Gamma-initiated iodination of methane in the gas phase

Gamma radiation has been used to initiate the gas phase reaction between iodine and methane. Under appropriate conditions, the products are hydrogen iodide and the iodomethanes. The experiments were conducted over a range of temperature, concentration, and at two levels of total absorbed dose. The existence of a chain reaction is presumed, on the basis of G-values, which were as high as 7 × 10⁷. In view of the propensity of iodine as a radical scavenger, this high efficiency might seem surprising, but may be attributable to the known autocatalyic effect of iodine in substitution reactions.     

Electrophilic chlorination of methane over superacidic sulfated zirconia

Catalytic chlorination of methane was studied over SO ₄ ^2– /ZrO₂, Pt/SO ₄ ^2– /ZrO₂, and Fe/Mn/SO ₄ ^2– /ZrO₂ solid superacid catalysts. The reactions were carried out in a continuous flow reactor under atmospheric pressure, at temperatures below 240°C, with a gaseous hourly space velocity of 1000 ml/g h and a methane to chlorine ratio of 4 to 1. At 200°C with 30% chlorine converted the selectivity in methyl chloride exceeds 90%. At more elevated temperatures, the selectivity decreases but stays above 80% in methyl chloride at 225°C using the sulfated zirconia catalysts. The selectivity can be enhanced by adding platinum to sulfated zirconia catalysts. An iron and manganese-doped catalyst exhibited excellent selectivities at somewhat lower conversions. Methyl chloride is obtained at 235°C in selectivities greater than 85%. No chloroform or carbon tetrachloride is formed. The electrophilic insertion involves electron-deficient metal-coordinated chlorine into the methane C-H bond.Catalysis by solid superacids, 29. For part 28 see ref. [14].     

Stability of catalysts for the oxidative chlorination of methane

The effects on the stability of catalysts for the oxidative chlorination of methane due to evaporation of the active component (copper chloride) of the catalyst are studied. The volatility of copper chloride is shown to depend mainly on the catalyst composition and temperature. At a moderate 350°C in the reactor, the evaporation of copper chlorides after 5 h is 0.45% on a catalyst containing copper and potassium chloride and 0.72% on a catalyst containing lanthanum chloride. The stability of catalyst operation can be effectively maintained not only by decreasing the volatility of copper chloride, but also by feeding hydrochloric acid with dissolved copper chloride isolated from the reaction gas of methane oxychlorination at the outlet of the reactor (for the removal of reaction heat and the recycling of unconverted hydrogen chloride) back into the reactor.     

On the synthesis of LaCl3 catalysts for oxidative chlorination of methane

LaCl₃ is an active and selective catalyst for oxidative chlorination of methane to methyl chloride, generated in situ by chlorination from LaOCl. The latter is prepared by precipitation of La(OH)₂Cl and subsequent calcination. The synthesis route was modified by using different bases in order to synthesize high surface area LaOCl catalyst precursors. Ammonium hydroxide and the organic bases tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide are used as precipitating agents. The marked increase of the specific surface area by using organic bases indicates also that they may act as templating agents. After chlorination the specific surface areas of pure LaOCl samples decrease drastically, lanthanum carbonate, however, acts as structural promoter stabilizing the specific surface area during chlorination.     

Anodic chlorination of substituted benzenes - the choice of the chlorination reagents

Some substituted benzenes ArH were anodically chlorinated in acetonitrile LiClO₄ on a platinum electrode in the presence of either Cl^? anion or a chlorinated Lewis acid (such as AlCl₃). The overvoltage on the oxidation of Cl^? caused by a strong complexation by some Lewis acid allows consideration that the anodic reaction passes through the radical cation of the aromatic substrate. In such conditions, polychlorinations are possible and in the specific case of toluene, it is shown that the reaction favors the parachlorotoluene formation. The influence of different parameters (for example, the ratio of the concentrations AlCl₃/ArH, the nature of the Lewis acid) in such a reaction are discussed.     

Studies on chlorination of greywater

In view of the growing implementation of systems for treated greywater reuse, and as chlorination is an eventual step of the treatment to assure disinfection, a study of variables affecting the residual chlorine decay in greywater are reported in this paper. The investigation was carried out at laboratory scale with chlorinated samples, and the residual chlorine was measured spectrophotometrically with o-tolidine. To discuss the effects of these variables, decay curves were compared, or alternatively, fitted to a parallel first order decay model. Studied variables were: pH, surfactants, coliform bacteria, ammonia concentration, coagulant agents, potassium permanganate concentration, filtration and storage time. The obtained results showed that residual chlorine can be stabilized by: ammonia, by preoxidation with potassium permanganate or by treatment with coagulanting-flocculanting agents. Surfactants and bacteria were shown to favoured chlorine consumption. Results from this study can be useful to define the working conditions of full-scale systems where the reduction of chlorination dose is a matter of great interest to minimize the environmental impact of the systems.     

