Processes for washing a spent ion exchange bed and for treating biomass-derived pyrolysis oil, and apparatuses for treating biomass-derived pyrolysis oil

Processes and apparatuses for washing a spent ion exchange bed and for treating biomass-derived pyrolysis oil are provided herein. An exemplary process for washing a spent ion exchange bed employed in purification of biomass-derived pyrolysis oil includes the step of providing a ion-depleted pyrolysis oil stream having an original oxygen content. The ion-depleted pyrolysis oil stream is partially hydrotreated to reduce the oxygen content thereof, thereby producing a partially hydrotreated pyrolysis oil stream having a residual oxygen content that is less than the original oxygen content. At least a portion of the partially hydrotreated pyrolysis oil stream is passed through the spent ion exchange bed. Water is passed through the spent ion exchange bed after passing at least the portion of the partially hydrotreated pyrolysis oil stream therethrough.

TECHNICAL FIELD

The present invention generally relates to processes and apparatuses for washing a spent ion exchange bed and for treating biomass-derived pyrolysis oil. In particular, the present invention relates to processes and apparatuses for washing a spent ion exchange bed that is employed in purification of biomass-derived pyrolysis oil.

BACKGROUND

Growth of world energy demand has prompted widespread research and development to identify alternative energy sources for satisfying such demand. One such promising alternative energy source is biofuel, which encompasses various types of combustible fuels that are derived from organic biomass. There is a strong desire to develop biofuels that are not only cost-competitive with fossil fuels but also offer environmental benefits and are renewable. One particular type of biofuel is biomass-derived pyrolysis oil. 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 fossil fuel and reducing its environmental impact.

Biomass-derived pyrolysis oil is produced through pyrolysis, including through recently-developed fast pyrolysis processes. Fast pyrolysis is a process during which organic biomass, such as wood waste, agricultural waste, etc., are rapidly heated to about 450° C. to about 600° C. in the absence of air using a pyrolysis reactor. Under these conditions, a pyrolysis vapor stream including organic vapors, water vapor, and pyrolysis gases is produced, along with char (which includes ash and combustible hydrocarbon solids). A portion of the pyrolysis vapor stream is condensed in a condensing system to produce a biomass-derived pyrolysis oil stream. Biomass-derived pyrolysis oil is a complex, highly oxygenated organic liquid that typically contains about 20-30% by weight water with high acidity (TAN>150).

The biomass-derived pyrolysis oil stream often contains metal ions that may be detrimental to downstream processing and usage of the biomass-derived pyrolysis oil. For example, the metal ions may form deposits on equipment, may result in poor emission performance of the biomass-derived pyrolysis oil, and/or may cause catalyst poisoning in downstream fuel upgrading processes. To remove metal ions from the biomass-derived pyrolysis oil stream, ion exchange beds are commonly employed downstream of the pyrolysis reactor.

The ion exchange beds are frequently regenerated to clean the metal ions therefrom, which serves to maintain consistent performance of the ion exchange beds. Water is typically employed for regenerating the ion exchange beds. However, biomass-derived pyrolysis oil is immiscible with water and will prevent proper regeneration of the ion exchange bed with water if the biomass-derived pyrolysis oil is still present in the ion exchange bed in high amounts. As such, before the ion exchange bed can be regenerated using water, the ion exchange bed is generally drained of the biomass-derived pyrolysis oil and flushed with an appropriate flushing stream that is miscible with the biomass-derived pyrolysis oil to remove most biomass-derived pyrolysis oil that remains in the ion exchange bed after draining. Ethanol, which is generally miscible with both water and the biomass-derived pyrolysis oil, is typically used to flush the biomass-derived pyrolysis oil from the ion exchange bed before regeneration with water. The ethanol used for flushing generally mixes with the biomass-derived pyrolysis oil after flushing and is processed with the biomass-derived pyrolysis oil in the downstream fuel upgrading processes. However, one common upgrading process for the biomass-derived pyrolysis oil is hydrotreating, which serves to reduce the oxygen content of the biomass-derived pyrolysis oil, thereby increasing fuel value of the biomass-derived pyrolysis oil. Hydrotreating biomass-derived pyrolysis oil that also includes ethanol converts the ethanol to ethane, which downgrades the fuel value of the biomass-derived pyrolysis oil.

