樟木木屑真空热解工艺的响应面法优化及生物油组分分析

摘要

以樟木木屑为原料,采用真空热解系统进行了制取生物油的中心组合实验研究,以生物油产率为实验指标,利用响应面法( RSM)对热解液化工艺参数进行了优化,并对在最高产率条件下制取的生物油进行了理化特性、傅立叶变换红外光谱( FT-IR)和气质联用( GC-MS)分析。研究结果表明,热解终温、体系压力和升温速率对生物油产率的影响显著,但3者之间的交互作用并不显著。最佳热解工艺条件为：热解终温474.0℃、体系压力7.5 kPa、升温速率20.0℃/min,在此条件下,生物油产率可达50.25%。与预测值(50.41%)较为接近。樟木木屑真空热解所得生物油的含水量较低(21.35%),热值较高(26.82 MJ/kg),常温下的运动黏度为3.85 mm2/s,密度1.08 g/cm3、pH值3.24和残炭量5.54%；生物油成分较为复杂,其中多种有机物可被进一步提取用作工业原料；生物油中羧酸(8.45%)、醛(26.17%)、酮(14.24%)类等腐蚀性和不稳定组分含量较高,需对其进一步精制,以优化真空热解生物油品质,提高其稳定性。%Camphorwood sawdust from industrial processing was treated by vacuum pyrolysis for bio-oil preparation. The response surface methodology ( RSM) was employed to optimize the process for maximum yield of bio-oil. All factors that affected bio-oil yield, including pyrolysis temperature, reaction pressure and heating rate, were investigated. Furthermore, the physicochemical properties of the bio-oil obtained from vacuum pyrolysis at the optimal conditions were evaluated. The chemical composition was also examined using Fourier transform infrared ( FT-IR ) and gas chromatograph/mass spectroscopy ( GC-MS ) . The results showed that these three factors had obvious effects on bio-oil yield. However, the interaction between them was not remarkable. The optimal conditions for bio-oil yield were pyrolysis temperature 474. 0 ℃, reaction pressure 7. 5 kPa and heating rate 20. 0 ℃/min. At this condition, the bio-oil yield could reach 50. 25 % close to 50. 41%—the predicted value. Water content and high heat value of bio-oil was 21. 35% and 26. 82 MJ/kg, and its dynamic viscosity at room temperature, density, pH value and carbon residue content were 3. 85 mm2/s, 1. 08 g/cm3 , 3. 24 and 5. 54%, respectively. Bio-oil from camphorwood sawdust was a complex mixture, which involve aromatics (26.30%), alcohols (12.14%), carboxylic acids (8.45 %), aldehydes (26. 17 %), ketones (14. 24 %) and esters (1. 18%). It also contained some specific organic compounds, which could be further extracted for industrial raw materials. Further study on enhancing the properties of bio-oil should be performed to ensure economic feasibility in future.