Efficient cleavage of strong hydrogen bonds in sugarcane bagasse by ternary acidic deep eutectic solvent and ultrasonication to facile fabrication of cellulose nanofibers

Cellulose - From the perspective of green chemistry, it is of great significance to produce cellulose nanofibers (CNFs) with more environmentally friendly and sustainable materials. This study...     

Ultrasound-promoted solvent-free aza-Michael addition of p-toluenesulfonamide to fumaric esters by potassium carbonate: Synthesis of p-toluenesulfonamide derivatives

An efficient, mild, inexpensive and eco-friendly protocol for the synthesis of p-toluenesulfonamide derivatives by aza-Michael addition reaction of p-toluenesulfonamide to fumaric esters using potassium carbonate under ultrasound irradiation was developed. This method is simple, convenient and the desired compounds are produced in good to excellent yield. The bulkiness of alkoxy group (–OR) of fumaric esters did not affect significantly on the yields and reaction times. This reaction worked well on linear and nonlinear alkyl fumarates. The reaction, surprisingly, was not successful on methyl fumarate. In this case methyl fumarate has been hydrolyzed to fumaric acid under reaction conditions.     

Pretreatment of defatted wheat germ proteins (by-products of flour mill industry) using ultrasonic horn and bath reactors: Effect on structure and preparation of ACE-inhibitory peptides

The ultrasonic horn and bath reactors were compared based on production of angiotensin-converting-enzyme (ACE) inhibitory peptides from defatted wheat germ proteins (DWGP). The DWGP was sonicated before hydrolysis by Alcalase. Degree of hydrolysis, ACE-inhibitory activity, surface hydrophobicity, fluorescence intensity, free sulfhydryl (SH), and disulfide bond (SS) were determined. The highest ACE-inhibitory activity of DWGP hydrolysate was obtained at power intensity of 191.1 W/cm² for 10 min in the ultrasonic horn reactor. The fixed frequency of 33 kHz and the sweep frequency of 40 ± 2 kHz resulted in the maximum ACE-inhibitory activity. The combined irradiation of dual fixed frequency (24/68 kHz) produced significant increase in ACE-inhibitory activity compared with single frequency (33 kHz). The ultrasonic probe resulted in significant higher ACE-inhibitory activity compared with ultrasonic bath operating at single or dual fixed and sweep frequencies. The changes in conformation of the DWGP due to sonication were confirmed by the changes in fluorescence intensity, surface hydrophobicity, SH_f and SS contents and they were found in conformity with the ACE-inhibitory activity in case of the ultrasonic horn reactor but not in bath reactor.     

Transesterification Reaction of Dimethyl Terephthalate by 2-Ethylhexanol in the Presence of Heterogeneous Catalysts under Solvent-free Condition

In this study, the synthesis of bis-（2-ethylhexyl） terephthalate, via the transesterification reaction of dimethyl terephthalate （DMT） by 2-ethylhexanol in the presence of different heterogeneous catalysts, such as Pb（OAc）2·3H2O, Cd（OAc）2·2H2O, Zn（OAc）2·2H2O, Hg（OAc）2·Ca（OAc）2·H2O, Cu（OAc）2·H2O, NaOAc, CaCO3, CaO, ZnSO4·7H2O, and sulfated zirconia, has been investigated. The reactivity of the catalysts in the reaction progress has been studied and compared. It was found that, hydrated cadmium acetate and sulfated zirconia were reactive catalysts to this reaction. The extent of transesterification of methyl ester groups reached up to 93% and 85.6% using these catalysts, respectively.     

Pryce pre-analysis adapted to some DAE solvers

The ODE solver HBT(12)5 of order 12 (T. Nguyen-Ba, H. Hao, H. Yagoub, R. Vaillancourt, One-step 5-stage Hermite-Birkho-Taylor ODE solver of order 12, Appl. Math. Comput. 211 (2009) 313-328. doi:10.1016/j.amc.2009.01.043), which combines a Taylor series method of order 9 with a Runge-Kutta method of order 4, is expanded into the DAE solver HBT(12)5DAE of order 12. Dormand-Prince’s DP(8, 7)13M is also expanded into the DAE solver DP(8, 7)DAE. Pryce structural pre-analysis, extended ODEs and ODE first-order forms are adapted to these DAE solvers with a stepsize control based on local error estimators and a modified Pryce algorithm to advance integration. HBT(12)5DAE uses only the first nine derivatives of the unknown variables as opposed to the first 12 derivatives used by the Taylor series method T12DAE of order 12. Numerical results show the advantage of HBT(12)5DAE over T12DAE, DP(8, 7)DAE and other known DAE solvers.     

Polymer-clay nanocomposites: chemical grafting of polystyrene onto Cloisite 20A

An account of the experiments on preparing polystyrene(PS) nanocomposites through grafting the polymer onto organophilic montmorillonite is reported.Cloisite 20A was reacted with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinyl moiety.Because the reaction may liberate HC1,it was performed in the presence of sodium hydrogencarbonate to prevent the exchange of quaternary alkylammonium cations with H~+ ions.Only the silanol groups on the edge of the clay react with vinyltrichlorosilane.The radical polymerization of the product with styrene as a vinyl monomer leads to chemical grafting of PS onto the montmorillonite surface.The homopolymer formed during polymerization was separated from the grafted organoclay by Soxhlet extraction.Chemical grafting of the polymer onto Cloisite 20A was confirmed by infrared spectroscopy.The prepared nanocomposite materials and the grafted nano-particles were studied by XRD.Exfoliated nanocomposites may be obtained for 0.5 wt%-l wt%clay content.The nanocomposites were studied by thermogravimertic analysis(TGA) dynamic thermal analysis(DTA) and dynamic mechanical analysis (DMTA).