Daniel Curulla-Ferré

Indium Oxide as a Superior Catalyst for Methanol Synthesis by CO2 Hydrogenation

Methanol synthesis by CO2 hydrogenation is attractive in view of avoiding the environmental implications associated with the production of the traditional syngas feedstock and mitigating global warming. However, there still is a lack of efficient catalysts for such alternative processes. Herein, we unveil the high activity, 100 % selectivity, and remarkable stability for 1000 h on stream of In2 O3 supported on ZrO2 under industrially relevant conditions. This strongly contrasts to the benchmark Cu-ZnO-Al2 O3 catalyst, which is unselective and experiences rapid deactivation. In-depth characterization of the In2 O3 -based materials points towards a mechanism rooted in the creation and annihilation of oxygen vacancies as active sites, whose amount can be modulated in situ by co-feeding CO and boosted through electronic interactions with the zirconia carrier. These results constitute a promising basis for the design of a prospective technology for sustainable methanol production.

De Novo Design of Nanostructured Iron–Cobalt Fischer–Tropsch Catalysts

Audio cassettes hold the key to enhancing Fischer–Tropsch catalysis. Catalysts based on ultra‐thin cobalt shells surrounding cheap iron oxide cores (see picture) are developed, an approach previously optimized for preparing magnetic tape for audio cassettes. These particles are easily made on a large scale, and are excellent Fischer–Tropsch catalysts, giving good diesel fractions.

Operando Synchrotron X‐ray Powder Diffraction and Modulated‐Excitation Infrared Spectroscopy Elucidate the CO2 Promotion on a Commercial Methanol Synthesis Catalyst

Optimal amounts of CO2 are added to syngas to boost the methanol synthesis rate on Cu-ZnO-Al2 O3 in the industrial process. The reason for CO2 promotion is not sufficiently understood at the particle level due to the catalyst complexity and the high demands of characterization under true reaction conditions. Herein, we applied operando synchrotron X-ray powder diffraction and modulated-excitation infrared spectroscopy on a commercial catalyst to gain insights into its morphology and surface chemistry. These studies unveiled that Cu and ZnO agglomerate and ZnO particles flatten under CO/H2 and/or CO2 /H2 . Under the optimal CO/CO2 /H2 mixture, sintering is prevented and ZnO crystals adopt an elongated shape due to the minimal presence of the H2 O byproduct, enhancing the water-gas shift activity and thus the methanol production. Our results provide a rationale to the CO2 promotion emphasizing the importance of advanced analytical methods to establish structure-performance relations in heterogeneous catalysis.

Effect of the Polymeric Stabilizer in the Aqueous Phase Fischer-Tropsch Synthesis Catalyzed by Colloidal Cobalt Nanocatalysts

A series of small and well defined cobalt nanoparticles were synthesized by the chemical reduction of cobalt salts in water using NaBH4 as a reducing agent and using various polymeric stabilizers. The obtained nanocatalysts of similar mean diameters (ca. 2.6 nm) were fully characterized and tested in the aqueous phase Fischer-Tropsch Synthesis (AFTS). Interestingly, the nature and structure of the stabilizers used during the synthesis of the CoNPs affected the reduction degree of cobalt and the B-doping of these NPs and consequently, influenced the performance of these nanocatalysts in AFTS.

Carbon nanofibres-supported KCoMo catalysts for syngas conversion into higher alcohols

The development of industrially-viable heterogeneous catalysts for higher alcohol (HA) synthesis via direct syngas conversion is hindered by the limited understanding of structural and electronic descriptors of their performance. Here, K-promoted CoMo(5 wt%)-based catalysts were investigated to shed light onto property–function relations. Evaluation of impregnated oxides and C-based materials identified a higher HA selectivity for the catalyst supported on carbon nanofibres obtained by the simultaneous addition of all metals. Using this carrier, additional solids were synthesised via ball milling as well as a sol–gel method with citric acid, which enhanced the CO conversion. After confirming the positive influence of K and a unitary Co/Mo ratio, the impact of temperature (573–773 K) and pressure (0.1–5 MPa) upon activation through reduction by hydrogen was investigated. A combination of two steps, one at 723 K and ambient pressure, fostering the HA selectivity (22%), and a second, more extended, at 573 K and 5 MPa, boosting the CO conversion (14%), maximised the space time yield of HA, which matches that of the best comparable CoMo system reported in the literature (ca. 0.12 gHA gcat−1 h−1) in spite of the 13-times lower metal loading. Characterisation by X-ray diffraction, temperature-programmed reduction by H2, X-ray photoelectron spectroscopy, operando infrared spectroscopy and electron microscopy uncovered that this originated from the atomic intermixing of Co and Mo in binary oxide phases and their high dispersion, enabling proximity and an effective reduction to low oxidation states of the metal sites (0 and +2 for Mo and 0 for Co) upon activation and reaction.