Pyrolysis of Residual Tobacco Seeds: Characterization of Nitrogen

Aug 24, 2017 - Biomass is a generic term used for all material derived from plants or animals and that can be suitable as an alternative to convention...
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Pyrolysis of Residual Tobacco Seeds: Characterization of Nitrogen Compounds in Bio-oil Using Comprehensive Two-Dimensional Gas Chromatography with Mass Spectrometry Detection Bruna Onorevoli,† Maria E. Machado,‡ Allan dos S. Polidoro,† Valeriano A. Corbelini,§,† Elina B. Caramaõ ,‡,∥ and Rosângela A. Jacques*,†,∥ †

Instituto de Química, UFRGS, Porto Alegre, RS, Brasil Departamento de Biotecnologia, UNIT, ITP, Aracaju, SE, Brasil § Instituto de Química, UNISC, Santa Cruz do Sul, RS, Brasil ∥ INCT-EA, Bahia, Brasil ‡

S Supporting Information *

ABSTRACT: Energetic tobacco (EnT) is a type of genetically modified tobacco with a focus on energy. Its seeds are larger and appear in greater quantity than those of conventional tobacco. This plant easily adapts to unproductive soils and is practically free of nicotine. The oil seed from EnT can be used for producing biodiesel without competition with edible oils. Additionally, the resulting residual cake can be thermally degraded to bio-oil and biochar through pyrolysis processes. In this study, the fast pyrolysis (700 °C at 100 °C min−1) of the residual cake of EnT seeds was performed in a fixed bed reactor (quartz), yielding approximately 40% (in mass) liquid products (bio-oil and an aqueous phase). After removal of the aqueous phase, the organic phase was submitted to an acid−alkaline extraction of the N-compounds in a simple and efficient way. The bio-oil and alkaline extract were analyzed by comprehensive two-dimensional gas chromatography coupled to fast-quadrupole mass spectrometry. Compounds were tentatively identified by similarity with a commercial library of mass spectra and using retention indexes. The main classes of compounds identified were phenols, hydrocarbons, and N-compounds (imidazole, pyridine, and their derivatives), with the potential to be applied in the chemical and pharmaceutical industries as well as biofuel production. The alkaline extraction resulted in the isolation of the main N-components, a finding fundamental for the utilization of these compounds for the production of pharmaceuticals, pesticides, and polymers.

1. INTRODUCTION

Energetic tobacco is a variety of Solaris tobacco, developed in Italy. It is a type of genetically modified tobacco that has very low levels of nicotine and is useful for energy purposes.6,7 The oil is extracted from its seeds, which are larger and appear in greater quantity than those of conventional tobacco. Its use was started in Italy in 1990 at the Plantechno Company for the purpose of producing oil for biodiesel or biokerosene production and the residual extraction cake for animal feed. The crop has been recently started in the city of Santa Cruz do Sul (UNISC) in Brazil with the aim of planting it in the ground where previously there was tobacco production (used in the production of cigarettes).8 Studies done to date have been aimed at the production of oil from the energetic tobacco seeds.8 In this process, a residue called “residual cake” is generated, which represents a substantial volume and does not have an appropriate destination. In view of the current call for use of renewable energy, an alternative for residual cake can be its use as a source of biomass in the pyrolysis process, in order to obtain higher added value products. There are very few studies on energy tobacco because research on it has just

Biomass is a generic term used for all material derived from plants or animals and that can be suitable as an alternative to conventional fossil fuels. Over the last two decades, special attention has been given to the conversion of residual biomass and other renewable materials into bio-oil via pyrolysis.1,2 Biooil is a very complex mixture containing many organic compounds originating from the degradation of cellulose, hemicellulose, lignin, and other biomolecules in biomass.3 Most of the available biomasses are residues from important agricultural commodities, mainly for nonfood applications, and some new technological, economic, and ecological advances have been undertaken in this field. An important biomass residual is tobacco seed (Nicotiana tabacum), a well-studied plant that has leaves that are used to produce cigarettes and cigars. This plant is not suitable as a human food, and its production has been questioned for its environmental impact (soil contamination) and health hazards. Tobacco grows on nutrient-poor soil. Because of the intense use of agrotoxics in this crop, this soil presents low levels of organic matter and has significant levels of pesticides and herbicides. Consequently, it cannot be used in food production.4,5 Thus, one solution to these issues is the cultivation of tobacco for energetic uses. © XXXX American Chemical Society

