UPGRADING OF BIO-OIL USING SYNTHESIS GAS

Abstract

A method for producing biofuel and other hydrocarbons from bio-oil is disclosed. The method does not require the use of hydrogen derived from fossil fuel.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/697,918 by Steele, et al., filed Sep. 7, 2012, which is incorporated herein by reference in entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under 0221966 awarded by the National Institute of Food and Agriculture (NIFA) and DE-FG36-06GO86025 the U.S. Department of Energy. The government has certain rights in the invention.

FIELD OF THE INVENTION

The present invention is generally directed toward a method for producing fuel from bio-oil.

BACKGROUND OF THE INVENTION

Fuels from biomass have environmental advantages. The plant growth required to produce the biomass feedstock consumes carbon dioxide offsetting the carbon dioxide produced when the fuel is ultimately combusted. Carbon dioxide is a greenhouse gas generally recognized to be the cause of adverse climate effects. A zero carbon footprint is currently not economically feasible with fossil fuels. Another advantage of biofuels is that it reduces our reliance on foreign oil. An economically feasible biofuel is considered important to the US energy security particularly in the light of the current unstable political situation in many countries that supplies the US with its fuel.

One of the current drawbacks of bio-oil is that when it is produced it is unstable. The raw bio-oil must be treated to improve its stability and its suitability as a fuel. Treatment with hydrogen is routinely done to hydrogenate and hydrodeoxygenate thus improving heating value and stability while reducing oxygen content of the fuel. This treatment is commonly performed in the presence of a catalyst. The problem with this treatment is that, in the US, hydrogen is primarily produced from the steam reforming of natural gas—a fossil fuel. In our opinion, consuming a large quantity of fossil fuel to make a biofuel is counterproductive.

Biomass liquefaction to bio-oil leaves far more of the total caloric value of the starting biomass in the product liquid (bio-oil) than gasification to syngas followed by Fischer Tropsch (FT) synthesis of fuels. Thus, bio-oil's potential for fuel production is far greater than that of FT from bio-gasification Thus, there is a need in the art for alternative processes or methods for producing fuel and other hydrocarbons from bio-oil that does not require hydrogen derived from fossil fuels.

SUMMARY OF THE INVENTION

In a first object of the invention, we disclose a method for upgrading bio-oil into hydrocarbons and other fuel products that utilizes synthesis gas, or syngas, as a source of hydrogen from gasification of biomass or other sources to complete.

In a second object of the invention, we disclose a method for upgrading bio-oil into hydrocarbons and other fuel products that utilizes the water gas shift reaction (WGS) to provide hydrogen for the upgrading process.

We also disclose a method for upgrading bio-oil into hydrocarbons and other fuel products that utilizes syngas or WGS as a source for hydrogen to facilitate the upgrading process.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages of the invention will become apparent by reference to the detailed description of preferred embodiments when considered in conjunction with the drawings:

FIG. 1 depicts a diagram of a batch reactor.

FIG. 2 depicts a diagram of a flow system

FIG. 3 depicts a diagram of batch reactor with olefin or alcohol.

FIG. 4 depicts a another diagram of a reactor with olefin or alcohol.

DESCRIPTION OF THE TECHNOLOGY

The following detailed description is presented to enable any person skilled in the art to make and use the invention. For purposes of explanation, specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that these specific details are not required to practice the invention. Descriptions of specific applications are provided only as representative examples. Various modifications to the preferred embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the scope of the invention. The present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest possible scope consistent with the principles and features disclosed herein.

The technology described herein consists of a hydrodeoxygenation process where the hydrogen, from the synthesis gas, reacts with the bio-oil in the presence of a catalyst and removes oxygen atoms. With this process we see improvements in heating value, acidity, stability and compatibility with other fuels. In addition the CO (also from the synthesis gas) reacts with water present in the bio-oil to produce additional hydrogen and easily removed carbon dioxide. This helps to lower bio-oil water content.

The preparation of the catalyst used in this process is as follows. A copper based low temperature catalyst useful for promoting the water gas shift is acquired and used as received. HDO catalysts is prepared using 5 wt % metal loading with a ZSM-5 supporting material via incipient wetness impregnation method then calcined for 3 h at 500° C. and pelletized.

Synthesis gas (50/50 CO/H₂) or biosynthesis gas is used to first purge and then pressurized the reactor. The pressure ranged from 300 to 1200 PSI and at temperatures between 200 and 350° C. The catalyst, liquid product and gas are separated and analyzed while any char is discarded.

