EP2516593A2

EP2516593A2 - Low water biomass-derived pyrolysis oil and processes for preparing the same

Info

Publication number: EP2516593A2
Application number: EP10843484A
Authority: EP
Inventors: Timothy A. Brandvold; Stanley J. Frey
Original assignee: UOP LLC
Current assignee: Honeywell UOP LLC
Priority date: 2009-12-23
Filing date: 2010-12-15
Publication date: 2012-10-31
Also published as: RU2012130139A; AU2010341654A1; WO2011087675A3; EP2516593A4; CA2784478A1; CN102656253A; WO2011087675A2; BR112012014781A2; US20110146140A1

Abstract

Low water-containing biomass-derived pyrolysis oils and processes for preparing them are provided. Water-containing biomass-derived pyrolysis oil is distilled in the presence of an azeotrope-forming liquid to form an azeotrope. The azeotrope is removed at or above the boiling point of the azeotrope and low water biomass-derived pyrolysis oil is obtained.

Description

LOW WATER BIOMASS-DERIVED PYROLYSIS OIL AND PROCESSES

FOR PREPARING THE SAME

STATEMENT OF PRIORITY

[0001] This application claims priority to U.S. Application No. 12/646,203 filed on December 23, 2009.

FIELD OF THE INVENTION

[0002] The present invention generally relates to biofuels and processes for preparing biofuels, and more particularly relates to low water biomass-derived pyrolysis oil and processes for producing the same.

DESCRIPTION OF RELATED ART

[0003] Fast pyrolysis is a process during which organic biomass materials, such as wood waste, agricultural waste, etc., are rapidly heated to 450°C to 600°C in the absence of air using a process reactor. Under these conditions, organic vapors, pyrolysis gases and ash (char) are produced. The vapors are condensed to biomass-derived pyrolysis oil. Biomass- derived pyrolysis oil is a complex, highly oxygenated organic liquid typically containing 20-30% by weight water with high acidity (TAN >150).

[0004] Biomass-derived pyrolysis oil can be burned directly as fuel for certain boiler and furnace applications. Biomass-derived pyrolysis oil can also serve as a potential feedstock in catalytic processes for the production of fuel in petroleum refineries.

Biomass-derived pyrolysis oil has the potential to replace up to 60% of transportation fuels, thereby reducing the dependency on conventional petroleum and reducing its environmental impact.

[0005] Unfortunately, the high water content of the biomass-derived pyrolysis oil increases the storage instability of the oil. Biomass-derived pyrolysis oil may often be stored in tanks or the like for long periods of time. The high water content is correlated with increases in viscosity, phase separation and/or solids formation during such storage. As-produced biomass-derived pyrolysis oil cannot be simply distilled to completely remove water, as phase separation and/or solids formation result as volatiles are removed. If as-produced biomass-pyrolysis oil is heated to elevated temperatures, some volatiles may vaporize initially, but the majority of the oil solidifies and/or chars. [0006] Accordingly, it is desirable to provide low water biomass-derived pyrolysis oil having substantially increased storage stability and processes for producing the same. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.

SUMMARY OF THE INVENTION

[0007] Processes are provided for reducing water in a water-containing biomass-derived pyrolysis oil. In accordance with one exemplary embodiment, a process for reducing water comprises distilling the water-containing biomass-derived pyrolysis oil in the presence of an azeotrope-forming liquid to form an azeotrope and removing the azeotrope.

[0008] Processes are provided for preparing low water biomass-derived pyrolysis oil in accordance with yet another exemplary embodiment of the present invention. The process comprises the steps of introducing biomass-derived pyrolysis oil and an azeotrope-forming liquid into a distillation apparatus maintained at a temperature sufficient to form an azeotrope. The temperature is at least the minimum boiling point of the azeotrope. The azeotrope is removed from the distillation apparatus and the low water biomass-derived pyrolysis oil is removed from the distillation apparatus.

[0009] Low water biomass-derived pyrolysis oils produced by the processes are also provided in accordance with another exemplary embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:

[0011] FIG. 1 is a flow chart of a process for reducing the water content of biomass- derived pyrolysis oil to produce low water biomass-derived pyrolysis oils according to exemplary embodiments of the present invention; and

[0012] FIG. 2 is a schematic diagram of an apparatus for performing the process of FIG. 1 for reducing the water content of water-containing biomass-derived pyrolysis oil according to exemplary embodiments of the present invention. DETAILED DESCRIPTION

[0013] The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention.

