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Applied Catalysis A, General (v.427-428, #)

Contents (pp. iii-viii).

Editorial Board (pp. co2).

Carbon nanotube/titania composites prepared by a micro-emulsion method exhibiting improved photocatalytic activity by Youji Li; Leiyong Li; Chenwan Li; Wei Chen; Mengxiong Zeng (pp. 1-7).

Display Omitted► TiO₂-coated carbon nanotubes (METCNTs) are prepared by a micro-emulsion method. ► METCNTs possess a high surface area and uniform titania layer. ► METCNTs show higher photoactivity than sol–gel TiO₂/CNTs and commercial P25. ► A mechanism for highly efficient methylene blue degradation by METCNTs is proposed.A micro-emulsion method was used to prepare TiO₂-coated carbon nanotubes (ME-TCNTs). The physico-chemical properties of these composites were characterized by modern analytical tools. Crystalline TiO₂ within the composites was composed solely of anatase. Carbon nanotubes (CNTs) within the composites were virtually uniformly covered with TiO₂. CNT addition increased the surface area and the amount of hydroxyl groups on the composite surface, which suppressed the recombination of photo-generated electron/hole pairs (excitons). The composite photoactivity was greater than that of pure TiO₂ and the commercial photocatalyst P25 for methylene blue degradation, predominantly due to the effect of CNT addition. An optimal TiO₂ loading of 12% was found to result in the highest photoactivity in comparison with other two loadings (6% and 15%). Too little TiO₂ or excessive CNT addition shielded the TiO₂ and reduced the UV intensity, due to photon scattering by the bare CNTs. However, a high TiO₂ content was found to be ineffective in suppressing exciton recombination because of the large distance between the TiO₂ and CNTs. The photoactivity of ME-TCNTs was greater than that of TiO₂ coated carbon nanotubes (TiO₂-CNTs) prepared by the sol–gel method. The uniform nanometer-scale TiO₂ layer on the CNT surface provided a high concentration of surface hydroxyl groups, a low exciton recombination rate and a high surface area.

Keywords: Titania; Carbon nanotubes; Micro-emulsion; Photocatalysis

Carbon-supported iridium catalyst for reduction of chlorate ions with hydrogen in concentrated solutions of sodium chloride by Lidia I. Kuznetsova; Nina I. Kuznetsova; Sergei V. Koscheev; Vladimir I. Zaikovskii; Alexander S. Lisitsyn; Ksenia M. Kaprielova; Natalia V. Kirillova; Zbigniev Twardowski (pp. 8-15).

Display Omitted► Reductive elimination of chlorate in NaCl brine. ► Active and stable catalyst Ir nanoparticles on carbon Sibunit™. ► Strong impact from the nature of metal precursor.In production of chlorine by electrolysis of NaCl, chlorate is formed as by-product and must be removed. The back conversion of ClO₃⁻ to Cl⁻ via catalytic reduction with H₂ on Ir catalyst in NaCl brine has been studied. The catalysts contained 0.5–5wt.% of Ir and were prepared via impregnation of mesoporous carbon support (Sibunit™) with solutions of IrCl₃· xHCl· yH₂O or H₂IrCl₆ and reduction in flowing H₂ at 400 or 500°C. The Ir/C samples have been characterized with CO adsorption, XPS and HRTEM. The rate of ClO₃⁻ reduction in concentrated solutions of NaCl was found dependent on pH (in the range 2–6), content of Ir in the catalyst, dispersion and distribution of Ir on the support. The best properties have been shown by 5%Ir/C catalyst which was prepared with H₂IrCl₆ as the metal precursor and contained small Ir particles (∼1.5nm in diameter) located inside the cavities of carbon globules. Stable catalytic performance in multiple successive runs has been achieved.

Keywords: Ir/C catalyst; Chlorate; Reduction; Hydrogen

Nanospace constraints in mesoporous silica carriers—A factor of critical importance in promoting the catalytic activity of supported ruthenium (II) complex with hemilabile phosphine ligand by Dorota Duraczyńska; Ewa M. Serwicka; Alicja Drelinkiewicz; Dorota Rutkowska-Żbik; Małgorzata Witko; Robert Socha; Małgorzata Zimowska; Zbigniew Olejniczak (pp. 16-23).

