Fuel Processing Technology 101 (2012) 35–43

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Fuel Processing Technology

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Analysis of products from pyrolysis of Brazilian sugar cane straw

Maria Silvana Aranda Moraes a, Fernando Georges b, Suelen Rodrigues Almeida b,Flaviana Cardoso Damasceno a, Gabriela Pereira da Silva Maciel a, Claudia Alcaraz Zini a,Rosângela Assis Jacques a, Elina B. Caramão a,b,c,⁎a Programa de Pós Graduação em Química, Instituto de Química, Universidade Federal do Rio Grande do Sul (UFRGS), RS, Brazilb Programa de Pós Graduação em Ciência dos Materiais, Instituto de Química, Universidade Federal do Rio Grande do Sul (UFRGS), RS, Brazilc INCT E&A: Instituto Nacional de Ciência e Tecnologia em Energia e Ambiente, RS, Brazil

⁎ Corresponding author at: Programa de Pós GraduaQuímica, Universidade Federal do Rio Grande do Sul (U3308 7213.

E-mail address: elina@ufrgs.br (E.B. Caramão).URL: http://www.inct.cienam.ufba.br (E.B. Caramão

0378-3820/$ – see front matter © 2012 Elsevier B.V. Alldoi:10.1016/j.fuproc.2012.03.004

a b s t r a c t

a r t i c l e i n f o

Article history:Received 19 June 2011Received in revised form 27 December 2011Accepted 11 March 2012Available online 26 April 2012

Keywords:Bio-oilSugar cane strawPyrolysisGas chromatographyGC×GC/TOFMS

The main objective of this work is to investigate the chemical composition of the volatile compounds pro-duced during the pyrolysis of sugar cane straw (SCS). The pyrolysis was conducted in a vertical furnaceusing a quartz reactor at a temperature of 700 °C (7 g of SCS, heating rate of 60 °C/min, flux of 1 mL min−1

of N2 and 5 min of hold time at the final temperature). Pyrolysis products (solid residue and bio-oil) wereanalyzed. The original biomass and the residual solid phase were characterized by ThermogravimetricAnalysis (TGA) and Infrared Spectroscopy (FTIR). The biomass showed a TGA profile similar to celluloseand, according to FTIR analysis, it was rich in oxygenated compounds. The FTIR analysis of solid residueindicated that it was composed mainly by silica. Comprehensive two dimensional gas chromatographywith time of flight mass spectrometry detector (GC×GC/TOFMS) was applied in the identification andsemi-quantification of main compounds in bio-oil, allowing the identification of 123 compounds, mainlyoxygenated (acids, ethers, aldehydes, ketones and phenols) with a predominance of furfural and hexenoicacid. The GC×GC/TOFMS allowed a group type classification of the compounds and a spatial organizationthat facilitated the identification of the main compounds in the 2D diagram.

© 2012 Elsevier B.V. All rights reserved.

1. Introduction

Biomass is themost common form of renewable energy andwidelyconsidered to have a major potential for renewable energy for thefuture. Pyrolysis is a thermo-degradation technique which is usedfor transforming the biomass in a more valuable material (bio-oil).Over the last 2 decades, a special attention has been done to the con-version of residual biomass and renewable materials into bio-oil [1,2].

Pyrolysis allows the conversion of biomass into a liquid product,named bio-oil, which can be used as feedstock for fuels and valuablechemicals [3–6]. Bio-oil is a very complex mixture containing manyorganic compounds formed by the thermal degradation of cellulose,hemicellulose, lignin and other bio-molecules originally present invegetable biomass. According to Strezov et al. [7], thermal pyrolyticconversion is one of the promising methods for biomass conversion.The pyrolysis, mainly when developed at medium temperatures(550 °C) leads to the production of a pyrolysis gas composed by H2

and CO [8,9]. But this reaction is accompanied by the formation of

ção em Química, Instituto deFRGS), RS, Brazil. Tel.: +55 51

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other gases and particularly of tars, essentially composed by hydro-carbonaceus material, which are undesirable once they can blockthe furnace by condensation [10].

