철 기반 촉매의 Fischer-Tropsch 합성에서 γ-Al₂O₃/SiO₂ 혼합 지지체 조성의 영향

민선기 ( Seon Ki Min ),노성래 ( Seong-rae No ),유성식 ( Seong-sik You ) 한국화학공학회 2017 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.55 No.3

Fischer-Tropsch 합성(F-T 합성)은 석탄, 바이오매스, 천연가스 등을 개질하여 얻은 합성 가스(CO, H₂)를 촉매를 이용하여 탄화수소로 전환 하는 기술이다. Fischer-Tropsch 합성에 이용되는 촉매는 활성 금속, 조촉매, 지지체로 구성되는데 이들의 종류와 조성은 반응의 활성 및 생성물 선택도에 영향을 미친다. 본 연구에서는 γ-Al₂O₃와 SiO₂ 혼합 지지체의 조성이 Fiscsher-Tropsch 반응의 활성과 생성물 선택도에 미치는 영향을 알아 보기위해, γ-Al₂O₃/SiO₂ 혼합 지지체를(100/0 wt%, 75/25 wt%, 50/50 wt%, 25/75 wt%, 0/100 wt%) 이용하여 함침(impregnation)법으로 철 촉매를 제조하였다. 촉매의 물리적 특성은 질소 물리 흡착 법과 X-선 회절 분석법을 통해 분석 하였고, 고정층 반응기에서 Fischer-Trosch 반응을 300 ℃, 20 bar에서, 60시간 동안 수행 하였다. 촉매의 물리적 특성 분석 결과 촉매의 BET 표면적은 γ- Al₂O₃의 조성이 감소함에 따라 감소하였으며, 촉매 기공의 부피 및 평균 크기는 지지체 조성이 γ- Al₂O₃/SiO₂ (50/50 wt%)인 경우를 제외 하고 증가하는 경향을 보였다. 또한, X-선 회절 분석법을 통해 α-Fe₂O₃의 입자 크기를 계산한 결과 γ- Al₂O₃의 조성이 감소함에 따라 입자 크기가 감소 하였다. Fischer-Tropsch 합성 결과 γ- Al₂O₃의 조성이 감소함에 따라 CO 전환율은 감소 하였으며, C1-C4의 선택도는 γ- Al₂O₃의 조성이 25 wt%일 때 까지 감소하였으며 이와 반대로, C5+의 선택도는 γ- Al₂O₃의 조성이 25 wt%일 때 까지 증가 하였다. Fischer-Tropsch synthesis is the technology of converting a syngas (CO+H₂) derived from such as coal, natural gas and biomass into a hydrocarbon using a catalyst. The catalyst used in the Fischer-Tropsch synthesis consists of active metal, promoter and support. The types of these components and composition affect the reaction activity and product selectivity. In this study, we manufactured an iron catalyst using γ-Al₂O₃/SiO₂ mixed support (100/0 wt%, 75/25 wt%, 50/50 wt%, 25/75 wt%, 0/100 wt%) by an impregnation method to investigate how the composition of γ-Al₂O₃/SiO₂ mixed support effects on the reaction activity and product selectivity. The physical properties of catalyst were analyzed by N₂ physical adsorption and X-Ray diffraction method. The Fischer-Tropsch synthesis was conducted at 300 ℃, 20bar in a fixed bed reactor for 60h. According to the results of the N₂ physical adsorption analysis, the BET surface area decreases as the composition of γ-Al₂O₃ decreases, and the pore volume and pore average diameter increase as the composition of γ-Al₂O₃ decreases except for the composition of γ-Al₂O₃/SiO₂ of 50/50 wt%. By the results of the X-Ray diffraction analysis, the particle size of α-Fe₂O₃ decreases as the composition of γ-Al₂O₃ decreases. As a result of the Fischer-Tropsch synthesis, the CO conversion decreases as the composition of γ-Al₂O₃ decreases, and the selectivity of C1-C4 decreases until the composition of γ-Al₂O₃ was 25 wt%. In contrast, the selectivity of C5+ increases until the composition of γ-Al₂O₃ is 25 wt%.

