Sensitivity of the glycerol oxidation reaction to the size and shape of the platinum nanoparticles in Pt/SiO2 catalysts

Mesoporous silica-supported platinum nanocatalysts for colorimetric detection of glucose, cholesterol, and C-reactive protein

Noble metal nanoparticles decorated on a catalyst support with a large specific surface area can exhibit enhanced catalytic activity. To this end, a synthetic method to heterogeneously and evenly nucleate platinum nanoparticles (Pt NPs) onto mesoporous silica nanoparticles (MSNs) is developed. The obtained Pt NP-modified MSNs (Pt-MSNs) are characterized as a thin layer of 3 nm-sized Pt NPs densely assembled on the MSN surface, by which the throughput of the peroxidase-like activity of Pt-MSNs is greatly improved. The utility of Pt-MSNs in colorimetric detection of analytes is validated for two different assay schemes. Firstly, colloidally dispersed Pt-MSNs are employed as a peroxidase-mimic in a two-step cascade reaction to quantitate glucose/cholesterol based on the amount of H2O2 produced by glucose/cholesterol oxidase. Secondly, detection of C-reactive protein (CRP) is conducted on a solid substrate by adopting a sandwich immunoassay format. Detection limits are estimated to be 20 μM, 55 μM, and 3.9 pM for glucose, cholesterol, and CRP, respectively.

Stable and Active Au Catalyst Supported on CeMnO3 Perovskite for Selective Oxidation of Glycerol

The selective oxidation of glycerol holds promise to transform glycerol into value-added chemicals. However, it remains a big challenge to achieve satisfactory selectivity toward the specific product at high conversion due to the multiple reaction pathways. Here, we prepare a hybrid catalyst via supporting Au nanoparticles on CeMnO₃ perovskite with a modest surface area, achieving promoted conversion of glycerol (90.1%) and selectivity of glyceric acid (78.5%), which are much higher than those of CeMnO_x solid-solution-supported Au catalysts with larger surface area and other Ce-based or Mn-based Au catalysts. The strong interaction between Au and CeMnO₃ perovskite facilitates the electron transfer from the B-site metal (Mn) in the CeMnO₃ perovskite to Au and stabilizes Au nanoparticles, which results in the enhanced catalytic activity and stability for glycerol oxidation. Valence band photoemission spectral analysis reveals that the uplifted d-band center of Au/CeMnO₃ promotes the adsorption of the glyceraldehyde intermediate on the catalyst surface, which benefits further oxidation of glyceraldehyde into glyceric acid. The flexibility of the perovskite support provides a promising strategy for the rational design of high-performance glycerol oxidation catalysts.

Strengthening the Connection between Science, Society and Environment to Develop Future French and European Bioeconomies: Cutting-Edge Research of VAALBIO Team at UCCS

The development of the future French and European bioeconomies will involve developing new green chemical processes in which catalytic transformations are key. The VAALBIO team (valorization of alkanes and biomass) of the UCCS laboratory (Unité de Catalyse et Chimie du Solide) are working on various catalytic processes, either developing new catalysts and/or designing the whole catalytic processes. Our research is focused on both the fundamental and applied aspects of the processes. Through this review paper, we demonstrate the main topics developed by our team focusing mostly on oxygen- and hydrogen-related processes as well as on green hydrogen production and hybrid catalysis. The social impacts of the bioeconomy are also discussed applying the concept of the institutional compass.

Designing Sites in Heterogeneous Catalysis: Are We Reaching Selectivities Competitive With Those of Homogeneous Catalysts?

