Thomas M. Mezza

Rationalising the role of solid-acid sites in the design of versatile single-site heterogeneous catalysts for targeted acid-catalysed transformations

A versatile design strategy for rationalising the role of well-defined and isolated multifunctional solid-acid active centres, employing Mg(II)Si(IV)AlPO-5 nanoporous architectures has been demonstrated, with a view to affording structure–property correlations compared to its corresponding mono-substituted analogues (Mg(II)AlPO-5 and Si(IV)AlPO-5). The simultaneous incorporation of Mg(II) and Si(IV) ions, as isomorphous replacements for Al(III) and P(V) ions in the microporous architecture, plays an important role in modulating the nature and strength of the solid-acid active sites in the industrially-important, vapour-phase Beckmann rearrangement of cyclohexanone oxime to produce e-caprolactam (the precursor for renewable nylon-6) and in the isopropylation of benzene to cumene. The structural integrity, coordination geometry and local environment of the active (Bronsted-acid) sites could be rationalised at the molecular level, using in situ spectroscopic techniques, for tailoring the catalytic synergy by adroit design of the framework architecture.

Synthesis, characterization, and applications of the new zeolite UZM-5

Abstract A new zeolite, UZM-5, has been recently reported and assigned the IZA structure code UFI. Materials with different morphologies ranging from a plate-like structure to rosettes can be obtained by varying the synthesis conditions. Adsorption IR measurements McBain adsorption, and microreactor testing determined accessibility of external and internal acid sites consistent with the structure. Catalytic activity testing and multiple probe molecule adsorption studies indicate primarily external surface reactivity. Bronsted/Lewis acid site ratio and acid strength distribution can be varied through the control of morphology for optimized efficiency for targeted applications.

Understanding the role of designed solid acid sites in the low-temperature production of ϵ-Caprolactam

Modern society is placing increasing demands on commodity chemicals, driven by the ever‐growing global population and the desire for improved standards of living. As the polymer industry grows, a sustainable route to ϵ‐caprolactam, the precursor to the recyclable nylon‐6 polymer, is becoming increasingly important. To this end, we have designed and characterized a recyclable SAPO catalyst using a range of characterization techniques, to achieve near quantitative yields of ϵ‐caprolactam from cyclohexanone oxime. The catalytic process operates under significantly less energetically demanding conditions than other widely practiced industrial processes.

Influence of dopant substitution mechanism on catalytic properties within hierarchical architectures

A range of hierarchically porous (HP) AlPO-5 catalysts, with isomorphously substituted transition metal ions, have been synthesized using an organosilane as a soft template. By employing a range of structural and spectroscopic characterization protocols, the properties of the dopant-substituted species within the HP architectures have been carefully evaluated. The resulting nature of the active site is shown to have a direct impact on the ensuing catalytic properties in the liquid-phase Beckmann rearrangement of cyclic ketones.

Technique integration applied to structure solution: The case of UZM-5. Details of the structure, faulting and templating

Abstract The structure solution of the new zeolite framework UZM-5 is reviewed. It is shown how the structure solution emerges from integration of a number of zeolite characterization techniques such as powder X-ray diffraction, transmission electron microscopy, infrared spectroscopy and McBain adsorption. In addition to the ideal structure, faulting is evident in both powder X-ray diffraction and transmission electron microscopy. Details of the surface structure and faulting on the (001) planes are described.

Investigating the role of framework topology and accessible active sites in silicoaluminophosphates for modulating acid-catalysis

The structure–property correlations which direct the formation of specific active-acid sites in nanoporous silicoaluminophosphates (SAPOs) have been explored, to afford a molecular basis for the rational design of solid-acid catalysts. It is demonstrated that the influence of the specific zeotype framework extends beyond modulating Bronsted acidity, with the framework topology playing a fundamental role in reaction kinetics. The structural integrity and nature of the active site has been probed using a combined catalysis and multi-technique characterization study, aimed at optimizing the production of e-caprolactam.