Study on the transformation characteristic of heteroatoms during liquefaction of Naomaohu coal
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摘要: 以淖毛湖煤为原料，进行加氢直接液化，考察了加氢温度与转化率和油收率的关系，并解析了加氢条件下煤中硫、氮和氧的迁移转化特性。结果发现，淖毛湖煤具有良好的液化性能，400 ℃和2 MPa氢初压条件下即可达到69.6%的转化率和55.3%的油产率。结合气相色谱质谱联用(GC-MS)和气相色谱-原子发射光谱 (GC-AED)等方法对产物分析发现，以弱键合结构存在的硫、氮和氧等杂原子易发生加氢裂解生成H2S、NH3、H2O等。液化油品中含硫化合物主要以噻吩及噻吩同系物为主；含氮化合物含量极低，主要由含氮杂环化合物构成；含氧化合物在液化油中主要以酚及酚的同系物为主。存在于芳香结构中的杂原子会随着自由基缩合反应，生成更稳定的含杂原子稠环化合物富集在液化残渣中。Abstract: In this study, Naomaohu coal was used for directly hydrogenating liquefaction. The conversion ratio and oil yield as function of hydrogenating temperature during direct liquefaction were investigated. Moreover, the transformation characteristics of heteroatoms in raw coal and liquefaction products were clarified. The results show that, Naomaohu coal presented high liquefaction performance even under lower initial pressure of 2 MPa. The conversion rate and oil yield could reach 69.6% and 55.3% respectively at a pressure of 2 MPa and 400 ℃. Gas chromatography-mass spectrometry (GC-MS) and gas chromatography-atomic emission spectrometry (GC-AED) were combined to analyze the products. It was found that the weak bond structure containing heteroatoms was easier hydrogenated to fracture and removed in the form of H2S, NH3, H2O, etc. The sulfur-containing compounds in liquefied products were mainly thiophene and thiophene homologues. The content of nitrogen-containing compounds was too low and mainly consisted of nitrogen heterocyclic compounds. And, the oxygen-containing compounds in liquefied oil were dominantly phenols and their homologues. The heteroatoms in the aromatic structure would generate more stable heteroatom-containing compounds in the liquefaction residue with the free radical polycondensation reaction.
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Key words:
- Naomaohu coal /
- direct liquefaction /
- heteroatoms /
- transformation characteristics
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图 1 淖毛湖煤直接液化反应特性，（A）温度对直接液化的影响;；(B)温度对气产率及氢耗的影响
Figure 1. direct liquefaction characteristics of Naomaohu coal, (A) effect of temperature on the reactivity; (B) effect of temperature on gas production rate and hydrogen consumption.
图 3 液化前后固体样品官能团的变化
Figure 3. Variation of functional groups before and after liquefaction
图 5 GC-AED对液化油品分析，(A)含碳化合物分析(C193 nm)；(B)含硫物质分析（S181 nm）；(C)含氮物质分析(N174 nm)
Figure 5. GC-AED analysis of liquefied oil, (A) hydrocarbons (C193 nm); (B) sulfur-containing compounds (S181 nm); (C) nitrogen-containing compounds (N174 nm)
图 6 温度对直接液化油品组成的影响
Figure 6. The influence of temperature on the composition of coal direct liquefied oil
图 7 直接液化过程杂原子化合物转化机理
Figure 7. Mechanism on the transformation characteristics of heteroatoms during the direct liquefaction process
表 1 淖毛湖煤的煤质分析
Table 1. Proximate and ultimate analysis of raw coal
Proximate analysis /wt% ultimate analysis /wt% (daf) Mad Vdaf Ad FCdaf C H N St O* 7.02 52.41 5.41 47.59 77.03 6.01 1.01 0.39 15.56 Note：ad: air dried base；d: dry base；daf: dry and ash-free base；*: different. 
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表 2 液化产物组成
Table 2. Component distribution of liquefied oil
Items Compounds Content /% 350 ℃ 400 ℃ 450 ℃ Chain hydrocarbon Alkane（C7-C32 alkane, olefins） 1.91 1.29 2.69 Tetrahydronaphthalene 27.31 29.09 18.32 Aromatic hydrocarbons and their homologues Benzene and its homologues 0.15 0.85 2.68 Naphthalene 16.15 46.41 45.95 C1-C3 substituted naphthalene 0.60 4.64 7.74 Indene and its homologues 0.10 1.85 5.67 Diphenyl and its homologues 0.00 0.20 0.42 Anthracene and phenanthrene homologues 0.01 0.07 0.81 pyrene 0.00 0.22 2.24 Anthracene and pyrene homologues 0.01 2.05 1.98 Total 17.02 59.29 67.49 S-containing compound Quinoline and others 0.10 0.12 0.20 N-containing compound Thiophene and its homologues 0.21 0.12 0.23 Benzothiophene and its homologues 0.24 0.23 0.15 Total 0.45 0.35 0.38 O-containing compound Phenol 0.00 0.10 0.16 C1-C4 substituted phenol 0.05 0.65 1.57 Naphthol 0.00 0.01 0.04 Others 0.75 0.49 0.20 Total 0.80 1.25 1.97
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