查看更多>>摘要：Reduction pre-treatment at different temperatures were performed over Mo/HZSM-5 system before methane dehydroaromatiztion reaction. We have shown the crucial effect of reduction temperature on the final catalytic performance. Outstanding improvement in the aromatics conversion has been attained. Thus, H-2 formation form methane cracking reaction seems to be hindered for pre-treated catalysts. As a consequence, the deposition of coke in these samples appeared also notably suppressed. The optimum performance has been achieved for reduction pre-treatment at 550 degrees C. For this temperature, we have observed that the fraction of reduced Mo species is higher.
Gonsalves, Liliana P. L.Mielby, JerrikSoares, O. Salome G. P.Sousa, Juliana P. S....
13页
查看更多>>摘要：The development of novel cost-efficient, high-performing catalysts for CO2 methanation that are active at low temperatures can be optimized through the understanding of the reaction mechanism on different materials. A series of Ni-based catalysts supported on CeO2 and carbon/CeO2 composites was investigated, showing that Ni nanoparticles supported on a carbon/CeO2 composite with a 50:50 wt ratio and on pure CeO2 have excellent lowtemperature activity and achieve up to 87% CO2 conversion with full selectivity towards CH4 at 370 degrees C. Importantly, meaningful insights on the reaction mechanism were gathered for the different types of materials by using the emerging ME-PSD-DRIFTS technique. The study of the rate of formation/consumption of the various intermediates showed that the CO2 methanation reaction follows a combination of the CO and formate pathways in the case of Ni on pure CeO2; however, in the case of Ni on the carbon/CeO2 composite, it follows only the formate pathway.
查看更多>>摘要：Microscale zero-valent iron (mZVI) is used as a catalyst for peroxide activation and, has attracted considerable attention for the degradation of organic contaminants. However, surface inherent oxide films impedes electron transfer in mZVI and decrease its activation efficiency. Herein, the mZVI surface was modified by sodium disilicate (Si-mZVI(bm)) using a mechanical ball-milling approach. The mechanochemically silicified mZVI enhanced the sulfamethazine removal rate by 2.9-23.8 fold in relation to unmodified ZVI; this rate increased with the Si/Fe molar ratio (0-8%). Reactive intermediates, including radicals and non-radicals, were efficiently generated via peroxydisulfate (PDS) activation over Si-mZVI(bm) both SO(4)(center dot-& nbsp;)and Fe(IV) contributed toward sulfamethazine removal. The excellent performance of PDS activation over Si-mZVIbm particles was attributed to the continuous generation of ferrous ions, which was due to the accelerated iron release and more effective Fe3+/Fe2+ cycles in the Si-mZVI(bm)/PDS system after silicification.
查看更多>>摘要：Herein, a homojunction carbon nitride photocatalyst integrated with three crystallization levels (Tri-crystallinity) is developed to enhance the degradation activity of organic pollutants. The increase in crystallinity induces the Fermi level and band position to decrease. This difference constructs an internal electric field (IEF) at the interface with a lower to higher crystallinity direction. The multiple contact interfaces in Tri-crystallinity reinforce the interfacial IEF twice compared to a conventional single-interface. The interfacial IEF improves charge separation and transfer, and the degradation of antibiotics by Tri-crystallinity carbon nitride is at least 20 times greater than primary carbon nitride. Further, the Tri-crystallinity carbon nitride loading on a nonwoven fabric in a continuous-flow reactor achieves 91.0% purification of the organic wastewater at a flow rate of 14.2 L h-1 m- 2 from 11:00 a.m. to 3:00 p.m. This work provides a strategy for engineering interfacial IEF of future efficient photocatalysts.
Vutolkina, A. V.Baigildin, I. G.Glotov, A. P.Pimerzin, Al. A....
16页
查看更多>>摘要：We report efficient hydrodeoxygenation of guaiacol via in situ hydrogen generated through Water Gas Shift (WGS) reaction over nanosized unsupported NiMoS catalysts with tunable selectivity toward cyclohexene. This strategy possesses a direct reaction route of oxygen-containing compounds from bio-oils depending on catalysts precursors and reaction conditions. The active catalytic species were formed in situ through the high-temperature decomposition of oil-soluble metal precursors followed by sulfidation in water-in-oil sulfur-containing emulsions. Unsupported NiMoS catalysts were found to provide 100% guaiacol conversion at 320-380 degrees C and 5 MPa CO pressure. Reaction routes and mechanisms for hydrodeoxygenation of guaiacol were proposed. Ni:Mo= 1:3 and sulfur content of 1.2-1.5 wt% favor higher cyclohexene selectivity decreases at low temperature and short reaction time (30-40 wt% water content, CO pressure of 5 MPa). The catalysts were found to be reusable at least 6 cycles in the sulfur-assisted hydrodeoxygenation of guaiacol with maintaining conversion, and active component evolution was studied.
