Development of Mn and Mo double-substituted La5.5WO11.25-δ based membranes with enhanced hydrogen permeation flux

Mixed protonic-electronic ceramic lanthanum tungstate membranes of La_5.5W_1-xMn_xO_11.25-δ (LWMn_x, x = 0.1, 0.15 and 0.2) and La_5.5W_0.8-yMn_0.2Mo_yO_11.25-δ (LWMn_0.2Mo_y, y = 0.1, 0.2, 0.3 and 0.4) were developed in present work. The H₂ permeation flux through lanthanum tungstate membrane was increased by substitution of Mn ions into W sites. However, the impurity of La₂O₃ formed in LWMn_0.15 and LWMn_0.2 membranes. Introduction of a moderate amount of Mo ions in LWMn_0.2 was beneficial to single phase formation and H₂ permeation. LWMn_0.2Mo_0.2 exhibited a pure cubic phase structure without any impurities. LWMn_0.2Mo_0.2 membrane had a H₂ permeation flux about 0.12 mL/min?cm² at 1000 °C, which was 1.7 times higher than that through LWMn_0.2 membranes.     

CO2-tolerance and oxygen permeability of novel cobalt-free mixed-conductor oxygen-permeable Pr0.6Sr0.4Fe1-xNbxO3-δ membranes

A series of novel cobalt-free dense oxygen-permeable membranes of the type with Pr_0.6Sr_0.4Fe_1-xNb_xO_3-δ (PSFN_x, x = 0–0.1) were synthesized. Subsequently, the effects of Nb-doping on the microstructure, oxygen permeability, and stability of PSFN_x were studied under a pure He or CO₂ atmosphere. The structure of the material did not change in either atmospheres and its stability of the material was enhanced as the level of Nb-doping increased. For the sample with x = 0 and 0.075, carbonates and sulfates were present on the sweep side of the PSF membrane, but no impurities were detected on the sweep side of the PSFN_0.075. In addition, the oxygen-permeation performance exhibited almost no attenuation when the Nb-doping content were 0.075. As revealed by X-ray photoelectron spectroscopy, the CO₂ resistance of the material was enhanced by reducing the basicity of PSFN_x, which was induced by the substitution of Fe with Nb.     

Fabrication and H2 flux measurement of asymmetric La27W3.5Mo1.5O55.5-δ − La0.87Sr0.13CrO3-δ membranes

Novel asymmetric hydrogen permeable membranes consist of a dense ceramic–ceramic (cercer) composite layer of La_0.87Sr_0.13CrO_3-δ and La₂₇W_3.5Mo_1.5O_55.5-δ deposited on a tubular porous support of the latter composition. The membranes were produced by extrusion and dip-coating with various thermal cycles required for adjusting the thermal shrinkage of the different layers and obtaining gas tight membrane layers. The produced asymmetric membranes have a dense cercer layer thicknesses ranging from 25 to 50 μm on supports exhibiting a porosity of up to 40 vol%. The effect of processing parameters, such as volume of pore former, coating steps, sintering temperature and soaking time on the microstructure of the membranes is discussed to highlight critical steps in the manufacturing protocol. Hydrogen fluxes were measured as a function of temperature with both wet and dry Ar sweep gas. Results are discussed with respect to membrane architectures and materials properties.     

Na2WO4-2 Na2CO3·3 H2O2体系催化氧化乙腈的反应研究

以钨酸钠为催化剂、过碳酸钠为氧化剂,选择性氧化乙腈制备乙酰胺.研究了该碱性氧化体系的作用,比较了反应时间、温度对反应的影响.考察了钨酸钠的催化性能以及不同碳酸钠用量在体系中的反应结果.反应时间的延长和温度的升高并不利于提高转化率,因此反应选择在室温条件下进行.碳酸钠和氧化体系碱性的增加能促进产物乙酰胺的生成.以钨酸钠为催化剂,反应条件:室温25℃,时间4 h,V[H2O]/V[methnol]=2/3时,乙腈的转化率可达100%左右,生成的乙酰胺的选择性可达94.3%.     

