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Applied Catalysis A, General (v.383, #1-2)
Conventional synthesis methods of short-chain dialkylcarbonates and novel production technology via direct route from alcohol and waste CO2 by E. Leino; P. Mäki-Arvela; V. Eta; D. Yu. Murzin; T. Salmi; J.-P. Mikkola (pp. 1-13).
Display Omitted▶ Chemical fixation of carbon dioxide has been reviewed. ▶ Main focus on diethyl carbonate. ▶ Conventional technologies suffer from toxicity phosgene, corrosion and low production rate. ▶ Direct synthesis of DMC from methanol and CO2 is thermodynamically unfeasible. ▶ Butylene oxide can be used as a chemical water trap.The aim of this work is to review different synthesis methods of dialkylcarbonates with special emphasis on diethyl carbonate synthesis methodologies. The novel synthesis route for dimethyl carbonate and diethyl carbonate based on the utilization of alcohol and carbon dioxide as the raw materials, together with heterogeneous catalysts, is presented.
Keywords: Dimethyl carbonate; Diethyl carbonate; Carbon dioxide; Zirconia; Palladium-copper chloride
Inhibiting effect of oxygenated model compounds on the HDS of dibenzothiophenes over CoMoP/Al2O3 catalyst by M. Philippe; F. Richard; D. Hudebine; S. Brunet (pp. 14-23).
The impact of model oxygenated molecules, representative of those present in bio-oils from lignocellulosic starting materials, on deep HDS of gas oil was investigated. An inhibiting effect was observed for low amount of guaiacol and phenol in the transformation of 46DMDBT and DBT the most refractory model molecules of gas oils.The effect of oxygen compounds (guaiacol and phenol) on the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (46DMDBT) and dibenzothiophene (DBT) was studied on a sulfided CoMoP/Al2O3 catalyst in a fixed bed microreactor (340°C, 4.0MPa). The reaction scheme of the transformation of guiaicol and of phenol (the main intermediate in the transformation of phenol) was established under deep HDS operating conditions. The transformation of phenol involved two main routes: a hydrogenation pathway (HYD) involving first the hydrogenation of the aromatic rings followed by C–O bond rupture (leading to the formation of benzene) and a direct deoxygenation (DDO) pathway involving only a C–O bond rupture (leading to cyclohexane). These two ways were independent, no transformation of benzene into cyclohexane was observed. Both oxygen compounds inhibited the hydrodesulfurization of sulfur compounds due to competitive adsorption between the oxygen and sulfur containing compounds, with the effect of guaiacol being stronger than the effect of phenol. The inhibition was similar in the transformation of 46DMDBT and DBT for the same oxygen molecule, showing that the two main routes (HYD and DDS) involved in the HDS were affected in the same way. This corresponds to a competitive adsorption between the oxygen and sulfur compounds containing on the catalyst surface according to a Langmuir–Hinshelwood model.
Keywords: Deep hydrodesulfurization; Hydrodeoxygenation; 4,6-Dimethyldibenzothiophene; Dibenzothiophene; Guaiacol; Phenol; CoMoP/Al; 2; O; 3; Inhibiting effects
Thin layer of carbon-nano-fibers (CNFs) as catalyst support for fast mass transfer in hydrogenation of nitrite by Jitendra Kumar Chinthaginjala; Johannes Hendrik Bitter; Leon Lefferts (pp. 24-32).
Reduction of nitrite in aqueous solution was studied over CNF-supported Pd catalysts and compared with conventional supports with similar diffusion-lengths. It appears that CNF based catalysts are at least three times more active per surface area of palladium, which is due to improved mass transfer as well as due to apparent enhancement intrinsic activity.CNF-foam ‘hairy foam’ and CNF aggregates supported Pd catalysts were studied for the reduction of aqueous nitrite solution and also compared with conventional catalysts. Relatively large Pd particle size and similar Pd particle size distribution on all the catalyst supports excludes any structure sensitive effects on reaction. Intrinsic rates over hairy foam catalysts were independent of CNF-layer thickness (8–28μm) and Pd loading (0.5–2wt%), demonstrating the absence of any mass transfer limitations. When compared to conventional catalysts at comparable diffusion layers, CNF based catalysts showed at least three times higher rates of nitrite conversion per mole of surface palladium (TOF). Increased TOF is due to the improved mass transfer provided by macroporous structure of the entangled CNFs, which offers low tortuosity, provides accessibility to all the active sites. The intrinsic activity of graphite and CNF-supported Pd contributes significantly to the high activity for nitrite reduction.
Keywords: Carbon-nano-fibers; Nitrite reduction; Structured catalysts
Reforming of ethanol on Pt/Al2O3-ZrO2 catalyst by M. Dömök; A. Oszkó; K. Baán; I. Sarusi; A. Erdőhelyi (pp. 33-42).
The steam reforming of ethanol was investigated at 723 K over Al2O3, ZrO2 and Al2O3- ZrO2 supported Pt catalysts. It was found that the hydrogen and carbon dioxide selectivity increased in the steady state in the presence of zirconia. Adsorbed CO and surface acetate were detected during the catalytic reaction at 723 K. It was established that the acetate located mainly on the Al2O3 surface and much smaller amount can be found on ZrO2 and on Al2O3-ZrO2 supported samples.The steam reforming of ethanol was investigated at 723K over Al2O3, ZrO2 and Al2O3-ZrO2 supported Pt catalysts. The samples were characterized by XPS and TPR methods. The surface species formed during the adsorption of ethanol and during the catalytic reaction were investigated by DRIFT and TPD. According to the XPS results the zirconia was partially reduced during the pretreatment and the surface of the catalysts was relatively poor in Zr. Adsorbed CO and surface acetate were detected during the catalytic reaction at 723K. It means that the formation rate of these species is higher than their decomposition or further reaction. It was established that the acetate located mainly on the Al2O3 surface and much smaller amount can be found on ZrO2 and on Al2O3-ZrO2 supported samples.The decay in the selectivity of H2 and CO2 caused by the surface acetate species on Pt/Al2O3 decreased in the presence of ZrO2. DRIFT and TPD measurements showed that the zirconia destabilized the acetate groups which resulted in the enhanced H2 and CO2 selectivity. The highest turnover number and yield was found on Pt/Al2O3-ZrO2 (1:3).
