No abstract

The aqueous extraction of hemicelluloses has gained increasing interest with new emerging applications for hemicelluloses in the modern forest-based biorefinery concept. The extraction kinetics play a key role in their industrial utilization. The traditional kinetic studies and models for the selective dissolution of softwoods, however, always incorporate high concentrations of sodium hydroxide and sodium sulfide relevant to pulping, and the kinetics in pure water is left outside the scope of these investigations. Aqueous extraction of hemicelluloses from spruce sapwood was investigated with a new cascade reactor setup, which was developed for intensified investigation of solid-liquid dissolution kinetics. The experiments were performed at 150-170 °C with a particle size of 1.25-2 mm and solid loads of about 6.25 g of dry wood/L in the kinetic regime of intrinsic kinetics. The pH of the liquid phase was measured during the reaction. The selectivity of the dissolution and degradation of hemicelluloses was examined qualitatively. The total concentrations of arabinose (Ara), xylose (Xyl), galactose (Gal), glucose (Glc), mannose (Man), rhamnose (Rha), glucuronic acid (GlcA), 4-O-methylglucuronic acid (4-O-MeGlcA), and galacturonic acid (GalA) were analyzed from the liquid and solid phases during the reaction. The dissolution was observed to be highly temperature dependent, and degradation of the compounds was observed. A kinetic model was developed for the overall extraction of the hemicelluloses. The activation energy was determined to be 135 kJ/mol. No significant influence of the pH on the actual extraction kinetics was observed, even though it influences strongly the degradation of the compounds through hydrolysis.

Hydrodeoxygenation of isoeugenol was investigated at 200 °C under 3 MPa total pressure in dodecane as a solvent, in hydrogen, over bifunctional Pt‐ and Ir‐modified Beta zeolites and mesoporous materials. As a comparison, Pt and Ir supported on Al2O3, SiO2 and mesoporous MCM‐41 were also tested. The catalysts were characterized by XRD, CO pulse chemisorption, transmission electron microscopy, scanning electron microscopy, nitrogen adsorption and FTIR pyridine adsorption desorption. The results revealed that the most active and selective catalyst was Pt‐H‐Beta‐300, which exhibits the lowest acidity and largest crystal size of Beta zeolite among the studied Pt‐ and Ir‐modified Beta zeolites. Complete conversion of isoeugenol and 89 % selectivity to propylcyclohexane was obtained with this catalyst in 240 min. The overall deoxygenation selectivity was 100 %, giving dialkylated cyclohexanes as the second major product. The catalyst was regenerated, reduced and reused in the hydrodeoxygenation of isoeugenol with almost the same performance as the fresh catalyst. Thermodynamic analyses and kinetic modelling of the data were also performed.

BACKGROUND: Stricter SO 2 emission regulations for power plants and maritime transport encourage a better understanding of the phenomena involved in wet flue gas desulfurization (WFGD) where limestone dissolution is regarded as one of the rate determining steps.

In this paper, estimation of the chemical composition of used oils collected from several European locations was performed on the basis of a comparative analysis of chemical composition of commercially available fresh and used motor oils. Although the motor oil undergoes a range of chemical and physical transformations during routine engine operations, information about the structure of hydrocarbons in the fresh oil allows for an estimation of the approximate ratio of different types of hydrocarbons in the same oil after its use. As an example, a particular type of fresh oil was used in the engine and then reanalyzed by the same analytical techniques. Gas chromatography–mass spectrometry (GC–MS), Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and elemental analysis (CHNS/O analysis) were used to characterize the chemical composition of the oil samples. A comparison of the obtained results showed correlations between chemical properties of the fresh oil and the collected used oil. Both oil FTIR spectra exhibited the bands that are related to the presence of carbonyl groups and amine-containing compounds, respectively. Opposite from the fresh oil, phenols were not found in the used oil. According to the obtained 1H NMR spectra, the paraffinic hydrocarbons of the fresh oil are more linear and have longer chains than those in the used oil.