A novel PdNi/Al2O3 catalyst prepared by galvanic deposition for low temperature methane combustion

Galvanic deposition method was used to prepare the Pd/Ni-Al₂O₃-GD catalyst for the combustion of methane under lean conditions. The new catalyst and compared catalysts (Pd/Al₂O₃-IW, Pd-Ni/Al₂O₃-IW, Pd/Ni-Al₂O₃-IW) prepared by incipient wetness impregnation were characterized by N₂-physisorption, XRD and TEM to clarify particle size and size distribution of palladium species. Combined O₂-TPD and XPS results with the catalytic data, it shows that the surface palladium species with low valence exhibits better combustion performance due to their stronger interaction with support. The results indicate that the galvanic deposition method is an effective route to prepare efficient catalyst for methane combustion, and it also provides useful information for improving the present commercial catalyst.     

乙醇辅助的化学沉积法制备硫化型Mo/γ-Al2O3加氢脱硫催化剂

以硫代乙酰胺为硫源,钼酸钠为钼源,乙醇为分散剂,采用化学沉积法制备了MoS₃/Al₂O₃催化剂前驱体,再用H₂高温处理得到高分散硫化型MoS₂/γ-Al₂O₃催化剂,运用N₂吸附-脱附、X射线光电子能谱以及高分辨透射电子显微镜等技术对MoS₂/γ-Al₂O₃催化剂进行了表征,并以二苯并噻吩作为模型化合物评价了催化剂的加氢脱硫(HDS)活性.结果表明,与浸渍法相比,所制催化剂具有更大的比表面积和孔体积、更高的活性金属分散度、更佳的Mo物种硫化度以及更短的MoS₂片层长度和更高的堆积度,因而在二苯并噻吩HDS反应中表现出远优于浸渍法所制催化剂的活性.乙醇可通过S?H-O氢键吸附至MoS₃纳米粒子表面,可有效防止其生长和团聚,起到分散剂的作用.     

TiO_2掺杂CuMnCe/Al_2O_3催化剂对甲烷催化燃烧脱氧反应的影响

以掺杂了不同TiO_2含量的Al_2O_3作为载体,通过等体积浸渍法制备了一系列不同TiO_2含量的CuMnCe/TiO_2-Al_2O_3催化剂,用BET、H_2-TPR、XRD和XPS表征技术对催化剂物理化学性质进行表征,并考察了催化剂在含甲烷气脱氧反应中的催化性能。结果表明,在载体中添加TiO_2对催化剂活性组分的晶相结构和分散度没有明显影响;但有效改善了Al_2O_3载体抗烧结能力;增加了CuMnCe/Al_2O_3催化剂表面Ce~(3+)/(Ce~(3+)+Ce~(4+))的相对含量,从而提高了活性氧的移动性,且使催化剂表面可氧化还原物种含量和表面吸附氧Osur/(Osur+Olatt)的含量增多。有效改善了催化剂在含甲烷气催化燃烧脱氧上的催化活性。其中,CuMnCe/4%TiO_2-Al_2O_3表现出最优的催化活性,在387℃时可使含甲烷气中氧气的转化率达到100%。     

Al2O3负载Pt催化剂的合成及其甲醇低温催化燃烧性能研究

采用一步合成法制备了Al₂O₃负载Pt催化剂Pt/Al₂O₃,以甲醇催化燃烧作为目标反应研究了其催化性能,考察了还原剂浓度、表面活性剂用量、表面活性剂浓度和煅烧温度对Pt/Al₂O₃甲醇低温催化燃烧性能的影响。结果表明,当还原剂浓度为0.1 mol/L、表面活性剂(CTAB)用量为8.53 g/g_cat.、表面活性剂浓度为0.1 mol/L、煅烧温度为600℃时,所得催化剂的活性最高,25℃下甲醇催化燃烧的转化率达到52%。而改进一步合成法制备的负载型催化剂Pt/Al₂O₃具有更高的甲醇催化燃烧活性,25℃下甲醇催化燃烧的转化率为84%。     

Partial oxidation of methane on Cr2O3/Al2O3

The oxidation of methane on supported chromia was studied at temperatures varying between 423 and 743 K and CH₄/O₂ ratios between 1 and 9 in a differential reactor. The main reaction products observed were carbon monoxide and formaldehyde. The rates of reaction obey a power law expression.

