MS studies of vegetable oils from Macauba fruit

J. Anal. Appl. Pyrolysis 72 (2004) 103–111

Pyrolysis–GC/MS studies of vegetable oils from Macauba fruit I.C.P. Fortes a,∗ , P.J. Baugh b a

Departamento de Qu´ımica—ICEx, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil b 121. Moss Lane, Timperley, Altrincham, Cheshire WA15 6JG, England, UK Accepted 12 March 2004 Available online 24 May 2004

Abstract Pyrolysates obtained from vegetable oils of the Macauba tree (Acrocomia sclerocarpa M.) and from components of the fruit, namely, (1) the endocarp in combination with the mesocarp and (2) the epicarp have been investigated by pyrolysis–CG/MS technique under different conditions of gas atmosphere: inert (He) and oxidative [O2 /N2 (1:1)]. The differences in pyrolysate profiles and features have also been studied under different pyrolysis conditions (temperature and time). The pyrolysis of the two oils, under inert and oxidative atmospheres, show complex profiles with more than 30 compounds detected. Under the conditions employed, the component oils studied undergo a process of partial pyrolysis to varying extents, generating considerable yields of carboxylic acid, aldehydes, alcohols, alkenes, and alkadienes. Py–GC/MS technique shown to be a very good analytical tool to study the influence of different atmospheres, pyrolysis time and temperature in the feature of the yield products as well as to obtain some information about the mechanism of pyrolysis of this material under different conditions. © 2004 Elsevier B.V. All rights reserved. Keywords: Py–GC/MS; Macauba fruit (Acrocomia sclerocarpa M.); Pyrolysis; Oxidative pyrolysis; Vegetable oils; Biomass

1. Introduction Since the advent of energy crisis, increasing emphasis has been placed on exploring the possibilities of recovering energy from solid wastes. In the light of this view many studies of biomass as renewable energy source [1] have been initiated during the past two decades. Biomass is the only renewable source of raw material available to the chemical industry and represents the only long-term source of carbon [2]. Biomass is, however, generally poorly suited for direct energy use and pre-treatment is necessary to change the physical and chemical form [1]. Gasification, combustion and pyrolysis are process routes available for recovering energy from biomass. Therefore, biomass a potential as a feedstock for pyrolysis to produce fuels including oil and gas for internal-combustion engines, power stations and heating supplies [3]. These bio-fuels are cleaner than fossil fuels such as coal and petroleum, because of the low nitrogen and sulphur contents [4,5].

∗

Corresponding author. E-mail address: [email protected] (I.C.P. Fortes).

0165-2370/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jaap.2004.03.005

Previous studies involving biomass pyrolysis have concentrated on paper, wood, cellulose and on the thermal degradation of polymer and rubber [6,8]. Most studies were on the laboratory scale [7–9], with primary emphasis on the reaction mechanisms and kinetics [10–13]. The operating conditions were mostly pertaining to “pure” pyrolysis where the degradation of macromolecular material was carried out, with heat alone in absence of oxygen. If waste is pyrolysed in a limited oxygen supply, this process is referred as oxidative pyrolysis. The chemistry of oxidative degradation is complex. Some assays rely on the measurement of effects on the sample caused by oxidation process, such as increase in weight by scission or cross-linking formation of conjugated carbonyl structures that leads to yellowing, or loss of weight by production of volatile decomposition products. Other methods assess the volatiles themselves [14,15]. The need for different alternative sources of energy and technology using Brazilian natural resources is driven by concern to preserve our environment. In order to direct our efforts towards developing new technology to increase the use of derivatives from biomass in the chemical industry, studies were carried out on pyrolysis of vegetable oils. Pyrolysis of biomass, in particular, vegetable oils, has been a