PtSn/SiO2 catalysts prepared by surface controlled reactions for the selective hydrogenation of cinnamaldehyde by Andrea B. Merlo; Bruno F. Machado; Virginia Vetere; Joaquim L. Faria; Mónica L. Casella (pp. 43-49).
PtSn/SiO2 (Sn:Pt 0–0.8) catalysts were prepared by SOMC/M techniques. The addition of tin caused a noticeable change both in product distribution and the reaction rate than for Pt/SiO2. The selectivity to cinnamyl alcohol increases as a function of Sn content and reaction rate too. Bimetallic catalysts using a water-soluble tin precursor Bu3SnOH, were also prepared. An enhanced performance regarding the monometallic catalyst was also obtained.Tin-modified platinum catalysts were prepared by means of a controlled surface reaction, varying the Sn:Pt atomic ratio between 0 and 0.8. The addition of tin caused a noticeable change both in product distribution and the reaction rate. The selectivity to cinnamyl alcohol increases as a function of Sn content, reaching a value of 80% for a Sn:Pt ratio of 0.8. Reaction rate is also higher for bimetallic catalysts than for Pt/SiO2, with the highest value obtained for systems with Sn:Pt=0.2–0.4. These results are indicative of the formation of a new type of active sites, compared to those present in the monometallic catalyst. Bimetallic catalysts using a water-soluble tin precursor Bu3SnOH, were also prepared. An enhanced performance regarding the monometallic catalyst was also obtained with these materials proving to be an environmentally friendlier alternative to obtain PtSn catalysts.
Keywords: Surface organometallic chemistry; Bimetallic catalysts; PtSn; Selective hydrogenation; Cinnamaldehyde
Effects of support and co-fed elements on steam reforming of palm fatty acid distillate (PFAD) over Rh-based catalysts by N. Laosiripojana; W. Kiatkittipong; S. Charojrochkul; S. Assabumrungrat (pp. 50-57).
The steam reformings of palm fatty acid distillate (PFAD) over Rh on MgO–Al2O3, Al2O3, and Ce–ZrO2 supports were studied. At 1023K, Rh/MgO–Al2O3 showed the greatest reactivity; nevertheless, above 1173K, the reforming reactivity of Rh/Ce–ZrO2 become greater due to the occurring of redox reactivity over Ce–ZrO2 simultaneously with the reaction taking place on the active site of Rh.The steam reformings of palm fatty acid distillate (PFAD) over Rh on MgO–Al2O3, Al2O3, and Ce–ZrO2 (with Ce/Zr ratios of 3/1, 1/1, and 1/3) supports were studied. At 1023K, the conversions of PFAD are almost 100%, while H2, CO, CO2, and CH4 are the major products from the reaction with some amount of high hydrocarbon compounds i.e. C2H4, C2H6, and C3H6 also detectable. Among all catalysts, the highest H2 yield with the greatest resistance toward carbon deposition and lowest formation of hydrocarbons in the product was achieved from Rh/MgO–Al2O3.The activities of all catalysts increased with increasing temperature; interestingly at temperatures above 1173K, H2 yields from the steam reforming over Rh/Ce–ZrO2 (with Ce/Zr ratio of 3/1) become greater than those observed over Rh/Al2O3 and Rh/MgO–Al2O3. This great improvement is due to gas–solid reactions between hydrocarbons present in the system with lattice oxygen(OOx) at Ce–ZrO2 surfaces simultaneously with the reaction taking place on the active sites of Rh. Rh/Ce–ZrO2 with Ce/Zr ratios of 3/1 was then selected for further study by adding O2 and H2 along with PFAD and steam at the feed. An addition of both components significantly reduced the degree of carbon deposition and promoted the conversion of hydrocarbons to CO and H2. Nevertheless, the presence of too much O2 could oxidize Rh particles and combust H2 to H2O, which results in low reforming reactivity. Addition of too much H2 also reduced the catalyst activity due to the active site competition with Rh particles and the inhibition of gas–solid redox reactions between the gaseous hydrocarbon components with lattice oxygen(OOx) on the surface of Ce–ZrO2 support.
Keywords: Hydrogen; Palm fatty acid distillate; Reforming; Rhodium
Water–gas shift reactions on potassium- and zirconium-promoted cobalt molybdenum carbide catalysts by Masatoshi Nagai; Amin Md. Zahidul; Yutaka Kunisaki; Yusuke Aoki (pp. 58-65).
The preparation of carburized CoMo with alumina, potassium or zirconium added and their activity values for the water–gas shift reaction at 453K were investigated. The presence of potassium significantly promoted water dissociation and that of zirconia prevented the oxidation of β-Mo2C during reaction on the carburized 5wt%Al2O3/Co46.5Mo46.5K2Zr5 catalyst.The preparation of carburized CoMo with alumina, potassium or zirconium added and their activity for the water–gas shift reaction at 453K were investigated on the basis of XRD, temperature-programmed desorption (TPD) after H218O adsorption, transmission electron microscopy, and X-ray photoelectron spectroscopy. The carburized 5wt% Al2O3/Co46.5Mo46.5K2Zr5 catalyst exhibited the highest CO conversion and TOF. The TPD experiment after H218O adsorption showed that the Zr-containing catalysts produced Co6Mo6C1 from β-Mo2C and Co metal, but the catalyst without zirconium produced MoO2 and Co3Mo. The presence of potassium significantly promotes water dissociation while zirconia prevented the oxidation of β-Mo2C. The Al2O3KZr-promoted CoMo catalyst exhibited a higher distribution of Co0 and Co2+ than the catalysts containing either zirconium or potassium in the presence of the Co3+ ions. The Al2O3KZr-promoted CoMo catalyst contained β-Mo2C, small Co metal particles and Co6Mo6C1 along with zirconia, potassium and alumina.
