Performance Of Water Gas Shift Reaction Research Articles

Addition of Sodium Additives for Improved Performance of Water-Gas Shift Reaction over Ni-Based Catalysts.

The effect of Na loading on water-gas shift reaction (WGSR) activity of Ni@TiOx-XNa (X = 0, 0.5, 1, 2, and 5 wt %) catalysts has been investigated. Herein, we report sodium-modified Ni@TiOx catalysts (denoted as Ni@TiOx-XNa) derived from Ni3Ti1-layered double hydroxide (Ni3Ti1-LDH) precursor. The optimized Ni@TiOx-1Na catalyst exhibits enhanced catalytic performance toward WGSR at relatively low temperature and reaches an equilibrium CO conversion at 300 °C, which is much superior to those for most of the reported Ni-based catalysts. The H2-temperature-programmed reduction (H2-TPR) result demonstrates that the Ni@TiOx-1Na catalyst has a stronger metal–support interaction (MSI) than the sodium-free Ni@TiOx catalyst. The presence of stronger MSI significantly facilitates the electron transfer from TiOx support to the interfacial Ni atoms to modulate the electronic structure of Ni atoms (a sharp increase in Niδ− species), inducing the generation of more surface sites (Ov–Ti3+) accompanied by more interfacial sites (Niδ−–Ov–Ti3+), revealed by X-ray photoelectron spectroscopy (XPS). The Niδ−–Ov–Ti3+ interfacial sites serve as dual-active sites for WGSR. The increase in the dual-active sites accounts for improvement in the catalytic performance of WGSR. With the tunable Ni–TiOx interaction, a feasible strategy in creating active sites by adding low-cost sodium addictive has been developed.

Plasma-induced defect engineering: Boosted the reverse water gas shift reaction performance with electron trap

The reverse water gas shift reaction is a promising approach to solve the problem of excessive CO2 emission and energy shortage. However, insufficient charge separation efficiency of numerous semiconductor photocatalysts hamper their CO2 photoreduction performance. Defect engineering is considered as a desired method to tackle that shortcoming by the boosting the electron capture process. Herein, the sulfur vacancies-rich CdIn2S4 (VS-CdIn2S4) was synthesized by an efficient low-temperature plasma-enhanced technology. The outstanding VS-CdIn2S4 shows a more excellent CO formation rate of 103.6 μmol g−1 h−1 comparing that of traditional CdIn2S4 (31.36 μmol g−1 h−1). The density function theory (DFT) calculation reveals the sulfur vacancy is the center of electron capture. Moreover, the formed defect level after introduce of surface vacancy effectively optimizes the light absorption propertie of the prepared material. Thus, the enhanced photocatalytic CO2 reduction performance can be attributed to the double improvement of light absorption and carrier separation. This work provides a novel and facile strategy to mediate carriers’ movement behavior via defect engineering for high-efficient CO2 photoreduction.

Synergetic effects of cerium and nickel in Ce-Ni-MFI catalysts on low-temperature water-gas shift reaction

Synergistic effects between nickel and cerium in catalytic water gas shift reaction (WGSR) have been widely reported, mostly using cerium as an active support coupled with nickel as a dispersed phase. Although, these metals are extensively used in industry, and their price has continuously raised, catalysts containing highly dispersed nickel and cerium are less investigated. This work tackles catalysts with low percentages (0–3 wt%) of well dispersed nickel and cerium in MFI framework. Catalysts containing only incorporated cerium exhibited no activity, while the single metal Ni-MFI series catalyzed the reaction. The prepared Ni-Ce-MFI series synergistically accelerated WGSR even at temperatures as low as 503 K, and some reach equilibrium conversion below 548 K. The catalytic performance increased by nickel content, and catalysts with similar mass percentage of cerium and nickel outperformed others. Furthermore, their maximum reduction temperatures occurred at ∼60 K lower, confirming their higher performance in WGSR.

Preparation of CuO/CeO2 Catalyst with Enhanced Catalytic Performance for Water–Gas Shift Reaction in Hydrogen Production

AbstractCuO/CeO2 is a promising catalyst for water–gas shift (WGS) reaction in H2 production. Much effort has been devoted to improving its catalytic activity and stability by CeO2 support modification or introduction of secondary active species. Here a method to enhance the catalytic performance by controlling the deposition rate of copper is reported. The nature of CuO and CuO‐CeO2 synergetic interaction are modulated by using different copper sources (Cu(NO3)2 and Cu[(NH3) ) and controlling reaction temperatures. The as‐prepared CuO‐CeO2 catalysts show distinguish catalytic performances for the WGS reaction. The one prepared by using Cu[(NH3) at the reaction temperature of 30 °C (CuCe‐30N) shows superior catalytic activity and stability. The CuCe‐30N catalyst possesses the largest Cu0 surface area (39.2 m2 ) and strongest CuO‐CeO2 synergetic interaction. The largest Cu0 surface area provides the most active sites for CO adsorption thus leading to its highest activity. The strong synergetic interaction prevents Cu crystallites from sintering during the WGS reaction, thus improving its thermal stability.

