ChemEngineering, Volume 2, Issue 4 (December 2018) – 17 articles

The worldwide production of hydrogen in 2010 was estimated to be approximately 50 Mt/a, mostly based on fossil fuels. By using lignocellulosic feedstock, an environmentally friendly hydrogen production route can be established. A flow sheet simulation for a biomass based hydrogen production plant was published in a previous work. The plant layout consisted of a dual fluidized bed gasifier including a gas cooler and a dust filter. Subsequently, a water gas shift plant was installed to enhance the hydrogen yield and a biodiesel scrubber was used to remove tars and water from the syngas. CO₂ was removed and the gas was compressed to separate hydrogen in a pressure swing adsorption. A steam reformer was used to reform the hydrocarbon-rich tail gas of the pressure swing adsorption and increase the hydrogen yield. Based on this work, a research facility was erected and the results were validated. These results were used to upscale the research plant to a 10 MW fuel feed scale. A validation of the system showed a chemical efficiency of the system of 60% and an overall efficiency of 55%, which indicates the high potential of this technology. Full article

Curcumin is a hydrophobic polyphenol compound exhibiting a wide range of biological activities such as anti-inflammatory, anti-bacterial, anti-fungal, anti-carcinogenic, anti-HIV, and anti-microbial activity. Recently, electrospraying has been successfully used to produce micro-or nano-sized particles for pharmaceutical use. In this work, polyvinylpyrrolidone (PVP) microspheres containing curcumin were prepared via electrospraying in order to improve the bioavailability of poorly-water-soluble curcumin. The influence of five processing parameters namely curcumin/PVP ratio, tip to collector distance, and electric voltage on physic-chemical properties was investigated. The characterization and aqueous solubility of particles were determined by using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and UV-Vis spectrophotometer. The result indicated that the spherical particles with particle size distribution of 164 to 730 nm obtained at a curcumin/PVP ratio of 1:30, a polymer solution concentration of 0.4%, electric voltage of 10 kV, and a tip-to-collector distance of 15 cm. Moreover, the dissolution of curcumin/PVP particle generated by electrospraying was higher than that of the original curcumin and pure curcumin particles produced by electrospraying. Full article

In order to develop wide bandgap p-type window materials to use in graded bandgap devices, the effects of magnesium (Mg) in n-CdTe layers were explored. In this work, magnesium-incorporated cadmium telluride (CdTe:Mg) layers were electroplated using two-electrode method. The layers were deposited on glass/FTO (flourine doped tin oxide) substrates, using an aqueous solution containing Cd²⁺, Mg²⁺ and tellurium dioxide (TeO₂) as the precursors. X-ray diffraction (XRD) studies indicate the reduction of crystallinity as the Mg concentration is increased in parts per million (ppm) level. Material becomes a completely amorphous layer at high Mg concentrations in the electrolytic bath. Photoelectrochemical (PEC) measurements show the gradual reduction of n-CdTe turning into p-CdTe layers when Mg concentration is increased in the electrolyte. Optical absorption measurements show the expansion of energy bandgap from CdTe bandgap (~1.48 eV) up to ~2.85 eV. The other characterisation results (energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL)) are also explored and presented together with above experimental results. Full article

Transfer of graphene, grown by chemical vapor deposition (CVD), to a substrate of choice, typically involves the deposition of a polymeric layer (for example, poly(methyl methacrylate) (PMMA), or polydimethylsiloxane, PDMS). These polymers are quite hard to remove without leaving some residues behind. One method to improve the graphene transfer is to coat the graphene with a thin protective oxide layer, followed by the deposition of a very thin polymer layer on top of the oxide layer (much thinner than the usual thickness), followed by a more aggressive polymeric removal method, thus leaving the graphene intact. At the same time, having an oxide layer on graphene may serve applications, such as channeled transistors or sensing devices. Here, we study the transfer of graphene with a protective thin oxide layer grown by atomic layer deposition (ALD). We follow the transfer process from the graphene growth stage through oxide deposition until completion. We report on the nucleation growth process of oxides on graphene, their resultant strain and their optical transmission. Full article

In the present study, the ANEMONA.XLT tool, an Excel template that was designed for calculation of enzyme kinetic parameters, has been successful adapted to some proposed models for dry reforming reaction, such as Eley-Rideal or Langmuir-Hinshelwood kinetic models. Model discrimination by non-linear regression analysis has been applied to data from the literature; the predicted kinetic parameters that were obtained using ANEMONA.XLT were fully comparable with those already published. Thus, the template can be a helpful and user-friendly alternative tool for researchers who do not have advanced skills in computer programming. Full article

Light from red (661 nm) and blue (417 nm) LEDs were applied for 12, 24, and 48 h on freshly harvested blueberry leaves of different cultivars mixed together. The extracts obtained through microwave extraction of these leaves were analysed in terms of total phenolic content, total monomeric anthocyanin content, and antioxidant activity as measured by % scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity and ferric reducing antioxidant potential (FRAP). It was observed that although the content of total phenolic content was high in the untreated leaves, there was an increase in the phenolic content and monomeric anthocyanin content of the leaves treated with blue light. DPPH inhibition activity and FRAP for all the samples were high; however, there was an increase in the FRAP of samples treated with light for different durations, which varied with type of light and the time of application of the LED light. Full article