A critical review of different prominent nanotechnologies adapted to catalysis is provided, with focus on how they contribute to the improvement of selectivity in heterogeneous catalysis. Ways to modify catalytic sites range from the use of the reversible or irreversible adsorption of molecular modifiers to the immobilization or tethering of homogeneous catalysts and the development of well-defined catalytic sites on solid surfaces. The latter covers methods for the dispersion of single-atom sites within solid supports as well as the use of complex nanostructures, and it includes the post-modification of materials via processes such as silylation and atomic layer deposition. All these methodologies exhibit both advantages and limitations, but all offer new avenues for the design of catalysts for specific applications. Because of the high cost of most nanotechnologies and the fact that the resulting materials may exhibit limited thermal or chemical stability, they may be best aimed at improving the selective synthesis of high value-added chemicals, to be incorporated in organic synthesis schemes, but other applications are being explored as well to address problems in energy production, for instance, and to design greener chemical processes. The details of each of these approaches are discussed, and representative examples are provided. We conclude with some general remarks on the future of this field.

A review of recent progress on electrocatalysts toward efficient glycerol electrooxidation

Glycerol electrooxidation has attracted immense attention due to the economic advantage it could add to biodiesel production. One of the significant challenges for the industrial development of glycerol electrooxidation process is the search for a suitable electrocatalyst that is sustainable, cost effective, and tolerant to carbonaceous species, results in high performance, and is capable of replacing the conventional Pt/C catalyst. We review suitable, sustainable, and inexpensive alternative electrocatalysts with enhanced activity, selectivity, and durability, ensuring the economic viability of the glycerol electrooxidation process. The alternatives discussed here include Pd-based, Au-based, Ni-based, and Ag-based catalysts, as well as the combination of two or three of these metals. Also discussed here are the prospective materials that are yet to be explored for glycerol oxidation but are reported to be bifunctional (being capable of both anodic and cathodic reaction). These include heteroatom-doped metal-free electrocatalysts, which are carbon materials doped with one or two heteroatoms (N, B, S, P, F, I, Br, Cl), and heteroatom-doped nonprecious transition metals. Rational design of these materials can produce electrocatalysts with activity comparable to that of Pt/C catalysts. The takeaway from this review is that it provides an insight into further study and engineering applications on the efficient and cost-effective conversion of glycerol to value-added chemicals.

Glycerol aerobic oxidation to glyceric acid over Pt/hydrotalcite catalysts at room temperature

Glycerol (GLY) aerobic oxidation in an aqueous solution is one of the most prospective pathways in biomass transformation, where the supported catalysts based on noble metals (mainly Au, Pd, Pt) are most commonly employed. Herein, Pt nanoparticles supported on rehydrated Mg_xAl₁-hydrotalcite (denoted as re-Mg_xAl₁-LDH-Pt) were prepared via impregnation-reduction method followed by an in situ rehydration process, which showed high activity and selectivity towards GLY oxidation to produce glyceric acid (GLYA) at room temperature. The metal-support interfacial structure and catalyst basicity were modulated by changing the Mg/Al molar ratio of the hydrotalcite precursor, and the optimal performance was achieved on re-Mg₆Al₁-LDH-Pt with a GLY conversion of 87.6% and a GLYA yield of 58.6%, which exceeded the traditional activated carbon and oxide supports. A combinative study on structural characterizations (XANES, CO-FTIR spectra, and benzoic acid titration) proves that a higher Mg/Al molar ratio promotes the formation of positively charged Pt^δ+ species at metal-support interface, which accelerates bond cleavage of α-C-H and improves catalytic activity. Moreover, a higher Mg/Al molar ratio provides a stronger basicity of support that contributes to the oxidation of terminal-hydroxyl and thus enhances the selectivity of GLYA. This catalyst with tunable metal-support interaction shows prospective applications toward transformation of biomass-based polyols.

Glycerol to Glyceraldehyde Oxidation Reaction Over Pt-Based Catalysts Under Base-Free Conditions

