Search results for: solid acid catalysts

Authors: Schirin Hanf, Carlos Lizandara-Pueyo, Timmo P. Emmert, Ivana Jevtovikj, Roger Gläser, Stephan A. Schunk

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Metal alkoxides are very versatile precursors for a broad array of complex functional materials. However, metal alkoxides, especially transition metal alkoxides, tend to form oligomeric structures due to the very strong M–O–M binding motif. This fact hinders their facile application in sol-gel-processes and complicates access to complex carbonate or oxidic compounds after hydrolysis of the precursors. Therefore, the development of a synthetic alternative with the aim to grant access to carbonates and hydroxycarbonates from simple metal alkoxide precursors via hydrolysis is key to this project. Our approach involves the reaction of metal alkoxides with unsaturated isoelectronic molecules, such as carbon dioxide. Subsequently, a stoichiometric insertion of the CO₂ into the alkoxide M–O bond takes place and leads to the formation of soluble metal alkyl carbonates. This strategy is a very elegant approach to solubilize metal alkoxide precursors to make them accessible for sol-gel chemistry. After hydrolysis of the metal alkyl carbonates, crystalline metal carbonates, and hydroxycarbonates can be obtained, which were then utilized for the synthesis of Cu/Zn based bulk catalysts for methanol synthesis. Using these catalysts, a comparable catalytic activity to commercially available MeOH catalysts could be reached. Based on these results, a complement for traditional precipitation techniques, which are usually utilized for the synthesis of bulk methanol catalysts, have been found based on an alternative solubilization strategy.

Keywords: metal alkoxides, metal carbonates, metal hydroxycarbonates, CO₂ insertion, solubilization

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Authors: Hyun Lim, Dong Sook Min, Han Eul Yun, Kil Tae Kim, Ya Nan Sun, Young Ho Kim, Hyun Pyo Kim

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Matrix metalloproteinase (MMP)-13 has an important role for degrading cartilage materials under inflammatory conditions such as arthritis. Since the 70% ethanol extract of Acanthopanax koreanum inhibited MMP-13 expression in IL-1β-treated human chondrocyte cell line, SW1353, two major constituents including acanthoic acid and impressic acid were initially isolated from the same plant materials and their MMP-13 down-regulating capacity was examined. In IL-1β-treated SW1353 cells, acanthoic acid and impressic acid significantly and concentration-dependently inhibited MMP-13 expression at 10 – 100 μM and 0.5 – 10 μM, respectively. The potent one, impressic acid, was found to inhibit MMP-13 expression by blocking the phosphorylation of signal transducer and activator of transcription-1/-2 (STAT-1/-2) and activation of c-Jun and c-Fos among cellular signaling pathway involved, but did not affect the activation of mitogen-activated protein kinases (MAPKs) and nuclear transcription factor-κB (NF-κB). Further, impressic acid was also found to inhibit the expression of MMP-13 mRNA (47.7% inhibition at 10 μM), the glycosaminoglycan release (42.2% reduction at 10 μM) and proteoglycan loss in IL-1-treated rabbit cartilage explants culture. For a further study, 21 impressic acid derivatives were isolated from the same plant materials and their suppressive activities against MMP-13 expression were examined. Among the derivatives, 3α-hydroxy-lup-20(29)-en-23-oxo,28-oic acid, (20R)-3α-hydroxy-29-dimethoxylupan-23,28-dioic acid, acankoreoside F and acantrifoside A clearly down-regulated MMP-13 expression, but impressic acid being most potent. All these results suggest that impressic acid, 3α-hydroxy-lup-20(29)-en-23-oxo,28-oic acid, (20R)-3α-hydroxy-29-dimethoxylupan-23,28-dioic acid, acankoreoside F, acantrifoside A and A. koreanum may have a potential for therapeutic agents to prevent cartilage degradation possibly by inhibiting matrix protein degradation.

Keywords: acanthoic acid, Acanthopanax koreanum, cartilage, impressic acid, matrix metalloproteinase

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Authors: Reza Samsami

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The aim of the study was to degradation of polycyclic aromatic hydrocarbons (PAHs) by proxy-acid method. The amounts of PAHs were determined in a silty-clay soil sample of an aged oil refinery field in Abadan, Iran. Proxy-acid treatment method was investigated. The results have shown that the proxy-acid system is an effective method for degradation of PAHs. The results also demonstrated that the number of fused aromatic rings have not significant effects on PAH removal by proxy-acid method. The results also demonstrated that the number of fused aromatic rings have not significant effects on PAH removal by proxy-acid method.

Keywords: proxy-acid treatment, silty-clay soil, PAHs, degradation

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Authors: I. Sarenkova, I. Ciprovica, I. Cinkmanis

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Lactobionic acid is a disaccharide formed from gluconic acid and galactose, and produced by oxidation of lactose. Productivity of lactobionic acid by microbial synthesis can be affected by various factors, and one of them is a presence of potassium, magnesium and manganese ions. In order to extend lactobionic acid production efficiency, it is necessary to increase the yield of lactobionic acid by optimising the fermentation conditions and available substrates for Pseudomonas taetrolens growth. The object of the research was to determinate the application of K₂HPO₄, MnSO₄, MgSO₄ × 7H₂O salts in different concentration for effective lactose oxidation to lactobionic acid by Pseudomonas taetrolens. Pseudomonas taetrolens NCIB 9396 (NCTC, England) and Pseudomonas taetrolens DSM 21104 (DSMZ, Germany) were used for the study. The acid whey was used as the study object. The content of lactose in whey samples was determined using MilcoScan^TM Mars (Foss, Denmark) and high performance liquid chromatography (Shimadzu LC 20 Prominence, Japan). The content of lactobionic acid in whey samples was determined using the high performance liquid chromatography. The impact of studied salts differs, Mn²⁺ and Mg²⁺ ions enhanced fermentation instead of K⁺ ions. Results approved that Mn²⁺ and Mg²⁺ ions are necessary for Pseudomonas taetrolens growth. The study results will help to improve the effectiveness of lactobionic acid production with Pseudomonas taetrolens NCIB 9396 and DSM 21104.

