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Title:
PRODUCTION OF LINEAR ALKANES BY HYDROTREATING MIXTURES OF TRIGLYCERIDES WITH VACUUM GASOIL
Document Type and Number:
WIPO Patent Application WO/2008/020048
Kind Code:
A2
Abstract:
A process is disclosed for mild hydro-conversion of oxygenated hydrocarbon compounds. The oxygenated hydrocarbon compounds are contacted with a hydro- conversion catalyst material at a reaction pressure below 100 bar. Preferred oxygenated hydrocarbon compounds are those obtained by the liquefaction of biomass. In a specific embodiment the process is used for production of normal alkanes by hydrotreating mixtures of triglycerides (or compounds derived-from triglycerides, including free fatty acids) and vacuum gasoil.

Inventors:
O'CONNOR, Paul (Hogebrinkerweg 9, KM Hoevelaken, NL-3871, NL)
STAMIRES, Dennis (29 St. Michael, Dana Point, California, 92629, US)
CORMA CAMOS AVELINO, Avelino (Universidad Politecnica, Instituto de Tecnologia Quimicaconsejo Superior Investigaciones Cientifica, Avenida de los Naranjos Valencia, E-46022, ES)
HUBER, George W. (University of Massachusetts, Department of Chemical Engineering159 Goessmann Lab,686N. Pleasant St, Amherst Massachusetts, 01003-9303, US)
Application Number:
EP2007/058468
Publication Date:
February 21, 2008
Filing Date:
August 15, 2007
Export Citation:
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Assignee:
BIOECON INTERNATIONAL HOLDING N.V. (Kaya W.F. G. Mensing 14, Curacao, AN)
O'CONNOR, Paul (Hogebrinkerweg 9, KM Hoevelaken, NL-3871, NL)
STAMIRES, Dennis (29 St. Michael, Dana Point, California, 92629, US)
CORMA CAMOS AVELINO, Avelino (Universidad Politecnica, Instituto de Tecnologia Quimicaconsejo Superior Investigaciones Cientifica, Avenida de los Naranjos Valencia, E-46022, ES)
HUBER, George W. (University of Massachusetts, Department of Chemical Engineering159 Goessmann Lab,686N. Pleasant St, Amherst Massachusetts, 01003-9303, US)
International Classes:
C10G3/00; C10G45/02
Domestic Patent References:
2007-11-08
Foreign References:
US4992605A1991-02-12
EP1693432A12006-08-23
Other References:
GUSMAO J ET AL: "UTILIZATION OF VEGETABLE OILS AS AN ALTERNATIVE SOURCE FOR DIESEL-TYPE FUEL: HYDROCRACKING ON REDUCED Ni/SiO2 AND SULPHIDED Ni-Mo/gamma-Al2O3" CATALYSIS TODAY, ELSEVIER, vol. 5, no. 4, 1989, pages 533-544, XP003014030 ISSN: 0920-5861
Attorney, Agent or Firm:
RASSER, Jacobus Cornelis et al. (Rembrandt Tower, 31st floorAmstelplein 1, HA Amsterdam, NL-1096, NL)
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Claims:

WHAT IS CLAIMED IS:

1. A process for the mild hydroconversion of oxygenated hydrocarbon compounds, comprising the step of contacting a reaction feed comprising an oxygenated hydrocarbon compound with a hydroconversion catalyst material at a reaction pressure below 100 bar.

2. The process of claim 1 wherein the reaction pressure is below 40 bar.

3. The process of claim 1 or 2 wherein the oxygenated hydrocarbon compound is derived from a biomass material.

4. The process of any one of claims 1 to 3 wherein the reaction feed further comprises water.

5. The process of any one of the preceding claims wherein the reaction feed further comprises a crude-oil derived material.

6. The process of claim 5 wherein the crude-oil derived material comprises vacuum gas oil.

7. The process of any one of the preceding claims wherein the oxygenated hydrocarbon compound comprises a material selected from the group consisting of polysaccharides, oligosaccharides, sugars, polyhydric alcohols; oligohydric alcohols, monohydhc alcohols, carboxylic acids, and mixtures thereof.

