Patent Application
20150152336
Embodiments disclosed herein relate generally to production of useful hydrocarbons, such as distillate fuels, from triacylglycerides-containing plant or animal fats-containing oils.
Hydrothermolysis of triacylglycerides-containing oils such as those derived from crops, animal fats or waste vegetable and animal-derived oils involves many types of chemical reactions. As one example, some prior art processes catalytically hydrotreat the triacylglyceride containing oils, converting the unsaturated aliphatic chains in the triacylglyceride containing oils to straight chain paraffins while simultaneously deoxygenating/decarboxylating the acid and glyceryl groups to form water, carbon dioxide and propane. Two downstream processes are then required to (a) skeletally isomerize the n-paraffins to isoparaffins to produce specification grade diesel fuels, and (b) hydrocracking the diesel range n-paraffins and isoparaffins to hydrocarbons to produce specification grade jet fuels.
U.S. Pat. No. 7,691,159, for example, discloses a hydrothermolysis process to convert triacylglycerides to smaller organic acids in the presence of hot compressed water at supercritical water conditions. During the process, the backbone of the triacylglycerides undergoes rearrangement reactions. These reactions may occur in hydrothermolysis zones contained in a fired furnace which provides endothermic heats of reaction. Coke formation in the fired furnace results from the contact of hydrothermolyzed intermediate products with high temperature metal surfaces.
In one aspect, embodiments disclosed herein relate to a process for converting triacylglycerides-containing oils or fatty acids derived from plants, algae, organic wastes or animal sources into crude oil precursors and/or distillate hydrocarbon fuels. The process may include feeding hydrogen, water, and a triacylglyceride-containing oil into a co-current reactor having a homogeneously catalyzed hydrothermolysis reaction zone and a heterogeneously catalyzed hydrotreatment zone, hydrothermolyzing at least a portion of the triacylglyceride-containing oil in the hydrothermolysis reaction zone to form a hydrothermolysis reaction product, and hydrotreating the hydrothermolysis reaction product directly without any componential separations in the catalytic hydrotreatment zone, and recovering an effluent from the catalytic hydrotreatment zone.
In another aspect, embodiments disclosed herein relate to a reactor system for converting triacylglycerides-containing oils into crude oil precursors and/or distillate hydrocarbon fuels. The reactor system may include a homogeneously catalyzed hydrothermolysis reaction zone for hydrothermolyzing at least a portion of a triacylglyceride-containing oil to form a hydrothermolysis reaction product, and a heterogeneously catalyzed hydrotreatment zone for hydrotreating the hydrothermolysis reaction product.
In another aspect, embodiments disclosed herein relate to a process for converting triacylglycerides-containing oils into crude oil precursors and/or distillate hydrocarbon fuels. The process may include mixing hydrogen with water to form a superheated mixed water stream, injecting the mixed water stream into a co-current reaction system comprising a hydrothermolysis adiabatic reaction zone and a catalytic adiabatic hydrotreatment zone, injecting a triacylglyceride-containing oil into the co-current reaction system, reacting the first portion of the mixed water stream and the triacylglyceride-containing oil in a first hydrothermolysis adiabatic reaction zone under reaction conditions sufficient to convert at least a portion of the triacylglycerides via hydrothermolysis to produce a hydrothermolysis reaction product comprising one or more of isoolefins, isoparaffins, cycloolefins, cycloparaffins, and aromatics, feeding hydrogen and the hydrothermolysis reaction product to a first catalytic adiabatic hydrotreatment zone to hydrotreat at least a portion of the reaction product, and recovering a hydrotreated effluent.
In another aspect, embodiments disclosed herein relate to a system for converting triacylglycerides-containing oils into crude oil precursors and/or distillate hydrocarbon fuels. The system may include a mixing device for mixing hydrogen with water to form a hydrogen-water mixture, at least one co-current adiabatic reaction system comprising, at least one hydrothermolysis reaction zone for reacting the hydrogen-water mixture and triacylglycerides-containing oils at a temperature in the range of 250° C. to about 650° C. and a pressure greater than about 75 bar to produce a hydrothermolysis effluent, and at least one hydrotreatment zone for hydrotreating the hydrothermolysis effluent.
In another aspect, embodiments disclosed herein relate to a process for converting triacylglycerides-containing oils into crude oil precursors and/or distillate hydrocarbon fuels. The process may include injecting a superheated mixed water stream comprising water and hydrogen into a co-current adiabatic reaction system, co-currently, injecting a triacylglyceride-containing oil into the co-current adiabatic reaction system, and reacting the mixed water stream and the triacylglyceride-containing oil in a plurality of adiabatic reaction zones under reaction conditions sufficient to convert the triacylglycerides via hydrothermolysis and hydrotreatment to produce a hydrotreated effluent comprising one or more of isoolefins, isoparaffins, cycloolefins, cycloparaffins, and aromatics.
