Methods and apparatuses for deoxygenating biomass-derived pyrolysis oil

Embodiments of methods and apparatuses for deoxygenating a biomass-derived pyrolysis oil are provided. In one example, a method comprises the steps of separating a low-oxygen biomass-derived pyrolysis oil effluent into a low-oxygen-pyoil organic phase stream and an aqueous phase stream. Phenolic compounds are removed from the aqueous phase stream to form a phenolic-rich diluent recycle stream. A biomass-derived pyrolysis oil stream is diluted and heated with the phenolic-rich diluent recycle stream to form a heated diluted pyoil feed stream. The heated diluted pyoil feed stream is contacted with a deoxygenating catalyst in the presence of hydrogen to deoxygenate the heated diluted pyoil feed stream.

TECHNICAL FIELD

The technical field relates generally to methods and apparatuses for producing biofuels, and more particularly to methods and apparatuses for producing low-oxygen biomass-derived pyrolysis oil from the catalytic deoxygenation of biomass-derived pyrolysis oil.

BACKGROUND

Fast pyrolysis is a process during which organic carbonaceous biomass feedstock, i.e., “biomass”, such as wood waste, agricultural waste, algae, etc., is rapidly heated to between about 300° C. to about 900° C. in the absence of air using a pyrolysis reactor. Under these conditions, solid products, liquid products, and gaseous pyrolysis products are produced. A condensable portion (vapors) of the gaseous pyrolysis products is condensed into biomass-derived pyrolysis oil (commonly referred to as “pyoil”). Biomass-derived pyrolysis oil can be burned directly as fuel for certain boiler and furnace applications, and can also serve as a potential feedstock in catalytic processes for the production of fuels in petroleum refineries. Biomass-derived pyrolysis oil has the potential to replace a substantial percentage of transportation fuels, thereby reducing the dependency on conventional petroleum and reducing its environmental impact.However, biomass-derived pyrolysis oil is a complex, highly oxygenated organic liquid having properties that currently limit its utilization as a biofuel. For example, biomass-derived pyrolysis oil has high acidity and a low energy density attributable (compared to hydrocarbon oil) in large part to oxygenated hydrocarbons (the water content also contributes to low energy density) in the oil, which can undergo secondary reactions during storage particularly if the oil is stored at elevated temperatures. “Oxygenated hydrocarbons” or “oxygenates” as used herein are organic compounds containing hydrogen, carbon, and oxygen. Such oxygenated hydrocarbons in the biomass-derived pyrolysis oil include carboxylic acids, phenol, cresol, alcohols, aldehydes, and the like, such as ethers, esters, anhydrosugars, and furans. Conventional biomass-derived pyrolysis oil comprises about 30% or greater by weight oxygen from these oxygenated hydrocarbons. Conversion of biomass-derived pyrolysis oil into biofuels and chemicals requires full or partial deoxygenation of the biomass-derived pyrolysis oil. Such deoxygenation may proceed via two main routes, namely the elimination of either water, or CO and CO2. Unfortunately, deoxygenating biomass-derived pyrolysis oil leads to rapid plugging or fouling of the processing catalyst in a hydroprocessing reactor caused by the formation of solids from the biomass-derived pyrolysis oil. Components in the pyrolysis oil form deposits on the processing catalysts causing catalytic bed fouling, reducing activity of the catalyst, and causing build up in the hydroprocessing reactor. It is believed that this plugging is due to an acid catalyzed thermal polymerization of the various components of the biomass-derived pyrolysis oil, e.g., reactions in which the various components of the oil polymerize with themselves, that create either a glassy brown polymer or powdery brown char that limits run duration and processibility of the biomass-derived pyrolysis oil.

Accordingly, it is desirable to provide methods and apparatuses for producing a low-oxygen biomass-derived pyrolysis oil without plugging of the catalyst, thereby increasing run duration and improving processibility of the biomass-derived pyrolysis oil. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.

