Microwave accelerated steam distillation of essential oil from lavender: A rapid, clean and environmentally friendly approach

A new process design and operation for microwave accelerated steam distillation (MASD) of essential oils was developed. A packed bed of lavender flowers (Lavandula angustifolia Mill., Lamiaceae) sits above the steam source generated by microwave heating. Only steam passes through it without the boiling water mixing with vegetable raw material, as is the case in hydro-distillation. MASD has been compared with a conventional technique, steam distillation (SD), for the extraction of essential oil from lavender flowers. Extraction of essential oils from lavender with MASD was better than SD in terms of energy saving, rapidity (10 min versus 90 min), product yield, cleanliness and product quality.     

蚕丝蒸汽闪爆改性后的形态结构研究

采用蒸汽闪爆技术对蚕丝进行物理改性 ,利用扫描电镜、红外光谱、X射线衍射、热分析等现代分析方法对处理前后的蚕丝进行形态结构表征 ,结果表明经蒸汽闪爆处理后 ,蚕丝表面形态 ,结晶结构 ,溶解性能有较大的改变 ,蚕丝的化学反应性能有了一定的改善 .     

The impact of ultrasound and steam blanching pre-treatments on the drying kinetics,energy consumption and selected properties of parsley leaves

In current study the influence of ultrasound pre-treatment and drying conditions (microwave power, air temperature) was analysed by the means of drying kinetics, energy consumption and selected quality properties of dried parsley leaves. Ultrasound treatment (US) was compared with conventional treatment – steam blanching. In comparison to untreated material, ultrasound applied at 21 kHz, 12 W/g, contributed to significant reduction of the drying time up to 29.8%. Moreover, the energy expenditures were reduced maximally by 33.6% for parsley dried at 30 °C and 300 W. For this sample the colour retention was the highest, as well. In turn, steam treated parsley was dried maximally by 28.9% faster and thus specific energy consumption decreased to 72.0% of the value for intact leaves when 20 °C and 300 W were set. The influence of pre-drying treatment on the quality properties depended on the drying conditions. Pre-drying treatment (US, blanching) did not affect the lutein content significantly, whereas the most considerable increase of chlorophyll a and b resistance and their relative concentration (Chl a/b ratio) was achieved in US-treated leaves dried at 30 °C and 100 W. The utilisation of drying pre-treatment and dehydration parameters should be considered with respect to further utilisation of dried parsley leaves. Nonetheless, sonication is worth to be taken into account due to a significant reduction of energy expenditures and an improvement of resistance of bioactive components.     

The oxidative stream reforming of methane to syngas in a thin tubular mixed-conducting membrane reactor

The oxidative stream reforming of methane (OSRM) to syngas, involving coupling of exothermic partial oxidation of methane (POM) and endothermic steam reforming of methane (SRM) processes, was studied in a thin tubular Al₂O₃-doped SrCo_0.8Fe_0.2O_3−δ membrane reactor packed with a Ni/γ-Al₂O₃ catalyst. The influences of the temperature and feed concentration on the membrane reaction performances were investigated in detail. The methane and steam conversions increased with increasing the temperature and high conversions were obtained in 850–900 °C. Different from the POM reaction, in the OSRM reaction the temperature and H₂O/CH₄ profoundly influenced the CO selectivity, H₂/CO and heat of the reaction. The CO selectivity increased with increasing the temperature or decreasing the H₂O/CH₄ ratio in the feed owing to the water gas shift reaction (H₂O + CO → CO₂ + H₂). And the H₂ selectivity based on methane conversion was always 100% because the net steam conversion was greater than zero. The H₂/CO in product could be tuned from 1.9 to 2.8 by adjusting the reaction temperature or H₂O/CH₄. Depending on the temperature or H₂O/CH₄, furthermore, the OSRM process could be performed auto-thermally with idealized reaction condition.     

Challenges for the utilization of methane as a chemical feedstock

The abundance of methane has led to a strong interest to use methane as a feedstock in the chemical industry. One of the main challenges is the initial activation of the methane molecule. This has resulted in the development of several different approaches to utilize methane, some more developed than others. In this work the current status of the different approaches is discussed and the main issues for industrial utilization described. A special focus of this work is the status of catalyst development.     