8. The process of any one of the preceding claims wherein the oxygenated hydrocarbon compound comprises glycerol.

9. The process of any one of the preceding claims which is carried out in a hydro-processing unit.

10. The process of claim 9 whereby the hydro-processing is carried out with a first feedstock of crude oil origin and a second feedstock comprising an oxygenated hydrocarbon compound, whereby the first feedstock is brought into the hydro-processing unit at a first point, and the second feedstock is

brought into the hydro-processing unit at a second point, separate from the first point.

11.The process of claim 10 wherein the second point is upstream from the first point.

12. The process of claim 10 wherein the second point is downstream from the first point.

13. The process of any one of claims 10 - 12, wherein the first feedstock comprises vacuum gas oil.

14. The process of any one of claims 10 - 12 wherein the second feedstock comprises glycerol.

15. The process of any one of claims 10 - 14 wherein the second feedstock further comprises water.

16. The process of any one of claims 10 - 15 wherein the second feedstock comprises a glycerol/water mixture produced in a biodiesel transestehfication process.

17. The process of any of the preceding claims whereby the catalyst comprises a basic material.

18. The process of Claim 17 wherein the basic material is a layered material, or a heat treated form thereof.

19. The process of claim 18 wherein the layered material is selected from the group consisting of smectites, anionic clays, layered hydroxy salts, and mixtures thereof.

20. The process according to claim 18 or 19 wherein the layered material is a Mg- Al, Mg-Fe or a Ca-Al anionic clay.

21.The process according to claims 17 to 20, wherein the catalytic material further comprises a conventional hydro-processing catalyst.

22. The process according to any of the preceding claims whereby the oxygenated hydrocarbons have been produced via the liquefaction of solid biomass.

23. The process according to any of the preceding claims whereby the oxygenated hydrocarbons have been produced via the liquefaction of solid biomass under mild conditions.

24. The process according to any of the preceding claims wherein the reaction feed contains an inorganic material.

25. The process according to any of the preceding claims wherein the reaction feed contains an organic fiber.

26. The process according to claim 24 wherein the inorganic material functions as a catalyst or a catalyst carrier.

27. The process according to claim 25 wherein the organic fiber functions as a catalyst or a catalyst carrier.

28. The process according to claims 25 or 27 wherein the organic fiber is in contact with a metal.

29. The process of claim 6 when used in the production of Ci 5 to C22 alkanes, said process comprising the step of hydrotreating a mixture comprising from 0.1 to 50.0 wt. % of a fatty acid compound and from 99.9-50.0 wt % vacuum gasoil, at a temperature in the range of from 300 to 45O 0 C, and a reactor inlet H 2 partial pressure of from 35 to 200 bar in the presence of a hydrotreating catalyst.

30. The process of claim 29 wherein the liquid hourly space velocity of the hydrotreating step is in the range of from 0.2 to 15 hr "1 .

31.The process of claim 29 or 30 wherein the fatty acid compound comprises a triglyceride.

32. The process of claim 31 wherein the triglyceride is selected from the group consisting of sunflower oil, rapeseed oil, canola oil, soybean oil, waste vegetable oil, brown grease, animal fat, and derivatives and mixtures thereof.

33. The process of claim 32 wherein the triglyceride comprises sunflower oil.

34. The process of any one of claims 29-33 wherein the hydrotreating catalyst comprises Mo, W, or mixtures thereof.

35. The process of any one of claims 29-34 wherein the catalyst comprises Ni, Co, or mixtures thereof.

36. The process of any one of claims 29-35 wherein the catalyst is in a sulfided form.

37. The process of any one of claims 29-36 wherein the catalyst is a Ni/Mo or a Co/Mo catalyst.

38. The process of any one of claims 29-37 wherein the catalyst is sulfided Ni/Mo on alumina, or sulfided Co/Mo on alumina.

Description:

PRODUCTION OF LINEAR ALKANES BY HYDROTREATING MIXTURES OF TRIGLYCERIDES WITH VACUUM GASOIL

BACKGROUND OF THE INVENTION

1. Field of the Invention

[oooi] The invention relates to a process for production of alkanes, alcohols, olefins, and other components with a higher hydrogen to carbon ratio, from oxygenated compounds, such as glycerol, carbohydrates, sugar alcohols or other oxygenated biomass-dehved molecules such as starches, cellulose, and hemicellulose-derived compounds, optionally mixed with petroleum derived feedstocks, in a mild hydroconversion process .

