Mn/Zr改性稀土尾礦催化劑NH3-SCR脫硝機(jī)理分析

焦坤靈,焦曉云,劉佳杰,李 娜,侯麗敏,武文斐*

Mn/Zr改性稀土尾礦催化劑NH3-SCR脫硝機(jī)理分析

焦坤靈1,2,焦曉云1,劉佳杰1,李 娜1,侯麗敏1,武文斐1,2*

(1.內(nèi)蒙古科技大學(xué)能源與環(huán)境學(xué)院,內(nèi)蒙古 包頭 014010；2.內(nèi)蒙古自治區(qū)高效潔凈燃燒重點(diǎn)實(shí)驗(yàn)室,內(nèi)蒙古 包頭 014010)

采用溶膠凝膠法制備了Mn、Mn/Zr負(fù)載稀土尾礦的NH3-SCR催化劑,通過(guò)催化劑活性評(píng)價(jià)系統(tǒng),結(jié)合H2-TPR、NH3-TPD、XRD和DRIFT研究了催化劑脫硝過(guò)程和反應(yīng)機(jī)理.結(jié)果表明:Mn、Mn/Zr改性稀土尾礦催化劑的脫硝活性顯著增強(qiáng),在200℃時(shí)6%Mn1%Zr/稀土尾礦催化劑脫硝活性可達(dá)96%.改性后催化劑表面氧空位、B酸性位點(diǎn)及吸附物種數(shù)量明顯增加,催化劑還原峰面積增大,其氧化還原性能的提升是活性提高的主要原因.催化劑B酸位NH4+與氣態(tài)NO2的反應(yīng)遵循E-R機(jī)理,NH4+與單齒、雙齒硝酸鹽物種的反應(yīng)遵循L-H機(jī)理.

稀土尾礦；Mn、Zr改性；催化劑；NH3-SCR；脫硝機(jī)理

白云鄂博礦是我國(guó)稀土儲(chǔ)量最大,以鐵、稀土、鈮為主的多金屬共伴生礦[1-2].早期主要以選鐵為主[3],后期選別工藝涵蓋了選鐵、稀土(RE)、鈮、螢石等,尾礦產(chǎn)物均存放于稀土尾礦壩[4].因受選礦目的及工藝技術(shù)、設(shè)備的制約,白云鄂博稀土尾礦中既有早期稀土富集品位較高的鐵尾礦物,又有選別稀土及其他有價(jià)物質(zhì)后的稀土尾礦.尾礦中含有鐵、稀土、鈮、螢石、鈧、釷等多種有價(jià)物質(zhì)[5],后期尾礦中有價(jià)物質(zhì)含量雖有所下降,但總量依然可觀.

白云鄂博稀土尾礦“二次資源”屬性和遷移轉(zhuǎn)化過(guò)程對(duì)環(huán)境、人體健康危害日漸引起重視[6],尾礦資源再利用成為行業(yè)關(guān)注和學(xué)者研究熱點(diǎn).利用尾礦中鐵、RE或其他礦物質(zhì)的理化性質(zhì),將其作為原材料或添加劑,應(yīng)用到其他領(lǐng)域產(chǎn)品的研發(fā)之中,如微晶玻璃[7-8]、催化材料[9]等新材料研究,以實(shí)現(xiàn)尾礦資源高值化利用[10],是尾礦資源再利用的熱點(diǎn)方向之一.

目前,控制燃煤煙氣中NO主要是采用NH3(或尿素,CH4N2O)作為還原劑的選擇性催化還原法(SCR).新型NH3-SCR脫硝催化劑研究中,主要采用Fe、Mn、RE等過(guò)渡金屬氧化物或復(fù)合金屬氧化物作為主活性物質(zhì)[11-12].白云鄂博稀土尾礦中Fe、RE元素含量較為豐富,具有制備N(xiāo)H3-SCR脫硝催化劑的天然優(yōu)勢(shì).