Glycerol valorization through partial oxidation is a good way of obtaining many different molecules with high added value such as glyceric acid, tartronic acid, dihydroxyacetone, etc. Among the potential products, glyceraldehyde is an interesting chemical compound for its various applications in different domains such as organic chemistry, medical, and cosmetic industries. In the present paper, we studied the effect of different supports on the glycerol oxidation reaction in a batch reactor applying base-free conditions. The tested catalysts were Pt-based materials deposited on various supports (i.e., SiO₂, TiO₂, ZSM-5, γ-Al₂O₃), which were synthesized using a deposition method followed by a chemical reduction. The catalysts were extensively characterized (BET, ICP, XRD, TEM, XPS), highlighting differences in terms of specific surface areas, textural properties, and Pt nanoparticles sizes. We evidenced a direct relation between glycerol conversion and glyceraldehyde selectivity (i.e., an increase in glycerol conversion leads to a decrease in glyceraldehyde selectivity). The Pt/γ-Al₂O₃ catalysts exhibited the highest activity, but their selectivity to glyceraldehyde significantly decreased with time on stream. Pt/SiO₂ presented the highest selectivity to glyceraldehyde owing to a slower reaction rate, which allows envisioning technical opportunities to continuously extract the formed glyceraldehyde from the mixture.

Nanostructured Metal Catalysts for Selective Hydrogenation and Oxidation of Cellulosic Biomass to Chemicals

Conversion of biomass to chemicals provides essential products to human society from renewable resources. In this context, achieving atom-economical and energy-efficient conversion with high selectivity towards target products remains a key challenge. Recent developments in nanostructured catalysts address this challenge reporting remarkable performances in shape and morphology dependent catalysis by metals on nano scale in energy and environmental applications. In this review, most recent advances in synthesis of heterogeneous nanomaterials, surface characterization and catalytic performances for hydrogenation and oxidation for biorenewables with plausible mechanism have been discussed. The perspectives obtained from this review paper will provide insights into rational design of active, selective and stable catalytic materials for sustainable production of value-added chemicals from biomass resources.

Platinum-Based Heterogeneous Catalysts for Nitrile Synthesis via Aerobic Oxidative Coupling of Alcohols and Ammonia

Transition-metal-catalyzed aerobic oxidative coupling of alcohols and ammonia represents an attractive atom-economical synthetic route to prepare nitriles. Heterogeneous platinum catalysts have been widely used for aerobic alcohol oxidation to aldehydes and carboxylic acids but have not been applied to nitrile synthesis. In this work, we show that carbon-supported Pt catalysts are effective for this transformation. Unpromoted Pt is competent with benzylic substrates bearing either electron-donating or electron-withdrawing substituents. Use of both K₂CO₃ and Bi additives accelerates the rate of alcohol oxidation and affords high yields with challenging heterocyclic alcohols.

Glycerol Production and Transformation: A Critical Review with Particular Emphasis on Glycerol Reforming Reaction for Producing Hydrogen in Conventional and Membrane Reactors

Glycerol represents an emerging renewable bio-derived feedstock, which could be used as a source for producing hydrogen through steam reforming reaction. In this review, the state-of-the-art about glycerol production processes is reviewed, with particular focus on glycerol reforming reactions and on the main catalysts under development. Furthermore, the use of membrane catalytic reactors instead of conventional reactors for steam reforming is discussed. Finally, the review describes the utilization of the Pd-based membrane reactor technology, pointing out the ability of these alternative fuel processors to simultaneously extract high purity hydrogen and enhance the whole performances of the reaction system in terms of glycerol conversion and hydrogen yield.

Selective glycerol oxidation over ordered mesoporous copper aluminum oxide catalysts

Ordered mesoporous Cu–Al₂O₃ catalysts were employed for the selective oxidation of glycerol into value-added products. Co-solvents such as ethanol, 1-propanol, and tert-butanol strongly improve the reaction kinetics.

Probing the spontaneous reduction mechanism of platinum ions confined in the nanospace by X-ray absorption fine structure spectroscopy

The reduction mechanism of Pt⁴⁺ ions confined in the channel of multi-walled carbon nanotubes was mainly investigated using X-ray absorption fine structure (XAFS) spectroscopy, with the aid of TEM, Raman, XRD and ICP-AES studies.

Factors affecting activity and selectivity in the oxidation of glycerol promoted by platinum catalysts

Selectivity in glycerol oxidation with Pt catalysts depends strongly on reaction conversion because of poisoning by the accumulated products.