Presence Of Homogeneous Catalysts Research Articles

A new strategy for PET depolymerization: Application of bimetallic MOF-74 as a selective catalyst

Large-volume production of poly(ethylene terephthalate) (PET), especially in the form of bottles and food packaging containers, causes problems with polymer waste management. Waste PET could be recycled thermally, mechanically or chemically and the last method allows to obtain individual monomers, but most often it is carried out in the presence of homogeneous catalysts, that are difficult to separate and reuse. In view of this, this work reports for the first time, application of bimetallic MOF-74 – as heterogeneous catalyst - for depolymerization of PET with high monomer (bishydroxyethyl terephthalate, BHET) recovery. The effect of type and amount of second metal in the MOF-74 (Mg/M) was systematically investigated. The results showed increased activity of MOF-74 (Mg/M) containing Co2+, Zn2+ and Mn2+ as a second metal, while the opposite correlation was observed for Cu2+ and Ni2+. It was found that the highest catalytic activity was demonstrated by the introduction of Mg–Mn into MOF-74 with ratio molar 1:1, which resulted in complete depolymerization of PET and 91.8% BHET yield within 4 h. Furthermore, the obtained catalyst showed good stability in 5 reaction cycles and allowed to achieve high-purity BHET, which was confirmed by HPLC analysis. The as-prepared MOF-74 (Mg/Mn) was easy to separate from the post-reaction mixture, clean and reuse in the next depolymerization reaction.

Technology for the production of disubstituted pyrroles

In this work, we studied the catalytic synthesis of pyrrole and their derivatives from ketoximes and acetylene in the liquid phase under normal conditions in the presence of homogeneous catalysts. Mathematical modeling of the experiment was carried out using the Box-Wilson method and the optimal conditions for the synthesis of a number of pyrroles were found. The catalytic synthesis of pyrrole under vapor phase conditions in the presence of heterogeneous catalysts has been studied. Low-temperature polyfunctional catalysts have been developed that provide the highest yield of pyrroles.

Revisiting the Kinetics and Mechanism of Glycerol Hydrochlorination in the Presence of Homogeneous Catalysts

Recent studies have provided new information on glycerol hydrochlorination in the presence of carboxylic acids as homogeneous catalysts; particularly interesting is the fact that a part of the carboxylic acid is esterified in some of the steps in the reaction mechanism. Inspired by this observation and the previously proposed mechanism for glycerol hydrochlorination, new kinetic equations were derived. By using the quasi-equilibrium approximation for the reaction intermediates, the rate equations take into account the fraction of catalyst that is present in the form of esters and epoxides. The model explains the initial zero-order kinetics with respect to glycerol. The parameters of the new kinetic equations were fitted by non-linear regression for the set of ordinary differential equations describing the mass balances of the system. Internal control variables were the experimentally recorded temperature inside the reactor and the measured hydrogen chloride concentration in the liquid phase. The kinetic model was fitted to experimental data, and it was confirmed that the rate equations are able to describe the concentration profiles under various conditions. Incorporation of the activity coefficient of hydrogen chloride improved slightly the model predictions. The new kinetic model reduces to the previously proposed kinetic model at carboxylic acid concentrations.

Heterogeneously-catalyzed competitive hydroarylation/hydromination of norbornene with aniline in the presence of Aquivion® ionomer

The hydroarylation of alkenes with aniline is a reaction of high interest, in particular for the manufacture of polyurethanes. This reaction has been mostly investigated in the presence of homogeneous catalysts. So far, heterogeneous catalysts have been scarcely reported for this reaction, mainly due to their inherent low activity and deactivation during the course of the reaction. Here we report the catalytic performance of Aquivion® ionomer, a perfluorinated solid acid polymer, in the hydroarylation of norbornene with aniline. We show that Aquivion® ionomer was robust and can be recycled for at least 6 runs without any decrease of its catalytic performances. Our results also highlight that Aquivion® ionomer improves the propensity of aniline to react through its aromatic ring, thus yielding a higher proportion of hydroarylation products as compared to other tested homogeneous and heterogeneous catalysts.

Optimization of Biodiesel Production Process from Restaurant Waste Frying Oils in the Presence of Homogeneous Catalyst

Optimization of Biodiesel Production Process from Restaurant Waste Frying Oils in the Presence of Homogeneous Catalyst

Validation and enhancement of waste cooking sunflower oil based biodiesel production by the trans-esterification process

ABSTRACTThis article predicts the optimum conditions for the production of fatty acid ethyl ester (Biodiesel) by trans-esterification process of waste cooking sunflower oil with ethanol in the presence of homogeneous catalyst (KOH). Response surface methodology (RSM) based on central composite rotatable design (CCRD) was used for predicting the mathematical regression equation and optimizing the biodiesel yield. The optimum reaction conditions were found to be 9.05 (mole mole−1) of (ethanol to waste cooking sunflower oil ratio), 0.99 (wt% to oil) of catalyst concentration, 57.31°C of reaction temperature, 77.12 minutes of reaction time, and 494.94 rpm of mixing rate to achieve 96.33% biodiesel yield by weight. The production rate of produced biodiesel also increased significantly. The fuel properties were measured and found closer to the ASTM standards of biodiesel. Therefore, the suggested biofuel has good scope for use in compression ignition (CI) engines.

