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Volume 5
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Catalysts, Volume 5, Issue 4 (December 2015) – 41 articles , Pages 1636-2323

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464 KiB  
Article
Switching off H2O2 Decomposition during TS-1 Catalysed Epoxidation via Post-Synthetic Active Site Modification
by Ceri Hammond and Giulia Tarantino
Catalysts 2015, 5(4), 2309-2323; https://doi.org/10.3390/catal5042309 - 21 Dec 2015
Cited by 22 | Viewed by 7643
Abstract
Despite its widespread use, the Lewis acidic zeolite, TS-1, still exhibits several unfavourable properties, such as excessive H2O2 decomposition, which decrease its overall performance. In this manuscript, we demonstrate that post-synthetic modification of TS-1 with aqueous NH4HF2 [...] Read more.
Despite its widespread use, the Lewis acidic zeolite, TS-1, still exhibits several unfavourable properties, such as excessive H2O2 decomposition, which decrease its overall performance. In this manuscript, we demonstrate that post-synthetic modification of TS-1 with aqueous NH4HF2 leads to modifications in epoxidation catalysis, which both improves the levels of epoxide selectivity obtained, and drastically minimises undesirable H2O2 decomposition. Through in situ spectroscopic study with UV-resonance enhanced Raman spectroscopy, we also observe a change in Ti site speciation, which occurs via the extraction of mononuclear [Ti(OSi)4] atoms, and which may be responsible for the changes in observed activity. Full article
(This article belongs to the Special Issue Zeolite Catalysis)
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1021 KiB  
Article
Experimental and Modeling Studies on the Conversion of Inulin to 5-Hydroxymethylfurfural Using Metal Salts in Water
by Boy Arief Fachri, Carolus Borromeus Rasrendra and Hero Jan Heeres
Catalysts 2015, 5(4), 2287-2308; https://doi.org/10.3390/catal5042287 - 21 Dec 2015
Cited by 13 | Viewed by 5712
Abstract
Inulin, a plant polysaccharide consisting of mainly d-fructose units, is considered an interesting feed for 5-hydroxymethylfurfural (HMF), a top 12 bio-based chemical. We here report an exploratory experimental study on the use of a wide range of homogeneous metal salts as catalysts [...] Read more.
Inulin, a plant polysaccharide consisting of mainly d-fructose units, is considered an interesting feed for 5-hydroxymethylfurfural (HMF), a top 12 bio-based chemical. We here report an exploratory experimental study on the use of a wide range of homogeneous metal salts as catalysts for the conversion of inulin to HMF in water. Best results were obtained using CuCl2. Activity-pH relations indicate that the catalyst activity of CuCl2 is likely related to Lewis acidity and not to Brönsted acidity. The effects of process conditions on HMF yield for CuCl2 were systematically investigated and quantified using a central composite design (160–180 °C, an inulin loading between 0.05 and 0.15 g/mL, CuCl2 concentration in range of 0.005–0.015 M, and a reaction time between 10 and 120 min). The highest experimental HMF yield in the process window was 30.3 wt. % (39 mol %, 180 °C, 0.05 g/mL inulin, 0.005 M CuCl2 and a reaction time of 10 min). The HMF yields were modelled using non-linear, multi variable regression and good agreement between experimental data and model were obtained. Full article
(This article belongs to the Special Issue Catalytic Conversion of Biomass)
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844 KiB  
Article
Washcoat Deposition of Ni- and Co-ZrO2 Low Surface Area Powders onto Ceramic Open-Cell Foams: Influence of Slurry Formulation and Rheology
by Riccardo Balzarotti, Mirko Ciurlia, Cinzia Cristiani and Fabio Paparella
Catalysts 2015, 5(4), 2271-2286; https://doi.org/10.3390/catal5042271 - 18 Dec 2015
Cited by 16 | Viewed by 7439
Abstract
The effect of formulations and procedures to deposit thin active layers based on low surface area powders on complex geometry substrates (open-cell foams) was experimentally assessed. An acid-free liquid medium based on water, glycerol, and polyvinyl alcohol was used for powder dispersion, while [...] Read more.
The effect of formulations and procedures to deposit thin active layers based on low surface area powders on complex geometry substrates (open-cell foams) was experimentally assessed. An acid-free liquid medium based on water, glycerol, and polyvinyl alcohol was used for powder dispersion, while a dip-coating technique was chosen for washcoat deposition on 30 PPI ceramic open-cell foams. The rheological behavior was explained on the bases of both porosity and actual powder density. It was proved that the use of multiple dippings fulfills flexibility requirements for washcoat load management. Multiple depositions with intermediate flash drying steps at 350 °C were carried out. Washcoat loads in the 2.5 to 22 wt. % range were obtained. Pore clogging was seldom observed in a limited extent in samples with high loading (>20 wt. %). Adhesion, evaluated by means of accelerated stress test in ultrasound bath, pointed out good results of all the deposited layers. Full article
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169 KiB  
Article
Heterogeneous Ru-Based Catalysts for One-Pot Synthesis of Primary Amines from Aldehydes and Ammonia
by Bo Dong, Xingcui Guo, Bo Zhang, Xiufang Chen, Jing Guan, Yunfei Qi, Sheng Han and Xindong Mu
Catalysts 2015, 5(4), 2258-2270; https://doi.org/10.3390/catal5042258 - 16 Dec 2015
Cited by 47 | Viewed by 7497
Abstract
The direct reductive amination of carbonyl compounds with NH3 and H2 is an alternative route to produce primary amines in practical production. The search for efficient and selective catalysts has attracted great interest. In the present work, the reductive amination of heptaldehyde with [...] Read more.
