Pyrolysis of fat from Nannochloropsis sp.and its effect on bio-oil from pyrolysis of all components
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摘要: 以酸水解法从微拟球藻中提取的粗脂肪为原料, 在管式裂解炉中考察不同热解温度下脂肪单组分的热解规律及对微拟球藻全组分各相产率及生物油性能的影响。利用热重分析仪分别考察粗脂肪及全组分的热失重特性, 并求出相应的动力学参数。结果表明, 脂肪热解能够提高全组分热解有机相产率并改善油品性能。随着温度的升高, 粗脂肪与全组分热解后的有机相产率及油品性能的变化趋势相同, 且生物油性能均在600 ℃时达到最佳。经热解, 粗脂肪中含氧化合物含量降低, 脂肪烃含量显著增加。对比全组分热解, 粗脂肪热解后的油品脱氧率及氢、碳元素比例更高, 因而增加全组分中脂肪的含量能够促进油品性能的进一步提高。对粗脂肪及全组分的热重数据进行计算, 发现两者均满足二级化学反应机理, 粗脂肪、全组分的活化能与指前因子分别为64.34 kJ/mol与2.94×105 min-1, 48.13 kJ/mol与2.96×103 min-1。Abstract: The crude fat was used as raw material, which was extracted from Nannochloropsis sp. by acid hydrolyzation. The pyrolysis characteristic of crude fat and its effect on the yield of each phase and the properties of bio-oil were examined at different temperatures in a bench-scale fixed bed reactor. In addition, the thermogravimetric characteristics of crude fat and all components were studied by means of thermogravimetric analyzer, and corresponding kinetic parameters were determined. The results show that both the yield of organic phase and the properties of bio-oil which is produced from the pyrolysis of all components are enhanced by the pyrolysis of fat. Moreover, with an increase in temperature, the yield of organic phase and the properties of bio-oil from crude fat and all components have same varying trend, and their best properties are obtained at 600 ℃. The content of oxygenated compounds in the crude fat including alcohols, acids and esters decreases and that of aliphatic hydrocarbon severely increases after being pyrolyzed. Compared with the pyrolysis of all components, the deoxidizing ratio and the content of carbon and hydrogen elements in crude fat after being pyrolyzed are higher, therefore the performance could be further improved with the increase of fat in the Nannochloropsis sp.. According to the kinetic data, the pyrolysis of crude fat and all components follows the second order reaction mechanism. The pyrolysis activation energy and pre-exponential factor are 64.34 kJ/mol and 2.94×105 min-1 for crude fat, and 48.13 kJ/mol and 2.96×103 min-1 for all components.
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Key words:
- Nannochloropsis sp. /
- acid hydrolyzation /
- crude fat /
- pyrolysis /
- bio-oil /
- kinetics
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图 1 粗脂肪及微拟球藻热解实验装置示意图
Figure 1 Schematic diagram of experimental apparatus for pyrolysis of crude fat and Nannochloropsis sp.
1:rotameter; 2:nitrogen gas cylinder; 3:pressure reducing valve; 4:temperature control system; 5:thermocouple; 6:porcelain boat or quartz tube; 7, 8, 12:tubular furnace tube; 9:condensation system; 10:receiving flask; 11:exhaust pipe
图 2 不同热解温度下粗脂肪热解后各相产率对比
Figure 2 Distribution of phases produced from pyrolysis of crude fat at different pyrolysis temperatures
图 3 不同热解温度下粗脂肪热解后油品性能
Figure 3 Properties of the bio-oil produced from pyrolysis of crude fat at different pyrolysis temperatures
图 4 不同热解温度下全组分热解后各相产率对比
Figure 4 Distribution of phases produced from pyrolysis of all components at different pyrolysis temperatures
图 5 不同热解温度下全组分热解后油品性能
Figure 5 Properties of the bio-oil produced from pyrolysis of all components at different pyrolysis temperatures
图 6 粗脂肪热解前后主要成分对比
Figure 6 Main components identified by GC-MS before and after pyrolysis of crude fat
图 7 微拟球藻粗脂肪热重分析TG和DTG曲线
Figure 7 TG and DTG curve of crude fat from Nannochloropsis sp.