查看更多>>摘要：This study investigates the effect of oxalate and borohydride ligands functionalization on the properties and activity of zeolite Y (ZY) supported copper nanoparticles in CO2 hydrogenation to specialty chemicals. The ZY-supported copper oxalate (CuX-ZY) and copper borohydride (CuB-ZY) catalysts exhibited a drastic difference in physicochemical properties compared to a benchmark copper supported on ZY (Cu-ZY) catalyst without any functionalization. The average Cu particle sizes are 7.74, 0.69, and 0.57 nm for Cu-ZY, CuX-ZY, and CuB-ZY, respectively. The smaller the copper oxide particle sizes, the higher the reduction temperatures to the metallic state due to strong-metal-support-interactions. The CO2 conversions (XCO2) at 270 degrees C are 28.3%, 26.4%, and 14.6%, for CuX-ZY, CuB-ZY, and Cu-ZY which aligns with the trend of basic site-strength, Cu particle sizes, and Cu dispersion of the catalysts. While methanol yield was maximum at 70.5 g(product) g(cat)(-1)center dot min(-1) over CuX-ZY, the dimethyl ether was maximum at 48.9 g(product) g(cat)(-1)center dot min(-1) over CuB-ZY. Furthermore, the oxalate and borohydride functionalization were effective in minimizing CO formation.
查看更多>>摘要：Reinforced adsorption enabled efficient degradation of formaldehyde was investigated with a unique flower-like Cu2_xSe/Cu2O heterojunction photocatalyst. Nonstoichiometric Cu2_xSe crystals are grown from a pliable Cu mesh through a self-sacrifice template strategy. Sintering Cu2_xSe in O-2/N-2 atmosphere enables the formation of Cu2_xSe/Cu2O heterojunction. The implantation of Cu2O lowers the work function of Cu2_xSe and boosts the gathering of electrons, qualifying the heterojunction as electron-rich area with those shared Cu atoms being active sites. Under illumination, abundant electrons on Cu2_xSe/Cu2O delocalize to attract formaldehyde molecules and convert them into semi-stable carbonates. Simultaneously, these electrons react with adsorbed oxygen to produce active center dot O-2(-) . With a continuous-flow operation mode, 100% removal percentage and 99.5% CO2 conversion rate are achieved when eliminating formaldehyde. By virtue of its integrity and pliability, the Cu mesh bearing Cu2_xSe/Cu2O can be applied in air purifier directly.
查看更多>>摘要：Alcohols are important chemicals, and are considered as high value-added products from Fischer-Tropsch synthesis (FTS). However, the unknown active sites and their unclear alcohol formation mechanism hinder the development of highly efficient catalysts. Herein, we report the design of low cost and scalable carbon-supported Fe (K-Fe/NC) catalyst with tailorable FTS selectivity via pyrolysis of Prussian Blue. Our K-Fe/NC catalyst exhibits alcohol selectivity as high as 30% containing 95% of C-2-C-13 fraction. The K-Fe/NC catalyst with a core-shell structure facilitates the investigation of iron structural evolution in FTS. The CO dissociation and association are thoroughly verified through theoretical calculations and the temperature-programmed surface reaction of CO. The synergistic effect between chi-Fe5C2/epsilon-Fe2C and Fe3O4 dual active sites is proposed for the alcohol formation mechanism. This work provides significant insight into the development of low cost and highly efficient iron-based catalysts for alcohols in FTS.
查看更多>>摘要：It is of challenge to improve the coke resistance of Fe-based oxygen carriers (OC) due to the conflict of Fe-0 sites for CH4 activation but causing coke formation. The present work reported that carbon-tolerant of Y3Fe2Al3O12-T garnets (YFAO-T, T indicates calcination temperature) could be remarkably promoted by tuning calcination temperature for chemical looping partial oxidation of methane (CLPOM). This was because the encapsulation degree of Fe-0 (1-Fe-exposed(0)/Fe-total(0)) became larger with reduction from 19% to 79% due to decreased oxygen mobility leading to more surface oxygen-deficiency for YFAO-T calcined at higher temperature, which not only resulted in Fe-0 sites for CH4 activation but also accessible lattice oxygen of garnet shell for carbon oxidation formed on Fe-0 sites. Comparatively, the encapsulation of Fe-0 was destroyed leading to progressively naked Fe-0 with large particle size with reduction for YFAO-T calcined at lower temperature, which induced carbon deposition due to inaccessible lattice oxygen of garnets.
查看更多>>摘要：The catalytic activity of single-atom catalysts (SACs) can be enhanced by engineering the coordination environment of metal centres. Herein, zeolitic imidazolate framework (ZIF) was used as a precursor to introduce P atoms into a Co-based SAC. With the P doping, the resultant ZIF-CoN3P-C could efficiently degrade 98.4% of sulfadiazine (10 mg L-1) within 5 min by activating peroxymonosulfate (PMS) with an elevated degradation rate constant 2.5 times that of ZIF-CoN4-C. Density functional theory (DFT) calculations indicate that the electron density and electron delocalisation were further concentrated around the Co centres by the P doping, which facilitated electron transfer from Co to PMS molecules and enhanced the generation of singlet oxygen (O-1(2)). The ZIF-CoN4P-C exhibited its universality and stability for the PMS-based oxidation process. Overall, these findings clarify the role of P atoms in tuning the electronic structure and reactivity of Co in ZIF-CoN3P-C for enhanced PMS activation and organic degradation.
NSTL
Elsevier