Catalyst Molar Ratio Research Articles

Textural and adsorption characteristics of carbon xerogel adsorbents for removal of Cu (II) ions from aqueous solution

Resorcinol–formaldehyde (RF) carbon xerogels were synthesized using different resorcinol/sodium carbonate catalyst molar ratios (R/C=50, 200, 500 and 1000) and heat treatment temperatures (HTT=500, 600 and 700) under no external gas flow. The carbon adsorbents were extensively characterized by CHO content, FTIR, TEM and nitrogen adsorption isotherm at 77K. The effect of R/C, HTT and oxygen content on the development of porosity within carbons was studied. Also, the adsorption capacity of these adsorbents was investigated by the removal of copper (II) ions from aqueous solution using single bottle test. The produced carbon xerogels exhibit a micro-mesopore character, but with different extents depending on the mechanism of porosity generation in relation to R/C, HTT and oxygen functional groups. Results show that the optimum conditions to obtain porous carbon xerogels were the highest R/C=500–1000 in combination with carbonization preferably at 600 or 700°C. Single bottle removal of Cu (II) ions indicated the developed carbons with appreciable capacity (qu=32–130mg/g) which are controlled by the surface area and surface chemical nature (acidic O-functional groups). Finally, the present investigation provides a new, nanoporous type of porous carbon adsorbents with high adsorption capacity for removal of heavy metals from wastewater media.

Alkaline earth layered benzoates as reusable heterogeneous catalysts for the methyl esterification of benzoic acid

This paper describes the synthesis and characterization of layered barium, calcium and strontium benzoates and evaluates the potential of these materials as catalysts in the synthesis of methyl benzoate. The methyl esterification of benzoic acid was investigated, where the effects of temperature, alcohol:acid molar ratio and amount of catalyst were evaluated. Ester conversions of 65 to 70% were achieved for all the catalysts under the best reaction conditions. The possibility of recycling these metallic benzoates was also demonstrated, evidenced by unaltered catalytic activity for three consecutive reaction cycles.

ChemInform Abstract: Chiral Phosphoric Acid‐Catalyzed Addition of Thiols to N‐Acyl Imines: Access to Chiral N,S‐Acetals.

The first catalytic asymmetric method to prepare enantioenriched N,S-acetals using chiral BINOL phosphoric acids is reported. The reaction combines N-acyl imines with thiols to generate products in excellent yield and enantioselectivity. The addition reaction could also be achieved with an exceptional substrate to catalyst (S/C) molar ratio. Electron-rich and electron-deficient aromatic N-acyl imines, as well as a broad range of aliphatic and aromatic thiols, showed excellent reactivity.

Manganese(II), cobalts(II) and nickel(II) complexes of tris(2-pyridyl)phosphine and their catalytic activity toward oxidation of tetralin

Monomeric Mn2+, Co2+ and Ni2+ complexes of tris(2-pyridyl)phosphine (P(2-py)3 were synthesized through the reaction of the hydrated metal(II) chlorides with P(2-py)3 in near-quantitative yields. The solid-state structure of the Mn complex was determined by single-crystal X-ray diffraction. All three complexes were tested as homogeneous catalysts for the oxidation of tetralin to α-tetralone with tert-butyl hydroperoxide (TBHP) as oxidant. The influences of temperature, solvent, catalyst molar ratio and time of the reaction on the catalyzed reactions were investigated.

Preparation of a New Rosin Ester Derivative

a new rosin derivative—methylthiomethyl dehydroabietate has been synthesized from dehydroabietic acid and DMSO. The effects of reaction temperature, time, the amount of catalyst and mixing molar ratio of reactants on the yield have been investigated. The optimum reaction conditions were: the reactants were kept at 215 oC for 3h with dimethyl sulfoxide/ dehydroabietic acid mixing molar ratio of 22: 1 in the presence of 0.4% KOH catalyst ( based on the mass of dehydroabietic acid). The yield of product could reach 90%. The precise structure of the product was characterized as methylthiomethyl dehydroabietate by GC-MS, UV, FT-IR, High-Resolution Mass Spectrometry, 1HNMR and 13C NMR.

Chiral Phosphoric Acid-Catalyzed Addition of Thiols to N-Acyl Imines: Access to Chiral N,S-Acetals

The first catalytic asymmetric method to prepare enantioenriched N,S-acetals using chiral BINOL phosphoric acids is reported. The reaction combines N-acyl imines with thiols to generate products in excellent yield and enantioselectivity. The addition reaction could also be achieved with an exceptional substrate to catalyst (S/C) molar ratio. Electron-rich and electron-deficient aromatic N-acyl imines, as well as a broad range of aliphatic and aromatic thiols, showed excellent reactivity.

