Evaluation of thermal reaction for two azo compounds by using 20-L apparatus and calorimetry

Azo compounds are widely involved in the industrial processes of dyes, pigments, initiators, and blowing agents. Unfortunately, these compounds have a bivalent unstable –NN– composition, which can be readily broken when the ambient temperature is elevated. Self-accelerating decomposition might cause a runaway reaction and lead to a fire, explosion, or leakage when the cooling system fails or other events occur. This study investigated the explosion properties, thermal stability parameters, and thermal hazard and mechanism of 2,2′–azobisisobutyronitrile (AIBN) and 2,2′–azobis–2–methylbutyronitrile (AMBN). We used a 20-L apparatus, vent sizing package 2, synchronous thermal analysis, and differential scanning calorimetry under explosive, adiabatic, and dynamic conditions to acquire the explosive curves, thermal curves, and thermodynamic parameters of the substances. Moreover, the differential isoconversional method (Friedman method) and ASTM E698 equation were employed to obtain the apparent activation energy E_a. All the experimental results revealed that AIBN is more dangerous than AMBN. The E_a of AIBN was lower than that of AMBN. The results can be used to construct an azo compound thermal hazard database for use for searches and reference examples by industry and related research areas.     

羟胺强化Fenton反应降解水中氯酚

针对传统Fenton体系Fe（Ⅲ）累积和pH适用范围过窄等缺点，采用羟胺（HA）强化的HA-Fenton体系，以对氯苯酚（4-CP）为目标污染物进行降解实验，考察了Fe（Ⅱ）投加量、H2O2投加量、HA投加量和溶液pH等工艺条件对4-CP去除率的影响。实验结果表明：HA-Fenton体系适用于酸性和弱酸性条件，最佳pH范围为3.0~4.0；在溶液pH为3.0、Fe（Ⅱ）投加量为5.0 μmol/L、H2O2投加量为0.4 mmol/L、HA投加量为0.20 mmol/L的最适条件下，反应10 min， 4-CP去除率达64.25 %。     

Alternative method to prevent thermal runaway in case of error on operating conditions continuous reactor

Thermal runaway was studied in a continuous tubular pilot reactor under steady-state regime. Different accident scenarii were conducted by making some errors on reactant concentrations and/or temperature feed. To prevent thermal runaway, control by direct contact by solvent injection was used at different reactor locations. This injection allowed controlling the maximum reaction temperature. A simplified analytical method to estimate the maximum reaction temperature along the reactor was used.Benefit of this control method was the diminution of computational time. Furthermore, by injecting solvent to control maximum reaction temperature, there is no need to shut down the unit. The control method was validated experimentally.     

丙烯腈生产废水中聚合物的资源化利用

以丙烯腈生产废水中的丙烯腈低聚物为原料制备聚丙烯酰胺。通过正交实验考察了水解反应条件和交联反应条件对反应的影响。FTIR表征结果显示,丙烯腈低聚物中的氰基已完全水解为酰胺基,产物聚丙烯酰胺中含有酰胺基和羧基。实验结果表明,在自来水加入量100 m L、水解反应温度95℃、m(Na OH)∶m(丙烯腈低聚物)=2.0、水解反应时间3 h的最佳水解反应条件,交联反应温度60℃、质量分数37%~40%的甲醛加入量6 m L、交联反应时间2 h的最佳交联反应条件下,处理20 g丙烯腈低聚物,可得到产物聚丙烯酰胺14.50 g,聚丙烯酰胺的水解度为21.1%、相对分子质量为2.7×106。产品性能满足Q/SH 0046—2007《钻井液用聚丙烯酰胺技术要求》中部分水解聚丙烯酰胺的性能要求。     

Hazard evaluation for chlorination and amination reactions of fluorocytosine production process

Reaction thermal runaway is one of the most important reasons leading to chemical accidents. With the rapid development of the chemical industry in the world, especially the fine chemical industry, various safety accidents also occur frequently. Therefore, it is necessary to study the exothermic behavior of the reaction process. In this study, reaction calorimeter was used to study the exothermic phenomena during the chlorination reaction and amination reaction. Differential scanning calorimetry was performed on the reactants, and thermogravimetric experiments were performed on the products. In addition, adiabatic experiment was performed to study the thermal runaway behavior of amination products under adiabatic conditions. The results showed that the target reactions generated a large amount of heat in the initial stage. The maximum temperature of amination reaction is higher than the initial decomposition temperature of the amination product under adiabatic condition. The pyrolysis of amination product was divided into three stages. The product had a high apparent activation energy at the beginning of decomposition, and the apparent activation energy decreased as the decomposition progressed.     

