【作者】 周金海；

【导师】 何正浩；

【作者基本信息】 华中科技大学 ， 环境工程， 2007， 硕士

【摘要】 燃煤烟气中SO₂的污染问题已经成为一个全球性难题,而且尚未有一种很好的解决方法,为此,近几年提出了烟气直接还原脱硫技术,因为烟气直接还原脱硫技术的最终产物是单质硫,无废水废渣排放。由于燃煤不可能完全燃烧而产生一定的CO有害气体,而CO又是一种还原性气体,因此,以烟气中的有害成分CO为还原剂脱除烟气中的SO₂,实现以废治废,成为La/γ-Al₂O₃催化剂直接还原脱硫技术的一大特点和优势。尽管该催化剂的脱硫反应温度较高,但是若能够通过改性解决这个问题,那么改催化剂的应用前景仍然是很好的。因此,本文用Ce、Fe和Ti对La/γ-Al₂O₃催化剂进行改性,使该催化剂在较低的还原脱硫反应温度下能够保持较高的脱硫活性。本文用Ce、Fe和Ti对γ-Al₂O₃负载型稀土催化剂进行改性,从一下几个方面进行了实验研究:1.采用浸渍法制备了一系列的γ-Al₂O₃负载型稀土催化剂: La/γ-Al₂O₃、La-Ce/γ-Al₂O₃、La-Fe-Ce/γ-Al₂O₃和La-Fe-Ce-Ti/γ-Al₂O₃;研究比较适宜的Ce、Fe、Ti和La的配比、制备工艺和焙烧条件;2.在实验室一模拟烟气脱硫装置中进行还原脱硫实验,研究改性催化剂的脱硫活性及不同焙烧温度对其脱硫活性的影响;3.通过BET、XRD和SEM等分析手段对改性催化剂进行表征,研究催化剂改性前后物相变化,探索改性催化剂催化还原脱硫机理。研究发现:500℃焙烧制得的催化剂的脱硫活性相对较高;经Ce改性制得的9%La-5%Ce/γ-Al₂O₃催化剂的脱硫活性明显高于单组分9%La/γ-Al₂O₃催化剂的脱硫活性,其反应所需温度为600℃,脱硫率为98.7% ;经Fe改性制得的9%La-3%Fe-5%Ce/γ-Al₂O₃催化剂的脱硫反应温度为500℃,脱硫率为98.8%;经过Ti改性制得的9%La-3%Fe-5%Ce-0.8%Ti/γ-Al₂O₃催化剂的脱硫反应温度为420℃,脱硫率为99.3%;该类催化剂脱硫反应中的活性相为La2O2S、FeS、FeS2及具有储氧和传递氧能力的CeO2和TiO2,其脱硫机理可能为中间产物机理与氧空位理论的协同作用。更多还原

【Abstract】 The pollution of SO₂ produced from coal-fired smoke has been becoming a global problem, and there is none effectual technique to resolve it. Therefore, the direct reduction of SO₂ technology has been brought forward nowadays, as the characteristics of this technology is that the finally production is element sufur and no water pollution or solid waste pollution in the process of desulphurization. Because coal can not be fired completely, in the coal-fired smoke, there must be some deoxidized CO which is deleterious. Using CO from flue gas as the reducing agent to reduce fulfur dioxids to element fulfur by catalyst is one of the distinct characteristics of rare earth catalyst supported onγ-Al₂O₃. Though, in the desulphurization process, the high reaction temperature needed is one prodigious disadvantage of this kind of catalyst for catalystic reduction of fulfur dioxides, if this problem can be solved by modification means, the modification catalyst may be used in the field of flue gas desulphurization gradually. So, in this thesis, CO is used as reducing agent and Ce, Fe and Ti are used as additive to modificate La/γ-Al₂O₃ aiming to prepare a kind of catalyst which can keep high activities in relatively lower reaction temperature in the process of desulphurization.Ce, Fe and Ti are used to modify La/γ-Al₂O₃ cataly, and the research content are described as following:1. a series of catalysts ofγ-Al₂O₃ loaded by rare earth: La/γ-Al₂O₃、La-Ce/γ-Al₂O₃、La-Fe-Ce/γ-Al₂O₃ and La-Fe-Ce-Ti/γ-Al₂O₃ have been prepared by dipping Ce,Fe,Ti and La intoγ-Al₂O₃ to study the feasible prepare ratio and bake temperature.2. In a suit of lab experimental simulation system, all the experiments are carried out in order to study the desulphurization activities of modification catalyst and the influence for the desulphurization activitie in deffrent baking temperature.3. In this thesis, BET, XRD and SEM are used to research the component changing of modification catalysts. And researching the desulphurization mechanism of modification catalysts is another aim of this thesis. Disquisitions indicate that, in the desulphurization experiment, the activity of catalyst 9%La-5%Ce/γ-Al₂O₃ is much higher than single catalyst 9%La/γ-Al₂O₃ and the reaction temperature of catalyst 9%La-5%Ce/γ-Al₂O₃ is 600 centigrade, while the SO₂ conversion rate is 98.7%; The reaction temperature of catalyst 9%La-3%Fe-5%Ce/γ-Al₂O₃ is 500 centigrade, while the SO₂ conversion rate is 98.8%; And, The reaction temperature of catalyst 9%La-3%Fe-5%Ce- 0.8%Ti/γ-Al₂O₃ is 420 centigrade, while the SO₂ conversion rate is 99.3%. La2O2S, FeS, FeS2 are the active phases of the catalyst 9%La-3%Fe-5%Ce-0.8%Ti/γ-Al₂O₃, furthermore, CeO2 and TiO2 which have the abilities to deposit and transport oxygen in the reaction are both the active phases too. The desulphurization mechanism of catalyst 9%La-3%Fe-5%Ce-0.8%Ti/γ-Al₂O₃ is the cooperative process of medial producetion mechanism and oxygen vacancy mechanism.更多还原