Keywords: lactobionic acid, lactose oxidation, Pseudomonas taetrolens, whey

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Authors: Jun Sun, Tsz Tin Yu, Maryam Mirabediny, Matthew Lee, Adele Jones, Denis M. O’Carroll, Michael J. Manefield, Björn Åkermark, Biswanath Das, Naresh Kumar

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Reductive defluorination has emerged as a sustainable approach to clean water from Per and polyfluoroalkyl substances (PFASs), also known as forever organic containments. For last few decades, nano zero valent metals (nZVMs) have been intensively applied in the reductive remediation of groundwater contaminated with chlorinated organic compounds due to its low redox potential, easy application, and low production cost. However, there is inadequate information on the effective reductive defluorination of linear or branched PFAS using nZVMs as reductants because of the lack of suitable catalysts. CoII-5,10,15,20-Tetraphenyl-21H,23H-porphyrin (CoTPP) has been recently reported for effective catalyzing reductive defluorination of branched (br-) perfluorooctane sulfonate (PFOS) by using TiIII citrate as reductant. However, the low water solubility of CoTPP limited its applicability. Here, we explored a series of structurally related soluble cobalt porphyrin catalysts based on our previously reported best performing CoTPP. All soluble porphyrins [[meso-tetra(4-carboxyphenyl)porphyrinato]cobalt(III)]Cl·₇H₂O (CoTCPP), [[meso-tetra(4-sulfonatophenyl) porphyrinato]cobalt(III)]·9H2O (CoTPPS), and [[meso-tetra(4-N-methylpyridyl) porphyrinato]cobalt(II)](I)₄·₄H₂O (CoTMpyP) displayed better defluorination efficiencies than CoTPP. Especially, CoTMpyP presented the best defluorination efficiency for br-PFOS (94 %), branched perfluorooctanoic acid (PFOA) (89 %), and 3,7-Perfluorodecanoic acid (PFDA) (60 %) after 1 day at 70 0C. CoTMpyP-nZn0 system showed 88-164 times higher defluorination rate than VB12-nZn0 system in terms of all investigated br-PFASs. The CoTMpyP-nZn0 also performed effectively at room temperature, demonstrating the potential prospect for in-situ reductive systems. Based on the analysis of the intermediate products, the calculated bond dissociation energies (BDEs) and possible first interaction between CoTMpyP and PFAS, degradation pathways of 3,7-PFDA and 6-PFOS are proposed.

Keywords: cationic, soluble porphyrin, cobalt, vitamin b12, pfas, reductive defluorination

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Authors: Aliakbar Sayadi, Thomas R. Neitzert, G. Charles Clifton, Min Cheol Han

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The present study aims to assess the performance of vermiculite concrete containing poly-lactic acid beads as an eco-friendly aggregate. Vermiculite aggregate was replaced by poly-lactic acid in percentages of 0%, 20%, 40%, 60% and 80%. Mechanical and thermal properties of concrete were investigated. Test results indicated that the inclusion of poly-lactic acid decreased the PH value of concrete and all the poly-lactic acid particles were dissolved due to the formation of sodium lactide and lactide oligomers when subjected to the high alkaline environment of concrete. In addition, an increase in thermal conductivity value of concrete was observed as the ratio of poly-lactic acid increased. Moreover, a set of equations was proposed to estimate the water-cement ratio, cement content and water absorption ratio of concrete.

Keywords: poly-lactic acid (PLA), vermiculite concrete, eco-friendly, mechanical properties

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Authors: Anushree, Chhaya Sharma, Satish Kumar

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Catalytic wet air oxidation (CWAO) is normally carried out at elevated temperature and pressure. This work investigates the potential of NiO-CeO₂ nano-catalyst in CWAO of paper industry wastewater under milder operating conditions of 90 °C and 1 atm. The NiO-CeO₂ nano-catalysts were synthesized by a simple co-precipitation method and characterized by X-ray diffraction (XRD), before and after use, in order to study any crystallographic change during experiment. The extent of metal-leaching from the catalyst was determined using the inductively coupled plasma optical emission spectrometry (ICP-OES). The catalytic activity of nano-catalysts was studied in terms of total organic carbon (TOC), adsorbable organic halides (AOX) and chlorophenolics (CHPs) removal. Interestingly, mixed oxide catalysts exhibited higher activity than the corresponding single-metal oxides. The maximum removal efficiency was achieved with Ce₄₀Ni₆₀ catalyst. The results indicate that the CWAO process is efficient in removing the priority organic pollutants from wastewater, as it exhibited up to 59% TOC, 55% AOX, and 54 % CHPs removal.

