一种新γ相氧化铝负载的铁铝双金属催化剂用于反向水煤气转化反应(英文)

In reverse water gas shift (RWGS) reaction CO₂ is converted to CO which in turn can be used to produce beneficial chemicals such as methanol. In the present study, Mo/Al₂O₃, Fe/Al₂O₃ and Fe-Mo/Al₂O₃ catalysts were synthesised using impregnation method. The structures of catalysts were studied using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, inductively coupled plasma atomic emission spectrometer (ICP-AES), temperature programmed reduction (H₂-TPR), CO chemisorption, energy dispersive X-ray (EDX) and scanning electron microscopy (SEM) techniques. Kinetic properties of all catalysts were investigated in a batch reactor for RWGS reaction. The results indicated that Mo existence in structure of Fe-Mo/Al₂O₃ catalyst enhances its activity as compared to Fe/Al₂O₃. This enhancement is probably due to better Fe dispersion and smaller particle size of Fe species. Stability test of Fe-Mo/Al₂O₃ catalyst was carried out in a fixed bed reactor and a high CO yield for 60 h of time on stream was demonstrated. Fe₂(MoO₄)₃ phase was found in the structures of fresh and used catalysts. TPR results also indicate that Fe₂(MoO₄)₃ phase has low reducibility, therefore the Fe₂(MoO₄)₃ phase signifificantly inhibits the reduction of the remaining Fe oxides in the catalyst, resulted in high stability of Fe-Mo/Al₂O₃ catalyst. Overall, this study introduces Fe-Mo/Al₂O₃ as a novel catalyst with high CO yield, almost no by-products and fairly stable for RWGS reaction.     

高浓度CO变换制氢催化剂本征动力学

采用石英玻璃管式反应器,考察B112型高温变换催化剂在高浓度CO(体积分率高于75%)氛围下的本征动力学特性,拟合实验数据并建立动力学模型,对幂函数动力学模型进行检验。结果表明:与传统铁系高温变换催化剂相比,该高温变换催化剂上变换反应活化能较低,其低温活性较好;该催化剂上CO对反应速率的影响偏小,是由反应组分中较高浓度的CO所导致;H_2O对反应速率的影响相对较大;CO_2对变换反应速率的抑制作用很大,因此为提高变换反应速率,应当减小CO_2的不利影响;H_2组分对反应速率的影响很小,实际应用中可以忽略。     

Low-Temperature Water Gas Shift Reaction on Combustion Synthesized Ce1−x Pt x O2−δ Catalyst

Catalytic activity of Pt²⁺ ion substituted CeO₂ synthesized by solution combustion method was tested for low-temperature water gas shift reaction in H₂ rich steam reformate. XPS studies show that Pt is dispersed as ions and there is no change in Pt oxidation state after the reaction. CO conversion is found to be maximum at 200 °C over Ce_1?x Pt _x O_2?δ catalysts without any methanation. The values of rate are 1.86 and 4.66 μmol/g/s at 125 and 150°C respectively with a dry gas flow rate of 6 Lh^?1 over 2% Pt/CeO₂.     

Significant Improvement in Activity and Stability of Pt/TiO2 Catalyst for Water Gas Shift Reaction Via Controlling the Amount of Na Addition

Na promoted Pt/TiO₂ catalysts have been studied under high severity, near equilibrium, conditions for use as a single stage WGS catalyst. Addition of 3 wt% Na to a 1 wt% Pt/TiO₂ catalyst has been found to improve water gas shift activity significantly compared to Pt/TiO₂, Pt/CeO₂, and Pt–Re/TiO₂ catalysts. This catalyst is stable when the reaction temperature is higher than 250 °C. Deactivation occurred when the reaction temperature was lower than 250 °C, however, returning the temperature to higher than 250 °C fully recovered activity. TEM observations revealed that addition of Na inhibited Pt particle sintering. These results suggest that Na promoted Pt/TiO₂ is a promising single stage water gas shift catalyst for small scale hydrogen production.     

Co－Mo－K／Al_2O_3系耐硫变换催化剂硫化过程的研究

以工厂实用的加有ＣＳ２的半水煤气为硫化气源，采用ＴＧ、ＤＴＡ、ＳＥＭ、ＥＤＳ、ＸＲＤ等表征技术，对Ｃｏ－Ｍｏ－Ｋ／Ａｌ２Ｏ３系耐硫变换催化剂的各个组份及其组合试样进行了恒温硫化及程序升温硫化实验研究。全面考察了温度对硫化过程的影响．比较了不同活性组份的硫化行为，探讨了各组份在硫化过程中的作用。     

Kinetics and Mechanism of the Water–Gas Shift Reaction Over Platinum Supported Catalysts

A dual-site reaction mechanism is proposed for Pt based water–gas shift catalysts. The sorption equilibrium parameters are evaluated in detail to validate their physical significance. The values of the van ‘t Hoff parameters for CO and H₂ correspond to those for chemisorption on platinum. The sorption parameters of H₂O and CO₂ on the supports have been quantitatively determined from temperature-programmed desorption experiments and have been compared to the values obtained from the kinetic study. Finally the proposed model is able to explain the different activities between the two catalysts.     