Display Omitted► Hemilabile Ru complex is immobilized on various mesoporous silica materials. ► The binding mode of Ru complex to the support influences catalytic activity. ► Location of Ru complex within the porous network results in high catalytic activity. ►³¹P MAS NMR is a diagnostic tool for prediction of the supported catalyst activity.Various mesoporous silica materials (FSM-16, HMS, SBA-15) aluminated via direct procedure or by a post-synthesis treatment, differing in the manner of Al distribution between the external surface and the mesoporous network, were employed for the immobilization of [(η⁵-MeC₅H₄)Ru(η³-DPVP)(η¹-DPVP)]⁺ (DPVP=PPh₂CHCH₂) complex. The catalysts of similar loading (ca. 5wt.%) of Ru-species were prepared by means of cation exchange. The samples were characterized with XRD, XPS, MAS NMR, N₂ adsorption/desorption techniques and quantum chemical calculations, and tested in the liquid phase hydrogenation of phenylacetylene. Two binding modes of Ru species were identified: (i) at the surface free of spatial constraints, with the participation of the hemilabile ligand in the electrostatic attraction and (ii) in the limited space of narrow mesopores, via peripheral areas of Ru coordination sphere, leaving hemilabile phosphine exposed to the reaction medium. It has been demonstrated that the latter location is a prerequisite of high catalytic activity of the supported system, while the former destroys the catalytic action.

Keywords: Hemilabile ruthenium (II) complex; Mesoporous silica; Hydrogenation; Phenylacetylene

Activity, propene poisoning resistance and hydrothermal stability of copper exchanged chabazite-like zeolite catalysts for SCR of NO with ammonia in comparison to Cu/ZSM-5 by Qing Ye; Lifeng Wang; Ralph T. Yang (pp. 24-34).

Display Omitted► Effects of propene on SCR activities of Cu exchanged catalysts were studied. ► The Cu exchanged chabazite-like catalysts showed higher SCR catalytic activities than Cu/ZSM-5. ► Cu exchanged chabazite-like catalysts showed better hydrocarbon poison resistance. ► Cu exchanged chabazite-like catalysts withstood the hydrothermal test at 800°C.Copper, iron, and mixed copper/iron exchanged zeolites containing ZSM-5 and chabazite-like zeolites (SSZ-13, SAPO-18 and SAPO-34) were studied for selective catalytic reduction (SCR) of NO with NH₃ with or without propene. Cu/ZSM-5, Cu/SSZ-13, Cu/SAPO-18 and Cu/SAPO-34 exhibited high NO conversions without propene. However, as compared to Cu/ZSM-5, NO conversions over Cu/SSZ-13, Cu/SAPO-18 and Cu/SAPO-34 were more stable with propene, due to coke formation over Cu/ZSM-5. The results of N₂-adsorption/desorption and XPS showed that the surface area, Cu⁺/Cu²⁺ ratio and the surface amount of Cu content of Cu/ZSM-5 catalysts changed from 324m²/g, 0.03 and 11.5wt% for the fresh Cu/ZSM-5 catalyst to 68m²/g, 0.34 and 5.3wt% for the used sample. However, there were little changes between fresh and used Cu/SSZ-13, Cu/SAPO-18 and Cu/SAPO-34 catalysts. Moreover, Cu/ZSM-5 catalyst showed a larger decline in NO conversion with time on stream and a higher adsorption amount of propene compared to Cu/SSZ-13, Cu/SAPO-18 and Cu/SAPO-34 catalysts. The resistance to hydrocarbon poisoning depended on the pore geometry of the zeolites. During NH₃-SCR, the presence of medium-pore sizes in Cu/ZSM-5 led to hydrocarbon deposition, which blocked the active sites and also decreased the active intermediates needed for NO conversion. Cu/SSZ-13, Cu/SAPO-18 and Cu/SAPO-34 catalysts, on the other hand, with small pores and cage diameters and with one-dimensional channel structures, showed higher hydrocarbon poison resistance. Moreover, these copper exchanged small-pore zeolites showed much higher hydrothermal stability than the medium-pore Cu/ZSM-5.

Keywords: SCR; Copper exchanged; Chabazite-like zeolites; Propene resistance; Hydrothermal stability

Platinum nanoparticle-decorated TiO₂ nanotube arrays as new highly active and non-poisoning catalyst for photo-electrochemical oxidation of galactose by Mir Ghasem Hosseini; Mohamad Mohsen Momeni (pp. 35-42).

Display Omitted► Anti-poisoning ability of TiO₂ makes Pt-TiO₂ re-usable after a short UV treatment. ► Pt-TiO₂ showed a remarkably enhanced performance for galactose oxidation under UV. ► For galactose oxidation, Pt-TiO₂ has high current density and good stability.Platinum nanoparticles were doped on the TiO₂ nanotube using a microemulsion method. The TiO₂ nanotube arrays were successfully fabricated by the anodizing of titanium sheets. The morphology and surface analysis of the Pt-TiO₂ nanotubes were investigated using SEM, EDX and XRD respectively. The electro-oxidation of galactose on this catalyst in alkaline medium was studied using cyclic voltammetry and chronoamperometry methods. The results showed that the oxidation peak currents on the Pt-TiO₂ nanotubes for galactose oxidation are larger than those on a smooth platinum electrode and confirmed the better electro-catalytic activity and stability of these new catalysts. The photo-catalytic properties of the TiO₂ make the Pt-TiO₂ nanotubes electrode reusable after a short UV treatment, and the electro-oxidation current density of the Pt-TiO₂ nanotubes after UV-cleaning can be re-established.