Keywords: catalysis, nano-materials, NiO-CeO2, paper mill, wastewater, wet air oxidation

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Authors: Illyas Md Isa, Maryam Musfirah Che Sobry, Mohamad Syahrizal Ahmad, Nurashikin Abd Azis

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A single-walled carbon nanotube (SWCNT) that has been modified with magnesium layered hydroxide 3-(4-methoxyphenyl)propionic acid nanocomposite was proposed for the determination of uric acid and bisphenol A by square wave voltammetry. The results obtained denote that MLH-MPP nanocomposites enhance the sensitivity of the voltammetry detection responses. The best performance is shown by the modified carbon nanotube paste electrode (CNTPE) with the composition of single-walled carbon nanotube: magnesium layered hydroxide 3-(4-methoxyphenyl)propionic acid nanocomposite at 100:15 (% w/w). The linear range where the sensor works well is within the concentration 1.0 10-7 – 1.0 10-4 and 3.0 10-7 – 1.0 10-4 for uric acid and bisphenol A respectively with the limit of detection of 1.0 10-7 M for both organics. The interferences of uric acid and bisphenol A with other organic were studied and most of them did not interfere. The results shown for each experimental parameter on the proposed CNTPE showed that it has high sensitivity, good selectivity, repeatability and reproducibility. Therefore, the modified CNTPE can be used for the determination of uric acid and bisphenol A in real samples such as blood, plastic bottles and foods.

Keywords: bisphenol A, magnesium layered hydroxide 3-(4-methoxyphenyl)propionic acid nanocomposite, Nanocomposite, uric acid

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Authors: Rajesh Chandra, Uttam K. Ghosh

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This study demonstrates microalgal bio-diesel generation from a cheap, abundant, non-edible fruit pulp of Cassia fistula L. The Cassia fistula L. fruit pulp aqueous extract (CFAE) was utilized as a growth medium for cultivation of microalga Chlorella minutissima (C. minutissima). This microalga accumulated a high amount of lipids when cultivated with CFAE as a source of nutrition in comparison to BG-11 medium. Different concentrations (10, 20, 30, 40 and 50%) of CFAE diluted with distilled water were used to cultivate microalga. Effects of light intensity and photoperiod were also observed on biomass and lipid yield of microalga. Light intensity of 8000 lux with a photoperiod of 18 h resulted in maximum biomass and lipid yield of 1.28 ± 0.03 and 0.3968 ± 0.05 g/L, respectively when cultivated with 40% CFAE. Fatty acid methyl ester (FAME) profile of bio-diesel obtained shown the presence of myristic acid (C14:0), palmitic acid (C16:0), palmitoleic acid (C16:1), stearic acid (C18:0), linoleic acid (C18:2), linolenic acid (C18:3), arachidic acid (C20:0), and gondoic acid (C20:1), as major fatty acids. These facts reflect that the fruit pulp of Cassia fistula L. can be used for cultivation of C. minutissima.

Keywords: biomass, bio-diesel, Cassia fistula L., C. minutissima, GC-MS, lipid

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Authors: Joudia Akil, Stephane Siffert, Laurence Pirault-Roy, Renaud Cousin, Christophe Poupin

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The CO2 emitted from anthropic activities is perceived as a constraint in industrial activity due to taxes, stringent environmental regulations, impact on global warming… To limit these CO2 emissions, reuse of CO2 represents a promising alternative, with important applications in chemical industry and for power generation. However, CO2 valorization process requires a gas as pure as possible Oxyfuel-combustion that enables obtaining a CO2 rich stream, with water vapor (10%) is then interesting. Nevertheless to decrease the amount of the by-products found with the CO2 (especially CO and NOx which are harmful to the environment) a catalytic treatment must be applied. Nowadays three-way catalysts are well-developed material for simultaneous conversion of unburned hydrocarbons, carbon monoxide (CO) and nitrogen oxides (NOx). The use of Pd attracted considerable attention on the basis of economic factors (the high cost and scarcity of Pt and Rh). This explains the large number of studies concerning the CO-NO reaction on Pd in the recent years. In the present study, we will compare a series of Pd materials supported on different oxides for CO2 purification from the oxyfuel combustion system, by reducing NO with CO in an oxidizing environment containing CO2 rich stream and presence of 8.2% of water. Al2O3, CeO2, MgO, SiO2 and TiO2 were used as support materials of the catalysts. 1wt% Pd/Support catalysts were obtained by wet impregnation on supports with a precursor of palladium [Pd(acac)2]. The obtained samples were subsequently characterized by H2 chemisorption, BET surface area and TEM. Finally, their catalytic performances were evaluated in CO2 purification which is carried out in a fixed-bed flow reactor containing 150 mg of catalyst at atmospheric pressure. The flow of the reactant gases is composed of: 20% CO2, 10% O2, 0.5% CO, 0.02% NO and 8.2% H2O (He as eluent gas) with a total flow of 200mL.min−1, in the same GHSV. The catalytic performance of the Pd catalysts for CO2 purification revealed that: -The support material has a strong influence on the catalytic activity of 1wt.% Pd supported catalysts. depending of the nature of support, the Pd-based catalysts activity changes. -The highest reduction of NO with CO is obtained in the following ranking: TiO2>CeO2>Al2O3. -The supports SiO2 and MgO should be avoided for this reaction, -Total oxidation of CO occurred over different materials, -CO2 purification can reach 97%, -The presence of H2O has a positive effect on the NO reduction due to the production of the reductant H2 from WGS reaction H2O+CO → H2+CO2

