【作者】 丁永杰；

【导师】 单永奎；

【作者基本信息】 华东师范大学 ， 无机化学， 2011， 博士

【摘要】 随着全球经济的高速发展,社会对能源和资源的需求迅速增长。而煤炭和石油类碳氢资源的日趋枯竭,将会对经济发展造成巨大的阻碍。以甲烷为主要成分的碳氢资源储量丰富,被人们认为是煤炭和石油的理想替代资源。然而,碳氢资源结构的这种变化势必要求相应的产业技术结构的改变,所以对以甲烷碳氢资源为原料的化学转化技术的研究是为未来化学工业的发展提供技术上的支撑和战略储备。甲烷C1碳氢资源转化的方法分为直接法和间接法。由于甲烷的分子特性,甲烷的直接转化研究虽经研究历了近百年,但仍然无法克服甲烷转化率和产物选择性的反比制约关系,即甲烷的高转化率与产物的高选择性无法同时获得。到目前为止,仍然没有开发出具有应用价值的甲烷直接转化技术。目前,甲烷转化具有实际应用价值的方法是间接转化法。合成气法是甲烷间接转化的传统方法。但合成气方法的高耗能、低碳氢利用率、巨大的设备投资是被公认的致命缺点。在碳氢资源日益短缺、低碳理念深入人心的今天,合成气法的缺点越来越受到人们的关注,所以开发低能耗、高效清洁的替代工艺势在必行。本文结合甲烷转化过程中存在的问题,本着清洁高效地转化甲烷的目的,设计了甲烷光化学溴代活化转化的工艺路线：(1)首先以甲烷光化学卤代活化合成高反应活性的低卤代甲烷替代高耗能、低利用率、高投资成本的合成气制备工艺；(2)然后以低卤代甲烷为活性中间产物合成多种下游化学化工产品替代合成气的下游工艺。由此完成甲烷光化学溴代活化转化工艺对甲烷合成气转化工艺的完整替代。通过研究发现本途径具有反应条件温和、设备投资小、碳氢资源利用率高等显著优点。在甲烷光化学溴代活化合成高反应活性的低溴代甲烷的研究中发现,对反应过程中的参数进行合理控制,能够高选择性地合成低溴代甲烷,其中液溴的扩散速度与光源强度的配合对选择性的影响较为明显；光源的特征谱线与产物的分布也具有明显的匹配关系：此外,适当延长反应时间,有利于提高二溴甲烷的选择性并降低高溴代甲烷的含量；放大反应中低溴代甲烷的选择性与溴的转化率均达到了小试时的最佳结果,其中溴的转化率大于99%,低溴代甲烷的选择性达到了91.3%。以高反应活性的甲烷光化学溴代产物二溴甲烷为起始原料,对其下游化学品的合成进行研究。其中,通过对二溴甲烷与正己醇合成己缩醛,然后己缩醛进一步催化水解得高浓度甲醛的研究发现：二溴甲烷与正己醇在碱性条件下,可以高收率地得到产物已缩醛。己缩醛在本文设计的连续水解装置中,以廉价的HZSM-5为催化剂连续水解得到高浓度的甲醛,其浓度可以达到18.9%，而且通过水解时水的加入量,以及延长连续水解反应的时间还可以进一步提高甲醛的浓度。以二溴甲烷与甲醇缩合制备的二甲氧基甲烷(甲缩醛,DMM)为原料,选择性催化氧化合成碳酸二甲酯(DMC),该工艺简单,副产物仅有水,具有替代现有DMC合成方法的潜力,通过研究筛选出了最佳的催化剂(Cu-MCM41-2)及催化反应条件(催化剂用量0.3g,NHPI用量1mmol,反应加热温度160℃,O2压力2MPa,反应时间2h),最优的催化效果为：DMC选择性86.2%, DMM转化率94.9%。催化剂在该体系下可以重复利用而且催化活性没有明显降低。该结果远高于文献报道值(Y/max=35.4%),而且催化剂制备简单,活性稳定,适宜于工业应用。此外,还初步研究了二溴甲烷和氨水反应合成尿素；与苯二酚反应合成聚苯醚类树脂的反应,并证明了其反应的可行性。在甲烷光化学溴代反应过程中,产生了副产物溴化氢,本文设计了以氧化铜吸收,以空气低温氧化回收的方法。该方法具有回收率高,吸收剂氧化铜可以重复利用,操作简便,适用于本文所研究工艺的特点。通过上述研究结论证明了甲烷光化学溴代活化转化的可行性,以及其相对于甲烷合成气转化路线具有的明显优势。更多还原

