Effects of Reaction Parameters in Catalysis of Glycerol Oxidation by Citrate-Stabilized Gold Nanoparticles

Abstract  

This work describes a catalytic oxidation of glycerol using citrate-stabilized gold nanoparticles (citrate-AuNPs) having a mean diameter of 22 ± 3 nm. A careful product analysis was performed by mean of high-performance liquid chromatography, liquid chromatography–mass spectrometry and nuclear magnetic resonance spectroscopy. Effects of reaction temperature, oxygen pressure, catalyst and reactant concentration, and NaOH/glycerol molar ratio on glycerol conversion, and product yields were investigated. The glycerol conversion and glyceric acid yield were optimum when the oxidation was performed using 0.6 M glycerol and NaOH at 80 °C under 3 bar of O₂ pressure in the presence of 50 ppm citrate-AuNPs catalyst for 3 h.     

The utilization of microencapsulated phase change material wallboards for energy saving

Wallboards with micro encapsulated phase changing material (micro PCM) were used to investigate the performance and the energy saving characteristics as building materials in winter and summer climate conditions. The test house consisted of a boiler with under floor heating system, an air conditioner, micro PCM wallboard room and conventional wallboard room. The outer temperature of the rooms could be artificially controlled at the temperature range of −12 to 35 °C. Micro PCM content in wallboards was 0–4 kg/m². The melting temperature and latent heat of Micro PCM are 23 °C and 211 J/g. Also, micro PCM shows stable mechanical strength under 500 psi. As micro PCM content increased, the temperature fluctuations decreased. In case of micro PCM wallboard, temperature profiles in the room show stable and comfortable ranges. The optimum amount of micro PCM in wallboard to maximize energy saving efficiency was around 3 kg/m².     

Methylation of methyltrichlorosilane with methyl chloride over active metals and activated carbon

Gas phase methylation of methyltrichlorosilane with methyl chloride to high-valued dimethyldichlorosilane was carried out by using metallic aluminum as a chlorine acceptor in the co-presence of activated carbon, tin, and zinc. The addition of activated carbon in metallic aluminum significantly enhanced the methylation of methyltrichlorosilane, and dimethyldichlorosilane was dominantly produced. Activated carbon played a catalyst role in the methylation reaction. When active metals, such as tin and zinc, were added in the mixture of aluminum and activated carbon, the active metals and activated carbon synergistically catalyzed the methylation of methyltrichlorosilane with methyl chloride toward the formation of dimethyldichlorosilane.     

Application of statistical experimental design for optimization of downstream process for recovery of pullulan produced by <Emphasis Type=Italic>Aureobasidium pullulans</Emphasis> HP-2001

The optimal conditions of the downstream process for recovery of pullulan produced by Aureobasidium pullulans HP-2001 were examined using response surface method (RSM). The optimal amount of diatomite in filter press and the optimal flow rate in a continuous flow centrifuge for removal of cells from the culture broth of A. pullulans HP-2001 were found to be 5.0% (v/v) and 2.0 L/min. Based on central composite design (CCD) experiments and analysis of variance (ANOVA) indicated that the optimal conditions for recovery of pullulan from the supernatant by precipitation were the volume ratio of ethanol (or isopropanol) to supernatant of 3.0: 1.0, the reaction time of 29.5 h, and the reaction temperature of 20.2 °C. The expected maximal recovery yields of pullulan using ethanol and isopropanol under optimized conditions were 79.2 and 85.5%, respectively.     

Examining the effects of velocity ratio of the pressurized flow to the main inlet flow on coagulants dispersion in pump diffusion mixer

This study was conducted to evaluate the ratio of the pressurized flow to the main inlet flow, which has been considered one of the most important parameters for operating the pump diffusion mixer (PDM). Computational fluid dynamics (CFD) simulation was employed to evaluate the conventional operation rule of PDM and to propose a supplementary operating parameter and criterion. Test simulation of CFD was carried out for the 21 cases of flow ratio in a full scale PDM. The values of local velocity gradient were calculated in each case to analyze the simulation results in more detail. A wet test was conducted to verify CFD simulation results, which measures the factual coagulant dispersion distribution at a distance of 5.4 m from deflector. From results of both CFD simulation and wet test, the flow ratio was adequate as an operating parameter or criterion; also, the velocity ratio (dimensionless) of the pressurized flow to the main inlet was useful in predicting the performance of PDM. In addition, the injected coagulant could be dispersed evenly in overall cross section on the condition that the velocity ratio is at least over 20.     

Physico-chemical properties of silica aerogels prepared from TMOS/MTMS mixtures

In the present work, results on the physico-chemical properties of the silica aerogels prepared by sol–gel process using mixtures of TMOS and MTMS as precursor are reported. The wide range of precursor mixture was studied with ratio of MTMS/TMOS in precursor mixtures as 0:100, 25:75, 50:50, 75:25, and 100:0 by volume. The gels with these precursor mixtures were successfully prepared using two step acid–base catalysis for gelation. Acetic acid (0.001 M) and NH₄OH (1.5 M) were used for catalysis and resulting alcogels were subsequently dried by supercritical solvent extraction method. FTIR spectroscopy revealed that the aerogels show more intense peak at 1,260 and 790 cm⁻¹ attributed to Si–CH₃ resulting in more hydrophobic nature and these results were concurrent with adsorbed water content measurements made using Karl Fischer’s titration technique. The resulted aerogels were characterized using differential thermal analysis, thermo gravimetric analysis and surface area measurements. The surface area measurements showed an interesting trend that the surface area increased from 395 to 1,037 m²/g with increase in MTMS content in the precursor mixture from 0 to 50% and then again decreased to 512 m²/g for further increase in MTMS content from 50 to 100% in the precursor mixture. It was observed from our studies that silica aerogels prepared using a starting mixture of 50% TMOS and 50% MTMS resulted in high moisture resistance (adsorbed water content of 0.721% w/w), low density of 90 kg/m³ and the highest surface area of 1,037 m²/g, which has great potential for catalysis support applications.     

