Patent Application
20080066374
High quality liquid fuels, in particular diesel and naphtha fuels, can be obtained from vegetable and/or animal oils in high yield by a process comprising hydrodeoxygenation and hydroisomerization. Triglycerides of fatty acids contained in the vegetable and/or animal oil are deoxygenated to form normal C12 to C18 or C14 to C18 paraffins, which are hydroisomerized in the same stage to form various isoparaffins. Minor cyclization and aromatization to alkyl cyclohexane and alkyl benzene may also occur. The deoxygenation can comprise removal of oxygen in the form of water and carbon oxides from the triglycerides. Hydrocracking is inhibited, so as to maintain the range of carbon number of hydrocarbons formed in the range of C12 to C18 or C14 to C18.
Hydrodeoxygenation of vegetable and/or animal oils alone would generate a mixture of long-chain straight C12 to C18 or C14 to C18 paraffins. While such long-chain straight C12 to C18 or C14 to C18 paraffins would be in the paraffin carbon number range of diesel fuels, the fuel properties of such long-chain straight C12 to C18 or C14 to C18 paraffins would be significantly different from those of diesel fuels. Therefore, production of diesel fuel requires hydroisomerization of the paraffins. Accordingly, the presently disclosed process for producing a liquid fuel composition comprises providing oil selected from the group consisting of vegetable oil, animal oil, and mixtures thereof and hydrodeoxygenating and hydroisomerizing the oil. In addition to hydrocarbon products within the diesel boiling range, the liquid fuel composition produced by the presently disclosed process may further comprise 2-10% lighter naphtha products boiling below 150° C. as well as heavier distillate products.
The hydrodeoxygenating and hydroisomerizing disclosed herein comprises feeding the oil to a tubular reaction unit containing a catalyst comprising an acidic component and a metal component, feeding effluent from the tubular reaction unit to a vapor-liquid separator, and feeding a vapor phase separated from the effluent from the tubular reaction unit to an adiabatic reaction unit comprising the same catalyst as in the tubular reaction unit comprising an acidic component and a metal component. While the effluent from the tubular reaction unit is primarily in a vapor phase, liquid separated from the effluent from the tubular reaction unit can be recycled to the tubular reaction unit. In an embodiment, the tubular reaction unit, which is contained within a shell, is a multi-tubular reaction unit and/or operates in trickle-bed mode and the adiabatic reaction unit comprises a single tube.
As exothermic hydrodeoxygenation and double-bond saturation reactions take place in the tubular reaction unit, a significant amount of heat of reaction is removed from the tube(s) (e.g., 1,000 or even 5,000 tubes) of the tubular reaction unit, for example, by coolant contained in a shell jacketing the tube(s) for optimal temperature control. The vapor-liquid separator disposed downstream of the tubular reaction unit functions as a heat exchanger and sets the temperature of the vapor phase exiting the vapor-liquid separator, which is to be fed to the reaction unit following the vapor-liquid separator. In an embodiment, the vapor phase leaves the vapor-liquid separator at a temperature of about 330 to 400° C. As mild, vapor-phase hydroisomerization and similar reactions take place in the reaction unit following vapor-liquid separation, the reaction unit is adiabatic, and thus, in addition to setting the temperature of the vapor phase exiting the vapor-liquid separator, the vapor-liquid separator also sets the temperature of the reaction unit following the vapor-liquid separator and allows for optimization of the process. Use of both tubular and adiabatic reaction units allows for optimization of the hydrodeoxygenating and hydroisomerizing and improved performance and stability of the catalyst. The tubular reaction unit, vapor-liquid separator, and adiabatic reaction unit may be contained within one or more reaction vessels.