Keywords: TiO; ₂; nanotubes; Platinum nanoparticle; Photo-catalytic; UV-cleaning; Galactose; Microemulsion

Catalytic reduction of NO by NH₃ over Fe–Cu–O_X/CNTs-TiO₂ composites at low temperature by Zhaoxia Ma; Hangsheng Yang; Qian Li; Junwei Zheng; Xiaobin Zhang (pp. 43-48).

Display Omitted► Fe–Cu–O_X/TiO₂-CNTs composites were prepared by a sol–gel method. ► A NO_X conversion of 90% was achieved at 150–300°C. ► The additions of FeO_X and CNTs synergistically promote the NO_X conversion. ► Adsorbed NO₂ on the surface is important for NO_X reduction at low temperature. ► The reactions follow both the L–H and E–R mechanism.Activity of iron–copper oxides supported on TiO₂ and carbon nanotubes (CNTs) for low-temperature selective catalytic reduction of NO by NH₃ in the presence of oxygen was investigated. The addition of FeO_X and CNTs synergistically promoted the NO conversion through the adsorption of NO and NH₃ and the catalytic oxidation of NO to NO₂. NO₂ adsorbed on the surface of the catalysts was found to be essential for NO reduction at low temperature, and approximately 90% NO conversion could be achieved at reaction temperature as low as 150°C. Moreover, it was found that the deactivation caused by H₂O could be recovered after H₂O was switched off, while the deactivation caused by SO₂ was dependent on the reaction temperature.

Keywords: Selective catalytic reduction; Carbon nanotubes; Iron–copper oxides; NO oxidation

Pruning of the surface species on Ni/Al₂O₃ catalyst to selective production of hydrogen via acetone and acetic acid steam reforming by Xun Hu; Lijun Zhang; Gongxuan Lu (pp. 49-57).

Display Omitted► The distinct Ni species on Ni/Al₂O₃ catalyst were identified and characterized. ► Capacities of the Ni species for activation of acetone were investigated. ► Activities of Ni species for secondary reactions in steam reforming were measured. ► Ni species on catalytic activity, selectivity and coke formation were investigated.Catalytic behaviors of the different metallic Ni species on Ni/Al₂O₃ catalyst surface were investigated in steam reforming of acetone and acetic acid to hydrogen. The different Ni species showed distinct activities for activation of acetic acid and acetone, gasification of coke precursors, and other secondary reactions such as methanation, water–gas shift reaction, CO disproportion and methane decomposition. The Ni species weakly interacted with alumina solely showed negligible reforming activity, while the Ni species mildly interacted with alumina was very active and efficient for steam reforming reaction. In comparison, the Ni species strongly interacted with alumina existed in bigger particle sizes, which resulted in the side reactions for by-product generation and consequently led to serious coking. Suppression of its presence on catalyst is the key point to obtain a highly selective and stable Ni/Al₂O₃ catalyst.

Keywords: Steam reforming; Acetone; Acetic acid; Ni/Al; ₂; O; ₃; catalyst; Nickel species

Mechanochemical preparation and characterization of CaO·ZnO used as catalyst for biodiesel synthesis by Željka Kesić; Ivana Lukić; Dragana Brkić; Jelena Rogan; Miodrag Zdujić; Hui Liu; Dejan Skala (pp. 58-65).

Display Omitted► Synthesis of biodiesel using CaO·ZnO catalyst was investigated. ► Catalyst was synthesized by ball milling of Ca(OH)₂ and ZnO powder mixture. ► Activity of catalyst compared to activity of catalyst prepared by co-precipitation procedure. ► Catalyst characterization using different analytical methods. ► Testing of catalyst activity at moderate temperature and for its potential reuse.In this study, the synthesis of biodiesel or fatty acid methyl esters (FAME) from sunflower oil and methanol using CaO·ZnO catalyst was investigated. Catalyst was synthesized by ball milling of Ca(OH)₂ and ZnO powder mixture with the addition of water (BMH), as well as solely by ball milling of mentioned powders (BM) and subsequent calcination at 700°C in air atmosphere. For comparison, the CaO·ZnO mixed oxide was also prepared using usual coprecipitation procedure (CP) followed by calcination at 700°C of the formed calcium zinc hydroxide hydrate. The BMH, BM and CP catalysts were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), infrared spectroscopy (FTIR), particle size distribution measurement and scanning electron microscopy (SEM and SEM-EDS). In addition, specific surface area (BET), solubility in methanol at 60°C and alkalinity (Hammett indicator method) were also determined. The activity of BMH, BM and CP catalysts for biodiesel synthesis were tested at 60°C and 1bar, using molar ratio of sunflower oil to methanol of 1:10 and with 2wt% of catalyst based on oil weight.

