煤化程度对煤基固体酸结构及其水解纤维素性能的影响

Effect of coal rank on structure of coal-based solid acids and their catalytic performance in cellulose hydrolysis

利用煤具有缩合芳环、脂肪侧链及含氧官能团的结构特点,采用不同煤化程度的煤为碳源,在不同炭化温度下制备了煤基固体酸催化剂(CSA)。通过XRD、FT-IR、13C NMR对催化剂结构进行了表征。以还原糖和葡萄糖的产率为考察指标,探讨了煤化程度和炭化温度对煤基固体酸非均相催化水解纤维素的影响。结果表明,煤作为碳源具有传统碳源所不具备的结构优势,煤基固体酸碳层片上除含有磺酸基、酚羟基和羧基外,还含有传统碳基固体酸不具备的桥键(-O-、-CH2-)和侧链(-CH3、-OCH3、-CH2CH3)。除磺酸基外,其余均由煤的结构演化而来。随着炭化温度的升高,催化剂的芳香度增大、活性基团的种类和数量减少、磺酸基密度逐渐下降,且随着煤化程度增加,煤基固体酸结构可调性降低,所需要的最佳炭化温度也逐渐降低。不同种类的煤基固体酸在水解纤维素过程中表现出了较高的活性,其中,霍林河煤基固体酸的活性最高。水解活性受催化剂芳香片层大小及堆叠高度、片层之间桥键和磺酸基密度等因素的影响,是众多活性基团协同作用的结果。

Coal-based solid acids（ CSAs） were successfully prepared from coals with different ranks at various carbonization temperatures. XRD,FT-IR and13C NMR were employed to characterize structure of the catalysts. The influence of coal rank and carbonization temperature on the heterogeneous catalytic hydrolysis of cellulose was investigated by comparing the yield of reducing sugar and glucose. The results showthat coal has a structure advantage over the other traditional carbon sources for solid acids. In contrast to the traditional carbon-based catalysts,the unit structure of CSA is fused aromatic rings linked by bridge bonds（- O-,- CH2-） and the fused aromatic rings are bearing side chains（- CH3,- OCH3,- CH2CH3） besides phenolic- OH,- COOH and-SO3H groups. In addition to the sulfonic groups,the others are derived from the rawcoal structure. With rising carbonization temperature,the species and amounts of functional groups and the density of sulfonic acid groups are found to decrease gradually in CSAs,while the aromaticity of CSAs is opposite. The adjustability of CSAs structure and required carbonization temperatures are reduced with increasing coal rank. The CSAs showa higher activity in the cellulose hydrolysis process,wherein the Huolinhe CSA has the highest catalytic activity. The hydrolytic activity is influenced by the size and the stack height of the aromatic sheet,the bridge bond and the sulfonic acid group density,which is a result of the synergistic effect of a number of reactive groups.