Hairong Yue

Synthesis of Ethanol via Syngas on Cu/SiO2 Catalysts with Balanced Cu0–Cu+ Sites

This paper describes an emerging synthetic route for the production of ethanol (with a yield of ~83%) via syngas using Cu/SiO(2) catalysts. The remarkable stability and efficiency of the catalysts are ascribed to the unique lamellar structure and the cooperative effect between surface Cu(0) and Cu(+) obtained by an ammonia evaporation hydrothermal method. Characterization results indicated that the Cu(0) and Cu(+) were formed during the reduction process, originating from well-dispersed CuO and copper phyllosilicate, respectively. A correlation between the catalytic activity and the Cu(0) and Cu(+) site densities suggested that Cu(0) could be the sole active site and primarily responsible for the activity of the catalyst. Moreover, we have shown that the selectivity for ethanol or ethylene glycol can be tuned simply by regulating the reaction temperature.

A copper-phyllosilicate core-sheath nanoreactor for carbon–oxygen hydrogenolysis reactions

Hydrogenolysis of carbon-oxygen bonds is a versatile synthetic tool in organic synthesis. Copper-based catalysts have been intensively explored as the copper sites account for the highly selective hydrogenation of carbon-oxygen bonds. However, the inherent drawback of conventional copper-based catalysts is the deactivation by metal-particle growth and unstable surface Cu(0) and Cu(+) active species in the strongly reducing hydrogen and oxidizing carbon-oxygen atmosphere. Here we report the superior reactivity of a core (copper)-sheath (copper phyllosilicate) nanoreactor for carbon-oxygen hydrogenolysis of dimethyl oxalate with high efficiency (an ethanol yield of 91%) and steady performance (>300 h at 553 K). This nanoreactor, which possesses balanced and stable Cu(0) and Cu(+) active species, confinement effects, an intrinsically high surface area of Cu(0) and Cu(+) and a unique tunable tubular morphology, has potential applications in high-temperature hydrogenation reactions.

An Alternative Synthetic Approach for Efficient Catalytic Conversion of Syngas to Ethanol

Ethanol is an attractive end product and a versatile feedstock because a widespread market exists for its commercial use as a fuel additive or a potential substitute for gasoline. Currently, ethanol is produced primarily by fermentation of biomass-derived sugars, particularly those containing six carbons, but coproducts 5-carbon sugars and lignin remain unusable. Another major process for commercial production of ethanol is hydration of ethylene over solid acidic catalysts, yet not sustainable considering the depletion of fossil fuels. Catalytic conversion of synthetic gas (CO + H2) could produce ethanol in large quantities. However, the direct catalytic conversion of synthetic gas to ethanol remains challenging, and no commercial process exists as of today although the research has been ongoing for the past 90 years, since such the process suffers from low yield and poor selectivity due to slow kinetics of the initial C-C bond formation and fast chain growth of the C2 intermediates. This Account describes recent developments in an alternative approach for the synthesis of ethanol via synthetic gas. This process is an integrated technology consisting of the coupling of CO with methanol to form dimethyl oxalate and the subsequent hydrogenation to yield ethanol. The byproduct of the second step (methanol) can be separated and used in circulation as the feedstock for the coupling step. The coupling reaction of carbon monoxide for producing dimethyl oxalate takes place under moderate reaction conditions with high selectivity (∼95%), which ideally leads to a self-closing, nonwaste, catalytic cycling process. This Account also summarizes the progress on the development of copper-based catalysts for the hydrogenation reaction with remarkable efficiencies and stability. The unique lamellar structure and the cooperative effect between surface Cu(0) and Cu(+) species are responsible for the activity of the catalyst with high yield of ethanol (∼91%). The understanding of nature of valence states of Cu could also guide the rational design of Cu-based catalysts for other similar reactions, particularly for hydrogenation catalytic systems. In addition, by regulating the reaction condition and the surface structure of the catalysts, the products in the hydrogenation steps, such as ethanol, methyl glycolate, and ethylene glycol, could be tuned efficiently. This synthetic approach enables a more sustainable ethanol, methyl glycolate, and ethylene glycol synthesis in industry and greatly reduces the dependence on petroleum resources and the emission of the greenhouse gas.

Scientific and Engineering Progress in CO 2 Mineralization Using Industrial Waste and Natural Minerals

ABSTRACT The issues of reducing CO 2 levels in the atmosphere, sustainably utilizing natural mineral resources, and dealing with industrial waste offer challenging opportunities for sustainable development in energy and the environment. The latest advances in CO 2 mineralization technology involving natural minerals and industrial waste are summarized in this paper, with great emphasis on the advancement of fundamental science, economic evaluation, and engineering applications. We discuss several leading large-scale CO 2 mineralization methodologies from a technical and engineering-science perspective. For each technology option, we give an overview of the technical parameters, reaction pathway, reactivity, procedural scheme, and laboratorial and pilot devices. Furthermore, we present a discussion of each technology based on experimental results and the literature. Finally, current gaps in knowledge are identified in the conclusion, and an overview of the challenges and opportunities for future research in this field is provided.

