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1.
Novel Ag/SiO2–Al2O3 catalysts with low silver content prepared by the sol–gel method exhibit excellent catalytic properties in the catalytic
oxidation of methanol to formaldehyde. The silver content was as low as 2% and the yield of formaldehyde was achieved as 90.3%,
which is 16% higher than that of pumice‐supported silver and even 5–6% higher than that of a commercial electrolytic silver
catalyst. XRD, XPS and SEM results reveal that all silver was present as Ag+ before catalytic reaction and was partially reduced to the metallic state after the reaction. It was also found that silver
was aggregated on the surface after its reduction.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
《Ceramics International》2023,49(16):26910-26919
Ce–P/γ-Al2O3 coatings applied with the freeze-drying technique were deposited on foam ceramics before being further prepared as Pd catalysts. According to the research, phosphoric acid replaced the hydroxyl on the surface of γ-Al2O3 to produce polyhydroxy P-containing sites that readily attracted cerium oxide. The palladium oxide was then embedded into the cerium oxide vacancy. The impacts of the drying technique on the catalysts were investigated, and the results indicated that freeze drying created a special coating with a large specific surface area and uniform mesoporous structure by inhibiting nanoparticle agglomeration. H3PO4's altering action was augmented to boost the number of active sites and the percentage of weakly acidic sites. Due to better P–Ce interactions, more Ce3+ was added into CeO2, which created numerous oxygen vacancies. By adjusting the P-containing sites, the dispersion of cerium oxide and the active phase could be controlled, which aided the activation and spillover of hydrogen. Furthermore, the capacity for oxygen adsorption and desorption was enhanced, and the amount of adsorbed oxygen species increased. As a result, the freeze-drying technique improved the advantages of the Ce–P/γ-Al2O3 coating, increasing the conversion and selectivity of CO2 methanation to 81% and 94%, respectively, and lowering the complete conversion temperature of CO oxidation to 116 °C. This research has a guiding influence on the development of foam ceramic-loaded palladium catalysts in the fields of energy and the environment. 相似文献
3.
钠基固体吸收剂脱除燃煤烟气CO2技术具有反应温度低、能耗低等优点,日益受到学术界的关注。该技术的主要不足是吸收剂的活性成分碳酸钠与CO2的反应(碳酸化反应)活性较低。针对这一问题,本文旨在研制一种新型改性钠基固体吸收剂,采用活性氧化铝作为载体、TiO2作为掺杂剂进行改性,利用热重分析装置、XRD、SEM和氮吸附仪研究钠基固体吸收剂的CO2捕捉性能。结果表明:掺杂TiO2后,钠基固体吸收剂与CO2的反应速率加快,CO2捕捉量增加;反应前后除TiO2外无其他含Ti化合物生成;碳酸化反应产物为NaHCO3和Na5H3(CO3)4;然而TiO2掺杂过多会堵塞吸收剂的微观孔道,不利于甚至阻碍碳酸化反应的进行,因此,TiO2的掺杂量应控制在一定的范围内。 相似文献
4.
Ki-Joong Kim Su-Il Boo Ho-Geun Ahn 《Journal of Industrial and Engineering Chemistry》2009,15(1):92-97
The bimetallic Pt–Au catalysts supported on ZnO/Al2O3 with different Pt/Au molar ratios were prepared by impregnation (IMP) method using a mixed solution of Pt and Au precursor. These were characterized by X-ray diffraction (XRD), CO chemisorption, temperature programmed reduction (TPR), and transmission electron microscopy (TEM) equipped energy dispersive spectroscopy (EDS). Catalytic activity for complete oxidation of toluene was measured using a flow reactor under atmospheric pressure. In the results, the aggregation of Au particles depended on the molar ratio in the bimetallic Pt–Au catalyst, and Pt particles was well dispersed homogeneously even by the IMP method. The Pt75Au25 and Pt67Au33 catalysts concurrently coated with Pt and Au precursors by IMP method showed higher activity than monometallic Pt and Au catalyst for toluene oxidation. Also, in order of the catalytic activity for toluene was very good agreement compare with the TPR results. The Au particles might promote the toluene oxidation over the bimetallic catalyst concurrently coated with Pt and Au particles. Therefore, the size of Pt and Au particles and catalytic activity were confirmed to be correlated to molar ratio of Pt and Au loaded. 相似文献
5.
6.
