Mesoporous Carbon Catalyst Research Articles

Hydrodechlorination of Silicon Tetrachloride to Trichlorosilane Over Ordered Mesoporous Carbon Catalysts: Effect of Pretreatment of Oxygen and Hydrochloric Acid.

This paper reports on the catalytic reaction for the conversion of silicon tetrachloride (STC) to trichlorosilane (TCS) over pretreated ordered mesoporous carbon (OMC) catalysts by oxygen (denoted as OMC-O2) and hydrochloric acid (denoted as OMC-HCl) at 300 degrees C under N2 atmosphere. The OMC-O2 shows significantly improved the surface area (1341.2 m2/g) and pore volume (1.65 cm3/g), which results in the highest conversion rate of 7.3% as compared to bare OMC (4.3%) and OMC-HCI (5.7%). It is found that the conversion rate of STC to TCS is proportional to the number of Si-O bond over OMC catalysts, which suggests that Si-O-C bond formation is crucial to the reaction as active sites. The O2 pretreatment seems to promote the generation of oxygenated species for the formation of Si-O-C.

Acid-functionalized mesoporous carbons for the continuous production of 5-hydroxymethylfurfural

The stability of solid acid catalysts is essential in the development of sustainable biomass conversion processes. Herein, we study the activity and stability of acid-functionalized periodic mesoporous carbons (CMK-3 and CMK-5) for the continuous production of 5-hydroxymethylfurfural from fructose. The acid-functionalized mesoporous carbon catalysts show comparable selectivities and turnover frequency (TOF) to that of propylsulfonic acid functionalized SBA-15. However, the first-order deactivation rate coefficient of the carbon-based materials are up to 60 times more stable than that for the acid-functionalized SBA-15 catalyst and up to 3 times more stable than commercial Nafion SAC-13. Of the catalysts studied, phenylsulfonic acid CMK-5 showed both the highest TOF for HMF production and lowest deactivation rate coefficient.

High catalytic activity of mesoporous Co–N/C catalysts for aerobic oxidative synthesis of nitriles

We report the synthesis and assessment of novel mesoporous cobalt-coordinated nitrogen-doped carbon catalysts (meso-Co–N/C) for highly efficient synthesis of nitriles.

Direct hydroxylation of benzene to phenol using H2O2 as an oxidant over vanadium-containing nitrogen doped mesoporous carbon catalysts

The integration of highly dispersed V species and NC support with superior properties endows xV/NC-y catalysts with excellent catalytic activity.

Adsorption-enhanced hydrolysis of glucan oligomers into glucose over sulfonated three-dimensionally ordered mesoporous carbon catalysts

The hydrolysis of cellulose and β(1 → 4) oligosaccharides on carbon catalysts is a promising approach for the selective production of glucose from cellulose and its derivatives.

Size-control growth of thermally stable Au nanoparticles encapsulated within ordered mesoporous carbon framework

Simultaneously controlling the size of Au nanoparticles and immobilizing their location to specific active sites while hindering migration and sintering at elevated temperatures is a current challenge within materials chemistry. Typical methods require the use of protecting agents to control the properties of Au nanoparticles and therefore it is difficult to decouple the influence of the protecting agent and the support material. By functionalizing the internal surface area of mesoporous carbon supports with thiol groups and implementing a simple acid extraction step, we are able to design the resulting materials with precise control over the Au nanoparticle size without the need for the presence of any protecting group, whilst simultaneously confining the nanoparticles to within the internal porous network. Monodispersed Au nanoparticles in the absence of protecting agents were encapsulated into ordered mesoporous carbon at various loading levels via a coordination-assisted self-assembly approach. The X-ray diffractograms and transmission electron microscopy micrographs show that the particles have controlled and well-defined diameters between 3 and 18 nm at concentrations between 1.1 and 9.0 wt%. The Au nanoparticles are intercalated into the pore matrix to different degrees depending on the synthesis conditions and are stable after high temperature treatment at 600 °C. N2 adsorption-desorption isotherms show that the Au functionalized mesoporous carbon catalysts possess high surface areas (1269–1743 m2/g), large pore volumes (0.78–1.38 cm3/g) and interpenetrated, uniform bimodal mesopores with the primary larger mesopore lying in the range of 3.4–5.7 nm and the smaller secondary mesopore having a diameter close to 2 nm. X-ray absorption near extended spectroscopy analysis reveals changes to the electronic properties of the Au nanoparticles as a function of reduced particle size. The predominant factors that significantly determine the end Au nanoparticle size is both the thiol group concentration and subjecting the as-made materials to an additional concentrated sulfuric acid extraction step.

