Applied Catalysis A, General (v.476, #C)
Editorial Board (CO2).
Investigation of photocatalytic behavior of l-aspartic acid stabilized Zn(1−x)Mn x S solid solutions on methylene blue by A. Silambarasan; Helen P. Kavitha; S. Ponnusamy; M. Navaneethan; Y. Hayakawa (1-8).
Water dispersible Zn(1−x)Mn x S solid solution photocatalysts stabilized with l-aspartic acid were synthesized by coprecipitation. Their photocatalytic activity was evaluated using methylene blue as a model pollutant. X-ray diffraction and Raman spectroscopy indicated the catalysts had a cubic crystal structure. The gradual increase in zinc sulphide (ZnS) lattice constant with increasing Mn2+ dopant concentration was due to the high ionic radius of Mn2+. Raman spectra exhibited two peaks at 260 and 345 cm−1. Ultraviolet–visible absorption spectra of the catalysts exhibited a strong excitonic peak at 270 nm, which was blue shifted compared with that of bulk ZnS (340 nm). This was attributed to quantum confinement and coupling effects. The hydrophilic l-aspartic acid on the photocatalyst surface had a positive effect on photocatalytic activity. The effects of dye and dopant concentrations on photocatalytic activity were investigated.
Keywords: Photocatalysis; Zn(1−x)Mn x S solid solution; Reusability of the photocatalyst; Effect of Mn on photocatalytic activity of Zn(1−x)Mn x S; Kinetic study;
Solar-Fenton removal of malachite green with novel Fe0-activated carbon nanocomposite by Pardeep Singh; Pankaj Raizada; Shailza Kumari; Amit Kumar; Deepak Pathania; Pankaj Thakur (9-18).
Zero valent iron-activated carbon nanocomposite (Fe0-AC) was synthesized using liquid phase reduction method. Both Fe0-AC and micro zero valent iron (ZVI) were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), UV-visible (UV-vis) spectral techniques. The size of Fe0-AC was observed to be 50 nm. The catalytic efficiency of Fe0-AC was explored for the removal of malachite green dye (MG) from aqueous phase. Fe0-AC induced solar-Fenton removal of MG was investigated in the presence of H2O2 and citrate (cit.). Solar/H2O2/cit./Fe0-AC system exhibited highest removal efficiency among investigated photocatalytic systems. The dye removal was strongly influenced by solar light, pH, Fe0-AC dosage, H2O2 and citrate concentration in reaction system. The reaction was maximal at pH 6.75. MG was completely decolorized in 60 min using solar/H2O2/cit./Fe0-AC system. Hydroxyl radicals (OH • ) were the main oxidizing specie during solar–Fenton process.Fe0-AC proved to be a potential adsorbent for MG. Fe0-AC showed high recycle efficiency due to easier separation from aqueous phase. The lower concentration of dissolved Fe(II) ions in reaction solution indicated the stability of Fe0-AC during MG removal. On the basis of obtained results, the most plausible mechanism for oxidative removal MG of was proposed.
Keywords: Fe0-AC; Solar-Fenton reaction; Oxidative removal; Recycle efficiency;
Transformation of ethylbenzene-m-xylene feed over MCM-22 zeolites with different acidities by Magdolna R. Mihályi; Márton Kollár; Szilvia Klébert; Vesselina Mavrodinova (19-25).
Transformation of ethylbenzene (EB, 22 wt%)-m-xylene (78 wt%) mixture was carried out over zeolite MCM-22 catalysts with different acidities. The modification of the number and strength of the acid sites was attained by: (i) dealumination by steaming and successive acid treatment and (ii) isomorphous substitution of framework Al for boron ([Al,B]MCM-22). The effect of platinum introduction was also investigated. The strong decrease in the Brønsted acidity, concomitant to the dealumination procedure, appears unfavorable since it leads to a drastic diminish of the degree of EB conversion, not compensated by satisfactory level of m-xylene isomerization. [Al,B]MCM-22 is a modification with much better performance, most probably because it contains both strong, Al-connected acid sites but in lower amount than in the parent sample, and weaker boron-generated sites and practically no any Lewis sites.Parent zeolite [Al]MCM-22 as well as B-substitution possess promising properties for ethylbenzene-m-xylene mixture transformation catalyst with adequate degree of EB conversion and extent of p-xylene approach to equilibrium as well as low xylene loss.
