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Applied Catalysis A, General (v.423-424, #)
Lewis acid/surfactant rare earth trisdodecylsulfate catalysts for biodiesel production from waste cooking oil by Flávia C.G. de Mattos; Joina A. da S. de Souza; Ana B. do A. Cotrim; Julio L. de Macedo; José A. Dias; Sílvia C.L. Dias; Grace F. Ghesti (pp. 1-6).
Display Omitted► Synthesis of rare earth trisdodecylsulfate Lewis acid-surfactant-combined catalysts. ► Production of biodiesel from waste cooking oil. ► Cerium(III) catalyst showed the highest activity for transesterification. ► Lanthanum(III) and gadolinium(III) materials were the most active for esterification. ► Gadolinium(III) catalyst was the best material for the conversion of waste feedstock.This work reports the synthesis, characterization and application of rare earth (La, Ce, Sm and Gd) trisdodecylsulfate materials as Lewis acid-surfactant-combined catalysts for the production of biodiesel from waste cooking soybean oil. All the solid materials showed a bilayer lamellar arrangement with the dodecylsulfate molecules in a head to head, tail to tail packing. The reaction between commercial feedstocks (soybean oil and oleic acid) with ethanol was used separately to study La, Ce, Sm and Gd catalyst activities for transesterification (conversions of 73, 92, 53 and 73%) and esterification (conversions of 87, 80, 75 and 85%) after 1h, respectively. Among them, cerium(III) trisdodecylsulfate showed the highest catalytic activity (TOF=29.5molh−1molcat−1) for transesterification, while lanthanum(III) and gadolinium(III) trisdodecylsulfates were the most active for esterification (TOF=28.7molh−1molcat−1). The application of the studied catalysts for the simultaneous transesterification and esterification reaction of waste cooking oil, containing 8.8wt.% of free fatty acids (FFAs), with ethanol showed conversions of 76 (3.3wt.% of FFAs), 79 (5.3wt.% of FFAs), 81 (2.5wt.% of FFAs) and 86% (0.0wt.% of FFAs) after 1h for La, Ce, Sm and Gd catalysts, respectively. Thus, gadolinium(III) trisdodecylsulfate was the best material for the conversion of waste feedstock to produce biodiesel. However, cerium(III) trisdodecylsulfate was less susceptible to deactivation, exhibiting conversion values of 92, 81 and 77% for the 1st, 2nd and 3rd reaction cycles. The catalysts were characterized by elemental analysis, X-ray powder diffraction (XRD),1H NMR, thermal analysis (TG/DTG/DTA) and FTIR measurements.
Keywords: Rare earth trisdodecylsulfate; Lewis acid-surfactant-combined catalyst; Transesterification; Esterification; Biodiesel
Influence of ethanol in the presence of H2 on the catalytic growth of vertically aligned carbon nanotubes by O. Guellati; I. Janowska; D. Bégin; M. Guerioune; Z. Mekhalif; J. Delhalle; S. Moldovan; O. Ersen; C. Pham-Huu (pp. 7-14).
Display Omitted► We have investigated the influence of EtOH addition on the VA-CNTs growth by CVD. ► The EtOH addition up to 9% to the reaction mixture increases the CNTs growth rate. ► The EtOH addition higher than 9% decreases the CNTs growth rate. ► A structure of CNTs array and the individual tubes change with EtOH content.The vertically aligned multi-walled carbon nanotubes (VA-MWNTs) were synthesized by a catalytic chemical vapor deposition (CCVD) technique, using ferrocene as an iron catalyst precursor and toluene/ethanol mixture with different ratio as a carbon source/etching agent, in the presence of H2. The growth rate, efficiency and the structure of the synthesized tubes were investigated. The CNTs growth rate and quality of tubes significantly improve up to 9vol.% of ethanol whereas a negative influence was observed for higher ethanol concentration (>17vol.%). Low ethanol content in the reaction mixture (5vol.%) results in the highest volume density of the tubes within the array along with highest specific surface area. The synergetic effect of EtOH/hydrogen on the growth rate of VA-MWNTs was observed as well.
Keywords: VA-MWNTs; Floated-catalyst; Ethanol-CCVD
The quantitative description of the effects of cesium doping on the activity and properties of Cu/ZnO/Al2O3 catalyst in low-temperature water–gas shift by Paweł Kowalik; Wiesław Próchniak; Marcin Konkol; Tadeusz Borowiecki (pp. 15-20).
Display Omitted► Inhibition of methanol synthesis in the LT-WGS process on Cu/ZnO/Al2O3 by cesium. ► Modification of the reduction process by alkali metals. ► Decrease of specific and active surface areas by alkali metals. ► Significant decrease of methanol formation with a slight effect on LT-WGS process. ► Decrease of catalytic activity upon thermal treatment favored by cesium.The effects of cesium doping (in the concentration range up to 5wt.% Cs2O) introduced into a copper catalyst with the composition corresponding to that for the industrial catalysts used for low-temperature water–gas shift process (LT-WGS) have been investigated. Precursors and catalysts have been characterized by XRD, ICP-OS, TPD-EGA, N2O chemisorption, TPR, N2 physisorption and reaction rates for WGS and methanol synthesis under the pressure of 2.5MPa have been determined. The results reveal that the cesium doping inhibits radically methanol synthesis, with the optimal Cs2O content being <1wt.%.
