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Aqueous stream characterization from biomass fast pyrolysis and catalytic fast pyrolysis Brenna A. Black, William E. Michener, Kelsey J. Ramirez, Mary J. Biddy, Brandon C Knott, Mark William Jarvis, Jessica Olstad, Ofei D. Mante, David C. Dayton, and Gregg T Beckham ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.6b01766 • Publication Date (Web): 05 Sep 2016 Downloaded from http://pubs.acs.org on September 11, 2016

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Aqueous stream characterization from biomass

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fast pyrolysis and catalytic fast pyrolysis

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Brenna A. Black†, William E. Michener†, Kelsey J. Ramirez†, Mary J. Biddy†, Brandon C. Knott†,

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Mark W. Jarvis†, Jessica Olstad†, Ofei D. Mante‡, David C. Dayton‡, and Gregg T. Beckham†, *

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7

Parkway, Golden CO 80401 USA

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9

Park NC 27709 USA

National Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver West

Energy Technologies Division, RTI International, 3040 E. Cornwallis Road, Research Triangle

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*

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Gregg T. Beckham

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Email: [email protected]

Corresponding author footnote:

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Key words

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Pyrolysis, Reforming, Wastewater, Biomass conversion, Biorefinery, Thermochemical

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Conversion

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Abstract

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Biomass pyrolysis offers a promising means to rapidly depolymerize lignocellulosic biomass for

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subsequent catalytic upgrading to renewable fuels. Substantial efforts are currently ongoing to

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optimize pyrolysis processes including various fast pyrolysis and catalytic fast pyrolysis

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schemes. In all cases, complex aqueous streams are generated containing solubilized organic

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compounds that are not converted to target fuels or chemicals, and are often slated for

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wastewater treatment, in turn creating an economic burden on the biorefinery. Valorization of the

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species in these aqueous streams, however, offers significant potential for substantially

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improving the economics and sustainability of thermochemical biorefineries. To that end, here

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we provide a thorough characterization of the aqueous streams from four pilot-scale pyrolysis

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processes: namely, from fast pyrolysis, fast pyrolysis with downstream fractionation, in situ

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catalytic fast pyrolysis, and ex situ catalytic fast pyrolysis. These configurations and processes

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represent characteristic pyrolysis processes undergoing intense development currently. Using a

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comprehensive suite of aqueous-compatible analytical techniques, we quantitatively characterize

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between 12 g kg-1 organic carbon of a highly aqueous catalytic fast pyrolysis stream and up to

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315 g kg-1 organic carbon present in the fast pyrolysis aqueous streams. In all cases, the analysis

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ranges between 75-100% of mass closure. The composition and stream properties closely match

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the nature of pyrolysis processes, with high contents of carbohydrate-derived compounds in the

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fast pyrolysis aqueous phase, high acid content in nearly all streams, and mostly recalcitrant

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phenolics in the heavily deoxygenated ex situ catalytic fast pyrolysis stream. Overall, this work

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provides a detailed compositional analysis of aqueous streams from leading thermochemical

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processes – analyses that are critical for subsequent development of selective valorization

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strategies for these current waste streams.

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Introduction

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Biomass pyrolysis is a promising high-temperature conversion approach to deconstruct

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lignocellulosic substrates to intermediates for upgrading to drop-in hydrocarbon fuels, or

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potentially to aromatic chemicals.1–3 However, multiple challenges remain to fully realize the

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cost-effective potential of biomass pyrolysis at the industrial scale.4,5 As such, multiple process

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configurations are being developed in parallel to address these challenges, which mostly differ in

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the means by which they deal with the pyrolysis products and where and how chemical catalysis

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is applied. In virtually all cases, biomass pyrolysis processes (and other high-temperature

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conversion processes such as hydrothermal liquefaction) reject a fraction of biomass carbon to

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the aqueous phase, creating a potentially costly wastewater treatment burden for thermochemical

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biorefineries. Emerging strategies to upgrade the aqueous fractions originating from

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thermochemical processing include aqueous-phase reforming to produce hydrogen for use in the

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biorefinery, catalytic hydrothermal gasification to produce fuel- or synthesis-gas, or fractionation

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and selective upgrading of components rejected to the aqueous stream.3,6 The two former

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strategies often require a significant process heat burden and the latter potentially costly

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separations depending on the target molecules and intended applications. Regardless, treating the

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aqueous streams as only wastewater represents a potentially significant carbon loss and high

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cost, relative to a potential revenue stream in a more holistic, efficient biorefinery scheme.

