助剂对NiMgAl催化剂的结构和甲烷二氧化碳重整反应性能的影响(英文)

向担载镍基催化剂NiMgAl中添加助剂(Co,Ir或Pt)制备了三种助剂促进型催化剂,通过氢气程序升温还原(H2-TPR),CO2/CH4程序升温表面反应(CO2/CH4-TPSR)和CO2程序升温脱附(CO2-TPD)等方法对催化剂进行表征.助剂对催化剂性能的影响通过甲烷干重整实验进行评价.添加少量的Pt或Ir助剂可以降低Ni活性组分的还原温度和提高反应性能.添加助剂的样品与原始NiMgAl催化剂相比能够降低反应的活化能,添加Co或Ir助剂的催化剂与NiMgAl催化剂相比活化能有了明显的降低.NiMgAl催化剂的活化能为51.8 kJ·mol-1,添加Pt助剂的NiPtMgAl催化剂活化能降至26.4 kJ·mol-1.NiMgAl催化剂中添加Pt助剂制备的催化剂具有较好的催化活性和较低的活化能.CH4-TPSR和CO2-TPSR结果表明添加Pt助剂可以在更低的温度下(与NiMgAl催化剂相比)提高CH4的活化能力,并在催化剂表面形成更多的碳物种.CO2-TPD结果显示,添加助剂的催化剂与NiMgAl样品相比在反应温度区间内增加了CO2的吸附/脱附量.     

Ni/Fe物质的量的比对Ni-Fe催化剂表面性质和二硝基甲苯加氢活性的影响

采用Fe粉置换氯化镍溶液中的Ni²⁺制备了Ni-Fe催化剂, 并应用于催化二硝基甲苯加氢合成甲苯二胺的反应中。运用XRD、低温氮吸附-脱附、H₂-TPD、XPS和TEM等技术手段对不同Ni/Fe物质的量的比(n_Ni/n_Fe)下催化剂进行了表征。结果表明, n_Ni/n_Fe对Ni-Fe催化剂表面性质影响显著。当n_Ni/n_Fe为1:4时, Fe抑制Ni氧化的作用达到最大, Ni-Fe催化剂化学氢吸附量和活性物种Ni的分散度分别达到了0.16 mmol·g^-1和23%, 催化剂性能得到较大的提升。在优化的催化剂制备条件下, DNT(二硝基甲苯)的转化率和TDA(甲苯二胺)的选择性分别达到了~100%和99%。另外, 对Ni-Zn漆原镍(Urushibara Ni)催化剂和Ni-Fe催化剂催化DNT加氢反应进程进行了研究, 发现它们有相同的加氢中间产物, 但反应不同阶段的催化速率存在差异。     

Study of catalytic hydrodeoxygenation performance for the Ni/KIT-6 catalysts

Ni/KIT-6 catalysts loaded with different amounts of metallic Ni were prepared by impregnation method. The prepared catalysts and their precursors were investigated through wide- and low-angle XRD, TEM, BET, H₂-TPR, and H₂-TPD analyzes. The catalytic hydrodeoxygenation performance of the catalysts was evaluated using ethyl acetate as a model bio oil compound. Results indicate that the catalytic hydrodeoxygenation performance of the prepared catalysts was directly related to hydrogen storage properties, hydrogen desorption properties, dispersion of the active component Ni, and so on. The ethyl acetate conversion and ethane selectivity of 25?wt% Ni/KIT-6 catalyst were 100 and 96.8%, respectively, at 300?°C, which shows the best performance. The hydrodeoxygenation activity of ethyl acetate was higher than that of methyl acetate and isopropyl acetate because of the effect of molecular polarity and size. And, this reaction is a structure sensitive reaction.     

Effect of Catalyst Properties on Hydrocracking of Pyrolytic Lignin to Liquid Fuel in Supercritical Ethanol

The metal-acid bifunctional catalysts have been used for bio-oil upgrading and pyrolytic lignin hydrocracking. In this work, the effects of the metal-acid bifunctional catalyst properties, including acidity, pore size and supported metal on hydrocracking of pyrolytic lignin in supercritical ethanol and hydrogen were investigated at 260 ^oC. A series of catalysts were prepared and characterized by BET, XRD, and NH₃-TPD techniques. The results showed that enhancing the acidity of the catalyst without metal can promote pyrolytic lignin polymerization to form more solid and condensation to produce more water. The pore size of microporous catalyst was smaller than mesoporous catalyst. Together with strong acidity, it caused pyrolytic lignin further hydrocrack to numerous gas. Introducing Ru into acidic catalysts promoted pyrolytic lignin hydrocracking and inhibited the polymerization and condensation, which caused the yield of pyrolytic lignin liquefaction product to increase significantly. Therefore, bifunctional catalyst with high hydrocracking activity metal Ru supported on materials with acidic sites and mesopores was imperative to get satisfactory results for the conversion of pyrolytic lignin to liquid products under supercritical conditions and hydrogen atmosphere.     

