Commercial Water Gas Shift Catalyst Research Articles

Accurate 3D Characterization of Catalytic Bodies Surface by Scanning Electron Microscopy

AbstractCatalytic bodies of millimetric dimensions are frequently used in industrial catalysis. The engineering process applied on the raw nanocatalyst during the fabrication and the working conditions affect the spatial and chemical relations of the exposed surface of the catalytic device. Hence, for improving their synthesis and for monitoring the evolution during its life cycle it is important understanding the actual heterogeneities of their surfaces. In this work scanning electron microscopy, photogrammetry and X‐Ray spectroscopy are combined to perform physico‐chemical characterization in three‐dimensions and with high resolution of the surface of commercial water gas shift catalyst bodies. By analyzing a phase of carbon present on their surface we show that the method provides measurements that are at the same time reliable, accurate and precise.

Operating strategies for fuel processing systems with a focus on water–gas shift reactor stability

This contribution deals with the development of suitable operating strategies for diesel/kerosene-fueled fuel cell APUs. The focus is on the autothermal reformer (ATR) and the water–gas shift (WGS) reactor. In the first part shutdown experiments under high-temperature shift (HTS) conditions were used to identify the possible detrimental effect of higher hydrocarbons on the activity and stability of two commercial WGS catalysts. The results indicated that 220ppmv higher hydrocarbons had no negative effect on the catalyst activity/stability. The second part presents fuel processing system experiments, which revealed much higher concentrations of higher hydrocarbons during transients like startup/shutdown than the concentrations investigated in the first part. Through the development of new startup/shutdown strategies concentrations of higher hydrocarbons were lowered by a factor of up to 10 for startup and of up to 400 for shutdown. The results were reproduced using four different diesel and kerosene fuels. The newly developed strategies improve fuel conversion in the reformer and may possibly prevent catalyst deactivation in the water–gas shift reactor during transient conditions.

Comparison of CuO-MO x (M=Ce, Zn, Cr and Zr) catalysts in various water-gas shift reactions

The water-gas shift (WGS) reaction in the temperature range of 100–350 °C for various feed compositions simulating forward, reverse and real WGS conditions was studied for a series of coprecipitated mixed metal oxide catalysts of 30 wt% of CuO and 70 wt% of metal oxide (CeO2, ZnO, Cr2O3, and ZrO2) as well as for a commercial WGS catalyst (ICI 83-3). The catalysts were characterized using BET, XRD, H2-TPR and N2O dissociation studies. Among the tested catalysts, CuO-Cr2O3 showed the best activity in the forward WGS, while the commercial catalyst was the best catalyst in the real and reverse WGS reactions. The effect of Cu content in the catalyst was also studied and, in the case of the real WGS, 50 wt% CuO-Cr2O3 was more active than 30 wt% CuO-Cr2O3. H2 and CO2 were found to inhibit the forward WGS, decreasing the reaction rate substantially, particularly at temperatures below 200 °C. The inhibition effect varied depending on the tested catalyst and increased with increasing H2 or CO2 concentration. As the inhibition effect was reversible, the competitive adsorption of H2 or CO2 on the active sites has been suggested to be responsible for the effect. The high activity of the commercial catalyst in the H2 rich real WGS could be described by the difference in the H2 inhibition between the catalysts. An easily reducible copper species was found in CuO-Cr2O3 and could be attributed to the high activity in the forward WGS. Keywords:Mixed Metal Oxide Catalysts, Water Gas Shift Reaction, H2 Inhibition, CO2 Inhibition, Copper Chromate Catalyst

WGS 반응에서 Pt-Na/Ce(1-x)Zr(x)O2촉매의 구조에 따른 Na 영향에 대한 연구

The interest in water gas shift (WGS) reaction has grown significantly, as a result of the recent advances in fuel cell technology and the need to develop small-scale fuel processors. Recently, researchers have tried to overcome the disadvantages of the commercial WGS catalysts. As a consequence, supported Pt catalysts have attracted a lot of researchers due to high activity and stability for WGS at low temperatures. In this study, Pt-Na/Ce(1-x)Zr(x)O2 catalysts with various Ce/Zr ratio have been applied to WGS at a gas hourly space velocity (GHSV) of 45,515 h -1 . According to TPR patterns of Pt-Na/Ce(1-x)Zr(x)O2 catalysts, the reducibility increases with decreasing the ZrO2 content. As a result, Cubic structure Pt-Na/Ce(1-x)Zr(x)O2 catalysts exhibited higher CO conversion than tetragonal structure Pt-Na/Ce(1-x)Zr(x)O2 catalysts. Expecially, Pt-Na/CeO2 exhibited the highest CO conversion as well as 100% selectivity to CO2. Moreover, Pt-Na/CeO2 catalyst showed relatively stable activity with time on stream. The high activity of cubic structure Pt-Na/CeO2 catalyst was correlated to its higher oxygen storage capacity (OSC) of CeO2 and easier reducibility of Pt/CeO2.

