The isopropylation of naphthalene with propene over H-mordenite: The catalysis at the internal and external acid sites

The isopropylation of naphthalene (NP) with propene over H-Mordenite (MOR) was studied under a wide range of reaction parameters: temperature, propene pressure, period, and NP/MOR ratio. Selective formation of 2,6-diisopropylnaphthalene (2,6-DIPN) was observed at reaction conditions, such as at low reaction temperature, under high propene pressure, and/or with high NP/MOR ratio. However, the decrease in the selectivities for 2,6-DIPN was observed at reaction conditions such as at high temperature, under low propene pressure, and/or with low NP/MOR ratio. The selectivities for 2,6-DIPN in the encapsulated products were remained high and constant under all reaction conditions. These results indicate that the selective formation of 2,6-DIPN occurs through the least bulky transition state due to the exclusion of the bulky isomers by the MOR channels. The decrease in the selectivities for 2,6-DIPN are due to the isomerization of 2,6-DIPN to 2,7-DIPN at the external acid sites, directing towards thermodynamic equilibrium of DIPN isomers

In Situ Mechanistic Investigation at the Liquid/Solid Interface by Attenuated Total Reflectance FTIR: Ethanol Photo-Oxidation over Pristine and Platinized TiO2 (P25)

Environment and Water Industry Program Office (EWI) under the National Research Foundation of Singapore [MEWR 651/06/160]There is growing interest in applying photocatalysis to help solve both the energy crisis and effectively combat environmental contamination. However, it is difficult to investigate photocatalytic reactions at the liquid/solid interface to unravel the reaction mechanism by conventional (ex situ) surface analytical techniques. In this study, Attenuated Total Reflectance-FTIR spectroscopy, adapted for optical pumping, was used to observe in situ the surface of TiO2 (Degussa P25, in both pristine and platinized forms) during photocatalytic oxidation of ethanol aqueous solution. It shows the feasibility to investigate not only the reaction pathway and the rate-determining step, but also the change in state of the catalyst under working conditions. During ethanol photo-oxidation over pristine TiO2, band gap excitation caused the progressive accumulation of trapped electrons, as recognized by their characteristic quasi-continuum absorption, implying that photoreduction does not proceed at a significant rate under these conditions. Consistent with this view, only weak infrared features due to adsorbed intermediates were observed. Over platinized TiO2., the noble metal nanodeposits promote photodehydrogenation and photoactivation of dioxygen. In addition to observing strong bands diagnostic of various intermediates, the presence or absence of a band around 2050 cm(-1), typical. of Pt-COad, served as a valuable spectroscopic marker of the instantaneous availability of the chemical oxidant. As such, mechanistic parallels were found between photoreforming (with H-2 generation) and photo-oxidation (to acetate), with acetaldehyde being a common intermediate in both processes. The rate-determining step in ethanol mineralization was found to be photodecomposition of adsorbed acetate

A Collective Case Screening of the Zeolites made in Japan for High Performance NH3-SCR of NOx

Zeolites demonstrating better SCR of NOx performance due to wide temperature activity, hydrothermal stability and N2 selectivity have been identified under a joint research initiative by the Research Association of Automotive Internal Combustion Engines (AICE), Japan. Based on the AICE’s standards, over 25 zeolites with different structures and pore dimensions were investigated and their SCR efficiency and durability have been compared. While the performances of the top contenders cannot be related to a single parameter, the results suggest that the SAR, Cu quality/quantity, pore dimensions, diffusivity and acidity play a combined role in deciding the SCR activity and selectivity

Cage type mesoporous ferrosilicate catalysts with 3D structure for benzylation of aromatics

The Friedel-Crafts benzylation of benzene and various substituted benzenes employing benzyl chloride as an alkylating agent over a series of three-dimensional cage type mesoporous ferrosilicate (FeKIT-5) catalysts was investigated. These FeKIT-5 materials with different n/n and ratios were synthesized hydrothermally using polymeric pluronic F127 surfactant in a highly acidic medium and characterized using various physicochemical techniques. The characterization results confirmed that the prepared materials exhibit a well-ordered 3D porous structure with cage type pores and excellent textural characteristics such as high surface areas (935-1130 m g) and large pore volumes (0.57-0.76 cm g). The unit cell constant of the samples increased with increasing the iron content of the samples, confirming the incorporation of iron in the silica framework structure of KIT-5. UV-vis results revealed that most of the Fe atoms in FeKIT-5 are in tetrahedral coordination and occupy framework position. It was found that the iron incorporated mesoporous silica materials exhibited a high conversion and selectivity for benzylation under liquid phase condition. The influence of various parameters such as temperature, time on stream, n/n ratio and the n /n ratio of the catalyst affecting the activity of the catalyst on the benzylation of benzene using benzyl chloride was investigated. The study was also extended to the benzylation of toluene, p-xylene, mesitylene and anisole in order to check the catalytic performance of the catalyst over different electron donating substituents. The reaction kinetics of benzene benzylation over FeKIT-5 catalyst was also investigated. The catalytic activity of FeKIT-5 catalyst was also compared with AlSBA-15, FeHMS and pure mesoporous silica KIT-5. Among the catalysts studied, FeKIT-5(7) showed the highest activity with a complete conversion of benzyl chloride and 100% selectivity to diphenylmethane in 35 min under the optimized reaction condition. Crown Copyrigh