Ni/Fe物质的量的比对Ni-Fe催化剂表面性质和二硝基甲苯加氢活性的影响

采用Fe粉置换氯化镍溶液中的Ni²⁺制备了Ni-Fe催化剂,并应用于催化二硝基甲苯加氢合成甲苯二胺的反应中。运用XRD、低温氮吸附-脱附、H₂-TPD、XPS和TEM等技术手段对不同Ni/Fe物质的量的比(n_Ni/n_Fe)下催化剂进行了表征。结果表明,n_Ni/n_Fe对Ni-Fe催化剂表面性质影响显著。当n_Ni/n_Fe为1:4时,Fe抑制Ni氧化的作用达到最大,Ni-Fe催化剂化学氢吸附量和活性物种Ni的分散度分别达到了0.16 mmol·g^-1和23%,催化剂性能得到较大的提升。在优化的催化剂制备条件下,DNT(二硝基甲苯)的转化率和TDA(甲苯二胺)的选择性分别达到了~100%和99%。另外,对Ni-Zn漆原镍(Urushibara Ni)催化剂和Ni-Fe催化剂催化DNT加氢反应进程进行了研究,发现它们有相同的加氢中间产物,但反应不同阶段的催化速率存在差异。     

Mn负载量对nMnO_x/TiO_2催化剂NH_3-SCR催化性能的影响

MnO_x/TiO_2催化剂由于具有优异的低温脱硝性能,已成为SCR催化剂的研究热点之一.我们通过浸渍法制备了一系列不同Mn负载量的nMnO_x/TiO_2(n=2.5%, 5%, 10%, 15%)(质量分数)催化剂,考察Mn负载量对催化剂脱硝性能的影响.利用N_2物理吸附, X-Ray Diffraction (XRD), Scanning Electron Microscope(SEM),Temperature Programmed Reduction with H_2(H_2-TPR),Temperature Programmed Desorption with NH_3(NH_3-TPD)和X-Ray Photoelectron Spectroscopy (XPS)对其结构进行表征.结果表明,催化剂的脱硝性能随着Mn负载量(2.5%～15%)(质量分数)的变化呈现"火山型"曲线,当Mn负载量为10%(质量分数)时,催化剂的脱硝性能最佳. H_2-TPR和XPS结果表明nMnO_x/TiO_2催化剂上表面氧比例和表面Mn~(4+)浓度均随着Mn负载量的增大,先增大后减小,具体顺序为10MnO_x/TiO_(2 ) 15MnO_x/TiO_(2 )5MnO_x/TiO_(2 ) 2.5MnO_x/TiO_2,与脱硝性能顺序完全一致.进一步关联表面氧的比例与T_(50)发现,催化剂的表面氧的比例与T_(50)呈线性关系,即表面氧比例越高, T_(50)越小,脱硝活性越高. NH_3-TPD结果表明,弱酸酸量的增加有助于低温脱硝活性的提高.这些结果揭示了Mn负载量影响脱硝性能的作用规律,为今后开发高效的锰基低温脱硝催化剂提供了技术支撑.     

丙烷选择氧化催化剂Mo-V-Zr-O的研究

研究了Zr添加量对Mo-V-O基催化剂丙烷选择氧化制丙烯醛催化性能的影响.对催化剂的BET、X射线衍射、H2-程序升温还原、NH3-程序升温脱附和异丙醇分解表征结果表明,Zr的添加改变了催化剂的物相结构、氧化还原性和酸碱性质,从而影响催化剂的催化性能,其中Mo2VZr0.5Ox催化剂表现出较好的催化活性和丙烯醛选择性.     