Keywords: Cobalt–molybdenum carbide; Potassium; Zirconium; Water dissociation; Oxidation resistance; Water–gas shift reaction; H; 2; 18; O-isotope
Sol–gel preparation of Ni/TiO2 catalysts with bimodal pore structures by Masayuki Numata; Ryoji Takahashi; Ikuya Yamada; Kazuki Nakanishi; Satoshi Sato (pp. 66-72).
Display Omitted▶ Ni/TiO2 with bimodal pore structure was prepared by a sol-gel process under acidic conditions in the presence of formamide. ▶ The Ni/TiO2 has continuous macropores which are formed by fixing the transitional structure of phase separation. ▶ The Ni/TiO2 prepared by sol-gel has higher dispersion of Ni compared with that prepared by impregnation. ▶ The Ni/TiO2 prepared by sol-gel shows catalytic activity for the selective hydrogenation of crotonaldehyde.Ni/TiO2 with bimodal pore structure was prepared from nickel nitrate and titanium alkoxide by a sol–gel process under acidic conditions in the presence of formamide. The Ni/TiO2 has continuous macropores which are formed by fixing the transitional structure of phase separation. Although the addition of nickel nitrate in the sol–gel reaction of titanium alkoxide steeply decreases the phase separation tendency, the macropore size can be controlled by changing the composition of preparation. The Ni/TiO2 prepared by sol–gel has higher dispersion of Ni compared with that prepared by impregnation, and shows catalytic activity for the selective hydrogenation of crotonaldehyde: selectivity in the hydrogenation of CC bond is much higher than that of CO bond over sol–gel-derived Ni/TiO2.
Keywords: Titania-supported nickel catalyst; Phase separation; Bimodal pore structure; Selective hydrogenation
Aqueous hydrogenolysis of glycerol over Ni–Ce/AC catalyst: Promoting effect of Ce on catalytic performance by Weiqiang Yu; Jing Zhao; Hong Ma; Hong Miao; Qi Song; Jie Xu (pp. 73-78).
The aqueous hydrogenolysis of glycerol was performed at 200°C under 5MPa of H2 over the Ce-promoted Ni/AC catalyst. The adding of Ce had a remarkable promoting effect on the activity, and glycerol 90.4% of glycerol conversion could be achieved in 6h, far higher than that of Ni/AC.The aqueous hydrogenolysis of glycerol was performed over Ni–Ce/AC catalyst. The addition of cerium showed a remarkable promoting effect on the catalytic performance compared with other metals including copper, tin, zinc, aluminum, iron and cobalt. For example, 90.4% of glycerol conversion could be achieved at 473K under 5MPa of H2 with 6h. The Ni–Ce/AC catalysts were characterized by N2 physisorption, XRD, TEM, NH3-TPD and H2-TPR. The results showed that the addition of cerium to the Ni/AC catalyst greatly changed the reductive behavior.
Keywords: Aqueous hydrogenolysis; Cerium; Glycerol; Nickel
Simultaneous promotion of hydrogenation and direct desulfurization routes in hydrodesulfurization of 4,6-dimethyldibenzothiophene over NiW catalyst by use of SiO2-Al2O3 support in combination with trans-1,2-diaminocyclohexane- N, N, N′ ,N′-tetraacetic acid by Naoto Koizumi; Yusuke Hamabe; Shohei Yoshida; Muneyoshi Yamada (pp. 79-88).
Display Omitted▶ Use of CyDTA and novel SiO2-Al2O3 support for NiW catalyst led to higher HDS activity. ▶ Both DDS and HYD routes were promoted by use of CyDTA and SiO2-Al2O3 support. ▶ Multilayered Ni-W-S phase was selectively formed by use of CyDTA and SiO2-Al2O3 support.Effect of novel SiO2-Al2O3 support on surface structure and hydrodesulfurization (HDS) activity of the NiW catalyst prepared using trans-1,2-diaminocyclohexane- N, N, N′ ,N′-tetraacetic acid (CyDTA) was investigated by combination of quasi in situ TEM, in situ diffuse reflectance FTIR spectroscopy (DRIFTS) coupled with NO adsorption, and 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS activity measurement. When the catalysts were prepared without using CyDTA, quasi in situ TEM observation showed that WS2-like slabs in the SiO2-Al2O3 supported W and NiW catalysts had higher stacking degree, but smaller basal plane sizes compared with the Al2O3 supported counterparts. In situ DRIFTS coupled with NO adsorption further revealed that the formation of the Ni–W–S phase was suppressed by use of SiO2-Al2O3 support. The SiO2-Al2O3 supported NiW catalyst showed higher activity for hydrogenation (HYD) of 4,6-DMDBT into tetrahydro-DMDBT (THDMDBT) than the Al2O3 supported counterpart. However, this catalyst failed to promote the HYD route because of lower activity for C–S bond cleavage of THDMDBT, and showed lower HDS activity than the Al2O3 supported NiW catalyst. On the other hand, the formation of the Ni–W–S phase was promoted when the SiO2-Al2O3 supported NiW catalyst was prepared using CyDTA, which was accompanied with further increase of stacking degree and decrease of the basal plane size of the WS2-like slabs. Double-layered slabs were predominant in the SiO2-Al2O3 supported NiW catalyst prepared with using CyDTA. This catalyst showed higher activity for both HYD of 4,6-DMDBT, and C–S bond cleavage of 4,6-DMDBT and THDMDBT. The HYD route and direct desulfurization (DDS) route were promoted simultaneously over this catalyst, leading to three times higher HDS activity than the Al2O3 supported NiW catalyst. These results suggest that the formation of the multi-layered Ni–W–S phase with the smaller basal plane size is crucial for promoting the HYD route in HDS of 4,6-DMDBT.
