Auto-thermal reforming of acetic acid for hydrogen production by ZnxNiyCrOm±δ catalysts: Effect of Cr promoted Ni-Zn intermetallic compound

A series of Zn_xNi_yCrO_m±δ catalysts were synthesized via a typical co-precipitation method, in which Zn-Cr layered double hydroxides (LDHs) were found and Ni-Zn intermetallic compound (IMC) was formed after reduction in hydrogen. During auto-thermal reforming (ATR) of acetic acid (HAc), the Ni-Zn IMC was transformed into Ni/(amorphous-ZnO)-ZnCr₂O₄ species with uniformed distribution and appropriate interaction within these Ni-Zn-Cr-O species; besides, the adsorbed oxygen promoted the activation and transfer of oxygen species; therefore, deactivation by oxidation, sintering and coking was inhibited. And the optimized Zn_2.37Ni_0.63CrO_4.5±δ catalyst presented high activity and stability in a 45-h ATR test with HAc conversion near 100% and hydrogen yield at 2.7 mol-H₂/mol-HAc, showing potential for hydrogen production via ATR of HAc.     

Controllable Fe/HCS catalysts in the Fischer-Tropsch synthesis: Effects of crystallization time

The Fischer–Tropsch synthesis (FTS) continues to be an attractive alternative for producing a broad range of fuels and chemicals through the conversion of syngas (H₂ and CO), which can be derived from various sources, such as coal, natural gas, and biomass. Among iron carbides, Fe₂C, as an active phase, has barely been studied due to its thermodynamic instability. Here, we fabricated a series of Fe₂C embedded in hollow carbon sphere (HCS) catalysts. By varying the crystallization time, the shell thickness of the HCS was manipulated, which significantly influenced the catalytic performance in the FTS. To investigate the relationship between the geometric structure of the HCS and the physic-chemical properties of Fe species, transmission electron microscopy, X-ray diffraction, N₂ physical adsorption, X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction, Raman spectroscopy, and Mössbauer spectroscopy techniques were employed to characterize the catalysts before and after the reaction. Evidently, a suitable thickness of the carbon layer was beneficial for enhancing the catalytic activity in the FTS due to its high porosity, appropriate electronic environment, and relatively high Fe₂C content.     

Terrain classification and adaptive locomotion for a hexapod robot Qingzhui

Frontiers of Mechanical Engineering - Legged robots have potential advantages in mobility compared with wheeled robots in outdoor environments. The knowledge of various ground properties and...     

Chiral metal-organic frameworks with tunable catalytic selectivity in asymmetric transfer hydrogenation reactions

Metal-organic frameworks(MOFs)have achieved great success in the field of heterogeneous catalysis,however,ifs still challenging to design MOF catalysts with enhanced selectivity.Here,we demonstrated a combination strategy of metal design and ligand design on the enantioselectivity—that is the enantioselectivities of chiral MOF(CMOF)catalysts could be significantly enhanced by the rational choice of metal ions with higher electronegativities and introducing sterically demanding groups into the ligands.Four isostructural Ca-,Sr-and Zn-based CMOFs were prepared from enantiopure phosphono-carboxylate ligands of 1,V-biphenol that are functionalized with 2,4,6-trimethyl-and 2,4,6-trifluoro-phenyl groups at the Supposition.The uniformly distributed metal phosphonates along the channels could act as Lewis acids and catalyze the asymmetric transfer hydrogenation of heteroaromatic imines(benzoxazines and quinolines).Particularly,the Ca-based MOF 1 with 2,4,6-trimethyl groups at the substituents exhibited enhanced catalytic performance,affording the highest enantioselectivity(up to 97%).It is also the first report of the heterogeneous catalyst with chiral non-noble metal phosphonate active sites for asymmetric transfer hydrogenation reactions with Hantzsch ester as the hydrogen source.The catalyst design strategy demonstrated here is expected to develop new types of chiral materials for asymmetric catalysis and other chiral applications.     

High mass loading Ni4Co1-OH@CuO core-shell nanowire arrays obtained by electrochemical reconstruction for alkaline energy storage

The design of three-dimensional(30)core-shell hetercistructures is an efficient method to achieve high mass specific capacity of electroactive materials under high mass loading.In this work,porous Ni₄Co1-0H nanosheets with a mass loading of 7.7 mg·cm^-2 are obtained by using Ni₄Cor(NO₃)₂(0H)₄ supported on the CuO nanowires as precursors via an unavoidable electrochemically induced phase reconstruction.During the electrochemical reconstruction process,the N03-anions in Ni₄Cor(N0₃)₂(0H)₄ are easily replaced by OH-anions in the electrolyte.The phase reconstruction is accompanied by the decrease of ionic diffusion.:resistance and the increase of pore volume,and the shift of binding energy.The obtained Ni4Co1-0H nanosheets show a high:mass specific capacity of 363.6 mAh·g^-1 at 5 mA·cm^-2.The as-fabricated alkaline hybrid supercapacitor and Ni-Zn battery deliver high energy density of 293.1 and 604.9 Wh·kg^-1,respectively,indicating.excellent alkaline energy storage performance.     