Accordingly, it is desirable to provide processes and apparatuses that enable alternative options for flushing biomass-derived pyrolysis oil from ion exchange beds that will not downgrade the fuel value of the biomass-derived pyrolysis oil. It is also desirable to provide processes and apparatuses that still enable effective regeneration of the ion exchange bed with water through use of an appropriate flushing stream that is sufficiently miscible with water. 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.

BRIEF SUMMARY

Processes and apparatuses for washing a spent ion exchange bed and for treating biomass-derived pyrolysis oil are provided herein. In an embodiment, a process for washing a spent ion exchange bed employed in purification of biomass-derived pyrolysis oil includes the step of providing an ion-depleted pyrolysis oil stream having an original oxygen content. The ion-depleted pyrolysis oil stream is partially hydrotreated to reduce the oxygen content thereof, thereby producing a partially hydrotreated pyrolysis oil stream having a residual oxygen content that is less than the original oxygen content. At least a portion of the partially hydrotreated pyrolysis oil stream is passed through the spent ion exchange bed. Water is passed through the spent ion exchange bed after passing at least the portion of the partially hydrotreated pyrolysis oil stream therethrough.

In another embodiment, a process for treating biomass-derived pyrolysis oil that includes a metal ion component and that has an original oxygen content includes the step of pyrolyzing a biomass feed in a pyrolysis reactor to form a biomass-derived pyrolysis vapor stream. At least a portion of the biomass-derived pyrolysis vapor stream is condensed in a condensing system to form a biomass-derived pyrolysis oil stream. The biomass-derived pyrolysis oil stream is passed through an ion exchange bed to form an ion-depleted pyrolysis oil stream. The ion-depleted pyrolysis oil stream is partially hydrotreated in a hydrotreating device to reduce the oxygen content thereof, thereby producing a partially hydrotreated pyrolysis oil stream having a residual oxygen content that is less than the original oxygen content. At least a portion of the partially hydrotreated pyrolysis oil stream is passed through the spent ion exchange bed. Water is passed through the spent ion exchange bed after passing at least the portion of the partially hydrotreated pyrolysis oil stream therethrough.

In another embodiment, an apparatus is provided for washing a spent ion exchange bed that is employed in purification of biomass-derived pyrolysis oil. The apparatus includes an ion exchange bed for receiving the biomass-derived pyrolysis oil and for forming an ion-depleted pyrolysis oil stream. The apparatus further includes a hydrotreating device for receiving the ion-depleted pyrolysis oil stream and for forming a partially hydrotreated pyrolysis oil stream. The hydrotreating device is in fluid communication with the ion exchange bed through the partially hydrotreated pyrolysis oil stream for passing at least a portion of the partially hydrotreated pyrolysis oil stream through the ion exchange bed.

