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Catalysts, Volume 6, Issue 7 (July 2016)

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Editorial

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Open AccessEditorial Surface Chemistry and Catalysis
Catalysts 2016, 6(7), 102; doi:10.3390/catal6070102
Received: 11 July 2016 / Revised: 12 July 2016 / Accepted: 12 July 2016 / Published: 15 July 2016
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Abstract
Nowadays, heterogeneous catalysis plays a prominent role.[...] Full article
(This article belongs to the Special Issue Surface Chemistry and Catalysis) Printed Edition available

Research

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Open AccessArticle A Novel Approach for Prediction of Industrial Catalyst Deactivation Using Soft Sensor Modeling
Catalysts 2016, 6(7), 93; doi:10.3390/catal6070093
Received: 13 January 2016 / Revised: 18 May 2016 / Accepted: 26 May 2016 / Published: 23 June 2016
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Abstract
Soft sensors are used for fault detection and prediction of the process variables in chemical processing units, for which the online measurement is difficult. The present study addresses soft sensor design and identification for deactivation of zeolite catalyst in an industrial-scale fixed bed
[...] Read more.
Soft sensors are used for fault detection and prediction of the process variables in chemical processing units, for which the online measurement is difficult. The present study addresses soft sensor design and identification for deactivation of zeolite catalyst in an industrial-scale fixed bed reactor based on the process data. The two main reactions are disproportionation (DP) and transalkylation (TA), which change toluene and C9 aromatics into xylenes and benzene. Two models are considered based on the mass conservation around the reactor. The model parameters are estimated by data-based modeling (DBM) philosophy and state dependent parameter (SDP) method. In the SDP method, the parameters are assumed to be a function of the system states. The results show that the catalyst activity during the period under study has approximately a monotonic trend. Identification of the system clearly shows that the xylene concentration has a determining role in the conversion of reactions. The activation energies for both DP and TA reactions are found to be 43.8 and 18 kJ/mol, respectively. The model prediction is in good agreement with the observed industrial data. Full article
Open AccessCommunication Brønsted Acid-Catalyzed Direct Substitution of 2-Ethoxytetrahydrofuran with Trifluoroborate Salts
Catalysts 2016, 6(7), 94; doi:10.3390/catal6070094
Received: 29 April 2016 / Revised: 9 June 2016 / Accepted: 10 June 2016 / Published: 25 June 2016
Cited by 1 | PDF Full-text (887 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Metal-free transformations of organotrifluoroborates are advantageous since they avoid the use of frequently expensive and sensitive transition metals. Lewis acid-catalyzed reactions involving potassium trifluoroborate salts have emerged as an alternative to metal-catalyzed protocols. However, the drawbacks to these methods are that they rely
[...] Read more.
Metal-free transformations of organotrifluoroborates are advantageous since they avoid the use of frequently expensive and sensitive transition metals. Lewis acid-catalyzed reactions involving potassium trifluoroborate salts have emerged as an alternative to metal-catalyzed protocols. However, the drawbacks to these methods are that they rely on the generation of unstable boron dihalide species, thereby resulting in low functional group tolerance. Recently, we discovered that in the presence of a Brønsted acid, trifluoroborate salts react rapidly with in situ generated oxocarbenium ions. Here, we report Brønsted acid-catalyzed direct substitution of 2-ethoxytetrahydrofuran using potassium trifluoroborate salts. The reaction occurs when tetrafluoroboric acid is used as a catalyst to afford functionalized furans in moderate to excellent yields. A variety of alkenyl- and alkynyltrifluoroborate salts readily participate in this transformation. Full article
(This article belongs to the Special Issue Metal-free Organocatalysis)
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Open AccessArticle The Performance of Electron-Mediator Modified Activated Carbon as Anode for Direct Glucose Alkaline Fuel Cell
Catalysts 2016, 6(7), 95; doi:10.3390/catal6070095
Received: 24 May 2016 / Revised: 19 June 2016 / Accepted: 23 June 2016 / Published: 28 June 2016
Cited by 1 | PDF Full-text (3092 KB) | HTML Full-text | XML Full-text
Abstract
Six different electron mediators were immobilized on the activated carbon (AC) anode and their effects on performance of a direct glucose alkaline fuel cell were explored. 2-hydroxy-1, 4-naphthoquinone (NQ), methyl viologen (MV), neutral red (NR), methylene blue (MB), 1, 5-dichloroanthraquinone (DA) and anthraquinone
[...] Read more.