The direct reductive amination of carbonyl compounds with NH3 and H2 is an alternative route to produce primary amines in practical production. The search for efficient and selective catalysts has attracted great interest. In the present work, the reductive amination of heptaldehyde with NH3 was investigated over a Ru-based catalyst. The product selectivities were found to be related with the supports of Ru. The alumina with spinel structure (γ-Al2O3, θ-Al2O3)-supported Ru catalysts exhibited selectivity favoring primary amines (94% yield) at 100% heptaldehyde conversion under optimal conditions. Purely basic (MgO, CaO) and relative acidic (Nb2O5, SnO2, MCM-41, HZSM-5) supports showed relatively poor selectivity towards primary amines (0%–53% yield). The reductive amination mechanism was also proposed. The Schiff base N-[heptylene]heptyl-1-amine was a key intermediate. Ru/γ-Al2O3 was shown to be an excellent hydrogenolysis catalyst to selectively produce primary amine by amination and hydrogenolysis of N-[heptylene]heptyl-1-amine. Full article
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301 KiB  
Article
High-Throughput Screening of Heterogeneous Catalysts for the Conversion of Furfural to Bio-Based Fuel Components
by Roberto Pizzi, Robert-Jan Van Putten, Hanneke Brust, Siglinda Perathoner, Gabriele Centi and Jan Cornelis Van der Waal
Catalysts 2015, 5(4), 2244-2257; https://doi.org/10.3390/catal5042244 - 16 Dec 2015
Cited by 38 | Viewed by 8791
Abstract
The one-pot catalytic reductive etherification of furfural to 2-methoxymethylfuran (furfuryl methyl ether, FME), a valuable bio-based chemical or fuel, is reported. A large number of commercially available hydrogenation heterogeneous catalysts based on nickel, copper, cobalt, iridium, palladium and platinum catalysts on various support [...] Read more.
The one-pot catalytic reductive etherification of furfural to 2-methoxymethylfuran (furfuryl methyl ether, FME), a valuable bio-based chemical or fuel, is reported. A large number of commercially available hydrogenation heterogeneous catalysts based on nickel, copper, cobalt, iridium, palladium and platinum catalysts on various support were evaluated by a high-throughput screening approach. The reaction was carried out in liquid phase with a 10% w/w furfural in methanol solution at 50 bar of hydrogen. Among all the samples tested, carbon-supported noble metal catalysts were found to be the most promising in terms of productivity and selectivity. In particular, palladium on charcoal catalysts show high selectivity (up to 77%) to FME. Significant amounts of furfuryl alcohol (FA) and 2-methylfuran (2-MF) are observed as the major by-products. Full article
(This article belongs to the Special Issue Catalytic Conversion of Biomass)
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807 KiB  
Article
Zeolite Catalysts for Phenol Benzoylation with Benzoic Acid: Exploring the Synthesis of Hydroxybenzophenones
by Gherardo Gliozzi, Sauro Passeri, Francesca Bortolani, Mattia Ardizzi, Patrizia Mangifesta and Fabrizio Cavani
Catalysts 2015, 5(4), 2223-2243; https://doi.org/10.3390/catal5042223 - 16 Dec 2015
Cited by 9 | Viewed by 9566
Abstract
In this paper, we report on the reaction of phenol benzoylation with benzoic acid, which was carried out in the absence of solvent. The aim of this reaction is the synthesis of hydroxybenzophenones, which are important intermediates for the chemical industry. H-beta zeolites [...] Read more.
In this paper, we report on the reaction of phenol benzoylation with benzoic acid, which was carried out in the absence of solvent. The aim of this reaction is the synthesis of hydroxybenzophenones, which are important intermediates for the chemical industry. H-beta zeolites offered superior performance compared to H-Y, with a remarkably high conversion of phenol and high yields to the desired compounds, when using a stoichiometric amount of benzoic acid. It was found that the reaction mechanism did not include the intramolecular Fries rearrangement of the primary product phenyl benzoate, but indeed, the bimolecular reaction between phenyl benzoate and phenol mainly contributed to the formation of hydroxybenzophenones. The product distribution was greatly affected by the presence of Lewis-type acid sites in H-beta; it was suggested that the interaction between the aromatic ring and the electrophilic Al3+ species led to the preferred formation of o-hydroxybenzophenone, because of the decreased charge density on the C atom at the para position of the phenolic ring. H-Y zeolites were efficient than H-beta in phenyl benzoate transformation into hydroxybenzophenones. Full article
(This article belongs to the Special Issue Zeolite Catalysis)
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1733 KiB  
Review
Zeolite Membranes in Catalysis—From Separate Units to Particle Coatings
by Radostina Dragomirova and Sebastian Wohlrab
Catalysts 2015, 5(4), 2161-2222; https://doi.org/10.3390/catal5042161 - 16 Dec 2015
Cited by 35 | Viewed by 11443
Abstract
Literature on zeolite membranes in catalytic reactions is reviewed and categorized according to membrane location. From this perspective, the classification is as follows: (i) membranes spatially decoupled from the reaction zone; (ii) packed bed membrane reactors; (iii) catalytic membrane reactors and (iv) zeolite [...] Read more.
Literature on zeolite membranes in catalytic reactions is reviewed and categorized according to membrane location. From this perspective, the classification is as follows: (i) membranes spatially decoupled from the reaction zone; (ii) packed bed membrane reactors; (iii) catalytic membrane reactors and (iv) zeolite capsuled catalyst particles. Each of the resulting four chapters is subdivided by the kind of reactions performed. Over the whole sum of references, the advantage of zeolite membranes in catalytic reactions in terms of conversion, selectivity or yield is evident. Furthermore, zeolite membrane preparation, separation principles as well as basic considerations on membrane reactors are discussed. Full article
(This article belongs to the Special Issue Zeolite Catalysis)
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448 KiB  
Article
Jet-Fuel Range Hydrocarbons from Biomass-Derived Sorbitol over Ni-HZSM-5/SBA-15 Catalyst
by Yujing Weng, Songbai Qiu, Longlong Ma, Qiying Liu, Mingyue Ding, Qian Zhang, Qi Zhang and Tiejun Wang
Catalysts 2015, 5(4), 2147-2160; https://doi.org/10.3390/catal5042147 - 15 Dec 2015
Cited by 62 | Viewed by 9384
Abstract
Aromatics and cyclic-hydrocarbons are the significant components of jet fuel with high energy-density. However, conventional technologies for bio-fuel production cannot produce these products without further aromatization and isomerization. In this work, renewable liquid fuel with high content of aromatics and cyclic-hydrocarbons was obtained [...] Read more.