Keywords: carbon dioxide, environmental chemistry, heterogeneous catalysis, oxyfuel combustion

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Authors: Tian Yangyang, Xu Zihe, Lu Junping, Yang Jizhou, Xu Yiqun, Wang Jiansong, Chen Chao, Yang Mengmeng, Guo Jianhua, Mu Wenjun, Wang Guiyao, Xue Chaoqun, Liang Taibo, Hu Liwei

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Cherry-red tobacco is receiving constant attention from cigarette enterprises because of its special flavor. This study aims to explore the material basis for the formation of the characteristic flavor of cherry-red tobacco and to clarify the distribution characteristics of the acidic aroma component groups in its mainstream smoke. In order to reach the aims of current study, this study employs GC/MS to examine the differences of distribution characteristics in particulate matter of mainstream cigarette smoke between cherry-red and common tobacco, meanwhile the aroma activity values (OVA) was used to compare the contribution of acidic aroma of cherry-red tobacco. The results showed that: 1) Isovaleric acid, acetic acid and butyric acid were the key acidic components in the mainstream smoke of the samples, followed by 3-methylvaleric acid, 4-methylvaleric acid and n-valeric acid. 2)Analysis of the release of these key sour fragrance components showed that the acidic aroma of "YUN 85" mainstream smoke was stronger than the leaf group, cherry-red tobacco was the weakest. In addition, aging had the effect of reducing the acidic components of cherry-red tobacco and the addition of cherry-red tobacco had little effect on the acidic components of the original leaf group. 3) For 14 acidic aroma(OAV>1) in smoke of cherry-red tobacco, 3-methylpentanoic acid, 4-methylpentanoic acid, pentanoic acid, and isovaleric acid were very prominent in contributing to acidic aroma, while pyruvic acid, 2-methylbutyric acid, hydrogenated acid, and propionic acid were less contribution.

Keywords: cherry-red tobacco, acidic aroma, GC/MS, mainstream cigarette smoke, odor activity value

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Authors: Juthamath Komvongsa, Bancha Mahong, Kannika Phasai, Sukanya Luang, Jong-Seong Jeon, James Ketudat-Cairns

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Os9BGlu31 is a rice transglucosidase that transfers glucosyl moieties to various acceptors such as carboxylic acids and alcohols, including phenolic acids and flavonoids, in vitro. The role of Os9BGlu31 transglucosidase in rice plant metabolism has not been reported to date. Methanolic extracts of rice bran and flag leaves were found to contain substrates to which Os9BGlu31 could transfer glucose from 4-nitrophenyl β -D-glucopyranoside donor. The semi-purified substrate from rice bran was found to contain oleic acid and linoleic acid and the pure fatty acids were found to act as acceptor substrates for Os9BGlu31 transglucosidase to form 1-O-acyl glucose esters. Os9BGlu31 showed higher activity with oleic acid (18:1) and linoleic acid (18:2) than stearic acid (18:0), and had both higher kcat and higher Km for linoleic than oleic acid in the presence of 8 mM 4NPGlc donor. This transglucosidase reaction is reversible, Os9bglu31 knockout rice lines of flag leaves were found to have higher amounts of fatty acid glucose esters than wild type control lines, these data conclude that fatty acid glucose esters act as glucosyl donor substrates for Os9BGlu31 transglucosidase in rice.

Keywords: fatty acid, fatty acid glucose ester, transglucosidase, rice flag leaf, homologous knockout lines, tandam mass spectrometry

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Authors: Flora Elvistia Firdaus

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The chemical structure of soybean oils have to be chemically modified through its tryglyceride to attain resemblance properties with petrochemicals. Sulfur acid catalyst in peracetic acid co-reagent has good performance on modified soybean oil strucutures through its unsaturated fatty acid moiety to the desired hydroxyl functional groups. A series of screening reactions have indicated that the ratio of acetic/peroxide acid 1:7.25 (mol/mol) with temperature of 600°C for soy-epoxide synthesis are prevailed for up-scaling of bodied soybean into 10 and 20 folds from initials. A two-step process was conducted for the preparation of soy-polyol in designated temperatures.

Keywords: soybean, polyol, up-scaling, polyurethane

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Authors: N. Stoeva, I. Spassova, R. Nickolov, M. Khristova

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Exhaust gases from stationary and mobile combustion sources contain nitrogen oxides that cause a variety of environmentally harmful effects. The most common approach of their elimination is the catalytic reaction in the exhaust using various reduction agents such as NH3, CO and hydrocarbons. Transition metals (Co, Ni, Cu, etc.) are the most widely used as active components for deposition on various supports. However, since the interaction between different catalyst components have been extensively studied in different types of reaction systems, the possible cooperation between active components and the support material and the underlying mechanisms have not been thoroughly investigated. The support structure may affect how these materials maintain an active phase. The objective is to investigate the addition of carbonaceous materials with different nature and texture characteristics on the properties of the resulting silica-carbon support and how it influences of the catalytic properties of the supported copper and cobalt catalysts for reduction of NO with CO. The versatility of the physico-chemical properties of the composites and the supported copper and cobalt catalysts are discussed with an emphasis on the relationship of the properties with the catalytic performance. The catalysts were prepared by sol-gel process and were characterized by XRD, XPS, AAS and BET analysis. The catalytic experiments were carried out in catalytic flow apparatus with isothermal flow reactor in the temperature range 20–300оС. After the catalytic test temperature-programmed desorption (TPD) was carried out. The transient response method was used to study the interaction of the gas phase with the catalyst surface. The role of the interaction between the support and the active phase on the catalyst’s activity in the studied reaction was discussed. We suppose the carbon particles with small sizes to participate in the formation of the active sites for the reduction of NO with CO along with their effect on the kind of deposited metal oxide phase. The existence of micropore texture for some of composites also influences by mass-transfer limitations.

