Strong metal-support interactions between highly dispersed Cu^(+) species and ceria via mix-MOF pyrolysis toward promoted water-gas shift reaction

The modulation of metal-support interfacial interaction is significant but challenging in the design of high-efficiency and high-stability supported catalysts.Here,we report a synthetic strategy to upgrade Cu-CeO_(2)interfacial interaction by the pyrolysis of mixed metal-organic framework(MOF)structure.The obtained highly dispersed Cu/CeO_(2)-MOF catalyst via this strategy was used to catalyze water-gas shift reaction(WGSR),which exhibited high activity of 40.5μmolCOgcat^(-1).s^(-1)at 300℃and high stability of about 120 h.Based on comprehensive studies of electronic structure,pyrolysis strategy has significant effect on enhancing metal-support interaction and then stabilizing interfacial Cu^(+)species under reaction conditions.Abundant Cu^(+)species and generated oxygen vacancies over Cu/CeO_(2)-MOF catalyst played a key role in CO molecule activation and H2O molecule dissociation,respectively.Both collaborated closely and then promoted WGSR catalytic performance in comparison with traditio nal supported catalysts.This study shall offer a robust approach to harvest highly dispersed catalysts with finely-tuned metal-support interactions for stabilizing the most interfacial active metal species in diverse heterogeneous catalytic reactions.

Effect of precipitants on Ni-CeO_2 catalysts prepared by a co-precipitation method for the reverse water-gas shift reaction

A series of Ni-CeO2 catalysts were prepared by co-precipitation method with Na2CO3, NaOH, and mixed precipitant （Na2CO3：NaOH; 1：1 ratio） as precipitant, respectively. The effect of the precipitants on the catalytic performance, physical and chemical properties of Ni-CeO2 catalysts was investigated with the aid of X-ray diffraction （XRD）, Bmmaner-Emmett-Teller method （BET）, Fou- rier-transform infrared spectroscopy （FT-IR）, thermogravimetry （TG）, and H2-TPR characterizations. The Ni-CeO2 catalysts were exam- ined with respect to their catalytic performance for the reverse water-gas shift reaction, and their catalytic activities were ranked as： Ni-CeO2-CP （Na2CO3：NaOH=I：I）〉Ni-CeO2-CP（Na2CO3）〉Ni-CeO2-CP（NaOH）- Correlating to the characteristic results, it was found that the catalyst prepared by co-precipitation with mixed precipitant （Na2CO3：NaOH; 1：1 ratio） as precipitant hadthe most amount of oxygen vacancies accompanied with highly dispersed Ni particles, which made the corresponding Ni-CeO2-CP（Na2CO3：NaOH=I： 1） catalyst exhibit the highest catalytic activity. While the precipitant of Na2CO3 or NaOH resulted in less or no oxygen vacancies in Ni-CeO2 catalysts. As a result, Ni-CeO2-CP（Na2CO3） and Ni-CeO2-CP（NaOH） catalysts presented poor catalytic performance.

Influence of preparation method on performance of Ni-CeO_2 catalysts for reverse water-gas shift reaction

This study investigated 1 wt.% Ni-CeO2 catalysts that were prepared using co-precipitation, deposition-precipitation, and impregnation methods for the reverse water-gas shift （RWGS） reaction. Characterizations of the catalyst samples were conducted by Brumauer-Emmett-Teller （BET）, atomic absorption spectrophotometer （AAS）, X-ray diffraction （XRD）, transmission electron microscopy （TEM）, high-resolution transmission electron microscopy （HR-TEM） and temperature programmed reduction （TPR）. The results showed that the Ni-CeO2 catalyst prepared using the co-precipitation method exhibited the best catalytic performance. In the Ni-CeO2 catalyst prepared using co-precipitation method, a combination of highly dispersed NiO and abundant oxygen vacancies was assumed to play a crucial role in determining the catalytic activity and selectivity of the RWGS reaction.