In another aspect, embodiments disclosed herein relate to a process for converting triacylglycerides-containing oils into crude oil precursors and/or distillate hydrocarbon fuels. The process may include mixing hydrogen with water to form a superheated mixed water stream, injecting a first portion of the mixed water stream into a co-current reactor system including a hydrothermolysis reaction zone, comprising at least a first hydrothermolysis reaction zone and a second hydrothermolysis reaction zone, and a hydrotreatment reaction zone, comprising at least a first hydrotreatement reaction zone and a second hydrotreatment reaction zone, injecting a triacylglyceride-containing oil into the co-current reaction system, reacting the first portion of the mixed water stream and the triacylglyceride-containing oil in the first hydrothermolysis reaction zone under reaction conditions sufficient to convert at least a portion of the triacylglycerides via hydrothermolysis to produce a first intermediate product comprising one or more of isoolefins, isoparaffins, cycloolefins, cycloparaffins, aromatics, and unreacted triacylglyceride-containing oil, mixing a second portion of the mixed water stream and the first intermediate product intermediate the first hydrothermolysis reaction zone and the second hydrothermolysis reaction zone, reacting the second portion of the mixed water stream and the first intermediate product in the second hydrothermolysis reaction zone under reaction conditions sufficient to convert at least a portion of the first intermediate product via hydrothermolysis to produce a hydrothermolysis product comprising one or more of isoolefins, isoparaffins, cycloolefins, cycloparaffins, and aromatics, mixing the hydrothermolysis product from the second hydrothermolysis reaction zone, with a first portion of an unheated hydrogen stream intermediate the second hydrothermolysis reaction zone and the first hydrotreatment reaction zone, hydrotreating a portion of the hydrothermolysis product in the first hydrotreatment reaction zone to form a partially hydrotreated product, mixing the partially hydrotreated product with a second portion of the unheated hydrogen stream intermediate the first and second hydrotreatment reaction zones, hydrotreating the partially hydrotreated product in the second hydrotreatment reaction zone to form a hydrotreated product, and recovering a hydrotreated effluent from the co-current reactor system.
Other aspects and advantages will be apparent from the following description and the appended claims.
In one aspect, embodiments disclosed herein relate generally to production of useful hydrocarbons, such as paraffins, from triacylglycerides-containing oils, such as from renewable feedstocks. In another aspect, embodiments disclosed herein relate to processes and systems for converting triacylglycerides-containing oils into crude oil precursors and/or distillate hydrocarbon fuels. The process typically includes catalytic hydrothermolysis, hydrotreating and fractionation.
Renewable feedstocks having triacylglycerides-containing oils useful in embodiments disclosed herein may include fatty acids, saturated triacylglycerides, and triacylglycerides having one or more olefinic bonds such as those from any plant, animal or algae. For example, triacylglycerides-containing oils may include oils from at least one of camelina, carinata, jatropha, karanja, moringa, lesquerella, physaria, palm, castor, cotton, corn, linseed, peanut, soybean, sunflower, tung, babassu, and canola, or at least one triacylglycerides-containing oil from at least one of shea butter, tall oil, tallow, waste vegetable oil, algal oil, and pongamia.
Hydrothermolysis under supercritical water conditions includes a number of different chemical reactions such as for example, but not limited to, hydrolysis, cyclization, cross-linking, conjugation, thermal cracking, decarboxylation, and Diels-Alder reaction. During homogeneously catalyzed hydrothermolysis, up to a maximum of about 9 wt % water, depending upon the carbon number of the free fatty acid associated with the triacylglycerides, is consumed and much of the glycerin byproduct (approximately 10-13 wt % of the feed), if not all, is further dehydrated and converted to gases or partially deoxygenated compounds. Low molecular weight organic acids are hydrogenated to their corresponding paraffins in the downstream heterogeneously catalyzed hydrotreatment step.
A triacylglycerides-containing oil may be reacted with water and hydrogen, fed as H2, diatomic hydrogen, at a temperature in the range from about 250° C. to about 650° C. and a pressure greater than about 75 Bar to about 250 Bar to convert at least a portion of the triacylglycerides via homogeneously catalyzed hydrothermolysis to a hydrocarbon or mixture of hydrocarbons comprising one or more of isoolefins, isoparaffins, cycloolefins, cycloparaffins, and aromatics. In some embodiments, the reaction conditions are such that the temperature and pressure are above the supercritical temperature and pressure of water. The resulting reaction effluent may then be further treated and separated to recover the hydrocarbon products.
To form the triacylglycerides-water-hydrogen mixture, a triacylglycerides-containing oil may be mixed with water and diatomic hydrogen in any order or with a mixture of water and diatomic hydrogen.
