수소분리용 MOF 기반 혼합기질막 제조 및 투과 특성 연구

Abstract

C2 탄화수소는 원유정제 과정에서 생산되지만, 화석연료는 빠르게 고갈되고 있다. 따라서, 고갈 염려가 없는 C2 탄화수소 생산 방법의 필요성이 대두되어지고 있다. CH4을 Ar 플라즈마 반응을 통해 C2 탄화수소로 이량화하여 생산하는 것은 그 중 하나의 방법으로 현재 연구가 진행 중이다. 본 연구에서는 Ar Plasma 반응에서 생성된 C2 탄화수소를 PSA(Pressure swing adsorption)를 통해 회수하면 H2, Ar, CH4 혼합기체가 남게 되며 이를 혼합기질막(Mixed matrix membrane)의 제조와 기체 투과실험을 통해 H2의 분리 가능성을 알아보았다. 혼합기질막은 MOF(metal organic frameworks)의 한 종류인 ZIF-8을 폴리이미드 고분자 매트릭스에 0-15 wt% 분산하여 제조하였으며 H2, Ar, CH4 단일기체 투과도 측정 및 혼합기체의 분리연구를 수행하였다. Time-lag을 이용한 단일기체 투과도를 35 ℃에서 측정한 결과, H2, CO, Ar, N2, CH4 기체는 kinetic diameter에 반비례하였으며 ZIF-8의 함량이 증가함에 따라 투과도 역시 증가하였다. ZIF-8의 함량이 가장 높은 15 wt% ZIF-8의 혼합기질막에서 투과도는 각각 H2, Ar, CH4(27.00, 0.49, 0.19 barrer)로 측정되었다. 이상선택도는 ZIF-8의 함량에 증가함에 따라 감소하였으며, 5 wt% ZIF-8의 H2/CH4, H2/Ar의 이상선택도는 각각 136.23, 53.25이다. 또한, 실제 Ar플라즈마를 이용해 CH4을 이량화 시키는 과정에서 발생되는 혼합기체 76.77% Ar, 3.99% CH4, 19.25% H2를 혼합기질막을 이용해 35 ℃, 1 bar에서 투과도를 측정한 결과, 15 wt%에서 H2의 투과도가 30.13 barrer로 가장 높게 나왔으며 H2의 투과농도는 폴리이미드막에서 94.47%로 가장 높게 나왔다. 실제 H2 회수 공정에서 적용하기 위한 분리막을 선정하기 위해서는 H2의 투과농도 뿐만 아니라 생산량도 중요한 요소이기 때문에, 생산성 측면에서는 15 wt% ZIF-8 혼합기질막이 우수한 성능을 낼 것이라 판단된다. | C2 hydrocarbon is an essential monomer material in the chemical industry, and is produced during the refining processes. However, as fossil fuels are getting depleted at a rapid rate, the need for alternative C2 hydrocarbon production methods needs to be developed. One of the promising methods is the dimerization of CH4 via an Ar plasma reaction. The product stream from the Ar plasma reaction is first purified using PSA (pressure swing adsorption), leaving a gas mixture of H2, Ar, and CH4 behind. In this study, the possibility of selectively separating H2 using MMMs (mixed matrix membranes) was investigated. MMMs were prepared by dispersing a set amount of ZIF-8 (0 - 15 wt%), a type of MOF (metal organic framework) material, in a polyimide polymer matrix, and the measurement of H2, Ar, CH4 single gas permeability and separation of mixed gas were performed. Using the time-lag method at 35 ℃, it was determined that the single gas permeability (H2, CO, Ar, N2, and CH4) was inversely proportional to the kinetic diameter, and the intrinsic permeability increased with the increasing ZIF-8 content. The H2, Ar, and CH4 permeabilities of the 15 wt% ZIF-8 MMMs were 27.00, 0.49, and 0.19 barrer, respectively. The ideal gas selectivity at 5 wt% ZIF-8 for H2/CH4 and H2/Ar were 136.23 and 53.25, respectively. Notably, the ideal gas selectivity decreased with increasing ZIF-8 content. Also, the mixed gas permeability and selectivity were determined at 35 ℃, 1 bar using a feed gas mixture of 76.77% Ar, 3.99% CH4, and 19.25% H2 (generated in the process of dimerizing CH4 using Ar plasma). For membranes with 15 wt% ZIF-8, the permeability of H2 was the highest at 30.13 barrer and the permeate concentration of H2 was also the highest at 94.47%. Since both the permeability and product concentration are important factors, 15 wt% ZIF-8 polyimide membrane is expected to be a suitable candidate for H2 recovery process.; C2 hydrocarbon is an essential monomer material in the chemical industry, and is produced during the refining processes. However, as fossil fuels are getting depleted at a rapid rate, the need for alternative C2 hydrocarbon production methods needs to be developed. One of the promising methods is the dimerization of CH4 via an Ar plasma reaction. The product stream from the Ar plasma reaction is first purified using PSA (pressure swing adsorption), leaving a gas mixture of H2, Ar, and CH4 behind. In this study, the possibility of selectively separating H2 using MMMs (mixed matrix membranes) was investigated. MMMs were prepared by dispersing a set amount of ZIF-8 (0 - 15 wt%), a type of MOF (metal organic framework) material, in a polyimide polymer matrix, and the measurement of H2, Ar, CH4 single gas permeability and separation of mixed gas were performed. Using the time-lag method at 35 ℃, it was determined that the single gas permeability (H2, CO, Ar, N2, and CH4) was inversely proportional to the kinetic diameter, and the intrinsic permeability increased with the increasing ZIF-8 content. The H2, Ar, and CH4 permeabilities of the 15 wt% ZIF-8 MMMs were 27.00, 0.49, and 0.19 barrer, respectively. The ideal gas selectivity at 5 wt% ZIF-8 for H2/CH4 and H2/Ar were 136.23 and 53.25, respectively. Notably, the ideal gas selectivity decreased with increasing ZIF-8 content. Also, the mixed gas permeability and selectivity were determined at 35 ℃, 1 bar using a feed gas mixture of 76.77% Ar, 3.99% CH4, and 19.25% H2 (generated in the process of dimerizing CH4 using Ar plasma). For membranes with 15 wt% ZIF-8, the permeability of H2 was the highest at 30.13 barrer and the permeate concentration of H2 was also the highest at 94.47%. Since both the permeability and product concentration are important factors, 15 wt% ZIF-8 polyimide membrane is expected to be a suitable candidate for H2 recovery process.