Received: February 9, 2017 Revised: July 26, 2017

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DOI: 10.1021/acs.energyfuels.7b00405 Energy Fuels XXXX, XXX, XXX−XXX

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Energy & Fuels started. Furthermore, there is no previous research on pyrolysis of energetic tobacco seeds. To the best of our knowledge, unlike tobacco leaves, tobacco seeds generally are not collected from the fields and have no commercial uses. However, tobacco seeds have the potential to become a commercial product, especially for biodiesel production.9 Tobacco has many nitrogen compounds,10−12 which is an important feature for exploration. Different procedures for extracting N-compounds have been described in the literature, such as column fractionation.13−15 One study employed acid−alkaline extraction to separate the nitrogen compounds, which is a simple and efficient procedure.16,17 This procedure was chosen for application in this study because it is a simple and reproductive process with many applications in all fields of organic analysis. The Ncompounds are recovered from the alkaline extraction by neutralization and back-extraction with an organic solvent. The main compounds extracted by this technique are pyridines, benzopyridines, benzoquinolines, and azabenzofurans. Some studies have demonstrated that energetic tobacco seed contains a significant amount of oil (35−49% by weight), and this oil does not contain nicotine.8,18,19 The tobacco plant is a promising bioenergy crop because of the large amount of oil within its seeds, which do not compete with food resources and the ability for its byproducts to be converted into animal feed.10 Therefore, the tobacco plant is a promising crop,20 and the residual cakes obtained after press extraction could be subjected to a pyrolysis process, producing bio-oil and biochar.2 Bio-oils are complex samples containing hundreds of compounds, including phenols, alcohols, aldehydes, esters, ketones, and hydrocarbons. Tobacco seed bio-oils additionally have a large amount of nitrogen-containing compounds. Bio-oil can be used in many applications, such as heat and energy generation15 and industrial and transport feedstocks, after an upgrading process.16 For the rational and productive use of biooil, it is necessary to characterize it in both its chemical and physical aspects. During pyrolysis, biomass compounds such as lignin are degraded to form compounds with high added value that can be used to manufacture polyurethane foams and phenolic resins and as sources of phenol and formaldehyde.21−23 Phenols are important industrial raw materials used in the manufacture of polymers and textile yarns, fibers, polymers, and plastics, as well as resins.24−26 2,6-Dimethoxyphenol (syringol), hydroquinone and catechol can be used in the production of antioxidants, aromas, and fragrances as well as antifungal and antibacterial products in the pharmaceutical and food industry.27 The extracted pyridines and phenols can be used as raw materials for chemical industries in the production of pharmaceuticals, surfactants, biodegradable polymers, resins, and fertilizers.13,17,18 One-dimensional gas chromatography (1D-GC) has been used for many years as the standard tool for separating bio-oils. However, obtaining the best component separation via 1D-GC is difficult because of the insufficient resolution power of a single column.28 The comprehensive two-dimensional gas chromatography (GC×GC) technique, however, has the advantage of increasing the resolution and detectability because of the reconcentration of the fractionation through the modulation process, allowing for the detection of a higher number of compounds even at trace levels.29 There are many studies in which GC×GC was used for the analysis of bio-oils that gave excellent results.30−33

The most used mass detector for GC×GC is time-of-flight mass spectrometry because of its high frequency of spectral acquisition. Currently, with the recent development of the rapid quadrupole, GC×GC is commercially available with a fastquadrupole mass spectrometric detector with a two-stage thermal loop modulator. This was possible only after an improvement of the quadrupole system that allowed a fast scanning process (approximately 50 Hz when using a range of masses from 45 to 500 Da).34 In this study, pyrolysis of residual energetic tobacco cake was applied to obtain bio-oil, and an alkaline extraction was employed to obtain nitrogen compounds for subsequent analysis by two-dimensional gas chromatography with fastquadrupole mass spectrometry (GC×GC/qMS), allied with the use of retention indexes.

