Jiaguang Zhang

Highly efficient, NiAu-catalyzed hydrogenolysis of lignin into phenolic chemicals

A highly efficient, stable NiAu catalyst that exhibits unprecedented low temperature activity in lignin hydrogenolysis was for the first time developed, leading to the formation of 14 wt% aromatic monomers from organosolv lignin at 170 °C in pure water.

Ni-based bimetallic heterogeneous catalysts for energy and environmental applications

Bimetallic catalysts have attracted extensive attention for a wide range of applications in energy production and environmental remediation due to their tunable chemical/physical properties. These properties are mainly governed by a number of parameters such as compositions of the bimetallic systems, their preparation method, and their morphostructure. In this regard, numerous efforts have been made to develop “designer” bimetallic catalysts with specific nanostructures and surface properties as a result of recent advances in the area of materials chemistry. The present review highlights a detailed overview of the development of nickel-based bimetallic catalysts for energy and environmental applications. Starting from a materials science perspective in order to obtain controlled morphologies and surface properties, with a focus on the fundamental understanding of these bimetallic systems to make a correlation with their catalytic behaviors, a detailed account is provided on the utilization of these systems in the catalytic reactions related to energy production and environmental remediation. We include the entire library of nickel-based bimetallic catalysts for both chemical and electrochemical processes such as catalytic reforming, dehydrogenation, hydrogenation, electrocatalysis and many other reactions.

Stabilizing a Platinum1 Single‐Atom Catalyst on Supported Phosphomolybdic Acid without Compromising Hydrogenation Activity

In coordination chemistry, catalytically active metal complexes in a zero- or low-valent state often adopt four-coordinate square-planar or tetrahedral geometry. By applying this principle, we have developed a stable Pt1 single-atom catalyst with a high Pt loading (close to 1 wt %) on phosphomolybdic acid(PMA)-modified active carbon. This was achieved by anchoring Pt on the four-fold hollow sites on PMA. Each Pt atom is stabilized by four oxygen atoms in a distorted square-planar geometry, with Pt slightly protruding from the oxygen planar surface. Pt is positively charged, absorbs hydrogen easily, and exhibits excellent performance in the hydrogenation of nitrobenzene and cyclohexanone. It is likely that the system described here can be extended to a number of stable SACs with superior catalytic activities.

Conversion of chitin derived N-acetyl-D-glucosamine (NAG) into polyols over transition metal catalysts and hydrogen in water

N-Acetyl-D-glucosamine (NAG), the monomer of the worlds second most abundant biopolymer chitin, has been for the first time converted to its corresponding amide/amino substituted sugar alcohols, smaller C2–4 polyols and N-acetylmonoethanolamine (NMEA), over noble metal catalysts in the presence of hydrogen in water. Four commercialized catalysts were investigated, and Ru/C exhibited the best performance—achieving 8.7% NMEA, 6.1% C4 polyols, and 71.9% C6 polyols (N-containing) under 180 °C, 40 bar H2, 1 h with 1 mol% loading. Kinetic studies were conducted, which revealed four major reaction pathways that lead to various products. In particular, retro-aldol reaction-hydrogenation was confirmed to be the pathway forming NMEA. The effects of additives (NaOH and WO3) on the reaction were also tested.

Thermally stable single atom Pt/m-Al2O3 for selective hydrogenation and CO oxidation

Single-atom metal catalysts offer a promising way to utilize precious noble metal elements more effectively, provided that they are catalytically active and sufficiently stable. Herein, we report a synthetic strategy for Pt single-atom catalysts with outstanding stability in several reactions under demanding conditions. The Pt atoms are firmly anchored in the internal surface of mesoporous Al2O3, likely stabilized by coordinatively unsaturated pentahedral Al3+ centres. The catalyst keeps its structural integrity and excellent performance for the selective hydrogenation of 1,3-butadiene after exposure to a reductive atmosphere at 200 °C for 24 h. Compared to commercial Pt nanoparticle catalyst on Al2O3 and control samples, this system exhibits significantly enhanced stability and performance for n-hexane hydro-reforming at 550 °C for 48 h, although agglomeration of Pt single-atoms into clusters is observed after reaction. In CO oxidation, the Pt single-atom identity was fully maintained after 60 cycles between 100 and 400 °C over a one-month period.

