羟基磷灰石负载钯催化剂用于H2和O2直接合成H2O2的动力学

H₂和O₂直接合成H₂O₂过程绿色环保,反应具有原子经济性,是最有潜力的H₂O₂合成新方法之一。采用等量浸渍法,将Pd负载于羟基磷灰石（HAp）载体上,得到了高分散的Pd/HAp纳米催化剂,Pd平均粒径2.5 nm。运用幂指数模型,研究该催化剂在H₂O₂加氢及H₂和O₂直接合成反应中的动力学,计算得到H₂O₂加氢、H₂O₂和H₂O的生成反应的表观活化能及O₂、H₂表观反应级数。结果表明低温及高O₂分压有利于H₂O₂的生成,而高H₂分压则有利于H₂O的生成。     

CeO2基水煤气变换催化剂COS中毒热力学研究

为探究COS对Ce O₂基水煤气变换催化剂的中毒机制，用HSC Chemistry 6.0热力学数据库对Ce O₂变换催化剂的COS中毒热力学进行了模拟计算，从热力学角度分析了在100～450℃水气变换温度下，COS分别与CO、H₂O和O₂共存时，Ce O₂催化剂可能发生的反应及产物。结果表明，温度分别高于150℃和300℃时，H₂O-COS-Ce O₂和CO-COS-Ce O₂体系中的Ce O₂硫中毒可被明显抑制；O₂对Ce O₂硫中毒的影响最大，整个催化温度范围内，O₂-COS-Ce O₂体系中所有反应均可自发进行，含S固态产物为Ce₂(SO₄)₃、Ce S₂和S。     

基于Langmuir-Hinshelwood动力学解析O2/CO2/H2O气氛下烟煤焦反应机理

流化床富氧燃烧湿烟气循环兼具经济与环保优势。湿烟气循环（O₂/CO₂/H₂O）条件下煤焦与O₂、CO₂及H₂O的反应同时发生。为探究O₂/CO₂/H₂O气氛下煤焦-O₂、煤焦-CO₂、煤焦-H₂O反应间的相互作用机制,在自制高精度热重实验装置上系统考察了O₂、CO₂、H₂O及其混合气氛下,典型烟煤焦在900℃的反应特性。基于吸附和脱附原理的Langmuir-Hinshelwood（L-H）机理性模型分别计算了烟煤焦与O₂、CO₂和H₂O反应的动力学参数。通过采用单独活性位点与竞争活性位点两种假设分析了O₂/CO₂、O₂/H₂O和CO₂/H₂O气氛下烟煤焦-O₂、烟煤焦-CO₂和烟煤焦-H₂O两两反应间的作用机制,揭示了H₂O分子优先吸附于烟煤焦表面活性位点,O₂分子次之,而CO₂分子相对滞后。O₂/CO₂/H₂O气氛下烟煤焦-O₂、烟煤焦-CO₂、烟煤焦-H₂O反应表现出部分竞争反应活性位点,传统的单独活性位点与竞争活性位点假设均无法准确描述其反应速率特性。基于H₂O分子优先,O₂分子次优先吸附的原理,建立了O₂、CO₂、H₂O混合气氛下煤焦反应速率L-H动力学方程,方程计算结果与实验值良好吻合。研究结果为深入分析煤焦颗粒流化床富氧燃烧特性及构建可靠、准确的燃烧反应模型提供了理论支撑。     

O2/H2O燃烧方式下石灰石的间接硫化反应特性

利用水平管式炉和热重实验台架,对O₂/H₂O、O₂/N₂和O₂/CO₂ 3种不同燃烧方式下石灰石的间接硫化反应特性进行了研究。重点探究了燃烧方式、水蒸气浓度对石灰石间接硫化反应的影响规律与机理。同时,对硫化产物进行了X射线荧光光谱（XRF）、X射线衍射（XRD）、孔结构特性和扫描电镜（SEM）分析。结果表明,O₂/H₂O燃烧方式相比于相同氧浓度下的O₂/N₂和O₂/CO₂燃烧方式,石灰石间接硫化反应的钙转化率在化学反应控制阶段基本相同,在扩散控制阶段O₂/H₂O燃烧方式下的钙转化率有显著的提高。主要原因是水蒸气促进了硫化反应后期产物层内的固态离子扩散。此外,O₂/H₂O燃烧方式下,不同的水蒸气浓度对石灰石的钙转化率基本没有影响。     

