昭通褐煤催化热溶解聚及其可溶物组成和结构特征

Catalytic thermal dissolution of Zhaotong lignite and composition and structural characterization of its soluble portions

温和热溶是从褐煤获取可溶有机质的有效途径,然而传统热溶过程可溶物收率较低。通过共沉淀法制备了一系列Al_(2)O_(3)负载金属催化剂,考察了昭通褐煤在异丙醇中的热溶和催化热溶行为。采用XRD、H_(2)-TPR、TEM和XPS研究了催化剂的物理化学特征,利用GC/MS、FTIR和MALDI-TOF-MS分析了热溶和催化热溶可溶物的组成和结构特征。结果表明,NiCu/Al_(2)O_(3)对昭通褐煤的催化热溶活性优于其他催化剂,该催化剂中活性组分以NiCu合金的形式存在,且Ni与Cu之间存在相互作用。热溶与催化热溶可溶物收率均随温度升高呈先上升后下降的趋势,320℃可溶物收率最高,分别为27.69%和50.54%。催化剂的引入可提高昭通褐煤可溶物中油、沥青烯(AS)和前沥青烯(PAS)收率,其中油和PAS的收率提升相较AS更明显。酚类化合物是非催化热溶衍生油的主要族组分,相对含量达到64.44%,而催化热溶衍生油主要由芳烃、酚类、醇类和酮类化合物组成,说明催化剂促进了可溶有机质碎片中共价键的断裂和酚类化合物加氢。与非催化热溶得到的AS和PAS相比,催化热溶得到的AS和PAS分子量分布范围窄,且FTIR谱图中羟基和醚键对应的吸收峰变弱或消失,说明催化热溶促进了C—O键加氢裂解。催化热溶可在相对温和的条件下从煤中直接高收率获取可溶有机质,研究结果为从褐煤直接获取化学品技术的开发提供参考。

Thermal dissolution(TD)under mild conditions is an effective way to obtain organic species from lignite.However,the conventional TD affords low yield of soluble portions(SPs).Herein,a series of Al_(2)O_(3)-loaded metal catalysts prepared by co-precipitation method were used to investigate the catalytic thermal dissolution(CTD)behavior of Zhaotong lignite in isopropanol.For comparison,TD of Zhaotong lignite was conducted under the same conditions.The physicochemical properties of the catalysts were investigated by XRD,H_(2)-TPR,TEM and XPS,and the compositions as well as structural features of SPs obtained from TD and CTD were analyzed by GC/MS,FTIR and MALDI-TOF-MS.The results show that NiCu/Al_(2)O_(3)exhibites superior performance to other catalysts on CTD of Zhaotong lignite,in which the active components exist in the form of NiCu alloy with interaction between Ni and Cu.The yields of SPs obtained by TD and CTD first increases and then decreases with the elevation of temperature,and the highest yields of SPs from TD and CTD at 320℃are 27.69%and 50.54%,respectively.The introduction of the catalyst can increase the yields of asphaltene(AS),preasphaltene(PAS)and oil in SPs,in which the enhancement of the latter two components is more obvious than that of AS.Phenols are the main group components in the TD derived oil with a relative content of 64.44%,while the CTD derived oil mainly consists of arenes,phenols,alcohols and ketones,indicating that the catalyst promotes the cleavage of covalent bond in the soluble organic fragments and the hydrogenation of phenols.Compared with the AS and PAS obtained from TD,those acquired from CTD possess a narrower molecular weight distribution range,and the intensity of adsorption peaks assigned to the hydroxyl group and ether bonds in the FTIR spectra become weaker or disappeared,suggesting that CTD facilitates the hydrogenolysis of C—O bonds.CTD can directly get soluble organic species with high yield from lignite under relatively mild conditions,and the results of the study may provide a reference to develope process for directly acquiring chemicals from lignite.