Keywords: Hydrodesulfurization (HDS); 4,6-Dimethyldibenzothiophene (4,6-DMDBT); NiW catalyst; SiO; 2; -Al; 2; O; 3; trans; -1,2-diaminocyclohexane-; N; ,; N; ,; N; ′; ,N; ′-tetraacetic acid (CyDTA)
Conversion of ethanol to propylene over HZSM-5 type zeolites containing alkaline earth metals by Daisuke Goto; Yasumitsu Harada; Yoshiyasu Furumoto; Atsushi Takahashi; Tadahiro Fujitani; Yasunori Oumi; Masahiro Sadakane; Tsuneji Sano (pp. 89-95).
Sr-HZSM-5 zeolite having a SiO2/Al2O3 ratio of 184 and a Sr/Al ratio of 0.1 exhibited the highest C3H6 yield of ca. 32 C-% and a high catalytic stability at the reaction condition of 500°C and W/F value of 0.03gcat/ml/min.Protonated ZSM-5 type zeolites containing alkaline earth metals (M-HZSM-5, M: alkaline earth metal) were prepared under various synthesis conditions and their catalytic performance in the conversion of ethanol to light olefins, especially propylene (C3H6), were investigated in detail. The C3H6 yield and the catalytic stability were strongly dependent on M/Al and SiO2/Al2O3 ratios as well as on the reaction conditions. Among M-HZSM-5 zeolites, the Sr-HZSM-5 zeolite having a SiO2/Al2O3 ratio of 184 and a Sr/Al ratio of 0.1 exhibited the highest C3H6 yield of ca. 32 C-% and a high catalytic stability at the reaction condition of 500°C and W/F value of 0.03gcat/ml/min.
Keywords: Ethanol; ZSM-5; Propylene; Alkaline earth metal; Strontium
Promoting effect of small amount of Fe addition onto Co catalyst supported on α-Al2O3 for steam reforming of ethanol by A. Kazama; Y. Sekine; K. Oyama; M. Matsukata; E. Kikuchi (pp. 96-101).
Display Omitted▶ Fe/Co/α-Al2O3 catalyst showed high activity for steam reforming of ethanol. ▶ The formation of CH4 and deposited-carbon was suppressed by our catalyst. ▶ Fe addition to the catalyst selectively promoted steam reforming of CH3CHO. ▶ Interactions among Co particles, Fe particles and catalyst-support were important.We examined the promotion effect of loading small amounts of Fe onto various Co catalysts for steam reforming of ethanol. Among these catalysts, catalysts supported on SrTiO3 and α-Al2O3 showed remarkable effects of iron loading onto cobalt catalyst. The Fe-loaded Co/α-Al2O3 showed higher yield of hydrogen, low coke deposition on the catalysts, and high activity for steam reforming of acetaldehyde, which was an intermediate of the steam reforming of ethanol. Characterization of the catalyst revealed that Fe and Co metal coexisted on the catalyst support. Synergetic effects of these two metals were observed.
Keywords: Steam reforming of ethanol; Promotion effect of iron; Cobalt catalyst
Effects of NaOH solution treatment on the catalytic performances of MCM-49 in liquid alkylation of benzene with ethylene by Kefeng Liu; Sujuan Xie; Guoliang Xu; Yuning Li; Shenglin Liu; Longya Xu (pp. 102-111).
The crystallinity of MCM-49 can be increased by mild alkali-treatment and mesopores can be introduced by severe alkali-treatment. The increased catalytic stability of the alkali-treated samples in the liquid alkylation of benzene with ethylene is mainly attributed to purification of zeolite crystals of the mild alkali-treated samples, and to the facilitated diffusion for substances in the case of severe alkali-treatment.MCM-49 zeolite was alkali-treated with NaOH solutions under mild and severe conditions. The samples before and after alkali-treatment were both used as catalysts in liquid alkylation reaction of benzene with ethylene. XRD, XRF, TPD, TPO, IR, SEM,29Si NMR, N2 adsorption and desorption techniques were employed to characterize the samples. The mildly alkali-treated samples exhibited higher catalytic stability than the parent HMCM-49, as the amorphous particles on the MCM-49 crystal surface were cleaned and the diffusion of the reactant and product was enhanced. The severe alkali-treatment condition resulted in the selective extraction of silicon atoms and the introduction of extra mesopores. The catalytic stability of the catalysts that had been severely alkali-treated was not as good as that of mildly treated ones, but was still better than that of the parent HMCM-49 catalyst if the alkali-treatment conditions were not too severe.
Keywords: MCM-49; Alkali-treatment; Benzene; Ethylene; Liquid alkylation
Hydrotreating of crude 2-ethylhexanol over Ni/Al2O3 catalysts: Influence of the Ni oxide dispersion on the active sites by Renchun Yang; Junsheng Wu; Xiaogang Li; Xin Zhang; Zhihua Zhang; Jintao Guo (pp. 112-118).
