Slow Pyrolysis Products Derived from Extrudates Produced from Discard Coal Fines and Recycled Plastics as Binders.

The pyrolysis products derived from both coal and plastics have been extensively evaluated in literature; however, their copyrolysis product yields together with the characterization of the generated products have received less attention. Most studies use high heating rates with small particle sizes of the mechanically mixed blends. This study aims to improve the understanding of the slow copyrolysis behavior of extrudates produced from coal fines from the South African Highveld coalfield combined with recycled waste low-density polyethylene (LDPE) and polypropylene (PP). The fraction of plastic was varied between 10 and 100 wt % during extrusion. The extrudates (10 mm diameter) underwent slow pyrolysis in a modified Fischer assay setup by increasing the temperature (5 °C/min) under a nitrogen atmosphere to 520, 720, and 920 °C. The pyrolysis products (char, condensable products, water, and gas) were collected and characterized. The coal fines produced up to 83% char, whereas the plastics produced over 90% condensable products. The slow heating rate and the small reactor volume favored the production of condensable products, which increased with plastic concentration. The extrudates produced char and condensable product yields that fit the additive model of the raw materials. Statistical equations were developed to predict the pyrolysis yields and characteristics as functions of coal and plastic composition. The equations accurately predict the char yield, condensable product yield, fixed carbon content, ash content, sulfur content of chars, and carbon and hydrogen contents of chars and condensable products. Gas chromatography-mass spectrometry results indicate that the extrudates' condensable products consist mainly of alkanes and alkenes, similar to the plastics. Furthermore, the condensable products derived from PP and coal extrudates have fewer components with lower boiling points compared with the raw materials.

The CO Tolerance of Pt/C and Pt-Ru/C Electrocatalysts in a High-Temperature Electrochemical Cell Used for Hydrogen Separation.

This paper describes an experimental evaluation and comparison of Pt/C and Pt-Ru/C electrocatalysts for high-temperature (100-160 °C) electrochemical hydrogen separators, for the purpose of mitigating CO poisoning. The performances of both Pt/C and Pt-Ru/C (Pt:Ru atomic ratio 1:1) were investigated and compared under pure hydrogen and a H2/CO gas mixture at various temperatures. The electrochemically active surface area (ECSA), determined from cyclic voltammetry, was used as the basis for a method to evaluate the performances of the two catalysts. Both CO stripping and the underpotential deposition of hydrogen were used to evaluate the electrochemical surface area. When the H2/CO gas mixture was used, there was a complex overlap of mechanisms, and therefore CO peak could not be used to evaluate the ECSA. Hence, the hydrogen peaks that resulted after the CO was removed from the Pt surface were used to evaluate the active surface area instead of the CO peaks. Results revealed that Pt-Ru/C was more tolerant to CO, since the overlapping reaction mechanism between H2 and CO was suppressed when Ru was introduced to the catalyst. SEM images of the catalysts before and after heat treatment indicated that particle agglomeration occurs upon exposure to high temperatures (>100 °C).

Hydrogen Separation and Purification from Various Gas Mixtures by Means of Electrochemical Membrane Technology in the Temperature Range 100-160 °C.

This paper reports on an experimental evaluation of the hydrogen separation performance in a proton exchange membrane system with Pt-Co/C as the anode electrocatalyst. The recovery of hydrogen from H2/CO2, H2/CH4, and H2/NH3 gas mixtures were determined in the temperature range of 100-160 °C. The effects of both the impurity concentration and cell temperature on the separation performance of the cell and membrane were further examined. The electrochemical properties and performance of the cell were determined by means of polarization curves, limiting current density, open-circuit voltage, hydrogen permeability, hydrogen selectivity, hydrogen purity, and cell efficiencies (current, voltage, and power efficiencies) as performance parameters. High purity hydrogen (>99.9%) was obtained from a low purity feed (20% H2) after hydrogen was separated from H2/CH4 mixtures. Hydrogen purities of 98-99.5% and 96-99.5% were achieved for 10% and 50% CO2 in the feed, respectively. Moreover, the use of proton exchange membranes for electrochemical hydrogen separation was unsuccessful in separating hydrogen-rich streams containing NH3; the membrane underwent irreversible damage.

Recent Advances in Membrane-Based Electrochemical Hydrogen Separation: A Review.