BRIEF SUMMARY

Methods and apparatuses for deoxygenating a biomass-derived pyrolysis oil are provided herein. In accordance with an exemplary embodiment, a method for deoxygenating a biomass-derived pyrolysis oil comprises the steps of separating a low-oxygen biomass-derived pyrolysis oil effluent into a low-oxygen-pyoil organic phase stream and an aqueous phase stream at first separation conditions in which phenolic compounds in the low-oxygen biomass-derived pyrolysis oil effluent are substantially miscible in the aqueous phase stream. The phenolic compounds are removed from the aqueous phase stream at second separation conditions in which the phenolic compounds are substantially immiscible in the aqueous phase stream to form a phenolic-rich diluent recycle stream. A biomass-derived pyrolysis oil stream is diluted and heated with the phenolic-rich diluent recycle stream to form a heated diluted pyoil feed stream. The heated diluted pyoil feed stream is contacted with a deoxygenating catalyst in the presence of hydrogen at hydroprocessing conditions effective to deoxygenate the heated diluted pyoil feed stream.

In accordance with another exemplary embodiment, a method for deoxygenating a biomass-derived pyrolysis oil is provided. The method comprises the steps of cooling and separating a low-oxygen biomass-derived pyrolysis oil effluent to form a low-oxygen-pyoil organic phase stream and a phenolic-containing aqueous phase stream. The phenolic-containing aqueous phase stream is cooled and separated to form a phenolic-rich diluent recycle stream and a water-rich stream. A biomass-derived pyrolysis oil stream is diluted and heated with the phenolic-rich diluent recycle stream to form a heated diluted pyoil feed stream. The heated diluted pyoil feed stream is introduced to a hydroprocessing reactor that contains a deoxygenating catalyst in the presence of hydrogen and that is operating at hydroprocessing conditions effective to deoxygenate the heated diluted pyoil feed stream.

An apparatus for deoxygenating a biomass-derived pyrolysis oil is provided. The apparatus comprises a first separation zone that is configured to receive a low-oxygen biomass-derived pyrolysis oil effluent. The first separation zone is further configured to separate the low-oxygen biomass-derived pyrolysis oil effluent into a low-oxygen-pyoil organic phase stream and an aqueous phase stream at first separation conditions in which phenolic compounds in the low-oxygen biomass-derived pyrolysis oil effluent are substantially miscible in the aqueous phase stream. A second separation zone is in fluid communication with the first separation zone. The second separation zone is configured to remove the phenolic compounds from the aqueous phase stream at second separation conditions in which the phenolic compounds are substantially immiscible in the aqueous phase stream to form a phenolic-rich diluent recycle stream. A reaction zone is in fluid communication with the second separation zone. The reaction zone comprises a hydroprocessing reactor that contains deoxygenating catalyst in the presence of hydrogen. The reaction zone is configured to dilute and heat a biomass-derived pyrolysis oil stream with the phenolic-rich diluent recycle stream to form a heated diluted pyoil feed stream for introduction to the hydroprocessing reactor operating at hydroprocessing conditions effective to deoxygenate the heated diluted pyoil feed stream.

DETAILED DESCRIPTION

Various embodiments contemplated herein relate to methods and apparatuses for deoxygenating a biomass-derived pyrolysis oil. Unlike the prior art, the exemplary embodiments taught herein produce a low-oxygen biomass-derived pyrolysis oil effluent by contacting a heated diluted pyoil feed stream with a deoxygenating catalyst in the presence of hydrogen at hydroprocessing conditions to deoxygenate the heated diluted pyoil feed stream. It should be appreciated that while the deoxygenated oil produced according to exemplary embodiments are generally described herein as a “low-oxygen biomass-derived pyrolysis oil,” this term generally includes any pyoil produced having a lower oxygen concentration (i.e. a lower residual oxygen content) than conventional biomass-derived pyrolysis oil. The term “low-oxygen biomass-derived pyrolysis oil” is pyoil having some oxygen, i.e., a biomass-derived pyrolysis oil in which a portion of the oxygenated hydrocarbons have been converted into hydrocarbons (i.e. a “hydrocarbon product”). In an exemplary embodiment, the low-oxygen biomass-derived pyrolysis oil comprises an aqueous phase and a hydroprocessed organic phase (i.e. oil comprising primarily oxygenates and hydrocarbons) that comprises oxygen in an amount of from about 5 to about 25 weight percent (wt. %), for example about 10 to about 20 wt. %, of the hydroprocessed organic phase. “Hydrocarbons” as used herein are organic compounds that contain principally only hydrogen and carbon, i.e., oxygen-free. “Oxygenated hydrocarbons” as used herein are organic compounds containing hydrogen, carbon, and oxygen. Exemplary oxygenated hydrocarbons in biomass-derived pyrolysis oil include alcohols such as phenol and cresol, carboxylic acids, aldehydes, and the like, such as ethers, esters, anhydrosugars, and furans.

