Li Dong-Liang, Sheng Shu-Mei, Zhang Ye, Liang De-Qing, Wu Xiao-Ping
Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences Guangzhou 510640 China.
CAS Key Laboratory of Gas Hydrate Guangzhou 510640 China.
RSC Adv. 2018 Mar 14;8(18):10089-10096. doi: 10.1039/c8ra01124a. eCollection 2018 Mar 5.
Hydrate formation is an important technology for gas storage and transportation. In this work, the effect of multiwalled carbon nanotubes (MWCNTs) on CH hydrate formation was examined by determining the phase equilibrium conditions and kinetics characteristics of a mixed system of CH, tetra--butyl ammonium bromide (TBAB), and MWCNTs. The phase equilibrium was examined in the temperature range of 286.13-293.04 K and the pressure range of 0.55-6.56 MPa for various mass fractions of MWCNTs (0.004, 0.1, 0.5, and 1.0 wt%). In the CH + TBAB system, the presence of MWCNTs was found to shift the phase equilibrium conditions to a lower temperature by about 1 K compared with those in the absence of MWCNTs. However, the concentration of MWCNTs had little effect on the phase equilibrium conditions. When the concentration of MWCNTs was 1.0 wt%, the addition of MWCNTs reduced the induction time of hydrate formation by 79.5%. When the concentration of MWCNTs was 0.1 wt%, the addition of MWCNTs enhanced the hydrate growth rate by 61.5%. Powder X-ray diffraction patterns revealed that hydrates with orthorhombic structures (corresponding to TBAB·38HO with 3D cages) were formed in the systems with and without MWCNTs. Moreover, peaks corresponding to MWCNTs were not observed in the patterns of the hydrates and the addition of MWCNTs had no influence on the structure and type of hydrate. Thus, MWCNTs were not incorporated into the hydrate cages.
水合物形成是气体储存和运输的一项重要技术。在本研究中，通过测定甲烷（CH）、四丁基溴化铵（TBAB）和多壁碳纳米管（MWCNTs）混合体系的相平衡条件和动力学特性，研究了MWCNTs对CH水合物形成的影响。在286.13 - 293.04 K的温度范围和0.55 - 6.56 MPa的压力范围内，对不同质量分数（0.004、0.1、0.5和1.0 wt%）的MWCNTs进行了相平衡研究。在CH + TBAB体系中，发现与不存在MWCNTs的情况相比，MWCNTs的存在使相平衡条件向更低温度移动了约1 K。然而，MWCNTs的浓度对相平衡条件影响不大。当MWCNTs的浓度为1.0 wt%时，添加MWCNTs使水合物形成的诱导时间减少了79.5%。当MWCNTs的浓度为0.1 wt%时，添加MWCNTs使水合物生长速率提高了61.5%。粉末X射线衍射图谱表明，在有和没有MWCNTs的体系中均形成了具有正交结构（对应于具有三维笼状结构的TBAB·38H₂O）的水合物。此外，在水合物图谱中未观察到与MWCNTs对应的峰，并且MWCNTs的添加对水合物的结构和类型没有影响。因此，MWCNTs未被纳入水合物笼中。