Keywords: Biodiesel; Heterogeneous catalyst; Methanolysis; CaO; ZnO

Carbon-coated structured supports. Preparation and use for nitrobenzene hydrogenation by Philippe Rodriguez; Florica Simescu-Lazar; Valérie Meille; Thierno Bah; Stéphanie Pallier; Isabelle Fournel (pp. 66-72).

Display Omitted► We examined a simple way to coat stainless steel foams with carbon supported catalysts. ► Carbon coating obtained from a slurry is compared to carbon from polymer. ► The polymer method gives adherent layer with small pores. ► The suspension method leads to a mesoporous material.Whereas carbon is a major catalyst support, namely in pharmaceutical industry, its immobilisation on structured objects has scarcely been studied. This article presents the comparison of two methods aiming at coating ceramic and metallic supports with a carbon layer. The method involving a suspension of black carbon is easy to use but leads to less adherent layers than the method involving the carbonisation of poly(furfuryl alcohol). On the other hand, the former method is the one that allows to prepare more active catalysts for nitrobenzene hydrogenation. Then, the suspension formulation has been improved to enhance the carbon adhesion.

Keywords: Carbon washcoating; Resin; Structured catalytic reactors; Stainless steel; Foam; Slurry; Nitrobenzene hydrogenation

Low temperature combustion of ethylene in a carbon dioxide stream over a cordierite monolith-supported Cu–Mn Hopcalite catalyst by Hong Chen; Jihui Wang; He Li; Dongfang Wu; Mingfa Yao; Yongdan Li (pp. 73-78).

Display Omitted► Cordierite monolith-supported Cu–Mn Hopcalite catalyst was prepared by a dip-coating method. ► Solid reaction between the Hopcalite washcoat and cordierite monolith was observed. ► Solid reaction improves the adhesion strength and catalytic stability of the monolithic catalyst.Complete combustion of trace amount of ethylene in food-grade carbon dioxide is examined over a copper-manganese Hopcalite monolithic catalyst which is prepared with co-precipitation of Hopcalite powder, followed by washcoating on cordierite monolith via a dip-coating method. It is shown that the combustion activity of the Hopcalite monolithic catalyst is closely dependent on the washcoat loading and calcination temperature, and that the calcination temperature has a great effect on the adhesion strength of the Hopcalite washcoat. It is proposed that the catalyst combustion activity originates from a synergic effect of the CuO and amorphous Cu–Mn oxide phases. Solid reaction between the Hopcalite washcoat and cordierite monolith not only improves the adhesion strength of the Hopcalite washcoat, but also prevents the formation and growing of the Cu_1.5Mn_1.5O₄ crystalline particles and thus develops the combustion activity. Furthermore, it leads to doping of Mg in the Hopcalite washcoat, which improves the catalytic stability of the Hopcalite monolithic catalyst.

Keywords: Ethylene combustion; Hopcalite catalyst; Monolithic catalyst; Adhesion strength; Carbon dioxide purification

Redox properties and oxidation catalysis of potassium salts of transition metal-substituted α₂-K₈P₂W₁₇O₆₁(M·OH₂) (M=Mn^II, Zn^II, Fe^II, Co^II, Cu^II, and Ni^II) Wells-Dawson heteropolyacids by Jung Ho Choi; Jeong Kwon Kim; Sunyoung Park; Ji Hwan Song; In Kyu Song (pp. 79-84).

