Method for the in situ preparation of a single layer of zeolite Beta crystals on a molybdenum substrate for microreactor applications

A method for the hydrothermal synthesis of a single layer of zeolite Beta crystals on a molybdenum substrate for microreactor applications has been developed. Before the hydrothermal synthesis, the surface of the substrate was modified by an etching procedure that increases the roughness at the nanoscale level without completely eliminating the surface lay structure. Then, thin films of Al2O3 (170 nm) and TiO2 (50 nm) were successively deposited by atomic layer deposition (ALD) on the substrate. The internal Al2O3 film protects the Mo substrate from oxidation up to 550 degrees C in an oxidative environment. The high wettability of the external TiO2 film after UV irradiation increases zeolite nucleation on its surface. The role of the metal precursor (TiCl4 vs TiI4), deposition temperature (300 vs 500 degrees C), and film thickness (50 vs 100 nm) was investigated to obtain titania films with the slowest decay in the superhydrophilic behavior after UV irradiation. Zeolite Beta coatings with a Si/Al ratio of 23 were grown at 140 degrees C for 48 It. After ion exchange with a 10(-4) M cobalt acetate solution, the activity of the coatings was determined in the ammoxidation of ethylene to acetonitrile in a microstructured reactor. A maximum reaction rate of 220 mu mol C2H3N g(-1) s(-1) was obtained at 500 degrees C, with 42% carbon selectivity to acetonitrile. (C) 2007 Elsevier Inc. All rights reserved.

The preparation of highly ordered single layer ZSM-5 coating on prefabricated stainless steel microchannels

An elegant way to prepare catalytically active microreactors is by applying a coating of zeolite crystals onto a metal microchannel structure. In this study the hydrothermal formation of ZSM-5 zeolitic coatings on AISI 316 stainless steel plates with a microchannel structure has been investigated at different synthesis mixture compositions. The procedures of coating and thermal treatment have also been optimized. Obtaining a uniform thickness of the coating within 0.5 mm wide microchannels requires a careful control of various synthesis variables. The role of these factors and the problems in the synthesis of these zeolitic coatings are discussed. In general, the synthesis is most sensitive to the H2O/Si ratio as well as to the orientation of the plates with respect to the gravity vector. Ratios of H2O/Si=130 and Si/template=13 were found to be optimal for the formation of a zeolitic film with a thickness of one crystal at a temperature of 130 degreesC and a synthesis time of about 35 h. At such conditions, ZSM-5 crystals were formed with a typical size of 1.5 mu mx1.5 mu mx1.0 mum and a very narrow (within 0.2 mum) crystal size distribution. The prepared samples proved to be active in the selective catalytic reduction (SCR) of NO with ammonia. The activity tests have been carried out in a plate-type microreactor. The microreactor shows no mass transfer limitations and a larger SCR reaction rate is observed in comparison with pelletized Ce-ZSM-5 catalysts; (C) 2001 Elsevier Science B.V. All rights reserved.

Preparation and characterisation of novel thick sol-gel titania film photocatalysts

The preparation and characterization of thick (9 mum), clear, mechanically robust and photocatalytically active films of nanocrystalline anatase titania are described. XRD and SEM analysis show the films comprise 13 nm particles of anatase TiO2. Thin (54 nm) films of the 'paste' TiO2, along with sol-gel titania films made by a more traditional route are also prepared and characterised. All titania films mediate the photocatalytic destruction of stearic acid with a quantum yield of 0.0016 +/- 0.0003. using either 365 nm (i.e. BLB) or 254 nm (germicidal) light. P25 TiO2 films also appear to mediate the same process with a similar formal quantum efficiency. Of all the films tested, the thick paste TiO2 films are the most ideally suited for use with near UV light, for reasons which are discussed. All the titania films tested exhibit photoinduced superhydrophilicity.