Synthesis and physico‐chemical properties of novel dialkyl diphosphate gemini surfactants based on octadecanol

AbstractA series of dialkyl diphosphate gemini surfactants has been synthesized using C18 as hydrophobic chains and phosphate as head groups. Three flexible spacers have been used. In the present study, an attempt has also been made to synthesize mono octadecyl phosphate (MOP) at 35°C, which was used as an intermediate in the synthesis of geminis. This long chain of MOP has been effectively converted to gemini surfactants and subsequently converted to their disodium salts. The effect of reaction variables like temperature, duration, molar ratios of reactants, catalyst and spacer on the yield of dialkyl diphosphate gemini surfactant has also been reported. The MOP, gemini surfactants and disodium salt of gemini surfactants were characterized using FT‐IR and 1H‐NMR. Surface active and physico‐chemical properties of synthesized gemini surfactants and their monomer were also determined. The results revealed that the yield of dialkyl diphosphate gemini surfactants ranged from 80 to 90%. Among all synthesized dialkyl diphosphate gemini surfactants D, S‐1,6‐GSOD had maximum anionic content, i.e. 80.7%, showed highest foaming ability and superior dispersing ability, whereas D, S‐1,8‐GSOD showed low cmc values, i.e. 0.00012 mM/L; minimum surface tension and interfacial tension, i.e. 39.1 and 36.3 mN/m, respectively.

Enantioselective hydrogenation of dimethyl itaconate with immobilised rhodium-duphos complex in a recirculating fixed-bed reactor

The catalytic hydrogenation of dimethyl itaconate was studied in lab-scale shake flask and transferred to continuous flow with recirculation in a trickle bed reactor. All experiments were performed under ambient conditions (20 °C and atmospheric pressure). The catalyst complex [Rh((R,R)-Me-DuPhos)(COD)]BF 4 was anchored to powder and trilobe alumina supports using phosphotungstic acid (PTA) as an anchoring agent. For the powder alumina, tests were conducted in the shake flask to ensure that the reaction was not influenced by mass transfer limitations by varying the stirrer speed and catalyst mass, thus ensuring the reported data are in the kinetic regime. In the shake-flask [substrate to catalyst molar ratio of 60, atmospheric pressure (101,317 Pa), room temperature (293.15 K), H 2 flow rate of 100 ml min −1 (1.7 × 10 −6 m 3 s −1) and agitation speed of 200 rpm], a turnover frequency (TOF) of 50 h −1 (1.4 × 10 −2 s −1) was achieved with powder alumina support in comparison to a TOF of 20 h −1 (5.6 × 10 −3 s −1) obtained with the trilobes. Under these conditions, the enantioselectivities obtained from immobilising the catalyst complex onto the powder and trilobe supports were 96% and 97%, respectively. Fitting Osborn–Wilkinson kinetics to the concentration profiles indicated that complexation with the olefin before reaction with hydrogen was the preferred path. The trickle bed reactor (TBR) was operated in the trickle flow regime using the trilobe support. Optimal gas and liquid flow rates were selected which were found to have a noticeable effect on initial reaction rate and enantioselectivity. Under optimized conditions in the TBR [substrate to catalyst molar ratio of 223, atmospheric pressure (101,317 Pa), room temperature (293.15 K), gas flow rate of 100 ml min −1 (1.7 × 10 −6 m 3 s −1) and liquid flow rate of 20 ml min −1 (3.3 × 10 −7 m 3 s −1)], 99% conversion and enantioselectivity of up to 99.9% were achieved.

Statistical optimisation of methanolysis of jatropha oil using immobilised R. oryzae cells in n‐hexane system

The ability of immobilised whole cells of R. oryzae cells to catalyse the alcoholysis of jatropha oil with methanol in n‐hexane system was investigated. Response surface methodology using central composite design was used to study the effects of important parameters: reaction time, reaction temperature, catalyst concentration, molar ratio of alcohol to oil and water content in five levels on percentage yield of biodiesel. The linear effects of reaction time and catalyst concentration and the quadratic effects of catalyst concentration and molar ratio of alcohol to oil were found to be the significant parameters. The optimum conditions for biodiesel production were found to be: reaction time, 77.25 h; reaction temperature, 40.18°C; catalyst concentration, 3.70 w/v; molar ratio of alcohol to oil, 1:2.88 and water content, 11.20% (w/w of oil). The predicted yield of biodiesel was 79.87% (w/w) and the experimental yield at the optimised condition was 80.5% (w/w). This confirmed the validity of the proposed model.