[0002] In a specific embodiment this invention relates to a process for production of alkanes by hydrotreating mixtures of triglycerides with vacuum gas-oil.

2. Description of the Related Art

[0003] Declining petroleum resources, combined with increased demand for petroleum by emerging economies, as well as political and environmental concerns about fossil fuels, are causing society to search for new sources of liquid fuels. In this respect, plant biomass is the only current sustainable source of organic carbon, and biofuels, fuels derived from plant biomass, are the only current sustainable source of liquid fuels (Klass 2004; Wyman, Decker et al. 2005). Biofuels have significantly less greenhouse gas emissions than fossil fuels, and can even be greenhouse gas neutral if efficient methods for biofuels production are developed (Lynd, Cushman et al. 1991 ; Wyman 1994). Vegetable oils, which consist of thglyercies, are one of the most promising feedstocks for biofuels production (Huber, lborra et al. In Press). Inexpensive triglycerides sources, such as yellow (waste restaurant oil) and trap (which are collected at wastewater treatment plants) greases, can also be used as feedstocks for fuel production (Schumacher, Gerpen et al. 2004). Vegetable oils can be used directly in diesel engines, however there are a number of disadvantages of pure vegetable oils including: high viscosity, low volatility, and engine problems (including coking on the injectors, carbon deposits, oil ring sticking, and thickening of lubricating oils) (Ma and Hanna 1999; Knothe, Krahl

et al. 2005). These problems require that vegetable oils be upgraded if they are to be used as a fuel in standard diesel engines.

[0004] The most common way of upgrading vegetable oils is by transesterification into alkyl-fatty esters (bio-diesel). The economics of biodiesel production depend heavily upon the price of co-product glycerol. As biodiesel production increases, the price of glycerol is projected to significantly drop, and the price of glycerol has already dropped by almost half over the last few years (McCoy 2005). The decrease in the price of glycerol would cause the production price of biodiesel to increase.

[0005] Another option for biofuels production is to use biomass-dehved feedstocks in a petroleum refinery. Petroleum refineries are already built and using this existing infrastructure for biofuels production would require little capital cost investment. The European Commission has set a goal that by 2010, 5.75 % of transportation fuels in the EU will be biofuels, and co-feeding biomass-derived molecules into a petroleum refinery could rapidly decrease our dependence on petroleum feedstocks. Hydrotreating is a common process used in the petroleum refinery, and is mainly used to remove S, N 2 and metals from petroleum derived feedstocks (Farrauto and Bartholomew 1997).

[0006] In 1991 Craig and Soveren patented a process to produce liquid paraffins (mainly normal C15-C18 alkanes) by hydrotreating of vegetable oils including canola oil, sunflower oil, soy bean oil, rapeseed oil, palm oil, fatty acid fraction of tall oil, and mixtures of the above compounds (Craig and Soveran 1991 ). In their patent they disclosed the production of a diesel fuel additive that was high in C15-C18 alkanes. These normal alkanes have a high cetane number (above 98), whereas typical diesel fuel has a cetane number around 45. Craig and Soveran recommend that the alkanes produced by hydrotreating of vegetable oils be mixed with diesel fuel in the range of 5-30 % by volume. They claim a process for hydroprocessing of vegetable oils at a temperature of from 350 to 450 0 C, H 2 partial pressure 48-152 bar, and a liquid-hourly space velocity (LHSV) of 0.5-5.0 hr "1 . The catalysts they disclose are typical commercial hydroprocessing catalysts including cobalt-molybdenum (Co-Mo), nickel molybdenum (Ni Mo) or other transition metal based hydroprocessing catalysts.