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subject area of study since World War II. Early on, studies concerning the chemical composition of the volatile compounds obtained were not complete, owing to the limitations in instrumental and analytical methods [16]. It have been reported [17–21] that a mixture of triglycerides (TGs) submitted to a thermal cracking process should undergo decarboxylation, disproportionation and successive elimination of ethylene molecules, yielding several classes of compounds, such as, hydrocarbons and carbonylic compounds. In addition, the sample of evolved primary volatiles can undergo subsequent reactions, so-called secondary reactions, including dehydrogenation, recombination, repolymerization and, in some instances, oxidation. The last-mentioned effect accounts for the major difference between the cracking of vegetable oils and petroleum since the latter does not generate carbonyl groups in the products [17,19–21]. During the last two decades, the search for pyrolysis processes leading to higher oil yields and the application of new analytical techniques to elucidate the mechanisms of formation and constitution of resulting pyrolysates has undergone a technological renaissance involving investigations in the area of pyrolysis. [17–19]. Natural sources of a composite mixture of triglycerides are the oleaginous plants, which comprises a large part of the vast and diversified flora of Brazil. The plant of prime interest is the Macauba tree (Acrocomia sclerocarpa M.) in particular, the oils from Macauba fruit. This tree is native to different regions in Brazil and is located mainly in the centre of the country and, in particular, in the state of Minas Gerais [19–21]. Here we report a study carried on by Py–GC/MS technique, which allows the simultaneous mass spectrometric detection and identification of pyrolysis products. Experiments were performed using a filament pyrolyser coupled to a GC/MS, using a flash pyrolysis procedure employing the oils from Macauba fruit to investigate the effects of time of pyrolysis, temperature of the pyrolytic process, and how different atmospheres affect the yield and composition of the pyrolysate. Studies were performed to obtain information on the influence of these parameters upon the mechanism of pyrolysis of these oils, of which is still largely unknown.

2. Materials and analysis 2.1. Sampling The Macauba fruit has a spherical slightly flattened shape with an external diameter in the range of 3–6 cm and colour varying from a shade of brown to yellowish green [23]. The fruit comprises an epicarp or external shell, a mesocarp or pulp and an endocarp or kernel which envelopes one or two nuts [23]. The Macauba fruit was divided into two parts the outer part comprising a mixture of external shell and pulp and the

Table 1 Composition of fatty acids (as methylesters) present in nut and pulp oils from Macauba (Acrocomia sclerocarpa M.) Fatty acids (methylesters)

Caprylic acid Capric acid Lauric acid Myristic acid Palmitic acid Palmitoleic acid Margarinic acid Stearic acid Oleic acid Linoleic acid

GC peak area (%) Nut

Pulp

2.10 3.72 38.89 11.00 17.35 – – 4.34 22.60 –

Traces Traces 2.93 1.88 22.30 5.28 4.34 5.75 52.82 4.69

inner part, the endocarp nut. Both components were dried at 80 ◦ C to constant weight, ground into powder, extracted with hexane under a Soxhlet reflux for 72 h and concentrated by distillation to give the vegetable oil extracts [19,20]. The relative amounts of the fatty acids in the extracted oils from different parts of Macauba plant were determined as methylesthers, summarised in Table 1. 2.2. Conditions and methodology Pyrolysis was performed using a filament pyrolyser, Girdel Pyrolyser 75-Py-1. Helium (high purity, 99.9995%) was used both as the GC carrier gas and the inert atmosphere for pyrolysis, and a mixture of O2 /N2 (1:1) was used as oxidative atmosphere. The sample was dispensed as a thin film onto the filament and the solvent was allowed to evaporate before commencing the pyrolysis procedure. The system was purged for a short time (30 s) with the carrier gas before each injection and the probe connected directly to the GC injector. The carrier gas was diverted through the control unit and probe, ensuring that the volatile material was transferred from this device to GC–MS without significant loss. The oxidative atmosphere was introduced through a six-port valve attached externally to the pyrolyser enabling a switch from an oxidative to inert atmosphere or vice versa. Experiments were carried out at a given temperature (700–800 ◦ C) and over a range of pyrolysis times (5, 10, 20 and 30 s) to study the behaviour and reproducibility of the pyrolytic process under both atmospheres. Under both atmospheres some problems were experienced under the above condition, such as, partial pyrolysis, column overloading, which were difficult to eliminate and leads to variation in the results reproducibility. 2.3. GC/MS analysis General profiles for pyrolysates were obtained using EI–MS. Analyses were conducted on a Finnigan Mat model 1020 automated GC/MS/DS using a fused capillary column

