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.

Transformation of biomass into valuable nitrogen-containing compounds is highly desired, yet limited success has been achieved. Here we report an efficient catalyst system, partially reduced Ru/ZrO , which could catalyze the reductive amination of a variety of biomass-derived aldehydes/ketones in aqueous ammonia. With this approach, a spectrum of renewable primary amines was produced in good to excellent yields. Moreover, we have demonstrated a two-step approach for production of ethanolamine, a large-market nitrogen-containing chemical, from lignocellulose in an overall yield of 10 %. Extensive characterizations showed that Ru/ZrO -containing multivalence Ru association species worked as a bifunctional catalyst, with RuO as acidic promoter to facilitate the activation of carbonyl groups and Ru as active sites for the subsequent imine hydrogenation.

This review provides critical analysis on various downstream processes to convert lignin derived feedstock into fuels, chemicals and materials.

Single-atom catalysts have recently been applied in many applications such as CO oxidation. Experimental in situ investigations into this reaction, however, are limited. Hereby, we present a suite of operando/in situ spectroscopic experiments for structurally well-defined atomically dispersed Rh on phosphotungstic acid during CO oxidation. The identification of several key intermediates and the steady-state catalyst structure indicate that the reactions follow an unconventional Mars-van Krevelen mechanism and that the activation of O2 is rate-limiting. In situ XPS confirms the contribution of the heteropoly acid support while in situ DRIFT spectroscopy consolidates the oxidation state and CO adsorption of Rh. As such, direct observation of three key components, i.e., metal center, support and substrate, is achieved, providing a clearer picture on CO oxidation on atomically dispersed Rh sites. The obtained information are used to engineer structurally similar catalysts that exhibit T20 values up to 130 °C below the previously reported Rh1/NPTA.

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Lignin is a promising feedstock for the production of biofuels due to its availability (15-30 wt % of wood-based biomass) and markedly lower oxygen content than polysaccharides. [1] Considerably more efforts have been paid to the conversion of polysaccharides; [2] nevertheless, the development of ligninbased biofuels is attracting increased attention. Current strategies to produce biofuel from lignin are typically based on two-step processes, in which lignin is first depolymerized into a mixture of simple aromatic compounds (mostly phenols) either by hydrogenation, [3] alkaline [4] or acid [5] hydrolysis, or fast pyrolysis, [6] which is then followed by upgrading into fuels, preferably by hydrodeoxygenation into alkanes. Many advances have been made in the degradation of lignin into phenols; for example, phenolic fractions can be readily obtained by fast pyrolysis from pure lignin [3c,d, 6a] or directly from wood biomass, [6b-e] the latter now being a commercialized process.[7] The second step, that is, the transformation of phenolic compounds into hydrocarbon fuels or other chemicals remains a challenge.[8] The conventional hydrodeoxygenation process based on NiMo and CoMo sulfite catalysts is potentially problematic due to sulfur contamination, coke accumulation, and water-induced catalyst deactivation.[9] Recently, aqueous-phase catalytic systems that convert phenolic compounds into alkanes in a series of hydrogenation and dehydration reactions have been reported (Scheme 1), [10, 3e] which overcome the problems encountered with conventional catalytic systems. While the new system is ideally suited for lignin-based phenolic substrates, it contains several intrinsic limitations-the most obvious is that a dehydration reaction takes place in water. In fact, a previous case study on the dehydration reaction of cyclohexanol to cyclohexene showed that at 100 8C the equilibrium is > 50 % cyclohexanol in water and decreases dramatically to 2 % when the water content in the system is reduced to 10 %.[11] Consequently, high reaction temperatures exceeding 250 8C are required in aqueous systems, which not only implies demanding process engineering, but also high energy consumption.The use of ionic liquids (ILs) could, in principle, overcome these problems as well as maintain the advantages of a waterbased system (high efficiency, phase separation, etc.). Indeed, ILs have been shown to be promising solvents in biofuel production, especially in the transformation of cellulose [12] and in the production of biodiesel.[13] Nevertheless, examples of lignin-based fuel production in ILs remain scarce.[14] Here, we describe the development of a bifunctional catalytic system based on metal nanoparticles (NPs) and ILs, which can effectively convert lignin-derived phenols into alkanes under mild conditions.As can be seen in Scheme 1, the reaction pathway includes catalyzed hydrogenations and a dehydration step that is catalyzed by a Brønsted acid. Following Duponts pioneering work, [15] many notable examples of hydrogenation react...

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The upgrading of plastic waste is one of the grand challenges for the 21 st century owing to its disruptive impact on the environment. Here,w es howt he first example of the upgrading of various aromatic plastic wastes with C À Oand/or C À Cl inkages to arenes (75-85 %y ield) via catalytic hydrogenolysis over aR u/Nb 2 O 5 catalyst. This catalyst not only allows the selective conversion of single-component aromatic plastic,a nd more importantly,e nables the simultaneous conversion of am ixture of aromatic plastic to arenes.T he excellent performance is attributed to unique features including:(1) the small sized Ru clusters on Nb 2 O 5 ,whichprevent the adsorption of aromatic ring and its hydrogenation;(2) the strong oxygen affinity of NbO x species for C À Ob ond activation and Brønsted acid sites for CÀCb ond activation. This study offers ac atalytic path to integrate aromatic plastic waste back into the supply chain of plastic production under the context of circular economy.