The preparation, solubilisation and binding characteristics of a beta 2-adrenoceptor isolated from transfected Chinese hamster cells

beta2-Adrenoceptor agonists (beta -agonists) are well known for their growth promoting and repartitioning effects in many species. Although the use of these compounds to increase muscle mass in stockfarming is prohibited within the EU, under directive 96/22/EC, significant illegal use still occurs. With legal and illegal synthesis of new structurally related compounds, the detection of traditional beta -agonists and new derivatives becomes increasingly problematical. This method describes the isolation and solubilisation of a beta2-adrenoceptor from a transfected Chinese hamster ovary cell line, using the detergent digitonin. The solubilised receptor retained its activity and was isolated from the cell membrane at a concentration of 550 +/- 100 fmol mg(-1) of solubilised protein. Competition analysis using the tritiated antagonist dihydroalprenolol revealed receptor affinity for five structurally different beta -agonists, with IC50 values ranging from 2.1 +/- 0.76 X 10(-7) M for salmeterol to 1.1 +/- 0.62 x 10(-5) M for ractopamine. This study has demonstrated that transfected cell lines with a high expression of beta2-adrenoceptors are a convenient source of active receptor material. Solubilised beta (2)-adrenoceptors could form the basis of a multi-analyte screening assay for use in routine screening.

The preparation, solubilisation and binding characteristics of a beta 2-adrenoceptor isolated from transfected Chinese hamster cells

beta2-Adrenoceptor agonists (beta -agonists) are well known for their growth promoting and repartitioning effects in many species. Although the use of these compounds to increase muscle mass in stockfarming is prohibited within the EU, under directive 96/22/EC, significant illegal use still occurs. With legal and illegal synthesis of new structurally related compounds, the detection of traditional beta -agonists and new derivatives becomes increasingly problematical. This method describes the isolation and solubilisation of a beta2-adrenoceptor from a transfected Chinese hamster ovary cell line, using the detergent digitonin. The solubilised receptor retained its activity and was isolated from the cell membrane at a concentration of 550 +/- 100 fmol mg(-1) of solubilised protein. Competition analysis using the tritiated antagonist dihydroalprenolol revealed receptor affinity for five structurally different beta -agonists, with IC50 values ranging from 2.1 +/- 0.76 X 10(-7) M for salmeterol to 1.1 +/- 0.62 x 10(-5) M for ractopamine. This study has demonstrated that transfected cell lines with a high expression of beta2-adrenoceptors are a convenient source of active receptor material. Solubilised beta (2)-adrenoceptors could form the basis of a multi-analyte screening assay for use in routine screening.

Comparison and evaluation of the specificity and binding capacity of commercial and in house affinity columns used in sample preparation for analysis of growth-promoting drugs

Immunoaffinity chromatography (IAC) and affinity chromatography (AC:) are widely used for extraction of drugs from biological samples. Fifteen column types were purchased from five different manufacturers and;their ability to bind specific drugs including beta-agonists and anabolic steroids over a range of analyte concentrations in fortified bovine urine samples was assessed. The performance data obtained from these columns were compared with columns produced in this laboratory (in house columns). The in house columns gave the highest recoveries, ranging from 92 to 100% at the 1 ng spiking concentration, for five of the seven analytes assessed. Forty percent (11 of 27) of all the commercial column assessments recorded recoveries of less than 50% even when the lowest spiking concentration was applied (1 ng). For one manufacturer, only one of seven different columns purchased delivered extraction efficiencies greater than 50%. The extraction efficiencies of the clenbuterol columns were the highest with all commercially prepared columns showing at least 50% binding of radiolabelled tracer. Recoveries of alpha-nortestosterone were the lowest. The variability of these products with respect to quality control requires constant monitoring.

Investigation of the effect of the preparation method on the activity and stability of Au/CeZrO4 catalysts for the low temperature water gas shift reaction

The impact of the preparation method on the activity and stability of gold supported on ceria-zirconia low temperature water-gas shift (WGS) catalysts have been investigated. The influence of the gold deposition method, nature of the gold precursor, nature of the washing solution, drying method, Ce: Zr ratio of the support and sulfation of the support have been evaluated. The highest activity catalysts were obtained using a support with a Ce: Zr mole ratio 1: 1, HAuCl4 as the gold precursor deposited via deposition precipitation using sodium carbonate as the precipitation agent and the catalyst washed with water or 0.1 M NH4OH solution. In addition, the drying used was found to be critical with drying under vacuum at room temperature found to be most effective.