Search results for: Gold catalyst

Authors: Srinivas Bathini, Duraichelvan Raju, Simona Badilescu, Muthukumaran Packirisamy

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A bio-sensing method, based on the plasmonic property of gold nano-islands, has been developed for detection of exosomes in a clinical setting. The position of the gold plasmon band in the UV-Visible spectrum depends on the size and shape of gold nanoparticles as well as on the surrounding environment. By adsorbing various chemical entities, or binding them, the gold plasmon band will shift toward longer wavelengths and the shift is proportional to the concentration. Exosomes transport cargoes of molecules and genetic materials to proximal and distal cells. Presently, the standard method for their isolation and quantification from body fluids is by ultracentrifugation, not a practical method to be implemented in a clinical setting. Thus, a versatile and cutting-edge platform is required to selectively detect and isolate exosomes for further analysis at clinical level. The new sensing protocol, instead of antibodies, makes use of a specially synthesized polypeptide (Vn96), to capture and quantify the exosomes from different media, by binding the heat shock proteins from exosomes. The protocol has been established and optimized by using a glass substrate, in order to facilitate the next stage, namely the transfer of the protocol to a microfluidic environment. After each step of the protocol, the UV-Vis spectrum was recorded and the position of gold Localized Surface Plasmon Resonance (LSPR) band was measured. The sensing process was modelled, taking into account the characteristics of the nano-island structure, prepared by thermal convection and annealing. The optimal molar ratios of the most important chemical entities, involved in the detection of exosomes were calculated as well. Indeed, it was found that the results of the sensing process depend on the two major steps: the molar ratios of streptavidin to biotin-PEG-Vn96 and, the final step, the capture of exosomes by the biotin-PEG-Vn96 complex. The microfluidic device designed for sensing of exosomes consists of a glass substrate, sealed by a PDMS layer that contains the channel and a collecting chamber. In the device, the solutions of linker, cross-linker, etc., are pumped over the gold nano-islands and an Ocean Optics spectrometer is used to measure the position of the Au plasmon band at each step of the sensing. The experiments have shown that the shift of the Au LSPR band is proportional to the concentration of exosomes and, thereby, exosomes can be accurately quantified. An important advantage of the method is the ability to discriminate between exosomes having different origins.

Keywords: Exosomes, gold nano-islands, microfluidics, plasmonic biosensing.

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Authors: Peyman Moradi, Matin Parvari

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Hydrodesulfurization (HDS) of dibenzothiophene (DBT) in a high pressure batch reactor was done at 320 °C on CoMoS/Al2O3-B2O3 (4, 10, and 16 wt. % of Boria) using nhexadecane as solvent, dimethyldisulfide (DMDS) in tetradecane as sulfur agent, and stirring at 1000 rpm. The effects of boria were investigated by using X-ray diffraction (XRD), Temperature programmed desorption (TPD) of ammonia, and Brunauer-Emmet- Teller (BET) experiments. The results showed that the catalyst prepared with low boria content (4 wt. %) had HDS activity (in pseudo first order kinetic constant basis) value ~1.45 times higher to that of CoMoS/Al2O3 catalyst.

Keywords: Alumina-boria mixed oxides, dibenzothiophene, hydrodesulfurization.

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Authors: Flora Elvistia Firdaus

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Polyurethane foam (PUF) were prepared by reacting polyols synthesized from soy-oil into mixture of 2,4- Toluene diisocyanate (TDI) with 4,4--Methylene Diamine Isocyanate (MDI) with ratio of 70:30. The polyols obtained via esterification reaction were categorize into different temperature of reaction and by used of varied concentration of phosphoric acid catalyst. The purpose of catalysts is to shifting selectivity to a desired and value added of product. The effect of stoichiometric balance (molar ratio of epoxide/ethylene glycol) to the concentration of the catalyst on the final properties was evaluated.

Keywords: temperature, phosphate, soy polyurethane

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Authors: Volodymyr Chegel

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The computer modeling is carried out for parameter of sensitivity of optoelectronic chemical and biosensors, using phenomena of surface plasmon resonance (SPR). The physical model of SPR-sensor-s is described with (or without) of modifications of sensitive gold film surface by a dielectric layer. The variants of increasing of sensitivity for SPR-biosensors, constructed on the principle gold – dielectric – biomolecular layer are considered. Two methods of mathematical treatment of SPR-curve are compared – traditional, with estimation of sensor-s response as shift of the SPRcurve minimum and proposed, for system with dielectric layer, using calculating of the derivative in the point of SPR-curve half-width.