Aromatics and cyclic-hydrocarbons are the significant components of jet fuel with high energy-density. However, conventional technologies for bio-fuel production cannot produce these products without further aromatization and isomerization. In this work, renewable liquid fuel with high content of aromatics and cyclic-hydrocarbons was obtained through aqueous catalytic conversion of biomass sorbitol over Ni-HZSM-5/SBA-15 catalyst. Texture characteristics of the catalyst were determined by physisorption of N2, which indicated its bimodal pore structures were microporous (HZSM-5, pore width: 0.56 nm) and mesoporous (SBA-15, pore width: 8 nm). The surface acidity included weak and strong acid sites, predominantly Lewis type, and was further confirmed by the NH3-TPD and Py-IR analysis. The catalytic performances were tested in a fixed-bed reactor under the conditions of 593 K, WHSV of 0.75 h−1, GHSV of 2500 h−1 and 4.0 MPa of hydrogen pressure, whereby oil yield of 40.4 wt. % with aromatics and cyclic-hydrocarbons content of 80.0% was obtained. Full article
(This article belongs to the Special Issue Catalytic Conversion of Biomass)
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719 KiB  
Article
Facile Synthesis of Yolk/Core-Shell Structured TS-1@Mesosilica Composites for Enhanced Hydroxylation of Phenol
by Houbing Zou, Qingli Sun, Dongyu Fan, Weiwei Fu, Lijia Liu and Runwei Wang
Catalysts 2015, 5(4), 2134-2146; https://doi.org/10.3390/catal5042134 - 14 Dec 2015
Cited by 14 | Viewed by 5904
Abstract
In the current work, we developed a facile synthesis of yolk/core-shell structured TS-1@mesosilica composites and studied their catalytic performances in the hydroxylation of phenol with H2O2 as the oxidant. The core-shell TS-1@mesosilica composites were prepared via a uniform coating process, [...] Read more.
In the current work, we developed a facile synthesis of yolk/core-shell structured TS-1@mesosilica composites and studied their catalytic performances in the hydroxylation of phenol with H2O2 as the oxidant. The core-shell TS-1@mesosilica composites were prepared via a uniform coating process, while the yolk-shell TS-1@mesosilica composite was prepared using a resorcinol-formaldehyde resin (RF) middle-layer as the sacrificial template. The obtained materials were characterized by X-ray diffraction (XRD), N2 sorption, Fourier transform infrared spectoscopy (FT-IR) UV-Visible spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The characterization results showed that these samples possessed highly uniform yolk/core-shell structures, high surface area (560–700 m2 g−1) and hierarchical pore structures from oriented mesochannels to zeolite micropores. Importantly, owing to their unique structural properties, these composites exhibited enhanced activity, and also selectivity in the phenol hydroxylation reaction. Full article
(This article belongs to the Special Issue Zeolite Catalysis)
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358 KiB  
Article
Selective Production of Aromatics from 2-Octanol on Zinc Ion-Exchanged MFI Zeolite Catalysts
by Masakazu Iwamoto, Ryota Takezawa and Masao Morimoto
Catalysts 2015, 5(4), 2122-2133; https://doi.org/10.3390/catal5042122 - 10 Dec 2015
Cited by 3 | Viewed by 5280
Abstract
The aromatization of 2-octanol derived from castor oil as a byproduct in the formation of sebacic acid was investigated on various zeolite catalysts. Zn ion-exchanged MFI (ZSM-5) zeolites with small silica/alumina ratios and zinc contents of 0.5 to 2.0 wt. % were determined [...] Read more.
The aromatization of 2-octanol derived from castor oil as a byproduct in the formation of sebacic acid was investigated on various zeolite catalysts. Zn ion-exchanged MFI (ZSM-5) zeolites with small silica/alumina ratios and zinc contents of 0.5 to 2.0 wt. % were determined to exhibit good and stable activity for the reaction at 623 to 823 K. The yield of aromatics was 62% at 773 K and the space velocity 350 to 1400 h−1. The temperature and contact time dependences of the product distributions indicated the reaction pathways of 2-octanol→dehydration to 2-octene→decomposition to C5 and C3 compounds→further decomposition to small alkanes and alkenes→aromatization with dehydrogenation. Alcohols with carbon numbers of 5 to 8 exhibited similar distributions of products compared to 2-octanol, while corresponding carbonyl compounds demonstrated different reactivity. Full article
(This article belongs to the Special Issue Catalytic Conversion of Biomass)
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133 KiB  
Editorial
Electrocatalysis in Fuel Cells
by Minhua Shao
Catalysts 2015, 5(4), 2115-2121; https://doi.org/10.3390/catal5042115 - 9 Dec 2015
Cited by 23 | Viewed by 5994
Abstract
Low temperature fuel cells are expected to come into widespread commercial use in the areas of transportation and stationary and portable power generation, and thus will help solve energy shortage and environmental issues. [...] Full article
(This article belongs to the Special Issue Electrocatalysis in Fuel Cells)
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396 KiB  
Article
Adsorption and Diffusion of Xylene Isomers on Mesoporous Beta Zeolite
by Aixia Song, Jinghong Ma, Duo Xu and Ruifeng Li
Catalysts 2015, 5(4), 2098-2114; https://doi.org/10.3390/catal5042098 - 8 Dec 2015
Cited by 22 | Viewed by 6175
Abstract
A systematic and detailed analysis of adsorption and diffusion properties of xylene isomers over Beta zeolites with different mesoporosity was conducted. Adsorption isotherms of xylene isomers over microporous and mesoporous Beta zeolites through gravimetric methods were applied to investigate the impact of mesopores [...] Read more.
A systematic and detailed analysis of adsorption and diffusion properties of xylene isomers over Beta zeolites with different mesoporosity was conducted. Adsorption isotherms of xylene isomers over microporous and mesoporous Beta zeolites through gravimetric methods were applied to investigate the impact of mesopores inside Beta zeolites on the adsorption properties of xylene isomers in the pressure range of lower 20 mbar. It is seen that the adsorption isotherms of three xylene isomers over microporous and mesoporous Beta zeolites could be successfully described by the single-site Toth model and the dual-site Toth model, respectively. The enhanced adsorption capacities and decreased Henry’s constants (KH) and the initial heats of adsorption (Qst) for the all xylene isomers are observed after the introduction of mesopores in the zeolites. For three xylene isomers, the order of Henry’s constant is o-xylene > m-xylene > p-xylene, whereas the adsorption capacities of Beta zeolite samples for xylene isomers execute the following order of o-xylene > p-xylene > m-xylene, due to the comprehensive effects from the molecular configuration and electrostatic interaction. At the same time, the diffusion properties of xylene isomers in the mesoporous Beta zeolites were also studied through the desorption curves measured by the zero length column (ZLC) method at 333–373 K. It turned out that the effective diffusion time constant (Deff/R2) is a growing trend with the increasing mesoporosity, whereas the tendency of the activation energy is just the reverse, indicating the contribution of mesopores to facilitate molecule diffusion by shortening diffusion paths and reducing diffusion resistances. Moreover, the diffusivities of three xylene isomers in all Beta zeolites follow an order of p-xylene > m-xylene > o-xylene as opposed to KH, conforming the significant effects of adsorbate-adsorbent interaction on the diffusion. Full article
(This article belongs to the Special Issue Zeolite Catalysis)
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316 KiB  
Article
Co-Pyrolysis Behaviors of the Cotton Straw/PP Mixtures and Catalysis Hydrodeoxygenation of Co-Pyrolysis Products over Ni-Mo/Al2O3 Catalyst
by Derun Hua, Yulong Wu, Yu Chen, Jian Li, Mingde Yang and Xinning Lu
Catalysts 2015, 5(4), 2085-2097; https://doi.org/10.3390/catal5042085 - 8 Dec 2015
Cited by 18 | Viewed by 6220
Abstract
The doping of PP (polypropylene) with cotton straw improved the bio-oil yield, which showed there was a synergy in the co-pyrolysis of the cotton straw and PP at the range of 380–480 °C. In a fixed-bed reactor, model compounds and co-pyrolysis products were [...] Read more.
