Green acetylation of solketal and glycerol formal by heterogeneous acid catalysts to form a biodiesel fuel additive

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.

A concise review of glycerol derivatives for use as fuel additives

Due to renewable fuel mandates worldwide, the increase in biodiesel production has caused an oversupply of low-cost glycerol on the markets, which can negatively affect the sustainability of the biodiesel industry as a whole. In order to avoid that scenario, the transformation of glycerol into value-added products has been investigated, and the production of additives for internal combustion engine fuels is one good example of glycerol valorization. The present work presents a summary of the literature describing the most important chemical pathways through which glycerol can be converted into fuel additives, to be subsequently mixed with either gasoline, biodiesel, or diesel fuel. The focus is on the three major categories, namely glycerol acetals/ketals, ethers, and esters (acetates). Moreover, the effectiveness of the different glycerol-derived compounds is illustrated through several examples from the literature. Finally, a few research gaps on the topic are identified and suggestions for future work are described.

Valorization of Solketal Synthesis from Sustainable Biodiesel Derived Glycerol Using Response Surface Methodology

Biodiesel production has gained considerable importance over the last few decades due to the increase in fossil fuel prices as well as toxic emissions of oxygen and nitrogen. The production of biodiesel via catalytic transesterification produces crude glycerol as a co-product along with biodiesel, amounting to 10% of the total biodiesel produced. Glycerol has a low value in its impure form, and the purification of glycerol requires sophisticated technologies and is an expensive process. The conversion of crude glycerol into value-added chemicals such as solketal is the best way to improve the sustainability of biodiesel synthesis using the transesterification reaction. Therefore, the conversion of crude glycerol into the solketal was investigated in a batch reactor simulation model developed by the Aspen Plus V11.0. The non-random two liquid theory (NRTL) method was used as a thermodynamic property package to study the effect of four input ketalization parameters. The model was validated with the findings of previous experimental studies of solketal synthesis using sulfuric acid as a catalyst. The influence of the following operating parameters was investigated: reaction time of 10,000 to 60,000 s, reaction temperature of 303 to 323 K, acetone to glycerol molar ratio of 2:1 to 10:1, and catalyst concentration of 0.005 to 0.03 wt %. The optimum solketal yield of 81.36% was obtained at the optimized conditions of 313 K, 9:1, 0.03 wt %, and 40,000 s. The effect of each input parameter on the ketalization process and interaction between input and output parameters was investigated by using the response surface methodology (RSM) optimizer. The relationship between independent and response variables developed by RSM fit most of the simulation data, which showed the accuracy of the model. A second-order differential equation fit the simulation data well and showed an R2 value of 0.99. According to the findings of RSM, the influence of catalyst amount, acetone to glycerol molar ratio, and reaction time were more significant on solketal yield. The effect of temperature on the performance of the reaction was not found to be significant because of the exothermic nature of the process. The findings of this study showed that biodiesel-derived glycerol can be effectively utilized to produce solketal, which can be used for a wider range of applications such as a fuel additive. However, further work is required to enhance the solketal yield by developing new heterogeneous catalysts so that the industrial implementation of its production can be made possible.

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.

Propylsulfonic Acid Functionalized SBA-15 Mesoporous Silica as Efficient Catalysts for the Acetalization of Glycerol

As the main by-product obtained from biomass, glycerol could be converted into valuable chemicals. Tunable propylsulfonic acid functionalized SBA-15 and KIT-6 with different structural parameters have been prepared by different methods while using 3-mercaptopropyltrimethoxysilane (MPTMS) as the source of sulfur. The composition and structure of the synthesized catalysts have been well-characterized by N2 adsorption-desorption (BET), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The catalytic performance of the prepared catalysts have been evaluated and compared in glycerol acetalization with formaldehyde to the mixture of 1,3-dioxane-5-ol and 1,3-dioxolane-4-methanol. Optimum reaction parameters were investigated to enhance the yield of products and control the distribution of glycerol formals. More than 90% yield of cyclic acetals were obtained with the ratio of two isomers 5R to 6R of 42:58.

Kinetics of Thermal Unimolecular Decomposition of Acetic Anhydride: An Integrated Deterministic and Stochastic Model

An integrated deterministic and stochastic model within the master equation/Rice-Ramsperger-Kassel-Marcus (ME/RRKM) framework was first used to characterize temperature- and pressure-dependent behaviors of thermal decomposition of acetic anhydride in a wide range of conditions (i.e., 300-1500 K and 0.001-100 atm). Particularly, using potential energy surface and molecular properties obtained from high-level electronic structure calculations at CCSD(T)/CBS, macroscopic thermodynamic properties and rate coefficients of the title reaction were derived with corrections for hindered internal rotation and tunneling treatments. Being in excellent agreement with the scattered experimental data, the results from deterministic and stochastic frameworks confirmed and complemented each other to reveal that the main decomposition pathway proceeds via a 6-membered-ring transition state with the 0 K barrier of 35.2 kcal·mol^-1. This observation was further understood and confirmed by the sensitivity analysis on the time-resolved species profiles and the derived rate coefficients with respect to the ab initio barriers. Such an agreement suggests the integrated model can be confidently used for a wide range of conditions as a powerful postfacto and predictive tool in detailed chemical kinetic modeling and simulation for the title reaction and thus can be extended to complex chemical reactions.

Bifurcated dissociative photoionization mechanism of acetic acid anhydride revealed by imaging photoelectron photoion coincidence spectroscopy

PEPICO allows us a peek beyond the transition state to identify bifurcated reaction pathways.