Tuning zeolite properties for highly efficient synthesis of propylene from methanol

Series of nanosized ZSM-5 samples is synthesized at 170 °C, 150 °C, 120 °C and 100 °C. Experimental data show that the decrease of crystallization temperature leads to significant changes in zeolite properties. Crystals synthesized at 100 °C exhibit many framework defects with lower acid sites density, strength and larger external surface area. The selectivity to light olefins and the propylene-to-ethylene ratio increases as the crystallization temperature decreases. Propylene-to-ethylene ratio above 6 with the highest selectivity to propylene of 53 % is obtained over ZSM-5 catalyst prepared at 100 °C. Stability of the nanosized zeolite in MTO is also improved compared to industrial sample with similar Si/Al ratio. This catalytic performance is a result of the decrease in the acid sites density, strength and the crystals’ size, providing shorter diffusion path and larger external surface area. The presence of structural defects and different external surface are of the crystals has been shown to play an important role in the MTO catalyst performance

Self-Regeneration of Cobalt and Nickel Catalysts Promoted with Bismuth for Non-deactivating Performance in Carbon Monoxide Hydrogenation

International audienc

Selective Oxidation of Alcohols to Carbonyl Compounds over Small Size Colloidal Ru Nanoparticles

International audienc

Opportunities for intensification of Fischer-Tropsch synthesis through reduced formation of methane over cobalt catalysts in microreactors

Due to the global growth in production of synthetic fuels via the Gas-to-Liquid (GTL), Coal-To-Liquid (CTL) and Biomass-To-Liquid (BTL) processes, academic and industrial interest in Fischer-Tropsch synthesis (FTS) research has increased during the past decade. The undesired product of FTS is methane and it is formed in amounts higher than expected according to the current understanding of the FTS mechanism. Therefore, it is important to gain better understanding of methane formation in order to optimize the FTS process. In this review we discuss the reasons responsible for higher than expected methane selectivity under FTS conditions over cobalt-based FTS catalysts and describe novel microreactors for use in FTS. These novel reactors could help improve reaction selectivity and yield, as well as offer significant economic benefits. Recommendations are given for intensification of FTS in terms of product selectivity by improved selection of catalysts, process conditions and reactor configurations

Selective electrogenerative oxidation of 5-hydroxymethylfurfural to 2,5-furandialdehyde

2,5‐furandialdehyde (DFF) was synthesized by electrogenerative oxidation of 5‐hydroxymethylfurfural (HMF) over a PtRu catalyst with 89 % selectivity at 50 °C after 17 h. This approach opens an avenue for a selective, energy‐efficient and green oxidation of biomass‐derived platform alcohols to added‐value chemicals

Impact and Detailed Action of Sulfur in Syngas on Methane Synthesis on Ni/γ-Al₂O₃ Catalyst

Stability and deactivation phenomena are of utmost importance for metal nanocatalysts from both fundamental and industrial points of view. The presence of small amounts of sulfur at ppm and ppb levels in the synthesis gas produced from fossil and renewable sources (e.g., biomass, coal) is a major reason for deactivation of nickel catalysts for carbon monoxide hydrogenation. This paper addresses reaction pathways and deactivation mechanisms of alumina-supported nickel catalysts for methane synthesis from pure syngas and syngas containing small amounts of sulfur. A combination of SSITKA and operando FTIR is indicative of both reversible molecular and irreversible dissociative carbon monoxide adsorption on nickel nanoparticles under the reaction conditions. Methanation reaction involves irreversible carbon monoxide adsorption, dissociation, and hydrogenation on nanoparticle steps and edges. Hydrogenation of adsorbed carbon species leading to methane seems to be the reaction kinetically relevant step. Molecular forms of carbon monoxide reversibly adsorbed on nickel terraces are likely not to be involved in carbon monoxide hydrogenation. The results suggest a competition between sulfur and carbon monoxide for nickel surface sites. During methanation, sulfur preferentially adsorbs on the sites of reversible molecular carbon monoxide adsorption, whereas the low-coordinated nickel sites responsible for carbon monoxide dissociation and hydrogenation are affected to a lesser extent by sulfur poisoning. The active sites of carbon monoxide hydrogenation are poisoned much more rapidly by sulfur, when the catalyst has been exposed to small amounts of H₂S in the absence of methanation

Dual Metal-Acid Pd-Br Catalyst for Selective Hydrodeoxygenation of 5-Hydroxymethylfurfural (HMF) to 2,5-Dimethylfuran at Ambient Temperature

Supported metal catalysts have found broad applications in heterogeneous catalysis. In the conventional bifunctional catalyst, the active metal sites are associated with the metal nanoparticles, while the acid sites are usually localized over the oxide support. Herein, we report a novel type of supported metal bifunctional catalyst, which combined the advantages of the promotion and bifunctionality. The catalyst was designed by the pretreatment of supported palladium catalysts with bromobenzene. The promotion with bromine creates Bronsted acid sites, which are localized directly on the surface of metal nanoparticles. An intimacy between metal and acid functions in this bifunctional catalyst generates unique catalytic properties in hydrodeoxygenation of 5-hydroxymethylfurfural to dimethylfuran, occurring with the yield up to 96% at ambient temperature under 5 bar of H-2. The catalyst exhibits stable catalytic performance

Etude des mécanismes d’activation des catalyseurs à base de Fe et Sb par des techniques operando TEM et XAS

International audienc

Soldering of Iron Catalysts for Direct Synthesis of Light Olefins from Syngas under Mild Reaction Conditions

High-temperature Fischer–Tropsch synthesis represents a sustainable alternative for direct light olefin synthesis from syngas derived from fossil and renewable feedstocks. It is found that the promotion of iron catalysts with metals used for soldering (Bi and Pb) results in a remarkable increase in the light olefin production rate with a possibility to conduct Fischer–Tropsch synthesis at low reaction pressure. A combination of characterization techniques uncovered notable migration of the promoting elements during the reaction and decoration of iron carbide nanoparticles with the promoters. The promoters seem to facilitate CO dissociation by removing O atoms from iron carbide

Direct Photocatalytic Synthesis of Acetic Acid from Methane and CO at Ambient Temperature Using Water as Oxidant

International audienceDirect functionalization of methane selectively to value-added chemicals is still one of the main challenges in modern science. Acetic acid is an important industrial chemical produced nowadays by expensive and environmentally unfriendly carbonylation of methanol using homogeneous catalysts. Here, we report a new photocatalytic reaction route to synthesize acetic acid from CH4 and CO at room temperature using water as the sole external oxygen source. The optimized photocatalyst consists of a TiO2 support and ammonium phosphotungstic polyoxometalate (NPW) clusters anchored with isolated Pt single atoms (Pt1). It enables a stable synthesis of 5.7 mmol·L–1 acetic acid solution in 60 h with the selectivity over 90% and 66% to acetic acid on liquid-phase and carbon basis, respectively, with the production of 99 mol of acetic acid per mol of Pt. Combined isotopic and in situ spectroscopy investigation suggests that synthesis of acetic acid proceeds via a photocatalytic oxidative carbonylation of methane over the Pt1 sites, with the methane activation facilitated by water-derived hydroxyl radicals