反应吸附强化C2/C3烃水蒸气重整制氢反应热力学计算

为拓宽反应吸附强化水蒸气重整制氢（ReSER）原料的应用范围,采用化工流程模拟软件Aspen Plus,针对包括C₂H₄、C₂H₆、C₃H₆、C₃H₈ 的C2/C3轻烃 ReSER制氢反应可行性和优化条件进行热力学分析计算。在选择的反应压力0.1～5 MPa,温度200～800℃,水碳摩尔比（S/C）1～8和吸附剂中氧化钙和原料碳摩尔比（Ca/C）0～5条件下进行热力学分析计算。计算结果表明：在优选的水碳比（S/C）4,钙碳比（Ca/C）2.5,温度200～650℃,压力0.1～1.8 MPa的条件下, C₂H₄、C₂H₆、C₃H₆、C₃H₈均可分别通过ReSER反应获得H₂含量在95%以上的产物,产物中H₂浓度均随着水碳比和钙碳比的增大而提高。在假设的水碳比4,钙碳比2.5条件下,当CO₂脱除率达到0.9以上,C₂H₄、C₂H₆、C₃H₆、C₃H₈的反应温度分别高于250、400、250、350℃时,产物中H₂摩尔分数均可达到95%以上,产物中的H₂浓度随着反应温度的升高和CO₂脱除率的增加而提高。当CO₂脱除率低于0.9,产物H₂摩尔分数要达到95%时,C₂H₄、C₂H₆、C₃H₆、C₃H₈的反应温度均需升高50℃。在相同长度C链的烃类中,烯烃比烷烃更容易发生ReSER反应。而原料的碳链越长,则越容易发生ReSER制氢反应。     

硅烷/纳米CeO2·ZrO2复合膜层的制备及其性能研究

针对低温多效海水淡化过程中金属换热管路的腐蚀问题,采用硅烷（APS）、纳米氧化锆（Zr O₂）及纳米氧化铈（Ce O₂）在铝合金表面制备硅烷/纳米Zr O₂·Ce O₂复合膜层,研究其抑制金属腐蚀的效果。结果表明,当纳米Zr O₂、纳米Ce O₂添加浓度为50 mg/L时,复合膜层的综合性能较好;通过动电位极化法和电化学阻抗法探究了复合膜层在不同温度下的耐蚀性能,结果表明硅烷/纳米Zr O₂·Ce O₂复合膜层的防护效果较单一硅烷膜层有明显提升。随着溶液温度的升高,硅烷/纳米Zr O₂·Ce O₂复合膜层的耐蚀性能降低较少,纳米Zr O₂、纳米Ce O₂的协同作用使得硅烷膜更能适应高温高盐环境。     

不同烟气组分对粉状活性焦吸附汞的影响机理

在模拟燃煤热烟气为热源和介质条件下，以准东褐煤为原料，通过一维沉降炉进行炭化活化（一步法）制备粉状活性焦，考察了活性焦对Hg⁰的吸附能力，探索了SO₂、H₂O、O₂、CO₂、H₂O+O₂、SO₂+O₂及H₂O+SO₂+O₂气氛对活性焦吸附Hg⁰的影响机理。结果表明：一步法获得的活性焦对Hg⁰具有较高的吸附性能。N₂气氛作对比，H₂O、H₂O+O₂、CO₂和SO₂气氛下抑制活性焦对Hg⁰的吸附；O₂、SO₂+O₂和H₂O+SO₂+O₂促进活性焦对Hg⁰的吸附。通过Hg 4f的XPS分析证明了不同气氛组成对活性焦吸附Hg⁰的抑制和促进机理。H₂O覆盖在活性焦活性位上和堵塞孔隙而抑制活性焦对Hg⁰的吸附；SO₂与Hg⁰在活性焦上发生竞争吸附而抑制对Hg⁰的吸附；CO₂ 吸附在活性焦微孔上而抑制对Hg⁰的吸附；O₂气氛下主要形成了HgO, SO₂+O₂气氛下Hg⁰被氧化成HgSO₃，进一步氧化成HgSO₄； H₂O+SO₂+O₂气氛下，Hg⁰被氧化成HgO和HgSO₄。     