Identifying the roles of Ce^(3+)-OH and Ce-H in the reverse water-gas shift reaction over highly active Ni-doped CeO_(2) catalyst

Nickel-CeO_(2)-based materials are commonly used for the thermal catalytic hydrogenation of CO_(2).However,high Ni loadings and low CO selectivity restrict their use in the reverse water–gas shift(RWGS)reaction.Herein,we demonstrate a highly active,robust,and low-Ni-doped(1.1 wt.%)CeO_(2) catalyst(1.0-Ni-CeO_(2)).The Ni-based-mass-specific CO formation rate reaches up to 1,542 mmol·gNi^(−1)·h^(−1) with 100%CO selectivity at 300°C for 100 h,among the best values reported in the literature.Density functional theory(DFT)and diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)results reveal that the enhanced catalytic activity is attributed to the abundant Ce–H species,while the high selectivity results from low CO affinity.More importantly,a new reaction mechanism is proposed,which involves the reduction of bicarbonate to generate formate intermediate and CO by the H−released from Ce–H species.The new findings in this work will benefit the design of economic,efficient,and robust catalysts for low-temperature RWGS reactions.

Reverse water gas shift reaction over Co-precipitated Ni-CeO_2 catalysts

The Ni-CeO2 catalysts with different Ni contents were prepared by a co-precipitation method and used for Reverse Water Gas Shift （RWGS） reaction. 2wt.%Ni-CeO2 showed excellent catalytic performance in terms of activity, selectivity, and stability for RWGS reaction. Characterizations of the catalyst samples were conducted by XRD and TPR. The results indicated that, in Ni-CeO2 catalysts, there were three kinds of nickel, nickel ions in ceria lattice, highly dispersed NiO and bulk NiO. Oxygen vacancies were formed in CeO2 lattice due to the incorporation of Ni^2＋ ions into ceria lattice. Oxygen vacancies formed in ceria lattice and highly dispersed Ni were key active components for RWGS, and bulk Ni was key active component for methanation of CO2.

Catalytic Reduction of CO2 to CO via Reverse Water Gas Shift Reaction:Recent Advances in the Design of Active and Selective Supported Metal Catalysts

The catalytic conversion of CO2 to CO via a reverse water gas shift(RWGS)reaction followed by well-established synthesis gas conversion technologies may provide a potential approach to convert CO2 to valuable chemicals and fuels.However,this reaction is mildly endothermic and competed by a strongly exothermic CO2 methanation reaction at low temperatures.Therefore,the improvement in the low-temperature activities and selectivity of the RWGS reaction is a key challenge for catalyst designs.We reviewed recent advances in the design strategies of supported metal catalysts for enhancing the activity of CO2 conversion and its selectivity to CO.These strategies include varying support,tuning metal–support interactions,adding reducible transition metal oxide promoters,forming bimetallic alloys,adding alkali metals,and enveloping metal particles.These advances suggest that enhancing CO2 adsorption and facilitating CO desorption are key factors to enhance CO2 conversion and CO selectivity.This short review may provide insights into future RWGS catalyst designs and optimization.

Copper Promoted Au/ZnO-CuO Catalysts for Low Temperature Water-gas Shift Reaction

Various copper promoted Au/ZnO-CuO catalysts with different atomic ratios of Cu to Zn prepared by means of co-precipitation were tested for the low temperature water-gas shift（WGS） reaction. The catalytic activity of the catalyst depends largely on the ratio of Cu to Zn. The addition of an appropriate amount of copper can considerably improve both the catalytic activity and the stability of the catalyst in comparison with those of copper-free Au/ZnO cata- lysts. The enhanced reducibility of copper oxide in the Au/ZnO-CuO ternary-component catalysts, which was confirmed by H2-TPR, may be related to the high activity and stability of the catalyst for the low temperature WGS reaction.