《Ceramics International》2016,42(9):10892-10901
Au–TiO2/SiO2 heterogeneous catalysts with different Au contents were successfully synthesized by a facile hydrothermal process and their photocatalytic activity towards reduction of Rose Bengal (RB), Methyl Blue (MB), Rhodamine B (RhB) and Congo Red (CR) was investigated in the presence of sodium borohydride (NaBH4) for advanced oxidation process (AOP). The results reveal that 3 wt% Au loaded in TiO2/SiO2 can significantly degrade high RB concentration dye (>95%, 0.3 g/L, 12 pH) within 20 min of irradiation time. All catalysis reaction followed the pseudo-first order rate reaction with high correlation coefficient. The effect of loading of Au nanoparticles (1–5 wt%) along with variation in dye concentration (100–500 ppm), pH of solution (2–12), catalysts dosage (0.1–0.5 g/L), and reaction temperature (30–80 °C) were also studied. The present works shows the superior performance of Au–TiO2/SiO2 heterogeneous catalysts to be related to the high dispersion of Au nanoparticles in the TiO2/SiO2 and to the catalytic effect between gold and TiO2. 相似文献
7.
Infrared spectra of adsorbed CO have been used as a probe to monitor changes in Pt site character induced by the coking of
Pt/Al2O3 and Pt–Sn/Al2O3 catalysts by heat treatment in heptane/hydrogen. Four distinguishable types of Pt site for the linear adsorption of CO on
Pt/Al2O3 were poisoned to different extents showing the heterogeneity of the exposed Pt atoms. The lowest coordination Pt atoms (ν(CO)
< 2030 cm−1) were unpoisoned whereas the highest coordination sites in large ensembles of Pt atoms (2080 cm−1) were highly poisoned, as were sites of intermediate coordination (2030–2060 cm−1). Sites in smaller two‐dimensional ensembles of Pt atoms (2060–2065 cm−1) were partially poisoned, as were sites for the adsorption of CO in a bridging configuration. The addition of Sn blocked
the lowest coordination sites and destroyed large ensembles of Pt by a geometric dilution effect. The poisoning of other sites
by coke was impeded by Sn, this effect being magnified for Cl‐containing catalyst. Oxidation or oxychlorination of coked catalyst
at 823 K followed by reduction completely removed coke from the catalyst surfaces.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
用沉积-沉淀法制备了Au/La2O3/TiO2催化剂,考察了制备条件和反应条件对催化剂活性的影响,并利用X射线衍射(XRD)、透射电子显微镜(TEM)等测试手段对催化剂进行了表征. 结果表明La2O3的加入可使催化剂催化甲醇水重整的催化活性明显提高,且明显降低产物气体中CO和CH4的含量,使氢气选择性明显增加. 当nH2O/nCH3OH=1.0、液体进料空速WHSV=3.42 h-1、反应温度为275℃时,Au/La2O3/TiO2催化剂催化甲醇水蒸汽重整制氢反应的效果最佳. 相似文献
9.
Naoyoshi Nunotani Zhuowei Li Nobuhito Imanaka 《International Journal of Applied Ceramic Technology》2022,19(2):746-752
Novel catalysts of Pt/La1−xBixOF/SBA-16 (SBA-16: Santa Barbara Amorphous No. 16) were synthesized, and their catalytic activities for phenol decomposition in the liquid phase were investigated. Lanthanum oxyfluoride (LaOF) was selected as the promoter due to its contribution to the smooth migration of oxygen species in the lattice and the acceleration of phenol adsorption on the catalyst surface. Reducible Bi3+ ions were introduced in the LaOF lattice to provide oxygen supply ability to LaOF. Among the prepared catalysts, the highest activity was obtained for the 7 wt% Pt/16 wt% La0.99Bi0.01OF/SBA-16 catalyst, which could remove 97% of phenol after 5 h of reaction at 80°C in an open-air atmosphere. 相似文献
10.
María A. Vicerich Viviana M. Benitez María A. Sánchez Catherine Especel Florence Epron Carlos L. Pieck 《加拿大化工杂志》2020,98(3):749-756
Alumina and silica-alumina supported Ru-Pt catalysts were evaluated for the ring opening of naphthenes. Pt, Ru, and Ru-Pt catalysts were prepared by the impregnation of inorganic precursors over γ-alumina and silica-alumina supports. The catalysts were evaluated by temperature programmed reduction (TPR), pyridine temperature programmed desorption (TPD), CO-FTIR, and by test reactions of 33DM1B isomerization, cyclohexane dehydrogenation, cyclopentane hydrogenolysis, and the ring opening of decalin. The strong interaction between the metals (Pt-Ru) was attributed to their reductions occurring simultaneously. The acidity and strength of the acid sites of the monometallic Ru catalyst were higher than those of the monometallic Pt catalyst. The total acidity (Lewis and Brønsted) and the strength of the acid sites were higher for the silica-alumina supported catalysts. The silica-alumina catalysts had 10 times more Brønsted acidity than the γ-alumina ones and an increased activity and selectivity to decalin ring opening products. Supported monometallic Ru had the best performance for the ring opening reaction. 相似文献
11.