[0014] In accordance with exemplary embodiments of the present invention, the water content in biomass-derived pyrolysis oil is reduced by azeotropic distillation. One or more azeotrope-forming liquids are added to the biomass-derived pyrolysis oil such that an azeotrope with water forms upon distillation. As used herein, an "azeotrope" is a mixture of two or more substances whose liquid and gaseous forms have the same composition (at a certain pressure). The azeotrope is removed from the biomass-derived pyrolysis oil leaving low-water biomass-derived pyrolysis oil. It should be appreciated that while treated oil is generally described herein as a "low water biomass-derived pyrolysis oil", "low water biomass-derived pyrolysis oil" generally includes any treated oil having a lower weight percent (wt%) of water than in the starting biomass-derived pyrolysis oil as a result of the azeotropic distillation according to exemplary embodiments of the present invention. The wt% water in the starting and low water biomass-derived pyrolysis oils may be measured, for example, by Karl Fischer Reagent Titration Method (ASTM D1364) as known to one skilled in the art.

[0015] As shown in FIGS. 1 and 2, the present invention is directed to a process 100 for reducing the water content of biomass-derived pyrolysis oil to prepare low water biomass- derived pyrolysis oil. The process 100 includes the step of providing biomass-derived pyrolysis oil 112 (step 102). The biomass-derived pyrolysis oil 112 is provided from a source such as a feed tank (not shown) or other source operative to provide such biomass- derived pyrolysis oil. The biomass-derived pyrolysis oil composition is somewhat dependent on feedstock and processing variables. The weight percent (wt%) water in the biomass-derived pyrolysis oil generally ranges from 20 to 30%. Such biomass-derived pyrolysis oil is available from, for example, Ensyn Technologies Inc., Ontario, Canada.

[0016] The biomass-derived pyrolysis oil may be produced, for example, from fast pyrolysis of wood biomass. However, the invention is not so limited. Virtually any form of biomass can be considered for pyrolysis to produce biomass-derived pyrolysis oil. In addition to wood, biomass-derived pyrolysis oil may be derived from biomass material such as agricultural wastes/residues, nuts and seeds, algae, grasses, forestry residues, cellulose and lignin or the like. The biomass-derived pyrolysis oil may be obtained by different modes of pyrolysis, such as fast pyrolysis, vacuum pyrolysis, catalytic pyrolysis, and slow pyrolysis (also known as carbonization), under different processing parameters.

[0017] Process 100 continues with the step of distilling the biomass-derived pyrolysis oil 112 by introducing the biomass-derived pyrolysis oil and one or more azeotrope- forming liquids ("Azeotrope Liquid A" and/or "Azeotrope Liquid B") 114 and 116 into a distillation apparatus 118 maintained at an effective temperature to form an azeotrope 120 (step 104). The minimum effective temperature is the boiling temperature of the azeotrope to be formed, as shown below in Table 1. The biomass-derived pyrolysis oil may be introduced into the distillation apparatus as a single stream as shown or as more than one stream. The added azeotrope-forming liquid(s) 114 and 116 utilized to form the azeotrope with water (from the water-containing biomass-derived pyrolysis oil) during distillation may be added to the distillation apparatus as a separate stream or streams, in which case the azeotrope-forming liquid(s) should be added below the lowest feed point of the starting biomass-derived pyrolysis oil 112. Alternately, it may be mixed with the biomass-derived pyrolysis oil stream(s) before it is fed to the distillation apparatus 118, or a combination of adding the azeotrope-forming liquid(s) to both the distillation apparatus 118 and the starting biomass-derived pyrolysis oil may be used. If two azeotrope-forming liquids 114 and 116 are added to the biomass-derived pyrolysis oil 112, a ternary azeotrope with the water is formed. To form binary azeotropes with water, one azeotrope-forming liquid may be added to the biomass-derived pyrolysis oil.

[0018] Effective azeotrope-forming liquids for preparing low water biomass-derived pyrolysis oil include toluene, ethanol, acetone, 2-propanol, cyclohexane, 2-butanone, octane, benzene, ethyl acetate, and combinations thereof. Exemplary suitable azeotropes formed during process 100 include binary azeotropes such as ethanol/water, toluene/water, acetone/water, 2-propanol/water, cyclohexane/water, 2-butanone/water, and octane/water and ternary azeotropes such as ethanol/toluene/water, 1-butanol/octane/water, benzene/2- propanol/water, ethanol/2-butanone/water, and ethanol/ethyl acetate/water. The weight ratio and boiling point of each of these azeotropes at atmospheric pressure is shown below in Table 1 : TABLE 1

Source: Gorden, Arnold J.; Ford Richard A. The Chemist's Companion: A Handbook of Practical Data Techniques and References. 1972; John Wiley and Sons (New York); pp. 24-30.