A Novel γ-Alumina Supported Fe-Mo Bimetallic Catalyst for Reverse Water Gas Shift Reaction

在反向的水气体，移动(RWGS ) 反应 CO2 被变换成能接着被用来生产象甲醇那样的有益的化学药品的公司。在现在的学习， Mo/Al2O3， Fe/Al2O3 和 Fe-Mo/Al2O3，催化剂是用受精方法的 synthesised。催化剂的结构用 X 光检查衍射(XRD ) 被学习， Brunauer-Emmett-Teller (赌注) 方法，诱导地联合的血浆原子排放分光计(ICP-AES ) ，温度规划了减小(H2-TPR ) ，公司化学吸着，精力散 X 光检查(EDX ) 和扫描电子显微镜学(SEM ) 技术。所有催化剂的运动性质为 RWGS 反应在一个批反应堆被调查。结果显示在 Fe-Mo/Al2O3 催化剂的结构的那瞬间存在作为与 Fe/Al2O3 相比提高它的活动。这改进可能由于更好的 Fe 分散和 Fe 种类的更小的粒子尺寸。Fe-Mo/Al2O3 催化剂的稳定性测试在一个固定的床反应堆和高公司收益被执行因为溪流上的时间的 60 h 被表明。3 阶段在新鲜、使用的催化剂的结构被发现的 Fe2 (MoO4 ) 。TPR 结果也显示 3 分阶段执行的 Fe2 (MoO4 ) 有低 reducibility，因此， 3 显著地分阶段执行的 Fe2 (MoO4 ) 在催化剂禁止留下的 Fe 氧化物的减小，导致了 Fe-Mo/Al2O3 的高稳定性催化剂。总的来说，这研究与高公司产量作为新奇催化剂介绍 Fe-Mo/Al2O3，几乎没有副产品并且为 RWGS 反应相当稳定。

Effects of the partial replacement of La by M(M=Ce,Ca and Sr) in La_(2-x)M_xCuO_4 perovskites on catalysis of the water-gas shift reaction

The performance of La2-x M x CuO4 perovskites （where M=Ce,Ca or Sr） as catalysts for the water-gas shift reaction was investigated at 290℃ and 360℃.The catalysts were characterized by EDS,XRD,N2 adsorption-desorption,XPS and XANES.The XRD results showed that all the perovskites exhibited a single phase （the presence of perovskite structure）,suggesting the incorporation of metals in the perovskite structure.The XPS and XANES results showed the presence of Cu2＋ on the surface.The perovskites that exhibited the best catalytic performance were La 2 x Ce x CuO 4 perovskites,with CO conversions of 85% 90%.Moreover,these perovskites have higher surface areas and larger amounts of Cu on the surface.And Ce has a higher filled energy level than the other metals,increasing the energy of the valence band of Ce and providing more electrons for the reaction.Besides,the La1.80Ca0.20CuO4 perovskite showed a good catalytic performance.

Selective synthesis of carbon monoxide via formates in reverse water–gas shift reaction over alumina-supported gold catalyst

Thermal decomposition of formic acid on SiO2, CeO2 and γ-Al2O3 was studied as an elementary step of reverse water–gas shit reaction（RWGS） over supported Au catalysts. γ-Al2O3 showed the highest CO selectivity among the tested oxides in the decomposition of formic acid. Infrared spectroscopy showed the formation of four formate species on γ-Al2O3： three η~1-type and one μ~2-type species, and these formates decomposed to CO at 473 K or higher. Au-loaded γ-Al2O3 samples were prepared by a depositionprecipitation method and used as catalysts for RWGS. The supported Au catalyst gave CO with high selectivity over 99% from CO2 and H2, which is attributed to the formation of formates on Au and subsequent decomposition to CO on γ-Al2O3.