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(14 m × 0.25 mm i.d.; d.f. = 0.15 ␮m; DB1, J&W Scientific) with polydimethylsiloxane as the stationary phase. Helium was used as the carrier gas at a nominal flow rate of 1 ml/min. Aliquots of 1 ␮l of the sample in hexane, together with 1 ␮l of a mixture of standard compounds (d10 -biphenyl, d10 -anthracene, d10 -pyrene) at 100 ␮g/ml as an internal standard, were spread onto the filament prior to pyrolysis. This set of standards was employed as a parameter to monitor the reproducibility of the pyrograms, for correlation of retention times to locate compounds (EI and CI–MS retention data) and as an aid to correlating the relative molecular/molar mass (RMM) when library matching was performed. Analysis were performed using the following conditions; injection mode was short splitless with a 1 s delay. The column was held at 35 ◦ C for 2 min and then heated to 300 ◦ C, at 20 ◦ C/min. The final temperature was held constant for 2 min. For the oxidative atmosphere, the injection mode was splitless with 40 s delay. The column was held at 50 ◦ C for 2 min and the raised to 300 ◦ C at 15 ◦ C/min. The final temperature was held constant for 2 min. Analyses employing the positive ion chemical ionisation (PCI) mode were carried out on a GC model HP 5890 series II interfaced (oven set at 280◦ ) to an MS model VG Trio 1000, using a fused capillary column (11 m × 0.32 mm i.d., d.f. = 0.25 ␮m, DB5, J&W Scientific). Helium was employed as the carrier gas and methane as the reagent gas. The GC conditions used were the same as for the EI mode. The presence of different classes of compound present in the pyrolysates was confirmed using the total ion chromatogram (TIC) and selected ion mass chromatogram (SIMC) analyses, in addition to fragmentation patterns and library matching (NIST). Identification was carried out according to pre-established criteria for the analysis of the data. Quantification of the peaks in terms of relative percentage was carried out using the appropriate software on the data system: SR and QL-QR-MQ-EQL.

3. Results and discussion 3.1. Inert atmosphere The pulp and nut oils only undergo partial pyrolysis and the pulp was more resistant to this process probably due to its higher degree of unsaturation. Both oils led to carboxylic acid compounds (see Table 1) generated from triglycerides of which the original oil is composed. A major ion peak (m/z, 44), at the beginning of the chromatographic run, indicated the presence of carbon dioxide, probably, originating from the decarboxylation of fatty acids. The total ion chromatograms of the pyrolysates from the pulp and nut oils are illustrated in Figs. 1 and 2 and show the presence of a number of compounds, some of which have been identified.

105

3.1.1. Pulp oil Pyrolysis of the pulp oil in an inert atmosphere leads to the formation of aldehydes, cycloalkanes, alkenes, and dienes. Any peaks of carboxylic acids were not detected in the pyrograms. The major product generated was 2-propenal or acrolein, a known product when triglycerides are pyrolysed [16]. Several products could not be identified unambiguously; these are referred to as unknown with specific ions at m/z 55 and 67, respectively. In addition, the presence of small amounts of alkanes, alkene-ynes, alkylbenzene and cycloalkene was also evident. 3.1.2. Nut oil The pyrolysis of the nut oil leads to alkenes, aldehydes and carboxylic acids as major products, as indicated in Fig. 2 and Table 3. The pyrolysate also exhibits cycloalkane, alcohol, alkane, some components, with base ion peaks at m/z 54 or 67, and other constituents with base ion peaks at m/z 55 and 57 were also observed. The presence of compounds with base ion at m/z 54 or 67 was noticed in both oils and according to literature [24,26] they could belong to cyclohexene derivatives or any cyclic olefins which can suffer retro Diels-Alder decomposition. The products generated by the pyrolytic process from the two oil components are quite different from those of calcium soaps of corresponding carboxylic acids [19]. In the latter case, the main products comprised a homologous series of n-alkanes, 1-alkenes and some carboxylic compounds. 3.2. Oxidative atmosphere The two oils undergo partial pyrolysis in an oxidative atmosphere. This atmosphere promotes the pyrolytic process for the nut oil, resulting in a decreased yield of carboxylic acids. The pyrolysis of the pulp oil was seemingly not facilitated. The GC/MS chromatograms of the oxidative pyrolysis are displayed in Figs. 3 and 4. 3.2.1. Pulp oil The yield of aldehydes, cycloalkanes and alkenes (main pyrolysis products) decreased considerably due to the oxidative atmosphere, while that of an unknown compound characterised by a base ion peak at m/z 56 largely increased (see Table 4). 3.2.2. Nut oil For the nut oil, the oxidative atmosphere favours the enhancement of the process resulting in lower yields of alkenes, aldehydes and carboxylic acids. At the same time the yield of alcohols increased (see Table 5). Moreover, the presence of a series of compounds of base ion at m/z 71 was also observed, the ion chromatogram of which is shown in Fig. 5. This fragment is characteristic of molecules containing oxygen and may be generated by a different pathway during the oxidative process, such as; via ␣-cleavage of ketones generating the fragment, C3 H7 CO+ ; from diketones [24–27] for

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Fig. 1. Total ion chromatogram of pulp oil pyrolysate under inert atmosphere. [1] 2-Propenal; [2] 1,3-cyclohexadiene; [6] unknown m/z 67; [7] 1-octene; [9] propylbenzene; [16] butylbenzene; [17] cyclodecene (-E) isomer; [19] unknown m/z 67; [20] unknown m/z 67; [28] unknown m/z 81; unknown m/z 55; 1-dodecene.

