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The properties of crude bio-oils attained by the pyrolysis of lignocellulosic biomass can be greatly enhanced by means of catalytic upgrading. Here, we demonstrate an efficient process concept coupling the production of pyrolysis oil from pine wood with a consecutive catalytic upgrading step over hierarchically structured ZSM-5 zeolites to attain aromatic-rich bio-oils. The selective upgrading of these complex mixtures is shown to be tightly connected to the extent of mesopore development and the density of Brønsted acid sites at the mesopore surface. A full product analysis enables elucidation of the impact of mesopore introduction and the acidic properties on the complex reaction network. The preferential occurrence of decarbonylation reactions in hierarchical zeolites versus dehydration transformations in the bulk counterparts is believed to be decisive in promoting increased aromatics formation., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

High-silica zeolites have been reported recently as efficient catalysts for liquid- and gas-phase condensation reactions because of the presence of a complementary source of basicity compared to Al-rich basic zeolites. Herein, we describe the controlled generation of these active sites on silica-rich FAU, BEA, and MFI zeolites. Through the application of a mild base treatment in aqueous Na2CO3, alkali-metal-coordinating defects are generated within the zeolite whereas the porous properties are fully preserved. The resulting catalysts were applied in the gas-phase condensation of propanal at 673 K as a model reaction for the catalytic upgrading of pyrolysis oil, for which an up to 20-fold increased activity compared to the unmodified zeolites was attained. The moderate basicity of these new sites leads to a coke resistance superior to traditional base catalysts such as CsX and MgO, and comparable activity and excellent selectivity is achieved for the condensation pathways. Through strategic acid and base treatments and the use of magic-angle spinning NMR spectroscopy, the nature of the active sites was investigated, which supports the theory of siloxy sites as basic centers. This contribution represents a key step in the understanding and design of high-silica base catalysts for the intermediate deoxygenation of crude bio-oil prior to the hydrotreating step for the production of second-generation biofuels., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Hierarchical zeolites have been established as a superior type of aluminosilicate catalysts compared to their conventional (purely microporous) counterparts. An impressive array of bottom-up and top-down approaches has been developed during the last decade to design and subsequently exploit these exciting materials catalytically. However, the sustainability of the developed synthetic methods has rarely been addressed. This paper highlights important criteria to ensure the ecological and economic viability of the manufacture of hierarchical zeolites. Moreover, by using base leaching as a promising case study, we verify a variety of approaches to increase reactor productivity, recycle waste streams, prevent the combustion of organic compounds, and minimize separation efforts. By reducing their synthetic footprint, hierarchical zeolites are positioned as an integral part of sustainable chemistry., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Wax on, wax off: Bifunctional cobalt-based catalysts on zeolite supports are applied for the valorization of biosyngas through Fischer-Tropsch chemistry. By using these catalysts, waxes can be hydrocracked to shorter-chain hydrocarbons, increasing the selectivity towards the C5 -C11 (gasoline) fraction. The zeolite topology and the amount and strength of acid sites are key parameters to maximize the performance of these bifunctional catalysts, steering Fischer-Tropsch product selectivity towards liquid hydrocarbons., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Last site standing: A new generation of hierarchical Pt/H-ZSM-22 zeolites is designed for the efficient processing of upcoming renewable feedstocks. The enhanced accessibility of the active sites is vital for the superior activity and exceptional selectivity in the hydroisomerization of model molecules such as nonadecane and pristane., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The need for more sustainable products and processes has led to the use of new methodologies with low carbon footprints. In this work, an efficient tandem process is demonstrated for the liquid‐phase catalytic upgrading of lignocellulosic biomass‐derived γ‐valerolactone (GVL) with trioxane (Tx) to α‐methylene‐γ‐valerolactone (MeGVL) in flow system using Cs‐loaded hierarchical beta zeolites. The introduction of mesopores along with the presence of basic sites of mild strength leads to MeGVL productivity 20 times higher than with the bulk beta zeolite, reaching 0.325 mmol min−1 gcat−1 for the best‐performing catalyst, the highest value reported so far. This catalyst proves stable upon reuse in consecutive cycles, which is ascribed to the partial depletion of the basic sites. The obtained MeGVL is subjected to visible‐light‐induced polymerization, resulting in a final material with similar properties to the widely used poly(methyl) methacrylate. [ABSTRACT FROM AUTHOR]

Highlights from the article: Cover Feature: Sustainable Continuous Flow Valorization of -Valerolactone with Trioxane to -Methylene- -Valerolactone over Basic Beta Zeolites (ChemSusChem 12/2019) B The Front Cover b shows a sustainable continuous-flow process for upgrading lignocellulosic-biomass-derived -valerolactone to -methylene- -valerolactone by utilizing a tailored Cs-loaded hierarchical beta catalyst. Heterogeneous catalysis, sustainable chemistry, biomass, zeolites, flow chemistry.

The Cover picture illustrates the importance of considering the ecological and economical footprint associated with the manufacture of newly developed (catalytic) materials. These aspects, which ultimately determine the large‐scale implementation of catalysts, usually receive little attention in the open literature. Prof. Javier Pérez‐Ramírez and Dr. Danny Verboekend consider the case of hierarchical zeolites (HZ), which are superior heterogeneous catalysts for numerous established and emerging applications. Focusing on the use of demetallation treatments, they present approaches to prepare these advanced materials more efficiently by increasing reactor productivity, recycling waste streams, avoiding the combustion of organics, and minimizing work‐up efforts. More detail is given in the Full Paper by Verboekend and Pérez‐Ramírez on page 753, while more information about the research group is available in the Cover Profile (DOI: 10.1002/cssc.201400062). [ABSTRACT FROM AUTHOR]