DETAILED DESCRIPTION

Processes and apparatuses for washing a spent ion exchange bed employed in purification of biomass-derived pyrolysis oil, as well as processes and apparatuses for treating biomass-derived pyrolysis oil, are provided herein. As referred to herein, “purification” refers to removing at least some metal ions from the biomass-derived pyrolysis oil. The processes and apparatuses described herein enable regeneration of spent ion exchange beds that are used in the processes and apparatuses and provide an alternative manner in which the ion exchange beds are flushed of biomass-derived pyrolysis oil prior to washing with water during regeneration. As referred to herein, “regeneration” refers to removal of at least a portion of metal ions from the ion exchange bed, which metal ions were retained in the ion exchange bed as a result of passing biomass-derived pyrolysis oil that contains metal ions therethrough. As also referred to herein, “washing” refers generally to removing biomass-derived pyrolysis oil from the ion exchange bed, and may further include regeneration of the ion exchange bed (although the term “washing” is not to be interpreted as requiring regeneration of the ion exchange bed). In particular, a partially hydrotreated pyrolysis oil stream is passed through the spent ion exchange bed, and is used to flush the biomass-derived pyrolysis oil from the spent ion exchange bed. Because the partially hydrotreated pyrolysis oil is only partially hydrotreated, heteroatoms including oxygen remain in the partially hydrotreated pyrolysis oil, thereby enabling the partially hydrotreated pyrolysis oil stream to be sufficiently miscible with both the biomass-derived pyrolysis oil to be flushed from the spent ion exchange bed and with water. In particular, the partially hydrotreated pyrolysis oil may have a solubility in the biomass-derived pyrolysis oil of at least about 10 g per 100 g of the biomass-derived pyrolysis oil, such as from about 25 to about 100 g per 100 g of the biomass-derived pyrolysis oil. Additionally, the partially hydrotreated pyrolysis oil may have a solubility in water of at least about 5 g per 100 g of water, such as from about 10 to about 50 g per 100 g of water. As such, the partially hydrotreated pyrolysis oil stream is effective for flushing the biomass-derived pyrolysis oil from the ion exchange bed in anticipation of washing with water, which would otherwise be difficult due to immiscibility between biomass-derived pyrolysis oil and water. The partially hydrotreated pyrolysis oil stream may be readily available from downstream processing of the biomass-derived pyrolysis oil, thereby avoiding the need to supply an external flushing stream. Further, unlike flushing with alcohols such as ethanol, the instant processes and apparatuses will not downgrade the fuel value of the biomass-derived pyrolysis oil upon mixing of the partially hydrotreated pyrolysis oil stream (after flushing the ion exchange bed) with other biomass-derived pyrolysis oil that is passed through the ion exchange bed under the normal course of operation.

An exemplary embodiment of a process for washing a spent ion exchange bed12that is employed in purification of biomass-derived pyrolysis oil will now be addressed with reference to an exemplary apparatus10as shown inFIG. 1. Referring toFIG. 1, the apparatus10includes an ion exchange bed12and a hydrotreating device14. In this embodiment, a biomass-derived pyrolysis oil stream16is passed through the ion exchange bed12to form an ion-depleted pyrolysis oil stream18. The biomass-derived pyrolysis oil stream16is a complex, organic liquid having an original oxygen content, and may also contain water. For example, the original oxygen content of the biomass-derived pyrolysis oil stream16can be from about 30 to about 60 weight %, such as from about 40 to about 55 weight %, based on the total weight of the biomass-derived pyrolysis oil stream16. Water can be present in the biomass-derived pyrolysis oil stream16in an amount of from about 10 to about 35 weight %, such as from about 20 to about 32 weight %, based on the total weight of the biomass-derived pyrolysis oil stream16. The ion exchange bed12becomes spent after accumulating a threshold amount of metal ions therein as a result of passing the biomass-derived pyrolysis oil stream16that contains metal ions therethrough. The threshold amount of metal ions that accumulate in the ion exchange bed12to deem the ion exchange bed12as “spent” is an application-specific value and may depend upon a variety of factors including, but not limited to, the type of ion exchange resins used and/or the desired purity of the ion-depleted pyrolysis oil stream18. For purposes of the instant application, the ion exchange bed12may be considered spent upon measurement by ICP-AAS of effluent metals concentration in the ion-depleted pyrolysis oil stream18that exceeds the requirement of the downstream processes, e.g. >10 parts per million (ppm) total metals, such as from about 50 to about 100 ppm total metals. An alternative measure by which the ion exchange bed12may be deemed “spent” is when it reaches from 30 to 40% of its theoretical ion exchange capacity as calculated from a quantity of ion exchange resin in the ion exchange bed12and an average concentration of ions in the biomass-derived pyrolysis oil stream16that is passed through the ion exchange bed12. The biomass-derived pyrolysis oil stream16can be provided from any source. It is to be appreciated that in other embodiments, the ion exchange bed12is provided in spent form and the processes do not actually require the step of passing biomass-derived pyrolysis oil stream16through the ion exchange bed12.

When the biomass-derived pyrolysis oil stream16is passed through the ion exchange bed12in accordance with the exemplary process, the biomass-derived pyrolysis oil stream16may be passed through the ion exchange bed12at a Liquid Hourly Space Velocity (LHSV) of from about 0.1 to about 20 hr−1, such as from about 1 to about 10 hr−1. When an amount of metal ions in the ion-depleted pyrolysis oil stream18reach a target concentration, or when ion concentration is constant (as determined by repeat measurements) over an extended time period, ion-exchange is deemed “complete” and the ion-depleted pyrolysis oil stream18is passed from the ion exchange bed12. Ion concentrations in the ion-depleted pyrolysis oil stream18may be measured by Atomic Absorption Spectroscopy (AAS), Inductively-Coupled Plasma-Atomic Absorption Spectroscopy (ICP-AAS) or other known methods.

