Physical and light oxidative properties of eugenol encapsulated by molecular inclusion and emulsion–diffusion method

The aim of this research was to study the encapsulation of eugenol as a volatile active substance by inclusion with β-cyclodextrin (β-CD) and 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD), and by an emulsion–diffusion method with polycaprolactone (PCL). After formulation of each type of complex, size, zeta-potential, and thermal properties were determined by using Nanosizer®, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Overall, the mean sizes of encapsulated eugenol were the same at 320 nm. However, the size distribution of the β-CD and 2-HP-β-CD inclusion complex was poly-disperse as compared with eugenol encapsulated with polycaprolactone (PCL). TGA analysis revealed the encapsulation efficiency of PCL, β-CD eugenol and 2-HP-β-CD eugenol inclusion complexes were 100%, 90.9% and 89.1%, respectively. The study of oxidation stability revealed the emulsion–diffusion method was more efficient than the molecular inclusion method resulting from high stability depending on storage time. On the other hand, β-CD was more effective than 2-HP-β-CD for eugenol encapsulation. It is supposed that the side chain of hydroxypropyl group of 2-HP-β-CD might interrupt eugenol inclusion within the cavity of 2-HP-β-CD molecule. From our experiments, we concluded that the emulsion–diffusion method was the most effective for eugenol encapsulation to protect from light oxidation during storage time due to their complete wrapping of eugenol by PCL layer from TEM analysis.     

Physical characteristics of fish oil encapsulated by β-cyclodextrin using an aggregation method or polycaprolactone using an emulsion–diffusion method

Fish oils have many dietary benefits, but have strong odours and are easily oxidised. For these reasons, β-cyclodextrin (β-CD) a water-soluble polymer and polycaprolactone (PCL) a water-insoluble polymer were used to encapsulate fish oil in this study. In addition, the stabilities of freeze-dried fish oil (FO) in encapsulated complexes were investigated to determine fish oil release rates at different relative humidities and storage temperatures. In order to facilitate the practical applications of the water-soluble and insoluble fish oil complexes produced, release studies of fish oil were performed in de-ionised water, NaCl solution and fish sauce. Based on our studies, fish oil loaded β-CD at a mixing ratio of 10:20 (β-CD:FO (w:w)) was the best composition in terms of encapsulation efficiency (84.1%), fish oil loading (62.7%), fish oil leakage after freeze-drying (11.0%), and eicopentaenoic acid (EPA) encapsulation efficiency (6.5%). In addition, fish oil release rates from β-CD particles were slower in de-ionised water and in 15% and 25% NaCl than in fish sauce at all mixing ratios between β-CD and FO. The storage stabilities of freeze-dried β-CD–FO complexes at 10:20 (w:w) mixing ratio at various relative humidities retained 97% of fish oil within the particles during 3 days. However, the release rate of fish oil from β-CD–FO complexes of 10:20 mixing ratio was accelerated in fish sauce. In terms of the emulsion–diffusion method, PCL more efficiently retarded the release of FO in liquid or powder form, although particles were broken by freeze-drying. It is supposed that PCL better protected FO because of its water insolubility.     

ENERGY EFFICIENCY EVALUATION FOR A “GREEN” POWER GENERATION PROCESS WITH MINIMUM EFFORT ON CARBON DIOXIDE CAPTURE AND STORAGE

This study evaluates the use of cracking for the removal of carbon from fuels to be used in a power generation process. Unlike conventional power generation systems, the proposed system includes a cracking unit, the function of which is to convert primary fuels into H₂ rich syngas and solid carbon, thus avoiding the emission of CO₂ and the need for carbon capture and storage (CCS) in the power generation system. Based on the thermodynamic analysis of equilibrium reactions in the cracker, it is demonstrated that the operating temperature has a significant influence on the carbon capture rate achieved and the composition of the syngas. Carbon in the fuel can be captured in solid form from hydrocarbon fuels when operating the cracker at sufficiently high temperatures; however, only a portion of carbon can be captured in a solid form from oxygenated hydrocarbon fuels, with the maximum carbon capture rate being achieved at an optimum temperature. An energy analysis, which takes into account the energy penalty of CCS for the conventional power generation system, reveals that the net available energy from the proposed system is still not as high as that of the conventional system with CCS; however, the solid carbon can be of high commercial value when appropriate technology is employed to convert the carbon byproduct into a high-added-value carbon product such as carbon black or carbon nanotubes (CNTs).     

