Selective Hydrolysis of Arabinogalactan into Arabinose and Galactose Over Heterogeneous Catalysts

Abstract  

The application of solid acid catalysts for the production of monomers from hemicelluloses can be one of the key steps in developing the concept of an integrated forest biorefinery. Arabinogalactans (AG) are hemicelluloses which can be extracted on an industrial scale from larch wood species and has a great potential as a sustainable feedstock for bio-based products. Hydrolysis of AG to monomers over acidic heterogeneous catalysts (Smopex-101 and Amberlyst 15) was successfully demonstrated for the first time to selectively produce arabinose as the primary product, followed by the release of galactose without further degradation of the monomers.     

Praxisnahe Bestimmung von Wärmeübergangskoeffizienten an Körpern unterschiedlicher Geometrie

A simple method is presented by which the mean heat transfer coefficient at arbitrary geometries in a steady flow field can be determined. It is based on the measurement of the time dependent temperature and an evaluation that takes into account the conservation of thermal energy. For spheres of various sizes the method is exemplified demonstrating that the results agree well with those from the heat transfer literature.     

Raman spectra of high‐density,low‐density,and linear low‐density polyethylene pellets and prediction of their physical properties by multivariate data analysis

Raman spectra have been measured for pellets of five samples of high‐density polyethylene (HDPE), seven samples of low‐density polyethylene (LDPE), and six samples of linear low‐density polyethylene (LLDPE). The obtained Raman spectra have been compared to find out characteristic Raman bands of HDPE, LDPE, and LLDPE. Principal component analysis (PCA) was applied to the Raman spectra in the 1600–650 cm^?1 region after multiplicative scatter correction (MSC) to discriminate the Raman spectra of the three different PE species. They are classified into three groups by a score plot of PCA factor 1 vs. 2. HDPE with high density and high crystallinity gives high scores on the factor 1 axis, while LDPE with low density and low crystallinity yields negative scores on the same axis. It seems that factor 1 reflects the density or crystallinity. A PC weight loadings plot for factor 1 shows six upward peaks corresponding to the bands arising from the crystalline parts or all‐trans ? (CH₂)_n? groups and seven downward peaks ascribed to the bands of the amorphous or anisotropic regions and those arising from the short branches. Partial least‐squares (PLS‐1) regression was applied to the Raman spectra after MSC to propose calibration models that predict the density, crystallinity, and melting points of the polyethylenes. The correlation coefficient was calculated to be 0.9941, 0.9800, and 0.9709 for the density, crystallinity, and melting point, respectively, and their root‐mean‐square error of cross validation (RMSECV) was found to be 0.0015, 3.3707, and 2.3745, respectively. The loadings plot of factor 2 for the prediction of melting point is largely different from those for the prediction of density and crystallinity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 443–448, 2002     

Rapid detection of vegetable oils in milk fat by on‐line LC‐GC analysis of β‐sitosterol as marker

On‐line liquid chromatography‐gas chromatography (LC‐GC) has been applied to the detection of vegetable oils in milk fat using β‐sitosterol as marker. The method involves transesterification of the fat, pre‐separation of the sterol fraction from other lipid constituents and on‐line transfer to the capillary GC system. The on‐line approach avoids time‐consuming sample preparation steps prior to GC analysis. The suitability of this analytical approach was tested with model mixtures of milk fat with cotton and rapeseed oil. The method allows the detection of adulterations at low levels. Simultaneous quantification of cholesterol in milk fat is also possible. Considering the rapid sample preparation, the described method can be applied for screening of large sample numbers.     

Syntheses and reactions of urethanes of cellobiose and cellulose-containing uretdione groups

Urethanes of cellobiose and cellulose-containing uretdione groups are synthesized by the reaction of aliphatic and aromatic diisocyanate uretdiones with the saccharides. The syntheses are performed as a heterogeneous reaction in dimethyl acetamide using dibutyl tin dilaurate as a catalyst, as well as a homogeneous reaction in dimethyl acetamide-lithium chloride. Thus, Semisynthetic prepolymers are formed that offer the reactivity of (blocked) isocyanate groups. To demonstrate their reactivity, ring opening of the uretdiones is performed by the addition of a secondary amine to yield the corresponding ureas.     

Improved thin film stability of differently formulated,printed, and crosslinked polymer layers against successive solvent printing

Interface control remains a top challenge of solution-processed organic light emitting diodes (OLED) stacks since the device performance heavily relies on it. Film stability of an inkjet deposited and crosslinked layer against subsequent exposure to a suitable inkjet printed solvent has been investigated. Impact of processing solvent (solvent used to prepare the polymer layer) on solution-cast thin film properties has already been shown for polymer films. To our knowledge, this study is the first one analyzing thin films stability against solvent exposure using technology relevant materials processed via inkjet printing (IJP). The outcome of this research showed that the stability of the crosslinked films is affected by the solvent used for ink formulation. These findings are of great interest for multilayered semiconductors devices, such as OLEDs, field-effect transistors and dye-sensitized solar cells. Differential scanning calorimetry (DSC) was used to quantify the efficiency of the polymer crosslinking reaction in pure powder and in thin films, as processed from different solvents. Crosslinking efficiency measured by DSC correlated well with the deformation induced by the solvent and observed on layer surfaces. The interaction in solution between polymer and solvent has also been evaluated to explain its impact on thin film stability against successive solvent printing. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48895.     

Phase separation of a hafnium alkoxide-modified polysilazane upon polymer-to-ceramic transformation—A case study

The polymer-to-ceramic transformation of a hafnium alkoxide-modified polysilazane was investigated via thermogravimetric analysis coupled with in situ mass spectrometry (TG/MS), nuclear magnetic resonance (MAS NMR) and transmission electron microscopy (TEM). The results indicate that the structural evolution of the polysilazane upon ceramization is strongly affected by the modification with hafnium alkoxide. Thus, the content of carbon in the ceramic backbone was relatively low, whereas a large amount of SiN₄ sites and a segregated carbon phase was present in the sample. Furthermore, this study revealed the formation of a SiHfCNO amorphous single phase ceramic via pyrolysis of the polymer at 700 °C, whereas at higher pyrolysis temperatures precipitation of hafnia was observed, leading to an amorphous hafnia/silicon carbonitride ceramic nanocomposite. The precipitation of hafnia was shown to not rely on decomposition processes, but to be a result of rearrangement reactions occurring within the ceramic material.     

An experimental investigation on the influence of phenol on the solubility of CO2 in aqueous solutions of NaOH

Experimental results are presented for the solubility of CO₂ in an aqueous solution of phenol and NaOH (molalties in water: phenol: 0.5; NaOH: 1.0) at (314, 354, and 395) K and pressures up to 10 MPa. The experimental work extends recent investigations on the influence of phenol as well as of (phenol + NaCl) on the solubility of CO₂ in water. In contrast to those previous investigations, the strong electrolyte reacts with carbon dioxide and also with phenol. The experimental results are compared with predictions from a thermodynamic model. That model combines a model for the “chemical” solubility of CO₂ in aqueous solutions of NaOH with a model for the “physical” solubility of CO₂ in aqueous solutions of phenol. An extension is introduced to account for the chemical reaction between the weak acid phenol and the strong base sodium hydroxide. The prediction results nicely agree with the new experimental data. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2832–2840, 2015