Six different electron mediators were immobilized on the activated carbon (AC) anode and their effects on performance of a direct glucose alkaline fuel cell were explored. 2-hydroxy-1, 4-naphthoquinone (NQ), methyl viologen (MV), neutral red (NR), methylene blue (MB), 1, 5-dichloroanthraquinone (DA) and anthraquinone (AQ) were doped in activated carbon (AC), respectively, and pressed on nickel foam to fabricate the anodes. NQ shows comparable performance with MV, but with much lower cost and environmental impact. With NQ-AC anode, the fuel cell attained a peak power density of 16.10 Wm−2, peak current density of 48.09 Am−2, and open circuit voltage of 0.76 V under the condition of 1 M glucose, 3 M KOH, and ambient temperature. Polarization curve, EIS and Tafel measurements were also conducted to explore the mechanism of performance enhancement. The high performance is likely due to the enhanced charge transfer and more reactive sites provided on the anode. Full article
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Open AccessArticle Preparation of PdCu Alloy Nanocatalysts for Nitrate Hydrogenation and Carbon Monoxide Oxidation
Catalysts 2016, 6(7), 96; doi:10.3390/catal6070096
Received: 4 April 2016 / Revised: 2 June 2016 / Accepted: 24 June 2016 / Published: 30 June 2016
Cited by 3 | PDF Full-text (4632 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Alloying Pd with Cu is important for catalytic reactions such as denitrification reaction and CO oxidation reaction, but understanding of the catalyst preparation and its correlation with the catalyst’s activity and selectivity remains elusive. Herein, we report the results of investigations of the
[...] Read more.
Alloying Pd with Cu is important for catalytic reactions such as denitrification reaction and CO oxidation reaction, but understanding of the catalyst preparation and its correlation with the catalyst’s activity and selectivity remains elusive. Herein, we report the results of investigations of the preparation of PdCu alloy nanocatalysts using different methods and the catalytic properties of the catalysts in catalytic denitrification reaction and CO oxidation reaction. PdCu alloy nanocatalysts were prepared by conventional dry impregnation method and ligand-capping based wet chemical synthesis method, and subsequent thermochemical activation as well. The alloying characteristics depend on the bimetallic composition. PdCu/Al2O3 with a Pd/Cu ratio of 50:50 was shown to exhibit an optimized hydrogenation activity for the catalytic denitrification reaction. The catalytic activity of the PdCu catalysts was shown to be highly dependent on the support, as evidenced by the observation of an enhanced catalytic activity for CO oxidation reaction using TiO2 and CeO2 supports with high oxygen storage capacity. Implications of the results to the refinement of the preparation of the alloy nanocatalysts are also discussed. Full article
(This article belongs to the Special Issue Rational Synthesis of Supported Bimetallic Catalysts)
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Open AccessFeature PaperArticle Influence of Cobalt Precursor on Efficient Production of Commercial Fuels over FTS Co/SiC Catalyst
Catalysts 2016, 6(7), 98; doi:10.3390/catal6070098
Received: 30 November 2015 / Revised: 6 June 2016 / Accepted: 28 June 2016 / Published: 7 July 2016
Cited by 3 | PDF Full-text (5642 KB) | HTML Full-text | XML Full-text
Abstract
β-SiC-supported cobalt catalysts have been prepared from nitrate, acetate, chloride and citrate salts to study the dependence of Fischer–Tropsch synthesis (FTS) on the type of precursor. Com/SiC catalysts were synthetized by vacuum-assisted impregnation while N2 adsorption/desorption, XRD, TEM, TPR, O
[...] Read more.