In an embodiment, catalysts for the presently disclosed process are dual-functional catalysts comprising a metal component and an acidic component. In an embodiment, metal components are platinum or palladium. In an embodiment, the metal component is platinum. The acidic component can comprise an acidic function in a porous solid support. In an embodiment, acidic components include, for example, amorphous silica aluminas, fluorided alumina, ZSM-12, ZSM-21, ZSM-22, ZSM-23, ZSM-35, ZSM-38, ZSM-48, ZSM-57, SSZ-32, ferrierite, SAPO-11, SAPO-31, SAPO-41, MAPO-11, MAPO-31, Y zeolite, L zeolite and Beta zeolite. In an embodiment, the catalyst is Pt/SAPO-11, specifically 0.5-1 wt % Pt/SAPO-11, more specifically 1 wt % Pt/SAPO-11.
The type and content of metal, acid strength, type and concentration of acid sites, solid porosity and pore size affect the type and quality of the diesel fuel produced. U.S. Pat. Nos. 5,082,986, 5,135,638, 5,246,566, 5,282,958, and 5,723,716, the entire contents of which are hereby incorporated by reference, disclose representative process conditions using said catalysts for isomerization of different hydrocarbon feedstock. Further, typical processes and catalysts for dewaxing and hydroisomerization are described, for example, in U.S. Pat. No. 6,702,937, the entire content of which is hereby incorporated by reference, and the references cited therein.
The process is carried out at relatively mild conditions, for example, the tubular reaction unit is operated at conditions comprising a liquid hourly space velocity (LHSV) in the range of 0.5-5 h−1, for example, 0.6-3 h−1, 0.7-1.2 h−1, or 1-2.5 h−1, at a temperature varying between 300 and 450° C., for example, between 320 and 400° C., at a pressure varying between 10 and 60 atm, for example, 20-40 atm, and a H2/oil ratio of about 300-1200 NL/L, for example, 500-1000 NL/L. More severe conditions result in liquid fuel compositions with poorer lubricity, while more moderate to mild conditions result in liquid fuel compositions with better lubricity.
Lubricity is especially important with regard to modern diesel fuels, as modern engines have very high injection pressures in excess of 24,000 pounds per square inch. Good lubricity is necessary to prevent risk of catastrophic engine failure. In general, an acceptable lubricity refers to a lubricity that would allow modern engines to operate more efficiently. In an embodiment, the diesel fuel has a maximum high-frequency reciprocating rig (HRFF) lubricity of 400 μm (according to International Organization for Standardization (ISO) standard 12156/1), in accordance with the recommendation of the World Wide Fuel Charter, Category 4. In an embodiment, the lubricity is less than 300 μm according to ISO 12156/1, for example, the lubricity is less than 200 μm according to ISO 12156/1.
Any vegetable and/or animal oil can be used in the presently disclosed process. For example, suitable vegetable oils include soybean oil, palm oil, corn oil, sunflower oil, oils from desertic plants such as, for example, jatropha oil and balanites oil, rapeseed oil, colza oil, canola oil, tall oil, safflower oil, hempseed oil, olive oil, linseed oil, mustard oil, peanut oil, castor oil, coconut oil, and mixtures thereof. In an embodiment, vegetable oils include soybean oil, palm oil, corn oil, sunflower oil, jatropha oil, balanites oil, for example, from Balanites aegyptiaca, and mixtures thereof. The vegetable oil may be genetically modified oil, produced from transgenic crops. The vegetable oil may be crude vegetable oil or refined or edible vegetable oil. If crude vegetable oil is used, the vegetable oil can be pretreated, for example, to separate or extract impurities from the crude vegetable oil. Suitable animal oils include, for example, lard oil, tallow oil, train oil, fish oil, and mixtures thereof. Further, the vegetable and/or animal oil may be new oil, used oil, waste oil, or mixtures thereof.
The oil, or mixture of oils, used in the presently disclosed process can contain a high content of fatty acids (e.g., greater than or equal to 70 wt % fatty acids). Additionally, compositions derived from vegetable and/or animal oil that contains a high content of fatty acids can be used in the presently disclosed process. The phrase “compositions derived from vegetable and/or animal oil” refers to compositions which originate from or are the byproduct of processing vegetable and/or animal oil (e.g., vapor overhead stream from distilling vegetable and/or animal oil, residual non-vaporizable remaining portion, etc.). Thus, palm oil distillate containing greater than 70 wt % fatty acids can be used in the presently disclosed process.