A simple room temperature synthesis of mesoporous silica nanoparticles for drug storage and pressure pulsed delivery

Mesoporous silica nanoparticles (MSN) have been synthesized at room temperature under assistance of n-hexane by using tetraethyl orthosilicate (TEOS) as a silica source and cetyltrimethylammonium bromide (CTAB) as a structure directing agent. Powder X-ray diffraction studies showed that the quantity of n-hexane added into the solution was critical for the ordering of the final mesostructures. The particle size of MSN was between 200 and 400 nm, which is suitable for endocytosis by human cells. The drug loading capability of MSN prepared through this route was measured and the influence of the pulsed pressure drop on drug delivery was studied. This study showed that the delivery rate of ibuprofen in a simulated body fluid solution increased dramatically under the pulsed pressure drop.     

Microbial nitrogen dynamics in south central Chilean agricultural and forest ecosystems located on an Andisol

The natural soil N supply in volcanic soils (Andisols) can be a significant source of plant-available N for agro-ecosystems. Nevertheless, intensive farming systems in south Chile apply high fertilization rates, which lead to high production costs and involve a risk for adverse ecosystem effects. In order to achieve sustainable land management, a better understanding of the processes that govern soil N availability and loss, and their external drivers, is required. In this study, we selected a winter-cropland, a summer crop-winter fallow rotation, and a forest, used as a reference ecosystem. Gross N transformations (¹⁵N isotope dilution) and microbial community structure (phospho-lipid fatty acid analysis) in the topsoil were determined. Gross N mineralization was about ten times lower in the agro-ecosystems than in the forest, while gross nitrification was low in all sites. Gross N immobilization equalized or exceeded the gross inorganic N production in all sites. Microbial biomass was 3–5 times more abundant in the forest than in the agro-ecosystems. A positive relationship between the ratio fungi/bacteria and total microbial biomass was observed in these Andisols. We suggest that the reduction in fungal biomass induced a lower extracellular enzyme production and limited soil organic matter depolymerisation in the agro-ecosystems. We conclude that soil N cycling was unable to provide a significant N input for the croplands, but also the risk for ecosystem N losses was low, even under fallow soil conditions. Current fertilization practices appropriately anticipated the soil N cycling processes, but further research should indicate the potential of alternative land management to reduce fertilizer cost.     

Phosphorus dynamics in permanent pastures: differential fertilizing and the animal effect

The general objective of this study was to evaluate the deviation between measured and estimated soil phosphorus (P) content, over 3 years, in a permanent bio-diverse pasture system in Southern Portugal with grazing sheep, and subjected to annual, differential P fertilization. The results can be a contribution to the development of practical and effective site-specific management strategies to minimize pasture yield variation. The soil and pasture samples were taken from a 6 ha field and were geo-referenced with RTK GPS. This procedure was carried out, each year, from March to May, according to the vegetative growth of the pasture. In October of each year the field was fertilized in a differential manner, as a function of soil P concentration measured at the end of the pasture growth cycle (May–June). Maps were developed in ARCGIS 9.3 considering: (1) the soil P concentration and pH; (2) the average P plant uptake; (3) the differential P application; and (4) the extractable P. The significant temporal variability of soil P concentration and pasture dry matter yield confirm the complexity of soil P dynamics in pastures involving two biological systems: plant and animal, under Mediterranean conditions and the consequent difficulties in implementing precision agriculture techniques. The results of this work indicate that 3 years of P variable-rate application rate were not sufficient to obtain homogeneous and adequate levels of P in the whole field for crop production. Despite differential P fertilization with the objective of obtaining homogenous values of soil P content in experimental field, the undulating topography of the experimental field associated with the presence of grazing animals adds a notable short-range spatial variation in nutrients that generally arises from heterogeneous excreta depositions. The small and positive final deviation between measured and estimated P levels suggests the irregular and gradual release of P by the fertilizer over years, contributing to an increase in soil P concentration. P input in fertilizer and removal in the crop greatly exceed all other inputs and outputs. However, the pH effect on extractable P, the estimation of amounts of export/import by livestock, atmospheric deposition or erosion/leaching losses are complex and justify more experiments to evaluate the confidence of long-term estimated P dynamic balance before sustained decision making is possible for differential pasture fertilization and site-specific management strategy implementation.     

Effects of cereal breakfasts on postprandial glucose,appetite regulation and voluntary energy intake at a subsequent standardized lunch; focusing on rye products

Background  

Rye products have been demonstrated to lower the acute insulin demand, induce a low and prolonged blood glucose response (high Glycemic Profile, GP) and reduce subclinical inflammation. These products may therefore contribute to a lowered risk of obesity, type 2 diabetes and cardio vascular disease. The objective of the present paper was to evaluate the mechanism for a reduced postprandial insulin demand with rye products, and to explore possible appetite regulating properties.