生物质催化热解制取轻质芳烃

以轻质芳烃苯、甲苯、二甲苯和萘(BTXN)为目的产物,采用双颗粒流化床反应器对3种木材生物质进行了热解实验. 结果表明,木材生物质的初次热解终止温度低,有利于低温催化转化. 生物质中92%的挥发分在673 K时已释放完全,且生物质在初期热解得到的焦油经过二次分解反应可以转化为其它产物,通过有效控制生物质热解二次气相反应,能够改变其产物的分布,从而获得不同的目的产物. 生物质的催化加氢热解实验结果表明,催化剂种类和热解温度对加氢热解产物收率及其分布均有影响, BTXN是热解或加氢热解过程中二次气相反应的中间产物. 为了获得高产率的BTXN, 必须选择加氢活性适度的催化剂. 当CoMo-S/Al2O3催化剂作为流化介质进行加氢热解时,在863 K时, BTXN的收率可达6 3%(干燥无灰质量基准), 而NiMo/Al2O3催化剂表现出了很强的加氢活性, CH4的收率高达99 5%.

Production of Light Aromatic Hydrocarbons from Biomass by Catalytic Pyrolysis

Catalytic pyrolysis of three kinds of woody biomass was carried out using a dual-particle powder fluidized-bed reactor to produce light aromatic hydrocarbons such as benzene,toluene,xylene,and naphthalene(BTXN).The results showed that pyrolysis temperature of biomass was very low,and about 92% of the volatile matter in the biomass can be released at 673 K,indicating that the biomass was suitable for catalytic pyrolysis at low temperature.The tar in the volatile matter was the product of the primary decomposition,and it was then transformed to lower molecular hydrocarbon compounds at higher temperature during the secondary reaction.The biomass pyrolysis product distribution could be controlled by adjusting the secondary reaction parameters.The test results of the catalytic hydropyrolysis of the biomass over different catalysts showed that the pyrolysis product distribution depended much on the catalyst types and the pyrolysis temperature.BTXN were the intermediates of the secondary reaction during the pyrolysis or hydropyrolysis process.When biomass was hydropyrolyzed in the fluidized bed with the CoMo-S/Al2O3 catalyst,BTXN yield reached 6.3%(BTX: 5.5%;N: 0.8%) at 863 K.However,the highest CH4 yield of 99.5% was obtained when a NiMo/Al2O3 catalyst was used.Therefore,it is important to select a catalyst with proper hydrogenation activity to obtain the highest yield of BTXN.Different types of woody biomass with similar compositions results in similar product distributions.