The heated diluted pyoil feed stream is formed by diluting and heating a biomass-derived pyrolysis oil stream with a phenolic-rich diluent recycle stream. The phenolic-rich diluent recycle stream is formed from a portion of the low-oxygen biomass-derived pyrolysis oil effluent that has been selectively separated to be rich in phenolic compounds that are mutually miscible with the biomass-derived pyrolysis oil. As used herein, the term “phenolic compounds” are a class of chemical compounds that include a hydroxyl group bonded directly to an aromatic hydrocarbon group. Examples of phenolic compounds include phenol, alkylphenol such as cresol and the like, and/or other phenol substituted compounds. In an exemplary embodiment, the phenolic-rich diluent recycle stream comprises phenolic compounds that are present in an amount of about 50 wt. % or greater, such as from about 50 to about 100 wt. %. The non-phenolic components in the phenolic-rich diluent stream include water and other organic oxygenates such as alcohols and carboxylic acids, which are co-soluble with the phenolic compounds. In an exemplary embodiment, the biomass-derived pyrolysis oil stream is diluted with the phenolic-rich diluent recycle stream such that the heated diluted pyoil feed stream contains from about 10 to about 25 wt. % of the biomass-derived pyrolysis oil stream and from about 75 to about 90 wt. % of the phenolic-rich diluent recycle stream.

It has been found that by contacting the deoxygenating catalyst with the heated diluted pyoil feed stream in the presence of hydrogen at the hydroprocessing conditions, the amount of glassy brown polymer or powdery brown char formed on the deoxygenating catalyst is substantially reduced or minimized relative to conventional methods. Without being limited by theory, it is believed that by diluting the biomass-derived pyrolysis oil stream with the phenolic-rich diluent recycle stream, simple reactions of the biomass-derived pyrolysis oil with hydrogen to form a lower-oxygen biomass-derived pyrolysis oil are effectively increased and dominate while secondary polymerization reactions of biomass-derived pyrolysis oil components with themselves are reduced or minimized, thereby reducing or minimizing the formation of glassy brown polymers or powdery brown char on the deoxygenating catalyst. Therefore, a low-oxygen biomass-derived pyrolysis oil can be produced in a reactor without plugging the deoxygenating catalyst, thereby increasing run duration and improving processibility of the biomass-derived pyrolysis oil.

Referring to the FIGURE, a schematic depiction of an apparatus10for deoxygenating a biomass-derived pyrolysis oil in accordance with an exemplary embodiment is provided. The apparatus10comprises a reaction zone12, a separation zone14, a separation zone16, and a separation zone18that are in fluid communication with each other. As used herein, the term “zone” can refer to an area including one or more equipment items and/or one or more sub-zones. Equipment items can include one or more reactors or reactor vessels, heaters, coolers, exchangers, pipes, pumps, compressors, and controllers. Additionally, an equipment item, such as a reactor, dryer, or vessel, can further include one or more zones or sub-zones.

As illustrated, a biomass-derived pyrolysis oil stream20comprising the biomass-derived pyrolysis oil is introduced to the reaction zone12. The biomass-derived pyrolysis oil may be produced, such as, for example, from pyrolysis of biomass in a pyrolysis reactor. Virtually any form of biomass can be used for pyrolysis to produce the biomass-derived pyrolysis oil. The biomass-derived pyrolysis oil may be derived from biomass material, such as, wood, agricultural waste, nuts and seeds, algae, forestry residues, and the like. The biomass-derived pyrolysis oil may be obtained by different modes of pyrolysis, such as, for example, fast pyrolysis, vacuum pyrolysis, catalytic pyrolysis, and slow pyrolysis or carbonization, and the like.