β-SiC-supported cobalt catalysts have been prepared from nitrate, acetate, chloride and citrate salts to study the dependence of Fischer–Tropsch synthesis (FTS) on the type of precursor. Com/SiC catalysts were synthetized by vacuum-assisted impregnation while N2 adsorption/desorption, XRD, TEM, TPR, O2 pulses and acid/base titrations were used as characterization techniques. FTS catalytic performance was carried out at 220 °C and 250 °C while keeping constant the pressure (20 bar), space velocity (6000 Ncm3/g·h) and syngas composition (H2/CO:2). The nature of cobalt precursor was found to influence basic behavior, extent of reduction and metallic particle size. For β-SiC-supported catalysts, the use of cobalt nitrate resulted in big Co crystallites, an enhanced degree of reduction and higher basicity compared to acetate, chloride and citrate-based catalysts. Consequently, cobalt nitrate provided a better activity and selectivity to C5+ (less than 10% methane was formed), which was centered in kerosene-diesel fraction (α = 0.90). On the contrary, catalyst from cobalt citrate, characterized by the highest viscosity and acidity values, presented a highly dispersed distribution of Co nanoparticles leading to a lower reducibility. Therefore, a lower FTS activity was obtained and chain growth probability was shortened as observed from methane and gasoline-kerosene (α = 0.76) production when using cobalt citrate. Full article
(This article belongs to the Special Issue Surface Chemistry and Catalysis) Printed Edition available
Open AccessFeature PaperArticle Gold Catalysts on Y-Doped Ceria Supports for Complete Benzene Oxidation
Catalysts 2016, 6(7), 99; doi:10.3390/catal6070099
Received: 14 May 2016 / Revised: 28 June 2016 / Accepted: 1 July 2016 / Published: 8 July 2016
Cited by 1 | PDF Full-text (2911 KB) | HTML Full-text | XML Full-text
Abstract
Gold (3 wt. %) catalysts on Y-doped (1, 2.5, 5 and 7.5 wt. % Y2O3) ceria supports prepared by coprecipitation (CP) or impregnation (IM) were studied in complete benzene oxidation (CBO). A low-extent Y modification was chosen to avoid
[...] Read more.
Gold (3 wt. %) catalysts on Y-doped (1, 2.5, 5 and 7.5 wt. % Y2O3) ceria supports prepared by coprecipitation (CP) or impregnation (IM) were studied in complete benzene oxidation (CBO). A low-extent Y modification was chosen to avoid ordering of oxygen vacancies. The samples were characterized by XRD, TGA, XPS and TPR techniques. A positive role of air pretreatment at 350 °C as compared to 200 °C was established for all Y-containing catalysts and it was explained by cleaning the active sites from carbonates. The oxygen supply cannot be considered as a limiting step for benzene oxidation except for the high 7.5%-doped samples, as suggested by TGA and TPR data. On the basis of XPS results of fresh and used in CBO catalysts, the presence of cationic gold species does not seem important for high CBO activity. The gold catalyst on an IM support with 1% Y-doping exhibited the best performance. A 100% benzene conversion was achieved only over this catalyst and Au/ceria, while it was not reached even at 300 °C over all other studied catalysts. Gold and ceria particle agglomeration or coke formation should be excluded as a possible reason, and the most probable explanation could be associated with the importance of the benzene activation stage. Full article
(This article belongs to the collection Gold Catalysts)
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Open AccessArticle Regenerable Subnanometer Pd Clusters on Zirconia for Highly Selective Hydrogenation of Biomass-Derived Succinic Acid in Water
Catalysts 2016, 6(7), 100; doi:10.3390/catal6070100
Received: 8 June 2016 / Revised: 1 July 2016 / Accepted: 4 July 2016 / Published: 7 July 2016
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Abstract
The size of metal particles is an important factor to determine the performance of the supported metal catalysts. In this work, we report subnanometer Pd clusters supported on zirconia by the microwave-assisted hydrothermal method. The presence of subnanometer Pd clusters on the zirconia
[...] Read more.
