Rapid evaluation of coke resistance in catalysts for methane reforming using low steam-to-carbon ratio

Jeon, Jiyoon,Nam, Seongju,Ko, Chang Hyun Elsevier 2018 CATALYSIS TODAY - Vol.309 No.-

<P><B>Abstract</B></P> <P>The formation and subsequent accumulation of coke is one of the major reasons for the catalyst deactivation in methane reforming reaction. Although the investigation of coke-resistant catalysts is closely related to their long-term stability of given catalysts, it takes a long time to quantitatively measure the amount of carbon deposition on catalysts under normal reaction operational conditions. To overcome this problem, we used the steam deficient reaction condition, i.e. a low steam-to-carbon ratio (S/C) of 0.5 to accelerate the carbon deposition on catalysts. In this condition, the base catalyst of 10wt.% Ni/alumina rapidly lost its catalytic activity, indicating fast coke deposition. However, adding proper additives, such as Ru among various precious metals (Ru, Rh, Pt, and Pd) and alkaline earth metals (Mg, Ca, Sr, and Ba) with the appropriate loading (5wt.%) effectively suppressed coke formation. The optimized catalyst composition is 0.5wt.% Ru/5wt.% Mg/10wt.% Ni/alumina, which displayed coke resistance in the long-term stability test of steam methane reforming and 40h test of dry reforming of methane. These experimental results indicate that the method developed in this study is useful for the rapid evaluation of given catalysts for their coke resistance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effect of steam-to-carbon ratio on coke formation during methane reforming studied. </LI> <LI> Coke formation measured within 5h using low steam-to-carbon ratio and high WHSV. </LI> <LI> Quick development of Ru-Mg catalysts with high coke resistance. </LI> <LI> Long-term stability for both steam and dry methane reforming demonstrated. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Low Temperature Methane Steam Reforming for Hydrogen Production for Fuel Cells

Hyun-Seog Roh,전기원 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.1

Low temperature methane steam reforming to produce H2 for fuel cells has been calculated thermodynamically considering both heat loss of the reformer and unreacted H2 in fuel cell stack. According to the thermodynamic equilibrium analysis, it is possible to operate methane steam reforming at low temperatures. A scheme for the low temperature methane steam reforming to produce H2 for fuel cells by burning both unconverted CH4 and H2 to supply the heat for steam methane reforming has been proposed. The calculated value of the heat balance temperature is strongly dependent upon the amount of unreacted H2 and heat loss of the reformer. If unreacted H2 increases, less methane is required because unreacted H2 can be burned to supply the heat. As a consequence, it is suitable to increase the reaction temperature for getting higher CH4 conversion and more H2 for fuel cell stack. If heat loss increases from the reformer, it is necessary to supply more heat for the endothermic methane steam reforming reaction from burning unconverted CH4, resulting in decreasing the reforming temperature. Experimentally, it has been confirmed that low temperature methane steam reforming is possible with stable activity.

Low Temperature Methane Steam Reforming for Hydrogen Production for Fuel Cells

Roh, Hyun-Seog,Jun, Ki-Won Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.1

Low temperature methane steam reforming to produce $H_2$ for fuel cells has been calculated thermodynamically considering both heat loss of the reformer and unreacted $H_2$ in fuel cell stack. According to the thermodynamic equilibrium analysis, it is possible to operate methane steam reforming at low temperatures. A scheme for the low temperature methane steam reforming to produce $H_2$ for fuel cells by burning both unconverted $CH_4$ and $H_2$ to supply the heat for steam methane reforming has been proposed. The calculated value of the heat balance temperature is strongly dependent upon the amount of unreacted $H_2$ and heat loss of the reformer. If unreacted $H_2$ increases, less methane is required because unreacted $H_2$ can be burned to supply the heat. As a consequence, it is suitable to increase the reaction temperature for getting higher $CH_4$ conversion and more $H_2$ for fuel cell stack. If heat loss increases from the reformer, it is necessary to supply more heat for the endothermic methane steam reforming reaction from burning unconverted $CH_4$, resulting in decreasing the reforming temperature. Experimentally, it has been confirmed that low temperature methane steam reforming is possible with stable activity.

