Influence Of Different Reaction Conditions Research Articles

Response surface methodology approach for the optimization of tartrazine removal by heterogeneous photo-Fenton process using mesostructured Fe2O3-suppoted ZSM-5 prepared by chitin-templating

ABSTRACTA statistical optimization of tartrazine dye removal process from aqueous solution by heterogeneous photo–Fenton process using Fe2O3-supported ZSM-5 catalyst was performed. ZSM-5 support was prepared by chitin-templating technique to obtain a mesoporous structure. Thereafter, Fe2O3 was supported on ZSM-5 through wet impregnation method. This material was characterized by different techniques and posteriorly evaluated as a catalyst for the removal of tartrazine from aqueous solution. A central composite rotational design coupled with response surface methodology approach was used to evaluate the influence of different reaction conditions on the decolorization of a solution containing tartrazine and to obtain the optimum conditions. Under the optimum experimental conditions of dye decolorization, a mineralization experiment was conducted through analysis of total organic carbon. In these conditions, 95% of decolorization was achieved at 30 min of reaction and a significant mineralization of 80% was observed at 180 min. Therefore, the photo-Fenton process using Fe2O3-supported ZSM-5 prepared by chitin-templating was proved to be feasible for both the decolorization and mineralization of tartrazine in aqueous solution.

Hydrogen storage properties of highly cross-linked polymers derived from chlorinated polypropylene and polyethylenimine

Highly cross-linked polymer derived from chlorinated polypropylene (CPP) grafted with polyethylenimine (PEI) was synthesized by hydrothermal amination reaction. The influence of different reaction conditions on the structure and properties of highly cross-linked polymer was investigated. The structures of the polymers named CPP-g-PEI were characterized by Fourier transform infrared (FT-IR) spectroscopy, elemental analysis (EA), 13C solid-state NMR (13C NMR), thermogravimetric analysis (TG), scanning electron microscopy (SEM), transmission electron microscope (TEM), powder X-ray diffraction (PXRD) and nitrogen sorption technique. CPP-g-PEI had honeycomb-like pores with an average size of between 5.37 and 13.54 nm and was thermally stable up to 250 °C. CPP-g-PEI was amorphous porous polymer with some spherulites. The N content of CPP-g-PEI increased and the Cl content of CPP-g-PEI decreased after hydrothermal amination reaction. The hydrogen storage properties of different CPP-g-PEI samples were determined by a hydrogen storage analyzer. Among all samples, hydrogen storage capacity of CPP-g-PEI at 100 °C and triethylamine solvent (CPP-g-PEI-2) achieved the highest hydrogen uptake 11.26 wt% at 77 K, 5 MPa. In addition, OH− type CPP-g-PEI (CPP-g-PEIOH−) exhibited a hydrogen uptake of 2.47 wt% at 300 K, 5 MPa. BET specific surface area of the sample was not directly associated with hydrogen storage capacity. Hydrogen adsorption enthalpy of CPP-g-PEI-2 was calculated by the Arrhenius equation to be 38.79 kJ/mol and the adsorption process of CPP-g-PEI was investigated to be reversible physical adsorption.

Hepatoprotective, Antihyperglycemic and Cytotoxic Activities of Jacaranda acutifolia Leaf Extract

Biochemical processing involving enzymatic catalysis of hydrolysis reactions of oils and fats must overcome significant technological barriers before the full benefits of the technology can be realized. Owing to their selectivity and mild reaction conditions, lipases are becoming increasingly important as biocatalysts provided that their kinetics and optimum reaction conditions are well-understood. In this study we report on the development and validation of a kinetic model for the degradation of oils using Candida rugosa lipase, from which a better understanding of the influence of different reaction conditions on hydrolysis kinetics is elucidated. Variations of reaction temperature, mixing speed, enzyme loading and substrate concentrations yielded a maximum lipase activity of 25.67 lipase units (LU), and an activation energy of 4.32 Kcal/gmol. Significantly higher enzyme loading at 0.7 mg/ml was achieved, a 169% increase over most recently reported loading by other investigators. Optimum operating ranges for medium pH and substrate concentration were established to be 7.5 to 8.5, and 30 to 55%, respectively. Reported findings mark a significant improvements over previously reported much narrower ranges of 8.0 for pH and 30 to 43% for the substrate concentration under similar experimental conditions. Developed kinetics model closely predicted and matched experimental results, rendering it suitable for biochemical engineering design application.