The doping of PP (polypropylene) with cotton straw improved the bio-oil yield, which showed there was a synergy in the co-pyrolysis of the cotton straw and PP at the range of 380–480 °C. In a fixed-bed reactor, model compounds and co-pyrolysis products were used for reactants of hydrodeoxygenation (HDO) over Ni-Mo/Al2O3. The deoxygenation rate of model compounds decreased over Ni-Mo/Al2O3 in the following order: alcohol > aldehyde > acetic acid > ethyl acetate. The upgraded oil mainly consisted of C11 alkane. Full article
(This article belongs to the Special Issue Catalytic Conversion of Biomass)
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216 KiB  
Article
Microbial Stereoselective One-Step Conversion of Diols to Chiral Lactones in Yeast Cultures
by Filip Boratyński, Ewa Szczepańska, Jakub Pannek and Teresa Olejniczak
Catalysts 2015, 5(4), 2068-2084; https://doi.org/10.3390/catal5042068 - 8 Dec 2015
Cited by 3 | Viewed by 5279
Abstract
It has been shown that whole cells of different strains of yeast catalyze stereoselective oxidation of meso diols to the corresponding chiral lactones. Among screening-scale experiments, Candida pelliculosa ZP22 was selected as the most effective biocatalyst for the oxidation of monocyclic diols 3a–b [...] Read more.
It has been shown that whole cells of different strains of yeast catalyze stereoselective oxidation of meso diols to the corresponding chiral lactones. Among screening-scale experiments, Candida pelliculosa ZP22 was selected as the most effective biocatalyst for the oxidation of monocyclic diols 3a–b with respect to the ratio of high conversion to stereoselectivity. This strain was used in the preparative oxidation, affording enantiomerically-enriched isomers of lactones: (+)-(3aR,7aS)-cis-hexahydro-1(3H) -isobenzofuranone (2a) and (+)-(3aS,4,7,7aR)-cis-tetrahydro-1(3H)-isobenzofuranone (2b). Scaling up the culture growth, as well as biotransformation conditions has been successfully accomplished. Among more bulky substrates, bicyclic diol 3d was totally converted into enantiomerically-pure exo-bridged (+)-(3aR,4S,7R,7aS)-cis-tetrahydro-4,7-methanoisobenzofuran -1(3H)-one (2d) by Yarrovia lipolytica AR71. Microbial oxidation of diol 3f by Candida sake AM908 and Rhodotorula rubra AM4 afforded optically-pure cis-3-butylhexahydro-1(3H) -isobenzofuranone (2f), however with low conversion. Full article
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335 KiB  
Communication
Ionic Liquids as Carbene Catalyst Precursors in the One-Pot Four-Component Assembly of Oxo Triphenylhexanoates (OTHOs)
by Anton Axelsson, Linda Ta and Henrik Sundén
Catalysts 2015, 5(4), 2052-2067; https://doi.org/10.3390/catal5042052 - 27 Nov 2015
Cited by 11 | Viewed by 5713
Abstract
Ionic liquids (ILs) are a convenient and inexpensive source of N-heterocyclic carbenes (NHCs). In this study, dialkyl imidazolium-based ILs are used as carbene precursors in a four-component synthesis of oxo triphenylhexanoates (OTHOs), where it was found that IL outperformed commonly used NHC precatalysts [...] Read more.
Ionic liquids (ILs) are a convenient and inexpensive source of N-heterocyclic carbenes (NHCs). In this study, dialkyl imidazolium-based ILs are used as carbene precursors in a four-component synthesis of oxo triphenylhexanoates (OTHOs), where it was found that IL outperformed commonly used NHC precatalysts in terms of reaction efficiency. The reaction is highly stereoselective, delivering the anti-diastereomer (20:1 dr), and the OTHOs can be obtained in high-to-excellent yields. By virtue of the four-component reaction-setup, facile construction of the OTHO scaffold with a diverse set of functional groups (21 examples) can be achieved. In the context of sustainability, the IL can be recovered and reused several times without affecting selectivity or yield. Moreover, most compounds can be isolated by precipitation and filtration, mitigating the use of solvent-demanding chromatography. Full article
(This article belongs to the Special Issue Ionic Liquids in Catalysis 2015)
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312 KiB  
Article
Selective Oxidation of Glycerol with 3% H2O2 Catalyzed by LDH-Hosted Cr(III) Complex
by Gongde Wu, Xiaoli Wang, Taineng Jiang and Qibo Lin
Catalysts 2015, 5(4), 2039-2051; https://doi.org/10.3390/catal5042039 - 27 Nov 2015
Cited by 12 | Viewed by 7461
Abstract
A series of layered double hydroxides (LDHs) –hosted sulphonato-salen Cr(III) complexes were prepared and characterized by various physico-chemical measurements, such as Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), powder X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM) and elemental [...] Read more.
