Alexander J. O'Malley

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.

Comprehensive Vibrational Spectroscopic Characterization of Nylon-6 Precursors for Precise Tracking of the Beckmann Rearrangement

As a key step in nylon-6 synthesis, the Beckmann rearrangement is an ongoing target of catalytic studies that seek to improve the sustainability of polymer manufacture. Whilst solid-acid catalysts (predominantly zeotypes) have proven effective for this transformation, the development of more active and selective systems demands an understanding of fundamental catalytic mechanisms. In this undertaking, in situ and operando characterization techniques can be informative, provided rigorous spectroscopic groundwork is in place. Thus, to facilitate mechanistic studies we present a detailed investigation of the vibrational spectra of cyclohexanone, cyclohexanone oxime, ϵ-caprolactam and their D10-isotopomers, in the solid state. Variable-temperature infrared (150-300 K) and Raman (10-300 K) spectra are reported alongside inelastic neutron scattering data. Moreover, where key vibrational modes have been assigned with the aid of periodic density functional theory calculations, it has been possible to include hydrogen-bonding interactions explicitly.

The effects of MTG catalysis on methanol mobility in ZSM-5

We analyse the dynamics of methanol in ZSM-5 catalysts both with and without the hydrocarbon pool, resulting from the methanol to gasoline (MTG) reaction taking place at 623 K and 673 K for three days, to determine the effects of catalyst use on molecular mobility. Using quasielastic neutron scattering (QENS), we observe that methanol is immobile on the QENS instrumental time scale in the fresh catalyst (ZSM-5-F) and in the sample used to convert methanol for 3 days at 623 K (ZSM-5-623). However, in zeolite ZSM-5-673 (MTG at 673 K for 3 days) we observe isotropic methanol rotation with an immobile fraction of 0.58 and a rotational diffusion coefficient of DR = 3 × 1010 s−1. The observed differences between the zeolites in methanol dynamics are attributed to the development of mesoporosity in ZSM-5-673 due to the high reaction temperature of 673 K, leading to dislodgement of lattice Al as is evident from NMR data.

Sorbate Dynamics in Zeolite Catalysts

Microporous catalysts, in particular zeolites, are among the most intensively investigated systems in materials chemistry owing to the intrinsic challenges they provide in the characterization of their structures and properties, and to their major industrial applications. As discussed below, the microporous structure of the materials allows for the adsorption and diffusion of small- to medium-sized molecules into their pores—processes that are of crucial importance for the applications in both separations and catalysis. Studies of molecular diffusion are therefore a core area of zeolite science. As sorption and diffusion studies in zeolites are strongly focussed on hydrogen-containing molecules, neutron-based techniques have proved to be particularly effective in elucidating and quantifying the microscopic processes of molecular diffusion; and the interpretation of the data obtained from these techniques can be significantly enhanced by the concerted use of molecular simulation techniques. This chapter therefore outlines some notable studies using quasielastic neutron scattering probing molecular transport and dynamics in zeolites, which we place into the broader context of the investigation of sorbate behavior in these widely studied materials. Though we have focused on this specific class of materials, we note the applicability of all the following techniques to other classes of porous or framework materials (e.g., metal organic frameworks, carbon nanotubes, clathrates, polymers, and porous carbons).

Catalyst design from theory to practice: general discussion

Hans-Joachim Freund opened the discussion of the paper by Alberto Roldan:How is the atomic hydrogen produced on the greigite surface? In the paper (DOI:10.1039/C5FD00186B) there is no comment whether you studied dissociatehydrogen adsorption.