Display Omitted► α₂-K₈P₂W₁₇O₆₁(M·OH₂) heteropolyacids with different metals (M) were prepared. ► Reduction potentials were measured by an electrochemical method. ► Absorption edge energies were determined by UV–vis spectroscopy. ► Yield for benzaldehyde increased with increasing redox properties.Potassium salts of transition metal-substituted α₂-K₈P₂W₁₇O₆₁(M·OH₂) (M=Mn^II, Zn^II, Fe^II, Co^II, Cu^II, and Ni^II) Wells-Dawson heteropolyacids were prepared to investigate their redox properties and oxidation catalysis. Successful formation of α₂-K₈P₂W₁₇O₆₁(M·OH₂) catalysts was confirmed by FT-IR,³¹P NMR, and ICP-AES measurements. Reduction potential and absorption edge energy of α₂-K₈P₂W₁₇O₆₁(M·OH₂) catalysts were determined by an electrochemical method and UV–vis spectroscopy in solution, respectively. Absorption edge energy of α₂-K₈P₂W₁₇O₆₁(M·OH₂) catalysts decreased with increasing reduction potential of the catalysts. It was also found that reduction potential of α₂-K₈P₂W₁₇O₆₁(M·OH₂) catalysts increased and absorption edge energy of the catalysts decreased with decreasing Tanaka electronegativity of substituted transition metal. Vapor-phase benzyl alcohol oxidation was also carried out as a model reaction in order to probe oxidation catalysis of α₂-K₈P₂W₁₇O₆₁(M·OH₂) catalysts. Yield for benzaldehyde increased with increasing reduction potential and with decreasing absorption edge energy of α₂-K₈P₂W₁₇O₆₁(M·OH₂) catalysts. Reduction potential and absorption edge energy of α₂-K₈P₂W₁₇O₆₁(M·OH₂) catalysts could be utilized as a probe of oxidation catalysis of the catalysts.

Keywords: Heteropolyacid; Transition metal; Reduction potential; Absorption edge energy; Oxidation catalysis

Pt dispersion control in Pt/SiO₂ by calcination temperature using chloroplatinic acid as catalyst precursor by Shinji Kaneko; Miyuki Izuka; Asako Takahashi; Masaaki Ohshima; Hideki Kurokawa; Hiroshi Miura (pp. 85-91).

Display Omitted► Pt dispersion of Pt/SiO₂ depends heavily on the calcination temperature. ► Highly dispersed Pt catalyst was obtained after calcination at the optimum temperature (375°C) and reduction. ► The change in Pt dispersion can be explained by the distribution state of Pt precursor on the support.The effect of pretreatment conditions on the dispersion of Pt/SiO₂ was studied. The catalysts were prepared by impregnation with H₂PtCl₆ as the Pt precursor. Direct reduction of the supported Pt precursor in hydrogen flow was compared to calcinations of the precursor in air flow at various temperatures followed by reduction in hydrogen flow. When the supported precursor was directly reduced in hydrogen flow, Pt dispersion was independent of the reduction temperature. In contrast, when the supported precursor was calcined and then reduced, Pt dispersion was not affected by the reduction temperature but depended heavily on the calcination temperature, ranging widely from 7 to 70%. A good correlation was seen between the particle size calculated from CO adsorption and that observed with transmission electron microscope. Furthermore, it was found that calcination at the temperature at which PtCl₂ is stable gives the highest Pt dispersion. X-ray fluorescence analysis of the calcined samples confirmed the formation of PtCl₂. High Pt dispersion after calcination at optimum temperature was also corroborated with X-ray diffraction analysis from the absence of sharp diffraction peaks. The results suggest that prompt formation and redispersion of PtCl₂ caused high Pt dispersion.

Keywords: Platinum silica catalyst; Platinum dispersion; Calcination temperature; Platinum precursor; Dispersed PtCl; ₂

Effect of support materials on platinum lattice strain and its oxygen reduction activity by Shuichi Suzuki; Taigo Onodera; Jun Kawaji; Takaaki Mizukami; Kenji Yamaga (pp. 92-97).

Display Omitted► Oxygen reduction activity of Pt films was examined. ► Pt films were deposited on amorphous carbon (a-C), WO₃, and TiO₂. ► Activity of Pt/a-C decreased with Pt thickness, while that of metal oxides did not. ► Activity of catalysts correlated with Pt lattice strain caused by support materials. ► Pt lattice expansion resulted in decrease of catalytic activity.The oxygen reduction activities of sputter-deposited platinum (Pt) thin films of various thicknesses on amorphous carbon (a-C), tungsten oxide (WO₃), and titanium oxide (TiO₂) were examined to investigate the effect of the support materials. An X-ray diffraction analysis showed that the Pt lattice constant clearly increased with decreasing Pt thickness on the a-C, while it did not change on the WO₃ and TiO₂. The oxygen reduction activity of the catalysts was measured electrochemically in 0.5mol/L sulfuric acid at 308K. The measurements showed that the activity of Pt/a-C catalysts decreased with the Pt thickness. However, decrease of activity was not observed in the Pt/WO₃ and Pt/TiO₂ catalysts. The correlation between catalytic activity and Pt lattice strain was obtained from these results; Pt lattice expansion, which was observed on the a-C support, resulted in the decrease of catalytic activity for an oxygen reduction reaction. The metal-oxide support, such as the WO₃ and TiO₂, suppresses the Pt lattice expansion and maintains the Pt catalytic activity in the case of decreasing Pt thickness compared to the a-C support.