Keywords: Dealuminated and B-substituted zeolite MCM-22; Pt/H-MCM-22; Ethylbenzene + m-xylene mixture transformation;
Biodiesel production via transesterification of palm olein using sodium phosphate as a heterogeneous catalyst by Khritsayaporn Thinnakorn; Jirdsak Tscheikuna (26-33).
The production of Fatty Acid Methyl Esters (FAMEs) via the transesterification reaction of palm olein and methanol using sodium phosphate (Na3PO4) as a heterogeneous catalyst has been investigated. This study determined the influence of various parameters, such as the methanol to oil molar ratio, the operating temperature, the amount of catalyst, and the presence of water and free fatty acid in the raw materials, on the rate of reaction. The study demonstrated that Na3PO4 can be used effectively as a heterogeneous catalyst in transesterification process. It was determined that increasing the methanol to oil molar ratio results in an increase in equilibrium conversion. A molar ratio of methanol to oil of 18:1 provides the fastest rates of reaction and the highest FAME content. The operating temperatures have a strong effect on FAME yield; increasing the reaction temperature tends to accelerate the rate of reaction but reduces the glycerol by-product quality. Under the study conditions, with a methanol to oil molar ratio of 18:1 and a reaction temperature of 210 °C 98.5% FAME yield was obtained within 30 min with only 1 wt.% of Na3PO4. When a large excess of methanol was used, the experimental results agreed with the irreversible 1st order kinetic model, while the activation energy was found to be 32.59 kJ/mol palm olein.
Keywords: Transesterification; Palm olein; Heterogeneous catalyst; Sodium phosphate;
Chemoselective hydrogenation of aromatic aldehydes over SiO2 modified Co/γ-Al2O3 by Xiangjin Kong; Ligong Chen (34-38).
With benzaldehyde as a model compound, the hydrogenation of aromatic aldehydes to corresponding benzyl alcohols was investigated in a fixed-bed reactor. Co/γ-Al2O3 doped with a amount of SiO2 displayed excellent catalytic performance for this reaction, Co/γ-Al2O3 is modified by SiO2 in two ways, the strong interaction between metal oxide and support is obviously reduced, and also a large number of acid sites are diminished on the catalyst. The first aspect apparently facilitated the reduction of metal oxide, and improved the hydrogenation activity of the catalyst; while the second aspect greatly inhibited the hydrogenolysis of the ―C―O bond, and thus increased the selectivity toward benzyl alcohol.
Keywords: Chemoselective hydrogenation; Aromatic aldehyde; Benzyl alcohol; Hydrogenolysis; Co/γ-Al2O3–SiO2;
Microwave synthesis of hydrophobic Ti-TUD-1 mesoporous silica for catalytic oxidation of cycloolefins by Sung-Min Jeong; Abhishek Burri; Nanzhe Jiang; Sang-Eon Park (39-44).
A simple microwave method was successfully adopted for the synthesis of various amount of Ti loaded TUD type mesoporous silica (Ti-TUD-1) using triethanolamine (TEA) as both templating and chelating agent. The time-cost was reduced dramatically due to the microwave heating which could accelerate the atrane formation as well as their following hydrolysis and condensation steps. Three dimensional mesopore structures were obtained with narrowed pore size distribution (2–8 nm) and high surface area (700–1000 m2/g). Ti species incorporated as tetrahedral structure were active in the liquid phase oxidation of cycloolefins. Further, microwave synthesis brought the hydrophobic nature to Ti-TUD-1 which could be attributed to the improved catalytic activity compared to conventionally prepared catalysts.
Keywords: Microwave synthesis; Ti- TUD-1; Mesoporous silica; Oxidation; Cycloolefin;
Corrigendum to “Performance and deactivation of Ir-based catalyst during hydroxylammonium nitrate catalytic decomposition” [Appl. Catal. A: Gen. 452 (2013) 64–68] by Rachid Amrousse; Toshiyuki Katsumi; Yosui Niboshi; Nobuyuki Azuma; Ahmed Bachar; Keiichi Hori (45-46).
