Name: qualitative characterization of the aqueous fraction from hydrothermal liquefaction of algae using 2d gas chromatography with time-of-flight mass spectrometry
Uploaded: 2016-03-06T15:00:00
Description: Watch this Scientific Journal Video about Qualitative Characterization of the Aqueous Fraction from Hydrothermal Liquefaction of Algae Using 2D Gas Chromatography with Time-of-flight Mass Spectrometry

This manuscript has been authored by Battelle Memorial Institute under Contract No. DE-AC05-76RL01830 with the U.S. Department of Energy. The U.S Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. Government purposes.

1. Sample Preparation
<ol>
	<li>Generate a mixed aqueous/organic product stream via continuous flow HTL of algae according to the reactor design and experimental procedure found in the literature10,11.</li>
	<li>Use a gravity separator to separate the product stream into an aqueous phase and organic phase.</li>
	<li>Filter 10 ml of the HTL aqueous phase using a 0.45 &#181;m syringe filter and store in a refrigerator maintained at 4 &#176;C for GC &#215; GC&#8211;TOF-MS analysis.</li>
</ol>
<p class="jove_tit...

Results clearly illustrate the ability of the column combination of polar &#215; non-polar to resolve polar compounds and light volatiles present in the aqueous fraction of algae bio-crude without prior sample preparation techniques. Drastic peak tailing was observed for organic acids and N-compounds while using the non-polar&#215; polar column combination. This peak tailing was not observed for the early eluting light organics. This behavior has been reproducible when verifying the instrument is free of leaks (the vacuu...

Steady growth in demand for liquid fuels, finite fossil fuel resources, uncertainty of fossil fuel supplies, and concerns over the increasing concentration of greenhouse gases in the atmosphere have increased global awareness for renewable resources1. Solar energy (including photovoltaics and solar-thermal), wind energy, hydropower, geothermal, and biomass are the primary renewable sources that could potentially replace fossil-derived energy2. Of these, biomass is the only carbon-based alternative energy resource for the production of liquid transportation fuels and high-value chemicals3. Biomass includes any organic material such as forest resources, agricultural residue, algae, oilseeds, municipal solid waste, and carbon-rich industrial wastes (e.g. from pulp and paper industry or from food processing)1. Biomass is classified into two broad categories: lignocellulosic and non-ligneous feedstocks based on compositional characteristics. Lignocellulosic biomass consists of carbohydrates and lignin, while non-ligneous feedstocks have proteins, carbohydrates and lipids/oils4. Lignocellulosic feedstocks, derived from terrestrial plants, can only satisfy 30% of the current liquid fuel (gasoline, jet fuel, and diesel) demand if sustainably cultivated and harvested5,6. Hence, non-ligneous aquatic microorganisms, such as microalgae and fungi, are considered potential feedstocks for the production of renewable liquid fuels to complement lignocellulosic resources.
Microalgae feedstocks have the potential to satisfy current liquid transportation fuels demand7,8. Algae have many advantages: high areal productivity8, the ability to grow in low-quality, brackish, or sea water9, and the ability to accumulate energy-dense triglycerides or hydrocarbons7,8. Hydrothermal liquefaction (HTL) is a viable and scalable conversion process which utilizes water naturally associated with algal or aquatic feedstocks10,11. It is a thermo-chemical process with operating temperatures of 250-400 &#176;C and operating pressures of 10-25 MPa which produces a liquid product, or bio-crude, which can be upgraded into a fuel blend stock. Bio-crude produced from HTL of algae has distinguishable and easily separable organic and aqueous fractions. The organic fraction of bio-crude can be efficiently converted into a refinery ready blend stock via catalytic hydro-treating processes11. The aqueous fraction of bio-crude contains ~30% of the total carbon present in the algal feedstock. Although thousands of compounds have been identified in the HTL aqueous stream, the predominant fractions consist of low molecular weight oxygenates (including acids, alcohols, ketones, and aldehydes) formed by the degradation of carbohydrates and lipids, and nitrogen heterocyclics (including pyrroles, pyridines, pyrazines, and imidazoles) derived from protein decomposition12. Studies on utilizing the aqueous fraction to improve overall process economics as well as sustainability are ongoing. Synthesis gas can be produced from the aqueous fraction of algae bio-crude via catalytic hydrothermal gasification10,13,14. Alternatively, organics in the aqueous fraction can also be catalytically converted to fuel additives and specialty chemicals. Research on optimizing catalytic hydrothermal gasification and catalyst screening studies for conversion of organics in the aqueous liquid phase is currently underway at the Pacific Northwest National Laboratory (PNNL). For this work, qualitative as well as quantitative characterization of the aqueous fraction of algae bio-crude is required. Since the aqueous fraction of algae bio-crude is considered a waste stream, there are very few studies that have analyzed the aqueous fraction of algae bio-crude13,15. Moreover, recent studies concluded that converting this HTL algae water into high-value bio-products would improve the sustainability as well as economics of an HTL-based bio-refinery11. Therefore, this study focused on developing a method for qualitative characterization of the aqueous fraction of bio-crude obtained from HTL of algae by two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC &#215; GC&#8211;TOF-MS).
GC &#215; GC&#8211;TOF-MS is the most promising chromatographic analytical technique to increase resolution (or separation of chemical compounds in a sample), peak capacity (i.e. number of resolved peaks), signal-to-noise ratio (for identification of chemical compounds with high confidence), and to avoid co-elution of chemical compounds16. In order to maximize resolution, peak capacity, and signal-to noise ratio, two GC columns with different stationary phases are connected in series using a press-fit connector or micro-union17(see Figure 1 which is a block diagram of GC &#215; GC&#8211;TOF-MS system used in this study). A modulator is located between the press-fit connector and secondary columns to trap, refocus, and re-inject the effluents from the primary column into the secondary column18. Modulation occurs on the secondary column in the present study as shown in Figure 1. The secondary column is then connected to the TOF-MS via a transfer line assembly.
GC &#215; GC&#8211;TOF-MS was used previously for qualitative as well as quantitative analysis of organic samples such as crude oil16,19, gasoline, jet-fuel, diesel, bio-diesel, and the organic fraction of bio-fuel20-22 produced from thermo-chemical as well as thermo-catalytic conversion processes23,24. For characterization of these organic samples in GC &#215; GC&#8211;TOF-MS instruments, a long non-polar column was used as the primary column, while a short polar column was used as the secondary column. This conventional column configuration resolves chemical compounds based on differences in volatility over the first dimension, followed by polarity in the second dimension18. Aqueous or water samples from biological processes, food processing, and environmental wastes were also characterized using similar primary/secondary column configurations after the sample had been through preparation steps17,25-30. Sample preparation techniques such as derivatization, solid-phase extraction, and organic solvent extraction have all been utilized prior to GC &#215; GC&#8211;TOF-MS analysis17,27-29,31,32. These techniques were aimed at decreasing the polarity of compounds in the sample for analysis using a conventional column configuration33. An alternative strategy was employed in this study based on the nature of the sample (here polar organic compounds in water) utilizing the reverse primary/secondary column configuration for GC &#215; GC&#8211;TOF-MS analysis. Since the aqueous fraction of bio-crude produced from HTL has polar compounds13, a column combination of a primary polar column and a secondary non-polar column was used in the GC &#215; GC&#8211;TOF-MS without any upstream sample preparation. This primary/secondary column combination resolves chemical compounds based on differences in polarity over the first dimension, followed by volatility in the second dimension. Limited analytical methods exist in the literature for characterization of aqueous samples using two-dimensional gas chromatography without prior sample processing15.
The objective of this study was to determine the chemical compounds present in the aqueous fraction of algae bio-crude. To achieve this objective, a GC &#215; GC&#8211;TOF-MS data acquisition method was developed with a column combination of polar column (primary) &#215; non-polar (secondary). Klenn et al. (2015) suggested that increasing the length of the primary column (especially 60 m GC columns) and lowering the offset temperature of the secondary column with respect to the primary column would maximize peak capacity and resolution16-18. Therefore, a 60 m primary column and 5 &#176;C offset temperature of the secondary column with respect to the primary column were used in this study. The optimum modulation period was determined following a protocol described in this study (see section 4). The optimum ramp rate of GC column temperature was determined by a trial and error method and is similar to the value suggested in the literature16-18. To discuss the advantages of this column combination for aqueous samples, we have analyzed HTL algae water samples with the conventional column combination of non-polar &#215; polar. Operating parameters suggested in the literature were employed for analyzing the aqueous fraction of algal bio-crude with a non-polar &#215; polar column combination18.