Fe계 Fischer-Tropsch 반응에서 촉매활성에 대한 Cu와 K의 첨가 효과

이찬용,김의용 한국청정기술학회 2019 청정기술 Vol.25 No.1

본 연구에서는 Fischer-Tropsch 반응에서 Fe계 촉매의 환원조건과 Cu, K의 첨가에 대한 영향을 연속흐름 반응기를 통하여살펴보았다. 반응을 위해 촉매는 균일상 침전에 의한 초기 습식함침법으로 제조하였으며 XRD, TPR, SEM 등의 기기를 통해 Al2O3에 담지 된 Fe 촉매에 대한 물리화학적 특성을 분석하였다. 216 h의 장시간 반응운전을 통해 Fe/Cu/K 촉매의 활성과안정성에 대하여 조사하였다. H2와 CO의 혼합물로 촉매를 환원시키면 촉매의 활성이 향상되었는데, 이는 촉매의 표면에iron carbides가 형성되기 때문인 것으로 XRD 분석을 통해 확인되었다. 촉매에 Cu가 첨가되면 촉매의 환원성 향상으로 인하여 반응이 빠르게 안정되어 정상상태에 일찍 도달하였다. K를 첨가하게 되면 CO의 전화율은 향상되지만 함량을 5%까지 올리면 촉매의 물리적 안정성이 감소되었다. Fe/Cu (5%)/K (1%) 촉매로 Fischer-Tropsch 반응을 수행한 결과 120 h 이후에 약15% 정도 CO의 전화율이 감소되었으나 장기간 안정된 반응을 수행할 수 있었다. Effects of the Cu and K addition and the reduction condition of Fe-based catalysts for Fischer-Tropsch reaction arestudied in a continuous flow reactor in this research. The catalysts for the reaction were prepared by homogeneous precipitationfollowed by incipient wetness impregnation. Physicochemical properties of the Al2O3 supported Fe-based catalysts are characterizedby various methods including X-ray diffraction (XRD), temperature programmed reduction (TPR), and scanning electronmicroscopy (SEM). Catalytic activities and stabilities of the Fe/Cu/K catalyst are investigated in time-on-stream for an extendedreaction time over 216 h. It is found that a reduction of the catalysts using a mixture of CO and H2 can promote their catalyticactivities, attributed to the iron carbides formed on the catalysts surface by X-ray diffraction analysis. The addition of Cu inducesa fast stabilization of the reaction reducing the time to reach at the steady state by enhancement of catalytic reduction. Theaddition of K to the catalysts increases the CO conversion, while the physical stability of catalyst decreases with potassiumloading up to 5%. The Fe/Cu (5%)/K (1%) catalyst shows an enhanced long term stability for the Fischer-Tropsch reaction underthe practical reaction condition, displaying about 15% decrease in the CO conversion after 120 h of the operation.

전산유체역학을 이용한 Fischer-Tropsch 마이크로채널 반응기의 채널 구조 영향 분석

나종걸 ( Jong Geol Na ),정익환 ( Ik Hwan Jung ),( Krishnadash S. Kshetrimayum ),박성호 ( Seong Ho Park ),박찬샘 ( Chan Saem Park ),한종훈 ( Chong Hun Han ) 한국화학공학회 2014 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.52 No.6

