이산화탄소의 상거동에 관한 분자 열역학적 고찰 및 화학공정에의 응용

Abstract

본 연구에서는 이산화탄소 혼합물의 상거동을 분자 열역학적 접근 방법을 통해 해석하였다. 물질의 고유한 특성을 수식적으로 표현하기 위해서 semi-soft core (SSC) 포텐셜 함수를 사용하였다. 먼저 비리얼 계수들을 수치적분을 통해 4차항까지 계산하였다. 계산된 계수들에 대한 함수들과 SSC 포텐셜 함수 및 Auxilod-Teller-Muto의 비가산적 삼체 포텐셜 함수를 이용해 혼합물에 대한 비리얼 상태 방정식을 만들었다. 이렇게 만들어진 비리얼 상태 방정식을 이산화탄소를 포함하는 천연 가스 시스템의 압축인자를 예측하는데 응용하였다. 구형 성분들로 이루어진 밀도가 큰 유체를 설명하기 위해 HSE-VEOS를 통계역학적인 방법을 통해 개발하였다. 덧붙여, 이온을 성분으로 포함하는 용액을 설명하기 위해 개선된 Debye-Hückel 이론을 도입하였다. 이렇게 만들어진 상태방정식을 이용하여 이온성 액체 ([bmim][PF6], [bmim][Tf2N])에 이산화탄소의 용해도를 계산하였다. 마지막으로 비구형 물질을 구성성분으로 포함하는 용액을 설명하기 위해 HBE-VEOS 상태 방정식을 도입하였다. HBE-VEOS를 이용해 naphthalene, benzoic acid 및 phenanthrene의 초임계 상태에 있는 CO2에의 용해도를 계산하였다. CO2의 상거동을 포함하는 화학공정들이 이번 연구에 도입된 이론으로 낮거나 중간 정도의 압력영역에서 대체적으로 잘 설명됨을 알 수 있었다.|The phase behaviors of carbon dioxide mixture solutions were examined through molecular thermodynamic approach. Semi-soft core (SSC) potential function was employed to describe the characteristics of each component. Virial equation of state (VEOS) truncated beyond fourth order was developed by numerical integration of each virial coefficient with the SSC potential function and Axilrod-Teller-Muto (ATM) non-additive three-body potential function. The developed VEOS was applied to the prediction of the compressibility factor of natural gas systems including CO2 and the result was good in custody transfer regime. For dense fluids composed spherical molecules, the hard sphere expanded VEOS (HSE-VEOS) was developed through perturbation method in statistical mechanics. The HSE-VEOS was expanded to ionic systems by introducing the corrected Debye-Hückel theory. Using the ionic HSE-VEOS, the solubility of CO2 in ionic liquids was calculated for two ionic liquid systems: [bmim][PF6] and [bmim][Tf2N]. The fitting result was good for ambient temperature, but accurate prediction for different temperatures needed the temperature dependent parameter. Finally, the dense fluid with non-spherical shape was explained using hard body expanded VEOS (HBE-VEOS), with which the solubility of organic solids in supercritical CO2 was calculated. The experimental data of naphthalene, benzoic acid and phenanthrene were studied, and the results showed that the calculated values using the developed expressions agreed well with the experimental data in low pressure region, but deviation enlarged in high pressure region. Overall, the examined chemical processes could be well explained using the theories developed from the SSC potential function and other relations in low to moderate pressure region.; The phase behaviors of carbon dioxide mixture solutions were examined through molecular thermodynamic approach. Semi-soft core (SSC) potential function was employed to describe the characteristics of each component. Virial equation of state (VEOS) truncated beyond fourth order was developed by numerical integration of each virial coefficient with the SSC potential function and Axilrod-Teller-Muto (ATM) non-additive three-body potential function. The developed VEOS was applied to the prediction of the compressibility factor of natural gas systems including CO2 and the result was good in custody transfer regime. For dense fluids composed spherical molecules, the hard sphere expanded VEOS (HSE-VEOS) was developed through perturbation method in statistical mechanics. The HSE-VEOS was expanded to ionic systems by introducing the corrected Debye-Hückel theory. Using the ionic HSE-VEOS, the solubility of CO2 in ionic liquids was calculated for two ionic liquid systems: [bmim][PF6] and [bmim][Tf2N]. The fitting result was good for ambient temperature, but accurate prediction for different temperatures needed the temperature dependent parameter. Finally, the dense fluid with non-spherical shape was explained using hard body expanded VEOS (HBE-VEOS), with which the solubility of organic solids in supercritical CO2 was calculated. The experimental data of naphthalene, benzoic acid and phenanthrene were studied, and the results showed that the calculated values using the developed expressions agreed well with the experimental data in low pressure region, but deviation enlarged in high pressure region. Overall, the examined chemical processes could be well explained using the theories developed from the SSC potential function and other relations in low to moderate pressure region.