Keywords: catalysts, no reduction, composites, bet analysis

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Authors: Kazunori Takai, Weng Kaiwei, Sadao Araki, Hideki Yamamoto

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HFC and PFC gases have been commonly and widely used as refrigerant of air conditioner and as etching agent of semiconductor manufacturing process, because of their higher heat of vaporization and chemical stability. On the other hand, HFCs and PFCs gases have the high global warming effect on the earth. Therefore, we have to be decomposed these gases emitted from chemical apparatus like as refrigerator. Until now, disposal of these gases were carried out by using combustion method like as Rotary kiln treatment mainly. However, this treatment needs extremely high temperature over 1000 °C. In the recent year, in order to reduce the energy consumption, a hydrolytic decomposition method using catalyst and plasma decomposition treatment have been attracted much attention as a new disposal treatment. However, the decomposition of fluorine-containing gases under the wet condition is not able to avoid the generation of hydrofluoric acid. Hydrofluoric acid is corrosive gas and it deteriorates catalysts in the decomposition process. Moreover, an additional process for the neutralization of hydrofluoric acid is also indispensable. In this study, the decomposition of C2F6 using zeolite and zeolite/CaO mixture as reactant was evaluated in the dry condition at 923 K. The effect of the chemical structure of zeolite on the decomposition reaction was confirmed by using H-Y, H-Beta, H-MOR and H-ZSM-5. The formation of CaF2 in zeolite/CaO mixtures after the decomposition reaction was confirmed by XRD measurements. The decomposition of C2F6 using zeolite as reactant showed the closely similar behaviors regardless the type of zeolite (MOR, Y, ZSM-5, Beta type). There was no difference of XRD patterns of each zeolite before and after reaction. On the other hand, the difference in the C2F6 decomposition for each zeolite/CaO mixtures was observed. These results suggested that the rate-determining process for the C2F6 decomposition on zeolite alone is the removal of fluorine from reactive site. In other words, the C2F6 decomposition for the zeolite/CaO improved compared with that for the zeolite alone by the removal of the fluorite from reactive site. HMOR/CaO showed 100% of the decomposition for 3.5 h and significantly improved from zeolite alone. On the other hand, Y type zeolite showed no improvement, that is, the almost same value of Y type zeolite alone. The descending order of C2F6 decomposition was MOR, ZSM-5, beta and Y type zeolite. This order is similar to the acid strength characterized by NH3-TPD. Hence, it is considered that the C-F bond cleavage is closely related to the acid strength.

Keywords: hexafluoroethane, zeolite, calcium oxide, decomposition

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Authors: Arturo Ayala-Hernandez, Humberto Hijar

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We propose a new alternative method for imposing fluid-solid boundary conditions in simulations of Multiparticle Collision Dynamics. Our method is based on the introduction of an explicit potential force acting between the fluid particles and a surface representing a solid boundary. We show that our method can be used in simulations of plane Poiseuille flows. Important quantities characterizing the flow and the fluid-solid interaction like the slip coefficient at the solid boundary and the effective viscosity of the fluid, are measured in terms of the set of independent parameters defining the numerical implementation. We find that our method can be used to simulate the correct hydrodynamic flow within a wide range of values of these parameters.

Keywords: Multiparticle Collision Dynamics, fluid-solid, boundary conditions, molecular dynamics

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Authors: Maria V. Morozova, Yulia V. Emelyanova, Anastasia A. Levina, Elena S. Buyanova, Zoya A. Mikhaylovskaya, Sofia A. Petrova

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The solid solutions of lanthanum niobates substituted by yttrium, bismuth and tungsten were synthesized. The structure of the solid solutions is either LaNbO4-based monoclinic or BiNbO4-based triclinic. The series where niobium is substituted by tungsten on B site reveals phase-modulated structure. The values of cell parameters decrease with increasing the dopant concentration for all samples except the tungsten series although the latter show higher total conductivity.

Keywords: impedance spectroscopy, LaNbO4, lanthanum ortho-niobates, solid electrolyte

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Authors: Wen Po Cheng, Chen Zhao Feng, Ruey Fang Yu, Lin Jia Jun, Lin Ji Ye, Chen Yuan Wei

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Humic acid was used as the removal target for evaluating the coagulation efficiency in this study. When the coagulant ions mix with a humic acid solution, a Fluorescence quenching effect may be observed conditionally. This effect can be described by Stern-Volmer linear equation which can be used for quantifying the quenching value (Kq) of the Fluorescence quenching effect. In addition, a Complex-Formation Titration (CFT) theory was conducted and the result was used to explain the electron-neutralization capability of the coagulant (AlCl₃) at different pH. The results indicated that when pH of the ACl₃ solution was between 6 and 8, fluorescence quenching effect obviously occurred. The maximum Kq value was found to be 102,524 at pH 6. It means that the higher the Kq value is, the better complex reaction between a humic acid and aluminum salts will be. Through the Kq value study, the optimum pH can be quantified when the humic acid solution is coagulated with aluminum ions.