Keywords: Surface Plasmon Resonance, modeling, sensitivity, biosensor

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Authors: Liberty L Mguni, Reinout Meijboom, Kalala Jalama

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Nano-MgO was successfully deposited on titania using deposition-precipitation method. The catalyst produced was characterised using FTIR, XRD, BET and XRF and its activity was tested on the transesterification reaction of soybean oil to biodiesel. The catalyst activity improved when the reaction temperature was increasedfrom 150 and 225 OC. It was also observed that increasing the reaction time above 1h had no significant benefit on conversion. The stability fixed MgO on TiO2 was investigated using XRF and ICP-OES. It was observed that MgO loss during the reaction was between 0.5-2.3 percent and that there was no correlation between the reaction temperature and the MgO loss.

Keywords: Nano-MgO, TiO2, transesterification

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Authors: Krasimir I. Ivanov, Elitsa N. Kolentsova, Dimitar Y. Dimitrov, Georgi V. Avdeev, Tatyana T. Tabakova

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In recent research copper and manganese systems were found to be the most active in CO and organic compounds oxidation among the base catalysts. The mixed copper manganese oxide has been widely studied in oxidation reactions because of their higher activity at low temperatures in comparison with single oxide catalysts. The results showed that the formation of spinel CuxMn3−xO4 in the oxidized catalyst is responsible for the activity even at room temperature. That is why the most of the investigations are focused on the hopcalite catalyst (CuMn2O4) as the best coppermanganese catalyst. Now it’s known that this is true only for CO oxidation, but not for mixture of CO and VOCs. The purpose of this study is to investigate the alumina supported copper-manganese catalysts with different Cu/Mn molar ratio in terms of oxidation of CO, methanol and dimethyl ether. The catalysts were prepared by impregnation of γ-Al2O3 with copper and manganese nitrates and the catalytic activity measurements were carried out in two stage continuous flow equipment with an adiabatic reactor for simultaneous oxidation of all compounds under the conditions closest possible to the industrial. Gas mixtures on the input and output of the reactor were analyzed with a gas chromatograph, equipped with FID and TCD detectors. The texture characteristics were determined by low-temperature (- 196oС) nitrogen adsorption in a Quantachrome Instruments NOVA 1200e (USA) specific surface area & pore analyzer. Thermal, XRD and TPR analyses were performed. It was established that the active component of the mixed Cu- Mn/γ–alumina catalysts strongly depends on the Cu/Mn molar ratio. Highly active alumina supported Cu-Mn catalysts for CO, methanol and DME oxidation were synthesized. While the hopcalite is the best catalyst for CO oxidation, the best compromise for simultaneous oxidation of all components is the catalyst with Cu/Mn molar ratio 1:5.

Keywords: Supported copper-manganese catalysts, CO and VOCs oxidation.

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Authors: Victor R. Thulari, John Akach, Haleden Chiririwa, Aoyi Ochieng

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Solar-light activated titanium dioxide photocatalysts were prepared by hydrolysis of titanium (IV) isopropoxide with thiourea, followed by calcinations at 450 °C. The experiments demonstrated that methyl orange in aqueous solutions were successfully degraded under solar light using doped TiO₂. The photocatalytic oxidation of a mono azo methyl-orange dye has been investigated in multi ion doped TiO₂ and solar light. Solutions were irradiated by solar-light until high removal was achieved. It was found that there was no degradation of methyl orange in the dark and in the absence of TiO₂. Varieties of laboratory prepared TiO₂ catalysts both un-doped and doped using titanium (IV) isopropoxide and thiourea as a dopant were tested in order to compare their photoreactivity. As a result, it was found that the efficiency of the process strongly depends on the working conditions. The highest degradation rate of methyl orange was obtained at optimum dosage using commercially produced TiO₂. Our work focused on laboratory synthesized catalyst and the maximum methyl orange removal was achieved at 81% with catalyst loading of 0.04 g/L, initial pH of 3 and methyl orange concentration of 0.005 g/L using multi-ion doped catalyst. The kinetics of photocatalytic methyl orange dye stuff degradation was found to follow a pseudo-first-order rate law. The presence of the multi-ion dopant (thiourea) enhanced the photoefficiency of the titanium dioxide catalyst.

Keywords: Degradation, kinetics, methyl orange, photocatalysis.

