Mesoporous material as catalyst for the production of fine chemical: Synthesis of dimethyl phthalate assisted by hydrophobic nature MCM-41

Aluminum, iron and zinc containing MCM-41 molecular sieves were prepared by the hydrothermal method. The catalyst was characterized by the XRD, BET (surface area), FT–IR and ²⁹Si, ²⁷Al MAS–NMR techniques. The catalytic activity of these molecular sieves was tested with esterification reaction used with phthalic anhydride (PAH) and methanol (MeOH) in the autoclave at 135 °C, 150 °C and 175 °C. Conversion increases with an increase in temperature and mole ratio. The activity of these catalysts followed the order: Al-MCM-41 (112) > Fe-MCM-41 (115) > Al-MCM-41 (70) > Al-MCM-41 (52) > Fe-MCM-41 (61) > Al, Zn-MCM-41 (104) > Al-MCM-41 (30). The reaction yielded both monomethyl phthalate (MMP) and dimethyl phthalate (DMP). The nature of the catalyst sites has been proposed using with water as an impurity. The selectivity of the dimethyl phthalate increases with increase in temperature and mole ratio. The weight of the catalyst was optimized at 0.07 g. The hydrophilic and hydrophobic nature of the catalyst has been explained by the influence of water and the external surface acidity also facilitates the reaction and this has been confirmed by the supporting reaction.     

One‐Pot Synthesis of Highly Substituted Polyheteroaromatic Compounds by Rhodium(III)‐Catalyzed Multiple C?H Activation and Annulation

A new method for the synthesis of highly substituted naphthyridine‐based polyheteroaromatic compounds in high yields proceeds through rhodium(III)‐catalyzed multiple C H bond cleavage and C C and C N bond formation in a one‐pot process. Such highly substituted polyheteroaromatic compounds have attracted much attention because of their unique π‐conjugation, which make them suitable materials for organic semiconductors and luminescent materials. Furthermore, a possible mechanism, which involves multiple chelation‐assisted ortho C H activation, alkyne insertion, and reductive elimination, is proposed for this transformation.     

Synthesis of activated carbon foams with high specific surface area using polyurethane elastomer templates for effective removal of methylene blue

Carbon foams have gained significant attention due to their tuneable properties that enable a wide range of applications including catalysis, energy storage and wastewater treatment. Novel synthesis pathways enable novel applications via yielding complex, hierarchical material structure. In this work, activated carbon foams (ACFs) were produced from waste polyurethane elastomer templates using different synthesis pathways, including a novel one-step method. Uniquely, the produced foams exhibited complex structure and contained carbon microspheres. The ACFs were synthesized by impregnating the elastomers in an acidified sucrose solution followed by direct activation using CO₂ at 1000 ℃. Different pyrolysis and activation conditions were investigated. The ACFs were characterized by a high specific surface area (S_BET) of 2172 m²/g and an enhanced pore volume of 1.08 cm³/g. Computer tomography and morphological studies revealed an inhomogeneous porous structure and the presence of numerous carbon spheres of varying sizes embedded in the porous network of the three-dimensional carbon foam. X-ray diffraction (XRD) and Raman spectroscopy indicated that the obtained carbon foam was amorphous and of turbostratic structure. Moreover, the activation process enhanced the surface of the carbon foam, making it more hydrophilic via altering pore size distribution and introducing oxygen functional groups. In equilibrium, the adsorption of methylene blue on ACF followed the Langmuir isotherm model with a maximum adsorption capacity of 592 mg/g. Based on these results, the produced ACFs have potential applications as adsorbents, catalyst support and electrode material in energy storage systems.     

Coupling RSM with soot model for the study of soot formation in a momentum-dominated strained jet flames

Journal of Thermal Analysis and Calorimetry - This paper presents a comparison between the numerically determined soot volume fraction (SVF) in a momentum-dominated turbulent diffusion strained jet...     

Transformation of a 4-membered ring zinc phosphate SBU to a sodalite-related 3-dimensional structure through a linear chain structure

A zero-dimensional zinc phosphate, comprising a 4-membered ring, is shown to spontaneously transform at room temperature, to a linear chain structure consisting of corner-shared 4-membered rings, the latter transforming to a 3-dimensional sodalite-related structure under mild conditions.     

聚合物负载的钯-咪唑催化烯烃加氢

A polymer-supported palladium-imidazole catalyst was used to catalyze the hydrogenation of various olefins under mild conditions. The rate of hydrogenation was studied. The effects of factors such as substrate concentration,catalyst concentration,partial pressure of hydrogen and temperature on initial rate of reaction of selected olefins were investigated. A mechanism for the reaction was proposed from the rate equation. The effects of the solvent and structure of the olefin on the rate of hydrogenation were investigated. The catalyst showed good reusability without any leaching of metal from the support. The homologous analog of the polymer-supported catalyst could not be used as catalyst for the hydrogenation of olefins in methanol because there was precipitation of the metal during reaction.     

Synthesis of biarylketones and phthalides from organoboronic acids and aldehydes catalyzed by cobalt complexes

A cobalt-catalyzed addition of aryl- and alkenylboronic acids to aldehydes and phthalaldehyde to give the corresponding biarylketones and 3-aryl phthalides in good to excellent yields in one pot is described.     

Third-order nonlinear optical studies of newly synthesized polyoxadiazoles containing 3,4-dialkoxythiophenes

The third-order nonlinear optical properties of newly synthesized soluble polyoxadiazoles containing 3,4-dialkoxythiophenes were investigated by using Z-scan and degenerate four-wave mixing (DFWM) techniques. The measurements were performed at 532 nm with 7 ns pulses from a Nd:YAG laser. We found a good agreement between the values of χ⁽³⁾ determined from both the experiments. Z-scan results indicate a negative nonlinear refractive index, n₂, whose magnitude is of the order of 10⁻¹⁰ esu for all the copolymers. The variation of nonlinear response among the copolymers clearly indicates the dependence of χ⁽³⁾ on donor and acceptor type of units present in these copolymers. The copolymers exhibit strong reverse saturable absorption and good optical limiting properties at 532 nm.     

Studies towards iodine-catalyzed dehydrative-cycloisomerization of pent-4-yne-1,2-diols to di- and tri-substituted furans

An efficient and single-step iodine catalyzed and metal-free synthesis of di and tri-substituted 2-methylfuran derivatives were achieved from 1-popargyl-1,2-diols. Stereospecific synthesis of starting 1,2-diols was achieved by indium mediated Barbier type propargylation on corresponding keto-alcohols or by sodium borohydride mediated reduction of 2-hydroxy-2-propargyl ketones. The furan synthesis proceeded through iodine mediated 5-exo-trig cyclization, dehydration and reductive deiodination. The method was applied to the synthesis of 2-methylfuran fused to phenanthrene, pyrene and acenaphthylene rings.