Keywords: humic acid, fluorescence quenching effect, complex reaction, titration

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Authors: Yaseen Muhammad, Zhenxia Zhao, Zhangfa Tong

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A key problem with hydrodesulfurization (HDS) process of fuel oils is the application of severe operating conditions. In this study, we proposed the catalytic HDS of dibenzothiophene (DBT) integrated with ionic liquids (ILs) application at mild temperature and pressure over low loaded (0.5 wt.%) Pd promoted Co-Mo@Al₂O₃ and Ni-Mo@Al₂O₃ catalysts. Among the thirteen ILs tested, [BMIM]BF₄, [(CH₃)₄N]Cl, [EMIM]AlCl₄, and [(C₈H₁₇)(C₃H₇)₃P]Br enhanced the catalytic HDS efficiency while the latest ranked the top of activity list as confirmed by DFT studies as well. Experimental results revealed that Pd incorporation greatly enhanced the HDS activity of classical Co or Ni based catalysts. At mild optimized experimental conditions of 1 MPa H₂ pressure, 120 oC, IL:oil ratio of 1:3 and 4 h reaction time, the % DBT conversion (21 %) by Ni-Mo@Al₂O₃ was enhanced to 69 % (over Pd-Ni-Mo@ Al₂O₃) using [(C₈H₁₇) (C₃H₇)₃P]Br. The fresh and spent catalysts were characterized for textural properties using XPS, SEM, EDX, XRD and BET surface area techniques. An overall catalytic HDS activity followed the order of: Pd-Ni-Mo@Al₂O₃ > Pd-Co-Mo@Al₂O₃ > Ni-Mo@Al₂O₃ > Co-Mo@Al₂O₃. [(C₈H₁₇) (C₃H₇)₃P]Br.could be recycled four times with minimal decrease in HDS activity. Reaction products were analyzed by GC-MS which helped in proposing reaction mechanism for the IL coupled HDS process. The present approach attributed to its cost-effective nature, ease of operation with less mechanical requirements in terms of mild operating conditions, and high efficiency could be deemed as an alternative approach for the HDS of DBT on industrial level applications.

Keywords: DFT simulation, GC-MS and reaction mechanism, Ionic liquid coupled HDS of DBT, low Pd loaded catalyst, mild operating condition

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Authors: Reza Vakili, Xiaolei Fan, Alex Walton

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The first near ambient pressure (NAP)-XPS study of CO oxidation over Pt nanoparticles (NPs) incorporated into Zr-based UiO (UiO for Universitetet i Oslo) MOFs was carried out. For this purpose, the MOF-based Catalysts were prepared by wetness impregnation (WI-PtNPs@UiO-67) and linker design (LD-PtNPs@UiO-67) methods along with PtNPs@ZrO₂ as the control catalyst. Firstly, the as-synthesized catalysts were reduced in situ prior to the operando XPS analysis. The existence of Pt(II) species was proved in UiO-67 by observing Pt 4f core level peaks at a high binding energy of 72.6 ± 0.1 eV. However, by heating the WI-PtNPs@UiO-67 catalyst in situ to 200 °C under vacuum, the higher BE components disappear, leaving only the metallic Pt 4f doublet, confirming the formation of Pt NPs. The complete reduction of LD-PtNPs@UiO-67 is achieved at 250 °C and 1 mbar H₂. To understand the chemical state of Pt NPs in UiO-67 during catalytic turnover, we analyzed the Pt 4f region using operando NAP-XPS in the temperature-programmed measurements (100-260 °C) with reference to PtNPs@ZrO₂ catalyst. CO conversion during NAP-XPS experiments with the stoichiometric mixture shows that LD-PtNPs@UiO-67 has a better CO turnover frequency (TOF, 0.066 s⁻¹ at 260 °C) than the other two (ca. 0.055 s⁻¹). Pt 4f peaks only show one chemical species present at all temperatures, but the core level BE shifts change as a function of reaction temperature, i.e., Pt 4f peak from 71.8 eV at T < 200 °C to 71.2 eV at T > 200 °C. As this higher BE state of 71.8 eV was not observed after in situ reductions of the catalysts and only once the CO/O₂ mixture was introduced, we attribute it to the surface saturation of Pt NPs with adsorbed CO. In general, the quantitative analysis of Pt 4f data from the operando NAP-XPS experiments shows that the surface chemistry of the Pt active phase in the two PtNPs@UiO-67 catalysts is the same, comparable to that of PtNPs@ZrO₂. The observed difference in the catalytic activity can be attributed to the particle sizes of Pt NPs, as well as the dispersion of active phase in the support, which are different in the three catalysts.

