Search

For the efficient utilization of CO2 into valuable product, the attractive carbon nitride catalysts have been widely studied. In this work, heptazine‐related materials with varying degree of polymerization were designed by an intrinsically modification strategy and employed in the cycloaddition of CO2 with the bisepoxide 1, 4‐butanediol diglycidyl ether (BDODGE). We initially figured out that the sample prepared at 450 °C contained more melem hydrate, exhibiting the best performance. The epoxides conversion and corresponding cyclic carbonates selectivity could achieve 93.1 % and 99.3 % at 140 °C for 20 h without any cocatalyst and solvent, respectively. Results of the catalytic tests suggested that the high catalytic activity was dependent on big size porous structure and the synergetic effect of active amino groups and −OH groups. The role of water in maintaining the specific structure and providing active site has been proved. Moreover, the CN‐450‐W catalyst exhibited outstanding recycling stability. And finally, a plausible reaction mechanism was proposed. [ABSTRACT FROM AUTHOR]

Artificial photosynthesis of CO 2 at various atomic active sites proves an eyes-attaching means with high catalytic efficiency in simultaneously eliminating carbon dioxide and producing valuable chemical feedstocks. However, the distinct reaction pathways and product selectivity among the same types of atomic active sites significantly inhibit the acquirement of the high ratio of the target product from CO 2 photosynthesis in practical application. Given this gap, this review pays attention to systemically discussing the effects of the atom-level local reaction centre, including the atomic active sites centred photocatalyst and the local environment, on the affinity to the reactants, the photoelectrons transfer, and the affinity of atomic active sites to the intermediates, such as single atom, vacancy, and frustrated Lewis pairs, in the process of CO 2 photoconversion. This work aims to provide instructions for a more profound understanding of the mechanism of artificial photosynthesis, and the reaction pathways at the atomic active sites. [Display omitted] • Reaction pathways and selectivity depend on the atomic active sites centered photocatalyst and the local environment. • Atomic active site affects with the kinds, concentration, frustrated Lewis pairs' distance, and co-active sites' existence. • The local environment impacts via diffusion gradients, substrate access, and non-covalent interactions. [ABSTRACT FROM AUTHOR]

The Zn–Co double metal cyanide (DMC) complex is regarded as a promising catalyst for the copolymerization of CO 2 and propylene epoxide (PO). Various methods have been adopted to improve the catalytic performance of DMC. In this study, polyvinylpyrrolidone (PVP), as a co-complexing agent, was innovatively used to modify DMC and applied to the synthesis of poly(ether–carbonate) polyols from CO 2 , PO, and a chain transfer agent. The modified catalysts exhibited higher catalytic activity than the catalysts prepared by conventional methods, with a nearly 10 % increase in PO conversion. The most critical breakthrough was a reduction of nearly 5 wt% in the byproduct propylene–carbonate. The results confirmed that amide groups in PVP could coordinate with active center Zn2+, providing the modified catalysts with advantages such as low-symmetry structure, high specific surface area, and strong acidity. Moreover, the dual effects of PVP coordination and dispersion led to dramatic differences in the microstructure and activity of the catalysts when added during different preparation processes of DMC. The coordination effect of PVP was dominant in the nucleation stages which affected the crystal structure and morphology, whereas, the dispersion effect was dominant in the aging stages which prevented the catalyst particles from growing and thus a higher specific surface area. This is critical for paving the way towards exploring the introduction of groups with high steric hindrance into Zn–Co complex catalysts. In addition, a detailed and in-depth insight into the structure–activity relationship of DMC for poly(ether–carbonate) polyols synthesis was summarized. [Display omitted] • Polyvinylpyrrolidone (PVP) was first used to modify double metal cyanide catalysts. • PVP added in different preparing stages affected crystal structure of the catalyst. • PVP-modified catalysts showed low symmetry, high surface area, and strong acidity. • N of PVP coordinated to Zn2+ helped to activate CO 2 and epoxide. • Modified catalysts showed higher activity and selectivity for CO 2 copolymerization. [ABSTRACT FROM AUTHOR]

This paper studies a novel sustainable ship routing problem considering a time window concept and bunker fuel management. Ship routing involves the decisions corresponding to the deployment of vessels to multiple ports and time window concept helps to maintain the service level of the port. Reducing carbon emissions within the maritime transportation domain remains one of the most significant challenges as it addresses the sustainability aspect. Bunker fuel management deals with the fuel bunkering issues faced by different ships, such as selection of bunkering ports and total bunkered amount at a port. A novel mathematical model is developed capturing the intricacies of the problem. A hybrid particle swarm optimization with a basic variable neighborhood search algorithm is proposed to solve the model and compared with the exact solutions obtained using Cplex and other popular algorithms for several problem instances. The proposed algorithm outperforms other popular algorithms in all the instances in terms of the solution quality and provides good quality solutions with an average cost deviation of 5.99% from the optimal solution. [ABSTRACT FROM AUTHOR]