Keywords: Water–gas shift; Cu/ZnO/Al; 2; O; 3; catalyst; Cesium oxide; Methanol synthesis
Pulsed laser deposition of Co3O4 nanoparticles assembled coating: Role of substrate temperature to tailor disordered to crystalline phase and related photocatalytic activity in degradation of methylene blue by T. Warang; N. Patel; A. Santini; N. Bazzanella; A. Kale; A. Miotello (pp. 21-27).
.Display Omitted► Co3O4 NPs assembled coating synthesized by PLD at low temperature (150°C). ► Complete degradation of MB over Co3O4 NPs heterogeneous catalyst by Photo-Fenton reaction. ► Photo-degradation activity obtained by Co3O4 NPs heterogeneous catalyst is significantly higher than homogenous Co+2 ions. ► Co3O4 NPs assembled coating is recovered and reused easily.Cobalt oxide (Co3O4) nanoparticles (NPs) assembled coating have been prepared by reactive pulsed laser deposition of Co, in O2 atmosphere, on Si or glass substrate ranging from room temperature to 250°C. The NPs, having narrow size distribution with average values of around 25–50nm, were characterized by Raman, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The Co3O4 NPs synthesized at 150°C comprise a mixed amorphous–nanocrystalline phase (that is unique property for catalysis) while complete crystallization of Co3O4 occurs at 250°C with formation of spinel structure. Photocatalytic properties of Co3O4 NPs assembled coating for degradation of methylene blue solution under visible light irradiation are reported. The effect of H2O2 concentration and effect of pH variation on dye degradation rate has been reported. The reusability of the Co3O4 NPs assembled thin coating catalyst was further evaluated in several recycling runs. The activity of heterogeneous Co3O4 NPs assembled thin coating catalyst was compared with homogenous catalyst producing Co+2 ions in methylene blue solution.
Keywords: Pulsed laser deposition; Co; 3; O; 4; nanoparticles; Photocatalytic degradation; Water purification
Dependency on chloride concentration and ‘in-sphere’ oxidation of H2O for the effective TiO2-photocatalysed electron transfer from H2O to [PdCl n(H2O)4− n]2− n ( n=0–4) in the absence of an added sacrificial reducing agent by R.J. Kriek; F. Mahlamvana (pp. 28-33).
Display Omitted► Successful photocatalytic reduction of Pd(II) in the absence of a sacrificial reducing agent. ► Water is oxidised to supply electrons for the photocatalytic reduction of Pd(II). ► Highest photocatalytic reduction rate observed for the neutral Pd(II) species.The photocatalytic reduction trends of palladium chloride aqua complexes, [PdCl n(H2O)4− n]2− n ( n=0–4), have been investigated employing titanium dioxide (TiO2) as photocatalyst in the absence of an added sacrificial reducing agent (SRA). Solutions were prepared at those Cl−-concentrations that coincide with the maximum of each species and the photocatalytic reduction behaviour of Pd(II) at these chloride-concentrations is related to the complex present in greater abundance. The photocatalytic reduction rate trend is observed to have the following decreasing order: PdCl2(H2O)2>[PdCl(H2O)3]+>[Pd(H2O)4]2+>[PdCl3(H2O)]−>[PdCl4]2−, with [PdCl4]2− showing resistance to photocatalytic reduction in the absence of an added SRA. It is postulated that oxidation of the coordinated water molecules impacts on the rate of reduction. For those complexes for which the ratio H2O:Cl− is greater than 50%, the oxidation of coordinated ‘in-sphere’ water molecules is working against an expected increase in the rate of reduction as predicted by the complexes’ standard reduction potentials. Interplay between thermodynamics and adsorption/interaction of the palladium species on the catalyst surface is clearly at work in this system.
Keywords: Chloride; Palladium; Photocatalytic reduction; Sacrificial reducing agent (SRA); Speciation
Photocatalytic activity of single and mixed nanosheet-like Bi2WO6 and TiO2 for Rhodamine B degradation under sunlike and visible illumination by S. Murcia-López; M.C. Hidalgo; J.A. Navío (pp. 34-41).
Display Omitted► Bi2WO6–TiO2 systems were obtained by mixing single Bi2WO6 nanosheets and TiO2-P25. ► Rhodamine B photodegradation was studied under different illumination conditions. ► The mixtures showed a synergy compared to Bi2WO6 and P25 photocatalysts. ► It was observed the influence of the preparation method on the obtained material.The photocatalytic activity, under sunlike illumination, for Rhodamine B ( RhB) degradation using Bi2WO6–TiO2 samples, is reported. Two different kinds of Bi2WO6–TiO2 samples were studied, obtained by distinct methods: first, a mechanical mixing, by adding to synthesized nanosheet-like Bi2WO6 powder the corresponding amount of TiO2 nanoparticles (P25) in order to obtain physical mixtures of both catalysts with different percentages of TiO2 (5, 10 and 50wt%); second, a single Bi2WO6–TiO2 heterostructure was prepared by adding commercial TiO2-P25 to the Bi2WO6 precursors (50wt%) prior to the hydrothermal treatment, thus obtaining a sample with “in situ” TiO2 incorporation. Comparisons between the photocatalytic behaviour of these samples and those exhibited by the single materials Bi2WO6 and TiO2 (P25) were carried out, in order to establish the effect not only of the TiO2 addition but also of the way in which TiO2 (P25) is incorporated. The role of each single photocatalyst in the mixtures in the RhB degradation and mineralization under sunlike and just visible illumination was also studied.