The gas/liquid phase separation of CO₂ from a water-methanol solution at the anode side of a µDirect-Methanol-Fuel-Cell (µDMFC) plays a key role in the overall performance of fuel cells. This point is of particular importance if the µDMFC is based on a “Lab-on-a-Chip” design with transient working behaviour, as well as with a recycling and a recovery system for unused fuel. By integrating a membrane-based micro contactor downstream into the µDMFC, the efficient removal of CO₂ from a water-methanol solution is possible. In this work, a systematic study of the separation process regarding gas permeability with and without two-phase flow is presented. By considering the µDMFC working behaviour, an improvement of the overall separation performance is pursued. In general, the gas/liquid phase separation is achieved by (1) using a combination of the pressure gradient as a driving force, and (2) capillary forces in the pores of the membrane acting as a transport barrier depending on the nature of it (hydrophilic/hydrophobic). Additionally, the separation efficiency, pressure gradient, orientation, liquid loss, and active membrane area for different feed inlet temperatures and methanol concentrations are investigated to obtain an insight into the separation process at transient working conditions of the µDMFC. Full article

As a result of their high tuneability and low volatility, room temperature ionic liquids have been proposed as replacement solvents in a wide range of industrial applications. They are particularly well-suited for use as an entrainer (or solvent) in extractive distillation processes to separate close boiling and azeotropic mixtures. The limiting selectivity is a common, fundamental parameter used to screen and rank entrainer candidates. In the present study, we present a detailed thermodynamic analysis to understand the basis for its use along with the necessary, underlying assumptions. We find that, while for many cases the limiting selectivity can correctly rank ionic liquid entrainer candidates for homogeneous extractive distillation processes, it is not always able to capture the correct phase behavior. We, instead, recommend the use of composition dependent activity coefficients. Full article

The goal of this work is to assess the application of ultrasonic power to the reactive dissolution of limestone particles in an acidic environment; this would represent a novel method for improving wet Flue Gas Desulfurization industrial systems. In this study a stepwise titration method is utilized; experiments were done by using different particle size distributions with and without the application of ultrasound. The use of ultrasonic power sensibly affected the reaction rate of limestone and its dissolution; a major difference could be observed when samples from the Wolica region in Poland were studied. In this case, the overall dissolution rate was found to increase by more than 70%. The reactive dissolution of limestone does not follow the same mathematical model when sonication is in effect; in this case, an extra Ultrasonic Enhancement Constant was introduced. It was demonstrated that the dissolution is proportional to an Effective Reaction Surface and, therefore, surface interactions should also be taken into consideration. For this purpose, a study is presented here on the Z-potential and electrophoretic mobility of limestone samples measured in aqueous dispersions by means of Laser Doppler Micro-Electrophoresis. Full article

Coating open-cell foams by a catalytic layer is a necessary step to obtain structured catalytic foam reactors. The dip-coating method, consisting of immersing the foam in a suspension or in a sol-gel, is generally used to obtain the coating. The excess of liquid has to be evacuated from the foam to obtain a thin layer. Different methods to remove this excess of liquid have been investigated in the present work. The objective was to show that 3D X-ray tomography coupled to image analysis could be a tool to discriminate the methods by analysing the spatial localisation of the catalyst layer throughout the whole foam samples. A simple blowing by air in every direction seems to not be appropriate to obtain uniform coatings. Full article

A volume-of-fluid (VOF) finite volume model under the ANSYS^® Fluent framework was coupled with the response surface method (RSM) to find the best operating conditions within a jettability window for two selected responses in a drop-on-demand inkjet printing process. Twenty-five runs were generated using a face centred design and numerical simulations were carried out using viscosity, surface tension, nozzle diameter, and inlet velocity as input factors. A mesh study was first conducted to establish the necessary number of cells to best combine accuracy and expended time. Selected runs were discussed, identifying the underpinning mechanisms behind the droplet generation at different time periods. Each one of the responses was evaluated under different input factors and their effects were identified. Finally, the desirability function concept was advantageously used to proceed with a multiple optimization where all the responses were targeted under usual jettability/printability conditions. Full article

In this study, a directly irradiated, milli-scale chemical reactor with a simple nickel catalyst was designed for dry reforming of methane for syngas. A milli-scale reactor was used to facilitate rapid heating, which is conducive to combating thermal transience caused by intermittent solar energy, as well as reducing startup times. Milli-scale reactors also allow for a distributed and modular process to produce chemicals on a more local scale. In this setup, the catalyst involved in the reaction is located directly in the focal area of the solar simulator, resulting in rapid heating. The effects of mean residence time and temperature on conversion and energy efficiency were tested. The process, which is intended to store thermal energy as chemical enthalpy, achieved 10% thermal-to-chemical energy conversion efficiency at a mean residence time of 0.028 s, temperature of 1000 °C, and molar feed ratio of 1:1 CO₂:CH₄. A significant portion of the thermal energy input into the reactor was directed toward sensible heating of the feed gas. Thus, this technology has potential to achieve solar-to-chemical efficiency with the integration of recuperative heat exchange. Full article

