Microwave-assisted Ni–La/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst for benzene hydrogenation

A series of Ni–La/γ-Al₂O₃ catalysts were prepared by adopting the methods of isometric impregnation and microwave impregnation. The catalysts were characterized with XRD, BET, and SEM, respectively. Inspecting the effects of adding La and the methods of impregnation on the hydrogenation activity of catalysts. The results show that adding a moderate amount of La promotes the dispersing of Ni on the carrier, the methods of microwave impregnation weaks the interaction between Ni and the carrier further, inhibits the formation of NiAl₂O₄, and the activity of catalyst prepared by the methods of microwave impregnation was significantly higher than that prepared by the methods of isometric impregnation. The hydrogenation activity of the Ni–La/γ-Al₂O₃ (WB) dipped with n(Ni): n(La) = 4: 1, microwave irradiation time 30 min with power 600W as well as calcined at 400°C exhibited the best performance. The conversion rate is 91.21% with reaction conditions: T = 160°C, p = 0.8 MPa, air speed 5 h^–1, n(H₂): n(benzene) = 2: 1.     

Synthesis and catalytic activity to Li/SOCl<Subscript>2</Subscript> battery of asymmetric and symmetric binuclear metal phthalocyanines

In our present work, the asymmetric and symmetric binuclear metal phthalocyanines (M₂(PcTN)₂ and M₂(PcTN)₂S), battery catalysts, were synthesized through microwave reaction and characterized by EA, IR and UV-vis spectroscopy. Their catalytic activity in the Li/SOCl₂ battery was evaluated by adding right amount catalysts into the electrolyte. The results indicated that the capacity of the catalyzed battery increased by 6.74–67.26% and 13.41–84.36%, and the energy increased by 9.29–65.72% and 14.77–88.15% respectively, compared with the battery without phthalocyanines.     

Effects of titanium silicalite and TiO2 nanocomposites on supported Co‐based catalysts for Fischer–Tropsch synthesis

Titanium silicalite (TS) and TiO₂ nanocomposites were prepared by mixing TS and TiO₂ with different ratios in ethanol. They were impregnated with 15 wt% Co loading to afford Co‐based catalysts. Fischer–Tropsch synthesis (FTS) performance of these TS–TiO₂ nanocomposite‐supported Co‐based catalysts was studied in a fixed‐bed tubular reactor. The results reveal that the Co/TS–TiO₂ catalysts have better catalytic performance than Co/TS or Co/TiO₂ each with a single support, showing the synergistic effect of the binary TS–TiO₂ support. Among the TS–TiO₂ nanocomposite‐supported Co‐based catalysts, Co/TS–TiO₂‐1 presents the highest activity. These catalysts were characterized using N₂ adsorption–desorption measurements, X‐ray diffraction, X‐ray photoelectron spectroscopy, H₂ temperature‐programmed reduction, H₂ temperature‐programmed desorption and transmission electron microscopy. It was found that the position of the active component has a significant effect on the catalytic activity. In the TS–TiO₂ nanocomposites, cobalt oxides located at the new pores developed between TS and TiO₂ can exhibit better catalytic activity. Also, a positive relationship is observed between Co dispersion and FTS catalytic performance for all catalysts. The catalytic activity is improved on increasing the dispersion of Co.     

Multidisciplinary green approaches (ultrasonic,co-precipitation,hydrothermal, and microwave) for fabrication and characterization of Erbium-promoted Ni-Al2O3 catalyst for CO2 methanation

The dispersion of nickel catalysts is crucial for the catalytic ability of CO₂ methanation, which can be influenced by the fabrication method and the operation process of the catalysts. Therefore, a series of fabrication methods, including ultrasonic, hydrothermal, microwave, and co-precipitation, have been applied to prepare 25Ni-5Er-Al₂O₃ catalysts. The fabrication method can partially influence the structural and catalytic activity of the nickel aluminate catalysts. Among the catalysts modified by Erbium prepared with various methods, the catalyst fabricated by ultrasonic pathway exhibited better catalytic performance and CH₄ selectivity especially, at a temperature (400 ℃). The impact of the temperature of the reaction (200–500 °C) was examined under a stoichiometric precursor ratio of (H₂:CO₂) = 4: 1, atmospheric pressure, and space velocity (GHSV) of 25000 mL/gcath. The results demonstrate that the ultrasonic method is strongly efficient for fabricating Ni-based catalysts with a high BET surface area of about 190.33 m²g^?1. The catalyst composed via the ultrasonic technique has 69.38 % carbon dioxide conversion and 100 % methane selectivity at 400 °C for excellent catalytic performance in CO₂ methanation reactions. The fabrication effect can be associated with its high surface area, which is achieved via the hot spot mechanism. Besides, the addition of Erbium promotes the Ni dispersion on the supports and stimulates the positive reaction because of the erbium oxygen vacancies.     