A MOF-derived nickel based N-doped mesoporous carbon catalyst with high catalytic activity for the reduction of nitroarenes

A Ni/m-CN nanocatalyst was prepared in a facile manner by the carbonization of Ni-MOFs, and showed excellent catalytic activity for the reduction of nitroarenes under mild conditions.

Doping effect of boron and phosphorus on nitrogen-based mesoporous carbons as electrocatalysts for oxygen reduction reaction in acid media

Doped mesoporous carbons comprising nitrogen, boron, and phosphorus (N, B, and P, respectively) were prepared as non-Pt catalysts for oxygen reduction reaction (ORR) in an acidic solution. The N-doped carbons were varied to increase their catalytic activity through by additionally doping of B and P. All the mesoporous carbons were synthesized by carbonizing polyaniline at 900 °C for the N species, while the B and P species were inserted into the carbon structure at the carbon growth step. The linear sweep voltammogram recorded in the acidic solution showed that the ORR activity of the N-doped carbon catalysts increased significantly after the addition of B. An approximately 19 % increase in the pyridinic N content at the carbon surface was observed, along with B-N-C moieties with a binding energy of 399.5 eV. The non-precious metal ORR catalysts were prepared via pyrolysis, with the insertion of an additional transition metal (iron, Fe). The deconvoluted X-ray photoelectron spectroscopy (XPS) results showed that the Fe-N peak was generated after the pyrolysis. The peak intensity of the quaternary N also increased compared with the pyridic and pyrrolic N, which indicates that Fe serves to catalyze the modification of N species. The numerical examinations showed that N- and B-doped mesoporous carbon (NBC) 1.5 % Fe had the highest limited current (4.94 mA/cm2), with the B-doped carbon still the most active mesoporous carbon catalyst for ORR. As a result, it can be said that Fe positively contributes to the formation of graphitic N, which is known to be an active site for ORR. The cyclic voltammetry results showed that the peak area of the NBC 1.5 % Fe catalyst was larger than that of the N-doped mesoporous carbon (NC) 1.5 % Fe catalyst. It was concluded that B doping enhances the ORR activity and the stability of carbon materials even after 1000 cycles under acidic conditions.

Highly stable and active Ni-doped ordered mesoporous carbon catalyst on the steam reforming of ethanol application

A novel one-step direct synthesis of nickel embedded in an ordered mesoporous carbon catalyst (NiOMC) is done in a basic medium of nonaqueous solution by a solvent evaporation-induced self-assembly process. The NiOMC sample is characterized by a variety of analytical and spectroscopy techniques, e.g., N2 adsorption/desorption isotherm measurement, X-ray diffraction (XRD), transmission electron microscopy (TEM) and temperature-programed reduction (TPR). In this study, the NiOMC catalyst is found to exhibit superior catalytic activity for the steam reforming of ethanol (SRE), showing high hydrogen selectivity and durability. Ethanol can be completely converted at 350°C over the NiOMC catalyst. Also, the durability of the NiOMC catalyst on the SRE reaction exceeds 100h at 450°C, with SH2 approaching 65% and SCO of less than 1%.