Low temperature decomposition of hydrous hydrazine over FeNi/Cu nanoparticles by Khachatur V. Manukyan; Allison Cross; Sergei Rouvimov; Jeffrey Miller; Alexander S. Mukasyan; Eduardo E. Wolf (47-53).
A simple, surfactant-free liquid-phase reduction of Cu, Ni and Fe salts (e.g. nitrates, chlorides) was used to prepare nanostructured FeNi/Cu catalysts for hydrous hydrazine (N2H4·H2O) decomposition. The synthesis of nanomaterials includes reduction of copper salt using N2H4, followed by rapid reduction of iron and nickel salts by NaBH4. The catalysts were characterized by XRD, BET, TEM, XPS, XANES/EXAFS techniques and their activity and selectivity was studied during hydrous hydrazine decomposition at temperatures ranging from 300 to 345 K. The selectivity to hydrogen increases to ∼100% with increasing temperature up to ∼345 K. The catalytic performance of these materials depends on the structure of NiFe layer formed over a Cu core, which may be controlled by changing of NiFe/Cu mass ratio. Investigation of the catalytic performance for bi- and tri-metallic materials show that main active metal is nickel but a NiFe alloy could be responsible for the increased selectivity. Alloying of nickel with iron coupled with a favorable dispersion on copper nanoparticles remarkably enhances the catalytic conversion and selectivity of hydrogen evolution.
Keywords: Hydrous hydrazine; Catalytic decomposition; Hydrogen storage; NiFe/Cu nanoparticles;
Mesoporous, ligand free Cu-Fe solid catalyst mediated CS cross coupling of thiols with aryl halides by Deepa K. Dumbre; P.R. Selvakannan; S.K. Patil; Vasant R. Choudhary; Suresh K. Bhargava (54-60).
Solid catalyst derived from Cu-Fe hydrotalcite was demonstrated to be a novel, ligandless, efficient and environmentally greener catalyst for the synthesis of diaryl sulfurs from the C–S cross coupling reaction of substituted thiols with different aryl halides. This catalyst has shown higher product yield in the presence of dimethylformamide (as a solvent) and K2CO3 (as a base) at 120 °C. Influence of different solvents and bases on the product yield has also been investigated. The catalyst can be easily separated from the reaction mixture, simply by filtration and reused several times without a significant loss of its activity. The catalyst has been fully characterized for its surface and bulk properties and the mesoporous CuO:Fe2O3 phase was attributed for its catalytic activity towards S-arylation reactions.
Keywords: C–S cross coupling; S-arylation; Cu-Fe-hydrotalcite;
Effect of W addition on the hydrodeoxygenation of 4-methylphenol over unsupported NiMo sulfide catalysts by Changlong Wang; Dezhi Wang; Zhuangzhi Wu; Zhiping Wang; Chaoyun Tang; Pan Zhou (61-67).
Unsupported NiMo sulfide catalysts modified by tungsten were prepared by a mechanical activation method. They were characterized by XRD, XPS, SEM, TEM and BET specific surface area measurements. The effect of tungsten promoter on the structure and catalytic performance was also discussed. The present work suggested that the addition of tungsten could greatly enhance the hydrodeoxygenation (HDO) activity, and promote the direct deoxygenation (DDO) pathway. Moreover, the addition content affects the mount of active NiMo(W)S phase, resulting in various functions.
Keywords: Hydrodeoxygenation; 4-Methylphenol (4-MP); Promoter; Tungsten;
Rhodium-catalyzed codimerization of n-butenes with allylic halides by Arno Behr; Zeynep Bayrak; Stephan Peitz; Dietrich Maschmeyer; Guido Stochniol (68-71).
This paper describes the codimerization of n-butenes with allylic halides such as cinnamyl chloride and crotyl chloride. The highly active catalyst RhCl3·3H2O was investigated, resulting 70% yield of codimers with cinnamyl chloride and 1-butene. Furthermore, the reaction is dependent on the molar ratio of allylic chloride to RhCl3·3H2O ratio, where a ratio of 75:1 is optimal at a catalyst concentration of 2 mol%. Additionally allylic compounds such as cinnamyl chloride lead to higher yields of the codimer than other short chained allylic chlorides. So the codimerization of an allylic compound with 1-butene represents a simple method to produce short chained dienes at very mild reaction conditions.