CMK-3 mesoporous carbon was nanocast from SBA-15 silica. The obtained carbon was characterized by nitrogen sorption isotherms, X-ray diffraction and transmission electron microscopy (TEM). The batch adsorption tests were done at constant pH taking into account the initial metal ion concentration, adsorbent mass and temperature. A statistical study using a response surface design method was done to develop a mathematical model to predict copper adsorption on CMK-3 as a function of the mentioned experimental factors. It was found that all these parameters are significant, and copper concentration has the greatest effect on adsorption among them. Moreover, the obtained model proved to be adequate in predicting copper adsorption on CMK-3 and its performance under different experimental conditions. Full article

The present work is a study of CO₂ Reforming of Methane (DRM) carried out in a catalytic Pd-based membrane reactor. A detailed thermodynamic analysis is carried out, calculating the chemical equilibrium parameters in two different cases: (a) DRM along with the Reverse Water Gas Shift (RWGS) reaction and (b) DRM along with both RWGS and the Boudouard Reaction (BR). The performance of membrane reactor is then experimentally analyzed in terms of methane conversion, hydrogen recovery and H₂/CO reaction selectivity by varying feed pressure and CO₂/CH₄ feed molar ratio and 500 °C and GHSV = 100 h⁻¹. Among the obtained results, a CH₄ conversion of about 26% and a H₂ recovery of 47% are achieved at low feed pressures, exceeding the traditional reactor equilibrium conversion. This effect can be attributed to the favorable thermodynamics coupled to the hydrogen permeation through the membrane. This study further demonstrates the general effectiveness of membrane-integrated reaction processes, which makes the production of syngas more efficient and performing, providing important environmental benefits. Full article

In an aqueous enzymatic saccharification using cellulase, the dissolution of crystalline cellulose is one of the rate-limiting steps. Insoluble cellulose powder was preliminarily heat-treated with ionic liquids (ILs), such as [Bmim][Cl] (1-butyl-3-methylimidazolium chloride) and [Amim][Cl] (1-allyl-3-methylimidazolium chloride), which enable the production of soluble cellulose. On the other hand, the presence of ILs leads to a denaturation of enzymes. Using cellulase from Trichoderma viride, the effects of [Bmim][Cl] and [Amim][Cl] in the enzymatic saccharification were compared. The production of glucose was optimized with 5 wt%-ILs, both for [Bmim][Cl] and for [Amim][Cl]. The significant inhibiting effects of ILs (IL concentration >10 wt%) could be due to the denaturation of cellulase, because the peak shifts of intrinsic tryptophan fluorescence were observed in the presence of 7.5 wt%-ILs. To analyze kinetic parameters, the Langmuir adsorption model and the Michaelis-Menten model were employed. The investigation suggests that [Amim][Cl] can provide soluble cellulose more efficiently, and can promote enzymatic saccharification in the IL concentration below 5 wt%. Full article

This study aimed at investigating the effect of l-ascorbic acid on the Cu²⁺-induced oxidation of quercetin, within a pH range from 6.7 to 8.3 and temperatures varying from 53 to 87 °C. Initial examinations showed that quercetin degradation obeyed apparent first-order kinetics and it was significantly affected by temperature. Modelling of the effect of l-ascorbic acid by implementing response surface methodology suggested that l-ascorbic acid did not impact quercetin oxidation significantly (p < 0.05) and led to an empirical kinetic model based on temperature (T) and pH. Liquid chromatography–diode array–mass spectrometry analyses revealed the presence of typical quercetin degradation and oxidation products, including protocatechuic acid and 2-(hydroxybenzoyl)-2-hydroxybenzofuran-3(2H)-one. It was concluded that the formation of l-ascorbyl or other radicals (superoxide anion) may be involved in quercetin oxidation and this fact merits further attention to illuminate the possible beneficial or adverse nutritional consequences of such reactions in foods. Full article

Lignocellulosic agricultural side products like wheat straw are widely seen as an important contribution to a sustainable future economy. However, the optimization of biorefinery processes, especially the pretreatment step, is crucial for an economically viable biorefinery. The monitoring of this pretreatment process in terms of delignification and the generation of the fermentation inhibitors acetic acid, furfural, and hydroxymethylfurfural (HMF) is essential in order to adapt the process parameters for a desired outcome and an economical operation. However, traditional wet chemistry methods are time-consuming and not suitable for on-line process monitoring. Therefore, UV-Vis spectroscopy in combination with partial least-squares regression was used for the determination of the concentrations of lignin, acetic acid, furfural, and HMF. Five different data blocks with increasing amounts of impurities were investigated to evaluate the influence of the inevitable impurities on the calibration models. Lignin showed a good prediction accuracy with 95% tolerance intervals between ±0.46 to ±1.6 mg/L for concentrations up to 30 mg/L. Also, the other components could be predicted with a sufficient accuracy for on-line process monitoring. A satisfactory calibration can be obtained with 10 to 20 reference samples valid at process temperatures between 160 °C and 180 °C. Full article