生物质-CaO共热解中“类CO2活性中间体”的形成及演化机理

Based on the process idea named "copyrolysis of biomass and CaO in dual circulation fluidized bed biomass for in-situ bio-oil deoxygenation", investigation including experiments with different devices and product analysis has been initially carried out. The results showed that CaO fixed some acidic precursors named "the active quasi-CO2 intermediates" with chemical bonds that was not completely closed in the copyrolysis process of biomass and CaO, which was a very important non-catalytic deoxygenation path in the process. In this study, The solid- pyrolysis/synchrotron vacuum ultraviolet photoionization mass spectrometry apparatus (Solid-Py/SVUV-PIMS) and other means will be used for the experimental study on the copyrolysis of biomass and CaO to directly determine the presence and compositions of "the active quasi-CO2 intermediates". A thorough research on the important contributions of this non-catalytic deoxygenation path will also be done. Combined with quantum chemical calculations and other means, the formation mechanism and influencing factors of "the active quasi-CO2 intermediates" will be explored. Furthermore, the reaction and evolution mechanism of adsorption and subsequent reaction of “the active quasi-CO2 intermediates" with CaO particles to produce organic calcium salts, and further decomposition into CaCO3 after being heated will be investigated in detail. The research achievements have great theoretical significance and practical value for biomass fast pyrolysis for in-situ bio-oil deoxygenation, and could contribute to the promotion of the formation of biomass utilization industry with China's independent intellectual property.

基于“双循环流化床生物质-CaO共热解制油在线脱氧”这一工艺构想，前期已通过不同装置的实验及产物分析研究初步推测得到：生物质-CaO共热解过程中存在CaO固定含有化学键尚未完全闭合的酸性基团前驱物的“类CO2活性中间体”的重要非催化脱氧路径。本研究采用固体热解/同步辐射真空紫外光电离质谱分析(Solid-Py/SVUV-PIMS)等手段进行生物质-CaO共热解实验研究，直接检测“类CO2活性中间体”的存在，判定其具体成分，深入研究非催化脱氧路径的重要贡献。进而结合量子化学等手段，探索“类CO2活性中间体”的形成机理及影响因素，并弄清其被CaO 颗粒吸附并与之反应生成有机钙盐，以及升温后进一步分解生成CaCO3的演化机理，本项目研究成果对于生物质快速热解制油在线脱氧工艺的成功开发有着极其重要的理论意义和实用价值，有助于促进形成具有我国自主知识产权的生物质利用产业。

基于“双循环流化床生物质-CaO共热解制油在线脱氧”这一工艺构想，前期研究初步推测得到：生物质-CaO共热解过程中存在CaO固定含有化学键尚未完全闭合的酸性基团前驱物的“类CO2活性中间体”的重要非催化脱氧路径。然而，对于“类CO2活性中间体”的存在及形成机理有待进一步深入研究。.同时，前人研究发现K3PO4、K2HPO4均可以促进杨木热解中酚类产物的生成；小分子酸产率在大剂量K3PO4加入后减小，K2HPO4加入后增大。而生物质-CaO共热解后甲酸、乙酸等酸类及愈创木酚等高含氧量酚类降低，苯酚等低含氧量酚类升高。可以设想，CaO与K3PO4或K2HPO4会对生物质热解产生一定的协同作用。.本项目利用热重-质谱联用(TG-MS)技术，对CaO与K2HPO4.3H2O或者K3PO4.3H2O单独或者协同作用下纤维素、木质素、樟木粉热解过程进行实验研究，部分同时采用原位红外（in situ DRIFT）分析手段，深入探究生物质-CaO共热解过程中“类CO2活性中间体”的存在及形成机理，同时，探讨K2HPO4.3H2O或者K3PO4.3H2O催化生物质热解机理及其与CaO对生物质热解过程的协同行为及机理。同时，项目进一步完善前期纤维素-CaO共热解落体实验及分析，深入探究共热解过程“类CO2活性中间体”的形成路径及机理。.研究发现： (1) CaO会固定纤维素、木质素、樟木粉热解过程中产生的中产生的“类CO2活性中间体”，从而分别降低271~465℃等区间内CO2的析出量，并使CO2在560℃以后出现第二个析出区间。(2) K2HPO4.3H2O，K3PO4·3H2O均显著使得热解反应提前并明显改变热解反应历程。(3) CaO与K2HPO4.3H2O或K3PO4.3H2O混合加入后热解起始的失重过程相对于单独添加K2HPO4.3H2O或K3PO4.3H2O较为缓和。主要热解阶段产物变化表明CaO与K2HPO4.3H2O或K3PO4.3H2O在热解过程中产生较强的协同作用。(4) CaO直接固定纤维素单体一次分解乙烯酮二碳分子碎片等“类CO2活性中间体”生成羧酸钙等有机钙盐，阻碍了乙醇醛或乙酸的生成，并促使LG含量降低，Acetol含量升高。.项目研究成果对于生物质快速热解制油在线脱氧工艺及高品质生物油协同制备方法的成功有着重要的理论意义和实用价值。