Keywords: Photocatalysis; Bi; 2; WO; 6; TiO; 2; Rhodamine B; Sunlike illumination
Effect of ZrO2 addition method on the activity of Al2O3-supported CuO for NO reduction with CO: Impregnation vs. coprecipitation by Qiang Yu; Xiaojiang Yao; Hongliang Zhang; Fei Gao; Lin Dong (pp. 42-51).
Display Omitted► Cu–Zr–Al catalysts were prepared from two different procedures. ► The addition of ZrO2 improves the catalytic activity, depending on the addition method. ► The enhanced activity is attributed to highly dispersed copper species interacting with ZrO2.Supported copper oxide catalysts (CuO/Al2O3, CuO/ZrO2/Al2O3, CuO/ZrO2–Al2O3) were prepared from different procedures and tested in the catalytic reduction of NO with CO to investigate the effect of ZrO2 addition method. The catalysts were characterized by means of ICP, BET, XRD, Raman, H2-TPR, XPS, FTIR of NO or/and CO adsorption. Activity results demonstrated that the addition of ZrO2 could improve catalytic performance, which is dependent on the addition method. The sequence of activity is CuO/ZrO2–Al2O3>CuO/ZrO2/Al2O3>CuO/Al2O3. Based on the results of composition and texture, CuO/ZrO2–Al2O3 sample shows more surface zirconia species and larger surface area than CuO/ZrO2/Al2O3. XRD and Raman results suggest amorphous ZrO2 and highly dispersed copper oxide species are mainly present in the ZrO2-added catalysts except for a few CuO crystallites in CuO/ZrO2/Al2O3. Highly dispersed copper oxide species strongly interacting with amorphous zirconia (Cu⋯O⋯Zr species) was observed in H2-TPR and XPS, which was considered as the origin of the enhanced activity. In addition, the adsorption type and configuration of NO was similar over these catalysts. However, CuO/ZrO2–Al2O3 sample shows the greater capacity to activate the adsorbed NO species than CuO/ZrO2/Al2O3.
Keywords: Copper oxide; Zirconia; Alumina; NO reduction with CO; Cu⋯O⋯Zr species
Nanoshell carbon-supported cobalt catalyst for the aerobic oxidation of alcohols in the presence of benzaldehyde: An efficient, solvent free protocol by Yongbo Kuang; Yuta Nabae; Teruaki Hayakawa; Masa-aki Kakimoto (pp. 52-58).
Display Omitted► The system oxidizes aliphatic alcohols as efficiently as benzylic alcohols. ► Oxidation reactions are carried out under solvent free conditions. ► Nanoshell carbon with cobalt nano-particles supported is a highly stable and easily recoverable heterogeneous catalyst. ► Cobalt particles hidden in the bulk of carbon are also accessible for reactions.A versatile, solvent free aerobic alcohol oxidation system has been established in the presence of benzaldehyde based on a heterogenous cobalt catalyst supported on nanoshell carbon (Co/NSC), which was prepared through the pyrolysis of a mixture of Co(II) phthalocyanine and phenol resin. The established system features equal efficiency toward both benzylic alcohols and aliphatic alcohols. The nanoshell carbon has been demonstrated to be a better supporting material for the present reaction than some other carbon materials, e.g., activated carbon. Mechanistic studies suggest that Co/NSC can catalyze the formation of oxidative intermediate peroxybenzoic acid as efficiently as homogeneous cobalt catalyst, and moreover, suppress the undesired Baeyer–Villiger side reaction. Co/NSC also exhibits good reusability, i.e., it can be reused for at least 10 times without significant loss of performance.
Keywords: Alcohol oxidation; Solvent free; Aerobic; Carbon; Cobalt
The role of RWGS in the dehydrogenation of ethylbenzene to styrene in CO2 by Christian Nederlof; Güliz Talay; Freek Kapteijn; Michiel Makkee (pp. 59-68).
Display Omitted► Styrene yield over iron, vanadia and chromia catalysts is improved in the presence of CO2. ► Coke improves the RWGS activity of the vanadia catalysts. ► Hydrogen spill-over from coke to the catalyst, in a two-step mechanism, is proposed for dehydrogenation in CO2. ► RWGS takes place via redox and associative mechanism, the redox mechanism is dominant.The addition of CO2 to the dehydrogenation of ethylbenzene (EB) to styrene over promoted and un-promoted vanadia, iron, and chromia catalysts on alumina improves the yield of styrene, in comparison with the use of N2 as diluent. Depending on the catalyst, EB conversion increases 5–10%, while selectivity does not change significantly. The potassium promoted vanadium catalyst shows the highest CO2 conversion for dehydrogenation with the largest increase in EB conversion. The activity of these catalysts in the reverse water–gas-shift (RWGS) reaction, in the presence and absence of the dehydrogenation, is very different. Vanadium catalysts exhibit the lowest CO2 RWGS activity. The presence of coke on the catalyst suppresses the RWGS reaction over chromium and iron catalysts, but improves the activity of the vanadium catalyst. This is attributed to hydrogen spill-over from the coke to the metal catalyst. A two-step mechanism with a hydrogen spill-over is proposed for the EB dehydrogenation in CO2. Step-response experiments show that the redox mechanism for the RWGS and the two-step pathway for dehydrogenation in CO2 are the dominant routes. A slight RWGS activity of the bare alumina support is attributed to an associative mechanism.