The size of metal particles is an important factor to determine the performance of the supported metal catalysts. In this work, we report subnanometer Pd clusters supported on zirconia by the microwave-assisted hydrothermal method. The presence of subnanometer Pd clusters on the zirconia surface was confirmed by two-dimensional Gaussian-function fits of the aberration-corrected high-angle annual dark-field images. These subnanometer Pd catalysts exhibit high catalytic performance for the hydrogenation of biomass-derived succinic acid to γ-butyrolactone in water and avoid the formation of overhydrogenated products, such as 1,4-butanediol and tetrahydrofuran. The catalyst with an ultra-low Pd loading of 0.2 wt. % demonstrated high selectivity (95%) for γ-butyrolactone using water as a solvent at 473 K and 10 MPa. Moreover, it can be reused at least six times without the loss of catalytic activity, illustrating high performance of the small Pd clusters. Full article
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Open AccessArticle Base-Free Selective Oxidation of Glycerol over LDH Hosted Transition Metal Complexes Using 3% H2O2 as Oxidant
Catalysts 2016, 6(7), 101; doi:10.3390/catal6070101
Received: 9 June 2016 / Revised: 8 July 2016 / Accepted: 12 July 2016 / Published: 15 July 2016
Cited by 2 | PDF Full-text (2155 KB) | HTML Full-text | XML Full-text
Abstract
A series of transition metal sulphonato-Schiff base complexes were intercalated into Mg–Al layered-double hydroxides (LDHs). The obtained catalysts were characterized by FTIR, XRD, N2 sorption, SEM and elemental analysis, and then were used in the selective oxidation of glycerol (GLY) using 3%
[...] Read more.
A series of transition metal sulphonato-Schiff base complexes were intercalated into Mg–Al layered-double hydroxides (LDHs). The obtained catalysts were characterized by FTIR, XRD, N2 sorption, SEM and elemental analysis, and then were used in the selective oxidation of glycerol (GLY) using 3% H2O2 as an oxidant. It was found that their catalytic performances were closely related to the loading of active complexes, the Schiff base ligands and the metal centers of the catalysts, as well as the reaction conditions. The optimal conversion of GLY was 85.0%, while the selectivity of 1,3-dihydroxyacetone (DHA) was 56.5%. Moreover, the catalysts could be reused at least 10 times. Full article
(This article belongs to the Special Issue Organometallic Catalysis for Organic Synthesis)
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Open AccessArticle Hydrothermal Method Using DMF as a Reducing Agent for the Fabrication of PdAg Nanochain Catalysts towards Ethanol Electrooxidation
Catalysts 2016, 6(7), 103; doi:10.3390/catal6070103
Received: 21 June 2016 / Revised: 5 July 2016 / Accepted: 12 July 2016 / Published: 15 July 2016
Cited by 3 | PDF Full-text (2100 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this article, we developed a facile one-step hydrothermal method using dimethyl formamide (DMF) as a reducing agent for the fabrication of PdAg catalyst. The scanning electron microscope (SEM) and transmission electron microscopy (TEM) images have shown that the as-synthesized PdAg catalyst had
[...] Read more.
In this article, we developed a facile one-step hydrothermal method using dimethyl formamide (DMF) as a reducing agent for the fabrication of PdAg catalyst. The scanning electron microscope (SEM) and transmission electron microscopy (TEM) images have shown that the as-synthesized PdAg catalyst had a nanochain structure. The energy-dispersive X-ray analyzer (EDX) spectrum presented the actual molar ratio of Pd and Ag in the PdAg alloy. Traditional electrochemical measurements, such as cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectrometry (EIS), were performed using a CHI 760D electrochemical analyzer to characterize the electrochemical properties of the as-synthesized catalyst. The results have shown that the PdAg catalyst with a nanochain structure displays higher catalytic activity and stability than pure Pd and commercial Pd/C catalysts. Full article
(This article belongs to the Special Issue Catalysis for Low Temperature Fuel Cells)
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Open AccessFeature PaperArticle Zr-Based MOF-808 as Meerwein–Ponndorf–Verley Reduction Catalyst for Challenging Carbonyl Compounds
Catalysts 2016, 6(7), 104; doi:10.3390/catal6070104
Received: 13 June 2016 / Revised: 6 July 2016 / Accepted: 13 July 2016 / Published: 19 July 2016
Cited by 4 | PDF Full-text (2763 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In the fine chemical industry, transfer hydrogenation of carbonyl compounds is an important route to selectively form the corresponding allyl alcohol. The Meerwein–Ponndorf–Verley reduction (MPV) is catalyzed by a Lewis acid catalyst and easily oxidizable alcohols serve as hydrogen donor. We successfully used
[...] Read more.
