Facile method for the preparation of the WS2 nanoparticles

A facile and simple synthetic route was proposed for the synthesis of WS2 nanoparticles. The as-prepared WS2 nanoparticles can be characterized with X-ray diffraction spectrum (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The average particle size of the product is about 85 nm that was calculated from XRD pattern by the Debye-Scherrer formula.     

Extended moving horizon estimation for chemical processes under non-Gaussian noises

Studies on moving horizon estimation (MHE) for applications featuring process uncertainties and measurement noises that follow time-dependent non-Gaussian distributions are absent from the literature. An extended version of MHE (EMHE) is proposed here to improve the estimation for a general class of non-Gaussian process uncertainties and measurement noises at no significant additional computational costs. Gaussian mixture models are introduced to the proposed EMHE to approximate offline the non-Gaussian densities of these random variables. Moreover, the proposed EMHE-based estimation scheme can be updated online by re-approximating the corresponding Gaussian mixture models when the distributions of noises/uncertainties change due to sudden or seasonal changes in the operating conditions. These updates are not expected to increase the central processing unit times considerably. Illustrative case studies featuring open-loop operation and closed-loop control using nonlinear model predictive control have shown that the practical features offered by EMHE resulted in significant improvements in state estimation and online control.     

Evaluation and modeling of Fischer-Tropsch synthesis in presence of a Co/ZrO2 catalyst

Abstract

The present work focused on the application of response surface methodology (RSM), Box–Behnken design (BBD), for prediction of products distribution of Fischer-Tropsch synthesis (FTS) using a Co/ZrO₂ catalyst in a fixed bed reactor. The effect of four independent operating variables such as reaction temperature, pressure, space velocity and H₂/CO ratio on the responses (CH₄ and C₅⁺ selectivities) in FTS were investigated. The analysis of variance (ANOVA) results showed that the suggested quadratic models could well predict CH₄ and C₅⁺selectivities. The optimized operating condition was temperature 200.73?°C, pressure 20?bar, space velocity 1662.58?h^?1 and H₂/CO ratio 1.93.     

Steam methane reforming on LaNiO3 perovskite-type oxide for syngas production,activity tests,and kinetic modeling

The kinetic experiments at various working conditions (ie, temperature: 500°C-900°C, pressure: 1-15 bar, H₂O/CH₄ ratio [S/C ratio] of 1-2.5, and gas hourly space velocity of 900-1700 1/h) in the presence of LaNiO₃ perovskite-type oxide were done to consider and assess the outcome of steam methane reforming (SMR) and to build up its kinetic models depending on Langmuir-Hinshelwood method in a fixed bed reactor. The outcomes demonstrate, the methane conversion, H₂ and CO yields and formed CO₂ are affected by the working parameters. Elevated temperature is profitable for more methane conversion, H₂ and CO yield. While high temperature has a negative effect on mol% of CO₂ in outlet products. The high working pressure will not profit SMR respect to CH₄ conversion and products distribution. The efficacy of S/C ratio on the CH₄ conversion and CO yield depended on temperature range. H₂ yield considerably diminishes with an increment in S/C ratio, while the trend was reverse for CO₂ value in outlet gas. The accuracy of suggested kinetic model was evaluated by correlation and statistical tests. Outcomes exhibited that the obtained data were well anticipated through the suggested model, owning to presumption of nonideal gas phase and by utilizing reasonable equation of state of PPR78.     

Effect of electrostatic charge of particles on hydrodynamics of gas-solid fluidized beds

The aim of this work was to investigate effect of electrostatic charge of particles on the fluidization hydrodynamics. Behavior of bubbles in beds of polyethylene particles was studied through analysis of pressure fluctuations in the frequency domain. Fluidized beds of uncharged, pre-charged and bed-charged particles were used in the experiments. Results revealed that in the bed of pre-charged particles, compared to uncharged experiments, particle-particle repulsive force increases the bed voidage and reduces equilibrium bubble size while the transition velocity to turbulent fluidization is decreased. In the case of bed-charged particles, at low gas velocities bubble fraction is greater compare to the other cases due to faster bubble coalescence in the presence of particle-wall attractive electrostatic force. Electrostatic charge of bulk increases by increasing the gas velocity. At high gas velocities, the repulsion force between highly charged particles overcomes the particle-wall effect on bubble formation and reduces the bubble size to less than in uncharged experiments. Accumulation of particles near the wall in the bed od bed-charged particles affects the hydrodynamics in two ways: first it accelerates bubble growth via bubble coalescence at low gas velocities, second it limits the bubble growth and reduces the transition velocity to turbulent regime to a value less than for pre-charged particles.     