Degradation and detoxification of the 4-chlorophenol by non-thermal plasma-influence of homogeneous catalysts

Abstract Experimental results of non-thermal plasma (NTP) utilization for degradation of 4-chlorphenol (4CP) with screening of toxicity were presented in this study. Degradation of 4CP was tested in the presence of homogeneous catalysts: hydrogen peroxide (H2O2) and iron (II) (Fe2+). The rate of degradation through eight consecutive passes of the 4CP solution in the NTP reactor was considered. Products of degradation as organic acids (acetic, formic or oxalic acid) and chloride were quantified using ion chromatography (IC). Artemia salina was used for the toxicity screening assay in order to estimate the potential and consequences of NTP reactor application in water treatment. The measured concentration of 4CP and degradation products confirmed very efficient removal of these substances from the water during the NTP treatment with the addition of a catalyst. Concerning bioassay, a significant difference in toxicity was determined between initial solution of 4CP in comparison with the solution exposed to catalytic NTP treatment.

Kinetic modeling of hemicellulose hydrolysis in the presence of homogeneous and heterogeneous catalysts

Kinetic models were developed for the hydrolysis of O‐acetyl‐galactoglucomannan (GGM), a hemicellulose appearing in coniferous trees. Homogeneous and heterogeneous acid catalysts hydrolyze GGM at about 90°C to the monomeric sugars galactose, glucose, and mannose. In the presence of homogeneous catalysts, such as HCl, H2SO4, oxalic acid, and trifluoroacetic acid, the hydrolysis process shows a regular kinetic behavior, while a prominent autocatalytic effect was observed in the presence of heterogeneous cation‐exchange catalysts, Amberlyst 15 and Smopex 101. The kinetic models proposed were based on the reactivities of the nonhydrolyzed sugar units and the increase of the rate constant (for heterogeneous catalysts) as the reaction progresses and the degree of polymerization decreases. General kinetic models were derived and special cases of them were considered in detail, by deriving analytical solutions for product distributions. The kinetic parameters, describing the autocatalytic effect were determined by nonlinear regression analysis. The kinetic model described very well the overall kinetics, as well as the product distribution in the hydrolysis of water soluble GGM by homogeneous and heterogeneous catalysts. The modelling principles developed in the work can be in principle applied to hydrolysis of similar hemicelluloses as well as starch and cellulose. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1066–1077, 2014

Investigation of the influence of the catalyst in the process of producing biodiesel using supercritical methanol

The article discusses various ways to produce biodiesel fuel: in the presence of homogeneous catalysts, in the presence of heterogeneous catalysts, in supercritical methanol. There was experimentally confirmed that the process of obtaining methyl ethers of fatty acids (FAME) in the supercritical methanol on the selectivity, on replacement of the target product and process stability in time can compete with catalytic methods. There was studied the efficiency of the catalyst at the transesterification of rapeseed oil in supercritical methanol under the following process parameters: temperature of 300°C, the pressure of 300 atmospheres, the volume fraction of oil 0,5. There was evaluated that during the first hours after the filing of the reagents into the reactor in the presence of a catalyst TiO2/Ti concentration FAME in the oil layer of the reaction products is more than in not catalysed reaction. However, approximately one hour after the beginning of the process of catalytic activity was sharply reduced, and the output of the FAME becomes less, than without a catalyst. By means of mass-spectral analysis of the product, extracted from the surface of the catalyst, it is discovered a tumor in the process of interesterification low-volatile and poorly soluble substances, blocking the active centres of the catalyst. In addition, the reduction in catalytic activity became the result of partial destruction of the surface layer of TiO2. It is established, that the washing of the spent catalyst mixture of solvents with the subsequent heating at 350°C allows largely to restore the activity of the catalyst.