Sustainable production of acetaldehyde from lactic acid over the carbon catalysts

The synthesis of acetaldehyde from lactic acid over the carbon material catalysts was investigated. The carbon materials were characterized by scanning electron microscopy for morphologic features, by X-ray diffraction for crystal phases, by Fourier transform infrared spectroscopy for functional group structures, by N2 sorption for specific surface area and by ammonia temperature-programed desorption for acidity, respectively. Among the tested carbon catalysts, mesoporous carbon displayed the most excellent catalytic performance. By acidity analysis, the medium acidity is a crucial factor for catalytic performance: more medium acidity favored the formation of acetaldehyde from lactic acid. To verify, we compared the catalytic performance of fresh activated carbon with that of the activated carbon treated by nitric acid. Similarly, the modified activated carbon also displayed better activity due to a drastic increase of medium acidity amount. However, in contrast to fresh carbon nanotube, the treated sample displayed worse activity due to decrease of medium acidity amount. The effect of reaction temperature and time on stream on the catalytic performance was also investigated. Under the optimal reaction conditions, 100% lactic acid conversion and 91.6% acetaldehyde selectivity were achieved over the mesoporous carbon catalyst.

Effect of pyrolysis conditions on nitrogen-doped ordered mesoporous carbon electrocatalysts

Pt is the most effective and widely used electrocatalyst for the oxygen reduction reaction (ORR) in fuel cells; however, its scarcity and high cost pose a great challenge to the commercialization of the fuel cell technology. N-doped carbon materials have been regarded as one of the most promising Pt-alternative catalysts. In this work, the N-doped ordered mesoporous carbon was synthesized by the nanocasting method using SBA-15 as the template. The effect of the pyrolysis conditions (pyrolysis temperature, pyrolysis duration, and ramp rate) on this material was investigated. N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy, and Raman spectroscopy were used to investigate the intrinsic properties of the resultant materials. Cyclic voltammetry and rotating ring-disk electrode were used to investigate the electrochemical behavior for ORR in an alkaline medium. It was found that the resultant mesoporous carbon materials exhibit high electrical conductivity, high specific surface area, and unique pore structure. The pyrolysis temperature was the most important parameter in determining the thermodecomposition of the carbon precursor, and the microstructure, elemental composition, and chemical configuration of the resultant mesoporous carbon materials. To achieve reasonable electrocatalytic activity and selectivity, a high pyrolysis temperature above 800 °C is required for effective N doping to form active sites and for graphitization to facilitate charge transfer, whereas the pyrolysis duration and ramp rate have a much less significant effect. This indicates that both the surface composition/structure and consequent electrochemical properties are more dependent on the thermodynamics than the kinetics during the pyrolysis process. Finally, the optimal N-doped ordered mesoporous carbon catalyst showed superior electrochemical activity for ORR than the commercial Pt catalyst and is promising for fuel cell and metal–air battery applications.

PH Effect on Electrochemistry of Nitrogen-Doped Carbon Catalyst for Oxygen Reduction Reaction

In this work, the effect of pH on a nitrogen-doped ordered mesoporous carbon catalyst for the oxygen reduction reaction (ORR) is extensively investigated. Electrochemical methods, including cyclic voltammetry (CV), rotating ring-disk electrode (RRDE), and cathodic stripping voltammetry, are applied to investigate the electrochemical behavior in electrolyte solutions of different pHs (0–2, 7, 12–14). The CV result reveals that nitrogen-doped carbon has a variety of enriched reversible redox couples on the surface, and the pH has a significant effect. Whether these redox couples are electrochemically active or inactive to the ORR depends on the electrolyte used. In acid media, an oxygen molecule directly interacts with the redox couple, and its reduction proceeds by the surface-confined redox-mediation mechanism, yielding water as the product. Similarly, the first electron transfer in alkaline media is achieved by the surface-confined redox-mediation mechanism at the higher potentials. With decreasing poten...

