Fast Pyrolysis of Laurel (Laurus Nobilis L.) Seed in a Fixed-bed Tubular Reactor

Transcription

1 Fast Pyrolysis of Laurel (Laurus Nobilis L.) Seed in a Fixed-bed Tubular Reactor Özlem ONAY Anadolu University Porsuk Vocational School Eskisehir, Turkey oonay@anadolu.edu.tr Abstract The daphne seed can be utilized as a biomass feedstock for conversion to bio-oil with pyrolysis process. The samples were initially pyrolyzed on a lab-scale resistively heated fixed-bed pyrolysis system at different values in the ranges of C and Cmin -1 to determine the effects of operation temperature and heating rate on the yields on products, respectively. Then, the bio-oil in the highest yield (35.2%) which was obtained at pyrolysis final temperature (600 0 C) temperature, heating rate (350 0 Cmin - 1), and sweeping flow rate of 100 cm 3 min -1 was characterized by Fourier Transform infra-red (FT-IR) spectroscopy, gas chromatography/mass spectrometry (GC-MS) and column chromatography. The characterization results revealed that the pyrolytic oils which were complex mixtures of C 11 C 23 organic compounds. The elemental analysis and calorific value of the bio-oil were determined, the calorific value of 24.4 MJkg -1 and the empirical formula of CH 1.69 N 0.04 O Based on the determined properties of the pyrolytic oil, it was decided that the use of pyrolytic oil derived from the daphne seed may possible be for the production of the alternative liquid fuels such as fuel for combustion systems in industry and finely chemicals after the necessary improvements. Keywords Laurel (Laurus nobilis L.); pyrolysis; biomass; synthetic fuels; renewable energy Paper PS-40 1 of 7

2 Introduction Biomass represents a renewable and alternative energy source, and due to the advantages of being CO 2 neutral, having low sulfur content, and being easy to transport, will become more important in the future. Biomass material can be converted to the many useful products such as charcoal, liquid fuels, gas fuel, etc. with suitable conversion process such as pyrolysis (slow, fast, flash and vacuum), gasification, liquefaction, hydrothermal upgrading (in water or solvent) and combustion, etc. Among these processes, pyrolysis is the most widely used thermochemical conversion process which is the chemical decomposition of organic material by heating in the absence of oxygen. The product distributions from the pyrolysis of biomass depend on pyrolysis parameters; pyrolysis reactor design, reaction parameters (temperature, heating rate, residence time, pressure, reaction atmosphere, i.e. N 2, H 2 or steam and catalyst), and biomass type and characteristics;particle size, shape, and structure (Murata et al.2012, Duman et al. 2011, Ucar et al. 2011). Slow pyrolysis conditions (long residence times at slow heating rates) at low temperature produce mainly charcoal, and high temperatures mainly produce gaseous products. On the other hand, fast heating rates at short residence times, and moderate temperatures favor a high yield of bio-oil (Huber et al. 2006). Bio-oil is a darkbrown organic liquid and also it includes a lot of the organic compounds like phenols, alcohols, ketones, esters, aldehydes, oxygenated hydrocarbons, etc. (Czernik et al. 2004, Goyal et al. 2008). Bio-oil can be readily stored, transported, and used as chemical feedstock for the production of various industrialized chemicals and also, it can be burned directly, cofired and upgraded to other fuels (Mckendry 2002). Turkey has considerable sources of renewable energy which include hydropower, wind, solar, geothermal and biomass. Among these energy sources, biomass will become precious sources of energy in the future since Turkey is an agricultural country and has abundant biomass sources. (Ogulata 2002). Sunflower, cotton, rape, safflower and euphorbia species are among the most promising renewable sources that have already been studied from the pyrolysis parameters and fuel properties. As an addition to biomass diversity of Turkey a wild growing evergreen tree Laurel is focused for possible use as a renewable fuel source. Laurel (Laurus nobilis L.), belongs to the family Lauraceae growing in most of the Mediterranean countries. Italy, former Yugoslavia and Turkey are among the most important producers of the botanical raw material. The tree is utilized mainly for its leaf for spice and essential oil industry and for its wood, which is very suitable for fence posts or supporters of wine plants. On the other hand Laurel berry contains, substantial amounts of fixed oil consisting mainly of odorless lauric acid, myristic acid and related compounds. From this point of view, laurel seed is of importance as a very important candidate of potential source of renewable fuels and chemical feedstock in Turkey. In the present study, this is the first time that fast pyrolysis of daphne seeds was investigated in a well swept resistively heated fixed-bed pyrolysis reactor. The yield and characterization of the pyrolysis oils was investigated using some chromatographic and spectroscopic techniques, such as gas chromatography mass spectrometry (GC MS), and elemental analysis. Methods Materials. The samples of daphne seed (Laurus nobilis L.) were obtained from the town of Silifke, located in the Mediterranean region of Turkey. Prior to use, the sample was air-dried, Paper PS-40 2 of 7