《Catalysis communications》2008,9(2):250-255
Ce–Zr mixed oxides calcined at 1000 °C are more active catalysts for soot oxidation than pure CeO2 calcined at the same temperature, both in loose and tight contact between soot and catalyst. 1000 °C sinterised-CeO2 presents a very low surface area (2 m2/g), a large crystal size (110 nm) and a lack of surface redox properties. Ce–Zr mixed oxides present higher BET surface areas (typically 17–19 m2/g), smaller crystal sizes and enhanced redox properties. The Zr molar fraction does not affect appreciably the catalytic activity of Ce–Zr mixed oxides in the range studied (Zr molar fraction from 0.11 to 0.51). 相似文献
12.
从热力学角度讨论了Al作为还原剂还原氮化TiO2制备复相TiN-Al2O3的可行性.利用综合热分析、X射线衍射仪、扫描电镜及能谱仪分析研究了在1 100~1 500℃TiO2和金属Al粉还原氮化过程中样品的质量变化、相组成和显微结构.结果表明:在1 100℃合成产物中已有少量的AlN和TiN,说明A1的氮化反应以及TiO2和Al的还原氮化反应都已开始.在1200~1 300℃,TiN含量明显增加,AIN含量逐渐减少.在1 350℃,合成产物中只有TiN和Al2O3,说明还原氮化反应完成.继续提高温度,在1400~1 500℃,TiN和刚玉的晶粒长大. 相似文献
13.
Yu.V. Maksimov M.V. Tsodikov E.A. Trusova I.P. Suzdalev J.A. Navío 《Catalysis Letters》2001,72(1-2):11-15
Peculiarities in catalytic activity in carbon monoxide oxidation as well as some structure, electronic and magnetic properties of the three oxide catalysts, Mn3+–O/Al2O3 (1), Mn3+–O–Fe/Al2O3 (Mn-substituted spinel, 2) and -Fe2O3/Al2O3 (3), were studied by kinetic measurements and by Mössbauer spectroscopy. The catalysts 1 and 2 showed a kinetic bistability with a sharp transition towards more reactive state at 200°C (ignition point). In contrast, for catalyst 3, at 200–250°C, the behavior of reaction rate against temperature did not display noticeable hysteresis. On cooling the catalysts 1 and 2, extinction was observed at about 170 and 120°C, respectively, i.e., at 30–80°C lower than the corresponding ignition points. Proximity of activation energy for the high and low activity (15–19 kJ/mol) for both Mn-containing catalysts suggests an increase in the number of active sites at high temperature with no changes in the reaction mechanism. The considerable difference between Mn-containing catalysts 1, 2 and Fe-containing catalyst 3 may be caused by Jahn–Teller (JT) type distortions of the oxygen polyhedron around Mn3+. A significant spontaneous axial bond stretching within the local polyhedron seems to diminish Mn–O binding energy, facilitate the participation of surface oxygen species, OS, in the oxidation of CO by a redox mechanism and promote oxygen vacancies at the surface that would cause considerable effect on the activity. An increase in the width of the counterclockwise hysteresis loop for the catalyst 2 compared to the catalyst 1 indicates that clusters of mixed spinel provide more active sites and more labile OS species than clusters of the binary Mn oxide. 相似文献
14.
A potassium and calcium co-promoted nickel catalyst (KCaNi/-Al2O3) prepared by a direct impregnation method possessed a high activity, high stability and excellent coke resistance properties in CH4 reforming with CO2. XRD, XPS and H2-TPR characterizations indicated that (i) Ca and K strengthened the interaction between Ni and -Al2O3 and promoted the formation of a unique NiAl2O4 phase on the surface of the catalyst and (ii) Ca and K increased the dispersion of Ni and retarded its sintering. Coking reactions (CH4 temperature-programmed decomposition and O2-TPO) disclosed that K reduced carbon formation via CH4 decomposition. 相似文献
15.