At supercritical water hydrothermolysis reaction conditions for homogeneously catalyzed hydrothermolysis, protonic hydrogen may be generated in situ. For example, U.S. Pat. No. 7,691,159 hypothesizes that, for each mole of soybean oil, 1.5 moles of H2 are extracted from the water and added to the resulting hydrocarbon. While presenting this in terms of diatomic hydrogen equivalents, the in situ derived protonic hydrogen atoms would rapidly react and incorporate into the carboxylate molecules derived from the triacylglycerides. The diatomic hydrogen feed used in embodiments herein is in addition to any hydrogen that may be generated in situ from water or other components in the homogeneously catalyzed hydrothermolysis reactor, and, although being an additional operating expense, may provide the benefits of enhanced reactivity within the homogeneously catalyzed hydrothermolysis reactor as well as an increased H/C ratio in the resulting product. Externally supplied diatomic hydrogen also provides an independent means of controlling the process performance, which cannot be obtained via in situ monoatomic hydrogen production alone, as it is dependent upon the homogeneously catalyzed hydrothermolysis reaction conditions and the composition of the triacylglycerides-containing feedstock. Overall, adding an external supply of diatomic hydrogen to the homogeneously catalyzed hydrothermolysis reactor, along with the super critical water and the renewable oil feed provides a different process, different reaction mechanism, and added performance over in situ monoatomic hydrogen generation alone.
Another advantage of co-feeding externally supplied diatomic hydrogen to the homogeneously catalyzed hydrothermolysis reactor is the hydrogen capping effect of stabilizing any free radicals formed during the homogeneously catalyzed hydrothermolysis reactions, thereby avoiding formation of oligomeric and/or polymeric materials, often referred to as coke or coke precursors or coke deposits, that would otherwise form as a result of condensation of these free radicals. Thus, co-feeding externally supplied diatomic hydrogen provides improved on-stream operability relative to processes that do not co-feed diatomic hydrogen gas.
In some embodiments, to form the triacylglycerides-water-diatomic hydrogen mixture, triacylglycerides-containing oil is first mixed with water to form a triacylglyceride-water mixture. The resulting triacylglycerides-water mixture is then mixed with diatomic hydrogen to form the triacylglycerides-water-diatomic hydrogen mixture.
The triacylglycerides-water-diatomic hydrogen mixture may have a water to triacylglycerides mass ratio in the range from about 0.001:1 to about 1:1 in some embodiments; from about 0.01:1 to about 1:1 in other embodiments; and from about 0.1:1 to about 1:1 in yet other embodiments.
The triacylglycerides-water-diatomic hydrogen mixture may have a diatomic hydrogen to triacylglycerides mass ratio in the range from about 0.001:1 to about 1:1 in some embodiments; from about 0.005:1 to about 0.5:1 or 1:1 in other embodiments; from about 0.01:1 to about 0.5:1 in other embodiments; and from about 0.1:1 to about 0.5:1 in yet other embodiments. In some embodiments, the diatomic hydrogen to triacylglycerides mass ratio may be in the range from about 0.1:1 to about 0.2:1. The total diatomic hydrogen feed rate in some embodiments may be sufficient to supply a portion or all of the hydrogen necessary for the homogeneously catalyzed hydrothermolysis as well as any close-coupled downstream processing steps, such as heterogeneously catalyzed hydrotreatment.
The triacylglycerides-water-hydrogen mixture may have a water to triacylglycerides mass ratio in the range from about 0.001:1 to about 1:1 in some embodiments; from about 0.01:1 to about 1:1 in other embodiments; and from about 0.1:1 to about 1:1 in yet other embodiments.
The water-hydrogen mixture may have a hydrogen to water mass ratio in the range from about 0.005:1 to about 500:1 in some embodiments; from about 0.1:1 to about 250:1 in other embodiments; and from about 5:1 to about 50:1 in yet other embodiments.
The homogeneously catalyzed hydrothermolysis reaction effluent may then be directly catalytically hydrotreated using heterogeneous catalysts, such as in the same reactor, without intermediate separations of water, unreacted diatomic hydrogen, or other light gas byproducts, to form additional distillate range hydrocarbons and/or to convert precursors in the reaction effluent to distillate range hydrocarbons. Homogeneously catalyzed hydrothermolysis produces a crude oil that requires heterogeneously catalyzed catalytic hydrotreatment to be converted to useful infrastructure-compatible distillate fuels. Heterogeneously catalyzed hydrotreatment processes may operate at elevated pressures, such as 500-2000+ psig, using supported catalysts having activity towards both heteroatom removal and double bond saturation reactions. Also required is an excess flow of diatomic hydrogen gas over and above the stoichiometric requirement, which for the case of homogeneously catalyzed hydrothermolysis-derived crude oil feedstocks may be in the range of 1000 to 2000 scf per barrel, the latter depending upon renewable feedstock type and homogeneously catalyzed hydrothermolysis reaction conditions. The need for excess diatomic hydrogen gas is to: a) drive the desired hydrotreatment reactions to a high degree of conversion; and b) to provide a heat sink to control unmanageable exotherms that would otherwise result from the high heats of hydrotreatment reactions. The adiabatic temperature rise, i.e., the temperature increase from reactant inlet stream to product effluent stream across the hydrotreating catalyst bed, can amount to about 180-200° F. per each thousand standard cubic feet hydrogen consumed. An advantage of co-feeding externally supplied diatomic hydrogen to the homogeneously catalyzed hydrothermolysis reactor is that the diatomic hydrogen contained in the effluent gas stream from the homogeneously catalyzed hydrothermolysis reactor can provide a part or all of the diatomic hydrogen gas feed requirement for the downstream heterogeneously catalyzed catalytic hydrotreating reactor, as well as enhancing the reaction within the homogeneously catalyzed hydrothermolysis reactor itself, as discussed above.