Kinetics of catalytic glycolysis of PET wastes with sodium carbonate

The kinetics of glycolysis of poly(ethylene terephthalate) wastes with ethylene glycol to give highly pure bis(2-hydroxyethyl terephthalate) was examined in a batch reactor. An excess of ethylene glycol (EG:PET molar ratio of 7.6:1) was used and the reaction was carried out in the presence of sodium carbonate as active catalyst. The influence of several operating conditions covering temperature (165–196 °C), mean particle size (0.14–3 mm), stirring rate (50–800 rpm), reaction time (0–10 h), and catalyst type and concentration was analysed. The selected PET particle size and stirring rate for kinetic calculations were 0.25 mm and 600 rpm, respectively. Using a PET:catalyst molar ratio of 100:1 about 80% BHET yield was attained at 196 °C after 1 h. A simple theoretical power-law model was developed to predict the time evolution of conversion. This kinetic model was found to be consistent with experimental data. The rate constants for both direct and reverse reactions were estimated. Also the values of the activation energy (185 kJ mol −1) and enthalpy of reaction (12 kJ mol −1) were derived.

Catalytic hydrolysis of lignocellulosic biomass into 5-hydroxymethylfurfural in ionic liquid

Production of 5-hydroxymethylfurfural (HMF) from cellulose catalyzed by solid acids and metal chlorides was studied in the 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) under microwave irradiation. Among the applied catalysts, the use of CrCl3/LiCl resulted in the highest yield of HMF. The effects of catalyst dosage (mole ratio of catalyst to glucose units in the feedstock) and reaction temperature on HMF yields were investigated to obtain optimal process conditions. With the 1:1mol ratio of catalyst to glucose unit, the HMF yield reached 62.3% at 160°C for 10min. Untreated wheat straw was also investigated as feedstock to produce HMF for the practical use of raw biomass, in which the HMF yield was comparable to that from pure cellulose. After the extraction of HMF, [BMIM]Cl and CrCl3/LiCl could be reused and exhibited no activity loss after three successive runs.

Modified crosslinked polyacrylamide anchored Schiff base–cobalt complex: A novel nano-sized heterogeneous catalyst for selective oxidation of olefins and alkyl halides with hydrogen peroxide in aqueous media

A new nano-sized polymer-supported Schiff base–cobalt complex catalyst based on crosslinked polyacrylamide was synthesized and characterized. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) of the catalyst show nanosize fiber-like image of the polymeric catalyst. The catalyst activity was studied in the oxidation of various olefins including non-activated terminal olefin in water with hydrogen peroxide as an oxygen source. The catalyst showed high degree of selectivity. The effects of reaction parameters such as solvent, oxidant, temperature, molar ratio of catalyst and catalyst structure on the oxidation of styrene were investigated. The oxidation of benzyl halides to their corresponding carbonyl compounds in the presence of this heterogeneous catalyst was studied as well. The catalyst can be recycled several times without significant loss in its activity.

ATRP of MMA initiated by 2-bromoisobutyric acid 4-(2- benzothiazole-2-yl-vinyl)-phenyl ester (BPBVE) and its fluorescent property in the presence of metal ions

Abstract2-Bromoisobutyric acid 4-(2-benzothiazole-2-yl-vinyl)-phenyl ester (BPBVE) was used for the heterogeneous atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) with a copper(I)bromide/2,2’-bipyridine catalytic system. Factors such as the reaction temperature and mole ratio of catalyst to initiator, which could affect the ATRP system, were discussed in the paper. The functional end group was characterized via UV-vis and 1H NMR spectroscopy. The rates of polymerizations exhibited first-order kinetics with respect to the monomer, and a linear increase in the number-average molecular weight with increasing monomer conversion was observed for these initiation systems. The polydispersity indices (PDI) of the polymer were relatively low (1.07- 1.23) up to high conversions. This PMMA with BPBVE as end group shows strong emission at blue-light area whether in solution or in solid. In particularly, emission was decreased (or quenched) with appearance of metal cations (Zn2+, Co2+, Ni2+, Pb2+, Mn2+, Cu2+, Fe3+, Ag+) in DMF solution.