Reductive amination of cyclohexanol/cyclohexanone to cyclohexylamine using SBA-15 supported copper catalysts

Amination of cyclohexanol was investigated in vapour phase over copper catalysts supported on mesoporous SBA-15. The different products identified during reductive amination of cyclohexanol reaction were cyclohexanone, cyclohexylamine, along with small amounts of N-Cyclohexylidinecyclohexylamine and dicyclohexylamine. Among several catalysts tested for the reductive amination, 5% Cu supported on SBA-15 exhibited better catalytic performance than other catalysts with 36% selectivity towards cylclohexylamine at 80% cyclohexanol conversion. The optimum reaction conditions employed to achieve the best catalyst performance were at 250 °C, 0.1 MPa of H₂/NH₃, TOS-10h. The active Cu sites, acidity of the catalyst, and effect of reaction parameters play a pivotal role in the reductive amination reaction. The prepared catalysts were characterized by XRD, BET, SEM, H₂-TPR and NH₃-TPD. The dispersion of Cu, particle size, and metal surface area (m²/g) calculated from pulse N₂O decomposition method. TPR findings reveal the presence of substantially dispersed copper oxide species at lower loadings which is easily reducible than the bulk copper oxide species found at higher Cu loadings. The acidity measurements by NH₃-TPD analysis suggest that the maximum acidic strength was obtained at 5 wt% copper on porous SBA-15, and decreased with Cu loadings. The catalytic properties are well in agreement with the findings of catalysts characterization.     

碳球为模板水热合成Mg-Co复合氧化物及其催化分解N2O

用自制的碳球为模板剂,尿素为沉淀剂,120℃水热合成尖晶石型Mg-Co复合氧化物（MgCo₂O₄）,在其表面浸渍K₂CO₃溶液制得K改性催化剂,用于催化分解N₂O。用X射线衍射（XRD）、N₂物理吸附-脱附、扫描电镜（SEM）、H₂程序升温还原（H₂-TPR）、O₂程序升温脱附（O₂-TPD）、X射线光电子能谱（XPS）等技术对催化剂进行结构表征,考察了钴镁离子/碳球的质量比、尿素/钴镁离子的物质的量比等制备参数对催化剂活性的影响。结果表明,钴镁离子/碳球的质量比为0.192、尿素/钴镁离子的物质的量比为2,制得的MgCo₂O₄催化剂活性较高。K改性MgCo₂O₄催化剂在400℃有氧无水、有氧有水条件下连续反应50 h,N₂O转化率分别保持在91%和62%,稳定性较好。     

Zn-Zr-Al oxides derived from hydrotalcite precursors for ethanol conversion to diethyl carbonate

Ethanol conversion to high-value-added products has attracted considerable attention in both academic research and industrial fields. In this study, we synthesized a series of tunable acid–base bifunctional Zn-Zr-Al metal oxides (represented as Zn₂Zr_xAl-MMO) in light of the structural topotactic transformation of Zn₂Zr_xAl-hydrotalcite precursors (Zn₂Zr_xAl-LDH). The resulting Zn₂Zr_xAl-MMO catalysts were employed in the conversion of ethanol to diethyl carbonate. The Zr⁴⁺ ion content of the LDH precursor plays a key role in modulating the acid-base properties and determining catalytic performance: the Zn₂Zr_0.1Al-MMO sample exhibits the optimal catalytic behavior with a diethyl carbonate (DEC) yield of 42.1%, which is the highest reported for metal oxide catalysts. Structure-property correlation investigations revealed that the synergic catalysis between medium-strong basic sites and weak acid sites plays a predominant role in the catalytic behavior. Furthermore, in situ Fourier transform infrared measurements showed that the weak acidic site promotes activation adsorption of the reactant (urea) and the intermediate product (ethyl carbamate), while the medium-strong basic site accelerates ethanol activation. Moreover, the Zn₂Zr_0.1Al-MMO catalyst has the advantages of cost effectiveness, good stability, and reusability. Therefore, the acid-base bifunctional catalysts developed in this work can be employed as promising candidates in acid-base catalytic reactions such as ethanol conversion.     

Structural,Magnetic and Catalytic Properties of a New Vacancy Ordered Perovskite Type Barium Cobaltate BaCoO2.67

A new vacancy ordered, anion deficient perovskite modification with composition of BaCoO_2.67 (Ba₃Co₃O₈□₁) has been prepared via a two-step heating process. Combined Rietveld analysis of neutron and X-ray powder diffraction data shows a novel ordering of oxygen vacancies not known before for barium cobaltates. A combination of neutron powder diffraction, magnetic measurements, and density functional theory (DFT) studies confirms G-type antiferromagnetic ordering. From impedance measurements, the electronic conductivity of the order of 10⁻⁴ S cm⁻¹ is determined. Remarkably, the bifunctional catalytic activity for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is found to be comparable to that of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3–y, confirming that charge-ordered anion deficient non-cubic perovskites can be highly efficient catalysts.     