Ion exchange beds useful in the processes and apparatuses described herein include one or more conventional ion exchange resins. Exemplary ion exchange resins include acidic cation-exchange resins. The acidic cation-exchange resins may be used in a protonated form, i.e., with all of the active groups being —SO3H. Neutralized sulfonic acid resins, in which some or all of the protons have been exchanged by a cation such as lithium, sodium, potassium, magnesium, and calcium, are also suitable. However, if the ion exchange resins are supplied with an alternate counterion (i.e sodium, Na+), then the acid form may be generated prior to use by treatment with aqueous acid (such as hydrochloric, nitric, or sulfuric acid, etc.). This is commonly known in the art as ion-exchange resin activation. Particular examples of suitable acidic cation-exchange resins include sulfonated copolymers of styrene.

Suitable sulfonic acid resins for use in the processes and apparatuses described herein include macroreticular resins. As used herein, “macroreticular resins” are made of two continuous phases—a continuous pore phase and a continuous gel polymeric phase. The continuous gel polymeric phase is structurally composed of small spherical microgel particles agglomerated together to form clusters, which, in turn, form interconnecting pores. The surface area arises from exposed surface of the microgel clusters. Macroreticular ion exchange resins can be made with different surface areas ranging from 7 to 1,500 m2/g, and average pore diameters ranging from about 5 to about 10,000 nm.

Gel-type resins may also be used as the ion exchange resin. As used herein, “gel-type resins” are generally translucent. There are no permanent pore structures for the gel-type resins. The pores are generally considered to be molecular-scale micropores. The pore structures are determined by the distance between the polymer chains and crosslinks which vary with the crosslink level of the polymer, the polarity of the solvent, and the operating conditions.

The exemplary process continues with partially hydrotreating the ion-depleted pyrolysis oil stream18to reduce the oxygen content thereof, thereby producing a partially hydrotreated pyrolysis oil stream20having a residual oxygen content that is less than the original oxygen content. The ion-depleted pyrolysis oil stream18that is partially hydrotreated can be provided from any source. For example, the ion-depleted pyrolysis oil stream18can be provided from the ion exchange bed12of the apparatus10. Alternatively, the ion-depleted pyrolysis oil stream18can be provided from a separate ion exchange bed (not shown) that is not part of the apparatus10.

The ion-depleted pyrolysis oil stream18can be partially hydrotreated in any conventional manner so long as the residual oxygen content is achieved in the partially hydrotreated pyrolysis oil stream20. In the exemplary embodiment of the process that is conducted in the apparatus10ofFIG. 1, the ion-depleted pyrolysis oil stream18can be partially hydrotreated within the hydrotreating device14, in a batch or semicontinuous or continuous process. Generally, the ion-depleted pyrolysis oil stream18is in a partially vaporized state and is introduced into the hydrotreating device14, which includes a hydrotreating reactor22having a hydrotreating catalyst bed. In embodiments, the hydrotreating reactor22may be a continuous flow reactor, such as a fixed-bed reactor, a continuous stirred tank reactor (CSTR), a trickle bed reactor, an ebulliating bed reactor, a slurry reactor, or any other reactor known to those skilled in the art for hydroprocessing.

Hydrotreating removes gross amounts of heteroatoms such as sulfur, nitrogen, and oxygen, as well as other contaminants such as asphaltenes, from the ion-depleted pyrolysis oil stream18, thereby upgrading the fuel value thereof. Partially hydrotreating the ion-depleted pyrolysis oil stream18includes contacting the ion-depleted pyrolysis oil stream18with a hydrotreating catalyst in the presence of a hydrogen-containing gas28. Suitable hydrotreating catalysts are known in the art and include, but are not limited to, those that contain at least one metal component chosen from non-noble Group VIII (CAS Notation) or at least one metal component selected from the Group VIB (CAS notation) elements or mixtures thereof. Group VIB elements include chromium, molybdenum and tungsten. Group VIII elements include iron, cobalt and nickel. The amount(s) of metal component(s) in the catalyst can range from about 0.1% to about 25% by weight of Group VIII metal component(s) and from about 0.1% to about 25% by weight of Group VIB metal component(s), calculated as metal oxide(s) per 100 parts by weight of total catalyst, where the percentages by weight are based on the weight of the catalyst. In one particular example, the hydrotreating catalyst comprises one or more components of nickel and/or cobalt and one or more components of molybdenum and/or tungsten.

