常压下玉米秸秆液化工艺的优化及其生物油分析

随着化石能源的日益短缺，可再生木质生物质资源的利用越来越受到重视，常压液化技术是生物质资源高效利用的主要方式之一。利用单因素方法，探讨液化温度、复配液化剂二甘醇（DEG）与1,2-丙二醇（PG）的混合比、液固比、催化剂磷酸的用量、反应时间等因素对玉米秸秆液化得率的影响，以便优化其液化工艺；然后采用热重分析仪（TGA）、气相色谱-质谱技术（GC-MS）和核磁共振（NMR）技术对此优化条件下所得生物油的挥发降解特性和主要组成成分进行了检测探讨。分析表明，玉米秸秆液化时优化工艺参数为：液化温度170 ℃，液化剂DEG与PG混合比1∶2，液固比5∶1，H₃PO₄用量10%，反应时间45 min；此时玉米秸秆液化得率高至99.50%。TGA结果表明，此条件下所得生物油含有80%以上碳数小于25的化合物，热解后最终残炭量约为15%。GC-MS表明，可以检测出此生物油中含有的39种有机物，其中，醇类有机物的含量最多，酚类有机物的含量次之，它们相对含量依次是70.70%和25.63%，其还含有一定量的有机酸（2.80%）、醚类（0.64%）、酯类（0.10%）和酮类（0.13%）等有机物；其组分十分复杂，高含氧量，稳定性较差。1H-和13C-NMR分析表明，不同化学位移δ与生物油中不同类型的质子和碳原子相对应，明确生物油中不同类型H和C的分布，有利于对其分子结构进行深入探讨。这些研究为非木材生物质高效液化条件的选择及液化产物制备化学品和生物燃油给予理论基础与应用支持，促进了生物质资源的有效转化利用及其生物质基产品的开发。

Optimization of Corn Stalk Liquefaction Conditions Under Atmospheric Pressure and Analysis of Biofuel

With the decline in the availability of petrochemical resources, lignocellulosic biomass as a renewable resource has been getting more and more attention. The atmospheric liquefaction technology has been used widely, which is one of the effective ways of biomass components utilization. In this paper, to optimize the liquefaction conditions, a single-factor method was used to study the effects of liquefaction temperature, mixing ratio of a compound liquefying agent, liquid-solid ratio, catalyst dosage and reaction time on the liquefaction yield of corn stalk. The thermo-gravimetric analyzer (TGA), gas chromatography and mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectra were adopted to detect the volatile degradability and components of the biofuel. The results indicated that the optimum conditions were determined as liquefaction temperature 170 ℃, diethylene glycol (DEG)/1,2-propanediol (PG)=1∶2, a liquid to solid ratio of 5∶1, phosphoric acid dosage 10% and reaction time 45 min. Under this condition, the liquefaction yield was up to 99.50%. The results of TGA showed that the biofuel contained more than 80% of compounds with a carbon number less than 25, and the final carbon content after pyrolysis was about 15%. GC-MS presented that 39 kinds of organic compounds were tested in biofuel, among which alcohols were the most, phenols were the second, and their relative contents were 70.70% and 25.63%, respectively. There were also some organic acids (2.80%), ethers (0.64%), esters (0.10%) and ketones (0.13%). Its components were complicated, and high oxygen content, so its stability was limited. 1H- and 13C-NMR explained that different chemical shifts δ corresponded to different types of protons and carbon atoms. The distribution of hydrogen and carbon in the biofuel was clarified, conducive to the further exploration of its molecular structure. Hence, theoretical foundation and technical support could be provided for the existing related liquefaction technology and then promote the efficient utilization of biomass resources and the development of biomass-based products.