层状氧化物NaCo_2O_4热催化H_2O_2降解亚甲基蓝

采用固相烧结法制备了NaCo_2O_4催化剂,构建了NaCo_2O_4-H_2O_2热催化体系降解亚甲基蓝(MB)。XRD和SEM表征结果显示,合成的NaCo_2O_4催化剂具有良好的稳定性。NaCo_2O_4对H_2O_2具有良好的热催化性能,反应温度越高,反应速率常数k越大,该催化反应符合一级动力学方程。NaCo_2O_4-H_2O_2体系对MB具有较好的降解效果,在反应温度为50℃、NaCo_2O_4加入量为50 mg、MB溶液加入量为100 mL、MB初始质量浓度为30 mg/L、H_2O_2加入量为1.00 mL的最优条件下,反应340 min时,MB降解率达87.00%;催化剂重复使用三次,MB降解率仍可达85%以上;经捕获剂效果对比实验发现,催化反应体系中存在h~+、·OH等催化活性物种。     

The use of nanovermiculite catalyst in the study of removal of the organic load and degradation of atrazine via ozone process in RPB reactor

Abstract

The main objective of this study is the degradation of a synthetic solution of atrazine by a modified vermiculite catalyzed ozonation, in a rotating packed bed (RPB) reactor. A 0.5?L RPB reactor was used to perform the experiments, using a Central Composite Design (CCD) response surface to construct the quadratic model based on the factors: pH, catalyst concentration and reactor rotation frequency. The response variable was the removal of the organic load measured in terms of Chemical Oxygen Demand (COD). After the complete quadratic model was constructed through the response surface, the COD degradation process had an optimal removal of 41% under the following conditions: pH 8.0, rotation of 1150?rpm and catalyst concentration 0.66?g L^?1.     

抛光铝粉爆炸及ABC粉体抑爆特性的实验研究

为研究抛光铝粉的爆炸危险和ABC粉体的抑爆特性，在对实验粉体粒径分布进行分析的基础上，采用20 L粉尘爆炸特性实验装置，分别对不同铝粉尘浓度、不同抑爆剂浓度条件下的爆炸特性参数进行测试。研究结果表明:在实验条件下，铝粉的爆炸下限为45 g/m3＜C＜60 g/m3；随铝粉浓度增加，爆炸烈度呈现出先增强后减弱的变化趋势，在浓度为400 g/m3时爆炸烈度最大。ABC抑爆剂能够有效抑制铝粉爆炸超压和爆炸反应进程，随着惰性粉体浓度的增加，抑制效果愈加明显，爆炸逐渐减弱。当ABC惰性粉体的质量占比增加到50%时，相较单一铝粉爆炸，反应过程时间由72 ms增加至785 ms，爆炸最大压力、最大压力上升速率分别下降了61.7%，89.5%；当ABC粉体质量占比为53%时，铝粉被完全惰化，未发生爆炸。     

超临界反应的应用

采用环境友好的溶剂在超临界状态下进行的化学反应,能加快化学反应速率,提高反应的产率和选择性,方便地实现反应分离过程的一体化,该技术以其独特的优越性获得了广泛研究与关注。笔者简述了近年来超临界反应在石油化工、环境保护、生物柴油制备领域的应用。     

光氧化反应脱汞技术发展综述

燃煤电厂烟气中汞污染的控制技术研究是目前重要的环保课题之一。气相元素汞成为大气中汞污染的主要来源。文章分析了光氧化反应脱汞技术(包括光化学氧化反应和光催化氧化反应)的反应机理,认为光化学氧化反应技术脱汞均是在紫外光作用下,产生具有强氧化性的基态原子或自由基,将难以脱除的Hg0氧化为高价汞,再通过配套的电除尘器等设备将高价汞捕集,进而达到汞污染控制的目的。不同的是,在光化学氧化反应中,汞的氧化需要借助于电厂烟气中的O2、H2O等成分,而在光催化氧化反应中,反应需要在光催化剂(TiO2或TiO2负载复合物等)的催化作用下进行。阐述了光氧化反应汞脱除技术研究进展。光氧化反应脱汞技术的汞脱除率均可达到60%~70%,具备设备简单、无二次污染等优点。