Partial hydrotreating of the ion-depleted pyrolysis oil stream18is conducted to only partially remove the heteroatoms and, in particular, the oxygen from the ion-depleted pyrolysis oil stream18for purposes of achieving the above-mentioned solubility of the partially hydrotreated pyrolysis oil stream20with the biomass-derived pyrolysis oil stream16and with water. As such, the partially hydrotreated pyrolysis oil stream20has the residual oxygen content that is less than the original oxygen content. For example, the ion-depleted pyrolysis oil stream18can be partially hydrotreated to have a residual oxygen content of from about 5 to about 30 weight %, such as from about 10 to about 20 weight %, based on the total weight of the partially hydrotreated pyrolysis oil stream20immediately after partial hydrotreating.

Hydrotreating devices and processes for hydrotreating ion-depleted pyrolysis oil streams are known to one skilled in the art, and conditions for partially hydrotreating the ion-depleted pyrolysis oil stream18can be controlled to achieve the above-referenced residual oxygen contents in the partially hydrotreated pyrolysis oil stream20, while also ensuring that the partially hydrotreated pyrolysis oil stream20has a liquid phase. Particular hydrotreating conditions in the hydrotreating device14that may impact the residual oxygen content of the partially hydrotreated pyrolysis oil stream20can include a temperature of the ion-depleted pyrolysis oil stream18immediately prior to hydrotreating. In an embodiment, temperature of the ion-depleted pyrolysis oil stream18can be increased by recycling a portion of partially hydrotreated oil stream20in a recycle stream38and mixing the recycle stream38with the ion-depleted pyrolysis stream18prior to partial hydrotreating. Without being bound by any particular theory, it is believed that mixing the recycle stream38and ion-depleted pyrolysis stream18to increase the temperature of the ion-depleted pyrolysis oil stream18retards the rate of solids formation and solubilizes any solids that are formed prior to hydrotreating the mixed recycle stream38and ion-depleted pyrolysis stream18. Furthermore, the additional volume minimizes residence time, which results in minimized solids formation in the partially hydrotreated pyrolysis oil stream20. For example, in an embodiment, the combined ion-depleted pyrolysis stream18and recycle stream38has a temperature of about 150° C. or greater, for example from about 150 to about 400° C., such as from about 300 to about 375° C., prior to partial hydrotreating in the hydrotreating reactor22. In an exemplary embodiment, the residence time is about 60 seconds or less, for example about 20 seconds or less, for example about 10 second or less, such as from about 10 to about 1 seconds. A liquid hourly space velocity of the combined ion-depleted pyrolysis stream18and recycle stream38, on a basis of volume of the combined stream/volume of catalyst/hour (hr−1), may be from about 0.5 to about 1 hr−1. The hydrogen-containing gas28may be provided at a treat rate of from about 1,000 to about 15,000 standard cubic feet per barrel (SCF/B). The hydrogen-containing gas28may be mixed with the ion-depleted pyrolysis oil stream18prior to partially hydrotreating the ion-depleted pyrolysis oil stream18in the hydrotreating reactor22, as shown inFIG. 1, or may be separately introduced from the ion-depleted pyrolysis oil stream18concurrent with partially hydrotreating the ion-depleted pyrolysis oil stream18in the hydrotreating reactor22.