Keywords: Codimerization; 1-Butene; Homogenous catalysis; Rhodium catalyst; Allylic compounds;
Catalytic properties of Au and Pd nanoparticles decorated on Cu2O microcubes for aerobic benzyl alcohol oxidation and Suzuki–Miyaura coupling reactions in water by K. Sudhakara Prasad; Hui-Bog Noh; S. Subba Reddy; A. Eswar Reddy; Yoon-Bo Shim (72-77).
The catalytic activities of Cu2O microcubes decorated with Au and Pd nanoparticles (Cu2O/Au and Cu2O/Pd) were synthesized by a microwave assisted technique and examined for the specific organic reactions, separately. Cu2O/Au and Cu2O/Pd catalysts were characterized and examined as the catalysts for the aerobic oxidation of benzyl alcohol to benzaldehyde and the Suzuki–Miyaura coupling reaction in water, separately. The yields of products were >90% with a selectivity of >99% for both catalytic reactions. The cheap, ligand free, efficient, non-toxic, and water soluble properties make the present catalyst ultimate for Suzuki and aerobic oxidation reaction.
Keywords: Cu2O microcubes; Nano-Au; Nano-Pd; Benzyl alcohol; Suzuki–Miyaura coupling reactions; Water;
Fiber based structured materials for catalytic applications by Erik Reichelt; Marc P. Heddrich; Matthias Jahn; Alexander Michaelis (78-90).
This review summarizes the resent research on fiber based structured materials for catalytic application. This material class comprises a wide range of differently structured supports made from ceramic, metal or glass. Within the last decades due to their flexibility fiber based catalysts were applied to several reactions ranging from pollutant control to fuel processing and showed significant advantages in mass and heat transfer, pressure drop and productivity. The review focusses on mass transfer and pressure drop characteristics and the published correlations for them. A classification in comparison to established support structures is done not only showing superior properties but also the demand for further studies in hydrodynamics and transfer processes.
Keywords: Catalyst support; Fiber based structured materials; Glass fiber; Metal fiber; Ceramic fiber; Trade-off index;
The structure and catalytic properties of amorphous phase in MoVTeO catalysts for propane ammoxidation by E.V. Ishchenko; T.V. Andrushkevich; G.Ya. Popova; T.Yu. Kardash; A.V. Ishchenko; L.S. Dovlitova; Yu.A. Chesalov (91-102).
The structure and catalytic properties of amorphous phase in MoVTeO catalysts for propane ammoxidation.This work presents an investigation of the chemical and phase composition of Mo1.0V0.3Te0.23O x catalyst prepared by spray drying. The changes in the catalyst after heat treatment at 220–550 °C were characterized by IR and Raman spectroscopy, XRD, HRTEM and differential dissolution methods. In the range of temperature 400–420 °C HRTEM revealed the presence of nanoscaled crystallites that are structurally and chemically related to M1 and M2 phases and randomly distributed in the amorphous matrix. The characteristic diffraction pattern of the amorphous product can be described by a model of nano-sized clusters built from the structure of M1 phase. Nanostructured catalysts are active and selective in propane ammoxidation. The increase of temperature of heat treatment of the catalyst above 450 °C leads to decomposition of nanostructured M1 phase and crystallization of M2 and a series of vanadium–molybdenum phases. The process is accompanied by a decrease in activity.
Keywords: Propane ammoxidation; MoVTe catalyst; Nanosized clusters; Nanostructure; M1 phase;
Influence of preparation method and palladium content on Pd/C catalysts activity in the liquid phase hydrogenation of nitrobenzene to aniline by Mária Turáková; Milan Králik; Peter Lehocký; Ľubomír Pikna; Miroslava Smrčová; Dagmar Remeteiová; Alexander Hudák (103-112).
