Promoted Fe2O3‐Al2O3‐CuO Chromium‐Free Catalysts for High‐Temperature Water‐Gas Shift Reaction

Promoted Fe₂O₃‐Al₂O₃‐CuO (FAC) chromium‐free catalysts were prepared for high‐temperature water‐gas shift reactions and characterized by X‐ray diffraction (XRD), Brunauer‐Emmett‐Teller method (BET), temperature‐programmed reduction (TPR), and transmission electron microscopy (TEM) techniques. The catalytic results revealed that among the investigated promoted catalysts with Ce, La, Zn, Y, and Mn as promoters, the Mn‐promoted sample showed higher activity compared to the other promoted catalysts. Increasing the Mn content improved the surface area and catalytic activity. The FAC catalyst promoted with a high Mn content exhibited maximum activity and relatively high stability in high‐temperature water‐gas shift reaction.     

Effect of Catalyst Supports on Water‐Gas Shift Reaction at Ultrahigh Temperatures Using Syngas

Monometallic and bimetallic catalysts (Pt, Ni, and Pt‐Ni) with single support (Al₂O₃, TiO₂) and composite support (CeO₂/Al₂O₃, CeO₂/TiO₂) were prepared and tested for water‐gas shift reaction in a tubular quartz reactor. Syngas and steam with different steam‐to‐carbon ratios served as feedstock. The operating pressure was fixed while the reaction temperature was varied. The measured results indicated that the monometallic Ni/Al₂O₃ catalyst exhibits the lowest CO conversion and H₂ yield as compared with other catalysts. About the same CO conversion can be obtained from Pt and Pt‐Ni catalysts with single or composite support. However, higher H₂ yield can be achieved from the TiO₂‐supported catalyst compared with those supported by Al₂O₃. The experimental data also indicated that good thermal stability can be reached for the Pt‐based catalysts studied.     

Comparison of Preparation Methods of Iron‐Based Catalysts for High‐Temperature Water‐Gas Shift Reaction

The influence of preparation methods on structural and catalytic properties of the Fe₂O₃‐Cr₂O₃‐CuO catalyst during the high‐temperature water‐gas shift reaction was determined. The prepared samples were characterized by X‐ray diffraction (XRD), Brunauer‐Emmett‐Teller method (BET), and temperature‐programmed reduction (TPR). The results revealed that the type of coprecipitation, i.e., simple, inverse, and differential, had a significant effect on both structural and catalytic properties. The catalyst prepared by the simple precipitation method exhibited higher activity than the catalysts generated by inverse and differential coprecipitation and the commercial catalyst. The types of precipitation agent and iron and chromium precursors were found to have a significant impact on the structural and catalytic features.     

Comparison of CuO/Ce0.8Zr0.2O2 and CuO/CeO2 Catalysts for Low-temperature CO Oxidation

CuO/Ce_0.8Zr_0.2O₂ and CuO/CeO₂ catalysts were prepared via a impregnation method characterized by using FT-Raman, XRD, XPS and H₂-TPR technologies. The catalytic activity of the samples for low-temperature CO oxidation was investigated by means of a microreactor-GC system. The influence of the calcination temperature and different supports on the catalytic activity was studied.     

氧化铈和铈锆固溶体对Pd催化剂抗硫性能影响的研究

采用等体积浸渍法制备了质量分数为1%Pd/γ－Al₂O₃、1%Pd/10%CeO₂/γ-Al₂O₃以及1% Pd/10%Ce_0.6Zr_0.4O₂ /γ－Al₂O₃催化剂,研究了CeO₂和Ce_0.6Zr_0.4O₂ 固溶体对Pd催化剂抗硫性能的影响。利用XRD和XPS技术表征了催化剂的固相结构、表面元素组成和反应后催化剂中硫物种（或表面硫酸盐）的存在形态。利用SO₂-TPD研究了SO₂在催化剂上的吸附和脱附行为。实验结果表明,在催化剂载体中引入CeO₂和Ce_0.6Zr_0.4O₂ 降低了催化剂起燃活性;SO₂ 在Pd/Ce_0.6Zr_0.4O₂ /γ－Al₂O₃催化剂表面上发生化学反应生成Zr(SO₄)₂,其热稳定性大于在Pd/γ－Al₂O₃和Pd/CeO₂/γ－Al₂O₃催化剂表面上的硫酸盐或硫酸盐物种。     

Cu/Ni‐Loaded CeO2‐ZrO2 Catalyst for the Water‐Gas Shift Reaction: Effects of Loaded Metals and CeO2 Addition

