Ethylene Glycol Electrooxidation on Smooth and Nanostructured Pd Electrodes in Alkaline Media

The electrooxidation of ethylene glycol (EG) has been studied either in situ on a smooth Pd electrode by FTIR spectroscopy or on nanostructured Pd‐based catalysts by cyclic voltammetry. The electrooxidation on the Pd electrode is dramatically influenced by the pH. Below pH 12, CO₂ is formed and detected in the thin layer by FTIR, while at higher pH values glycolate, carbonate and oxalate are formed almost simultaneously at a potential of ca. 0.4 V versus RHE. Above 0.9 V glycolate is oxidised to oxalate and carbonate. The nanostructured electrocatalysts Pd–(Ni–Zn)/C, Pd–(Ni–Zn–P)/C and Pd/C are much more active than the smooth Pd electrode (up to 3,300 A g(Pd)^–1) and give different distributions of the oxidation products. Pd/C is the most selective catalyst yielding glycolate, while mixtures of glycolate (major>60%), oxalate and carbonate are obtained with Pd–(Ni–Zn)/C or Pd–(Ni–Zn–P)/C. Carbonate is produced by oxidation of both glycolate (major contribution) and oxalate, while the major part of oxalate seems to be produced by the direct oxidation of EG.     

乙二醇电氧化的研究进展

乙二醇作为燃料电池阳极燃料,具有较高的比能量和电能转换效率,可作为燃料电池理想燃料之一.关于其电氧化机理、电氧化过程中的中间物种,国内外进行了大量的研究.本文综述了近几十年来乙二醇电氧化机理方面的一些进展.     

乙二醇的合成方法

阐述了乙二醇的几个主要合成方法,着重介绍了合成乙二醇的新技术方法：碳酸亚乙酯法。     

含催化剂的乙二醇和二甘醇黏度测定及关联

在常压、313~413 K下,采用ND J-1旋转式黏度计,测定了含NY2催化剂的乙二醇和二甘醇的黏度.采用黏度Andrade关系式,将黏度数据与NY2催化剂质量分数和温度进行关联,得到经验关系式.结果表明,由经验方程计算值与实验结果基本相符,为催化水合制乙二醇的反应器设计和优化分离设备提供必要的基础数据.     

环氧乙烷/乙二醇装置挖潜扩能改造的方案及优化

论述了中国石油化工股份有限公司茂名分公司化工分部环氧乙烷/乙二醇装置的挖潜扩能改造方案及对方案的优化。在EO反应器、循环气压缩机和氧气混合器不做改动的条件下,通过更换银催化剂、应用新型高通量和高效率塔板等措施对装置进行改造。改造后装置生产能力提高30%,由80kt/a当量环氧乙烷提高到104kt/a(按7200h/a设计),达到了扩能改造目标。     

Ultrahigh Durable PtPd/C Nanowire Networks Catalyst Synthesized by Modified Phase Transfer Method for Methanol Oxidation

A novel PtPd/C nanowire catalyst with interconnected network and fewer great grain boundaries has been successfully prepared by templateless and modified phase‐transfer method using cetyltrimethylammonium bromide as a capping in ethylene glycol solution by microwave‐assisted process. Its structure, composition, and morphology are characterized by X‐ray diffraction, energy dispersive analysis of X‐ray, and transmission electron microscopy, respectively. The electrochemical measurements demonstrate that the highly dispersed and uniform PtPd/C nanowire networks catalyst has a significantly higher electrocatalytic activity and durability for the methanol oxidation as compared to solid solution PtPd/C. The greatly improved durability of PtPd/C nanowire networks catalyst is mainly a consequence of the unique interconnected network structure with fewer grain boundaries, which provide more facile pathway for the electron transfer, and inhibit the particle growth and agglomeration, as well as prevent the particles embedded in the microporous of carbon support to enhance the Pt utilization.     