Mechanical properties of BaCe0.65Zr0.2Y0.15O3-δ – Ce0.85Gd0.15O2-δ dual-phase proton-conducting material with emphasis on micro-pillar splitting

BaCe_0.65Zr_0.2Y_0.15O_3-δ – Ce_0.85Gd_0.15O_2-δ (BCZ20Y15-GDC15) dual-phase material revealed potential for H₂ production technologies due to its exceptional H₂ permeation and chemical resistance. In this article, mechanical properties of BCZ20Y15-GDC15 dual-phase material were investigated to evaluate the mechanical behavior and develop strategies to warrant structural stability. Elastic modulus, hardness and fracture toughness values were studied using different indentation-based methods. The fracture experiments at different length-scales both revealed that the introduction of GDC15 makes the material tougher, facilitating the further design of robust and reliable components.     

Enhanced CO2 response of La1-xFeO3-δ perovskites with A-site deficiency synthesized by flame spray pyrolysis

Measuring the CO₂ concentration is the base of carbon accounting which aims to abate the greenhouse gas emission. This paper pays attention to developing sensitive material for CO₂ detection in vehicle exhaust. For this purpose, La_1-xFeO_3-δ nanoparticles with A-site deficiency were synthesized by flame spray pyrolysis (FSP). The dynamic response of the prototype CO₂ sensors was evaluated by checking the gas-mixture with 5%–15% CO₂. It was observed that the amount of A-site deficiency would obviously affect the performance of the material. La_0.95FeO_3-δ sensor exhibits the highest response (S = 3.38) and a relatively short response time (t₉₀ = 114s) among the serial La_1-xFeO_3-δ sensors (x = 0, 0.02, 0.05, 0.07 and 0.1). The improvement of the response might be attributed to the increase of oxygen vacancies and the higher valence of B-site cations caused by the introduction of A-site deficiency. Furthermore, the sensor exhibited good selectivity against NH₃, NO, NO₂ and CO, as well as good repeatability. However, water vapor is still a disturbance in the response. The response at 40% RH and 80% RH are 2.11 and 1.73, respectively. Finally, the sensing mechanism based on the participation of the oxygen vacancies was discussed.     

Pursuit of efficient CO2-capture membranes: graphene oxide- and MOF-integrated Ultrason® membranes

Polymer Bulletin - High-performance mixed-matrix membranes (MMMs) were developed to help control the global warming by capturing and sequestrating carbon dioxide (CO2) from post combustion flue gas...     

Na2WO4-2Na2CO3·3H202体系催化氧化乙腈的反应研究

以钨酸钠为催化剂、过碳酸钠为氧化剂,选择性氧化乙腈制备乙酰胺。研究了该碱性氧化体系的作用,比较了反应时间、温度对反应的影响。考察了钨酸钠的催化性能以及不同碳酸钠用量在体系中的反应结果。反应时间的延长和温度的升高并不利于提高转化率,因此反应选择在室温条件下进行。碳酸钠和氧化体系碱性的增加能促进产物乙酰胺的生成。以钨酸钠为催化剂,反应条件：室温25℃,时间4h,V[H2O]/V[methanol]=2／3时,乙腈的转化率可达100％左右,生成的乙酰胺的选择性可达94．3％。     

Core-shell structured ZnO@Cu-Zn–Al layered double hydroxides with enhanced photocatalytic efficiency for CO2 reduction

Hierarchical ZnO@Cu-Zn–Al layered double hydroxide (LDH) heterostructures were synthesized by a facial deposition-precipitation method, and it exhibited an enhanced photocatalytic efficiency for CO₂ reduction. The physicochemical properties of as-prepared ZnO@LDHs were studied by SEM, XRD, BET, UV–vis and TEM technique. The improvement of photocatalytic efficiency is related to two factors. On the one hand, LDH species can increase the surface areas of catalysts effectively, which means that more adsorb active sites for CO₂ can be provided; on the other hand, the heterojunction was formed on the ZnO/LDHs interface hindering the recombination of excited charge carriers.     

High flux and CO2 stable La0.6Ca0.4Co0.2Fe0.8O3-δ hollow fiber membranes through internal coagulation bath optimization

La_0.6Ca_0.4Co_0.2Fe_0.8O_3-δ (LCCF) ceramic powder prepared by sol-gel method was used to fabricate LCCF hollow fiber (HF) membranes via a combined phase inversion-sintering technique. Three types of LCCF HF membranes were developed by changing the composition of the internal coagulation bath containing H₂O, EtOH or the mixture of NMP + EtOH. The best one was achieved via the mixture (0.7NMP + 0.3EtOH by weight). At 1000 °C, the oxygen flux reached 6.16 mL min⁻¹ cm⁻² under inert sweep gas; however, it reached 8.83 mL min⁻¹ cm⁻² when reactive CH₄ was used as the sweep gas, mirroring the high capability of oxygen transport through the membrane. The good stability of the developed LCCF membrane was confirmed by a series of long-term operation tests up to 300 h with sweep gas containing CO₂. The findings of this work can advance the applications of LCCF membranes to reactors where CO₂ atmosphere cannot be avoided.     