Two different types of metals (Cu and Ni) and the effect of CeO₂ addition to produce a CeO₂‐ZrO₂ co‐supporter were investigated through the water‐gas shift (WGS) reaction. It was found that the WGS activity could be enhanced with CeO₂ addition. At relatively high temperature, Ni‐loaded catalysts exhibited higher CO conversion while Cu‐loaded catalysts demonstrated better performance at low temperatures. The stability and yield of the CO₂ and H₂ products of the Cu catalysts were higher than those of the Ni catalysts. These results may be caused by an irreversible adsorption of CO on Ni and the reverse WGS reaction occurring on the Ni catalysts. In situ diffuse‐reflection infrared Fourier transform spectroscopy data suggests that the WGS mechanism likely proceeded via formate species.     

The effect of nickel on propane oxidation and sulfur resistance of Pt/Ce0.4Zr0.6O2 catalyst

The effect of nickel on propane oxidation and sulfur resistance of Pt/Ce_0.4Zr_0.6O₂ catalyst has been studied. Samples were characterized by X-ray diffraction, BET area, H₂ temperature programmed reduction. It has been found that the introduction of nickel not only enhances the surface area of the catalyst, but also decreases its reduction temperature. The nickel promoted catalyst is more active in complete oxidation of C₃H₈. Furthermore, the addition of nickel to the catalyst is able to improve the desorption amount of sulfur species under reducing atmosphere, which could decrease the accumulation of sulfur species in the catalyst. Consequently, the sulfur resistance of Pt/Ce_0.4Zr_0.6O₂ catalyst has been improved.     

Syngas Production via Reverse Water‐Gas Shift Reaction over a Ni‐Al2O3 Catalyst: Catalyst Stability,Reaction Kinetics,and Modeling

The synthesis of liquid fuels from CO₂, e.g., separated from flue gases of power plants, and H₂ from renewables, i.e., water electrolysis, is a concept for substituting fossil fuels in the transport sector. It consists of two steps, syngas production via reverse water‐gas shift (RWGS) and synfuel production by Fischer‐Tropsch synthesis. Research is concentrated on the RWGS using a Ni‐catalyst. The catalyst shows an appropriate performance in catalyzing the RWGS. The catalyst is stable at technically relevant temperatures. The intrinsic and effective kinetics were determined and considerations on a technical application of the process are proposed.     

Activity Patterns for the ‘‘Water Gas Shift Reaction Over Supported Precious Metal Catalysts’’

Activity patterns for the high temperature water gas shift reaction over oxide catalysts promoted by precious metals show that the performance of iron oxide–chromia catalysts can be significantly improved by promotion with small amounts of rhodium. The results suggest that reactions of hydrogen at the promoter–catalyst interface are the rate controlling process.     

Effects of Pretreatments of Cu/ZnO-Based Catalysts on Their Activities for the Water–Gas Shift Reaction

The effects of the pretreatments of Cu/ZnO-based catalysts prepared by a coprecipitation method on their activities for the water–gas shift reaction at 523K were investigated. The activity of a Cu/ZnO/ZrO₂/Al₂O₃ catalyst for the water–gas shift reaction was less affected by calcination at temperatures ranging from 673-973K and by H₂ treatment at 573 or 723K than that of a Cu/ZnO/Al₂O₃ catalyst. The catalyst activity could be correlated mainly to the Cu surface area of the catalyst.     

Chemical Characterization and Catalytic Activity of Pd-Supported Catalysts on Ce0.39Zr0.61O x /SiO2

The catalytic activity of Pd-supported catalysts over Ce_0.39Zr_0.61O _x /SiO₂ was studied by using methane combustion reaction. UV–visible and TPR results showed the presence of large PdO particles. CO/Pd ratio decreased with the increase of metal load. The light-off temperatures indicated that high Pd loading favored the reaction. The reduction treatment decreased the activity suggesting loss of the active phase.     

Surface and bulk changes of a Pt 1%/Ce0.6Zr0.4O2 catalyst during CO oxidation in the absence of O2

Topics in Catalysis - The reduction of a Pt 1%/Ce0.6Zr0.4O2 catalyst by CO in the absence of gaseous oxygen was studied by transient reactivity tests, temperature programmed surface reaction with...     