Preparation and characterization of Cu-Ce-La mixed oxide as water-gas shift catalyst for fuel cells application

Cu-Ce-La mixed oxides were prepared by three precipitation methods （coprecipitation, homogeneous precipitation, and deposition precipitation） with variable precipitators and characterized using X-ray diffraction, BET, temperature-programmed reduction, and catalytic reaction for the water-gas shift. The Cu-Ce-La mixed oxide prepared by coprecipitation method with NaOH as precipitator presented the highest activity and thermal stability. Copper ion substituted quadrevalent ceria entered CeO2 （111） framework was in favor of activity and thermal stability of catalyst. The crystallinity of fresh catalysts increased with the reduction process. La^3＋ or Ce^4＋ substituted copper ion entered the CeO2 framework during reduction process. The coexistence of surface copper oxide （crystalline） and pure bulk crystalline copper oxide both contributed to the high activity and thermal stability of Cu-Ce-La mixes oxide catalyst.

Insight into the Role of Isolated Gold Atoms-Ceria Conjunction in Catalyzing the Water-Gas Shift Reaction

As the promising catalysts for the water-gas shift(WGS)reaction,the activity of Au-CeO_(2) composites is susceptible to the aggregation size and electronic state of Au species.Previous reports were extensively focused on the discrepancy between nonmetallic Au and metallic Au nanoparticles,whereas the understanding of the authentic role of the isolated Au atoms was limited.Herein,we investigated the catalytic behavior and structural information over two types of Au/CeO_(2) catalysts,in which the predominant conjunctions were isolated Au1-CeO_(2) and Aun-CeO_(2),respectively.Based on comprehensive characterizations,particularly by in-situ Raman and in-situ DRIFTS,we found that the isolated Au atoms were responsible for enhancing the reducibility of the CeO_(2) matrix.The CO adsorption ability on the isolated Au sites was significantly inferior to clustered Au atoms,especially at relatively high temperatures(>200°C).As a result,the boosted O vacancy on the isolated Au1-CeO_(2) conjunctions could improve the H2O activation ability for the Au-CeO_(2) catalysts and demonstrate a comparable activity to the clustered Aun-CeO_(2) sites.This work might deepen understanding of the catalytic function for the isolated Au1 site within Au/CeO_(2) systems while catalyzing the WGS reaction.

铝源对Cu-Al尖晶石物化性质和逆水煤气变换性能的影响

基于高能球磨和固相焙烧的方法,采用杂质元素(Na、Fe、Si和S)含量不等的四种拟薄水铝石和氢氧化铜制备了Cu-Al尖晶石固溶体催化剂,通过ICP-AES、TG、XRD、H2-TPR和BET表征了催化剂的物化性质,并考察了对逆水煤气变换反应的催化性能。结果表明,拟薄水铝石中的杂质元素对于Cu-Al尖晶石催化剂的物相性质、还原性能、织构性质和催化性能有显著的影响,Si有助于合成高比表面积的催化剂,但不利于Cu-Al尖晶石生成,导致催化活性低;含有少量Na和Fe的尖晶石的催化活性较低;S物种经高温焙烧后分解,对催化活性没有影响;基于杂质元素含量最低的拟薄水铝石合成的催化剂中难还原尖晶石含量最高,表现出最高的逆水煤气变换催化活性。此外,基于活性最优样品的CO_(2)-TPDMS和In-situ DRIFTS分析表明,Al上形成的双齿甲酸盐是Cu-Al尖晶石固溶体催化CO_(2)加氢生成CO的主要中间产物,其含量与催化活性随反应时间的变化规律一致。