[0019] Azeotrope selection is driven by the amount and cost of the azeotrope-forming liquids, the desired boiling temperature, and the compatibility of the azeotrope-forming liquid with the low water biomass-derived pyrolysis oil. "Compatibility" as used herein means that the azeotrope-forming liquid is co-soluble with the biomass-derived pyrolysis oil, i.e., there is no phase separation upon mixing of the biomass-derived pyrolysis oil and the azeotrope-forming liquid(s). While certain azeotrope-forming liquids and azeotropes have been identified, the present invention is not so limited. Other azeotrope-forming liquids and azeotropes may be used if they form an azeotrope with water alone or with water in combination with other azeotrope-forming liquids.

[0020] The amount of azeotrope-forming liquid(s) and the minimum temperatures required for water removal depend on the desired level of water reduction and the specific azeotrope to be used. For example, the minimum amount of the azeotrope-forming liquid(s) added to the starting biomass-derived pyro lysis oil subjected to the azeotropic distillation may be determined based on the wt% of water in the biomass-derived pyrolysis oil (the "starting oil") and the desired wt% water in the low water biomass-derived pyrolysis oil (the "target oil"). The difference between these two numbers is the wt% of water that must be removed. The wt% of water that must be removed multiplied by the weight of the biomass-derived pyrolysis oil provides the weight of the water that must be removed from the starting oil to reach the desired wt% water in the target oil. The weight ratios of the water and azeotrope-forming liquid in the azeotrope can be used to calculate the minimum amount of each of the azeotrope-forming liquids to be added (in kilograms) to the starting oil according to the following calculations: weight ratio of azeotrope-forming liquid to water in azeotrope

x mass (in kilograms) of water to be removed from biomass-derived pyrolysis oil =Minimum amount of azeotrope-forming liquid to be added

(in kilograms) to the starting oil

The mass (in kg) of water to be removed = M_f *([H₂0]i -[H₂0]f)/(l-[H₂0]f). wherein:

Mf= mass of water-containing biomass-derived pyrolysis oil (in kilograms); and

[H₂0]i and [H₂0]f = water concentration in grams of water per gram of oil of the initial (water-containing biomass-derived pyrolysis oil) and final pyrolysis oil (low water biomass-derived pyrolysis oil) respectively.

[0021] For example, where 1 kg of water-containing biomass-derived pyrolysis oil ("starting oil) contains 25 wt% water as determined, for example, by Karl Fischer titrations, i.e., 0.250 kg, and the desired water content of the low water biomass-derived pyrolysis oil ("target oil") contains 15 wt% water, the water to be removed = lkg*(0.25- 0.15)/(1-0.15)=0.1 18 kg water. To form an ethanol/toluene/water azeotrope having a weight ratio of 37:51 : 12 as identified in Table 1 above, the amount of ethanol and toluene to be added to 1 kg of water-containing biomass-derived pyrolysis oil is calculated as follows:

Ethanol to be added= 37/12 x 0.1 18 kg = 0.364 kg

Toluene to be added= 51/12 x 0.1 18 kg= 0.501 kg . [0022] While the above calculations provide the minimum amount of the one or more azeotrope-forming liquids to be added to the starting oil, in practice, an excess amount of the one or more of the azeotrope-forming liquids is added to drive the water reduction and maintain phase homogeneity. The one or more azeotrope-forming liquid(s) to be added in excess is selected based on compatibility with the target oil as well as the relative costs of the azeotrope-forming liquids. The amount to be added in excess is determined

experimentally.

[0023] The temperature in the distillation apparatus 118 is maintained at least at the boiling temperature of the selected azeotrope. The temperature may be increased above the minimum boiling temperature to increase the distillation rate. However, the temperature in the distillation apparatus preferably is kept at least at the boiling temperature of the selected azeotrope but as low as possible to remove water (normal boiling point = 100°C) while also avoiding solids formation. Heat (not shown) is supplied to the distillation apparatus by any conventional means. The temperatures in the top and bottom of the distillation apparatus and where the feed stream enters the distillation apparatus may be different. Depending on the distillation apparatus, there may also be a temperature gradient in the distillation apparatus in which the temperature is lower at the top and higher at the bottom thereof. However, such temperature differences are not required.

