Carbon-containing Catalysts Research Articles

Oxidation of Diphenylacetylene in the Presence of Heterogeneous Carbon-Containing Catalysts Based on Palladium, Graphene, and Graphene Oxide

Oxidation of Diphenylacetylene in the Presence of Heterogeneous Carbon-Containing Catalysts Based on Palladium, Graphene, and Graphene Oxide

Design of assembled composite of Mn3O4@Graphitic carbon porous nano-dandelions: A catalyst for Low–temperature selective catalytic reduction of NOx with remarkable SO2 resistance

The biggest challenge for selective catalytic reduction (SCR) of NO by NH3 at low temperatures is to develop robust catalysts with high resistance to SO2. Mn-based catalysts have attracted great attention for their excellent activity, but the poor SO2 resistance limits their application. Herein, we report a novel assembled composite featuring Mn3O4 nanoparticles embedded in defect-abundant graphitic carbon frame (Mn3O4@G-A) via a confinement–pyrolysis–oxidation strategy derived from MOF. The Mn3O4@G-A exhibits excellent activity (reaching over 90 % NO conversion in 100, 000 h−1 GHSV at 160 °C) and significantly improved SO2 resistance in comparison to pristine Mn3O4, and all the performance tests were conducted with 5.6 vol.% water vapor. By combining synchrotron radiation-based X-ray absorption spectroscopy and density functional theory calculation, we further discovered the positive role and the origin of graphitic carbon for improving SO2 resistance. Over the Mn3O4@G-A sample, the electrons can be transferred from graphitic carbon to Mn3O4 nanoparticles, which can regulate the electronic properties and oxidizing ability of Mn3O4 nanoparticles. The proper oxidizing ability of Mn3O4@G-A can inhibit the oxidation of SO2 to SO3, thus further avoid the formation of NH4HSO4 and improve the SO2 resistance. Our work here not only solves the current problem of poor SO2 resistance of Mn-based catalysts, but also provides new insights into the design and synthesis of MOF-derived graphitic carbon-containing catalysts for SCR applications.

On the Role of the Support in Pt Anode Catalyst Degradation under Simulated H2 Fuel Starvation Conditions

In order to learn more about the effect of H2 fuel starvation on the degradation of Pt anode catalysts and in particular on the role of the support therein, we have investigated the impact of a simulated fuel starvation procedure on three different polymer electrolyte fuel cell anode catalysts, Pt/C, Pt/TiO2 and Pt/TiO2+C, by differential electrochemical mass spectrometry (DEMS) measurements. Monitoring the potential as well as the mass spectrometric signal transients of the possible reaction products CO2 (carbon oxidation reaction – COR) and O2 (oxygen evolution reaction – OER) upon switching from H2-saturated to N2-saturated electrolyte under galvanostatic oxidation conditions, we find a rapid increase of the potential to values at about 1.75 V upon electrolyte exchange, together with the onset of CO2 formation and O2 evolution, where the latter dominates at high potentials. The ratio of O2 evolution and carbon support oxidation differs significantly for different catalyst supports, with the COR contributing more for the carbon-containing catalysts in the initial stage of the fuel starvation period, and the OER prevailing for the Pt/TiO2 catalyst over the whole starvation time. The complex interplay between different catalyst degradation processes during fuel starvation is discussed.

Carbon-containing catalysts for the hydroprocessing of oil fractions: A review

Over the last 20 years, carbon-containing catalysts prepared using carbonized aluminum oxide and various carbon-based materials as carriers, along with metal carbides as active components, have been widely studied in the hydroprocessing of oil fractions. In this work, the properties of different groups of carbon-containing catalysts are discussed. The difficulties of using carbon-based carriers caused by their need for chemical pretreatment (oxidation and leaching), and the application of water–organic infiltrating solutions to form active catalyst components in finely dispersed form, is shown.

Carbon-Containing Catalysts for Hydrotreatment of Oil Fractions: Review

In the last two decades, intensive studies on hydrotreatment of oil fractions were focused on carbon-containing catalysts prepared with carbonized alumina, carbon materials as the supports and metal carbides as active components. In the Review, properties of various carboncontaining catalysts are discussed, peculiar applications of carbon supports demonstrated that result from their necessary chemical pretreatment (oxidation, leaching) and the use of aqueous organic solvents for impregnation to produce disperse active components of the catalysts.