The effect of the distance between acidic site and basic site immobilized on mesoporous solid on the activity in catalyzing aldol condensation

Acid-base bifunctional heterogeneous catalysts containing carboxylic and amine groups, which were immobilized at defined distance from one another on the mesoporous solid were synthesized by immobilizing lysine onto carboxyl-SBA-15. The obtained materials were characterized by X-ray diffraction (XRD), N₂ adsorption, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron micrographs (SEM), transmission electron micrographs (TEM), elemental analysis, and back titration. Proximal-C-A-SBA-15 with a proximal acid-base distance was more active than maximum-C-A-SBA-15 with a maximum acid-base distance in aldol condensation reaction between acetone and various aldehydes. It appears that the distance between acidic site and basic site immobilized on mesoporous solid should be an essential factor for catalysis optimization.     

Synthesis of bifunctional Pt/MgAPO-5 catalysts and their catalytic performance in the hydrogenation of nitrobenzene to p-aminophenol

MgAPO-5 molecular sieves have been synthesized using diethylaminoethanol as the templating agent in a wide range of the MgO/Al₂O₃ ratio. The samples were characterized by XRD, SEM, solid state NMR, FT-IR and NH₃-TPD. Using MgAPO-5 as acidic supports, bifunctional Pt/MgAPO-5 catalysts were prepared for hydrogenation of nitrobenzene to p-aminophenol (PAP). The results showed that the MgO/Al₂O₃ ratios influenced the Mg content and the acidity of MgAPO-5 samples, thereby greatly affecting the catalytic performance of Pt/MgAPO-5 catalysts. The selectivity to PAP over Pt/MgAPO-5 was dependent on the amount of strong acid sites of MgAPO-5. When the MgO/Al₂O₃ molar ratio was 0.5, the synthesized MgAPO-5 sample exhibited the largest amount of strong acid and a highest PAP yield of 41.1% was achieved over Pt/MgAPO-5 catalyst.     

Cooperative Effect of Platinum and Alumina on Catalyst Deactivation for Dehydrogenation Reaction

The cooperative effect on catalyst deactivation of Pt-based catalysts for dehydrogenation reaction was investigated using the combination of Pt-based/SiO₂ and Al₂O₃. The presence of the effect was confirmed by reaction test, CO adsorption, H₂-TPD and TPO. Considering conversion, active site, H₂ uptake and the nature and amount of coke, interestingly, the physical mixture of Pt-based catalyst supported on SiO₂ with 100-120 mesh and Al₂O₃ 60-80 mesh was similar to Pt-based Al₂O₃. The concept of combination of two catalytic functions, acidity and metallic species, will certainly provide the possibility of better catalyst design.     

A Bifunctional Hybrid Electrocatalyst for Oxygen Reduction and Oxygen Evolution Reactions: Nano-Co3O4-Deposited La0.5Sr0.5MnO3 via Infiltration

For rechargeable metal–air batteries, which are a promising energy storage device for renewable and sustainable energy technologies, the development of cost-effective electrocatalysts with effective bifunctional activity for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has been a challenging task. To realize highly effective ORR and OER electrocatalysts, we present a hybrid catalyst, Co₃O₄-infiltrated La_0.5Sr_0.5MnO_3-δ (LSM@Co₃O₄), synthesized using an electrospray and infiltration technique. This study expands the scope of the infiltration technique by depositing ~18 nm nanoparticles on unprecedented ~70 nm nano-scaffolds. The hybrid LSM@Co₃O₄ catalyst exhibits high catalytic activities for both ORR and OER (~7 times, ~1.5 times, and ~1.6 times higher than LSM, Co₃O₄, and IrO₂, respectively) in terms of onset potential and limiting current density. Moreover, with the LSM@Co₃O₄, the number of electrons transferred reaches four, indicating that the catalyst is effective in the reduction reaction of O₂ via a direct four-electron pathway. The study demonstrates that hybrid catalysts are a promising approach for oxygen electrocatalysts for renewable and sustainable energy devices.     

Bifunctional Onium and Potassium Iodides as Nucleophilic Catalysts for the Solvent-Free Syntheses of Carbonates,Thiocarbonates, and Oxazolidinones from Epoxides

The catalytic potential of organo-onium iodides as nucleophilic catalysts is aptly demonstrated in the synthesis of cyclic carbonates from epoxides and carbon dioxide (CO₂), as a representative CO₂ utilization reaction. Although organo-onium iodide nucleophilic catalysts are metal-free environmentally benign catalysts, harsh reaction conditions are generally required to efficiently promote the coupling reactions of epoxides and CO₂. To solve this problem and accomplish efficient CO₂ utilization reactions under mild conditions, bifunctional onium iodide nucleophilic catalysts bearing a hydrogen bond donor moiety were developed by our research group. Based on the successful bifunctional design of the onium iodide catalysts, nucleophilic catalysis using a potassium iodide (KI)-tetraethylene glycol complex was also investigated in coupling reactions of epoxides and CO₂ under mild reaction conditions. These effective bifunctional onium and potassium iodide nucleophilic catalysts were applied to the solvent-free syntheses of 2-oxazolidinones and cyclic thiocarbonates from epoxides.     

