Professor: Jae W. Lee
Fax 212.650.6660
Phone 212.650.6688
Office Steinman Hall, T-311
E-Mail lee@che.ccny.cuny.edu

Mailing Address
The City College of the CUNY
Department of Chemical Engineering., Steinman Hall, T-311
Convent Avenue at 140th Street, New York, New York 10031

 

Professor

Ph.D., 2000, Carnegie Mellon University;
M.S., 1992, Seoul National University;
B.S., 1990, Seoul National University;
2000-2001, Alexander von Humboldt Research Fellow;
1992-1997, Research Engineer in Ssangyong Oil Refining Company

 

 


Current Research Interests:

Pr. Lee proposed a new interpretation of macro-scale thermodynamics of integrated reaction and separation by visualizing the individual phenomena in composition space and by generalizing a mathematical algorithm for multi-dimensional systems. His research interest has been extended into an integration of clathrate formation and separation by carrying out high-pressure, low temperature experiments, investigating multi-scale interactions between surface active agents and hydrate surface for accelerating and inhibiting gas hydrate formation, molecular-level kinetics modeling studies, and thermodynamics studies based on the combination of ab-initio calculations and classical statistical mechanics. This fundamental aspect is being extended to process design of CO2 separation/sequestration, natural gas storage, and H2 storage using clathrate formation. The following fundamental research is currently going on.

 

1. Gas Hydrate Research 

Multi-Scale Investigation of the Role of Surface-Active Agents in Gas Hydrate Formation Kinetics:

The central purpose of this project is to understand the effect of surfactants and kinetic inhibitors on hydrate formation kinetics from the molecular level to the bulk phase level using various analytical techniques. Elucidating an active role of the surface-active agents can provide a control wheel for accelerating or retarding gas hydrate nucleation/growth. A significant contrast of their effects on hydrate formation exists between methane (CH4) and carbon dioxide (CO2) hydrate systems: surfactants promote CH4 hydrate formation and kinetic inhibitors retard it while both do not affect CO2 hydrate formation kinetics or sometimes surfactants inhibit CO2 hydrate formation. This understanding of this contrast can facilitate the rapid formation of CH4 and CO2 hydrates for storage/separation/sequestration systems, and may lead to more effective protocols for screening suitable kinetic inhibitors for preventing gas hydrate blockage in the gas/oil process and delivery lines. To investigate the multi-scale interaction between gas hydrate particles and surface-active agents from nanometer to centimeter scales, we will carry out the following fundamental studies in a sequential order of nucleation, initial growth, and packed growth:

1.       Effect of Surface-active Agents on Hydrate Nucleation: Statistical measurements of gas hydrate nucleation will be performed in a high-pressure and low temperature scanning differential calorimeter (DSC) to understand how different dosages of surfactants and kinetic inhibitors can affect induction times of CH4 and CO2 hydrates. The gas hydrate nucleation itself is a totally stochastic process. A reasonable number of repeated measurements are required to obtain consistent statistics for induction times of gas hydrate nucleation. The degree of super-cooling (DT = Tequilibrium - Toperation) until the phase transition occurs will be used as an indicator of the degree of difficulty in nucleation. We will also observe the effect of other guest molecules known as thermodynamic promoters (THF: tetrahydrofuran and CP: cyclopentane) on the CH4 and CO2 hydrate nucleation.

  1. Role of Surface-active Agents in CO2 and CH4 Hydrate Growth: One possible mechanism to be tested for surfactants?role in promoting gas hydrate growth is the co-adsorption of hydrate formers when the surface-active agents adsorb onto the hydrate surface. In other words, the hydrate formers are solubilized in the hydrocarbon tails of the adsorbed surface-active agents. This means that the first requirement for promoting gas hydrate formation is the adsorption of surfactants onto the hydrate surface and the second step is the co-adsorption of hydrate formers with surfactants so that they have an easy access to water molecules. We will investigate whether surfactants are adsorbed onto CO2 hydrate particles using a fluorescence probe in our high-pressure reactor and confocal laser scanning microscope (CLSM) by providing a UV light source.?It is not expected that surfactants adsorbed onto the CO2 hydrate surface because high concentrations of bicarbonate ions arising from dissolved CO2 in aqueous phase will occupy all of the adsorption sites in the hydrate surface based on our previous results. We will also confirm the adsorption of surfactants onto the CH4 hydrate surface using the same fluorescence probe in the two pieces of equipment.      
  2. Co-adsorption of Hydrate Formers with Surface-active Agents: We will identify the co-adsorption of lower-pressure hydrate formers (CP and THF) using a surface Raman microscope. In more detailed levels, Liquids Reflectometer (LR) will be employed to see what hydrate former has a closer contact with water molecules for binary hydrate systems. Specifically, the CO2 + CP binary hydrates with surfactants will be investigated using a high-pressure quartz cell because surfactants show an inhibitive effect of CO2 hydrate formation compared to the binary hydrates without any surfactant. We will investigate whether CP molecules are firstly co-adsorbed with surfactants onto the water-liquid CP interface and then prevent CO2 from being solubilized to the hydrocarbon tails of surfactants. The same mechanism will also be tested as to whether kinetic inhibitors prevent hydrate formers from accessing to water molecules.
  3. Effect of Surface-active Agents on Hydrate Morphology: Once surfactants or kinetic inhibitors adsorb onto the hydrate surface, they will affect the crystal size and the pattern of gas particle growth. The smaller the particle size, the more porous the gas hydrate particles and the better the hydrate growth via easier mass transfer of guest gas molecules. Cryoelectron microscopy (CEM) will be used to investigate the crystal size of gas hydrates and to obtain possible porosity for given snapshots of different hydrate growth stages. To visualize the interplay of surfactants and kinetic inhibitors in gas hydrate growth, we will use a confocal microscope (CLSM) and will model CO2 and CH4 hydrate growth using a reaction-diffusion equation.?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


2. Reactive Separation

Process intensification by integrating reaction and separation in a single unit.

The intensification of reaction and separation can lead to the simplification of a complex process, dramatic economic savings, and environmentally benign operation. The main difficulty in realizing this technology is the absence of a general understanding of the interaction between multiple reactions and separation. Past research has mainly focused on integrating a single reaction with V-L separation. This proposal aims at solving two unexplored problems for the integration of multiple reactions and distillation: 1) How to identify the thermodynamic conditions feasible to increase reaction selectivity of desired products and 2) For thermodynamically feasible combinations, how to determine the operating range of key design parameters. The feasible conditions will be identified by using the dynamic properties of singular points in the distillation map and by superimposing the reaction equilibrium manifolds on this map. To circumvent thermodynamic limitations and increase reaction selectivity, the structural variations of a column will be considered by using different stream connections, reaction locations, and the introduction of the so-called reactive Petlyuk column.? A new shortcut algorithm will be proposed to determine the feasible ranges of key design parameters for these structural variations without performing experiments or rigorous optimizations. One major impact of this research is that it will give academia and industry a general design framework for understanding reactive separation processes. It enables the creation of novel, environmentally benign, and cost-effective process units such as a gas hydrate-aided CO2 capture process with multi-functionality.