High-performance phosphate supported on HZSM-5 catalyst for dehydration of glycerol to acrolein

Green synthesis of solketal from glycerol using metal-modified ZSM-5 zeolite catalysts: process optimization

This study investigates the production of solketal (2,2-dimethyl-1,3-dioxolane-4-methanol) from glycerol via ketalization reaction using M-ZSM-5 catalysts (M = Fe, Co, Ni, Cu, and Zn). The wet impregnation method ensured precise metal loading and versatility in catalyst preparation. We present a novel approach by employing a suite of characterization techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), Thermogravimetric analysis (TGA), and Field-emission scanning electron microscopy (FE-SEM), to elucidate the catalyst's structure, bonding, surface area, thermal stability, and morphology, ultimately linking these properties to their performance. Solketal synthesis was optimized in a reactor, with parameters like temperature, glycerol:acetone molar ratio, catalyst amount, reaction time, and stirring speed. Optimal conditions were identified as 60 °C, 1:4, 0.2 g, 60 min, and 1200 rpm, respectively. Gas chromatography-mass spectrometry (GC-MS) analysis confirmed successful solketal formation. Among M-ZSM-5 catalysts tested, Cu-ZSM-5 emerged the most efficient, achieving an impressive 99% glycerol conversion and 96% solketal selectivity. Notably, Cu-ZSM-5 catalyst displayed exceptional reusability, regaining its initial activity through calcination, thus minimizing waste generation. This research unveils Cu-ZSM-5 as a highly efficient catalyst and promotes sustainability by utilizing a renewable glycerol feedstock to produce valuable solketal with applications in fuel additives, solvents, and pharmaceuticals. This work paves the way for developing environmentally friendly processes for waste valorization and producing valuable bio-based chemicals.

Amphiphilic HZSM-5 for Cyclopentene Hydration at the Liquid-Liquid Interface in Pickering Emulsion

Zeolite is considered an ideal catalyst for olefin hydration due to its high specific surface area and abundant acid sites. However, the immiscibility of the water-oil two phases in olefin hydration limits mass transfer, and the side reaction of etherification occurs acutely, resulting in a low yield of alcohol. Thus, water-oil amphiphilic HZSM-5 was prepared by sulfonating silanized zeolite. The successful introduction of organic and sulfonic acid groups is demonstrated by FT-IR, TG, and water contact angles. Amphiphilic HZSM-5 can stabilize the Pickering emulsion and catalyze cyclopentene hydration at the phase interface. In addition, NH3-TPD and Py-IR show that the amount of strong Bro̷nsted acid sites of zeolites increases significantly after sulfonation. This facilitates the rate-determining step of cyclopentene activation by H+ to form carbocation. Moreover, the nucleophilic side reactions are inhibited by a high concentration of H+. Finally, under the optimized reaction condition, the conversion of cyclopentene can achieve 5.066% with a selectivity of 85.37% to cyclopentanol, which almost reaches the reaction equilibrium.

An overview on the conversion of glycerol to value-added industrial products via chemical and biochemical routes

Glycerol is a common by-product of industrial biodiesel syntheses. Due to its properties, availability, and versatility, residual glycerol can be used as a raw material in the production of high value-added industrial inputs and outputs. In particular, products like hydrogen, propylene glycol, acrolein, epichlorohydrin, dioxalane and dioxane, glycerol carbonate, n-butanol, citric acid, ethanol, butanol, propionic acid, (mono-, di-, and triacylglycerols), cynamoil esters, glycerol acetate, benzoic acid, and other applications. In this context, the present study presents a critical evaluation of the innovative technologies based on the use of residual glycerol in different industries, including the pharmaceutical, textile, food, cosmetic, and energy sectors. Chemical and biochemical catalysts in the transformation of residual glycerol are explored, along with the factors to be considered regarding the choice of catalyst route used in the conversion process, aiming at improving the production of these industrial products.

Glycerol Dehydration to Acrolein over Supported Vanadyl Orthophosphates Catalysts

Biodiesel has been identified as one of the notable options for at least complementing conventional fuels. From a transesterification reaction, crude glycerol is produced as the main by-product. Given the difficultly in upgrading to high-grade glycerin and glycerol market saturation, alternative routes to more value-added products have aroused significant interest. In this work, we proposed supported vanadyl orthophosphates (VOP) as catalysts for the glycerol dehydration to acrolein. VOP supported on γ-Al2O3, TiO2, and ZrO2 were prepared, characterized by inductively coupled plasma mass spectrometry (ICP-MS), X-ray diffraction (XRD), N2 physisorption and temperature-programmed desorption of ammonia (NH3-TPD), and tested under different operating conditions. All the samples showed low coke formation in the presence of molecular oxygen in the feed. Acrolein is the main condensable product, with carbon balance being satisfactory under most operating conditions. VOP supported onto alumina provided the best catalytic performance, due to a good balance between the acid (weak and medium acid sites) and redox sites, thereby appearing as a good candidate for glycerol dehydration to acrolein.

Effect of synthesis pH on the structure and catalytic properties of FeMo catalysts

The effect of pH on polynuclear molybdenum species (isopolymolybdates) synthesis was investigated by Raman spectroscopy. As the pH decreased from 6.0 to 1.0, the main isopolymolybdates changed from MoO4 2- to Mo7O24 6- to Mo8O24 6- to Mo36O116 8-. They began to aggregate and their solubility decreased with decreasing pH. The FeMo catalysts comprised particle- and plate-like structures, which were Fe2(MoO4)3 and MoO3, respectively. When a low pH value was used in the catalyst preparation, there was severe aggregation of the particles which have a high Mo/Fe mole ratio and Mo enrichment on the surface layer, which decreased the activity and selectivity of the FeMo catalyst.