Keywords: Fuel cell; Oxygen reduction reaction; Platinum; Metal oxide; Amorphous carbon

Transformations of monoterpene hydrocarbons on ferrierite type zeolites by R. Rachwalik; M. Hunger; B. Sulikowski (pp. 98-105).

Display Omitted► H-ferrierite from Zeolyst and Tosoh as catalysts for α-pinene isomerization. ► High initial rates of α-pinene transformations in liquid phase. ► Pure limonene reacts readily on ferrierite from Tosoh, but not on zeolite from Zeolyst. ► Different strength of Brønsted acid sites results in various selectivity towards limonene. ► Deposition of oligomeric products on Zeolyst blocks effectively consecutive transformation of limonene formed.Transformations of α-pinene and limonene over hydrogen forms of commercial ferrierite type zeolites of different origin (Tosoh Corp. and Zeolyst Intern.) have been studied in the liquid phase at 313–363K. The catalysts were characterized by XRD, sorption of nitrogen, scanning electron microscopy, FTIR and²⁷Al &¹H MAS NMR. The concentration of Brønsted acid sites has been determined by¹H MAS NMR and FTIR quantitative measurements, while their strength was estimated by adsorption of CO. The liquid-phase isomerization of α-pinene proceeds smoothly on the two zeolite catalysts, and the initial reaction rates have been compared. Camphene and limonene were the main products, while the selectivity to these hydrocarbons differed. Isomerization of pure limonene was also studied, showing large difference in activity over the two ferrierite catalysts. The selectivity of α-pinene transformations has been rationalized in terms of retarded consecutive isomerization of limonene over the zeolite from Zeolyst.

Keywords: Ferrierite; Isomerization; α-Pinene; Limonene; Camphene; Secondary reactions

Synthesis, electronic property and photocatalytic applications of mesoporous cobalt-doped ZnS and ZnO nanoplates by Jum Suk Jang; Eun Sun Kim; Sun Hee Choi; Dong Hyun Kim; Hyun Gyu Kim; Jae Sung Lee (pp. 106-113).

Display Omitted► Zn_0.95Co_0.05S(en)_0.5 complex was prepared by hydrothermal synthesis. ► Zn_0.95Co_0.05S and Zn_0.95Co_0.05O nanoplates were produced by a topotactic solid transformation. ► Mesoporous Zn_0.95Co_0.05S nanoplates showed good photosensitivity and stability under visible light irradiation. ► The photocatalytic activity for the degradation of AR14 originates from the band-gap excited photons.Mesoporous cobalt-doped ZnS and ZnO nanoplates were fabricated by calcination of a Zn_0.95Co_0.05S(en)_0.5 complex (en=ethylenediamine), which was hydrothermally synthesized using ethylenediamine as a single solvent and chelating agent. When the as-prepared Zn_0.95Co_0.05S(en)_0.5 complex was calcined, mesoporous nanoplates of wurtzite Zn_0.95Co_0.05S were formed, which then transformed to Zn_0.95Co_0.05O platelets upon further oxidation. Photocatalytic performance of the as-prepared materials was investigated for decomposition of the azo dye (acid red 14) and photoelectrochemical current generation in aqueous Na₂S/Na₂SO₃ solution as probe reactions. The Zn_0.95Co_0.05S calcined at 500°C exhibited the highest photocatalytic activity under UV irradiation and also showed the photocatalytic performance under visible light irradiation.

Keywords: Mesoporous nanoplate; Co-doped ZnS; Photocatalysis; Visible light; Photocurrent

Continuous synthesis of bis(indolyl)phenylmethane over acid modified Hβ zeolite by Guoyi Bai; Zheng Ma; Lingjuan Shi; Xingwang Lan; Yalong Wang; Jie Han; Mande Qiu; Hailong Fu; Peide Liu (pp. 114-118).

Display Omitted► Modified Hβ zeolite was used for synthesis of bis(indolyl)phenylmethane (BIPM). ► A continuous process for synthesis of BIPM over zeolites was first established. ► A citric acid modified Hβ zeolite has shown good activity and excellent stability. ► Dealumination and weak acid sites were proven to favor the desired transformation.The continuous synthesis of bis(indolyl)phenylmethane has been successfully accomplished for the first time by Friedel-Crafts alkylation of indole with benzaldehyde in a fixed-bed reactor over different zeolites. A citric acid modified Hβ (CA-Hβ) zeolite showed better catalytic performance than parent Hβ zeolite due to its larger surface area and smaller amount of weak acid sites, confirmed by the Brunauer–Emmett–Teller (BET) method, NH₃ temperature-programmed desorption (NH₃-TPD) and Fourier Transform Infrared Spectrometer after adsorption of pyridine (Py-IR). Furthermore, it is proposed that citric acid treatment is appropriate for dealumination of Hβ zeolite, which results in the CA-Hβ zeolite having a larger number of active centers for the desired transformation. Significantly, CA-Hβ has shown good stability during a 100h test.

