Biomass allows us to obtain energy and high-value-added compounds through the use of different physical and chemical processes. The glycerol obtained as a by-product in the synthesis of biodiesel is considered a biomass compound that has the potential to be used as a raw material to obtain different chemical products for industry. The development and growth of the biodiesel industry allows for the projection of glycerol biorefineries around these plants that efficiently and sustainably integrate the biodiesel production process together with the glycerol transformation processes. This work presents a review of the ketalization and esterification of glycerol to obtain solketal and acetylglycerols, which are considered products of high added value for the chemical and fuel industry. First, the general aspects and mechanisms of both reactions are presented, as well as the related chemical equilibrium concepts. Subsequently, the catalysts employed are described, classifying them according to their catalytic nature (zeolites, carbons, exchange resins, etc.). The reaction conditions used are also described, and the best results for each catalytic system are presented. In addition, stability studies and the main deactivation mechanisms are discussed. Finally, the work presents the kinetic models that have been formulated to date for some of these systems. It is expected that this review work will serve as a tool for the advancement of studies on the ketalization and esterification reactions that allow for the projection of biorefineries based on glycerol as a raw material.

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.

Bentonites are natural clays found in abundance in deposits all over the planet and possess certain properties that make them interesting for various industrial applications. Through their activation or acid treatment, they can be used as catalysts in several reactions of interest. However, these materials form colloidal suspensions in water or in aqueous solutions, which makes their separation and recovery difficult and prevents their implementation on an industrial scale. To overcome these limitations, in the present work, a silica-resin-bentonite composite material was synthesized and activated with HNO₃. The activated solids were characterized and evaluated in the catalytic reaction of solketal synthesis from glycerol and acetone. The best results were obtained for a composite containing 47 wt.% acidified bentonite at 90 °C, with a HNO₃ concentration of 0.5 mol L⁻¹, which was attributed to both its acid site density—3.9 mmol per gram of bentonite—and the acidic strength of these sites.

Activated bentonites are low-cost acid catalysts used in several reactions. However, their application at an industrial scale is affected by the formation of colloidal suspensions when these bentonites are in aqueous solutions. In order to overcome these limitations, this work proposes obtaining a catalyst based on a composite containing natural bentonite within a silica–resin structure, which allows separating and re-utilizing the catalyst more easily and without centrifugal filtration requirements. By means of characterization techniques, the present study determined that the activated bentonite composite presented a total specific surface area of ~360 m² g⁻¹, ~4 mmol of acid sites per gram of bentonite, and sites with strong acid strength, all of which bestowed activity and selectivity in the solketal synthesis reaction from glycerol and acetone, reaching equilibrium conversion within a short reaction time. Furthermore, the present work developed a Langmuir–Hinshelwood–Hougen–Watson kinetic model, achieving an activation energy of 50.3 ± 3.6 kJ mol⁻¹ and a pre-exponential factor of 6.4 × 10⁶ mol g⁻¹ L⁻¹ s⁻¹, which are necessary for reactor design.

The aim of this work was to develop a kinetic model based on the power law to describe the evolution of glycerol conversion and product distribution in the crude glycerol (G) acetylation reaction with acetic acid (AA) without the use of a catalyst. For this purpose, experimental tests were carried out with analytical glycerol under different reaction conditions (T = 80–160 °C, AA/G = 1–9 molar ratio, t = 0.25–2 h). The results showed the formation of mono- (MAG), di- (DAG) and tri- (TAG) acetylglycerols, liquid products with multiple applications in the chemical industry. From these results, a kinetic model based on the power law was implemented, which could acceptably estimate the experimental concentrations with an average relative error of 14.9%. Then, crude glycerol samples from different biodiesel industries were characterized by identifying and quantifying the impurities present in them (H₂O, CH₃OH, NaOH, NaCOOH, MONG and NaCl), and employed as reactants in the reaction tests. Given the significant differences observed in the glycerol conversion values compared to those obtained with analytical glycerol, further reaction tests were conducted to elucidate the effect of each impurity over the glycerol conversion. In these tests, the different impurities were added individually, maintaining the same concentration range as that of the crude glycerol samples. From the results obtained, global activity factors were introduced, which allowed us to modify the kinetic model to estimate glycerol conversions in the crude glycerol samples with an average relative error of 7%. It is hoped that this kinetic model will be a powerful tool useful for designing reactors on an industrial scale.