Popping of Graphite Oxide: Application in Preparing Metal Nanoparticle Catalysts

A popcorn-like transformation of graphite oxide (GO) is reported and used to synthesize metal nanoparticle catalysts. The popping step is unique and essential, not only generating a high-surface-area support but also partially decomposing the metal precursors to form well-separated metal oxide nuclei, which would further evolve into highly dispersed and uniform-sized nanoparticles in the subsequent reduction.

Formic acid-mediated liquefaction of chitin

We report pure formic acid-mediated liquefaction of chitin for the first time. Formic acid exhibited a remarkable ability in the functionalization and depolymerization of ball-milled chitin as well as proto-chitin in raw shrimp shells. Up to 60% combined yield of a series of structurally identified monomeric products was obtained after reaction at 100 °C for 12 h. The product stream could also converge to a single compound, 5-(formyloxymethyl)furfural (FMF), in 35% yield after a longer reaction time. The product evolution was monitored by electrospray ionization mass spectrometry (ESI-MS), and the key finding is that the liquefaction involves several major chemical events in the following sequence: (1) the process starts with partial formylation of the hydroxyl groups in chitin side chains generating soluble polymeric derivatives; (2) formic acid catalyzes polymer chain breakage in a non-conventional, non-hydrolytic pathway forming dehydrated monomers and oligomers; (3) as formylation continues, water accumulates in the system, which induces more monomer and oligomer generation via hydrolysis, and the formation of rehydrated products. As such, water is constantly generated via formylation and subsequently consumed in hydrolysis and rehydration, making the process a self-sustained one.

Direct conversion of mono- and polysaccharides into 5-hydroxymethylfurfural using ionic-liquid mixtures

Platform chemicals are usually derived from petrochemical feedstocks. A sustainable alternative commences with lignocellulosic biomass, a renewable feedstock, but one that is highly challenging to process. Ionic liquids (ILs) are able to solubilize biomass and, in the presence of catalysts, convert the biomass into useful platform chemicals. Herein, we demonstrate that mixtures of ILs are powerful systems for the selective catalytic transformation of cellulose into 5-hydroxymethylfurfural (HMF). Combining ILs with continuous HMF extraction into methyl-isobutyl ketone or 1,2-dimethoxyethane, which form a biphase with the IL mixture, allows the online separation of HMF in high yield. This one-step process is operated under relatively mild conditions and represents a significant step forward towards sustainable HMF production.

Production of Glucosamine from Chitin by Co-solvent Promoted Hydrolysis and Deacetylation

Production of renewable chemicals with established market and high value is highly desirable in biomass utilization. Herein, glucosamine, an amino sugar with various applications, was generated in a single step by the acid‐catalyzed transformation of chitin. Aprotic polar solvents were mixed with water to promote the hydrolysis as well as the deacetylation reactions, significantly enhancing product yield and/or reducing the concentration and amount of acid catalyst required. By employing the optimized co‐solvent system, glucosamine was achieved with 80 % yield at 175 °C in 1 h from ball‐milled chitin, in sharp contrast with the pure water system with the same acid concentration in which less than 1 % glucosamine was obtained. Correlations between the promotional effect and various solvent property parameters were discussed and proposed, providing guidance on the choice of solvent for further optimization of the co‐solvent system for similar applications.

Rapid nanoparticle-catalyzed hydrogenations in triphasic millireactors with facile catalyst recovery

We report a triphasic segmented flow millireactor for rapid nanoparticle-catalyzed gas–liquid reactions with facile catalyst recovery. Process intensification using a pseudo-biphasic scheme of reactor operation allows order-of-magnitude reduction in reaction times for a variety of substrates and catalysts.