The correlations of Ni species dispersion and the surface active sites on Ni/γ-Al2O3 catalysts were studied. The samples with the highest Ni oxide dispersion (H-I) and the lowest Ni oxide dispersion (C-D) are not helpful to obtain more active sites, whereas the Ni oxide particles with an appropriate size (H-D) are beneficial to enhance the number of active centers.To analyze the correlation between the Ni species dispersion and the surface active sites, we prepared a series of Ni/γ-Al2O3 samples by conventional impregnation method (CI), conventional deposition method (CD), hydrothermal impregnation method (HI), and hydrothermal deposition method (HD). It was found that the number of surface active sites of the four samples with a similar Ni loading follows the order: H-D (13.2μmolgcat−1)>H-I (10.3μmolgcat−1)>C-I (8.6μmolgcat−1)>C-D (7.3μmolgcat−1). The samples with the highest Ni oxide dispersion (H-I) and the lowest Ni oxide dispersion (C-D) are all not of benefit to increase the number of active sites. Because the high dispersion results in most Ni ions embedding into the inner part of the support and the low dispersion suppresses the exposure of active sites, the Ni oxide particles with an appropriate size are helpful to obtain more active centers.
Keywords: Ni/γ-Al; 2; O; 3; Surface active sites; Dispersion; Particle size; Hydrotreating
Inactive aluminate spinels as precursors for design of CPO and reforming catalysts by Bjørn Christian Enger; Rune Lødeng; John Walmsley; Anders Holmen (pp. 119-127).
Display Omitted▶ Ni and Ni–Co aluminate spinels as catalyst precursors. ▶ Catalysts for partial oxidation and steam methane reforming. ▶ Hydrogen treatment at high temperature enables growth of nano-sized metal particles. ▶ Ni aluminate spinels does not activate methane at temperatures below 900K.We here illustrate the potential of inactive Ni- and Ni–Co aluminate spinels prepared at high temperatures (1393K) as precursors for the design of catalysts for partial oxidation (CPO) and steam methane reforming (SMR). By exposing the aluminate spinel to hydrogen atmosphere at 1073K for 2h, the inactive spinel was restructured to an active catalyst with excellent initial stability (20–40h). The hydrogen treatment enabled the growth of supported nano-sized (15–25nm) metal particles.Methane conversion during CPO over unreduced NiAl2O4 did not exceed the empty reactor conversion (6% at 1073K) and the unreduced NiAl2O4 catalyst showed no activity in SMR at 973K furnace temperature and 1atm. Thus, the reduction with H2 was critical for obtaining an active phase capable of activating methane and catalysing the CPO and SMR reactions. Once activated by high temperature reduction, close to equilibrium yields were obtained over the in situ reduced catalysts. Estimates of activation energies in SMR over reduced NiAl2O4 were in accordance with our expectations (about 110kJ/mol). The catalysts were characterized by H2-chemisorption, N2-sorption, XPS, XRD, STEM/EDS and TPx.
Keywords: Synthesis gas; Hydrogen production; Methane activation; Mixed metal oxide reduction; Partial oxidation; Steam reforming; Aluminate spinel; Ni; Co
Synthesis, characterization and visible-light photocatalytic properties of Bi2WO6 and Bi2W2O9 obtained by co-precipitation method by S. Obregón Alfaro; A. Martínez-de la Cruz (pp. 128-133).
Display Omitted▶ The bismuth tungstates Bi2WO6 and Bi2W2O9 were prepared by co-precipitation method. ▶ The presence of NH4NO3 in the precursors plays an important role in the final properties of the bismuth tungstates. ▶ The samples prepared by co-precipitation showed a better degradation of the rhodamine B dye than the samples of solid-state reaction. ▶ Two possible mechanisms of degradation of the dye are explained according other reports.The bismuth tungstates Bi2WO6 and Bi2W2O9 were prepared by co-precipitation method at different calcination temperatures. The oxides were characterized by different techniques such as simultaneous thermogravimetric and differential thermal analysis (TGA/DTA), X-ray powder diffraction (XRD), diffuse reflectance spectroscopy (DRS), nitrogen physisorption, and scanning electron microscopy (SEM). The photocatalytic activity of such bismuth tungstates was evaluated by degradation of rhodamine B under visible light irradiation. The degradation of the dye followed a first-order reaction with k′=5.6×10−3min−1 and t1/2=124min for the best sample, which was Bi2W2O9 prepared at 700°C.
Keywords: Bi; 2; WO; 6; Bi; 2; W; 2; O; 9; Bismuth tungstates; Photocatalysis
Synthesis of 3-buten-1-ol from 1,4-butanediol over indium oxide by Ryoji Takahashi; Ikuya Yamada; Aiko Iwata; Naoya Kurahashi; Satoshi Yoshida; Satoshi Sato (pp. 134-140).
Indium oxide prepared by precipitation and calcined over 800°C is composed of octahedral crystallites surrounded by 222 facets. It shows excellent activity in partial dehydration of 1,4-butanediol to 3-buten-1-ol.Dehydration of 1,4-butanediol (14BDO) was investigated over indium oxide. Over the indium oxide prepared by precipitation, both conversion of 14BDO and selectivity to unsaturated alcohol, 3-buten-1-ol (3B1ol), increase with the increase in calcination temperature of indium oxide irrespective of the decrease in the specific surface area. The maximum values of 79.6% conversion and 79.0% selectivity to 3B1ol are obtained over indium oxide calcined at 900°C. The values are much higher than the activities of commercial indium oxide. The activities of indium oxide depend on the shape of particles. Indium oxides prepared by the precipitation are composed of particles with diameter of 10–70nm. The size and shape of particles change by calcination: spherical shape at low temperature of <800°C varies to angular one at >800°C with a slight growth of particle size. The change in the shape of the particles means that indium oxide crystallites calcined at >800°C mainly expose 222 facets. The dehydration reaction of 14BDO to 3B1ol is preferentially promoted over 222 surface of bixbyite structure.
