添加Ce(La)的Pd/γ-Al2O3甲醇低温裂解催化剂的结构和性能

采用XRD、BET、NH3-TPD、TPR等方法对CeO2以及La2O3和CeO2共同改性的γ-Al2O3担载Pd催化剂的结构和性能进行研究。结果表明,CeO2改性的Pd／γ-Al2O3具有很高的甲醇低温分解活性,但表面酸性导致生成较多的二甲醚;lA2O3的加入掩蔽了催化剂的表面酸性,同时促进了CeO2在γ-Al2O3载体内外表面的分散,使活性组分Pd和CeO2之间的相互作用加强,从而大大提高了甲醇的裂解率。     

CO气相偶联合成草酸二乙酯钯系催化剂研究

利用XRD、XPS、SEM、EPMA技术 ,对CO气相催化氧化偶联制草酸二乙酯催化剂进行分析 ,研究表明不同焙烧温度得到的催化剂不同 ;在循环反应过程中 ,催化剂活性中心Pd原子经历了从Pd0 变成Pd+ 1到Pd+ 2 的过程 ,生成二烷氧基化合物 ;CO偶联反应进行时 ,活性中心Pd原子由Pd+ 2 还原为Pd0 ,活性中心原子Pd在循环反应中起价态调变作用 ,依据CO气相偶联合成草酸二乙酯的主要反应原理 ,初步证实反应历程是按“共催化循环”模式进行。     

Pd和甲醛对Ag/C催化四氯化碳原位液相加氢脱氯性能的影响

采用100 mL反应釜,在N₂存在条件下,研究了Ag/C催化剂催化CCl₄液相原位加氢脱氯反应,考察了助催化剂Pd以及助剂甲醛溶液对CCl₄原位催化转化反应转化率和产物选择性的影响,并结合XRD、XPS表征技术分析了甲醛自身分解反应。结果表明,助催化剂Pd可以提高Ag/C催化剂的活性,以n(Pd)/n(Ag)为0.03的Pd-Ag/C催化剂的活性最高;但对产物CH₂Cl₂和CHCl₃的选择性没有影响,二者选择性之比仍维持在6/4。甲醛的加入明显提高Ag/C催化剂上CCl₄的转化率,同时也改变了产物分布;反应4 h,CCl₄转化率和CH₂Cl₂选择性均达到90%。甲醛主要起促进Ag/C催化剂表面Ag-Cl物种还原为Ag的作用。     

Simultaneous utilization of two different membranes for intensification of ultrapure hydrogen production from recuperative coupling autothermal multitubular reactor

The potential of simultaneous hydrogen production and in situ water removal in a thermally coupled multitubular two-membrane reactor (TCTMR) were studied numerically. Methanol synthesis is carried out in exothermic side with H-SOD membrane and supplies the necessary heat for the endothermic side. Dehydrogenation of cyclohexane is carried out in endothermic side with hydrogen-permselective Pd/Ag membrane wall. Therefore, the proposed reactor consists of two membranes, one for separation of pure hydrogen from endothermic side and another one for separation of water from exothermic side. The motivation for in situ H₂O removal during methanol synthesis by using H-SOD membranes is to displace the water-gas shift equilibrium to enhance conversion of CO₂ to improve methanol productivity. A steady-state heterogeneous model is developed to analyze the operation of the coupled methanol synthesis. The proposed model has been used to compare the performance of a TCTMR with conventional reactor (CR) and thermally coupled membrane reactor (TCMR) at identical process conditions. This comparison shows that TCTMR in addition to possessing advantages of a TCMR has a more favorable profile of temperature and increased productivity compared with other reactors. Furthermore, lower water production rate in TCTMR reduces catalyst re-crystallization.     

Performance and stability of nano-structured Pd and Pd0.95M0.05 (M = Mn,Co, Ce,and Gd) infiltrated Y2O3–ZrO2 oxygen electrodes of solid oxide electrolysis cells

Nano-structured Pd infiltrated and Pd_0.95M_0.05 (M = Mn, Co, Ce, and Gd) co-infiltrated Y₂O₃–ZrO₂ (YSZ) electrodes are studied as the oxygen electrodes of solid oxide electrolysis cells (SOECs). The infiltrated Pd-YSZ electrodes show good electrocatalytic activity for the oxygen evolution reaction. For example, the electrode polarization resistance (R_E) for 2.0 mg cm⁻² Pd infiltrated YSZ is 0.36 Ω cm⁻² at 800 °C. R_E is not significantly affected by co-infiltrating Pd with Mn and Co, but is enhanced by co-infiltration of Ce and Gd. The co-infiltration of low concentrations of metals in particular Co, Ce and Gd significantly enhances the microstructure and performance stability of the Pd-YSZ electrodes. The results demonstrate that the addition of dopants to the Pd in the form of either an alloy (Co) or a separate phase (Ce and Gd) is beneficial to enhance the performance and stability of Pd based oxygen electrodes of SOECs.     