3 grounded in a high-speed rotary cutting mill and then screened to give a particle size between mm. Proximate analyses of the sample were performed according to The Standard Methods of the American Society for Testing and Materials (ASTM) procedure. Ultimate analyses were performed on safflower seed to determine the elemental composition LECO TruSpec CHN Elemental Analyzer was used to determine the weight fractions of carbon, hydrogen and nitrogen, and the weight fraction of oxygen was calculated by difference. Cellulose, oil and protein, being the main constituents of daphne seed, were also determined (Table 1). Table 1. Main characteristic of the daphne seed Proximate analysis(wt.%,as received) Moisture 6.6 H/C molar ratio 1.68 Volatile 85.8 O/C molar ratio 0.49 Fixed C 5.8 Empirical formula CH 1.68 N 0.04 O 0.49 Ash 1.8 Calorific value (MJ/kg) 22.9 Elemental analysis (wt%, daf.basis) Protein 16.4 C 54.2 Cellulose 4.9 H 7.6 Oil 21.8 N 2.7 O(by difference) 35.5 Pyrolysis. The fixed-bed pyrolysis experiments were conducted in a well-swept resistively heated fixed-bed reactor (8 mm i.d., 90 cm long). To determine the effect of pyrolysis temperature and heating rate on the pyrolysis yields, 3 g of air-dried sample, sieved to in the particle size range of mm was placed in the reactor and a sweep gas velocity of 100 cm 3 min -1 was controlled and measured with a rotameter. The sample was heated at a heating rate of either 30, 100, 350 or 700 C min -1 to the final pyrolysis temperature of either 400, 500, 550, 600 or 700 C and held at that temperature for 30 min or until no further significant release of gas was observed. Heating rate and pyrolysis temperature were controlled by a PID controller. The flow of the gas released was measured, using a soap film meter, for the duration of the experiments. The liquid phase was collected in a glass liner located in a cold trap maintained at about 0 C. Particularly, water was determined by refluxing the toluene solutions in a Dean&Stark apparatus. After pyrolysis, char yield was determined from the overall weight losses of the reactor tube. The gas yield was then calculated by difference. Characterization. The oil analyzed was obtained under the experimental conditions giving the maximum oil yield (pyrolysis temperature of 600 C and heating rate of 350 Cmin -1 ). The elemental composition and calorific value of the well-swept fixed-bed reactor oil were determined. The 1 H NMR of the oil was obtained at an H frequency of 90 MHz using a Jeol EX 90 A instrument. The sample was dissolved in chloroform-d. The I.R. spectrum of the oil was recorded using a Jasco FT: IR-300 E Fourier transform infrared spectrophotometer. The chemical class composition of the oil was determined by a liquid column chromatographic technique. The oils were separated into two fractions as n-pentane soluble and insoluble compounds (asphaltenes) by using n-pentane. The n-pentane soluble material was further separated on activated silica-gel ( mesh). The column was eluted successively with n- pentane, toluene and methanol to produce aliphatic, aromatic and polar fractions, respectively. The GC-MS analyses of the n-pentane fractions was performed on an Agilent HP 6890N gas chromatography equipped with an Agilent HP 5973N mass selective detector (GC/MS) and a 30 m 0.25 mm i.d.; 0.25 µm film thickness, HP-5MS column. Helium was the carrier gas at a flow rate of 0.8 ml/min. The column temperature was programmed from 50 C (kept for 2 min) to 280 C at 10 C min -1. The final temperature was held at 280 C for 5 min. Typical Paper PS-40 3 of 7

4 operating conditions were: ionization energy 70 ev; ion source temperature 230 C; scan per s over mass range electron (m/z) = Results and discussion Product yields. The product yields were discussed for effect of pyrolysis temperature and heating rate. First, to determine the effect of pyrolysis temperature on the pyrolysis product yields, experiments were conducted with final pyrolysis temperatures of either 400, 500, 550, 600 or 700 C at the heating rate of Cmin -1. The product yields of the fast pyrolysis in relation to pyrolysis temperature are given in Fig. 1. As shown in Figs. 1, the char yield significantly decreased as the final pyrolysis temperature was a raised from 400 to 700 C. In other words, the pyrolysis conversion increased. As the pyrolysis temperature increased to a level of 600 C the liquid product yield reached the highest value of 35.2%, but further increasing the temperature to 700 C, the conversion increased to a level of 83.6%, but in contrast liquid product yields go down to 30.2%, however, brought an increase in the total pyrolysis conversion, resulting in an increase in gas product yield only. This result is in agreement with the literature (Ates et al. 2009, Gonzalez, et al. 2005) Yield (%) Char Oil Water+Gas Pyrolysis Temperature ( 0 C) Fig. 1. Influence of temperature on product yield distributions Yield (%) Char Oil Water+Gas Heating rate ( 0 Cmin -1 ) Fig. 2. Influence of heating rate on product yield distributions. In order to determine the effect of heating rate on pyrolysis yields, experiments have been conducted at heating rates of either 30, 100, 350 or C min 1 (Figure 2). The maximum oil yield of 35.2% was obtained at pyrolysis temperature of C and a heating rate of C Paper PS-40 4 of 7