Two sets of Pd/C catalysts with 1–10 wt.% Pd content supported on active carbon were prepared by a conventional formaldehyde method. One set was prepared using H2[PdCl4] complex and other one with Na2[PdCl4]. In spite of different metal loadings, average crystallite size of palladium particles estimated by XRD and TEM analyses was virtually the same in all the cases, from 3 to 5 nm. Catalysts were tested for nitrobenzene hydrogenation in a stirred autoclave with the presence of methanol as a solvent, at 5 MPa and 50 °C. Ratio of Pd to nitrobenzene substrate was in every reaction mixture the same: 15.4 mg of palladium per mol of nitrobenzene. Specific initial catalyst activity (initial reaction rate) for catalysts with 1–4 wt.% Pd content for both sets of catalysts was comparable. It means that palladium complex used for the preparation had no-effect on catalyst activity. With palladium content higher than 4 wt.% a significant drop in the catalytic activity and increase in amount of the leached palladium were observed, which should be prescribed for the formation of agglomerates of palladium crystallites (revealed by TEM) and consequent decrease in concentration of catalytic sites. Because of a decrease in catalytic activity, the reaction times were longer, which caused a higher metal leaching.
Keywords: Liquid phase hydrogenation; Nitrobenzene; Palladium; Catalyst activity; Leaching;
The remote oxidation of soot separated by ash deposits via silver–ceria composite catalysts by Kiyoshi Yamazaki; Yuji Sakakibara; Fei Dong; Hirofumi Shinjoh (113-120).
In a new phenomenon referred to as remote catalysis, silver–ceria composites catalyzed the oxidation of soot particles from which they were separated by alumina or calcium sulphate ash deposits. The remote oxidation effect was found to extend across an ash thickness of more than 50 μm.One of the main issues of catalyzed diesel particulate filter is ash deposition onto catalyst coated on the filter. The effects of ash deposition on the catalysis of soot oxidation with gaseous oxygen were determined using multi-layered samples composed of a catalyst, an ash material and soot particles deposited on a thin cordierite plate in sequence. Catalysts composed of silver and ceria were used to enhance the oxidation of soot particles separated from the catalyst by ash deposits of either alumina or calcium sulfate. The effectiveness of remote soot oxidation was found to extend across an ash thickness of more than 50 μm for both ash materials, although a catalyst composed only of ceria did not show any catalytic performance for remote soot oxidation. Using an 18O/16O isotopic exchange reaction and electron spin resonance techniques, a possible mechanism for this phenomenon was proposed, whereby a superoxide ion (O2 −) species generated on the catalyst surface first migrates to the ash surface and then to the soot particles, which it subsequently oxidizes.
Keywords: Soot oxidation; Ash deposition; Remote catalysis; Silver; Ceria;
Catalytic performance of supported nanosized cobalt and iron–cobalt mixed oxides on MgO in oxidative degradation of Acid Orange 7 azo dye with peroxymonosulfate by M. Stoyanova; I. Slavova; St. Christoskova; V. Ivanova (121-132).
Cobalt and mixed iron–cobalt oxides immobilized on MgO and their bulk analogues were prepared and their catalytic behavior in advanced oxidation of Acid Orange 7 (AO7) in aqueous solution using sulfate radical was investigated. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Mössbauer spectroscopy. Results showed that nanostructured oxide materials having spinel structure were obtained with good dispersion on the surface of MgO in the case of supported compounds. The performance of the as-prepared nanocatalysts in the activation of peroxymonosulfate (PMS) to generate sulfate radicals for degradation of AO7 was studied. It was found that the spinel oxides loaded on MgO are far more efficient for heterogeneous PMS activation than the unsupported ones, resulting in much faster AO7 removal rate. Complete degradation of 50 mg/L AO7 (>99%) could occur within a short duration of 10 min (for Co/MgO) to 25 min (for CoFe2/MgO) by using very low catalysts concentration of 0.15 g/L. The supported catalysts were also found more active than the homogeneous Co(II) ions and physical mixtures of corresponding bulk oxide and MgO. Kinetic studies showed that heterogeneous oxidation of AO7 in supported catalyst/PMS systems followed first order kinetics. The effect of several operational parameters, such as catalyst loading, PMS concentration, and pH on the AO7 degradation kinetics and removal efficiency was investigated. The catalysts studied presented stable performance during three runs of reuse with minor Co and Fe leaching even under acidic condition. Quenching studies by using ethanol and tert-butyl alcohol as radical scavengers were conducted which indicated that sulfate radicals are the primary reactive species responsible for the AO7 degradation. Results obtained reveal that the as-prepared catalysts could be potentially used in advanced oxidation technologies for organic dyes removal in water.