In this work corrosion behavior of SUS 441, Crofer 22 APU and Canthal APM in molten Na 2 CO 3 -K 2 CO 3 at 800 °C is studied. The 441 and APU corrode heavily as the element Cr in the steel is oxidized to NaCrO 2. Cr diffuses along grain boundary preferentially and the molten salt penetrates through the corrosion layer. Several porous corrosion layers rich in Cr, O, Na or rich in Fe are formed alternatively on the APU surface. On the contrary, the APM alloy shows excellent corrosion resistance (0.02 mm/y) due to formation of a protective Al 2 O 3 layer. [Display omitted] • Alternate arrangement corrosion layer's formation mechanisms of steel in molten Na 2 CO 3 - K 2 CO 3. • APM's mass change during corrosion in molten Na 2 CO 3 - K 2 CO 3 is affected by surface roughness. • Canthal APM can be used as the R-SOCs thermal energy storage device material for molten Na 2 CO 3 - K 2 CO 3. [ABSTRACT FROM AUTHOR]

In this work, CO 2 was chemically fixed by reacting with 1, 4-butanediol diglycidyl ether in the presence of a basic polystyrene resin catalyst. Under the 100% conversion of 1, 4-butanediol diglycidyl ether, five-membered cyclocarbonate with a selectivity of 98.5% was obtained. The cyclocarbonate was then reacted with an excess of 1, 2-ethylenediamine and the product was characterized by Fourier transform infrared spectrometer and nuclear magnetic resonance spectrometer. The results confirmed the successful synthesis of NH 2 terminated product with a selectivity of 98.9%, accompanied by the formation of hydroxyls on β-C to the carbonyl groups, which can be regarded as a new amino-alcohol. Further, the obtained amino-alcohol was applied for the preparation of polyurethane urea as chain extender in a prepolymer way. Since the reactivity of isocyanate with NH 2 is much faster than that with OH, the OH groups can be maintained in the system and hence strengthen the hydrogen bonding in polyurethane urea, which endows the materials with some unique properties. Comparing with the polyurethanes yielded from 1, 6-hexanediamine and 1, 6-hexanediol, polyurethane urea synthesized from the new amino-alcohol possessed better water/solvents resistance, considerable mechanical and thermal properties. [ABSTRACT FROM AUTHOR]

Dye-containing wastewater has caused serious environmental pollution. Herein, rationally designed spherical polyelectrolyte brushes (SPBs) with cationic charges, polystyrene-poly(2-aminoethylmethacrylate hydrochloride) (PS-PAEMH) as the absorbent, and compressed carbon dioxide as the antisolvent are proposed for the separation of the anionic dye eosin Y (EY) from a solution of mixed dyes. The adsorption behavior of EY onto PS-PAEMH was highly dependent on CO2 pressure, contact time, and initial concentration. The maximum adsorption capacity of PS-PAEMH was 335.20 mg g−1. FTIR and UV/Vis measurements proved that the electrostatic interactions between EY and PS-PAEMH played an important role in the absorbance process. The adsorption process fitted the pseudo-second-order kinetic model and Freundlich isotherm model very well. The combined dye and polymer brush could be easily separated through ion exchange by adding an aqueous solution of NaCl. Recovered PS-PAEMH retained a high adsorption capacity even after ten cycles of regeneration. This method provides a simple and effective way to separate ionic materials for environmental engineering. [ABSTRACT FROM AUTHOR]

A series of hybrid polyhydroxyurethane (PHU) materials were prepared from CO 2 , polypropylene glycol diglycidyl ether, amines, and bisphenol-A diglycidyl ether (BADGE). Firstly, the five-membered cyclocarbonate (5CC) as the CO 2 -sourced monomer was synthesized by a cycloaddition reaction from CO 2 and polypropylene glycol diglycidyl ether at 120 °C under 10 bar CO 2 pressure in the presence of an amberlyst catalyst. The selectivity of 5CC was confirmed through an analog computation method based on the results of 1 H NMR. Then, 5CC was reacted with excessive amines to produce the −NH 2 terminated pre-polymers. Finally, the pre-polymers reacted with BADGE to produce hybrid PHU materials. The effect of amine type and BADGE content on the properties of PHUs was studied by means of Fourier transform infrared spectra, dynamic mechanical thermal analysis, and thermogravimetric analysis and solvent swelling test. The results indicated that introducing BADGE as a chain extender not only enhances the gelation rate of PHU, but also improve the mechanical and thermal properties of PHU materials. [ABSTRACT FROM AUTHOR]