In some embodiments, the above-mentioned triacylglycerides-containing oils, following homogeneously catalyzed hydrothermolysis, may be co-processed in either the homogeneously catalyzed hydrothermolysis or heterogeneously catalyzed hydrotreatment zone with other hydrocarbon feedstocks, such as atmospheric gas oil (AGO), vacuum gas oil (VGO), or other feeds derived from petroleum, shale oil, tar sands, coal-derived oils, organic waste oils, and the like. Organic waste oil examples may be selected from at least one of municipal solid wastes, sewage sludge solids, Kraft plant waste liquor, restaurant greases and used vegetable oils. Both the hydrothermolysis and hydrotreatment reactions occur within a co-current adiabatic reactor.
Following hydrotreatment, the hydrotreatment effluent may then be processed to separate water, unreacted diatomic hydrogen, and light gases from the hydrotreatment effluent and to fractionate the hydrocarbons into one or more hydrocarbon fractions, such as those boiling in the range of naphtha, diesel, or jet. The water and diatomic hydrogen may then be recycled for admixture with the triacylglycerides-containing oil as described above.
The reaction of the triacylglycerides to produce hydrocarbons may be primarily one or more hydrothermolysis reactions homogeneously catalyzed by water and performed at a reaction temperature in the range from about 250° C. to about 650° C.; from about 350° C. to about 550° C. in some embodiments; and from about 425° C. to about 525° C. in other embodiments. Reaction conditions may also include a pressure of greater than 75 bar; greater than 140 bar in other embodiments; greater than 218 bar in other embodiments; between about 75 bar and about 300 bar in some embodiments; and between about 165 bar and about 250 bar in other embodiments. Conditions of temperature and/or pressure may be selected to be above the critical temperature and/or pressure of water. In all embodiments, the homogeneously catalyzed hydrothermolysis reactions may be performed in the absence of added catalysts, such as an inorganic heterogeneous catalyst or a soluble metallic catalyst.
Referring now to
A triacylglycerides-containing oil 2 is also provided to reactor 24. The heated water-hydrogen mixture 22 and the triacylglycerides-containing oil 2 are injected to the top of the reactor 24 where they mix and equilibrate at the desired adiabatic bed inlet temperature. The reactor 24, as illustrated, is a co-current downflow adiabatic reactor; other co-current reactor types may also be used. The reactor 24 may include at least a first inert solids bed 26a in the upper portion of the reactor 24 wherein the homogeneously catalyzed hydrothermolysis reactions may occur. In some embodiments, a plurality of inert solids beds 26 may be used, such as a second inert solids bed 26b, as illustrated. The inert solids beds 26 promote heat transfer, mass transfer and mixing. The reactor 24 may also include at least a first heterogeneous hydrotreatment catalyst bed 28a in the lower portion of the reactor 24. In some embodiments, a plurality of heterogeneous hydrotreatment catalyst beds 28 may be used, such as a second hydrotreatment bed 28b, as illustrated. The number of inert solids beds 26 and hydrotreatment beds 28 will depend on the kinetics of the targeted chemical reactions for a particular triacylglycerides-containing oil and the residence time requirements for completing the targeted chemical reactions for a particular triacylglycerides-containing oil. Although
In an alternate embodiment, as shown in
The triacylglycerides-containing oil 2 may undergo homogeneously catalyzed hydrothermolysis reactions in the first inert solids bed 26a. The hydrothermolysis reactions in the first bed 26a may be endothermic and the temperature of the reactants and products may decrease through the first inert solids bed 26a. At the bottom of the first inert solids bed 26, a portion 30 of the heated water-hydrogen mixture 22 may be injected to elevate the temperature of the partially converted triacylglycerides-containing oil prior to entering the second inert solids bed 26b wherein the hydrothermolysis reactions will occur. The hydrothermolysis reactions in the second bed 26b may be more exothermic than those occurring in the first bed 26a and may elevate the temperature proximate the bottom of the second inert solids bed 26b in the range from about 490° C. to about 510° C.
The inert solids beds 26 may be maintained at reaction conditions, and flow rates may be adjusted to provide for a time sufficient to convert at least a portion of the triacylglycerides to distillate hydrocarbons or precursors thereof. Reaction conditions may include a temperature in the range from about 250° C. to about 650° C. and a pressure of at least 75 bar. The residence time required in the inert solids beds 26 to convert the triacylglycerides may vary depending upon the reaction conditions as well as the specific triacylglycerides-containing oil used. In some embodiments, residence times in the inert solids beds 26 may be in the range from about 1 second to about 10 minutes, such as from about 3 minutes to about 6 minutes. The hydrothermolysis reaction can also include some exothermic reactions, which may supply additional heat to maintain the required reaction temperature conditions and to reduce external heat input requirements. In some embodiments, one or more water feed lines (not shown) may be provided to control the exotherm and the temperature or temperature profile in the inert solids beds 26.