Hot water,UV‐C and superatmospheric oxygen packaging as hurdle techniques for maintaining overall quality of fresh‐cut pomegranate arils

BACKGROUND: In recent years there has been increasing consumer pressure to avoid the use of agrochemicals such as chlorine on fresh plant products for extending their shelf life. The combined use of eco‐sustainable techniques may be an alternative. The effect of hot water (HW), ultraviolet‐C (UV‐C) light and high oxygen packaging (HO) on the overall quality of fresh‐cut pomegranate arils stored under modified atmosphere packaging (MAP) for up to 14 days at 5 °C was studied. RESULTS: Arils extracted manually, washed with chlorine (100 µL L^?1 NaClO, pH 6.5, 5 °C water), rinsed and drained were exposed to single or combined (double and triple) hurdle techniques. The HW treatment consisted of a 30 s immersion in water at 55 °C followed by air surface drying. A 4.54 kJ m^?2 dose was used for the UV‐C treatment before packaging. Active MAP with initial 90 kPa O₂ was used in the HO treatment. The respiration rate remained relatively constant throughout shelf life, with no differences among treatments. CO₂ accumulation was higher within HO packages. HW induced a slight reduction in total soluble solids, while no changes in titratable acidity were found. HO‐treated arils had the highest phenolic content, while the lowest was found in HW‐treated arils. The lowest antioxidant activity was found in HW + UV‐C + HO and the highest in UV‐C + HO and HO treatments. HW alone or in combination with UV‐C and HO inhibited mesophile, mould and yeast growth, while UV‐C + HO was most effective for controlling yeast and mould growth. CONCLUSION: UV‐C and HO either alone or in combination are promising techniques to preserve the quality of pomegranate arils for up to 14 days at 5 °C. © 2012 Society of Chemical Industry     

Influence of hot‐air treatment,superatmospheric O2 and elevated CO2 on bioactive compounds and storage properties of fresh‐cut pomegranate arils

The impact of heat treatment using hot air (HT 45 °C and 55 °C for 1 h) and two active modified atmosphere packaging (MAP) conditions of high oxygen atmosphere (HOA: 80 kPa O₂, 20 kPa N₂) and high CO₂ atmosphere (HCA: 20 kPa CO₂, 80 kPa N₂), individually or combined, on the antioxidant capacity, polyphenols, vitamin C content, total anthocyanins, polyphenoloxydase (PPO) activity and shelf life of fresh‐cut (FC) pomegranate arils stored for 14 days at 4 °C was studied. The results indicate that HT 45 °C along with HOA inhibited PPO activity and prevented loss of antioxidant capacity, vitamin C and phenolic compounds in arils, in comparison with control and HT 55 °C. All treatments reduced the accumulation of anthocyanins, but HCA‐treated arils lost more anthocyanins besides having worse a* colour parameter values. No significant differences in titrable acidity (TA) and total soluble solids (TSS) were observed between treatments. The combination of HOA and HT 45 °C enhanced the benefits of applying each treatment separately and could be useful to improve and extend postharvest life of pomegranate FC arils.     

Investigation of TiO2 nanoparticle efficiency on decolourisation of industrial date syrup

The TiO₂ nanoparticle photocatalyst was used to decolourise industrial date syrup. The effect of TiO₂ concentration (1 and 4% w/v), UV power (15 and 30 w) and processing time (12 and 48 h) on date syrup characteristics was investigated using a factorial design. The colour, turbidity, sugar content, total phenolic compounds, ash content and mineral (K, Na, Ca, Mg and Fe) of date syrup were analysed. The results demonstrated that using TiO₂ nanoparticle as a photocatalyst for the decolourisation of date syrup is an effective and promising method. Colour in all treatments was significantly (P < 0.05) reduced between 30 and 53% in comparison with the initial date syrup (491 000 IU), and the reduction was even higher for date syrup turbidity (between 47 and 75%). The result showed that the process condition significantly affected the colour and turbidity reduction. On the basis of the result, the best treatment was TiO₂ 4%, 15 w and 48 h. Under this condition, date syrup colour, turbidity, ash content, sugar content reduced by 52%, 61%, 13% and 9%, respectively.