Generally, during hydrotreating in the hydrotreating reactor,14, pressure in the hydrotreating reactor14can be in a range of from about 2 to about 20 MPa, and temperature within the hydrotreating reactor14can be from about 150 to about 1000° C., such as from about 150 to about 750° C., for example from about 150 to about 400° C. In any event, residual oxygen content of the partially hydrotreated pyrolysis oil stream20can be monitored to ensure that a value within the above-stated ranges is achieved, or residual oxygen content within the above-stated ranges can be generally achieved through controlling the above-mentioned hydrotreating conditions without monitoring residual oxygen content. In embodiments, the partially hydrotreated pyrolysis oil stream20is an intermediate hydrotreated pyrolysis oil stream between multiple hydrotreating devices in conventional multi-stage hydrotreating systems.

In an exemplary embodiment of the process that is conducted in the apparatus10ofFIG. 1, a solids/aqueous component30, which includes entrained hydrotreating catalyst as well as water from hydrotreating of the ion-depleted pyrolysis oil stream18, is separated from the partially hydrotreated pyrolysis oil stream20by feeding the partially hydrotreated pyrolysis oil stream20to a separation unit32. Additionally, unreacted hydrogen34may be separated from the partially hydrotreated pyrolysis oil stream20and recovered for recycle to the hydrotreating device14, with make-up hydrogen36supplementing the unreacted hydrogen34that is recycled to the hydrotreating device14. In an alternative embodiment, no unreacted hydrogen is supplied to the hydrotreating device14and make-up hydrogen36supplies all of the hydrogen necessary for hydrotreating the ion-depleted pyrolysis oil stream18in the hydrotreating device14. The solids/aqueous component30may be treated to recover hydrotreating catalyst and to properly remediate water that is separated from the partially hydrotreated pyrolysis oil stream20through conventional techniques.

In the exemplary embodiments of the process and the apparatus10contemplated herein, after the separation unit32, the partially hydrotreated pyrolysis oil stream20is split into at least the recycle stream38and a flushing stream40. In an embodiment, the partially hydrotreated pyrolysis oil stream20is further split into a product stream42. For example, the product stream42can be split from the partially hydrotreated pyrolysis oil stream20prior to splitting the partially hydrotreated pyrolysis oil stream20into the recycle stream38and the flushing stream40. The recycle stream38may be combined with the ion-depleted pyrolysis oil stream18prior to partial hydrotreating in the hydrotreating reactor22. The product stream42may be further processed to produce an upgraded pyrolysis oil stream. The flushing stream40may be passed to the spent ion exchange bed12as described in further detail below. Splitting of the partially hydrotreated pyrolysis oil stream20may be conducted depending upon the desired flow in the aforementioned recycle stream38, product stream42, and flushing stream40. For example, at times during operation of the hydrotreating device14when flushing of the ion exchange bed12is unnecessary, the apparatus10ofFIG. 1may be configured to split the partially hydrotreated pyrolysis oil stream20into the recycle stream38and product stream42, with the flushing stream40split on an as-needed basis.

In an optional embodiment, the partially hydrotreated pyrolysis oil stream20is cooled to condense the partially hydrotreated pyrolysis oil stream20and/or to transfer heat to other streams prior to separating the solids/aqueous component30from the partially hydrotreated pyrolysis oil stream20. Conventional techniques can be employed for cooling, including passing the partially hydrotreated pyrolysis oil stream20through a cooling device46such as a heat exchanger, a contact cooler, or the like. Alternatively, and as also shown inFIG. 1, the partially hydrotreated pyrolysis oil stream20may be cooled after splitting into at least the recycle stream38and the flushing stream40. In particular, the flushing stream40can be cooled in accordance with the instant process in a second cooling device48, which may be provided in addition or as an alternative to the cooling device46that is upstream of separation of the solids/aqueous component30from the partially hydrotreated pyrolysis oil stream20.