Keywords: Cobalt and iron–cobalt mixed oxides; Supported catalysts; Peroxymonosulfate; Sulfate radicals; Acid Orange 7 degradation;
Magnetically separable carbon nanocomposite catalysts for efficient nitroarene reduction and Suzuki reactions by Mohammadreza Shokouhimehr; Taeho Kim; Samuel Woojoo Jun; Kwangsoo Shin; Youngjin Jang; Byung Hyo Kim; Jaeyun Kim; Taeghwan Hyeon (133-139).
Novel magnetically recyclable carbon nanocomposites were synthesized to support various nanocatalysts using a simple, economical and scalable method. The designed nanocomposites, which are composed of porous carbon and Fe3O4 nanocrystals, can be used as an expandable platform to load versatile nanoparticle catalysts such as Pd and Pt. These nanocomposites with high surface area and permeable porous structure can contain abundant and accessible small-sized catalyst nanoparticles. These characteristics led to efficient catalytic reactions and enhanced catalytic activity, which were verified in selective reduction of nitroarenes and Suzuki cross-coupling reactions. The nanocomposite catalysts provided excellent catalytic activities to yield the desired products in short reaction time and mild reaction conditions. The catalysts could be easily separated from the reaction mixture by a magnet, and recycled five consecutive cycles in reduction of nitrobenzene and Suzuki cross-coupling of bromobenzene without losing significant activities.
Keywords: Palladium nanoparticles; Heterogeneous catalysis; Magnetic separation; Suzuki cross-coupling; Reduction; Nanocomposite; Carbon materials;
First demonstration of rainbow photocatalysts using ternary Cd1-x Zn x Se nanorods of varying compositions by An T. Nguyen; Wei-Hao Lin; Yi-Hsuan Lu; Yao-De Chiou; Yung-Jung Hsu (140-147).
We demonstrated for the first time that the assembly of Cd1-x Zn x Se nanorods (NRs) with five compositions (x = 0, 0.35, 0.54, 0.61, 1) may absorb the whole visible spectrum in a gradient fashion for photoconversion applications. The samples were prepared by conducting cation exchange reactions on Ag2Se NRs with excess Cd2+ and Zn2+ ions. By modulating the molar ratio of Cd2+ to Zn2+ employed, the composition of the resulting Cd1-x Zn x Se NRs can be delicately controlled. Because of the tunability of band edge with stoichiometry, Cd1-x Zn x Se NRs of varying compositions absorbed light at different wavelength regions, which spanned almost the entire visible spectrum. As compared to the individual constituent NRs, the NRs assembly exhibited greatly improved photoactivity in photoelectrochemical water splitting as well as superior photocatalytic performance toward methylene blue degradation under white light illumination. This superiority emanates from the composition-gradient configuration that significantly improves the light harvesting efficiency by absorbing almost the whole visible spectrum of the incident white light. The full visible photon harvesting of the NRs assembly was validated by the photocurrent action spectrum which showed spectral accordance with the absorption spectrum. The recycling test manifests that the NRs assembly displayed substantially high stability during its use as photocatalyst. Furthermore, the result of performance evaluation under natural sunlight reveals that the present NRs assembly can be used as practical rainbow photocatalysts which may effectively harvest energy from sunlight. The demonstration from this work may facilitate the use of sophisticated assembly of semiconductor nanocrystals in relevant photoconversion processes where the effectiveness of photon harvesting is determinant.
Keywords: Rainbow photocatalysts; Solar fuel production; Cd1-x Zn x Se; Cation exchange;
Catalytic behavior of alkali-treated Pt/HMOR in n-hexane hydroisomerization by R. Monteiro; C.O. Ania; J. Rocha; A.P. Carvalho; A. Martins (148-157).
