In the present paper, the performance of monolithic catalysts
obtained
from a catalytic converter was analyzed in the partial hydrogenation
of sunflower oil. The monoliths were reimpregnated with palladium
and installed as a blade in a monolithic stirrer reactor. The use
of this type of reactor was explored in the reaction at 373 K and
413 kPa, analyzing the effect variables such as stirrer speed, hydrogen
supply, and stirrer design on the catalyst activity and selectivity
to trans-isomers and saturated product. The volumetric gas–liquid
and liquid–solid mass transfer coefficients were calculated,
and the influence of the stirrer speed was examined. Estimations of
the Carberry numbers and Weisz–Prater modulus were used for
establishing the presence or absence of mass transfer resistances.
The performance of the catalyst was studied in consecutive tests,
and different procedures for catalyst regeneration were applied.
Glycerol carbonate (GC) is a value-added product originating from the valorization of widely available glycerol (Gly), a side stream from the production of biodiesel. Here we approach the production of this chemical comparing two reactions based on the transesterification of Gly with dimethyl carbonate (DMC) and ethylene carbonate (EC). When using DMC, it was observed that the free enzyme CALB (lipase B from Candida antarctica) gave the best results, whereas Eversa Transform (a genetic modification of Thermomyces lanuginosus lipase) performed better than the rest if EC was the reagent. With the selected catalysts, their immobilized analogous enzymes Novozym 435 and Lypozyme TL IM, respectively, were also tested. Observing that the yields for the reaction with EC were significantly faster, other operating variables were evaluated, resulting the best performance using a closed system, tert-butanol as solvent, a concentration of enzyme Eversa Transform of 3% w/w, a molar excess of EC:Gly of 9:1 and a temperature of 60 °C. Finally, several runs were conducted at different temperatures and molar ratios of EC:Gly, fitting a kinetic model to all experimental data for the reaction catalyzed with Eversa Transform. This model included the bimolecular transesterification reaction of Gly and EC catalyzed by the lipase and a reversible ring-opening polymerization of EC.
Experimental and theoretical studies on the partial hydrogenation of vegetable oil in a monolithic stirrer reactor are reported. A complete mathematical model of the reactor was developed, including hydrogenation and isomerization kinetics, catalyst deactivation, external gas-liquid and liquid-solid as well as internal mass transfer. The experimental studies were carried out in a Pd/Al 2 O 3 /Al monolithic stirrer reactor, at a wide range of temperatures (353-373 K), pressures (414-552 kPa), and catalyst loadings (0.00084-0.00527 kg Pd,exp m 23 ). Based on this model, simulated data can be used to evaluate the catalyst (Pd/Al 2 O 3 /Al) and the hydrogenation process in consecutive catalytic tests under different operating conditions.
In
this work, natural sediment was used as an alternative and green
inorganic source to synthesize valuable structured Al-MCM-41 material
by a hydrothermal process. This intertidal sediment contains a mixture
of clay minerals (montmorillonite and ilite) and minerals (quartz
and feldspar) providing large SiO2 (∼64%) and Al2O3 (∼15%) content which were efficiently
extracted by alkaline fusion. The synthesized mesoporous material
was characterized by X-ray diffraction (XRD), scanning electron microscopy
(SEM), high-resolution transmission electron microscopy (HRTEM), diffuse
reflectance infrared Fourier transform spectroscopy (FT-IR), N2 physisorption, and 27Al solid-state magic angle
spinning nuclear magnetic resonance spectroscopy (27Al
MAS NMR). The results achieved reveal that pure and highly ordered
hexagonal mesoporous aluminosilicate MCM-41 containing structural
aluminum has been successfully synthesized. Moreover, it was evidenced
that the obtained solid presents uniform pore size distribution (3.6
Å) as well as high pore volume (0.59 cm3g–1) and elevated specific surface area (807 m2g–1).
The overall effectiveness factor for slab geometry applicable to uniform washcoats on a monolith surface for three-phase reaction systems was studied in the present work. Analytical solutions for zero-order reactions and Langmuir–Hinshelwood and power law kinetics were reported. The analysis of the theoretical results showed that not considering the geometry of the monolithic system in a proper way lead to 14% errors in reactions parameters when operating under mixed control (kinetic-internal diffusion) and negligible external mass-transfer resistances.
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