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Developing robust strategies to valorize the aqueous fractions from thermochemical processing

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will, however, undoubtedly need to be designed closely with the pyrolysis process scheme, and

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the composition of the aqueous fractions will need to be thoroughly characterized.

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Subsequent to biomass fast pyrolysis (FP), bio-oil can be fractionated via multiple strategies.

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Bio-oil can be partitioned through the addition of water, (mass ratios as high as 9:1 water-to-oil

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have been reported)7 creating a bio-oil and a carbon-rich aqueous phase containing a substantial

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amount of polysaccharide-derived compounds; the organic phase is typically hydrotreated and

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the aqueous fraction slated for wastewater treatment, thus representing a carbon loss for FP

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processes.1,8,10 Past work on characterizing the aqueous fraction produced via FP has utilized gas

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chromatography-flame ionization detection (GC-FID), gas chromatography- mass spectrometry

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(GC-MS), and high performance liquid chromatography (HPLC), where mass and carbon

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closures have generally not exceeded 60 wt%. The most prevalent compounds identified in FP

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aqueous streams are levoglucosan, 1-hydroxypropan-2-one (hydroxyacetone or acetol), acetic

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acid,

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(furfural).7,10–12 Brown et al. developed a strategy to overcome this carbon loss in FP via the use

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of a multistage separation strategy that combines condensers and electrostatic precipitation

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through “stage fractions” to produce up to 5 streams from FP of tunable composition, including

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an aqueous-rich stream with a high content of light oxygenates (Stage Fraction 5, SF5).13

2-hydroxyacetaldehyde,

benzene-1,2-diol

(catechol),

and

furan-2-carbaldehyde

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Conversely to FP, catalytic fast pyrolysis (CFP) has emerged as another promising biomass

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conversion approach. In particular, in situ CFP is conducted by mixing biomass and a catalyst

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together before pyrolysis, and partial deoxygenation occurs via dehydration, decarboxylation,

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and decarbonylation during the thermal deconstruction of biomass. Thus the water yield is

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increased in CFP relative to FP, as a sizable fraction of the biomass carbon can become

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solubilized in the aqueous phase.15 Ex situ CFP, on the other hand, passes pyrolysis vapors over

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metal, or metal free micro- and meso-porous zeolite catalysts for partial deoxygenation, thus

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physically separating the catalyst and solid biomass.15 Chemical characterization of CFP aqueous

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phase is limited, and if available is not detailed adequately for upgrading potential. Paasikallio et

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al. reported the composition of a solvent fractionated in situ CFP process as broad classes of

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compounds, such as “acids, aldehydes, ketones, alcohols, phenols” (11 wt%), and “sugar-type

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compounds” (22 wt%).16

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Each of these described pyrolysis processes are undergoing development at the pilot scale, and

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rigorous techno-economic and life-cycle analyses are being conducted to identify key cost

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drivers in these processes.17,18 In all cases, aqueous streams are produced, which to date have not

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been thoroughly characterized. To that end, here we employ a wide range of analytical methods,

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including aqueous based gel permeation chromatography (GPC), liquid chromatography - mass

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spectrometry (LC-MS), GC-MS, ultimate analysis, elemental analysis, and physicochemical

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measurements to fully characterize the aqueous fractions from five process streams (Figure 1).

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These streams include the aqueous fractions from FP, FP with fractionation from Iowa State

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University (ISU), two in situ CFP streams from RTI International, and one ex situ CFP stream

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from the National Renewable Energy Laboratory (NREL). The results highlight a broad range of

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compositions and chemical functionality with a strong dependence on the pyrolysis process and

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feedstock. Overall, these results will inform the development of selective valorization strategies

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of pyrolysis-derived aqueous streams based on thermal, catalytic, or biological approaches.