In the fine chemical industry, transfer hydrogenation of carbonyl compounds is an important route to selectively form the corresponding allyl alcohol. The Meerwein–Ponndorf–Verley reduction (MPV) is catalyzed by a Lewis acid catalyst and easily oxidizable alcohols serve as hydrogen donor. We successfully used the Zr-based metal-organic framework (MOF) MOF-808-P as MPV-catalyst with isopropyl alcohol as solvent and hydride donor. After only 2 h, 99% yield of cinnamyl alcohol was obtained. The highly active MOF-808-P is also a good catalyst for the selective reduction of more challenging substrates such as R-carvone and β-ionone. Two strategies were successfully used to shift the equilibrium towards the desired allylic alcohol products: (1) evaporation of formed acetone and (2) the use of the more strongly reducing 1-indanol. Carveol yield was increased to >70%. These results highlight the great potential of this recently discovered Zr-MOF as a chemically and thermally stable catalyst. Full article
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Open AccessArticle Enhancement of Degradation and Dechlorination of Trichloroethylene via Supporting Palladium/Iron Bimetallic Nanoparticles onto Mesoporous Silica
Catalysts 2016, 6(7), 105; doi:10.3390/catal6070105
Received: 15 March 2016 / Revised: 9 June 2016 / Accepted: 24 June 2016 / Published: 19 July 2016
Cited by 1 | PDF Full-text (19639 KB) | HTML Full-text | XML Full-text
Abstract
This study is aimed to prevent the agglomeration of Pd/Fe bimetallic nanoparticles and thus improve the efficiency toward degradation and dechlorination of chlorinated organic contaminants. A mesoporous silica with a primary pore diameter of 8.3 nm and a specific surface area of 688
[...] Read more.
This study is aimed to prevent the agglomeration of Pd/Fe bimetallic nanoparticles and thus improve the efficiency toward degradation and dechlorination of chlorinated organic contaminants. A mesoporous silica with a primary pore diameter of 8.3 nm and a specific surface area of 688 m2/g was prepared and used as the host of Pd/Fe nanoparticles. The Pd/Fe nanoparticles were deposited onto or into the mesoporous silica by reduction of ferrous ion and hexachloropalladate ion in aqueous phase. Batch degradation and dechlorination reactions of trichloroethylene were conducted with initial trichloroethylene concentration of 23.7 mg/L, iron loading of 203 or 1.91 × 103 mg/L and silica loading of 8.10 g/L at 25 °C. Concentration of trichloroethylene occurs on the supported Pd/Fe nanoparticles, with trichloroethylene degrading to 56% and 59% in 30 min on the supported Pd/Fe nanoparticles with weight percentage of palladium to iron at 0.075% and 0.10% respectively. The supported Pd/Fe nanoparticles exhibit better dechlorination activity. When the supported Pd/Fe nanoparticles with a weight percentage of palladium to iron of 0.10% were loaded much less than the bare counterpart, the yield of ethylene plus ethane in 10 h on them was comparable, i.e., 19% vs. 21%. This study offers a future approach to efficiently combine the reactivity of supported Pd/Fe nanoparticles and the adsorption ability of mesoporous silica. Full article
(This article belongs to the Special Issue Rational Synthesis of Supported Bimetallic Catalysts)
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Open AccessArticle Solvent-Free Selective Condensations Based on the Formation of the Olefinic (C=C) Bond Catalyzed by Organocatalyst
Catalysts 2016, 6(7), 106; doi:10.3390/catal6070106
Received: 6 June 2016 / Revised: 4 July 2016 / Accepted: 14 July 2016 / Published: 20 July 2016
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Abstract
Pyrrolidine and its derivatives were used to catalyze aldol and Knoevenagel condensations for the formation of the olefinic (C=C) bond under solvent-free conditions. The 3-pyrrolidinamine showed high activity and afforded excellent yields of α,β-unsaturated compounds. The aldol condensation of aromatic/heterocyclic aldehydes with ketones
[...] Read more.
