摘 要
二氧化硫是危害最为严重的大气污染物之一,它主要来自化石燃料的燃烧,
的控通过形成酸雨破坏生态环境,危害人类的生存环境。二氧化硫的脱除从SO
2
制途径可以分为:燃烧前脱硫、燃烧中脱硫及燃烧后脱硫。在诸多的脱硫方法中,催化还原法具有明显优势,可以将二氧化硫直接还原为元素硫,一方面减轻大气污染,另一方面可以缓解我国缺硫的境况。
本研究以低浓度SO2烟气为研究对象,采用催化还原二氧化硫生成元素硫的方法,选择了CH4为还原气体,利用浸渍法制备了铁、钴、镍、铜、钼形成的负载于γ-Al2O3的单组分、复合组分含量为8%共16种催化剂;考虑到浸渍顺序的影响,用相同活性组分,不同的浸渍顺序制备了10种分步浸渍的复合组分负载型催化剂并做了催化剂评价,优选出2种催化性能较好的催化剂,考察了在制备过程中浸渍温度和焙烧温度对催化剂性能的影响,最后考察反应温度、反应物配比以及空速等反应条件对催化还原SO2活性的影响。并在优化条件下,对催化还原SO2机理做探索性研究。同时利用XRD、SEM对催化剂的物相和表面形貌等进行了表征。得出如下结论:
(1)五种单组分催化剂的SO2转化率都比较低,都低于20%。
(2)复合组分催化剂SO2转化率都明显高于单组分催化剂,同时浸渍的两组分的负载型催化剂高于600℃都表现较高的转化率,在温度高于600℃时Fe3O4 - NiO /γ-Al2O3和Fe3O4 - CuO/γ-Al2O3的SO2转化率大于99.9%;
(3)分步浸渍法制备的复合相金属负载型催化剂的SO2 转化率都不高,并且明显低于同时浸渍的相同组分的催化剂,这可能在分步浸渍中后浸渍的组分将前浸渍组分的活性中心被全部或部分覆盖,没有起到相互协同的作用而使催化剂催化能力降低;
(4)优选出Fe3O4-Cu O/γ-Al2O3、 Fe3O4-NiO/γ-Al2O3两种催化剂,最佳浸渍温度为80℃,最佳焙烧温度为650℃;
(5)在确定浸渍温度和焙烧温度后,发现在反应温度大于600℃,SO2 转化率迅速上升,并确定反应温度为600℃;SO2/ CH4进料比在1.0-1.2的范围内SO2转化率大于99%;
(6)XRD衍射图谱表明衍射图谱表明,硫化物是催化SO2还原反应的活性相,该活性相的形成与催化剂的氧化还原能力有关。
关键词:甲烷 二氧化硫 催化氧化 元素硫 催化剂 SO2 转化率
ABSTRACT
Sulfur dioxide is one of the most harmful air pollutants. It results primarily from the combustion of fossil fuel, and forms the acid rain which damage the ecological environment as well as do harm to human being’s living environment. According to control mode of SO2, desulphurization can be classified as: desulphurization pre, in and post-combustion. Catalytic reduction takes clear advantage amang various types of desulphurization, which can directly reduce the sulfur dioxide to elementary sulfur so as to abate the air pollution while relieve the pressure the lack of the sulfur in the country.
The study object is light concentration SO2 gas, reducing the sulfur dioxide to elementary sulfur by Catalytic reduction, choosing CH4 as reducing gas, utilizing immersion method to create 16 catalyst, which contains 8% of single and compound constituent formed by the iron, cobalt, nickel, copper, molybdenum, and loaded in γ-Al2O3. In consideration of effects of immersion order, using the same active component in different order to make 10 types of components loading catalysts and evaluating it at the same time. Selecting 2 of catalyst with better performance on the basis of above steps, taking which as the study objects to review how the immersion and roasting temperature impact the performance of the catalysts. At last reviewing how the reaction condition, such as temperature, reactant ratio, airspeed, etc. impact catalyzing and deoxidizing SO2.Conduct an explor
山河壮丽
atory study on mechanism of catalyzing and deoxidizing SO2 under the advanced condition. It comes to the following conclusion after taking the pha & surface topography of the catalysts by using XRD、SEM:
(1) SO2 conversion rate of five single constituent catalysts is lower that 20%.