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Authors: Suthat Turapan, Cattareya Yotkamchornkun, Kamchai Nuithitikul

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The production of biodiesel from crude palm oil with a homogeneous base catalyst is unlikely owing to considerable formation of soap. Free fatty acids (FFA) in crude palm oil need to be reduced, e.g. by esterification. This study investigated the activity of sulfated zirconia calcined at various temperatures for esterification of FFA in crude palm oil to biodiesel. It was found that under a proper reaction condition, sulfated zirconia well catalyzes esterification. FFA content can be reduced to an acceptable value for typical biodiesel production with a homogeneous base catalyst. Crystallinity and sulfate attachment of sulfated zirconia depend on calcination temperature during the catalyst preparation. Too low temperature of calcination gives amorphous sulfated zirconia which has low activity for esterification of FFA. In contrast, very high temperature of calcination removes sulfate group, consequently, conversion of FFA is reduced. The appropriate temperature range of calcination is 550-650 oC.

Keywords: Biodiesel, Esterification, Free fatty acids, Sulfatedzirconia.

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Authors: M. L. Dinis, M. C. Vila, A. Fiúza, A. Futuro, C. Nunes

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The present paper describes the study of paste tailings prepared in laboratory using gold tailings, produced in a Finnish gold mine with the incorporation of coal ash. Natural leaching tests were conducted with the original materials (tailings, fly and bottom ashes) and also with paste mixtures that were prepared with different percentages of tailings and ashes. After leaching, the solid wastes were physically and chemically characterized and the results were compared to those selected as blank – the unleached samples. The tailings and the coal ash, as well as the prepared mixtures, were characterized, in addition to the textural parameters, by the following measurements: grain size distribution, chemical composition and pH. Mixtures were also tested in order to characterize their mechanical behavior by measuring the flexural strength, the compressive strength and the consistency. The original tailing samples presented an alkaline pH because during their processing they were previously submitted to pressure oxidation with destruction of the sulfides. Therefore, it was not possible to ascertain the effect of the coal ashes in the acid mine drainage. However, it was possible to verify that the paste reactivity was affected mostly by the bottom ash and that the tailings blended with bottom ash present lower mechanical strength than when blended with a combination of fly and bottom ash. Surface paste disposal offer an attractive alternative to traditional methods in addition to the environmental benefits of incorporating large-volume wastes (e.g. bottom ash). However, a comprehensive characterization of the paste mixtures is crucial to optimize paste design in order to enhance engineer and environmental properties.

Keywords: Coal ash, gold tailings, paste, surface disposal.

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Authors: Hendriëtte van der Walt, Lesley Chown, Richard Harris, Ndabenhle Sosibo, Robert Tshikhudo

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The use of magnetic and magnetic/gold core/shell nanoparticles in biotechnology or medicine has shown good promise due to their hybrid nature which possesses superior magnetic and optical properties. Some of these potential applications include hyperthermia treatment, bio-separations, diagnostics, drug delivery and toxin removal. Synthesis refinement to control geometric and magnetic/optical properties, and finding functional surfactants for biomolecular attachment, are requirements to meet application specifics. Various high-temperature preparative methods were used for the synthesis of iron oxide and gold-coated iron oxide nanoparticles. Different surface functionalities, such as 11-aminoundecanoic and 11-mercaptoundecanoic acid, were introduced on the surface of the particles to facilitate further attachment of biomolecular functionality and drug-like molecules. Nanoparticle thermal stability, composition, state of aggregation, size and morphology were investigated and the results from techniques such as Fourier Transform-Infra Red spectroscopy (FT-IR), Ultraviolet visible spectroscopy (UV-vis), Transmission Electron Microscopy (TEM) and thermal analysis are discussed.

Keywords: Core/shell, Iron oxide, Gold coating, Nanoparticles.

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Authors: X. Zhao, F. Tian

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Mycotoxins are secondary metabolic products of fungi. These are poisonous, carcinogens and mutagens in nature and pose a serious health threat to both humans and animals, causing severe illnesses and even deaths. The rapid, simple and cheap detection methods of mycotoxins are of immense importance and in great demand in the food and beverage industry as well as in agriculture and environmental monitoring. Lateral flow immunochromatographic strips (ICSTs) have been widely used in food safety, environment monitoring. 46 papers were identified and reviewed on Google Scholar and Scopus for their limit of detection and nanomaterial on Lateral flow ICSTs on different types of mycotoxins. The papers were dated 2001-2021. 25 papers were compared to identify the lowest limit of detection of among different mycotoxins (Aflatoxin B1: 10, Zearalenone: 5, Fumonisin B1: 5, Trichothecene-A: 5). Most of these highly sensitive strips are competitive. Sandwich structures are usually used in large scale detection. In conclusion, the limit of detection of Aflatoxin B1 is the lowest among these mycotoxins. Gold-nanoparticle based immunochromatographic test strips have the lowest limit of detection. Five papers involve smartphone detection and they all detect aflatoxin B1 with gold nanoparticles.