A large portion of bio-oil (about 55%) is composed by semi-volatileproducts which are analyzable through GC/qMS [11,12], while theremaining solid residue can be carbon rich charcoal or, dependingon the pyrolytic conditions, formed by silica. Originally the mainproduct of interest was the charcoal [13], but more recently, pyrolysishas been considered as a technology suitable for re-using of agricul-tural waste for the energy conversion [6,7,14] and also for producingimportant raw material for the chemical industry, like phenols andother oxygenated compounds [15–19].

The thermochemical transformation (gasification and pyrolysis)represents certainly more than 95% of the energetic valorization ofbiomass. The composition of both phases (vapor and bio-oil) dependson numerous parameters: the raw material (elemental composition,humidity, size) and the operating conditions as temperature, humid-ity and residence time [11].

Brazil is the largest producer of sugarcane of the world, generating400 million tons per year, on average [20,21]. The crop of sugarcane isinitiated with the burn of the sugar cane plantations, for productivityreasons and safety, but this practice produces a great amount of par-ticulate material (black soot's cane) and toxic gases. This burn is made“in situ”, on a controlled way, in small and delimited areas, with the

36 M.S.A. Moraes et al. / Fuel Processing Technology 101 (2012) 35–43

objective of quickly eliminating the leaves and pointers, so that thestem of the cane it is not burned [21,22].

The main proposals for the reduction and/or elimination of theburning of the cane in Brazil are regulated by two Laws, one Federal(no. 2.661/98) and another of the São Paulo State (no. 11.241/2002), which have the objective of promoting a gradual reduction ofthe sugar cane burning, until its totality in 2031 [21,23,24].

The pyrolysis is an alternative of the burning, producing bio-oil,bio-gas, ashes, charcoal and aggregating value to this material. Theuse of the sugarcane straw for production of energy appears as analternative and environmental friendly use of this material, once it isan agricultural residue, that doesn't have another important use [21].

The development of a viable “biorenewable agro-industry” needsto integrate all of the co-products of pyrolysis in the process [22].Bio-gas and bio-oils are attractive co-products of pyrolysis and theyare possible energy carriers and feedstock for bio-diesel andpetrochemicals.

The complex nature of bio-oil requires the use of high resolutionchromatographic techniques, mainly if coupled to mass spectrometry

Fig. 1. Equipment for the pyrolysis of sugar cane straw: (a) complete sys

detection [25–27]. More recently, the development of the multidi-mensional chromatography, specially the GC×GC/TOFMS emergedas a powerful tool in this field. Many works had been publishedapplying the GC×GC/TOFMS in the resolution of complex mixtures,like crude oils, environmental samples and fragrances. Severalreviews have also been published in GC×GC showing the advantagesof this technique in terms of separation capacity, resolution, sensitiv-ity, selectivity, … [28–33].

Recently, Sfetsas et al. [25] describe the analysis and quantificationof three different bio-oils by GC×GC/FID and GC×GC/TOFMS showingthe identification of more than 230 compounds in each oil. Marsmanet al. [34,35] also describe the application of GC×GC/FID in the grouptype classification of the compounds of bio-oils. Fullana et al. [36]compared the efficiency of GC×GC and 1D GC in the characterizationof bio-oils and found that around 70% of total chromatogram peakscould be identified with GC×GC but only 47% with conventional GC.

Beside the high separation capacity of GC×GC/TOFMS for qualita-tive purposes, the quantitative analysis has also been used [25,30]coupled to statistical tools [37,38].

tem, (b) vertical furnace and reactor; and (c) dimensions of reactor.

Fig. 2. Thermogravimetric curves of SDS.

Table 1Thermogravimetric analysis of sugar cane straw.

Step Tinitial (°C) Tfinal (°C) Weight loss (%) Explanation

1 25.0 81.8 8.6 CO2 and water2 81.8 212.0 2.0 Water3 212.0 370.4 50.0 Organic volatiles4 370.4 509.6 7.8 Organic semi-volatiles5º 509.6 900.0 5.8 Organic fixedResidual mass 25.8 Inorganic residue (ashes)

37M.S.A. Moraes et al. / Fuel Processing Technology 101 (2012) 35–43

This work explores the production of bio-oils from the pyrolysisof SCS and its characterization by chromatographic methods, mainlyGC×GC/TOFMS. The solid residue of the pyrolysis was also charac-terized by FTIR Spectroscopy and Scanning Electron Microscopy(SEM).

