Shape-selective Valorization of Biomass-derived Glycolaldehyde using Tin-containing Zeolites

Synthesis and Catalytic Applications of Advanced Sn- and Zr-Zeolites Materials

The incorporation of isolated Sn (IV) and Zr (IV) ions into silica frameworks is attracting widespread attention, which exhibits remarkable catalytic performance (conversion, selectivity, and stability) in a broad range of reactions, especially in the field of biomass catalytic conversion. As a representative example, the conversion route of carbohydrates into valuable platform and commodity chemicals such as lactic acid and alkyl lactates, has already been established. The zeotype materials also possess water-tolerant ability and are capable to be served as promising heterogeneous catalysts for aqueous reactions. Therefore, dozens of Sn- and Zr-containing silica materials with various channel systems have been prepared successfully in the past decades, containing 8 membered rings (MR) small pore CHA zeolite, 10-MR medium pore zeolites (FER, MCM-56, MEL, MFI, MWW), 12-MR large pore zeolites (Beta, BEC, FAU, MOR, MSE, MTW), and 14-MR extra-large pore UTL zeolite. This review about Sn- and Zr-containing metallosilicate materials focuses on their synthesis strategy, catalytic applications for diverse reactions, and the effect of zeolite characteristics on their catalytic performances.

Production of Methyl Lactate with Sn-USY and Sn-β: Insights into Real Hemicellulose Valorization

Potassium exchanged Sn-β and Sn-USY zeolites have been tested for the transformation of various aldoses (hexoses and pentoses), exhibiting outstanding catalytic activity and selectivity toward methyl lactate. Insights into the transformation pathways using reaction intermediates-dihydroxyacetone and glycolaldehyde-as substrates revealed a very high catalytic proficiency of both zeolites in aldol and retro-aldol reactions, showcasing their ability to convert small sugars into large sugars, and vice versa. This feature makes the studied Sn-zeolites outstanding catalysts for the transformation of a wide variety of sugars into a limited range of commercially valuable alkyl lactates and derivatives. [K]Sn-β proved to be superior to [K]Sn-USY in terms of shape selectivity, exerting tight control on the distribution of produced α-hydroxy methyl esters. This shape selectivity was evident in the transformation of several complex sugar mixtures emulating different hemicelluloses-sugar cane bagasse, Scots pine, and white birch-that, despite showing very different sugar compositions, were almost exclusively converted into methyl lactate and methyl vinyl glycolate in very similar proportions. Moreover, the conversion of a real hemicellulose hydrolysate obtained from Scots pine through a simple GVL-based organosolv process confirmed the high activity and selectivity of [K]Sn-β in the studied transformation, opening new pathways for the chemical valorization of this plentiful, but underutilized, sugar feedstock.

Saccharide formation by sustainable formose reaction using heterogeneous zeolite catalysts

The formose reaction is a unique chemical reaction for the preparation of saccharides from formaldehyde, a single carbon compound. We applied zeolite materials as heterogeneous catalysts to the formose reaction. The simple addition of Linde type A zeolite containing calcium ions (Ca-LTA) to an aqueous solution of formaldehyde and glycolaldehyde produced saccharides at room temperature. A quantitative analysis performed by high-performance liquid chromatography revealed that triose, tetrose, pentose, and hexose saccharides were produced with few byproducts. Ca-LTA was recovered from the reaction mixture by filtration, and the retrieved zeolite was found to be reusable under the same conditions. The catalytic activity of Ca-LTA was higher than those of conventional calcium catalysts and other solid materials such as silica, alumina, and hydroxyapatite. Several other types of zeolites with different crystal structures and alkali/alkali-earth metal ions also showed catalytic activity for saccharide formation. Based on the analytical results obtained by infrared spectroscopy, temperature-programmed desorption profiles and NMR measurements, we propose a reaction mechanism in which C-C bond formation is promoted by the mild basicity of the oxygen atoms and acidity on the metal ions of the aluminosilicate on the zeolite surfaces with low SiO2/Al2O3 ratios.