Nitrogen-sensitized dual phase titanate/titania for visible-light driven phenol degradation

A dual-phase material (DP-160) comprising hydrated titanate (H2Ti3O7·xH2O) and anatase (TiO2) was synthesized in a low-temperature one-pot process in the presence of triethylamine (TEA) as the N-source. The unique structure exhibits strong visible light absorption. The chromophore is linked to Ti–N bonds derived from both surface sensitization and sub-surface (bulk) doping. From transmission electron microscope (TEM) and textural studies by N2 physisorption, the composite exists as mesoporous particles with a grain size of ∼20 nm and mean pore diameter of 3.5 nm, responsible for the high surface area (∼180 m2/g). DP-160 demonstrated photocatalytic activity in the degradation of phenol under visible light (λ>420 nm). The activity of the composite was further enhanced by a small addition (0.001 M) of H2O2, which also gave rise to some visible light activity in the control samples. This effect is believed to be associated with the surface peroxo-titanate complex. GC–MS analyses showed that the intermediate products of phenol degradation induced by visible light irradiation of DP-160 did not differ from those obtained by UV (band-gap) irradiation of TiO2. The overall performance of the composite is attributed to efficient excitation via inter-band states (due to N-doping), surface sensitization, improved adsorptive properties of aromatic compounds due to the N-carbonaceous overlayer, and the presence of heterojunctions that are known to promote directional charge transfer in other mixed-phase titanias like Degussa P25

Dual-phase titanate/anatase with nitrogen doping for enhanced degradation of organic dye under visible light

Synergy at work! A dual-phase photocatalyst comprising anatase and protonated titanate, synthesized by a low temperature one-pot process, synergistically adsorbs and degrades methylene blue dye under visible light. The two phases (see figure) work harmoniously to give accelerated breakdown of the organic dye

Nitrogen-doped TiO2 nanotube array films with enhanced photocatalytic activity under various light sources

Highly ordered nitrogen-doped titanium dioxide (N-doped TiO2) nanotube array films with enhanced photocatalytic activity were fabricated by electrochemical anodization, followed by a wet immersion and annealing post-treatment. The morphology, structure and compostition of the N-doped TiO2 nanotube array films were investigated by FESEM, XPS, UV-vis and XRD. The effect of annealing temperature on the morphology, structures, photoelectrochemical property and photo-absorption of the N-doped TiO2 nanotube array films was investigated. Liquid chromatography and mass spectrometry were applied to the analysis of the intermediates coming from the photocatalytic degradation of MO. The experimental results showed that there were four primary intermediates existing in the photocatalytic reaction. Compared with the pure TiO2 nanotube array film, the N-doped TiO2 nanotubes exhibited higher photocatalytic activity in degradating methyl orange into non-toxic inorganic products under both UV and simulated sunlight irradiation.Accepted versio

Direct synthesis and characterization of highly ordered cobalt substituted KIT-5 with 3D nanocages for cyclohexene epoxidation