Application of the Shvo catalyst in homogeneous hydrogenation of bio-oil obtained from pyrolysis of white poplar: New mild upgrading conditions

Upgrading of bio-oils obtained from the fast pyrolysis of biomasses requires the development of efficient catalysts able to work under mild conditions and to cope with the complex chemical nature of the reactant. The present work focuses on the use of the ruthenium based Shvo homogeneous catalyst for the hydrogenation of model mixtures (vanillin, cinnamaldehyde, methylacetophenone, glycolaldehyde, acetol, acetic acid) and of a real bio-oil. The hydrogenation of model compounds has been investigated both in mono- and biphasic mixtures under a P(H2)=10atm in the temperature range of 90–145°C varying the substrate to catalyst molar ratio from 2000:1 to 200:1. Employing the most active reaction conditions (substrate/catalyst 200:1, T=145°C, P(H2)=10atm) the Shvo catalyst maintains its performances under acidic “bio-oil conditions” leading to the almost quantitative conversion of the polar double bonds within 1h. The activity of the Shvo catalyst was also investigated for the hydrogenation of a bio-oil from poplar in solvent free conditions. Hydrogenation deeply changed the chemical nature of the pyrolysis oil. Aldehydes, ketones and non-aromatic double bonds were almost totally hydrogenated. The catalytic system also promoted the hydrolysis of sugar oligomers into monomers.

Direct Synthesis of Hydrogen Peroxide and Benzyl Alcohol Oxidation Using Au−Pd Catalysts Prepared by Sol Immobilization

We report the preparation of Au-Pd nanocrystalline catalysts supported on activated carbon prepared via a sol-immobilization technique and explore their use for the direct synthesis of hydrogen peroxide and the oxidation of benzyl alcohol. In particular, we examine the synthesis of a systematic set of Au-Pd colloidal nanoparticles having a range of Au/Pd ratios. The catalysts have been structurally characterized using a combination of UV-visible spectroscopy, transmission electron microscopy, STEM HAADF/XEDS, and X-ray photoelectron spectroscopy. The Au-Pd nanoparticles are found in the majority of cases to be homogeneous alloys, although some variation is observed in the AuPd composition at high Pd/Au ratios. The optimum performance for the synthesis of hydrogen peroxide is observed for a catalyst having a Au/Pd 1:2 molar ratio. However, the competing hydrogenation reaction of hydrogen peroxide increases with increasing Pd content, although Pd alone is less effective than when Au is also present. Investigation of the oxidation of benzyl alcohol using these materials also shows that the optimum selective oxidation to the aldehyde occurs for the Au/Pd 1:2 molar ratio catalyst. These measured activity trends are discussed in terms of the structure and composition of the supported Au-Pd nanoparticles.

Chemical recycling of post-consumer PET wastes by glycolysis in the presence of metal salts

Chemical recycling of poly(ethylene terephthalate) (PET) has been the subject of increased interest as a valuable feedstock for different chemical processes. In this work, glycolysis of PET waste granules was carried out using excess ethylene glycol in the presence of different simple chemicals acting as catalysts, namely zinc acetate, sodium carbonate, sodium bicarbonate, sodium sulphate and potassium sulphate. Comparable high yields (≈70%) of the monomer bis(2-hydroxyethyl terephthalate) were obtained with zinc acetate and sodium carbonate as depolymerisation catalysts at 196 °C with a PET:catalyst molar ratio of 100:1 in the presence of a large excess of glycol. The purified monomer was characterised by elemental analysis, differential scanning calorimetry, infrared spectroscopy, and nuclear magnetic resonance. These results revealed that, although the intrinsic activity of zinc acetate was significantly higher than that of sodium carbonate, this latter salt could indeed act as an effective, eco-friendly catalyst for glycolysis. Also an exploratory study on the application of this catalytic recycling technology for complex PET wastes, namely highly coloured and multi-layered PET, was performed.

