Study on effect of dispersant on semi-coke water slurry property based on quantum chemistry calculation
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摘要: 为高效利用半焦资源，选择适宜的水焦浆分散剂以提高兰炭制备水焦浆的性能，本研究以陕北半焦及四种不同分散剂（腐植酸钠SH、木质素磺酸钠SLS、十二烷基磺酸钠SDS和一种自制衣康酸型分散剂IPMS）为研究对象，探讨了不同添加剂对水焦浆成浆特性的影响。利用Material Studio（MS）软件计算了分散剂的结构参数及半焦与分散剂间的相互作用能，从量子化学角度对分散剂的作用进行探讨，并与制浆实验结果进行比较。结果表明，加入分散剂可有效降低液体表面张力，增大半焦颗粒表面电负性，从而增强颗粒间静电排斥作用使得浆体更加稳定。相同制备条件下，分散剂IPMS制备水焦浆时效果较优，在剪切速率为100 s-1时，其表观黏度为625 mP·s，7 d析水率仅为2.38%且无硬沉淀。通过计算机模拟得出吸附过程中分散剂的氧原子向半焦的羟基一侧靠近，产生电荷转移，四种分散剂活性大小顺序为IMPS > SH > SLS > SDS，IMPS与半焦相互作用的吸附作用较强与实验结果一致。证明了采用量子化学计算结合实验数据可以对水焦浆分散剂的性能进行评价，为浆体燃料制备技术及新型药剂的设计开发提供了理论基础。Abstract: In order to utilize semi-coke resources efficiently and select the suitable dispersant to improve the performance of slurry prepared by semi-coke, the effects of different dispersants (sodium humate, sodium lignosulfonate, sodium dodecyl sulfonate and a self-made itaconic acid dispersant IPMS) on the pulping property of semi-coke slurry were studied. The structure parameters of dispersant and the interaction energy between semi-coke and dispersants were calculated by the software-Material Studio (MS) and compared with experimental value. The results show that the addition of dispersants can effectively reduce the surface tension of liquid and increase the electronegativity of semi-coke particles, enhancing the electrostatic repulsion between particles and making the slurry more stable. The self-made itaconic acid dispersant IPMS has a better effect on the property of semi-coke water slurry under the same preparation conditions. The apparent viscosity is 625 mP·s when the shear rate is 100 s-1, the water-liberating rate in 7 d of slurry is only 2.38% and there is no hard precipitation. The adsorption simulation indicates that the oxygen atom of the dispersant approaches to the hydroxyl side of the semi-coke and makes charge transfer, and the order of activity of four dispersants is IMPS > SH > SLS > SDS. The interaction between IMPS and the semi-coke leads to a strong adsorption, which is consistent with the experimental results. It is proven that the performance of dispersants can be evaluated by quantum chemical calculation combined with experimental data, providing a theoretical basis for the preparation technology of slurry fuel as well as the design and development of new reagents.
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Key words:
- semi-coke water slurry /
- dispersant /
- molecular structure /
- quantum chemistry
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图 1 半焦及分散剂分子结构模型示意图
Figure 1 Molecular structure of semi-coke and the dispersants
(a): semi-coke; (b): SH; (c): SLS; (d): SDS; (e): IPMS
图 4 分散剂对半焦制水焦浆流变性的影响
Figure 4 Effect of dispersant on the rheological properties of semi-coke water slurry
图 6 不同分散剂的HOMO轨道图, 等值面值为0.03 electrons/Å3
Figure 6 HOMO orbital of different dispersants, the isovalue is 0.03 electrons/Å3
(a): SH; (b): SLS; (c): SDS; (d): IPMS
图 7 半焦含氧结构单元与四种不同分散剂分子结构模型的吸附最优构型示意图
Figure 7 Optimal configuration of semi-coke oxygen structural unit and different dispersants (a): SH; (b): SLS; (c): SDS; (d): IPMS
表 1 半焦的工业分析和元素分析
Proximate analysis w/% Ultimate analysis wad/% Mad Aad Vdaf FCad C H O* N 3.24 13.30 13.74 69.72 70.67 1.96 8.60 0.964 *: by difference 
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表 2 不同分散剂的前线轨道能量
Table 2 Frontier orbital energy of different dispersants
Dispersant E/eV |ΔELUMO-HOMO| HOMO LUMO SH -3.461 -1.455 2.006 SLS -4.412 -1.123 3.289 SDS -3.772 -1.412 2.360 IPMS -2.549 -1.933 0.616
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表 3 半焦-不同水焦浆分散剂间的吸附能
Table 3 Adsorption energy between semi-coke and different dispersants
Adsorption site SH SLS SDS IPMS Eads/(kJ·mol-1) -65.87 -81.18 -98.18 -131.27
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表 4 半焦与分散剂吸附前后的Mulliken电荷分布(以半焦中H原子为例)
Table 4 Mulliken charge populations of atoms before and after dispersant adsorbed on semi-coke
Adsorption site Atom Bond length d/nm Mullinken charge of H/e before after semi-coke+ SH H(C-H73…O14) 0.1378 0.283 0.315 semi-coke+ SLS H(C-H88…O15) 0.1359 0.283 0.334 semi-coke+ SDS H(C-H53…O5) 0.1379 0.283 0.323 semi-coke+ IPMS H(C-H92…O31) 0.1352 0.283 0.339
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