C-C Bond Formation Coupled with C-C Bond Cleavage during Oxidative Upgrading of Glycerol on a Nanoporous BiVO4 Photoanode

Production of biodiesel generates glycerol as a 10 wt% byproduct. Therefore, efficient and selective glycerol upgrading is critical for the sustainable production of biodiesel as well as for the production of chemicals from renewable feedstocks. In this study, the photoelectrochemical glycerol oxidation reaction (GOR) was investigated using a nanoporous BiVO4 photoanode in pH 9.3 and pH 2 buffer solutions. In both solutions, glycolaldehyde (GCAD), a C2 species, was the major product, which has never been the major product in any previous electrochemical or photoelectrochemical GOR study. To produce GCAD from the C3 species glycerol, C-C cleavage should occur to produce C2 and C1 species with a 1:1 ratio. Intriguingly, our results show that, during photoelectrochemical GOR on BiVO4, more GCAD is produced than can be explained by simple C-C cleavage, meaning that GCAD is also produced from C-C coupling of two C1 species produced from C-C cleavage. This is equivalent to converting two glycerol molecules to three GCAD molecules, which offers an extraordinary way to maximize GCAD production. To gain further insight into the nature of this unprecedented C-C coupling during GOR, photoelectrochemical oxidation of intermediate oxidation products (glyceraldehyde and 1,3-dihydroxyacetone) and glycerol-1,3-13C2 was compared to that of standard glycerol. Photoelectrochemical GOR was also compared with electrochemical GOR on BiVO4 to interrogate whether light is critical for the observed C-C coupling. Results obtained from comprehensive control experiments revealed critical information about C-C cleavage and C-C coupling during GOR on BiVO4.

Engineering Lewis Acidity in Zeolite Catalysts by Electrochemical Release of Heteroatoms during Synthesis

The creation of heteroatom nodes in zeolite frameworks is a challenging but rewarding pathway to superior materials for numerous catalytic applications. Here, we present a novel method for precise control over heteroatom incorporation by in situ anodic release of a desired metal during hydrothermal zeolite synthesis. The generic character of the technique and the applicability of the new synthesis reactor are shown across 3 zeolite structures crystallized and 4 electrode metals in two pH zones and by offering access to a new mixed-metal zeolite. The timed and voltage-controlled metal release offers a minimized interference between the metal precursor state and critical events in the zeolite's crystallization. A mechanistic study for Sn-MFI revealed the key importance of controlled release: while keeping its concentration lower than in batch, a lot more Sn can be incorporated into the framework. The method grants access to 10× increased framework Lewis acid site densities (vs batch controls) for the most relevant stannosilicates. As a proof, the electro-made materials demonstrate higher productivity than their classic counterparts in lactate catalysis. This innovative approach effectively expands the synthesis space of zeolites.

Advances in catalytic routes for the production of carboxylic acids from biomass: a step forward for sustainable polymers

Polymers are ubiquitously present in our daily life because they can meet a wide range of needs and fields of applications. This success, based on an irresponsible linear consumption of plastics and the access to cheap oil, is creating serious environmental problems. Two lines of actions are needed to cope with them: to adopt a circular consumption of plastics and to produce renewable carbon-neutral monomers. This review analyses the recent advances in the chemocatalytic processes for producing biomass-derived carboxylic acids. These renewable carboxylic acids are involved in the synthesis of relevant general purpose and specialty polyesters and polyamides; some of them are currently derived from oil, while others can become surrogates of petrochemical polymers due to their excellent performance properties. Polyesters and polyamides are very suitable to be depolymerised to other valuable chemicals or to their constituent monomers, what facilitates the circular reutilisation of these monomers. Different types of carboxylic acids have been included in this review: monocarboxylic acids (like glycolic, lactic, hydroxypropanoic, methyl vinyl glycolic, methyl-4-methoxy-2-hydroxybutanoic, 2,5-dihydroxypent-3-enoic, 2,5,6-trihydroxyhex-3-enoic acids, diphenolic, acrylic and δ-amino levulinic acids), dicarboxylic acids (2,5-furandicarboxylic, maleic, succinic, adipic and terephthalic acids) and sugar acids (like gluconic and glucaric acids). The review evaluates the technology status and the advantages and drawbacks of each route in terms of feedstock, reaction pathways, catalysts and economic and environmental evaluation. The prospects and the new research that should be undertaken to overcome the main problems threatening their economic viability or the weaknesses that prevent their commercial implementation have also been underlined.

