다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Owing to the increasing emissions of carbon dioxide (CO2), human life and the ecological environment have been affected by global warming and climate changes. To mitigate the concentration of CO2 in the atmosphere various strategies have been implemented such as separation, storage, and utilization of CO2. Although it has been explored for many years, hydrogenation reaction, an important representative among chemical conversions of CO2, offers challenging opportunities for sustainable development in energy and the environment. Indeed, the hydrogenation of CO2 not only reduces the increasing CO2 buildup but also produces fuels and chemicals. In this critical review we discuss recent developments in this area, with emphases on catalytic reactivity, reactor innovation, and reaction mechanism. We also provide an overview regarding the challenges and opportunities for future research in the field (319 references).

Recent advances in catalytic hydrogenation of carbon dioxide

Catalysis for the valorization of exhaust carbon: from CO2 to chemicals, materials, and fuels. technological use of CO2.

Carbon capture and storage (CCS) is broadly recognised as having the potential to play a key role in meeting climate change targets, delivering low carbon heat and power, decarbonising industry and, more recently, its ability to facilitate the net removal of CO2 from the atmosphere. However, despite this broad consensus and its technical maturity, CCS has not yet been deployed on a scale commensurate with the ambitions articulated a decade ago. Thus, in this paper we review the current state-of-the-art of CO2 capture, transport, utilisation and storage from a multi-scale perspective, moving from the global to molecular scales. In light of the COP21 commitments to limit warming to less than 2 °C, we extend the remit of this study to include the key negative emissions technologies (NETs) of bioenergy with CCS (BECCS), and direct air capture (DAC). Cognisant of the non-technical barriers to deploying CCS, we reflect on recent experience from the UK's CCS commercialisation programme and consider the commercial and political barriers to the large-scale deployment of CCS. In all areas, we focus on identifying and clearly articulating the key research challenges that could usefully be addressed in the coming decade.

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Carbon capture and storage (CCS): the way forward

Renewable resources are used increasingly in the production of polymers. In particular, monomers such as carbon dioxide, terpenes, vegetable oils and carbohydrates can be used as feedstocks for the manufacture of a variety of sustainable materials and products, including elastomers, plastics, hydrogels, flexible electronics, resins, engineering polymers and composites. Efficient catalysis is required to produce monomers, to facilitate selective polymerizations and to enable recycling or upcycling of waste materials. There are opportunities to use such sustainable polymers in both high-value areas and in basic applications such as packaging. Life-cycle assessment can be used to quantify the environmental benefits of sustainable polymers.

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Sustainable polymers from renewable resources

https://purehost.bath.ac.uk/ws/files/10904963/Kember_etal_manuscript_rev_5.pdf

Catalysts for CO2/epoxide copolymerisation

https://spiral.imperial.ac.uk/bitstream/10044/1/10059/4/Williams%2c%20C%20-%20A%20bimetallic%20Iron%20%28III%29.pdf