Effects of tar model compounds on commercial water gas shift catalysts

One attractive application of the catalytic water gas shift (WGS) reaction is the production of a syn-gas with high hydrogen concentration from gasification of solid combustibles. The catalyst's behavior can be affected by the hydrocarbons with high molecular weight (tar) still present in the gas after its purification. In this work the effect of some tar model compounds on two typical commercial WGS catalysts were investigated. A low temperature catalyst composed of Cu/Zn/Al and a high temperature catalyst based mainly on Fe and Cr were tested. N-hexadecane, fluorene, phenol, and octanol were used as tar model compounds. Besides these compounds, the effect of biodiesel was also investigated. In all cases a concentration of 0.5g/Nm3 was used. Generally it was observed that a low concentration is often sufficient to produce a rapid deactivation. Catalysts were characterized by means of BET and XRD.

Selection of CO2 chemisorbent for fuel-cell grade H2 production by sorption-enhanced water gas shift reaction

Abstract New experimental data are reported to demonstrate that high purity H2 can be directly produced by sorption-enhanced water gas shift (WGS) reaction using synthesis gas (CO + H2O) as sorber-reactor feed gas. An admixture of a commercial WGS catalyst and a proprietary CO2 chemisorbent (K2CO3 promoted hydrotalcite or Na2O promoted alumina) was used in the sorber-reactor for removal of CO2, the WGS reaction by-product, from the reaction zone. The promoted alumina was found to be a superior CO2 chemisorbent for this application because (a) it could directly produce a fuel-cell grade H2 product (

Effect of Reaction Temperature on the Performance of Thermal Swing Sorption-Enhanced Reaction Process for Simultaneous Production of Fuel-Cell-Grade H2 and Compressed CO2 from Synthesis Gas

A novel cyclic thermal swing sorption-enhanced reaction (TSSER) process concept was recently proposed for the simultaneous production of fuel-cell-grade H2 and compressed CO2 from synthesis gas containing CO and H2O. The process carried out the catalytic water−gas shift (WGS) reaction (CO + H2O ↔ CO2 + H2) with simultaneous removal of CO2 from the reaction zone by a reversible, water-tolerant, CO2-selective chemisorbent in order to circumvent the thermodynamic limitation of the WGS reaction and enhance the rate of the forward reaction. The chemisorbent was periodically regenerated using the principles of thermal swing adsorption by purging the sorber−reactor with superheated steam at different pressures and temperatures. Several intermediate process steps were employed to produce a pure and compressed CO2 byproduct during the thermal desorption process. The present work reports (a) new experimental data demonstrating the concept of the sorption-enhanced WGS reaction at different temperatures using a commercial WGS catalyst and Na2O-promoted alumina as the CO2 chemisorbent and (b) the effect of the sorption−reaction temperature on the TSSER process performance estimated by model simulation. Relatively slower kinetics of the sorption-enhanced WGS reaction imposes a lower bound (∼200 °C), whereas the thermal stability of the chemisorbent and the use of carbon steel sorber−reactors set the upper bound (∼550 °C) of temperatures for practical operation of the TSSER process. Simulated process performances (sorption−reaction at 200 and 400 °C and regeneration at 550 °C) show that the operation of the sorption−reaction step at 200 °C increases the H2 and CO2 productivities of the process by ∼38% and 35%, respectively, without changing (a) the number of moles of H2 produced per mole of CO in the feed gas or (b) the net CO2 recovery as a compressed byproduct gas. The total steam duty for the sorbent regeneration increases by ∼14% for operation at the lower sorption−reaction temperature. Another major benefit of operation at the lower reaction temperature is a very large increase in the pressure of the CO2 byproduct (e.g., 40 and 21 atm at 200 and 400 °C, respectively) when the reactor feed gas contained 20% CO + 80% H2O at a total pressure of 15 atm.

Optimization of a water–gas shift reactor over a Pt/ceria/alumina monolith

The water–gas shift (WGS) reaction is an important step in the purification of hydrogen for fuel cells. It lowers the carbon monoxide content and produces extra hydrogen. The constraints of automotive applications render the commercial WGS catalysts unsuitable. Pt/ceria catalysts are cited as promising catalysts for onboard applications as they are highly active and non-pyrophoric. This paper reports on a power law rate expression for a Pt/CeO 2/Al 2O 3 catalyst. This rate equation is used to compare different reactor configurations for an onboard water–gas shift reactor. A one-dimensional heterogeneous model that accounts for the interfacial and intraparticle gradients has been used to optimize a dual stage adiabatic monolith reactor.

