Ines Lezcano-Gonzalez

2.5% of global carbon emissions result from air travel, underscoring the need for sustainable aviation fuels (SAF) derived from second‐generation lignocellulosic biomass to enhance the green credentials of the aviation sector. This study demonstrates the first solvent‐free photocatalytic conversion of furfural (FAL) and cyclopentanone (CPO) to produce 2,5‐bis(2‐furylmethylidene)cyclopentanone (F ₂ Cp), a jet fuel precursor, using Ti‐SBA‐15 catalysts, synthesized via alkoxide grafting and controlled titanium surface coverage. Sub‐monolayer titania films on SBA‐15 supports are achieved with tuneable Ti content, confirmed by XPS (X‐ray photoelectron spectroscopy), UPS (ultraviolet photoelectron spectroscopy), REELS (reflectance electron energy loss spectroscopy), ISS (ion scattering spectroscopy), and Raman analysis. XPS analyses reveal coverage‐dependent Ti speciation, transitioning from isolated Ti atoms to interconnected Ti‐O‐Ti networks, with corresponding shifts in Auger parameters, indicating increased surface polarizability and Lewis acidity. Optimized Ti‐SBA‐15 catalysts exhibit a fourfold activity enhancement in photocatalytic activity over bulk TiO₂, attributed to improved mass transport, active site accessibility, and surface stability. This work highlights the potential of rationally designed hierarchical catalysts for scalable, energy‐efficient biomass valorization into SAF precursors, offering a scalable, energy‐efficient pathway for sustainable jet fuel production. By elucidating the structure‐function relationships in sub‐monolayer Ti‐SBA‐15 materials, this study provides critical insights for advancing photocatalytic technologies in renewable energy applications.

Resonance Raman spectroscopy can provide insights into complex reaction mechanisms by selectively enhancing the signals of specific molecular species. In this work, we demonstrate that, by changing the excitation wavelength, Raman bands of different intermediates in the methanol-to-hydrocarbons reactions can be identified. We show in particular how UV excitation enhances signals from short-chain olefins and cyclopentadienyl cations during the induction period, while visible excitation better detects later-stage aromatics. However, visible excitation is prone to fluorescence that can obscure Raman signals, and hence, we show how fast fluorescence rejection techniques like Kerr gating are necessary for extracting useful information from visible excitation measurements.

Small pore zeolites have shown great potential in a number of catalytic reactions. While Mo-containing medium pore zeolites have been widely studied for methane dehydroaromatisation (MDA), the use of small pore supports has drawn limited attention due to the fast deactivation of the catalyst. This work investigates the structure of the small pore Mo/H-SSZ-13 during catalyst preparation and reaction by operando X-ray absorption spectroscopy (XAS), in situ synchrotron powder diffraction (SPD), and electron microscopy; then, the results are compared with the medium pore Mo/H-ZSM-5. While SPD suggests that during catalyst preparation, part of the MoO_x anchors inside the pores, Mo dispersion and subsequent ion exchange was less effective in the small pore catalyst, resulting in the formation of mesopores and Al₂(M_OO₄)₃ particles. Unlike Mo/H-ZSM-5, part of the Mo species in Mo/H-SSZ-13 undergoes full reduction to Mo⁰ during MDA, whereas characterisation of the spent catalyst indicates that differences also exist in the nature of the formed carbon deposits. Hence, the different Mo speciation and the low performance on small pore zeolites can be attributed to mesopores formation during calcination and the ineffective ion exchange into well dispersed Mo-oxo sites. The results open the scope for the optimisation of synthetic routes to explore the potential of small pore topologies.

The methanol-to-hydrocarbons reaction refers collectively to a series of important industrial catalytic processes to produce either olefins or gasoline. Mechanistically, methanol conversion proceeds through a ‘pool’ of hydrocarbon species. For the methanol-to-olefins process, these species can be delineated broadly into ‘desired’ lighter olefins and ‘undesired’ heavier fractions that cause deactivation in a matter of hours. The crux in further catalyst optimization is the ability to follow the formation of carbonaceous species during operation. Here, we report the combined results of an operando Kerr-gated Raman spectroscopic study with state-of-the-art operando molecular simulations, which allowed us to follow the formation of hydrocarbon species at various stages of methanol conversion. Polyenes are identified as crucial intermediates towards formation of polycyclic aromatic hydrocarbons, with their fate determined largely by the zeolite topology. Notably, we provide the missing link between active and deactivating species, which allows us to propose potential design rules for future-generation catalysts.