直接氯化反应工艺的改进

分析了直接氯化反应产品二氯乙烷纯度降低的原因,采取了控制反应温度、压力,改善催化系统和改进氯气进料分布情况等改进措施后提高了二氯乙烷纯度。     

甲苯及其衍生物侧链α-H的取代氯化

本文阐述了甲苯及其衍生物侧链α-H的取代氯化原理及其反应特征,重点介绍了它的研究现状及其氯化产物用途.     

甲基三氯硅烷的氯化方法

简要介绍了国内外CH3SiCl3氯化研究情况,概述了CH3SiCl3各种氯化方法,重点介绍了氯气氯化法,详细介绍氯气热氯化法的工艺流程、最佳工艺条件及热氯化工艺条件对ClCH2SiCl3收率的影响,指出了氯气热氯化法是具有广阔应用前景的方法,可实现大规模工业化生产。     

Electrothermal fluidized bed chlorination of zircon

Zircon sand, ZrSiO₄, is chlorinated in an electrothermally-heated fluidized bed reactor using calcined petroleum coke as the reducing agent and chlorine as the chlorinating agent. The electrothermally-heated fluidized bed reactor proved to be versatile and effective for the chlorination of zircon sand. The rate of the reaction can be expressed by the formula The reaction was found to be of zero order with respect to the chlorine concentration, which suggests that chlorine is strongly adsorbed on the solid particles; as such, the concentration of chlorine in the gas phase has no effect on the reaction rate. The activation energy for the reaction was found to be 10.55 Kcal/gram mole which is indicative of control by the rate of a surface reaction or adsorption step.     

炭黑的氯化改性

采用气－固相搅拌式氯化法对炭黑进行氯化改性,并利用二元回归分析法研究了氯化炭黑中氯质量分数与反应温度、时间和氯气流量的关系。结果表明,氯化反应条件为：温度 １３０℃,时间１．５～２ｈ,氯气流量５５４ｍＬ．ｍｉｎ＾－１时反应效果较好;氯化炭黑后处理的方法可采用充氮气法替代水洗处理法;扫描电镜照片表明,氯休徨的炭黑,其聚集结果有所变化,但链状结构没有被破坏。     

On the PVC chlorination mechanism

Summary A radiochemical method was used to study PVC chlorination. A reaction mechanism was proposed based on the results obtained from chlorination of ³⁶chlorine labeled PVC. A mechanism was proposed also for chain transfer reaction to polymer in vinyl chloride polymerization.     

石蜡氯化反应异常停止的原因

氯化石蜡生产中因液氯质量问题引起反应终止,分析了影响液氯质量的因素（主要是液氯中硫酸、二氧化硫、铁的化合物、水分、光气及二氧化氯等含量超标）,提出了解决措施.     

Kinetics of gaseous-phase catalytic chlorination of ethane

A study was made of kinetics of catalytic chlorination of ethane on modified silica gel at temperatures of 200 to 300°. Kinetic parameters of ethane consumption, the formation and chlorination of ethyl chloride were determined.     

Amorphous carbon nanostructures from chlorination of ferrocene

The chlorination of ferrocene at different temperature conditions yields several carbon nanostructures, which were studied by means of transmission and scanning electron microscopies. Amorphous carbon nanotubes (α-CNTs) up to 10 μm long with thick walls and ∼15 nm of internal diameter were observed in a sample treated at 200 °C during 30 min. They consisted on ∼90% of carbon, while the remaining 10% consists on iron and chlorine. At this temperature, amorphous carbon bags and open-ended branches were also found. When chlorinating ferrocene at the same temperature but with longer reaction time (180 min), no α-CNTs were formed. At higher temperature (300 °C, 30 min), amorphous carbon bags were found, with lower content of residual chlorine and iron, and presenting thinner walls. In the sample treated at even higher temperature (900 °C, 30 min) the carbon nanobags (wall thickness ∼12 nm) were almost spherical and more graphitic, and without impurities.     

反式-1,4-聚异戊二烯的氯化改性

采用水相悬浮法，在常压下对反式-1，4-聚异戊二烯（TPI）进行氯化改性。研究了温度、时间、粒径等对氯化反式-1，4-聚异戊二烯（CTPI）氯含量的影响。得到适宜的反应条件是：采用两阶段升温的方法，控制一定的通氯量，第一阶段，反应温度为35℃，反应时间为2～3h；第二阶段．反应温度为50～55℃，反应时间为1～6h，可获得氯质量分数在50％以内的CTPI，产品为可溶解的白色疏松颗粒。     

Some aspects of the chlorination of bauxite

Removal of iron and titanium impurities in bauxite by selective chlorination has been obtained by controlling the addition doses of coke and restricting the temperatures to below 323 K. The chlorination of iron and titanium free bauxite has been studied as regards the effect of coke addition, Cl₂ flow rates and partial pressures and temperatures. The rate equation 1-(1 - R)^1/3 = kt has been shown to fit the experimental data. It is concluded that the diatomic Cl₂ molecule does not dissociate to atomic Cl during chlorination.