Prediction of Multicomponent Adsorption Equilibrium in Industrial Microporous Adsorbents

本研究从理论和实验两方面对多孔固体的平衡物理吸附过程进行了研究，重点研究了吸附剂孔隙多分散性对吸附过程的影响。理论上，大正则系综中的蒙特卡罗模拟将在分子水平上研究多组分流体混合物在碳固相中的狭缝状孔隙中的吸附过程。在模拟中，流体分子之间的相互作用将用Lennard-Jones势表示，流体分子与吸附剂之间的相互作用将用9-3势表示。对于类流体分子之间的相互作用，通过将纯组分模拟对液体密度和蒸汽压的预测与实验值相匹配，得到相互作用参数。将使用一组组合规则从相似流体相互作用的相互作用参数中获得不同流体相互作用参数。模拟将建立纯组分和混合组分的等温线作为温度和压力的函数。除了蒙特卡罗模拟外，还将发展一种基于理想吸附溶液理论的吸附理论。实验上，平衡吸附测量将进行使用石墨化碳和小分子，如甲烷，乙烷，乙烯，二氧化碳和丙烯在一个开放流动装置。在该装置中，将所需成分的气体混合物通过吸附剂，并监测排出气体，直到其成分与进料的成分相同。此时，系统关闭，测量压力，通过加热吸附剂并允许解吸的物质流向先前抽真空的解吸槽来启动解吸。通过测量脱酸槽内的压力和成分，可以计算出吸附在吸附剂上的物料量及其成分。除了吸附测量外，孔径分布将通过氮吸附测量。吸附结果的解释将利用基于密度泛函理论的孔中氮吸附的新统计力学模型，该模型适用于微孔（20 a及以下）和介孔（20-5000 a）。孔径分布将被考虑到理论中，理论预测将与实验进行比较。

This research studies, theoretically and experimentally, the process of equilibrium physical adsorption onto porous solids, particularly focusing on the effect of polydispersity of the adsorbent pores. Theoretically, Monte Carlo simulations in the Grand Canonical Ensemble will be undertaken to study the adsorption process of multicomponent fluid mixtures at a molecular level, in slit shaped pores within a solid phase of carbon. In the simulation, interactions among fluid molecules will be represented by a Lennard-Jones potential, and interactions among the fluid molecules and the adsorbent will be accounted for using a 9-3 potential. For the interactions between like fluid molecules, interaction parameters will be obtained by matching the predictions of pure component simulations for the liquid density and vapor pressure with experimental values. A set of combining rules will be used to obtain the unlike fluid interaction parameters from those of the like interactions. The simulations will establish pure and mixed component isotherms as a function of temperature and pressure. In addition to the Monte-Carlo simulations, an adsorption theory will be developed which will be based on the Ideal Adsorbed Solution theory (IAS). Experimentally, equilibrium adsorption measurements will be undertaken using graphitized carbon and small molecules such as methane, ethane, ethylene, carbon dioxide and propylene in an open flow apparatus. In this apparatus, a gas mixture of desired composition is passed over the adsorbent, and the effluent gas is monitored until its composition is identical to that of the feed. At that point, the system is closed, the pressure is measured, and desorption is initiated by heating the adsorbent and allowing the desorbed material to flow to a previously evacuated desorbate tank. The pressure and composition in the desorbate tank is measured, and from these measurements the amount of material which had been adsorbed onto the adsorbent, and its composition, can be calculated. In addition to the adsorption measurements, pore size distributions will be measured by nitrogen adsorption. The interpretation of the adsorption results will utilize a new statistical mechanical model for nitrogen adsorption in a pore which is based on density functional theory and which is valid for micropores (20 A and smaller) as well as mesopores (20-5000 A). The pore size distribution will be factored into the theory, and theoretical predictions will be compared with experiments.