Study on the Pretreatment Process and Removal Rules of Sulfur-Containing Compounds for Medium- and Low-Temperature Coal Tar

Jiaojiao Liu; Yonghong Zhu; Zhengpeng Miao; Louwei Cui; Jieping Liu; Xiaoyong Fan; Chongpeng Du; Yong Dan; Haipeng Teng; Dong Li

doi:10.1021/acsomega.1c00355

Study on the Pretreatment Process and Removal Rules of Sulfur-Containing Compounds for Medium- and Low-Temperature Coal Tar

ACS Omega. 2021 May 5;6(19):12541-12550. doi: 10.1021/acsomega.1c00355. eCollection 2021 May 18.

Authors

Jiaojiao Liu¹, Yonghong Zhu^{1

2}, Zhengpeng Miao¹, Louwei Cui³, Jieping Liu¹, Xiaoyong Fan¹, Chongpeng Du¹, Yong Dan¹, Haipeng Teng¹, Dong Li¹

Affiliations

¹ School of Chemical Engineering, Northwest University, Chemical Engineering Research Center of the Ministry of Education for Advanced Use Technology of Shanbei Energy, Shaanxi Research Center of Engineering Technology for Clean Coal Conversion, Xi'an 710069, Shaanxi, China.
² Hydrocarbon High-Efficiency Utilization Technology Research Center, Yanchang Petroleum Company Ltd., Xi'an 710075, Shaanxi, China.
³ Northwest Research Institute of Chemical Industry, Xi'an 710600, Shaanxi, China.

Abstract

The heteroatoms (sulfur and nitrogen) and metals (ferrum and calcium) in coal tar can easily cause the corrosion of hydrogenation equipment, catalyst poisoning, and environmental pollution. These should be removed before coal tar is hydrogenated. In this study, with the acid refining method, the effects of three polyether demulsifiers (i.e., PD1, PD2, and PD3), polyamine carboxylate demetallizers (i.e., PCD1, PCD2, and PCD3), and separation temperature on the removal of ferrum, calcium, sulfur, and nitrogen in medium- and low-temperature coal tar were determined. PD2 was selected, and the added amount was 200 μg·g^-1. When the PD2 demulsifier was added alone or PD2 demulsifier with various demetallization agents was added, heteroatoms in coal tar could be effectively removed. For the experiments and analysis, the pretreatment conditions of coal tar were as follows: the addition amount of the PD2 demulsifier was 200 μg·g^-1, the addition amount of the PCD3-type demetallization agent was 400 μg·g^-1, and the stirring temperature was 80 °C. Before and after pretreatment, the methods of inductively coupled plasma-atomic emission spectrometer, gas chromatography-mass spectrometry (MS), and Fourier transform-ion cyclotron resonance MS were used in the present study to explore and analyze the distribution, occurrence form, and removal law of sulfur in coal tar. As revealed from the results, sulfur compounds in coal tar <360 °C fraction (light coal tar fraction, LF) before being pretreated had a lower content, which existed as benzothiophene and dibenzothiophene largely. Sulfur compounds S1 and S2 achieved the maximum relative abundance in >360 °C fraction (heavy coal tar fraction, HF). After the compounds were pretreated, the sulfur removal rate reached 40.0% in LF, and the sulfur compounds were primarily removed. For HF, the sulfur removal rate reached 20.1%. In addition, S1 compounds within the dibenzothiophene derivatives exhibiting more side chains and a larger condensation degree were basically removed. S2 compounds, mainly linked to several quinolines or more aromatic rings and thioether-aliphatic amine sulfur compounds exhibiting small molecular weight and simple structures, were relatively easy to remove. The SO class (e.g., the sulfones and thiophene-ketone group) was more difficult to remove.