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Figure 1. Simplified process flow diagram of FP and CFP tracking aqueous streams collected for

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compositional and chemical characterization.13,19,20

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Materials and Methods

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Vapor phase upgrading system

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To produce the CFPNREL stream, the Vapor Phase Upgrading system was used, which comprises

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two separate units, the pyrolysis reactor and the Davison Circulating Riser (DCR), both of which

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can be operated independently when not integrated (Figure 2). The pyrolysis system consisted of

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a 2” fluidized bed reactor (500°C, 25 psig, 1.5 s) with dual stage cyclonic char removal and hot

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gas filtration (400°C) to provide char free pyrolysis vapor in nitrogen to the DCR (1 kg hr-1

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total). A mixture of hardwood (red and white oak) biomass was fed into the system at a rate of

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1.75 kg hr-1 with 3.5 kg hr-1 of nitrogen for fluidization, for a biomass to nitrogen ratio of 0.5.

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The primary flow of vapors was condensed in a spray tower with dodecane at 25°C and

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separated from the quench fluid in a horizontal phase separator. A slipstream of the hot pyrolysis

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products was monitored via molecular beam mass spectrometry and the permanent gases via

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nondispersive infrared (NDIR) detection (CO2, CO, CH4).

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Catalytic upgrading of the pyrolysis vapor was conducted in the DCR. The DCR was operated

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adiabatically, similar to industrial fluid catalytic cracking (FCC) units. During DCR operation,

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the system was operated at a pressure of 20 psig, a riser temperature of 550°C, and a pyrolysis

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vapor feed rate of 1 kg hr-1. The catalyst circulation rate (the source of heat to the riser) varies to

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maintain the desired target temperatures. Product was removed from the catalyst via stripping

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(500°C, steam rate of 30 ml hr-1). Air was introduced into the regenerator (600°C) for in situ

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catalyst regeneration, and the resulting flue gas was analyzed via NDIR (CO and CO2) to

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determine coke deposition on the catalyst. The post-stripper product stream, which was

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composed of nitrogen, steam, and hydrocarbons, was sent through a reflux condenser that uses a

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countercurrent flow of cold product liquids to scrub the product gases. The condensed product

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was allowed to drain and separates into a hydrocarbon phase and an aqueous phase. Residual

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product gases were analyzed via GC. For the current work, fresh ZSM-5 catalyst (containing

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FCC additive, 1.8 kg) was used to upgrade the pyrolysis vapors, with a catalyst to biomass ratio

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of 12.9. The resulting aqueous phase was collected and analyzed. It is important to note that,

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although the direct relationship was not studied in this work, the process conditions of CFP, such

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as the catalyst to biomass ratio, directly affect the quality and quantity of the aqueous stream,

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which will be reported in a future study.

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Figure 2. Schematic of the integrated pyrolysis and DCR units

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Aqueous phase sample collection

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Production of FP aqueous samples at NREL was conducted in a pilot-scale system by pyrolyzing

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white oak particles (Quercus alba) (Country Boy, Gamaliel, KY) at 500°C in an entrained flow

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reactor with a nitrogen carrier gas, as similar to the setup described previously without hot gas

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filtration.19 The aqueous fraction of the oil was made using a 1 HP high shear lab mixer with a

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3.5 cm dispersing head in batch mixing mode (Model ME 100LC, Charles Ross and Sons Co.,

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Hauggauge, NY). The mixer was operated at 3300 rpm while 200 g min-1 pyrolysis oil was added

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to deionized water for a final ratio of water/oil (2:1, w/w), and mixed for an additional 10 min.

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After allowing the bulk material to phase separate, the upper aqueous phase was decanted,

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collected and characterized.

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The aqueous fraction of fast pyrolysis from ISU was produced using red oak biomass (Quercus

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rubra) (Wood Residual Solutions LLC, Montello, WI), as previously described.13 Briefly, the

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biomass was fed into a fluidized bed pyrolysis reactor (8 kg h-1 process development unit) with a

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five-stage recovery system. The biomass was pyrolized at 500°C and fluidized with nitrogen in

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the reactor prior to stage fractionation. The fifth and final fraction designed to remove water and

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light oxygenate compounds was collected and characterized.