해양 중소규모 가스전의 경제성에 대한 화두가 던져진 이후 전통 석유의 가격변동과 세계적인 환경규약 등에 맞물려 석유화학관련 산업계에서는 이를 효과적으로 대처하고 천연가스를 활용할 수 있는 공정을 개발하고자 하였다. 이에 Fischer-Tropsch 반응을 기반으로 하는 해상 GTL 공정(offshore gas-to-liquid process)이 제안되었고 부유시스템platform으로 공정을 적용시키고자 마이크로채널 반응기가 떠오르고 있다. 본 논문에서는 단일 마이크로채널 반응기를 Fischer-Tropsch 반응을 기반으로 하여 Matlab과 ASPEN Hysys를 연동하여 모사하고 이로 얻어진 반응열을 도입해 상용 전산유체역학(computational fluid dynamics, CFD) 소프트웨어인 ANSYS fluent로 멀티 마이크로채널 반응기 모델을 제작하였다. 그리고 4가지의 설계변수인 냉각채널 넓이, 높이, 냉각채널과 반응채널의 간격, 냉각채널 간의 간격을 설정하고 이들의 변화에 따른 열유동을 3가지의 변수인 열유속, 냉각 및 반응채널의 최대온도의 변화를 시각화하여 그경향성을 확인하였다. 경향성 분석 결과, 냉각채널의 넓이와 높이는 짧을수록 총 열유속이 높아졌으며 최대온도 역시높아졌으나 냉각채널과 반응채널의 간격은 열유동에 거의 영향을 미치지 못하였다. 냉각채널 간의 간격은 짧을수록 총열유속이 높아졌으며 최대온도는 낮아졌다. 따라서 적절한 냉각채널의 넓이와 높이를 제안하고 짧은 간격의 냉각채널구조를 도입하여 반응채널의 열량을 충분히 제거할 수 있는 반응기설계에 대한 휴리스틱을 제안할 수 있었다. 이처럼멀티채널 반응기의 모델을 설계하고 이로부터 적절한 변수를 선택해 그 경향성을 확인할 수 있는 방법을 통해 설계 단계에서부터 적절한 반응기 구조에 대한 제안을 하는데 도움을 줄 것이다. Driven by both environmental and economic reasons, the development of small to medium scale GTL(gasto- liquid) process for offshore applications and for utilizing other stranded or associated gas has recently been studied increasingly. Microchannel GTL reactors have been prefrered over the conventional GTL reactors for such applications, due to its compactness, and additional advantages of small heat and mass transfer distance desired for high heat transfer performance and reactor conversion. In this work, multi-microchannel reactor was simulated by using commercial CFD code, ANSYS FLUENT, to study the geometric effect of the microchannels on the heat transfer phenomena. A heat generation curve was first calculated by modeling a Fischer-Tropsch reaction in a single-microchannel reactor model using Matlab-ASPEN integration platform. The calculated heat generation curve was implemented to the CFD model. Four design variables based on the microchannel geometry namely coolant channel width, coolant channel height, coolant channel to process channel distance, and coolant channel to coolant channel distance, were selected for calculating three dependent variables namely, heat flux, maximum temperature of coolant channel, and maximum temperature of process channel. The simulation results were visualized to understand the effects of the design variables on the dependent variables. Heat flux and maximum temperature of cooling channel and process channel were found to be increasing when coolant channel width and height were decreased. Coolant channel to process channel distance was found to have no effect on the heat transfer phenomena. Finally, total heat flux was found to be increasing and maximum coolant channel temperature to be decreasing when coolant channel to coolant channel distance was decreased. Using the qualitative trend revealed from the present study, an appropriate process channel and coolant channel geometry along with the distance between the adjacent channels can be recommended for a microchannel reactor that meet a desired reactor performance on heat transfer phenomena and hence reactor conversion of a Fischer-Tropsch microchannel reactor.

철 촉매를 이용한 Fischer-Tropsch 합성 반응과 수성 가스 전환 반응에 대한 반응 속도 연구

양정일 ( Jung Ii Yang ),천동현 ( Dong Hyun Chun ),박지찬 ( Ji Chan Park ),정헌 ( Heon Jung ) 한국화학공학회 2012 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.50 No.2

The kinetics of the Fischer-Tropsch synthesis and water gas shift reactions over a precipitated iron catalyst were studied in a 5 channel fixed-bed reactor. Experimental conditions were changed as follows: synthesis gas H2/CO feed ratios of 0.5~2, reactants flow rate of 60~80ml/min, and reaction temperature of 255~275˚C at a constant pressure of 1.5 MPa, The reaction rate of Fischer-Tropsch synthesis was calculated from Eley-Rideal mechanism in which the rate-determining step was the formation of the monomer species (methylene) by hydrogenation of associatively adsorbed CO. Whereas water gas shift reaction rate was determined by the formation of a formate intermediate species as the rate-determining step. As a result, the reaction rates of Fischer-Tropsch synthesis for the hydrocarbon formation and water gas shift for the CO2 production were in good agreement with the experimental values, respectively. Therefore, the reaction rates (r FT, r WGS, -r CO) derived from the reaction mechanisms showed good agreement both with experimental values and with some kinetic models from literature.