Thermodynamic analysis of hydrogen production from glycerol at energy self‐sufficient conditions

A thermodynamic analysis based on the principle of minimising the Gibbs free energy is performed for hydrogen production from glycerol. When the operating parameters such as water/glycerol ratio (WGR), oxygen/glycerol ratio (OGR) and operating temperature (T) are carefully chosen, the energy self‐sufficient conditions can be achieved. Two levels of energy self‐sufficient, (i) within the reformer and (ii) within the overall system, are considered. Unlike the consideration in the reformer level reported in most works in literature, the consideration in the overall system level represents more realistic results based on the fact that some energy is required for heating up the feeds to a desired operating temperature. The obtained results demonstrate that the maximum hydrogen production significantly decreases from 5.65 mol H₂/mol glycerol for the reformer level to 3.31 mol H₂/mol glycerol for the system level, emphasising the significant demand of energy for feed preheating. © 2011 Canadian Society for Chemical Engineering     

Synergetic removal of aqueous phenol by ozone and activated carbon within three-phase fluidized-bed reactor

Synergetic removal of aqueous phenol by decomposition with ozone and adsorption on activated carbon was experimentally investigated. To enhance phenol removal performance, two activated carbons (AC1 and AC2) with BET surface areas of 1106 and 1150 m² g^?1 and average pore diameters of 2.3 and 1.7 nm, respectively, were employed. While the slowest initial removal of phenol was achieved with introduction of ozone only, the much better removal of phenol was obtained with utilization of activated carbon with ozone. Some intermediate products, which were detected as total organic carbon (TOC), were found to remain even after phenol was completely decomposed. Regarding to higher mesopore fraction, AC1 could better remove intermediates than AC2. With the synergetic performance of AC1 and ozone it was found that the highest removal of phenol and TOC was up to 100% and 89%, respectively.     

Thermodynamic analysis of calcium oxide assisted hydrogen production from biogas

This paper investigates calcium oxide assisted hydrogen production from biogas. Preliminary experiments were performed to compare the catalytic performance of combined carbon dioxide reforming and partial oxidation of biogas among four different adsorbent (CaO)/catalyst (Ni/SiO₂·MgO) arrangements; i.e. (i) Ni/SiO₂·MgO before CaO, (ii) CaO before Ni/SiO₂·MgO, (iii) Ni/SiO₂·MgO mixed with CaO, and (iv) Ni/SiO₂·MgO without CaO. The mixture of CaO and Ni/SiO₂·MgO was found to be the best arrangement, offering the highest hydrogen yield. Thermodynamic investigation of the integrated sorption-reaction systems for hydrogen production from biogas was performed. The system can be operated under thermal neutral condition when appropriate operating parameters are adjusted. Finally based on the thermal neutral operation, the effects of H₂O/CH₄ and CaO/CH₄ ratios on the required O₂/CH₄ ratio, hydrogen yield, hydrogen concentration and CO/H₂ ratio in product were determined. Obviously the use of CaO adsorbent can improve hydrogen production and there is an optimum H₂O/CH₄ ratio which offers the highest hydrogen production at each CaO/CH₄ ratio. Increasing H₂O/CH₄ ratio generally increases H₂/CO ratio but decreases hydrogen concentration in the product.     

Technical and economic study of integrated system of solid oxide fuel cell,palladium membrane reactor,and CO2 sorption enhancement unit

This paper deals with the integrated system of solid oxide fuel cell (SOFC), palladium membrane reactor (PMR), and CO₂ sorption enhancement (SE) unit. Three configurations of the SOFC systems fed by biogas are considered, i.e., PMR–SOFC, SE–PMR–SOFC, and SE–PMR–SOFC with a retentate gas recycling (SER–PMR–SOFC). The SOFC system equipped with a conventional reformer (CON–SOFC) is considered as a base case. The simulation results show that the capture of CO₂ in biogas before being fed to PMR (SE–PMR–SOFC) can improve H₂ recovery. The performance of SE–PMR–SOFC can be further enhanced by recycling retentate gas from PMR to CO₂ sorption enhancement unit (SER–PMR–SOFC). Compared to CON–SOFC, both SE–PMR–SOFC and SER–PMR–SOFC give higher power density and thus require smaller stack size (the stack size reduction of 1.55% and 8.27% are observed for SE–PMR–SOFC and SER–PMR–SOFC, respectively). The economic analysis is performed to identify the potential benefits of each SOFC configuration. The results indicate that SE–PMR–SOFC and SER–PMR–SOFC are not cost-effective systems compared with CON–SOFC; however, the capture of CO₂ in these SOFC systems offers an environmental benefit. High %total CO₂ capture and low cost of CO₂ capture are achieved under these SOFC systems.     