Keywords: Heterogeneous catalysis; Reverse water–gas-shift reaction; Ethylbenzene; Styrene; Dehydrogenation; CO; 2; Hydrogen spill-over; Coke; Vanadia; Iron; Chromia; Redox mechanism; Associative mechanism
The effects of partial replacement of TiCl4 by Ti(OR)4 on the performance of MgCl2-supported Ziegler–Natta catalysts by Cristóvão de Lemos; Fernando Franceschini; Claudio Radtke; João H.Z. dos Santos; Carlos R. Wolf (pp. 69-77).
Display Omitted► Partial replacement of TiCl4 by Ti(OR)4 in Ziegler–Natta catalysts. ► Reduction of preparation time and reagents. ► Similar characteristics to the industrial plant catalyst in terms of activity and high density polyethylene properties.In a Ti-based Ziegler–Natta catalyst with in situ generated MgCl2, the titanium tetrachloride (TiCl4) was partially replaced by titanium tetra-alkoxide (Ti(OR4)), where R was either ethyl or n-butyl, and the effect of the addition order of the titanium compound was evaluated. For comparison, two other catalysts were synthesized: (1) one had the same amount of Ti, exclusively from TiCl4; (2) the other is employed in industrial processes and was used as the reference. Ti3+ comprised 85% of the total amount of titanium added during the catalyst synthesis. The amount of soluble Ti in the supernatant phase was at most 0.002molL−1, indicating that the added Ti reacted with the support. In general, Ziegler–Natta catalysts demand a significant amount of raw materials, while these catalysts require a lower amount of titanium compounds and save a significant amount of solvent in particular during the synthesis (approximately 80%). The preparation time of the catalysts was also reduced. The performance of these catalysts during ethylene polymerization suggests that adding Ti(OR)4 created a catalyst with a similar activity and ability to form high-density polyethylene as the reference catalyst.
Keywords: Ziegler–Natta catalyst; High-density polyethylene; Titanium tetra-alkoxide
A novel catalyst containing palladium nanoparticles supported on poly(2-hydroxyethyl methacrylate)/CMK-1: Synthesis, characterization and comparison with mesoporous silica nanocomposite by Roozbeh Javad Kalbasi; Neda Mosaddegh; Alireza Abbaspourrad (pp. 78-90).
Display Omitted► Pd-PHEMA/CMK-1 nanocomposite was prepared as a novel heterogeneous catalyst. ► CMK-1 acted as an ideal support for Pd-poly(2-hydroxyethyl methacrylate). ► The nanocomposite showed reasonable activity for Heck reaction in water. ► Pd-PHEMA/CMK-1 showed higher thermal stability than Pd-PHEMA/MCM-48.A novel catalyst containing palladium nanoparticles supported on poly(2-hydroxyethyl methacrylate)/CMK-1 (Pd-PHEMA/CMK-1) was prepared, and its application was investigated as a heterogeneous catalyst in Heck coupling reaction. PHEMA/CMK-1 was prepared by in situ polymerization method and used as a support for palladium nanoparticles obtained through the reduction of palladium acetate by hydrazine hydrate. The structural and morphological characterizations of Pd-PHEMA/CMK-1 nanocomposite were carried out using XRD, FT-IR, BET, TGA, XPS, UV–vis, SEM and TEM techniques. This catalytic system exhibited good activity in cross-coupling reactions of aryl iodides, bromides and also chlorides with olefinic compounds in Mizoraki–Heck reactions in short reaction time and high yields. The catalytic activity of this purely organic hybrid catalyst was compared with Pd-PHEMA/MCM-48 to clarify the advantages of mesoporous carbon on mesoporous silica as support. The results showed that the activity and reusability of Pd-PHEMA/CMK-1 was much higher than Pd-PHEMA/MCM48 in Heck reaction.
Keywords: Nanocomposite; Mesoporous carbon; Pd nanoparticles; Heck reaction; Water
Reduction of Cr(VI) polymerization catalysts by non-olefinic hydrocarbons by Eric Schwerdtfeger; Richard Buck; Max McDaniel (pp. 91-99).
Display Omitted► Normally Cr(VI)/silica catalysts are reduced by alkenes to form the lower-valent active species. ► Cr(VI) catalysts can also be reduced by alkanes during storage, to produce ketones and alcohols. ► Reduction of Cr(VI)/silica by alkanes lowers the activity and melt index.The Phillips Cr(VI)/silica catalyst, which is widely used for commercial ethylene polymerization, is usually considered to be reduced to a lower-valent active Cr species in the reactor upon contact with ethylene or other α-olefin monomers. In this paper, however, the case is presented that Cr(VI) is actually quite reactive with other hydrocarbons to which it is also often exposed, including alkanes and aromatics. Redox products from these reactions are identified, and the effect on catalyst polymerization activity and polymer character is described.
Keywords: Phillips catalyst; Ethylene polymerization; HDPE; Polyethylene; Reduction; Chromium; Alkane oxidation
A study on the effect of support's reducibility on the reverse water-gas shift reaction over Pt catalysts by Sung Su Kim; Hyun Hee Lee; Sung Chang Hong (pp. 100-107).