Keywords: Indium oxide; Selective dehydration to unsaturated alcohol; Bixbyite; 1,4-Butanediol; 3-Buten-1-ol
Hydroisomerization of n-octane on molybdenum based catalyst by H. Al-Kandari; F. Al-Kharafi; A. Katrib (pp. 141-148).
Display Omitted▶ Preparation and characterization of a bifunctional Mo based catalyst. ▶ Identification of the oxidation state of Mo and the presence of metallic and acidic functions by XPS-UPS techniques. ▶ Hydroisomerization of n-octane on this bifunctional Mo catalyst.Balanced metal–acid bifunctional MoO2− x(OH) y catalytic system has been prepared. 2–3 monolayers of this phase on the sample surface were obtained following controlled reduction by hydrogen of equivalent 5 monolayers of MoO3 deposited on TiO2. Hydroisomerization reaction of n-octane on this Mo bifunctional phase, at similar experimental conditions to those employed in the case of nC5–nC7 hydrocarbons, produce branched species of relatively high octane numbers as compared to parent molecule, in contrary to Pt based catalysts in which hydrocracking reactions were observed. Bench scale catalytic experiments were carried out using 15g catalyst under 5bar hydrogen pressure, 25SLPH, 0.4h−1LHSV and 623K reaction temperature. Time on stream (TOS) experiments for several days did not show any changes in neither the conversion nor the isomerization selectivity. The stability and the resistance of the catalytic system towards poisoning by hydrocarbon species as well as its high performances towards n-octane hydroisomerization are attributed to its specific spatial geometry in which Mo atoms are present in alignment positions placed along the C-axis of the deformed rutile structure of MoO2 phase, as well as the moderate (metal–acid) functions strength of the surface MoO2− x(OH) y phase.
Keywords: MoO; 3; TiO; 2; Bifunctional catalyst; Isomerization of nC8; LHSV; TOS; Catalyst poisoning
Syntheses of 5-hydroxymethylfurfural and levoglucosan by selective dehydration of glucose using solid acid and base catalysts by Mika Ohara; Atsushi Takagaki; Shun Nishimura; Kohki Ebitani (pp. 149-155).
Selective dehydration of glucose was examined using a solid acid catalyst individually or a combination of solid acid and base catalysts to form anhydroglucose or 5-hydroxymethylfurfural (HMF), respectively. A low reaction temperature is advantageous in formation of fructose by base catalysis and limits the amount of anhydroglucose formation by acid catalysis. The preferential formation of fructose results in high selectivity for HMF.Selective dehydration of glucose, the most abundant monosaccharide, was examined using a solid acid catalyst individually or a combination of solid acid and base catalysts to form anhydroglucose (levoglucosan) or 5-hydroxymethylfurfural (HMF), respectively. Glucose was dehydrated to anhydroglucose by acid catalysis in polar aprotic solvents including N, N-dimethylformamide. Amberlyst-15, a strongly acidic ion-exchange resin, functioned as an efficient solid acid catalyst for anhydroglucose production with high selectivity. In the presence of solid base, aldose–ketose isomerization of glucose to fructose preferentially occurred by base catalysis, even in coexistence with the solid acid, resulting in successive dehydration of fructose to 5-hydroxymethylfurfural by acid catalysis with high yield in a one-pot reaction. A combination of Amberlyst-15 and hydrotalcite, an anionic layered clay, afforded high HMF selectivity under a moderate reaction temperature, owing to prevention of anhydroglucose formation.
Keywords: Biorefinery; Dehydration; Carbohydrate; One-pot synthesis; Acid–base catalysis
Steam reforming of methane over highly active and KOH-resistant Ni/γ-Al2O3 catalysts for direct internal reforming (DIR) in a molten carbonate fuel cell (MCFC) by Hyun-Seog Roh; Youshick Jung; Kee Young Koo; Un Ho Jung; Yong-Seog Seo; Wang Lai Yoon (pp. 156-160).
Display Omitted▶ 52% Ni/γ-Al2O3 catalyst exhibited higher KOH resistance than the commercial catalyst. ▶ This is due to selective adsorption of KOH on strong acid sites of a γ-Al2O3 support. ▶ The urea concentration is a key parameter to prepare highly KOH-resistant catalyst.For direct internal reforming (DIR) in molten carbonate fuel cells (MCFCs), steam reforming of methane has been carried out over Ni/γ-Al2O3 catalysts prepared by a homogeneous precipitation method. During the synthesis of Ni/γ-Al2O3 catalysts, various synthesis parameters have been systematically manipulated to develop a highly active and KOH-resistant catalyst for DIR in MCFCs. Compared with a commercial catalyst, 52% Ni/γ-Al2O3 prepared with a precursor concentration of 0.18M and a urea concentration of 6M exhibited very high activity with strong resistance against KOH due to the selective adsorption of KOH on the γ-Al2O3 support.
Keywords: Direct internal reforming; Molten carbonate fuel cell; KOH; Ni/γ-Al; 2; O; 3
Epoxidation of styrene with molecular O2 over sulfated Y–ZrO2 based solid catalysts by Beena Tyagi; Basha Shaik; H.C. Bajaj (pp. 161-168).