The composition of the biomass-derived pyrolysis oil can vary considerably and depends on the feedstock and processing variables. Examples of biomass-derived pyrolysis oil “as-produced” can contain, for example, from about 1,000 to about 116,000 ppm total metals, about 20 to about 33 weight percent (wt. %) of water that can have high acidity (e.g. total acid number (TAN)>150), and can have a solids content of from about 0.1 wt. % to about 5 wt. %. The biomass-derived pyrolysis oil may be untreated (e.g. “as produced”). However, if needed the biomass-derived pyrolysis oil can be selectively treated to reduce any or all of the above to a desired level. In an exemplary embodiment, the biomass-derived pyrolysis oil comprises an organic phase (i.e., oil comprising primarily oxygenates and/or hydrocarbons) that has a residual oxygen content of about 30 wt. % or greater, such as from about 30 to about 50 wt. %, for example from about 35 to about 45 wt. % of the organic phase.

The biomass-derived pyrolysis oil can be thermally unstable and may be stored and/or handled so as to reduce its exposure to higher temperatures, minimizing any secondary polymerization reactions of the various components in the biomass-derived pyrolysis oil with themselves prior to hydroprocessing. In an exemplary embodiment, the biomass-derived pyrolysis oil stream20has as an initial temperature (e.g., storage temperature) of about 80° C. or less, such as from about 15 to about 80° C., such as from about 15 to about 50° C., for example about ambient, to minimize secondary polymerization reactions.

As will be discussed in further detail below, a phenolic-rich diluent recycle stream22, which is formed in the separation zone16, is passed along to the reaction zone12. The phenolic-rich diluent recycle stream22is a partially deoxygenated pyoil stream that has been selectively separated to be rich in phenolic compounds and is being recycled. As such, the phenolic-rich diluent recycle stream22has less pyoil reactant components that can form solids by secondary polymerization reactions and is mutually miscible with the biomass-derived pyrolysis oil stream20. In an exemplary embodiment, the phenolic-rich diluent recycle stream22comprises phenolic compounds that are present in an amount of about 50 wt. % or greater, such as about 75 wt. % or greater, for example from about 90 to about 100 wt. % of the phenolic-rich diluent recycle stream22. In another exemplary embodiment, the phenolic compounds comprise phenol, cresol, other alkylphenols, and/or other phenol substituted compounds, such as, for example, various isomers of methylphenol, tert-butylphenol, trimethylphenol, dimethylphenol, dimethoxyphenol, cyclopentylphenol, ethylphenol, ethyl-methylphenol, methoxyphenol, methoxy-propylphenol, methyl-isopropylphenol, propylphenol, methyl-propylphenol, ethyl-methoxyphenol, methoxy-propenylphenol, and/or dimethoxy-propenylphenol.

The reaction zone12comprises a hydroprocessing reactor24. Upstream from the hydroprocessing reactor24, the biomass-derived pyrolysis oil stream20is diluted and heated with the phenolic-rich diluent recycle stream22to form a heated diluted pyoil feed stream26. In one embodiment, the biomass-derived pyrolysis oil stream20is diluted and heated with the phenolic-rich diluent recycle stream22by passing the phenolic-rich diluent recycle stream22through a heater27to form a heated phenolic-rich diluent recycle stream28that is combined with the biomass-derived pyrolysis oil stream20proximate an inlet of the hydroprocessing reactor24. In one example, the heater27heats the phenolic-rich diluent recycle stream22to a temperature of from about 285 to about 425° C. and the heated phenolic-rich diluent recycle stream28is combined with the biomass-derived pyrolysis oil stream20to form the heated diluted pyoil feed stream26having a temperature of from about 260 to about 375° C. In another embodiment, the biomass-derived pyrolysis oil stream20is diluted and heated with the phenolic-rich diluent recycle stream22by combining the biomass-derived pyrolysis oil stream20(advanced along dashed line30) with the phenolic-rich diluent recycle stream22upstream from the heater27to form a combined stream that is passed through the heater27to form the heated diluted pyoil feed stream26. In one example, the combined stream is heated to a temperature of from about 260 to about 375° C. to form the heated diluted pyoil feed stream26.