The diesel fuel composition produced by the presently disclosed methods comprises a mixture of C12 to C18 or C14 to C18 paraffins with a ratio of iso to normal paraffins from 0.5 to 8, for example, from 2 to 8, from 2 to 6, from 2 to 4, from 1 to 4, or from 4 to 7; less than 5 ppm sulfur, for example, less than 1 ppm sulfur; and acceptable lubricity. Specifically, the diesel fuel composition can have a lubricity of less than 400 μm, for example, less than 300 μm or less than 200 μm, according to ISO 12156/1.
Additionally, the diesel fuel composition can comprise less than or equal to 0.6 wt %, for example, 0.1-0.6 wt %, of one or more oxygenated compounds, which, without wishing to be bound by any theory, are believed to contribute to the acceptable lubricity of the diesel fuel composition. In an embodiment, the one or more oxygenated compounds comprise acid, for example, one or more fatty acids. In an embodiment, the one or more oxygenated compounds (e.g., acid), is present in an amount of less than or equal to 0.4 wt %, for example, 0.1-0.4 wt %. As used herein, the phrase “fatty acids” refers to long chain saturated and/or unsaturated organic acids having at least 8 carbon atoms, for example, 12 to 18 or 14 to 18 carbon atoms. Without wishing to be bound by any theory, it is believed that the low content of one or more oxygenated compounds, for example, one or more fatty acids, in the diesel fuel composition may contribute to the acceptable lubricity of a diesel fuel composition; such oxygenated compounds, present in the vegetable and/or animal oil feedstock, may survive the non-severe hydrodeoxygenation/hydroisomerization conditions employed in the presently disclosed process. The diesel fuel composition may comprise alkyl cyclohexane, for example, less than 10 wt %, and/or alkyl benzene, for example, less than 15 wt %.
The characteristics of the diesel fuel composition, and naphtha, produced by the presently disclosed methods may vary depending on the vegetable and/or animal oil starting product, process conditions, and catalyst used. In an embodiment, selection of vegetable and/or animal oil starting product, process conditions, and catalyst allows for high yield of high quality diesel fuel composition, with preferred properties, and minimized production of lighter components including, for example, naphtha, carbon oxides and C1 to C4 hydrocarbons. The paraffinic diesel fuel compositions produced by the presently disclosed methods provide superior fuel properties, especially for low temperature performance (e.g., density, viscosity, cetane number, lower heating value, cloud point, and CFPP), to biodiesel, a mixture of methyl or ethyl esters. In contrast to the products of the process disclosed in U.S. Patent Publication No. 2004/0230085, disclosed herein are method for producing diesel fuel compositions with acceptable lubricities produced from vegetable and/or animal oil. More specifically, fuel properties, such as, for example, lubricity, may be controlled through variation of process conditions and/or catalyst(s). In general, with regards to the distillation curve of the diesel fuel composition produced by the presently disclosed methods, the initial boiling point (IBP) is in the range of 160° C.-240° C. and the 90 vol % distillation temperature is in the range of 300° C.-360° C. The produced naphtha is highly pure and particularly suitable for use as a solvent and/or chemical feedstock, e.g., a cracking stock.
The following examples are intended to be non-limiting and merely illustrative.
Refined soybean oil was fed to a fixed-bed reactor packed with a granulated Ni—Mo catalyst operated at an LHSV of 1.0 h−1, 375° C., 40 atm, and an H2/oil ratio of 1200 NL/L (Stage 1). The total liquid product was separated into two phases, water and an organic phase. The organic phase was fed to a fixed-bed reactor packed with a granulated 1 wt % Pt/SAPO-11 catalyst operated at an LHSV of 3.0 h−1, 380° C., 50 atm, and an H2/oil ratio of 500 NL/L (Stage 2). The organic phase from Stage 1 and the diesel product from Stage 2 were analyzed according to ASTM methods and their compositions were measured by GC-MS and confirmed by NMR. The results can be found in Table 3.