Display Omitted▶ Sulfated catalysts showed enhanced activity values than non-sulfated catalysts. ▶ DMF solvent favored the formation of styrene oxide. ▶ In the absence of DMF solvent benzaldehyde formation predominantly occurred. ▶ Sulfated Co–Y–ZrO2 showed maximum styrene conversion of 61% with 80% styrene oxide.Liquid phase epoxidation of styrene was studied over non-sulfated and sulfated yttria–zirconia (Y–ZrO2) based solid catalysts using molecular O2 in the presence of DMF solvent. All catalysts yielded styrene oxide and benzaldehyde as two major products. Among all the catalysts studied, sulfated Co–Y–ZrO2 catalyst resulted in the maximum (61%) styrene conversion with 80% styrene oxide selectivity. Reactions studied in the absence of DMF solvent or in the presence of a small amount of water favored benzaldehyde formation predominantly. Thermally regenerated catalysts showed slight lower conversion (54%) without affecting the selectivity through three reaction cycles.
Keywords: Styrene epoxidation; Molecular O; 2; Y–ZrO; 2; Sulfated Co–Y–ZrO; 2; Solid catalysts
Activity and stability of polyaniline-sulfate-based solid acid catalysts for the transesterification of triglycerides and esterification of fatty acids with methanol by A. Zięba; A. Drelinkiewicz; E.N. Konyushenko; J. Stejskal (pp. 169-181).
Display Omitted▶ Transesterification of triglycerides with methanol yielding bio-esters. ▶ Solid polyaniline-sulfate catalysts for transesterification. ▶ Activity and stability of polyaniline-sulfate composites catalysts.A polymeric catalyst, polyaniline-sulfate, was studied in the transesterification of triglycerides (triacetin, castor oil) and esterification of fatty acid, ricinoleic acid with methanol at mild conditions (temperature of 50–60°C). Polymer powder (PANI-S) and three samples of various contents of polymer deposited on carbon support were examined. The samples of catalysts, before and after catalytic tests were characterized by BET, FT-IR, XRD and SEM techniques. The acid capacity was also determined. All the samples were found to be active solid acid catalysts in both tested reactions. Catalytic performance of polyaniline-sulfate-based catalysts for methanolysis of triacetin (glycerol triacetate) the shortest triglyceride molecule differed from that for vegetable oil, castor oil, consisting of long chain triglycerides of ricinoleic acid. In transesterification of triacetin PANI-S powder was more active than carbon-supported catalysts. In methanolysis of vegetable oil the outermost surface of catalysts was mainly involved and much higher activity was exhibited by carbon-supported catalysts with deposited polymer, especially with low content of polymer (13.1wt.%). The activity of polyaniline-sulfate-based catalysts was almost stable during recycling use in tested reactions. After five successive catalytic runs, their activities were found to be ca. 80–95% relative to the activities of fresh catalysts.
Keywords: Biodiesel; Transesterification; Triacetin; Castor oil; Ricinoleic acid; Polyaniline
Sulfur release from a model Pt/Al2O3 diesel oxidation catalyst: Temperature-programmed and step-response techniques characterization by Jin-Yong Luo; Darren Kisinger; Ali Abedi; William S. Epling (pp. 182-191).
Display Omitted▶ S release from Pt/Al2O3 is inhibited by O2. ▶ S release from Pt/Al2O3 has a low, positive dependency on H2.▶ S release from Pt/Al2O3 is surface diffusion controlled at high temperature.The S release, or desulfation process, of a model Pt/Al2O3 diesel oxidation catalyst (DOC) was investigated using temperature-programmed techniques and step-response methods. During the temperature-programmed experiments, the sulfur loading, H2 concentration and gas composition, in terms of H2O and/or CO2 presence, were systematically investigated. The results show that desulfation is promoted as the gas environment changes from oxidizing to inert and then to reducing conditions. Compared to CO, H2 is more active in a dry environment, and the presence of H2O further promotes the desulfation while CO2 has no obvious effect. Changing the H2 concentration influences the desulfation products, with higher H2 concentrations generating larger amounts of H2S. The data indicate that the desulfation process can be viewed as a stepwise reduction of sulfates to SO2 and then to H2S. Meanwhile, the sulfur loading also affects the SO2/H2S ratio due to the distribution of the sulfur species, and a relatively medium sulfur loading (equivalent to 3g/L) yields the largest SO2/H2S ratio. The results of the step-response methods show that the desulfation process has a low kinetic dependence on H2. Furthermore, the apparent reaction order with respect to sulfur is temperature dependent, and decreases with increasing temperature. These results suggest that desulfation is mass-transfer limited by the diffusion of sulfur species to the active Pt sites or hydrogen tot he sulfur sites. The apparent activation energy for desulfation was initially 59.1kJ/mol, but decreased as more S was released to 39.0kJ/mol due to mass-transfer limitation.
Keywords: Desulfation kinetics; Diesel oxidation catalyst (DOC); Sulfur poisoning; NOx emissions
La–Mn perovskite-type oxide prepared by combustion method: Catalytic activity in ethanol oxidation by H. Najjar; H. Batis (pp. 192-201).
Display Omitted▶ La–Mn oxides are prepared using solution combustion synthesis. ▶ Use of citric acid as fuel molecule results to a high carbonate surface concentration. ▶ Use of glycine as fuel molecule results to a minimum superficial La/Mn atomic ratio. ▶ Catalytic activity in ETOH combustion decreases as the surface carbonate concentration increases.The present work deals with the use of the combustion method to synthesize a series of lanthanum manganite (LM) and to study their physico-chemical and catalytic properties in ethanol deep oxidation. Some synthesis parameters such as chemical nature of the fuel molecules (glycine and citric acid) and additional thermal treatment were used and their effects on the powder characteristics were studied. XRD patterns showed a single phase perovskite-type oxide for all studied samples. Additional lanthanum oxocarbonate was observed on powder patterns of samples obtained with citric acid. The presence of chemisorbed carbonate species was studied by IR spectra analysis in the 2000–500cm−1, XRD and XPS analyses of the C1s and O1s levels. Their concentration was higher on surface samples prepared with citric acid than on those prepared with glycine. From XPS results, the use of glycine as gelling agent rather than citric acid and additional thermal treatment resulted in a decrease in superficial La/Mn atomic ratio and carbonate content and in an increase in relative content of the surface O22−/O− species. These preparation parameters determined the best catalytic activity of the studied LM materials. Our results indicated that the catalytic activity in deep oxidation of ethanol over lanthanum manganite may be described as a synergetic effect of lanthanum and manganese. Ethanol activation was favoured by the strong basicity of lanthanum oxide at the surface of perovskite-structure and deep oxidation to CO2 was enhanced by the activation of oxygen species on manganese site through a redox cycle.