고정층 Fischer-Tropsch 반응기의 액상 왁스 정체 현상 모델링

박찬샘(Chansaem Park),정익환(Ikhwan Jung),박성호(Seongho Park),나종걸(Jonggeol Na),Krishnadash Kshetrimayum,한종훈(Chonghun Han),이종열(Jong Yeol Lee),정종태(Jongtae Jung) 한국가스학회 2014 한국가스학회지 Vol.18 No.4

Fischer-Tropsch 합성은 주로 긴 carbon 사슬을 가지고 있는 높은 점도의 왁스를 product로 생산한다. 촉매 고정층 반응기를 이용하여 Fischer-Tropsch 합성을 수행할 경우, 왁스는 촉매입자의 표면에서 생산되어 촉매입자 표면에 흡착되어 있다. 이런 왁스의 hold-up 현상이 반응기 전체의 압력강하는 증가시키고 내부 흐름을 막는 문제를 일으킨다. 따라서 반응기 내부에 왁스가 hold-up되는 현상에 대한 모델링을 통해 왁스 hold-up 현상을 최소화 할 수 있는 반응기 및 촉매 입자의 크기를 결정하는 설계 과정이 필요하다. 본 연구에서는 왁스가 hold-up된 촉매 입자와 기체 흐름 사이의 대류 물질 전달 실험 모델을 이용하여 반응기 구조 및 운전 조건을 고려할 수 있는 반응기 내부 왁스 hold-up 모델을 개발하였다. 개발된 모델은 실험 데이터를 제공한 Knochen의 연구 결과와 비교하여 모델의 우수성을 검증하였다. 이 모델을 이용하여 반응기의 길이와 단면이 반응기 내부 왁스 hold-up 현상에 어떻게 영향을 미칠 수 있는지 분석해 보았다. Fischer-Tropsch synthesis mainly produces a wax which is a viscous liquid for long carbon chain. When a catalytic fixed-bed reactor is used for Fischer-Tropsch synthesis, the wax generated on a catalyst surface can keep adsorbing on the catalyst surface. This liquid hold-up causes significant pressure drop and clogging problems through the reactor. Thus, the model for liquid hold-up is required to design the size of reactor and catalyst particles. In this study, the liquid hold-up model considering structural and operational conditions was proposed based on empirical equations for convective mass transfer between the syngas flow and the wax-adsorbed catalyst. The developed model was validated by comparing with the experimental data from Knochen’s work (2010). The influence of reactor length and coross section on the wax hold-up in reactor were analyzed and the optimal reactor size were proposed.

A durable nanocatalyst of potassium-doped iron-carbide/alumina for significant production of linear alpha olefins via Fischer-Tropsch synthesis

Park, Ji Chan,Jang, Sanha,Rhim, Geun Bae,Lee, Jin Hee,Choi, Hyunkyoung,Jeong, Heon-Do,Youn, Min Hye,Lee, Dong-Wook,Koo, Kee Young,Kang, Shin Wook,Yang, Jung-Il,Lee, Ho-Tae,Jung, Heon,Kim, Chul Sung,Ch Elsevier 2018 Applied catalysis. A, General Vol.564 No.-

