Hydrodeoxigenation process of vegetable oils for obtaining green diesel

Abstract

The present disclosure relates to a process for the hydrodeoxygenation of vegetable oils or animal fats to produce green diesel, which comprises contacting the vegetable oil or animal fat with a Nickel-Molybdenum or Cobalt-Molybdenum catalyst supported on alumina-titania or titania, respectively; in a fixed bed reactor in the presence of hydrogen. The process involves hydrocracking, hydrogenation, decarboxylation, decarbonylation, carried out in a fixed bed reactor at temperature of about 270 C. to about 360 C., pressure of about 40 kg.sub.f/cm.sup.2 to about 60 kg.sub.f/cm.sup.2, liquid hourly space velocity (LHSV) between about 0.8 h.sup.1 to about 3.0 h.sup.1, and H.sub.2/oil ratio of about 2,700 ft.sup.3/bbl to about 7,000 ft.sup.3/bbl, that allows to obtain a conversion up to 99% and up to 92.7% yield on green diesel.

Claims

1. A hydrodeoxygenation process, comprising: activating a catalyst, the catalyst selected from a group consisting of Nickel-Molybdenum supported on alumina-titania, or Cobalt-Molybdenum supported on alumina, wherein activating the catalyst comprises a sulfuration process at a temperature range of about 310 C. to about 330 C., a pressure in a range of about 45 kg/cm.sup.2 to about 60 kgf/cm.sup.2 for a period of about five hours to ten hours; and a reaction between one of vegetable oils or animal fats with hydrogen, the reaction in the presence of the activated catalyst; wherein the reaction is loaded in a fixed bed reactor; and wherein the process results in a green diesel yield greater than 82% and a conversion rate greater than 99%.

2. The process according to claim 1, wherein the reaction breaks the CO bonds present in triacylglycerides of the vegetable oils or animal fats in order to obtain diaclyglycerides, monoacylglycerides, and carboxylic acids.

3. The process according to claim 2, wherein the carboxylic acids are transformed into paraffins, carbon dioxide, carbon monoxide, and water through chemical reactions of deoxygenation, decarboxylation, and decarbonylation.

4. The process according to claim 3, wherein the chemical reactions of deoxygenation, decarboxylation, and decarbonylation occur in the following order: first deoxygenation, followed by decarboxylation, and finally decarbonylation.

5. The process according to claim 1, wherein the fixed bed reactor has a temperature in a range of 270 C. to 360 C.

6. The process according to claim 1, wherein the fixed bed reactor has a medium pressure in a range of 40 kgf/cm.sup.2 to 60 kgf/cm.sup.2.

7. The process according to claim 1, wherein the fixed bed reactor has a liquid hourly space velocity (LHSV) in a range of about 0.8 h.sup.1 to 3.0 h.sup.1.

8. The process according to claim 1, wherein the fixed bed reactor has a hydrogen/oil ration in a range of about 2,500 ft.sup.3/bbl to 7,000 ft.sup.3/bbl.

9. The process according to claim 1, wherein the catalyst has a compact density in a range of about 0.5 g/cm.sup.3 to about 1 g/cm.sup.3, a fracture resistance in a range of about 2 lbf/mm to 8 lbf/mm, a surface area in a range of about 100 m.sup.2/g to about 200 m.sup.2/g, a pore volume in a range of about 0.1 cm.sup.3/g to about 1 cm.sup.3/g, a Molybdenum content in a range of about 1% wt to about 20% wt, a Nickel content in a range of about 1% wt to about 10% wt, and a Titanium content in a range of about 1% wt to about 10% wt.

10. The process according to claim 1, wherein the process results in a green diesel yield greater than 92%.

11. The process according to claim 1, wherein triacylglycerides of the vegetable oils or animal fats are converted to green diesel (mixture of paraffins) by hydrocracking, saturation, and deoxygenation reactions.