---

, 423 743 CH₄/O₂ 1 9, . . .

     

Fe2O3/Al2O3氧载体用于甲烷化学链燃烧：负载量与制备方法的影响

以不同方法制备了系列Fe₂O₃/Al₂O₃氧载体,采用XRD、H₂-TPR、CH₄-TPR、O₂-TPD和BET等分析技术对氧载体进行了表征。研究了不同Fe₂O₃负载量氧载体的甲烷化学链燃烧性能,考察了不同制备方法对Fe₂O₃/Al₂O₃氧载体结构、反应性和产物选择性的影响。结果表明,Fe₂O₃负载量对氧载体活性及产物中CO₂选择性的影响较大,负载量较低时氧载体活性较低且引起甲烷部分氧化产物CO含量增加。制备方法亦对氧载体与甲烷的反应活性有所影响,整体上共沉淀法制备的质量分数60％Fe₂O₃/Al₂O₃氧载体具有较高的氧化活性和化学链循环稳定性。其在反应温度850℃、反应时间15 min、30次循环后甲烷转化率及产物中CO₂选择性均未见明显降低。     

Characterization and evaluation of Fe2O3/Al2O3 oxygen carrier prepared by sol–gel combustion synthesis

The sol-gel combustion synthesis (SGCS) for oxygen carrier (OC) to be used in chemical looping combustion (CLC) was first designed and experimented in this work, which is a new method of OC synthesis by combining sol-gel technique and solution combustion synthesis. Cheap hydrated metal nitrates and urea were adopted as precursors to prepare Fe₂O₃/Al₂O₃ OC at the molar ratio to unity (Fe1Al1), which was characterized through various means, including Fourier transforms infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA), X-ray diffractor (XRD), and N₂ isothermal adsorption/desorption method. FTIR analysis on the chemical structure of the dried gel of Fe1Al1 indicated that urea was partly hydrolyzed and the hydrated basic carbonate was formed by the combination of groups such as (Fe(_1−yAl_y)_1−xO_1−3x, CO₃²⁻ and -OH-. By analyzing the staged products during SGCS, calcination was found as a necessary step to produce Fe₂O₃/Al₂O₃ OC with separate phases of α-Fe₂O₃ and α-Al₂O₃. Through TGA-DTA, the decomposition of the dried gel was found to undergo five stages. The analysis of the evolved gases from the gel decomposition using FTIR partially confirmed the staged decomposition and assisted a better understanding of the mechanism of SGCS. XRD identification further substantiated the necessity of calcination to synthesize Fe₂O₃/Al₂O₃ OC with separate phases of α-Fe₂O₃ and α-Al₂O₃, though it was not necessary for the synthesis of single phase α-Fe₂O₃ and α-Al₂O₃. Structural characterization performed on N₂ adsorption analyzer displayed that the pore shape of Fe1Al1 particles was heterogeneous. Finally, H₂ temperature-programmed reduction (TPR) of Fe1Al1 products in TGA indicated that the reduction reaction of Fe1Al1 OC after calcination was a single step reaction from α-Fe₂O₃ to Fe, and calcination benefited to improve the transfer rate of the lattice oxygen from the OC to fuel H₂. Furthermore, four times of reduction and oxidization (redox) reaction by alternating with H₂ and air demonstrated the synthesized OC had good reactivity and sintering-resistance, much suitable to be used in the realistic CLC. Overall, the SGCS method was found superior to other existent methods to prepare Fe₂O₃/Al₂O₃ OC for CLC application.     