A synthesis of high performance nickel hybrid nanocatalyst for steam methane reforming with 0.1 N㎥/h H₂ production

강신욱,박지찬,양정일 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

Steam methane reforming (SMR) reaction has been a promising approach to generate hydrogen by using natural gas mainly consisting of methane (CH₄ + H₂O -> CO + 3H₂), which was commonly operated using a nickel-based catalyst at the high temperatures above 700 ℃. However, the commercial nickel catalysts for steam reforming of methane showed low activity caused by non-monodispersed and sintering of active particles at high temperature as well as poor stability resulting from coke deposition during reaction. In this study, we developed nickel/silica-alumina hybrid nanocatalyst, combined Ni@SiO₂ yolk-shell with Ni/γ-alumina catalysts, for the steam reforming of methane. The prepared nanocatalyst with high contents of Ni (~40 wt%) was applied to 0.1 N㎥/h-scaled reformer for the H₂ production at the 700 ℃ with high GHSV condition of 33,000 h^-1 and showed high CH₄ conversion (>86%) with the H₂ production (>125 L/h ) in the steam methane reforming reaction.

Thermal design of methane steam reformer with low-temperature non-reactive heat source for high efficiency engine-hybrid stationary fuel cell system

Shin, Gahui,Yun, Jinwon,Yu, Sangseok Pergamon Press 2017 International journal of hydrogen energy Vol.42 No.21

<P><B>Abstract</B></P> <P>In hybrid fuel cell systems, the fuel-lean anode-off gas is very useful to improve the system efficiency via additional power generation or utilization of thermal energy for heating up of auxiliary devices. In this study, the thermal energy of the hybrid systems is firstly utilized in homogeneous charge combustion engine for additional power and is then supplied to heat up the external reformer. Different from other hybrid fuel cell systems, it is very difficult to utilize heat energy of exhausted gas from engine due to its low temperature characteristics. This study is concentrated on the computation analysis of external methane steam reformers with engine out exhausted gases. Computational model is validated with experiment and parametric study is conducted. Results show that the temperature uniformity of the longitudinal and radial directions is crucial for the methane conversion efficiency. Additionally, the methane conversion rate also depends on the performance of tube-side heat transfer. When the total methane flow is fixed, the methane conversion rate shows trade-off with increasing steam-to-carbon ratio (SCR). Finally, the sensitivity study shows that heat transfer area and reactor length are dominant parameters for steam reforming with engine out exhausted gases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> 3D computational methane steam reforming model was developed and validated. </LI> <LI> Simulation was carried out with low temperature, non-reactive heat source. </LI> <LI> Characteristics of heat transfer dominate the methane conversion rate. </LI> <LI> Sensitivity of design parameters were investigated. </LI> </UL> </P>

Utilization of CO2 arising from methane steam reforming reaction: Use of CO2 membrane and heterotic reactors

Sunggeun Lee,임한권 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.91 No.-

The new reactor design concepts of reforming are proposed as a way of utilization of carbon dioxide (CO2)produced in the methane (CH4) steam reforming: (a) by applying CO2 separation membranefilled withcatalysts for dry reforming (mainly discussed), connected MSR and MDR (b) axially and (c) concentrically. The membrane selects CO2 produced in ordinary steam methane reforming and consumed as a reactantfor dry reforming inside membrane. This carbon dioxide separation membrane in the reactor of themethane steam reforming is reported recently. Permeated CO2 reacts with methane to produce syngas,hydrogen and carbon monoxide (i.e., dry reforming). Based on the numerical modeling for heat and masstransfer the conversion of methane and carbon dioxide is also considered. In that the conversion ofmethane is quite low compared to other previous studies, further study is necessary tofind a way toimprove them. Finally, we briefly suggest two other reactor types consisting of MSR and MDR connectedin a series and concentric way (reaction occurs in axial and radial direction, respectively).