Production of synthetic natural gas by CO methanation over Ni/Al2O3 catalyst in fluidized bed reactor

In order to obtain the reaction characteristics, CO methanation process is numerically investigated in fluidized bed catalytic reactor over Ni/Al2O3 catalyst. The catalysts flow behavior is analyzed, which has significant effect on the activity of catalysts. The influences of operation parameter on CO conversion and CH4 yield are evaluated. The inventory of catalysts and superficial gas velocity will not influence the output of methane but the reaction rates. Meanwhile, the performance of water-gas shift reaction on CH4 yield is taken consideration during reactions.

The impact of synthesis method of CNT supported CeZrO2 and Ni-CeZrO2 on catalytic activity in WGS reaction

Carbon nanotube (CNT) supported catalysts containing ceria-zirconia mixed oxide (CeZrO2) and nickel were synthesized and tested in water gas shift (WGS) reaction. Physicochemical characterization including N2 adsorption, X-ray diffraction (XRD), scanning and transmission microscopy (SEM/TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and temperature programmed reduction with H2 (H2-TPR), as well as catalytic tests of WGS reaction showed that the synthesis method had significant impact on composition, morphology, structural properties and catalytic performance of obtained hybrid materials. The catalysts obtained by co-precipitation of metal oxides (NiO and/or CeZrO2) on CNT walls demonstrated better dispersion of active phase and smaller particle size than catalyst obtained by depositing of powder CeZrO2 or Ni-CeZrO2. Moreover, the catalyst obtained by co-precipitation revealed better performance in WGS reaction; however, some CH4 formation was noticed over Ni-CeZrO2/CNT system. The role of CeZrO2 in catalysts performance in WGS as well as the importance of good metal-oxide contact were confirmed.

Study on water–gas shift reaction performance using Pt-based catalysts at high temperatures

The water–gas shift reaction (WGSR) performance was experimentally studied using Pt-based catalysts for temperature, time factor and steam to carbon (S/C) molar ratio at ranges of 750–850 °C, 10–20 gcat h/molCO, and 1–5, respectively. Al2O3 spheres were used as the catalyst support. For the high S/C cases, it was found that CO conversion can be enhanced when Pt/CeO2/Al2O3 catalyst was used as compared with Pt/Al2O3. For the low S/C ratio cases, CO conversion enhancement was not significant with the addition of CeO2. It was also found that CO conversion was not influenced by the CeO2 amount to a large extent. Using bimetallic Pt–Ni/CeO2/Al2O3 catalyst, it was found that higher CO conversion can be obtained as compared with CO conversions obtained from monometallic catalysts (Pt/Al2O3 or Pt/CeO2/Al2O3). The experimental data also indicated that good thermal stability can be obtained for the Pt-based catalysts studied.

Application of one-body hybrid solid pellets to sorption-enhanced water gas shift reaction for high-purity hydrogen production

Interest in hydrogen, regarded as a new clean energy carrier, has been increasing with expectation of the approaching hydrogen economy. In the hydrogen economy, hydrogen will replace the conventional fuels that have caused pollution problems. As one of the methods for the mass production of hydrogen, water gas shift (WGS) reaction (CO + H2O ↔ H2 + CO2) has been highlighted for synthesis gas feed, which is produced by coal and biomass gasification. Recently, the performance of WGS reaction has been improved significantly through application of the sorption-enhanced WGS (SE-WGS) reaction concept, where WGS reaction and CO2 sorption are carried out simultaneously. High-purity hydrogen can be directly produced through the SE-WGS reaction, without need for further purification processes. In the SE-WGS reaction, uniform packing of the mixture of catalyst and sorbent is important; however, this is difficult to manage with conventional catalyst and sorbent pellets. In this study, novel one-body hybrid solid pellets consisting of the mixture of catalyst and sorbent were prepared to address this shortcoming and applied to SE-WGS reactions. From experiments, the effect of different ratio of catalyst/sorbent in one-body hybrid solid pellets was studied. A novel multi-section packing concept was also applied to SE-WGS reaction with one-body hybrid solid pellets. The experimental results showed that one-body hybrid solid pellets can be successfully used and that multi-section packing can increase the hydrogen productivity in SE-WGS reaction.