2. Experimental

2.1. Samples and materials

Dichloromethane (DCM), anhydrous Na2SO4, NaOH and HCl, p.a.grade, were purchased from Merck (Darmstadt, Germany). DCMwas bi-distilled to prevent interference in the analytical process.The chromatographic standards were purchased from Supelco(Supelco Park, PA, USA). The sugar cane straw sample was kindly pro-vided by the alembic Dom Braga, located in the city of Dois Irmãos,southern Brazil). The sample was triturated in a mill (Wiley MillModel no. 2, Arthur H. Thomas, Philadelphia, USA) to produce asub-sample at 0.830 mm.

2.2. Thermogravimetric Analysis (TGA)

TGA analysis was conducted in a Thermal Analyzer Instruments(SDT Q600 V20.9 Build 20) operating at a heating rate of 10 °C/minfrom 25 °C to 900 °C in an alumina sample vial with N2 flux of10 mL/min. The TGA was conducted with approximately 7.3 mg ofthe sample [39].

2.3. Infrared Spectroscopy (FT-IR)

The FT-IR spectrum of biomass (SDS) and its pyrolytic products(bio-oil and solid residue) was obtained using a VARIAN 640-IR spec-trometer in the IR range of 400–4000 cm−1 using the KBr pelletingmethod, with a resolution of 4 cm−1 with 200 and 100 scansperformed for the background and sample spectra, respectively.

2.4. Pyrolysis process

The procedure of pyrolysis was based in the work of Tsai et al. [17]and Quiang et al. [40]. The pyrolysis was conducted in a vertical fur-nace, using a quartz reactor, both were home made. Fig. 1 showsthe illustration of the furnace and the reactor with the specification

of each part of them. The bio-oil was collected at the top with ahelp of a condensator.

The conditions of the biomass pyrolysis were previously optimizedand the following conditionswere used: temperature=700 °C, heatingrate=60 °C min−1, final time=5min and N2 flow=1mLmin−1.

A weighed amount of SDS (about 7 g) was introduced into thequartz reactor (Fig. 1) in the pyrolysis oven and the apparatus wasfluxed with a nitrogen stream at 1 mL min−1 for 5 min and the sam-ple was heated from 25 °C to 700 °C (set temperature) at 60 °C min−1

and remains at this temperature for 5 min (till no more vapors areformed). After each pyrolysis, the reactor and all the connectionswere cleaned with acetone and were dried accurately with a hot airstream at 150 °C prior to a new analysis.

2.5. GC×GC/TOFMS analysis

The GC×GC/TOFMS — Pegasus-IV system (LECO, St. Joseph, USA)equipped with cryogenic modulator and CTC Combi Pal auto samplerwas used. The separation was carried out at a constant flowof 1.0 mL/min, using Helium (Linde Gases, Canoas, Brazil, 99.999%purity) as carrier gas. All samples were introduced using the splitmode with a split ratio of 10:1. The injector was kept at 275 °C.The columns set used were: DB-5 (30 m×0.25 mm×0.25 μm) andDB-17 ms (1.2 m×0.18 mm×0.18 μm), both acquired from AgilentTechnologies — J&W Scientific, Folsom, CA, USA.

The modulator was a cryogenic quadjet refrigerated with liquidnitrogen, and the modulation period was 10 s with hot and coldpulse of 0.4 s and 2.1 s, respectively. The temperature programof the first column started at 40 °C for 5 min and reached a final tem-perature of 315 °C at 3 °C min−1, where it was kept for 10 min. Thesecond column temperature was 10 °C above the temperature ofthe main oven. Transfer line was held at 275 °C and the electron

Fig. 3. Thermogravimetric curves of cellulose and lignin.Modified from Ref. [42].

38 M.S.A. Moraes et al. / Fuel Processing Technology 101 (2012) 35–43

impact ionization source operated at 250 °C with collision energy of−70 eV. Detector voltage was −1400 V, mass range was 45–500 Daand data acquisition rate was 100 Hz. Data processing was achievedusing integrated Leco ChromaTOF software, version 3.32. The iden-tification of compounds was performed by comparison with the

Fig. 4. Comparison between the FTIR spect

Fig. 5. Two dimensional color diagram of GC×G

library of the equipment, mass spectral examination, retention timeand elution order.