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A pilot-scale, 1 tonne per day, circulating fluidized bed reactor system was used for the CFP of

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both loblolly pine (Pinus taeda) and white oak feedstock by RTI International, as described

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previously.20 Briefly, biomass was continuously fed into an entrained reactor system with

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fluidizing nitrogen, into which, the catalyst was also circulated into the mixing zone and

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pyrolysis reactions occurred between approximately 450-500°C, 20-30 psi at a residence time of

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0.5 – 1 min. Aqueous products were collected after condensation of pyrolysis vapors in the

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quench system. The quench products were allowed to settle and phase separate over time, after

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which the aqueous phase was collected and characterized.

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The ultimate and proximate compositional analyses of all woody feedstocks used in this study

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are presented in Table 1. All samples have lower ash contents and the compositions are typical

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to that of woody biomass.21

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Table 1. Biomass composition in dry weight basis (wt%) Fast Pyrolysis Catalytic Fast Pyrolysis CFPRTI-pine18 CFPRTI-oak CFP NREL-oak FPNREL-oak17 SF5ISU-oak11 Properties ex-situ in-situ in-situ 48.6 46.4 49.7 46.0 48.7 Carbon 5.1 6.4 6.6 6.0 6.6 Hydrogen 0.1 0.1 0.1 0.5 0.5 Nitrogen 39.9 46.8 43.3 47.0 44.2 Oxygen* 5.8 4.8 3.6 10.6 10.1 Moisture** 0.5 0.3 0.4 0.6 0.4 Ash 79.1 NR 88.6 82.5 82.8 Volatile carbon 14.6 NR 11.0 17.2 16.8 Fixed carbon *Calculated by difference of CHN and ash; **as received; NR = not reported

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Compositional analysis

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Approximately 30 mg aliquots of aqueous fractions were analyzed for water content using Karl

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Fisher titration according to the standard ASTM E203-08. The analysis was performed using a

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Metrome 701 Titrino titration system using methanol as a solvent and Hydranal®-Composite 5

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reagent (Sigma Aldrich, St. Louis, MO) as the titrant, which was standardized against a National

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Institute of Standards and Technology traceable water standard prior to titration. TOC analysis

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was measured by a Shimadzu TOC-LCSH analyzer (Shimadzu, Columbia, MD) via a combustion

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catalytic oxidation method after sample acidification by concentrated hydrochloric acid. COD

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measurements were performed following a digestion with the addition of an acidified dichromate

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solution (Hach COD Digestion Vials, high range) for two hours at 150°C. The resulting material

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was measured for the reduction of the dichromate ion (Cr2O72-) into a green chromic ion (Cr3+) at

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620 nm using a DR600 Benchtop spectrometer (Hach, Loveland, CO). Ultimate analysis was

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performed via high temperature combustion using a LECO TruSpec module (LECO Corp., St.

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Joseph, MI) for carbon, hydrogen, and nitrogen with oxygen by difference. Approximately 100

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mg of each sample was combusted at 950°C under a flow of oxygen for 200 sec. The gas

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produced during combustion was collected and analyzed using infrared spectroscopy to calculate

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hydrogen and carbon content. After which, the gas was scrubbed and reduced to calculate

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nitrogen via the change in thermal conductivity. Ethylenediaminetetraacetic acid (EDTA) was

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used as standard for CHN determination and to assess drift. Inductively coupled plasma atomic

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emission spectroscopy (ICP-AES) was performed following a concentrated nitric acid digestion

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of samples at a concentration of 0.05 g mL-1 with a microwave oven temperature gradient of

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23°C to 150°C over 10 min and then held constant at 150°C for an additional 10 min. Aluminum

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(Al), calcium (Ca), chromium (Cr), copper (Cu), iron (Fe), potassium (K), magnesium (Mg),

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manages (Mn), sodium (Na), nickel (Ni), phosphorus (P), sulfur (S), and zinc (Zn) measurements

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were performed using a Spectro Arcos ICP analyzer monitoring elemental emission lines in the

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range of 130 to 773 nm (Spectro Analytical Instruments Inc., Kleve, Germany). All lines were

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acquired at 1425 W plasma. The instrument was calibrated with commercial standards and

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samples were run in nine independent measurements (n=9). Determination of carbonyl groups

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was done using potentiometric titration with triethanolamine using 0.1 g sample, as outlined

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previously.22 Total acid number (TAN) was determined similarly to an adjusted solvent method23

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from that of ASTM D664, using a Metrohm 842 Titrando automatic titrator (Metrohm,

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Riverview, FL) for potentiometric titrations. A 4:1 ethanol/water (v/v) solution was added at 40

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mL to each 0.5 – 0.8 g aqueous sample and titrated to a pH of 13 with standardized 50 mM

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sodium hydroxide in water. The sodium hydroxide solution was standardized with potassium

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hydrogen phthalate, and carboxylic acids of known concentration were used to ensure validity of

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the method. Compositional evaluation of pyrolysis aqueous streams was measured in triplicate

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analysis unless otherwise stated.