12. The process according to claim 10, wherein the green diesel has a density in a range of 0.75 g/cm.sup.3 to 0.85 g/cm.sup.3, a kinematic viscosity in a range of 2 cSt to 4 cSt, a higher heating value in a range of 40 MJ/kg to 50 MJ/kg, and a cloud point range between about 15 C. to 20 C.

13. The process according to claim 10, wherein the green diesel has a density of 0.77 g/cm.sup.3, a kinematic viscosity of 3 cSt, and a higher heating value of 46 MJ/kg.

14. The process according to claim 10, wherein the green diesel has a concentration of total sulfur of less than about 5 ppmw, and a total nitrogen concentration of less than about 5 ppmw.

15. The process according to claim 10, wherein the paraffins are in the range of 8 to 24 carbon atoms (n-C.sub.8 to n-C.sub.22).

16. The process according to claim 10, wherein the green diesel has aromatic compounds in concentrations less than 5% vol, and olefinic compounds in concentrations less than 5% vol.

17. The process according to claim 1, wherein activating the catalyst further comprises bringing the catalyst into contact with a primary light gas oil (LGO) doped with dimethyldisulfide (DMDS), under a hydrogen atmosphere for about 8 to 23 hours.

18. The process according to claim 10, wherein the paraffins are in the range of 15 to 18 carbon atoms (n-C.sub.15 to n-C.sub.18).

19. The process according to claim 1, wherein the vegetable oils or animal fats are transformed into paraffinic hydrocarbons with a carbon range of naphtha, kerosene, or diesel.

Description

DESCRIPTION OF THE DISCLOSURE

(1) The hydrodeoxygenation (HDO) process of non-edible vegetable oils or animal fats described in the present disclosure is useful for obtaining green diesel, also called renewable diesel. This process consists in contacting the vegetable oil with a supported bimetallic catalyst (IMP-DSD-17), as well as with excess H.sub.2 in a continuous fixed bed reactor, which under certain reaction conditions (temperature, pressure, and space velocity), it is aimed to favor the selective deoxygenation of the raw material in order to obtain a product or effluent consisting of water, carbon oxides, light hydrocarbons, hydrogen, and liquid hydrocarbons in the range of about C.sub.8 to about C.sub.24. The transformation of triacylglycerides to green diesel or renewable diesel is carried out through reactions of hydrocracking, hydrogenation, deoxygenation, decarboxylation, and decarbonylation.

(2) Raw Material:

(3) The raw material consists of renewable non-edible vegetable oils, consisting of triacylglycerides, diglycerides, monoglycerides and free-fatty acids; such as palm, used cooking oil, Jatropha curcas, castor oils, among others. As an example of the present disclosure, the palm oil was selected as raw material, its properties are shown in Table 1.

(4) Catalyst for HDO:

(5) To carry out the hydrodeoxygenation process, it is necessary for the presence of a catalyst to convert the triacylglycerides of vegetable oils to a mixture of hydrocarbons in the boiling range of diesel. High yields of green diesel require catalysts that exhibit high hydrodeoxygenation (HDO) activity to convert the triacylglicerides. The conventional catalysts for HDO contain active metals on alumina with moderate surface area. The best known commercial catalysts consist of molybdenum (Mo) or Tungsten (W) sulfides promoted by Nickel (Ni) or Cobalt (Co), supported on alumina, and with them high yields of diesel fractions are obtained. The supported material comprises any substrate of refractory metal oxide such as alumina, silica, titania, or combinations thereof, which has specific physical and chemical properties. For the present invention, the catalyst selected for the HDO tests of the non-edible vegetable oil is the catalyst IMP-DSD-17, whose holder is the Mexican Petroleum Institute (Patents Nos. MX 985494 and U.S. Pat. No. 6,383,975), which consists of a formulation of Molybdenum promoted by Nickel and Phosphorus as an additive supported on an alumina-titania material.

