Methane–propane hydrate formation and memory effect study with a reaction kinetics model

IF 2.1 4区 化学 Q3 CHEMISTRY, PHYSICAL
Wei Ke, Guangjin Chen, Daoyi Chen
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引用次数: 4

Abstract

Although natural gas hydrates and hydrate exploration have been extensively studied for decades, the reaction kinetics and nucleation mechanism of hydrate formation is not fully understood. In its early stage, gas hydrate formation can be assumed to be an autocatalytic kinetic reaction with nucleation and initial growth. In this work, a reaction kinetics model has been established to form structure II methane–propane hydrate in an isochoric reactor. The computational model consists of six pseudo-elementary reactions for three dynamic processes: (1) gas dissolution into the bulk liquid, (2) a slow buildup of hydrate precursors for nucleation onset, and (3) rapid and autocatalytic hydrate growth after onset. The model was programmed using FORTRAN, with initiating parameters and rate constants that were derived or obtained from data fitted using experimental results. The simulations indicate that the length of nucleation induction is determined largely by an accumulation of oligomeric hydrate precursors up to a threshold value. The slow accumulation of precursors is the rate-limiting step for the overall hydrate formation, and its conversion into hydrate particles is critical for the rapid, autocatalytic reaction. By applying this model, the memory effect for hydrate nucleation was studied by assigning varied initial amounts of precursor or hydrate species in the simulations. The presence of pre-existing precursors or hydrate particles could facilitate the nucleation stage with a reduced induction time, and without affecting hydrate growth. The computational model with the performed simulations provides insight into the reaction kinetics and nucleation mechanism of hydrate formation.
用反应动力学模型研究甲烷-丙烷水合物的形成和记忆效应
尽管几十年来人们对天然气水合物和水合物勘探进行了广泛的研究,但水合物形成的反应动力学和成核机理仍未完全了解。在天然气水合物形成的早期阶段,可以认为是一个具有成核和初始生长的自催化动力学反应。本文建立了甲烷-丙烷水合物在等共压反应器中形成II型结构的反应动力学模型。该计算模型包括6个准元素反应的3个动态过程:(1)气体溶解到散装液体中;(2)开始成核的水合物前体的缓慢积累;(3)开始后水合物的快速自催化生长。模型采用FORTRAN编程,初始参数和速率常数由实验数据拟合得到。模拟表明,成核诱导的长度在很大程度上取决于低聚水合物前体的积累达到一个阈值。前驱体的缓慢积累是整个水合物形成的限速步骤,其转化为水合物颗粒对于快速的自催化反应至关重要。应用该模型,通过在模拟中指定不同初始量的前驱体或水合物种类,研究了水合物成核的记忆效应。预先存在的前驱体或水合物颗粒的存在可以促进成核阶段,缩短诱导时间,而不影响水合物的生长。计算模型与所进行的模拟提供了深入了解反应动力学和水合物形成的成核机理。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
CiteScore
2.10
自引率
0.00%
发文量
5
审稿时长
2.3 months
期刊介绍: The journal covers the fields of kinetics and mechanisms of chemical processes in the gas phase and solution of both simple and complex systems.
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