基于TiO2溶胶杂化的分子筛炭膜制备及其结构与性能

以聚酰亚胺为前体,TiO₂溶胶为掺杂剂,经成膜和炭化制得杂化炭膜。采用热失重、电子显微镜、X-射线衍射、红外光谱和渗透法对前体的热性能、炭膜的微观形貌、微结构、表面官能团和气体分离性进行了表征。考察了TiO₂溶胶用量、渗透温度和渗透压力对炭膜的结构与性能影响。结果显示,掺杂TiO₂溶胶显著提高了最终炭膜渗透性和选择性;采用TiO₂溶胶量为10%前体所制备的杂化炭膜对H₂、CO₂、O₂渗透性分别为1993.8、1555.6、266.9 Barrer,同时H₂/N₂、CO₂/N₂、O₂/N₂选择性分别为93.6、73.0、12.5。     

聚乙烯胺/埃洛石纳米管混合基质膜的制备及其CO2/N2分离

制备高性能的气体分离膜,是实现CO₂高效回收的关键。为了提高CO₂分离膜的性能,将中空管状结构的埃洛石纳米管（HNTs）添加到聚乙烯胺（PVAm）中配制涂膜液,并将PVAm-HNTs涂膜液涂覆到聚砜（PSf）超滤膜上制备PVAm-HNTs/PSf混合基质膜。其中PSf超滤膜作为支撑层,PVAm-HNTs致密涂层作为功能层,功能层结构与形态对CO₂分离具有关键作用。采用XRD、SEM对HNTs的结构与形态进行表征,并借助FTIR和SEM对膜的形态与结构进行分析。在进料气为纯气条件下,系统地研究了HNTs添加量、进料压力、PVAm-HNTs涂层厚度对PVAm-HNTs/PSf膜的CO₂分离性能影响,并考察了混合基质膜的CO₂/N₂混合气分离性能。结果显示：在水溶液中显示正电性的PVAm与负电性的HNTs具有较好的界面相容性。HNTs添加量为1%（质量）、PVAm-HNTs湿涂层厚度为50 μm的混合基质膜,表现出最优的CO₂分离性能。在进料气压力为0.1 MPa、测试温度为25℃、CO₂/N₂（15/85,体积比）混合气进料的条件下,膜的CO₂渗透速率为178 GPU,CO₂/N₂选择性为83;该膜具有较好的稳定性,经过120 h运行后,渗透性和选择性仍能保持稳定。     

载Ni2+/Fe3+海泥催化污泥蒸汽气化制富氢燃气

以滩涂海泥(SM)为催化剂载体，通过共浸渍法制备了Fe³⁺、Ni²⁺、Ni-Fe基低负载催化剂并进行表征分析。考察了负载金属、负载率、温度等因素对污泥蒸汽气化效果的影响。结果表明：所制备催化剂的催化性能为SM-Ni-Fe-6%> SM-Ni-6%> SM-Ni-Fe-12%>SM-Fe-6%。Ni-Fe低负载SM催化剂具有优异的催化活性：在相同气化条件下，可有效提高合成气产率、H₂纯度及H₂产率；在相同H₂产率条件下，可显著降低气化温度。t=850℃,催化剂Ni-Fe负载率为6%时，获得最大合成气产率(0.38 m³/kg)、H₂纯度(49.34%)和H₂产率(8.40 mol/kg),相比无催化剂(对照组)分别提高了74.77%、17.45%和105.73%。Ni-Fe基催化剂中NiFe₂O₄的形成可有效协同Fe³⁺裂解C—O和...     

Scale-up of NaA zeolite membranes onα-Al2O3 hollow fibers by a secondary growth method with vacuum seeding

NaA zeolite membranes were prepared by secondary growth method on the outer surface ofα-Al2O3 hollow fiber supports. Vacuum seeding method was used for planting zeolite seeds on the support surfaces. Hydrother-mal crystallization was then carried out in a synthesis solution with molar ratio of Al2O3:SiO2:Na2O:H2O=1:2:2:120 at 100 °C for 4 h. Effects of seeding conditions on preparation of hollow fiber NaA zeolite membranes were extensively investigated. Moreover, hollow fiber membrane modules with packing membrane areas of ca. 0.1 and 0.2 m2 were fabricated to separate ethanol/water mixture. It is found that the thickness of seed layer is obviously affected by seed suspension concentration, coating time and vacuum degree. Close-packing seed layer is required to obtain high-quality membranes. The optimized seeding conditions (seed suspension mass concentration of 0.5%–0.7%, coating time of 5 s and vacuum degree of 10 kPa) lead to dense NaA zeolite layer with a thickness of 6–8μm. Typically, an as-synthesized hollow fiber NaA zeolite membrane exhibits good pervaporation performance with a permeation flux of 7.02 kg·m?2·h?1 and separation factor N 10000 for sepa-ration of 90%(by mass) ethanol/water mixture at 75 °C. High reproducibility has been achieved for batch-scale production of hollow fiber NaA zeolite membranes by the hydrothermal synthesis approach.     