Direct Oxidation of Propylene with Molecular Oxygen over Ti-Modified Sulfated Zirconia Catalyst, 1. Characterization of the Catalyst and Catalytic Performances

Some zirconia-based catalysts were tested for the reaction of propylene in the presence of molecular O₂ without any additive at 428 K under atmospheric pressure. The catalyst TiSZ, which was prepared by a direct impregnation of titanium sulfate on amorphous zirconia, was found to show the highest yields of oxygenated compounds such as propylene oxide, with C4-C6 hydrocarbons. Characterization of the catalysts, by using XRD, XPS, and NH₃-TPD, exhibited that the catalytic performances were dependent on the surface acidity.     

Catalytic synthesis of isoprenol from fatty acid ester over bimetallic Cu–Fe catalysts

Supported bimetallic Cu–Fe catalysts revealed high activity and selectivity in isoprenyl acetate hydrogenation to isoprenol under mild reaction conditions (2 MPa H₂ and 170 °C). The nature of the carrier has a significant impact on the catalytic properties of Cu–Fe catalysts. The best catalytic properties were found for the 5% Cu–5% Fe/Al₂O₃ bimetallic catalyst, which provides a 98% isoprenyl acetate conversion in 4 h with the isoprenol selectivity of 82%.     

Synthesis and properties of MoO3/ZrO2 solid acid catalysts for the preparation of polydimethylsiloxane (PDMS) via octamethylcyclotetrasiloxane (D4) ring-opening

A series of MoO₃/ZrO₂ catalysts were prepared by impregnation method, and characterized by X-ray diffraction (XRD), specific surface area (BET) and temperature-programmed desorption of NH₃ (NH₃-TPD). The polydimethylsiloxane (PDMS) was prepared by ring-opening polymerization from D₄ and MM with MoO₃/ZrO₂ catalysts. The effects of MoO₃/ZrO₂ catalysts preparation conditions on PDMS molecular weight and reaction conversion rate were discussed. Moreover, the effects of reaction conditions on the ring-opening polymerization were also studied. During the preparation of PDMS, the molecular weight of the product can be controlled by adjusting the mass ratio of D₄:MM. The MoO₃/ZrO₂ catalyst was compared with other catalysts during the ring-opening process, and the repeated times of MoO₃/ZrO₂ catalysts were also studied. The results showed that MoO₃/ZrO₂ catalyst had more excellent catalytic performance, for ring-opening process, and when the repeated times was more than 5, the catalytic activity decreased significantly. In addition, the kinetics of D₄ ring-opening polymerization with the MoO₃/ZrO₂ catalyst was investigated.     

Catalytic Performance of Modified HMCM‐22 Catalysts in Xylene Isomerization

HMCM‐22 catalysts modified with La₂O₃ (5% La) and MgO (≈0.87% Mg) were prepared respectively by impregnation method, and were characterized by scanning electron microscopy, X‐ray diffraction, N₂ physical adsorption‐desorption and temperature‐programmed desorption of NH₃. The effect of supported metallic oxides (La₂O₃, MgO) on catalytic performance in xylene isomerization of C8 aromatics (ethylbenzene, m‐xylene and o‐xylene) was investigated in detail. The experimental results showed that 5% La/HMCM‐22 catalyst had higher isomerization activity and stronger shape‐selectivity than 0.87% Mg/HMCM‐22 catalyst, owing to its more acid sites and smaller pore size. And the loading amount of La was optimized to be about 7%. Moreover, supporting metal over 7% La/HMCM‐22, respectively with 0.3% Pt, 3% Ni and 3% Mo, was carried out to prepare bifunctional isomerization catalysts. In comparison, 3% Mo/7% La/HMCM‐22 showed the best catalytic performance with both high activity and high selectivity, with the low hydrocracking of m‐xylene and o‐xylene. Besides, the optimal reaction conditions were found: 340°C, 1.5 MPa H₂, WHSV 4 h^?1 and H₂/C8 4 mol/mol. Under the above conditions, ethylbenzene conversion was up to 20%, para‐selectivity was over 23% with low xylene loss of 2.9%.