【Abstract】 With the development of the global economy, the requirements of energy and resources are increasing greatly. The shortage of hydrocarbons resources of coal and petroleum will inevitably hinder economic development. The technologies in the chemical industry have to be changed with the change of hydrocarbons resources structure. It is necessary to investigate new method for chemical conversion of hydrocarbons resources containing methane, which is very more abundant in nature.The indirect and direct method for conversion of methane was reported. Due to the properties of methane, high methane conversion and products selectivity can not be obtained at the same time, because there is a mutual restraint relationship between them. So far, the operative technology of methane direct conversion has not yet formed.At present, methane indirect conversion is an applied method. Methane conversion via syngas is a traditional indirect way. The method has suffer the disadvantages such as high consumption of energy, low hydrocarbons utilization rate, huge equipment investments. With the exhaustion of the coal and petroleum resources and low-carbon development concept gradually being accepted by the community. The disadvantages of syngas method attract much attention nowadays. So the clean and efficient alternative processes should be required.In order to clean and efficient converse methane into high value-added chemicals, the methane conversion method via photochemical brominating was improved in this thesis. Firstly, methane is conversed into bromomethane and dibromomethane via bromination reaction by photochemical method. Secondly, some valuable derivatives of bromomethane or dibromomethane can be prepared.The processes of methane converse into bromomethane and dibromomethane via photochemical brominating was studied in more detail. The results indicate that bromomethane and dibromomethane can be obtained with high selectivity through suitably controlling reaction conditions. It is found that diffusion rate of bromine, intensity of light source and reaction time are the main influencing factors of the process. Moreover, the matching regulation between the product distribution and characteristic wavelength of light source was explored. The products (bromomethane and dibromomethane) were synthesized with high selectivety (91.3%) and99%conversion based on bromine at the optimum conditions.The development of dibromomethane down-stream product was studied in detail. High concentration mehtanal solution was obtained using dibromomethane and hexanol as starting material by condensation and hydrolysis reaction. In the continuous hydrolytic equipment designed in the thesis, the reaction equilibrium can be moved by removing the hexanol produced in the hydrolysis reaction. The concentration of methanal solution reached to18.9%in the present of catalyst HZSM-5.The synthesis of dimethyl carbonate (DMC) from selective oxidation of dimethoxymethane (DMM) with dioxygen was investigated. The by-product is water in the reaction. Comparing to conventional synthesis of DMC, the synthesis process of DMC from selective oxidation of DMM is simple, high atom-economic and eco-friendly. The highest the DMM conversion(94.9%) and the DMC selectivity (86.2%) was obtained over the0.3g Cu-MCM41-2catalysts under2.0MPa O2pressure at160℃for2h in presence of the initiator NHPI(lmmol). In the five-time recycling operations, no deactivation was observed, which shown catalyst of Cu-MCM41-2is steady in the reaction system and is in favor of the large-scale production of DMC from DMM with dioxygen in chemical industry.In addition, the urea was synthesized through reaction between dibromomethane and ammonia, Modified polyphenylene oxide resin was obtained by the reaction between dibromomethane and benzenediol.The recycle of HBr was carried out by the method designed in the thesis. The advantages of the method are clean and relatively cheap oxidant, high recycle ratio and simple process.Through these studies suggest that the method of methane conversion via photochemical brominating was feasible and has a number of obvious advantages over the traditional method.更多还原