[0024] The pressure of the azeotrope is typically defined at 1 atmosphere. Alternate pressures (0.1 atm (sub atmospheric) to 10 atmospheres (superatmospheric)) may be used but the azeotrope composition may need to be adjusted by adding more or less of the azeotrope-forming liquid(s). Absolute pressures of the vapor above the boiling liquid near 1 atmosphere, 0.8 to 1.2 atmosphere, are preferred. The pressure is maintained by application of a vacuum (for less than 1 atm) or use of a back pressure regulating device (for greater than 1 atm). Process 100 continues with the step of removing the azeotrope 120 after its formation (step 106). The azeotrope is removed as overhead vapors from a top portion of the distillation apparatus 118.

[0025] Low water biomass-derived pyro lysis oil 124 is removed from a bottom portion of the distillation apparatus (step 108). The distilling step 104 may be repeated with the low water biomass-derived pyrolysis oil to further reduce the water content, as illustrated by dotted lines in FIGS. 1 and 2. The low water biomass-derived pyrolysis oil may then be sent for further processing into biofuel. [0026] The resultant low water biomass-derived pyrolysis oil 124 is of a single phase, is substantially storage-stable, and has a higher energy density than the starting biomass- derived pyrolysis oil 112. Higher energy density means that the low water biomass- derived pyrolysis oil has an increased heat of combustion. Low water biomass-derived pyrolysis oil having as low as 3 to 4 wt% by weight water can be produced with increased thermal and phase stability from biomass-derived pyrolysis oil having 20 to 30% by weight water.

[0027] The low water biomass-derived pyrolysis oil may include residual azeotrope- forming liquid(s). Such residual azeotrope-forming liquid(s) in the low water biomass- derived pyrolysis oil help to improve the flow properties, energy density, and may help the storage stability of the low water biomass-derived pyrolysis oil. It is known, for example, that the addition of ethanol to biomass-derived pyrolysis oil helps to keep the oil phase stable during storage.

[0028] In addition, if the one or more azeotrope-forming liquids are alcohols, reaction with some fraction of carboxylic acids that may be in the biomass-derived pyrolysis oil may occur to form esters and reaction of aldehydes and ketones (implicated in

solidification reactions) in the biomass-derived pyrolysis oil may form acetals and ketals.

This may result in reduced acidity in the low water biomass-derived pyrolysis oil.

[0029] The present invention is further described in detail through the following examples. However, the scope of the present invention is by no means restricted or limited by the examples, which only have an illustrative purpose.

EXAMPLE

[0030] A mixture of biomass-derived pyrolysis oil (123 g, starting water content 33 wt%), toluene (160g) and ethanol (246 g) was placed in a rotary evaporator and heated to 90°C. Volatiles were collected and both overhead vapors (348 g) and distillation apparatus remnants (185g) (i.e., low water biomass-derived pyrolysis oil) were characterized. The distillate composition (excluding water) was >99+% toluene and ethanol (as determined by gas chromatography) with little or no biomass-derived pyrolysis oil mass loss to overhead vapors. 96% of the toluene and 63% of ethanol was recovered in the distillate. The resultant bottoms product (i.e., distillation apparatus remnants) was low water biomass-derived pyrolysis oil having 6.7 wt% water. Thus, 185 g of low water biomass- derived pyrolysis oil with 6.7 wt% water = 12.4 g of water. The starting biomass-derived pyrolysis oil (132 g, 33 % water) had 43.6 g water. Thus, 43.6-12.4/43.6 = 71.6% of the water was removed from the starting biomass-derived pyrolysis oil. The acid number of the bottoms product was reduced slightly (from 186 to >145 mg KOH/g), but this may be a dilution effect as substantial ethanol remained in the distillation apparatus. The distilling step was then repeated with the low water biomass-derived pyrolysis oil to further reduce the water content to 3 to 4 wt%.

[0031] From the foregoing, it is to be appreciated that the low water biomass-derived pyrolysis oil is a single phase liquid which exhibits greater storage stability and higher energy density. The low water biomass-derived pyrolysis oil is thus more suitable for use as a bio fuel than the starting biomass-derived pyrolysis oil.

[0032] While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.