Pyrrolidine and its derivatives were used to catalyze aldol and Knoevenagel condensations for the formation of the olefinic (C=C) bond under solvent-free conditions. The 3-pyrrolidinamine showed high activity and afforded excellent yields of α,β-unsaturated compounds. The aldol condensation of aromatic/heterocyclic aldehydes with ketones affords enones in high conversion (99.5%) and selectivity (92.7%). Good to excellent yields of α,β-unsaturated compounds were obtained in the Knoevenagel condensation of aldehydes with methylene-activated substrates. Full article
(This article belongs to the Special Issue Metal-free Organocatalysis)
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Open AccessArticle An Oxygen Reduction Study of Graphene-Based Nanomaterials of Different Origin
Catalysts 2016, 6(7), 108; doi:10.3390/catal6070108
Received: 13 June 2016 / Revised: 8 July 2016 / Accepted: 12 July 2016 / Published: 22 July 2016
Cited by 6 | PDF Full-text (6136 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The aim of this study is to compare the electrochemical behaviour of graphene-based materials of different origin, e.g., commercially available graphene nanosheets from two producers and reduced graphene oxide (rGO) towards the oxygen reduction reaction (ORR) using linear sweep voltammetry, rotating disc electrode
[...] Read more.
The aim of this study is to compare the electrochemical behaviour of graphene-based materials of different origin, e.g., commercially available graphene nanosheets from two producers and reduced graphene oxide (rGO) towards the oxygen reduction reaction (ORR) using linear sweep voltammetry, rotating disc electrode and rotating ring-disc electrode methods. We also investigate the effect of catalyst ink preparation using two different solvents (2-propanol containing OH ionomer or N,N-dimethylformamide) on the ORR. The graphene-based materials are characterised by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. Clearly, the catalytic effect depends on the origin of graphene material and, interestingly, the electrocatalytic activity of the catalyst material for ORR is lower when using the OH ionomer in electrode modification. The graphene electrodes fabricated with commercial graphene show better ORR performance than rGO in alkaline solution. Full article
(This article belongs to the Special Issue Carbon Materials for Green Catalysis)
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Open AccessArticle The Reaction Mechanism of Acetaldehyde Ammoximation to Its Oxime in the TS-1/H2O2 System
Catalysts 2016, 6(7), 109; doi:10.3390/catal6070109
Received: 11 May 2016 / Revised: 15 July 2016 / Accepted: 16 July 2016 / Published: 22 July 2016
Cited by 1 | PDF Full-text (5081 KB) | HTML Full-text | XML Full-text
Abstract
A qualitative analysis for the ammoximation of acetaldehyde to its oxime in the TS-1(Titanium Silicalite-1)/H2O2 system was investigated using an in situ infrared spectrometer (ReactIR15). NH3 is first oxidized to NH2OH by TS-1/H2O2;
[...] Read more.
A qualitative analysis for the ammoximation of acetaldehyde to its oxime in the TS-1(Titanium Silicalite-1)/H2O2 system was investigated using an in situ infrared spectrometer (ReactIR15). NH3 is first oxidized to NH2OH by TS-1/H2O2; then, CH3CH=NOH forms after NH2OH reacts with CH3CHO. That means the intermediate of this reaction is NH2OH instead of CH3CH=NH. Experiments have been conducted to verify the mechanism, and the results are in good agreement with the infrared findings. Full article

Review

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Open AccessFeature PaperReview Catalysts for the Selective Oxidation of Methanol
Catalysts 2016, 6(7), 92; doi:10.3390/catal6070092
Received: 1 April 2016 / Revised: 23 May 2016 / Accepted: 27 May 2016 / Published: 23 June 2016
Cited by 8 | PDF Full-text (11040 KB) | HTML Full-text | XML Full-text
Abstract
In industry, one of the main catalysts typically employed for the selective oxidation of methanol to formaldehyde is a multi-component oxide containing both bulk Fe2(MoO4)3 and excess MoO3. It is thought that the excess MoO3
[...] Read more.