[0007] In 1998 another patent appeared for hydroprocessing of tall oil, vegetable oil, animal fats or wood oils by Monnier et al. using standard hydroprocessing catalysts, temperatures of from 350 to 370 0 C, H 2 partial pressure of 40-150 bar, and a LHSV of 0.5-5.0 hr "1 (Monnier, Tourigny et al. 1998). Tall oil is a by-product in the Kraft pulping of pine and spruce trees, which can have very little economic value. Tall oil contains large amount of unsaturated fatty acids (30-60 wt%). Alkanes were produced from hydrotreating of tall oil, and a ten month on-road test of six postal delivery vans showed that engine fuel economy was greatly improved by a blend of petrodiesel with hydrotreated tall oil (Stumborg, Wong et al. 1996). According to Stumborg et al. the advantages of hydrotreating over trans-estehfication are that it has lower processing cost (50% that of transesterification), compatibility with current infrastructure, engine compatibility, and feedstock flexibility (Stumborg, Wong et al. 1996).

[0008] In a typical petroleum refinery hydrotreating is done with vacuum-gas oil. The objective of hydrotreating in a petroleum refinery is to remove sulfur (Hydro- desulfurization, HDS), nitrogen (Hydrodenitrogenation, HDN), metals (hydrodemetalation, HDM), and oxygen (hydrodeoxygenation, HDO) from the heavy gas oil feedstock. Hydrogen is added with the heavy gas oil feed. Typical catalysts used for hydrotreating include sulfided CoMo and NiMo. Typical reaction conditions include temperatures of from 300 to 450 0 C, 35-170 bar H 2 partial pressure, and LHSV of from 0.2 to 10 h "1 .

[0009] Oxygenated hydrocarbon compounds, such as bio-oils obtained in the liquefaction of biomass, or glycerol as obtained in the transesterification of triglycerides in bio-diesel production processes, do not normally contain significant amounts of aromatics, sulfur compounds, or nitrogen compounds. Accordingly, there is no need to treat these materials in HDS, HDN, or HDA processes.

[ooio] Chen et al. report the major challenge with biomass conversion to be the removal of oxygen from the biomass and enriching the hydrogen content of the hydrocarbon product. They define the effective hydrogen to carbon ratio (H/C θ ff) defined in Equation 1. The H/C θ ff ratio of biomass derived-oxygenated hydrocarbon compounds is lower than petroleum-derived feedstocks due to the high oxygen content of biomass-derived molecules. The H/C θff ratio of carbohydrates, sorbitol and glycerol (all biomass-derived compounds) are 0, 1/3 and 2/3 respectively. The

H/Ceff ratio of petroleum-derived feeds ranges from 2 (for liquid alkanes) to 1 (for benzene). In this respect, biomass can be viewed as a hydrogen deficient molecule when compared to petroleum-based feedstocks.

„ . _ H - 2O - 3N - 2S

* = ϊ ( D where H, C, O, N and S are the moles of hydrogen, carbon, oxygen, nitrogen and sulfur respectively.

[ooii] Glycerol is currently a valuable by-product of biodiesel production, which involves the transestehfication of triglycerides to the corresponding methyl or ethyl esters. As biodiesel production increases, the price of glycerol is projected to drop significantly. In fact, the price of glycerol has already dropped by almost half over the last few years. [McCoy, 2005 #6] Therefore it is desirable to develop inexpensive processes for the conversion of glycerol into chemicals and fuels.

[0012] Methods for conversion of solid biomass into liquids by acid hydrolysis, pyrolysis, and liquefaction are well known [Klass, 1998 #12]. Solid materials including lignin, humic acid, and coke are byproducts of the above reaction. A wide range of products are produced from the above reactions including: cellulose, hemicellulose, lignin, polysaccharides, monosaccharides (e.g. glucose, xylose, galatose), furfural, polysaccharides, and lignin derived alcohols (coumaryl, coniferyl and sinapyl alcohols).

[0013] The object of the present invention is to provide a process for improving the H/Ceff ratio of oxygenated hydrocarbon compounds. It is a further object of the present invention to provide such a process that makes optimum use of existing refinery equipment and existing hydroconversion catalysts. It is yet another object of the present invention to provide a process that can be carried out under mild conditions of pressure and temperature so as to minimize equipment cost and undesirable side reactions.