(6) HDO Process:

(7) Hydrogenation and deoxygenation reactions are carried out in the hydrotreatment process (which in turn involves decarboxylation, decarbonylation and deoxygenation reactions), which remove O.sub.2 in the form of H.sub.2O and CO.sub.x, producing paraffinic hydrocarbons useful as fuel. The renewable raw materials are acylglycerides and fatty acids, that are currently found in vegetable oils and animal fats. The majority of the acyglycerides will be triacylglycerides but monoacylglycerides and diacylglycerides may also be present, which can also be processed. The breaking of CO and CC bonds is carried out in the chemical conversion of the triacylglycerides to obtain paraffins. Likewise, carbon dioxide, carbon monoxide, propane and water are obtained as by-products.

(8) The reactions involved are hydrocracking, hydrogenation, deoxygenation, decarboxylation, and decarbonylation. With this process, a mixture of paraffinic hydrocarbons as valued product is obtained, which can be used individually or mixed with fossil diesel. The catalystic process involves the hydrodesoxygenation of biomass, that is carried out at high temperature and pressure in the presence of a catalytic material, and with an atmosphere of hydrogen in excess. Table 2 shows a summary of the operating condition for the hydrodeoxigenation of liquid biomass reported in the literature, with Nickel-Molybdenum (NiMo) catalysts.

(9) Since the catalyst selected in this invention is a catalyst of NiMo/alumina-titania formulation (IMP-DSD-17) that initially is in the form of an oxide, and therefore inactive, it is necessary to be activated through a sulfuration process, using a mixture of light gas oil (LGO) with Dimethyldisulfide (DMDS), at temperature in a range of about 310 C. to about 330 C., a pressure in a range of about 45 kg.sub.f/cm.sup.2 to about 60 kg.sub.f/cm.sup.2, and an H.sub.2/HC ratio of about 2000 ft.sup.3/bbl to about 3000 ft.sup.3/bbl, during a period of about 5 hours to about 10 hours, where the metal oxide state is transformed to the corresponding sulfide, which is the active phase. Once the catalyst is activated and prior to establishing the operating conditions for the hydrodeoxygenation of vegetable oils, a free-DMDS LGO is fed to the reactor for a period of about 40 hours to about 80 hours, after this, the feeding of the vegetable oil, here palm oil, is carried out to start the hydrodeoxygenation process. As an option, the vegetable oil (palm oil) can be mixed with DMDS at a sulfur concentration of 0.1% wt with the purpose of preventing the catalyst deactivation. The main variables for the hydrotreatment of palm oil are: type of catalyst, space velocity, partial pressure of hydrogen, temperature, and hydrogen/oil ratio. The feedstock (vegetable oil) is pre-heated in the range of about 40 C. to about 70 C., after that, the feedstock are entered together with hydrogen into the reactor that operate at a pressure of about 40 kg.sub.f/cm.sup.2 to about 60 kg.sub.f/cm.sup.2, a temperature of about 270 C. to about 380 C., a liquid hourly space velocity of about 0.8 h.sup.1 to about 3.0 h.sup.1, and an H.sub.2/oil ratio of about 2500 ft.sup.3/bbl to about 7000 ft.sup.3/bbl. The liquid product obtained from the separator is treated with a nitrogen flow of about 5 L/h to about 10 L/h to remove the hydrogen sulfide traces (H.sub.2S; depletion process), in order to obtain a better product quality. When the experimental program considers a change in the operating conditions like temperature, pressure, and/or space velocity; it is recommended that before starting a new balance, a stabilization period of at least about 10 hours is going to be done to establish a steady state condition and thus ensure the reliability of the experimental measures for each balance.

(10) Before finishing each balance, the sampling of the liquid and its experimental analysis is done. The physical and chemical analysis are: total sulfur content (ASTM D-5453), total nitrogen content (ASTM D-4629), specific gravity (ASTM D-1282), atmospheric distillation (ASTM D-86), aromatics content (ASTM D-5186), metals content (e.g. Ca, Mg, Na, and K; EN 14538), phosphorus content (ASTM D-4951), water content (ASTM D-6304), paraffins composition that is determined by gas chromatography with a selective mass detector (GC-MS), calorific value (ASTM D-240), flash point (ASTM D-93), cloud point (ASTM D-2500), and kinematic viscosity at 40 C. (ASTM D-445).