A kind of core–shell catalyst with Fe–Zn–Zr as the core and a zeolite (HZSM-5, Hbeta, and HY) as the shell was synthesized by a simple cladding method. The catalyst has an obvious confinement effect on the synthesis of isoalkanes by CO2 hydrogenation. Especially, the Fe–Zn–Zr@HZSM-5–Hbeta catalyst with a double-zeolite shell exhibits an extraordinary high i-HC/t-HC ratio. [ABSTRACT FROM AUTHOR]

A highly efficient melem based mesoporous metal-free catalyst with amino and hydroxyl groups was successfully developed by template method with melamine as precursor and nano-SiO 2 as template. In the absence of any co-catalyst and solvent, the catalyst mp-CN-450 exhibits high catalytic activity for catalytic cycloaddition reaction between CO 2 and polyfunctional epoxides, and the epoxides conversion and corresponding cyclic carbonates selectivity are 99.7 % and 99.5 %, respectively. And the catalyst has hardly loss of catalytic activity after being reused for four cycles. The characterization results disclose that the high catalytic activity of the catalyst is closely related to its large specific surface area, abundant mesoporous structure and synergistic effect of N species and hydroxyl groups of melem hydrates. Additionally, through the study of different N-containing compounds, it was found that the primary amine may underwent a ring-opening reaction with epoxide. But with the addition of CO 2 , amine groups prior to reacted with CO 2 to form carbamate salt, avoided the formation of by-products, thereby improved the selectivity of cyclic carbonate. Finally, based on the above research, a possible reaction mechanism for the coupling of CO 2 to epoxides was proposed. [Display omitted] • A melem based mesoporous heterogeneous catalyst was prepared by template method. • The catalyst exhibited high catalytic activity and stability for CO 2 cycloaddition. • The reaction was catalyzed by metal-free catalyst without any cocatalyst and solvent. • Melem hydrate provided different amino and hydroxyl active sites in the reaction. • Effect of different N-containing species on cycloaddition reaction was investigated. [ABSTRACT FROM AUTHOR]

• A novel amino-alcohol chain extender derived from CO 2 was synthesized. • The chain extender was used in the preparation of green waterborne polyurethane-urea. • CO 2 -AA based WPUs showed excellent water/solvents resistance and hydrolysis/oxidation resistance. • WPU films from CO 2 -AA chain extender showed promising mechanical performances and considerable thermal properties. Carbon dioxide based amino-alcohol compound (CO 2 -AA) with both alcohol and amino units in the molecular was prepared by chemical fixation of CO 2 with 1, 4-butanediol diglycidyl ether and ethylenediamine, which was further used as chain extender to the preparation of waterborne polyurethanes (CO 2 -WPUs). Since the reacting activity of isocyanate groups in WPU prepolymer with NH 2 was much faster than that with OH, hydroxyl groups could be maintained in the system and strengthen the hydrogen bonding interaction in WPU endowing the materials with some special properties. Specifically, the unique structure of CO 2 -AA improved mechanical, water/solvents resistance and hydrolysis/oxidation resistance properties of CO 2 -WPUs. Mechanical properties of the CO 2 -WPUs changed slightly during immersion in water, 0.25% NaOH and 6.00% H 2 O 2 solution, while the WPUs prepared from typical chain extender ethylenediamine almost lost their mechanical properties after immersed in the solutions for 5 h. Moreover, the CO 2 -WPU films showed considerable thermal stability. The study suggested the novel CO 2 -AA might be a promising chain extender to improve the water/solvent resistance and hydrolysis/oxidation resistance of WPU. [ABSTRACT FROM AUTHOR]

To overcome the weak carbon dioxide (CO2) conversion ability of Zn‐Co double metal cyanide (DMC) catalyst, zinc glutarate (ZnGA) catalyst was introduced into the DMC catalytic system and applied for the synthesis of oligo (propylene‐carbonate) diols. The DMC/ZnGA composite catalyst (mass ratio = 10:1) exhibited an excellent synergistic effect which had enhanced CO2 activation ability, high yield and good selectivity. In copolymerization process, ZnGA catalyst not only provided activated CO2 for DMC catalyst, but also transferred the propagating chain with more alternating structures to DMC catalyst. Both of the two effects increased the carbonate content in the final products. Overall, DMC catalyst dedicated to the polymer chain growth, while the increased CO2 conversion mainly attributed to ZnGA catalyst. Oligo (propylene‐carbonate) diols with carbonate unit content of 45.1 mol%, Mn of 1228 g/mol, WPC of 4.3 wt% and high yield of 1689 g/g cat was obtained. [ABSTRACT FROM AUTHOR]

