Preparation and Uses of Chlorinated Glycerol Derivatives

Heterogeneous Catalysts for Glycerol Biorefineries: Hydrogenolysis to 1,2-Propylene Glycol

Research on the use of biomass resources for the generation of energy and chemical compounds is of great interest worldwide. The development and growth of the biodiesel industry has led to a parallel market for the supply of glycerol, its main by-product. Its wide availability and relatively low cost as a raw material make glycerol a basic component for obtaining various chemical products and allows for the development of a biorefinery around biodiesel plants, through the technological integration of different production processes. This work proposes a review of one of the reactions of interest in the biorefinery environment: the hydrogenolysis of glycerol to 1,2-propylene glycol. The article reviews more than 300 references, covering literature from about 20 years, focusing on the heterogeneous catalysts used for the production of glycol. In this sense, from about 175 catalysts, between bulk and supported ones, were revised and discussed critically, based on noble metals, such as Ru, Pt, Pd, and non-noble metals as Cu, Ni, Co, both in liquid (2-10 MPa, 120-260 °C) and vapor phase (0.1 MPa, 200-300 °C). Then, the effect of the main operational and decision variables, such as temperature, pressure, catalyst/glycerol mass ratio, space velocity, and H₂ flow, are discussed, depending on the reactors employed. Finally, the formulation of several kinetic models and stability studies are presented, discussing the main deactivation mechanisms of the catalytic systems such as coking, leaching, and sintering, and the presence of impurities in the glycerol feed. It is expected that this work will serve as a tool for the development of more efficient catalytic materials and processes towards the future projection of glycerol biorefineries.

Preparation and Optical Properties of Compound Nanopowder Art Ceramics

The fluorescent glass of white LEDs has high physical and chemical stabilities, good heat dissipation performance, and can maintain an excellent performance of fluorescent powder itself. In order to realize luminescent materials such as white LED lighting, laser lighting, and long-term lighting, this study proposes the preparation of a compound nanopowder art ceramic and its optical properties. In order to play the role of nanoparticles in optoelectronic or photonic devices, it is necessary to explore the preparation process and performance research of dielectric ceramics. This study uses high-purity aluminate (MgAl2O4) powder for transparent ceramics, doped with yellow nanophosphor as raw materials, through a sintering process in oxygen atmosphere, sintering combined with heat treatment, and isostatic pressing to prepare transparent ceramics. The ceramic sample is placed in a high-temperature and high-pressure environment for heat and other static pressure, and fluorescent samples are obtained. The results show that under 350 mA driving current, high-power white LEDs in the fluorescent ceramic package have almost no attenuation after 700 h, and the average attenuation of the LED package of the phosphor package is about 10%. The use of fluorescent ceramics can be packaged not only to improve the LED device's light efficiency but also to increase the life of the white LED device.

Perspectives for the Upgrading of Bio-Based Vicinal Diols within the Developing European Bioeconomy

The previous decade has witnessed a drastic increase of European incentives aimed at pushing forward the transition from an exclusively petro-based economy toward a strong and homogeneous bio-based economy. Since 2012, numerous programs have been developed to stimulate and promote research and innovation relying on sustainable and renewable resources. Terrestrial biomass is a virtually infinite reservoir of biomacromolecules, the biorefining of which provides platform molecules of low complexity yet with tremendous industrial potential. Among such bio-based platform molecules, polyols and, more specifically, molecules featuring vicinal diols have gained tremendous interest and have stimulated an increasing research effort from the chemistry and chemical engineering communities. This Review revolves around the most promising process conditions and technologies reported since 2012 that specifically target bio-based vicinal diols and promote their transformation into value-added molecules of wide industrial interest, such as olefins, epoxides, cyclic carbonates, and ketals.

Mechanistic Kinetic Modelling Framework for the Conversion of Waste Crude Glycerol to Value-Added Hydrogen-Rich Gas

The kinetics for crude glycerol autothermal reforming was studied over S/C ratio of 2.6 and O2/C ratio of 0.125 using 5% Ni/CeZrCa catalyst. Both power law and mechanistic kinetic models were studied. The overall power law model for crude glycerol autothermal reforming was investigated with a pre-exponential factor of 4.3 × 1010 mol/gcat.min and activation energy of 8.78 × 104 J/mol. The reaction orders with respect to crude glycerol, water and oxygen are 1.04, 0.54 and 1.78 respectively. The power law model presented an absolute average deviation of 5.84%, which showed a good correlation between the predicted and experimental rate. Mechanistic models were developed for crude glycerol autothermal reforming. For steam reforming, the Eley–Rideal approach best described the reaction rate with the surface reaction being the rate-determining step (AAD < 10%). The kinetics of the total oxidation reaction was best described by the power law model with an AAD of less than 1%, whereas for the TOR process, the molecular adsorption of crude glycerol with an AAD of 14.6% via Langmuir Hinshelwood Hougen-Watson approach was best. CO2 methanation resulted in an AAD of 5.8% for the adsorption of carbon dioxide (CO2) by the Eley–Rideal mechanism.

Effect of Novel Deep Eutectic Solvents on the Endo/Exo Ratio of Diels-Alder Reactions at Room Temperature

The Diels-Alder reaction is a prototypical example of a thermally allowed [4 + 2] cycloaddition with good control over the regio- and stereochemical outcomes. Therefore, Diels-Alder reactions in which adjacent stereocenters are generated at the two ends of the newly formed single bonds imply two different possible stereochemical outcomes. In cases where the dienophile has a single electron-withdrawing substituent, the outcome can often be predicted by applying the known "endo rule". Furthermore, the use of chiral eutectic solvents in asymmetric synthesis has become a novel tool to maintain sustainability in organic synthesis. In the present work, a set of recyclable and sustainable bio-based deep eutectic solvents (DESs) was designed using hydrogen bond acceptors (HBAs) with a chiral center. These compounds were used in their racemic and enantiomerically enriched forms to prepare DESs with lactic acid (LA), glycerol (Gly), and ethylene glycol, which act as hydrogen bond donors (HBDs) in the corresponding eutectic mixture. These DESs were used as solvents to study the reaction between cyclopentadiene and ethyl acrylate or butyl acrylate in typical [4 + 2] cycloadditions. The best yields and endo-selectivity were achieved using LA as the HBD in the eutectic mixtures. The results and adduct ratios obtained show that these DESs were able to improve both reaction yields and selectivity when compared to those observed in organic solvents or ionic liquids. Moreover, the reaction products (adducts) were easily recovered with diethyl ether from the reaction mixture, where they appeared as an upper layer.