Pd-supporting LaCoO3 catalyst with structured configuration for water gas shift reaction

The purpose of this study was to develop a structured perovskite-type oxide catalyst for the water gas shift (WGS) reaction, which could make lattice oxygen mobile at a low external heat energy by preparing it as a thin catalyst layer on a metal plate. The thickness of the formed LaCoO3 layer was about 20μm, which was confirmed by FE-SEM and EDX analysis. For enhancing its WGS reaction performance, a palladium (Pd) component was supported on the structured catalyst using various Pd precursors. When using a PdCl2 aqueous solution which was prepared by filtration of the PdCl2 slurry (the filtration liquid), the Pd-supporting LaCoO3 structured catalyst showed a high and stable activity. The reason for such an enhanced activity was that the supported Pd was in a highly dispersed state, which was derived from the electrostatic interaction between [PdCl3(H2O)]− as the anionic charged precursor in the filtration liquid and the oppositely charged LaCoO3 support surface confirmed by a UV–vis measurement. In order to remove the remaining chloride ligand from the Pd-supporting LaCoO3 catalyst surface, a washing treatment was performed by immersing the as-made catalyst in water, NH3 (aq) or NaOH (aq) at pH 11.5 for 30min. Consequently, these washing processes were effective for eliminating the remaining chloride ion from the catalyst surface and improving the shift activity of the catalyst. The catalyst washed using NH3 (aq) showed the highest activity among these catalysts.

Thermodynamic analysis of hydrogen production from methane via autothermal reforming and partial oxidation followed by water gas shift reaction

Reaction characteristics of hydrogen production from a one-stage reaction and a two-stage reaction are studied and compared with each other in the present study, by means of thermodynamic analyses. In the one-stage reaction, the autothermal reforming (ATR) of methane is considered. In the two-stage reaction, it is featured by the partial oxidation of methane (POM) followed by a water gas shift reaction (WGSR) where the temperatures of POM and WGSR are individually controlled. The results indicate that the reaction temperature of ATR plays an important role in determining H 2 yield. Meanwhile, the conditions of higher steam/methane (S/C) ratio and lower oxygen/methane (O/C) ratio in association with a higher reaction temperature have a trend to increase H 2 yield. When O/C ≤ 0.125, the coking behavior may be exhibited. In regard to the two-stage reaction, it is found that the methane conversion is always high in POM, regardless of what the reaction temperature is. When the O/C ratio is smaller than 0.5, H 2 is generated from the partial oxidation and thermal decomposition of methane, causing solid carbon deposition. Following the performance of WGSR, it suggests that the H 2 yield of the two-stage reaction is significantly affected by the reaction temperature of WGSR. This reflects that the temperature of WGSR is the key factor in producing H 2. When methane, oxygen and steam are in the stoichiometric ratio (i.e. 1:0.5:1), the maximum H 2 yield from ATR is 2.25 which occurs at 800 °C. In contrast, the maximum H 2 yield of the two-stage reaction is 2.89 with the WGSR temperature of 200 °C. Accordingly, it reveals that the two-stage reaction is a recommended fuel processing method for hydrogen production because of its higher H 2 yield and flexible operation.

Experimental and simulation of both Pd and Pd/Ag for a water gas shift membrane reactor

The study of the water gas shift reaction performance in terms of complete conversions is presented. The behaviour of a membrane reactor (MR) consisting of a tubular microporous ceramic within a thin palladium membrane was compared with a membrane reactor using a palladium/silver membrane. Membranes were developed in order to obtain a metallic layer thick enough to avoid any defects of the metallic layer and ensure infinite hydrogen selectivity with respect to other gases. The lumen of both membrane reactors was filled with the catalyst. The experiments were carried out by using nitrogen as inert gas in the streep having a flow rate ranging between 1×10−4 and 4×10−4 mol s−1 in co-current and counter-current mode in the temperature range 331–350°C and in the feed molar flow range 3.05×10−5–7.1×10−5 mol s−1. Hydrogen was the only one gas passing through both membranes. A complete separation of hydrogen from the other gases of the reaction system was obtained. The water gas shift reaction conversion was close to 100% by using the Pd/Ag membrane. A mathematical model was developed to interpret the experimental data. It described the system under isothermal conditions and considered an axial differential mass balance in terms of partial pressure for each chemical species. The simulation study and the experimental results show a satisfactory agreement and both highlight the possibility to shift towards 100% the conversion of the considered reaction.