ABSTRACT
The promising influences of K+ and Ca2+ ions in the development of effective MnO2 for the selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid (FDCA) were studied for the catalytic performance under a high-pressure reaction of aqueous O2 (0.5 MPa) in a basic system. Various oxidation states of manganese in MnO2 were able to accelerate the oxidation of 5-formyl-2-furancarboxylic acid to FDCA in the rate-determining step. The results were in good agreement that Ca2+ played a key role in the highest FDCA yield up to 85% due to the associated cations on the local coordination to enhance the high surface area and the electronic effect on the manganese ion. Both K-MnO2 and Ca-MnO2 catalysts showed excellent catalytic activities without a significant change in the efficiency in the reusability experiments.
ABSTRACT
The synthesis of 5-(hydroxymethyl)furfural (HMF) and conversion to the corresponding HMF-monoesters upon certain treatment are presented with their properties that are validated in a diesel engine. With a collection of fatty acids (C8-C18) using cyanuric acid as a catalyst under mild reaction conditions, the subsequent reduction of the HMF-monoesters with NaBH4 produced the corresponding alcohols. After purification, both HMF-monoesters and their alcohol derivatives were determined for their solubility, cetane index, heat of combustion, viscosity, and specific gravity. HMF-Capric (1-C10), HMF-Oleic (1-C18:1), HMF-Caprylic-OH (2-C8), and HMF-Oleic-OH (2-C18:1) were soluble in a neat diesel fuel. The observed highest cetane index and heat of combustion of 1-C10 and 1-C18:1 were evaluated for combustion characteristics in a single-cylinder compression ignition engine. The diesel fuel containing 3% 1-C10 displayed comparable properties during burning in terms of thermal efficiency, cylinder pressure, and heat release rate with respect to the neat diesel fuel (D100) for all usage engine speeds. In general, all tested fuels initiated their burning onset with a similar ignition delay period. The 3% 1-C10-blended diesel fuel emitted slightly higher smoke opacity but an equivalent nitric oxide level compared to those of D100. The HMF-Capric (1-C10) synthesized in this study represents a promising additive for diesel fuel. Blended fuel lubricity and other unregulated emissions upon broader engine test cycles are suggested to be accomplished in future work.
ABSTRACT
A new fluorescent sensor based on oxazolidine derivative, (2-(pyridin-2-yl)oxazolidine-4,4-diyl)dimethanol; TN), was designed and synthesized successfully in high yield (82%) under Schiff base reaction. The structural elucidation of the sensor has been confirmed by Infrared Spectroscopy, Nuclear Magnetic Resonance Spectroscopy, and High Resolution Mass Spectrometry - Electrospray Ionization - Time of Flight. The designed TN sensor exhibited high sensitivity and selectivity towards an aqueous solution of cerium(III) over various metal ions under biologically relevant conditions (100.0 mM HEPES buffer pH 7.4). The limit of detection (LOD) was reported as 54.0 nM. The geometry of tridentate based-oxazolidine (TN) and its coordination of cerium(III) (TN-Ce3+) was proven by using the density functional theory (DFT) calculations. The highest occupied molecular orbital - lowest unoccupied molecular orbital energy gap was decreased when TN-Ce3+ is formed. The results indicated that TN can be used as a fluorescent probe for high sensitivity and selectivity detection of cerium(III) ions.