Following reaction of the triacylglycerides in the inert solids beds 26, the hydrothermolysis effluent may then be passed to the hydrotreatment beds 28 to further treat the effluent. Hydrotreatment beds 28 may contain a hydroconversion catalyst to convert at least a portion of the hydrothermolysis effluent to distillate hydrocarbons.
The effluent from the second inert solids bed 26b may be cooled to desirable catalytic hydrotreatment bed temperatures, such as from about 300° C. to about 400° C., utilizing unheated hydrogen 32 prior to entering the first hydrotreatment bed 28a. Optionally, the effluent from the second inert solids bed 26b may also be heated to desirable catalytic hydrotreatment bed temperatures, such as from about 300° C. to about 400° C., utilizing direct heat exchange with a hydrogen/water mixture stream 52 prior to entering the first hydrotreatment bed 28a. A first portion 32a of unheated hydrogen may be injected below the second inert solids bed 26b to cool the hydrothermolysis effluent. The reactions in the first hydrotreatment bed 28a are exothermic, e.g., saturation of olefinic bonds on the acyl backbone of the triacylglycerides-rich feedstocks. A resulting rise in temperature should be limited to a maximum temperature of about 425° C. which may be achieved by injecting a second portion 32b of unheated hydrogen intermediate the first hydrotreatment bed 28a and the second hydrotreatment bed 28b to reduce the reacting stream temperature back within a range from about 300 to about 400° C. While two catalytic hydrotreatment adiabatic beds are shown on the figure, more or less beds may be required. The exact number of adiabatic beds and quench requirements may, for example, be determined from a simulation of the catalytic hydrotreatment reactions using kinetics obtained in bench-scale test units, for a given feedstock.
The homogeneously catalyzed hydrothermolysis and the heterogeneously catalyzed hydrotreatment systems may be “close-coupled,” where the effluent from the inert solids beds 26 is passed to the hydrotreatment beds 28 without phase separation (no separation of water, oil, and diatomic hydrogen). In some embodiments, the effluent from the hydrothermolysis reaction step may be passed to the hydrotreatment system under autogenous pressure, i.e., without any pressure letdown between hydrothermolysis and hydrotreatment other than that which may occur by normal flow-induced pressure drops in piping and feed-effluent heat exchangers. Additionally, due to the diatomic hydrogen feed to the hydrothermolysis reactor, little or no additional diatomic hydrogen, and thus minimal or no hydrogen compression or re-compression is necessary for hydrotreatment. Due to compatible reaction conditions, including pressures, diatomic hydrogen to triacylglycerides ratios, and space velocities, the diatomic hydrogen may be carried through the entire reaction system, providing enhanced system performance including suppressed coking rates and at higher thermal efficiencies and lower cost.
The effluent 34 from the hydrotreatment beds 28 may then be fed to an effluent treatment system 36 for separation and recovery of reaction products. For example, the resulting hydrocarbons may be fractionated into two or more fractions, which, as illustrated, may include distillate hydrocarbons boiling in the range of naphtha 38, diesel 41, or jet 40, and vacuum gas oil (VGO) 42. Some offgas 44 may also be produced. The effluent treatment system 36 may also separate water and hydrogen from the hydrocarbons. Excess hydrogen may also be recovered and recycled back as recycle hydrogen 14b. A purge may be necessary to remove unwanted components, such as CO, CO2, CH4, etc., that would otherwise buildup and lower the hydrogen purity to an undesirably low level.
As noted above, the effluent from the inert solids beds 26 may be close-coupled, being passed to the hydrotreatment beds 28 under autogeneous pressure, i.e., without any pressure letdown between hydrothermolysis and hydrotreatment other than that which may occur by normal flow-induced pressure drops in piping and feed-effluent heat exchangers. In such embodiments, a pressure letdown valve or valves (not shown) may be provided intermediate hydrotreatment beds 28 and effluent treatment system 36 to decrease the pressure from an autogeneous pressure, for example, at or above the supercritical pressure of water, to a pressure less than the supercritical pressure of water, such as atmospheric pressure, in one or more letdown steps. The pressure letdown system may also provide for an initial phase separation of light gases (including diatomic hydrogen), water, and hydrocarbons.
In some embodiments, effluent 34 may be sent to a heat exchanger 50 to be cooled while simultaneously preheating the triacylglycerides-containing oil 2 prior to being sent to the effluent treatment system 36. Optionally, the effluent 34 may also be quenched prior to entering the heat exchanger by a stream of hydrogen 54.
