No abstract

Cationic starch ethers prepared by the chemical reaction of starch with a quaternary ammonium reagent are commercially important derivatives. Cationic potato starch derivatives were produced under pilot‐scale conditions, employing four different principles. Wet cationisation was carried out by the slurry and paste processes, in which the cationic reagent and catalyst are added to the starch. Besides being prepared by these more commonly used processes, cationic starches were also produced by dry cationisation and by adding the cationic reagent during extrusion of starch. The cationic reagent used was 2,3‐epoxypropyltrimethylammonium chloride. Derivatives with three graded degrees of substitution (DS) between 0.03 and 0.12 were prepared by each process. The physical properties of the derivatives were analysed by the following methods: polarised light microscopy, X‐ray scattering, differential scanning calorimetry (DSC), solubility and swelling behaviour, and High‐Performance Size‐Exclusion Chromatography‐Multiangle Laser Light Scattering (HPSEC‐MALLS). The degree of substitution was determined by high resolution 13C‐NMR spectroscopy after hydrolysis with trifluoroacetic acid.The properties of the cationic starch derivatives were highly dependent on the derivatisation method. The granular structure of the starch was not visibly affected by the slurry process. Products from the semi‐dry reaction showed some granular damage, which was particularly evident after suspension of the granules in water. In the paste and extrusion processes, the starch granules were completely destroyed. Swelling temperatures and enthalpies can be determined only for starch derivatives that still retain a granular structure. As a result, samples from the paste and extrusion reactions exhibited no swelling endotherm in DSC. The samples from the slurry process showed a shift in the swelling temperature range towards lower temperature and a decrease in swelling enthalpy both as compared to native potato starch and also with increasing DS. Similar behaviour was found for the samples from the semi‐dry process. The swelling temperature region was comparable to that of the slurry samples for the same DS but the swelling enthalpy was distinctly lower, indicating that the granular structure of the starch was altered far more by the semi‐dry than the slurry process. Swelling in excess water and solubility were affected primarily by the cationisation process, while the influence of DS was of minor importance. The extrusion products had pronounced cold‐water solubility, the semi‐dry products showed increasing cold‐water solubility with increasing DS, the paste products were highly swollen in cold water and the slurry products were insoluble in cold water. All products were soluble in hot water but the state of dissolution was different.The molar mass distributions of the samples were determined after dissolution by pressure cooking. The different derivatisation methods resulted in characteristic molar mass distributions. The average molar mass decreased in the order slurry, semi‐dry‐, paste and extrusion process.

Hydrothermal carbonization (HTC) of wheat straw digestate was performed at 180–260 °C for 2–8 h. The resulted hydrochars were analyzed by ultimate analyzer. Elemental carbon and oxygen concentration of hydrochars were fitted with power law correlation. Moreover, chemical structures of feedstocks and hydrochars were investigated by 13C cross-polarization magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR) spectroscopy. In particular, a procedure including CP dynamics analysis was applied to obtain semi-quantitative information on the composition of the analyzed materials from 13C CP/MAS spectra. Up to a process temperature of 220 °C, digestate-derived hydrochar contained primarily crystalline cellulose and lignin. At 260 °C, crystalline cellulose was degraded and more aliphatic carbon and lignin-rich hydrochars were produced. Ester bands corresponding to hemicellulose disappeared at mild HTC conditions at 180 °C and 2 h

This study describes a systematic characterization of lignin samples fractionated from industrial black liquor and an evaluation of their suitability as a component (50 wt.%) in thermoplastic blends with polyethylene with a special emphasis on tensile and impact properties. Industrial softwood kraft lignin was isolated from three different cooking stages and subsequently fractionated by sequential acid precipitation. Altogether, nine lignin fractions were subjected to several chemical/thermal analyses to compare their structural features and thermal decomposition properties. Lignin samples precipitated at pH 10.5 exhibited the highest molecular weight (M w) and purity, demonstrated by the lowest content of sulfur and polysaccharides. In contrast, samples precipitated at a low pH in general exhibited higher amount of impurities and low methoxyl group content. It was found that lignin precipitated at low pH contained the biggest share of sulfur present in kraft lignin. However, about 70 % of sulfur in these samples is present in non-bounded form and could be extracted with CS2. Additionally, low M w lignin exhibited a significantly lower T g value, which could favor material processing. A notable decrease in the thermal stability of the tested lignin samples was observed with a decrease in the molecular weight. In addition, lignin with a low M w, high phenolic hydroxyl groups, and lower number of double bonds seems to be favorable for increased tensile strength and elastic modulus of the polyethylene–lignin blend materials