2. EXPERIMENTAL SECTION 2.1. Samples and Reagents. The residual cake, produced by the pressing of energetic tobacco seeds, was obtained from a pilot plant of biodiesel production located at the University of Santa Cruz (UNISC), in Santa Cruz do Sul, Southern Brazil. The energetic tobacco was cultivated at a farm of the Vale do Rio Pardo region. All the solvents and reagents used were p.a. grade (Merck, Darmstadt, Germany). 2.2. Pyrolysis Methodology. Prior to pyrolysis, samples of residual cake of energetic tobacco were dried in an oven at 100 °C for 1 h. Pyrolysis experiments were carried out under a nitrogen atmosphere in a tubular fixed bed oven with a quartz reactor as described by Moraes et al.2 Ten grams of dried residual cake of tobacco seeds was employed in each pyrolysis run. The reactor was heated to the desired temperature (700 °C) at 100 °C·min−1 and maintained at 700 °C for 10 min with a constant flow of nitrogen. The maximum temperature used in the pyrolysis process was defined based on thermogravimetric analysis (TGA) and experimental planning. The bio-oil was subjected to liquid−liquid extraction with dichloromethane (DCM) for a better separation of the organic and aqueous phase. The organic phase was dried with anhydrous sodium sulfate (Na2SO4) to remove residual moisture and filtered. A solution of 5 g·L−1 of the biooil (BO) was prepared in dichloromethane and analyzed by GC×GC. The procedure was done in triplicate. 2.3. Acid−Alkaline Extraction of Bio-oil. The goal of acid− alkaline extraction was to obtain an extract rich in N-compounds. Acid−alkaline extraction was adapted from Conegero et al.9,24 Approximately 0.2 g of dried bio-oil (BO) was placed in a decantation funnel along with 10 mL of DCM. HCl was added to adjust the pH to 2. After stirring and decantation, the organic phase (acid extract) was collected. The N-compounds were recovered from the aqueous phase by adding NaOH (1 M) adjusted to pH 12 and were extracted with three aliquots (3 mL each) of DCM. This extract was named AOE (alkaline organic extract) and was analyzed by GC×GC/qMS after filtration in a Na2SO4 column to remove residual moisture. Solutions of 5 g L−1 of both BO and AOE were prepared for GC×GC/qMS analysis. The procedure was done in triplicate. 2.4. Analysis of Bio-oil of the Residual Cake of the Energetic Tobacco and Alkaline Extract Using GC×GC/qMS. BO and AOE were analyzed by GC×GC/qMS (Shimadzu QP2010 Plus system) equipped with a modulator ZX1-GC×GC (Zoex, Houston, TX, USA). This modulator utilized liquid nitrogen (Linde Gases, Porto Alegre, RS) for the cold jet (which was continuous) and gaseous nitrogen for the hot jet (activated only for a short period of time, in fractions of a second). The chromatographic separation in the first dimension was performed in a low-polar DB-5 (5% phenyl−95% dimethylpolysiloxane) column of 60 m length × 0.25 mm i.d. × 0.10 μm film thickness (Ohio Valley Specialty Company, United States). In the second dimension, a medium-polar column (DB-17, 50% phenyl and 50% dimethylpolysiloxane (2.15 m × 0.18 mm × 0.18 μm, J&W Scientific, Agilent Technologies, United States) was used. B