To produce additional distillate range fuels, such as where C20+ hydrocarbons are produced in hydrothermolysis reactor 18, some of the VGO fraction 42, or other hydrocarbon fractions heavier than diesel, may be recycled back to the reactor 24 for additional processing, such as within the inert solids beds 26.
As described with respect to the embodiments of
Additional hydrocarbon feedstocks may be co-processed with triacylglycerides-containing oil 2. The additional hydrocarbon feedstocks may be fed to the reactor 24 along with the triacylglycerides-containing oil 2. Non-renewable hydrocarbon feedstocks, for example, may include one or more of petroleum distillates; shale oil distillates; tar sands-derived distillates; coal gasification byproduct oils; and coal pyrolysis oils, among others. If necessary, some sulfur-containing compound such as, for example, dimethyl disulfide dissolved in a suitable hydrocarbon solvent, may be fed, either intermittently or continuously, to hydrotreatment beds 28 in order to maintain the catalysts in their most active states.
In an alternate embodiment, as shown in
The effluent stream 61 may be heated in heat exchanger 53 and introduced into a hydrodeoxygenation reactor 55 where it is contacted with a hydrogen-rich gas stream 70. Reactor 55 may include more than one co-current downflow adiabatic catalyst beds containing suitable hydrogenation catalysts with activity and selectivity towards the production of paraffins via hydrodeoxygenation of the hydroxyl and carbonyl groups on the free fatty acids as well by hydrodeoxygenation of any alcohols, ketones or aldehydes contained in reactor inlet stream 62. The hydrodeoxygenation reactions can proceed over the range of about 315° C. to about 400° C. The hydrodeoxygenation reactions are exothermic and this results in a temperature rise. The quantity of hydrogen stream 70 can be controlled to maintain the outlet of the catalyst beds of reactor 55 to less than 385° C. and preferably less than 357° C. For the case of multiple catalyst beds (not shown on diagram), hydrogen split off from stream 70 can be introduced between catalyst beds to control bed temperature profiles. The effluent stream 63 is cooled sequentially in a first heat exchanger 51 and a second heat exchanger 86 and then fed to a cold high pressure separator 57 wherein the following three streams are recovered; high pressure hydrogen-rich gas stream 75, hydrotreated liquid product stream 67 and aqueous product stream 66.
The inert solids beds 26 may include, but are not limited to, one or more of aluminas, alundum, ceramics, foams, sand, fused glass, wires, meshes, rods, tubes having little or no chemical conversion activity for pyrolysis, hydrothermolysis or hydrotreatment reactions and which have geometric properties which promote mixing of reactants and products without resulting in adversely high pressure drops. In other embodiments, the inert solids beds 26 may be void of any internals.
Catalysts useful in hydrotreatment beds 28 may include catalysts that may be used for the hydrotreating or hydrocracking of a hydrocarbon feedstock. In some embodiments, the hydrotreating catalyst may effectively hydrodeoxygenate and/or decarboxylate the oxygen bonds contained in the hydrotreatment feed and reduce or eliminate the organic acid concentration in effluent 34. In some embodiments, greater than 99%, 99.9%, or 99.99% of the organic acids may be converted over the hydrotreatment catalyst.
Hydrotreating catalysts that may be useful include catalysts selected from those elements known to provide catalytic hydrogenation activity. At least one metal component selected from Group 8-10 elements and/or from Group 6 elements is generally chosen. Group 6 elements may include chromium, molybdenum and tungsten. Group 8-10 elements may include iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum. The amount(s) of hydrogenation component(s) in the catalyst suitably range from about 0.5% to about 10% by weight of Group 8-10 metal component(s) and from about 5% to about 25% by weight of Group 6 metal component(s), calculated as metal oxide(s) per 100 parts by weight of total catalyst, where the percentages by weight are based on the weight of the catalyst before sulfiding. The hydrogenation components in the catalyst may be in the oxidic and/or the sulfidic form. If a combination of at least a Group 6 and a Group 8 metal component is present as (mixed) oxides, it will be subjected to a sulfiding treatment prior to proper use in hydrocracking. In some embodiments, the catalyst comprises one or more components of nickel and/or cobalt and one or more components of molybdenum and/or tungsten or one or more components of platinum and/or palladium. Catalysts containing nickel and molybdenum, nickel and tungsten, platinum and/or palladium are useful.
In some embodiments, hydrotreatment beds 28 may include two or more beds or layers of catalyst, such as a first layer including a hydrotreating catalyst and a second layer including a hydrocracking catalyst.