The diesel product from Stage 2 exhibited a poorer lubricity (502 μm) as compared to that of the organic phase from Stage 1 (352 μm). Without wishing to be bound by any theory, it is believed that the increase in ratio of branched to linear paraffins in the diesel product from Stage 2, as compared to the organic phase from Stage 1, resulted in a change of fuel properties.
Refined soybean oil was fed to a fixed-bed reactor packed with a granulated 1 wt % Pt/SAPO-11 catalyst operated at an LHSV of 1.0 h−1, 380° C., 20 atm, and an H2/oil ratio of 1200 NL/L (Stage 1). The total liquid product was separated into two phases, water and diesel product. The diesel product from Stage 1 was fed to a fixed-bed reactor packed with a granulated 1 wt % Pt/SAPO-11 catalyst operated at an LHSV of 4.5 h−1, 360° C., 30 atm, and an H2/oil ratio of 1200 NL/L (Stage 2). The diesel product from Stage 1 and the diesel product from Stage 2 were analyzed according to ASTM methods and their compositions were measured by GC-MS and confirmed by NMR. The results can be found in Table 4.
The diesel product from Stage 1 exhibited acceptable properties, including a lubricity of 306 μm. As the composition of the diesel product from Stage 2 did not significantly differ from the diesel product from Stage 1, the properties of the diesel product from Stage 2 are similar to those of the diesel product from Stage 1. However, the diesel product from Stage 2 exhibited a poorer lubricity (437 μm) as compared to that of the diesel product from Stage 1 (306 μm), similar to the diesel production from Stage 2 of Comparative Example 1. Without wishing to be bound by any theory, it is believed that water may act as an inhibitor to isomerization, which requires higher catalyst activity, and the removal of water between Stage 1 and Stage 2 in Comparative Example 1 and Comparative Example 2 may also remove acid, thereby affecting final product lubricity.
Adding 0.1 wt % of oleic acid to the diesel product of Stage 2 improved its lubricity from 437 μm to 270 μm. Thus, as noted above, without wishing to be bound by any theory, it is believed that the low content of one or more oxygenated compounds, such as one or more fatty acids, in the product of the process may contribute to the acceptable lubricity of the diesel product.
The reactor setup and the operating conditions of Example 3 were based on the results of kinetic studies and reactor simulations using soybean oil. In the kinetic studies, concentrations of the soybean oil, acids, paraffins, olefins, cyclohexanes, aromatics and light compounds were measured as a function of residence time and temperature. Vapor-liquid equilibrium was provided by the reactor simulations. For a residence time of 15 to 25 minutes, the soybean oil was nearly completely converted. The acid content in the product(s) peaked at about 10 to 15 minutes, and then decreased with additional residence time. Again, diesel fuel compositions produced in accordance with the presently claimed methods can comprise less than or equal to 0.6 wt % of one or more oxygenated compounds (e.g., acids). In part due to the operating pressure, conversion of the soybean oil (e.g., for a residence time of 15 to 25 minutes) resulted in vapor phase products with only very small amounts of liquid products, which contain heavy compounds (e.g., C20+ hydrocarbons).
Accordingly, refined soybean oil was fed to a single (electrically heated) wall-cooled reactor tube, packed with a granulated 1 wt % Pt/SAPO-11 catalyst, and operated in trickle-bed mode at an LHSV of 3.5 h−1, 382° C., 30 atm, and an H2/oil ratio of 550 NL/L. The effluent of the single wall-cooled reactor tube flowed through a gas-liquid separator maintained at 30 atm and 373° C., in which a very small amount of liquid (i.e., 0.2 wt % of the refined soybean oil fed to the single wall-cooled reactor tube) was separated from a vapor phase. The vapor phase from the separator flowed upward to a single tube, adiabatic, fixed-bed reaction unit packed with a granulated 1 wt % Pt/SAPO-11 catalyst operated at an LHSV of 1.4 h−1, 373-375° C., 30 atm, and an H2/oil ratio of 550 NL/L. The diesel product from the adiabatic reaction unit was analyzed according to ASTM methods and its composition was measured by GC-MS. The results can be found in Table 5.