(11) Green Diesel:

(12) The hydrotreatment process of this disclosure has the purpose to produce green diesel, also called renewable diesel, which has the appropriate physical and chemical properties to be used individually or mixed with fossil diesel. In order to clarify, it is necessary to emphasize the difference between biodiesel and green diesel. Biodiesel is defined as a fuel that is composed of monoalkyl esters of long chain fatty acids derived from vegetable oil or animal fats and that complies with ASTM D-6751. Green diesel is defined as a fuel produced from non-fossil renewable resources, including agricultural or forestry plants, animal fats, wastes and wastes generated by the production, processing and marketing of agricultural, forestry and other renewable resources. Green diesel must comply with applicable ASTM specifications for diesel (Reference North Dakota Century Code 57-43.2-01). The biodiesel specifications are in the US ASTM D-6751 standard, some of them are showed in Table 3.

EXAMPLES

(13) Below are some examples for the use of the IMP-DSD-17 catalyst in the hydrodeoxygenation of palm oil in accordance with the present disclosure, it must be well understood that each example is only illustrative, and it is not intended to limit the scope of the invention.

Example 1: NiMo/Alumina-Titania as Catalyst (IMP-DSD-17), Palm Oil as Raw Material

(14) 10 mL of the IMP-DSD-17 catalyst (NiMo/alumina-titania) was loaded in a fixed bed reactor at a micro plant scale; the palm oil was feeded into the reactor at up-flow stream. The catalyst was activated in situ using the sulfurization procedure described above. Once the catalyst was activated, the vegetable oil was fed to start the hydrodeoxygenation process; the vegetable oil might be added with DMDS to have a sulfur concentration of 0.1% wt in order to prevent catalyst deactivation. The composition of the palm oil used is shown in Table 4. The palm oil was mixed with hydrogen and fed to the reactor, where the following operating conditions were fixed: pressure of 50 kg.sub.f/cm.sup.2, temperature of 280, 310 and 340 C., LHSV of 1 h.sup.1, and H.sub.2/oil ratio of 5600 ft.sup.3/bbl.

Example 2: CoMoP/Alumina as Commercial Catalyst, Palm Oil as Raw Material

(15) For comparison with the catalyst used in this invention, a commercial catalyst owned by the Mexican Petroleum Institute, IMP-DSD-14+(Mexican Patent MX 198590) with CoMoP/alumina catalytic formulation was tested in the hydrodeoxygenation process, following the activation procedure described above, and using palm oil as raw material. In this example, the palm oil is mixed with hydrogen and fed to the reactor at a pressure of 50 kg.sub.f/cm.sup.2, temperature of 340, 360, and 380 C., LHSV of 1 h.sup.1, and H.sub.2/oil ratio of 5600 ft.sup.3/bbl.

(16) Table 4 shows the results with the NiMo/alumina-titania catalyst (IMP-DSD-17) at temperature of about 280 C. to about 340 C., we observed that the conversion of HDO was greater than 99%, the green diesel yield is greater than 82%, and the paraffin distribution was in the range of n-C.sub.9 to n-C.sub.18, but mostly in the range between n-C.sub.15 to n-C.sub.18.

(17) Similar results were obtained with the CoMo catalyst (IMP-DSD-14+) in the temperature range of about 340 C. to about 380 C. The NiMo catalyst (IMP-DSD-17) is considered suitable for this process, because it operates at a lower temperature but the former one gives higher yields on green diesel.

(18) Triacylglycerides are the main components of vegetable oils. The reaction mechanism involved in the conversion of triacylglycerides by hydrodeoxygenation consists of two main stages. In the first stage, the saturation of double bonds occurs and the cracking of triacylglycerides to produce intermediate compounds (diacylglycerides and monoacylglycerides), as well as the formation of propane, and a mixture of carboxylic acids. In the second stage, the carboxylic acids are transformed into paraffins through three different routes: deoxygenation, decarboxylation, and decarbonylation. The products of the first reaction are paraffins and water, the products of the second one are paraffins and CO.sub.2, and the products from the latter are paraffins, water and CO. The liquid product is composed of two immiscible phases, water (aqueous phase) and a mixture of hydrocarbons, mainly paraffins (organic phase) constituted by alkanes of 15 to 18 carbon atoms.