Mesoporous Cu-SSZ-13 was created by first synthesizing zeolite H-SSZ-13 and subsequently desilicating the material by base leaching using NaOH in different concentrations. The catalyst materials were prepared by ion exchanging the leached samples back to their acidic form using NH₄NO₃, and to their active Cu form by ion exchanging them with CuSO₄. For comparison, H- and Cu-SSZ-13 were steamed using a wide variety of different conditions. Using a 0.10 M NaOH solution for base leaching, it was found that Cu-SSZ-13 becomes more active in the selective catalytic reduction of NO_x with NH₃ (NH₃-SCR) over the entire temperature region but especially in the low temperature region (3-SCR activity. Ar physisorption coupled with SEM and confocal fluorescence microscopy in combination with two differently sized fluorescent organic probe molecules (i.e., 4-(4-dimethyl-aminostyryl)-1-methyl-pyridinium-iodide and 4-(4-dicyclohexyl-aminostyryl)-1-methyl-pyridinium-iodide) show an increase in the external surface area due to the creation of mesopores. The development of mesoporosity starts from the crystal surface and continues into the crystal with increasing alkaline solution strength, but under our conditions it never reaches the center. On the other hand, zeolite steaming did not successfully introduce mesoporosity and mainly managed to deactivate the Cu-SSZ-13 zeolite catalysts.

A combination of time-resolved synchrotron μ-X-ray diffraction computed tomography (μ-XRD-CT) and μ-pair distribution function computed tomography (μ-PDF-CT) has been applied for the study of an individual Co/γ-Al₂O₃ catalyst pellet during reduction and the early stages of the Fischer–Tropsch synthesis (FTS) reaction, revealing insight into the solid-state changes occurring from within such crystalline materials. Both sets of data were of sufficient quality so as to be able to follow the spatial dependency of Co speciation evolution from Co₃O₄ to CoO to face-centered cubic (fcc) Co metal nanoparticles. These data revealed the samples to be highly heterogeneous and contain two types of Co species: small (≤6.5 nm) nanoparticles that interact strongly with the γ-Al₂O₃ support which are difficult to reduce (remaining as CoO) and nanoparticles that agglomerate and have little interaction or else are weakly interacting with the support but readily reduce in H₂. The Co phase evolution under FTS conditions shows a strong dependence on the Co nanoparticle location; the complementarity between the observations made using μ-XRD-CT vs μ-PDF-CT allowed us to conclude that at the sample periphery a significant amount of agglomerated, weakly interacting with the support, small fcc Co metal nanoparticles (≤7.5 nm) oxidize to CoO/Co₃O₄ during FTS, most likely due to the presence of water vapor produced during the reaction. Catalytic tests demonstrated that this oxidation coincided with a decrease in CH₄ selectivity and increased water-gas shift (WGS) activity. This oxidation of fcc Co nanoparticles (i.e., the removal of the contribution to the XRD signal) also explains the observation of sintering previously reported for such catalysts in the early stages of the FTS reaction.

Here we present the results of a synchrotron-based in situ, time-resolved PXRD study during activation of two Cu-SSZ-13 catalysts under O₂/He and one during standard NH₃-SCR reaction conditions to obtain insight into the migration behaviour of Cu ions.

Combined high‐resolution fluorescence detection X‐ray absorption near‐edge spectroscopy, X‐ray diffraction, and X‐ray emission spectroscopy have been employed under operando conditions to obtain detailed new insight into the nature of the Mo species on zeolite ZSM‐5 during methane dehydroaromatization. The results show that isolated Mo–oxo species present after calcination are converted by CH₄into metastable MoC_xO_yspecies, which are primarily responsible for C₂H_x/C₃H_xformation. Further carburization leads to MoC₃clusters, whose presence coincides with benzene formation. Both sintering of MoC₃and accumulation of large hydrocarbons on the external surface, evidenced by fluorescence‐lifetime imaging microscopy, are principally responsible for the decrease in catalytic performance. These results show the importance of controlling Mo speciation to achieve the desired product formation, which has important implications for realizing the impact of CH₄as a source for platform chemicals.