<P><B>Abstract</B></P> <P>Improvement of activity, selectivity, and stability of the catalyst used in Fischer-Tropsch synthesis (FTS) to produce targeted hydrocarbon products has been a major challenge. In this work, the potassium-doped iron-carbide/alumina (K-Fe<SUB>5</SUB>C<SUB>2</SUB>/Al<SUB>2</SUB>O<SUB>3</SUB>), as a durable nanocatalyst containing small iron-carbide particles (∼ 10 nm), was applied to high-temperature Fischer-Tropsch synthesis (HT-FTS) to optimize the production of linear alpha olefins. The catalyst, suitable under high space velocity reaction conditions (14–36 N L g<SUB>cat</SUB> <SUP>−1</SUP> h<SUP>−1</SUP>) based on the well-dispersed potassium as an efficient base promoter on the active iron-carbide surface, shows very high CO conversion (up to ∼90%) with extremely high activity (1.41 mmol<SUB>CO</SUB> g<SUB>Fe</SUB> <SUP>−1</SUP> s<SUP>−1</SUP>) and selectivity for C<SUB>5</SUB>–C<SUB>13</SUB> linear alpha olefins.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The potassium-doped iron-carbide/alumina nanocatalyst was prepared for effective production of linear alpha olefins. </LI> <LI> The active iron-carbide nanoparticles (∼10 nm) with potassium on gamma-alumina could enhance catalytic performance. </LI> <LI> The catalyst showed high stability and activity for high-temperature Fischer-Tropsch synthesis. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>A potassium-doped iron-carbide/alumina nanocatalyst shows very high CO conversion (∼90%) and significant productivity for C<SUB>5</SUB>–C<SUB>13</SUB> linear alpha olefins in Fischer-Tropsch synthesis under high space velocity conditions.</P> <P>[DISPLAY OMISSION]</P>

Effects of metal-support interaction to product distributions on Co-based Fischer-Tropsch synthesis catalysts

구현모,배종욱 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

Many previous studies have been focused to confirm the changes of product distributions according to metal-support interactions on Cobased Fischer-Tropsch synthesis (FTS) catalysts. In the present study, the correlations between CH₄ selectivity and DOR (degree of reduction of the similar cobalt particle size in the range of 10 ~ 16 nm) were investigated by using Co/SBA-15, Co/P-Al₂O₃ and Co/Al₂O₃-SiC. Depending on the metal-support interactions, the oxidation states of active cobalt nanoparticles and their reducibility were significantly changed with different product distributions. The more strongly interacted Co nanoparticles with higher oxidation states were responsible for a higher tendency for CH₄ formation due to the preferential formation of partially oxidized Co nanoparticles.

합성가스로부터 경질탄화수소 및 중산유분을 생산하기 위한 Fischer-Tropsch의 국내연구동향

김진호,김효식,김지현,류재홍,강석환,박명준 한국화학공학회 2019 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.57 No.4

Fischer-Tropsch synthesis process is a typical method for synthesizing hydrocarbons from syngas and is mainly known as iron (Fe) and cobalt (Co) catalysts. Currently, some technologies such as CTL (Coal to Liquid) and GTL (Gas to Liquid) are operated on a commercial scale depending on the products, but the research to produce light hydrocarbons and middle distillates directly has not been commercialized. Therefore, in this study, domestic studies for direct production of light hydrocarbons and middle distillates are summarized and the effect of catalyst preparation, promoter addition, zeolite combination on product selectivity is investigated. Fischer-Tropsch 합성공정은 합성가스로부터 탄화수소를 합성하는 대표적인 방법이며, 주로 철(Fe)계와 코발트(Co) 계 촉매로 알려져 있다. 현재 생성물에 따라 일부 기술(CTL, GTL 등)은 상용 규모로 운전되고 있으나, 경질탄화수소와 중간유분을 직접 생산하는 연구는 아직 상용화되지는 않았다. 그러므로, 본 연구에서는 국내에서 현재까지 경질탄화수소와 중간유분을 직접 생산하기 위한 연구들을 정리하였으며, 촉매의 제조법, 조촉매 첨가, 제올라이트의 조합과같은 영향이 생성물의 선택도에 미치는 영향을 고찰하였다.

전통적인 유체역학 방법론과 CFD 결합을 통한 Fischer-Tropsch 고정층 반응기 내부 흐름의 체계적 모델링

김현승(Hyunseung Kim),조재훈(Jaehoon Cho),홍기훈(Gi Hoon Hong),문동주(Dong Ju Moon),신동일(Dongil Shin) 한국가스학회 2016 한국가스학회지 Vol.20 No.4