5 min 1. Fig. 2 shows that at the higher heating rate of 350 C min -1 the overall conversion of the pyrolysis was only about 2.5% higher than that of the lower heating rate of 30 C min -1. However, the oil yield was about 16.9% higher than that of 30 C min -1. As can be seen, employing the higher heating rate of 350 C min -1 breaks the heat and mass transfer limitation in the pyrolysis, resulting in the maximum oil yield. Above this heating rate increase in the oil yield is negligible, remaining constant at the maximum level of 35%. Table 2. The elemental compositions and calorific values of pyrolysis oils Elemental analysis a Oil C 56.2 H 7.9 N 2.4 O b 33.5 H/C molar ratio 1.69 Calorific value (MJkg -1 ) 24.4 a Weight percentage on dry ash free basis b By difference Product characterization. The elemental composition of the sample of the oil characterized and the calorific values are listed in Table 2. The average chemical composition of the oil analyzed is CH 1.69 N 0.04 O Further comparison of H/C ratio with conventional fuels indicates that the H/C ratios of the oil obtained in this study (1.69) were very similar to that between light and heavy petroleum products. Also, calorific value indicates that the energy content of the oil is very close to that of petroleum. The IR spectrum of the oil is given in Figure 3. The O H stretching vibrations between 3200 and 3400 cm 1 indicate the presence of phenols and alcohols. The C H stretching vibrations between 2800 and 3000 cm 1 and C H deformation vibrations between 1350 and 1475 cm 1 indicate the presence of alkanes. The C=O stretching vibrations with absorbance between 1650 and 1750 cm 1 indicate the presence of ketones and aldehydes. The absorbance peaks between 1575 and 1675 cm 1 represent C=C stretching vibrations indicative of alkenes and aromatics. Fig. 3. The IR spectra of the pyrolysis oil The GC chromatogram of the oil is given in Figure 4. The straight chain alkanes range from C 11 to C 23, and distribution of straight chain alkanes exhibit a maximum in the range of C 13 to C 19 in the oil. At the same time, the compounds recognized in this fraction were listed in Table 5. Moreover, it was determined that oil contains mostly paraffinic and olefinic hydrocarbons. Paper PS-40 5 of 7

6 Abundance TIC: SEG37.D Time--> Fig. 4. The GC-MS chromatogram of the pyrolytic oil Conclusion Fixed-bed pyrolysis of daphne seed has shown significant recoveries of liquid hydrocarbon. The pyrolysis conversion increased with a final pyrolysis temperature up to C, but the oil yield increased with temperature up to C, after which there was a significant decrease in the oil yield. As a result of breaking heat and mass transfer limitations in the pyrolysis of daphne seed by increasing the heating rate from 30 0 C min 1 to C min 1, there was a significant change in the oil yield. As a result, the final pyrolysis temperature of 600 C temperature, heating rate of 350 Cmin -1 and sweeping gas flow rate of 100 cm 3 min -1 were more suitable for high-quality bio-oil production. References 1. Murata, K., Liu, Y., Inaba, M., Takahara, I Catalytic fast pyrolysis of jatropha wastes. Journal of Analytical and Applied Pyrolysis. 94: Duman, G., Okutucu, Ç., Ucar, S., Stahl, R., Yanik, J The slow and fast pyrolysis of cherry seed. Bioresource Technology. 102: Uçar, S., Karagöz, S The slow pyrolysis of pomegranate seeds: The effect of temperature on the product yields and bio-oil properties. Biomass and Bioenergy. 3 5: Huber, G.W., Iborra, S., Corma, A Synthesis of transportation fuels from biomass: chemistry, catalysts, and engineering. Chem. Rev. 106: Czernik, S., Bridgwater, A.V Overview of applications of biomass fast pyrolysis oil. Energ and Fuel. 18: Goyal, H.B., Seal, D., Saxen, R.C Bio-fuels from thermochemical conversion of renewable resources: a review. Renew Sust Energ Rev. 12: Mckendry, P Energy production from biomass (part 2): conversion technologies. Bioresour Technol. 83: Ogulata, R.T Energy from Renewable Sources in Turkey: Status and Future Direction. Renew. Sustain. Energy Rev. 6: Ateş,F., Isıkdag, M.A., Influence of temperature and alumina catalyst on pyrolysis of corncob. Fuel.88: Paper PS-40 6 of 7

7 10. Gonzalez, J.F., Ramiro, A., Gonzalez-Garcia, C.M., Ganan, J., Encinar, J.M., Sabio, E., Rubiales, J Pyrolysis of almond shells. Energy applications of fractions. Ind. Eng. Chem. Res. 44: Paper PS-40 7 of 7