Production of concentrates of CLA obtained from sunflower and safflower and their application to the lipase‐catalyzed acidolysis of egg yolk phosphatidylcholine

The process of acidolysis of egg yolk phosphatidylcholine (PC) with concentrates of conjugated linoleic acid (CLA) was performed. CLA was obtained by the alkali isomerization of sunflower and safflower oils. Analysis of the influence of different reaction conditions on the process of isomerization was investigated. Reactions were carried out in preparative scale at 150°C in the ethylene glycol and afforded the mixture of isomers: cis‐9,trans‐11 and trans‐10,cis‐12. Their content was 30.8 and 32.3% for product obtained from sunflower oil and 30.4 and 36.4% for the product obtained from safflower oil. Crude concentrates were purified by urea complexation with 1:3 fatty acids to urea weight ratio. Enzymatic modification of phosphatidylcholine from egg yolk with CLA concentrates was carried out using lipase from Rhizomucor miehei. The process was performed at 45°C with controlled water activity. The highest effective incorporation (42%) of CLA into PC and lysophosphatidylcholine molecules was obtained using concentrate from the sunflower and safflower oils after 36 h of reaction.Practical applications: Results of this research are useful for the development of scaled up acidolysis reaction to produce phosphatidylcholine enriched in biologically active isomers of CLA using the sunflower or safflower oil as a rich source of linolenic acid.Application of the concentrates of CLA obtained from sunflower and safflower oils to the enzymatic acidolysis of egg yolk phosphatidylcholine.

A comprehensive study on the synthesis and paramagnetic properties of PEG-coated Fe3O4 nanoparticles

The PEG-coated Fe3O4 (PEG-Fe3O4) nanoparticles had been fabricated through chemical coprecipitation method. We comprehensively investigated the influence of different reaction conditions, such as vapor pressures with opening or sealing the beaker, molecular weights and amounts of PEG, on the structural and paramagnetic properties of PEG-Fe3O4 nanoparticles. The well-dispersed magnetic PEG-Fe3O4 nanoparticles with better size distribution can be obtained with adding 4g PEG1000 while sealing the beaker. The possible growth mechanism was also discussed in detail.

Development and testing of ilmenite granules for packed bed chemical-looping combustion

Abstract Chemical-looping combustion (CLC) is a promising technology that integrates power production and CO 2 capture with a low energy penalty. CLC has been successfully demonstrated using interconnected fluidized bed reactor systems. However, high pressure operation allows the use of inherently more efficient power cycles than low pressure fluidized bed solutions. With the aim to work at elevated pressures, dynamically operated packed-bed reactors have been proposed for CLC. In a packed-bed CLC reactor bigger oxygen carrier particles are used to avoid very large pressure drops and the required mechanical properties of these particles are quite different from the properties needed in a fluidized bed CLC system. In this work different particles have been developed and tested for application in a packed-bed CLC reactor. Ilmenite was chosen as base material because of its good reactivity with syngas, the natural availability and related low cost. Different ilmenite pellets with different composition and shape were developed and their mechanical properties before and after thermal and chemical cycling were analysed and compared. The reactivity of the particles and the influence of different reaction conditions were also studied in a thermogravimetric analyser. It was found that the thermal and chemical stresses produced an important deterioration of the mechanical properties of the pellets. The type of additive used during the production process showed an important effect on the mechanical properties of the granules. Only the granules produced with Mn 2 O 3 as additive demonstrated acceptable suitable mechanical properties after thermal and chemical cycling.