Numerical simulation of streamwise fluidelastic instability of tube bundles subjected to two-phase cross flow

This work aims to develop and validate a numerical model to simulate the flow-structure interaction in tube bundles subjected to two-phase flow. The model utilizes a mixture multiphase module in which a drift flux formulation is used to account for the slip between the phases. Two methods of numerical flow-structure interaction are used to predict the onset of fluidelastic instability (FEI) in the streamwise direction for a two-phase air–water flow mixture in parallel triangular tube bundles. These models are the hybrid analytical-flow field model and the direct numerical flow/structure coupling model. This work investigates the effects of void fractions in the range of 20% to 80% and several pitch-to-diameter ratios (P/D) in the range of 1.3 to 1.7. The results of the fluidelastic forces and the stability threshold are validated against the experimental data available in the literature and show an excellent agreement. The streamwise FEI threshold shows a significant dependency on the pitch-to-diameter ratio while the void fraction exhibits a lesser effect. Generally, the stability threshold increases as the pitch-to-diameter ratio increases. The model that was developed paves the way for devising of more reliable prediction tools for FEI in steam generators.     

Adsorption characteristics of activated carbons obtained from corncobs

Dried, crushed, corncobs were carbonized at 500°C and steam activated (in one- or two-step schemes), or activated with H₃PO₄. The products were characterized by N₂ adsorption at 77 K, using the BET, _s and DR methods. Adsorption capacity was demonstrated by the iodine and phenol numbers, and the isotherms of methylene blue and Pb²⁺ ions, from aqueous solutions. A distribution of porosity in the carbons was estimated within the various ranges (ultra-, super-, meso- and macropores). Simple carbonization yields a poor adsorbing carbon; only its uptake for iodine was high and proposed to be due to an addition reaction on residual unsaturation of the parent lignocellulosic structures. Enhanced porosity was best associated with chemical activation and/or steam pyrolysis at 700°C. These activated carbons proved highly porous and rich in mesopores, and showed high adsorption capacity for methylene blue and Pb²⁺ ions. Phenol uptake was found to depend on surface chemical nature of the carbon rather than its porous properties. Corncobs were postulated to be feasible as feedstock to produce good adsorbing carbons, under the one-step activation schemes outlined here.     

XPS and IGC characterization of steam treated triticale straw

The surface chemical composition and surface energy of native and steam treated triticale straws have been investigated by X-ray photoelectron spectroscopy (XPS) and inverse gas chromatography (IGC) to reveal the effect of steam treatment temperature and time. The XPS results show that the contents of C elements and C-C group on the exterior surface of native triticale straw are much higher than those on the interior surface, indicating that there was a high quantity of wax on the exterior surface of the native triticale straw. Upon steam treatment, both carbon levels and C-C groups reduce with increasing steam temperature and treatment time of the exterior surfaces. However, the effect of steam treatment on the interior surface is very limited. In terms of the surface acid and base properties, the steam treated samples exhibited higher acid and base properties than the native sample, indicating a more polar surface of the steam treated sample.     

Surface structure–activity relationships of Cu/ZnGaOX catalysts in low temperature water–gas shift (WGS) reaction for production of hydrogen fuel

A new species’ class of Cu-, Ga- and Zn-based rate catalysts was prepared by a systematic co-precipitation technique at the different related pH values (6.5–8.0) along with calcination functional conditions, influencing components’ physical properties, these were characterized, and their application performance for water–gas shift (WGS) reaction was researched. Substances were analysed by various experimental methods, namely chemisorption, temperature-programmed reduction (TPR) characterisation, diffraction, physisorption and microscopy. A homogenous size dispersion of the compounds with smaller granular particles was obtained for catalysis, implemented with high pH-resulting outputs. H₂ TPR profiles revealed a tailored stronger effect of Cu–Zn on Ga for process, operated with low pH-conditioned forms. Over Cu/ZnGaO_X, WGS was sensitive to Cu, which was primarily active. Catalytic chemical reactivity, activity and selectivity were also found to be critically dependent on material lattice structure, copper surface area and metal–support interaction phenomena. The temperature-programmed surface reaction with mass spectrometry (TPSR–MS) measurements showed that formulations, synthesised at the pH of 8.0, enabled reaching >99% of the equilibrium yield CO conversion at 260 °C. An increase in the converted CO, oxidation and H₂ productivity with the integral steam content in gaseous feed flow was achieved. The heterogeneous phase processing at the correlated pH of 7.6 demonstrated the highest formed CO product at the temperature of 200 °C, compared with literature. This is particularly promising for reagent purity hydrogen-fed fuel cells. The kinetics for each co-precipitated solid was evaluated regarding the efficiency for the WGS in a fixed bed reactor.