Keywords: Aflatoxin B1, limit of detection, gold nanoparticle, lateral flow immunochromatographic strips, mycotoxins, smartphone.

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Authors: S. Chauhan, T.P.K. Grewal, S.K. Aggarwal, V.K. Srivastava

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Solution for the complete removal of carbon monoxide from the exhaust gases still poses a challenge to the researchers and this problem is still under development. Modeling for reduction of carbon monoxide is carried out using heterogeneous reaction using low cost non-noble metal based catalysts for the purpose of controlling emissions released to the atmosphere. A simple one-dimensional model was developed for the monolith using hopcalite catalyst. The converter is assumed to be an adiabatic monolith operating under warm-up conditions. The effect of inlet gas temperatures and catalyst loading on carbon monoxide reduction during cold start period in the converter is analysed.

Keywords: carbon monoxide, catalytic, modeling, monolith

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Authors: Worawoot Prasitturattanachai, Kamchai Nuithitikul

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The conventional production of biodiesel from crude palm oil which contains large amounts of free fatty acids in the presence of a homogeneous base catalyst confronts the problems of soap formation and very low yield of biodiesel. To overcome these problems, free fatty acids must be esterified to their esters in the presence of an acid catalyst prior to alkaline-catalyzed transesterification. Sulfated metal oxides are a promising group of catalysts due to their very high acidity. In this research, aluminadoped sulfated tin oxide (SO4 2-/Al2O3-SnO2) catalysts were prepared and used for esterification of free fatty acids in crude palm oil in a batch reactor. The SO4 2-/Al2O3-SnO2 catalysts were prepared from different Al precursors. The results showed that different Al precursors gave different activities of the SO4 2-/Al2O3-SnO2 catalysts. The esterification of free fatty acids in crude palm oil with methanol in the presence of SO4 2-/Al2O3-SnO2 catalysts followed first-order kinetics.

Keywords: Methyl ester, Biodiesel, Esterification, Sulfated tin oxide, Fatty acid.

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Authors: Jing Zhang, Lian Wu, Jie-ming Qu, Chun-xue Bai, Mervyn J Merrilees, Peter N Black

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COPD is characterized by loss of elastic fibers from small airways and alveolar walls, with the decrease in elastin increasing with disease severity. It is unclear why there is a lack of repair of elastic fibers. We have examined fibroblasts cultured from lung tissue from normal and COPD subjects to determine if the secretory profile explains lack of tissue repair. In this study, fibroblasts were cultured from lung parenchyma of bronchial carcinoma patients with varying degrees of COPD; controls (non-COPD, n=5), mild COPD (GOLD 1, n=5) and moderate-severe COPD (GOLD 2-3, n=12). Measurements were made of proliferation, senescence-associated beta-galactosidase-1, mRNA expression of IL-6, IL-8, MMP-1, tropoelastin and versican, and protein levels for IL-6, IL-8, PGE2, tropoelastin, insoluble elastin, and versican. It was found that GOLD 2-3 fibroblasts proliferated more slowly (p<0.01) and had higher levels of senescence-associated beta-galactosidase-1 (p<0.001) than controls (non-COPD). GOLD 2-3 fibroblasts showed significant increases in mRNA and/or protein for IL-6, IL-8, MMP-1, PGE2, versican (p<0.01) and tropoelastin (p<0.05). mRNA expression and/or protein levels of tropoelastin (p<0.01), versican (p<0.02), IL-6 (p<0.05) and IL-8 (p<0.05) were negatively correlated with FEV1%. Insoluble elastin was not increased. In summary, fibroblasts from moderate to severe COPD subjects display a secretory phenotype with up-regulation of inflammatory molecules including the matrix proteoglycan versican, and increased soluble, but not insoluble, elastin. Versican inhibits assembly of tropoelastin into insoluble elastin and we conclude that the pro-inflammatory phenotype of COPD fibroblasts it is not compatible with repair elastic fibers.