A series of layered double hydroxides (LDHs) –hosted sulphonato-salen Cr(III) complexes were prepared and characterized by various physico-chemical measurements, such as Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), powder X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM) and elemental analysis. Additionally, their catalytic performances were investigated in the selective oxidation of glycerol (GLY) using 3% H2O2 as an oxidant. It was found that all the LDH-hosted Cr(III) complexes exhibited significantly enhanced catalytic performance compared to the homogeneous Cr(III) complex. Additionally, it was worth mentioning that the metal composition of LDH plates played an important role in the catalytic performances of LDH-hosted Cr(III) complex catalysts. Under the optimal reaction conditions, the highest GLY conversion reached 85.5% with 59.3% of the selectivity to 1,3-dihydroxyacetone (DHA). In addition, the catalytic activity remained after being recycled five times. Full article
(This article belongs to the Special Issue Catalysts for Selective Oxidation)
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962 KiB  
Article
Effect of Surface Passivation on Photoelectrochemical Water Splitting Performance of WO3 Vertical Plate-Like Films
by Yahui Yang, Renrui Xie, Yang Liu, Jie Li and Wenzhang Li
Catalysts 2015, 5(4), 2024-2038; https://doi.org/10.3390/catal5042024 - 24 Nov 2015
Cited by 27 | Viewed by 7711
Abstract
WO3 vertical plate-like arrays provide a direct pathway for charge transport, and thus hold great potential as working electrodes for photoelectrochemical (PEC) water splitting. However, surface recombination due to surface defects hinders the performance improvement. In this work, WO3 vertical plate-like arrays films [...] Read more.
WO3 vertical plate-like arrays provide a direct pathway for charge transport, and thus hold great potential as working electrodes for photoelectrochemical (PEC) water splitting. However, surface recombination due to surface defects hinders the performance improvement. In this work, WO3 vertical plate-like arrays films with HfO2 passivation layer were fabricated via a simple dip-coating method. In the images of transmission electron microscope, a fluffy layer and some small sphere particles existed on the surface of WO3 plate. X-ray photoelectron spectroscopy (XPS) showed a higher concentration of Hf element than the result of energy-dispersive X-ray spectroscopy (EDX), which means that HfO2 is rich on the surface of WO3 plates. A higher photocurrent under visible light irradiation was gained with surface passivation. Meanwhile, the results of intensity modulated photocurrent spectrum (IMPS) and incident photon to current conversion efficiency (IPCE) indicate that HfO2 passivation layer, acting as a barrier for the interfacial recombination, is responsible for the improved photoelectrochemical performance of WO3 vertical plate-like arrays film. Full article
(This article belongs to the Special Issue Photocatalytic Water Splitting-1)
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136 KiB  
Editorial
Feature Papers to Celebrate the Landmarks of Catalysts
by Keith L. Hohn
Catalysts 2015, 5(4), 2018-2023; https://doi.org/10.3390/catal5042018 - 24 Nov 2015
Viewed by 3446
Abstract
Catalysis is a critical scientific field that underpins much of the world’s chemical industry. For example, it is often quoted that catalysis plays a role in 90% of all industrial chemical products. This importance has led to numerous academic journals and specialized conferences [...] Read more.
Catalysis is a critical scientific field that underpins much of the world’s chemical industry. For example, it is often quoted that catalysis plays a role in 90% of all industrial chemical products. This importance has led to numerous academic journals and specialized conferences on the subject, as practitioners seek outlets to publish their cutting-edge research on catalysis. [...] Full article
(This article belongs to the Special Issue Feature Papers to Celebrate the Landmarks of Catalysts)
620 KiB  
Article
Synthesis of Ethylene or Propylene/1,3-Butadiene Copolymers Possessing Pendant Vinyl Groups with Virtually No Internal Olefins
by Kenji Michiue, Makoto Mitani and Terunori Fujita
Catalysts 2015, 5(4), 2001-2017; https://doi.org/10.3390/catal5042001 - 20 Nov 2015
Cited by 10 | Viewed by 6668
Abstract
In general, ethylene/1,3-butadiene copolymerizations provides copolymers possessing both pendant vinyls and vinylenes as olefinic moieties. We, at MCI, studied the substituent effects of C2-symmetric zirconocene complexes, rac-[Me2Si(Indenyl’)2]ZrCl2 (Indenyl’ = generic substituted indenyl), after activation on [...] Read more.
In general, ethylene/1,3-butadiene copolymerizations provides copolymers possessing both pendant vinyls and vinylenes as olefinic moieties. We, at MCI, studied the substituent effects of C2-symmetric zirconocene complexes, rac-[Me2Si(Indenyl’)2]ZrCl2 (Indenyl’ = generic substituted indenyl), after activation on the ratio of the pendant vinyls and vinylenes of the resultant copolymers. Complexes examined in this study were rac-dimethylsilylbis (1-indenyl)zirconium dichloride (1), rac-dimethylsilyl-bis[1-(2-methyl-4,5-benzoindenyl)] zirconium dichloride (2), rac-dimethylsilyl-bis[l-(2-methyl -4-phenylindenyl)]zirconium dichloride (3), rac-dimethy1si1y1- bis(2-ethyl-4-phenylindenyl) zirconium dichloride (4), rac-dimethylsilyl-bis[l-(2-n-propyl -4-(1-naphthyl)indenyl)]zirconium dichloride (5), rac-dimethylsilyl-[1-(2-ethyl-4-(5-(2,2-dimethyl-2,3-dihydro-1H-cyclopenta [a]naphthalenyl)indenyl))][1-(2-n-propyl-4-(5-(2,2-dimethyl-2,3-dihydro-1H-cyclopenta[a] naphthalenyl)indenyl))]zirconium dichloride (6), rac-dimethylsilyl-bis[1-(2-ethyl-4-(9-phenanthryl)indenyl)]zirconium dichloride (7), and rac-dimethylsilyl-bis[l-(2-n-propyl-4-(9-phenanthryl)indenyl)]zirconium dichloride (8). We found that the ratio of the pendant vinyls and vinylenes is strongly affected by the bulkiness of the substituent on the complexes examined. The vinyl content increased linearly in the following order, 8 > 7 > 6 > 5 > 4 > 3 > 2 > 1. Notably, complex 8/DMAO formed ethylene/1,3-butadiene copolymers possessing predominant vinyl groups, which can be crucial precursors for functionalized polyolefins. Likewise, complex 8/DMAO afforded propylene/1,3-butadiene copolymers with predominant vinyl groups. Full article
(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization and ROP 2015)
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272 KiB  
Article
Effects of Catalyst Preparation on Hydrocarbon Product Distribution in Hydrocracking of the Fischer-Tropsch Product with Low Pt-Loaded Catalysts
by Toshiaki Hanaoka, Tomohisa Miyazawa, Katsuya Shimura and Satoshi Hirata
Catalysts 2015, 5(4), 1983-2000; https://doi.org/10.3390/catal5041983 - 20 Nov 2015
Cited by 5 | Viewed by 4851
Abstract
For the effective production of hydrocarbon liquid fuel in the hydrocracking of the Fischer-Tropsch (FT) product, the catalytic performance of Pt-loaded catalysts with low Pt content was investigated using an autoclave at 250 °C, an initial H2 pressure of 0.5 MPa, and [...] Read more.