Pd–Co/MWCNTs Catalyst for Electrooxidation of Hydrazine in Alkaline Solution

Multiwall carbon nanotubes supported Pd–Co electrocatalysts (Pd–Co/MWCNTs) for hydrazine electrooxidation in alkaline electrolytes were prepared. Their morphology and structure were characterized by scanning electron microscopy, transmission electron microscope, and X‐ray diffraction. The effect of the mass ratio of Pd to Co on the catalytic performance was examined via cyclic voltammetric and chronoamperometric measurements. The Pd–Co/MWCNTs with a mass ratio of 1:1 for Pd:Co shows higher catalytic performance than both Pd/MWCNTs and Co/MWCNTs and it has good stability for catalyzing the electrooxidation of hydrazine. The gas collection measurements indicated that hydrazine electrooxidation on Pd–Co/MWCNTs proceeded via a near 4‐electron pathway.     

Electrooxidation of methanol and formic acid on PtCu nanoparticles

Improving the catalytic activity of the anode catalyst is an important task in direct methanol and formic acid fuel cell development. In the present work, catalytic activity of shape-controlled PtCu nanoparticles toward methanol and formic acid oxidation was investigated. The results show that the addition of Cu to Pt increases the catalytic activity of both reactions. In addition, the shape of PtCu nanoparticles plays an important role on improving the reactivity of both reactions. Cubic PtCu nanoparticles are more active for methanol oxidation while spheres are better for formic acid oxidation. The present study demonstrates controlling shape of Pt alloy catalysts is an effective way of improving catalytic activity. Likely mechanisms of the activity enhancement are briefly discussed.     

Oxide (CeO2, NiO, Co3O4 and Mn3O4)-promoted Pd/C electrocatalysts for alcohol electrooxidation in alkaline media

This study investigated Pt/C, Pd/C and oxide (CeO₂, NiO, Co₃O₄ and Mn₃O₄)-promoted Pd/C for electrooxidation reactions of methanol, ethanol, ethylene glycol and glycerol in alkaline media. The results show that Pd/C electrocatalysts alone have low activity and very poor stability for the alcohol electrooxidation. However, addition of oxides like CeO₂, NiO, Co₃O₄ and Mn₃O₄ significantly promotes catalytic activity and stability of the Pd/C electrocatalysts for the alcohol electrooxidation. The Pd-Co₃O₄ (2:1, w:w)/C shows the highest activity for the electrooxidation of methanol, EG and glycerol while the most active catalyst for the ethanol electrooxidation is Pd-NiO (6:1, w:w)/C. On the other hand, Pd-Mn₃O₄/C shows significantly better performance stability than other oxide-promoted Pd/C for the alcohol electrooxidation. The poor stability of the Pd-Co₃O₄/C electrocatalysts is most likely related to the limited solubility of cobalt oxides in alkaline solutions.     

乙二醇装置中高通量再沸器的改造

针对原 5 0 0 # 再沸器存在的问题选用进口高通量管 ,使用双面三层爆炸复合管板 ,管子管板进行 4种试验比较 ,采用强度焊加贴胀方法 ,制造过程使用了多种创新工艺方法 ,消除了原 5 0 0 # 再沸器换热能力不足和腐蚀的问题     

Efficient Anchorage of Palladium Nanoparticles on the Multi‐Walled Carbon Nanotubes as Electrocatalyst for the Hydrazine Electrooxidation in Strong Acidic Solutions

A facile homogeneous precipitation–reduction reaction method, which involves PdCl₂ → PdO · H₂O → Pd⁰ reaction path, is used to synthesize the multi‐walled carbon nanotubes (MWCNTs) supported Pd nanoparticles (Pd/MWCNTs) catalysts. The particle size of Pd/MWCNTs catalysts can be easily tuned by controlling the hydrolysis temperature of PdCl₂. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) measurements show the particle size of Pd/MWCNTs catalysts increases with hydrolysis temperature of PdCl₂, which is ascribed to the fact that the particle size of PdO · H₂O nanoparticles increases with hydrolysis temperature of PdCl₂. At the lower hydrolysis temperature, the as‐prepared Pd/MWCNTs catalyst possesses the higher dispersion and the smaller particle size. Consequently, the resultant Pd/MWCNTs catalyst exhibits the big electrochemical active surface area and the excellent electrocatalytic performance for hydrazine electrooxidation in strong acidic solutions. In addition, the electrochemical measurement indicate that particle size effect of Pd‐NPs occurs during the N₂H₄ electrooxidation. In brief, the mass activity and specific activity of the Pd/MWCNTs catalyst increases and decreases with decreasing the particle size of Pd‐NPs for the N₂H₄ electrooxidation, respectively.     