Display Omitted► The Pt/TiO2 catalyst shows a high level of activity in the RWGS reaction. ► Catalytic activity was dependent on Pt dispersion and support's reducibility. ► The RWGS reaction was in agreement with the surface redox mechanism.In this study, the effect of the reducibility of the support on the mechanism of the reverse water gas shift reaction over Pt/TiO2 and Pt/Al2O3 catalysts was examined using a differential and fixed bed reactor. The kinetic study showed that the reverse water gas shift reaction using the Pt/TiO2 and Pt/Al2O3 catalysts were consistent with the redox mechanism. An elementary reaction test and XPS analysis further confirmed that the reverse water gas shift reaction proceeded through the redox mechanism via oxidation and reduction at the Pt sites and reducible support sites on the catalyst surface. In the H2 TPR and FT-IR experiments, the Pt/TiO2 was shown to have a new active site located at the metal–support interface. Therefore, the Pt/TiO2 catalyst produced greater CO2 conversion and TOFs due to the presence of the new active site, which resulted from the strong metal–support interaction and higher reducibility of the support relative to the Pt/Al2O3 catalyst.
Keywords: Pt; TiO; 2; RWGS; Catalyst
ZSM-5 crystals grown on the wall of a long tubular reactor as a structured catalyst for cracking of endothermic fuels by Hui-hui Wu; Gang Li (pp. 108-113).
Display Omitted► ZSM-5/Ni-alloy composites were prepared by in situ hydrothermal synthesis. ► The composites were stable against a heating (750°C)/fast-cooling cycle. ► ZSM-5 crystals were grown on the wall of a long tube to form a structured catalyst. ► The structured catalyst was catalytically active for cracking of endothermic fuels.In situ growth of ZSM-5 crystals on the surface of Ni-based alloy supports by hydrothermal synthesis and their mechanical, structural stability were investigated. ZSM-5 crystals grown on the wall of a long (750mm) tubular reactor with a small inner diameter (1mm) was evaluated as a structured catalyst for cracking of n-heptane as a model endothermic fuel. The results have shown that the adhesion strength between ZSM-5 crystals and the support was strong enough to resist a heating/fast-cooling cycle (the sample was immersed into water immediately after being heated to be 750°C). The crystalline structure of ZSM-5 crystals was also stable against the heating/fast-cooling cycle. The structured catalyst was shown to be catalytically active for cracking of n-heptane (LHSV=200h−1) at 700°C. The formation rates of gaseous cracking products were 9.8mlmin−1 and 29.3mlmin−1 for the bare tubular reactor and the tubular reactor with ZSM-5 crystals grown on the wall, respectively. These structured catalysts show high promise for cracking of endothermic fuels at high temperatures.
Keywords: Key words; Ni-based alloy; ZSM-5; Structured catalysts; Catalytic cracking; Endothermic fuels
Effect of flash calcined alumina support and potassium doping on the activity of Co–Mo catalysts in sour gas shift process by Katarzyna Antoniak; Paweł Kowalik; Wiesław Próchniak; Marcin Konkol; Anna Wach; Piotr Kuśtrowski; Janusz Ryczkowski (pp. 114-120).
Display Omitted► Flash calcined alumina and alkali promotion of Co–Mo catalysts for sour gas shift.► Catalysts with two methods of preparation and varying promoter content.► High activity catalysts by cobalt precursor addition to carrier followed by Mo and K salts incorporation.► Strong relationship between activity and surface concentration of Co–Mo–S and Mo5+ species.► Optimal potassium content and preparation method of industrial catalysts.Potassium promoted Co–Mo catalysts supported on flash-calcined alumina for sour WGS process have been prepared. The oxide form of samples has been characterized by ICP-OES method, N2 adsorption, temperature-programmed reduction (TPR) and the sulfides form after the catalytic activity test by means of XPS. Catalytic activity measurements were carried out in gradientless reactor in a kinetic region at low partial pressure of reagents.A strong effect of the promoter addition sequence to the support has been observed. The highest activity in the WGS process was determined for the potassium promoted Co–Mo/Al2O3 catalyst with a K/Mo ratio of 0.06 obtained by a simultaneous impregnation of flash-calcined alumina with aqueous solution of K and Mo salts. Potassium addition significantly changes reducibility and decreases total surface area of catalysts. XPS results show that the catalyst activity is correlated with the surface concentration of Mo5+ and Co–Mo–S species. Potassium addition enhances the formation of such species. The method of potassium incorporation to the catalyst has been suggested and its optimal content has been determined. The catalyst obtained can be implemented in industrial processes of hydrogen and syngas production from feedstocks with high sulfur content.
Keywords: Water gas shift reaction; Sulfur tolerant catalysts; Co–Mo catalysts; Flash calcined alumina; Potassium promoter
A facile approach for the preparation of biomorphic CuO–ZrO2 catalyst for catalytic combustion of methane by Jingjie Luo; Huiyuan Xu; Yuefeng Liu; Wei Chu; Chengfa Jiang; Xiusong Zhao (pp. 121-129).
Display Omitted► Biomorphic CuO–ZrO2 catalysts were synthesized by cotton template. ► Superior activity for catalytic combustion of methane. ► A mixture of m-ZrO2 and t-ZrO2 was forced after adding the bio-template. ► Evidences of better oxygen mobility and synergy in the biomorphic samples. ► 20mol% CuO for the biomorphic catalysts was found as the threshold.A series of novel biomorphic CuO–ZrO2 catalysts were prepared using a cotton bio-template and compared with conventional CuO–ZrO2 catalysts. The physical and chemical properties of the as-obtained catalysts were characterized by techniques including X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), H2-temperature programmed reduction (H2-TPR), and O2-temperature programmed desorption (O2-TPD). The catalytic combustion of methane was chosen as the probe reaction. The results suggested that the bio-template method prepared porous biomorphic CuO–ZrO2 catalysts consist of hollow microtubes. Comparing with conventional CuO–ZrO2 catalysts, biomorphic CuO–ZrO2 catalysts displayed better reducibility and oxygen mobility, stronger metal-oxides synergistic effect, appropriate particle size distribution, and lower activation energy. The crystalline state of zirconia transformed from a single crystallite phase of t-ZrO2 into a complex of m-ZrO2 and t-ZrO2 after introducing the bio-template. With proper CuO content (20mol%), the biomorphic CuO–ZrO2 catalyst displayed preponderant properties. The compensation of surface lattice oxygen from bulk lattice oxygen was more available at high reaction temperatures.