A bimetallic iron(III) catalyst for CO2/epoxide coupling

A novel dizinc complex having a macrocyclic ancillary ligand shows remarkable activity at only one atmosphere of CO2 for the copolymerization of CO2 and cyclohexene oxide. Carbon dioxide is an attractive reagent for synthetic chemistry as it is abundant, inexpensive, of low toxicity, and is the waste product of many chemical processes. The copolymerization of carbon dioxide and epoxides, known for several decades, is a particularly promising route to activate and use CO2 as a renewable C-1 source. [1–5] Furthermore, if cyclohexene oxide is used, the resulting copolymer has a high glass transition temperature and tensile strength, but it is also degradable. The first report of this type of copolymerization came from Inoue et al. in 1969, and they used diethyl zinc and alcohols to produce poly(propylene carbonate), albeit with very low turnover numbers (TONs). Subsequently several research groups developed more active and controlled catalysts, and notable for their activity are the zinc phenoxide, zinc b-diiminate, and chromium(III)– or cobalt(III)–salen complexes. The zinc b-diiminate complexes show very high turnover frequencies (TOFs), as well as excellent control for the copolymerization of CO2 and cyclohexene oxide. Recent mechanistic studies by Coates and co-workers suggest that the most effective b-diiminate complexes are loosely associated dimers under the polymerization conditions. This proposal has led to the deliberate preparation of various dimetallic zinc catalysts, and among these dizinc catalysts, the anilido aniline complexes show particularly high TONs and TOFs because they can operate at low catalyst loadings. 24] However, all of the known high activity catalysts require substantial (> 7 atm) pressures of carbon dioxide, which significantly increases the overall energy requirement of the process. Although catalysts which operate at only one atmosphere of CO2 are known, 23, 26,27] so far the best reported TON was 20 and the highest TOF was 3.3 h . We report the preparation of a dimetallic zinc complex (Scheme 1) having a macrocyclic ancillary ligand, which shows very high activity for the copolymerization of cyclohexene oxide and carbon dioxide under mild pressures. The macrocyclic ligand H2L 1 was prepared in two steps with 84% overall yield from commercial reagents (see the Supporting Information) by using an adaptation of a synthetic route described previously. The dimetallic zinc complex, [LZn2(OAc)2] was synthesized by the deprotonation of H2L 1 using potassium hydride, and subsequent reaction with zinc acetate. The complex was isolated as a white solid in 70 % yield (Scheme 1). The stoichiometry of the complex was confirmed by elemental analysis, which was in agreement with the calculated values, and the identification of a fragment peak in the FAB mass spectrum for the molecular ion less an acetate group. The H NMR spectrum at 25 8C shows broadened resonances, consistent with several diastereoisomers being present, which are fluxional on the NMR timescale. When the sample was heated to 110 8C coalescence was observed (see Figure S1 in the Supporting Information). A single resonance was observed for the aromatic protons and the signal for the NH groups was a broadened resonance at d = 4.78 ppm. The methylene groups are diastereotopic, therefore four broadened resonances were observed from d = 3.32–2.46 ppm, each with an integral corresponding to 4H. The signals for the tertbutyl groups and the methyl group of the acetate resonate as singlets with integrals corresponding to 18H and 6H, respectively. The methyl groups on the ligand backbone are also diastereotopic and are observed as two singlets, each with a relative integral corresponding to 6H. The complex was tested at low pressures for the copolymerization of carbon dioxide and cyclohexene oxide (Table 1). Thus, at only one atmosphere of CO2, 80–100 8C, and a 0.1 mol% catalyst loading, poly(cyclohexene carbonate) was produced with a TON in the range of 430–530 and a TOF in the range of 18–25 h 1 (Table 1, entries 1–3). There are very few catalysts that are effective at such a low pressure, 23, 26,27] the most active of which is a dizinc Scheme 1. The synthesis of the dizinc complex [LZn2(OAc)2]. Reagents and conditions: a) KH, THF, 78 8C!RT, 1 h; b) Zn(OAc)2, THF, RT, 16 h.

Highly Active Dizinc Catalyst for the Copolymerization of Carbon Dioxide and Cyclohexene Oxide at One Atmosphere Pressure

The synthesis and characterization of three highly active dimagnesium catalysts for the copolymerization of cyclohexene oxide and carbon dioxide, active under just 1 atm of carbon dioxide pressure, are reported. The catalysts have turnover numbers up to 6000 and turnover frequencies of up to 750 h–1. These values are, respectively, 75 and 20 times higher than those of the other three known magnesium catalysts. Furthermore, the catalysts operate at 1/500th the loading of the best reported magnesium catalyst. The catalyst selectivities are excellent, yielding polymers with 99% carbonate repeat units and >99% selectivity for copolymer. Using a dimagnesium bis(trifluoroacetate) catalyst, and water as a renewable chain transfer reagent, poly(cyclohexene carbonate) polyols are synthesized with high selectivity.

Efficient magnesium catalysts for the copolymerization of epoxides and CO2; using water to synthesize polycarbonate polyols.

The reaction kinetics of the copolymerization of carbon dioxide and cyclohexene oxide to produce poly(cyclohexene carbonate), catalyzed by a dizinc acetate complex, is studied by in situ attenuated total reflectance infrared (ATR-IR) and proton nuclear magnetic resonance (1H NMR) spectroscopy. A parameter study, including reactant and catalyst concentration and carbon dioxide pressure, reveals zero reaction order in carbon dioxide concentration, for pressures between 1 and 40 bar and temperatures up to 80 °C, and a first-order dependence on catalyst concentration and concentration of cyclohexene oxide. The activation energies for the formation of poly(cyclohexene carbonate) and the cyclic side product cyclohexene carbonate are calculated, by determining the rate coefficients over a temperature range between 65 and 90 °C and using Arrhenius plots, to be 96.8 ± 1.6 kJ mol–1 (23.1 kcal mol–1) and 137.5 ± 6.4 kJ mol–1 (32.9 kcal mol–1), respectively. Gel permeation chromatography (GPC), 1H NMR spectroscopy, a...

Mechanistic investigation and reaction kinetics of the low-pressure copolymerization of cyclohexene oxide and carbon dioxide catalyzed by a dizinc complex.

Michael Kember

Papers

Catalysts for CO2/epoxide copolymerisation

A bimetallic iron(III) catalyst for CO2/epoxide coupling

Highly Active Dizinc Catalyst for the Copolymerization of Carbon Dioxide and Cyclohexene Oxide at One Atmosphere Pressure

Efficient magnesium catalysts for the copolymerization of epoxides and CO2; using water to synthesize polycarbonate polyols.

Mechanistic investigation and reaction kinetics of the low-pressure copolymerization of cyclohexene oxide and carbon dioxide catalyzed by a dizinc complex.