查看更多>>摘要：The combined Ca-Cu looping process is a promising CO2 capture technology, in which the exothermic reduction of CuO with methane is used in situ to provide the heat required to calcine CaCO3. However, the CO2 capture capacity of CaO/CuO composites decreases rapidly during multiple cycles. Herein, we proposed an aluminum-oxide deposited CaO/CuO composites synthesized by the space-confined chemical vapor deposition method and systematically investigated in accordance carbonation, calcination-reduction, and oxidation cycles. The deposited CaO/CuO composites feature highly porous structures and fine grain sizes, demonstrating significantly enhanced CO2 capture performance with only 5 mol.% of Al stabilizer. The CO2 absorption amount of Cu1CaAl0.05 is 0.2183 g(CO2)/g(material) in the first cycle. After 20 cycles, it still maintains 86.6% of the original absorption capacity, exceeding that of the undeposited CaO/CuO composites by 115%. Moreover, during the 20 cycles, the oxidation conversion of Cu(1)CaAl(0.05 )always keeps above 95%, much higher than undeposited CaO/CuO composites. Various evidences indicate that the uniform deposition of aluminum-oxide on the CaO/CuO sorbent plays a vital role in improving the CO2 absorption performance and cycling stability.
查看更多>>摘要：The adsorptive separation of C3H6 and C3H8 gases using molecular sieves is a challenging process due to the similarity in molecular sizes for the two molecules. In this work, we report that organic phosphonic acid (PA) monolayers on zeolites significantly enhanced the ideal selectivity of C3H6/C3H8 adsorption by changing the diffusion mechanism based on the properties of the alkyl tail. With an n-octadecylphosphonic acid (ODPA) coating on zeolite 5A, the kinetic selectivity of C3H6/C3H8 was initially >8 at 25 degrees C, whereas for uncoated 5A, it was limited to ~1.2. Kinetic modeling showed that in ODPA-coated 5A, the diffusion of C3H6 and C3H8 was limited by the PA monolayer at the external surface of the zeolite. In contrast, for uncoated 5A, it was controlled by the pore channels, so that the enhanced kinetic selectivity from 5A-ODPA was related to a different limiting transport mechanism. The kinetic selectivity was not temperature sensitive in the range of 25-150 degrees C in 5AODPA as the diffusion activation energies of C3H6 and C3H8 were both small. Modification of 5A with other PAs also increased the kinetic selectivity. Coating with n-butylphosphonic acid yielded lower kinetic selectivity than ODPA, ostensibly due to its shorter alkyl tail. Coating with tert-butylphosphonic acid, a sterically bulky ligand, decreased kinetic selectivity still further. However, methylphosphonic acid, which partially penetrated the near-surface region of the zeolite, severely lowered the diffusion rates. The use of organic films may enable rational design of selective adsorbents based on providing gas-specific resistance at the pore entrance.
查看更多>>摘要：The ionic liquid-templated TON- and MFI-type zeolites having 10-membered rings were synthesized and their catalytic performances on propene dimerization were studied. The comparable acid site strength among TON- or MFI-type zeolites accounted for the nearly identical propene dimerization turnover rates despite their different Si/Al ratios. At the low propene conversion (<5%), the TON- and MFI-type zeolites (with a Si/Al ratio of 30-120) obtained a dimer selectivity of over 70% and less than 42%, respectively. The different channel structures and acid properties of zeolite were responsible for the different catalytic selectivity in TON- and MFI-type zeolites. Compared to MFI zeolite, TON with a smaller void size was much more suitable for stabilizing the transition states and intermediates for dimers under the reaction conditions. In addition, a three-stage and a three-in-one dimerization reaction pathways were proposed for the ZSM-22 and ZSM-5 zeolites, respectively.