For the effective production of hydrocarbon liquid fuel in the hydrocracking of the Fischer-Tropsch (FT) product, the catalytic performance of Pt-loaded catalysts with low Pt content was investigated using an autoclave at 250 °C, an initial H2 pressure of 0.5 MPa, and a reaction time of 1 h. A screening study using Pt-loaded catalysts with a Pt content of 0.1 wt. % indicated that zeolite supports were more favorable for jet fuel (carbon numbers 9–15) production than amorphous oxide supports. The small particle size of the supported Pt particles and the high amount of medium acid sites for the supports led to higher performance of the Pt-loaded zeolite catalysts. In the hydrocracking reaction over Pt catalysts using the zeolite support with the high amount of medium acid sites, the yields of the corresponding jet fuel at 0.02 and 0.1 wt. % were almost the same. Pt-loaded catalysts with a Pt content of 0.02 wt. % were prepared using water-in-oil (w/o) microemulsions and their particle size was controlled between 1.0 and 2.6 nm. While the yield of the corresponding jet fuel was independent of Pt particle size, smaller Pt particles typically promoted the production of lighter hydrocarbons. Full article
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170 KiB  
Article
Two Carbonylations of Methyl Iodide and Trimethylamine to Acetic acid and N,N-Dimethylacetamide by Rhodium(I) Complex: Stability of Rhodium(I) Complex under Anhydrous Condition
by Jang-Hwan Hong
Catalysts 2015, 5(4), 1969-1982; https://doi.org/10.3390/catal5041969 - 19 Nov 2015
Cited by 5 | Viewed by 10529
Abstract
Rhodium(I)-complex [Rh(CO)2I2−] (1) catalyzed two carbonylations of methyl iodide and trimethylamine in NMP (1-methyl-2-pyrolidone) to acetic acid and DMAC (N,N-dimethylacetamide) in the presence of calcium oxide and water. The carbonylation of trimethylamine [...] Read more.
Rhodium(I)-complex [Rh(CO)2I2−] (1) catalyzed two carbonylations of methyl iodide and trimethylamine in NMP (1-methyl-2-pyrolidone) to acetic acid and DMAC (N,N-dimethylacetamide) in the presence of calcium oxide and water. The carbonylation of trimethylamine continued during the carbonylation and consumption of methyl iodide. In total, 183.8 mmol of carbonylated products was produced while consuming 24.1 mmol methyl iodide via acetic acid formation. These results clearly indicated that there were two carbonylation routes of trimethylamine and methyl iodide and the carbonylation rate of trimethylamine was faster than that of methyl iodide. Rhodium(I)-complex [Rh(CO)2I2]− (1) in the presence of trimethylamine was stable enough to be used 25 times with TON (Turnover Number) of 368 for DMAC and TON of 728 for trimethylamine. Inner-sphere reductive elimination in stepwise procedure was suggested for the formation of DMAC instead of acyl iodide intermediate under anhydrous condition. Full article
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795 KiB  
Article
Information-Driven Catalyst Design Based on High-Throughput Intrinsic Kinetics
by Kristof Van der Borght, Kenneth Toch, Vladimir V. Galvita, Joris W. Thybaut and Guy B. Marin
Catalysts 2015, 5(4), 1948-1968; https://doi.org/10.3390/catal5041948 - 16 Nov 2015
Cited by 38 | Viewed by 7687
Abstract
A novel methodology is presented for more comprehensive catalyst development by maximizing the acquired information rather than relying on statistical methods or tedious, elaborate experimental testing. Two dedicated high-throughput kinetics (HTK) set-ups are employed to achieve this objective, i.e., a screening (HTK-S) and [...] Read more.
A novel methodology is presented for more comprehensive catalyst development by maximizing the acquired information rather than relying on statistical methods or tedious, elaborate experimental testing. Two dedicated high-throughput kinetics (HTK) set-ups are employed to achieve this objective, i.e., a screening (HTK-S) and a mechanistic investigation one (HTK-MI). While the former aims at evaluating a wide range of candidate catalysts, a limited selection is more elaborately investigated in the latter one. It allows focusing on an in-depth mechanistic analysis of the reaction mechanism resulting in so called “kinetic” descriptors and on the effect of key catalysts properties, also denoted as “catalyst” descriptors, on the catalyst performance. Both types of descriptors are integrated into a (micro)kinetic model that allows a reliable extrapolation towards operating conditions and catalyst properties beyond those included in the high-throughput testing. A case study on ethanol conversion to hydrocarbons is employed to illustrate the concept behind this methodology. The methodology is believed to be particularly useful for potentially large-scale chemical reactions. Full article
(This article belongs to the Special Issue High-Throughput Catalysts)
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604 KiB  
Article
Molybdenum (VI) Imido Complexes Derived from Chelating Phenols: Synthesis, Characterization and ɛ-Caprolactone ROP Capability
by Yahya Al-Khafaji, Timothy J. Prior, Mark R. J. Elsegood and Carl Redshaw
Catalysts 2015, 5(4), 1928-1947; https://doi.org/10.3390/catal5041928 - 12 Nov 2015
Cited by 18 | Viewed by 5479
Abstract
Reaction of the bulky bi-phenols 2,2′-RCH[4,6-(t-Bu)2C6H2OH]2 (R = Me L1MeH2, Ph L1PhH2) with the bis(imido) molybdenum(VI) tert-butoxides [Mo(NR1)(NR2)(Ot-Bu)2 [...] Read more.