Keywords: CO oxidation, heterogeneous catalysis, MOFs, Metal Organic Frameworks, NAP-XPS, Near Ambient Pressure X-ray Photoelectron Spectroscopy

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Authors: F. Adjel, S. Almi, D. Barkat

Abstract:

The synergistic solvent extraction of cobalt (II) from 0.33 mol dm-3 Na2SO4 aqueous solutions with capric acid (HL) in the absence and presence of tri-n-octylphosphine oxide (TOPO) in chloroform at 25°C, has been studied. The extracted species when the capric acid compound was used alone, is CoL2(HL)2. In the presence of TOPO, a remarkable enhancement on the extraction of nickel (II) with 0.02 mol dm-3 capric acid was observed upon the addition of 0.0025 to 0.01 mol dm-3 TOPO in chloroform. From an synergistic extraction- equilibrium study, the synergistic enhancement was ascribed to the adduct formation CoL2(HL)2 n(TOPO). The TOPO-HL interaction strongly influences the synergistic extraction efficiency. The synergistic extraction stoichiometry of cobalt (II) with capric acid and TOPO is studied with the methods of slope analysis. The equilibrium constants were determined.

Keywords: solvent extraction, cobalt (II), capric acid, TOPO, synergism

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Authors: Jian Huang, Weixin Qian, Haitao Zhang, Weiyong Ying

Abstract:

Cobalt-gadolinium catalyst for Fischer-Tropsch synthesis was prepared by impregnation method with commercial silica gel, and its texture properties were characterized by BET, XRD, and TPR. The catalytic performance of the catalyst was tested in a fixed bed reactor. The results showed that the addition of gadolinium to the cobalt catalyst might decrease the size of cobalt particles, and increased the dispersion of catalytic active cobalt phases. The carbon number distributions for the catalysts was calculated by ASF equation.

Keywords: Fischer-Tropsch synthesis, cobalt-based catalysts, gadolinium, carbon number distributions

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Authors: Malika Foudia, Larbi Zerroual

Abstract:

The objective of this work is to improve the electrical proprieties of lead-acid battery with the addition of additives in electrolyte and in the cured plates before oxidation. The results showed that the addition of surfactant in sulfuric acid and 3% mineral additive in the cured plates change the morphology and the crystallite size of PAM after oxidation. The discharge capacity increases with the decrease of the crystallite size and the resistance of the active mass. This shows that the addition of mineral additive and the surfactant additive to the PAM, the electrical performance and the cycle life of lead- acid battery are significantly increases.

Keywords: lead-acid battery, additives, positive plate, impedance (EIS).

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Authors: F. Adjel, C. Bensmail, S. Almi, D. Barkat

Abstract:

The synergistic solvent extraction of cobalt (II) from 0.33 mol dm^-3 Na2SO4 aqueous solutions with capric acid (HL) in the absence and presence of methyl isobutyl cétone (MIBK) in chloroform at 25°C, has been studied. The extracted species when the capric acid compound was used alone, is CoL2(HL)2. In the presence of MIBK, a remarkable enhancement on the extraction of nickel (II) with 0.02 mol dm^-3 capric acid was observed upon the addition of 0.0025 to 0.01 mol dm^-3 MIBK in chloroform. From a synergistic extraction-equilibrium study, the synergistic enhancement was ascribed to the adduct formation CoL2(HL)2 n(MIBK). The MIBK-HL interaction strongly influences the synergistic extraction efficiency. The synergistic extraction stoichiometry of cobalt (II) with capric acid and MIBK is studied with the methods of slope analysis. The equilibrium constants were determined.

Keywords: solvent extraction, cobalt (II), capric acid, MIBK, synergism

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Authors: Qasar Saleem

Abstract:

The aim of this project was to synthesize and analyze Polylactic acid-grafted TiO2 nanocomposite. When dispersed at the nanoscale TiO2 can behave as see through transparent UV filters and thermomechanical materials. The synthesis plan involved three stages. First, dispersion of TiO2 white powder in water/ethanol solvent system. Second grafting TiO2 surface by oligomers of lactic acid aimed at changing its surface features. Third polymerization of lactic acid monomer with grafted TiO2 in the presence of anhydrous stannous chloride as a catalyst. Polylactic acid grafted-TiO2 nanocomposite was synthesized by melt polycondensation in situ of lactic acid onto titanium oxide (TiO2) nanoparticles surface. The product was characterized by TGA, DSC, FTIR, and UV analysis and degradation observation. An idea regarding bonds between the grafting polymer and surface modified titanium oxide nanoparticles. Characteristics peaks of Ti–carbonyl bond, the related intensities of the Fourier transmission absorption peaks of graft composite, the melt and decomposition behavior stages of Polylactic acid-grafted TiO2 nanocomposite convinced that oligomers of polylactic acid were chemically bonded on the surface of TiO2 nanoparticles. Through grafting polylactic acid, the Polylactic acid grafted -TiO2 sample shown good absorption in UV region and degradation behavior under normal atmospheric conditions. Regaining transparency of degraded white opaque Polylactic acid-grafted TiO2 nanocomposite on heating was another character. Polylactic acid-grafted TiO2 nanocomposite will be a potential candidate in future for biomedical, UV shielding and environment friendly material.

Keywords: condensation, nanocomposites, oligomers, polylactic

Procedia PDF Downloads 185

Authors: U. A. Asli, H. Hamid, Z. A. Zakaria, A. N. Sadikin, R. Rasit

Abstract:

This study investigated the effect of a dilute acid, lime and ammonia aqueous pretreatment on the fermentable sugars conversion from empty fruit bunch (EFB) biomass. The dilute acid treatment was carried out in an autoclave, at 121ºC with 4 % of sulphuric acid. In the lime pretreatment, 3 wt % of calcium hydroxide was used, whereas the third method was done by soaking EFB with 28 % ammonia solution. Then the EFB biomass was subjected to a two-stage-acid hydrolysis process. Subsequently, the hydrolysate was fermented by using instant baker’s yeast to produce bioethanol. The highest glucose yield was 890 mg/g of biomass, obtained from the sample which underwent lime pretreatment. The highest bioethanol yield of 6.1mg/g of glucose was achieved from acid pretreatment. This showed that the acid pretreatment gave the most fermentable sugars compared to the other two pretreatments.

