气相裂解1,1,2-三氯乙烷选择性脱HCl的高效催化剂研究

发布时间：2018-07-20 17:13

【摘要】：氯代烃类物质1,1,2-三氯乙烷(TCE)排放会严重污染环境,造成酸雨、温室效应、臭氧层空洞等环境问题,因此如何处理氯代烃类物质是一个重要的课题。一般通过两类方法处理TCE,一类是直接分解氯代烃类物质,包括直接焚烧法、催化燃烧法、生物降解法和光催化分解法；另外一类是将这些氯代烃类物质转化为有用的化学品,显然后者更具有研究价值。目前氯代烃的主要转化形式为加氢脱氯和脱氯化氢,其中催化剂起着重要作用。本论文主要研究气相裂解1,1,2-三氯乙烷选择性脱氯化氢的催化剂,设计并筛选催化性能高、选择性好的有机胺和Mg基催化剂,分别用于合成1,1-二氯乙烯(1,1-DCE)和顺-1,2-二氯乙烯(cis-1,2-DCE)两种产品,考察了催化剂负载量、预处理温度、载体类型等对脱氯化氢效率和选择性的影响,探明了TCE脱氯反应机理和催化剂失活原因。具体内容如下：1.研究了有机胺催化剂气相催化裂解TCE制备1,1-DCE反应。1,1-DCE的聚合物PVDC是绿色食品保鲜包装材料,目前工业上采用NaOH强碱液的皂化工艺裂解TCE脱氯化氢来生产1,1-DCE,虽然VDC选择性较高,但会产生大量高盐有机废水,因此采用负载型催化剂气相催化制备1,1-DCE是一个绿色工艺路线。本部分主要考察了负载型五乙烯六胺(PEHA)催化裂解TCE反应,发现PEHA/SiO2催化剂得到1,1-DCE选择性高达98%,且在脱氯过程中保持稳定,但TCE转化率从99%迅速下降到10%以下。通过对PEHA/SiO2催化剂上脱氯机理研究,发现在强碱性的PEHA作用下,TCE消除HCl遵循E2机理,有机胺与原位产生的HCl反应生成了较难分解的氯化胺物种,是催化剂失活的主要原因。2.采用浸渍法制备一系列Mg基催化剂,用于气相催化裂解TCE反应。研究表明Mg基催化剂对TCE裂解都有很高的活性,并选择性生成cis-1,2-DCE.催化剂的活性与Mg负载量有关,与Mg物种前驱体无关,以Mg(NO3)2·6H2O口MgCl2·6H2O为前驱体制备的Mg基催化剂活性一致。Mg负载量为10%的催化剂具有最好的活性和稳定性,TCE的转化率高达92%, cis-DCE的选择性高达91%。在反应过程中Mg基催化剂表面逐步形成了含氯的Mg物种,Cl/Mg的摩尔比为1：1,进一步表征证明该物种为Mg(OH)Cl,且是TCE脱氯反应的的活性物种。
[Abstract]:The emission of chlorinated hydrocarbons (TCEs) will pollute the environment seriously and cause environmental problems such as acid rain, Greenhouse Effect, ozone layer hole and so on. Therefore, how to deal with chlorinated hydrocarbons is an important subject. TCEs are generally treated in two ways, one is the direct decomposition of chlorinated hydrocarbons, including direct incineration, catalytic combustion, biodegradation and photocatalytic decomposition, and the other is the conversion of these chlorinated hydrocarbons into useful chemicals, Obviously the latter has more research value. At present, the main conversion forms of chlorinated hydrocarbons are hydrodechlorination and dehydrochlorination, among which catalysts play an important role. In this paper, the catalyst for selective dehydrochlorination of 1 ~ 1H ~ (2 +) trichloroethane from gas phase cracking was studied, and the organic amines and Mg-based catalysts with high catalytic performance and good selectivity were designed and screened. The effects of catalyst loading, pretreatment temperature and carrier type on the efficiency and selectivity of dehydrochlorination were investigated. The mechanism of TCE dechlorination and the reason of catalyst deactivation were investigated. The details are as follows: 1. The organic amine catalyst was prepared by gas phase catalytic pyrolysis (TCE) to prepare 1 (1-DCE). 1 (1-DCE) polymeric PVDC is a green food packaging material. At present, the saponification process of NaOH strong base solution is used to produce 1H _ (1-DCE) by pyrolysis of TCE, although the selectivity of VDC is high. However, a large amount of high salt organic wastewater will be produced, so it is a green process route to use supported catalyst to catalyze the preparation of 1hl-DCE in gaseous phase. In this part, the catalytic cracking TCE reaction of supported pentaethylenehexamine (PEHA) was investigated. It was found that the selectivity of 1-DCE reached 98% over PEHA / SiO2 catalyst, and remained stable during dechlorination, but the conversion of TCE decreased rapidly from 99% to less than 10%. The mechanism of dechlorination on PEHA / Sio _ 2 catalyst was studied. It was found that the elimination of HCl by TCE followed the E2 mechanism under the action of PEHA / Sio _ 2, and the reaction of organic amine with HCl produced in situ produced more difficult species of amine chloride, which was the main reason for the deactivation of the catalyst. A series of Mg-based catalysts were prepared by impregnation method for gas phase catalytic cracking of TCE. The results show that the Mg-based catalysts have high activity for TCE cracking and selectively produce cis-1n 2-DCE. The activity of the catalyst was related to the amount of mg loaded, but not to the precursor of mg species. Mg (no _ 3) _ (2) 6H _ (2) O was used as the precursor to prepare MgCl _ (2) 6H _ 2O. The catalyst with the same activity and 10% mg loading had the best activity and stability. The conversion of TCE was up to 92%, and the selectivity of cis-DCE was up to 91%. The molar ratio of Cl / mg was 1: 1 on the surface of Mg-based catalyst. It was further characterized that the species was mg (OH) Cl and was an active species for TCE dechlorination.
【学位授予单位】：浙江师范大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36

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