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Developing efficient solid catalysts is necessary when for example moving from batch chemistry to continuous flow systems. In this work, scale‐up effects of zeolite‐based catalyst materials have been tested in aldol condensation as a model reaction for bio‐oil upgrading via deoxygenation. For this purpose, shaped catalyst bodies were obtained via extrusion of ultrastable Y zeolite (USY) using either attapulgite (Att.) or bentonite (Bent.) as clay binder, followed by post‐alkali metal ion grafting of K+ after (rather than before) extrusion. This approach proved essential to preserve the catalysts' crystallinity. The Att.‐bound catalyst body was more active than its Bent.‐counterpart, correlating well with the observed changes in physicochemical properties. The K‐(USY/Att.) catalyst showed new basic oxygen and strong Lewis acidic sites resulting from clay incorporation, in addition to the Lewis acid (K+) and basic sites (K−OH) created upon grafting. For K‐(USY/Bent.), the grafting proved less efficient, likely due to pore blockage caused by the binder. Bent. addition resulted in acid sites of moderate Brønsted and strong Lewis acidity, but hardly any of the basicity desired for the aldol condensation reaction. The poor potassium grafting yet led to some cation exchange with the binder (likely with the Na+ naturally present in the Bent. material). The results obtained demonstrate the critical importance of the choice of the binder material and the synthesis protocol adopted for upscaling solid base materials in the form of catalyst bodies. [ABSTRACT FROM AUTHOR]

The efficient utilization of biomass, the only globally available, renewable and abundant carbon-neutral source, is of high significance in green and sustainable chemistry. Polyoxometalates (POMs) and POM-based composites have been widely applied in green catalytic reactions, due to their tunable Brønsted/Lewis-acidity and redox properties enabling high reactivity in a wide range of chemical transformations. This review covers recent advances in the chemocatalytic conversion of biomass into chemicals and fuels over POMs and POM–metal composites. For biomass valorisation over POMs, the advances of acid catalysis including hydrolysis, dehydration, etherification, alcoholysis, transesterification and esterification are summarised. Furthermore, applications in chemical oxidation for the synthesis of organic acids and furan chemicals are discussed. For biomass valorisation over metal–POM composites, an overview of tandem reactions (e.g. hydrolysis–hydrogenation, hydrolysis–oxidation, and hydrogenolysis–hydrodeoxygenation) is highlighted. The future prospects of biomass valorisation over POM-based catalysts are finally presented. [ABSTRACT FROM AUTHOR]

Alkaline-assisted stannation is applied as a facile one-step post-synthetic approach for the preparation of the Lewis-acid Sn-BEA from a high-silica commercial beta (BEA) zeolite. The concentration of base, tin and protective additive tetrapropylammonium as well as the nature of the tin precursor are identified as key parameters of the metallation process determining the acidic and structural properties of the stannated zeolite and, in turn, its performance in the isomerisation of bio-based substrates. [ABSTRACT FROM AUTHOR]

Galliation of USY zeolites in alkaline media creates tetracoordinated Lewis-acid centres linked to the framework which display outstanding selectivity in the isomerisation of dihydroxyacetone to ethyl lactate and full reusability. This simple and affordable post-synthetic route enables to tune the amount of Lewis acidity in the zeolite and has great potential for application in related biomass conversions. [ABSTRACT FROM AUTHOR]

Desilication of commercial MFI-type (ZSM-5) zeolites in solutions of alkali metal hydroxides is demonstrated to generate highly selective heterogeneous catalysts for the aqueous-phase isomerization of biobased dihydroxyacetone (DHA) to lactic acid (LA). The best hierarchical ZSM-5 sample attains a LA selectivity exceeding 90 %, which is comparable to that of the state-of-the-art catalyst (i.e., the Sn-beta zeolite); this optimized hierarchical catalyst is recyclable over three runs. The Lewis acid sites, which are created through desilication along with the introduction of mesoporosity, are shown to play a crucial role in the formation of the desired product; these cannot be achieved by using other post-synthetic methods, such as steaming or impregnation of aluminum species. Desilication of other metallosilicates, such as Ga-MFI, also leads to high LA selectivity. In the presence of a soluble aluminum source, such as aluminum nitrate, alkaline-assisted alumination can introduce these unique Lewis acid centers in all-silica MFI zeolites. These findings highlight the potential of zeolites in the field of biomass-to-chemical conversion, and expand the applicability of desilication for the generation of selective catalytic centers. [ABSTRACT FROM AUTHOR]

Highlights: [•] Alkyl lactates production is studied over gallium-modified FAU zeolites. [•] Alkaline-assisted galliation outperforms dry impregnation and ion exchange of Ga3+. [•] The method is successfully applied to MOR, MFI, FER, and BEA zeolites. [•] Galliated FAU is the best tin-free catalyst for C2–C4 alkyl lactates production. [•] Retained performance upon 5-fold increase in substrate feed concentration. [ABSTRACT FROM AUTHOR]