A new family of rhenium‐based catalysts bearing HZSM‐5 zeolite exhibits remarkable performances for the catalytic dehydrocondensation
of methane with CO/CO2 towards ethylene, benzene, and naphthalene in high selectivity of above 90% at 1–3 atm and 973–1023 K. In contrast to Mo/HZSM‐5
catalysts, the EXAFS and TG/DTA/Mass studies reveal that the metallic Re on HZSM‐5 zeolite is a catalytically active and stable
phase for the reaction.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
《Catalysis communications》2011,16(1):41-45
Mesoporous CuO/TixZr1 − xO2 catalysts were prepared by a surfactant-assisted method, and characterized by N2 adsorption/desorption, TEM, XPS, in-situ FTIR and H2-TPR. The catalysts exhibited high specific surface area (SBET = 241 m2/g) and uniform pore size distribution. XPS and in-situ FTIR displayed that Cu+ and Cu2+ species coexisted in the catalysts. The CuO/TixZr1 − xO2 catalysts presented obviously higher activity in CO oxidation reaction than the CuO/TiO2 and CuO/ZrO2 catalysts. Effect of molar ratios of Ti to Zr and calcination temperature on catalytic activity was investigated. The CuO/Ti0.6Zr0.4O2 catalyst calcined at 400 °C exhibited excellent activity with 100% CO conversion at 140 °C. 相似文献
17.
MoO3–V2O5/Al2O3 catalysts were characterized by B.E.T., XRD, LRS, XPS and TPR and the effect of MoO3 addition to alumina supported vanadia catalysts on the catalytic activity for the selective catalytic reduction of NO by ammonia was investigated. Upon the addition of MoO3, catalytic activity was enhanced and the particle size of V2O5 which is shown by the results of B.E.T., XRD and Raman spectroscopy decreased. This was one reason for increased catalytic activity. The results obtained by XPS and TPR showed that MoO3 addition to alumina supported vanadia catalysts increased the reducibility of vanadia and this was the another reason for synergy effect between MoO3 and V2O5 in MoO3–V2O5/Al2O3 catalysts. 相似文献
18.
利用热重分析仪、扫描电镜和氮吸附仪对不同粒径的K2CO3颗粒和负载型K2CO3/Al2O3二氧化碳吸收剂的碳酸化特性进行研究。负载后的吸收剂比表面积和孔隙结构得到较大改善,使得碳酸化反应速率和转化率均提高,吸收剂碳酸化特性得到改善。纯K2CO3颗粒吸收剂的反应速率和转化率随着粒径的增加而减小,负载型吸收剂的反应速率和转化率随着粒径的增加略增大。研究了不同粒径和反应时间对K2CO3/Al2O3颗粒微观结构的影响,结果表明K2CO3/Al2O3颗粒具有较稳定的微观结构。采用负载型粒子模型对K2CO3/Al2O3吸收剂吸收CO2碳酸化过程进行研究,所建立的粒子模型计算结果与试验值吻合较好。利用建立的模型对不同CO2浓度下K2CO3/Al2O3吸收剂碳酸化反应特性进行模拟计算,模拟结果具备一定的合理性和准确性,为开展进一步研究提供了基础。 相似文献
19.
《Catalysis communications》2005,6(4):287-292
A very strong promotion effect of the presence of 1000 ppmV C3H8 in the reaction feed on CH4–O2 reaction was found over unsulfated 1%Pt/γ-Al2O3 catalyst. This promotion was further increased on pre-sulfated 1%Pt/γ-Al2O3. The promoting effect of pre-sulfation on the activity of 1%Pt/γ-Al2O3 for propane combustion results in a further improvement on methane combustion due to propane combustion heat which is generated at lower temperatures, activating methane combustion over pre-sulfated 1%Pt/γ-Al2O3 at even lower temperatures relative to unsulfated 1%Pt/γ-Al2O3. These results suggest that small amounts of propane in the gas feed during CH4–O2 reaction over a pre-sulfated Pt/γ-Al2O3 catalyst may eliminate methane emissions at low temperatures from lean-burn NGV exhausts without being deactivated by sulfur poisoning as Pd supported catalysts. 相似文献
20.
O3/UV,O3/TiO2/UV,O3/VO2/TiO2降解磺基水杨酸 总被引:1,自引:0,他引:1
实验利用O3/UV,O3/TiO2/UV,O3/VO2/TiO2降解了磺基水杨酸.结果表明,在这三种高级氧化技术中,O3/VO2/TiO2的氧化效果最好,如在相同的条件下,30 min后取样表明三者COD的去除率分别为47%,55%和70%.在不同pH条件下研究表明O3/TiO2/UV对水体pH的影响较为敏感.通过加入自由基猝灭剂研究表明三者产生羟基自由基的活性顺序是O3/VO2/TiO2>O3/TiO2/UV>O3/UV. 相似文献