Keywords: COPD, pulmonary fibroblasts, pro-inflammatory phenotype, versican, elastin

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Authors: Sushil Kumar Saraswat, K. K. Pant

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Co metal supported on SiO2 and Al2O3 catalysts with a metal loading varied from 30 of 70 wt.% were evaluated for decomposition of methane to COx free hydrogen and carbon nanomaterials. The catalytic runs were carried out from 550-800oC under atmospheric pressure using fixed bed vertical flow reactor. The fresh and spent catalysts were characterized by BET surface area analyzer, XRD, SEM, TEM and TG analysis. The data showed that 50% Co/Al2O3 catalyst exhibited remarkable higher activity at 800oC with respect to H2 production compared to rest of the catalysts. However, the catalytic activity and durability was greatly declined at higher temperature. The main reason for the catalytic inhibition of Co containing SiO2 catalysts is the higher reduction temperature of Co2SiO4. TEM images illustrate that the carbon materials with various morphologies, carbon nanofibers (CNFs), helical-shaped CNFs and branched CNFs depending on the catalyst composition and reaction temperature were obtained.

Keywords: Carbon nanotubes, Cobalt, Hydrogen Production, Methane decomposition.

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Authors: Abdul Rahim Yacob, Mohd Khairul Asyraf Amat Mustajab, Nur Syazeila Samadi

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Nano MgO has been synthesized by hydration and dehydration method by modifies the commercial MgO. The prepared MgO had been investigated as a heterogeneous base catalyst for transesterification process for biodiesel production using palm oil. TGA, FT-IR and XRD results obtained from this study lie each other and proved in the formation of nano MgO from decomposition of Mg(OH)2. This study proved that the prepared nano MgO was a better base transesterification catalyst compared to commercial MgO. The nano MgO calcined at 600ºC had gives the highest conversion of 51.3% of palm oil to biodiesel.

Keywords: Hydration-dehydration method, nano MgO, transesterification, biodiesel.

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Authors: V. Eramo, L. Piazzo, M. Listanti, A. Germoni, A Cianfrani

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The performance of the Optical Code Division Multiplexing/ Wavelength Division Multiplexing (WDM/OCDM) technique for Optical Packet Switch is investigated. The impact on the performance of the impairment due to both Multiple Access Interference and Beat noise is studied. The Packet Loss Probability due to output packet contentions is evaluated as a function of the main switch and traffic parameters when Gold coherent optical codes are adopted. The Packet Loss Probability of the OCDM/WDM switch can reach 10-9 when M=16 wavelengths, Gold code of length L=511 and only 24 wavelength converters are used in the switch.

Keywords: Optical code division multiplexing, bufferless optical packet switch, performance evaluation.

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Authors: Ke Zhang, Fang Li, Haitao Zhang, Hongfang Ma, Weiyong Ying, Dingye Fang

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Three alumina-supported Pt-Sn catalysts have been prepared by means of co-impregnation and characterized by XRD and N2 adsorption. The influence of catalyst composition and reaction conditions on the conversion and selectivity were investigated in the hydrogenation of acetic acid in an isothermal integral fixed bed reactor. The experiments were performed on the temperature interval 468-548 K, liquid hourly space velocity (LHSV) of 0.3-0.7h-1, pressures between 1.0 and 5.0Mpa. A good compromise of 0.75%Pt-1.5%Sn can act as an optimized acetic acid hydrogenation catalyst, and the conversion and selectivity can be tuned through the variation of reaction conditions.

Keywords: Acetic acid, hydrogenation, Pt-Sn catalysts, ethanol.

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Authors: Farouq Twaiq, Ishaq Al-Anbari, Mustafa Nasser

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The kinetics of palm oil catalytic cracking over aluminum containing mesoporous silica Al-MCM-41 (5% Al) was investigated in a batch autoclave reactor at the temperatures range of 573 – 673 K. The catalyst was prepared by using sol-gel technique and has been characterized by nitrogen adsorption and x-ray diffraction methods. Surface area of 1276 m2/g with average pore diameter of 2.54 nm and pore volume of 0.811 cm3/g was obtained. The experimental catalytic cracking runs were conducted using 50 g of oil and 1 g of catalyst. The reaction pressure was recorded at different time intervals and the data were analyzed using Levenberg- Marquardt (LM) algorithm using polymath software. The results show that the reaction order was found to be -1.5 and activation energy of 3200 J/gmol.

Keywords: Batch Reactor, Catalytic Cracking, Kinetics, Palm Oil.

