Search Results (6)

The immobilization of suspension catalysts in flexible, fibrillated films offers a promising solution to the mass transfer limitations often encountered in three-phase hydrogenation reactions. This study investigates the catalytic performance and mass transfer properties of fibrillated films in the hydrogenation of nitrobenzene to aniline, comparing them to free-flowing powdered catalysts. Fibrillated films were prepared from Pd/C catalysts with varying thicknesses (100–400 µm), and their performance was evaluated through kinetic studies in both batch reactors and microreactors. The specific activity of the films was significantly influenced by film thickness with thinner films demonstrating lower mass transfer limitations. However, mass transfer limitations were observed in thicker films, prompting the development of alternative film designs, including enhanced macro-porous films and sandwich structures. These modifications successfully minimized diffusion limitations, achieving similar specific activity to the powder catalysts while maintaining the mechanical stability of the films. This work demonstrates the feasibility of using fibrillated films for continuous catalytic processes and highlights their potential for efficient catalyst reuse, avoiding filtration steps and enhancing process sustainability. Furthermore, while PTFE remains indispensable for producing such films due to its mechanical and thermal stability, ongoing research focuses on identifying more environmentally friendly alternatives without compromising performance. Full article

Large-scale hydrogen production by the steam reforming of long-chain hydrocarbon fuel is highly desirable for fuel-cell application. In this work, LaNiO₃ perovskite materials doped with different rare earth elements (Ce, Pr, Tb and Sm) were prepared by a sol-gel method, and the derivatives supported Ni-based catalysts which were successfully synthesized by hydrogen reduction. The physicochemical properties of the as-prepared catalysts were characterized by powder X-ray diffraction, high-resolution transmission electron microscopy, N₂ adsorption–desorption isotherms, H₂ temperature-programmed reduction, and X-ray photoelectron spectroscopy. The catalytic performance of the as-prepared catalysts for hydrogen production was investigated via the steam reforming of n-dodecane. The results showed that the catalyst forms perovskite oxides after calcination with abundant mesopores and macropores. After reduction, Ni particles were uniformly distributed on perovskite derivatives, and can effectively reduce the particles’ sizes by doping with rare earth elements (Ce, Pr, Tb and Sm). Compared with the un-doped catalyst, the activity and hydrogen-production rate of the catalysts are greatly improved with rare earth element (Ce, Pr, Tb and Sm)-doped catalysts, as well as the anti-carbon deposition performance. This is due to the strong interaction between the uniformly distributed Ni particles and the support, as well as the abundant oxygen defects on the catalyst surface. Full article

Herein, we present an in-depth investigation into the enhancement of catalytic soot oxidation through cerium-doped three-dimensional ordered macroporous (3DOM) La-Co-Ni-based perovskites synthesized with the colloidal crystal template (CCT) method. The 3DOM structure significantly contributes to the accessibility and interaction efficiency between soot and catalyst. Based on the results of powder X-ray diffraction (XRD), N₂ adsorption-desorption measurements, scanning electron microscopy (SEM), temperature-programmed oxidation of NO (NO-TPO), temperature-programmed reduction of H₂ (H₂-TPR), in situ infrared Fourier transform spectroscopy (In-situ DRIFTS), and temperature-programmed oxidation (TPO) reactions, the role of cerium doping in modifying the structural and catalytic properties of 3DOM perovskite-type La_2−xCe_xCoNiO₆ catalysts was investigated systematically. The optimized cerium doping ratio in La_2−xCe_xCoNiO₆ catalysts can improve the microenvironment for efficient soot-catalyst contact, enhancing the catalytic activity of soot oxidation. Among the catalysts, the 3DOM La_0.8Ce_1.2CoNiO₆ catalyst shows the highest catalytic activity for soot oxidation, whose T₁₀, T₅₀, and T₉₀ values are 306 °C, 356 °C, and 402 °C, respectively. The mechanism of the cerium doping effect for boosting soot oxidation is proposed: The doping of Ce ions can increase the surface oxygen species, which is the main active species for promoting the key step of NO oxidation to NO₂ in catalyzing soot oxidation. This research provides a new strategy to develop high-efficient non-noble metal catalysts for soot oxidation in pollution control and sustainable environmental practices. Full article

Soot-catalyst contact represents the main critical issue for an effective regeneration of catalytic (i.e., catalyst-coated) diesel particulate filters (DPFs). Most of the literature reviews on this topic have mainly been focused on studies dealing with powdered soot-catalyst mixtures. Although the results obtained on powders surely provide significant indications, especially in terms of intrinsic activity of materials towards soot oxidation, they cannot be directly extended to DPFs due to completely different soot-catalyst contact conditions generated during filtration and subsequent regeneration. In this work, attention is devoted to catalytic DPFs and, more specifically, studies on both catalyst dispersion and soot distribution inside the filter are critically reviewed from the perspective of soot-catalyst contact optimization. The main conclusion drawn from the literature analysis is that, in order to fully exploit the potential of catalytic DPFs in soot abatement, both a widespread and homogeneous presence of catalyst in the macro-pores of the filter walls and a suitably low soot load are needed. Under optimal soot-catalyst contact conditions, the consequent decrease in the temperature required for soot oxidation to values within the temperature range of diesel exhausts suggests the passage to a continuous functioning mode for catalytic filters with simultaneous filtration and regeneration, thus overcoming the drawbacks of periodic regeneration performed in current applications. Full article

Macroporous cardo polyetherketone (PEK-C) powder catalyst bearing covalently ionic liquids (PEK-C-ILs) was prepared, it exhibited a high catalytic performance for biomass hydrolysis. A hydrolysis mechanism of inulin over this new catalyst was proposed as well. The influences of degree of chloromethylation of PEK-C, catalyst dosage, reaction temperature, pore size of PEK-C-ILs and inulin concentration were investigated. A high conversion of inulin of 99.7% was obtained under the optimal reaction conditions. Meanwhile, the hydrolysis kinetics was studied under different conditions. The proposed kinetic model of inulin hydrolysis catalyzed by PEK-C-ILs was established and it successfully predicted the inulin hydrolysis in wider ranges of experimental conditions. The results demonstrated that the catalytic inulin hydrolysis performance of PEK-C-ILs is better than that of homogenous ILs due to that there was a high-density spatial distribution of active sites on the surface and inner pore wall of PEK-C after the ILs was immobilized. Furthermore, the stability including chemical structure and physical appearance and reusability tests showed that PEK-C-ILs catalyst could be effectively separated and recovered from hydrolysates and has excellent reusability. Importantly, using the PEK-C-ILs as catalyst makes the recycling of ILs simplified, efficient and the hydrolysis process more economical. At the same time, it avoided the potential hazards of homogenous ILs to the environment. Therefore, it is a kind of green catalyst with potential application prospect in many catalysis fields. Full article

Synthetic zeolites are widely used as catalysts/carriers for many petrochemical reactions and in refining processes. These materials are usually synthesized in a powder form and must be shaped prior to use in industrial reactors. This review presents the state-of-the-art of the zeolite shaping technology describing the main modifications induced by the interactions between the zeolite and the binder. Additionally, a strategy is presented to overcome the diffusion limitations associated to the microporous structure of zeolites, consisting in the introduction of hierarchical porosity in the binder. Several developments in the field of hierarchical aluminas are summarized in this article, highlighting the possibility to design different ordered/disordered mesoporous and macroporous structures. Full article