Highly preorganized pyrazolate-bridged palladium(ii) and nickel(ii) complexes in bimetallic norbornene polymerization

New derivatives of pyrazolate-based binucleating ligands HL with appended imine functions have been synthesized to provide a versatile set of ligand systems with different backbone substituents both at the pyrazole-C(4) and the imine-C (H, Me, Ph). These scaffolds have two adjacent coordination compartments akin to the alpha-diimine type. A series of binuclear palladium(II) complexes [LPd(2)Cl(3)] (1-4) and tetranuclear nickel(II) complexes [L(2)Ni(4)Br(6)(solvent)(4)] (5, 6) of the various ligands have been prepared and characterized, including X-ray structural analyses for two representative Pd and the two Ni complexes. Complexes 5 and 6 were found to contain an unusual central mu(4)-bromide. Mononuclear nickel(II) complexes [L(2)Ni] were detected as intermediates in the formation of the tetranuclear complexes and have been characterized by X-ray analyses in two cases (7, 8). The interconversion between 5' and 7 has been investigated by UV/Vis spectroscopy and ESI mass spectrometry, and magnetic coupling in the [L(2)Ni(4)Br(6)(solvent)(4)] complexes has been studied (SQUID). Trans-coupling via the central mu(4)-bromide is suggested to mediate significant antiferromagnetic interaction. The reactivity of such types of Pd and Ni complexes has been tested for the vinyl/addition polymerization of norbornene. In the presence of an excess of cocatalyst methylaluminoxane (MAO) the palladium complexes show high activity up to 5.9 x 10(6) g(PNB) mol(Pd)(-1) h(-1) at 20 degrees C, while activities of the nickel systems are much lower, but strongly solvent dependent. Detailed studies on the dependence of activity on polymerization conditions such as molar ratios of catalyst and cocatalyst, temperature, reaction time and solvent were carried out. All obtained polynorbornenes (PNB) were noncrystalline and insoluble, but have high glass transition temperatures (T(g)). Microstructures were analyzed by IR spectroscopy and solid state (CP/MAS) (13)C NMR, revealing distinct patterns for the PNB produced by Ni- or Pd-catalysts. Structure/activity correlations deduced for the complexes with different ligand systems suggest that activities and polymer microstructures depend rather on the metal type than on ligand intricacies.

Poly(1‐octene) synthesis using high performance supported titanium catalysts

AbstractPoly(1‐octene) was synthesized by polymerization of 1‐octene using high performance MgCl2‐supported TiCl4 in combination with triethyl aluminum (TEAl) as cocatalyst in n‐hexane for 2 h. Two catalysts, C1 (diester catalyst) having di‐isobutyl phthalate as internal donor and C2 (monoester catalyst) having ethyl benzoate as internal donor were utilized for the atmospheric polymerizations to evaluate the influence of structurally different internal donors on the productivity, rate of polymerization and molecular weight profiles. The kinetic profile assessed in terms of variation of reaction parameters like temperature, cocatalyst to catalyst molar ratio and monomer concentration was found to be dependent on them. From these kinetic analyses, optimize conditions for polymerizations of 1‐octene using diester as well as monoester catalyst were elucidated. The difference in the performance of diester and monoester catalyst system can be explained in terms of stability of active titanium species and chain transfer process. NMR spectroscopy of synthesized poly(1‐octene) indicate predominantly isotactic nature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Highly active polymerization of methyl methacrylate catalyzed by Pd-based β-ketoiminato complexes/MAO systems

The substituted β-ketoiminato palladium(II) complexes, Pd[CH 3C(O)CHC(NAr)CH 3](Pph 3)(Me) ( 1 Ar = α-napthyl, 2 Ar = fluorenyl) , when was activated by methylaluminoxane (MAO), were used as highly active catalysts for methyl methacrylate (MMA) polymerization. The effects of temperature, co-catalyst to catalyst molar ratio and polymerization time on catalyst activities were reported. Structural analyses of the polymers by 1H NMR spectra indicated that polymerization yielded poly(methyl methacrylate) (PMMA) with moderate syndiotactic microstructures. The polymerization results showed that PMMAs obtained using these complexes possibly arose from a coordination-insertion mechanism rather than a radical mechanism.

Preparation of biodiesel from waste oils catalyzed by a Brønsted acidic ionic liquid

Preparation of biodiesel from waste oils catalyzed by a novel Brønsted acidic ionic liquid with an alkane sulfonic acid group was investigated. The acidity and the activity of the ionic liquid were very low at lower temperature when the ionic liquid was crystalloid; they recovered at higher temperature when the crystallized ionic liquid was liquefied. When methanol:oils:catalyst molar ratios were 12:1:0.06, the yield of fatty acid methyl esters can reach 93.5% after the reaction of acidic oil with methanol had taken place at 170 °C for 4 h. In addition, the ionic liquid had a good reusability and can be easily separated from the biodiesel by simple decantation.