Keywords: Bio-template method; Biomorphic CuO–ZrO; 2; catalyst; Methane catalytic combustion
Controlling the selectivity to chemicals from lignin via catalytic fast pyrolysis by Zhiqiang Ma; Ekaterina Troussard; Jeroen A. van Bokhoven (pp. 130-136).
Selective conversion of lignin to chemicals via catalytic fast pyrolysis.Display Omitted► Selective conversion of lignin to chemicals via catalytic fast pyrolysis is described. ► The influence of acidity, pore size, and zeolite structure was determined. ► A reaction pathway of lignin non-catalytic/catalytic fast pyrolysis was proposed.The catalytic fast pyrolysis of alkaline lignin to useful chemicals was investigated using zeolite catalysts with different acidity and pore size. The catalyst played dual roles in this process. In its acid form, it catalytically converted the depolymerized intermediates into desirable and more stable products. This and their surface prevented repolymerization and coke formation. The yield of liquid and the selectivity to desired products can be controlled by tuning of the acidity and pore size of the catalyst. Using no catalyst yielded 40wt.% of liquid, which mainly consisted of 6wt.% (carbon yield) of phenols and 19wt.% (carbon yield) of phenol alkoxy species. The highest yield of phenol alkoxy species was obtained over H-ZSM5 of extremely low number of acid sites; liquid yield of 51wt.% and carbon yield of 24wt.%. The highest yield of liquid (75wt.%) was obtained over H-USY, which had the largest pore size and lowest Si/Al ratio, thus the largest number of acid sites among all the catalyst tested; the carbon yield of aromatic hydrocarbons was around 40wt.% at 650°C. Depolymerized lignin products undergo consecutive reaction to form phenol alkoxy, phenols, and eventually aromatic hydrocarbons.
Keywords: Aromatic hydrocarbons; Biomass; Fast pyrolysis; Lignin; Zeolites
Gold supported cryptomelane-type manganese dioxide OMS-2 nanomaterials deposited on AISI 304 stainless steels monoliths for CO oxidation by L.M. Martínez T.; F. Romero-Sarria; W.Y. Hernández; M.A. Centeno; J.A. Odriozola (pp. 137-145).
Display Omitted► Non-conventional method for preparation of gold supported on cryptomelane-type OMS-2. ► Cryptomelane deposition on AISI 304 stainless steels monoliths. ► The deposition saves the textural and structural properties of the OMS-2 powder material. ► Partial loss of K+ into the channels and an increment of the average oxidation state of manganese. ► The oxidation of the alloy is favoured by the presence of gold.Gold supported on cryptomelane-type OMS-2 catalysts deposited on AISI 304 stainless steels monoliths have been prepared for the first time, characterised and tested in the CO oxidation reaction. An easy and non-conventional method of incorporation of gold to the cryptomelane solid is used. This method allows the preparation of the monolithic catalysts without altering the structural and textural characteristics of the parent OMS-2 material. Although these catalysts do not show an optimal performance for the oxidation of CO, the presence of small gold particles enhances the catalytic performances of the cryptomelane producing promissory CO oxidation catalysts. The non-conventional gold deposition favours a partial loss of K+ into the channels, resulting in an increment of the average oxidation state of manganese which favours the catalytic behaviour of these kinds of materials. This study can be taken as a starting point to obtain very active gold catalysts supported on OMS-2 materials through the optimisation of the gold–support interaction and the decrease in the gold particle size.
Keywords: OMS-2; Gold catalysts; Metallic monolith; Austenitic stainless steels; CO oxidation
Bimetallic Co-Fe nanocrystals deposited on SBA-15 and HMS mesoporous silicas as catalysts for Fischer–Tropsch synthesis by L.F.F.P.G. Bragança; M. Ojeda; J.L.G. Fierro; M.I. Pais da Silva (pp. 146-153).
Display Omitted► Bimetallic catalysts Co-Fe/HMS and Co-Fe/SBA-15 were used for Fischer–Tropsch synthesis. ► They promoted a high alcohols formation, being ethanol the main oxygenated product. ► Among the olefins both Co-Fe catalysts were more selective toward the propylene. ► The Co-Fe/HMS showed higher selectivity to C5+ and alcohols than Fe/HMS catalyst. ► The Co-Fe/SBA-15 exhibited a higher selectivity to C2–C4 hydrocarbons than Fe/SBA-15.Fischer–Tropsch synthesis (493K, 0.62MPa CO, 1.24MPa H2) has been performed over monometallic and bimetallic Co and/or Fe clusters deposited on mesoporous silicas (HMS and SBA-15). Catalysts have been prepared by incipient wetness impregnation and characterized by N2 adsorption–desorption isotherms, X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), and transmission electron microscopy (TEM).HMS supported Co-Fe catalyst showed the highest activity and C5+ hydrocarbon selectivity, while Co-Fe/SBA-15 catalyst revealed the highest selectivity to alcohols. Both bimetallic catalysts were more active toward the C2–C4 hydrocarbon fraction, with an enhancement in the selectivity to C2, C3 and 1-C4 olefins. Both bimetallic catalysts showed greater chain growth probability values than the monometallic iron based catalysts although their performance in catalytic tests were more close to the iron catalyst.