The relief of hypoxic microenvironment using an O2 self-sufficient fluorinated nanoplatform for enhanced photodynamic eradication of bacterial biofilms

Hypoxia,an important characteristic of bacterial biofilms,can hinder the generation of reactive oxygen species(ROS)in photodynamic therapy(PDT),leading to reduced therapeutic efficacy of PDT.In order to address this issue,fluorinated liposome was fabricated as an oxygen-sufficient nanoplatform for enhanced photodynamic eradication of bacterial biofilms.The liposomes(denoted as Lip-Ce6-PFH@O₂)were prepared by co-encapsulation of O₂ carrier perfluorohexane(PFH)and photosensitizer chlorin e6(Ce₆).Lip-Ce6-PFH@O₂ could achieve efficient biofilm penetration due to the positively charged surface.The hypoxic microenvironment of biofilms would then be relieved,leading to the generation of more ROS under laser irradiation.Therefore,the bactericidal capability of PDT could be significantly improved because of the co-delivered O₂ carrier PFH.Lip-Ce6-PFH@O₂ exhibited much better antibiofilm ability than that of Lip-Ce6 both in vitro and in vivo.Meanwhile,Lip-Ce6-PFH@O₂ also effectively alleviated inflammation symptoms and accelerated wound healing in the mice model.In general,this study provides a new paradigm to enhance the therapeutic efficacy of PDT for efficient biofilm eradication.     

Lanthanide doped fluorosilicate glass-ceramics:A review on experimental and theoretical progresses

Significant developments have been made in the past few decades for lanthanide(Ln)ions doped fluorosilicate glass-ceramics(Flusi-GCs).As novel generation of luminescence materials with a wide range of applications,Flusi-GCs as a single host combine the advantages of glass and ceramics/crystals as well as fluorides and silicates.In this review,the chemical design principles and experimental procedures of Flusi-GCs are summarized in detail.Flusi-GCs are categorized as those containing PbxCd_1-xF₂,RF₃(R=Y,La,Gd),MF₂(M=Ca,Sr,Ba),xMF₂-yRF₃(R=Y,La-Lu),mAF-nRF₃(A=Li,Na,K),KTF₃(T=Zn,Mn)and K2 SiF6 nanocrystals(NCs).Theoretical breakthroughs mainly by molecular dynamic(MD)simulation have been recapitulated as efficient routes for composition-design,nano-crystallization-prediction,and performance-optimization of Flusi-GCs containing target fluoride NCs.Essential research progresses pertaining photonic applications have been made in random lasers,communication amplifiers,optical fibers,spectral converters,white light-emitting-diodes(WLEDs),and thermal sensors.In the end,we propose three future research directions for Flusi-GCs.     

Effect of inhaled formaldehyde on learning and memory of mice

In this study, we investigated the effect of inhaled formaldehyde on learning and memory capacity. After exposure to 0 (control), 1 and 3 mg/m(3) of gaseous formaldehyde respectively, the behavior of mice in a Morris water maze, the expression of NR1, NR2B mRNA and oxidative damage levels in mice brain were analyzed. The water maze performance, the activities of dismutase superoxide (SOD) and levels of glutathione (GSH) decreased significantly in 3 mg/m(3) group (P < 0.01, compared with control group); while malondialdehyde (MDA) contents and expression of NR1 and NR2B genes increased significantly after exposure to 3 mg/m(3) of gaseous formaldehyde (P < 0.05, <0.01, <0.01, compared with control group). These findings indicate that inhaled formaldehyde negatively affects learning and memory at 3 mg/m(3) of gaseous formaldehyde but not at lower levels. Oxidative stress-induced neuron damages in the brain may be the possible mechanism for these effects. PRACTICAL IMPLICATIONS: This study indicates that inhaled formaldehyde starts to negatively affect learning and memory at a middle concentration of formaldehyde without interference of other indoor air pollutants. Oxidative damage, and the alteration of NMDA receptor expression, which were induced by formaldehyde inhalation, may be the possible mechanism for gaseous formaldehyde-induced neurotoxicity.     

Fabrication and characterization of hierarchical porous Ni2+ doped hydroxyapatite microspheres and their enhanced protein adsorption capacity

Hydroxyapatite (HAP) is a common bio-adsorbent, which performance depends heavily upon its morphology and microporous structure. In this study, a novel synthesis strategy was proposed for hierarchical porous HAP microspheres by a simple “one-pot” hydrothermal reaction. In the strategy, L-glutamic acid serves as soft template to modulate the morphology and inner crystalline of HAP. To evaluate the application potential, doping Ni²⁺ on hierarchical porous HAP microspheres gives metal chelated affinity adsorbents. The prepared adsorbents show a perfect spherical shape, particles size of 96.6 μm, relatively specific surface area of 48.5 m²·g^-1 and hierarchical pores (mesopores: 4 nm and macropores: 53 nm). By the adsorption evaluation, it reveals that the Ni²⁺-HAP adsorbents have high adsorption capacities of 275.11 and 97.55 m²·g^-1 for hemoglobin and bovine serum albumin, respectively, which is comparable to other similar adsorbent. Therefore, this work provides a promising method for high-efficiency hydroxyapatite microspheres for proteins purification.     

Structural optimization of a settler via CFD simulation in a mixer-settler

This work is aimed at optimizing a settler structure in a mixer-settler.Two different aspects have been considered.Firstly,the flowcharacteristics of a settler have been examined by computational fluid dynamics(CFD)simulation with various agitation speeds of the mixer,as well as organic phase volume fractions ranging from 0.075 to 0.6.The aqueous and organic phase turbulent flow fields were measured by particle image velocimetry(PIV) technique to verify the CFD simulation.Two organic phases with different physical properties were assessed in the CFD simulation to simulate the liquid-liquid systems related to rare earth element extraction,i.e.,0.072 mol·L~(-1) P507/kerosene and 1.8 mol·L~(-1) P507/kerosene.Secondly,the CFD simulation was carried out in a settler equipped with baffles.The effects of number and location of the baffle in the settler on flow features and entrainments of the aqueous and organic outlet were analyzed.Meanwhile,different settler/mixer volume ratios were also examined.By analyses and comparisons,an optimal design for settler was proposed.CFD can provide a significant guidance to better mixer-settler design.