Saccharification of plant biomass by pyrolytic molecular distillation

为了提高纤维素热分解产生的脱水糖(左旋葡聚糖，LG)的产量，激光热解可以从材料的开放表面加热材料。确定了产生快速热解的最小激光辐照条件为：75~100W，脉冲长度大于14ms；150~250W，脉冲长度大于8ms。真空热解会产生大量的气溶胶(白烟)，并长期存在，阻碍了捕集器的有效回收。大气惰性气体冲洗能有效地将出口气溶胶排入棉花捕集器。该方法的最高LG产率为20~25%。35%。以玻璃瓶间歇式真空热解为对照，LG产率为35~56%。这种变化是由冷诱捕方法引起的，而诱捕器靠近加热区的放置是非常重要的。基于这一发现，设计了一种新型的热解炉，并进行了广泛的试验。该装置由一对平行、朝向的金属皮带输送机组成。下带从下加热到热解温度，上带从上冷却。该装置的LG产率强烈依赖于真空度，较低的残气量有利于获得较高的产率。最佳压力约为。5kpa时，纯纤维素得率最高可达70%，玉米淀粉得率最高可达50%。纤维素的价值大大超过了55%的最高报告价值。由于该裂解炉可以连续运行，可以用于以纤维素为原料生产LG的工业生产。作为该热解器的一个辅助应用，尝试了从咖啡和绿茶中热提取咖啡因。结果表明，该方法具有较高的计算效率。处理350℃时，咖啡因的回收率为80%~90%。这些结果表明，新型热解炉在从生物质原料中提取有用成分方面具有优势。

For improving anhydrosugar (levoglucosan, LG) yield from thermal decomposition of cellulose, laser pyrolysis which can heat the material from its open surface. Minimum laser irradiation condition for causing fast pyrolysis was determined as : 75〜100W, pulse length more than 14 ms ; 150〜250W, pulse length more than 8 ms. Pyrolysis under vacuum caused significant generation of aerosol (white smoke), which remained for a long time and obstructed efficient recovery by trap. Flushing by atmospheric inert gases was effective in expelling the aerosol into cotton trap at exit. Maximum LG yield by this method was 20〜25%, max. 35%. Batch-type vacuum pyrolysis in glass bottle for comparison gave LG yield of 35〜56%. This variation was caused by the method of cold trapping, and close placing of trap to the heated area was found very important. Based on this finding, a novel pyrolyzer was designed and tested extensively. The apparatus consisted of a pair of metal belt conveyers, arranged parallel and facing with each other. The lower belt was heated to pyrolysis temperature from beneath, and the upper belt was cooled from above. The LG yield by this apparatus strongly depended on the vacuum level, and the low level of residual air was advantageous for higher yields. Optimal pressure was approx. 5 KPa, which gave maximum yield of 70% from pure cellulose and 50% from corn starch. The value for cellulose significantly exceeded the highest reported value of 55%. Since this pyrolyzer can operate continuously, it can be used for industrial production of LG from cellulose. As a side application of this pyrolyzer, thermal extraction of caffeine from coffee and green tea was attempted. The results showed high efficiency, i.e. approx. 80〜90% of caffeine was recovered from ground materials at 350℃ treatment. These results showed advantages of the novel pyrolyzer in extracting useful components from biomass materials.