Saccharification of plant biomass by pyrolytic molecular distillation

为了提高纤维素热分解的脱水糖（左旋葡聚糖，LG）产率，激光热解可以从其开放表面加热材料。真空条件下，激光辐照导致快速热解的最小条件为：75 × 100 W，脉冲长度大于14 ms ; 150 × 250 W，脉冲长度大于8 ms。真空条件下热解导致大量气溶胶（白色烟）产生，并在很长时间内保留，阻碍了捕集器的有效回收。用惰性气体冲洗能有效地将气溶胶排出到出口处的棉阱中。该法最高产率为20 ~ 25%，最大产率为100%。百分之三十五在玻璃瓶中进行间歇式真空热解，LG产率为35 ± 56%。这种变化是由冷捕集方法引起的，并且发现捕集器靠近加热区域的放置是非常重要的。在此基础上，设计了一种新型的热解器，并进行了广泛的试验。该装置由一对平行布置且彼此面对的金属带式过滤器组成。将下部带从下方加热至热解温度，并将上部带从上方冷却。该装置的LG产率强烈依赖于真空度，并且低水平的残余空气有利于更高的产率。最佳压力接近。5 KPa的压力下，纤维素的最大得率为70%，玉米淀粉的最大得率为50%。纤维素的值显著超过了55%的最高报告值。该裂解炉可连续操作，可用于纤维素裂解制LG的工业生产。作为该热解器的副应用，尝试从咖啡和绿色茶中热提取咖啡因。结果显示出高效率，即约。在350℃处理下，咖啡因的回收率可达80 ~ 90%。这些结果表明了新型热解器在从生物质材料中提取有用组分方面的优势。

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.