Rapid screening method to study the reactivity of UV filter substances towards skin proteins by high‐performance thin‐layer chromatography

Most UV filters used in sunscreens and other cosmetic products contain carbonyl groups, which generally are able to react with peptides or free amino acids of the human skin. To estimate their reactivity, we studied different prominent UV filter substances, octocrylene, ethylhexyl salicylate, 4-t-butyl-4'-methoxydibenzoylmethane, ethylhexyl methoxycinnamate, benzophenone-3, hydroxymethylbenzoyl sulphonic acid, octyldimethyl p-aminobenzoic acid, 3-benzylidene camphor, 4-methylbenzylidene camphor, diethylhexyl butamido triazone and ethylhexyl triazone. A simple screening method using an amino HPTLC plate as protein model was established. The influence of different reaction conditions like heating and irradiation was determined. The ketones BP-3, HMBS and BM-DBM revealed the highest binding rates after both irradiation and heating. After 1h of irradiation, 82%, 28% and 96%, respectively, were bonded to the amino phase, while heating resulted in values of 52%, 36% and 16%. For BP-3 and HMBS, even storage in the dark at room temperature resulted in a low binding. Contrarily, for the two camphor derivatives 3-BC and 4-MBC, only irradiation led to a slightly turnover. UV filters with ester groups also showed a different behaviour depending on their main skeleton. While OCR especially reacted under heating with the amino phase, resulting in 36% of bound species after one hour, UV irradiation particularly encouraged a reaction of the other esters. After 1h irradiation, 15% of EHMC, 38% of EHS and 48% of OD-PABA were bonded to the amino groups of the HPTLC plate, whereas the reactivity of the two triazones, EHT and DEBT, was comparatively low. Especially the UV filters BP-3, BM-DBM, HMBS, EHMC or OCR, which are commonly known to cause contact dermatitis, showed a high tendency to form adducts with the amino layer. Thus, the amino plate seems to be a proper tool to screen for skin sensitizers.

Study on Preparation of TiO<sub>2</sub> Nanoparticle by Sol-Gel Method

With C2H5OH as solvent and Ti(OBu)4as precursor, the process for preparing TiO2nanoparticles by sol-gel method was studied. The influence of different reaction conditions on gel time was studied in this study. Experiments show that nano-TiO2can be well prepared by sol-gel method, the optimum volume ratio of Ti(OBu)4to ethanol to acetic acid to water is 5:25:2:2, and that when the roasting temperature is 400°C,the crystalline phase is anatase; when the roasting temperature is 600°C, the crystalline phase is rutile.

Electrochemical Reduction of Quinones in Different Media: A Review

The electron transfer reactions involving quinones, hydroquinones, and catechols are very important in many areas of chemistry, especially in biological systems. The therapeutic efficiency as well as toxicity of anthracycline anticancer drugs, a class of anthraquinones, is governed by their electrochemical properties. Other quinones serve as important functional moiety in various biological systems like electron-proton carriers in the respiratory chain and their involvement in photosynthetic electron flow systems. The present paper summarizes literatures on the reduction of quinones in different solvents under various conditions using different electrochemical methods. The influence of different reaction conditions including pH of the media, nature of supporting electrolytes, nature of other additives, intramolecular or intermolecular hydrogen bonding, ion pair formation, polarity of the solvents, stabilization of the semiquinone and quinone dianion, catalytic property, and adsorption at the electrode surface, are discussed and relationships between reaction conditions and products formed have been presented.

