Different catalytic systems on hydroxyl-terminated GAP and PET with poly-isocyanate: Curing kinetics study using dynamic in situ IR spectroscopy

Reactions of hydroxyl-terminated glycidyl azide polymer (GAP) or poly(ethylene oxide-co-tetrahydrofuran) (PET) polymers with poly-isocyanate (N100) were monitored by dynamic in situ Fourier transform infrared spectroscopy. The influence of catalytic systems on the cure kinetics of polyurethane reaction was investigated. From the comparison between GAP/N100 and PET/N100 systems, it was found that primary and secondary hydroxyl groups were differentiated due to the effects of steric hindrance. Using Arrhenius law and Eyring equation, the activation parameters of polyurethane reaction were calculated at different catalytic systems. The negative value of the activation entropy demonstrated an associative mechanism within the transition state.     

Aromatic Compounds Mannich Reaction Using Economical Acidic Ionic Liquids Based on Morpholinium Salts as Dual Solvent-Catalysts

Economical acidic ionic liquids containing an alkanesulfonic acid group in a morpholinium cation were found to be effective catalysts for the Mannich reactions of various kinds of aromatic aldehydes, acetophenone and aromatic amines at mild reaction conditions. The satisfactory results were obtained with short reaction time, good yields of the Mannich bases and simplicity in the experimental procedure. These ionic liquids could be recycled and reused for up to five times without considerable decreasing in the catalytic activity.     

HY Zeolite as an Extremely Active and Reusable Catalyst in Acylation of Alcohols with Acid Anhydride in a Solventless System

HY Zeolite is a practical and useful catalyst for acylation of various alcohols and phenols.     

POLYPROPYLENE: AN INTRODUCTION

Polypropylene now has a history of nearly 45 years since its discovery and 40 years since its commercialization. It has established itself as one of the most important polymers that has engineering plastic properties at commodity plastics prices. The end of the growth of polypropylene is not in sight.      

SYNTHESIS AND PROPERTIES OF POLY(1,6-HEPTADIYNE) HAVING A BULKY AND RIGID t-BUTYLBENZOYL GROUP

The polymerization of 4,4-bis(t-butylbenzoylmethyl)-1,6-hepta-diyne (BTBH) was carried out by group 5,6-transition metal catalysts. MoCl₅- as well as WCl₆-based catalysts were effective for the cyclopolymerization of BTBH. The polymer structure was analyzed to have conjugated backbone and recurring 5-membered ring by various spectroscopes. The polymer showed good solubility in common organic solvents. The polymer had good thermal stability and mechanical property. The oxygen permeability coefficient (PO₂) and permselectivity of oxygen to nitrogen (PO₂/PN₂) of poly(BTBH) with bulky and rigid t-butyl benzoyl group were 23.2 barrer and 4.63, respectively.     

Ceria nanospindles: Template-free solvothermal synthesis and shape-dependent catalytic activity

The ceria nanospindles have been successfully synthesized via a simple template-free solvothermal treatment by employing a mixture of glycerin and water as the reaction solvent. The properties of the ceria nanospindles were characterized. A series of control experiments confirms that the reaction solvents, reaction temperature and time are the crucial factors determining the formation of ceria nanospindles, and by adjusting the experimental parameters the other ceria micro/nanostructures such as columns, spheres, and rods were obtained. The platinum coated ceria nanospindles show the excellent low-temperature catalytic activity in the oxidation of carbon monoxide as compared with other micro/nanostructures, which is mainly due to their special shape and uniformly-distributed active sites.     

On the Influence of Oxygen on the Degradation of Fe‐N‐C Catalysts

Fe‐N‐C catalysts containing atomic FeN_x sites are promising candidates as precious‐metal‐free catalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. The durability of Fe‐N‐C catalysts in fuel cells has been extensively studied using accelerated stress tests (AST). Herein we reveal stronger degradation of the Fe‐N‐C structure and four‐times higher ORR activity loss when performing load cycling AST in O₂‐ vs. Ar‐saturated pH 1 electrolyte. Raman spectroscopy results show carbon corrosion after AST in O₂, even when cycling at low potentials, while no corrosion occurred after any load cycling AST in Ar. The load‐cycling AST in O₂ leads to loss of a significant fraction of FeN_x sites, as shown by energy dispersive X‐ray spectroscopy analyses, and to the formation of Fe oxides. The results support that the unexpected carbon corrosion occurring at such low potential in the presence of O₂ is due to reactive oxygen species produced between H₂O₂ and Fe sites via Fenton reactions.     

Microwave-assisted degradation of acid orange using a conjugated polymer,polyaniline, as catalyst

Microwave-assisted photocatalytic degradation of dyes is one of the emerging technologies for waste water remediation. Microwave effectively accelerates photocatalytic degradation, when microwave electrodeless lamp (MEL) substitutes traditional UV lamp as light source. This setup can be extremely simplified if MEL and photocatalyst can be replaced by a catalyst which can work under microwave irradiation in the absence of any light source. The present work reports for the first time degradation of acid orange 7 (AO) under microwave irradiation using polyaniline (PANI) as catalyst in the absence of any UV lamp as light source. The degradation/decolourization was carried out in neutral acidic and basic media and was monitored spectrophotometrically to evaluate the ability of microwave irradiation to degrade AO. Microwave irradiation showed excellent performance as it completely decolourizes AO dye solution in 10 min. With the advantages of low cost and rapid processing, this novel catalyst is expected to gain promising application in the treatment of various dyestuff wastewaters on a large scale.     

Stereoselective synthesis of dihydrofurans under phase-transfer catalyzed conditions

Treatment of cyclic or acyclic -haloenones with various carbon nucleophiles involving active methylene functions afforded the corresponding dihydrofurans in a stereoselective manner with good to high yields. This reaction system can provide a general and practical methodology for the construction of dihydrofuran rings.     

Solvent-Free Crossed Aldol Condensation of Cyclic Ketones with Aromatic Aldehydes Assisted by Microwave Irradiation

Summary. A fast alumina-promoted crossed aldol-condensation reaction of aldehydes and cyclic ketones under microwave irradiation is described. This process is simple, efficient, and environmentally benign and proceeds in fairly high yield without any self-condensation.