Claims

CLAIMS:

1. A process (100) for reducing water in a water-containing biomass-derived pyrolysis oil comprising the steps of:

distilling the water-containing biomass-derived pyrolysis oil in the presence of an azeotrope-forming liquid to form an azeotrope (104); and

removing the azeotrope (106).

2. The process of claim 1, wherein the step (104) of distilling the water- containing biomass-derived pyrolysis oil comprises heating the water-containing biomass- derived pyrolysis oil to a minimum distillation temperature of the boiling point of the azeotrope at a given atmospheric pressure.

3. A process (100) for preparing low water biomass-derived pyrolysis oil comprising the steps of:

introducing biomass-derived pyrolysis oil and an azeotrope-forming liquid into a distillation apparatus maintained at a temperature sufficient to form an azeotrope, the temperature being at least the minimum boiling point of the azeotrope (104);

removing the azeotrope from the distillation apparatus at or above the boiling point of the azeotrope (106); and

removing low water biomass-derived pyrolysis oil from the distillation apparatus

(108).

4. The process (100) of claim 1 or 3, wherein the azeotrope-forming liquid is selected from the group consisting of toluene, ethanol, acetone, 2-propanol, cyclohexane, 2-butanone, octane, benzene, and ethyl acetate.

5. The process (100) of claim 1 or 3, wherein the azeotrope is selected from the group consisting of ethanol/water, toluene/water, acetone/water, 2-propanol/water, cyclohexane/water, 2-butanone/water, octane/water, ethanol/toluene/water, 1- butanol/octane/water, benzene/2-propanol/water, ethanol/2-butanone/water, and ethanol/ethyl acetate/water.

6. The process (100) of claim 1 or 3, wherein a minimum amount of the azeotrope-forming liquid to be added (in kilograms) is calculated according to the following calculations:

weight ratio of azeotrope-forming liquid to water in azeotrope

x mass (in kilograms) of water to be removed from biomass-derived pyrolysis oil

=Minimum amount of azeotrope-forming liquid to be added

(in kilograms) to the starting oil wherein the mass (in kg) of water to be removed = M_f *([H₂0]i -[H₂0]f)/(l-[H₂0]f); and wherein:

M_f= mass of water-containing biomass-derived pyrolysis oil (in kilograms); and

7. The process (100) of claim 6, wherein the azeotrope-forming liquid is added to the biomass-derived pyrolysis oil, the distillation apparatus, or a combination thereof.

8. A low water biomass-derived pyrolysis oil (124) produced by a process which comprises the steps of:

distilling water-containing biomass-derived pyrolysis oil (112) in the presence of an azeotrope-forming liquid (114 and 116) to form an azeotrope (120); and

removing the azeotrope (120) and obtaining low water biomass-derived pyrolysis oil (124), the low water biomass-derived pyrolysis oil having a water content less than the water-containing biomass-derived pyrolysis oil and containing residual azeotrope-forming liquid.

9. The low water biomass-derived pyrolysis oil (124) of claim 8, wherein the azeotrope-forming liquid (114 and 116) is selected from the group consisting of toluene, ethanol, acetone, 2-propanol, cyclohexane, 2-butanone, octane, benzene, and ethyl acetate and the azeotrope (120) is selected from the group consisting of ethanol/water, toluene/water, acetone/water, 2-propanol/water, cyclohexane/water, 2-butanone/water, octane/water, ethanol/toluene/water, 1-butanol/octane/water, benzene/2-propanol/water, ethanol/2-butanone/water, and ethanol/ethyl acetate/water.

10. The low water biomass-derived pyrolysis oil (124) of claim 9, wherein the azeotrope-forming liquid (1 14 and 1 16) is present in at least an amount calculated according to the following calculations:

weight ratio of azeotrope-forming liquid to water in azeotrope

x mass (in kilograms) of water to be removed from biomass-derived pyrolysis oil =Minimum amount of azeotrope-forming liquid present

(in kilograms) in the starting oil wherein the mass (in kg) of water to be removed = M_f *([H₂0]i -[H₂0]_f)/(l-[H₂0]_f); and wherein: M_f= mass of water-containing biomass-derived pyrolysis oil (in kilograms); and

[H₂0]i and [H₂0]_f = water concentration in grams of water per gram of oil of the initial (water-containing biomass-derived pyrolysis oil) and final pyrolysis oil (low water biomass-derived pyrolysis oil) respectively.