Keywords: Bis(indolyl)phenylmethane; Continuous synthesis; Hβ zeolite; Citric acid modification; Stability

Microreactor containing platinum nanoparticles for nitrobenzene hydrogenation by Sho Kataoka; Yasutaka Takeuchi; Atsuhiro Harada; Toshiyuki Takagi; Yasumasa Takenaka; Norihisa Fukaya; Hiroyuki Yasuda; Takao Ohmori; Akira Endo (pp. 119-124).

Display Omitted► Pt nanoparticles immobilized inside a microreactor. ► Hydrogenation of nitrobenzene to aniline. ► Deactivation mechanism for a longtime reaction.Pt nanoparticles were immobilized inside a microreactor to catalyze the hydrogenation of nitrobenzene to aniline. Catalyst support layers were provided on the inner wall of the microreactor to enhance the adsorption and reaction of the Pt nanoparticles. Using this immobilization method, the Pt nanoparticles inside the microreactor exhibited a good catalytic activity and also were easily regenerated even after they were deactivated. During a 14-h continuous experiment, the average yield of aniline was higher than 92% for 50mM initial nitrobenzene concentration with the retention time of 12s. This is equivalent to a turnover frequency of 3200h⁻¹. The deactivation mechanism of the Pt nanoparticles was also discussed in a long-time reaction.

Keywords: Microreactor; Pt nanoparticles; Immobilization; Slug flow; Nitrobenzene hydrogenation

Bimodal N-doped P25-TiO₂/AC composite: Preparation, characterization, physical stability, and synergistic adsorptive-solar photocatalytic removal of sulfamethazine by Pow-Seng Yap; Yan-Ling Cheah; Madhavi Srinivasan; Teik-Thye Lim (pp. 125-136).

Display Omitted► Bimodal composite was prepared via combined N-P25 and N-TiO₂ (sol). ► AC support served to maintain anatase–rutile phase at high calcination temperature. ► Physical stability of the composite was examined via ultrasonication disruption. ► Photocatalytic effect could be governed by weight distribution of bimodal titania. ► Photocatalytic kinetics was mainly ascribed to N-P25 and anatase–rutile mixture.A novel nitrogen-doped P25-TiO₂ of bimodal structure with activated carbon supported (N-P25-TiO₂/AC) was synthesized via the modified sol–gel techniques. Besides adding urea as N-source, the N-doping could also be induced through calcination under mixed NH₃/N₂ atmosphere. The composite was characterized using XRD, porosimetry, UV–vis spectrophotometry, FTIR, XPS, SEM/EDX and TEM. The physical stability of the composite was examined through ultrasonication disruption, and the composite exhibited good physical stability. The synergistic effects of the adsorption-solar photocatalysis of sulfamethazine (SMZ) as exhibited by the composites were examined. The best performing bimodal composite was N-P25-TiO₂ (25+10)/AC, which comprised 25% of N-P25 and 10% N-TiO₂ (sol) by weight composition (wt%). The maximum adsorption capacity ( S_max) for the N-P25-TiO₂ (25+10)/AC, at pH 3.0, 6.0 and 10.0 was 183±3, 194±3, and 103±2mgg⁻¹, respectively. The effects of the total loading of N-doped titania, sol–gel synthesis technique, weight distribution of N-P25 and N-TiO₂ (sol), composite dosage, light wavelength spectrum and solution pH on the photocatalytic degradation (PCD) of SMZ were investigated. The N-P25-TiO₂ (25+10)/AC composite exhibited enhanced PCD efficiency under solar irradiation with a pseudo first-order rate constant ( k_app) of 0.48h⁻¹, as compared to other types of bimodal composites because its higher N-P25 content led to a greater photocatalytic activity.

Keywords: Activated carbon; Bimodal titania; Solar photocatalysis; Sulfamethazine; Physical stability

Ph-SO₃H-modified mesoporous carbon as an efficient catalyst for the esterification of oleic acid by Liang Geng; Gang Yu; Yu Wang; Yuexiang Zhu (pp. 137-144).