5kW급 중온형 메탄-수증기 개질기의 운전 조건 변화에 따른 성능 특성

조경인(Kyungin Cho),윤진원(Jinwon Yun),유상석(Sangseok Yu) 대한기계학회 2018 大韓機械學會論文集B Vol.42 No.4

수증기 개질법은 연료전지에 연료로 공급되는 수소를 고효율로 생산하는 기술이다. 개질 반응은 흡열 반응으로 고온의 열원을 공급해주기 위해 보통 연소기를 사용하지만, 최근 새롭게 개발되고 있는 연료전지-엔진 하이브리드 시스템에서는 연소기 대신 2차 동력발생 장치를 사용하여 추가적인 전기에너지를 생산하고 남은 폐열을 개질에 활용하고 있다. 그러므로 개질기에 공급해줄 수 있는 열원이 현저히 줄어들기 때문에 중온의 열원으로 운전 가능한 열전달 촉진형 개질 기술의 개발이 필요하다. 이를 위해 본 연구에서는 중온형 메탄-수증기 개질기의 특성 평가 장치를 구축하고, 중온의 열원 하에서 운전과 설계에 필요한 각종 변수들에 따라 개질 특성이 어떻게 영향을 받는지에 대하여 조사하였다. 결론적으로 고온 운전과 달리 중온에서는 열전달에 영향을 주는 변수들이 개질에 더 큰 영향을 준다는 결과를 얻었다. Steam reforming is a technology that efficiently produces hydrogen for a fuel cell. Because the reforming reaction is endothermic, a conventional burner is used in a normal fuel cell system to supply the high temperature heat source. However, the solid oxide fuel cell-homogeneous charge compression ignition hybrid system that uses a secondary power generation device provides limited heat. Thus, the thermal activation of the reformer remains different from the high-temperature steam reformer. Because the heat source of the reformer decreases remarkably, it is necessary to investigate the performance of reforming reactions that can operate with a mid-temperature heat source. A performance evaluation system of the methane-steam reformer is constructed, and experimental analysis is carried-out using various parameters with a mid-temperature heat source. As a result, the refined heat transfer mechanism becomes crucial to operate the steam reformer at mid-temperatures.

Combined steam and CO₂ reforming of methane over La_1-xSr_xNiO₃ perovskite oxides

Yang, Eun-hyeok,Noh, Young Su,Hong, Gi Hoon,Moon, Dong Ju Elsevier 2018 CATALYSIS TODAY - Vol.299 No.-

<P><B>Abstract</B></P> <P>The effect of Sr addition to LaNiO<SUB>3</SUB> perovskite catalysts was studied for the steam-CO<SUB>2</SUB> reforming of methane. X-ray diffraction (XRD) patterns indicate that different ionic radii caused distortion of the perovskite lattice and produced alien phases such as La<SUB>2-x</SUB>Sr<SUB>x</SUB>NiO<SUB>3±δ</SUB> and Sr<SUB>0.5</SUB>La<SUB>1.5</SUB>NiO<SUB>4</SUB>. Moreover, these different phases affected reduction behavior. The influence of Sr mainly appeared in the steam-CO<SUB>2</SUB> reforming of methane reaction. SrO species adsorbed CO<SUB>2</SUB> during the reaction and produced SrCO<SUB>3</SUB>, which has a better ability of eliminating carbon sources by producing La<SUB>2</SUB>O<SUB>2</SUB>CO<SUB>3</SUB>, and by this means, carbon formation was significantly suppressed. However, the addition of Sr species covered the support sites leading to large-sized nickel particles by reducing the interaction between the support and active metals, thus the catalytic activity was decreased by an increase in Sr concentration on the catalysts. Therefore, we recommend using a small amount of Sr in the perovskite-based catalysts to obtain superior resistance to carbon deposition with moderate catalytic activity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> La<SUB>1-x</SUB>Sr<SUB>x</SUB>NiO<SUB>3</SUB> was prepared by EDTA-cellulose method. </LI> <LI> Each catalyst showed different physicochemical properties. </LI> <LI> Sr played role as increase in basicity and suppression of carbon formation. </LI> <LI> La<SUB>0.9</SUB>Sr<SUB>0.1</SUB>NiO<SUB>3</SUB> showed moderate catalytic activity and good resistance to carbon formation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Hydrogen production by steam methane reforming in a membrane reactor equipped with a Pd composite membrane deposited on a porous stainless steel

