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The industrial viability of heterogeneous catalysts for the gas-phase conversion of lactic acid to acrylic acid will strongly depend on their selectivity and durability. Here, we initially screened various aluminum-rich zeolites confirming that NaY is the most efficient catalyst for this reaction. This material was modified by sequential dealumination and alkaline treatment attaining a solid featuring a hierarchical distribution of micro- and mesopores, reduced Lewis acidity, and increased basicity owing to the presence of well-dispersed sodium ions interacting with external siloxy groups, as evidenced by in-depth characterization. These properties were crucial for determining higher selectivity (75 %) and minimizing the activity loss in a 6 h run. Remarkably, the catalyst gained in selectivity and stability upon reuse in consecutive cycles. This was ascribed to the depletion of the stronger basic sites and the clustering of sodium into oxidic particles upon the intermediate calcination. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A literature survey reveals a prominent reduction in the concentration of Brønsted acid sites in hierarchically organized zeolites with increasing mesoporous or external surface area independent of the framework type or synthesis route; this suggests a common fundamental explanation. To determine the cause, nature, and impact of the underlying changes in aluminum speciation, this study combines a multitechnique analysis that integrates basic characterization, a detailed synchrotron XRD and multiple-quantum NMR spectroscopy assessment, and catalytic tests to correlate evolution of the properties with performance during successive steps in the preparation of hierarchical MFI-type zeolites by desilication. The findings, subsequently generalized to FAU- and BEA-type materials, identify the crucial impact of calcination on the protonic form, which is an integral step in the synthesis and regeneration of zeolite catalysts; on aluminum coordination; and the associated acidity trends. [ABSTRACT FROM AUTHOR]

The Cover shows how rENewable ‐ based processes challENge existing oil ‐ based routes for a more sustainable manufacture of consumer products. The establishmENt of alternative technologies is contingENt upon the idENtification of effective heterogENeous catalysts and suitable feedstocks. In their Full Paper, G.   M. Lari, B. Puértolas et   al. describe the design of a zeolite ‐ based catalyst for the gas ‐ phase transformation of lactic acid, a versatile platform easily obtained from glycerol or sugars, into acrylic acid, a commodity chemical used in paints, plastics, glues, and superabsorbENts. Simple and scalable acid and alkaline treatmENts ENable the introduction of basicity and mesoporosity and the reduction of Lewis acidity in a commercial aluminosilicate, gENerating a material that shows superior selectivity and remarkably ENhanced stability. More information can be found in the Full Paper by G.   M. Lari, B. Puértolas et   al. on page   1507 in Issue 8, 2016 (DOI: 10.1002/cctc.201600102). [ABSTRACT FROM AUTHOR]

Abstract: The combination of dealumination and desilication of ZSM-5 zeolites has been investigated in order to decouple mesoporosity creation and modification of acidity. Individually, desilication by treatment in alkaline medium leads to a spectacular mesoporosity development, without distinct modification of the acidic properties, while dealumination by steam treatment mainly impacts on the acidity of the ZSM-5 zeolite. It is shown that application of the alkaline treatment first followed by steam treatment results in MFI zeolites with independently tailored pore architecture and acidic properties, with proven hydrothermal stability under severe conditions. The independent modification of porous and acidic properties cannot be accomplished if the alkaline treatment is performed after the steam treatment, since the presence of extra-framework Al species inhibit Si extraction and related mesopore formation. A promising outlook of the successive alkaline-steam treatment is expected in catalytic applications of microporous materials. [Copyright &y& Elsevier]

Highlights: [•] Hierarchization of ZSM-22 favors hydroisomerization and limits hydrocracking [•] Hierarchical ZSM-22 has lower acidity in micropores and higher acidity in pore mouths [•] Branching occurs in pore mouths; hydrocracking in pore mouths and micropores [•] Hierarchization is a unique tool to design superior hydroisomerization catalysts [•] Pristane is a convenient model molecule for probing pore mouth catalysis [Copyright &y& Elsevier]

Abstract: Desilication of ITQ-4 (IFR code, 1-dimensional 12-MR channel system of 0.62nm×0.72nm) in aqueous NaOH solutions was practiced in order to produce the zeolite in the hierarchical form, i.e. combining the native micropores with a secondary network of intracrystalline mesopores. The parent material (Si/Al=32) was synthesized using benzylquinuclidinium as the structure-directing agent in the presence of fluoride anions. The samples were characterized by ICP-OES, XRD, TEM, N2 adsorption, and FTIR spectroscopy. In a representative treatment, the mesopore surface area of the ITQ-4 experienced a sevenfold increase (from 29 to 206m2 g−1) upon optimized NaOH post-treatment, whereas the microporosity was reduced by 70% (from 0.20 to 0.06cm3 g−1). Chemical analysis and infrared spectroscopy of adsorbed pyridine showed that after alkaline treatment the amount of Brønsted acid sites remains practically constant whereas a significant increase in Lewis acid sites was obtained. Infrared studies with adsorbed 2,4,6-collidine concluded that the accessibility of acid sites in the hierarchical zeolite increased substantially due to an increase in the available active sites at the pore mouths of the hierarchical zeolite. [Copyright &y& Elsevier]