Ordered Mesoporous Porphyrinic Carbons for Oxygen Reduction Reaction: Pt-like Activity in Acidic Media and Active Site

The high cost of polymer electrolyte fuel cell (PEFC) systems, predominantly dictated by the platinum-based cathode catalysts for the oxygen reduction reaction (ORR), has critically impeded the widespread application of PEFCs. Therefore, the quest for low-cost yet high-performance non-precious metal catalysts has been of prime importance in recent years. We present a new class of self-supported, transition metal-doped ordered mesoporous porphyrinic carbon (M-OMPC; M=transition metal) catalysts, which were prepared by nanocasting mesoporous silica templates with metalloporphyrin precursors [1]. The preparation of M-OMPC catalysts is simple, tunable, scalable, and highly reproducible. Among the M-OMPC catalysts, FeCo-OMPC exhibits a very high ORR activity in an acidic medium, which is one of the best performances among the non-precious M/N/C catalysts, and outperformed the carbon-supported commercial Pt/C catalyst. Furthermore, the FeCo-OMPC showed superior long-term durability in ORR, compared to Pt/C; after cycling 10,000 times under O2 bubbling, the FeCo-OMPC exhibited 6-fold higher ORR activity than the Pt/C. The weakening of the interaction between oxygen atom and the FeCo-OMPC compared to Pt/C as well as high surface area of the former could be responsible for its significantly high ORR activity. We also systematically investigated the potential active sites for the ORR in the FeCo-OMPC catalysts, and could correlate the local coordination structure around metal centers and corresponding ORR activities [2]. The M-OMPC catalysts could suggest a new concept for future design of non-precious metal-based high-performing ORR catalysts. [1] J. Y. Cheon, T. Kim, Y. Choi, H. Y. Jeong, M. G. Kim, Y. J. Sa, J. Kim, Z. Lee, T.-H. Yang, K. Kwon, O. Terasaki, G.-G. Park, R. R. Adzic, S. H. Joo, Scientific Reports 3, 2715 (2013). [2] J. Y. Cheon, M. G. Kim, G.-G. Park, S. H. Joo, manuscript in preparation.

Metal-Free and Solvent-Free Oxidative Coupling of Amines to Imines with Mesoporous Carbon from Macrocyclic Compounds

A new series of carbon-based heterogeneous catalysts aiming at the oxidative coupling of amines to imines is disclosed here, which are easily synthesized by pyrolysis of macrocyclic compounds, including phthalocyanine and porphyrin under different temperatures. Silica colloid or ordered mesoporous silica SBA-15 is employed as the hard template to fulfill the mesoporous structures. The most active catalyst fabricated from phthalocyanine and silica colloid shows remarkable catalytic activity, excellent selectivity, and robust stability toward the imine formation in the presence of molecular oxygen under neat conditions. Kinetic analysis demonstrates that the apparent activation for benzylamine oxidation is 47.6 kJ mol–1 and that cationic species are involved in the reaction. The unprecedented performance of mesoporous carbon catalysts can be attributed to their high surface area, profitable pore volume, as well as homogeneous distribution of defect sites.

Synthesis–structure–performance correlation for poly-aniline–Me–C non-precious metal cathode based on mesoporous carbon catalysts for oxygen reduction reaction in low temperature fuel cells

In this work, attempt is made to development of active non-precious metal catalysts (NPMCs) for the oxygen reduction reaction in polymer electrolyte fuel cells (PEFCs) based on the heat treatment of poly-aniline/transition metal/carbon precursors. All the materials have been characterized by X-ray diffraction (XRD) small and wide angle, N2 adsorption–desorption isotherms, high-resolution transmission electron microscopy (TEM), Scanning electron microscope (SEM) and X-ray photo-electron spectroscopy (XPS). Moreover for electrochemical evaluation of samples, Rotating Disk electrode (RDE) technique and Fuel Cell test were employed. The results showed that onset potential for the optimized sample is about 0.1 v less than the commercial catalyst whereas exchange current density of the optimized sample (at 0.2 V vs. Reversible Hydrogen Electrode (RHE)) is about 15 mA cm−2 more than platinum electro-catalyst. Finally, the polarization curves for the fabricated membrane electrode assembly (MEAs) with overall catalyst loading of 2 mg cm−2 demonstrated that the optimized catalyst shows suitable performance compared with E-tek commercial platinum sample.