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Aqueous gel permeation chromatography analysis

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Molecular weight distribution was performed using an HPLC Agilent 1260 Infinity series,

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including a refractive index detector (RID) (Agilent Technologies, Santa Clara, CA). Samples

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were injected at a 10-fold dilution at 20 µL onto a TSKgel Alpha column (7 µm, 7.8 mm i.d. ×

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300 mm). Analytes were separated using an isocratic flow of 40 mM LiBr in water/methanol

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(1:1, v/v) at a flow rate of 0.5 mL min-1. A temperature of 55°C was maintained for both the

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column and the RID. Data from the RID was processed using Cirrus GPC software version 3.4.1

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(Agilent Technologies, Santa Clara, CA). The software was calibrated using 8K and 3K

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polyethylene glycol standards, as well as acetic acid, glucose, xylobiose, xylotriose, and

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xylotetraose. Masses were also confirmed by coupling the GPC chromatography to an Ion Trap

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mass spectrometer monitoring masses between 40 – 2200 Da with mass parameters as described

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subsequently.

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High resolution infusion-tandem mass spectral analysis

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Infusion-mass analysis was performed for initial identification of residual water-soluble analytes.

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Samples were diluted 1000-fold in a solvent mixture of methanol/isopropyl alcohol (3:1, v/v);

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additionally, to ensure the ionization of analytes, a modifier of either 25 mM ammonium

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hydroxide or 4 mM ammonium formate was added to each mixture. Sample solutions were

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directly infused at 10 µL min-1 into a Waters Micromass Q-Tof micro™ with MassLynx™ V4.1

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software (Waters Corp., Milford, MA). External and internal calibration of the mass analyzer

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was implemented to provide a mass measurement accuracy of less than five parts-per-million

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facilitating elemental composition assignment. To ensure mass accuracy of the mass

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spectrometer, a LockSpray™ interface was used to infuse a concentration of 20 pmol µL-1

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glucose in methanol/water (1:1, v/v) with either 4 mM ammonium acetate (negative-ion mode)

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or sodium chloride (positive-ion mode) was infused at a flow rate of 0.2 µL min-1. The frequency

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of the LockSpray™ was set at 10 sec and averaged over 10 spectra to provide an in-line

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correction factor.

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Positive- and negative-ion ESI/MS and tandem mass spectrometry (MS/MS) in centroid data

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collection mode was performed. For both ion modes, the nebulization gas was set to 550 L h-1 at

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a temperature of 250°C, the cone gas was set to 10 L h-1 and the source temperature was set to

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110°C. For negative-ion mode, the capillary and cone voltages were set to 2650 V and 25 V,

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respectively and for positive-ion mode the capillary voltage was 3000 V and the cone voltage

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was 35 V. For MS experiments, data were collected between m/z 20-1500 with collision energy

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of 8 eV and an acquisition rate of 0.4 sec spectrum-1. MS/MS experiments were performed by

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increasing the collision energy to 15-45 eV, specific to each analyte.

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Liquid chromatography quantitative analysis

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Sugars were separated and quantified using a Waters Acquity ultra performance liquid

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chromatography (UPLC) system coupled to an evaporative light scattering detector (ELSD) and

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a Waters Micromass Q-Tof micro™ mass spectrometer (Waters Corp., Milford, MA). A Shodex

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Sugar SZ5532, 6 mm i.d. × 150 mm column (Showa Denko America Inc., New York, NY) was

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used at 65°C and a flow rate of 0.9 mL min-1 with a gradient of A) water and B) acetonitrile:

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starting with 20 % A; 9 min, 17% A; 25 min, 30% A; and lastly, 40 min, 40% A for a total run

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time of 45 min. Sugars were monitored post-column, with the eluent flow split (2:1, v/v) to the

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ELSD and the MS. Sugars were identified by positive-ion ESI/MS aided with a source

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temperature of 100°C, a capillary voltage of 3000 V with a nebulization gas of 550 L h-1 at a

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temperature of 250°C, and a cone gas and voltage of 10 L h-1 and 25 V, respectively.

