摘要 :
? 2021 Elsevier LtdDeveloping heterogeneous catalyst containing both CO2-philic groups and catalytic active sites is highly desirable for efficient CO2 chemical fixation. In this work, a triazine-functionalized poly(ionic liquid) ...
展开
? 2021 Elsevier LtdDeveloping heterogeneous catalyst containing both CO2-philic groups and catalytic active sites is highly desirable for efficient CO2 chemical fixation. In this work, a triazine-functionalized poly(ionic liquid) (T-PIL) was designed and synthesized. This metal free catalyst showed extremely enhanced CO2 adsorption and improved catalytic ability for the cycloaddition reaction of CO2 without co-catalysts. Especially for the epoxides of large size and strong steric hindrance, the yields of the cyclic carbonates were improved up to three times in the presence of triazine motifs. An intramolecular synergistic mechanism of triazine and imidazolium motifs was proposed on the basis of density functional theory (DFT) calculations and diffused reflectance infrared Fourier transform spectroscopy (DRIFTS). The imidazolium groups with paired bromine anions acted as catalytic active sites and would enhance CO2 activation and the ring-opening of epoxides. While the triazine groups acting as CO2-philic groups could enhance the CO2 adsorption and activation. This work highlights that the incorporation of two motifs with synergistic effect in one catalyst can significantly improve its catalytic performance.
收起
摘要 :
CO2 fixation and conversion are desirable to solve the exceeding CO2 emission. Traditional CO2 cycloaddition needs strict conditions, co-catalyst and solvent, causing energy intensive and complex recycle process. In this work, an ...
展开
CO2 fixation and conversion are desirable to solve the exceeding CO2 emission. Traditional CO2 cycloaddition needs strict conditions, co-catalyst and solvent, causing energy intensive and complex recycle process. In this work, an integrated ionic polymers (IPs) and phosphomolybdate (PM012) co-modified CuTCPPCo MOF all-in-one composite catalyst (PBPCT*) is designed for solar driven, solvent-free and co-catalyst-free CO2 cycloaddition. The PMo_(12) clusters and IPs offer abundant active sites for reactants activation and ring opening. The activation energy significandy decreases from 66.36 kJ·mol~(-1) of CuTCPPCo MOF to 49.47 kJ·mol~(-1) of PBPCT*, and guarantees higher efficient with 99.2% yield of styrene carbonate at 353 K for 12 h. The TOF of 580.73 h~(-1) under light density of 0.8 W/cm~2 superior to traditional heating with TOF of 473.0 h~(-1). This provides a new avenue to gather all the advantages in one catalyst, furnishing a promising approach for reducing CO2 emission and utilization.
收起
摘要 :
The polymerization of vinylidene fluoride in supercritical carbon dioxide was studied in a continuous stirred tank reactor using diethylperoxydicarbon ate. as the free radical initiator. Experiments were carried out to investigate...
展开
The polymerization of vinylidene fluoride in supercritical carbon dioxide was studied in a continuous stirred tank reactor using diethylperoxydicarbon ate. as the free radical initiator. Experiments were carried out to investigate the effect of inlet monomer concentration, temperature, average residence time, and agitation on the polymerization rate, the average molecular weights, and the, molecular weight distribution of the poly(vinylidene fluoride). A homogeneous kinetic model that includes inhibition due to chain transfer to monomer predicted the polymerization rates reasonably well. However, imperfect mixing, rather than a chemical effect, may have caused the apparent inhibition observed at high monomer concentrations. At inlet monomer concentrations greater than about 1.5 M, broad and bimodal molecular weight distributions were observed. An extended homogeneous kinetic model that includes chain transfer to polymer predicted the polydispersities reasonably well. This model also predicted a region of inoperability that matched the experimental results. However, the extended homogeneous model could not account for the bimodal distributions. [References: 26]
收起
摘要 :
Methanol synthesis via CO2 hydrogenation has been documented as a promising route for CO2 catalytic utilization and clean energy supply, yet conventional catalysts should be further improved to facilitate methanol generation. Here...
展开
Methanol synthesis via CO2 hydrogenation has been documented as a promising route for CO2 catalytic utilization and clean energy supply, yet conventional catalysts should be further improved to facilitate methanol generation. Herein, oxygen vacancy rich Cu-ZnO-ZrO2 catalysts were prepared via a facile solid-state method. Asobtained CZZ catalysts perform dramatically in CO2 hydrogenation reactions with high methanol selectivity up to 93.5% at 240 degrees C and 3.0 MPa. They consist of metallic copper, zinc oxide and amorphous zirconium species, and present considerable surface areas. Benefited from the facile preparation process, no wastewater is produced, and no reduction is required. The samples also contain high proportions of oxygen vacancies (up to 60.4%) compared with the conventional catalyst (only 47.6%). Accordingly, these oxygen vacancies benefit adsorption of CO2 and migration of intermediates, and therefore benefit the methanol formation and elevate the methanol selectivity. Remarkable catalytic properties are therefore achieved using these catalysts.
收起
摘要 :
In this paper we show that every cotorsion-free and reduced abelian group of any finite rank (in particular, every free abelian group of finite rank) appears as the kernel of a cellular cover of some cotorsionfree abelian group of...
展开
In this paper we show that every cotorsion-free and reduced abelian group of any finite rank (in particular, every free abelian group of finite rank) appears as the kernel of a cellular cover of some cotorsionfree abelian group of rank 2. This situation is the best possible in the sense that cotorsion-free abelian groups of rank 1 do not admit cellular covers with free kernel except for the trivial ones. This work is motivated by an example due to Buckner–Dugas, and recent results obtained by Fuchs–G¨obel, and G¨obel–Rodr′?guez–Str¨ungmann.