Pt/Al2O3 and Pt/Ba?Al2O3 catalysts studied by temperature programmed desorption of oxygen: Evidence for a low temperature desorbing species

For fresh and aged Pt/Al₂O₃ catalysts, TPD of oxygen is fairly well related to the noble metal surface areas and to the catalytic activity in butane combustion, whereas for aged Pt/Ba−Al₂O₃ solids, the catalytic activity is still preserved despite a tremendous sintering of the metallic phase and seems to be connected to a surface barium superoxide.     

Carbon deposition on meso-porous Al2O3 supported Ni catalysts in methane reforming with CO2

Summary 4-(Trialkylammonio)propansultans (TAAPSs), synthesized by the addition reaction of 1,3-propane sultone (PS) and trialkylamines (TAAs), were developed as new phase transfer catalysts for synthesizing dialkoxymethane. The reaction between alcohol and dibromomethane in a highly alkaline solution of KOH/organic solvent two-phase medium were carried out under phase-transfer catalysis (PTC) using TAAPSs as the catalyst. High conversion of dibromomethane and high selectivity of the product were obtained using TAAPSs as the catalyst.</o:p>     

Kinetics of catalytic combustion in air over Pt/Al2O3/Al catalyst

Summary Catalytic combustion of toluene, propylene and CO over Pt/Al₂O₃ /Al catalyst was investigated. Strong inhibition effects are observed when the mixture of toluene, propylene and CO is oxidized. A reaction mechanism of catalytic combustion over Pt/Al₂O/Al is proposed. The results from kinetic models are in good agreement with the experimental data.     

Active site for hydrogenation on reduced V2O5/Al2O3 catalyst

Active sites for C₂H₄ hydrogenation produced by reduction of V₂O₅/Al₂O₃ catalyst pretreated at 450°C were found to be composed of both strong Lewis acid sites associated with V⁴⁺ and basic sites of Al₂O₃. C₂H₄ polymerization concurrent with hydrogenation was assumed to occur on Lewis acid sites with higher acid strengths than those of the hydrogenation sites.

---

C₂H₄, V₂O₅/Al₂O₃, 450°C, , Al₂O₃. , , , C₂H₄.

     

Mechanistic studies of methane partial oxidation to syngas over LiNiLaOx/Al2O3 catalyst

Reduction of vanadium-titanium oxide catalysts with hydrogen in the temperature range of 150–450°C results in the increase of the content of V⁴⁺ ions in substitution positions of TiO₂ with the anatase structure. The temperature increase up to 250°C results in the growth of the spectral intensity of V⁴⁺ associates in substitution positions of anatase. At higher treatment temperatures their intensity decreases due to the formation of VO₂ fragments in anatase. At 400°C and higher temperatures a solid solution of V⁴⁺ ions in rutile is formed.     

Interaction of propylene with a V2O5/Al2O3 catalyst

IR-spectroscopic studies indicate that on the oxidized surface of V₂O₅/Al₂O₃ catalysts propylene interacts mainly with Brönsted acid centers to form an alcoholate type complex transforming into acetone. On the reduced surface propylene is stabilized as a -complex of V³⁺ and V⁴⁺ ions.

---

- , V₂O₅/Al₂O₃ , . - V³⁺ V⁴⁺.

     

Cu修饰的Fe2O3/Al2O3氧载体的循环反应稳定性研究

采用冷冻干燥法制备了经Cu修饰（10%）的Fe₂O₃/Al₂O₃氧载体。利用热重分析仪分别在850、900和950 ℃等温环境下,使氧载体交替接触还原气体和氧化气体,来模拟氧载体在化学链燃烧中的循环过程。结果表明,经Cu修饰的Fe₂O₃/Al₂O₃氧载体在850和900 ℃下的等温循环过程中反应性能都很稳定,在950 ℃时的循环反应前期有微量烧结,但在循环后期反应性能也很稳定。随着反应温度的升高,氧载体氧化速率增大,还原速率和载氧率先减小后增大。与未经修饰的Fe₂O₃/Al₂O₃氧载体相比较,在900 ℃下作等温循环实验,经Cu修饰的Fe₂O₃/Al₂O₃氧载体具有较高的载氧能力和还原速率,但氧化速率较低;两者都具有较好的循环稳定性。     