Influence of the Reaction Conditions on the Evolution of the Michael Addition of β‐Keto Sulfones to α,β‐Unsaturated Aldehydes

AbstractWe have studied the influence of different reaction conditions on the conjugated addition of β‐keto sulfones to α,β‐unsaturated aldehydes catalyzed by silyl prolinol ethers. Small changes in the starting material and/or in the experimental protocol are able to produce significant variations in the structures of the final products. The high chemical versatility of the resulting Michael adducts make possible their use in a variety of tandem and one‐pot reactions to afford polysubstituted cyclic products bearing multiple chiral centers.

Controllable Synthesis of Mesoporous Co3O4 Nanostructures with Tunable Morphology for Application in Supercapacitors

Novel and complex mesoporous 2D and 3D architectures of the oxide semiconductor Co(3)O(4), including nanosheets, nearly monodisperse microspheres that are self-assembled from nanosheets, and copper-coin-like nanosheets, have been synthesized through a facile binary-solution route and sequential thermal decomposition at atmospheric pressure. The influence of different reaction conditions on the morphology of the products has been discussed in detail. The results revealed that the volume ratio of H(2)O and ethanolamine (EA) play a crucial role in the morphology of the precursor. The thermal decomposition of the corresponding precursor leads to the formation of the mesoporous structure. The products have been characterized by X-ray diffraction techniques, field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and Raman spectroscopy. The electrochemical properties of the Co(3)O(4) electrodes were investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge measurements. The electrochemical experiments revealed that the specific capacitance of the Co(3)O(4) nanosheets was higher than that of the Co(3)O(4) microspheres in a KOH electrolyte solution (3 m). Furthermore, the Co(3)O(4) nanosheet electrodes exhibited good rate capabilities, and maintained 93% of the initial capacity at a current density of 5 mA cm(-2) in a KOH (3 m) electrolyte solution. The results show that Co(3)O(4) nanosheets might have potential applications as electrode materials for supercapacitors.

Candida rugosa Lipase-Catalyzed Intramolecular O- to N-Transacylation of Butyryl Propranolol in the Presence of Cyclodextrins

In the present paper, a novel enzymatic reaction between (R,S)-O-butyryl propranolol (O-BP) and lipase from Candida rugosa in the presence of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) is described. Under the used condition, lipase catalyzed the intramolecular transacylation of O-BP into N-butyryl propranolol (N-BP). Propranolol, the product of the expected hydrolysis reaction, was not detected in the reaction medium. A chiral analysis of the reaction product indicated that lipase showed a preference for (R)-O-butyryl propranolol since it first transformed the (R)-enantiomer and then the corresponding (S)-enantiomer. The influence of different reaction conditions on the initial rate is also studied.

Glycation of a lysine-containing tetrapeptide by d-glucose and d-fructose—influence of different reaction conditions on the formation of Amadori/Heyns products

The site specificity, extent, and nature of modification of the tetrapeptide, Leu-Ser-Lys-Leu ( 1), incubated with d-glucose or d-fructose in methanol, or in phosphate buffer of pH 5.7, 7.4, and 8.0 were investigated. The generated mono- and di-glycated Amadori (1-deoxy- d-fructosyl derivatives) and Heyns rearrangement products (N-alkylated glucosamine/mannosamine derivatives) were isolated and characterized by NMR and mass spectrometry. The results identified the ε-amino group of the Lys residue as the preferential glycation site in tetrapeptide 1. Under all conditions investigated, glucose afforded higher yields of glycation products than fructose. In the reactions carried out in buffer, glycation at pH 7.4 and 8.0 was much faster than at pH 5.7.

Catalytic combustion of toluene on Cu-Mn/MCM-41 catalysts: Influence of calcination temperature and operating conditions on the catalytic activity

Catalytic combustion of toluene on Cu-Mn/MCM-41 catalyst was performed in tubular flow reactor operated at atmospheric pressure. The effect of catalyst pre-treatment temperatures on the catalytic activity and stability was investigated. Some reaction variables, such as inlet concentration of toluene and oxygen, reaction temperatures and space velocities were varied over wide ranges, and the influence of different reaction conditions on toluene conversion was discussed. It is showed that the catalytic activity was significantly affected by calcination temperatures between 300 and 800 °C, and oxygen concentration, toluene concentration and space velocity are all key experimental factors to optimize the toluene combustion activities. The objective of this study was to investigate catalytic properties of Cu-Mn/MCM-41 catalysts prepared at different calcination temperatures, in order to obtain additional information to prepare an efficient and highly active catalyst at low temperature.