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Organic acids, select aldehydes, and select aldehydes were quantified via an Agilent 1100 HPLC

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system fitted with a RID and a diode array (DAD) (Agilent Technologies, Santa Clara, CA).

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Analytes were separated using an Aminex HPX-87H 9 µm, 7.8 mm i.d. × 300 mm column (Bio-

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Rad Laboratories, Hercules, CA) using an isocratic mobile phase of 5 mM H2SO4 at a flow rate

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of 0.6 mL min-1. Column and detector temperatures were maintained at 55°C.

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Analysis of phenolic, aromatic, nitrogen-containing and larger molecular mass ketone

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compounds was performed on an Agilent 1100 HPLC system equipped with a DAD and an Ion

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Trap SL (Agilent Technologies, Santa Clara, CA) MS with in-line ESI. Each sample was

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injected undiluted at a volume of 50 µL into the LC/MS system. Compounds were separated

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using an YMC C30 Carotenoid 0.3 µm, 4.6 mm i.d. × 150 mm column (YMC America,

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Allentown, PA) at an oven temperature of 30°C. The chromatographic eluents consisted of A)

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water modified with 0.03% formic acid, and B) acetonitrile/water (9:1, v/v) also modified with

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0.03% formic acid. At a flow rate of 0.7 mL min-1, the eluent gradient was as follows: 0-3 min,

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0% B; 16 min, 7% B; 21 min, 8.5% B; 34 min, 10% B; 46 min, 25% B; 51-54 min, 30% B; 61

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min, 50% B; and lastly 64-75 min, 100% B before equilibrium. Flow from the HPLC-DAD was

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directly routed in series to the ESI-MS ion trap. The DAD was used to monitor chromatography

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at 210 and 264 nm for a direct comparison to MS data. MS and MS/MS parameters are as

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follows: smart parameter setting with target mass set to 165 Da, compound stability 70%, trap

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drive 50%, capillary at 3500 V, fragmentation amplitude of 0.75 V with a 30 to 200 % ramped

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voltage implemented for 50 msec, and an isolation width of m/z 2 (He collision gas). The ESI

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nebulizer gas was set to 60 psi, with dry gas flow of 11 L min-1 held at 350°C. Into each sample

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and standard mixture, 0.01 g L-1 3,4-dihydroxybenzaldehyde (97% purity, Sigma Aldrich, St.

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Louis, MO) was added to adjust for chromatographic shift and detector response. MS scans and

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precursor isolation-fragmentation scans were performed across the range of 40-750 Da. All LC

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quantitative analysis was performed in triplicate independent experiments (n=3) and all

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quantitative standard curves were maintained with an R2 value of ≥ 0.995 with five or more

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points of reference ranging between concentrations of 1 to 100 µg mL-1. Authentic standards

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were obtained for quantitation in the highest purity available as listed in Table S3. Samples were

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diluted with methanol accordingly to fit within the linear regions of the calibration curves. LC-

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DAD/MS was also used to confirm the quantitation of many organic acids, sugars, furfural, and

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5-hydroxymethylfurfural as indicated in Table S2.

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Gas chromatography quantitative analysis

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The aqueous fractions were diluted in methanol to fit within the linear range of calibration curves

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prior to analysis by GC-MS for select ketone, aldehyde, and alcohol compounds. An Agilent

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6890N gas chromatograph and Agilent 5973N mass-selective detector (Agilent Technologies,

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Santa Clara, CA) was used for the identification of analytes. Using a splitless injection, 1 µL

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sample volume was introduced onto a 30 m × 0.25 mm i.d., 0.25 µm film thickness DB-Wax

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capillary column (J & W Scientific Inc., Folsom, CA) at 260°C. The helium flow was kept

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constant at 1 ml min-1 with an oven program as follows: the initial column temperature of 35°C

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was held for 3 min and then increased to 225°C at 5°C min-1 with a hold time of 1 min, and