An ultra high performance multi-element doped mesoporous carbon catalyst derived from poly(4-vinylpyridine)

An ordered mesoporous carbon catalyst derived from iron-complexed poly(4-vinylpyridine), with a much higher ORR performance than a commercial Pt/C catalyst.

High activity ordered mesoporous carbon-based solid acid catalyst for the esterification of free fatty acids

Sulfonated mesoporous carbon catalysts were synthesized using a carbonization–sulfonation method and employed to the pre-esterification of free fatty acids contained in high acid value oil. Various synthesis parameters, such as composition of carbon precursor, carbonization and sulfonation temperature, were systematically investigated. The catalysts were characterized by N2 adsorption, small angle XRD, HRTEM, FT-IR and strong acid density analysis. The results indicated that they have a high surface area, uniform pore size, large mesopore volume, high acid density and good catalytic activity. Among them, MC600-S160 exhibited a highest activity and good stability for the esterification of FFA with methanol, the FFA conversion reached 94.6% after reaction for 3h.

Direct hydroxylation of benzene to phenol using H2O2 as an oxidant over vanadium-containing mesoporous carbon catalysts

A series of vanadium-containing mesoporous carbon catalysts were synthesized by the co-assembly method using phenolic resol, vanadyl acetylacetonate [VO(acac)2], and Pluronic F127 as carbon source, metal source, and template, respectively. The effects of the calcination temperature on the transformation of vanadium species and the carbon framework were investigated. During the calcination treatment, the nanoparticles of vanadium species mainly confined in the carbon matrix were formed along with the further cross-linking and carbonization of the phenolic resol network. The obtained catalysts exhibited the two-dimensional hexagonal mesostructures, high surface areas, and uniform pore sizes. Their catalytic activity in the benzene hydroxylation reaction was tested and the 0.2-V-C-600 catalyst showed the high performance with the benzene conversion of 31.8% and phenol selectivity of 94.9% as well as the good stability in recycles.

A facile method to synthesis a mesoporous carbon supported methanol catalyst containing well dispersed Cu/ZnO

Alumina supported CuO/ZnO is the commercial catalyst for methanol synthesis from syngas. Though so far, this catalyst has been regarded as the dominant catalyst for methanol synthesis. The catalyst is still facing some fundamental challenges such as the dispersion of active center CuO/ZnO. Meanwhile, to prepare this catalyst, large amount of nitrate precursor was used and produced lots of environmentally harmful wastewater. In the current work, a bimodal carbon channel-confined CuO/ZnO supported on mesoporous carbon catalyst was synthesized by using a simple impregnation method followed by ammonia hydrolysis and pyrolysis. The results demonstrated that the method we developed was an effective way to control the dispersion of metal oxides particles.

Effect of sulfuric acid on textural properties and catalytic performance of ruthenium-containing ordered mesoporous carbon prepared via a direct RuCl3/SBA-15 hard templated method.

Ruthenium-containing ordered mesoporous carbon (Ru-OMC) catalysts with highly dispersed Ru nanoparticles semi-embedded in carbon framework were prepared via a direct RuCl3/SBA-15 hard templated method. The effect of sulfuric acid on the texture structure and catalytic performance of Ru-OMC were studied. The status of Ru nanoparticles and mesoporous structure of Ru-OMC catalysts were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), nitrogen sorption, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and CO chemisorption techniques. The addition of appropriate amount of sulfuric acid is necessary to improve the ordered mesoporous structure of Ru-OMC catalysts. The framework of carbon structure shrinks with the increase in sulfur acid contents, which is proved by a slight decrease in surface area and increase in pore diameters for Ru-OMC with different sulfur contents. The turnover frequency (TOF) for Ru-OMC reaches the highest up to 3.98 s(-1) in benzene hydrogenation with optimized sulfur acid content of 0.08 mmol/g sucrose.