Keywords: Perovskite; Combustion synthesis; Ethanol oxidation; Basic and redox sites
Catalyst discrimination for olefin production by coupled methanol/n-butane cracking by Diana Mier; Andrés T. Aguayo; Ana G. Gayubo; Martin Olazar; Javier Bilbao (pp. 202-210).
Display Omitted▶ Production of olefins from row materials alternative to oil and secondary interest streams in refineries. ▶ Performance of an autothermic process through the integration of two processes, one endothermic and the other one exothermic. ▶ Improvement of olefin yield by the synergy of the two reactions. ▶ Production of a hydrothermically stable catalyst, required in a reaction medium with a high water content.The joint transformation of n-butane and methanol has been studied on catalysts prepared based on HZSM-5 zeolites (with different SiO2/Al2O3 ratios and doped with Ni) and SAPO-18. A methanol/n-butane molar ratio of 3 has been used, which corresponds to an energy-neutral integrated process. The kinetic behaviour of the catalysts has been compared based on C2–C4 olefin yield, deactivation by coke deposition for 5h time on stream and hydrothermal stability by operating in reaction–regeneration cycles. The results show a good performance of the catalyst prepared based on HZSM-5 with SiO2/Al2O3=30, which has high levels of acidity and acid strength (≥120kJmolNH3−1). This catalyst allows obtaining 24.4% of C2–C4 olefin yield (11.5% of propene), with a selectivity of 43% at 575°C and a space time of1.1gcathmolCH2−1. The catalyst fully recovers its initial kinetic behaviour after 10 reaction–regeneration cycles.
Keywords: Cracking; n-Butane; Methanol; Olefins; HZSM-5 zeolite
Post-synthesis alumination of MCM-41: Effect of the acidity on the HDS activity of supported Pd catalysts by A.M. Venezia; R. Murania; V. La Parola; B. Pawelec; J.L.G. Fierro (pp. 211-216).
Display Omitted▶ Post-alumination of siliceous MCM-41 promotes thiophene HDS activity of supported Pd. ▶ The addition of Al3+ to MCM-41 increases the acidity of the Pd catalysts. ▶ Bi-functional mechanism for the activation of thiophene over Pd catalysts. ▶ Direct correlation between catalyst deactivation and catalyst acidity.Siliceous MCM-41 with different amount of alumina, from 0.25 up to 4.0wt%, were prepared by impregnation of the MCM-41 with aqueous solution of Al(NO)3·9H2O. The modified mesoporous silicas were then used as supports for Pd catalysts prepared by wet-impregnation from PdCl2 precursor. Supports and corresponding Pd catalysts were characterized by XRD, XPS and NH3-TPD. The catalytic behavior was tested in the hydrodesulfurization (HDS) reaction of thiophene. An increase of the hydrodesulfurization activity with increasing alumina amount up to 0.5wt% was observed. On the basis of the acidity change of the support and the structural modification underwent by the deposited palladium, the improved catalytic behavior was associated to the increased acidity of the supports and also to its effect on the palladium dispersion. A bi-functional mechanism, implying that metallic palladium activates the hydrogen and the thiophene molecules are adsorbed on the acid sites of the support, could be operative. However, the increased acidity was also responsible for the larger catalyst deactivation which limited the beneficial effect up to a certain amount of alumina content.
Keywords: Thiophene HDS; Pd/MCM-41; Alumina modification
Isomerization of styrene oxide to phenylacetaldehyde over supported phosphotungstic heteropoly acid by Vinícius V. Costa; Kelly A. da Silva Rocha; Ivan V. Kozhevnikov; Elena V. Gusevskaya (pp. 217-220).
Display Omitted▶ The liquid-phase conversion of styrene oxide into phenylacetaldehyde was studied. ▶ Phenylacetaldehyde is an important intermediate in the production of fine chemicals. ▶ H3PW12O40/SiO2 was found to be an active and environmentally friendly catalyst. ▶ A 92% yield was obtained with a catalyst turnover number of 19600. ▶ The catalyst does not undergo leaching and can be recovered and reused.Silica-supported H3PW12O40 (PW), the strongest heteropoly acid in the Keggin series, is an efficient, environmentally friendly heterogeneous catalyst for the liquid-phase isomerization of styrene oxide into phenylacetaldehyde, an industrially important intermediate for fine chemical synthesis. The reaction occurs in cyclohexane as a solvent under mild conditions at 25–70°C with low catalyst loadings and without PW leaching in solution. At 60°C, the yield of phenylacetaldehyde reaches 92% at 97% styrene oxide conversion, with a catalyst turnover number of 19600. The catalyst can be recovered and reused.
Keywords: Isomerization; Styrene oxide; Phenylacetaldehyde; Acid catalysis; Heteropoly acid
Corrigendum to “Alkylation of isobutane/1-butene on methyl-modified Nafion/SBA-15 materials” [Appl. Catal. A: Gen. 377 (2010) 1–8]
by Wei Shen; Yi Gu; Hualong Xu; David Dubé; Serge Kaliaguine (pp. 221-221).