3.3.1. Inert atmosphere Studies of the behaviour of the pulp and nut oils at different temperatures, pyrolysis time and under different atmospheres show different trends in profiles summarized in Tables 2 and 3.

secondary products (3–10%) and tertiary products (<3%). The overall trend was the same for the two temperatures employed. At 700 ◦ C, the main products (aldehyde, cycloalkane, alkene and diene) range from 71 to 79% of the total products; the secondary products (unknowns at m/z 55 and 67, other constituents and alkylbenzene) from 19 to 26% and the remaining products (alkenyne, alkane, cycloalkene) from 3 to 4%. At the higher temperature −800 ◦ C, however, a slight decrease in the main products (61–76%) and an increase in the secondary products was observed (22–34%). The percentage of tertiary products remained constant. As indicated in Table 2, a short pyrolysis time (5 s) tends to favour cyclization and generation of multiple bonds whereas a longer pyrolysis time favours secondary reactions. These trends can be rationalised in terms of the extent to which the sample undergoes secondary reactions.

3.3.1.1. Pulp oil. For pulp oil, the pyrolysate products can be placed in three categories: main products (>10%),

3.3.1.2. Nut oil. For nut oil, the composition of the resulting pyrolysate was as follows: main products (aldehyde,

which fragmentation occurs predominantly at the carbonyl group to give acylium ions and from unsaturated ethers [26] by ␣-cleavage with preferential loss of the larger alkyl group leading to abundant fragment ions which, if R3 is ethyl or larger, decompose by elimination of an olefin. Expulsion of the alkoxyl radical is also observed and this process is especially pronounced if R1 and R2 are methyl; it is of diminishing importance with larger alkyl substituents. 3.3. Pyrolysis temperature and time

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Fig. 2. Total ion chromatogram of nut oil pyrolysate under inert atmosphere. [1] 2-Propenal; [2] 2-methyl-pentene; [3] n-hexane; [4] cycloheptane; [10] nonane; [19] 2-dodecenal, [22] dodecanoic acid; [23] unknown m/z 57.

alkene and carboxylic acid) ranging from 59 to 74%; secondary products (cycloalkane, alkane with unknowns at m/z 55) from 24 to 37% and tertiary products (alcohol and unknowns at m/z 54 and 57) from 5 to 7%. The relative percentage of carboxylic acids and unknowns at m/z 55 increases with pyrolysis time at both working temperatures. Other products, such as alkene, aldehyde and

alkane have a tendency to decrease (Table 3). The inference is that the generation of these classes of compound is dependent on the cracking of carboxylic acids, whereas, the formation of unknowns at m/z 55 is not. An additional trend is that compounds representing smallest fraction of the total pyrolysate (alcohol and unknowns at m/z 54 and 57) increase with temperature and pyrolysis time. This

Fig. 3. Total ion chromatogram of pulp oil pyrolysate under oxidative atmosphere. [10] 2-Octanal; [12] butylbenzene; [13] nonanal; [15] 2-nonenal; [16] unknown m/z 57; [18] pentylbenzene; [22] unknown m/z 55; [23] unknown m/z 55; [26] 1-dodecene.

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Fig. 4. Total ion chromatogram of nut oil pyrolysate under oxidative atmosphere. [8] n-Octane; [12] 4-methylhexanal; [16] 2-octenol; [17] 1-decene; [22] unknown m/z 71; [23] unknown m/z 55; [26] undecanal; 1-dodecanol; carboxylic acid.

observation may be explained by the occurrence of secondary reactions, which should be facilitated under these conditions. A short pyrolysis time (10 s) at both temperatures leads to high amounts of alkanes, alkenes and aldehydes instead

of carboxylic acids. On the other hand, higher temperature and long pyrolysis time did not favour extensive pyrolysis of this material. In this case, a desorption-like process becomes more prominent than the pyrolytic process.

Fig. 5. Mass chromatogram of m/z 71 indicating a series of compounds for nut oil under oxidative atmosphere; spectrum of a typical unknown compounds with base ion peak of m/z 71.

