Enhanced catalyst selectivity in the direct synthesis of H2O2 through Pt incorporation into TiO2 supported AuPd catalysts

The introduction of small quantities of Pt into supported AuPd nanoparticles is found to result in enhanced catalytic efficiency in the direct synthesis of H2O2. This is attributed to a combination of superior H2O2 synthesis rates, as determined through calculation of initial rates of reaction, and an inhibition of H2O2 degradation pathways, achieved through the modification of Pd oxidation states. Through gas replacement experiments we demonstrate that it is possible to reach concentrations of H2O2 approaching those produced during initial stages of the current industrial means of H2O2 production

Synthesis and catalysis of chemically reduced metal–metalloid amorphous alloys

This is the published version. Copyright 2012 Royal Society of ChemistryAmorphous alloys structurally deviate from crystalline materials in that they possess unique short-range ordered and long-range disordered atomic arrangement. They are important catalytic materials due to their unique chemical and structural properties including broadly adjustable composition, structural homogeneity, and high concentration of coordinatively unsaturated sites. As chemically reduced metal–metalloid amorphous alloys exhibit excellent catalytic performance in applications such as efficient chemical production, energy conversion, and environmental remediation, there is an intense surge in interest in using them as catalytic materials. This critical review summarizes the progress in the study of the metal–metalloid amorphous alloy catalysts, mainly in recent decades, with special focus on their synthetic strategies and catalytic applications in petrochemical, fine chemical, energy, and environmental relevant reactions. The review is intended to be a valuable resource to researchers interested in these exciting catalytic materials. We concluded the review with some perspectives on the challenges and opportunities about the future developments of metal–metalloid amorphous alloy catalysts

Catalytic Production of Functional Monomers from Lysine and Their Application in High-Valued Polymers

Lysine is a key raw material in the chemical industry owing to its sustainability, mature fermentation process and unique chemical structure, besides being an important nutritional supplement. Multiple commodities can be produced from lysine, which thus inspired various catalytic strategies for the production of these lysine-based chemicals and their downstream applications in functional polymer production. In this review, we present a fundamental and comprehensive study on the catalytic production process of several important lysine-based chemicals and their application in highly valued polymers. Specifically, we first focus on the synthesis process and some of the current industrial production methods of lysine-based chemicals, including ε-caprolactam, α-amino-ε-caprolactam and its derivatives, cadaverine, lysinol and pipecolic acid. Second, the applications and prospects of these lysine-based monomers in functional polymers are discussed such as derived poly (lysine), nylon-56, nylon-6 and its derivatives, which are all of growing interest in pharmaceuticals, human health, textile processes, fire control and electronic manufacturing. We finally conclude with the prospects of the development of both the design and synthesis of new lysine derivatives and the expansion of the as-synthesized lysine-based monomers in potential fields

Green Production Technology of the Monomer of Nylon-6: Caprolactam

After two decades’ endeavor, the Research Institute of Petroleum Processing (RIPP) has successfully developed a green caprolactam (CPL) production technology. This technology is based on the integration of titanium silicate (TS)-1 zeolite with the slurry-bed reactor for the ammoximation of cyclohexanone, the integration of silicalite-1 zeolite with the moving-bed reactor for the gas-phase rearrangement of cyclohexanone oxime, and the integration of an amorphous nickel (Ni) catalyst with the magnetically stabilized bed reactor for the purification of caprolactam. The world’s first industrial plant based on this green CPL production technology has been built and possesses a capacity of 200 kt·a−1. Compared with existing technologies, the plant investment is pronouncedly reduced, and the nitrogen (N) atom utilization is drastically improved. The waste emission is reduced significantly; for example, no ammonium sulfate byproduct is produced. As a result, the price difference between CPL and benzene drops. In 2015, the capacity of the green CPL production technology reached 3 × 106 t·a−1, making China the world’s largest CPL producer, with a global market share exceeding 50%

Enhanced catalyst selectivity in the direct synthesis of H2O2 through Pt incorporation into TiO2 supported AuPd catalysts

The introduction of small quantities of Pt into supported AuPd nanoparticles is found to result in enhanced catalytic efficiency in the direct synthesis of H2O2. This is attributed to a combination of superior H2O2 synthesis rates, as determined through calculation of initial rates of reaction, and an inhibition of H2O2 degradation pathways, achieved through the modification of Pd oxidation states. Through gas replacement experiments we demonstrate that it is possible to reach concentrations of H2O2 approaching those produced during initial stages of the current industrial means of H2O2 production

Fischer–Tropsch Synthesis to Lower Olefins over Potassium-Promoted Reduced Graphene Oxide Supported Iron Catalysts

Fischer–Tropsch synthesis to lower olefins (FTO) opens up a compact and economical way to the production of lower olefin directly from syngas (CO and H₂) derived from natural gas, coal, or renewable biomass. The present work is dedicated to a systematic study on the effect of K in the reduced graphene oxide (rGO) supported iron catalysts on the catalytic performance in FTO. It is revealed that the activity, expressed as moles of CO converted to hydrocarbons per gram Fe per second (iron time yield to hydrocarbons, termed as FTY), increased first with the content of K, passed through a maximum at 646 μmol_CO g_Fe^–1 s^–1 over the FeK1/rGO catalyst, and then decreased at higher K contents. Unlike the evolution of the activity, the selectivity to lower olefins increased steadily with K, giving the highest selectivity to lower olefins of 68% and an olefin/paraffin (O/P) ratio of 11 in the C₂–C₄ hydrocarbons over the FeK2/rGO catalyst. The volcanic evolution of the activity is attributed to the interplay among the positive effect of K on the formation of Hägg carbide, the active phase for FTO, and the negative roles of K in increasing the size of Hägg carbide at high content and blocking the active phase by K-induced carbon deposition. The monotonic increase in the selectivity to lower olefins is ascribed to the improved chain-growth ability and surface CO/H₂ ratio in the presence of K, which favorably suppressed the unwanted CH₄ production and secondary hydrogenation of lower olefins

Undercoordinated Site-Abundant and Tensile-Strained Nickel for Low-Temperature CO_<i>x</i> Methanation

By means of the rapid quenching (RQ) technique, we fabricate RQ Ni with peculiar undercoordinated site (UCS) abundant and tensile-strained structural characteristics. In liquid-phase CO methanation at 473 K, RQ Ni displays markedly higher specific activity and CH₄ selectivity in comparison to Raney Ni, supported Ni, and Al₂O₃-supported Pd and Pt. RQ Ni shows comparable activity but higher CH₄ selectivity in comparison to Ru/Al₂O₃, with Ru being documented as the most active metal for CO methanation. Density functional theory (DFT) calculations confirm that the UCSs are the active centers and reveal that the tensile-strain effect can further accelerate the rate-limiting CO dissociation step. Attractively, RQ Ni is also powerful in converting the greenhouse gas CO₂ to CH₄ at 473 K with an unprecedentedly high TOF of CO₂ of 86.9 × 10^–3 s^–1 and impressively high selectivity of >99%