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Figure 1. Results of GC×GC/qMS analysis of bio-oil and its alkaline fraction: (A1) three-dimensional diagrams of BO, (B1) three-dimensional diagrams of AOE, (A2) dispersion graphics of BO, and (B2) dispersion graphics of AOE. Chromatographic conditions described in Experimental Section and hydrocarbons, phenols, and N-compounds are marked in the dispersion graphics. The temperature program of the GC oven was set as follows: 40 °C for 2 min and then an increase to 280 °C at 4 °C·min−1, followed by 3 min at this temperature. The injector (splitless mode), ion source, and interface temperature were held at 280 °C. Helium (ultrapure, Linde Gases, Porto Alegre, RS, Brazil) was used as a carrier gas at a flow rate of 0.89 mL·min−1. The mass scan range used was from 40 to 400 Da. The modulation period was 5 s, and the hot jet time was 0.275 s (amount of time in which the hot jet is turned on). The data obtained from GC×GC/qMS was processed using the GC Image software (ZOEX Corporation, Houston, TX). To calculate the linear temperature-programmed retention indexes (LTPRIs),35 a linear C6−C30 n-alkane mixture was analyzed using identical GC×GC/qMS conditions. Compounds were tentatively identified by comparing the similarity of their fragmentation with a commercial database (NIST)36 and their LTPRI with those reported in the literature.37 A similarity above 70% and a difference between the sample and literature LTPRI of no greater than ±20 units were determined to be acceptable for tentative compound identification. The relative amounts of individual compounds were calculated based on GC×GC/qMS peak volume obtained from the integration of the peak detected on the chromatographic surface, without using a correction factor. As well as the area normalization used in qualitative studies involving onedimensional gas chromatography, the volume normalization approach is quite usual in qualitative studies involving GC×GC.38−40

After the acid−alkaline extraction was performed, 3.40 ± 0.81 wt % of N-compounds and 42.70 ± 6.45 wt % of acid fraction were obtained. The overall losses were very high (54%), which is the result of losses in the decantation funnel. 3.2. Analysis by GC×GC/qMS. For comparison purposes, the BO and AOE were analyzed in the same day by GC×GC/ qMS. The results obtained are shown in the 3D-diagram (Figure 1 A1, B1). To favor the detailed characterization of each class of compound in the complex samples, Excel software was used to elaborate dispersion graphs. Compound retention time graphs (second dimension versus first dimension) were constructed for each class of compounds identified. Figure 1 also shows the dispersion graphics for the same samples (Figure 1 A2, B2). In these, only peaks identified by LPTRI are shown. They are classified according their classes, allowing observation of the structured distribution on the two-dimensional space. In the bio-oil without extraction (Figure 1 A1, B1), 148 compounds (phenols, nitrogen compounds, esters, ketones, acids, alcohols, and hydrocarbons) were tentatively identified, while 40 compounds (Figure 1 A2, B2), mainly N-compounds, were detected in the AOE. The lowest amount of nitrogen compounds were confirmed by LTPRI because there is insufficient information in the literature about LTPRI for these compounds. Tables S1 and S2, with all the compounds identified in the samples with the respective LPTRI, are available in the Supporting Information. Relative to identified compounds, a large number of peaks of phenols, hydrocarbons (saturated and unsaturated), and Ncompounds were identified in bio-oil, while only N-compounds predominated in AOE. In bio-oil, these classes of compounds are important for the chemical and pharmaceutical industries and for biofuel production.27 A higher content of nitrogenous AOE compounds is of great importance for the pharmaceutical

3. RESULTS AND DISCUSSION 3.1. Yields of Pyrolysis and Liquid Extraction on NCompounds. The pyrolysis yield of the energetic tobacco seed waste was 40.98 ± 4.12 wt % of liquid products (bio-oil + aqueous phase). After a decantation, 15.89 ± 1.61 wt % of biooil and 25.09 ± 2.53 wt % of aqueous phase were obtained. The yield of crude bio-oil from waste tobacco seed was considered high when compared to the yields of other studies using different biomasses.3,33,41 C

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Energy & Fuels industry (pyridines) and for the production of pesticides (nitriles).42−44 The identification of compounds using a dispersion graphic is a tool (Microsoft Excel) to better discern the spatial distribution of compounds, as seen in Figure 1A2,B2. It was reconstructed as a two-dimensional graphic using retention data (first and second dimension retention times) as x- and y-axes for each sample. Through dispersion graphics, it was possible to confirm the higher complexity of the BO as compared to AOE. In BO, there was a large amount of peaks due to hydrocarbons. From these, only the aliphatic hydrocarbons were extracted with N-compounds in AOE. Figure 2 was constructed based on the data in Tables S1 and S2 for comparing both samples according their major

Figure 3. Graphics with the distribution of classes of compounds for BO and AOE according to the peak volume percent (vol %) and relative number of peaks (peak %).