The bio-oil was previously derivatized with MSTFA providingtrimethylsilyl derivatives of phenols, alcohols, and acids for betteridentification and resolution.

ra of (A) SCDS, (B) py-SCS and BO (C).

C/TOFMS of the bio-oil with marked apices.

Table 2Identification and semi quantification of the compounds in bio-oil of SDS.

Peak RT 1D(min)

RT 2D(s)

Namea Area %b Formula Chemical class

1 6.5 3.5 Toluene 2.02 C7H8 Hydrocarbon2 7.5 3.0 Propenoic acid 1.04 C6H12O2Si Acid3 7.5 5.0 Cyclopentanone 0.54 C5H8O Ketone4 8.0 2.9 Propanoic acid 4.39 C6H14O2Si Acid5 8.3 5.6 Furfural (isomer 1) 0.69 C5H4O2 Aldehyde6 9.2 6.1 Furfural (isomer 2) 18.05 C5H4O2 Aldehyde7 9.3 6.4 C1 furan 2.38 C5H6O Ether8 9.7 2.8 Butanoic acid 0.12 C7H16O2Si Acid9 9.7 6.5 Cyclopentenone 0.07 C5H6O Ketone10 10.5 4.1 C2-benzene 0.25 C8H10 Hydrocarbon.11 10.5 5.3 Furanmethanol 0.08 C5H6O Alcohol12 11.0 6.0 C2 furan 0.07 C6H8O Ether13 11.0 6.2 Furanone 0.38 C4H4O2 Ketone14 11.7 7.2 Cyclopentenedione 0.31 C5H4O2 Ketone15 12.8 6.2 C1 cyclopentenone (isomer 1) 0.81 C6H8O Ketone16 13.0 3.4 Butenoic acid 0.28 C7H14O2Si Acid17 13.2 6.2 Furanyl ethanone 0.94 C6H6O2 Ketone18 13.2 9.5 Dehydro-furanone 0.14 C4H6O2 Ketone19 13.2 9.9 C1 furanone (isomer 1) 2.87 C5H6O2 Ketone20 13.7 3.6 Butenone, hydroxy (isomer 1) 0.59 C7H14O2Si Ketone21 13.7 6.6 Cyclopentenone, hydroxy 0.34 C2H6O2 Ketone22 14.0 3.0 Pentanoic acid (isomer 1) 0.05 C8H18O2Si Acid23 14.2 6.9 Cyclohexenone 0.25 C6H8O2 Ketone24 14.5 3.1 Pentanoic acid (isomer 2) 0.10 C8H18O2Si Acid25 14.5 5.6 C2 cyclopentenone (isomer 2) 0.08 C7H10O Ketone26 14.5 8.5 C1 furanone (isomer 2) 0.75 C5H6O2 Ketone27 14.8 3.8 Butenone, hydroxy (isomer 2) 2.04 C7H14O2Si Ketone28 15.5 6.8 Cyclohexanodione (isomer 1) 0.05 C6H6O2 Ketone29 15.8 6.7 C1 furfural 1.20 C6H6O2 Aldehyde30 15.8 7.2 C1 Cyclopentenone (isomer 2) 0.29 C6H8O Ketone31 16.3 3.4 Pentenoic acid (isomer 1) 0.34 C8H16O2Si Acid32 16.5 6.5 C1 Furanyl hydroxy ketone 0.07 C6H6O3 Ketone33 16.5 8.8 C1 Furanone (isomer 3) 0.38 C5H6O2 Ketone34 17.3 6.4 C2 