Example 3: NiMo Catalyst (IMP-DSD-17), Feedstock: Palm Oil

(19) 10 mL of the NiMo/alumina-titania catalyst was loaded into the reactor (fixed bed) at a micro plant scale; the palm oil is fed to the reactor at up-flow. The catalyst is activated in situ using a sulfurization procedure described above. Once the catalyst is activated, the vegetable oil is fed to start the HDO process; the vegetable oil can be added with DMDS at sulfur concentration of 0.1% p to prevent the catalyst of deactivation. Palm oil is mixed with hydrogen and fed to the reactor that is maintained at a pressure of 50 kg.sub.f/cm.sup.2, temperature of about 280 C. to about 340 C., LHSV of 1 h.sup.1, H.sub.2/oil ratio of 5600 ft.sub.3/bbl. The period of the evaluation in the micro plant was 65 days, during this period the main product (green diesel) was recovered and analyzed. The properties obtained are shown in Table 5, a comparison of our results with typical fossil diesel and biodiesel is included.

(20) TABLE-US-00001 TABLE 1 Palm oil properties Units Method Value Property Molecular weight g/mol Estimated from the 853 composition of fatty acids of the vegetable oil* Density @ 15.5 C. kg/m.sup.3 ASTM D-1298 913.6 Viscosity @ 40 C. cSt ASTM D-445 39.48 Flash point C. ASTM D-97 314 Acid value mg KOH/g AOCS Ca 5a-40 0.26 Iodine value g I.sub.2/g AOCS Cd 1-25 58.9 Melting point C. 15 Cloud point C. 3 Ash % wt 0.0013 Fatty acid composition in the palm oil Lauric acid (C12:0) % wt AACCI 58-18.01 0.12 Myristic acid (C14:0) 0.86 Palmitic acid (C16:0) 39.35 Stearic acid (C18:0) 3.25 Oleic acid (C18:1) 45.38 Linoleic acid (C18:2) 10.51 Arachidic acid (C20:0) 0.53 *M.sub.aceite = 3 .sub.i=1.sup.nw.sub.iMW.sub.i + 39.049 where w.sub.i is the mass fraction of the i-th fatty acid, MW is the molecular weight of the i-th fatty acid, and the 38.049 figure corresponds to the molecular weight of the CHCCH molecular structure present in the triacylglyceride.

(21) TABLE-US-00002 TABLE 2 Operating conditions reported in the literature for the HDO of biomass using the Nickel-Molybdenum (NiMo) catalyst. Temperature ( C.) Pressure LHSV (h.sup.1) H.sub.2/HC ratio Reference 330-398 80-140 bar 0.5-2.5 543-890 Nm.sup.3/m.sup.3** [1] 350-370 20-40 bar 1 500 m.sup.3/m.sup.3 [2] 275-325 500 psi 0.01-0.0111* 188 mol/mol [3] 300-450 2-18 MPa .sup.1-7.6 250-1600 Nm.sup.3/m.sup.3 [4] 260-420 3.5-18 MPa [5] 330 1200 psi 1 505.9 L/L [6] 320 3.5 MPa 1.5 [7] 300-400 2-8 MPa 1-4 600 m.sup.3/m.sup.3 [8] 300-400 50-80 bar 1-2 1500 NL/L *** [9] 623 K 4 MPa 7.6 800 mL/mL [10] *Residence time in the micro-reactor. **Nm.sup.3 = Normal cubic meters. *** NL = Normal liters