Fracture Toughness of a Silane Coupled Polymer-Metal Interface: Silane Concentration Effects

Fracture toughness of joints made from a glassy, 343,000 molecular weight polystyrene block bonded to chromic-sulfuric acid etched or phosphoric acid anodized aluminum are investigated. The fracture tests are performed with a 90-degree peel apparatus under “dry” laboratory conditions and “wet” conditions created by submerging the apparatus in a temperature controlled water bath. The bond strengths are controlled using various concentrations of styrl silane coupling agent added directly into the styrene monomer solution that polymerizes against the aluminum. Ellipsometric measurements on smooth silicon surfaces verify that the thickness of bound polymer is controlled by the silane to polystyrene mole ratio. X-ray photoelectron spectroscopy (XPS) analysis of fractured surfaces indicates that the fracture is near the aluminum surface. Both the wet and dry fracture energy as a function of bound polymer thickness on acid etched aluminum joints resemble quite closely the adhesion literature results obtained by fracturing pairs of fused, immiscible glassy polymers. Reasons for this similarity are discussed.     

Effect of operating conditions and gas flow patterns on the system performances of IIR-SOFC fueled by methanol

Mathematical models of an indirect internal reforming solid oxide fuel cells (IIR-SOFC) fueled by methanol were developed to analyze the thermal coupling of the internal endothermic steam reforming with exothermic electrochemical reactions and predict the system performance. The simulations indicated that IIR-SOFC fueled by methanol can be well performed as autothermal operation, although slight temperature gradient occurred at the entrance of the reformer chamber. Sensitivity analysis of five important parameters (i.e. operating voltage, reforming catalyst reactivity, inlet steam to carbon ratio, operating pressure and flow direction) was then performed. The increase of operating voltage lowered the average temperature along the reformer chamber and improved the electrical efficiency, but it oppositely reduced the average current density. Greater temperature profile along the system can be obtained by applying the catalyst with lower reforming reactivity; nevertheless, the current density and electrical efficiency slightly decreased. By using high inlet steam to carbon ratio, the cooling spot at the entrance of the reformer can be reduced but both current density and electrical efficiency were decreased. Lastly, with increasing operating pressure, the system efficiency increased and the temperature dropping at the reformer chamber was minimized.     

Effect of mode of operation on hydrogen production from glycerol at thermal neutral conditions: Thermodynamic analysis

Thermodynamic analysis of hydrogen production from glycerol under thermal neutral conditions is studied in this work. Heat requirement from the process can be achieved from the exothermic reaction of glycerol with oxygen in air fed to the system. Two modes of operation for air feeding are considered including (i) Single-feed mode in which air is fed in combination with water and glycerol to the reformer, and (ii) Split-feed mode in which air and part of glycerol is fed to a combustor in order to generate heat. The thermal neutral conditions are considered for two levels including Reformer and System levels. It was found that the H₂ yield from both modes is not significantly different at the Reformer level. In contrast, the difference becomes more pronounced at the System level. Single-feed and Split-feed modes offer high H₂ yield in low (600–900 K) and high (900–1200 K) temperature ranges, respectively. The maximum H₂ yields are 5.67 (water to glycerol ratio, WGR = 12, oxygen to glycerol ratio, OGR = 0.37, T = 900 K, Split-feed mode), and 3.28 (WGR = 3, OGR = 1.40, T = 900 K, Single-feed mode), for the Reformer and System levels, respectively. The difference between H₂ yields in both levels mainly arises from the huge heat demand for preheating feeds in the System level, and therefore, a higher amount of air is needed to achieve the thermal neutral condition. Split-feed mode is a favorable choice in term of H₂ purity because the gas product is not diluted with N₂ from the air. The use of pure O₂ and afterburner products (ABP) stream were also considered at the System level. The maximum H₂ yield becomes 3.75 (WGR = 5.21, OGR = 1.28, T = 900 K, Split-feed mode) at thermal neutral condition when utilizing heat from the ABP stream. Finally comparisons between the different modes and levels are addressed in terms of yield of by-products, and carbon formation.