<table border="0" cellpadding="0" cellspacing="0" width="867">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">GC &#215; GC - TOF/MS</td>
			<td style="width:199px;">Leco</td>
			<td style="width:151px;">PEG4D11DLN15</td>
			<td style="width:268px;">Commercial Pegasus 4D</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">ChromaTOF version 4.50&#160;</td>
			<td style="width:199px;">Leco</td>
			<td style="width:151px;"></td>
			<td style="width:268px;">Data analysis software</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Rxi-5MS GC column</td>
			<td style="width:199px;">Restek</td>
			<td style="width:151px;">13420</td>
			<td style="width:268px;">2.3 m column was used from this column.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Stabilwax GC column</td>
			<td style="width:199px;">Restek</td>
			<td style="width:151px;">10626</td>
			<td style="width:268px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">HP-5 GC column</td>
			<td style="width:199px;">Agilent</td>
			<td style="width:151px;">19091J-416</td>
			<td style="width:268px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Stabilwax GC column</td>
			<td style="width:199px;">Restek</td>
			<td style="width:151px;">15121</td>
			<td style="width:268px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Presstight Connector</td>
			<td style="width:199px;">Restek</td>
			<td style="width:151px;">20430</td>
			<td style="width:268px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">GC injector liner</td>
			<td style="width:199px;">Restek</td>
			<td style="width:151px;">23305.5</td>
			<td style="width:268px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">GC Injector ferrules</td>
			<td style="width:199px;">Agilent</td>
			<td style="width:151px;">5181-3323</td>
			<td style="width:268px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Non-stick liner O-rings</td>
			<td style="width:199px;">Agilent</td>
			<td style="width:151px;">5188-5365</td>
			<td style="width:268px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Transfer line ferrules</td>
			<td style="width:199px;">Restek</td>
			<td style="width:151px;">20212</td>
			<td style="width:268px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Ethanol</td>
			<td style="width:199px;">Sigma-Aldrich</td>
			<td style="width:151px;">459844</td>
			<td style="width:268px;">Chromatography grade</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Acetone</td>
			<td style="width:199px;">Sigma-Aldrich</td>
			<td style="width:151px;">414689</td>
			<td style="width:268px;">Chromatography grade</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Acetic acid</td>
			<td style="width:199px;">Sigma-Aldrich</td>
			<td style="width:151px;">320099</td>
			<td style="width:268px;">Chromatography grade</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">2-butanone</td>
			<td style="width:199px;">Sigma-Aldrich</td>
			<td style="width:151px;">360473</td>
			<td style="width:268px;">Chromatography grade</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Propanoic acid</td>
			<td style="width:199px;">Sigma-Aldrich</td>
			<td style="width:151px;">402907</td>
			<td style="width:268px;">Chromatography grade</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Butanoic acid</td>
			<td style="width:199px;">Sigma-Aldrich</td>
			<td style="width:151px;">19215</td>
			<td style="width:268px;">Chromatography grade</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Pyridine</td>
			<td style="width:199px;">Sigma-Aldrich</td>
			<td style="width:151px;">270970</td>
			<td style="width:268px;">Chromatography grade</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Pyrazine</td>
			<td style="width:199px;">Sigma-Aldrich</td>
			<td style="width:151px;">65693</td>
			<td style="width:268px;">Chromatography grade</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Acetamide</td>
			<td style="width:199px;">Sigma-Aldrich</td>
			<td style="width:151px;">695122</td>
			<td style="width:268px;">Chromatography grade</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">2,5-pyrrolididione</td>
			<td style="width:199px;">Sigma-Aldrich</td>
			<td style="width:151px;">S9381</td>
			<td style="width:268px;">Chromatography grade</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">N-methylsuccinimide</td>
			<td style="width:199px;">Sigma-Aldrich</td>
			<td style="width:151px;">325384</td>
			<td style="width:268px;">Chromatography grade</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:249px;">N-(2-hydroxyethyl)succinimide</td>
			<td style="width:199px;">Sigma-Aldrich</td>
			<td style="width:151px;">444073</td>
			<td style="width:268px;">Chromatography grade</td>
		</tr>
	</tbody>
</table>

