hydrocarbon emissions from fuel sources in order to reduce ground ozone levels. Volatile organic compounds (VOCs) from evaporative sources are a major source for the generation of this urban ozone. Thus, restrictions on light hydrocarbon streams become more and more stringent forcing the lightest components out of the available fuel pool. With increased ethanol blending, this problem will be exacerbated since blending ethanol requires a lower RVP base stock to achieve overall final fuel RVP specifications.
In 2012, about four hundred ninety thousand barrels per day of renewable fuels (mainly comprising ethanol) will be mandated. The use of ethanol in reformulated gasoline (RFG) will not be optional for many refiners as they will need to use it to achieve octane. If by 2012 all the gasoline pool is mandated to be RFG then the displaced C5 would further double assuming the required volume of renewables remains constant. In addition, these objectives must be met without negatively impacting other fuel parameters such as octane and distillation points.
In accordance with the present invention, a process has been discovered which comprises, consists of, or consists essentially of
Still another embodiment of the invention is a process which comprises, consists of, or consists essentially of:
Other objects and advantages will become apparent from the detailed description and the appended claims.
One embodiment of the present invention is a process comprising, consisting of, or consisting essentially of:
Any zeolite-containing catalyst which is effective for the oligomerization of hydrocarbons can be used. Generally, the molar ratio of SiO2 to Al2O3 in the crystalline framework of the zeolite is in the range of from about 10:1 to about 150:1. The molar ratio of SiO2 to Al2O3 in the zeolite framework can also be in the range of from about 30:1 to about 100:1. Examples of zeolites that can be used include, but are not limited to mordenites. Examples of mordenites that can be used include but are not limited to Mordenite 40, Mordenite 90 and their hydrogen-promoted counterparts.
Any olefin can be oligomerized by the process of the present invention. Generally, the olefins have in the range of from 2 to 20 carbon atoms per molecule. The olefins can also have in the range of from 3 to 6 carbon atoms per molecule, and, additionally, the olefins can have 4 to 5 carbon atoms per molecule.
Generally, the oligomerization reaction conditions in the oligomerization reaction zone include a temperature in the range of from about 35° C. to about 260° C. The temperature can also be in the range of from about 65° C. to about 150° C., and, additionally, the temperature can be in the range of from 90° C. to 130° C.
The oligomerization reaction conditions also include a pressure in the range of from about 100 psi to about 800 psi. The pressure can also be in the range of from about 300 psi to about 500 psi, and, additionally, the pressure can range from 200 psi to 600 psi. The desired pressure maintains the process stream in the liquid form.
Before contacting the zeolite catalyst with olefins in an oligomerization zone, the zeolite can optionally be treated with one or more metal compounds in order to increase the acidity of the zeolite. The zeolite can be treated with compounds containing metals selected from the group consisting of zinc, cadmium, copper, silver, gold, gallium, indium, silicon, germanium, and tin. Generally, the compound contains zinc or tin. The metal compound can be incorporated into or onto the zeolite. One method of incorporating is to impregnate using any standard incipient wetness impregnation technique (i.e. essentially completely or partially filling the pores of a substrate material with a solution of the incorporating elements) for impregnating a substrate. This method uses an impregnating solution comprising the desirable concentration of a metal containing compound. Metal containing compounds that can be used include, but are not limited to, metal salts such as metal chlorides, metal nitrates, metal sulfates, and the like and combinations thereof. Metal-containing organic compounds can also be used. Examples of metal containing compounds useful in the present invention include, but are not limited to, zinc nitrate and dibutyltin bis(2-ethylhexanoate). An impregnating solution comprises a solution formed by dissolving a metal containing compound in a solvent such as water, alcohols, esters, ethers, ketones, hydrocarbons and combinations thereof. The concentration of the metal in the solution can be in the range of from about 0.01 gram of metal per gram of solution to about 0.9 grams of metal promoter per gram of solution.
