Patent Application
20100228068
1. Field of the Invention
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-derived molecules such as starches, cellulose, and hemicellulose-derived compounds, optionally mixed with petroleum derived feedstocks, in a mild hydroconversion process .
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
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 triglyercies, are one of the most promising feedstocks for biofuels production (Huber, Iborra 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.
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.
Another option for biofuels production is to use biomass-derived 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, N2 and metals from petroleum derived feedstocks (Farrauto and Bartholomew 1997).
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° C., H2 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.
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° C., H2 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-esterification 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).
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° C., 35-170 bar H2 partial pressure, and LHSV of from 0.2 to 10 h−1.
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.
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/Ceff) defined in Equation 1. The H/Ceff 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/Ceff ratio of carbohydrates, sorbitol and glycerol (all biomass-derived compounds) are 0, ⅓ and ⅔ 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.
where H, C, O, N and S are the moles of hydrogen, carbon, oxygen, nitrogen and sulfur respectively.
Glycerol is currently a valuable by-product of biodiesel production, which involves the transesterification 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.
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).
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.
A specific object of the present invention is to provide a process for co-treating vacuum gas oil and vegetable oil
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.
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-derived 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/Al2O3, CoMo/Al2O3 or other standard hydrotreating catalysts known to those skilled in the art. The hydrotreating reaction conditions include temperatures from 300 to 450° C., inlet H2 partial pressures of 35 to 200 bar, and LHSV of 0.2 to 15 h−1.
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.
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-derived 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.
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 inorganic particles. It is not necessary to remove the inorganic particles from the oxygenated hydrocarbon compounds prior to the use of these compounds in the process of the present invention. To the contrary, it may be advantageous to leave the inorganic particles in the oxygenated hydrocarbon feed, in particular if the inorganic material is a catalytically active material. In the alternative the inorganic material may be used as a catalyst carrier.
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 Jul. 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.
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.
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.
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.
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, H2 quenching, etc. between the two stages.
The process conditions for a preferred embodiment of the process according to the invention may be as follows. The temperature generally is 200-500° C., preferably 300-400° 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 NI/I, preferably less than 600 NI/I. The process is carried out in the liquid phase.
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.
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.
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.
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).
The basic catalytic materials may be used as such, or may be used in admixture with a conventional hydro-processing catalyst.
The empirical formula of cellulose is (C6H10O5)n. Chemically cellulose is a polymer of glucose, which has the empirical formula C6H12O6. Both cellulose and glucose have a H/Ceff 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/Ceff 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.
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 triglyceride-derived molecules such as diglycerides, monoglyceries 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/Al2O3, CoMo/Al2O3 or other standard hydrotreating catalysts known to those skilled in the art. The hydrotreating reaction conditions include temperatures from 300 to 450° C., inlet H2 partial pressures of 35 to 200 bar, and LHSV values of 0.2-15 h−1.
During the hydrotreating of vegetable oils the C═C bonds of the vegetable oils are first hydrogenated as shown in
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.
Experiments described in this patent were performed in a fixed bed hydrotreating reactor. The catalyst (NiMo/Al2O3, 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 H2S/H2 (9 vol % H2S) at atmospheric pressure and 400° C. for 9 h. The reaction conditions for these examples were as follows: temperatures 300 to 450° C., pressures 50 bar, LHSV 4.97 h−1, and H2-to-feed ratio of 1600 ml H2 gas/ml liquid feed. The gas inlet was 91% H2 with the balance being Ar, which was used as an internal standard.
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.
The reaction gases were analyzed using a Varian 3800-GC equipped with three detectors, a Thermal Conductivity Detector (TCD) for analysis of H2 and N2, which were separated in a 15 m molecular sieve column, and a Flame Ionization Detector (FID) for C1 to C6 hydrocarbons separated in a 30 m Plot/Al2O3 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.
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
In
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Lynd, L. R., J. H. Cushman, et al. (1991). “Fuel ethanol from cellulosic biomass.” Science 251: 1318-23.
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Wyman, C. E. (1994). “Alternative fuels from biomass and their impact on carbon dioxide accumulation.” Appl. Biochem. Biotechnol. 45/46: 897-915.
Wyman, C. E., S. R. Decker, et al. (2005). Hydrolysis of cellulose and hemicellulose. Polysaccharides. S. Dumitriu. New York, N. Y, Marcel Dekker, Inc.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 60837932 | Aug 2006 | US | national |
| 60858709 | Nov 2006 | US | national |
This application is a continuation of International Application No. PCT/EP 2007/058468, filed on Aug. 15, 2007, which was published under PCT Article 21(2) in English, the contents of which are hereby incorporated by reference, in their entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2007/058468 | 8/15/2007 | WO | 00 | 2/13/2009 |