qualitative characterization of the aqueous fraction from hydrothermal liquefaction of algae using 2d gas chromatography with time-of-flight mass spectrometry

Two-dimensional gas chromatography coupled with time-of-flight mass spectrometry is a powerful tool for identifying and quantifying chemical components in complex mixtures. It is often used to analyze gasoline, jet fuel, diesel, bio-diesel and the organic fraction of bio-crude/bio-oil. In most of those analyses, the first dimension of separation is non-polar, followed by a polar separation. The aqueous fractions of bio-crude and other aqueous samples from biofuels production have been examined with similar column combinations. However, sample preparation techniques such as derivatization, solvent extraction, and solid-phase extraction were necessary prior to analysis. In this study, aqueous fractions obtained from the hydrothermal liquefaction of algae were characterized by two-dimensional gas chromatography coupled with time-of-flight mass spectrometry without prior sample preparation techniques using a polar separation in the first dimension followed by a non-polar separation in the second. Two-dimensional plots from this analysis were compared with those obtained from the more traditional column configuration. Results from qualitative characterization of the aqueous fractions of algal bio-crude are discussed in detail. The advantages of using a polar separation followed by a non-polar separation for characterization of organics in aqueous samples by two-dimensional gas chromatography coupled with time-of-flight mass spectrometry are highlighted.

A total ion chromatogram (TIC) obtained for the aqueous fraction of algae bio-crude analyzed with a column combination of polar &#215; non-polar is shown in Figure 4. Retention times and similarity or match factor values of compounds identified by searching against a National Institute of Standards and Technology (NIST) library are tabulated in Table 1. Oxygenates (such as cyclopenatanone, furanic compounds and dianhydromannitol) and organic acids (includ...

Watch this Scientific Journal Video about Qualitative Characterization of the Aqueous Fraction from Hydrothermal Liquefaction of Algae Using 2D Gas Chromatography with Time-of-flight Mass Spectrometry

Qualitative Characterization of the Aqueous Fraction from Hydrothermal Liquefaction of Algae Using 2D Gas Chromatography with Time-of-flight Mass Spectrometry

A two-dimensional gas chromatography-time-of-flight mass spectrometry method is described for characterization of the aqueous fraction of bio-crude produced from hydrothermal liquefaction of algae. This protocol can also be employed to analyze the aqueous fraction of liquid products from fast pyrolysis, catalytic fast pyrolysis, catalytic deoxygenation and hydro-treating.

Two-dimensional gas chromatography coupled with time-of-flight mass spectrometry is a powerful tool for identifying and quantifying chemical components in ...

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