High-temperature synthesis of magnetically active and SO3H-functionalized ordered mesoporous carbon with good catalytic performance

Facile preparation protocol of magnetic mesoporous carbon acid catalysts via soft-template self-assembly method and their applications in conversion of xylose into furfural

Furfural is a valuable dehydration product of xylose. It has a broad spectrum of industrial applications. Various catalysts containing SO₃H have been reported for the conversion of xylose into furfural. Nevertheless, the multi-step preparation is tedious, and the catalysts are usually fine powders that are difficult to separate from the suspension. Novel magnetic mesoporous carbonaceous materials (Fe/MC) were successfully prepared via facile self-assembly in a single step. A facile subsequent hydrothermal sulfonation of Fe/MC with concentrated H₂SO₄ at 180°C gave mesoporous carbon bearing SO₃H groups (SO₃H@Fe/MC) without loss of the magnetic properties. Various techniques were employed to characterize the SO₃H@Fe/MC as a candidate catalyst. It showed strong magnetism due to its Fe particles and possessed a 243 m² g^-1 BET-specific surface area and a 90% mesopore volume. The sample contained 0.21 mmol g^-1 of SO₃H and gave a high conversion and an acceptable furfural yield and selectivity (100%, 45% and 45%, respectively) when used at 170°C for 1 h with γ-valerolactone as solvent. The catalyst was easily separated after the catalytic tests by using a magnet, confirming sufficient magneticstability. This article is part of the theme issue 'Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 2)'.

Polystyrene sulphonic acid resins with enhanced acid strength via macromolecular self-assembly within confined nanospace

Tightening environmental legislation is driving the chemical industries to develop efficient solid acid catalysts to replace conventional mineral acids. Polystyrene sulphonic acid resins, as some of the most important solid acid catalysts, have been widely studied. However, the influence of the morphology on their acid strength--closely related to the catalytic activity--has seldom been reported. Herein, we demonstrate that the acid strength of polystyrene sulphonic acid resins can be adjusted through their reversible morphology transformation from aggregated to swelling state, mainly driven by the formation and breakage of hydrogen bond interactions among adjacent sulphonic acid groups within the confined nanospace of hollow silica nanospheres. The hybrid solid acid catalyst demonstrates high activity and selectivity in a series of important acid-catalysed reactions. This may offer an efficient strategy to fabricate hybrid solid acid catalysts for green chemical processes.

Fabrication of magnetic carbonaceous solid acids from banana peel for the esterification of oleic acid

Magnetic carbonaceous solid acids with high catalytic activities were fabricated from banana peel and were successfully used for the esterification of oleic acid.

Synthesis, characterization and properties of Ce-modified S2O82−/ZnAl2O4 solid acid catalysts

A new S₂O₈²⁻/ZnAl₂O₄-4 wt% Ce solid acid catalyst with stable spinel structure performed the high activity and well reusability in esterification of acetic acid and n-butanol.

Development of oxidized sulfur polymer films through a combination of plasma polymerization and oxidative plasma treatment

A novel two-step process consisting of plasma polymerization and oxidative plasma treatment is introduced in this article for the first time for the fabrication of -SO(x)(H)-functionalized surfaces. Plasma-polymerized thiophene (PPT) was initially deposited onto silicon wafers and subsequently SO(x)(H)-functionalized using air or oxygen plasma. The effectiveness of both air and oxygen plasma treatments in introducing sulfur-oxygen groups into the PPT film was investigated as the plasma input specific energy and treatment time were varied. The surface chemistries of untreated and treated PPT coatings were analyzed by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS), whereas spectroscopic ellipsometry was used to evaluate the film thickness and ablation rate. Surface chemistry analyses revealed that high concentrations of -SO(x)(H) functionalities were generated on the surface upon either air or oxygen plasma treatment. It was found that, at low plasma input energies, the oxidation process was dominant whereas, at higher energies, ablation of the film became more pronounced. The combination of thiophene plasma polymerization and air/oxygen plasma treatment was found to be a successful approach to the fabrication of -SO(x)(H)-functionalized surfaces.

Preparation of a sulfonated carbonaceous material from lignosulfonate and its usefulness as an esterification catalyst

Sulfonated carbonaceous material useful as a solid acid catalyst was prepared from lignosulfonate, a waste of the paper-making industry sulfite pulping process, and characterized by 13C-NMR, FT-IR, TGA, SEM and elemental analysis, etc. The sulfonic acid group density and total density of all acid groups in the sulfonated carbonaceous material was determined by titration to be 1.24 mmol/g and 5.90 mmol/g, respectively. Its catalytic activity in the esterification of cyclohexanecarboxylic acid with anhydrous ethanol was shown to be comparable to that of the ionic exchange resin Amberlyst-15, when they were used in the same amount. In the meantime, the sulfonic acid group was found to be leached out by 26%-29% after it was exposed to hot water (95 °C) for 5 h. The catalytic usefulness of the prepared carbonaceous material was investigated by performing esterifications.

Direct synthesis of ordered mesoporous carbons

Ordered mesoporous carbon materials have recently aroused great research interest because of their widespread applications in many areas such as adsorbents, catalysts and supports, gas storage hosts, and electrode materials. The direct synthesis strategy from organic-organic self-assembly involving the combination of polymerizable precursors and block copolymer templates is expected to be more flexible in preparing mesoporous carbons, compared with the traditional nanocasting strategy of complicated and high-cost procedures using mesoporous silica materials as the hard template. In this review, we present the fundamentals and recent advances related to the field of ordered mesoporous carbon materials from the direct synthesis strategy of block copolymer soft-templating, with a focus on their controllable preparation, modification and potential applications. Under the guidance of their formation mechanism, the preparation of ordered mesoporous carbons are discussed in detail by consulting different experimental conditions, including synthetic pathways, precursors, catalysts and templates. Both the mesopore size and morphology control are introduced. The potential applications of pure mesoporous carbons, nonmetallic- and metallic-modified mesoporous carbons, and some interpenetrating carbon-based composites are demonstrated. Furthermore, remarks on the challenges and perspectives of research directions are proposed for further development of the ordered mesoporous carbons (232 references).