CO‐Free Hydrogen Production by Ethanol Steam Reforming in a Pd–Ag Membrane Reactor

In this work, the ethanol steam reforming (ESR) reaction has been studied by using a dense Pd–Ag membrane reactor (MR) by varying the water/ethanol molar ratio between 3:1 and 9:1 in a temperature range of 300–400 °C and at 1.3 bar as reaction pressure. The MR was packed with a commercial Ru‐based catalyst and a constant sweep gas flow rate in counter current mode was used. The influence of the temperature and the feed molar ratio on different parameters such as the ethanol conversion, the hydrogen production, the hydrogen yield and the CO‐free hydrogen recovery has been evaluated.     

Pd/Al2O3 composite hollow fibre membranes: Effect of substrate resistances on H2 permeation properties

Al₂O₃ hollow fibres with different asymmetric macrostructures, i.e. various thickness ratios between a finger-like layer and a sponge-like layer, have been prepared by a phase inversion/sintering technique. Such asymmetric hollow fibres are used as substrates on which Pd membrane is deposited directly by an electroless plating (ELP) technique without any pre-treatment on substrate surface. Influences of the substrate macrostructure on hydrogen permeation through the Pd/Al₂O₃ composite membranes have been investigated both experimentally and theoretically. The hydrogen permeation through the Pd/Al₂O₃ composite membranes was not only determined by the Pd membrane thickness, but also by the macrostructural parameters of the substrate, such as effective porosity, mean pore size and pore size distribution etc. The thinner the Pd membrane, the higher the effective porosity is required to alleviate the substrate effect on the hydrogen permeation. Also, the deviation of the pore size is suggested to be around 1.2 for the further improved hydrogen permeation through the composite hollow fibre membranes.     

含氟体系中MFI型分子筛膜的制备及其乙醇/水分离性能

以氟化铵为矿化剂、四丙基溴化铵为模板剂,在负载晶种的钇稳定氧化锆(YSZ)中空纤维支撑体表面合成了MFI型分子筛膜,并用于乙醇/水的分离;系统考察了氟硅比(n_NH4F/n_SiO2)、合成时间等条件对膜分离性能的影响,在n_NH4F/n_SiO2为0.8、合成时间为8 h下合成出高性能膜,其通量达8.2 kg·m^-2·h^-1、乙醇/水分离因子为47;同时研究了MFI型分子筛膜在乙醇/水体系中的分离稳定性,揭示出该方法所合成膜表面无Si-OH,从而避免了Si-OH与乙醇反应而带来膜分离性能的下降.     

Preparation of porous aluminium oxide (Al2O3) hollow fibre membranes by a combined phase-inversion and sintering method

Al₂O₃ hollow fibre membranes were prepared by a combined phase-inversion and sintering method. An organic binder solution (dope) containing suspended aluminium oxide (Al₂O₃) powders, either in mono size or a distributed size, is spun to a hollow fibre precursor, which is then sintered at elevated temperatures. In spinning the hollow fibre precursor, polyethersulfone (PESf), N-methyl-2-pyrrolidone (NMP) and polyvinyl pyrrolidone (PVP) were used as a polymer binder, a solvent and an additive, respectively. The Al₂O₃ hollow fibre membranes prepared were characterized using a scanning electron microscope (SEM) and gas permeation techniques. Effects of Al₂O₃ particle size and size distribution, the sintering temperature and Al₂O₃/PESf ratio on the structure and performance of the resulting membranes were studied extensively. The prepared Al₂O₃ hollow fibre membranes retains its asymmetric structure (mainly resulted from the phase inversion technique) even after the sintering process. Preparation of the Al₂O₃ hollow fibre membrane with a high mechanical strength and moderate permeation characteristics is feasible if the Al₂O₃ powders with a distributed particle size in the spinning (dope) solution is employed.     

Effect of the Addition of Fructose on the Pervaporation of Ethanol/Water Mixtures by Silicone-Rubber-Coated Polyethersulfone Membranes

Abstract

Composite hollow fiber membranes were prepared by coating polyethersulfone hollow fibers with silicone rubber. The hollow fiber membranes so produced were found to be water selective when they were used for the separation of feed ethanol/water mixtures by pervaporation. When fructose was added to feed ethanol/water mixtures, a decrease in permeation rate and an increase in water selectivity were observed. The decrease in the permeation rate was possible to assume, but the noticed increase in water selectivity was against our expectation, since the vapor pressure of water decreases while that of ethanol increases when sugars are added to mixtures of ethanol and water. Water selectivity of the membrane was enhanced with an increase in the amount of fructose in the feed.     