二氧化碳捕集-加氢转化一体化技术研究进展与展望

开发与应用CO_(2)捕集-加氢转化一体化技术是应对当前全球气候变化危机、实现“双碳”目标的重要途径之一。其中具有吸附和催化组分的双功能材料研发与优化是技术核心。系统总结了国内外主要科研机构对应用于CO_(2)捕集原位甲烷化和原位逆水煤气变换这2类主要CO_(2)捕集-加氢转化一体化技术双功能材料的主要工作,包括合成方法、吸附性能、反应动力学、促进机理、失活机理和应用模式等方面,并详细介绍了国内外主要科研机构在CO_(2)捕集-加氢转化一体化方面取得的最新进展。DFM是兼具催化和吸附组分的复合材料,在催化组分选择上,贵金属催化剂虽然活性高,但成本昂贵,Ni基催化剂成本较低,但还原性较差、在含氧气氛下易失活;在吸附组分选择上,金属氧化物(如CaO、MgO)和碱金属碳酸盐(如Na 2 CO 3、K 2 CO 3)是具有潜力的吸附组分,特别是MgO和CaO因其理论吸附量高而被视为最有前景的吸附组分,尽管面临实际吸附量不理想和循环稳定性差的挑战。目前研究主要通过碱金属熔盐掺杂提升MgO实际吸附量,通过掺杂金属助剂(如La、Co、Fe等)提高CaO吸附剂的循环性能和抗烧结能力。动力学研究表明反应速率高度依赖于H 2分压,通过调节吸附和催化的时间可提高CH 4平均产量。ICCU技术展现出广阔的应用前景,尤其是在钢铁、能源、化工等关键领域。然而,全面评估技术的环境影响,特别是从生命周期评估(LCA)角度,对于全面理解ICCU技术的环境可持续性及其在碳减排中的贡献至关重要。未来,通过持续研究和技术创新,解决现有挑战,ICCU技术有望在工业化应用中取得显著成果,为全球碳减排做出重要贡献。

逆水汽变换反应铜基催化剂研究进展

逆水汽变换(RWGS)反应是将CO_(2)转化为化学品或碳氢化合物的关键步骤,在CO_(2)资源化利用中发挥着重要作用。综述逆水汽变换反应的热力学分析、反应机理,以及近十年来国内外逆水汽变换反应催化剂的研究进展。总结发现,Cu基催化剂具有低成本、高活性和高CO选择性优势。但在反应中易积炭失活,且在高温条件下容易烧结团聚导致稳定性下降。目前,研究者对Cu基催化剂的研究主要集中在Cu活性中心调控和优化反应操作条件两个方面。Cu活性中心调控主要包括:①调控Cu位点的结构特性,如分散度、粒径大小等;②助剂的添加,包括碱金属助剂(Na、K)、过渡金属助剂(Fe、Ce、Co)等;③引入适宜载体,如Al_(2)O_(3)、Mo_(2)C、CeO_(2)等以增强金属-载体的相互作用。操作工艺条件优化主要通过改变反应温度、空速、调节H_(2)/CO_(2)物质的量比增强RWGS反应中CO选择性和CO_(2)转化率。最后指出基于RWGS反应将CO_(2)与其它产氢反应进行耦合,如低碳烷烃脱氢、甲醇芳构化等,可达到目标产物收率提升与CO_(2)减排目的。

Effect of doping rare earth oxide on performance of copper-manganese catalysts for water-gas shift reaction

Rare earth-doped copper-manganese mixed oxide catalysts were prepared by coprecipitation and mechanical mixing using copper sulfate, manganese sulfate, and rare-earth oxides REO （REO indicates La2O3, CeO2, Y2O3, or Pr6O11） as raw materials. The samples were characterized by X-ray diffraction （XRD）, temperature-programmed reduction （TPR）, temperature-programmed reduc-tion of oxidized surfaces （s-TPR）, and temperature-programmed desorption （TPD）. Catalytic activities were tested for a water-gas shift reaction. Doping rare earth oxides did not alter the crystal structure of the original copper-manganese mixed oxides but changed the interplanar spacing, adsorption performance and reaction performance. Doping with La2O3 enhanced the activity and stability of Cu-Mn mixed oxides because of high copper distribution and fine reduction. Doping with CeO2 and Y2O3 also decreased the reduc-tion temperatures of the samples to different degrees while improving the dispersion of Cu on the surface, thus, catalytic activity was better than that of undoped Cu-Mn sample. The Pr6O11-doped sample was difficult to reduce, the dispersion of surface coppers was lowered, resulting in poor activity.