Effects of pH Value on Composition Structure and Catalytic Activity of Pt‐SnOx/C Prepared by Ethylene Glycol Method

Pt‐SnO_x nanoparticles were synthesized by the ethylene glycol (EG) method in solution of H₂PtCl₆ and SnCl₂, with the same concentrations of Pt and Sn, but different pH values. The pH value after the end of platinum reduction reaction was not changed any more, except that a certain amount of water was added to deposit the Pt‐SnO_x nanoparticles on the carbon support. The pre‐nanocatalysts were characterized by X‐ray photoelectron spectroscopy (XPS) to investigate the contents of Pt and Sn, and their catalytic activities for ethanol electrooxidation were tested by cyclic voltammetry (CV). The result was that the Sn contents were increasing as the Pt/Sn atomic ratios of 2.2, 2.6, 5.1, 7.4, 8.7, with the decreasing end pH values of 4.5, 5.0, 5.5, 6.5, 7.5, and the Pt contents became less than the addition in the preparation solution while the end pH values were <5.5, but the catalytic activities for ethanol electrooxidation were not so much regularly changed. Besides, from the end pH value of 5.5 to the increasing 9.0, all the platinum nanoparticles could be completely deposited on the carbon support, under the condition that only a certain amount of water was added.     

Electrochemical Deposition of Highly Dispersed Palladium Nanoparticles on Nafion‐Graphene Film in Presence of Ferrous Ions for Ethanol Electrooxidation

An efficient method was developed to produce highly dispersed Pd nano particles (NPs), supported on Nafion‐graphene film by electrochemical deposition at constant potential in presence of ferrous ions. The Fe²⁺ ions govern the size, shape and morphology of Pd NPs. The as‐prepared catalyst was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray diffraction (XRD). It was obeserved from TEM that the mean diameter of electrodeposited Pd NPs was 6.4 ± 1.3 nm with narrow diameter range from 4 to 10 nm. The electrocatalytic performance of the Pd NPs deposited on Nafion‐graphene (Nf‐G) catalyst was studied by cyclic voltametry (CV) and chronoamperometric measurements. The highly dispersed Pd NPs on Nf‐G film were obtained in presence of Fe²⁺ ions. This alters electrochemical active surface area and hence catalytic activity of Pd NPs. The prepared Pd/Nf‐G catalyst exhibit highest tolerance to the intermediate poisoning species (ratio I_f/I_b = 2.2). The as‐obtained catalyst shows an efficient electrocatalytic activity and good stability for ethanol oxidation in alkaline medium.     

聚乙二醇改性聚乳酸及其在药物载体中的应用

综述了聚乙二醇改性聚乳酸及其端基化的制备方法,介绍了聚乙二醇-聚乳酸嵌段共聚物作为药物载体的研究进展,并对今后的研究进行了展望.     

Investigations of Compositions and Performance of PtRuMo/C Ternary Catalysts for Methanol Electrooxidation