In some embodiments, the layered catalyst system may include a lower catalyst layer that includes a bed of a hydrocracking catalyst suitable for hydrocracking any vacuum gas oil (VGO) range hydrothermolysis products or added feeds to diesel range or lighter hydrocarbons. The hydrocracking catalysts used may also be selected to minimize or reduce dearomatization of the alkylaromatics formed in the hydrothermolysis reactor. VGO hydrocracking catalysts that may be used according to embodiments herein include one or more noble metals supported on low acidity zeolites wherein the zeolite acidity is widely distributed throughout each catalyst particle. For example, one or more catalysts as described in U.S. Pat. No. 4,990,243, U.S. Pat. No. 5,069,890, U.S. Pat. No. 5,071,805, U.S. Pat. No. 5,073,530, U.S. Pat. No. 5,141,909, U.S. Pat. No. 5,277,793, U.S. Pat. No. 5,366,615, U.S. Pat. No. 5,439,860, U.S. Pat. No. 5,593,570, U.S. Pat. No. 6,860,986, U.S. Pat. No. 6,902,664, and U.S. Pat. No. 6,872,685 may be used in embodiments herein, each of which are incorporated herein by reference with respect to the hydrocracking catalysts described therein. In some embodiments, the inclusion of the VGO hydrocracking may result in extinctive hydrocracking of the heavy hydrocarbons, such that the only net hydrocarbon products include diesel range and lighter hydrocarbons.
One skilled in the art will recognize that the various catalyst layers may not be made up of only a single catalyst, but may be composed of an intermixture of different catalysts to achieve the optimal level of metals or carbon residue removal and deoxygenation for that layer. Although some olefinic bond hydrogenation will occur in the lower portion of the zone, the removal of oxygen, nitrogen, and sulfur may take place primarily in the upper layer or layers. Obviously additional metals removal also will take place. The specific catalyst or catalyst mixture selected for each layer, the number of layers in the zone, the proportional volume in the bed of each layer, and the specific hydrotreating conditions selected will depend on the feedstock being processed by the unit, the desired product to be recovered, as well as commercial considerations such as cost of the catalyst. All of these parameters are within the skill of a person engaged in the petroleum processing industry and should not need further elaboration here.
As described above, processes according to embodiments herein provide for converting triacylglycerides-containing oils into crude oil precursors and/or distillate hydrocarbon fuels. In some embodiments, the process may include feeding hydrogen, water, and a triacylglyceride-containing oil into a co-current reactor having a homogeneously catalyzed hydrothermolysis reaction zone and a heterogeneously catalyzed hydrotreatment zone. The reactor may be operated at conditions suitable for hydrothermolyzing at least a portion of the triacylglyceride-containing oil in the homogeneously catalyzed hydrothermolysis reaction zone to form a hydrothermolysis reaction product, and for hydrotreating the hydrothermolysis reaction product in the heterogeneously catalyzed hydrotreatment zone. A reaction effluent may then be recovered from the catalytic hydrotreatment zone.
The homogeneously catalyzed hydrothermolysis reaction zone and the heterogeneously catalyzed hydrotreatment zone are adiabatic reaction zones. Such zones may also be contained within the same reactor, such as a co-current reactor, including downflow co-current reactors.
The homogeneously catalyzed hydrothermolysis reaction zone may contain one or more beds of inert solids to promote mixing. The homogeneously catalyzed hydrotreatment zone may include one or more catalyst beds containing a hydrotreating catalyst. To control temperature, as well as reactant concentrations, at least one of hydrogen and water may be fed to the co-current reactor intermediate the one or more homogeneously catalyzed hydrothermolysis reaction zones, intermediate the one or more heterogeneously catalyzed hydrotreatment zones, as well as intermediate the hydrothermolysis reaction zones and the hydrotreatment zones.
Embodiments herein also relate to a reactor system for converting triacylglycerides-containing oils into crude oil precursors and/or distillate hydrocarbon fuels. The reactor system may include: a homogeneously catalyzed hydrothermolysis reaction zone for hydrothermolyzing at least a portion of a triacylglyceride-containing oil to form a hydrothermolysis reaction product; and a heterogeneously catalyzed hydrotreatment zone for hydrotreating the hydrothermolysis reaction product. The homogeneously catalyzed hydrothermolysis reaction zone and the heterogeneously catalyzed hydrotreatment zone are fluidly coupled within the same reactor, and may have one or more adiabatic reaction zones. The hydrothermolysis reaction zone contains one or more beds of inert solids to promote mixing, and the catalytic hydrotreatment zone may include one or more beds containing a hydrotreating catalyst. The catalytic hydrotreatment zone may include, for example, a first catalyst bed containing a catalyst having hydrogenation activity and a second catalyst bed containing a catalyst having hydrocracking activity.
While the above-described systems are described with respect to a single reactor having multiple inert solids beds 26 and multiple hydrotreatment beds 28, the reaction zones may include two or more reactors arranged in series or in parallel. Likewise, back-up compressors, filters, pumps, and the like may also be used. Further, compressors may be single stage or multi-stage compressors, which in some embodiments may be used to compress a single gas stream in sequential stages or may be used to compress separate gas streams, depending on plant layout.
As described above with respect to
As described above, processes disclosed herein may be performed in a system or apparatus for converting triacylglycerides-containing oils into crude oil precursors and/or distillate hydrocarbon fuels. The system may include one or more mixing devices for mixing a triacylglycerides-containing oil feed with water and hydrogen. For example, the system may include a first mixing device for mixing a triacylglycerides-containing oil feed with water to form an oil-water mixture, and a second mixing device for mixing the oil-water mixture with hydrogen to form a feed mixture.