Fischer-Tropsch 반응기 내 복잡한 반응과 흐름을 상세히 모델링하는 것은 CFD 분야에 있어 도전적 과제이다. Fischer-Tropsch 반응은 여러 가지 탄소수를 가진 탄화수소들을 만들어내는데, 탄화수소에는 무수히 많은 이성질체가 존재하는 이유로 모든 화학종에 대해서 각각의 반응속도식을 도출해 적용하는 것은 어렵다. 이의 극복을 위해 기존 연구들에서 사용된 반응속도식 모델링 방법론들을 분석한 뒤, 화학종별 상세한 반응속도식 적용을 위해 non-Anderson-Schulz-Flory 방법론을 선정하여 상세 모델링을 진행하였다. 또한 반응 특성상 다상 흐름 형태를 띠는데, 다상 흐름 모델링의 경우 상간의 간섭이나 분산상의 분포 및 유동 형태 등에 따라 적합한 모델링 방법론이 다르다. 그러나 기존 연구들에서는 타당성에 대한 논의나 근거 제시 없이 각양각색의 내부 흐름 모델링 방법론이 사용되고 있다. 실험을 통해 내부 흐름 형태를 관찰한 뒤 유동 형태에 따른 모델링을 진행하는 것이 최선이나, 자원 여건상 어려움이 있어, 본 연구에서는 전통적인 유체역학 이론에 근거해 내부 흐름 형태를 먼저 추론하고 Mixture 모델 방법론을 선정하여 체계적인 CFD 모델링을 진행함으로써, 사용된 방법론에 대한 근거를 마련하고자 하였다. 10가지 실험조건에서 진행한 실험 결과와 본 연구의 시뮬레이션 결과를 비교하였으며, 이를 통해 본 연구가 제안하는 체계적 모델링 방법론의 타당성을 입증하였다. Modeling for complex reacting flow in Fischer-Tropsch reactor is one of the challenges in the field of Computational Fluid Dynamics (CFD). It is hard to derive each and every reaction rate for all chemical species because Fisher-Tropsch reaction produces many kinds of hydrocarbons which include lots of isomers. To overcome this problem, after analyzing the existing methodologies for reaction rate modeling, non-Anderson-Schulz-Flory methodology is selected to model the detailed reaction rates. In addition, the inside flow has feature of multi-phase flow, and the methodologies for modeling multi-phase flow depend on the interference between the phases, distribution of the dispersed phase, flow pattern, etc. However, existing studies have used a variety of inside flow modeling methodologies with no basis or rationale for the feasibility. Modeling inside flow based on the experimental observation of the flow would be the best way, however, with limited resources we infer the probable regime of inside flow based on conventional fluid dynamics theory; select the appropriate methodology of Mixture model; and perform systematic CFD modeling. The model presented in this study is validated through comparisons between experimental data and simulation results for 10 experimental conditions.

Combined FTIR and Temperature Programmed Fischer-Tropsch Synthesis over Ru/SiO2 and Ru-Ag/SiO2 Supported Catalysts

Syed T. Hussain*,M. Arif Nadeem,M. Mazhar,Faical Larachi 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.4

Combined temperature programmed reaction (TPR) and infrared (IR) spectroscopic studies for Fischer-Tropsch reaction have been performed over Ru/SiO2 and Ru-Ag/SiO2 supported catalysts. Reaction of linearly absorbed CO with hydrogen starts at 375 K over Ru/SiO2 catalyst and reaches maximum at 420 K accompanied with an intensity decrease of linear CO absorption. The reaction with bridged absorbed CO peaks around 510-535 K. Addition of Ag yields mixed Ru-Ag bimetallic sites while it suppresses the formation of bridged bonded CO. Formation of methane on this modified surface occurs at 390 K and reaches maximum at 444 K. Suppression of hydrogen on the Ag-doped surface also occurs resulting in the formation of unsaturated hydrocarbons and of CHx intermediates not observed with Ru/SiO2 catalyst. Such intermediates are believed to be the building blocks of higher hydrocarbons during the Fischer-Tropsch synthesis. Linearly absorbed CO is found to be more reactive as compared to bridged CO. The Ag-modified surface also produces CO2 and carbon. On this surface, hydrogenation of CO begins at 390 K and reaches maximum at 494 K. The high temperature for hydrogenation of absorbed CO and C over Ru-Ag/SiO2 catalyst as compared to Ru/SiO2 catalyst is due to the formation of Ru-Ag bimetallic surfaces impeding hydrogen adsorption.