In industry, one of the main catalysts typically employed for the selective oxidation of methanol to formaldehyde is a multi-component oxide containing both bulk Fe2(MoO4)3 and excess MoO3. It is thought that the excess MoO3 primarily acts to replace any molybdenum lost through sublimation at elevated temperatures, therefore preventing the formation of an unselective Fe2O3 phase. With both oxide phases present however, debate has arisen regarding the active component of the catalyst. Work here highlights how catalyst surfaces are significantly different from bulk structures, a difference crucial for catalyst performance. Specifically, Mo has been isolated at the surface as the active surface species. This leaves the role of the Fe in the catalyst enigmatic, with many theories postulated for its requirement. It has been suggested that the supporting Fe molybdate phase enables lattice oxygen transfer to the surface, to help prevent the selectivity loss which would occur in the resulting oxygen deficit environment. To assess this phenomenon in further detail, anaerobic reaction with methanol has been adopted to evaluate the performance of the catalyst under reducing conditions. Full article
(This article belongs to the Special Issue Catalysts for Selective Oxidation)
Open AccessReview Bimetallic Catalysts Containing Gold and Palladium for Environmentally Important Reactions
Catalysts 2016, 6(7), 97; doi:10.3390/catal6070097
Received: 11 April 2016 / Revised: 8 June 2016 / Accepted: 24 June 2016 / Published: 5 July 2016
Cited by 6 | PDF Full-text (4897 KB) | HTML Full-text | XML Full-text
Abstract
Supported bimetallic nanoparticles (SBN) are extensively used as efficient redox catalysts. This kind of catalysis particularly using SBN has attracted immense research interest compared to their parent metals due to their unique physico-chemical properties. The primary objective of this contribution is to provide
[...] Read more.
Supported bimetallic nanoparticles (SBN) are extensively used as efficient redox catalysts. This kind of catalysis particularly using SBN has attracted immense research interest compared to their parent metals due to their unique physico-chemical properties. The primary objective of this contribution is to provide comprehensive overview about SBN and their application as promising catalysts. The present review contains four sections in total. Section 1 starts with a general introduction, recent progress, and brief summary of the application of SBN as promising catalysts for different applications. Section 2 reviews the preparation and characterization methods of SBN for a wide range of catalytic reactions. Section 3 concentrates on our own results related to the application of SBN in heterogeneous catalysis. In this section, the oxidation of cyclohexane to adipic acid (an eco-friendly and novel approach) will be discussed. In addition, the application of bimetallic Pd catalysts for vapor phase toluene acetoxylation in a fixed bed reactor will also be highlighted. Acetoxylation of toluene to benzyl acetate is another green route to synthesize benzyl acetate in one step. Finally, Section 4 describes the summary of the main points and also presents an outlook on the application of SBN as promising catalysts for the production of valuable products. Full article
(This article belongs to the Special Issue Rational Synthesis of Supported Bimetallic Catalysts)
Open AccessFeature PaperReview Biomass Derived Chemicals: Furfural Oxidative Esterification to Methyl-2-furoate over Gold Catalysts
Catalysts 2016, 6(7), 107; doi:10.3390/catal6070107
Received: 16 March 2016 / Revised: 13 July 2016 / Accepted: 14 July 2016 / Published: 20 July 2016
Cited by 3 | PDF Full-text (4525 KB) | HTML Full-text | XML Full-text
Abstract
The use of heterogeneous catalysis to upgrade biomass wastes coming from lignocellulose into higher value-added chemicals is one of the most explored subjects in the prospective vision of bio-refinery. In this frame, a lot of interest has been driven towards biomass-derived building block
[...] Read more.
The use of heterogeneous catalysis to upgrade biomass wastes coming from lignocellulose into higher value-added chemicals is one of the most explored subjects in the prospective vision of bio-refinery. In this frame, a lot of interest has been driven towards biomass-derived building block molecules, such as furfural. Gold supported catalysts have been successfully proven to be highly active and selective in the furfural oxidative esterification to methyl-2-furoate under mild conditions by employing oxygen as benign oxidant. Particular attention has been given to the studies in which the reaction occurs even without base as co-catalyst, which would lead to a more green and economically advantageous process. The Au catalysts are also stable and quite easily recovered and represent a feasible and promising route to efficiently convert furfural to methyl-2-furoate to be scaled up at industrial level. Full article
(This article belongs to the collection Gold Catalysts)
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