The diesel product according to Example 3 exhibited acceptable properties, including a lubricity of 346 μm.
The temperature of the adiabatic reaction unit following the vapor-liquid separator is set by the temperature of the vapor-liquid separator. Heat loss can cause a temperature drop in the vapor phase products from the tubular reaction unit. Assuming that heat loss is avoided, if the temperature of the vapor-liquid separator is low (i.e., lower than the temperature of the vapor phase products from the tubular reaction unit), the vapor phase products may undesirably condense to liquid prior to hydroisomerization in the adiabatic reaction unit. Therefore, the temperature of the vapor-liquid separator can be set such that the temperature of the vapor-liquid separator is close to the temperature of the tubular reaction unit, and more specifically, the temperature of the vapor phase products from the tubular reaction unit. Most of the heat of the hydrodeoxygenation and hydroisomerization reaction is generated in the tubular reaction unit, which can be a wall-cooled reactor. Accordingly, the reaction unit downstream of the vapor-liquid separator can be run adiabatically. The vapor-liquid separator, which can provide different conditions in the downstream adiabatic reaction unit than in the upstream tubular reaction unit, can also ensure that the downstream adiabatic reaction unit is run in vapor phase.
For example, the temperature of the adiabatic reaction unit following the vapor-liquid separator can be set in the range of about 350 to 400° C. or about 360 to 385° C. In particular, the temperature of the vapor-liquid separator in Example 3 was maintained at 373° C. and the temperature of the adiabatic reaction in Example 3 was operated at 373° C., to minimize condensation of vapor phase products to liquid prior to hydroisomerization in the adiabatic reaction unit. Thus, the vapor-liquid separator can be used to set the temperature of the adiabatic reaction unit following the vapor-liquid separator.
As noted above, the effluent from the single wall-cooled reactor tube is primarily in a vapor phase (e.g., vapor phase can comprise about 95 to 99.9 wt % of the effluent). The liquid separated from the vapor phase in the vapor-liquid separator can contain as much as 40 wt % acids. The catalyst contained in the reaction units is sensitive to coking and deactivation as a result of contact with heavy compounds (e.g., acids) in the liquid products. Thus, liquid products can negative affect selectivity of desired products and stability of the catalyst. Accordingly, separation of liquid from the vapor phase in the vapor-liquid separator (i.e., the vapor phase to be fed to the adiabatic reaction unit), protects catalyst in the adiabatic reaction unit and prevents deactivation thereof. Consequently, while catalyst in the upstream tubular reaction unit can be prone to deactivation as a result of contact with heavy compounds (e.g., acids) in the liquid products, separating liquid product in the vapor-liquid separator prior to the downstream adiabatic reaction unit can avoid the need to regenerate catalyst in the downstream adiabatic reaction unit. Thus, use of both tubular (e.g., single wall-cooled reactor tube or multi-tubular) and adiabatic reaction units, and a vapor-liquid separator disposed therebetween, allows for improved performance and stability of the catalyst, especially the catalyst contained within the adiabatic reaction unit. In particular, the life of the catalyst contained within the adiabatic reaction unit can be extended as a result of using a vapor-liquid separator disposed between the tubular and adiabatic reaction units.
While various embodiments have been described, it is to be understood that variations and modifications can be resorted to as will be apparent to those skilled in the art. Such variations and modifications are to be considered within the purview and scope of the claims appended hereto.
| Number | Date | Country | |
|---|---|---|---|
| 60845508 | Sep 2006 | US |
