Acetylation of glycerol over bimetallic Ag–Cu doped rice husk silica based biomass catalyst for bio-fuel additives application

Comparative Surface Study of Ru/Cu- and Ag/Cu-Doped RHS Catalysts from Waste Biomass for Biofuel Application

The present study compares the surface, textural, and catalytic properties of porous silica doped with bimetallic metal ions that was made from rice husk (RH) biomass. Due to the use of a surfactant during the synthesis process, porous RH-silica (RHS) was derived. In situ doping of silver/copper and ruthenium/copper has been achieved via the xerogel and hydrogel formation methods. The prepared catalysts have been analyzed by various methods, such as surface area and narrow pore size distribution, to confirm their porosity. Powder X-ray diffraction, Fourier transform infrared, and electron microscopy examination were further performed for physicochemical characterization of the synthesized materials. Transmission electron microscopy images showed that ruthenium and copper ions were incorporated perfectly, forming a hexagonal mesoporous (MCM-41) texture due to hydrogel formation and the method of preparation. Copper oxide nanoparticles with silver incorporation in RHS form cube-shaped particles for CuO formation on the surface of the silica matrix instead due to the method of preparation. In this case, ruthenium/copper-doped porous silica forms hexagon-shaped particles of RuO formation in the mesoporous matrix. Finally, the acetylation of glycerol using acetic acid on as-prepared catalysts has been studied. The catalytic activity increases with an increase in temperature and optimization of the molar ratio of glycerol and acetic acid. Increases in temperature result in higher selectivity toward triacetin formation instead of the conventional formation of monoacetin. Hence, we compared the surface physicochemical properties, catalytic conversion, and selectivity nature of bimetallic metal (Ru/Cu and Ag/Cu) ions incorporated in RHS prepared by different synthetic routes.

Effect of Basic Promoters on Porous Supported Alumina Catalysts for Acetins Production

A facile strategy for the design of porous supports was obtained by modifying the sol-gel method followed by the wet impregnation technique. In this respect, herein, the acidity of the γ-Al2O3 phase was modulated by adding basic MgO, La2O3 or ZnO promoters to form binary supported catalysts. The Ni and Co dispersion on the supports associated with their tunable acidity and morphologies resulted in highly porous supported alumina-based catalysts. The physicochemical properties of the solids were comprehensively investigated by XRD, textural properties, Raman and FTIR spectroscopy, SEM-EDS, TEM, EPR and XPS analyses. The catalytic performances in the esterification of glycerol in the presence of acetic acid (EG) for the acetins production were evaluated. The highly dispersed NiO and Co3O4 active species on binary porous supports produced synergistic effects appearing to be the reason for the activity of the solids in the EG reaction. Under the optimized reaction conditions, NiCo/MgO-Al2O3 was found to be a robust solid with superior catalytic performance and improved stability in four reaction cycles with 65.0% of glycerol conversion with an exclusive selectivity of 53% for triacetin. The presence of Co2+/Co3+ and Ni2+ strongly interacting with the spinel γ-Al2O3 and MgAl2O4 phases, the latter having a large number of lattice oxygen species, was considered another active component besides those of Ni and Co in the esterification of glycerol.

Current Trends in Acetins Production: Green versus Non-Green Synthesis

To utilize excess glycerol produced from the biodiesel industry, researchers are developing innovative methods of transforming glycerol into value-added chemicals. One strategy adopted is the conversion of glycerol into acetins, which are esters of glycerol that have wide applications in cosmetics, pharmaceuticals, food and fuel additives, and plasticizers and serve as precursors for other chemical compounds. Acetins are synthesized either by traditional chemical methods or by biological processes. Although the chemical methods are efficient, productive, and commercialized, they are "non-green", meaning that they are unsafe for the environment and consumers. On the other hand, the biological process is "green" in the sense that it protects both the environment and consumers. It is, however, less productive and requires further effort to achieve commercialization. Thus, both methodologies have benefits and drawbacks, and this study aims to present and discuss these. In addition, we briefly discuss general strategies for optimizing biological processes that could apply to acetins production on an industrial scale.

Assessment on the Effect of Sulfuric Acid Concentration on Physicochemical Properties of Sulfated-Titania Catalyst and Glycerol Acetylation Performance

In this research, a solid acid catalyst was synthesized to catalyse glycerol acetylation into acetins. The sulphated-titania catalysts were prepared via the wet impregnation method at different sulfuric acid concentrations (5%, 10%, 15%, and 20%) and denoted as 5SA, 10SA, 15SA, and 20SA, respectively. The synthesized catalysts were characterized using FTIR, XRD, TGA, BET, NH3-TPD, XRF, and SEM-EDX. The synthesized catalysts were tested on glycerol acetylation reaction at conditions: 0.5 g catalyst loading, 100–120 °C temperature, 1:6 glycerol/acetic acid molar ratios, and 2–4 h reaction time. The final product obtained was analysed using GC-FID. An increment in sulfuric acid concentration reduces the surface area, pore volume, and particles size. However, the increment has increased the number of active sites (Lewis acid) and strong acid strength. 15SA catalyst exhibited excellent glycerol conversion (>90%) and the highest selectivity of triacetin (42%). Besides sufficient surface area (1.9 m2 g−1) and good porosity structure, the great performance of the 15SA catalyst was attributed to its high acid site density (342.6 µmol g−1) and the high active site of metal oxide (95%).

Producción de acetinas (aditivos para combustibles) a partir de glicerol

La elevada producción de glicerol, un subproducto de bajo costo proveniente de la industria del biodiésel, ha supuesto una amenaza tanto para el medio ambiente como para la economía. La transformación de glicerol en productos de valor agregado contribuiría positivamente a la economía del biodiésel. En este artículo de revisión se describen las rutas de valorización del glicerol y se presenta la esterificación como una de las más prometedoras para la transformación de glicerol en aditivos para combustibles; igualmente, se describen los resultados más relevantes entre 2010 y 2020 relacionados con las condiciones experimentales (temperatura, relación molar y tiempo de reacción), los catalizadores heterogéneos y la actividad catalítica (en términos de la conversión del glicerol y la selectividad) para la transformación de glicerol en acetinas (monoacetina, diacetina y triacetina). Se espera que esta revisión permita abordar esta técnica de valorización de manera rentable y ambientalmente sostenible.

Influence of Heterogeneous Catalysts and Reaction Parameters on the Acetylation of Glycerol to Acetin: A Review

Glycerol, a polyhydric alcohol, is currently receiving greater attention worldwide in view of its glut in the market occasioned by the recent upsurge in biodiesel production. The acetylation of glycerol to acetin (acetyl glycerol) is one of the many pathways of upgrading glycerol to fine chemicals. Acetin, which could be mono, di, and or triacetin, has versatile applications in the cosmetics, medicines, food, polymer, and fuel industries as a humectant, emulsifier, plasticizer, and fuel additive and so it is of high economic value. Given the critical role of catalysts in green chemistry, this paper reports the influence of the different heterogeneous catalysts used in glycerol acetylation. It also reviewed the influence of catalyst load, temperature, molar ratio, and the time on the reaction.

Single-pot template-free synthesis of a glycerol-derived C–Si–Zr mesoporous composite catalyst for fuel additive production

The C–Si–Zr material synthesized from bio-derived waste glycerol, ZrO(NO₃)₂ and TEOS exhibits excellent catalytic activity for tri-acetin production from low-value glycerol.