0.1 0.04 0.4 0.4 ± ± ± ± 0.5 0.46 1.2 1.7 0.4 0.2 0.3 0.3 ± ± ± ± 1.4 1.3 0.9 0.8 0.1 0.2 0.2 0.4 ± ± ± ± 0.9 1.0 0.9 1.9 0,3 0.3 0.3 1 ± ± ± ± 4,1 6.8 8.2 9 0.08 0.3 0.4 1 ± ± ± ± 2.25 6.9 7.8 8.2 0.4 0.6 0.5 0.7 ± ± ± ± 4.2 5.3 7.9 8.9 0.6 0.3 0.4 0.8 ± ± ± ± 11.0 9.6 7.7 8.2 2 1 1 1 ± ± ± ± 13 16 14 10 1 1 1 0.5 ± ± ± ± 8 8 9 6.4 2 1 1 1 ± ± ± ±

± ± ± ± 2.58 2.30 0.9 1.8 0.1 0.2 1 0.6 ± ± ± ± 2.8 3.2 6 7.4 0.5 0.2 0.2 0.4 ± ± ± ± 2.7 2.8 3.4 5.6 0.4 0.5 0.8 0.05 ± ± ± ± 5.5 6.1 7.3 5.86 1 0.5 0.2 0.7 ± ± ± ± 9 7.2 7.3 6.9 0.8 0.4 0.3 0.4 ± ± ± ± 10.7 8.5 7.3 5.8 0.5 1 3 1 ± ± ± ± 11.1 13 13 10 2 1 4 3 ± ± ± ± 2 3 2 4

3 3 3 3

± ± ± ±

± ± ± ± 35 26 25 22

T= 5 10 20 30 T = 800 ◦ C 5 10 20 30

34 34 29 32

21 23 24 23

109

20 19 18 23

0.7 1.1 1.2 1.48 ± ± ± ± 0.06 0.05 0.2 0.3

0.9 0.48 0.6 0.16

Alkane Alkene-yne Alkyl benzene Unknown/others Unknown m/z 67 Unknown m/z 55 Diene Alkene Cycloalkane Aldehyde 700 ◦ C

The major difference in the profiles obtained when the pulp oil was pyrolysed under different atmospheric conditions was the yield of some classes of product (see Tables 2 and 4). For most classes of compound, the yields were independent of the atmospheric conditions except for alkane, alkene-yne and compounds with base ion peak at m/z 67, which were only present under inert conditions. Under

Pyrolysis time (s)

3.4. Profile and yield trends for pulp oil pyrolysed under different atmospheres

Table 2 Composition (TIC peak area %) of the pulp oil pyrolysate under inert atmosphere

3.3.2.2. Nut oil. The overall behaviour of the nut oil under oxidative conditions at a given temperature and for different pyrolysis times is summarized in Table 5. For a given pyrolysis temperature, as the pyrolysis time is increased a general tend can be noticed. There is a reduction in the yields of carboxylic acids and compounds referred to as unknown at m/z 55 and 71. On the other hand, the yields of a number of some constituents remained almost constant such as alkane and compounds refereed as unknown\others, while others such as aldehydes and alkane increased. For a given pyrolysis time (see Table 5), when the temperature was raised the yields of alkene and unknown compounds (m/z 55 and 71) decreased while the yields of alcohol and aldehyde increased. In these conditions the yield of alkane, carboxylic acid and unknown/others tend to remain constant.

0.4 0.04 0.1 0.02

3.3.2.1. Pulp oil. The variation in profile of the pulp oil at a given temperature and for different pyrolysis times, using oxidative conditions are shown in Table 4. The pulp oil pyrolysate leads mainly to aldehydes, cycloalkenes and compounds referred to as unknowns at m/z 56, the yield of which corresponds to 43–77% of the total pyrolysate. Alkenes, alkyl benzenes, dienes and unknowns at m/z 55 are secondary products, their contribution varying between 24 and 55%. The oxidative pyrolytic process for pulp oil also yields a low amount of cycloalkanes ranging from 0.3 to 2, and 4%. Under these conditions, as the pyrolysis time was increased the amount of aldehydes, alkenes, alkylbenzenes remained practically constant with only slight variations while dienes, and the compounds referred to as unknown at m/z 55 and unknown/other components were enhanced. Cycloalkanes yields were variable, while for compounds referred to as unknown at m/z 56, there was a decrease in yield. A particular trend is observed regarding the yields of compounds referred to as unknown at m/z 56, and other constituents. As the pyrolysis time is increased, there is a reduction in their yields. Correspondingly, the yields of dienes, unknowns at m/z 55, and unknown/other constituents increased. It is inferred that longer pyrolysis times lead preferentially to secondary reactions that generate mainly the latter constituents.