In this paper an overview of commercial hydrogen separation technologies is given. These technologies are discussed and compared-with a detailed discussion on membrane-based technologies. An emerging and promising novel hydrogen separation technology, namely, electrochemical hydrogen separation (EHS) is reviewed in detail. EHS has many advantages over conventional separation systems (e.g., it is not energy intensive, it is environmentally-friendly with near-zero pollutants, it is known for its silent operation, and, the greatest advantage, simultaneous compression and purification can be achieved in a one-step operation). Therefore, the focus of this review is to survey open literature and research conducted to date on EHS. Current technological advances in the field of EHS that have been made are highlighted. In the conclusion, literature gaps and aspects of electrochemical hydrogen separation, that require further research, are also highlighted. Currently, the cost factor, lack of adequate understanding of the degradation mechanisms related to this technology, and the fact that certain aspects of this technology are as yet unexplored (e.g., simultaneous hydrogen separation and compression) all hinder its widespread application. In future research, some attention could be given to the aforementioned factors and emerging technologies, such as ceramic proton conductors and solid acids.

Dataset on the carbon dioxide, methane and nitrogen high-pressure sorption properties of South African bituminous coals.

The dataset presented in this article supplements the result and information published in the report "The carbon dioxide, methane and nitrogen high-pressure sorption properties of South African bituminous coals" (Okolo t al., 2019). Four run of mine coal samples from selected underground coal mines from the Highveld, Witbank, and Tshipise-Pafuri coalfields of South Africa were used for the study. The CO2, CH4, and N2 sorption data were acquired from an in-house built high-pressure gravimetric sorption system (HPGSS) at the CSIRO Energy, North Ryde, Australia; at an isothermal temperature of 55 °C, in the pressure range: 0.1-16 MPa. The resulting excess sorption isotherm data were fitted to the modified Dubinin-Radushkevich isotherm model (M-DR) and a new Dubinin-Radushkevich - Henry law hybrid isotherm model (DR-HH). The dataset provided in this article, apart from being informative will be useful for comparison with available and future data and for testing other sorption isotherm models developed by other investigators in the area of CO2 storage in geological media, especially coal seams.

The carbon dioxide gasification characteristics of biomass char samples and their effect on coal gasification reactivity during co-gasification.

The carbon dioxide gasification characteristics of three biomass char samples and bituminous coal char were investigated in a thermogravimetric analyser in the temperature range of 850-950 °C. Char SB exhibited higher reactivities (Ri, Rs, Rf) than chars SW and HW. Coal char gasification reactivities were observed to be lower than those of the three biomass chars. Correlations between the char reactivities and char characteristics were highlighted. The addition of 10% biomass had no significant impact on the coal char gasification reactivity. However, 20 and 30% biomass additions resulted in increased coal char gasification rate. During co-gasification, chars HW and SW caused increased coal char gasification reactivity at lower conversions, while char SB resulted in increased gasification rates throughout the entire conversion range. Experimental data from biomass char gasification and biomass-coal char co-gasification were well described by the MRPM, while coal char gasification was better described by the RPM.

Chemical and structural characterization of char development during lignocellulosic biomass pyrolysis.

The chemical and structural changes of three lignocellulosic biomass samples during pyrolysis were investigated using both conventional and advanced characterization techniques. The use of ATR-FTIR as a characterization tool is extended by the proposal of a method to determine aromaticity, the calculation of both CH2/CH3 ratio and the degree of aromatic ring condensation ((R/C)u). With increasing temperature, the H/C and O/C ratios, XA and CH2/CH3 ratio decreased, while (R/C)u and aromaticity increased. The micropore network developed with increasing temperature, until the coalescence of pores at 1100°C, which can be linked to increasing carbon densification, extent of aromatization and/or graphitization of the biomass chars. WAXRD-CFA measurements indicated the gradual formation of nearly parallel basic structural units with increasing carbonization temperature. The char development can be considered to occur in two steps: elimination of aliphatic compounds at low temperatures, and hydrogen abstraction and aromatic ring condensation at high temperatures.

Structural and chemical modifications of typical South African biomasses during torrefaction.

Torrefaction experiments were carried out for three typical South African biomass samples (softwood chips, hardwood chips and sweet sorghum bagasse) to a weight loss of 30 wt.%. During torrefaction, moisture, non-structural carbohydrates and hemicelluloses were reduced, resulting in a structurally modified torrefaction product. There was a reduction in the average crystalline diameter (La) (XRD), an increase in the aromatic fraction and a reduction in aliphatics (substituted and unsubstituted) (CPMAS (13)C NMR). The decrease in the aliphatic components of the lignocellulosic material under the torrefaction conditions also resulted in a slight ordering of the carbon lattice. The degradation of hemicelluloses and non-structural carbohydrates increased the inclusive surface area of sweet sorghum bagasse, while it did not change significantly for the woody biomasses.

The adsorption of copper in a packed-bed of chitosan beads: modeling, multiple adsorption and regeneration.