Reaction of the bulky bi-phenols 2,2′-RCH[4,6-(t-Bu)2C6H2OH]2 (R = Me L1MeH2, Ph L1PhH2) with the bis(imido) molybdenum(VI) tert-butoxides [Mo(NR1)(NR2)(Ot-Bu)2] (R1 = R2 = 2,6-C6H3-i-Pr2; R1 = t-Bu, R2 = C6F5) afforded, following the successive removal of tert-butanol, the complexes [Mo(NC6H3i-Pr2-2,6)2L1Me] (1), [Mo(NC6H3i-Pr2-2,6)2L1Ph] (2) and [Mo(Nt-Bu)(μ-NC6F5)(L1Me)]2 (3). Similar use of the tri-phenol 2,6-bis(3,5-di-tert -butyl-2-hydroxybenzyl)-4-methylphenol (L2H3) with [Mo(NC6H3i-Pr2-2,6)2(Ot-Bu)2] afforded the oxo-bridged product [Mo(NC6H3i-Pr2-2,6)(NCMe)(μ-O)L2H]2 (4), whilst use of the tetra-phenols α,α,α′,α′-tetrakis(3,5-di-tert-butyl-2-hydroxyphenyl)-p- or -m-xylene L3pH4/L3mH4 led to {[Mo(NC6H3i-Pr2-2,6)2]2(μ-L3p)} (5) or {[Mo(NC6H3i-Pr2-2,6)2]2(μ-L3m)} (6), respectively. Similar use of [Mo(NC6F5)2(Ot-Bu)2] with L3pH4 afforded, after work-up, the complex {[Mo(NC6F5)(Ot-Bu)2]2(μ-L3p)}·6MeCN (7·6MeCN). Molecular structures of 1, 2·CH2Cl2, 3, 4·6MeCN, 6·2C6H14, and 7·6MeCN are reported and these complexes have been screened for their ability to ring open polymerize (ROP) ε-caprolactone; for comparative studies the precursor complex [Mo(NC6H3i-Pr2-2,6)2Cl2(DME)] (DME = 1,2-dimethoxyethane) has also been screened. Results revealed that good activity is only achievable at temperatures of ≥100 °C over periods of 1 h or more. Polymer polydispersities were narrow, but observed molecular weights (Mn) were much lower than calculated values. Full article
(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization and ROP 2015)
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585 KiB  
Article
Zr-SBA-15 Lewis Acid Catalyst: Activity in Meerwein Ponndorf Verley Reduction
by Jose Iglesias, Juan Antonio Melero, Gabriel Morales, Jovita Moreno, Yolanda Segura, Marta Paniagua, Alberto Cambra and Blanca Hernández
Catalysts 2015, 5(4), 1911-1927; https://doi.org/10.3390/catal5041911 - 12 Nov 2015
Cited by 69 | Viewed by 9277
Abstract
Zr-SBA-15 Lewis acid catalyst has demonstrated an outstanding catalytic activity in the reduction of several carbonyl compounds by means of Meerwein Ponndorf Verley (MPV) reaction, using several secondary alcohols, and showing a very high selectivity towards the desired products. Special focus was addressed [...] Read more.
Zr-SBA-15 Lewis acid catalyst has demonstrated an outstanding catalytic activity in the reduction of several carbonyl compounds by means of Meerwein Ponndorf Verley (MPV) reaction, using several secondary alcohols, and showing a very high selectivity towards the desired products. Special focus was addressed in the catalytic activity of Zr-SBA-15 material in the production of furfuryl alcohol from furfural, which is an important reaction for the lignocellulosic biomass valorization. In this transformation, both the reaction temperature and the i-PrOH:Furfural molar ratio exert a positive influence on the rate of the MPV transformation, with the influence of the former being much higher. i-propyl-furfuryl ether, a by-product resulting from the etherification of the target product with the sacrificing alcohol, is also found together with the main product. The production of this side-product is highly influenced by the reaction temperature, so that low temperatures and high sacrificing alcohol to substrate molar ratios have to be applied to keep its production at low levels. Full article
(This article belongs to the Special Issue Catalytic Conversion of Biomass)
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289 KiB  
Article
Direct Conversion of Carbohydrates into Ethyl Levulinate with Potassium Phosphotungstate as an Efficient Catalyst
by Shiqiang Zhao, Guizhuan Xu, Chun Chang, Shuqi Fang, Ze Liu and Fengguang Du
Catalysts 2015, 5(4), 1897-1910; https://doi.org/10.3390/catal5041897 - 12 Nov 2015
Cited by 60 | Viewed by 8538
Abstract
A series of metal-modified phosphotungstates were prepared and performed for direct synthesis of ethyl levulinate from fructose in ethanol. Considering the cost of catalysts, catalytic activity of catalysts, and easy separation of catalysts together, K-HPW-1 was chosen as the most suitable catalyst for [...] Read more.
A series of metal-modified phosphotungstates were prepared and performed for direct synthesis of ethyl levulinate from fructose in ethanol. Considering the cost of catalysts, catalytic activity of catalysts, and easy separation of catalysts together, K-HPW-1 was chosen as the most suitable catalyst for synthesis of ethyl levulinate from fructose. A high ethyl levulinate yield of 64.6 mol% was obtained at 150 °C within 2 h in ethanol. The introduction of low polar toluene as a co-solvent improved the yield of ethyl levulinate to 68.7 mol%. The recovered catalyst remained high activity with the yield of ethyl levulinate converted from fructose above 50 mol% after being used five times. Moreover, the generality of the catalyst was further demonstrated by glucose, sucrose, inulin, and cellulose with ethyl levulinate yielding 14.5, 35.4, 52.3, and 14.8 mol%, respectively. Full article
(This article belongs to the Special Issue Catalytic Conversion of Biomass)
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723 KiB  
Article
Hydrogen Production by Steam Reforming of Ethanol on Rh-Pt Catalysts: Influence of CeO2, ZrO2, and La2O3 as Supports
by Bernay Cifuentes, Manuel F. Valero, Juan A. Conesa and Martha Cobo
Catalysts 2015, 5(4), 1872-1896; https://doi.org/10.3390/catal5041872 - 11 Nov 2015
Cited by 38 | Viewed by 7481
Abstract
CeO2-, ZrO2-, and La2O3-supported Rh-Pt catalysts were tested to assess their ability to catalyze the steam reforming of ethanol (SRE) for H2 production. SRE activity tests were performed using EtOH:H2O:N2 (molar [...] Read more.
