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Journal of Natural Gas Chemistry 2006年第1期15卷 45-51页

作者： Feifei Sun Shunhe Zhong Department of Chemistry School of Science Tianjin University Tianjin 300072 China College of Chemical Engineering and Technology Tianjin University Tianjin 300072 China

The supported Au/TiO2 and Au/TiO2-SiO2 catalysts were prepared by deposition precipitation method. The TPD study reveals that propylene oxide competes with propylene to be adsorbed on the same adsorptive center-Ti^n＋ site on the surface of the catalyst and that the adisorbing capacity of the catalyst for propylene oxide is larger than that for propylene. Catalytic behavior for propylene epoxidation with H2 and O2 was tested in a micro-reactor. Under typical conditions, the selectivity for propylene oxide is over 87%. The TG curves show that PO successive oxidation cause carbon deposition on the active center and deactivation of the Au catalysts. Because the amounts of Tin＋ site decrease significantly, and consequently the separation between Ti^n＋ sites increases, the Au/TiO2-SiO2 catalyst is more stable than Au/TiO2.

关键词： Au/TiO2 Au/TiO2-SiO2 propylene propylene oxide epoxidation catalyst stability

Utilizing bimetallic catalysts to mitigate coke formation in dry reforming of methane

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Journal of Energy Chemistry 2022年第5期31卷 124-142页

作者： Jaylin Sasson Bitters Tina He Elizabeth Nestler Sanjaya D.Senanayake Jingguang G.Chen Cheng Zhang College of Liberal Arts and Sciences Long Island University(Post)BrookvilleNY 11548United States Department of Molecular Biosciences University of Texas at AustinAustinTX 78712United States Chemistry Division Brookhaven National LaboratoryUptonNY 11973United States Department of Chemical Engineering Columbia UniversityNew YorkNY 10027United States

Dry reforming of methane(DRM) involves the conversion of carbon dioxide(CO_(2)) and methane(CH_(4)) into syngas(a mixture of hydrogen, H_(2), and carbon monoxide, CO), which can then be used to produce a wide range of products by means of Fischer–Tropsch synthesis. DRM has gained much attention as a means of mitigating damage from anthropogenic greenhouse gas(GHGs) emissions to the environment and instead utilizing these gases as precursors for value-added chemicals or to synthesize sustainable fuels and chemicals. Carbon deposition or coke formation, a primary cause of catalyst deactivation, has proven to be a major challenge in the development of DRM catalysts. The use of nickel-and cobalt-based catalysts has been extensively explored for DRM for their high activity and low cost but suffer from poor stability due to coke formation that has hindered their commercialization. Numerous articles have reviewed the various aspects of catalyst deactivation and strategies for mitigation, but few has focused on the benefit of bimetallic catalysts for mitigating coke formation. Bimetallic catalysts, often improve the catalytic stability over their monometallic counterparts due to synergistic effects resulting from two metal-tometal interactions. This review will cover DRM literature for various bimetallic catalyst systems, including the effect of supports and promoters, on the mitigation of carbonaceous deactivation.

关键词： Dry reforming of methane Carbon dioxide Bimetallic catalysts Coke formation catalyst stability

Hydrogen absorption/desorption cycling performance of Mg-based alloys with in-situ formed Mg_(2)Ni and LaH_(x)(x=2,3)nanocrystallines

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Journal of Magnesium and Alloys 2023年第4期11卷 1180-1192页

作者： Fenghai Guo Tiebang Zhang Limin Shi Lin Song State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China School of Materials and Chemical Engineering Xi’an Technological UniversityXi’an 710072China

Aiming to elucidate the hydrogen absorption/desorption cycling properties of Mg-based alloys with in-situ formed Mg_(2)Ni and LaH_(x)(x=2,3)nanocrystallines,the hydrogen storage cycle stability,hydriding/dehydriding cycling kinetics and thermodynamic stability of the experimental alloys have been investigated in detail.The results show that the Mg-Ni-La alloys exhibit improved hydrogen storage cycling properties and can remain storage hydrogen above 5.5 wt%after 200 cycles.With the increase of cycling numbers,the dehydrogenation rates of the experimental samples increase firstly and then gradually decrease,and eventually maintain relative stable state.Microstructure observation reveals that powders sintering and hydrogen decrepitation both exist during hydrogen absorption/desorption cycles due to repeated volume expansion and contraction.Meanwhile,the in-situ formed LaH_(x)(x=2,3)and Mg_(2)Ni nanocrystallines stabilize the microstructures of the particles and hinder the powders sintering.After 200 cycles,the average particle size of the experimental samples decreases and the specific surface area apparently increases,which leads to the decomposition temperatures of MgH_(2)and Mg_(2)NiH_(4)slightly shift to lower temperatures.Moreover,Mg_(2)Ni and LaH_(x)(x=2,3)have been proven to be stable catalysts during long-term cycling,which can still uniformly distribute within the powders after 200 cycles.