In this study, exoskeletons of Cape rock lobsters were used as raw material in the preparation of chitin that was successively deacetylated to chitosan flakes. The chitosan flakes were modified into chitosan beads and the beads were cross-linked with glutaraldehyde in order to study copper adsorption and regeneration in a packed-bed column. Five consecutive adsorption and desorption cycles were carried out and a chitosan mass loss of 25% was observed, after the last cycle. Despite the loss of chitosan material, an improved efficiency in the second and third cycles was observed with the adsorbent utilizing 97 and 74% of its adsorbent capacity in the second and third cycles, respectively. The fourth and fifth cycles, however, showed a decreased efficiency, and breakage of the beads was observed after the fifth cycle. In the desorption experiments, 91-99% of the adsorbed copper was regenerated in the first three cycles. It was also observed that the copper can be regenerated at a concentration of about a thousand fold the initial concentration. The first cycle of adsorption could be accurately described with a shrinking core particle model combined with a plug flow column model. The input parameters for this model were determined by batch characterization methods, with as only fitting parameter, the effective diffusion coefficient of copper in the bead.

The influence of the degree of cross-linking on the adsorption properties of chitosan beads.

The influence of the degree of cross-linking (DCL) on chitosan beads was studied. Chitosan was prepared from the exoskeleton of Cape rock-lobsters, collected from the surroundings of Cape Town, South Africa. The chitosan beads were characterized; the beads water contents and pKa varied in the range of 90-96% and 4.3-6.0, respectively, and were found to decrease with increasing DCL (0.0-34.0%). A pH-model, which described the reversibility of the metal adsorbed onto the beads, was used to predict the equilibrium properties of copper adsorption onto the cross-linked beads. The model accounts for the effect of pH and the important model parameters, the equilibrium adsorption constant (Kads) and to a lesser extent the adsorbent adsorption capacity (qmax) showed to decrease with the DCL. The adsorbent capacity and the adsorption constant were determined as 3.8-5.0mmol/g chitosan and (9-90)x10(-4), respectively. The adsorption kinetics could be described using a shrinking core model and the effective diffusion coefficient (Deff) was determined as (8.0-25.8)x10(-11)m2/s. It was found that Deff decreases with the DCL mainly due to the decreased in water content of the beads at high DCL.

A comparison of glycans and polyglycans using solid-state NMR and X-ray powder diffraction.

Individual polyglycans and their corresponding monomers have been studied separately for several decades. Attention has focused primarily on the modifications of these polyglycans instead of the simple relationship between the polyglycans themselves and their corresponding monomers. Two polyglycans, chitin and chitosan, were examined along with their respective monomeric units, N-acetyl-D-glucosamine (GlcNAc) and (+)D-glucosamine (GlcN) using solid-state proton decoupling Magic Angle Turning (MAT) techniques and X-Ray Powder Diffraction (XRPD). A down-field shift in isotropic (13)C chemical shifts was observed for both polymers in Cross Polarization/Magic Angle Spinning (CP/MAS) spectra. An explanation of misleading peak assignments in previous NMR studies for these polyglycans was determined by comparing sideband patterns of the polymers with their corresponding monomers generated in a 2D FIve pi REplicated Magic Angle Turning (FIREMAT) experiment processed by Technique for Importing Greater Evolution Resolution (TIGER). Structural changes in the crystalline framework were supported by XRPD diffraction data.

Adenoviruses and enteroviruses as pathogens in myocarditis and dilated cardiomyopathy.

BACKGROUND: Enteroviruses were detected in up to 50% in myocardium of patients with myocarditis and dilated cardiomyopathy, the latter being considered as a result of a prior subclinical myocarditis. A wide range of other infectious agents are being discussed as pathogens, often only based on reports of single cases. Adenovirus genome was recently identified in a significant number in the myocardium of paediatric patients with myocarditis. However, data on the role of adenoviruses for the aetiopathogenesis of myocarditis in adult patients is missing so far. Therefore, we studied the prevalence of adenoviral and enteroviral genome in myocardium of adults with myocarditis and dilated cardiomyopathy. METHODS: 15 patients were diagnosed at baseline with myocarditis, 16 patients with dilated cardiomyopathy according to clinical and histological criteria. Endomyocardial biopsies of these patients and 8 control patients with non-infectious heart diseases were evaluated by polymerase chain reactions for enterovirus and adenovirus genome. RESULTS: Enteroviral genome was detected in 27.3% patients with myocarditis or dilated cardiomyopathy, whereas adenoviral genome was not identified in any patient. Samples from control subjects systematically yielded negative results. CONCLUSIONS: From our data, it seems doubtful that adenoviruses are major pathogens of myocarditis or DCM, whereas enterovirus genome was identified in a significant number of patients with both diseases.