(2) SO2 conversion rate of compound constituent catalysts is distinctly higher than single one. The conversion rates of two types loading catalysts are higher when it comes to 600℃. SO2 conversion rate Fe3O4 - CuO /γ-Al2O3 and Fe3O4 - CuO/γ-Al2O3 is more than 99.9% when the temperature exceeds 600℃.
(3) The SO2 conversion rate of compound metal activator which conducted by Step immersion method is not high, but lower than the other activator with same component while simultaneity immersion. It is probably that after step immersion, the
post-immersion component covered the whole or part activity center of their fore-component, which did not take the interoperation effect and reduce the catalyzing ability.
(4) After lecting Fe3O4-CuO/γ-Al2O3、Fe3O4-NiO/γ-Al2O3 the two activators at first, then t their optimal immersion temperature to 80℃,and the optimal roasting temperature to 650℃
(5) After fixing the immersion and roasting temperature, it shows that the conversion rate of SO2 will speed up when the respon temperature exceeds 600℃,and make sure that 650℃ is the respon temperature .The conversion rate would more than 99% when the filling material rates of SO2/ CH4 between 1.0~1.2.
(6) XRD diffraction graphics indicate that sulphide is the active components to catalyze the deoxidize reaction of SO2, and the formation of which is related with the ability of oxidation deoxidizing.
Key words: firedamp, Sulfur dioxide (SO2), catalyzed oxidation, elemental sulphur, catalysts SO2 conversion rate泡沫轻质土
独创性声明
本人声明所呈交的论文是我个人在导师指导下进行的研究工作及取得的研究成果。尽我所知,除了文中特别加以标注和致谢的地方外,论文中不包括其他人已经发表或撰写过的研究成果,也不包含为获得西北师范大学或其他教育机构的学位或证书而使用过的材料。与我一同工作的对本研究所做的任何贡献均已在论文中作了明确的说明并表示了谢意。
签名:日期:
关于论文使用授权的说明
大学社团的意义本人完全了解西北师范大学有关保留、使用学位论文的规定,即:学校有权保留送交论文的复印件,允许论文被查阅和借阅;学校可以公布论文的全部或部分内容,可以采用影印、缩印或其他复制手段保存论文。
(保密的论文在解密后应遵守此规定)
签名:导师签名:日期:
prefers王维甲烷催化还原二氧化硫为元素硫催化剂的研究
1文献综述
计算机二级资料1.1 我国二氧化硫污染现状
随着全球工业发展和人口的增长,环境问题已经引起了人们的普遍关注。各国对废水、废气、废渣的排放都作了严格规定。二氧化硫是最严重的大气污染物其处理方法已经成为一个重要的研究课题。
我国是世界上最大的煤炭生产和消费的国家之一。自从80年代以来,随着
已经我国的经济的迅速发展,煤炭的消耗量和二氧化硫的排放量日益增加。SO
2
成为世界第一大污染物,是造成大气污染和酸雨形成的主要原因之一。人类每年向大气排放的SO2达1.8亿吨。据国家环保部历年的空气质量状况统计,2006 年,二氧化硫排放量为2588.8 万吨。由于这种情况,我国人民的身体健康受到了严重的威胁和极大地损害,每年造成巨大的经济损失。另外,在二氧化硫的作用下,我国的生态环境也受到了严重的破坏。目前我国受到酸雨威胁的地区已达国土总面积的40%。每年造成上百亿元的经济损失。所以,二氧化硫的污染不仅对人民的身体健康造成了极大的损害,而且阻碍了我国的持续发展,所以减小二氧化硫的排放量,防治大气污染,已经成为我国目前及未来相当长的时间内的主要问题。2006 年,全国二氧化硫年均浓度达到或优于二级标准的城市占86.8%,超过三级标准的城市占3.6%。与2005年相比(可比城市),二氧化硫年均浓度达到或优于国家二级标准的城市比例提高4.3 个百分点;超过国家三级标准的城市比例减少2.1 个百分点,二氧化硫污染水平有所降低。家常炒鸡
二氧化硫污染较重的城市主要分布在:山西、内蒙古、云南、新疆、贵州、甘肃、河北、湖北、广西、湖南、四川、辽宁、河南、重庆、天津等省(自治区、直辖市)。
故人西辞黄鹤楼烟花三月下扬州表1 可比城市二氧化硫分级年际比较
空气质量级别 2006年 2005年
达到二级(达标)﹪81.7 77.4
三级﹪13.9 16.1
劣三级﹪ 4.4 6.5
2006 年,全国参加酸雨监测统计的524 个城市(县)中,出现至少1 次以上
>刘佳璐