Controlling hydrogenation selectivity with Pd catalysts on carbon nitrides functionalized silica

Enhanced stability of sub-nanometric iridium decorated graphitic carbon nitride for H2 production upon hydrous hydrazine decomposition

Stabilizing metal nanoparticles is vital for large scale implementations of supported metal catalysts, particularly for a sustainable transition to clean energy, e.g., H₂ production. In this work, iridium sub-nanometric particles were deposited on commercial graphite and on graphitic carbon nitride by a wet impregnation method to investigate the metal-support interaction during the hydrous hydrazine decomposition reaction. To establish a structure-activity relationship, samples were characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. The catalytic performance of the synthesized materials was evaluated under mild reaction conditions, i.e. 323 K and ambient pressure. The results showed that graphitic carbon nitride (GCN) enhances the stability of Ir nanoparticles compared to graphite, while maintaining remarkable activity and selectivity. Simulation techniques including Genetic Algorithm geometry screening and electronic structure analyses were employed to provide a valuable atomic level understanding of the metal-support interactions. N anchoring sites of GCN were found to minimise the thermodynamic driving force of coalescence, thus improving the catalyst stability, as well as to lead charge redistributions in the cluster improving the resistance to poisoning by decomposition intermediates.

A ruthenium nanocatalyst for the atmospheric hydrogenation of 1,5-cyclooctadiene

A ruthenium nanocatalyst is utilized for the first time for the highly efficient and selective hydrogenation of 1,5-cyclooctadiene under atmospheric hydrogen pressure. Under the optimized reaction conditions, the conversion of 1,5-cyclooctadiene and the selectivity for cyclooctene are >99% and 95%, respectively. The turnover frequency is 451 h−1, which is higher than that ever reported for Ru complex catalysts.

Pd nanoparticles confined in mesoporous N-doped carbon silica supports: a synergistic effect between catalyst and support

Palladium nanoparticles of similar size were deposited on different supports, layers of carbon materials (with and without nitrogen doping) on the surface of a MCF (mesocellular foam) silica.

Assessment of Chitosan Based Catalyst and their Mode of Action

Introduction:

The popularity of chitosan is increasing among the researchers due to its environment friendly nature, high activity and easy approachability. Chitosan based catalysts are not only the most active and selective in catalytic reaction, but their “green” accessibility also makes them promising in organic catalysis. Chitosan is commonly extracted from chitin by alkaline deacetylation and it is the second abundant biopolymer in nature after cellulose. Chitosan based catalysts are advantageous by means of non-metallic activation as it involves small organic molecules. The robustness, nontoxicity, the lack of metal leaching possibility, inertness towards moisture and oxygen, easy handling and storage are the main advantages of organocatalysts. Traditional drawbacks associated with the metal-based heterogeneous catalysts, like longer reaction times during any synthesis, metal-leaching after every reaction and structural instability of the catalyst for prolonged recycling experiments are also very negligible for chitosan based catalysts. Besides, these catalysts can contribute more in catalysis due to their reusability and these special features increase their demand as the functionalized and profitable catalysts.

Objective:

The thorough description about the preparation of organocatalysts from chitosan and their uniqueness and novel activities in various famous reactions includes as the main aim of this review. Reusable and recycle nature of chitosan based organocatalysts gain the advantages over traditional and conventional catalyst which is further discussed over here.

Methods and Discussions:

In this article only those reactions are discussed where chitosan has been used both as support in heterogeneous catalysts or used as a catalyst itself without any co-catalyst for some reactions. Owing to its high biodegradability, nontoxicity, and antimicrobial properties, chitosan is widely-used as a green and sustainable polymeric catalyst in vast number of the reactions. Most of the preparations of catalyst have been achieved by exploring the complexation properties of chitosan with metal ions in heterogeneous molecular catalysis. Organocatalysis with chitosan is primarily discussed for carbon-carbon bond-forming reactions, carbon dioxide fixation through cyclo- addition reaction, condensation reaction and fine chemical synthesis reactions. Furthermore, its application as an enantioselective catalyst is also considered here for the chiral, helical organization of the chitosan skeleton. Moreover, another advantage of this polymeric catalyst is its easy recovery and reusability for several times under solvent-free conditions which is also explored in the current article.