Influence of the reaction conditions on the activity properties of vanadium–aluminium oxynitride propane ammoxidation catalyst

The influence of different reaction conditions on the catalytic activity of vanadium–aluminium oxynitride “VAlON” in propane ammoxidation is investigated. This new catalytic material exhibits amorphous character, high specific surface area, basic-redox properties and remarkable acrylonitrile production per hour and amount of catalyst. Optimal performance is achieved when the reaction temperature is 500 °C and the molar ratio of propane, oxygen, and ammonia in the gas feed is 1.25:3:1. Under these optimal reaction conditions, the catalyst showed a propane conversion level of 60%, an acrylonitrile selectivity of 56%, and an acrylonitrile productivity of 812 l/kg h. The formation of a propylene intermediate compound as well as hydrogen cyanide was detected only for those reaction conditions where the NH 3:C 3H 8 ratio was lower than 1. This suggests differences in the reaction mechanism with respect to conventional V–Me-oxide propane ammoxidation catalysts. In propane ammoxidation over VAlON catalysts, ammonia seems to play a double role: (i) as a reagent necessary for the thermal nitridation and generation of nitrogen species, (ii) participating in N-insertion step for the acrylonitrile formation from propane. The catalytic performances depend on the generation of nitrogen species as a function of the reaction conditions, which determine the level of propane conversion and selectivity to the reaction products.

Synthesis of phenylacetic acid by carbonylation

The carbonylation of benzyl alcohol to phenylacetic acid and its derivatives in the presence of rhodium catalysts is reported in this work. The influence of different reaction conditions, such as total reaction pressure, hydrogen partial pressure, catalyst, promoter and reactant concentrations, as well as reaction temperature on the catalytic activity and selectivity has been investigated. The activation parameters of the carbonylation have been measured and a possible mechanism of the reaction has been proposed.

Enzymatic Starch Saccharification in an Ultrafiltration Membrane Reactor

Enzymatic hydrolysis of starch has traditionally been performed in large volume batch reactors using soluble enzyme during long time. Introduction of the membrane bioreactor brings possibility of continuous operation in lower volume reactors in shorter reaction time. Studies on the simultaneous enzyme action of glucoamylase and pullulanase on liquefied potato starch in a continuous membrane reactor were made with the application of the various cut-off and transmembrane pressure of membranes. Influence of different reaction conditions namely enzyme concentration, substrate: enzyme ratio and residence time on glucose content were measured. Membrane reactor with 3.000 Da produced almost pure glucose at residence time of 3–4 h.

Novel regio- and stereoselective O-6-desulfation of the glucosamine moiety of heparin with N-methylpyrrolidinone–water or N,N-dimethylformamide–water mixtures

