Studies of the oxidation of palladium complexes by the advanced oxidation process Pretreatment of model catalysts for precious metal analysis

The advanced oxidation process (AOP) for the pretreatment of model palladium catalysts has been studied. Most standard metal analysis techniques are for metal ions free of organic ligands. Spent palladium catalysts contain organic ligands that need to be removed prior to analysis. AOP uses a combination of hydrogen peroxide and UV light to generate radicals that decompose such ligands, freeing up metals for further analysis. Palladium acetate Pd(OAc)₂, palladium acetylacetonate Pd(acac)₂, and tris(dibenzylideneacetone)dipalladium (Pd₂(dba)₃) were chosen as model precious metal catalysts for investigation. AOP was found to decompose ligands in Pd(OAc)₂, Pd(acac)₂ and give accurate Pd(II) quantification, while ligand decomposition and oxidation of Pd(0) to Pd(II) were demonstrated in treatments involving Pd₂(dba)₃. The effects of solubility of the palladium complexes, continuous addition of H₂O₂ during AOP treatments, sample pH, concentration of H₂O₂, and length of UV irradiation are reported.     

Following the evolution of morphology, composition and crystallography of alumina based catalysts after laser ablation: Implications for analysis by LA-ICP-AES

Fundamental understanding of aerosol formation during laser ablation is important for the development of LA-ICP analysis of complex samples. Using a Lina Spark Atomizer™, the application of this technique to the field of heterogeneous catalysis gave an accuracy of 5–15% while extreme values of +100% could be obtained in some cases. To improve understanding of laser ablation processes, particles generated during ablation of alumina based catalysts were collected and analysed using different microscopy and surface analysis techniques. Morphological study by scanning electron microscopy showed that most of the particles leaving the ablation cell were nanoparticle aggregates generated from vapor condensation. An XRD study of these aerosols revealed that the condensation converge on the formation of a spinel structure with large coherence domains. Elemental composition of the aerosol was also followed and exhibited differences between a catalyst containing large Mo concentration or low Pt concentration.     

甲醇阳极电氧化催化剂的研究

采用化学还原沉积法制备了Ｐｔ－ＷＯ３／Ｃ，Ｐｔ－Ｒｕ／Ｃ和Ｐｔ－ＷＯ３／Ｃ系列催化剂，通过循环伏安与电流－电位极化研究了甲醇在不同催化剂／Ｎａｆｉｏｎ奄极上的电催化氧化。结果表明，三种催化剂的催化活性顺序为：Ｐｔ－Ｒｕ－ＷＯ３／Ｃ〉Ｐｔ－Ｒｕ／Ｃ〉Ｐｔ－ＷＯ３／Ｃ。同时研究了甲醇浓度和催化剂的配比对阳极性能的影响。     

甲烷氧化偶联MgO／BaCO3催化剂的表面结构与催化活性

用ＣＯ２－ＴＰＤ，ＣＯ，ＣＨ４脉冲以及ＥＰＲ，ＸＰＳ等方法对ＭｇＯ／ＢａＣＯ３的表面结构及催化活性进行研究，结果表明，催化剂的碱性，氧扩散速率等对催化剂的活性均有影响。ＢａＣＯ３和ＭｇＯ的共同作用可以增强催化剂的碱性强度?增加强碱中心的量，调变晶格氧的移动性，提高Ｃ２烃的收率和选择性。ＥＰＲ和ＸＰＳ测试结果表明，表面吸附态的氧物种Ｏ＾－２作为甲烷氧化偶联活性氧物种的前驱态在反应反应条件下可转化为活     

Hydrogenolysis of methylcyclopentane over the bimetallic Ir-Au/γ-Al2O3 catalysts

The gas-phase hydrogenolysis of methylcyclopentane (MCP) was investigated over the bimetallic Ir-Au/γ-Al₂O₃ catalysts. The bimetallic systems containing the atomic Au/Ir ratios in the range of 0.125-8 and a fixed total metal content of 8 wt.%, were prepared by the sequential impregnation (SI) and co-impregnation (CI) methods. The corresponding monometallic Ir/γ-Al₂O₃ and Au/γ-Al₂O₃ catalysts were also prepared. The materials were characterized by ICP, XRD, N₂ adsorption, TEM, and H₂ chemisorption. Highly dispersed Ir nanoparticles were obtained in all cases, while the size of Au nanoparticles increased (up to 50 nm) upon the increasing Au content in the catalyst. The monometallic gold catalyst did not adsorb H₂. The incorporation of Au increased the amount of irreversible adsorbed H₂ in the Ir-Au/γ-Al₂O₃ catalysts with respect to the monometallic ones. The products obtained in the MCP hydrogenolysis were 2-methylpentane (2-MP), 3-methylpentane (3-MP) and n-hexane (n-H). The initial rate (molecules of MCP reacted s⁻¹ g_Ir⁻¹) increased with the Au content. The deactivation was lower for bimetallic catalysts, particularly for the CI ones. The addition of Au played a significant effect on chemisorption and catalytic properties of Ir.     

ICP-AES法测定Pd/Al_2O_3中钯的干扰问题

本文研究了用 ICP- AES法测定 Pd/Al2 O3催化剂中钯所存在的干扰问题。考察了基体及所用试剂对钯测定的影响 ,发现氧化铝基体、硫酸等对钯的测定均有负干扰 ,提出采用基体匹配法测定 Pd/Al2 O3中的钯含量。方法回收率在 96%以上 ,9次测定相对标准偏差小于 3%     

Different catalytic systems on hydroxyl-terminated GAP and PET with poly-isocyanate: Curing kinetics study using dynamic in situ IR spectroscopy

Reactions of hydroxyl-terminated glycidyl azide polymer (GAP) or poly(ethylene oxide-co-tetrahydrofuran) (PET) polymers with poly-isocyanate (N100) were monitored by dynamic in situ Fourier transform infrared spectroscopy. The influence of catalytic systems on the cure kinetics of polyurethane reaction was investigated. From the comparison between GAP/N100 and PET/N100 systems, it was found that primary and secondary hydroxyl groups were differentiated due to the effects of steric hindrance. Using Arrhenius law and Eyring equation, the activation parameters of polyurethane reaction were calculated at different catalytic systems. The negative value of the activation entropy demonstrated an associative mechanism within the transition state.     

Aromatic Compounds Mannich Reaction Using Economical Acidic Ionic Liquids Based on Morpholinium Salts as Dual Solvent-Catalysts

Economical acidic ionic liquids containing an alkanesulfonic acid group in a morpholinium cation were found to be effective catalysts for the Mannich reactions of various kinds of aromatic aldehydes, acetophenone and aromatic amines at mild reaction conditions. The satisfactory results were obtained with short reaction time, good yields of the Mannich bases and simplicity in the experimental procedure. These ionic liquids could be recycled and reused for up to five times without considerable decreasing in the catalytic activity.     

HY Zeolite as an Extremely Active and Reusable Catalyst in Acylation of Alcohols with Acid Anhydride in a Solventless System

HY Zeolite is a practical and useful catalyst for acylation of various alcohols and phenols.     

POLYPROPYLENE: AN INTRODUCTION

Polypropylene now has a history of nearly 45 years since its discovery and 40 years since its commercialization. It has established itself as one of the most important polymers that has engineering plastic properties at commodity plastics prices. The end of the growth of polypropylene is not in sight.