MTBE装置设备腐蚀的探讨

甲基叔丁基醚(MTBE)装置生产过程中普遍存在设备酸腐蚀的问题,通过对MTBE生产装置各工艺系统中可能产生的酸进行理论分析,认定甲酸的存在是设备腐蚀的主要原因。甲酸的来源为甲醇原料带入(甲酸质量分数在0.001 5%以下)、甲酸盐与催化剂磺酸离子交换产生、甲醇原料带入的甲酸甲酯(质量分数0.01%以上)在生产过程中水解产生。根据理论分析结合实际生产数据推断,甲酸甲酯水解是甲酸的主要来源,因此提出在甲醇原料的采购指标中增加甲酸甲酯含量分析的监控指标,要求甲酸甲酯的质量分数控制在0.005%以下,能有效减少甲酸的生成,达到控制设备腐蚀的目的。     

Metal‐Free Autoxidative Nitrooxylation of Alkenyl Oximes with Molecular Oxygen

A metal‐free aerobic autoxidative nitrooxylation of alkenyl oximes mediated by tert‐butyl nitrite is described. Molecular oxygen is used as the oxidizing reagent, avoiding use of organic trapping reagents such as 2,2,6,6‐tetramethylpiperidine 1‐oxyl (TEMPO). The desired products were obtained in generally high yields.

     

Palladium‐Catalyzed Oxidative Carbonylation of Aromatic C−H Bonds with Alcohols using Molybdenum Hexacarbonyl as the Carbon Monoxide Source

With molybdenum hexacarbonyl as the carbon monoxide source, a general palladium‐catalyzed carbonylative transformation of the C−H bond on aromatic rings to produce esters has been developed. Good yields of the corresponding products have been obtained with wide functional group tolerance and excellent regioselectivity. A variety of aliphatic alcohols are suitable reactants here.

     

Enantioselective Construction of Cyclic Enaminone‐Based 3‐Substituted 3‐Amino‐2‐oxindole Scaffolds via Catalytic Asymmetric Additions of Isatin‐Derived Imines

The first catalytic asymmetric construction of the cyclic enaminone‐based 3‐substituted 3‐amino‐2‐oxindole scaffold with potential bioactivity has been developed via chiral phosphoric acid‐catalyzed enantioselective addition reactions of cyclic enaminones to isatin‐derived imines, which afforded a series of cyclic enaminone‐based 3‐substituted 3‐amino‐2‐oxindoles in high yields and excellent enantioselectivities (up to 99% yield, 97% ee). The investigation of the reaction mechanism suggested that it was facilitated by a dual hydrogen‐bonding activation mode between the two substrates and the chiral phosphoric acid. Besides, this method could be utilized for a large‐scale synthesis with maintained enantioselectivity. This approach will not only offer a useful method for enantioselective construction of the cyclic enaminone‐based 3‐substituted 3‐amino‐2‐oxindole scaffold, but also enrich the research on catalytic asymmetric addition reactions of isatin‐derived imines by using electron‐rich olefins as nucleophiles. More importantly, a preliminary evaluation on the cytotoxicity of some selected products revealed that two of the enantio‐pure compounds exhibited moderate to strong cytotoxicity to A549, 786‐0, ECA109 and BT474 cancer cell lines.

     

Stability analysis of deep-buried hard rock underground laboratories based on stereophotogrammetry and discontinuity identification

Bulletin of Engineering Geology and the Environment - In a tunnel, instabilities in the surrounding rock mostly occur within the sidewalls and crown. After acquiring the rock mass structure, a...     

喷涂聚脲弹性体改性的研究进展

综述了喷涂聚脲弹性体的改性方法,重点介绍了环氧树脂、有机硅、酚醛树脂、液态聚硫橡胶改性喷涂聚脲弹性体的反应机理及改性后材料的性能变化特点.利用不同材料改性的方法,喷涂聚脲弹性体除保留原有的性能优势外,收缩率还明显减小,附着力得到改善,耐温及耐化学介质等方面性能也得以提高,扩大了其应用范围.     

离心式循环压缩机叶轮内部流场的数值模拟

运用大型CFD软件FLUENT采用标准κ-ε湍流模型进行数值模拟,研究了一台离心式循环压缩机叶轮的流场,分析了速度、压力和湍流强度的分布情况,为叶轮的改进提出了参考依据.     

2-RRR+RRS球面并联机构的静刚度分析

基于计算杆件变形方法及小变形叠加原理,推导2-RRR RRS机构动平台的角位移、球心点线位移与机构各支链构件上的力的关系.依据静力学分析的结果,即支链构件上的力与动平台上的外载荷的关系,建立机构的动平台上球心点的位移与外载荷关系,进而得到机构的整体柔度、刚度矩阵.通过正交变换,得到了机构的6个主刚度指标及所在的主方向.分析与计算结果表明,主刚度在三个主方向上较大、另三个方向则较小,且差值巨大.零点附近刚度较小、离零点越远刚度越大.而刚度数量级(值)比3-RRs大、比3-RRR小,证明了过约束使机构刚度增大.为该机构的工程设计和应用提供理论基础.