具有高效單質(zhì)汞氧化性能SCR催化劑的制備及表征
發(fā)布時(shí)間：2018-10-05 07:45
【摘要】：汞單質(zhì)及其化合物排放到空氣中會(huì)造成嚴(yán)重的環(huán)境污染,燃煤煙氣汞排放受到全球廣泛關(guān)注。燃煤煙氣中汞的形態(tài)有三種:單質(zhì)汞(Hg0)、氧化態(tài)汞(Hg2+)和顆粒態(tài)汞(Hgp),其中的Hg0很難被現(xiàn)有空氣污染物控制裝置脫除,從而會(huì)通過(guò)煙囪直接排入大氣中。研究發(fā)現(xiàn),燃煤電廠用來(lái)煙氣脫硝的SCR催化劑可一定程度上催化氧化煙氣中的Hg0,氣態(tài)氧化汞可在濕法脫硫系統(tǒng)中被吸收,兩者實(shí)現(xiàn)了對(duì)煙氣中Hg元素的協(xié)同脫除。為了在不影響SCR催化劑脫硝性能的同時(shí)提高其汞氧化效率,可以選擇對(duì)傳統(tǒng)SCR催化劑進(jìn)行改性。本文采用濕混法制備了CuCl2改性SCR催化劑,并在催化劑性能評(píng)價(jià)實(shí)驗(yàn)臺(tái)上,模擬煙氣組分,在不同溫度下測(cè)試單質(zhì)汞的催化氧化效率�；谛阅茉u(píng)價(jià)實(shí)驗(yàn)結(jié)果、XRD、BET、XRF、XPS等表征手段,結(jié)合化學(xué)吸附、程序升溫還原實(shí)驗(yàn),探討改性SCR催化劑的氧化還原能力、酸堿位、比表面積以及組分含量等,分析改性催化劑對(duì)單質(zhì)汞催化氧化作用的可能機(jī)制,為優(yōu)化改性催化劑性能提供理論支持。研究結(jié)果表明,在固定比例的模擬煙氣工況下,隨著溫度的提高,單質(zhì)汞催化氧化效率呈現(xiàn)先升后降的趨勢(shì),改性前后SCR催化劑在350℃下的汞催化氧化效率均達(dá)到最高。研究發(fā)現(xiàn),CuCl2的摻雜有效地增加了催化劑的酸性位點(diǎn),這對(duì)提高其脫硝活性有一定的意義,改性后SCR催化劑的氧化還原性能較改性前有一定幅度的增強(qiáng),結(jié)合活性評(píng)價(jià)結(jié)果,可以認(rèn)為SCR催化劑對(duì)單質(zhì)汞的催化活性與其還原性有關(guān)。SCR催化劑元素分析結(jié)果顯示,改性SCR催化劑中Cu元素主要以Cu2+的形式存在,在性能測(cè)試后,Cu2+含量減少,相應(yīng)的低價(jià)態(tài)Cu元素比例增大,而且反應(yīng)后催化劑中晶格氧被消耗,相應(yīng)的化學(xué)吸附氧比例增大,說(shuō)明在反應(yīng)過(guò)程中Cu和O均參與了電子轉(zhuǎn)移。根據(jù)性能實(shí)驗(yàn)和表征結(jié)果分析,改性SCR催化劑對(duì)單質(zhì)汞的催化氧化機(jī)理符合Mars-Maessen機(jī)理。
[Abstract]:The emission of mercury and its compounds into the air will cause serious environmental pollution, and mercury emissions from coal-fired flue gas have attracted worldwide attention. There are three forms of mercury in coal-fired flue gas: elemental mercury (Hg0), oxidized mercury (Hg2) and particulate mercury (Hgp), the Hg0 of which is difficult to be removed by the existing air pollutant control devices, which will be discharged directly into the atmosphere through the chimney. It is found that the SCR catalyst used for flue gas denitrification in coal-fired power plants can be used to catalyze the oxidation of Hg0, gaseous mercury oxide in flue gas to a certain extent and can be absorbed in the wet desulfurization system. The two catalysts can achieve the synergistic removal of Hg elements in flue gas. In order to improve the mercury oxidation efficiency of SCR catalyst without affecting its denitrification performance, the traditional SCR catalyst can be modified. In this paper, CuCl2 modified SCR catalyst was prepared by wet mixing method. The catalytic oxidation efficiency of elemental mercury was measured at different temperatures on the catalyst performance evaluation bench. Based on the experimental results of performance evaluation, the redox ability, acid and base sites, specific surface area and component content of modified SCR catalysts were investigated by means of chemical adsorption and temperature programmed reduction experiments. The possible mechanism of the catalytic oxidation of elemental mercury over modified catalysts is analyzed, which provides theoretical support for optimizing the performance of the modified catalysts. The results showed that the catalytic oxidation efficiency of mercury increased first and then decreased with the increase of temperature under the condition of fixed proportion of simulated flue gas. The catalytic oxidation efficiency of SCR catalyst reached the highest at 350 鈩，
本文編號(hào)：2252570
[Abstract]:The emission of mercury and its compounds into the air will cause serious environmental pollution, and mercury emissions from coal-fired flue gas have attracted worldwide attention. There are three forms of mercury in coal-fired flue gas: elemental mercury (Hg0), oxidized mercury (Hg2) and particulate mercury (Hgp), the Hg0 of which is difficult to be removed by the existing air pollutant control devices, which will be discharged directly into the atmosphere through the chimney. It is found that the SCR catalyst used for flue gas denitrification in coal-fired power plants can be used to catalyze the oxidation of Hg0, gaseous mercury oxide in flue gas to a certain extent and can be absorbed in the wet desulfurization system. The two catalysts can achieve the synergistic removal of Hg elements in flue gas. In order to improve the mercury oxidation efficiency of SCR catalyst without affecting its denitrification performance, the traditional SCR catalyst can be modified. In this paper, CuCl2 modified SCR catalyst was prepared by wet mixing method. The catalytic oxidation efficiency of elemental mercury was measured at different temperatures on the catalyst performance evaluation bench. Based on the experimental results of performance evaluation, the redox ability, acid and base sites, specific surface area and component content of modified SCR catalysts were investigated by means of chemical adsorption and temperature programmed reduction experiments. The possible mechanism of the catalytic oxidation of elemental mercury over modified catalysts is analyzed, which provides theoretical support for optimizing the performance of the modified catalysts. The results showed that the catalytic oxidation efficiency of mercury increased first and then decreased with the increase of temperature under the condition of fixed proportion of simulated flue gas. The catalytic oxidation efficiency of SCR catalyst reached the highest at 350 鈩，
本文編號(hào)：2252570
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