In order to reduce potential catalyst poisons, it is desirable to pass the olefins through a series of one or more guard beds before the olefins are contacted with a zeolite catalyst. The guard beds are generally arranged in a series containing from one to four separate guard beds. The guard beds can contain a compound selected from the group consisting of a molecular sieve, silica gel and combinations thereof. The molecular sieves are commonly either 3 Angstrom or 13× molecular sieves. The guard beds can contain any combination of 3 Angstrom molecular sieves, silica gel, and 13× molecular sieves. The guard beds can be regenerated by any suitable regeneration stream. The guard beds can be regenerated by contact with air or with a gaseous organic compound. The gaseous organic compound can be for example, gaseous isobutane. The guard bed regeneration process comprises, consists of, or consists essentially of the steps of: (a) contacting a regeneration stream with the guard bed to form an adsorbed stream, (b) condensing the adsorbed stream to form a condensed stream, (c) adding water to the condensed stream to form a waste stream, and (d) disposing of the waste stream.
The zeolite catalyst can also be regenerated. The catalyst can be regenerated by any suitable regeneration stream. Examples of suitable regeneration streams include, but are not limited to, air, nitrogen, supercritical isobutane, and other light hydrocarbons. Generally the regeneration conditions include a regeneration pressure in the range of from about 500 psi to about 1500 psi. The regeneration pressure can also be in the range of from about 529 psi to about 800 psi. The pressure can additionally be in the range of from 529 psi to 650 psi. The regeneration temperature depends on which regeneration stream is being used. Generally the temperature is in the range of from about 50° C. to about 900° C. For example, when air is used, the temperature can be in the range of from about 250° C. to about 650° C., and additionally can be in the range of from 350° C. to 550° C. When nitrogen is used, the temperature can be in the range of from about 100° C. to about 500° C., and additionally can be in the range of from 200° C. to 400° C. When supercritical isobutane is used, the temperature can be in the range of from about 135° C. to about 500° C., and additionally can be in the range of from 135° C. to 300° C.
The process of the first embodiment of the invention can also further comprise: (5) separating compounds comprising n-alkenes from the oligomerization product, (6) contacting the compounds comprising n-alkenes with an isomerization catalyst in an isomerization reaction zone under isomerization conditions to form an isomerization product; and (7) returning the isomerization product to the oligomerization zone.
Referring to
Meanwhile, guard bed 34 and reactor 62 go through a regeneration cycle. Regeneration fluid in conduit 50 passes into guard bed 34 via conduit 46. The regeneration fluid removes the water that was collected in guard bed 34 and both the regeneration fluid and water exit guard bed 34 via conduit 38 and pass through cooler 54 and then to vessel 52 via conduit 81. Vessel 52 separates the regeneration fluid from water and other impurities. Additional water can enter vessel 52 via opening 85 to help with this process. The water and other impurities exit vessel 52 via conduit 83. The now separated regeneration fluid exits vessel 52 via conduit 50, passes through pump 87 which raises the pressure, and continues via conduit 50, is vaporized by heater 140 and then enters guard bed 34 via conduit 46 to begin the regeneration process once more.
While reactor 60 is active, reactor 62 is in the regeneration phase. Air enters air compressor 86 via conduit 84. The air then travels via conduit 88, mixes with recycle gas in conduit 90, then joins a nitrogen stream in conduit 80. The air/nitrogen stream then travels to conduit 70 and enters reactor 62 via conduit 66. The stream exits reactor 62 via conduit 58 and travels via conduit 92 to cooling unit 94, then to vessel 96, where condensed water is knocked out of the stream, exiting vessel 96 through conduit 98. Inert gases leave vessel 96 via conduit 100 then conduit 101. Some off gases are purged, while regenerator off-gas passes through recycle compressor 102 and back to conduit 90. In this process, valves 104, 108, 114, 118, 122, 126, 128 and 132 are open while valves 106, 110, 112, 116, 120, 124, 130 and 134 are closed. After the desired regeneration is finished the open valves can be closed and the closed valves can be opened, in order to enable guard bed 34 and reactor 62 to be in the process phase, while guard bed 32 and reactor 60 enter the regeneration phase. In this process, the C4/C5 stream enters guard bed 34 via conduit 30, and exits via conduit 44, and subsequently enters reactor 62 via conduit 58 and exits reactor 62 via conduit 66. Meanwhile, regeneration fluid enters guard bed 32 via conduit 42 and exits via conduits 28 and 36. An air/nitrogen regeneration stream can enter reactor 60 via conduit 64 and exits via conduit 56. The rest of the process continues to operate in the manner described above.