It was observed by semiquantitative analysis that 27% (Figure 3) of the tentatively identified compounds present in bio-oil corresponded to N-compounds, corresponding to 25% of the identified peak volume in the chromatogram, which is strongly related to the concentration of these compounds in the sample. This is a very particular characteristic of this bio-oil because most bio-oils from other biomasses described in the literature have low levels of N-compounds and higher oxygen content.52−54,39,55 After the preconcentration of N-compounds, their amount increased considerably: 45% of the peaks (59% of the volume) in AOE, demonstrating the efficiency of extraction. This technique is very simple, fast, and inexpensive, and the consumption of solvents is not very high, making the method amenable to analytical purposes. On an industrial scale, it will be necessary to adjust the technique, perhaps using solid-phase extraction. It is interesting to observe that the majority of the N-compounds identified in the AOE fraction was not identified in the bio-oil, that is, the extraction promoted a cleanup in the sample, allowing the peaks to appear more clearly. The main N-compounds identified in AOE are those with one (pyridines and indoles) or two (pyrazine, pyrazoles, and imidazoles) nitrogen atoms in the molecule (Figure S1). From these, pyrydines and pyrazines are more basic than the others and were more easily extracted from the BO. Pyridines have pharmaceutical importance and are rarely found in pure form. Industrially, they are obtained from coal tar, but only at low concentration (approximately 0.1%),56 and their production is commonly performed by organic synthesis from acetaldehyde and NH3 (Hantzsch synthesis).57,58

Figure 2. Graphics with the major compounds (peak volume % > 3% in at least one of the samples) found in BO and AOE.

compounds (peak volume %>3 in at least one of the samples). On the other hand, in Figure 3, it is possible to observe a comparison of the compound class distribution in both samples according to the number of peaks and according to the volume % of all the peaks in each chemical class. Comparison of the mass spectra of components and the digital library showed good similarity and consequently high spectral purity. Previous studies using GC×GC/qMS for other samples of complex structures have shown results similar to those of this study.30,45 The large amount of alkylphenols, methoxyphenols, pyridines, and anilines is of interest for the chemical and pharmaceutical industries, or even as additives in materials such as ceramics and in the manufacture of polymers and phenolic resins, while the hydrocarbons could be used for biofuel production.24,25,46,47 Bulushev and Ross studied the catalytic hydrotreating for deoxygenation of the bio-oil with use of catalysts, such as a ZSM-5 zeolite.48 Other researchers have also been successful in obtaining bio-oils with higher hydrogen content for use in biofuels.49−51 Results of previous research for obtaining N-compounds (majority in this bio-oil) show that they are derived from raw tobacco.10

4. CONCLUSIONS A detailed qualitative study regarding the separation and tentative identification of compounds in the bio-oil from pyrolysis of the waste cake of energetic tobacco seed pressing, using GC×GC/qMS, is reported for the first time. GC×GC/ qMS proved to be an efficient technique for this analysis, allowing the identification of 148 and 40 compounds in bio-oil and basic extract, respectively. The alkaline extraction of the D