Intrinsically Conductive Perovskite Oxides with Enhanced Stability and Electrocatalytic Activity for Oxygen Reduction Reactions

The oxygen reduction reaction (ORR) is traditionally catalyzed by carbon-supported precious metals, heteroatom-doped carbons, and transition-metal–carbon hybrids. Despite their good electric conductivity and high catalytic activities, these carbon-containing catalysts suffer from electrochemical carbon corrosion which limits their utility in metal–air batteries and fuel cells. Here, we report a class of perovskite La0.5Sr0.5Mn1–xNixO3−δ nanocrystals that are intrinsically conductive with good electrocatalytic activity for the ORR. Among these perovskites, La0.5Sr0.5Mn0.9Ni0.1O3−δ (δ = 0.06, LSMN) exhibited the highest electrocatalytic activity for ORR with an onset potential of 1.02 V, a half-wave potential of 0.80 V, and a Tafel slope of −68 mV decade–1 in 0.1 M potassium hydroxide aqueous solution. Negligible degradation of oxygen reduction currents was observed after 300 cyclic voltammetry scans from 1.08 to 0.15 V. We demonstrated that the electrically conductive perovskites with transition-metal redo...

Preparation of Glyphosate from Catalytic Oxidation N-Phosphonomethyl Iminodiacetic Acid

The activated carbon-containing catalysts (Pd/C and Pt/C) have been prepared by surface modification of the activated carbon with palladium chloride and chloroplatinic acid solution, respectively. The Pt/C catalyst is characterized by XRD pattern. The glyphosate is prepared from catalytic oxidation N-phosphonomethyl iminodiacetic acid. Effect of different catalysts and amount of the catalyst in catalytic oxidation are investigated. Compared with Pt/C catalyst, Pd/C catalyst is more active. Optimum amount of Pd/C catalyst is 45 mol/m3 PMIDA.

Research Nanostructurized Carbon-Containing Catalysts on the тonkeris Clay Base by Physico-Chemical Methods

In this work are presented research results of physical and chemical characteristics of carbon-containing catalysts on Tonkeris clay base. A magnetic property of these catalysts was studied. It was established that the structure of the catalysts are contains а nano-sized carbon particles in a different morphology. Gydrocracking processes were investigated on the bases synthesized catalysts.

Beneficial Effect of Carbon on Hydrotreating Catalysts

The role of carbonaceous species on the activity of hydrotreating catalysts has been controversial for a long time. On one hand, carbon deposit is known to be one cause of catalyst deactivation, and on the other, the presence of organic thiocompounds (DMDS, tertiononyl-pentasulfide, etc.) or gas–oil during the sulfidation is recognized to provide an activity enhancement. In this work, we attempted to investigate the effect of carbon on the HDS properties of an industrial CoMo catalyst. For this purpose two carbon-containing catalysts were compared to a carbon-free catalyst. Carbon introduction was performed either by impregnating the oxide precursor with a C20 gas oil cut and subsequent drying, or by contacting the precursor with a solution of a commercial coleseed oil and further coking. After activation by H 2/H 2S, the catalytic properties of the catalysts were evaluated in thiophene conversion and real feedstock desulfurization. In both cases, and for the two preparations, a positive effect of C was observed. Several characterizations were performed (TEM, XPS, TPO, BET-BJH, EXAFS) in order to determine the role of carbon, starting from several assumptions. From these results, it was concluded that at least one identifiable beneficial effect of carbon is a geometrical one. However, structural effects may not be excluded.

Visible light photodegradation of 4-chlorophenol with a coke-containing titanium dioxide photocatalyst

Photocatalysts based on titanium dioxide have been prepared by a modified sol–gel process using different alkoxide precursors. Depending on the precursor and the calcination temperature of the gels, carbon-containing catalysts with large surface areas, capable to photodegrade p-chlorophenol (4CP) with visible light (λ>400nm), have been obtained. Photodegradation and mineralisation were confirmed by HPLC and TOC measurements. The catalysts were characterised by physisorption of argon, elemental analysis, EPR, UV/VIS, X-ray powder diffraction (XRD), FT-IR and high-resolution transmission electron microscopy (HRTEM). A highly condensed, carbonaceous species formed during calcination is responsible for the photosensitisation. When used as a photoelectrode, the appearance of a photocurrent indicated the semiconductor nature of these novel materials. The catalysts exhibit a surprisingly good long-time stability despite of the carbonaceous nature of the sensitising species. It is also shown, that commercially available TiO2 can be photosensitised by impregnation with suitable alcohols followed by pyrolysis.