Crystal Chemistry of 1:1 Molecular Complexes of Carbamate Salts Formed by Slow Aerial Carbonation of Amines

Abstract  Amines do have rare tendency to undergo aerial carbonation to form carbamic acid. Four different 1:1 molecular complex of carbamate salts reported herein obtained by the aerial carbonation of cyclic amines. X-ray crystal structures show a systematic change in the molecular structure did bring some gradual supramolecular change from one structural motif to another. Index Abstract  Amines do have rare tendency to undergo aerial carbonation to form carbamic acid. Four different 1:1 molecular complexes of carbamate salts reported herein obtained by the aerial carbonation of cyclic amines. X-ray crystal structures show a systematic change in the molecular structure did bring some gradual supramolecular change from one structural motif to another.      

Hypothetical transformation of Ca(OH)<Subscript>2</Subscript> into CaCO<Subscript>3</Subscript> in solid-state reactions of portland cement

Summary Previous study of the hydration and ageing products of two cement pastes created the basis for the postulate of the course of solid-state reactions between the portlandite Ca(OH)₂ and the CO₂ from air in the hydrated and air dry cement. XRD basal spacing d(001) of portlandite exceeded the nominal value and increased with ageing, with the wetting and drying procedure and with carbonate content of the paste, indicating that a part of OH^- ions was gradually substituted by CO₃^2- ions, which are about twice bigger. IR spectroscopy showed a considerable content of portlandite, of CO₃^2- of water and silicates. Also HCO₃^- H₂O and CO₂ in cavities between hexagonal rings and hexagonal hydrates were indicated. By MS (mass spectrometry) in vacuum the evaporation of sorbed water was detected at 100-120°C, of gel water at 350°C of portlandite water at 400°C and of high temperature water between 500 and 700°C, simultaneously with CO₂ escape. Slightly higher peak temperatures were found by the TG test either in air or in argon. From these results and from geometric considerations it is postulated that the solid-state reactions take place on ageing of the cement paste and on its heating: hexagonal portlanditecalcium carbonate hydroxy hydratecalcium carbonate hydratehexagonal vaterite and/or orthorhombic aragoniterhombohedral calcite The analysis of the standard files of the calcium carbonate hydroxy hydrates supports this postulate and indicates a gradual transformation.     

基于扩散路径映射的混凝土碳化细观模拟方法

对碳化作用细观求解方法进行梳理改进,利用传输和反应过程状态变化的路径依赖特点,规避了传统方法大规模矩阵求解,提出了基于扩散路径映射的碳化细观模拟方法。方法基于Dijkstra路径算法对界面层影响进行修正,建立水泥浆体扩散路径算法,得到环境表面到水泥浆体的最短路径网络;通过水泥浆体代理模型,模拟水化反应、碳化反应以及材料孔隙率变化的耦合碳化过程,得到关键指标（氢氧化钙浓度）沿扩散路径的时变分布;最终依据相同的扩散路径长度进行结果映射,实现碳化作用中关键物质浓度随时间空间分布的高效精准预测。通过材料试验对比校验,扩散路径映射方法模拟结果能够准确反应混凝土碳化深度范围;与传统偏微分求解方法对比,扩散路径映射方法能够在细观尺度精准模拟关键物质空间分布情况,且求解效率提升20倍以上,存储空间需求降低为偏微分求解的2%以内。     

利用上浮法提高碳酸法糖厂优级品率的研究

以碳酸法糖厂生产的粗糖浆作为研究对象,用上浮法澄清新技术来进一步降低其色值,以提高优级品率等.研究结果已在实际生产中应用,效果良好。     

高水胶比粉煤灰砂浆抗碳化性能机理

用人工加速法测定粉煤灰的质量分数分别为0,0．20,0．36和0．45,水胶比为0．50时的水泥砂浆碳化深度,砂浆的碳化深度随碳化龄期的延长而增加,且粉煤灰的质量分数越大,碳化深度增加的幅度越高,通过XRD,TG－DTA,SEM和压汞法性定量测定相应浆体碳化前（标准养护28d)的CH含量、微观结构特征和孔结构参数,分析表明,影响粉煤灰水泥砂浆碳化深度的主要因素是浆体碱度的降低,但碳化速率还受浆体孔结构特征的影响。     

Ligand Exchange by Halogenation of PIIICompounds

Abstract

The chlorination of several acyclic and cyclic P^III cornpounds at O°C is discussed. Often a ligand exchange reaction is observed.     

考虑应力状态的二维混凝土碳化过程数值模拟

混凝土碳化过程的数值模拟为研究碳化机理、碳化影响因素、碳化过程与力的耦合作用等提供了新的定量分析工具.为定量分析应力状态对混凝土截面角部碳化发展的影响,建立了混凝土碳化过程的2维数值计算模型,使得混凝土组分、应力状态等影响可以得到定量考虑,并模拟应力状态下混凝土构件角部的碳化过程.详细介绍了这一模型的数值计算实现过程,研究了网格尺寸及时间步长对数值计算结果的影响.该模型数值计算结果与快速碳化试验和长期暴露碳化试验结果的对比验证了模型计算结果的准确性.最后,对某混凝土构件的角部混凝土碳化过程进行了数值分析.结果表明,混凝土截面角部双向碳化作用以及拉应力状态均会加速混凝土碳化,角部是整个构件截面碳化发展最为迅速的部位,其耐久性应当予以考虑.     

合成二氟尼柳的方法改进

以4-(2’,4’-二氟苯基)苯酚为原料,采用微波辅助无溶剂Kolbe-Schmitt羧化反应合成了二氟尼柳,其结构经1H NMR确证。     

含铁粉尘碳酸化球团孔的结构特性

通过压汞法测量研究了不同CaO含量、不同造球时间的生球以及不同反应温度、不同CO2分压条件下固结生成的碳酸化球团的孔隙结构特征.结果表明:随着CaO含量增加和造球时间延长,生球的平均孔径、显孔隙度、临界孔径和最可几孔径都相应有所降低,生球凝胶孔含量随CaO含量增加而升高,孔隙比表面积增大,利于反应进行的10~300nm孔隙数量增多.优化反应温度、提高CO2分压,有利于促进球团CaCO3微晶大量生成,细化孔径,形成连接桥,冷固结强度显著提高.     

SO2对钙基CO2吸收剂循环煅烧/碳酸化反应的影响

在循环煅烧/碳酸化反应系统中,研究了SO₂对钙基吸收剂CaCO₃捕集CO₂的影响,获得了SO₂对钙基吸收剂碳酸化特性、煅烧特性以及循环稳定性的影响规律,并结合SEM分析结果,从循环煅烧/碳酸化反应角度,分析了可能存在的原因。结果表明,钙基吸收剂吸收CO₂的能力随着循环反应次数的增加逐渐发生衰减,在SO₂影响下,这种衰减会进一步加剧,且衰减程度随着SO₂浓度的增加而增大,经过十次循环后,碳酸化转化率分别为25.5%(0%SO₂)、16.9%(0.1%SO₂)和5.2%(0.2%SO₂)。造成这种衰减加剧的主要原因是反应产生较厚的硫酸化产物层,硫酸化产物层使颗粒表面孔隙发生堵塞,阻碍了CO₂在吸收剂内部的扩散,降低了碳酸化转化率。