Power output and load following in a fuel cell fueled by membrane reactor hydrogen

Hydrogen for current polymer electrolyte membrane (PEM) and alkaline fuel cells must be supplied with not more than a few tens of ppm of CO or CO 2 , respectively. If the hydrogen is generated, as it is used, it must be produced efficiently over a broad fuel cell demand range, and follow load changes on the order of seconds. We generated hydrogen for a broad variety of demands from a 1.09/1 molar mix of methanol/water using a commercial water–gas shift catalyst and a membrane reactor. The reactor output hydrogen was fed directly into a PEM fuel cell. Demand was varied between 0 and 0.9 A/cm 2 , both in flow through operation and in dead-end operation. We found power densities virtually identical to those with bottled gas. We also demonstrated inherent load following on a time scale ≤2000 μs.

Molybdenum carbide catalysts for water-gas shift

Molybdenum carbide (Mo2C) was demonstrated to be highly active for the water–gas shift of a synthetic steam reformer exhaust stream. This catalyst was more active than a commercial Cu–Zn–Al shift catalyst under the conditions employed (220–295°C and atmospheric pressure). In addition, Mo2C did not catalyze the methanation reaction. There was no apparent deactivation or modification of the structure during 48 h on‐stream. The results suggest that high surface area carbides are promising candidates for development as commercial water–gas shift catalysts.

Kinetics of the water-gas shift reaction over several alkane activation and water-gas shift catalysts

The water-gas shift reaction (WGS) over three commercial WGS catalysts and four oxide catalysts used for alkane activation has been studied at atmospheric pressure and in the temperature range of 160 to 600 °C. The oxide catalysts used were two ethane oxydehydrogenation catalysts, namely Mo 19V 5Nb 1O x and V 5Nb 1O x , and two methane coupling catalysts, namely Ca 3NiK 0.05O x and LiMgO x . The commercial water-gas shift catalysts used were two Fe 3O 4-Cr 2O 3 catalysts and one CuZnO/Al 2O 3 catalyst. All catalysts except the ethane oxidehydrogenation catalysts and LiMgO x showed high activity for the water-gas shift reaction below 400°C. It is evident that Fe, Cr, Zn, Cu and Ni oxides or metals enhance the water-gas shift reaction. The commercial CuZnO/Al 2O 3 catalyst was the most active WGS catalyst per gram of the catalyst at 160–250°C, whereas the Fe 3O 4-Cr 2O 3) catalysts showed high activity above 300 °C. The specific rates of Ca 3NiK 0.05O x , and LiMgO x were, however, higher than the specific rates of the commercial catalysts. The apparent activation energies for the conversion of carbon monoxide to carbon dioxide were 53 kJ/mol for CuZnO/Al 2O 3, 68 kJ/mol for LiMgO x , 86 kJ/mol for Ca 3NiK 0.05O x , 95 kJ/mol and 110 kJ/mol for the Fe 3O 4-Cr 2O 3 catalysts, 101 kJ/mol for Mo 19V 5Nb 1O x , and 132 kJ/mol for V 5Nb 1O x . For the commercial catalysts, the power-law rate model with concentration exponents of carbon monoxide and water close to one and zero, respectively, gave the best results. For V 5Nb 1O x , and Ca 3NiK 0.05O x , the concentration exponents of carbon monoxide and water close to 0.5 fit the results best. For Mo 19V 5Nb 1O x , the reaction was first order in carbon monoxide concentration whereas for LiMgO x , it was zero order in carbon monoxide concentration and 0.5 order in water concentration. Ca 3NiK 0.05O x and LiMgO x were active for the water-gas shift reaction in the temperature range of oxidative methane coupling. Thus, it is probable that the water-gas shift reaction can occur during methane coupling when these catalysts are used. The water-gas shift reaction is, however, unlikely to occur during the oxidative dehydrogenation of ethane since the conversions of carbon monoxide to carbon dioxide were very low at 350–500°C.

The activity of commercial water gas shift catalysts

AbstractPublished kinetic data for commercial water gas shift catalysts are interpreted in terms of pore diffusional effects. The Arrhenius plots of apparent activity show the curvature typical of the transition from reaction to pore diffusion control and the apparent activities of different catalyst pellets vary quite widely. Effective diffusivity data are used to calculate intrinsic rate constants from the apparent activity data and it is found that the intrinsic activities of the catalysts considered are all similar. Furthermore the intrinsic activities, calculated in this way, give linear Arrhenius plots and activation energies which are in good agreement with values obtained experimentally using small catalyst particles (22–27 K. Cals). The effect of pressure on apparent catalyst activity is also discussed and it is shown that this effect may be accounted for satisfactorily by pore diffusional effects and it is not necessary to assume a change in the intrinsic rate equation at least at pressures below 20 atms.