Bifunctional Pt-HMOR catalysts were prepared by incipient wetness impregnation of various desilicated MOR obtained by alkaline treatment using NaOH concentrations ranging from 0.1 to 0.5 M. The zeolite structural changes upon modification were investigated by several techniques including powder X-ray diffraction, 27Al and 29Si MAS-NMR spectroscopy, N2 adsorption, pyridine adsorption followed by infrared spectroscopy and the catalytic model reaction of m-xylene transformation. For low alkaline concentration the zeolite acidity is preserved, along with a slight increase of the volume correspondent to the larger micropores due to the removal of extra-framework debris already existent at the parent zeolite. At higher NaOH concentrations there is a significant loss of crystalinity and acidity as well as the formation of mesoporosity. The characterization of the metal function shows similar patterns for Pt-HMOR and Pt-M/0.1 samples, with Pt particles located mainly inside the inner porosity. In contrast, large Pt particles become visible at the intercrystalline mesoporosity of MOR crystals developed during the desilication treatments at severe alkaline conditions. The catalytic results obtained for n-hexane hydroisomerization showed an improved selectivity for dibranched over monobranched isomers for Pt-M/0.1 sample, likely due to the preservation of the support acidity and the slight enlargement of the micropores. This work is a new example in which the mesoporous development does not improve the catalytic efficiency of the zeolites, whereas mild alkaline desilication might be considered as an effective solution to produce customized catalysts with enhanced performance for a given application.
Keywords: MOR; Desilication; Bi-functional catalysts; Acidity; Platinum; n-Hexane hydroisomerization;
Indirect coal to liquid technologies by Erlei Jin; Yulong Zhang; Leilei He; H. Gordon Harris; Botao Teng; Maohong Fan (158-174).
Indirect coal liquefaction has enormous potential applications. Increasingly, new synthetic technologies have been concentrating in this area, and a number of new large-scale indirect coal liquefaction plants have been set up during very recent years. Further, a large volume of papers on indirect coal liquefaction have been published over the last two decades, including those on Fischer–Tropsch synthesis, syngas to ethylene glycol, syngas to methanol, dimethyl ether as well as methanol to olefins. In this review, the recent literature of indirect liquefaction, including Fischer–Tropsch and syngas to chemicals, are summarized, with an emphasis on the reaction mechanisms, conditions and novel catalysts.
Keywords: Coal liquefaction; Fischer–Tropsch; MTO; Ethylene glycol; Syngas;
Ceria and lanthana as blocking modifiers for the external surface of MFI zeolite by Hoi-Gu Jang; Kwang Ha; Jong-Ho Kim; Yoshihiro Sugi; Gon Seo (175-185).
Display OmittedThe ceria- and lanthana-modified MFI zeolites were prepared and extensively investigated to verify the function of lanthanide oxides as blocking modifiers. Their catalytic behavior in the methanol-to-olefin (MTO) conversion was explained by the characterization results regarding crystallinity, agglomeration, porosity, surface composition, and the uptakes of o-xylene and methanol. The ceria impregnated on the MFI formed nano-sized small particles with two oxidation states of +3 and +4 (Ce2O3 and CeO2) on the surface and was located predominantly on the external surface. So, the ceria impregnation maintained the porosity and activity of the MFI, and induced little change in the conversion and product composition of MTO. However, the lanthana impregnated on the MFI dispersed as a single lanthana (La2O3) phase in its micropores, as well as on the external surface. The blocking of the micropores and reduction of acidity by lanthana impregnation lowered the activity of the lanthana-modified MFI in MTO. The ceria located on the external surface of MFI did not have any negative effects on the catalytic performance, while the lanthana dispersed in the micropores lowered the conversion in MTO. The locations and dispersed states of ceria and lanthana were systematically discussed in the relation to their catalytic performance as blocking modifiers.
Keywords: MFI zeolite; Ceria and lanthana impregnation; MTO reaction; Catalytic performance;
Esterification of levulinic acid with ethanol over sulfated Si-doped ZrO2 solid acid catalyst: Study of the structure–activity relationships by Yasutaka Kuwahara; Wako Kaburagi; Koji Nemoto; Tadahiro Fujitani (186-196).