± ± ± ±

Cycloalkene

3.3.2. Oxidative atmosphere

0.2 0.2 0.5 0.05

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Table 3 Composition (TIC peak area %) of the nut oil pyrolysate under inert atmosphere Pyrolysis time (s)

Alkene

Aldehyde

Carboxylic acid

Unknown m/z 55

Cycloalkane

Alkane

Unknown m/z 54

Alcohol

Unknown m/z 67

T = 700 ◦ C 10 20 30

41 ± 3 37 ± 3 25 ± 3

25 ± 4 18 ± 1 16 ± 1

8.2 ± 0.4 11.7 ± 0.7 17.4 ± 0.9

8±2 16 ± 1 24 ± 2

6.0 ± 0.9 8.4 ± 0.8 10.2 ± 0.7

10.3 ± 0.6 6.5 ± 0.4 2.9 ± 0.6

1.1 ± 0.4 1.8 ± 0.6 3.4 ± 0.4

0.4 ± 0.2 0.5 ± 0.2 1.0 ± 0.4

0.15 ± 0.02 0.33 ± 0.03 0.34 ± 0.02

T = 800 ◦ C 10 20 30

30 ± 6 27 ± 5 18 ± 2

21 ± 3 14 ± 3 15 ± 1

14 ± 1 24 ± 4 36 ± 3

10 ± 2 15 ± 3 19 ± 3

9±1 8±1 2.7 ± 0.3

15 ± 3 8±2 3.1 ± 0.2

1.4 ± 0.3 2.7 ± 0.4 2.8 ± 0.2

0.32 ± 0.06 1.1 ± 0.4 2.5 ± 0.3

0.49 ± 0.07 0.57± 0.03 2.01 ± 0.6

Table 4 Composition (TIC peak area %) of the pulp oil pyrolysate under oxidative atmosphere. Pyrolysis time (s) T = 700 ◦ C 5 10 15 20 T = 800 ◦ C 5 10 15 20

Aldehyde

Alkene

Alkyl benzene

Cycloalkane

25 19 24 21

± ± ± ±

2 2 4 2

3.1 2.4 2.6 3.5

± ± ± ±

0.2 0.3 0.5 0.6

3.3 2.9 3.2 3.1

± ± ± ±

0.9 0.3 0.3 0.4

0.27 0.78 1.0 2.4

25 30 24 35

± ± ± ±

3 4 2 3

5.1 5.0 4.2 5.3

± ± ± ±

0.6 0.5 0.8 0.4

4.1 3.4 3.7 2.9

± ± ± ±

0.2 0.5 0.3 0.2

0.9 2.0 0.8 1.9

± ± ± ±

0.01 0.05 0.2 0.1

+ 0.1 + 0.2 + 0.1 + 0.4

oxidative conditions, the pulp oil exhibited a major component peak at the beginning of the acquisition characterised by the base ion peak at m/z 56, which was not identifiable. The pulp oil appears to have a dissimilar behaviour under inert and oxidative atmosphere when different temperatures and pyrolysis times are employed. Under inert conditions, at a given temperature and for different pyrolysis times, the yield of aldehyde, alkene and cycloalkane had a slightly decreased, cycloalkene and unknown/others increased, while the yields of other constituents varied as the pyrolysis time increased. Under oxidative conditions, the yields of aldehydes, alkenes and alkyl benzenes were almost constant, while dienes and compounds referred to as unknown/other constituents increased. On the other hand, the yields of cy-