[0014] A specific object of the present invention is to provide a process for co- treating vacuum gas oil and vegetable oil

SUMMARY of the INVENTION

[0015] The invention relates generally to a process for the mild hydroconversion of oxygenated hydrocarbon compounds, comprising the step of contacting a reaction feed comprising an oxygenated hydrocarbon compound with a hydroconversion catalyst material at a reaction pressure below 100 bar.

[0016] In a specific embodiment the invention relates to a process for production of normal alkanes by hydrotreating mixtures of triglycerides (or compounds derived- from triglycerides, including free fatty acids) and vacuum gasoil. The mixtures are 99.5 to 50 wt% vacuum gasoil, with the remainder of the feedstock being triglycerides, or triglyceride-dehved molecules such as diglycerides, monoglyceries and free-fatty acids. The triglycerides may include sunflower oil, rapeseed oil, soybean oil, canola oil, waste vegetable oil (yellow grease), animal fats, or trap grease. Tall oil or other biomass derived oils, containing mixtures of free fatty acids and triglycerides can also be used for the hydrotreating process. The catalysts that can be used include sulfided NiMo/AI 2 θ3, COMO/AI2O3 or other standard hydrotreating catalysts known to those skilled in the art. The hydrotreating reaction conditions include temperatures from 300 to 450 0 C, inlet H 2 partial pressures of 35 to 200 bar, and LHSV of 0.2 to 15 h "1 .

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Fig. 1 shows the reaction mechanism for conversion of triglycerides.

[0018] Fig. 2 represents sulfur conversion for hydrotreating of vegetable oil- heavy gas oil feeds.

[0019] Fig 3. represents the nitrogen conversion for hydrotreating of vegetable oil-heavy gas oil feeds.

[0020] Fig 4. shows simulated distillation yields for hydrotreating of vegetable oil-heavy gas oil feeds.

[0021] Fig 5. shows normal alkane, CO, CO 2 , and propane yields for hydrotreating of vegetable oil-heavy gas oil feeds.

[0022] Fig 6. shows the percentage of normal C15 to Cis alkanes in a 250 to

380 0 C simulated distillation fraction as a function of hydrotreating temperature and percentage of vegetable oil in vacuum gasoil.

[0023] Fig 7. shows the percentage of maximum theoretical yields of n-C-15-

C18 alkanes for hydrotreating of vegetable oil-heavy gas oil feeds.

DETAILED DESCRIPTION OF THE INVENTION

[0024] This invention generally relates to a process for mild hydroconversion of oxygenated hydrocarbon compounds, comprising the step of contacting a reaction feed comprising an oxygenated hydrocarbon compound with a hydroconversion catalyst material at a reaction pressure of less than 100 bar. In a preferred embodiment the reaction pressure is less than 40 bar.

[0025] This invention more specifically relates to a process for the hydroconversion of glycerol, carbohydrates, sugar alcohols or other biomass derived oxygenated compounds such as starches, cellulose-derived compounds, and hemicellulose- derived compounds. In a preferred embodiment these compounds are co-fed with petroleum derived feedstocks in a standard or modified hydroconversion process. Mixtures of oxygenated compounds, such as those found in bio-oils derived from pyrolysis or liquefaction, are also included in the definition of biomass-dehved oxygenated compound. In general, oxygenated hydrocarbon compounds that have been produced via the liquefaction of a solid biomass material are particularly preferred. In a specific embodiment the oxygenated hydrocarbon compounds are produced via a mild hydrothermal conversion process, such as described in co- pending application EP 061135646, filed on May 5, 2006, the disclosures of which are incorporated herein by reference. In an alternate specific embodiment the oxygenated hydrocarbon compounds are produced via a mild pyrolysis process, such as described in co-pending application EP 061135679, filed on May 5, 2006, the disclosures of which are incorporated herein by reference.

