Prasert Reubroycharoen

Synthesis, biological evaluation and molecular modeling study of novel tacrine–carbazole hybrids as potential multifunctional agents for the treatment of Alzheimer's disease

New tacrine-carbazole hybrids were developed as potential multifunctional anti-Alzheimer agents for their cholinesterase inhibitory and radical scavenging activities. The developed compounds showed high inhibitory activity on acetylcholinesterase (AChE) with IC50 values ranging from 0.48 to 1.03 μM and exhibited good inhibition selectivity against AChE over butyrylcholinesterase (BuChE). Molecular modeling studies revealed that these tacrine-carbazole hybrids interacted simultaneously with the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE. The derivatives containing methoxy group showed potent ABTS radical scavenging activity. Considering their neuroprotection, our results indicate that these derivatives can reduce neuronal death induced by oxidative stress and β-amyloid (Aβ). Moreover, S1, the highest potency for both radical scavenging and AChE inhibitory activity, exhibited an ability to improve both short-term and long-term memory deficit in mice induced by scopolamine. Overall, tacrine-carbazole derivatives can be considered as a candidate with potential impact for further pharmacological development in Alzheimers therapy.

Green biodiesel production from waste cooking oil using an environmentally benign acid catalyst.

The application of an environmentally benign sulfonated carbon microsphere catalyst for biodiesel production from waste cooking oil was investigated. This catalyst was prepared by the sequential hydrothermal carbonization and sulfonation of xylose. The morphology, surface area, and acid properties were analyzed. The surface area and acidity of the catalyst were 86m(2)/g and 1.38mmol/g, respectively. In addition, the presence of sulfonic acid on the carbon surface was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The catalytic activity was tested for biodiesel production from waste cooking oil via a two-step reaction to overcome reaction equilibrium. The highest biodiesel yield (89.6%) was obtained at a reaction temperature of 110°C, duration time of 4h, and catalyst loading of 10wt% under elevated pressure 2.3bar and 1.4bar for first and second step, respectively. The reusability of the catalyst was investigated and showed that the biodiesel yield decreased by 9% with each cycle; however, this catalyst is still of interest because it is an example of green chemistry, is nontoxic, and makes use of xylose waste.

Conversion of cellulose into lactic acid using zirconium oxide catalysts

The possibility of converting cellulose into lactic acid using stable, easily prepared solid catalysts has attracted much attention. In this study, the catalytic activities of various transition metal oxides for cellulose conversion were determined; ZrO2 showed the highest activity for lactic acid production from cellulose. Various types of ZrO2 were tested for catalytic activity. The correlation between lactic acid yields and the characteristic properties of the ZrO2 indicated that the concentrations of acid and base sites on the ZrO2 played an important role in lactic acid production. The conversion of fructose into glyceraldehyde and dihydroxyacetone by a retro-aldol reaction was probably enhanced by the combination of acid and base sites on the ZrO2. The ZrO2 catalyst was stable in high-temperature water (473 K), and almost no Zr leached out of the catalyst into solution during the reaction.

Catalytically active supercritical fluid to accelerate methanol synthesis

Supercritical phase 2-butanol significantly increased the conversion of methanol synthesis from syngas not only by the conventional promotion effect of supercritical fluid but also by the catalytic effect of 2-butanol solvent itself, breaking through the thermodynamic limitation of this reaction effectively.

Fabrication and evaluation of nanocellulose sponge for oil/water separation

Nanocellulose sponge was fabricated by a facile method: freeze-drying of nanocellulose aqueous suspension to sponge state, following by hydrophobic treatment with stearoyl chloride at 50 °C for 1 h. The obtained nanocellulose sponge showed superhydrophobicity (160° of water contact angle) and superoleophilicity with high protection from water but selective absorption of oil. Its absorption capacities for various kinds of oil and non-polar liquids were 25-55 times higher than its dry weight and exhibited excellent selectivity for absorbing of oil which spilled on the surface of water or underwater with high separation efficiency. This superhydrophobic nanocellulose sponge can be easily recovered by simple squeezing and reused at least 10 cycles with remained high separation efficiency. It is expected that such a biodegradable nanocellulose sponge can be applied to solve the oil spill accident and treat the oily wastewater from households and industries.

Accelerated methanol synthesis in catalytically active supercritical fluid

Abstract The conversion of methanol synthesis was significantly increased when supercritical 2-butanol was used. According to the property of a supercritical fluid, which facilitates heat and product removal, supercritical 2-butanol conventionally promoted the conversion of the methanol synthesis from syngas. Furthermore, supercritical 2-butanol, used as a solvent, had a catalytic effect accelerating a new reaction route. The combination of supercritical fluid and catalytic solvent effects broke through the thermodynamic limitation of the reaction efficiency.