SLPC用于H2／CO控制

一、前言从前,我厂曾经以触媒层温度为主环,进行过甲醇变换炉自动控制试验,由于变换炉控制扰动因素较多,而一般调节器功能简单,交换炉控制效果不甚十分理想。随着仪器仪表技术高速发展,于是,我们才有可能采用高精度、高稳定性的在线分析器和多功能SLPC可编程调节器,组成具有负荷前馈的H_2/CO比值控制系统,应用     

Preparation of cobalt coated TiO2 and WO3–TiO2 nanotube films via photo-assisted deposition with enhanced photocatalytic activity under visible light illumination

Highly ordered TiO₂ and WO₃–TiO₂ nanotubes were prepared by one-step electrochemical anodizing method and cobalt has been successfully deposited on these nanotubes by photo-assisted deposition process. The morphology, crystal structure, elemental composition and light absorption capability of samples were characterized by field emission scanning electron microscope, X-ray diffraction, energy dispersive X-ray spectrometer and ultraviolet–visible spectroscopy methods. All cobalt loaded samples show an appearance of red shift relative to the unloaded samples. The degradation of methylene blue was used as a model reaction to evaluate the photocatalytic activity of these novel visible-light-responsive photocatalysts. Results showed that the photocatalytic activity of bare WO₃–TiO₂ samples is higher than that with undoped TiO₂ sample. Compared with unmodified TiO₂ and WO₃–TiO₂, the Co/TiO₂ and Co/WO₃–TiO₂ samples exhibited enhanced photocatalytic activity in the degradation of methylene blue. Kinetic research showed that the reaction rate constant of Co/WO₃–TiO₂ is approximately 2.26 times higher than the apparent reaction rate constant of bare WO₃–TiO₂. This work provides an insight into designing and synthesizing new TiO₂–WO₃ nanotubes-based hybrid materials for effective visible light-activated photocatalysis. The catalysts prepared in this study exhibit industrially relevant interests due to the low cost and high photocatalytic activity.     

Oxygen separation from air using Ba0.95La0.05FeO3−δ membranes fitted with porous La1−xSrxFeO3−δ layers

Selective oxygen separation from air was performed using perovskite-type oxide membranes made of Ba_0.95La_0.05FeO_3−δ. We demonstrated that surface modification of Ba_0.95La_0.05FeO_3−δ membranes with La_1−xSr_xFeO_3−δ catalyst layers led to an increase in oxygen permeation fluxes at 700–930 °C. We studied the effects of oxygen vacancy amounts, surface area, particles size, surface treatment of La_1−xSr_xFeO_3−δ on the oxygen permeability of the membranes fitted with La_1−xSr_xFeO_3−δ catalyst layers. Among the catalyst layers tested, the membranes fitted with La_0.9Sr_0.1FeO_3−δ (x=0.1) showed the highest oxygen permeation flux probably because of its higher porosity and uniform morphology without open voids, which would increase the number of surface reaction sites. The obtained results suggest the feasibility of further upgrading the membrane performance by using surface catalyst layers having a homogeneous morphology and a different composition from that of the mother membrane.     

WO3基H2S气敏材料的研究

采用正交试验法和单水平试验法研究了热处理温度及掺杂元素对ＷＯ３基Ｈ２Ｓ气敏元件灵敏度、选择性、稳定性,响应恢复特性及元件阻值的影响,得到了较为理想的Ｈ２Ｓ气敏元件。根据提出的气敏机理模型较好地解释了热处理温度、掺杂氧化物酸碱性及催化活性等对Ｈ２Ｓ气体灵敏度的影响。     

High CO2 resistance of indium-doped cobalt-free 60 wt.%Ce0.9Pr0.1O2-δ-40 wt.%Pr0.6Sr0.4Fe1-xInxO3-δ oxygen transport membranes