Thermal Cracking of Sugars for the Production of Glycolaldehyde and Other Small Oxygenates

Thermal cracking of sugars for production of glycolaldehyde, a potential renewable platform molecule, in yields up to 74 % with up to 95 % carbon recovered in the condensed product is demonstrated using glucose as the feed. The process involves spraying an aqueous sugar solution into a fluidized bed of glass beads. Continuous operation is carried out for more than 90 h with complete conversion and stable product selectivity. Besides glycolaldehyde, the other identified condensed products are pyruvaldehyde (9 %), formaldehyde (7 %), glyoxal (2 %), acetol (2 %), and acetic acid (1 %). The effects of temperature, glucose feed concentration, and type of sugar feedstock are investigated. Cracking the monosaccharides fructose and xylose leads to very different product distributions from glucose, but similar carbon recovery. A reaction network in agreement with the main observed products from cracking of monosaccharide sugars is proposed.

Stanosilicates based on Sn-magadiites applied in conversion of fructose at moderate temperatures

Sn-Magadiite stanosilicates were successfully synthesized by the hydrothermal method.

Recent Advances in the Development of 5-Hydroxymethylfurfural Oxidation with Base (Nonprecious)-Metal-Containing Catalysts

5-Hydroxymethylfurfural (HMF) is one of the versatile platform molecules that can be derived from biomass, and a promising starting substrate for producing 2,5-diformylfuran (DFF) and 2,5-furandicarboxylic acid (FDCA). DFF is a platform chemical with applications in pharmaceuticals, macrocyclic ligands, and functional polymeric materials. Importantly, FDCA is being considered as a potential alternative to replace terephthalic acid for producing the bioplastic polyethylene furanoate, instead of polyethylene terephthalate, by blending with ethylene glycol. A significant number of studies have focused on the oxidation of HMF to FDCA with metal-containing heterogeneous catalysts in both aqueous and organic media in the presence of peroxides/air/molecular oxygen as the oxidant. In this regard, articles have recently been published related to HMF oxidation with base (nonprecious)-metal-containing catalysts that exhibit appealing activity towards DFF or FDCA in terms of yield. Thus, this Minireview focuses on recent developments in efficient transformations of HMF to DFF and FDCA with base-metal-containing heterogeneous catalysts in aqueous and organic media. This review further focuses on the direct transformation of glucose/fructose to DFF and/or FDCA with nonprecious-metal-containing catalysts in various solvents. Photocatalytic approaches for HMF oxidation with nonprecious metal- containing catalysts are also briefly discussed.

Selective formation of formic acid from biomass-derived glycolaldehyde with supported ruthenium hydroxide catalysts

Ceria-supported ruthenium hydroxide catalysts, Ru(OH)_x/CeO₂, with micro- and nanoparticle supports were applied for selective aerobic oxidation of glycolaldehyde (GAD) to formic acid (FA) in water under mild and base-free conditions.

Production of liquid fuel intermediates from furfural via aldol condensation over Lewis acid zeolite catalysts

Aldol condensation reactions between furfural and acetone can be used to produce liquid fuel intermediates.

Facile and benign conversion of sucrose to fructose using zeolites with balanced Brønsted and Lewis acidity

A simple and robust two-step process with zeolites as catalysts converts sucrose in high yield into the versatile monosaccharide fructose.