Theoretical and Experimental Study on Reaction Coupling: Dehydrogenation of Ethylbenzene in the Presence of Carbon Dioxide

Dehydrogenation of ethylbenzene （EB） to styrene （ST） in the presence of CO2, in which EB dehydrogenation is coupled with the reverse water-gas shift （RWGS）, was investigated extensively through both theoretical analysis and experimental characterization. The reaction coupling proved to be superior to the single dehydrogenation in several respects. Thermodynamic analysis suggests that equilibrium conversion of EB can be improved greatly by reaction coupling due to the simultaneous elimination of the hydrogen produced from dehydrogenation. Catalytic tests proved that iron and vanadium supported on activated carbon or Al2O3 with certain promoters are potential catalysts for this coupling process. The catalysts of iron and vanadium are different in the reaction mechanism, although ST yield is always associated with CO2 conversion over various catalysts. The two-step pathway plays an important role in the coupling process over Fe/Al2O3, while the one-step pathway dominates the reaction over V/Al2O3. Coke deposition and deep reduction of active components are the major causes of catalyst deactivation. CO2 can alleviate the catalyst deactivation effectively through preserving the active species at high valence in the coupling process, though it can not suppress the coke deposition.

Atomic-layered Au clusters on α-MoC as catalysts for the low-temperature water-gas shift reaction

Subject Code:B03With the support by the National Natural Science Foundation of China,a collaborative study by the research groups led by Prof.Ma Ding(马丁)from Peking University,Senior Scientist JoséA.Rodriguez from Brookhaven National Laboratory and Prof.Shi Chuan(石川)from Dalian University of

Atomically dispersed copper species on ceria for the low-temperature water-gas shift reaction

The structure of copper species,dispersed on nanostructured ceria(particles,rods and cubes),was analyzed by scanning transmission electron microscopy(STEM)and X-ray photoelectron spectroscopy(XPS).It was interestingly found that the density of surface oxygen vacancies(or defect sites),induced by the shape of ceria,determined the geometrical structure and the chemical state of copper species.Atomically dispersed species and monolayers containing few to tens of atoms were formed on ceria particles and rods owing to the enriched anchoring sites,but copper clusters/particles co-existed,together with the highly dispersed atoms and monolayers,on cubic ceria.The atomically dispersed copper sites and monolayers interacted strongly with ceria,involving a remarkable charge transfer from copper to ceria at their interfaces.The activity for the low-temperature watergas shift reaction of the Cu/CeO_(2) catalysts was associated with the fraction of the positively-charged copper atoms,demonstrating that the active sites could be tuned by dispersing Cu species on shape-controlled ceria particles.

NiCe bimetallic nanoparticles embedded in hexagonal mesoporous silica (HMS) for reverse water gas shift reaction

Reverse water gas shift(RWGS)reaction is a crucial process in CO_(2)utilization.Herein,Ni-and NiCe-containing hexagonal mesoporous silica(Ni-HMS and NiCe-HMS)catalysts were synthesized using an insitu one-pot method and applied for RWGS reaction.At certain reaction temperatures 500-750℃,Ni-HMS samples displayed a higher selectivity to the preferable CO than that of conventionally impregnated Ni/HMS catalyst.This could be originated from the smaller NiO nanoparticles over Ni-HMS catalyst.NiCe-HMS exhibited higher activity compared to Ni-HMS.The catalysts were characterized by means of TEM,XPS,XRD,H_(2)-TPR,CO_(2)-TPD,EPR and N_(2) adsorption-desortion technology.It was found that introduction of Ce created high concentration of oxygen vacancies,served as the active site for activating CO_(2).Also,this work analyzed the effect of the H_(2)/CO_(2)molar ratio on the best NiCe-HMS.When reaction gas H_(2)/CO_(2)molar ratio was 4 significantly decreased the selectivity to CO at low temperature,but triggered a higher CO_(2)conversion which is close to the equilibrium.