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(9) Usta, N.; Aydogan, B.; Ç on, A. H.; Uguzdogan, E.; Ö zkal, S. G. Energy Convers. Manage. 2011, 52, 2031−2039. (10) Schmeltz, I.; Hoffmann, D. Chem. Rev. 1977, 77, 295−311. (11) Baliga, V.; Sharma, R.; Miser, D.; McGrath, T.; Hajaligol, M. J. Anal. Appl. Pyrolysis 2003, 66, 191−215. (12) Baker, R. R. J. Anal. Appl. Pyrolysis 1987, 11 (C), 555−573. (13) Burchill, P.; Herod, A. A.; Pritchard, E. Fuel 1983, 62, 20. (14) Oliveira, E. C.; de Campos, M. C. V.; Rodrigues, M. R. A.; Pérez, V. F.; Melecchi, M. I. S.; Vale, M. G. R.; Zini, C. A.; Caramão, E. B. J. Chromatogr. A 2006, 1105, 186. (15) Qi, J.; Yan, W.; Fei, Y.; Su, Y.; Dai, Y. Fuel 1998, 77, 255. (16) Couto, A. B.; Ramos, L. A.; Cavalheiro, E. T. G. Quim. Nova 1998, 21 (2), 221−227. (17) Burchill, P.; Herod, A. A.; Mahon, J. P.; Pritchard, E. J. Chromatogr. 1983, 265, 223−238. (18) Giannelos, P. N.; Zannikos, F.; Stournas, S.; Lois, E.; Anastopoulos, G. Ind. Crops Prod. 2002, 16 (1), 1−9. (19) Bedmutha, R.; Booker, C. J.; Ferrante, L.; Briens, C.; Berruti, F.; Yeung, K. K. C.; Scott, I.; Conn, K. J. Anal. Appl. Pyrolysis 2011, 90 (2), 224−231. (20) Usta, N.; Aydoǧan, B.; Ç on, A. H.; Uğuzdoğan, E.; Ö zkal, S. G. Energy Convers. Manage. 2011, 52 (5), 2031−2039. (21) Bae, Y. J.; Ryu, C.; Jeon, J.-K.; Park, J.; Suh, D. J.; Suh, Y.-W.; Chang, D.; Park, Y.-K. Bioresour. Technol. 2011, 102 (3), 3512−3520. (22) Akhtar, J.; Amin, N. A. S. Renewable Sustainable Energy Rev. 2011, 15 (3), 1615−1624. (23) Ogeda, D. L.; Petri, D. F. S. Quim. Nova 2010, 33, 1549. (24) Patel, R. N.; Bandyopadhyay, S.; Ganesh, A. Energy 2011, 36 (3), 1535−1542. (25) Marsman, J. H.; Wildschut, J.; Evers, P.; de Koning, S.; Heeres, H. J. J. Chromatogr. A 2008, 1188 (1), 17−25. (26) Pakdel, H.; De Caumia, B.; Roy, C. Biomass Bioenergy 1992, 3 (1), 31−40. (27) Stephanidis, S.; Nitsos, C.; Kalogiannis, K.; Iliopoulou, E. F.; Lappas, A. A.; Triantafyllidis, K. S. Catal. Today 2011, 167 (1), 37−45. (28) Purcaro, G.; Tranchida, P. Q.; Jacques, R. A.; Caramão, E. B.; Moret, S.; Conte, L.; Dugo, P.; Dugo, G.; Mondello, L. J. Sep. Sci. 2009, 32 (21), 3755−3763. (29) Adahchour, M.; Beens, J.; Brinkman, U. a T. J. Chromatogr. A 2008, 1186 (1−2), 67−108. (30) Djokic, M. R.; Dijkmans, T.; Yildiz, G.; Prins, W.; Van Geem, K. M. J. Chromatogr. A 2012, 1257, 131−140. (31) Marsman, J. H.; Wildschut, J.; Mahfud, F.; Heeres, H. J. J. Chromatogr. A 2007, 1150 (1−2), 21−27. (32) Marsman, J. H.; Wildschut, J.; Evers, P.; de Koning, S.; Heeres, H. J. J. Chromatogr. A 2008, 1188 (1), 17−25. (33) Kanaujia, P. K.; Naik, D. V.; Tripathi, D.; Singh, R.; Poddar, M. K.; Siva Kumar Konathala, L. N.; Sharma, Y. K. J. Anal. Appl. Pyrolysis 2016, 118, 202−224. (34) Tranchida, P. Q.; Purcaro, G.; Dugo, P.; Mondello, L.; Purcaro, G. TrAC, Trends Anal. Chem. 2011, 30 (9), 1437−1461. (35) van Den Dool, H.; Dec. Kratz, P. J. Chromatogr. A 1963, 11, 463−471. (36) NIST 11 Mass Spectral Library. (37) National Institute of Standards and Technology. NIST WebBook. http://webbook.nist.gov/ (accessed Feb 19, 2016). (38) Saucier, C.; Polidoro, A.; dos Santos, A. L.; Schneider, J. K.; Caramão, E. B.; Jacques, R. A. Ind. Crops Prod. 2014, 62, 507−514. (39) da Cunha, M. E.; Schneider, J. K.; Brasil, M. C.; Cardoso, C. A.; Monteiro, L. R.; Mendes, F. L.; Pinho, A.; Jacques, R. A.; Machado, M. E.; Freitas, L. S.; Caramão, E. B. Microchem. J. 2013, 110, 113−119. (40) Polidoro, A. d. S.; Scapin, E.; Malmann, M.; do Carmo, J. U.; Machado, M. E.; Caramão, E. B.; Jacques, R. A. Microchem. J. 2016, 128, 118−127. (41) Migliorini, M. V.; Moraes, S. A. M.; Machado, M. E.; Caramão, E. B. Sci. Chromatogr 2013, 5 (1), 47−65. (42) Dalcomo, M. P. Pulmão RJ 2012, 21 (1), 55. (43) Queiroz, M. E. C. Sci. Chromatogr. 2009, 1 (2), 13.