Ordered mesoporous carbon decorated with rare earth oxide as electrocatalyst support for Pt nanoparticles

Ordered mesoporous carbon with large porosity was surface-modified with PrO_x and subsequently deposited with Pt nanoparticles by microwave heating. Transmission electron microscopy images indicated that PrO_x could improve the dispersion of Pt nanoparticles. The electrocatalytic activity of Pt catalysts was evaluated according to hydrogen adsorption region of cyclic voltammograms and electrochemical impedance spectroscopy. Pt/C–PrO_x exhibited excellent performance in H₂SO₄, with a larger electrochemical active area and lower charge-transfer resistance than that of Pt/C. It is mainly due to enhanced dispersion of Pt nanoparticles and improved hydrogen adsorption on support.     

Environmental remediation by an integrated microwave/UV illumination technique: IX. Peculiar hydrolytic and co-catalytic effects of platinum on the TiO2 photocatalyzed degradation of the 4-chlorophenol toxin in a microwave radiation field

The photocatalyzed degradation of the 4-chlorophenol toxin (4-CP) in aqueous naked TiO₂ and platinized TiO₂ suspensions simultaneously subjected to UV light and microwave radiation was revisited to examine the fate of this toxin in the microwave-assisted photocatalytic process by monitoring loss of total organic carbon (TOC; mineralization), formation of chloride ions (dechlorination of 4-CP), and identification of intermediates using HPLC and electrospray mass spectral (LC–MSD) techniques. Attempts are made to delineate microwave thermal and nonthermal factors that impinge on the degradation by comparing experimental results from microwave-generated heat versus results from a conventional (externally heated) thermally-assisted process, and from results in which the thermal factors were minimized by examining the degradative process at constant ambient temperature (25 °C). Possible microwave radiation effects on the Pt co-catalyst supported on TiO₂ were also probed through comparison of the degradation of 4-CP occurring on Pt/TiO₂ and on naked TiO₂ photocatalysts. Results suggest that, in a microwave radiation field, naked TiO₂ and Pt/TiO₂ particle surfaces interact with the microwaves. The degradation pathway exhibited characteristics of hydrolysis of reactants and intermediates. Nonthermal microwave effects play a role in the overall degradative process occurring in platinized TiO₂ dispersions. The possible nature of these unusual microwave effects is briefly discussed.     

Sb modified Fe–Mn/TiO<Subscript>2</Subscript> catalyst for the reduction of NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> with NH<Subscript>3</Subscript> at low temperatures

Manganese-based catalysts have attracted much attention due to their excellent performance for NO reduction with NH₃ (NH₃-SCR) at low temperatures. In the current study, the novel metal Sb was modified into Mn/TiO₂ and Fe–Mn/TiO₂, and the NO _x conversion was compared with those of Mn/TiO₂ and Fe–Mn/TiO₂ catalysts to investigate the effect of the Sb. The NO _x reduction activities of the catalysts were evaluated in the temperature range of 100–250 °C at a space velocity of 60,000 h^?1. The physicochemical properties of all the catalysts were characterized by Brunauer–Emmett–Teller surface area, temperature-programmed desorption of ammonia, temperature-programmed reduction, X-ray photoelectron spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy. Interestingly, the Sb-promoted Mn-based catalysts showed significantly higher NO _x conversion than the other catalysts with or without 6 vol% of H₂O. The high performance of the Sb-modified catalysts could be related to the increase of acid sites and redox properties.     

Chemically dealloyed Pt–Au–Cu ternary electrocatalysts with enhanced stability in electrochemical oxygen reduction

We report simple synthesis of ternary Pt–Au–Cu catalysts consisting of active Pt-rich shell and Pt transition-metal alloy core for use as highly active and durable electrocatalysts in oxygen reduction reactions. The ternary Pt–Au–Cu catalysts were synthesized by chemical coreduction followed by thermal treatment and chemical dealloying. During synthesis, thermal treatment formed metal particles into high-degree alloys, and chemical dealloying led to selective dissolution of soluble Cu species from the outer surface layer of the thermally treated alloy particles, resulting in Pt-based alloys@Pt-rich surface core–shell configuration. Compared with a commercial Pt/C catalyst, our Pt_1?xAu _x Cu₃/C-AT catalysts exhibited approximately 2.4-fold enhanced performance in oxygen reduction reactions. Among the catalysts employed in this work, Pt_0.97Au_0.3Cu₃/C-AT showed the highest performance in terms of mass activity, specific activity, and electrochemically active surface area loss with negligible change during 10,000 potential cycles. The synthesis details, electrochemical characteristics, oxygen reduction reaction performance, and durability of the chemically dealloyed ternary Pt–Au–Cu catalysts are presented and discussed.     