Display Omitted► Ph-SO₃H-modified mesoporous carbon catalysts were synthesized by Al₂O₃ and RF resin. ► Such catalysts have thin carbon walls (∼1.7nm) and high BET area (∼1000m²/g). ► Such carbon catalysts were tested in the esterification of oleic acid and methanol. ► TOF of optimal catalyst was 128h⁻¹, eight times that of Amberlyst-15. ► Such carbon catalysts were a type of stable solid acid.Mesoporous carbon materials with thin pore walls (∼1.7nm) were synthesized using low-cost γ-Al₂O₃ as a hard template and in situ polymerized resorcinol–furfural resin as the carbon precursor. Compared with sugar, resin, a widely used carbon precursor, has higher carbon yield and simplifies the synthetic process. Ph-SO₃H modified mesoporous carbon was synthesized by covalent grafting of Ph-SO₃H groups on mesoporous carbon via the diazonium salt. The resulting materials were characterized by means of nitrogen adsorption analysis, TEM,¹³C NMR, XRD, FTIR and sulfur elemental analysis. The modified carbons were shown to possess high surface area (∼1000m²/g), a bimodal pore size distribution and high strong acid density (1.86mmolH⁺/g). These sulfonated carbons were used as solid acid catalysts in the esterification of oleic acid and methanol, a key reaction in biodiesel production. Compared with the traditional solid acid Amberlyst-15, the optimized carbon catalyst exhibited much higher activity with a rate constant (1.34h⁻¹) three times to that of Amberlyt-15 and a turnover frequency (TOF) of 128h⁻¹ eight times that of Amberlyst-15. The efficient catalytic ability was attributed to the high surface area and a proper mesopore texture. This carbon catalyst could then be easily separated from the product by filtration. The catalyst was reused six times, and no distinct activity drop was observed after the initial deactivation.

Keywords: Mesoporous carbon; Carbon-based solid acid; Alumina template; Diazonium modification; Esterification

Characterization of redox and acid properties of mesoporous Cr–TiO₂ and its efficient performance for oxidative dehydrogenation of propane by Fei Ma; Shu Chen; Yang Wang; Fang Chen; Weimin Lu (pp. 145-154).

Display Omitted► Mesoporous Cr–TiO₂ materials with high content of Cr have been synthesized. ► They exhibit high catalytic activity in propane oxidative dehydrogenation. ► Cr³⁺ was related to propane conversion and Cr⁶⁺ to the selectivity. ► The mesoporous structure is beneficial for the dispersion of Cr species and could modulate the acid properties.Mesoporous Cr–TiO₂ materials with chromium content from 0.02 to 0.30 (Cr/Ti molar ratio) were synthesized using a nonionic Pluronic F127 surfactant, and the mesostructure was confirmed by BET, SAXS and TEM. The stability of the mesoporous structure under the atmospheres of propane oxidative dehydrogenation (PODH) and air was investigated. The variety in valence states and the distribution of Cr species on the surface were also evaluated by WXRD, XPS, UV–vis and H₂-TPR methods. The acid properties including kinds, number and strength were measured by NH₃-TPD and IR-Py experiment. Propane oxidative dehydrogenation to propylene employed as a probe reaction suggested that the catalytic performance relates closely with the content of Cr, the easily reducible soluble Cr species, and the modification of the acid properties on the surface, while TiCr_0.15 catalyst performs good conversion and selectivity, with a yield of propylene near 19%.

Keywords: Mesoporous material; Redox process; Acid properties; Propane oxidative dehydrogenation

Incorporation of zirconia onto silica for improved Pt/SiO₂ catalysts for the selective reduction of NO by H₂ by Se Min Park; Hoi-Gu Jang; Eun Seok Kim; Hyun-Sik Han; Gon Seo (pp. 155-164).

Display Omitted► Zirconia incorporated on silica improves the stability of platinum dispersed on it. ► Ammonia is produced over Pt(1.0)/Zr–SiO₂ under excess oxygen. ► Pt/Zr–SiO₂ exhibits good catalysis in the H₂-SCR of NO at 75–150°C. ► Zirconia incorporation improves platinum catalysts in the H₂-SCR of NO.The incorporation of zirconia onto the silica supports of platinum catalysts improved the selective reduction of NO by hydrogen in comparison to platinum catalysts supported on silica and alumina. The catalysts were characterized by X-ray diffraction, transmission electron microscopy, the temperature-programmed desorption of ammonia, X-ray photoelectron spectroscopy, and the adsorption of carbon monoxide. Their performances were examined in a flow microreactor and by in situ IR spectroscopy. The incorporation of zirconia onto silica created many strong acid sites and stabilized the dispersed platinum. It aided the adsorption of NO and enhanced the formation of ammonia on the platinum catalysts, even in the presence of excess oxygen. The formation of ammonia from NO and the subsequent removal of NO through reaction with ammonia considerably improved the conversion of NO and the yield of N₂. The presence of zirconia also improved the stability of the supported platinum against hydrothermal treatment.

Keywords: Selective catalytic reduction (SCR); NO; Hydrogen; Platinum; Silica; Zirconia incorporation

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Applied Catalysis A, General (v.427-428, #)

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Applied Catalysis A, General (v.427-428, #)