Zn–Co double metal cyanide (DMC) complexes are promising catalytic systems for copolymerization of epoxide and CO2. In the work reported, Zn–Co DMC catalysts were prepared by parallel‐flow dropping, forward dropping and reverse dropping methods, aiming to provide an insight into the effect of addition mode on catalyst structure and catalytic performance. Catalytic properties were evaluated using the copolymerization reaction of propylene oxide (PO) and CO2 in the presence of chain transfer agent. The results indicated that the factors that affect crystalline state are different for different modes. And excess zinc chloride is the prerequisite for organic ligands to be retained in the catalyst and affect the structure. In addition, a catalyst with flower‐like morphology was obtained with the parallel‐flow dropping method which provided larger surface area. An appropriate O/Zn value ensured abundant active PO which would suppress the backbiting process by forming consecutive PO units adjacent to CO2 units. Oligo(propylene‐carbonate) diols with average molecular weight of 1020 g mol−1, CO2 incorporation of 24.92% and WPC of 5.14 wt% were obtained at 80 °C and 2 MPa. Effects of dropping mode on Zn–Co double metal cyanide (DMC) catalyst are investigated using three different dropping methods. The factors that affect crystalline state are summarized and a flower‐like morphology is observed which endows the DMC catalyst with a large surface area. In copolymerization reaction, appropriate O/Zn value is beneficial to suppress the formation of by‐product. And a catalyst with excellent catalytic performance is prepared by an improved parallel‐flow dropping method. [ABSTRACT FROM AUTHOR]

[Display omitted] Electrocatalytic CO 2 reduction (ECR) into valuable chemicals, especially driven by renewable energy, presents a promising pattern to realize carbon neutrality. Site-isolated metal complexes flourish in the area of ECR as single-atom-like catalysts because of their competent and tailorable activity. In this study, salophen-based metal (Fe, Co, Ni and Cu) complexes were anchored onto carbon nanotubes (CNTs) to construct efficient catalysts for electrochemically converting CO 2 to CO. Both experimental and theoretical results verified that CO 2 activation was the rate-determining step for the catalytic performance of these hybrid molecular catalysts. The coordinate activation ability can be manipulated by varying the metal centers. The as-synthesized Fe-salophen hybrid CNT (Fe-salophen/CNT) shows the best activity and selectivity of −13.24 mA·cm−2 current density with 86.8% Faradaic efficiency for generating CO (FE CO) at −0.76 V vs. RHE in aqueous solution, whereas Cu-salophen/CNT only achieved a −2.22 mA·cm−2 current density and 57.9% FE CO under the same reaction conditions. These distinct catalytic performances resulted from the different coordination activation abilities of CO 2 on various metal centers. [ABSTRACT FROM AUTHOR]

The cycloaddition of CO 2 and epoxide is regarded as an eco-friendly, sustainable, and promising way to utilize CO 2. However, it is crucial to design and prepare efficient and low-cost catalysts for this reaction. Herein, through controlling condensation temperature, a series of boron modified urea-derived g-C 3 N 4 (x-BCN) were prepared. Notably, more edge defect (−NH 2 /−NH−) formed at low roasting temperatures and both basic and acidic sites increased after introducing B. 0.30-BCN exhibited superior catalytic performance for cycloaddition of CO 2 with 1, 4-butanediol diglycidyl ether and 99% cyclic carbonate yield was acquired at 130 ℃, 2.0 MPa after 20 h reacting. Additionally, 0.30-BCN showed outstanding recyclability and substrate adaptability. The synergistic effects of edge defects, rich mesoporous structure and Lewis acid-base sites were conductive to promoting CO 2 cycloaddition. Moreover, a possible multi-synergetic mechanism was proposed. An originality option was provided for preparing a simple, eco-friendly, and efficient metal-free catalyst for practical CO 2 fixation. [Display omitted] • Metal-free x-BCN with acid-base duality was prepared via a simple method. • More surface edge defects (−NH 2) was obtained at lower preparation temperature. • The insertion site of B and effect on N-containing groups were verified by XPS. • 0.30-BCN exhibited high catalytic activity without co-catalyst and solvent. • A possible multi-synergetic mechanism was proposed. [ABSTRACT FROM AUTHOR]