收起
摘要 :
Exploring novel and metal-free electrocatalysts for CO2 reduction is of great significance not only for reducing of CO2 emission but also for energy storage. However, searching metal-free and highly efficient electrocatalysts for ...
展开
Exploring novel and metal-free electrocatalysts for CO2 reduction is of great significance not only for reducing of CO2 emission but also for energy storage. However, searching metal-free and highly efficient electrocatalysts for CO2 reduction is still challenging. Here, we report that a metal-free and metallic borophene can be used as an efficient electrocatalyst for CO2 reduction. Through a comprehensive DFT investigation of CO2 activation and conversion on newly fabricated metallic 2D boron sheets (borophene, beta(12) or chi(3) boron sheets), our calculational results indicate that electron deficient borophene can provide electrons to CO2 and effectively activate the inserted CO2 by breaking pi bond of CO2. Moreover, the study demonstrates that the most feasible product of CO2 reduction on the borophene is CH4 with a limiting potential of -0.27 V and the largest activation barrier of 0.98 eV along the minimum energy pathway. The very small values of the limiting potential and activation barrier indicate that CO2 reduction reaction on borophene is both thermodynamically and kinetically feasible. Overall, our work provides insight that the metal free and metallic borophene can be used as an excellent electrocatalyst for CO2 reduction.
收起
摘要 :
The capture and utilization of CO by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) were performed in the absence of transition-metal complexes. The reaction of TBD with CO afforded TBD-CO adducts, which were converted to formylated TB...
展开
The capture and utilization of CO by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) were performed in the absence of transition-metal complexes. The reaction of TBD with CO afforded TBD-CO adducts, which were converted to formylated TBD (TBD-CHO). TBD-CO adducts may include an interaction of CO with positively charged species based on NMR and IR analysis. In the presence of amines, CO was transferred from TBD-CO to amines, producing formylated amines with good yields. The reaction mechanism involving TBD-CO adducts is presented based on theoretical calculations.
收起
摘要 :
The emf method was employed to determine thermodynamic properties of cobalt orthosilicate, taking into account two different crystallographic forms of silica: amorphous and quartz. Results were then compared to available literatur...
展开
The emf method was employed to determine thermodynamic properties of cobalt orthosilicate, taking into account two different crystallographic forms of silica: amorphous and quartz. Results were then compared to available literature data and used along with other experimental information of the system to evaluate a thermodynamic description by the CALPHAD method. [References: 16]
收起
摘要 :
Global climate changes may cause heat-induced sterility in rice, threatening the global production of this important crop. Although little is currently known about the combined effects of the concentration of atmospheric CO_(2) ([...
展开
Global climate changes may cause heat-induced sterility in rice, threatening the global production of this important crop. Although little is currently known about the combined effects of the concentration of atmospheric CO_(2) ([CO_(2)]) and temperature on heat-induced sterility, elevated [CO_(2)] (E-[CO_(2)]) will likely increase the panicle temperature and thereby exacerbate heat-induced sterility, but this was not tested in open fields. Therefore, we investigated the effect of E-[CO_(2)] on heat-induced sterility and sterility-related traits in rice by increasing E-[CO_(2)] by approximately 200?μmol?mol~(?1) above ambient levels using a free-air CO_(2) enrichment (FACE) facility for six growing seasons with variable growing season temperatures. The percentage fertility was not significantly correlated with the air temperature (T _(a)) between 09:00 and 12:00 on each flowering day, but it did significantly vary among the years, with 2011 experiencing cool temperatures resulting in chilling-induced mild sterility. When data from 2011 were removed, there was a significant negative correlation between fertility and T _(a) between 09:00 and 12:00 on each flowering day under E-[CO_(2)], whereas no such effect was seen under ambient [CO_(2)]. E-[CO_(2)] also significantly reduced the number of pollen grains deposited on the stigma by 10%, but it slightly increased the anther length by 1.3%, indicating that it had both negative and positive effects on heat-induced sterility. These findings suggest that E-[CO_(2)] affects many traits related to heat-induced sterility and may sometimes exacerbate sterility by reducing pollen grain deposition.
收起
摘要 :
Herein, this report uses Co3O4 nanoneedles to decorate Mo-Co3O4 nanosheets over Ni foam, which were fabricated by the hydrothermal route, in order to create a supercapacitor material which is compared with its counterparts. The su...
展开
Herein, this report uses Co3O4 nanoneedles to decorate Mo-Co3O4 nanosheets over Ni foam, which were fabricated by the hydrothermal route, in order to create a supercapacitor material which is compared with its counterparts. The surface morphology of the developed material was investigated through scanning electron microscopy and the structural properties were evaluated using XRD. The charging storage activities of the electrode materials were evaluated mainly by cyclic voltammetry and galvanostatic charge-discharge investigations. In comparison to binary metal oxides, the specific capacities for the composite Co3O4@Mo-Co3O4 nanosheets and Co3O4 nano-needles were calculated to be 814, and 615 C g?1 at a current density of 1 A g?1, respectively. The electrode of the composite Co3O4@Mo-Co3O4 nanosheets displayed superior stability during 4000 cycles, with a capacity of around 90%. The asymmetric Co3O4@Mo-Co3O4//AC device achieved a maximum specific energy of 51.35 Wh Kg?1 and power density of 790 W kg?1. The Co3O4@Mo-Co3O4//AC device capacity decreased by only 12.1% after 4000 long GCD cycles, which is considerably higher than that of similar electrodes. All these results reveal that the Co3O4@Mo-Co3O4 nanocomposite is a very promising electrode material and a stabled supercapacitor.
收起
原文获取