Cycloalkene

Diene

Unknown m/z 55

13.8 5.0 9.8 12

± ± ± ±

0.5 0.4 1 1

6.6 6.4 11 20

± ± ± ±

0.5 0.3 2 2

8 8.6 7.8 16

± ± ± ±

14.2 16 9.8 14

± ± ± ±

0.9 1 0.9 1

5.2 6.4 8.6 9

± ± ± ±

0.1 0.8 0.9 1

8.4 8 9 9

±0.8 ±1 ±1 ±1

Unknown m/z 56

1 0.5 0.8 2

Unknown/ others

35 52 35 9.5

± ± ± ±

3 4 1 0.1

32 25 35 12

± ± ± ±

4 3 4 1

5.3 3.5 5.9 12.1

± ± ± ±

0.3 0.7 0.9 0.9

5.0 3.8 4.7 11

± ± ± ±

0.8 0.6 0.5 1

cloalkanes and cycloalkenes varied and compounds referred to as unknown at m/z 56 had a tendency to decrease as the pyrolysis time was raised. For a given pyrolysis time (see Tables 2 and 4), the oil exhibited the following behaviour as the temperature was raised. The yield of aldehydes exhibited some variation, ranging from 19 to 35% under both atmospheric conditions. The yields of alkenes, cycloalkenes and cycloalkanes decreased under inert conditions and increased under oxidative conditions, although the yield of cycloalkanes exhibited was variable under oxidative conditions. The yields of dienes and alkanes were enhanced under inert conditions while the former decreased under oxidative conditions. Alkylbenzene had shown a variable behaviour under inert

Table 5 Composition (TIC peak area %) of the nut oil pyrolysate under oxidative atmosphere Pyrolysis time (s)

Alcohol

Aldehyde

Alkane

Alkene

Carboxylic acid

Unknown m/z 55

Unknown m/z 71

Unknown/others

700 ◦ C

T= 5 10 15 20 T = 800 ◦ C 5 10 15 20

25 23 22 22

± ± ± ±

2 2 5 2

8.9 13 13.7 16

± ± ± ±

0.5 1 0.7 3

8 9 8 9.4

± ± ± ±

1 1 1 0.2

21 20 25 27

± ± ± ±

3 4 8 2

9 6 6 3.6

±1 ±2 ±1 ± 0.5

18 16 15 12

± ± ± ±

3 1 2 2

5 5.8 4.8 3.7

± ± ± ±

1 0.6 0.4 0.6

5 7 5.2 6

± ± ± ±

1 1 0.4 2

30 26 24 23

± ± ± ±

2 4 1 2

10.6 14.3 22.1 28

± ± ± ±

0.4 0.8 0.8 3

8 10 10 8

± ± ± ±

2 1 1 1

19 21 19 18

± ± ± ±

1 3 4 2

8±2 5.8 ± 0,7 6.9± 0.6 5±1

14 13 11 10

± ± ± ±

0.9 2 4 3

3.9 4.4 3.2 3.3

±0.4 ± 0.4 ± 0.3 ± 0.4

6.3 5.5 4.0 5.1

± ± ± ±

0.5 0.3 0.4 0.4

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conditions and an increase under oxidative conditions. Unknowns, characterised by m/z 55, remained constant under oxidative conditions but diminished under inert conditions. Yields of compounds referred to as unknown at m/z 67, and alkene-ynes were variable under inert conditions. 3.5. Profiles and yield trends for nut oil pyrolysed under different atmospheres The pyrolysis of the nut oil under different atmospheres exhibits a unique profile (see Tables 3 and 5). While pyrolysis under inert conditions yields major products comprising alkene, aldehyde and carboxylic acids, under oxidative conditions the main products were alcohol, alkane and aldehyde. Moreover, a series of compounds for which the base ion peak is at m/z 71, is only detectable under oxidative conditions (see Fig. 5). The presence of cycloparaffins and compounds referred to as unknowns, characterised by the base ion peaks are at m/z 54 and 67, were only detected when the nut oil was pyrolysed under inert conditions. Under inert conditions, the yield of alkane varied with the temperature and pyrolysis time, whereas, under oxidative conditions, the yield remained almost constant (see Table 5). It was observed that under oxidative conditions, the temperature and pyrolysis time did not affect the yields of compounds. Under inert conditions, increasing the temperature and pyrolysis time led to changes in the yields of compounds in a way that affected the extent to which the pyrolytic process occurred. At a higher temperature and for shorter pyrolysis times, the oils undergo pyrolysis to a greater extent.

4. Conclusion The technique of pyrolysis using on-line analysis with capillary GC/EI– and PCI–MS has been demonstrated to be a good analytical tool for characterising and quantifying the main constituents generated during pyrolysis of the oils originating from the components of the Macauba fruit. Under the conditions employed, the component oils studied undergo a process of partial pyrolysis to varying extents, generating considerable yields of carboxylic acid, aldehydes, alcohols, alkenes, and alkadienes. In general, the relative amount of main products was decreased as pyrolysis temperature was increased for both oils under inert atmosphere. Under oxidative atmosphere, the yield of the main products was not changed but the amounts of the compounds referred as unknown m/z 56 and 55 were reduced with increasing pyrolysis temperature for pulp oil. As pyrolysis temperature was increased there was a reduction in the amounts of compounds referred as unknown m/z 56 and 55. However, for nut oil, under at higher temperatures the amounts of the main products

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(alcohol and aldehyde) increased while the amounts of the others constituents decreased but the amounts of alkane and carboxylic acids remained constant. Pyrolysis time influenced the formation of the whole pyrolysate under both atmospheres and at different pyrolysis temperatures. Some compound classes appeared only at under a given atmosphere. For instance, the compounds referred as unknown m/z 67 and 54 only occurred under inert atmosphere while compound referred as unknown m/z 71 appeared under oxidative atmosphere, for nut oil.