The kinetics of oxidation of 1-butene to methylethylketone in the presence of a homogeneous catalyst (complex of palladium + Mo-V-P heteropoly acid)

The kinetics of the direct oxidation of 1-butene to methylethylketone (MEK) is studied in the presence of the new homogeneous catalyst namely an aqueous solution of a Pd salt and Mo-V-P heteropoly acid having non-Keggin-type composition Н12P3Mo18V7O85 (HPA-7′). The catalyst (Pd+HPA-7′) is characterized by an increased stability and high selectivity (>97%) in the MEK production. The process (1) is realized in two stages: (2)+(3). In stage (2), 1-butene reacts with the catalyst in a butylene reactor 1 with the formation of MEK and a reduced form of the catalyst. After stripping of the product, the reduced catalyst is oxidized by air in a reactor 2 under increased pressure (stage 3). The experimental data allowed us to obtain the kinetic equation for the reaction rate of 1-butene oxidation used for the calculation of the tubular plug-flow reactor 1.

Scalable Reactor Design for Pharmaceuticals and Fine Chemicals Production. 3. A Novel Gas−Liquid Reactor for Catalytic Asymmetric Transfer Hydrogenation with Simultaneous Acetone Stripping

For the asymmetric transfer hydrogenation of acetophenone to its chiral alcohols, in the presence of homogeneous catalyst (1R,2S-amino-indanol/pentamethylcyclopentadienylrhodium), with isopropanol as hydrogen donor, prior investigation revealed that removal of the byproduct acetone from the reaction system shortens the required reaction time to achieve high conversion and reduces enantiomeric excess erosion. Since acetone removal efficiency is different in different batch reactor scales, this issue poses a scalability problem. Regardless of scale, the stirred vessel operated as a gas/liquid batch reactor has limitations with regards to allowable gas flow rate through the vessel due to impeller flooding. Therefore, reactor systems where high gas/liquid flow rate ratio can be employed are advantageous. In this work, a continuous reactor that utilises a micromesh structure to stabilise the gas/liquid interface is presented. The reactor can operate with high gas/liquid flow rate, resulting in efficient aceton...

Kinetics and mechanism of the wet oxidation of propene to acetone in the presence of Pd2+ ions and Mo-V-phosphoric heteropoly acids

Oxidation of propene to acetone in water solutions in the presence of homogeneous catalysts (Pd2+ + HPA-x, where HPA-x = H3+xPVxMo12-xO40, x = 1-4) is studied. This reaction is shown to be of the 1st order with respect to C3H6 and of the 0.5th order with respect to Pd. The reaction rate does not depend on the concentration of HPA-x and acidity of the catalyst solution. The apparent activation energy of the reaction is 21 kJ/mol. A reaction mechanism is proposed.

Polyoxyethylene esters of fatty acids: an alternative synthetic route for high selectivity of monoesters

Esterification reaction of fatty acids with polyoxyethylenes has been studied in the presence of solid acid catalysts and the results are compared with those obtained with a classical homogeneous catalyst, p-toluene sulphonic acid. Solid acid catalysts showed very high selectivities for monoesters even under less favorable reaction conditions of 1:1 molar ratios of oleic acid to PEG. Excess amount of PEG is normally required to ensure high selectivity for monoesters in the presence of homogeneous catalysts. The yields for monoesters given by heterogeneous catalysts such as zeolites, HPA and nafion were comparable to that with p-toluene sulphonic acid after 24 h of reaction. Results suggest that solid acid catalysts are potential catalysts for selective synthesis of monoesters from oleic acids and PEG even under severe reaction conditions. A screening study of different solid acid catalysts showed ZSM-5, zeolite-β, and nafion to be better catalysts than zeolite USY and mordenite, the former giving higher selectivity and yield to monoesters. The results suggest that the most important parameters in optimization catalyst performance for monoesters production is the acid strength and less so on other properties such as shape selectivity and concentration of active sites.

Kinetics of oxidation of butene-1 to butanone in aqueous solution in the presence of ions pd2+ and Mo-V-phosphoric heteropoly acid

Oxidation of butene-1 to butanone in the presence of homogeneous catalysts (PdSO4 + HPA-x), where HPA-x = H3+xPVxMo12-xO40, 1 £ x £ 4, was investigated. This reaction is found to be of the 1st order with respect to C4H8, and of the 0.64th order with respect to Pd. The reaction rate does not depend on the HPA-x concentration and pH of the solution. The activation energy of the reaction is variable. A kinetic expression of the reaction is obtained for 303-343 K.