The degree of completeness and selectivity of the solvolytic O-6-desulfation reactions of the glucosamine moiety adjacent to the 2- O-sulfoiduronic acid group of heparin was systematically studied. Using solutions of various ammonium salts of heparin (salts of tributylamine, quinoline and pyridine) in mixtures of 9:1 aprotic solvents and water (solvents of medium polarity, in order of decreasing polarity: Me 2SO>Me 2NCHO>Me 2NAc> N-methylpyrrolidinone), the influence of different reaction conditions were studied. The ammonium salt of heparin with a strong base (e.g., tributylamine) in Me 2SO showed almost no desulfation, while in Me 2NCHO a relatively low degree of completeness of O-6-desulfation (30%) with moderate selectivity (15% [I-2(OS)]-desulfation) was observed. Weak bases like quinoline or pyridine in Me 2SO–water resulted in nearly complete [A-6(OS)]-desulfation (95 and 94%, respectively) with low selectivity [I-2(OS)]-desulfation (49 and 35%, respectively). The heparin pyridinium salt in Me 2NCHO–water showed both a relatively high degree of completeness and high selectivity (72% [A-6(OS)]- and 8% [I-2(OS)]-desulfation). The highest regioselectivity (i.e., a high degree of completeness accompanied by high selectivity) was achieved using an N-methylpyrrolidinone–water mixture (88% [A-6(OS)]-desulfation and 10% [I-2(OS)]-desulfation). A nearly complete O-6-desulfation (95%), accompanied by a lower selectivity (18% [I-2(OS)]-desulfation), was achieved when the reaction was carried out twice. Lower temperature improved selectivity (5% [I-2(OS)]-desulfation) but reduced the completeness of [A-6(OS)]-desulfation (72%). In comparison with the variety of O-6-desulfations reported to date, the novel reactions presented in this article led to remarkable increase in completeness and regioselectivity of the reactions that were investigated.

Low-energy electron-diffraction profile analysis of reaction-induced substrate changes on Pt(110) during catalytic CO oxidation.

The substrate changes that occur during catalytic CO oxidation on a Pt(110) surface have been investigated with a high-resolution low-energy electron-diffraction (LEED) instrument of \ensuremath{\sim}2000 \AA{} transfer width. The influence of different reaction conditions on the substrate changes was investigated by varying ${\mathit{p}}_{\mathrm{CO}}$, while ${\mathit{p}}_{\mathrm{O}2}$=2.0\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$ Torr and T=480 K were kept constant. Spot-profile-analysis LEED was used to characterize the surface in terms of terrace-width distributions and the roughening depth. During catalytic CO oxidation, the Pt(110) surface is attacked by the reaction, but with the degree of roughening and the long-range order being strongly dependent on the reaction conditions. On the high-rate branch, the surface roughens such that the roughening depth increases as ${\mathit{p}}_{\mathrm{CO}}$ approaches the position of the rate maximum in the functional dependence of the reaction rate on ${\mathit{p}}_{\mathrm{CO}}$. In the transition region in between the high- and the low-rate branch, one observes the formation of regularly spaced (430) facets. The reaction-induced substrate changes can be traced back to the mass transport of 50% of the surface atoms that is associated with the CO-induced 1\ifmmode\times\else\texttimes\fi{}1\ensuremath{\leftrightarrows}1\ifmmode\times\else\texttimes\fi{}2 phase transition. Upon annealing the faceted Pt(110) surface, a thermal-reordering process restores the flat (110) surface. One can distinguish between two stages in the restoration of the original flat surface. At relatively low temperature near 500 K, a reordering process in the vertical direction removes the surface roughness almost completely. In contrast, the lateral ordering is more strongly activated, and annealing above 800 K is required in order to produce an average terrace width above 100 \AA{}.

Influences of reaction conditions on the enantioselective transesterification using Pseudomonas cepacia lipase

The influences of different reaction conditions on Pseudomonas cepacia lipase (PCL) catalyzed esterification of several chiral allylic alcohols (2-(1-hydroxyethyl)acrylonitrile and some closely related compounds) have been investigated. These compounds are possible precursors in the synthesis of the antibiotic Nyccomycin. An increase in the reaction temperature led to an increased final conversion, decreased enantioselectivity of the reaction, and a reduction of the residual activity of the lipase. PCL is thermostable and catalytically active for more than 100 hours at 100 °C. Variation of the chain length of the acyl group of the esters used as cosubstrates had only a small influence on the conversion. As expected, the alcohol generated during the synthesis had a strong negative influence on the progress of the reaction. PCL showed strong substrate selectivity for some of the tested allylic alcohols. The enantioselectivity changed from substrate to substrate.