Kinetic Characteristics of Methane Hydrate in Functionalized Multi-walled Carbon Nanotubes and L-leucine Compounding System
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摘要: 加快天然气水合物形成,对基于水合物法的天然气储运、气体分离和二氧化碳捕集技术的推动具有重要意义。采用恒温恒容法研究了0.05 wt% 功能化(羟基化、羧基化和氨基化)多壁碳纳米管和1.0 wt% L-亮氨酸复配体系甲烷水合物动力学特征。研究表明,多壁碳纳米管、羧基化和羟基化多壁碳纳米管与L-亮氨酸的复配,可使甲烷水合物诱导成核时间大幅缩短至25、22和13 min左右,促进效果与典型促进剂十二烷基硫酸钠相当,且促进效果优于单一添加剂体系。复配体系甲烷储气密度具有良好表现,可达136~142 mg/g。甲烷平均吸收速率和瞬时吸收速率分析表明,多壁碳纳米管对生长阶段甲烷水合物的生长动力学影响很小。复配体系和L-亮氨酸体系中甲烷水合物的生长具有相似性,均呈现出甲烷气体吸收速率快速增加到最大值,然后迅速下降并完成生长的特点。综合分析表明,多壁碳纳米管和L-亮氨酸的复配对甲烷水合物的成核速率具有协同增强效应,而生长阶段的进程与速率主要受L-亮氨酸影响。该研究为探索不同类型添加剂在强化甲烷水合物生成动力学上的差异化机理提供了新思路。Abstract: Accelerated natural gas hydrate formation is important for the promotion of natural gas storage, gas separation and CO2 capture technologies based on hydrate method. The kinetic characteristics of methane hydrate of 0.05 wt% functionalized (hydroxylated, carboxylated and aminated) multi-walled carbon nanotubes and 1.0 wt% L-leucine complexed system were investigated by constant temperature and constant volume method. It is shown that the compounding of multi-walled carbon nanotubes, carboxylated and hydroxylated multi-walled carbon nanotubes with L-leucine can significantly reduce the nucleation time of natural gas hydrate induction to about 25, 22 and 13 min, the promotion effect is comparable to that of typical promoter sodium dodecyl sulfate, and the promotion effect is better than that of the single additive system. The methane storage density of the compounded system has good performance up to 136-142 mg/g. The analysis of the average and instantaneous methane uptake rate shows that the multi-walled carbon nanotubes have little effect on the growth kinetics of methane hydrate in the growth phase. The growth of methane hydrate in the compounded and L-leucine systems had similarities, both showed a rapid increase of uptake rate to the maximum value, follwed by a rapid decrease and completion of growth. The comprehensive analysis indicates that the compounding system of multi-walled carbon nanotubes and L-leucine has a synergistic enhancement effect on the nucleation rate of methane hydrate, while the process and rate of the growth phase are mainly influenced by L-leucine. This study provides a new idea to explore the differentiation mechanism of different types of additives in enhancing the kinetics of methane hydrate generation.
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Key words:
- Methane hydrate /
- Multi-walled carbon nanotubes /
- L-leucine /
- Synergistic promotion /
- Nucleation /
- Growth
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