In an exemplary embodiment, the biomass-derived pyrolysis oil stream20and the phenolic-rich diluent recycle stream22(e.g., the heated phenolic-rich diluent recycle stream28if previously heated by heater27) are combined at a predetermined recycle ratio of from about 3:1 to about 10:1 to form the heated diluted pyoil feed stream26. The predetermined recycle ratio is defined by a mass flow rate of the phenolic-rich diluent recycle stream22to a mass flow rate of the biomass-derived pyrolysis oil stream20.

As illustrated, a hydrogen-containing gas stream32is combined with the phenolic-rich diluent recycle stream22upstream from the heater27so that the heated diluted pyoil feed stream26is formed and introduced to the hydroprocessing reactor24together with the hydrogen-containing gas stream32. Alternatively, the biomass-derived pyrolysis oil stream20may be diluted and heated without the hydrogen-containing gas stream32, and the hydrogen-containing gas stream32can be introduced to the hydroprocessing reactor24separately from the heated diluted pyoil feed stream26.

The heated diluted pyoil feed stream26is directed into the hydroprocessing reactor24. The hydroprocessing reactor24can be a continuous flow reactor, such as a fixed-bed reactor, a continuous stirred tank reactor (CSTR), a trickle bed reactor, an ebullating bed reactor, a slurry reactor, or any other reactor known to those skilled in the art for hydroprocessing.

The hydroprocessing reactor24contains a deoxygenating catalyst in the presence of hydrogen. In an exemplary embodiment, the deoxygenating catalyst comprises a metal or a combination of metals, such as a base metal(s), a refractory metal(s), and/or a noble metal(s), such as platinum, palladium, ruthenium, nickel, molybdenum, tungsten, and/or cobalt. The metal(s) may be on a support, such as a carbon support, a silica support, an alumina support, a silica-alumina support, a gamma alumina support, and/or a titanium support. Other hydroprocessing catalysts known to those skilled in the art may also be used.

The hydroprocessing reactor24is operating at hydroprocessing conditions. In an exemplary embodiment, the hydroprocessing conditions include a reactor temperature of from about 260 to about 375° C., for example from about 270 to about 320° C. (e.g., 280° C.), a reactor pressure of from about 2 to about 20 MPa gauge, a liquid hourly space velocity on a basis of volume of the biomass-derived pyrolysis oil/volume of catalyst/hour (hr−1) of from about 0.5 to about 1 hr−1, and a hydrogen-containing gas treat rate of from about 1,000 to about 15,000 standard cubic feet per barrel (SCF/B).

In an exemplary embodiment, the heated diluted pyoil feed stream26is formed just upstream of the hydroprocessing reactor24and the temperature of the heated diluted pyoil feed stream26is at about the reactor temperature to facilitate rapid catalytic deoxygenation of the heated diluted pyoil feed stream26with a short or minimal residence time. The term “residence time” as used herein is the amount of time from when the biomass-derived pyrolysis oil stream20is diluted and heated with the phenolic-rich diluent recycle stream22to when the heated diluted pyoil feed stream26initially contacts the deoxygenating catalyst. By having a relatively short residence time, less solids can form in the heated diluted pyoil feed stream26at elevated temperatures by secondary polymerization reactions before hydroprocessing begins. In an exemplary embodiment, the residence time is about 60 seconds or less, such as about 20 seconds or less, such as about 10 second or less, for example from about 10 to about 1 seconds.

