Yuan Kou

Ionic liquids: applications in catalysis

Abstract The use of room temperature ionic liquids as either solvents or catalysts has been the subject of considerable recent attention because of the prospects for “green” catalysis. This paper presents a review of the potential applications of these unique liquid materials in industrial catalysis.

Highly Selective Catalytic Conversion of Phenolic Bio‐Oil to Alkanes

Oil and water: A new energy-efficient and atom-economical catalytic route for the production of alkanes and methanol by upgrading the phenolic fraction of bio-oil has been developed. The one-pot aqueous-phase hydrodeoxygenation process is based on two catalysts facilitating consecutive hydrogenation, hydrolysis, and dehydration reactions.

Selective degradation of wood lignin over noble-metal catalysts in a two-step process.

Direct conversion of lignin into alkanes and methanol was carried out in a two-step process (hydrogenolysis and hydrogenation) involving initial treatment of white birch wood sawdust with H2 in dioxane/water/phosphoric acid using carbon supported Ru, Pd, Rh, or Pt as catalysts. The resulting monomers and dimers obtained by selective C-O hydrogenolysis were then hydrogenated in near-crit. water empolying Pd/C as the catalyst. The study is of interest with respect to prodn. of biofuel from lignin.

Hydrodeoxygenation of Lignin-Derived Phenols into Alkanes by Using Nanoparticle Catalysts Combined with Brønsted Acidic Ionic Liquids**

The transformation of lignin-derived phenolic compds. to alkanes was achieved using catalysts based on Bronsted acidic ionic liqs. (ILs). The catalytic system is composed of metal nanoparticles (NPs) and a functionalized Bronsted acidic IL immobilized in a nonfunctionalized IL, allowing hydrogenation and dehydration reactions to occur in tandem. Compared to previous systems that are either performed with metal sulfite or with mineral acid/ supported metal catalysts in water, this system allows lignin derivs. to be upgraded in an efficient and less energy-demanding process.

Preparation, characterization and application of amino acid-based green ionic liquids

A family of novel ionic liquids with amino acids and their derivatives as cations and environmentally benign materials as anions have been synthesized using easy preparation techniques. The ionic liquids obtained have the same characteristics as conventional imidazolium ionic liquids and the same chiralities as natural amino acids. Thermal stabilities, phase behaviour, viscosities and miscibilities of the representative family members have been investigated, generally showing no difference from conventional ionic liquids. These amino acid ionic liquids may be used as catalysts and “fully green” solvents in the cycloaddition of cyclopentadiene to methyl acrylate, which is a typical Diels–Alder reaction. This approach to treating amino acids and their derivatives can serve as an alternative to traditional ionic liquids having synthetic chemical components.

New generation ionic liquids: cations derived from amino acids

Two families of a new generation of ionic liquids, in which the chiral cations are directly derived from naturally occurring alpha-amino acids and alpha-amino acid ester salts, have been obtained via very simple preparations.

Biphasic Hydrogenation over PVP Stabilized Rh Nanoparticles in Hydroxyl Functionalized Ionic Liquids

Polyvinyl pyrrolidone stabilized rhodium nanoparticles are highly soluble in hydroxyl-functionalized ionic liquids, providing an effective and highly stable catalytic system. In hydrogenation reactions, excellent results were obtained, and transmission electron microscopy, solubility determinations, and leaching experiments were employed to quantify the advantages of this catalytic system.

Platinum-Modulated Cobalt Nanocatalysts for Low-Temperature Aqueous-Phase Fischer−Tropsch Synthesis

Fischer-Tropsch synthesis (FTS) is an important catalytic process for liquid fuel generation, which converts coal/shale gas/biomass-derived syngas (a mixture of CO and H2) to oil. While FTS is thermodynamically favored at low temperature, it is desirable to develop a new catalytic system that could allow working at a relatively low reaction temperature. In this article, we present a one-step hydrogenation-reduction route for the synthesis of Pt-Co nanoparticles (NPs) which were found to be excellent catalysts for aqueous-phase FTS at 433 K. Coupling with atomic-resolution scanning transmission electron microscopy (STEM) and theoretical calculations, the outstanding activity is rationalized by the formation of Co overlayer structures on Pt NPs or Pt-Co alloy NPs. The improved energetics and kinetics from the change of the transition states imposed by the lattice mismatch between the two metals are concluded to be the key factors responsible for the dramatically improved FTS performance.

Development of Palladium Surface-Enriched Heteronuclear Au-Pd Nanoparticle Dehalogenation Catalysts in an Ionic Liquid

Heteronuclear Au-Pd nanoparticles were prepared and immobilized in the functionalized ionic liquid [C(2)OHmim][NTf(2)]. The structural and electronic properties of the nanoparticles were characterized by a range of techniques and the surface of the nanoparticles was found to be enriched in Pd. Moreover, the extent of Pd enrichment is easily controlled by varying the ratio of Au and Pd salts used in the synthesis. The heteronuclear nanoparticles were found to be effective catalysts in dehalogenation reactions with no activity observed for the pure Au nanoparticles and only limited activity for the pure Pd nanoparticles. The activity of the heteronuclear nanoparticles may be attributed to charge transfer from Pd to Au and consequently to more efficient reductive elimination.

Highly selective hydrogenation of aromatic chloronitro compounds to aromatic chloroamines with ionic-liquid-like copolymer stabilized platinum nanocatalysts in ionic liquids

Platinum nanoparticles (PtNPs stabilized by an ionic-liquid-like-copolymer (IP) immobilized in various ionic liquids (ILs)) effectively catalyze the selective hydrogenation of aromatic chloronitro compounds to aromatic chloroamines, a reaction of considerable commercial significance. The preparation of 2,4-dichloro-3-aminophenol (DAP) has been primarily studied due to its important industrial applications. DAP is usually prepared from 2,4-dichloro-3-nitrophenol (DNP) by reduction with hydrogen using Ni- or Pt-based catalysts. Compared to reactions in molecular (organic) solvents, the ILs system provides superior selectivity with functionalized ILs containing an alcohol group demonstrating the best recyclability, and ultimately achieving a turnover number of 2025 which is 750 fold higher than Raney nickel catalyst. A universal catalyst–ionic liquid system for the conversion of aromatic chloronitro compounds to aromatic chloroamines was also established. TEM, XPS, IR spectroscopy were used to characterize the morphology of the nanocatalysts allowing their structure to be correlated to their activity.