A New Synthetic Process of Lansoprazole.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A New Synthetic Process of Lansoprazole

Lansoprazole is the generic name of 2-[[[3-Methyl-4(2,2,2-trifluoroethoxy)-2-pyridyl]methyl]sulfinyl]-1 H-benzimidazole, 1 (see Scheme 1). It is a proton pump inhibitor that reduces gastric acid secretion and has successfully been used to heal and relieve symptoms of gastric or duodenal ulcers and gastro-esophagal reflux. 1 Lansoprazole has been synthesized by an oxidation of sulfide 9 produced from a substitution reaction between 2mercaptobenzimidazole and pyridine derivatives such as 2chloromethyl-3-methyl-4-(2,2,2-trifluoroethoxy)pyridine, 8. 2,3 The transformation of sulfide 9 into lansoprazole has been generally carried out with peroxyacid such as mCPBA or hydrogen peroxide in the presence of homogeneous catalyst. 3 Recently, we found that trirutile type solid oxides catalyze the hydrogen peroxide oxidation of sulfides to sulfoxides very efficiently. 4 The reaction was very selective producing sulfoxide with negligible amount of sulfone. Since the reaction is performed under heterogeneous conditions, the solid catalyst can be easily recovered by a simple filtration of the final reaction mixture. Because of these advantages in purification of the product, we decided to apply the heterogeneous sulfoxidation method to the synthesis of lansoprazole. In our approach to the synthesis of lansoprazole, we tried to devise a new process that could use 3-picoline as a starting material because it is more readily available than 2,3-lutidine, the most widely used starting material. 2,3 This strategy has become possible by adopting Matsumura’s method in the synthesis of 2-cyano-3-methyl-4-nitropyridine (3). 5 Thus, here we report a new synthetic process for lansoprazole as shown in scheme 1. 2-Cyano-3-methyl-4-nitropyridine (3), the key compound of the present approach for lansoprazole was prepared from 2 according to the literature method, with a yield of 81%. 5 The normal coupling constant (5 Hz) between H-5 and H-6 in 1 H-NMR of 3 indicates that the cyano group was selectively introduced into C2-position instead of C6. To understand the selectivity, the heat of formation of intermediates A and B (Table 1) expected in the course of substitution reaction on C2 and C6, respectively, according to the Reissert-Kaufmann type reaction mechanism (Scheme 2) 6 was calculated using semiempirical method (AM1 and PM3). 7

Secondary syndiotactic-specific propene insertion in the presence of homogeneous V-based catalysts

This paper shows, by terminating the polymerization through deuterolysis with CF 3CH 2OD, that the propyl end groups of syndiotactic polypropylene obtained in the presence of homogeneous catalysts, based on vanadium salts and alkylaluminium halides, such as VCl 4–Al(C 2H 5) 2Cl–Anysole, arise, at least mostly, from termination, thus confirming the Coleman–Fox type of the statistical model of the propagation already proposed in previous papers. Direct evidence is also provided that secondary insertion of propene is the only syndiotactic specific polymerization step. In view of this, the early hypotheses concerning the structure of the active species promoting syndiotactic specific polymerization are critically reconsidered.

ChemInform Abstract: Isomerization of 2‐Methyl‐2,3‐epoxybutane in the Presence of Homogeneous Catalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Identification of 2,3-butanedione monoxime hydrogenation products by gas chromatography–mass spectrometry in an ion trap mass spectrometer

The reduced products of 2,3-butanedinone monoxime by reaction with hydrogen in the presence of homogeneous catalysts were identified by gas chromatography coupled to an ion trap mass spectrometer operating either in the electron impact or chemical ionization mode. The major hydrogenation products were found to be several heterocyclic nitrogen-containing compounds: tetramethylpyrazine, 2,4-dimethyl-3-ethylpyrrole, 3,4,5-trimethylpyrazole, 2,5-dimethyl-1-propylpyrrole, 3-acetyl-2,4-dimethylpyrrole, 3,5-dimethyl-4-allypyrazole and tetramethylpyrazine N-monoxide.

Esterification of formic acid, acrylic acid and methacrylic acid with cyclohexene in batch and distillation column reactors: ion-exchange resins as catalysts

Esterification of formic acid, acrylic acid and methacrylic acid with cyclohexene was carried out in the presence of cation-exchange resins as catalysts. Effect of various parameters, e.g. speed of agitation, catalyst particle size, catalyst loading, types of catalyst, temperature, mole ratio of the reactants, was studied to optimise the reaction conditions. The reaction of formic acid, with different concentrations in aqueous solutions, with cyclohexene was studied. Experiments were carried out in the presence of homogeneous catalyst, p-toluene sulphonic acid ( p-TSA), to compare results with the heterogeneous catalyst. A comparison of anhydrous esterification between acrylic acid and that of methacrylic acid with cyclohexene has been reported. The conversion of formic acid in aqueous solutions to cyclohexyl formate, by reaction with cyclohexene, in a distillation column reactor (DCR), packed with an acidic ion-exchange resin catalyst was studied; the effect of variables such as feed flow rate, molar ratio of reactants, amount of catalyst in the reboiler, concentration of formic acid, location of the feed point, etc., was studied. A comparison between the rate of esterification of formic acid with cyclohexene in batch mode and in distillation column reactor has been made. An attempt was also made for the selective esterification of formic acid with cyclohexene from a mixture of formic acid and acetic acid in a DCR.