The oxygen transport membrane (OTM) has huge application prospects in gas separation and carbon neutralization based on oxygen enriched combustion. In this paper, the family 60 wt.%Ce_0.9Pr_0.1O_2-δ-40 wt.%Pr_0.6Sr_0.4Fe_1-xIn_xO_3-δ (CPO-PSF_1-xI_xO, x = 0.01, 0.025, 0.05, 0.075, 0.1) cobalt-free dual-phase MIEC OTMs doped with indium have been successfully prepared by Pechini method. The phase structure, surface morphology, element distribution, oxygen permeability, and long-term operation stability of these OTMs are systematically explored. Among these OTMs, the champion oxygen permeable flux of CPO-PSF_0.99I_0.01O reaches 1.07 mL min^?1·cm^?2 and 0.80 mL min^?1·cm^?2 at 1000 °C under air/He gradient and air/CO₂ gradient. Meanwhile, CPO-PSF_0.99I_0.01O maintains the value of 0.80 mL min^?1·cm^?2 steadily at 1000 °C for 100 h when pure CO₂ as the sweep gas. The surface element distribution and phase structure of the OTMs after long-term oxygen permeability reaction are investigated by XRD, SEM combining with EDS, where the spent membranes retain the same structure and component as the fresh membranes, demonstrating that the In-doped OTMs have an excellent CO₂ tolerance. Suitable indium substitution for iron of these OTMs not only improves the oxygen permeability, but also maintains the long-term reaction stability of the material.     

CO、CO2、H2直接合成二甲醚与甲醇的化学平衡

由ＣＯ、ＣＯ２、Ｈ２直接合成二甲醚与甲醇为一复合反应体系,本文分析对ＣＯ加Ｈ２、ＣＯ２加Ｈ２、合成气（即ＣＯ、ＣＯ２同时加Ｈ２）直接合成二甲醚与甲醇的化学平衡进行了计算,合成反应的单程转化率受到化学平衡的限制。     

Effects of Al content on the oxygen permeability through dual-phase membrane 60Ce0.9Pr0.1O2-δ-40Pr0.6Sr0.4Fe1-xAlxO3-δ

Ceramic dual-phase oxygen transport membranes with the composition of 60 wt% Ce_0.9Pr_0.1O_2-δ-40 wt%Pr_0.6Sr_0.4Fe_1-xAl_xO_3-δ (x = 0.05, 0.1, 0.2, 0.3, 0.4, 0.6, 0.8, 1.0) (60CPO-40PSF_1-xA_xO) based on 60Ce_0.9Pr_0.1O_2-δ-40Pr_0.6Sr_0.4FeO_3-δ doped Al was successfully synthesized through a modified Pechini method. Crystal structure, surface microtopography and oxygen permeability are investigated systematically. The cell parameters of perovskite phase first increased and then decreased with the increase of Al content, which is related to the radius of the Al³⁺ and the formation of impurity phase. As x ranges from 0.1 to 0.8, the oxygen permeability of the materials first increases and then decreases, and the maximum value of oxygen permeation rate for 60CPO-40PSF_1-xA_xO membranes with 0.4 mm thickness at 1000 °C is 1.12 mL min⁻¹ cm⁻² when x = 0.4. XRD measurements revealed high temperature stability and CO₂-tolerant property of the dual-phase composites. The partial replacement of Fe³⁺/Fe⁴⁺ by Al³⁺ causes the material not only to exhibit good stability, but also to increase the oxygen permeability of the membranes.     

Ruddlesden-Popper-type Nd2-xNi1-yCuyO4±δ layered oxides as candidate materials for MIEC-type ceramic membranes

Series of Nd_2-xNi_1-yCu_yO_4±δ Ruddlesden-Popper-type oxides is obtained by auto-combustion synthesis method and systematically characterized concerning phase composition, formation of solid state solution, crystal structure, oxygen content, as well as regarding transport properties and oxygen permeability when applied as mixed conducting ceramic membranes. The A-site deficiency x is discussed in terms of structural stability and its effect on the oxygen content, with ongoing modification of total electrical conductivity observed. In selected Nd_2-xNi_0.75Cu_0.25O_4±δ oxides the dominating oxygen defects at high temperatures can be changed from oxygen interstitials to vacancies by the induced A-site deficiency, which affects bulk- and surface-related transport coefficients, as it is observed in electrical conductivity relaxation studies. The optimized Nd_1.9Ni_0.75Cu_0.25O_4±δ sinters having increased ionic conductivity, as well as fine, well-sintered microstructure allow to achieve one of the higher reported oxygen fluxes for CO₂-stable Ruddlesden-Popper-based ceramic membranes (e.g. 0.49 mL cm⁻² min⁻¹ at ca. 880 °C for 1.05 mm thickness).