[0026] The oxygenated hydrocarbon compounds may be mixed with an inorganic material, for example as a result of the process by which they were obtained. In particular, solid biomass may have been treated with a particulate inorganic material in a process such as described in co-pending application EP 061135810, filed May 5, 2006, the disclosures of which are incorporated herein by reference. These materials may subsequently be liquefied in the process of EP 061135646 or that of EP 061135679, cited herein above. The resulting liquid products contain the

[0027] Similarly, the oxygenated hydrocarbon compounds may have been obtained by liquefaction of a biomass material comprising an organic fiber, as disclosed in co- pending application EP 06117217.7, filed July 14, 2006, the disclosures of which are incorporated herein by reference. In this case the oxygenated hydrocarbon compounds may contain organic fibers. It may be advantageous to leave these fibers in the reaction feed, as they may have catalytic activity. The fibers may also be used as a catalyst carrier, for example by bringing the fibers into contact with a metal.

[0028] In a specific embodiment the reaction feed further comprises a crude oil- derived material, for example vacuum gas-oil. Crude oil-derived materials are generally less reactive than oxygenated hydrocarbon compounds. For this reason it is preferred to use a continuous process, and to inject the oxygenated compounds at a point downstream from the injection point of the crude oil-derived compounds, to ensure a shorter contact time of the former with the hydroconversion catalyst material.

[0029] It has been found that the reaction feed may comprise some amounts of water. This is particularly advantageous, because feedstocks such as bio-oil and glycerol derived from biomass conversion processes tend to be mixed with water.

[0030] The process according to the invention can be carried out in a fixed bed, in a moving bed, or in an ebullating bed. Carrying out the process in an ebullating bed is particularly preferred. It is possible to carry out the reaction in a conventional hydro- processing reactor.

[0031] The process according to the invention can be carried out in a single reactor or in multiple reactors. If multiple reactors are used, the catalyst mixture used in the two reactors may be the same or different. If two reactors are used, one may or may not perform one or more of: intermediate phase separation, stripping, H 2 quenching, etc. between the two stages.

[0032] The process conditions for a preferred embodiment of the process according to the invention may be as follows. The temperature generally is 200-500 0 C, preferably 300-400 0 C. The pressure generally is in the range of 20-100 bar, preferably less than 40 bar The liquid hourly space velocity generally is 0.1-3 h "1 , preferably 0.3-2 h "1 . The hydrogen to feed ratio generally is 300-1 ,500 Nl/I, preferably less than 600 Nl/I. The process is carried out in the liquid phase.

[0033] Any conventional hydroprocessing or hydroconversion catalyst as used in oil refining is suitable for use in the process of the present invention. Suitable examples include bimetallic catalysts comprising a metal from Group VIB and a metal from Group VIIIB of the Periodic Table of the Elements. The Group VIIIB metal preferably is a non-noble metal. Examples include Co/Mo, Ni/W, Co/W catalysts.

[0034] For hydrodesulfurization it is in general advantageous to pre-sulfide the catalyst. Pre-sulfidization is in general not required for the hydroconversion of oxygenated hydrocarbons.

[0035] In the alternative the hydroconversion catalyst material comprises a basic material. Examples of suitable basic materials include layered materials, and materials obtained by heat-treating layered materials. Preferably the layered materials are selected from the group consisting of smectites, anionic clays, layered hydroxy salts, and mixtures thereof. Hydrotalcite-like materials, in particular Mg-Al, Mg-Fe, and Ca-Al anionic clays, are particularly preferred. It has surprisingly been found that basic materials are also suitable for the hydro-processing of a crude-oil derived material, such as VGO, as may be used as a first feedstock in certain embodiments of the process of the present invention.

[0036] Preferably, the particles also contain metals like W, Mo, Ni, Co, Fe, V, and/or Ce. Such metals may introduce a hydrotreating function into the particles (especially W, Mo, Ni, Co, and Fe) or enhance the removal of sulfur- and/or nitrogen- containing species (Zn, Ce, V).

[0037] The basic catalytic materials may be used as such, or may be used in admixture with a conventional hydro-processing catalyst.

[0038] The empirical formula of cellulose is (C 6 Hi 0 Os) n - Chemically cellulose is a polymer of glucose, which has the empirical formula Both cellulose and glucose have a H/C eff ratio of 0. Although it might be desirable to fully convert

cellulose to alkanes, it is not necessary to fully hydrogenate cellulose, or oxygenated hydrocarbon compounds derived from cellulose, in order to obtain useful liquid fuels. In many cases partial hydrogenation is sufficient, and more desirable from the perspective of hydrogen consumption. The hydro-conversion reaction is considered successful if it results in an increase of the H/C eff ratio by about 0.2, for example from 0 to 0.2 (in the case of cellulose or glucose), or from 0.3 to 0.5 in the case of glycerol. Accordingly, the molar ratio of hydrogen in the reaction mixture to oxygen in the oxygenated hydrocarbon feed suitably is in the range of from 0.1 to 0.3.