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Authors: Deepa Govindarajan, Debdut Roy

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Pt-Sn catalysts have been prepared using magnesium aluminate as a support with two different Mg/Al ratio. The supports/catalysts have been characterized by N₂-adsorption, XRD, and temperature programmed desorption of NH₃ and thermogravimetry analysis (TGA). The catalysts have been evaluated at 595 ⁰C for the propane dehydrogenation reaction at 0.5 barg pressure using a feed containing pure propane with steam to hydrocarbon ratio of 1 mol/mol and weight hourly space velocity (WHSV) 0.9 h^-1. Chlorine quantification studies have been developed using Carbon-Hydrogen-Nitrogen-Sulphur (CHNS) analyzer. The dechlorinated catalyst with higher alumina content showed better performance (38-43% propane conversion, 91-94% propylene selectivity) in propane conversion and propylene selectivity than Pt-Sn-MG-AL-DC-1 (30-18% propane conversion, 83-90% propylene selectivity).

Keywords: Dehydrogenation, alumina, platinum-tin catalyst, dechlorination.

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Authors: Vanessa Romanovicz, Beatriz A. Berns, Stephen D. Carpenter, Deyse Carpenter

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This article deals with the carbon nanotubes (CNT) synthesized from a novel precursor, sugar cane and Anodic Aluminum Oxide (AAO). The objective was to produce CNTs to be used as catalyst supports for Proton Exchange Membranes. The influence of temperature, inert gas flow rate and concentration of the precursor is presented. The CNTs prepared were characterized using TEM, XRD, Raman Spectroscopy, and the surface area determined by BET. The results show that it is possible to form CNT from sugar cane by pyrolysis and the CNTs are the type multi-walled carbon nanotubes. The MWCNTs are short and closed at the two ends with very small surface area of S_BET= 3.691m^,/g.

Keywords: Carbon nanotubes, sugar cane, fuel cell, catalyst support.

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Authors: Yuxuan Huang, Weixin Qian, Hongfang Ma, Haitao Zhang, Weiyong Ying

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Light olefins are important building blocks for chemical industry. Direct conversion of syngas to light olefins has been investigated for decades. Meanwhile, the limit for light olefins selectivity described by Anderson-Schulz-Flory (ASF) distribution model is still a great challenge to conventional Fischer-Tropsch synthesis. The emerging strategy called oxide-zeolite concept (OX-ZEO) is a promising way to get rid of this limit. ZnCrO_x was prepared by co-precipitation method and (NH₄)₂CO₃ was used as precipitant. SAPO-34 was prepared by hydrothermal synthesis, and Tetraethylammonium hydroxide (TEAOH) was used as template, while silica sol, pseudo-boehmite, and phosphoric acid were Al, Si and P source, respectively. The bifunctional catalyst was prepared by mechanical mixing of ZnCrO_x and SAPO-34. Catalytic reactions were carried out under H₂/CO=2, 380 ℃, 1 MPa and 6000 mL·g_cat^-1·h^-1 in a fixed-bed reactor with a quartz lining. Catalysts were characterized by XRD, N₂ adsorption-desorption, NH₃-TPD, H₂-TPR, and CO-TPD. The addition of Al as structure promoter enhances CO conversion and selectivity to light olefins. Zn/Cr ratio, which decides the active component content and chemisorption property of the catalyst, influences CO conversion and selectivity to light olefins at the same time. C_2-4⁼ distribution of 86% among hydrocarbons at CO conversion of 14% was reached when Zn/Cr=1.5.

Keywords: Light olefins, OX-ZEO, syngas, ZnCrOx.

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Authors: Rana Th. A. Al-Rubaye, Burcin Atilgan, Richard J. Holmes, Arthur A. Garforth

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Structured catalysts formed from the growth of zeolites on substrates is an area of increasing interest due to the increased efficiency of the catalytic process, and the ability to provide superior heat transfer and thermal conductivity for both exothermic and endothermic processes. However, the generation of structured catalysts represents a significant challenge when balancing the relationship variables between materials properties and catalytic performance, with the Na2O, H2O and Al2O3 gel composition paying a significant role in this dynamic, thereby affecting the both the type and range of application. The structured catalyst films generated as part of this investigation have been characterised using a range of techniques, including X-ray diffraction (XRD), Electron microscopy (SEM), Energy Dispersive X-ray analysis (EDX) and Thermogravimetric Analysis (TGA), with the transition from oxide-on-alloy wires to hydrothermally synthesised uniformly zeolite coated surfaces being demonstrated using both SEM and XRD. The robustness of the coatings has been ascertained by subjecting these to thermal cycling (ambient to 550oC), with the results indicating that the synthesis time and gel compositions have a crucial effect on the quality of zeolite growth on the FeCrAlloy wires. Finally, the activity of the structured catalyst was verified by a series of comparison experiments with standard zeolite Y catalysts in powdered pelleted forms.