The following exemplary embodiments depicts methods that may be used. The numbers in each drawing are only illustrative and correspond only to the figure shown.

As will be appreciated from FIG. 1, raw bio-oil from bio-oil storage tank 1 is transferred to a stirred tank 3 which contains a dual catalyst system including a WGS catalyst and a hydrodeoxygenation (HDO) catalyst. Synthesis gas from the synthesis gas storage tank 2 is transferred to tank 3. The reactor is then mixed and heated resulting in upgraded bio-oil. The upgraded bio-oil is then transferred to an upgraded bio-oil storage tank 4 for subsequent shipment.

In a flow system embodiment shown in FIG. 2, raw bio-oil from bio-oil storage tank 1 and synthesis gas from synthesis gas storage tank 2 are transferred to a flow reactor 3 which contains a dual catalyst system including a WGS catalyst and a HDO catalyst. The reactor is heated to a fixed temperature between 200 and 350° C. while maintaining a constant synthesis gas pressure and reactant flows from tanks 1 and 2. As the bio-oil travels through the reactor upgraded bio-oil is produced. Bio-oil flow through the system will depend on reactor diameter, catalyst packing length and reaction temperature. The upgraded bio-oil is then transferred to an upgraded bio-oil storage tank 4 for subsequent shipment.

FIG. 3 depicts an embodiment of a batch reactor that uses alcohol. As will be appreciated from figure, raw bio-oil from bio-oil storage tank 1, alcohol from storage tank 2 and synthesis gas from synthesis gas storage tank 3 are transferred to a stirred tank 4 which contains a dual catalyst system including a WGS catalyst and a HDO catalyst. The reactor is then mixed and heated resulting in upgraded bio-oil. The upgraded bio-oil is then transferred to an upgraded bio-oil storage tank 5 for subsequent shipment. In an alternative embodiment, the alcohol in storage tank 2 is replaced with an olefin.

As will be appreciated from the embodiment depicted in FIG. 4, raw bio-oil from bio-oil storage tank 1, alcohol from storage tank 2 and synthesis gas from synthesis gas storage tank 3 are transferred to a flow reactor 4 which contains a dual catalyst system including a WGS catalyst and a HDO catalyst. The reactor is heated to a fixed temperature between 200 and 350° C. while maintaining a constant synthesis gas pressure and reactant flows from tanks 1 and 2. As the bio-oil travels through the reactor upgraded bio-oil is produced. Bio-oil flow through the system will depend on reactor diameter, catalyst packing length and reaction temperature. The upgraded bio-oil is then transferred to an upgraded bio-oil storage tank 4 for subsequent shipment. An additional embodiment would be to replace the alcohol with an olefin in storage tank 2.

It is expected that upgrading bio-oil with syngas has many advantages over pure hydrogen: 1) Syngas can be produced from the same renewable feedstock used to produce the bio-oil. 2) It is a renewable source of hydrogen—hydrogen treatment is a proven step in stabilizing and improving fuel quality. 3) Particularly exciting is the presence of carbon monoxide in syngas.

Theory and Laboratory Results

Under the correct combination of reaction conditions and catalyst the carbon monoxide can undergo the water gas shift reaction:

CO+H₂O→CO₂+H₂

The use of the water gas shift reaction provides a way to remove water present in the bio-oil. The CO in syn-gas reacts with water to make CO₂ (which is a gaseous product that separates) and hydrogen (which then proceeds to be consumed as the upgrading occurs). Therefore, syn-gas refining provides a unique way to dewater the bio-oil while providing additional hydrogen.

The Invention

This invention utilizes pressurized syngas which can be produced from biomass to replace the hydrogen produced by steam reforming of natural gas. Hydroprocessing of bio-oil is currently performed by applying pressurized hydrogen in the presence of a catalyst at appropriate pressure and temperature. We have preliminary results indicating significant hydroprocessing effectiveness utilizing pressurized syngas from gasification of biomass. However, the syngas can come from any source and preserve the novelty of the invention.

This invention also employs the water gas shift reaction (WGS) to produce additional hydrogen, above that contained in the syngas itself, for hydroprocessing upgrading of the bio-oil to hydrocarbons. The WGS equilibrium consumes CO abundant (˜23%) in the syngas to generate H₂ via: H₂O+CO=H₂+CO₂. By consuming the H₂ in upgrading, the WGS equilibrium will be driven toward completion. This means that water removal can continue to occur and the decrease of water will not be equilibrium limited. The WGS approach is expected to remove much of the water present in the bio-oil which is a primary objective of bio-oil upgrading.