Kinetics of methane combustion on Fe2O3/TiO2 catalysts

The objective of this work was to study the kinetics of methane combustion for a series of Fe₂O₃/TiO₂ catalysts. An increase in activity is observed as iron loading increases, and can be attributed to an increase of surface coverage by Fe₂O₃ species. Kinetic studies revealed that the reaction orders with respect to methane, oxygen, carbon dioxide and water are 1, 0, 0 and -1 respectively. This revised version was published online in June 2006 with corrections to the Cover Date.     

Sulfuration of Pt/Al2O3, Pt?Re/Al2O3 and Pt?Ir/Al2O3 catalysts

Three reforming catalysts Pt/Al₂O₃, Pt–Ir/Al₂O₃ and Pt–Re/Al₂O₃ have been sulfurated by H₂S and tested by their activities in benzene hydrogenation. By treatment at 500°C under hydrogen flow only a part of the initial activity of the non-sulfurated catalyst is retained. So only a part of the adsorbed sulfur is easily removed in these conditions. The remaining sulfur for each of the catalysts (Pt/Al₂O₃, Pt–Ir/Al₂O₃ and Pt–Re/Al₂O₃) gives the same atomic ratio of 0.5 sulfur atom per accessible metallic atom.

---

Pt/Al₂O₃, Pt–Ir/Al₂O₃ Pt–Pe/Al₂O₃ . 500°C H₂ . . ., . (Pt/Al₂O₃, Pt–Ir/Al₂O₃ Pt–Pe/Al₂O₃) 0,5.

     

Partial oxidation of methane to syngas over Ni-Fe/Al2O3 catalyst with plasma enhanced activity

A novel Ni-Fe/Al₂O₃ catalyst for partial oxidation of methane has been prepared by glow discharge treatment followed by calcination thermally. The catalyst prepared exhibits better activity and selectivity. This revised version was published online in June 2006 with corrections to the Cover Date.     

TPR studies on steam reforming of 2-propanol on Rh/Al2O3, Ru/Al2O3 and Pd/Al2O3

Reaction pathways for steam reforming of 2-propanol (isopropyl alcohol, IPA) on Rh/Al₂O₃, Ru/Al₂O₃ and Pd/Al₂O₃ have been studied by temperature-programmed reactions (TPRs) of IPA and acetone in the presence of steam. The results of TPRs suggest that that of IPA on Rh/Al₂O₃ and Ru/Al₂O₃ proceeds via acetone, while the steam reforming of IPA on Pd/Al₂O₃ takes place via propene from acetone. This revised version was published online in August 2006 with corrections to the Cover Date.     

Kinetics of Co?Mo/Al2O3 catalyst reduction

According to kinetic studies on the reduction of commercial Co–Mo/Al₂O₃ and model catalysts in H₂ at 523–773 K, the kinetic curves for the reduction process have been determined. The reduction rate is shown to be higher for the commercial catalyst. Activation energies E_act for the reduction of several forms of Mo and Co in Co–Mo/Al₂O₃ catalysts are presented.

---

H₂ 523–773 . , : Mo Co .

     

Sulfurization of Pt/Al2O3?Cl catalysts. IV. Adsorption sites of H2S on Al2O3, Al2O3?Cl and Pt/Al2O3?Cl

Chemisorption of H₂S on Al₂O₃, Al₂O₃–Cl and Pt/Al₂O₃–Cl has been studied by gravimetry and IR spectroscopy. The influence of the amount of Cl on the H₂S adsorption equilibrium value and the nature of the adsorption sites at low and high coverages are discussed.

---

H₂S Al₂O₃, Al₂O₃–Cl Pt/Al₂O₃–Cl . Cl H₂S, .