查看更多>>摘要：A facile and green method is developed to synthesize cobalt species embedded in a nitrogen-doped carbon matrix (P-Co@NCs). The materials are synthesized using hard template precursors via single-step in-situ thermal treatment under free solvent conditions. The optimal P-Co@NC composite prepared through rational synthesis and synergic composition shows an efficient electrocatalytic performance for oxygen evolution reduction (OER). The P-Co@NC exhibits the OER overpotential of 350 mv at 10 mA cm(-2) and low Tafel 73 mv.dec(-1) in 0.1 M KOH electrolyte. The advantage of catalyst is the dispersion of Co species, which are in close interaction with nitrogen-doped carbon matrix. The Co-Nx plays a dominating role among Co species in P-Co@NC and is well protected by the nitrogen-doped carbon matrix layer. That resulted in efficient electron transport on CNTs (high conductivity) that improves the OER performance of P-Co@NC compared to the reference catalysts (IrO2 and B-Co@NC). The P-Co@NC also showed excellent cycling performance from long-term chronoamperometry testing. Interestingly, the P-Co@NC catalyst could be synthesized straightforward via a short solvent-free singlestep process that introduced it as a green and environmental friendly method, which can be potential to develop catalyst based on metal embedded N-doped carbon.
查看更多>>摘要：Hetematoms substituted zeolites (HSZ) are important absorbents/catalysts for many industrial processes. However, precisely locating the heteroatoms in the desired zeolite frameworks is still challenged by the low crystallization rate. Herein, we report that poly dimethyl diallyl ammonium chloride (PDDA) can greatly accelerate the HSZ crystallization with the simultaneous creation of mesopores. Significantly, highly crystallized Sn-MFI single crystals are obtained within 6 h, which is over one hundred times faster than that of the available methods (similar to 720 h). The addition of PDDA is revealed to speed up the in-situ depolymerization and re-condensation of nanosized silica precursors, leading to the rapid crystallization of MFI framework with the concomitantly homogeneous incorporation of tetra-coordinated Sn atoms. The obtained Sn-MFI mesoporous zeolites exhibit excellent catalytic performance for the hydration of epichlomhydrin to 1, 2-diol. More importantly, the realization of Sn-MEL, ZSM-11, Ga-MFI and ZSM-5 zeolites with prominently short time and the diversity of the cationic polyelectrolyte make the thus developed strategy a highly efficient and general method for synthesizing HSZ.
查看更多>>摘要：The suitability of the preferential heating of the substrate by conduction for the preparation of coatings of EMT-type zeolites was investigated. For this aim, synthesis experiments were performed by using the substrate heating method and the results were compared to those obtained by conventional synthesis where the substrate is heated by convection. EMT zeolites represent an extreme case of metastability, which renders the preparation of their coatings of notable thickness quite difficult. Various synthesis conditions were tested and the coatings obtained were characterized by X-ray diffraction (XRD), field emission gun scanning electron microscopy (FEGSEM), energy dispersive X-ray spectroscopy (EDX) and thermogravimetry (TG). It was determined that template-free preparation of relatively thick EMT coatings (identified as ZSM-3, an intergrowth of EMT and FAU zeolites) was possible by using the substrate heating method. Conventional synthesis also yielded coatings of EMT-type, but with only a few microns thickness, at similar substrate temperatures. The zeolite crystallinity was improved by varying the synthesis conditions. Some coatings exhibited quite high water capacities and low regeneration temperatures, favorable for use in applications, such as adsorption heat pumps.
查看更多>>摘要：In this work, a novel nitrogen-rich hierarchical porous hyper-crosslinked polymer (HCP) is fabricated from tetrazolium (TTC) to effectively remove p-nitrophenol (4-NP) from aqueous solution. HCP is prepared through the facile Friedel-Crafts alkylation, using dimethoxymethane as the crosslinker and benzene as the co-monomer, which is aimed at adjusting the degree of crosslinking, as well as the pore structures of the material. HCP presents hierarchical flocculent structures formed by the random accumulation of tremendous nanoparticles, with a BET surface area up to 1185 m(2) g(-1). Its adsorption capacity for 4-NP is ca. 434.8 mg g(-1 )at room temperature in a solution with an initial concentration of 1 mg g-1. Its adsorption complies with pseudo-second-order dynamic model and its isotherms accord with Freundlich equation. The adsorption is an enthalpy-driven spontaneous process and the equilibrium can be established in 10 min. Thermodynamic properties and IR spectra analyses reveal that electrostatic attraction, H-bonds and pi-pi interactions collaboratively contribute to the adsorption. The HCP is stable enough that its adsorption capacity retains more than 90% after 6 cycles, which offers guarantee for its practical application in phenol removal.