The heated diluted pyoil feed stream26contacts the deoxygenating catalyst at the hydroprocessing conditions in the presence of hydrogen and forms a low-oxygen biomass-derived pyrolysis oil effluent34by converting a portion of the oxygenated hydrocarbons in the biomass-derived pyrolysis oil into hydrocarbons. In particular, hydrogen from the hydrogen-containing gas stream32removes oxygen from the biomass-derived pyrolysis oil as water to produce the low-oxygen biomass-derived pyrolysis oil effluent34that comprises an aqueous phase and a hydroprocessed organic phase. The hydroprocessed organic phase comprises oil that is deoxygenated with some residual oxygenated hydrocarbons, such as, for example, various phenolic compounds, alcohols, aldehydes, and the like. In an exemplary embodiment, the hydroprocessed organic phase of the low-oxygen biomass-derived pyrolysis oil effluent34has a residual oxygen content of from about 10 to about 20 wt. %, for example from about 10 to about 15 wt. % of the hydroprocessed organic phase.

It is believed that the benefits of catalytically deoxygenating the biomass-derived pyrolysis oil stream20that is diluted and heated with the phenolic-rich diluent recycle stream22may result in increasing hydrogen solubility, immolating the exotherm by dilution of the reactive species in the biomass-derived pyrolysis oil, and reducing the reaction rate of bimolecular reactants that lead to secondary polymerization reactions. As such, simple reactions of the biomass-derived pyrolysis oil with hydrogen to form a lower-oxygen biomass-derived pyrolysis oil dominate while secondary polymerization reactions of biomass-derived pyrolysis oil components with themselves are reduced or minimized, thereby reducing or minimizing the formation of glassy brown polymers or powdery brown char on the deoxygenating catalyst.

In an exemplary embodiment, the low-oxygen biomass-derived pyrolysis oil effluent34is removed from the hydroprocessing reactor24and is introduced to the separation zone14. As illustrated, the separation zone14comprises a cooler36, e.g., chiller, exchanger, or the like, and a separator38, e.g., three-phase separator or the like, that is in fluid communication with the cooler36. The low-oxygen biomass-derived pyrolysis oil effluent34is passed through the cooler36and cooled to form a partially cooled low-oxygen biomass-derived pyrolysis oil effluent40that is introduced to the separator38at first separation conditions. In one embodiment, the partially cooled low-oxygen biomass-derived pyrolysis oil effluent40is at a temperature in which the phenolic compounds in the hydroprocessed organic phase are substantially miscible in the aqueous phase. As used herein, the term “the phenolic compounds are substantially miscible in the aqueous phase” means that the phenolic compounds are capable of being dissolved in the aqueous phase to about 50 wt. % or greater of the aqueous phase at a particular temperature. It has been found that the phenolic compounds, such as phenol, cresol, other alkyl phenol, and other phenol substituted compounds typically form a two-phase mixture with water except at certain temperatures in which the phenolic compounds become miscible with water and form a single phase. As such, a substantial portion of the phenolic compounds in the hydroprocessed organic phase are effectively extracted from the hydroprocessed organic phase into the aqueous phase of the partially cooled low-oxygen biomass-derived pyrolysis oil effluent40. In an exemplary embodiment, the first separation conditions include a temperature of from about 60 to about 150° C.

In an exemplary embodiment, the separator38separates the partially cooled low-oxygen biomass-derived pyrolysis oil effluent40at the first separation conditions into a water-H2gas containing stream42, an aqueous phase stream44, and a low-oxygen-pyoil organic phase stream46. The water-H2gas containing stream42comprises water vapors, unreacted hydrogen, and other residual components, the aqueous phase stream44comprises the aqueous phase including a portion of the phenolic compounds miscible in the aqueous phase, and the low-oxygen-pyoil organic phase stream46comprises the hydroprocessed organic phase less the portion of the phenolic compounds miscible in the aqueous phase.