The exemplary process continues with washing the spent ion exchange bed12. In an embodiment, the spent ion exchange bed12is drained of biomass-derived pyrolysis oil prior to regeneration, with the drained biomass-derived pyrolysis oil passed on in the ion-depleted pyrolysis oil stream18. Draining of the biomass-derived pyrolysis oil from the spent ion exchange bed12can be conducted with assistance, such as through air or nitrogen purge, or can be conducted gravimetrically depending upon the configuration of the ion exchange bed12. Once the biomass-derived pyrolysis oil is drained from the spent ion exchange bed12, the exemplary process continues with passing at least a portion of the partially hydrotreated pyrolysis oil stream20through the spent ion exchange bed12. In particular, for the process conducted in the apparatus10as shown inFIG. 1, the flushing stream40that is separated from the partially hydrotreated pyrolysis oil stream20is passed through the spent ion exchange bed12. However, it is to be appreciated that in other embodiments, the partially hydrotreated pyrolysis oil stream20can be passed through the spent ion exchange bed12without separating the recycle stream38and, optionally, the product stream42therefrom. Because the partially hydrotreated pyrolysis oil stream20is sufficiently miscible with the biomass-derived pyrolysis oil due to the residual oxygen content of the partially hydrotreated pyrolysis oil stream20, the partially hydrotreated pyrolysis oil stream20is effective to remove residual biomass-derived pyrolysis oil from the spent ion exchange bed12in anticipation of passing water50through the spent ion exchange bed12.

In the exemplary process as contemplated herein, passing at least the portion of the partially hydrotreated pyrolysis oil stream20through the spent ion exchange bed12produces a flushed pyrolysis oil stream53. In an embodiment, the flushed pyrolysis oil stream53is discharged from the spent ion exchange bed12and is mixed with the ion-depleted pyrolysis oil stream18that is passed from the ion exchange bed12. Alternatively or additionally (although not shown), the flushed pyrolysis oil stream53may be recycled to the biomass-derived pyrolysis oil stream16prior to passing into the ion exchange bed12for purposes of removing metal ions therefrom under circumstances in which the flushed pyrolysis oil stream53has an excessively high metal ion content.

The exemplary process continues with passing water50through the spent ion exchange bed12after passing at least the portion of the partially hydrotreated pyrolysis oil stream20therethrough. In particular, the process may include draining the partially hydrotreated pyrolysis oil stream20from the spent ion exchange bed12, followed by passing the water50through the spent ion exchange bed12. One or more cycles of water50can be passed through the spent ion exchange bed12, with the same water50passed through the ion exchange bed12multiple times. Again, because the partially hydrotreated pyrolysis oil stream20has the above-described solubility with water, the partially hydrotreated pyrolysis oil stream20can be effectively washed from the spent ion exchange bed12with the water50.

After washing the spent ion exchange bed12with water50, the spent ion exchange bed12can be regenerated through conventional steps. In particular, the water50can be drained, optionally with assistance such as with air purge. One or more cycles of sodium chloride solution52(e.g., 10 mol % in water) can be passed through the spent ion exchange bed12, followed by draining of the sodium chloride solution52. An acidic ion-exchange regenerant54can then be passed through the spent ion exchange bed12to regenerate the spent ion exchange bed12. In particular, one or more cycles of the acidic ion-exchange regenerant54, such as sulfuric acid (e.g., 10 mol % in water), can be passed through the spent ion exchange bed12to regenerate the spent ion exchange bed12and thereby form a regenerated ion exchange bed12. The acidic ion-exchange regenerant54is then drained and the regenerated ion exchange bed12can be washed with one or more cycles of water50. After draining the water50, the regenerated ion exchange bed12can be filled with ion-depleted pyrolysis oil stream18and returned to conventional operation.

An exemplary embodiment of a process for treating biomass-derived pyrolysis oil will now be addressed with reference to an exemplary apparatus110as shown inFIG. 2. In accordance with the exemplary process of this embodiment, a biomass feed56is pyrolyzed in a pyrolysis reactor58to form a biomass-derived pyrolysis vapor stream57. As known in the art, pyrolysis is a thermochemical decomposition of organic material at elevated temperatures without the participation of oxygen. In this regard, pyrolysis is typically performed substantially in the absence of molecular oxygen, e.g., in the absence of air, as known in the art, although the presence of oxygen cannot be completely eliminated and some oxygen is typically present. The biomass-derived pyrolysis vapor stream57may be obtained by different pyrolysis processes, such as, but not limited to, fast pyrolysis, vacuum pyrolysis, catalytic pyrolysis, and slow pyrolysis (also known as carbonization). Fast pyrolysis, in particular, is a process during which organic biomass, such as wood waste, agricultural waste, etc., is rapidly heated to about 450° C. to about 600° C. in the absence of air. Under these conditions, the biomass-derived pyrolysis vapor stream57is produced in the pyrolysis reactor58, along with char (which includes ash and combustible hydrocarbon solids). The biomass-derived pyrolysis vapor stream57includes organic vapors, water vapor, and pyrolysis gases. At least a portion of the biomass-derived pyrolysis vapor stream57is condensed in a condensing system59to form a biomass-derived pyrolysis oil stream16having an original oxygen content, with uncondensed gases60and char62expelled from the condensing system59and remediated through conventional treatments.