Direct fabrication of catalytically active FexC sites by sol–gel autocombustion for preparing Fischer–Tropsch synthesis catalysts without reduction

Fe-based Fischer–Tropsch synthesis (FTS) catalysts, promoted by copper and potassium, were directly prepared through a novel modified sol–gel autocombustion without further reduction. It was disclosed that the citric acid contents controlled the reduction/carburization of the catalyst, and the performance of FTS reaction was investigated. The molar ratio of citric acid to nitrates (denoted as CA/N) played a noteworthy role in the phase change of the Fe active sites and catalytic performances of the catalysts. Adding CA not only considerably improved the Fe reduction/carburization during the preparation but also the FTS catalytic performance even without a reduction process. Enhancement of the CA/N molar ratio resulted in the increase of the reducibility of catalysts. However, the FTS performance increased first and then decreased because an unnecessary reductant could lead to accumulation of the carbonic residual on the catalyst surface and decreases the catalyst performance for FTS. The FeCuK catalysts prepared using the sol–gel autocombustion method with CA as a reductant could achieve a high FTS performance without further reduction; therefore, this method could be widely applied in designing other metallic nanoparticle catalysts.

Bio-Oil Production from Liquid-Phase Pyrolysis of Giant Leucaena Wood

Bio-oil production from giant leucaena wood was performed by liquid-phase pyrolysis in the presence of decane as the solvent. Three different types of catalyst (ZSM-5, NiMo/Al2O3 and Pt/Al2O3) were evaluated in terms of the bio-oil production yield and quality in an autoclave reactor at a reaction temperature of 350°C and initial hydrogen (H2) pressure of 1 MPa with decane as the solvent. Although the yield was not significantly affected by the catalyst type, CHN analysis revealed that the NiMo/Al2O3 catalysts yielded bio-oil with the lowest oxygen content (10.0 wt. %) in 4.30 wt. % yield so that it was selected as the optimal catalyst. Optimization of the reaction temperature (at 250, 300, 350, and 400°C) and the initial H2 pressure (at 0.5, 1, 2, and 3 MPa) by sequential univariate analysis revealed that the reaction temperature had the greatest influence on the oil yield and oxygen content, reaching a yield of 8.60 wt. % with the lowest oxygen content of 8.50 % at 400°C. Increasing the initial H2 pressure diminished only slightly the oil and char yield and decreased the gas yield.

Pretreatment of rice straw by hot-compressed water for enzymatic saccharification

The primary objective of this work was to measure the maximum amount of glucose that can be produced from Thai rice straw using hot-compressed water (HCW)-pretreatment before enzymatic saccharification. The optimal HCW-pretreatment temperature and time were found to be 180 °C/2MPa for 20–30 min. However, the concentrations of the yeast inhibitors were strongly dependent on the HCW-pretreatment temperature and time. At temperatures over 180 °C/2MPa or for more than 30 min at 180 °C/2MPa in the HCW-pretreatment the combined concentration of these two inhibitors (Furfural and 5-Hydroxymethylfurfural) increased exponentially, while the glucose levels were near the maximal asymptote. At the more optimal HCW-pretreatment condition of 180 °C/2MPa for 20 min, 25±3 kg of glucose could be produced from a 100 kg of rice straw, which is potentially economically competitive with other sources

Methanol synthesis in inert or catalytic supercritical fluid

This chapter describes that the low total carbon conversion of the gas-phase reaction results from the highly exothermic reaction from which heat and product cannot be removed rapidly from the catalyst bed. The heat and product removal from the catalyst bed, which would improve the reaction activity, was achieved when SC nhexane was introduced into the reaction. The highest total carbon conversion was obtained by using the alcohols as SC catalytic fluids. SC alcohol improved the conversion by promoting the reaction not only by the supercritical fluid (SCF) advantage, but also by the catalytic effect as behaved in the low temperature methanol synthesis. The methanol synthesis could significantly be improved by the combination of SCF advantage and catalytic effect when alcohol was used as an SCF. Among alcoholic solvents, 2-propanol exhibited the highest total carbon conversion whereas i-butanol showed the lowest total carbon conversion indicating that the conversion of methanol synthesis solely depends on the structure of alcohols. When electronic and spatial factors were balanced, 2- propanol exhibited the highest activity.