Cyclopentenone (isomer 3) 0.04 C7H10O Ketone35 17.3 7.3 Pyranodione 0.19 C5H4O3 Ketone36 17.7 3.5 Pentenoic acid (isomer 2) 0.54 C8H16O2Si Acid37 17.8 3.8 Furanyl methoxy 4.25 C8H14O2Si Alcohol38 17.8 7.5 C2 Dihydro furanone 0.29 C6H8O2 Ketone39 18.0 3.5 Pentenoic acid (isomer 3) 0.73 C8H16O2Si Acid40 18.2 6.3 Furanyl propanone 0.09 C7H8O2 Ketone41 18.7 7.7 Cyclohexanodione (isomer 2) 0.06 C6H6O2 Ketone42 19.2 7.7 Cyclohexenedione (isomer 1 0.17 C6H6O2 Ketone43 19.7 3.7 Pentenoic acid (isomer 4) 0.53 C8H16O2Si Acid44 19.7 6.6 C1 furan, acetyl 0.07 C7H8O2 Ether45 19.7 6.7 C2 cyclopentenone (isomer 1) 0.27 C7H10O Ketone46 19.7 7.9 Cyclohexenedione (isomer 2) 0.07 C6H6O2 Ketone47 20.7 4.0 Phenol 1.87 C9H14OSi Phenol48 21.7 8.9 C1 hexenone 0.18 C7H12O Ketone49 21.8 3.3 Hexanoic acid (isomer 1) 0.10 C9H20O2Si Acid50 21.8 4.1 Furancarboxylic acid (isomer 1) 0.07 C8H12O3Si Acid51 22.2 3.0 Etanediol 2.85 C8H22O2Si2 Alcohol52 22.3 6.5 Phenol, methoxy 0.06 C7H8O2 Phenol53 23.0 7.0 C2 cyclohexenone 0.05 C8H12O Ketone54 23.2 2.8 Decane 0.05 C11H24 Hydrocarbon55 23.3 9.2 Levoglucosenone 0.34 C6H6O3 Other56 23.5 7.5 Maltol 0.25 C6H6O3 Other57 23.7 5.2 Furanmethanol (isomer 1) 0.87 C8H14O2Si2 Alcohol58 24.2 3.9 Hydroxy butanoic acid 1.20 C8H18O3Si Acid59 24.5 4.7 Furanmethanol (isomer 2) 0.09 C8H14O2Si Alcohol60 24.7 3.9 C1 phenol (isomer 1) 0.71 C10H16OSi Phenol61 25.2 4.0 C1 phenol (isomer 2) 0.63 C10H16OSi Phenol62 25.2 5.3 Furanmethanol (isomer 3) 0.08 C8H14O2Si Alcohol63 25.7 4.0 C1 phenol (isomer 3) 1.75 C10H16OSi Phenol64 26.7 4.2 C3 furan 1.68 C7H10O Ether65 27.5 4.1 Furancarboxylic acid (isomer 2) 0.10 C9H14O3Si Acid66 28.0 5.0 Sorbic acid 3.55 C9H16O2Si Acid67 28.3 3.1 Propanedioic acid 0.10 C9H20O4Si2 Acid68 28.3 5.5 Hexenoic acid (isomer 1) 0.11 C9H18O2Si Acid69 28.3 5.7 Hexenoic acid (isomer 2) 9.64 C9H18O2Si Acid70 28.8 6.4 Benzofuran, dihydro 0.14 C8H8O Ether71 29.0 3.0 Hexanedioic acid 0.15 C12H24O4Si2 Acid72 29.0 5.7 Uracil 0.87 C7H12N2O2Si Other73 29.2 4.0 C2 phenol (isomer 1) 0.24 C11H18OSi Phenol

