RESUMO
Hydrodeoxygenation (HDO) kinetics of glycerol into 1,2-propanediol (1,2-PDO) in the liquid phase is studied on Cu-Pd/TiO2 catalysts. At a stirring speed higher than 480 rpm and an average diameter of the catalyst particles smaller than 89.5 µm, no mass transfer resistance artifacts are observed. The increasing temperature and H2 concentration promote the glycerol conversion and the selectivity to 1,2-PDO and disfavor the selectivity to acetol. Based on the experimental data, empirical kinetic pseudo-homogeneous expressions are proposed for glycerol disappearance, 1,2-PDO formation, and acetol formation in the catalytic system. Dependence of the disappearance rate of glycerol is closer to 1 with respect to glycerol and nonmeaningful with respect to H2. The formation rate of 1,2-PDO is not highly dependent on the initial concentration of glycerol or H2, and the formation rate of acetol is directly dependent on glycerol and inversely dependent on H2, since it accelerates acetol conversion to 1,2-PDO. The activation energies for glycerol disappearance (77.8 kJ/mol), 1,2-PDO formation (51.2 kJ/mol), and acetol formation (84.6 kJ/mol) evidenced the selective formation of 1,2-PDO in this catalytic system.
RESUMO
Chitin is an aminopolysaccharide of industrial interest commonly obtained from shrimp processing waste through chemical or biotechnological means. Current environmental concerns offer a stimulating perspective for chitin bioextraction with lactic acid bacteria since a considerable reduction in the use of corrosive and pollutant products is possible. Nevertheless, the efficiency of this bioprocess is still a matter of discussion. In this work, the experimental studies of chitin bioextraction from Pacific white shrimp (Litopenaeus vannamei) waste with a mixed culture of Lactobacillus plantarum, Lactobacillus bulgaricus and Streptococcus thermophilus are used in process simulation using Aspen Plus software for the analysis of the potential application of a bioprocess on plant scale. The experimental results of characterization in shake flasks and 1-litre bioreactor indicated that 50 h of fermentation with the mixed culture of lactic acid bacteria was enough to extract more than 90% of minerals and proteins from the shrimp waste. The use of experimental parameters in the simulation allowed a reliable representation of the bioprocess yielding normalized root mean square values below 10%. Simulation was used for the assessment of the impact of the raw material variability on the production costs and gross margin. In this regard, the gross margin of the operation ranged from 42 to 52% depending on the raw material composition and product yield.