CO偶联合成草酸酯催化剂国内专利技术进展

以煤炭为资源,通过CO气相偶联制备草酸酯、进而加氢合成乙二醇,成为间接法合成乙二醇的最佳工艺路线.在中国,已经利用该工艺建成了多套20× 104t/a级的工业装置,在“十二五”期间,还要陆续建设总产能约400×104t/a的乙二醇装置.中国在煤制乙二醇成套技术的开发和应用上走到了世界前列.CO偶联合成草酸酯催化剂技术,催化剂一般由载体、主催化剂和助催化剂组成.该催化剂的载体主要为α-A12O3,也可以是6-A12O3、SiO2、分子筛或以它们为主构成的复合载体;贵金属Pd几乎成为不可或缺的主催化剂.在此基础上,陆续开发了含一种、两种或三种助催化剂的催化剂体系,助催化剂主要选自La系元素、碱土金属元素、Fe、Cu、Mo、W、Co、Zn及Ti等过渡金属元素.同时,综述了复合载体催化剂、规整催化剂及金属骨架催化剂的进展.在一定的工艺条件下,CO单程转化率几乎接近75％,草酸酯选择性接近100％,草酸酯时空产率在1000g/(L·h).     

The property of hydrogen separation from CO2 mixture using Pd-based membranes for carbon capture and storage (CCS)

This study investigates the module configuration for upscaling CO₂ capture capacity to a bench-scale in hydrogen selective Pd-based composite membranes. In order to confirm effective upscaling, four plate-type membranes of two inch diameter were stacked in a newly designed plate-and-frame type module, reaching a total membrane surface area of 6.64 × 10⁻³ m² (66.4 cm²). A pure gas test carried out using H₂ and He confirmed that there were no effects of module configuration in gas permeation behavior, indicating that the upscale of the separation capacity by numbering-up of membranes using our module design was successful. The CO₂ enrichment test was conducted using a 40%CO₂ + 60%H₂ mixture (i.e. a similar composition for the coal gasifier after both the shift reaction and H₂O removal), under high feed pressure and flow rate, i.e. 600–2100 kPa and 0.48–0.72 N m³ h⁻¹. The mixture gas test confirmed that the bench-scale membrane module could enrich 40% of the CO₂ at a feed flow rate of 0.48 N m³ h⁻¹ up to 93% with a hydrogen recovery ratio of >90% at 673 K and a total feed pressure of 2100 kPa, i.e. ∼4 times CO₂ enrichment capacity of one membrane.     

One-step electroless deposition of Pd/Pt bimetallic microstructures by galvanic replacement on copper substrate and investigation of its performance for the hydrogen evolution reaction

A facile and one-step method for fabrication of Pd/Pt bimetallic microstructure using galvanic replacement reaction is presented. This electroless deposition was performed without any additive reagent via simple immersion of the copper sheet in cation aqueous solution of Pd and Pt. The as-prepared electrode was characterized by using the techniques of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and cyclic voltammetry and tested for the hydrogen evolution reaction (HER) in the acidic media. Comparison of the HER on the Pd/Pt bimetallic catalysts with different Pd:Pt percentage compositions indicated that the Pd₆₀Pt₄₀ catalyst had the highest HER activity among all the Pd/Pt catalysts and a better performance than the pure Pt. The effects of galvanic replacement time and concentration of H₂SO₄ on the catalytic activity of as-prepared electrode for HER were comparatively investigated.     

Electrocatalytic oxidation of formic acid on Pt–Pd decorated polyfluorenes with hydroxyl and carboxyl substitution

A series of novel Pt–Pd/polyfluorenes (PFs) composite catalysts were facilely prepared based on Pt/Pd precursor and PFs with hydroxyl and carboxyl substitution at the C-9 position by electrochemical method and their electrocatalytic performance toward formic acid oxidation were studied. Electrocatalytic experiments demonstrate that the Pt–Pd nanoparticles immobilized on poly(9-fluorenecarboxylic acid) (PFCA)-decorated glassy carbon (GC) electrode (Pt–Pd/PFCA/GC) show larger electrochemical active surface area, higher catalytic activity and stability toward formic acid oxidation than that of other Pt–Pd/PFs/GC, Pt–Pd/GC, as well as the commercial JM 20% Pt/C/GC electrodes, which can be attributed to the small-sized and well-dispersed Pt–Pd nanoparticles on PFCA matrix and the special electronic interaction between the metal nanoparticles and the polymer substrate. Moreover, the electron-withdrawing carboxyl substitution rather than the electron-donating hydroxyl on the polymer main chain is of great benefit to the removal of poison CO as well as the enhancement of catalytic activity of Pt–Pd toward formic acid oxidation.     

正己烷异构化催化剂Pd／SAPO—11的研究

通过临氢微型反应器中催化剂评价实验,对钯含量分别为0．1％、0．2％、0．3％、0．4％、0．5％的Pd／SAPO—11催化剂进行了评价,其裂解率分别为：0．14％、0．25％、0．25％、0．09％、0．03％,说明该系列催化剂对裂解有抑制作用;在考察的范围内,催化剂的活性、选择性、异构化率均随着钯含量的增加而上升;钯含量在0．25％～0．50％时,催化剂稳定性良好,钯含量过低催化剂较易失活。说明在考察的范围内,钯含量为0．5％时具有较好的催化性能：活性64．2％,选择性7．1％,C5异构化率67．0％,C6异构化率62．3％。