Keywords: FeCrAlloy, Structured catalyst, and Zeolite Y.

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Authors: Askar Sabet, Abdolrasoul Fakhraee, Motahahre Ramezanpour, Noorallah Alipour

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An efficient and green method for oxidation of thiols to the corresponding disulfides is reported using ionic liquid [HSO3N(C2H4OSO3H)3] in the presence of free nano-Fe2O3 at 60°C. Ionic liquid is selective oxidant for S-S Coupling variety aliphatic and aromatic of thiols to corresponding disulfide in the presence of free nano-Fe2O3 as recoverable catalyst. Reaction has been performed in methanol as an inexpensive solvent. This reaction is clean and easy work-up with no side reaction.

Keywords: Thiol, Disulfide, Ionic liquid, Free Nano-Fe2O3, Oxidation, Coupling.

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Authors: O. Frolov, K. Kolacek, J. Schmidt, J. Straus, V. Prukner, A. Shukurov

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Many applications require surface modification and micro-structuring of polymers. For these purposes is mainly used ultraviolet (UV) radiation from excimer lamps or excimer lasers. However, these sources have a decided disadvantage - degrading the polymer deep inside due to relatively big radiation penetration depth which may exceed 100 μm. In contrast, extreme ultraviolet (EUV) radiation is absorbed in a layer approximately 100 nm thick only. In this work, the radiation from a discharge-plasma EUV source (with wavelength 46.9 nm) based on a capillary discharge driver is focused with a spherical Si/Sc multilayer mirror for surface modification of PMMA sample or thin gold layer (thickness about 40 nm). It was found that the focused EUV laser beam is capable by one shot to ablate PMMA or layer of gold, even if the focus is significantly influenced by astigmatism.

Keywords: ablation, capillary discharge, EUV laser, surface modification

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Authors: Prathap S. Raghavendra, Mohamed S. Z. Shamshuddin, Thimmaraju N., Venkatesh

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The transesterification of dimethyl malonate (DMM) with phenol has been studied in vapour phase over cordierite honeycomb coated with solid acid catalysts such as ZrO2, Mo(VI)/ZrO2 and SO42-/ZrO2. The catalytic materials were prepared honeycomb coated, powder forms, and characterized for their total surface acidity by NH3-TPD and crystalinity by powder XRD methods. Phenyl methyl malonate (PMM) and diphenyl malonate (DPM) were obtained as the reaction products. A good conversion of DMM (up to 82%) of MPM with 95% selectivity was observed when the reactions were carried out at a catalyst bed temperature of 200 °C and flow-rate of 10 mL/h in presence of Mo(VI)/ZrO2 as catalyst. However, over SO4^2-/ZrO2 catalyst, the yield of DPM was found to be higher. The results have been interpreted based on the variation of acidic properties and powder XRD phases of zirconia on incorporation of Mo(VI) or SO42– ions. Transesterification reactions were also carried out over powder forms of the catalytic materials and the yield of the desired phenyl ester products were compared with that of the HC coated catalytic materials. The solid acids were found to be reusable when used for at least 5 reaction cycles.

Keywords: Cordierite honeycomb, methyl phenyl malonate, vapour phase transesterification, zirconia.

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Authors: Noor S. Nasri, Eric C. A. Tatt, Usman D. Hamza, Jibril Mohammed, Husna M. Zain

Abstract:

Catalytic combustion of methane is imperative due to stability of methane at low temperature. Methane (CH4), therefore, remains unconverted in vehicle exhausts thereby causing greenhouse gas GHG emission problem. In this study, heterogeneous catalysts of palladium with bio-char (2 wt% Pd/Bc) and Al2O3 (2wt% Pd/ Al2O3) supports were prepared by incipient wetness impregnation and then subsequently tested for catalytic combustion of CH4. Support-porous heterogeneous catalytic combustion (HCC) material were selected based on factors such as surface area, porosity, thermal stability, thermal conductivity, reactivity with reactants or products, chemical stability, catalytic activity, and catalyst life. Sustainable and renewable support-material of bio-mass char derived from palm shell waste material was compared with those from the conventional support-porous materials. Kinetic rate of reaction was determined for combustion of methane on Palladium (Pd) based catalyst with Al2O3 support and bio-char (Bc). Material characterization was done using TGA, SEM, and BET surface area. The performance test was accomplished using tubular quartz reactor with gas mixture ratio of 3% methane and 97% air. The methane porous-HCC conversion was carried out using online gas analyzer connected to the reactor that performed porous-HCC. BET surface area for prepared 2 wt% Pd/Bc is smaller than prepared 2wt% Pd/ Al2O3 due to its low porosity between particles. The order of catalyst activity based on kinetic rate on reaction of catalysts in low temperature was 2wt% Pd/Bc>calcined 2wt% Pd/ Al2O3> 2wt% Pd/ Al2O3>calcined 2wt% Pd/Bc. Hence agro waste material can successfully be utilized as an inexpensive catalyst support material for enhanced CH4 catalytic combustion.

Keywords: Catalytic-combustion, Environmental, Support-bio-char material, Sustainable, Renewable material.

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Authors: Phuong T. Dang, Hy G. Le, Giang T. Pham, Hong T. M. Vu, Kien T, Nguyen, Canh D. Dao, Giang H. Le, Hoa T. K. Tran, Quang K. Nguyen, Tuan A. Vu

Abstract:

Nanostructured catalysts were successfully prepared by acidification of diatomite and regeneration of FCC spent catalysts. The obtained samples were characterized by IR, XRD, SEM, EDX, MAS-NMR (27Al and 29Si), NH3-TPD and tested in catalytic pyrolysis of biomass (rice straw). The results showed that the similar bio-oil yield of 41.4% can be obtained by pyrolysis with catalysts at 450oC as compared to that of the pyrolysis without catalyst at 550oC. The bio-oil yield reached a maximum of 42.55% at the pyrolysis temperature of 500oC with catalytic content of 20%. Moreover, by catalytic pyrolysis, bio-oil quality was better as reflected in higher ratio of H/C, lower ratio of O/C. This clearly indicated high application potential of these new nanostructured catalysts in the production of bio-oil with low oxygenated compounds.

Keywords: Acidified diatomite, biomass, catalytic pyrolysis, bio-oil, nanostructured catalysts, regenerated FCC catalyst.

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Authors: Abhijit Mitra

Abstract:

Different pseudo-random or pseudo-noise (PN) as well as orthogonal sequences that can be used as spreading codes for code division multiple access (CDMA) cellular networks or can be used for encrypting speech signals to reduce the residual intelligence are investigated. We briefly review the theoretical background for direct sequence CDMA systems and describe the main characteristics of the maximal length, Gold, Barker, and Kasami sequences. We also discuss about variable- and fixed-length orthogonal codes like Walsh- Hadamard codes. The equivalence of PN and orthogonal codes are also derived. Finally, a new PN sequence is proposed which is shown to have certain better properties than the existing codes.

Keywords: Code division multiple access, pseudo-noise codes, maximal length, Gold, Barker, Kasami, Walsh-Hadamard, autocorrelation, crosscorrelation, figure of merit.

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Authors: Mohammad Asif

Abstract:

Heterogeneous catalysis is vital for a number of chemical, refinery and pollution control processes. The use of catalyst pellets of hollow cylindrical shape provide several distinct advantages over other common shapes, and can therefore help to enhance conversion levels in reactors. A better utilization of the catalytic material is probably most notable of these features due to the absence of the pellet core, which helps to significantly lower the effect of the internal transport resistance. This is reflected in the enhancement of the effectiveness factor. For the case of the first order irreversible kinetics, a substantial increase in the effectiveness factor can be obtained by varying shape parameters. Important shape parameters of a finite hollow cylinder are the ratio of the inside to the outside radii (κ) and the height to the diameter ratio (γ). A high value of κ the generally helps to enhance the effectiveness factor. On the other hand, lower values of the effectiveness factors are obtained when the dimension of the height and the diameter are comparable. Thus, the departure of parameter γ from the unity favors higher effectiveness factor. Since a higher effectiveness factor is a measure of a greater utilization of the catalytic material, higher conversion levels can be achieved using the hollow cylindrical pellets possessing optimized shape parameters.

Keywords: Finite hollow cylinder, Catalyst pellet, Effectiveness factor, Thiele Modulus, Conversion

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