应用超临界流体萃取改善煤沥青的炭化性质

MODIFICATION OF THE CARBONIZATION PROPERTIES OF COAL—TAR PITCH BY SUPERCRITICAL FLUID EXTRACTION

通过超临界流体(SCF)萃取,改善了煤沥青的炭化性质。经超临界甲苯萃取过的沥青(SCFE沥青)丝毫不含导致小单元尺寸各向异性结构的喹啉不溶物(QI)。由SCFE沥青产生的各向异性结构的尺寸与β—树脂(甲苯不溶—喹啉可溶物)含量密切相关。用搀混方法制取的沥青,使含有的β—树脂含量与SCFE沥青相同(经用常规溶剂萃取得到的甲苯可溶物(TS)和β—树脂搀混而得)比较,搀混沥青的各向异性结构较小。可以用溶解在萃取相一定量的TS溶解量来解释超临界甲苯萃取β—树脂的过程。萃取相中TS浓度高,则溶于该相中的β-树脂溶解度也高。减小萃余液相中TS的浓度,会引起不利于中间相结构发展的较重的β-树脂聚集,并形成不可萃取的QI。由于萃取相和萃余相中TS的浓度取决于萃取压力和超临界甲苯的量与沥青的量之比,因此,调节这两个参数就能控制SCFE沥青中β-树脂的含量。

The carbonization properties of coal-tar pitch were modified by supercritical fluid (SCF) extraction. Pitches extracted -with supercritical toluene (SCFE pitch) contained none of the quinoline insoluble(QI) matter responsible for anisotropic structures with small unit sizes. The size of anisotropic structures from SCFE pitches was closely related by the β-resin (toluene insoluble and quinoline soluble fraction) content. Anisotropic structures from blended pitches prepared to have the same β- resin content as SCFE pitches(by blending toluene soluble(TS) and β-resin fractions obtained through a conventional liquid solvent extraction) were smaller. Extraction of the |3-resin fraction with supercritical toluene could be interpreted by the co-solvent effects of the TS fraction dissolved intheextract phase. The high concerntration of TS fraction in the extract phase enhanced the solubility of the β-resin fraction into this phase. In the raffinate phase, the heavier β-resin components, which are unsuitable for the development of mesophase structures, coagulated and formed unextractable QI matter through reduction in the concentation of the TS fraction. Since the TS concentration in both the phases depends on pressure and the ratio of the amounts of supercritical toluene and pitch, the control of the β-resin content in the SCFE pitches is possible through the adjustment of these two parameters.