Another embodiment of the invention is a process comprising, consisting of, or consisting essentially of the steps of:
Generally, dehydrogenation conditions comprise a reaction temperature in the range of from about 150° C. to about 1000° C. The reaction temperature can also be in the range of from about 200° C. to about 650° C., and, additionally, the reaction temperature can be in the range of from about 300° C. to about 650° C.
The dehydrogenation product comprises olefins having either 4 or 5 carbon atoms per molecule. These olefins are then oligomerized in an oligomerization zone under oligomerization reaction conditions.
The oligomerization reaction conditions are the same as described above.
The oligomerization catalyst used in this embodiment can be any catalyst that is used in the previous embodiment, as described above. The catalyst can also be pre-treated with a metal-containing compound, such as, for example, a zinc or tin-containing compound, as described above.
The oligomerization process of step (2) produces a product comprised of oligomers and gasoline components. If the dehydrogenation product comprises C4s, then the oligomerization product comprises of compounds with 4, 8, and 12 or more carbon atoms per molecule. If the dehydrogenation product comprises C5s, then the oligomerization product comprises of compounds with 5, 10, and 15 or more carbon atoms per molecule. These different compounds are then separated via different separation zones. The compounds with 8 or 10 carbon atoms per molecule are then returned to an oligomerization zone, which can be the same oligomerization zone as in step (2) or a separate one. The compounds with 4 or 5 carbon atoms per molecule which comprise unreacted paraffins are returned to the dehydrogenation zone and the compounds with 12 or more carbon atoms per molecule are sent to a hydrotreating zone for the distillate pool.
Referring to
Another embodiment of the invention is a process comprising, consisting of, or consisting essentially of the steps of:
Any suitable paraffin, internal olefin and alpha olefin can be used. Examples of suitable paraffins include, but are not limited to propane, isobutanes, isopentanes, and isohexanes. Examples of suitable internal olefins include, but are not limited to, isobutene, isopentenes, and isohexenes. Examples of suitable alpha olefins include, but are not limited to, propene, 1-butene, 1-pentene, and 1-hexene. One example of a suitable feed is a feed comprising isopentane, isobutene, and 1-butene.
Generally, the olefins are present in the feed in an amount in the range of from about 0.1 weight percent to about 100 weight percent based on the total weight of the feed. The alpha olefin can be present in an amount in the range of from about 5 weight percent to about 35 weight percent, and the alpha olefin can also be present in the range of from 10 weight percent to 25 weight percent, based on the total weight of the feed. The internal olefin can be present in an amount in the range of from about 5 weight percent to about 35 weight percent, and the internal olefin can also be present in the range of from 10 weight percent to about 25 weight percent based on the total weight of the feed.
The catalyst used and the oligomerization reaction conditions in the oligomerization zone are the same as in the previous embodiments, as described above.
The following examples are presented to further illustrate this invention and are not to be construed as unduly limiting its scope.
Three different C5 feedstocks were oligomerized by the following process: a mordenite catalyst was placed into a cylindrical reactor tube. A feed was then passed from a feed pump to a series of two guard beds for treatment. The feed was then passed into the reactor tube, where it underwent oligomerization and was afterwards collected in a collection vessel. Table 1 below shows results for three C5 feeds, labeled as Feed 1, Feed 2, and Feed 3. Feed 2 has the highest sulfur content. Table 1 shows weight percent conversion after 4 days of oligomerization. For each feed there was a run with guard bed treatment and a run eliminating the guard bed treatment step.