Keywords: bioethanol, biomass, empty fruit bunch (EFB), fermentable sugars

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Authors: María R. Contreras, Diana Endara

Abstract:

Cyanide leaching is the most used technology for gold mining industry, which produces large amounts of effluents requiring treatment. In Ecuador the development of gold mining industry has increased, causing significant environmental impacts due to the highly use of cyanide, it is estimated that 10 gr of extracted gold generates 7000 liters of water contaminated with 300mg/L of free cyanide. The most common methods used nowadays are the treatment with peroxodisulfuric acid, ozonation, H₂O₂ and other reactants which are expensive and present disadvantages. Several methods have been developed to treat this contaminant such as heterogeneous catalysts. Layered double hydroxides (LDHs) have received much attention due to their wide applications like a catalysis support. Therefore, in this study, Mg-Al/ LDH was synthetized by coprecipitation method and then platinum was impregned on it, in order to enhance its catalytic activity. Two methods of impregnation were used, the first one, called incipient wet impregnation and the second one was developed by continuous agitation of LDH in contact with chloroplatinic acid solution for 24 h. The support impregnated was analyzed by X-ray diffraction, FTIR and SEM. Finally, the oxidation of cyanide ion was performed by preparing synthetic solutions of sodium cyanide (NaCN) with an initial concentration of 500 mg/L at pH 10,5 and air flow of 180 NL/h. After 8 hours of treatment, an 80% of oxidation of ion cyanide was achieved.

Keywords: catalysis, cyanide, LDHs, mining

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Authors: A. U. Adamu, Hamisu Abdu, A. A. Saidu

Abstract:

The enzymatic synthesis of 3-O-β-D-glucopyranoside-betulinic acid using Novozyme-435 as a catalyst was studied. The effect of various parameters such as substrate molar ratio, reaction temperature, reaction time, re-used enzymes and amount of enzymes were investigated. The optimum rection conditions for the enzymatic glycosidation of betulinic acid in an organic solvent using Novozym-435 was found to be at 1:1.2 substrate molar ratio, 55oC, 24 h and 180 mg of enzymes with percentage conversion of 88.69 %.

Keywords: betulinic acid, glycosidation, novozyme-435, optimization

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Authors: Edwin Oviedo, Carlos Linares, Philippe Ayrault, Sylvette Brunet

Abstract:

Nowadays, light conventional crude oils are going down. Therefore, the exploitation of heavy crude oils has been increasing. Hence, a major quantity of refractory sulfur compounds such as dibenzothiophene (DBT) should be removed. Many efforts have been carried out to modify hydrotreatment typical supports in order to increase hydrodesulfurization (HDS) reactions. The present work shows the synthesis of tertiaries MgFeAl(0.16), MgFeAl(0.32), CoFeAl, ZnFeAl hydrotalcites, as supports of CoMo based catalysts, where 0.16 and 0.32 are the Fe3+/Al3+ molar ratio. Solids were characterized by different techniques (XRD, CO2-TPD, H2-TPR, FT-IR, BET, Chemical Analysis and HRTEM) and tested in the DBT HDS reaction. The reactions conditions were: Temp=325°C, P=40 Bar, H2/feed=475. Results show that the catalysts CoMo/MgFeAl(0.16) and CoMo/MgFeAl(0.32), which were the most basics, reduced the sulfur content from 500ppm to less than 1 ppm, increasing the cyclohexylbenzene content, i.e. presented a higher selective toward the HYD pathway than reference catalyst CoMo/γ- Al2O3. This is suitable for improving the fuel quality due to the increase of the cetane number. These catalysts were also more active to the HDS reaction increasing the direct desulfurization (DDS) way and presented a good stability. It is advantageous when the gas oil centane number should be improved. Cobalt, iron or zinc species inside support could avoid the Co and Mo dispersion or form spinel species which could be less active to hydrodesulfuration reactions, while hydrotalcites containing Mg increases the HDS activity probably due to improved Co/Mo ratio.

Keywords: catalyst, cetane number, dibenzothiophene, diesel, hydrodesulfurization, hydrotreatment, MoS2

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Authors: Hellal Abdelkader, Chafaa Salah, Boudjemaa Fouzia

Abstract:

A new, convenient, and high yielding procedure for the preparation of diethyl α-aminophosphonates in water via Kabachnik-Fields reaction by one-pot reaction of aromatic aldehydes, ortho-aminophenols, and dialkylphosphites in the presence of a low catalytic amount of citric, malic, tartaric, and oxalic acids as a natural, bi-functional, and highly stable catalyst is described, the obtained products were characterized by elemental analyses, molar conductance, magnetic susceptibility, FTIR, Uv-Vis spectral data, NMR-C, NMR-H, and NMR-P analyses.

Keywords: α-aminophosphonates, aminophenols, natural acids, aqueous media, Kabachnik-Fields reaction

Procedia PDF Downloads 303