Conclusion:

Important organocatalyzed reactions with either native chitosan or functionalized chitosan as catalysts have attracted great attention in the recent past. Also, chitosan has been widely used as a very promising support for the immobilization of catalytic metals for many reactions. In this review, various reactions have been discussed which show the potentiality of chitosan as catalyst or catalyst support.

Identify the Active Phase of Fe–CN Composites for Oxidation Removal of Rhodamine B with H2O2

Fe-containing carbon nitrides (Fe–CN) prepared with various CN precursors, including dicyandiamide, melamine, guanidine hydrochloride and urea, were characterized by X-ray diffraction, thermal gravimetric analysis, N2 physisorption, transmission electron microscopy, X-ray photoelectron spectroscopy and atomic emission spectrometer measurements, and used as catalysts to catalyze the rhodamine B oxidation with H2O2 as oxidant. Characteristic results showed that Fe–CN exhibits different compositions, properties and catalytic performances if different CN precursors are used. The Fe–CN prepared from dicyandiamide contains mainly CN phase and certain amounts of surface Fe2O3 phase, exhibits the best activity; while that prepared from urea contains mainly Fe2O3 phase and few amounts of CN phase, exhibits the worst activity. Contrasting experiments conducted under light irradiation, with a supported Fe/CN_D catalyst, and that using a washed catalyst, suggested that the surface Fe2O3 is the active site of the reaction.

Direct Synthesis of Renewable Dodecanol and Dodecane with Methyl Isobutyl Ketone over Dual-Bed Catalyst Systems

For the first time, we demonstrated two integrated processes for the direct synthesis of dodecanol or 2,4,8-trimethylnonane (a jet fuel range C₁₂ -branched alkane) using methyl isobutyl ketone (MIBK) that can be derived from lignocellulose. The reactions were carried out in dual-bed continuous flow reactors. In the first bed, MIBK was selectively converted to a mixture of C₁₂ alcohol and ketone. Over the Pd-modified magnesium- aluminium hydrotalcite (Pd-MgAl-HT) catalyst, a high total carbon yield (73.0 %) of C₁₂ oxygenates can be achieved under mild conditions. In the second bed, the C₁₂ oxygenates generated in the first bed were hydrogenated to dodecanol over a Ru/C catalyst or hydrodeoxygenated to 2,4,8-trimethylnonane over a Cu/SiO₂ catalyst. The as-obtained dodecanol can be used as feedstock in the production of sodium dodecylsulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS), which are widely used as surfactants or detergents. The asobtained 2,4,8-trimethylnonane can be blended into conventional jet fuel without hydroisomerization.

Efficient hydrogen generation from formic acid using AgPd nanoparticles immobilized on carbon nitride-functionalized SBA-15

Bimetallic AgPd nanoparticles were successfully immobilized on graphitic carbon nitride (g-C₃N₄) functionalized SBA-15 for the first time by a facile co-reduction method.

Reactivity and mechanism investigation of selective hydrogenation of 2,3,5-trimethylbenzoquinone on in situ generated metallic cobalt

We successfully developed Co-based catalysts for efficient and selective hydrogenation of TMBQ. Metallic Co was proved to be responsible for TMBQ hydrogenation. The hydrogenation process was also investigated by DFT calculation.

Nickel–platinum nanoparticles immobilized on graphitic carbon nitride as highly efficient catalyst for hydrogen release from hydrous hydrazine

Here we demonstrate that the combination of NiPt alloy nanoparticles with a graphitic carbon nitride (g-C₃N₄) support facilitates H₂ production from hydrous hydrazine in an alkaline solution under moderate conditions.

Metal-free mesoporous carbon nitride catalyze the Friedel–Crafts reaction by activation of benzene

Graphitic carbon nitride is an active and stable catalyst for Friedel–Crafts acylation of benzene with hexanoyl chloride.