Methane OSR over Pt-Ni/δ-Al2O3: Performance and power law type kinetics

Methane oxidative steam reforming (OSR) performance of two bimetallic Pt-Ni/δ-Al₂O₃ catalysts, having Pt:Ni loadings, 0.2:10 and 0.3:10, were tested first. In the tests, residence time (W/F), carbon-to-oxygen (C/O₂) feed ratio, and temperature were used as the experimental parameters. Increase in temperature resulted in direct and indirect - through enhanced TOX yielding higher energy - increase in SR rate. As Pt:Ni metal loading ratio did not lead to significant changes in activity, the preliminary kinetic tests to determine merely kinetically controlled region were conducted over 0.2Pt-10Ni catalyst. Considering the outcomes of the preliminary tests, the kinetic experiments were performed for practical reaction conditions extending up to 20% methane conversion with feed ratio intervals of 4.0 < C/O₂ < 7.34 and 2.03 < S/C < 3.08 at two different residence time (W/F) values to obtain a power-law type rate equation. Reaction orders were estimated as 0.81, 1.60 and 0.44 for methane, oxygen and steam, respectively, by using multivariable non-linear optimization function of MATLAB?. The apparent activation energy of methane OSR was calculated as 24.61 kJ mol^?1 and pre-exponential factor as 0.110 μmol mgcat^?1 s^?1 kPa^?2.85 for the 375–450 °C temperature interval. The same analysis performed for a narrower temperature range, 375–425 °C, gave k₀ and E_A values as 0.251 μmol mgcat^?1 s^?1 kPa^?2.85 and 29.17 kJ mol^?1, respectively, confirming the high sensitivity of OSR pathway to temperature.     

Volatile compounds and proteolysis in traditional Beaten (Bieno sirenje) ewe's milk cheese

Beaten ewe's milk cheese is a traditional autochthonous type of cheese manufactured in Macedonia with a relatively high nutritional value and sensory characteristics. The objective of this study was to characterise the gross composition, proteolysis and volatile profiles of the cheese that is supplied from different retails. The ranges for gross composition were from 31.53% to 42.83% (w/w) for moisture, 41.99% to 50.98% (w/w) for fat‐in‐dry matter, 2.03% to 8.25% (w/w) for salt content and 20.74% to 33.35% (w/w) for protein. Proteolysis results showed various levels of soluble nitrogen ranged from 3.15 to 33.50 for water‐soluble nitrogen (WSN) and from 1.11% to 6.79% for nitrogen soluble in 12% trichloroacetic acid (TCA‐SN). The ranges for total free amino acids were from 1.65 to 8.06 mg Leu/g. Lower proteolysis was observed in the cheese samples due to high salt contents. In total, 65 volatile compounds were identified in Beaten cheese. As a conclusion, the variation of the peptide profile, electrophoresis and volatile contents of Beaten cheeses are due to the lack of standardised manufacture protocols.