Keywords: Fischer–Tropsch synthesis; Co-Fe bimetallic catalysts; HMS support; SBA-15 support; Mesoporous silica
Optimizing the aromatic yield and distribution from catalytic fast pyrolysis of biomass over ZSM-5 by Andrew J. Foster; Jungho Jae; Yu-Ting Cheng; George W. Huber; Raul F. Lobo (pp. 154-161).
Display Omitted► ZSM-5 for glucose, furan, and maple wood catalytic fast pyrolysis. ► Maximum aromatic yield from glucose pyrolysis on HZSM-5 at SiO2/Al2O3 ratio=30. ► Mesoporous HZSM-5 favors production of larger aromatics. ► Removing external surface acid sites does not affect product distribution.The conversion of glucose, furan and maple wood has been investigated over different types of ZSM-5 catalyst in semi-batch and fixed-bed reactors. The aromatic yield from glucose conversion goes through a maximum as a function of the framework silica-to-alumina ratio (SAR) of ZSM-5 with an optimum at SAR=30. This suggests that the concentration of acid sites inside the zeolite is critical for maximizing aromatic yield. Creating hierarchical mesopores within the zeolite slightly increased of coke formation and decreased the formation of the monocyclic aromatics. Mesoporous ZSM-5 was also observed to favor the production of larger alkylated monoaromatics. The selective removal of external acid sites from the ZSM-5 catalysts only slightly increased the catalyst activity but also decreased the selectivity to the desired aromatic products.
Keywords: ZSM-5; Zeolite; Catalyst; Biomass; Pyrolysis
Effects of added phosphorus on conversion of ethanol to propylene over ZSM-5 catalysts by Atsushi Takahashi; Wei Xia; Isao Nakamura; Hiromichi Shimada; Tadahiro Fujitani (pp. 162-167).
Display Omitted► The effect of added phosphorus on ethanol conversion over ZSM-5 was investigated. ► Phosphorus maintained the active sites in the presence of H2O. ► Carbon deposition on P-ZSM-5 was suppressed in the presence of H2O. ► Kinetics analysis indicated that the catalyst was deactivated by carbon deposition.We investigated the effects of added phosphorus on the conversion of ethanol to propylene over ZSM-5 zeolite catalysts. We found that the activity of the catalysts was enhanced by the addition of phosphorus, and we suggest that the added phosphorus suppressed oligomerization of propylene and butene by decreasing the acidity of the active sites of the zeolites. Furthermore, the addition of phosphorus greatly enhanced the hydrothermal stability of the zeolites and thus substantially improved the catalyst durability during ethanol conversion. Carbon deposition, which was the main cause of deactivation of the phosphorus-modified zeolites, was suppressed by H2O produced by dehydration of ethanol.
Keywords: Ethanol; Propylene; P-ZSM-5; Carbon deposition
Synthesis of C4 olefins from n-butane over a novel VO x/SnO2–ZrO2 catalyst using CO2 as soft oxidant by Gangadhara Raju; Benjaram M. Reddy; Burri Abhishek; Yong-Hwan Mo; Sang-Eon Park (pp. 168-175).
Display Omitted► CO2 has been utilized as a soft oxidant in oxidative dehydrogenation of n-butane. ► VO x/SnO2–ZrO2 mixed oxide exhibited a high conversion and product selectivity. ► Mixed oxide is more active than single oxide catalysts due to synergetic effects. ► CO2 exhibited a significant promoting effect on conversion and product selectivity.Oxidative dehydrogenation (ODH) of n-butane was investigated over ZrO2, SnO2 and SnO2–ZrO2 mixed oxide supported vanadium oxide catalysts with the aim of utilizing CO2 as the soft oxidant, and to study the effect of mixed oxide support on the ODH activity and C4 olefins selectivity. The acid–base properties, reducibility, surface area and morphology of the SnO2–ZrO2 mixed oxide and its individual component oxide supported vanadium oxide samples were thoroughly studied. The mixed oxide supported vanadia sample exhibited superior acid–base bifunctionality; in particular, more numbers of medium strength acid–base sites were observed. The reduction temperature of the vanadia was observed to decrease in the case of mixed oxide supported vanadia catalysts. The mixed oxide supported vanadia sample exhibited a high conversion and product selectivity than its individual component oxide supported vanadia samples. A significant difference in the catalyst activity was noted in the presence and absence (He) of CO2 feed gas. Among various catalysts evaluated, the VO x/SnO2–ZrO2 catalyst exhibited excellent performance (22.34 and 36.63% conversion of n-butane and selectivity of C4 olefins, respectively), which is attributed to a high specific surface area, superior acid–base bifunctionality and easily reducibility of the dispersed vanadium oxide.
Keywords: n-Butane; 1,3-Butadiene; Soft oxidant; CO; 2; VO; x; /SnO; 2; –ZrO; 2
Dimethyl ether (DME) reforming by microreactor using Cu and Cr as active components over γ alumina by Rehana Kousar; Do Hyung Kim; Byung-Yong Yu; Heon Phil Ha; Sang Hoon Kim; Ji Young Byun (pp. 176-184).
