Zr–Beta zeolite is a robust and active catalyst for the Meerwein–Ponndorf–Verley reduction of levulinic acid to γ-valerolactone, a versatile intermediate for bio-fuels and chemicals. In a batch reactor, γ-valerolactone was formed with a selectivity of >96%. In a continuous flow reactor, >99% yield of γ-valerolactone was obtained with a steady space-time-yield of 0.46 mol_GVLg_Zr ⁻¹ h⁻¹ within 87 h, on a par with that of noble metal based catalysts. The high activity of this catalyst was attributed to the presence of Lewis acidic sites with moderate strength. Due to the relatively few basic sites, it is not poisoned by the acidic reactant. Its robustness in liquid and gas phase reactants coupled with good thermal stability makes Zr–Beta a green regenerable catalyst that can be used directly on levulinic acid without the need for derivatization.

Zeolites are versatile catalysts not only for large scale petrochemical processes but also in applications related to fine chemicals synthesis, biomass conversion and CO₂ utilization. Introduction of mesopores and heteroatoms opens up additional applications. Heteroatoms in the crystalline framework create active sites where the diversity in the coordination offers tunability in acidity and redox properties. Their framework locations within the unit cell and their open/closed nature greatly influence the catalytic ability. Depending on the synthesis conditions, the properties of the pore walls can vary from hydrophobic to hydrophilic which affects the confinement of reactant and solvent molecules within the well-ordered pores. This mini-review traces the synthesis of heteroatom zeolites from traditional solvent-based methods to the more sustainable routes of post-synthesis and mechanochemistry. The properties of the zeolites formed by the different methods are compared and the impact on selected catalytic reactions is discussed.

The Meerwein-Ponndorf-Verley (MPV) transfer hydrogenation of aldehydes and ketones to the corresponding alcohols is distinguished by its exceptional chemoselectivity. This reaction is particularly suited for the reduction of unsaturated aldehydes and ketones, compared to catalytic reductions with molecular hydrogen using noble metal catalysts. The MPV reaction has traditionally been carried out using homogeneous catalysts like aluminium or titanium alkoxides. However, over the past two decades, an increasing number of reports on heterogeneous catalysts for the MPV reaction have been published. This interest is stimulated by the advantages of heterogeneous over homogeneous catalysis, particularly for larger-scale applications. The article provides a critical review of the recent literature on heterogeneous catalysts for the MPV reaction. The materials include hydrotalcites, metal oxides such as magnesium oxide, zirconia, silica and alumina, alkoxides of Al, La, Zr and Hf grafted to high surface area mesoporous materials, and zeolites. In particular, zeolite beta has been found to be a highly stereoselective catalyst in the MPV reduction of 4-tertbutylcyclohexanone, giving predominantly cis-4-tert-butylcyclohexanol rather than the thermodynamically stable transalcohol. The activity was improved with the incorporation of other metals such as Ti, Sn and Zr. These materials show good tolerance to moisture, lack of leaching and ease of regeneration, thus making them useful catalysts in MPV reduction. The activity of a catalyst depends on its ligand exchange capability with the reductant with a high ligand exchange rate enabling the use of catalytic amounts.