Esterification of levulinic acid with ethanol to produce ethyl levulinate was examined by using sulfated Si-doped ZrO2 solid acid catalysts with enlarged surface areas and the relationships between the structural properties and catalytic performances were investigated. Structures of the catalysts were verified by XRD, nitrogen physisorption, FE-SEM, UV–vis and FTIR measurements. Acidity of the catalysts that substantially affect the catalytic activity was evaluated by NH3-TPD measurement. Incorporation of Si atom into the lattice structure of ZrO2 (up to 30 mol% Si per Zr atom) afforded high-surface-area SiO2-ZrO2 mixed oxides, and their sulfated forms provided increased numbers of sulfate anions and the associated acid sites. Several distinct correlations were found between the structural properties/acidities and catalytic activities, which suggested that (i) the number of accessible active acid sites and (ii) the accessibility of the organic reactants to the active sites play crucial roles in determining the overall activity. Among the catalysts tested, sulfated Si-doped ZrO2 with optimum Si content (5.0–10 mol% Si per Zr) was found to be the best catalyst, the activity of which was far superior to that of the conventional sulfated ZrO2. In addition, direct conversion of cellulosic sugars (glucose and fructose) into levulinate esters was also examined, in view of their practical applications in acid-catalyzed biomass conversion processes.
Keywords: Biomass conversion; Levulinic acid; Esterification; Solid acid catalyst; Sulfated zirconia;
Catalytic epoxidation of propylene with CO/O2 over Au/TiO2 by Vladimir I. Sobolev; Konstantin Yu. Koltunov (197-203).
Gold nanoparticles supported on TiO2 are known to catalyze vapor-phase epoxidation of propylene with molecular oxygen in the presence of H2 as the necessary reducing co reagent. Here, we report that carbon monoxide can be employed instead of hydrogen to accomplish similar reaction. The reaction of propylene, CO and O2 can be carried out in a flow reactor over Au/TiO2 at a temperature of 40–90 °C. The propylene oxide selectivity attains 80–97% at propylene conversion of 1.7–3.7%. The propylene oxide yield goes through the maximum as a function of reaction time, the maximal value being twice higher compared to yield of propylene oxide achieved by “traditional” reaction with H2/O2 mixture. Utilization efficiency of CO reaches 25%, which is comparable to that of H2 in the analogous reaction of propylene, H2 and O2. Proposed mechanism for the reaction involves the formation of specific oxygen species arising from O2 on catalytic sites reduced with CO. This is in line with generation of highly reactive oxygen species (detectable by oxygen isotopic exchange) on Au/TiO2 surface treated preliminarily with CO.
Keywords: Gold catalysts; Au/TiO2; Propylene epoxidation; Propylene oxide; CO/O2;
Application of staged O2 feeding in the oxidative dehydrogenation of ethylbenzene to styrene over Al2O3 and P2O5/SiO2 catalysts by Christian Nederlof; Valeriya Zarubina; Ignacio V. Melián-Cabrera; Erik H.J. Heeres; Freek Kapteijn; Michiel Makkee (204-214).
Drastic improvements in styrene yield and selectivity were achieved in the oxidative dehydrogenation of ethylbenzene by staged feeding of O2. Six isothermal packed bed reactors were used in series with intermediate feeding of O2, while all EB was fed to the first reactor, diluted with helium or CO2 (1:5 molar ratio), resulting in total O2:EB molar feed ratios of 0.2–0.6. The two catalyst samples, γ-Al2O3 and 5P/SiO2, that were applied both benefitted from this operation mode. The ethylbenzene conversion per stage and the selectivity to styrene were significantly improved. The production of CO X was effectively reduced, while the selectivity to other side products remained unchanged. Compared with co-feeding at a total O2:EB molar feed ratio of 0.6, by staged feeding the EB conversion (+15% points for both catalysts), ST selectivity (+4% points for both samples) and O2 (ST) selectivity (+9% points for γ-Al2O3 and +17% points for 5P/SiO2) all improved. The ethylbenzene conversion over 5P/SiO2 can be increased from 18% to 70% by increasing the number of reactors from 1 to 6 with each reactor a total amount of O2 of 0.1 without the loss of ST selectivity (93%). For 5P/SiO2 a higher temperature (500 °C vs. 450 °C for Al2O3) is required. Essentially more catalyst (5P/SiO2) was required to achieve full O2 conversion in each reactor. Staged feeding of O2 does not eliminate the existing issues of the catalyst stability both in time-on stream and as a function of the number of catalyst regenerations (5P/SiO2), or the relatively moderate performance (relatively low styrene selectivity for γ-Al2O3).
Keywords: Oxidative dehydrogenation; Ethylbenzene; Styrene; Staged feeding; Selectivity; Alumina; Phosphorous; Silica; Catalyst coking; Catalyst stability;