Hydrogen–Deuterium Exchange Reactions of Aromatic Compounds and Heterocycles by NaBD4‐Activated Rhodium,Platinum and Palladium Catalysts

Conventional thermal and microwave conditions were compared for hydrogen–deuterium (H/D) exchange reactions of aminobenzoic acids catalysed by NaBD₄‐activated Pd/C or RhCl₃ with D₂O as the deuterium source. We also investigated different NaBD₄‐activated metal catalysts (including Pd/C, RhCl₃ and Pt/C) under microwave conditions for an efficient H/D exchange of aromatic and heterocyclic compounds. Even higher deuterium incorporations were obtained for Pd/C and Pt/C catalyst mixtures due to the previously observed synergistic effect. Finally, we have applied these optimised conditions for one‐step syntheses of the MS standards of several pharmaceutically active compounds.     

Effects of CeO_2 preparation methods on the catalytic performance of MoO_3/CeO_2 toward sulfur-resistant methanation

CeO_2 supports were prepared by calcination or precipitation method and 5% MoO_3/CeO_2 catalysts were prepared by incipient-wetness impregnation method. The catalytic performance of the 5% MoO_3/CeO_2 catalysts toward sulfur-resistant methanation was investigated. The results showed that the Mo/Ce-1 catalysts with CeO_2 support prepared by calcination method exhibited the best sulfur-resistant methanation activity and stability with CO conversion as high as 75% while the Mo/Ce-3 catalysts the poorest. The supports and catalysts were characterized by N_2-adsorption–desorption, temperature-programmed reduction(TPR), X-ray diffraction(XRD), Raman spectroscopy(RS) and scanning electron microscope(SEM). The results indicated that the saturated monolayer loading MoO_3 on Ce-3 support was lower than 5% and there were some crystalline MoO_3 particles on the surface of the Mo/Ce-3. The preparation method of CeO_2 had a big influence on the specific surface area, the crystalline of CeO_2, and the catalytic performance of the corresponding Mo-based catalyst for sulfur-resistant methanation.     

制备方法对CuO/CeO_2-ZrO_2催化CO低温氧化活性的影响

采用微波加热分解法(一步法)和微波加热处理共沉淀+浸渍法(两步法)制备了CuO/CeO2-ZrO2催化剂,并对其进行了X射线衍射、低温氮气吸附/脱附和程序升温还原等表征,采用色谱流动法考察了催化剂的催化CO低温氧化性能.结果表明,一步法比两步法更有利于使催化剂表面CuO高度分散,CuO与CeO2-ZrO2间的相互作用更强,CuO更容易被还原,从而具有更高的催化CO氧化活性.与CeO2-ZrO2有相互作用的高分散和小颗粒CuO有利于催化剂活性的提高,与CeO2-ZrO2无相互作用的大颗粒CuO对催化剂的活性有抑制作用.     

A Universal and Facile Way for the Development of Superior Bifunctional Electrocatalysts for Oxygen Reduction and Evolution Reactions Utilizing the Synergistic Effect

Increasing energy demands have stimulated intense research activities on reversible electrochemical conversion and storage systems with high efficiency, low cost, and environmental benignity. It is highly challenging but desirable to develop efficient bifunctional catalysts for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). A universal and facile method for the development of bifunctional electrocatalysts with outstanding electrocatalytic activity for both the ORR and OER in alkaline medium is reported. A mixture of Pt/C catalyst with superior ORR activity and a perovskite oxide based catalyst with outstanding OER activity was employed in appropriate ratios, and prepared by simple ultrasonic mixing. Nanosized platinum particles with a wide range of platinum to oxide mass ratios was realized easily in this way. The as‐formed Pt/C–oxide composites showed better ORR activity than a single Pt/C catalyst and better OER activity than a single oxide to bring about much improved bifunctionality (ΔE is only ≈0.8 V for Pt/C–BSCF; BSCF=Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3?δ), due to the synergistic effect. The electronic transfer mechanism and the rate‐determining step and spillover mechanism were two possible origins of such a synergistic effect. Additionally, the phenomenon was found to be universal, although the best performance could be reached at different platinum to oxide mass ratios for different oxide catalysts. This work thus provides an innovative strategy for the development of new bifunctional electrocatalysts with wide application potentials in high‐energy and efficient electrochemical energy storage and conversion.     