Display Omitted► Cu, Cr and Cu–Cr as catalyst for dimethyl ether reforming for hydrogen production. ► Catalysts were loaded on synthesized gamma alumina (129m2/g) by impregnation. ► Activity of three catalyst systems falls in order, CuCr/Al2O3>Cu/Al2O3>Cr/Al2O3. ► The maximum hydrogen yield was obtained by CuCr/Al2O3 (97.11%) at 400°C.A series of plate type anodic alumina (γ-Al2O3) supported Cu and Cr catalysts were employed to investigate their reactivity in the partial oxidation (PO) of dimethyl ether (DME) in a microreactor. The effect of metal concentration and reaction temperature on DME conversion to hydrogen was assessed. It was found that conversion of DME to hydrogen by PO depends both on reaction temperature and active metal concentration. The catalysts were characterized by surface area (BET), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) techniques. The metal loading as active component was investigated by electron probe micro analysis (EPMA) and X-ray fluorescence spectroscopy (XRF). The results showed that Cu as active component on γ-Al2O3 possessed better activity than Cr. Further, the catalytic activity of Cu was enhanced in the presence of Cr. The XRD and XPS analysis indicated that enhanced Cu activity in the presence of Cr could be correlated to the partial existence of CuCr2O4 along with CuO.
Keywords: γ alumina; Dimethyl ether Reforming; Hydrogen production; Cu; Cr Catalyst
Zirconia supported Cu systems as catalysts for n-butanol conversion to butyraldehyde by J. Requies; M.B. Güemez; P. Maireles; A. Iriondo; V.L. Barrio; J.F. Cambra; P.L. Arias (pp. 185-191).
Display Omitted► A novel ways of a butyraldehyde production in gas phase: n-butanol partial oxidation and dehydrogenation. ► Effective (high yield and selectivity) n-butanol conversion to butyraldehyde in dehydrogenation process. ► Higher coke deposition and higher Cu dispersion losses were observed under partial oxidation conditions.A promising alternative for the production of butyraldehyde is the use of n-butanol as raw material. This alcohol can be produced via fermentation from renewable resources. n-Butanol can be converted to butyraldehyde by dehydrogenation or by partial oxidation and for both reactions Cu catalysts show activity. In this work, Cu supported on both pure ZrO2 and ZrO2 modified with CeO2 catalysts were studied in these two catalytic reactions. The catalytic performance and the catalysts characterization (ICP, N2-physisorption, XRD, TPR, and XPS) suggest that the catalyst with the best Cu dispersion was the most active and stable in n-butanol dehydrogenation. However, in n-butanol partial oxidation, the initial dispersion of Cu on the supports is deteriorated during the time on stream, being Cu sintering and oxidation the main causes of the lower butyraldehyde yield observed in this catalytic process.
Keywords: Copper; Zirconia; Ceria; n-Butanol; Butyraldehyde; Dehydrogenation; Partial oxidation
Hydrogenation of CO on molybdenum and cobalt molybdenum carbides by Hiroyuki Tominaga; Yusuke Aoki; Masatoshi Nagai (pp. 192-204).
Display Omitted► CO bond cleavage occurred during the hydrogenation. ► CO bond was cleaved when H2O and CH2 were formed on the Mo carbide. ► On the CoMo carbide, CO bond was cleaved when O and CH3 were formed. ► Electronic structure calculation explained the mechanism of CO bond cleavage.The DFT calculation of CO hydrogenation was studied based on the reaction of co-adsorbed CO and 2H2 on β-Mo2C(100) and CoMo carbide slabs. The hydrogenation of CO occurred on the two carbide slabs; undissociative adsorbed CO reacted with three dissociative H's to successively yield CHO, CH2O and CH2OH adsorbed on the β-Mo2C(100) slab, while the fourth hydrogen attack produced the adsorbed CH2 and H2O. On the other hand, the CoMo carbide slab produced the adsorbed CH3, O and H through CHO and CH2O but not through CH2OH. CH3OH was not produced on both the β-Mo2C(100) and CoMo carbide slabs, which corresponded to the mass spectroscopic measurement results of no CH3OH formation. Furthermore, electronic structure calculations revealed the CO hydrogenation mechanism. A strong peak of the density of states on the Mo contributes to the CO activation, and the addition of Co increases the number of electrons around this peak position, which improves the CO activation.
Keywords: Molybdenum carbide; Cobalt molybdenum carbide; CO hydrogenation; Band structure
Preparation of Al, Ti, Zr-perfluoroheptanoate compounds and their use in ring opening polymerization by Gamze Yalcin; Ufuk Yildiz; Asgar Kayan (pp. 205-210).
Display Omitted► Preparation of new catalysts of aluminum, titanium and zirconium. ► Superiority of the catalysts in mild conditions with respect to the reported catalysts. ► Application of solvent free conditions in the polymerization reactions. ► Characterization of poly-GPTS by GPC and spectroscopic methods.Aluminum, titanium and zirconium perfluoroheptanoate (PFH) were prepared by reaction of Al, Ti and Zr-alkoxides with perfluoroheptanoic acid (PFHA) in alcohol. All compounds were characterized by NMR spectroscopy, FTIR, MS and elemental analysis and used in polymerization of 3-glycidyloxypropyltrimethoxysilane (GPTS) in order to see their catalytic activity over epoxides. These catalysts were effective in ring opening of epoxide. Poly-GPTS was characterized by1H,13C NMR and gel permeation chromatography (GPC).
Keywords: Catalyst; Metal alkoxides; Perfluoroheptanoate; Ring-opening