References [1] E.J. Soltes, T.A. Milne, Pyrolysis Oils Biomass: Producing, Analyzing and Upgrading, American Chemical Society, Division of Fuel Chemistry Abstracts, New York, 1988. [2] J.O.B. Carioca, Arora, Biomassa: Fundamentos e Aplicações Tecnológicas, UFC, Ceará,1985. [3] K. Raveendran, A. Ganesh, Fuel 75 (1996) 1715. [4] E. Churin, B. Delmon, What can we do with pyrolysis oil?, in: G.l. Ferrero, K. Maniatis, A. Buekens, A.V. Bridgwater (Eds.), Pyrolysis and Gasification, Elsevier, London, 1989, p. 326. [5] P. Ahuja, P.C. Singh, S.N. Upadhyay, S. Kumar, Indian J. Chem. Technol. 3 (1996) 306. [6] M.Y. Wey, S.C. Huang, C.L. Shi, Fuel 76 (1997) 115. [7] D.S. Scott, J. Piskorz, Can. J. Chem. Eng. 62 (1984) 404. [8] K.EiichiM. Yelian, Y. Shigeru, J. Chem. Eng. Jpn. 24 (1990) 8. [9] S.Y. Wu, M.Y. Wey, C.S. Lo, Y.T. Lee, in: Proceedings of the Fourth Asian Conference on Fluidized-Bed and Three-Phase Reactors, 1994, p.122. [10] P. R Solomon, D.G. Hamblen, R.M. Carangelo, M.A. Serio, G.V. Deshpande, Combust. Flame 71 (1988) 137. [11] A.A. Merchant, M.A. Petrich, AIChE J. 39 (1993) 1370. [12] W. Kaminsky, J. Menzel, H. Sinn, Conserv. Recycl. 1 (1976) 91. [13] M.Y. Wey, C.L. Chang, Polymer Degradat. Stability 48 (1995) 25. [14] D.M. Bate, R.S. Lehrle, Polymer Degradat. Stability 64 (1999) 75. [15] M.R. Grimbley, R.S. Lehrle, R.J. Williams, D.M. Bate, Polymer Degradat. Stability 48 (1995) 143. [16] H.L. Hsu, J.O. Osburn, C.S. Grove Jr., Ind. Eng. Chem. 42 (1950) 2141. [17] J.W. Alencar, P.B. Alves, A.A. Craveiro, J. Agric. Food Chem. 31 (1983) 1268. [18] D. Meier, O. Faix, Biores. Technol. 68 (1999) 71. [19] I.C.P. Fortes, P.J. Baugh, J. Anal. Appl. Pyrol. 29 (1994) 153. [20] I.C.P. Fortes, P.J. Baugh, J. Brazilian Chem. Soc. 10 (1999) 469. [21] A.A. Craveiro, F.J.A. Matos, J.W. Alencar, E.R. Silveira, Energia: Fontes Alternativas 3 (1981) 44. [22] A.A. Craveiro, A.S. Rodrigues, C.H.S. Andrade, F.J.A. Matos, J.W. Alencar, M.I.L. Machado, J. Nat. Prod. 44 (1981) 602. [23] K. Markley, Econom. Botany 10 (1956) 3. [24] R.M. Silverstein, G.C. Bassler, T.C. Morril, Spectrometric Identification of Organic Compounds, fifth ed., Willey & Sons Inc., Singapore, 1991. [25] F.M. McLafferty, F. Turecek, Interpretation of Mass Spectra University Sciences Books Mill Valley, California, 1993. [26] H. Budzikiewicz, C. Djerassi, D.H. Williams, Mass Spectrometry of Organic Compounds Holden-Day Inc., San Francisco, 1967. [27] J.H. Beynon, Mass Spectrometry and its Applications to Organic Chemistry, Elsevier, Amsterdam, 1960. [28] P.T. Williams, H. Nittaya, A. Patrick, in: A.V. Bridgwater (Ed.), Biomass Gasif. Pyrolysis, CPL Press, Newbury, UK, 1997, p. 422.