(continued on next page)

39M.S.A. Moraes et al. / Fuel Processing Technology 101 (2012) 35–43

Table 2 (continued)

Peak RT 1D(min)

RT 2D(s)

Namea Area %b Formula Chemical class

74 29.2 9.1 C1 furfural, hydroxy 0.16 C6H6O3 Aldehyde75 29.3 4.7 Methoxyphenol (isomer 2) 1.79 C10H16O2Si Phenol76 29.8 4.1 Benzaldehyde, hydroxy (isomer 1) 1.31 C10H14O2Si Aldehyde77 29.8 4.7 Hexenoic acid (isomer 3) 0.03 C8H16O2Si Acid78 30.2 4.7 Benzoic acid 0.28 C10H14O2Si Acid79 30.2 5.1 Cyclohexanoic acid 0.11 C10H20O2Si Acid80 30.3 4.2 C2 phenol (isomer 2) 0.04 C11H18OSi Phenol81 30.8 4.2 C2 phenol (isomer3) 0.05 C11H18OSi Phenol82 31.0 5.3 Heptenoic acid 2.10 C10H20O2Si Acid83 31.8 6.3 Hexanoic acid (isomer 2) 0.42 C9H20O2Si Acid84 32.0 4.8 Methoxyphenol (isomer 1) 0.04 C10H16O2Si Phenol85 32.7 5.3 Nitrocatechol 0.11 C6H5NO4 Phenol86 32.7 5.4 Furan acetic acid 0.26 C9H14O3Si Acid87 32.8 8.3 Acetoxy C1-furfural 0.07 C8H8O4 Aldehyde88 33.2 6.7 Methoxy vinyl phenol 0.07 C9H10O2 Phenol89 33.3 5.4 C1 furan carboxylic acid (isomer 1) 2.69 C9H14O3Si Acid90 33.7 3.7 Benzenodiol (isomer 1) 1.40 C12H22O2Si2 Phenol91 33.8 2.8 Tridecane 0.05 C13H28 Hydrocarbon92 33.8 5.7 C1 furan carboxylic acid (isomer 2) 0.30 C9H14O3Si Acid93 34.3 5.4 Octenoic acid 0.21 C11H22O2Si Acid94 34.8 3.8 Butenedioic acid 0.15 C10H20O4Si2 Acid95 35.7 4.7 C2 xanthene 0.03 C15H14O Ether96 35.8 5.3 Benzaldehyde, hydroxy (isomer 2) 0.29 C10H14O2Si Aldehyde97 37.0 4.5 Benzaldehyde, methoxy hydroxy (isomer 1) 0.69 C11H16O3Si Aldehyde98 37.2 5.4 C2 benzaldehyde, trimethoxy 1.81 C12H16O4 Aldehyde99 37.3 3.6 Benzenodiol (isomer 2) 0.20 C12H22O2Si2 Phenol100 37.5 6.0 C2 cyclohexanol 0.13 C9H18O2Si2 Alcohol101 37.7 5.3 Acetophenone, hydroxy (isomer 2) 0.05 C11H16O2Si Ketone102 37.7 5.4 Ketocaproic acid 0.04 C9H18O3Si Acid103 39.8 3.6 Benzenediol, C1 0.07 C13H24O32Si2 Phenol104 39.8 3.6 Phenyl ethanol hydroxy 2.54 C14H22O2Si2 Phenol105 39.8 5.5 Acetophenone, hydroxy (isomer 2) 0.10 C11H16O11Si Ketone106 40.0 3.7 Ethoxy phenol 1.59 C14H26O2Si2 Phenol107 40.2 4.7 C3 benzenediol 0.09 C13H20OSi2 Phenol108 40.7 5.2 Methoxy phenazine 0.81 C13H10N2O Other109 41.7 3.6 Nonanol 0.03 C12H28OSi Alcohol110 42.5 6.0 Benzaldehyde, methoxy hydroxy (isomer 2) 0.45 C11H16O3Si Aldehyde111 43.2 4.0 C2 benzenediol 0.06 C14H26O2Si2 Phenol112 43.3 3.4 Benzenetriol 0.87 C15H30O3Si3 Phenol113 43.3 4.1 Vanillyl alcohol 0.06 C14H26O3Si2 Alcohol114 43.5 5.0 Benzaldehyde, dimethoxy, hydroxy 0.07 C12H18O4Si Aldehyde115 44.0 4.1 Benzoic acid, hydroxy 0.06 C13H22O3Si2 Acid116 44.0 4.9 C3 phenol 0.44 C13H20O2Si Phenol117 44.7 3.3 Dodecanol 0.03 C12H26O Alcohol118 45.8 6.0 Acetophenone, hydroxy (isomer 1) 0.11 C11H16O11Si Ketone119 47.8 2.8 Benzoic acid, bis hydroxy 0.02 C16H30O4Si3 Acid120 48.2 4.3 C1 benzoic acid, hydroxy 0.02 C14H24O3Si2 Acid121 49.7 3.5 Levoglucosan 0.48 C15H34O5Si3 Other122 51.2 4.3 Hydrocinnamic acid 0.22 C15H26O3Si2 Acid123 51.3 4.5 Benzoic acid, methoxy hydroxy 0.04 C14H24O4Si2 AcidArea % acids 30.07 (35 compounds)Area % alcohols 8.47 (10 compounds)Area % aldehydes 24.81 (11 compound)sArea % ethers 4.36 (6 compounds)Area % hydrocarbons 2.38 (4 compounds)Area % ketones 12.55 (31 compounds)Area % others 2.87 (6 compounds)Area % phenols 14.50 (20 compounds)

a Cx = alkyl chain with x Carbons atoms.b % Area=(Ai/ΣAi)×100, considering only the tentatively identified peaks.