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lastly, to 250°C at 15°C min-1 with a hold time of 5 min. Electron impact ionization was used at

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70 eV electron energy and a mass scan range of m/z 25 – 450. An internal standard of 1,2-

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diphenylbenzene (99.9+% purity, AccuStandard, New Haven, CT) was added to all standards

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and samples at a concentration of 0.05 g L-1 to adjust for any detector response shift. An Agilent

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Environmental ChemStation G1701DA version D.00.00.38 and NIST 2011 library was used for

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data analysis. All gas chromatography quantitative analysis was performed in triplicate

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independent experiments (n=3) and all quantitative standard curves ranged between 1 to 100 µg

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mL-1 with no less than four points of reference and were maintained with a high correlations of

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an R2 value of ≥0.995 Extracted ions specific to each analyte were used as quantitation markers

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as presented in Table S2; additionally, GC-MS was used to confirm the quantitation of many

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aldehydes, organic acids and aromatic compounds from LC analysis. Authentic standards were

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obtained for quantitation in the highest purity available as listed in Table S3.

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Results

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Efforts to characterize the organic matter from lignocellulosic biomass pyrolysis aqueous

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streams focused on compositional and chemical characterization. Analysis was performed on the

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aqueous fractions of FP processes from NREL (FPNREL) and Stage Fraction 5 from ISU (SF5ISU),

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in addition to the aqueous fractions of CFP processes from NREL (CFPNREL ex situ), and RTI

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International (CFPRTI-pine and CFPRTI-oak in situ). Samples from these streams are shown in Figure

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3.

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Figure 3. Aqueous FP and CFP streams studied in this work (from left) CFPNREL, CFPRTI-oak,

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CFPRTI-pine, SF5ISU, and FPNREL.

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Compositional characterization

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The physicochemical properties of the five aqueous streams are presented in Table 2 (with

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deviations presented in Table S1). Unsurprisingly, given the differences in pyrolysis conditions

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and configurations, each process notably produced compositionally distinct fractions, further

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altered by feedstock selection, as seen between the RTI hardwood and softwood aqueous

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streams. The water content ranged from 60 to 98 wt% between aqueous samples, indicating a

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considerable amount of organic and inorganic matter remaining in select aqueous fractions.

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Table 3 provides the inorganic composition of individual elements of the aqueous fractions

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measured on a dry weight basis. The total inorganics (wet weight basis) were 0.01 wt% FPNREL,

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0.01 wt% SF5ISU, 0.07 wt% CFPNREL, 0.01 wt% CFPRTI-pine, and 0.02 wt% CFPRTI-oak. The

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inorganic content of CFPNREL was likely high due to recent reactor commissioning, and a

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reduction will be examined in further experiments. The inorganic composition accounted for a

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minor fraction of the non-aqueous matter from the pyrolysis aqueous streams. The total organic

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carbon (TOC) was measured to estimate organic matter content of each sample. Organic matter

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was determined using a conversion factor of 2.5, which was selected due to the low organic

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carbon content of the aqueous streams.24 Table 2. Physicochemical properties of pyrolysis aqueous streams Fast Pyrolysis Catalytic Fast Pyrolysis CFPNREL CFPRTI-pine CFPRTI-oak FPNREL SF5ISU ex-situ in-situ in-situ 80.6 59.6 97.5 86.4 93.9 Water (wt%) a 39.7 40.1 24.8 40.0 32.9 TOC (wt%) 105.1 188.3 105.1 87.0 24.3 TAN (mg NaOH g-1)a 5.9 9.6 42.8 12.0 5.5 Carbonyl (mmole g-1)a -1 a 765 808 1255 801 810 COD (mg g ) 2.3 2.1 1.6 2.8 5.3 pH a presented on a dry weight basis

354 Table 3. ICP-AES elemental analysis of pyrolysis aqueous streams presented in parts per million (ppm) on a dry weight basis Fast Pyrolysis Catalytic Fast Pyrolysis Element CFPRTI-pine CFPRTI-oak CFPNREL FPNREL SF5ISU (ppm) ex-situ in-situ in-situ 28.3 12.8 2887.0 76.1 94.1 Al 134.6 17.9 716.6 77.6 232.2 Ca