[0039] In a specific embodiment this invention relates to a process for the production of normal alkanes by hydrotreating mixtures of triglycerides (or compounds derived-from triglycerides including free fatty acids) and vacuum gasoil. The mixtures are 99.5 to 50.0 wt% vacuum gasoil with the remainder of the feedstock being triglycerides or triglycehde-derived molecules such as diglycerides, monoglycehes and free-fatty acids. The triglycerides can include sunflower oil, rapeseed oil, soybean oil, canola oil, waste vegetable oil (yellow grease), animal fats, or trap grease. Tall oil or other biomass derived oils, containing mixtures of fatty acids and triglycerides can also be used for the hydrotreating process. The catalysts that can be used include sulfided NiMo/AI 2 O 3 , CoMo/AI 2 O 3 or other standard hydrotreating catalysts known to those skilled in the art. The hydrotreating reaction conditions include temperatures from 300 to 45O 0 C, inlet H 2 partial pressures of 35 to 200 bar, and LHSV values of 0.2-15 h "1 .

[0040] During the hydrotreating of vegetable oils the C=C bonds of the vegetable oils are first hydrogenated as shown in Figure 1 . The hydrogenated vegetable oils then form free fatty acids, diglyehdes and monoglycerides. Operation at low temperature and high space velocities will cause the hydrogenated vegetable oils and products derived from the hydrogenated vegetable oils to form waxes. These waxes could plug the reactor. The free fatty acids, diglycerides, monoglycerides and triglycerides undergo two different pathways to produce normal alkanes. The first is decarbonylation, which produces normal liquid alkanes (Ci 7 if from a Ci 8 free fatty acid), CO or CO 2 , and propane. Alternatively, these feeds may undergo a dehydration/ hydrogenation pathway to produce a normal liquid alkane (Ci 8 if from a Ci 8 acid) and propane. The liquid normal alkanes produced undergo isomerization and cracking to produce less valuable lighter and isomerized alkanes.

These alkanes are less valuable for diesel fuel usage because they have a lower cetane number. The isomerization and cracking reactions are a function of the reaction temperature, and the concentration of vegetable oil in the vegetable oil- vacuum gasoil mixture, as we will show in this patent. The fractions coming from the hydrotreating reactor can then be separated by distillation.

Examples

[0041] The following Examples are included solely to provide a more complete disclosure of the subject invention. Thus, the following Examples serve to illustrate the nature of the invention, but do not limit the scope of the invention disclosed and claimed herein in any fashion.

[0042] Experiments described in this patent were performed in a fixed bed hydrotreating reactor. The catalyst (NiMo/AI 2 O3, Haldor-Topsoe XXX) was loaded into a stainless steel tubular reactor (2.54-cm I. D. and 65 cm in length). The catalysts were pre-sulfided using a mixture of H 2 S/H 2 (9 vol% H 2 S) at atmospheric pressure and 400 0 C for 9 h. The reaction conditions for these examples were as follows: temperatures 300 to 450 0 C, pressures 50 bar, LHSV 4.97 h "1 , and H 2 -to- feed ratio of 1600 ml H 2 gas/ml liquid feed. The gas inlet was 91 % H 2 with the balance being Ar, which was used as an internal standard.

[0043] Vacuum gasoil (VGO) was obtained from the Huelva refinery (CEPSA group). The VGO feed had a carbon content of 88 weight %. The carbon yields are defined as the moles of carbon in each product divided by the carbon in the feed. Sunflower oil (Califour brand) was purchased for mixing with vacuum gasoil.