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.     

逆水煤气变换催化剂的制备及反应性能

为解决逆水煤气变换反应环境下催化剂抗还原性和稳定性较差的问题,采用浸渍法和共沉淀法制备了Mn基催化剂,对逆水煤气变换反应进行了热力学分析和催化剂初步筛选,初步考察了不同反应温度、反应压力、氢碳体积比和气体空速下的催化活性和反应选择性,并进行了催化剂稳定性评价和物化表征。结果表明,与浸渍法相比,共沉淀法制备的催化剂性能较好。适宜的逆水煤气变换反应条件为550~600℃,常压~0.5 MPa,氢碳体积比1~1.5,空速10 000~15 000 h-1。在入口温度580℃,压力0.5 MPa,氢碳体积比1.5和气体空速6 000 h-1的条件下,CO2转化率达45%,CO选择性为90%。催化剂500 h稳定性良好,这主要是由于形成了稳定的Mn基尖晶石活性相。     

Microemulsion Prepared Pt in Ceria: Catalytically Active for Water Gas Shift Reaction but Totally Inert for Methanation

A core–shell Pt in ceria type of catalyst prepared by a microemulsion technique shows high activity for both water gas shift and reverse water gas shift reactions but it does not catalyze methanation from carbon oxides and hydrogen feeds at all, whereas Pt-ceria catalysts prepared by traditional methods are effective for all these reactions under comparable reaction conditions. This clearly reveals the fact that the nature of active sites for shift reactions is different from those of methanation reactions, where a special metal-support interface in catalysts created by microemulsion offers the differentiation.     

Synthesis of Highly Active Nano-Sized Pt/CeO<Subscript>2</Subscript> Catalyst via a Cerium Hydroxy Carbonate Precursor for Water Gas Shift Reaction

Abstract  

A novel precipitation/digestion route has been developed to synthesize crystalline cerium hydroxy carbonate (CHC: Ce(OH)CO₃) by using an equimolar quantity of cerium nitrate (Ce(NO₃)₃·6H₂O) and mixed precipitants (KOH + K₂CO₃) at room temperature. Nano-sized CeO₂ supports could be prepared by the pre-calcination of CHC at 400 °C for 4 h. A highly active water gas shift (WGS) catalyst, 1 wt.% Pt/CeO₂ catalyst showed almost equilibrium CO conversion with 100% CO₂ selectivity at 320 °C even at the gas hourly space velocity (GHSV) of 45,625 h⁻¹.     

Pt/Pd催化燃烧催化剂处理含苯系物废气技术研究

采用Pt/Pd催化燃烧催化剂对含苯系物的有机废气进行了处理.通过对单组分和多组分关键污染物模拟废气的催化燃烧考察实验表明,Pt/Pd催化剂对含苯系物有机废气中各关键污染组分具有较强的脱除效果.在反应器人口温度250℃,空速20 000 h-1的条件下,污染物去除率达到97％以上.净化后气体符合国家排放标准.     

Catalysis at Metal/Oxide Interfaces: Density Functional Theory and Microkinetic Modeling of Water Gas Shift at Pt/MgO Boundaries

Topics in Catalysis - The impact of metal/oxide interfaces on the catalytic properties of oxide-supported metal nanoparticles is a topic of longstanding interest in the field of heterogeneous...     

低水气比耐硫变换工艺及催化剂在HT-L煤气化制甲醇装置中的应用

介绍了低水气比耐硫变换工艺在首套HT-L煤气化制甲醇装置中的应用情况,以及在运行过程中出现的问题和解决的方法。生产实践证明,低水气比耐硫变换工艺和QDB-05/QDB-04变换催化剂,完全能适应HT-L煤气化生产甲醇的需求,其应用前景广阔。     

Study on the Mechanism of CO Formation in Reverse Water Gas Shift Reaction Over Cu/SiO2 Catalyst by Pulse Reaction, TPD and TPR

The mechanism of reverse water gas shift reaction over Cu catalyst was studied by pulse reaction with QMS monitoring, temperature programmed desorption (TPD) and temperature programmed reduction (TPR) of Cu/SiO₂ catalyst. The reduced and/or oxidized copper offered low catalytic activity for the dissociation of CO₂ to CO in the pulse reaction study with 1 ml volume of He/CO₂, but the rate of CO formation was significantly enhanced with H₂ participating in the reaction. The TPD spectra of CO₂ obtained by feeding H₂/CO₂ over copper at 773 K provided strong evidence of the formation of formate at high temperature. The formate derived from the association of H₂ and CO₂ is proposed to be the key intermediate for CO production. The formate dissociation mechanism is the major reaction route for CO production.     

Direct Hydrogenolysis of Highly Concentrated Glycerol Solutions Over Supported Ru,Pd and Pt Catalyst Systems

Abstract  

The evaluation of supported precious metal catalysts, in combination with and without solid acids, for the hydrogenolysis of highly concentrated glycerol solutions, with the aim to produce lower alcohols, in particular 1-propanol was studied. GCMS analysis of the product mixtures obtained has shed some light on the possible mechanism leading to unwanted condensation products, as well as the composition of these compounds.