Ag/Ce0.75Zr0.25O2催化剂中Ag的负载量对碳烟燃烧活性的影响

开发低温下高催化活性的柴油机碳烟颗粒燃烧催化剂是当前环境催化领域的热点问题。利用共沉淀的方法制备了用于碳烟催化燃烧反应的Ag/Ce_0.75Zr_0.25O₂催化剂。活性评价结果表明,相对于Ce_0.75Zr_0.25O₂催化剂,Ag的引入可显著降低碳烟催化燃烧温度。而且,Ag的负载量存在一个最佳值。以XRD、in-situ XRD、BET、TPR等表征手段探究了该系列催化剂结构性质及其变化产生的影响。结果表明,Ag与Ce物种间的相互作用可显著降低催化剂（特别是CeO₂表面氧）的还原温度。该相互作用使Ag/Ce_0.75Zr_0.25O₂催化剂在一定温度下（>200℃）就表现出Ag⁺的性质。这些性质与该催化剂具有较高的碳烟氧化活性相关。而且,该催化剂也表现出良好的稳定性。     

nx：ny对PdO／CexZryO2催化剂三效催化性能的影响

采用溶胶-凝胶法制备了一系列CexZryO2(x=0～1,y=1～x)复合氧化物,并以该复合氧化物为栽体制备负栽贵金属的PdO/CexZryO2催化剂,选择NO-CO反应和CO以及CH4氧化反应为模型反应对催化剂的三效催化性能进行评价,并通过XRD、H2-TPR等手段对栽体和催化剂进行初步表征.结果表明:nx:ny对CexZryO2栽体及负栽PdO催化剂三效催化性能均存在重要影响,不同nx:ny的CexZryO2复合氧化物栽体具有不同的晶相结构及还原性能,由其负载的PdO催化剂也各不相同.同时,催化剂的NO还原活性与CO氧化活性与α还原峰存在一定的对应关系.     

Dielectric Properties and Low‐Temperature Sintering of the Ba0.6Sr0.4TiO3 Ceramics with B2O3/CuO Additions

The sintering behaviors and dielectric properties of Ba_0.6Sr_0.4TiO₃ ceramics were investigated as a function of B₂O₃ and CuO content. The addition of both B₂O₃ and CuO reduced the sintering temperature of Ba_0.6Sr_0.4TiO₃ about 500°C. It was suggested that a liquid phase BaCu(B₂O₅) was formed and assisted the densification of Ba_0.6Sr_0.4TiO₃ ceramics. Ba_0.6Sr_0.4TiO₃ ceramics co‐doped with 3.0 mol% B₂O₃, and 2.0 mol% CuO, sintered at 950°C for 5 h, had a dense microstructure and showed good microwave dielectric properties of a moderate dielectric constant (ε = 1048), low dielectric loss (0.0090) and high tunability (42.2%) at dc electric field of 30 kV/cm.     

一种轻质高效焦炉气甲烷化催化剂的性能研究

考察了温度、压力、空速等条件对所制备的焦炉气甲烷化催化剂活性的影响,结果显示所制备的催化剂活性高,并具有良好的抗结炭性能,能满足焦炉气甲烷化反应过程的要求。     

Thermodynamic Simulation of CO2 Capture for an IGCC Power Plant using the Calcium Looping Cycle

A CO₂ capture process for an integrated gasification combined cycle (IGCC) power plant using the calcium looping cycle was proposed. The CO₂ capture process using natural and modified limestone was simulated and investigated with the software package Aspen Plus. It incorporated a fresh feed of sorbent to compensate for the decay in CO₂ capture activity during long‐term cycles. The sorbent flow ratios have significant effect on the CO₂ capture efficiency and net efficiency of the CO₂ capture system. The IGCC power plant, using the modified limestone, exhibits higher CO₂ capture efficiency than that using the natural limetone at the same sorbent flow ratios. The system net efficiency using the natural and modified limestones achieves 41.7 % and 43.1 %, respectively, at the CO₂ capture efficiency of 90 % without the effect of sulfation.     

Conversion of Carbon Monoxide‐Rich Synthesis Gas to Hydrocarbons and Alcohols over Cu/Co/ZnO/SiO2 Catalysts

Catalysts of the type Cu/Co/ZnO/SiO₂ were prepared by impregnation, subsequent calcination and reduction with hydrogen. Characterization of the catalysts was carried out by ICP‐AES, BET measurements and powder X‐ray diffraction analyses. Furthermore, temperature programmed reduction was employed to investigate their reduction behavior. The catalysts were tested in the conversion of synthesis gas to hydrocarbons and alcohols. High CO conversions could be reached in a single reactor pass. Selectivity was highest for methane, and short‐chain hydrocarbons, but alcohols were also formed.