PtRuMo/C catalyst was prepared by impregnation reduction method and characterised. Comparison is made between a home‐made PtRu/C prepared by similar method and Pt/C (E‐Tek Co., Pt/C‐ET) catalysts. One glassy carbon disc electrode for ternary alloy catalyst was used to evaluate the catalytic performances by cyclic voltammetric, chronoamperometric, amperometric i–t curves, and electrochemical impedance spectra (EIS). The electrochemical measurement results indicated that the performance of PtRuMo/C with a molar ratio of 6:3:1 was the highest among 15 Pt_xRu_yMo_10–x–y/C catalysts with different molar ratios. The composition, particle size, lattice parameter and morphology of the PtRuMo(6:3:1)/C catalyst were determined by means of X‐ray energy dispersive analysis, X‐ray diffraction (XRD) and transmission electron micrographs (TEM). The result of XRD analysis exhibits that PtRuMo(6:3:1)/C has the fcc structure with the smaller lattice parameter than the home‐made PtRu/C and Pt/C‐ET. Its typical particle sizes is only about 5 nm. With respect to the catalytic activity and stability, the PtRuMo(6:3:1)/C catalyst is superior to PtRu/C despite their comparable active areas. Though the electrochemically active surface area of Pt/C‐ET is the biggest, its performance is the lowest. EIS results also indicate that the reaction resistances for methanol electrooxidation on the PtRuMo(6:3:1)/C catalyst are smaller than those of PtRu/C at different polarisation potentials.     

乙二醇合成工艺进展及前景分析

乙二醇是一种重要的化工原料。介绍了石油路线和煤路线生产乙二醇的工艺进展,并对国内生产乙二醇进行了分析。在我国石油路线仍是主要方法,但易受到国际油价的限制,而煤路线将是国内未来发展的重点。但应加强乙二醇的新型催化剂和技术的研发,并拓展煤化工的多元化发展。     

Synthesis of Truncated‐Octahedral Pt–Pd Nanocrystals Supported on Carbon Black as a Highly Efficient Catalyst for Methanol Oxidation

A novel PtPd/C nanocrystals catalyst with truncated‐octahedral structure has been successfully prepared by ethylene glycol reduction to induce anisotropic growth in an isotropic medium by adding a small amount of Fe³⁺ species. Its structure, composition, and morphology are characterized by X‐ray diffraction, transmission electron microscopy, and scanning transmission electron microscopy‐energy dispersive spectroscopy elemental maps, respectively. The electrochemical measurements demonstrate that the highly dispersed and uniform PtPd/C nanocrystals have excellent poisoning tolerance, significantly higher electrocatalytic activity and durability for the methanol oxidation, as compared to solid solution PtPd/C and Pt/C catalysts. This may be ascribed to the stepped atoms and dangling bonds, which served as active sites for breaking chemical bonds during oxidation–reduction reaction; the high density of preferred crystal planes of (111) facets greatly enhanced the oxidation of poisonous residues during reaction.     

Anodic Oxidation of Polyhydric Alcohols on a Pt Electrode in Alkaline Solution

The electrochemical oxidation of various polyhydric alcohols, ethylene glycol, glycerol, meso-erythoritol, and xylitol, on a platinum electrode was investigated systemematically in acidic H₂SO₄, and in alkaline KOH and K₂CO₃ solutions to evaluate the potential of these polyhydric alcohols as fuels in micro-fuel cells for portable electronic devices. All polyhydric alcohols tested in the present study showed high reactivities in both alkaline solutions. Ethylene glycol showed the highest reactivity. Although the reactivity of ethylene glycol was lower in K₂CO₃ than in KOH, the carbonate solution is a potential candidate as an electrolyte solution due to its resistance to solution carbonation. Furthermore, ethylene glycol showed much less significant electrode poisoning by adsorbed CO upon oxidation in alkaline solution.     

不同形态乙烯原料混合裂解技术分析

就气态、液态、气液混合体等不同乙烯原料混合裂解时的裂解性能变化情况、相互之间的互相作用情况进行了初步分析探讨,在实验室装置上进行 了各种不同形态乙烯原料单独裂解和混合裂解情况的考察试验,试验表明,不同原料混合裂解时宜按照“相似相混”的原则进行.     

乙二醇循环系统再生工艺研究

在乙二醇循环系统中,重点是乙二醇的再生问题。乙二醇再生效果的好坏,直接关系到天然气处理工艺是否能够正常运行和产品气的质量。详细介绍了三种乙二醇再生的方法:传统再生、预热—换热再生、换热—预热再生,并说明各自工艺的特点、存在的问题和应用情况。最后指出了乙二醇再生工艺的发展趋势并提出了建议。