Low CO content hydrogen production from oxidative steam reforming of ethanol over CuO-CeO2 catalysts at low-temperature

CuO-CeO₂ catalysts were prepared by a urea precipitation method for the oxidative steam reforming of ethanol at low-temperature. The catalytic performance was evaluated and the catalysts were characterized by inductively coupled plasma atomic emission spectroscopy, X-ray diffraction, temperature-programmed reduction, field emission scanning electron microscopy and thermo-gravimetric analysis. Over CuO-CeO₂ catalysts, H₂ with low CO content was produced in the whole tested temperature range of 250–450 °C. The non-noble metal catalyst 20CuCe showed higher H₂ production rate than 1%/oRh/CeO₂ catalyst at 300–400 °C and the advantage was more obvious after 20 h testing at 400 °C. These results further confirmed that CuO-CeO₂ catalysts may be suitable candidates for low temperature hydrogen production from ethanol.     

A new strategy to improve catalytic activity for chlorinated volatile organic compounds oxidation over cobalt oxide: Introduction of strontium carbonate

Co₃O₄–SrCO₃ catalysts with various Sr/Co ratios were synthesized by the coprecipitation method, and their properties were tuned by adjusting the Sr/Co molar ratio. Furthermore, the catalytic combustion of vinyl chloride (VC) was used to evaluate the catalytic activity of the Co₃O₄–SrCO₃ catalysts. The physicochemical properties of the catalysts were studied by X-ray diffraction (XRD), infrared spectroscopy (IR), N₂ sorption, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), H₂ temperature-programmed reduction (H₂-TPR) and VC temperature-programmed desorption (VC-TPD). The results showed that the Co₃O₄–SrCO₃ catalysts exhibited composite phases of Co₃O₄ and SrCO₃ and the presence of interactions between them. As a result, the crystallization of the Co₃O₄ phase for the Co₃O₄–SrCO₃ catalysts was restrained, and the state of Co on the catalyst surface was adjusted. Furthermore, the reducibility and VC adsorption capacity of the Co₃O₄–SrCO₃ catalysts with Sr/Co molar ratios of 0.2 and 0.4 were enhanced compared with those of the Co₃O₄ catalyst. Otherwise, catalyst SrCo-0.4 exhibited excellent catalytic performance, accompanied by the highest reaction rate and the lowest apparent activation energy. More importantly, the optimized SrCO₃–Co₃O₄ catalyst showed superior catalytic performance compared with other transition metal oxides in previous literature. These results brought a new idea for promoting the activity of transition metal catalysts for the deep oxidation of chlorinated volatile organic compounds (CVOCs) by introducing alkaline-earth metal salts.     

Solar UV Irradiances Modulate Effects of Ocean Acidification on the Coccolithophorid Emiliania huxleyi

Emiliania huxleyi, the most abundant coccolithophorid in the oceans, is naturally exposed to solar UV radiation (UVR, 280–400 nm) in addition to photosynthetically active radiation (PAR). We investigated the physiological responses of E. huxleyi to the present day and elevated CO₂ (390 vs 1000 μatm; with pH_NBS 8.20 vs 7.86) under indoor constant PAR and fluctuating solar radiation with or without UVR. Enrichment of CO₂ stimulated the production rate of particulate organic carbon (POC) under constant PAR, but led to unchanged POC production under incident fluctuating solar radiation. The production rates of particulate inorganic carbon (PIC) as well as PIC/POC ratios were reduced under the elevated CO₂, ocean acidification (OA) condition, regardless of PAR levels, and the presence of UVR. However, moderate levels of UVR increased PIC production rates and PIC/POC ratios. OA treatment interacted with UVR to influence the alga's physiological performance, leading to reduced specific growth rate in the presence of UVA (315–400 nm) and decreased quantum yield, along with enhanced nonphotochemical quenching, with addition of UVB (280–315 nm). The results clearly indicate that UV radiation needs to be invoked as a key stressor when considering the impacts of ocean acidification on E. huxleyi.     

Microwave Synthesis of Co,Ni, Cu,Zn Ferrites

Solid-phase synthesis of cobalt, nickel, copper, and zinc ferrites with spinel structure was performed from oxides of these metals and natural magnetite under the action of microwave radiation. The optimal conditions in which the corresponding ferrites can be formed were determined by varying the irradiation parameters affecting the reaction (magnetron power and reaction duration). It was found that the solid-phase interaction of oxides of Ni, Zn, Cu, Co(II) metals gives in practically acceptable yields metal-substituted ferrospinels (NiFe₂O₄, CoFe₂O₄, ZnFe₂O₄, CuFe₂O₄) constituting the main phase of the samples. A high capacity of the precursors and target synthesis products for absorption of the microwave radiation energy at a frequency of 2.45 GHz and its transformation into heat was demonstrated. This gives reason to use these compounds when preparing catalysts for microwave-stimulated reactions.     