Both low temperature and high temperature WGS catalysts are well known. Low temperature catalysts can be employed in the hydrotreating stage where temperatures are maintained below 300° C. High temperature WGS catalysts can then be applied during the 2^nd stage hydrocracking that requires temperatures up to 500° C. Some well-known low temperature WGS catalysts useful in the temperature range of 180 to 350° C. include the following: CuO—ZnO, Cu—(La)O, Fe₂O₃/Cr₂O₃, CuO—ZnO—Al₂O₃, CuO—ZnO—Cr₂O₃, Cu/CeO₂ and Ni/CeO₂. Our invention is not limited to these catalysts and any effective WGS catalyst may be applied to preserve the novelty of our invention.

A heterogeneous acid catalyst is required to catalyze the hydroprocessing reactions. The catalyst type may include at least one or more metals selected from nickel (Ni), chromium (Cr), molybdenum (Mo), and tungsten (W), cobalt (Co), rhodium (Rh), iridium (Ir), ruthenium (Ru), rhenium (Re), platinum (Pt), and palladium (Pd) supported on all types of alumina, silica, silica-alumina, titania, zirconia and all types of zeolites. In some cases acids are also used as catalysts such as sulfuric acid, hydrochloric acid, phosphoric acid and nitric acid. The heterogeneous catalyst may have WGS reaction capabilities to improve the production of hydrogen from WGS catalyst alone.

A novel aspect of our approach is the potential utilization of a dual catalyst combining a WGS catalyst with a hydroprocessing catalyst. The combination of these catalysts has the potential to increase hydrogen production significantly above that possible with the use of each catalyst type alone. The hydroprocessing step produces a high percentage of water. The WGS reaction will use the water produced from the hydroprocessing step to increase hydrogen production.

The terms “comprising,” “including,” and “having,” as used in the claims and specification herein, shall be considered as indicating an open group that may include other elements not specified. The terms “a,” “an,” and the singular forms of words shall be taken to include the plural form of the same words, such that the terms mean that one or more of something is provided. The term “one” or “single” may be used to indicate that one and only one of something is intended. Similarly, other specific integer values, such as “two,” may be used when a specific number of things is intended. The terms “preferably,” “preferred,” “prefer,” “optionally,” “may,” and similar terms are used to indicate that an item, condition or step being referred to is an optional (not required) feature of the invention.

The invention has been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope of the invention. It will be apparent to one of ordinary skill in the art that methods, devices, device elements, materials, procedures and techniques other than those specifically described herein can be applied to the practice of the invention as broadly disclosed herein without resort to undue experimentation. All art-known functional equivalents of methods, devices, device elements, materials, procedures and techniques described herein are intended to be encompassed by this invention. Whenever a range is disclosed, all subranges and individual values are intended to be encompassed. This invention is not to be limited by the embodiments disclosed, including any shown in the drawings or exemplified in the specification, which are given by way of example and not of limitation.

While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

All references throughout this application, for example patent documents including issued or granted patents or equivalents, patent application publications, and non-patent literature documents or other source material, are hereby incorporated by reference herein in their entireties, as though individually incorporated by reference, to the extent each reference is at least partially not inconsistent with the disclosure in the present application (for example, a reference that is partially inconsistent is incorporated by reference except for the partially inconsistent portion of the reference).

Claims

1. A method for upgrading bio-oil into hydrocarbons and other fuel products that utilizes synthesis gas, or syngas, as a source of hydrogen from gasification of biomass or other sources to complete.

2. A method for upgrading bio-oil into hydrocarbons and other fuel products that utilizes the water gas shift reaction (WGS) to provide hydrogen for the upgrading process.

3. A method for upgrading bio-oil into hydrocarbons and other fuel products that utilizes syngas or WGS as a source for hydrogen to facilitate the upgrading process.

4. A method for upgrading bio-oil into hydrocarbons and other fuel products that utilizes syngas or WGS as a source for hydrogen and a catalyst composed of CuO—ZnO, Cu—(La)O, Fe2O3/Cr2O3, CuO—ZnO—Al2O3, CuO—ZnO—Cr2O3, Cu/CeO2, Ni/CeO2, and/or other catalysts useful for the upgrading process including those that contain at least one or more of the following metals Ni, Cr, Mo, W, Co, Rh, Ir, Ru, Re, Pt, and Pd along with a suitable support material.