A C5 feedstock was oligomerized by the following process: a 26.25-gram quantity of an H-Mordenite 90 catalyst was placed into a cylindrical reactor tube. The feed was then passed from a feed pump to a series of two guard beds, which contained a 3 Å sieve, silica gel, and a 13× sieve. The feed then passed into the reactor tube, where it then underwent oligomerization and was afterwards collected in a collection vessel. The guard beds were regenerated at 230° C. with dilute air and the catalyst was regenerated with dilute air at 550° C. The reaction system was run for 137.4 hours. The results are shown in Table II below.
A C5 feedstock was oligomerized by the process of Example II.
Control
A C4 feedstock was oligomerized by the following process: 6.5 grams of H-Mordenite 40 catalyst, diluted with a 30 mL volume of 14 grit alundum was placed into a cylindrical reactor tube. The feed was then passed from a feed pump to a series of two guard beds, which contained a 3 Angstrom sieve, silica gel, and a 13× sieve. The feed then passed into the reactor tube, where it then underwent oligomerization and was afterwards collected in a collection vessel. The reaction system ran for about 144.2 hours. The results are shown in Table III below.
Inventive (Catalyst Treated with Zinc)
An H-Mordenite 40 catalyst was treated with zinc nitrate. A 0.1 gram quantity of zinc nitrate hexahydrate was dissolved in 8 mL of water. The mixture was then heated to a temperature of 250° C to dissolve the zinc nitrate. This mixture was then added to 15 grams of a H-Mordenite 40 catalyst in 3 increments. The catalyst was then dried.
The catalyst was then tested for oligomerization activity with a C4 feed by the following process: 6.5 grams of the catalyst, diluted with a 30 mL volume of 14 grit alundum was placed into a cylindrical reactor tube. The feed was then passed from a feed pump to a series of two guard beds, which contained a 3 Angstrom sieve, silica gel, and a 13× sieve. The feed then passed into the reactor tube, where it then underwent oligomerization and was afterwards collected in a collection vessel. The reaction system ran for about 148 hours. The results are shown in Table IV below.
Inventive (Catalyst Treated with Tin)
An H-Mordenite 40 catalyst was treated with dibutyltin bis(2-ethylhexanoate). A 0.25 gram quantity of dibutyltin bis(2-ethylhexanoate) was dissolved in 8 mL of acetone. This mixture was heated, and then added to 15 grams of a H-Mordenite 40 catalyst in 3 increments. The catalyst was then dried.
The catalyst was then tested for oligomerization activity with a C4 feed by the following process: 6.5 grams of the catalyst, diluted with a 30 mL volume of 14 grit alundum was placed into a cylindrical reactor tube. The feed was then passed from a feed pump to a series of two guard beds, which contained a 3 Angstrom sieve, silica gel, and a 13× sieve. The feed then passed into the reactor tube, where it then underwent oligomerization and was afterwards collected in a collection vessel. The reaction system ran for about 145.5 hours. The results are shown in Table V below.
I. Control
A feed comprising 10% 1-butene in isopentane was oligomerized by the following process: 8 grams of an H-Mordenite 40 catalyst which was treated with zinc nitrate as described in Example IV was placed into a cylindrical reactor tube. The feed was then passed from a feed pump to a series of two guard beds, which contained a 3 Å sieve, silica gel, and a 13× sieve. The feed then passed into the reactor tube, where it then underwent oligomerization and was afterwards collected in a collection vessel. The reaction system ran for about 145 hours. The results are shown in Table VI below.
II. Inventive
A feed comprising 10% 1-butene and 1% isobutene in isopentane was oligomerized by the following process: 8 grams of an H-Mordenite 40 catalyst which was treated with zinc nitrate as in Example V was placed into a cylindrical reactor tube. The feed was then passed from a feed pump to a series of two guard beds, which contained a 3 Angstrom sieve, silica gel, and a 13× sieve. The feed then passed into the reactor tube, where it then underwent oligomerization and was afterwards collected in a collection vessel. The reaction system ran for about 145.8 hours. The results are shown in Table VII below.
Reasonable variations, modifications, and adaptations may be made within the scope of this disclosure and the appended claims without departing from the scope of this invention.
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