The furnace 20 may be, for example, an electrically heated furnace, or a furnace fired with a fuel gas, such as a natural gas, synthesis gas, or light hydrocarbon gases, including those produced in and recovered from the adiabatic reactor. Reaction conditions may be achieved by use of one or more pumps, compressors, and heat exchangers. A separator may then be used for separating water and hydrogen from hydrocarbons in the reaction effluent.
The system may also include a compressor for compressing hydrogen recovered from the separator, as well as one or more fluid conduits for recycling the compressed hydrogen and/or the recovered water to the mixing device for mixing hydrogen or the mixing device for mixing water.
The system may also include a fractionator for fractionating hydrocarbons in the hydrotreatment effluent to form one or more hydrocarbon fractions boiling in the naphtha, jet or diesel range.
To control reaction temperatures and exotherms in the adiabatic reactor, the system may include one or more fluid conduits for injecting water into the homogeneously catalyzed hydrothermolysis reactor beds.
As described above, embodiments disclosed herein provide processes for the conversion of renewable feedstocks to infrastructure-compatible distillate fuels. For example, in some embodiments, the jet fraction recovered may have a total acid number of less than 0.1 in some embodiments, expressed as mg KOH per gram; less than 0.015 expressed as mg KOH per gram in other embodiments; and less than 0.010 in other embodiments. The jet fraction may have an olefins content of less than about 5 vol % and an aromatics content of less than about 25 vol % in some embodiments. These properties, among others, may allow the jet and/or the diesel fractions produced in embodiments herein to be used directly as engine fuels without blending. In some embodiments, the whole hydrocarbon liquid product recovered from the hydrotreatment reaction zone may be used to produce distillate fuels meeting military, ASTM, EN, ISO, or equivalent fuel specifications.
The process may be carried out in an economically feasible method at a commercial scale. Embodiments herein may maximize the thermal efficiency of the triacylglycerides-containing oil conversion in an economically attractive manner without being hampered by operability problems associated with catalyst fouling. During the homogeneously catalyzed hydrothermolysis process, water, such as about 5% of the feed water, may be consumed in the upper inert-solids containing beds. In the hydrotreatment bed, any glycerin intermediate product that did not undergo extinctive hydrothermolysis reactions in the upstream homogeneously catalyzed hydrothermolysis reaction system may be further catalytically hydrogenated and converted to propane in the close-coupled heterogeneously catalyzed hydrotreatment reaction system. Hydrogen is consumed during the hydrotreatment step, and accordingly the average specific gravity of the product may be reduced, such as from approximately 0.91 to about 0.81. Decarboxylation reactions form COx and that carbon loss may result in a reduced mass yield of liquid products, and an equivalent lower volumetric yield. The actual crude yield may be in the range from about 75% to about 90%, such as in the range from about 80% to 84%, depending on how the hydrothermolysis/hydrotreatment processes are executed.
Naphtha, jet, and diesel fuels may be produced by processes disclosed herein. A higher boiling gas oil material may also be produced, and may contain high-quality, high hydrogen content paraffins in the C17 to C24 boiling range. These heavier hydrocarbons may be recycled to the hydrothermolysis beds of the concurrent adiabatic reactor for further treatment and production of naphtha, jet, and diesel range products. Fuel gases (off gases) may also be produced, which may be used in some embodiments for process heat, hydrogen production, or recovered as individual products (LPG, ethylene, propylene, n-butane, iso-butane, etc.). In another embodiment, these heavier hydrocarbons may be recycled to the catalytic hydrotreatment beds containing selective hydrocracking catalysts for further treatment and production of naphtha, jet and diesel range products.
Fuels produced by embodiments herein may: contain cycloparaffins and aromatics; exhibit high density; exhibit high energy density; exhibit good low-temperature properties (freezing point, cloud point, pour point, and viscosity); exhibit natural lubricity; exhibit a wide range of hydrocarbon types and molecular weights similar to petroleum distillates; and/or have good thermal stability. These fuels may thus be true “drop in” analogs of their petroleum counterparts and do not require blending to meet current petroleum specifications.
Close coupling of the homogeneously catalyzed hydrothermolysis reaction and the heterogeneously catalyzed hydrotreatment reaction system without separation of the intermediate products is unique and may result in many process and economic benefits. For example, benefits may include: elimination of reactions occurring in a fired furnace zone wherein high metal wall temperatures can promote coking, elimination of a hydrothermolysis product cool down step and separation step of gas, oil, and water components; elimination of acid water production and treatment; elimination of additional liquid pumping, gas compression, and heat exchange operations for the hydrotreatment feed; reduced heat loss; and/or reduced power consumption.
While the disclosure includes a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the present disclosure. Accordingly, the scope should be limited only by the attached claims.