The water-H2gas containing stream42is passed along to the separation zone18where it is passed through a condenser48and introduced to a separator50, e.g., three-phase separator or the like. In an exemplary embodiment, the condenser48cools the water-H2gas containing stream42to form a cooled water-H2gas containing stream51having a temperature of from about 10 to about 50° C., for example from about 20 to about 30° C. The separator50separates the cooled water-H2gas containing stream51into an aqueous stream52, a hydrogen-containing gas stream54, and a residual low-oxygen-pyoil stream56. The aqueous stream52is removed from the apparatus10for treatment, disposal, or the like, or alternatively, may be recycled with the aqueous phase stream44that is sent to the separation zone16and the water balance maintained using stream78. As illustrated, a portion of the hydrogen-containing gas stream54is used to form a hydrogen-containing recycle gas stream58that is combined with a fresh hydrogen feed60to form the hydrogen-containing gas stream32. The remaining portion of the hydrogen-containing gas stream54may be removed from the apparatus10for use as a fuel product or otherwise. The residual low-oxygen-pyoil stream56may be combined with the low-oxygen-pyoil organic phase stream46from the separation zone14to form a combined low-oxygen-pyoil stream62that is passed through a pump64and removed from the apparatus10for use as a fuel product, or alternatively, may be passed along for additional hydroprocessing to further lower its oxygen content.

In an exemplary embodiment, the aqueous phase stream44is removed from the separation zone14and is passed along to the separation zone16. The separation zone16comprises a cooler66, e.g., chiller, exchanger, or the like, and a separator68, e.g., two-phase separator or the like, that is in fluid communication with the cooler66. The aqueous phase stream44is passed through the cooler66and cooled to form a cooled aqueous phase stream70that is introduced to the separator68at second separation conditions. In particular, the cooled aqueous phase stream70is at a temperature in which the phenolic compounds are substantially immiscible in the aqueous phase. As used herein, the term “the phenolic compounds are substantially immiscible in the aqueous phase” means that the phenolic compounds are not capable of being dissolved in the aqueous phase to about 50 wt. % or greater of the aqueous phase at a particular temperature. As such, a substantial portion of the phenolic compounds in the cooled aqueous phase stream70separate from the aqueous phase, forming two distinct phases, a phenolic-rich phase and a water-rich phase. In an exemplary embodiment, the second separation conditions include a temperature of from about 10 to about 50° C.

In an exemplary embodiment, the separator68separates the cooled aqueous phase stream70at the second separation conditions into the phenolic-rich diluent recycle stream22and a water-rich stream72. The phenolic-rich diluent recycle stream22is passed through a pump74and is directed toward the reaction zone12as discussed above. In an exemplary embodiment, the water-rich stream72is passed through a pump75and a portion76of the water-rich stream72is recycled and combined with the partially cooled low-oxygen biomass-derived pyrolysis oil effluent40to increase the water content in the effluent40, which effectively increases the amount of the phenolic compounds that can be extracted from the hydroprocessed organic phase into the aqueous phase. The remaining portion78of the water-rich stream may be removed from the apparatus10for treatment, disposal, or otherwise to help maintain the water balance in the process.

Accordingly, methods and apparatuses for deoxygenating a biomass-derived pyrolysis oil have been described. The exemplary embodiments taught herein produce a low-oxygen biomass-derived pyrolysis oil effluent by contacting a heated diluted pyoil feed stream with a deoxygenating catalyst in the presence of hydrogen at hydroprocessing conditions to deoxygenate the heated diluted pyoil feed stream. The heated diluted pyoil feed stream is formed by diluting and heating a biomass-derived pyrolysis oil stream with a phenolic-rich diluent recycle stream. The phenolic-rich diluent recycle stream is formed from a portion of the low-oxygen biomass-derived pyrolysis oil effluent that has been selectively separated to be rich in phenolic compounds that are mutually miscible with the biomass-derived pyrolysis oil. It has been found that by contacting the deoxygenating catalyst with the heated diluted pyoil feed stream in the presence of hydrogen at the hydroprocessing conditions, the amount of glassy brown polymer or powdery brown char formed on the deoxygenating catalyst is substantially reduced or minimized relative to conventional methods. Therefore, a low-oxygen biomass-derived pyrolysis oil can be produced in a reactor without plugging the deoxygenating catalyst, thereby increasing run duration and improving processibility of the biomass-derived pyrolysis oil.