The gas holdup in a multiphase reciprocating plate column filled with carboxymethylcellulose solutions

Gas holdup was investigated in a gas–liquid and gas–liquid-solid reciprocating plate column (RPC) under various operation conditions. Aqueous carboxymethylcellulose (sodium salt, CMC) solutions were used as the liquid phase, the solid phase was spheres placed into interplate spaces, and the gas plase was air. The gas holdup in the RPC was influenced by: the vibration intensity, i.e., the power consumption, the superficial gas velocity, the solids content and the rheological properties of the liquid phase. The gas holdup increased with increasing vibration intensity and superficial gas velocity in both the two- and three-phase system. With increasing concentration of the CMC PP 50 solution (Newtonian fluid), the gas holdup decreased, because the coalescence of the bubbles was favored by the higher liquid viscosity. In the case of the CMC PP 200 solutions (non-Newtonian liquids), the gas holdup depends on the combined influence of the rheological properties of the liquid phase, the vibration intensity and the superficial gas velocity. The gas holdup in the three-phase systems was greater than that in the two-phase ones under the same operating conditions. Increasing the solids content has little influence on the gas holdup. The gas holdup was correlated with the power consumption (either the time-averaged or total power consuption) and the superficial gas velocity

Transesterification of used cooking sunflower oil catalyzed by hazelnut shell ash

Hazelnut shell ash was investigated as a new base catalyst for the transesterification of used cooking sunflower oil to biodiesel. To understand its catalytic properties, the prepared ash was characterized by EDX, XRD, TGA/DTA, Hg porosimetry, N-2 physisorption, FE-SEM, and basic strength measurements. The effects of the catalyst loading in the range of 1-5% of the oil weight and the methanol-to-oil molar ratio of 6:1-18:1 on the kinetics of the fatty acid methyl esters synthesis were established. Moreover, the leaching and reusability of the catalyst were assessed. The obtained results revealed that hazelnut shell ash was mostly composed of K, Ca, and Mg. The highest ester content (98%) was achieved at the catalyst loading of 5%, the methanol-to-oil molar ratio of 12:1, and the reaction time of 10 min. The contribution of homogeneous catalysis because of the catalyst leaching was confirmed but did not determine the overall reaction rate. The catalyst can be reused after the recalcination at 800 degrees C for 2 h achieving the high methyl esters content (>96%) in 30 min after three subsequent runs. The overall reaction followed the pseudo-first-order kinetics with respect to triacylglycerols. A linear relationship between the apparent reaction rate constant and the catalyst loading and the methanol-to-oil molar ratio was determined. The determined value of the reaction rate constant was 0.0576 dm(6)/(min.mol(2))