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3. Results and discussion

3.1. Initial characterization of the SDS

The crude SDS samples contained 0.16±0.01% moisture, deter-mined by the procedure described in the ASTM D 3173–87 [41].Fig. 2 shows the TGA curves for thermal decomposition of the sugarcane straw. The main losses are represented in this figure and are reg-istered in Table 1. Till 82 °C the losses are due to water and CO2, fromthis temperature and till 370 °C occurs the loss of volatiles and afterthis and till 500 °C all the organic materials are decomposed. At the

end of the process, 26% of inorganic material remains as residualmass in the form of ashes. As can be conclude, the total burning ofthis biomass can be promoted at temperatures bellow to 700 °C.

The amount of lignin and cellulose in the biomass is an importantfactor in the pyrolysis analysis and the simple comparison betweenthe thermogravimetric profiles of the biomass and these materials cansuggest which is the main constituent of the original biomass [42,43].Fig. 3 shows the thermogravimetric curve for cellulose and lignin(data modified from Rout et al. [42]) and it is possible to observe thatthe sugar cane straw has a behavior similar to cellulose, indicatingthat this is the main constituent of the original biomass [44,45].

41M.S.A. Moraes et al. / Fuel Processing Technology 101 (2012) 35–43

The literature indicates that normally in fast pyrolysis at relativelyhigh temperatures, the final ash residue of biomass consisted ofaround 95% silica [46–50].

3.2. Infrared Spectroscopy

Fig. 4 shows the infrared spectra of SDS, the solid residue of pyro-lysed SDS (py-SDS) and the bio-oil produced (BO). In this figure arealso showed all the main functional groups that can be identifiedin each spectrum. Contrasting with SDS and BO, the py-SDS-FTIRshowed a typical profile of silica, that is, an inorganic material,which corroborate with TGA data. On the other hand, the spectra ofSDS and BO are very similar. The main difference between them are

Fig. 6. Two dimensional graphics generated from retention time of GC×GC/TOFMS data of aacids; (b) alcohols and ethers; (c) aldehydes; (d) ketones, (e) phenols and (f) other classes

in the intensity of the bands, mainly those related to oxygenatedcompounds (O\H, C\O and C_O). These functional groups are char-acteristic of ketones, phenols, ethers, esters, acids and aldehydeswhich are the main compounds described in the literature as typicallyfound in bio-oil from ligneous–cellulosic material [18,19].

In general, the spectrum of bio-oil was dominated by peaks at≅3300 cm−1, which corresponded to the stretching vibrations ofO\H. A sharp peak at ≅1700 cm−1 represents carboxyl groups andhas been attributed to hemicelluloses [51]. These peaks are originatedfrom the stretching mode of carbonyls, mainly ketones and acids [52].Peaks from 1050 to 1250 cm−1 can represent C\H, O\H, or CH2

bending frequencies [51] and can be indicators of lignin. The largeband at ~1050 cm−1 corresponds to Si\O bonds.

nd classified according the chemical classes of the identified compounds: (a) carboxylic.

42 M.S.A. Moraes et al. / Fuel Processing Technology 101 (2012) 35–43

3.3. GC×GC/TOFMS of bio-oil

The mass yield in bio-oil was 23.9% related to the weight of biomassinitially used (≅7 g). The bio-oil produced in the pyrolysis of SDSshowed high amount of water (≅97,4%) which implied in extractingthe organic phase with dichloromethane and drying it with anhydroussodium sulfate, before the derivatization and the chromatographicanalysis. After the extraction of the excess of water, the bio-oil wasderivatized with MSTFA and directly analyzed by GC×GC/TOFMS.

