Effect of raw material composition on the development of semicoke mesophase structure

doi:10.16085/j.issn.1000-6613.2022-1276

Abstract

Abstract:

Semicoke with different microstructures was prepared from medium and low temperature coal tar full distillate hydrogenation tail oil (FHT) and >350℃ medium and low temperature coal tar pitch (CTP). The composition and structure of the raw materials were characterized by means of elemental analysis, ¹H NMR spectroscopy, Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry, and the influence of the raw material composition on the development of the mesophase structure was studied. The results showed that: FHT contained 25.94% naphthenic and the side chain of aromatic ring was dominated by naphthenic structure, while CTP contained 3.92% naphthenic and the side chain of aromatic ring was dominated by short alkyl groups. The content of oxygen-containing heterocyclic compounds in FHT was lower than that in CTP. Thermal polymerization experiments showed that the raw material (FHT) with high content of naphthenic structure and low content of oxygen-containing heterocyclic compounds was beneficial to reduce the carbonization reaction activity and viscosity of the reaction system, and promote the orderly development of the mesophase. Polarizing microscope, scanning electron microscope and X-ray diffraction were used to analyze the microstructure and crystallite parameters of the semicoke. The results showed that CTP had high oxygen content and QI content, which was easy to form mosaic structure, distorted crystallite arrangement, and poor orientation. On the other hand, FHT was rich in naphthenic structure and low in oxygen content, and the aromatic hydrocarbon sheet molecules were easier to stack in an orderly manner to form a fine fiber structure, and the internal carbon crystallites were arranged more regularly, making it easier to graphitize. In addition, the optical structure of the semicoke was quantitatively analyzed by fiber software, and it was found that the fiber structure content of the semi-coke prepared by FHT was 79.84%, while that of the semi-coke prepared by CTP was 22.18%.

Key words: medium and low temperature coal tar full distillate hydrogenation tail oil, medium and low temperature coal tar pitch, composition, mesophase, semicoke, microstructure

摘要：

以中低温煤焦油全馏分加氢尾油（FHT）和＞350℃中低温煤焦油沥青（CTP）为原料，制备出不同微观结构的半焦。采用元素分析、核磁共振氢谱、傅里叶变换红外光谱、气相色谱-质谱联用等手段对原料的组成结构进行表征，研究了原料组成对中间相结构发展的影响。结果表明：FHT含有25.94%环烷烃且芳环侧链以环烷结构为主，CTP中含有3.92%环烷烃且芳环侧链以短烷基为主，FHT的含氧杂环化合物含量比CTP低。热聚实验表明具有环烷结构含量高、含氧杂环化合物含量低的原料（FHT），有利于降低炭化反应活性和反应体系黏度，促进中间相有序发展。采用偏光显微镜、扫描电子显微镜和X射线衍射对半焦的微观结构和微晶参数进行分析，结果表明，CTP的氧含量和QI含量高，容易生成镶嵌结构，微晶排列扭曲，取向性差，而FHT中富含环烷结构以及氧含量低，芳烃片层分子更容易有序堆叠形成细纤维结构且内部碳微晶排列更加规整，更易石墨化。此外，利用纤维软件对半焦的光学组织结构进行了定量分析，发现FHT制备的半焦的纤维结构质量分数为79.84%，而CTP制备的半焦的纤维结构质量分数为22.18%。

关键词: 中低温煤焦油全馏分加氢尾油, 中低温煤焦油沥青, 组成, 中间相, 半焦, 微观结构

CLC Number:

TQ522.65

XU Xian, CUI Louwei, LIU Jie, SHI Junhe, ZHU Yonghong, LIU Jiaojiao, LIU Tao, ZHENG Hua’an, LI Dong. Effect of raw material composition on the development of semicoke mesophase structure[J]. Chemical Industry and Engineering Progress, 2023, 42(5): 2343-2352.

徐贤, 崔楼伟, 刘杰, 施俊合, 朱永红, 刘姣姣, 刘涛, 郑化安, 李冬. 原料组成对半焦中间相结构发展的影响[J]. 化工进展, 2023, 42(5): 2343-2352.

Figures/Tables 17

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显微组分名称	长度/μm	宽度/μm	长宽比
镶嵌	<10	<10
小片	10~30	10~30
大片	>30	>30
短纤维	<30	<30	2.5
细纤维	>10	<10	>5
粗纤维	>30	10~30

显微组分名称	长度/μm	宽度/μm	长宽比
镶嵌	<10	<10
小片	10~30	10~30
大片	>30	>30
短纤维	<30	<30	2.5
细纤维	>10	<10	>5
粗纤维	>30	10~30

分类	峰位置/cm^-1	质量分数/%
分类	峰位置/cm^-1	FHT	CTP
非对称RCH₃	2953	13.46	19.64
非对称R₂CH₂	2920	45.18	43.63
非对称R₃CH	2892	13.63	11.99
对称RCH₃	2872	4.51	6.72
对称R₂CH₂	2851	23.22	19.64
n(CH₂)/n(CH₃)		3.36	2.22
1H	865	18.25	3.46
2H	812	38.54	32.07
4H	764	5.98	56
(CH₂) _n_≥4	721	37.22	8.47

分类	峰位置/cm^-1	质量分数/%
分类	峰位置/cm^-1	FHT	CTP
非对称RCH₃	2953	13.46	19.64
非对称R₂CH₂	2920	45.18	43.63
非对称R₃CH	2892	13.63	11.99
对称RCH₃	2872	4.51	6.72
对称R₂CH₂	2851	23.22	19.64
n(CH₂)/n(CH₃)		3.36	2.22
1H	865	18.25	3.46
2H	812	38.54	32.07
4H	764	5.98	56
(CH₂) _n_≥4	721	37.22	8.47

化学位移	氢的类型	不同氢类型的质量分数/%
化学位移	氢的类型	FHT	CTP
0.5～1.1	H _γ （芳环≥γ位的CH₃的H，烷烃CH₃上的H）	24.75	10.82
1.1～2.1	H _β （芳环β碳上的H及β位以远的CH、CH₂上的H，烷烃CH、CH₂上的H）	52.10	32.46
2.1～4.5	H _α （与芳环α碳直接相连的H）	14.21	27.49
6.5～9.5	H_ar（芳香氢）	8.94	29.24