Microwave-assisted synthesis of Pt-WC/TiO2 in ionic liquid and its application for methanol oxidation

Tungsten carbide/titanium oxide (WC/titanium dioxide (TiO₂)) particles are prepared by microwave-assisted heating in conjunction with ionic liquid and the subsequent reduction–carbonization. The platinum particles are loaded on the WC/TiO₂ to prepare Pt-WC/TiO₂. The electrocatalytic performances of the Pt-WC/TiO₂ toward methanol oxidation are evaluated by cyclic voltammetry, chronoamperometry, and the CO stripping tests. It is found that electrocatalytic activity of Pt-WC/TiO₂ is enhanced by adding ionic liquid (IL) during sample preparation. The results indicate that better performance toward methanol oxidation and higher tolerance to CO are achieved with an optimal addition of 1.5 ml 1-methyl-imidazoliumtetr-afluoroborate for preparing Pt-WC/TiO₂. To investigate the function of IL, the phase structure and morphology of samples at different stages during preparation are examined by X-ray diffraction and transmission electron microscopy. Ionic liquid is found to act as not only a good solvent offering the excellent microwave absorption, but also a structure-directing agent to control the morphology and structure of sample, which affect the activity of the final catalysts.     

High Carbon-Resistance Ni@CeO<Subscript>2</Subscript> Core–Shell Catalysts for Dry Reforming of Methane

Ni@CeO₂ core–shell catalysts were synthesized via a facile surfactant-assisted hydrothermal method and their catalytic performance in the dry reforming of methane (DRM) reaction was evaluated. A variety of techniques including XRD, N₂ adsorption–desorption, SEM, TEM, TPO, TGA were employed to characterize the prepared or spent catalysts. The encapsulation by the CeO₂ shell, on one side, can restrict the sintering and growth of Ni nanoparticles under harsh reaction conditions. On the other side, compared to the conventional shell material of SiO₂, CeO₂ can provide more lattice oxygens and vacancies, which is helpful to suppress coke deposition. Consequently, the Ni@CeO₂ core–shell catalysts exhibited better catalytic activity and stability in the DRM reaction with respect to the referenced Ni@SiO₂ core–shell catalysts and Ni/CeO₂ supported catalysts.     

Catalytic degradation of gaseous benzene by using TiO2/goethite immobilized on palygorskite: Preparation,characterization and mechanism

The nano-TiO₂/goethite/palygorskite catalysts were prepared by sol–gel method. The morphology and structure of the catalysts were analyzed by X-ray diffraction (XRD), UV–Vis reflection spectrometer, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and N₂ adsorption-desorption measurement. The results indicated that the self-made catalysts had excellent catalytic performance on gaseous benzene degradation. In the case of benzene concentration at 30 mg/m³, the degradation efficiency, over TiO₂/goethite/palygorskite composite with mass ratio of 10:5:5, reached 70.4% after 180 min 254 nm UV irradiation. The reaction mechanism and kinetics study showed that palygorskite/goethite/TiO₂ composites photocatalytic degradation benzene was mainly caused by oxidizing property of electron–holes and oxygen synergy effect.     

Hydrogen production by methanol steam reforming on a cordierite monolith reactor coated with Cu–Ni/LaZnAlO<Subscript>4</Subscript> and Cu–Ni/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

The performance of Cu–Ni/LaZnAlO₄ and Cu–Ni/γ-Al₂O₃ catalysts in the methanol reforming process in a monolith reactor in the temperature range of 200–350 °C, feed flow rate of WHSV = 20.8 h^?1 and atmospheric pressure has been investigated. In order to perform a more thorough investigation, surface area, morphology and crystalline structure of the synthetic catalysts have been studied using BET, FE-SEM, TPR, FT-IR, TEM, TGA and XRD analyses. The results have shown that Cu–Ni/LaZnAlO₄ catalyst synthesized by combustion reaction method under ultrasound irradiation has a very high efficiency and catalytic activity, low reduction temperature, high mechanical resistance and large pore sizes. The latter causes a higher percentage of active metal impregnation and better distribution on the support, greater resistance against sintering and maintenance of catalyst inertness at temperatures over 1000 °C, in comparison with conventional catalysts such as Cu–Ni/γ-Al₂O₃. This make its substitution for currently used catalysts affordable.