查看更多>>摘要：Effective separation of olefins from hydrocarbon mixtures can provide more high-quality feed for steam cracking to produce ethylene and propylene. In this paper, metal organic framework material Cu-BTC (BTC = benzene1,3,5-tricarboxylic acid) was optimally synthesized by solvothermal method and the effects of synthesis condition on the adsorption capacity were investigated. The adsorption capacities of 1-hexene and n-hexane at 298 K were 122.31 mg/g (1.45 mmol/g) and 18.95 mg/g (0.22 mmol/g) respectively, and the selectivity was 6.45. Furthermore, by introducing acetic acid in the synthesis, three acetic groups replace one BTC linker to combined with the Cu paddlewheel clusters in the Cu-BTC skeleton, giving stronger attraction to carbon-carbon double bonds and improving the BET specific surface area, increasing from 859 m(2) g(-1) to 1297 m(2 )g(-1) . The adsorption capacity of 1-hexene was increased. Meanwhile, the adsorption of n-hexane was restrained. When n (H3BTC): n (AcOH) = 1:0.8, the BET specific surface area of the modified Cu-BTC reached 1297 m(2)/g. The adsorption capacity of 1-hexene and n-hexane were 187.90 mg/g (2.23 mmol/g) and 10.75 mg/g (0.12 mmol/g), respectively. The selectivity increased to 17.48. Furthermore, the modified Cu-BTC exhibited excellent performances for the separation of C-7 and C-8 olefin/paraffin mixtures.
Zanini, AliceCorradetti, StefanoCarturan, Sara MariaColombo, Paolo...
12页
查看更多>>摘要：An environment-friendly route for the synthesis of titanium carbide by sol-gel processing is reported. The initial solution is prepared via a simple one-pot approach, using titanium isopropoxide and sucrose as molecular precursors under acidic conditions, therefore promoting intimate interactions between the networks of sucrose and of the titanium alkoxide-derived inorganic polymer at the molecular level. Furthermore, the usage of sucrose represents an established and green solution, and provides a viable alternative to the use of toxic compounds. The resulting gels are dried at 120 ? and then undergo carbothermal reduction in Ar atmosphere at different temperatures ranging from 700 ? to 1750 ?. A systematic study of the obtained material is carried out by using FT-IR spectroscopy, X-ray diffraction, Scanning Electron Microscopy, Raman spectroscopy, N-2 physisorption and He pycnometry. The characterization techniques show that the sucrose-derived titanium carbide exhibits a tailored microporous structure and larger specific surface area values compared with those of materials produced using the hazardous phenolic resin-based system. This method thus allows the synthesis of titanium carbide with exquisite textural properties and attractive porous architectures, meeting the requirements for the fabrication of target materials in the field of nuclear medicine, with particular interest in the production and release of scandium radioisotopes.
查看更多>>摘要：Immobilized ionic liquids are one of the most popular catalysts for the cycloaddition of carbon dioxide (CO2) and epoxides with some distinguished advantages. However, the harsh reaction condition, especially for the high reaction pressure, is still the obstacle for its large-scale application. A series of amino-functionalized pyrazolium ionic liquids are grafted on SBA-15 in this work. Among them, SBA-15-APMPzBr(20) exhibits the best catalytic activity achieving 97.6% product yield under 0.5 MPa CO2 pressure at 100 C by using 100 mg SBA-15-APMPzBr (20) for 10 h. No solvent is added in the catalytic system. Moreover, SBA-15-APMPzBr(20) exhibits the good recyclability and generality. Its excellent catalytic performance is attributed to the contribution from both immobilized ionic liquids and the SBA-15 supporter. Besides the mesoporous feature, the hydroxyl groups in SBA-15 promote the ring-opening of substrate, which is testified by the experimental measurements and density functional theory calculations.
NSTL
Elsevier