Kim, Chang-Hyun,Han, Jae-Yun,Kim, Sehwa,Lee, Boreum,Lim, Hankwon,Lee, Kwan-Young,Ryi, Shin-Kun Elsevier 2018 International journal of hydrogen energy Vol.43 No.15

<P><B>Abstract</B></P> <P>With the aim of producing hydrogen at low cost and with a high conversion efficiency, steam methane reforming (SMR) was carried out under moderate operating conditions in a Pd-based composite membrane reactor packed with a commercial Ru/Al<SUB>2</SUB>O<SUB>3</SUB> catalyst. A Pd-based composite membrane with a thickness of 4–5 μm was prepared on a tubular stainless steel support (diameter of 12.7 mm, length of 450 mm) using electroless plating (ELP). The Pd-based composite membrane had a hydrogen permeance of 2.4 × 10<SUP>−3</SUP> mol m<SUP>−1</SUP> s<SUP>−1</SUP> Pa<SUP>−0.5</SUP> and an H<SUB>2</SUB>/N<SUB>2</SUB> selectivity of 618 at a temperature of 823 K and a pressure difference of 10.1 kPa. The SMR test was conducted at 823 K with a steam-to-carbon ratio of 3.0 and gas hourly space velocity of 1000 h<SUP>−1</SUP>; increasing the pressure difference resulted in enhanced methane conversion, which reached 82% at a pressure difference of 912 kPa. To propose a guideline for membrane design, a process simulation was conducted for conversion enhancement as a function of pressure difference using Aspen HYSYS<SUP>®</SUP>. A stability test for SMR was conducted for ∼120 h; the methane conversion, hydrogen production rate, and gas composition were monitored. During the SMR test, the carbon monoxide concentration in the total reformed stream was <1%, indicating that a series of water gas shift reactors was not needed in our membrane reactor system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CH<SUB>4</SUB> conversion reached ∼82% at a ΔP = 912 kPa at 823 K in Pd/PSS membrane reformer. </LI> <LI> H<SUB>2</SUB> ∼97.7% was obtained in the permeate stream with CO<SUB>2</SUB> 60% in the retentate stream. </LI> <LI> MSR results in Pd/PSS membrane reactor was well agreement with simulation results. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Methane Reforming Reactions over Stable Ni/ θ -Al₂O₃ Catalysts

Hyun-Seog Roh,전기원,Wen-Sheng Dong,Seung-Chan Baek,Sang-Eon Park 한국공업화학회 2002 Journal of Industrial and Engineering Chemistry Vol.8 No.5

NiO/θ-Al2O3 catalysts were prepared and investigated after reduction treatment in the methane conversion reactions, such as oxy-reforming, steam reforming and oxy-steam reforming. Among the catalysts with various Ni loading, 12% Ni loading exhibits not only the highest catalytic activity and selectivity but also remarkable stability. The TPR results reveal that strong interaction between Ni and support results in forming stable NiOx species. Reducibility of NiO and the population of NiOx compared with NiO and/or NiAl2O4 play very important roles in the catalytic activity and stability of Ni/θ-Al2O3. Metallic Ni sites formed from the reduction of both NiO weakly interacting with the support and NiOx strongly interacting with the support are active sites for methane reforming reactions. Even though free NiO sites are prerequisite for high activity, the increase of NiO population in high Ni loading favorably promotes Ni sintering resulting in undesirable catalytic properties.