(22) TABLE-US-00003 TABLE 3 Biodiesel specifications Property Value Norm Flash point, C. 93 ASTM D-93 Kinematic viscosity, mm.sup.2/s 1.9-6.0 ASTM D-445 Water and sediments, % vol. 0.050 mx. ASTM D-2709 Destillation at 90% vol, C. 360 ASTM D-1160 Density, kg/m.sup.3 820-845 Cetane number 47 ASTM D-613 Acid value, mgKOH/g 0.50 ASTM D-664 Mono, Di y Tri-acylgliceride, % wt 0.40 ASTM D-6584 Metals of group I (Na + K), mg/kg 5 mx. EN14538 Metals of group II (Ca + Mg), mg/kg 5 mx. EN14538 Phosphorus, % p 0.001 ASTM D-4951 Sulfur, ppm 15 ASTM D-5453

(23) TABLE-US-00004 TABLE 4 Hydrodeoxygenation of palm oil Sample 1 Sample 2 Feedstock Palm oil Palm oil Catalyst NiMo/alumina-titania CoMo/alumina Flow mode continuous upward continuous upward flow flow Pressure, kg.sub.f/cm.sup.2 50 50 LHSV, h.sup.1 1 1 H.sub.2/oil ratio, mol/mol 41.5 41.5 Temperature, C. 280 310 340 340 360 380 Product composition H.sub.2O, % wt 8.4 8.3 7.6 5.2 3 4.3 CO.sub.2 + CO, % wt 3.6 4.2 4.7 1.5 1.5 1.8 Propane, % wt 1.6 1.5 1.4 0.6 0.5 0.6 Sulfur, ppm 60 25 12 14 4.2 3.3 Total nitrogen, ppmw 5.2 1.2 <0.3 1.3 0.9 0.5 HDO, % >99 >99 >99 >99 >99 >99 Green diesel yield, % 87 82.7 84 89.9 92.7 90 Paraffin distribution, % wt n-C.sub.15 14.5 16.5 17 10.8 14.5 14.7 n-C.sub.16 21.9 20.9 20.7 29 26.6 28.2 n-C.sub.17 23.9 27.8 28.1 15.8 18.4 16 n-C.sub.18 39.7 34.8 34.1 39.3 30.5 26.6

(24) TABLE-US-00005 TABLE 5 Physical and chemical properties of Green diesel, fossil diesel, and biodiesel Green Fossil diesel (1) diesel (2) Biodiesel (3) Property Higher heating value, MJ/kg 43.47 42.34 41.3 Flash point, C. 138 104 174 Cloud point, C. 21 3 16 Kinematic viscosity at 40 C., 3.94 3.81 4.5 mm.sup.2/s Specific gravity at 20/4 C. 0.7781 0.8414 0.855 Sulfur, mg/kg 3.2 303 N.R.(4) Nitrogen, mg/kg <0.3 62 N.R.(4) Aromatics content, % vol 0.6 22.4 N.R.(4) Olefins, % vol 0.3 9.6 N.R.(4) Saturated compounds, % vol 99.1 68 N.R.(4) Distillation profile, C. (ASTM D-86) IBP 276.9 226.8 N.R.(4) At 5% vol 284.4 252.8 N.R.(4) At 10% vol 285.7 262.7 N.R.(4) At 20% vol 287 276.4 N.R.(4) At 30% vol 288.3 285.5 N.R.(4) At 40% vol 289.8 294.8 N.R.(4) At 50% vol 291.4 302.6 N.R.(4) At 60% vol 293.3 311 N.R.(4) At 70% vol 295.5 320.1 N.R.(4) At 80% vol 298.4 331.4 N.R.(4) At 90% vol 302.3 347.5 N.R.(4) At 95% vol 306.3 362.6 N.R.(4) FBP 320 362.9 N.R.(4) (1) Green diesel obtained in the present invention. (2) Fossil diesel from a Mexican refinery (U-700-2 plant) (3) Nagi et al. 2008. Palm Biodiesel an Alternative Energy for the Energy Demands of the future. ICCBT F(07) pp. 79-94. (4)Not reported by Nagi et al. (2008). IBP = Initial boiling point. FBP = Final boiling point.

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