Fig. 5 shows the color and apex diagram of the GC×GC/TOFMSanalysis of the derivatized bio-oil produced in the SDS pyrolysis.The apices are signaled in black and those that were tentatively iden-tified, are surrounded by a white circle. This analysis showed a totalof 363 compounds of which only 123 were tentatively identified(33.9%). Table 2 shows the tentative identification of the peaks,their Area% ([Ai/Σi] ·100), retention times (1D and 2D) and othercharacteristics. Only were considered identified (or tentatively identi-fied) those peaks with similarity between the spectra (library andsample) higher than 85%. The Area% was calculated considering thesum of peak areas of all the identified compounds, which correspondsto 42.1% of the total area detected.

As can be seen in Table 2 the majority of the compounds tenta-tively identified belong to the classes of acids, alcohols, aldehydes,ethers, ketones and phenols, among others minoritary (sugars,hydrocarbons, nitrogenated compounds, lactones).

The major compound found in the sample of bio-oil was furfural(18.05%) followed by hexenoic acid (9.65%). Twenty five compoundsshowed percentages of areas above 1% and the sum of these areasaccounted to 76.8% of the total area identified. For a better comprehen-sion of the data and also for promoting the classification and the distri-bution of the compounds in the sample, it was constructed anothergraphic (using the software Excel™) for each class of compound identi-fied, using the retention times (1D and 2D). Fig. 6 shows all the recon-structed diagrams for each class of identified compounds. Datapresented in these diagrams are only qualitative. This form of showingthe chromatographic data allows observing the spatial organization ofthe compound classes in the 2D diagram. This organization is useful inthe identification of some compounds and is impossible to observe inone-dimensional chromatography. On the other way, in the originaltwo dimensional diagram (Fig. 5) is difficult to realize this classificationdue to the high amount of compounds in a little region of the diagram.For this reason the use of Excel™ facilitates the analysis.

In Fig. 6 it is possible to clearly observe the families of saturated,unsaturated and aromatic carboxylic acids (Fig. 6a); furans andbenzofurans (Fig. 6b); furfurals and benzaldehydes (Fig. 6c); phenols,methoxy phenols and benzenediols (Fig. 6d) and cyclic unsaturatedketones and acetophenones (Fig. 6e).

Shen and Gu [12], discussed exhaustively the thermal decomposi-tion of cellulose and identified considerable amounts of furfural andother phenol derivatives. The literature shows that the primarychemical classification pyrolysis products of cellulosic biomass canbe summarized as follows: acids, alcohols, aldehydes, esters, ketones,phenols, guaiacols, syringols, furans, alkanes, alkenes, aromatics,nitrogen compounds, and miscellaneous oxygenates [15–19], con-firming the identification of the bio-oil studied in the present work.

It can be concluded that an industrial pyrolysis process of SDS inBrazil, a major producer of sugar cane in the world, would produce im-portant feedstocks for chemical industry and also for energy purposes.

4. Conclusions

The SCS showed to be a viable raw material for energy and indus-trial use, once Brazil (the major world producer of sugarcane) pro-duces thousands of tons of straw a year, generating agriculturalresidues with a considerable environmental impact.

It could be observed through TGA analysis that the burning of theSDS occurs around 500 °C, which allows to use temperatures below700 °C without significant losses in the yield of bio-oil.

The analysis of SDS and BO by FTIR indicated the presence of agreat variety of functional groups as phenols, alcohols, acids, alkanes,ketones, ethers and aldehydes while for py-SDS these groups wereeliminated during the pyrolysis, resulting in a solid residue rich ininorganic material (silica).

The characterization of the bio-oil for GC×GC/TOFMS was funda-mental for a larger understanding of the composition of the bio-oil,once the sample are composed by a complex mixture of chemicalcompounds (with high amount of isomers). This technique is moresensitive, selective and with larger resolution power that allowedthe identification of the chemical classes. More than 120 compoundswere tentatively identified in the bi-oil, mainly oxygenated ones(acids, aldehydes, alcohols, phenols, ethers and ketones).

Acknowledgment

Authors thank to PETROBRAS, CNPq and FINEP for the financialsupport of this work. Also thank to Prof. Dr. Edilson Volmir Benvenutti,from Chemistry Institute, Federal University of Rio Grande do Sul,for the discussion on FTIR results.

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