The exemplary embodiment of the process contemplated herein continues with passing the biomass-derived pyrolysis oil stream16through an ion exchange bed12to form an ion-depleted pyrolysis oil stream18, which step is described in detail above in the context of the exemplary process conducted in the apparatus10ofFIG. 1. In this embodiment, the ion-depleted pyrolysis oil stream18is partially hydrotreated in a hydrotreating device14to reduce the oxygen content thereof, thereby producing a partially hydrotreated pyrolysis oil stream20having a residual oxygen content that is less than the original oxygen content. In particular, the hydrotreating device14is in fluid communication with the ion exchange bed12through the ion-depleted pyrolysis oil stream18. The ion-depleted pyrolysis oil stream18is partially hydrotreated as described in detail above in the context of the exemplary process conducted in the apparatus10ofFIG. 1.

In accordance with the embodiment of the process that is conducted in the apparatus110ofFIG. 2, the ion exchange bed12is spent after accumulating a threshold amount of metal ions therein during the normal course of operation of the apparatus110. At least a portion of the partially hydrotreated pyrolysis oil stream20is passed through the spent ion exchange bed12as described in detail above in the context of the exemplary process conducted in the apparatus10ofFIG. 1, after optionally draining the biomass-derived pyrolysis oil stream16from the spent ion exchange bed12. In this embodiment, the hydrotreating device14is in fluid communication with the ion exchange bed12through the partially hydrotreated pyrolysis oil stream20for passing at least a portion of the partially hydrotreated pyrolysis oil stream20through the ion exchange bed12. In particular, like the embodiment of the process conducted in the apparatus10ofFIG. 1as described above, a solids/aqueous component30and unreacted hydrogen34is separated from the partially hydrotreated pyrolysis oil stream20in a separation unit32.

The partially hydrotreated pyrolysis oil stream20is split into at least a recycle stream38and a flushing stream40, the flushing stream40is passed through the spent ion exchange bed12, and the recycle stream38is combined with the ion-depleted pyrolysis oil stream18prior to partially hydrotreating the ion-depleted pyrolysis oil stream18in the hydrotreating reactor22. Additionally, the partially hydrotreated pyrolysis oil stream20can be further split into a product stream42, with the product stream42split from the partially hydrotreated pyrolysis oil stream20prior to splitting the partially hydrotreated pyrolysis oil stream20into the recycle stream38and the flushing stream40. In this embodiment, the product stream42is additionally hydrotreated in at least one additional hydrotreating device124that includes a secondary hydrotreating reactor26to further reduce the oxygen content thereof. The upgraded pyrolysis oil stream44may be substantially free of an oxygen content. In particular, the upgraded pyrolysis oil stream44may have an oxygen content of less than or equal to about 2 weight %, such as from about 0.01 to about 0.5 weight %, based on the total weight of the upgraded pyrolysis oil stream44immediately after additional hydrotreating. The upgraded pyrolysis oil stream44can be further separated in an additional separating unit132to separate secondary unreacted hydrogen134and a secondary solids/aqueous component130, which may include entrained hydrotreating catalyst as well as water, from the upgraded pyrolysis oil stream44. The secondary unreacted hydrogen134may be recycled and supplemented with additional make-up hydrogen136before mixing the resulting hydrogen-containing gas128with the product stream42that is additionally hydrotreated in the at least one additional hydrotreating device124.

After passing at least the portion of the partially hydrotreated pyrolysis oil stream20through the spent ion exchange bed12and optionally draining the partially hydrotreated pyrolysis oil stream20from the spent ion exchange bed12, water50is passed through the spent ion exchange bed12. The spent ion exchange bed12can then be regenerated in the same manner as described above in the context of the process conducted in the apparatus10ofFIG. 1.