CeO2-, ZrO2-, and La2O3-supported Rh-Pt catalysts were tested to assess their ability to catalyze the steam reforming of ethanol (SRE) for H2 production. SRE activity tests were performed using EtOH:H2O:N2 (molar ratio 1:3:51) at a gaseous space velocity of 70,600 h−1 between 400 and 700 °C at atmospheric pressure. The SRE stability of the catalysts was tested at 700 °C for 27 h time on stream under the same conditions. RhPt/CeO2, which showed the best performance in the stability test, also produced the highest H2 yield above 600 °C, followed by RhPt/La2O3 and RhPt/ZrO2. The fresh and aged catalysts were characterized by TEM, XPS, and TGA. The higher H2 selectivity of RhPt/CeO2 was ascribed to the formation of small (~5 nm) and stable particles probably consistent of Rh-Pt alloys with a Pt surface enrichment. Both metals were oxidized and acted as an almost constant active phase during the stability test owing to strong metal-support interactions, as well as the superior oxygen mobility of the support. The TGA results confirmed the absence of carbonaceous residues in all the aged catalysts. Full article
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247 KiB  
Article
Synthesis, Characterization and Catalytic Polymerization of N-Methyl Imidazolium Phosphotungstic Catalyst
by Dianyu Chen, Zhaoyi Deng, Xiaoqin Liu and Rong Wang
Catalysts 2015, 5(4), 1862-1871; https://doi.org/10.3390/catal5041862 - 9 Nov 2015
Cited by 6 | Viewed by 3955
Abstract
N-methyl imidazolium phosphotungstic salt has been synthesized and used as a special catalyst for photopolymerization of vinyl monomers. This is a fast and smooth reaction, and high molecular weight polymers with narrow polydispersity are obtained within 60 min. The compound was structurally [...] Read more.
N-methyl imidazolium phosphotungstic salt has been synthesized and used as a special catalyst for photopolymerization of vinyl monomers. This is a fast and smooth reaction, and high molecular weight polymers with narrow polydispersity are obtained within 60 min. The compound was structurally characterized by elemental analysis, IR spectroscopy, and 1H NMR spectroscopy. The electrochemical property is determined on a CHI 660 electrochemistry workstation. The polymerization initiated by N-methyl imidazolium phosphotungstic salt showed controlling characteristics, the catalyst can be easily isolated from polymer product, and reused for at least 10 times. Full article
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3574 KiB  
Article
Catalytic Hydrogenation of CO2 to Methanol: Study of Synergistic Effect on Adsorption Properties of CO2 and H2 in CuO/ZnO/ZrO2 System
by Chunjie Huang, Shaoyun Chen, Xiaoyao Fei, Dai Liu and Yongchun Zhang
Catalysts 2015, 5(4), 1846-1861; https://doi.org/10.3390/catal5041846 - 6 Nov 2015
Cited by 67 | Viewed by 9582
Abstract
A series of CuO/ZnO/ZrO2 (CZZ) catalysts with different CuO/ZnO weight ratios have been synthesized by citrate method and tested in the catalytic hydrogenation of CO2 to methanol. Experimental results showed that the catalyst with the lowest CuO/ZnO weight ratio of 2/7 [...] Read more.
A series of CuO/ZnO/ZrO2 (CZZ) catalysts with different CuO/ZnO weight ratios have been synthesized by citrate method and tested in the catalytic hydrogenation of CO2 to methanol. Experimental results showed that the catalyst with the lowest CuO/ZnO weight ratio of 2/7 exhibited the best catalytic performance with a CO2 conversion of 32.9%, 45.8% methanol selectivity, and a process delivery of 193.9 gMeOH·kgcat−1·h−1. A synergetic effect is found by systematic temperature-programmed-desorption (TPD) studies. Comparing with single and di-component systems, the interaction via different components in a CZZ system provides additional active sites to adsorb more H2 and CO2 in the low temperature range, resulting in higher weight time yield (WTY) of methanol. Full article
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278 KiB  
Article
Copolymerization of Ethylene and Vinyl Amino Acidic Ester Catalyzed by Titanium and Zirconium Complexes
by Jing Wang, Xianghui Shi, Yang Chen, Hongming Li, Runcong Zhang, Jianjun Yi, Jian Wang, Qigu Huang and Wantai Yang
Catalysts 2015, 5(4), 1831-1845; https://doi.org/10.3390/catal5041831 - 30 Oct 2015
Cited by 5 | Viewed by 5470
Abstract
A series of titanium and zirconium complexes with ligands based on di-isopropyl phosphorus-phenylamine and their derivatives were synthesized and characterized. These catalysts were utilized to catalyze the copolymerization of ethylene with N-acetyl-O-(dec-9-enyl)-L-tyrosine ethyl ester with high catalytic activity of 6.63 [...] Read more.
A series of titanium and zirconium complexes with ligands based on di-isopropyl phosphorus-phenylamine and their derivatives were synthesized and characterized. These catalysts were utilized to catalyze the copolymerization of ethylene with N-acetyl-O-(dec-9-enyl)-L-tyrosine ethyl ester with high catalytic activity of 6.63 × 104 g P (mol Ti)−1 h−1 after activation by methylaluminoxane (MAO). The effects of ligand structure, metal atoms (Ti, Zr) and polymerization conditions were investigated in detail. The obtained polymers were characterized by 13C-NMR, DSC, FT-IR, and GPC. The results showed that the obtained copolymer had a high comonomer incorporation rate of 2.56 mol % within the copolymer chain. The melting temperature of the copolymer was up to 138.9 °C, higher than that of the obtained homopolyethylene. Full article
(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization and ROP 2015)
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942 KiB  
Article
On the Effect of Preparation Methods of PdCe-MOR Catalysts as NOx CH4-SCR System for Natural Gas Vehicles Application
by Acácio Nobre Mendes, Maria Filipa Ribeiro, Carlos Henriques and Patrick Da Costa
Catalysts 2015, 5(4), 1815-1830; https://doi.org/10.3390/catal5041815 - 27 Oct 2015
Cited by 9 | Viewed by 5873
Abstract
In the present work, the effect of several parameters involved in the preparation of PdCe-HMOR catalysts active for NOx selective catalytic reduction with methane (NOx CH4-SCR) was studied. Results show that the catalytic performance of Pd-HMOR is better when [...] Read more.
In the present work, the effect of several parameters involved in the preparation of PdCe-HMOR catalysts active for NOx selective catalytic reduction with methane (NOx CH4-SCR) was studied. Results show that the catalytic performance of Pd-HMOR is better when palladium is introduced by ion-exchange, namely at room temperature. It was also shown that Pd loading does not influence the formation of cerium species, namely surface Ce4+ (CeO2) species and CeO2 species in interaction with Pd. However, when Ce is introduced before Pd, more surface CeO2 species are stabilized in the support and less CeO2 become in interaction with Pd, which results in a worse NOx CH4-SCR catalytic performance. Full article
(This article belongs to the Special Issue Automotive Emission Control Catalysts)
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