Adsorption and photocatalytic degradation behaviors of rhodamine dyes on surface-fluorinated TiO2 under visible irradiation

Surface-fluorinated TiO2 (F-TiO2) particles was synthesized by a simple fluorosilanization method to serve as a visible-light photocatalyst for rapid degradation of Rhodamine B (RhB) dyes. The fluroalkylsilane (FAS-17) was covalently immobilized on the TiO2 particles via robust Si–O bonds. The changes in surface properties of the F-TiO2 particles were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM) and zeta potential measurements. The optical property of the F-TiO2 particles was determined by UV-visible spectroscopy. Upon the fluorination modification, the zeta potential of TiO2 particles switched from positive to negative, whilst the optical property of bulk TiO2 particles remained almost unchanged. Photodegradation experimental results demonstrated that zwitterionic RhB dyes were more favorably adsorbed on F-TiO2 rather than on the Ti(IV) sites of the pristine TiO2, and that the photodegradation reaction of RhB on F-TiO2 proceeded much faster than that on the pristine TiO2. However, the adsorption and photodegradation rate of anionic methyl orange (MO) dyes did not show an obvious change on F-TiO2. These results suggested that the molecular structure of dyes played a key role in visible-light photodegradation reactions on F-TiO2 particles. Positive-charged diethylamine groups of RhB molecular structures were postulated to promote the adsorption of RhB dyes on the surface of F-TiO2 particles, thus leading to easy electron injection and induction of rapid photodegradation under visible-light illumination.

Insight into the synergism between MnO2 and acid sites over Mn–SiO2@TiO2 nano-cups for low-temperature selective catalytic reduction of NO with NH3

The rational synthesis of low-temperature catalysts with high catalytic activity and stability is highly desirable for the selective catalytic reduction of NO with NH3. Here we synthesized a Mn–SiO2/TiO2 nano-cup catalyst via the coating of the mesoporous TiO2 layers on SiO2 spheres and subsequent inlay of MnO2 nanoparticles in the narrow annulus. This catalyst exhibited superior catalytic SCR activities and stability for low-temperature selective catalytic reduction of NO with NH3, with NO conversion of ∼100%, N2 selectivity above 90% at a temperature ∼140 °C. The characterization results, such as BET, XRD, H2-TPR, O2/NH3-TPD and XPS, indicated that this nano-cup structure catalyst possesses high concentration and dispersion of Mn4+ active species, strong chemisorbed O− or O22− species and highly stable MnOX active components over the annular structures of the TiO2 shell and SiO2 sphere, and thus enhanced the low-temperature SCR performance.

Molybdenum Disulfide-Alumina/Nickel-Foam Catalyst with Enhanced Heat Transfer for Syngas Sulfur-Resistant Methanation

Sulfur‐resistant CO methanation by using MoS2‐based catalysts possesses potential to produce synthetic natural gas from the direct use of un‐desulfurized syngas with a low H2/CO ratio in industry. However, hotspots raised in the high exothermic reaction lead to catalyst deactivation and an uncontrollable reactor temperature, both of which hinder industrial applications. A metal‐structured MoS2‐Al2O3/Ni‐foam catalyst with stable MoS2 active species and high heat‐transfer efficiency was synthesized to resist deactivation and to remove the heat of the reaction through a hydrothermal synthesis process. This catalyst exhibited superior activity and stability in the sulfur‐resistant methanation of syngas and has potential applications in highly exothermic and endothermic reactions.

Microwave-assisted seed preparation for producing easily phase-transformed anatase to rutile

Titanium dioxide, as one of the most important optical materials, is usually manufactured by the hydrolysis of titanyl salts, in which the seeds are a key to affect product properties. In the sulfate process, hydrolysis normally leads to anatase which is then converted to rutile in a high-temperature calcination with the help of a crystal transforming agent. In this work, the initial seeds were prepared through microwave heating and then the seeds were introduced to the hydrolysis of dilute titanyl sulfate solution. The results showed that the hydrolysis product had a narrower particle size distribution compared with traditional processes, and it was much more easily converted to rutile product under low-temperature calcination in the absence of a crystal transforming agent. The microwave effects on the seed preparation conditions were evaluated, and the kinetic behavior of the seeds in hydrolysis was also studied.