Solar-driven upgrading of biomass by coupled hydrogenation using in situ (photo)electrochemically generated H2

With the increasing pressure to decarbonize our society, green hydrogen has been identified as a key element in a future fossil fuel-free energy infrastructure. Solar water splitting through photoelectrochemical approaches is an elegant way to produce green hydrogen, but for low-value products like hydrogen, photoelectrochemical production pathways are difficult to be made economically competitive. A possible solution is to co-produce value-added chemicals. Here, we propose and demonstrate the in situ use of (photo)electrochemically generated H2 for the homogeneous hydrogenation of itaconic acid-a biomass-derived feedstock-to methyl succinic acid. Coupling these two processes offers major advantages in terms of stability and reaction flexibility compared to direct electrochemical hydrogenation, while minimizing the overpotential. An overall conversion of up to ~60% of the produced hydrogen is demonstrated for our coupled process, and a techno-economic assessment of our proposed device further reveals the benefit of coupling solar hydrogen production to a chemical transformation.

Study of Methionine and Cumene Hydroperoxide Reaction Kinetics in the Presence of Nonionic Surfactant

The kinetics of the reaction methionine+cumene hydroperoxide in the presence of nonionic surfactant was studied both in the pre-micellar and post-micellar regions at different temperatures by iodometry. It was established that the rate of the methionine + cumene hydroperoxide reaction depends on the molecular/ionic/micellar form of surfactant in the reaction system. In the post-micellar region the rate of methionine+cumene hydroperoxide reaction slows down due to solubilization of the reacting substances in the micelles. Quantification of solubilization of cumene hydroperoxide and methionine in the micelles has been studied by HPLC analysis. It was obtained that about 30% of cumene hydroperoxide, which is more hydrophobic than methionine, is solubilized in the micelles, as a result the concentration of cumene hydroperoxide in the reaction environment decreases and the rate of reaction in the post-micellar region also decreases. Based on the kinetic studies the reaction rate constant was determined and the value of activation energy was obtained.

Activation, Deactivation and Reversibility Phenomena in Homogeneous Catalysis: A Showcase based on the Chemistry of Rhodium/Phosphine Catalysts

In the present work, the rich chemistry of rhodium/phosphine complexes, which are applied as homogeneous catalysts to promote a wide range of chemical transformations, has been used to showcase how the in situ generation of precatalysts, the conversion of precatalysts into the actually active species, as well as the reaction of the catalyst itself with other components in the reaction medium (substrates, solvents, additives) can lead to a number of deactivation phenomena and thus impact the efficiency of a catalytic process. Such phenomena may go unnoticed or may be overlooked, thus preventing the full understanding of the catalytic process which is a prerequisite for its optimization. Based on recent findings both from others and the authors’ laboratory concerning the chemistry of rhodium/diphosphine complexes, some guidelines are provided for the optimal generation of the catalytic active species from a suitable rhodium precursor and the diphosphine of interest; for the choice of the best solvent to prevent aggregation of coordinatively unsaturated metal fragments and sequestration of the active metal through too strong metal–solvent interactions; for preventing catalyst poisoning due to irreversible reaction with the product of the catalytic process or impurities present in the substrate.

Merging of a chemical reaction with microbial metabolismviainverse phase transfer catalysis for efficient production of redMonascuspigments

Cascade reactions,i.e., biosynthesis of OMPs and chemical modification of hydrophobic OMPs with water-soluble MSG, are carried out successfully by IPTC.

Rhodium-calix[4]pyrrole and rhodium-tetraphenyl porphyrin: preparation, surface grafting and their catalytic application in nitro-benzene reduction

Rhodium containing macromolecules calix[4]pyrrole (RhCP) and tetraphenyl porphyrin (RhTPP) were prepared, grafted on functionalized SBA-15 and demonstrated as promising catalysts for nitro-arene reduction.

Selective hydrogenation of α-pinene to cis-pinane over Ru nanocatalysts in aqueous micellar nanoreactors

Hydrogenation of α-pinene took place in the lipophilic core between the metal and the hydrogen-containing micelles.

Chiral surfactant-type catalyst: enantioselective reduction of long-chain aliphatic ketoesters in water

A series of amphiphilic ligands were designed and synthesized. The rhodium complexes with the ligands were applied to the asymmetric transfer hydrogenation of broad range of long-chained aliphatic ketoesters in neat water. Quantitative conversion and excellent enantioselectivity (up to 99% ee) was observed for α-, β-, γ-, δ- and ε-ketoesters as well as for α- and β-acyloxyketone using chiral surfactant-type catalyst 2. The CH/π interaction and the strong hydrophobic interaction of long aliphatic chains between the catalyst and the substrate in the metallomicelle core played a key role in the catalytic transition state. Synergistic effects between the metal-catalyzed site and the hydrophobic microenvironment of the core in the micelle contributed to high stereoselectivity.

Cooperative effects of ruthenium micellar catalysts and added surfactants in transfer hydrogenation of ketones in water

Added surfactants S boost the performances of surface-active catalysts RuLⁿ (n = 8, 16) in transfer hydrogenation of hydrophobic ketones in water by forming mixed micelles.

Mild water-promoted ruthenium nanoparticles as an efficient catalyst for the preparation of cis-rich pinane

Ru nanoparticles were prepared using P123 micelles in water as a stabilizing agent. Microreactors were formed in the hydrogenation reaction system.

Aqueous Sonogashira coupling of aryl halides with 1-alkynes under mild conditions: use of surfactants in cross-coupling reactions

Aqueous solutions of common and inexpensive surfactants (e.g. SDS and CTAB) are surveyed as an alternative to organic solvents in Sonogashira cross-coupling. Aryl-bromide substrates are best coupled under Cu-free conditions.

Combination of best promoter and micellar catalyst for chromic acid oxidation of 1-butanol to 1-butanal in aqueous media at room temperature

In aqueous acidic media, picolinic acid, 2,2'-bipyridine and 1,10-phenanthroline promoted Cr(VI) oxidation of 1-butanol produces 1-butanal. 1-butanal is separated from mixture by fractional distillation. The anionic surfactant (SDS) and neutral surfactant (TX-100) accelerate the process while the cationic surfactant (CPC) retards the reaction. Combination of bipy and SDS is the best choice for chromic acid oxidation of 1-butanol to 1-butanal in aqueous media.

Rhodium diphosphine complexes: a case study for catalyst activation and deactivation

The present work provides an overview of possible activation and deactivation phenomena in homogeneous catalytic processes promoted by different types of rhodium complexes containing diphosphine ligands.