图 8 微拟球藻全组分热重分析TG和DTG曲线
Figure 8 TG and DTG curve of the all components of Nannochloropsis sp.
表 1 实验用微拟球藻的物化性质参数
Table 1 Physico-chemical properties of Nannochloropsis sp. in the experiment
Proximate analysis w/% Ultimate analysis w/% Composition analysis w/% M V FC A C H Oa N protein polysaccharide lipid othersb 3.90 82.91 7.12 6.07 49.79 7.69 36.14 6.38 44 21 25 10 a: calculated by difference, O (%)=100-C-H-N; b: defined by difference, others (%)=100-protein-polysaccharide-lipid 
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表 2 微拟球藻粗脂肪的主要有机组分
Table 2 Main organic components of crude fat from Nanochloropsis sp.
Compound Peak area /% Boiling point t/℃* Compound Peak area /% Boiling point t/℃ 5, 8, 11, 14, 17-eicosapentaenoic 12.64 115-125 heptadecane 0.23 302 acid, methyl ester Isopropyl palmitate 0.10 160 tetradecanoic acid 9.45 326.2 5, 8, 11, 14-eicosatetraenoic 0.18 200-205 n-hexadecanoic acid 49.16 351.5 acid, methyl ester 3, 7, 11, 15-tetramethyl-2-hexadecen-1-ol 9.11 202-204 9, 12-octadecadienoic acid (Z, Z)- 9.67 365.2 Octanoic acid, ethyl ester 0.23 208.5 10-octadecenoic acid, methyl ester 0.81 368.6±11.0 Benzaldehyde, 2-ethyl- 0.17 210 1, 3-benzenedicarboxylic acid, 0.13 391.7±10.0 bis (2-ethylhexyl) Butylated hydroxytoluene 0.46 265 9-hexadecenoic acid, methyl ester, (Z)- 1.7 394.2 N-decanoic acid 0.12 268.7 5, 8, 11, 14, 17-eicosapentaenoic 1.35 402.8±34.0 acid, methyl ester Phenol, 3, 5-bis (1, 1-dimethylethyl)- 0.16 276.7±9.0 heptacosene 0.11 414.8±8.0 Hexadecane 0.14 286.5 hexadecanoic acid, methyl ester 1.13 417 Methyl tetradecanoate 0.17 295 cholest-5-en-3-ol (3á)-, acetate 0.64 493.3±24.0 Dodecanoic acid 0.49 298.9 sum 98.35 *: boiling point data from SciFinder
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表 3 脂肪与全组分600 ℃热解前后性能对比
Table 3 Comparison in the properties of the crude fat and all components before and after pyrolysis at 600 ℃
Property Crude fat All components before pyrolysis after pyrolysis before pyrolysis after pyrolysis Calorific value Q/(kJ·g-1) 39.413 41.358 21.357 31.742 Moisture content w/% 0.206 0.286 - 11.675
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表 4 脂肪与全组分600 ℃热解前后元素分析对比
Table 4 Element analysis of crude fat and all components before and after pyrolysis at 600 ℃
Element analysis w/% Crude fat All components before pyrolysis after pyrolysis before pyrolysis after pyrolysis C 79.10 80.86 49.79 61.77 H 13.51 14.37 7.69 8.93 Od 6.50 3.88 36.14 22.07 N 0.89 0.89 6.38 7.23 d：calculated by difference, O (%)=100-C-H-N
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表 5 常见动力学模型函数
Table 5 Algebraic expressions for G(α) for the most frequently used kinetics model functions