bio-oil yielded the preconcentration of N-compounds, mainly those with basic characteristics. The original bio-oil was rich in hydrocarbons and phenols, and this simple isolation of Ncompounds from BO can aid in the industrial application of this raw material for different purposes: N-compounds for pharmaceutical industry, phenols for resins, and hydrocarbons for biofuels. The acid−alkaline extraction proved to be a rapid and simple technique, with little solvent, allowing for the isolation of a larger amount of nitrogen compounds (59% in peak volume), with the major compounds being β-carboline, skatole, and indole. The predominance of nitrogen compounds is not a common characteristic of bio-oils, and these components may find use in the fertilizer industry. Pyridines and anilines are interesting for the chemical and pharmaceutical industries, while nitriles may be employed for the production of pesticides. It can also be used for other purposes such as ceramic or polymeric additives to enhance the properties of these materials.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.energyfuels.7b00405. Identification of compounds in BO sample and in AOE; chemical structures of the main nitrogen classes in AOE sample (PDF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: 5551996699495. ORCID

Rosângela A. Jacques: 0000-0002-6576-6045 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Authors thank PETROBRAS, CNPq, CAPES, and FINEP for the financial support of this study.

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REFERENCES

(1) Fatih Demirbas, M.; Balat, M.; Balat, H. Energy Convers. Manage. 2011, 52 (4), 1815−1828. (2) Moraes, M. S. A.; Georges, F.; Almeida, S. R.; Damasceno, F. C.; Maciel, G. P. D. S.; Zini, C. A.; Jacques, R. A.; Caramão, E. B. Fuel Process. Technol. 2012, 101, 35−43. (3) Moraes, M. S. A.; Migliorini, M. V.; Damasceno, F. C.; Georges, F.; Almeida, S.; Zini, C. A.; Jacques, R. A.; Caramão, E. B. J. Anal. Appl. Pyrolysis 2012, 98, 51−64. (4) Dabdoub, M. J.; Bronzel, J. L.; Rampin, M. A. Quim. Nova 2009, 32 (3), 776−792. (5) Khan, Z. S.; Girame, R.; Utture, S. C.; Ghosh, R. K.; Banerjee, K. J. Chromatogr. A 2015, 1418, 228−232. (6) Sunchem South Brasil. Energy Tobacco “Solaris”. http://www. sunchem.it/testo-il-gruppo/?lang=en (accessed March 29, 2017). (7) Poltronieri, P.; D’Urso, O. F. Biotransformation of Agricultural Waste and By-Products: The Food, Feed, Fibre, Fuel (4F) Economy, 1st ed.; Poltronieri, P., D’Urso, O. F., Eds.; Elsevier: Amsterdam, 2016. (8) Sunchem South Brasil. Tabaco Energético uma nova alternativa. http://www.sunchem.it/wp-content/uploads/2012/07/SunchemSouth-Brasil.pdf (accessed March 28, 2017). E

DOI: 10.1021/acs.energyfuels.7b00405 Energy Fuels XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.energyfuels.7b00405 Energy Fuels XXXX, XXX, XXX−XXX