Highly ordered cobalt incorporated KIT-5 silica (Co-KIT-5) with different Co contents and a well-ordered three-dimensional cage type porous structure were prepared for the first time by using Pluronic F127 as structure directing agent at different molar water to hydrochloric acid (nHO/) ratio. The amount of Co content in the silica framework of KIT-5 can be finely controlled with a simple adjustment of the nHO/ ratio as it controls the concentration of the H ions in the synthesis gel. It has been found that the nHO/ ratio of 463 is the best condition to obtain Co-KIT-5 with a high Co content. The obtained materials were characterized by various techniques such as powder X-ray diffraction (XRD), N adsorption studies, field emission high resolution scanning electron microscopy (FE-HRSEM), high resolution transmission electron microscopy (HRTEM), ultraviolet-visible diffused reflectance (UV-Vis DRS), electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS). Characterization results revealed that Co atom can be introduced in the silica framework without affecting the structural order and the textural parameters of the samples. ESR, XPS and UV-Vis DR spectra confirmed that the Co atoms are indeed occupy the tetrahedral coordination with the silica framework of KIT-5. The catalytic performance of Co-KIT-5 with different Co contents in the cyclohexene epoxidation has been investigated using TBHP/HO as oxidants and acetonitrile as a solvent. Co-KIT-5 exhibited a high catalytic performance with TBHP as oxidant and remained inactive when HO was used. The effect of various reaction parameters such as reaction time, reaction temperature, and reactant feed ratio and oxidant, affecting the catalytic activity of Co-KIT-5 has also been studied. Among the catalysts studied, Co-KIT-5-0.90 was found to be the best catalyst, affording a high conversion of cyclohexene. In addition, the catalyst was found to be highly stable and can be reused several times without affecting its catalytic activity under the optimized reaction conditions

Transesterification of ethylacetoacetate catalysed by metal free mesoporous carbon nitride

The basic catalytic performance of the mesoporous carbon nitride (MCN) for the transesterification of ethylacetoacetate with various alcohols such as 1-butanol, 1-octanol, cyclohexanol, benzyl alcohol and furfuryl alcohol under heterogeneous reaction conditions without using any solvents was demonstrated. The catalyst was prepared by using a nano-hard templating approach through a simple polymerisation reaction between ethylenediamine (EDA) and carbon tetrachloride (CTC) in the mesochannels of the SBA-15 followed by the carbonisation and the silica removal by HF. The material was thoroughly analysed by sophisticated characterisation techniques such as X-ray diffraction (XRD), N adsorption studies, high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy and CHN analysis. Structural investigation of the MCN by XRD, HRTEM and N adsorption revealed that the prepared catalyst exhibits highly ordered two-dimensional (2D) porous arrays with a high surface area and a large pore volume. The catalytic results revealed that the MCN was found to be an efficient catalyst in transesterifying long and short chain primary alcohols, and cyclic and aromatic alcohols to afford their corresponding β-keto esters in high yields. More importantly, the catalyst was highly active when 1-butanol was used. The influence of various parameters such as temperature, reactant feed ratio, catalyst weight, and time-on-stream on the yield of the final product was studied in detail. In addition, the activity of the catalyst was also compared with pure mesoporous carbon and the results were discussed. The recyclability studies revealed that the MCN catalyst was highly stable under the rigorous reaction conditions and can be reused several times without any significant loss of catalytic activity. Crown Copyrigh

Preparation of mesoporous titanosilicate molecular sieves with a cage type 3D porous structure for cyclohexene epoxidation

We report on the preparation of mesoporous titanosilicate with a 3D porous structure and Fm3m symmetry using Pluronic F127 as structure directing agent and titanium isopropoxide as a titanium source. The amount of titanium in the silica framework of the materials is controlled by a simple adjustment of the molar water to hydrochloric acid (n/n) ratio. The materials with different n/n ratios are also prepared by varying the amount of titanium source in the synthesis gel at an optimized n/n of 463. The structural order, the textural parameters, morphology, the nature and co-ordination of Ti species, and the amount of Ti content in the samples are analyzed by various techniques including X-ray diffraction (XRD), N adsorption, high resolution scanning electron microscopy (HRSEM), UV-vis diffused reflectance spectroscopy (UV-vis DRS), and inductively coupled plasma emission spectroscopy (ICP), respectively. All the materials prepared with various n/n ratios exhibit well-ordered porous structure and possess high BET surface areas (673-941 m g) and large pore volumes (0.46-0.71 cm g). The pore diameter of the samples also increases with increasing the Ti content in the samples. UV-vis results confirm that most of the Ti atoms are in the tetrahedral co-ordination. Finally, the materials are subjected to cyclohexene epoxidation using TBHP/HO as oxidant and acetonitrile as solvent in order to investigate their catalytic activity. Ti-KIT-5 samples display a high catalytic activity with TBHP as oxidant and remain inactive when HO was used. The amount of Ti plays a crucial role in controlling the catalytic activity of the samples. Of the catalysts studied, Ti-KIT-5(5) where the number in the parenthesis indicates the Si/Ti ratio shows the best activity, affording a high conversion to cyclohexene. Among the catalysts studied, Ti-KIT-5-5 exhibited better catalytic activity with respect to reaction time, reaction temperature, conversion and epoxide selectivity