Function name Functions G(α) Mechanism Parabolic rule α2 one-dimensional diffusion Valensi equation α+(1-α) ln (1-α) two-dimensional diffusion, cylindrical symmetry Jander equation ${\left[ {1 - {{\left( {1 - \alpha } \right)}^{\frac{1}{2}}}} \right]^{\frac{1}{2}}}$ two-dimensional diffusion, 2D, n=1/2, (Jander equation) Ginstling-brounstein equation $1 + \frac{2}{3}\alpha - {\left( {1 - \alpha } \right)^{\frac{2}{3}}}$ three-dimensional diffusion (Ginstling. Brounshtein equation) Anti-jander equation ${\left[ {{{\left( {1 + \alpha } \right)}^{\frac{1}{3}}} - 1} \right]^2}$ three-dimensional diffusion, 3D Zhuralev-lesokin-tempelman equation ${\left[ {{{\left( {1 - \alpha } \right)}^{\frac{1}{3}}} - 1} \right]^2}$ three-dimensional diffusion, 3D, Nucleation and growth Avrami-erofeev equation ${\left[ { - \ln \left( {1 - \alpha } \right)} \right]^{\frac{1}{3}}}$ nucleation and growth, n=1/3, m=3 Mample one way rule -ln (1-α) nucleation and growth, assuming only one core on every particle Globular contractile (volume) $1 - {\left( {1 - \alpha } \right)^{\frac{1}{3}}}$ phase boundary controlled reaction, spherical symmetry，n=1/3 Cylinder contractile (volume) $1 - {\left( {1 - \alpha } \right)^{\frac{1}{2}}}$ phase boundary controlled reaction, cylindrical symmetry, n=1/2 Order of reaction, n=2 (1-α)-1-1 second order reaction
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表 6 粗脂肪主热解区间动力学计算
Table 6 Result of the dynamics computation at the main temperature range of crude fat
Function name a b R SD A/min-1 E/(J·mol-1) Parabolic rule -2.004 0 -7 412.4 -0.917 6 0.669 7 1.99×104 61.63×103 Valensi equation -0.992 7 -8 257.3 -0.935 3 0.651 6 6.12×104 68.65×103 Jander equation -11.205 4 -1 330.0 -0.857 1 -0.857 1 0.36 11.06×103 Ginstling-brounstein equation -1.768 7 -8 622.3 -0.942 5 -0.942 5 2.94×104 71.69×103 Anti-jander equation -0.906 0 -6 689.4 -0.906 0 -0.906 0 5.41×104 55.62×103 Zhuralev-lesokin-tempelman equation 0.489 4 -12 001.3 -0.981 4 0.489 4 3.92×104 99.78×103 Avrami-erofeev equation -11.569 5 -793.3 -0.849 7 0.102 7 0.15 6.60×103 Mample one way rule -5.198 5 -4 716.1 -0.961 0 0.283 3 5.21×102 39.21×103 Globular contractile (volume) -7.513 9 -4 102.8 -0.940 2 0.310 2 44.76 34.11×103 Cylinder contractile (volume) -7.655 7 -3 828.2 -0.927 9 0.320 8 36.24 31.83×103 Order of reaction, n=2 0.642 9 -7 738.7 -0.986 8 0.296 6 2.94×105 64.34×103
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表 7 微拟球藻全组分主热解区间动力学计算
Table 7 Result of the dynamics computation at the main temperature range of all components
Function name a b R SD A/min-1 E/(J·mol-1) Parabolic rule -3.198 9 -7 274.5 -0.962 1 0.480 6 5.94×103 60.48×103 Valensi equation -2.584 7 -7 939.8 -0.971 0 0.455 7 1.20×104 66.01×103 Jander equation -11.736 6 -1 183.5 -0.916 2 0.120 7 0.19 9.84×103 Ginstling-brounstein equation -3.562 3 -8 209.8 -0.974 3 0.442 3 4.66×103 68.26×103 Anti-jander equation -6.705 1 -6 630.5 -0.955 2 0.479 0 1.62×102 55.13×103 Zhuralev-lesokin-tempelman equation 1.069 5 -10 595.2 -0.991 5 0.323 3 6.17×105 88.09×103 Avrami-erofeev equation -12.121 5 -599.3 -0.882 3 0.074 5 0.07 4.98×103 Mample one way rule -6.712 7 -4 212.2 -0.981 2 0.193 0 1.02×102 35.02×103 Globular contractile (volume) -8.659 8 -3 775.6 -0.971 3 0.215 4 13.10 31.39×103 Cylinder contractile (volume) -8.647 2 -3 574.1 -0.965 4 0.225 2 12.55 29.71×103 Order of reaction, n=2 -3.667 7 -5 788.8 -0.995 6 0.126 4 2.96×103 48.13×103
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