Development of polyion complex hollow fiber membrane for separation of water-ethanol mixtures

For the purpose of separating water-ethanol mixtures by the use of the pervaporation technique, a new hollow fiber membrane composed of the polyion complex (PIC) consisting of polyacrylic acid and polycation was developed. To obtain this a new technique was developed instead of coating. That is, polyacrylonitrile membrane was partially hydrolysed to introduce carboxylic groups and then converted to the polyion complex.

The hydrolysis reaction and the formation of a separating layer were analyzed by the use of IR, SEM and EDS. Through these observations it was found that carboxylic groups were uniformly formed by immersing the membrane into a NaOH aqueous solution. Moreover, the pores of less than 0.1 μm in diameter on the inner surface of the membrane disappeared with the proceeding of a hydrolysis reaction. The carboxylic layer was changed into the separating layer by immersing the membrane into an ionene aqueous solution. By varying the hydrolysis conditions and optimizing the post-treatment, the preparation of a hollow fiber having PIC as a separating layer became possible. An excellent module with an effective membrane area of 6 m² showed more than a 5,000 separation factor and approximately 400 g/m²·h in permeation rate for 95 wt% ethanol solution at 60°C.     

改性壳聚糖渗透蒸发膜用于酯化反应过程强化

壳聚糖(chitosan, CS)作为渗透蒸发膜材料来源广泛、亲水性好,但结构致密、渗透性较低。为改善CS膜的分离性能,将CS与聚醚-聚酰胺嵌段共聚物Pebax 1657共混,涂覆在NaOH水解处理的聚丙烯腈(polyacrylonitrile,PAN)超滤膜表面制备复合膜,用于渗透蒸发醇水分离过程,并进一步用渗透蒸发方法对乳酸-乙醇酯化反应进行强化。Pebax的聚酰胺与聚醚链段分别发挥调节膜结构与促进水跨膜传递的作用,有效地提高了膜分离性能。CS与Pebax质量比为2:1时,渗透蒸发醇水分离性能及对酯化反应强化的性能达到最优:渗透通量703 g·m^-2·h^-1、分离因子308,较未改性CS膜分别提高61%、65%;反应8 h后的乳酸乙酯产率由58%提高至73%。     

Evaluation of hollow fiber T-type zeolite membrane modules for ethanol dehydration

This work presents the design of hollow fiber T-type zeolite membrane modules with different geometric configurations. The module performances were evaluated by pervaporation dehydration of ethanol/water mixtures. Strong concentration polarization was found for the modules with big membrane bundles. The concen-tration polarization was enhanced at high temperature due to the higher water permeation flux. The increase of feed flow could improve water permeation flux for the membrane modules with small membrane bundle. Computational fluid dynamics was used to visualize the flow field distribution inside of the modules with different configurations. The membrane module with seven bundles exhibited highest separation efficiency due to the uniform distribution of flow rate. The packing density could be 10 times higher than that of the tubular membrane module. The hollow fiber membrane module exhibited good stability for ethanol dehydration.     

Oxyfuel combustion using a catalytic ceramic membrane reactor

Membrane catalytic combustion (MCC) is an environmentally friendly technique for heat and power generation from methane. This work demonstrates the performances of a MCC perovskite hollow fibre membrane reactor for the catalytic combustion of methane. The ionic–electronic La_0.6Sr_0.4Co_0.2Fe_0.8O₃₋ (LSCF6428) mixed conductor, in the form of an oxygen-permeable hollow fibre membrane, has been prepared successfully by means of a phase-inversion spinning/sintering technique. For this process polyethersulfone (PESf) was used as a binder, N-methyl-2-pyrrollidone (NMP) as solvent and polyvinylpyrrolidone (PVP, K16-18) as an additive. With the prepared LSCF6428 hollow fibre membranes packed with catalyst, hollow fibre membrane reactors (HFMRs) have been assembled to perform the catalytic combustion of methane. A simple mathematical model that combines the local oxygen permeation rate with approximate catalytic reaction kinetics has been developed and can be used to predict the performance of the HFMRs for methane combustion. The effects of operating temperature and methane and air feed flow rates on the performance of the HFMR have been investigated both experimentally and theoretically. Both the methane conversion and oxygen permeation rate can be improved by means of coating platinum on the air side of the hollow fibre membranes.