关键词： Mg-based hydrogen storage alloys Cycle stability Microstructure evolution catalyst stability Thermodynamics

Experimental investigation of fluidized-bed reactor performance for oxidative coupling of methane

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Journal of Natural Gas Chemistry 2012年第5期21卷 534-543页

作者： S.Jašo S.Sadjadi H.R.Godini U.Simon S.Arndt O.Görke A.Berthold H.Arellano-Garcia H.Schubert R.Schomäcker G.Wozny Chair of Process Dynamics and Operation Berlin Institute of TechnologyStraβe des 17 Juni 135Sekr.KWT910623 BerlinGermany Institute for Material Science and Technologies Berlin Institute of TechnologyHardenbergstr.4010623 BerlinGermany Institute for Technical Chemistry Berlin Institute of TechnologyStraβe des 17 Juni 12410623 BerlinGermany

Performance of the oxidative coupling of methane in fluidized-bed reactor was experimentally investigated using Mn-Na2WO4/SiO2,La2O3/CaO and La2O3-SrO/CaO catalysts.These catalysts were found to be stable,especially Mn-Na2WO4/SiO2 catalyst.The effect of sodium content of this catalyst was analyzed and the challenge of catalyst agglomeration was addressed using proper catalyst composition of 2%Mn2.2%Na2WO4/SiO2.For other two catalysts,the effect of Lanthanum-Strontium content was analyzed and 10%La2O 3-20%SrO/CaO catalyst was found to provide higher ethylene yield than La2O3/CaO catalyst.Furthermore,the effect of operating parameters such as temperature and methane to oxygen ratio were also reviewed.The highest ethylene and ethane （C2） yield was achieved with the lowest methane to oxygen ratio around 2.40.5% selectivity to ethylene and ethane and 41% methane conversion were achieved over La2O3-SrO/CaO catalyst while over Mn-Na2WO4 /SiO2 catalyst,40% and 48% were recorded,respectively.Moreover,the consecutive effects of nitrogen dilution,ethylene to ethane production ratio and other performance indicators on the down-stream process units were qualitatively discussed and Mn-Na2WO4/SiO2 catalyst showed a better performance in the reactor and process scale analysis.

关键词： oxidative coupling of methane （OCM） fluidized-bed reactor catalyst stability

Improved Performance of W/HZSM-5 catalysts for Dehydroaromatization of Methane

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Journal of Natural Gas Chemistry 2004年第3期13卷 148-159页

作者： Nor Aishah Saidina Amin Kusmiyati Department of Chemical Engineering Faculty of Chemical and Natural Resources EngineeringUniversiti Teknologi Malaysia 81310 UTM Skudai Johor Malaysia.Department of Chemical Engineering Faculty of Chemical and Natural Resources EngineeringUniversiti Teknologi Malaysia 81310 UTM Skudai Johor Malaysia.

The dehydroaramatization of methane over W-supported ZSM-5 with varying degrees of Li+ ion-exchanged catalysts was studied with and without oxygen at 1073 K and atmospheric pressure. catalyst activity and stability were found to be influenced by the catalyst acidity related to Bronsted acid sites and by the presence of oxygen in the feed. The NH3-TPD and FTIR-pyridine results demonstrated that partially exchanged of H+ ions by Li+ into the W/HZSM-5 catalysts could be used to control the amount of strong acid sites on the catalyst surface. Without oxygen, the 3WHLi-Z (5:1) catalyst that has strong acid sites equal to nearly 74% of the original strong acid sites in the parent HZSM-5 exhibited the highest methane conversion and selectivity towards aromatics. However, the catalyst deactivated in a five hour period. In the presence of oxygen, the catalyst activity and stability could be improved further. The results of this study revealed that a suitable amount of strong Bronsted acid sites as well as oxygen addition in the feed increased the catalyst activity and stability. The 3WHLi-Z(5:1) catalyst exhibited improved performance in the dehydroaromatization of methane.

关键词： dehydroaromatization methane W-supported ZSM-5 partial ion exchange H+ ion Li ion catalyst activity catalyst stability catalyst acidity oxygen presence improved performance