[0044] The reaction gases were analyzed using a Varian 3800-GC equipped with three detectors, a Thermal Conductivity Detector (TCD) for analysis of H 2 and N 2 , which were separated in a 15 m molecular sieve column, and a Flame Ionization Detector (FID) for Ci to Cβ hydrocarbons separated in a 30 m Plot/AI 2 O3 column. Liquids samples were analyzed for normal alkane content with a Varian 3900-GC chromatograph equipped with a Petrocol-100 fused silica column connected to a FID detector following PIONA procedure. In addition, simulated distillation of vacuum gas oil (VGO) cracking samples were carried out using a Varian 3800GC chromatograph according to the ASTM-2887-D86 procedure. The concentrations of sulfur and

nitrogen in the original feed and liquid products were determined by elemental analysis in a Fisons 1108 CHNS-O instrument.

[0045] The following feeds were hydrotreated including: 100 wt % HVO, 95 wt% HVO-5 wt% Sunflower oil, 85 wt% HVO-15 wt% Sunflower oil, 70 wt% HVO-30 wt% Sunflower oil, and 50 wt% HVO-50 wt% Sunflower oil. The results for the hydro- desulfurization and hydrodenitrogenation are shown in Figures 2 and 3 respectively. As can be seen from these figures, mixing vegetable oils does not decrease the ability of the hydrotreating process to remove sulfur or nitrogen from the HVO feed.

[0046] Figure 4 shows the simulated distillation results for hydrotreating the different feeds. Figure 5 shows the yields for the prominent alkanes, CO and CO2 for the hydrotreating of different feeds. The gas yield increases as the concentration of sunflower oil increases (Figure 4A). This is because propane, CO and CO 2 are formed during hydrotreating of triglyceride as shown in Figure 5. The yields from the 380-520 0 C and 520-1000 0 C fractions decrease with both increasing concentration of sunflower oil and temperature. The yields of the 250 to 380 0 C fraction (mainly diesel fuel) increases as the sunflower oil concentration increases. This fraction contains nCi 5 -nCi8 products, which are formed from the sunflower oil. The yield of nCi5-nCi8, shown in Figure 5E, increases with increasing concentration of sunflower oil. For the feeds containing 30 wt% and 50 wt% sunflower oil the nCi 5 -nCi8 yields decrease when the reaction temperature is increased above 35O 0 C. This is because the nCi5-nCis are cracked to lighter products at the higher temperature as shown by an increase in the 65-15O 0 C yield, 150-250 0 C yield and the nC 8 -nCi 2 yield.

[0047] Figure 6 shows the percentage of nCi 5 -nCi8 in the diesel fuel fraction (250- 38O 0 C). This percentage increases as the sunflower concentration in the feed increases. The percentage also decreases as the temperature increases from 350 to 45O 0 C for the 30 wt% and 50 wt% sunflower oil feeds.

[0048] In Figure 7 we show the percentage of maximum nCi 5 -nCi8 yield for the different HVO-Sunflower mixtures. The percentage of maximum nCi 5 -nCi 8 yield (PMCY) is defined as the yield of nCi 5 -nCi8 minus the yield of nCi 5 -nCi8 from the HVO divided by the maximum nCi 5 -nCi8 yield if all of the fatty acids present in the triglyceride were converted into nCi 5 -nCi8. The PMCY increases as the temperature increases for the 5 wt% sunflower feed as shown in Figure 7, and the PMCY for this

feed is 65-70 % at temperatures from 350 to 450 0 C. THE PMCY for the 15 wt% sunflower feed increases from 9 to 83 % as the temperature increases from 300 to 350 0 C, while a further increase in the temperature to 450 0 C decreases the PMCY to 40 %. The PMCY for the 30 wt% sunflower feed decreases from 85 % to 56 % to 26 % as the temperature increases from 350 0 C to 400 0 C and to 45O 0 C. The PMCY for the 50 wt% sunflower feed decreases from 70 to 26 % as the temperature increases from 35O 0 C to 45O 0 C. Thus there is both an optimal temperature and vegetable oil concentration for obtaining optimum yields for the nCi 5 -nCi8.

Works Cited

[0049] Craig, W. K. and D. W. Soveran (1991 ). Production of hydrocarbons with a relatively high cetane rating. US Patent 4992605. USA.

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[0062] Thus, the invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art.