近年來(lái),本課題組針對(duì)白云鄂博稀土尾礦NH3-SCR脫硝催化劑進(jìn)行了大量研究,目前稀土尾礦制備催化劑的改性方法主要包括機(jī)械力活化(球磨、微波)、酸處理和其他活性元素負(fù)載,元素負(fù)載主要采用溶膠凝膠法.稀土尾礦不經(jīng)處理直接用于NH3-SCR脫硝,其脫硝活性較差約為40%[11];采用球磨、微波活化[13],尾礦脫硝活性提升并不顯著;采用硫酸改性后[14],尾礦脫硝活性在400℃時(shí)可達(dá)到86%,主要是提升了尾礦活性組分分散度和表面酸位點(diǎn)數(shù)量,但引入硫酸改性,需考慮其環(huán)境效應(yīng);尾礦負(fù)載Ce、Ce/Mn、Ce/W、Ce/Co后[15],Ce的引入可將尾礦脫硝活性在350℃提升至85%以上,Mn負(fù)載可將脫硝溫度窗口拓寬至100～300℃,脫硝活性最高可達(dá)92%;尾礦負(fù)載Cu后[16],可能存在CuO與Fe2O3的協(xié)同作用,275℃脫硝活性可達(dá)80%;尾礦負(fù)載Ni后[17],NiFe2O4的存在促進(jìn)了Fe的電子轉(zhuǎn)移,在300℃脫硝活性可達(dá)84%.以上結(jié)果表明,稀土尾礦負(fù)載活性元素可提高尾礦催化脫硝活性.Mn元素拓寬尾礦脫硝溫度窗口具有可行性,進(jìn)一步深入研究尾礦催化劑脫硝機(jī)理對(duì)稀土尾礦高值化利用和新型催化劑研發(fā)具有重要意義.

本文在前期研究基礎(chǔ)上,采用溶膠凝膠法制備了不同Mn、Zr負(fù)載量的Mn/Zr/稀土尾礦脫硝催化劑, 通過(guò)脫硝性能評(píng)價(jià)實(shí)驗(yàn)裝置分析了催化劑脫硝活性,采用H2-TPR,NH3-TPD,XRD,FT-IR等手段研究了Mn、Zr改性稀土尾礦催化劑脫硝過(guò)程,以明確Mn、Zr提高稀土尾礦脫硝活性的理化特性,進(jìn)而揭示Mn/Zr/稀土尾礦催化劑脫硝機(jī)理,從而拓展稀土尾礦NH3-SCR脫硝催化劑的研究范疇,為稀土尾礦高值化利用提供有價(jià)值的借鑒和思路.

1 實(shí)驗(yàn)部分

1.1 脫硝催化劑制備

以白云鄂博稀土尾礦為原料,采用溶膠凝膠法制備稀土尾礦催化劑、(3%,6%,9%)Mn/稀土尾礦催化劑以及6%Mn(0.5%,1%,2%)Zr/稀土尾礦催化劑.稀土尾礦經(jīng)行星球磨機(jī)以400r/min球磨14h,按上述Mn、Zr不同負(fù)載比例加入不同質(zhì)量比的硝酸錳、硝酸鋯溶液,再添加4mL鈦酸丁酯,4mL乙酸,20mL乙醇的混合溶液,用磁力攪拌器攪拌2h,將浸漬后凝膠烘干,再經(jīng)馬弗爐400℃焙燒3h,即獲得實(shí)驗(yàn)用脫硝催化劑.

1.2 實(shí)驗(yàn)儀器

采用采用德國(guó)BRUKER公司D8-ADVANCE型XRD衍射儀分析催化劑物相組成;采用北京彼奧德電子技術(shù)有限公司PCA-1200型紅外分析儀對(duì)催化劑進(jìn)行吸附特性(NH3-TPD)和氧化還原性能(H2-TPR)分析,FT-IR實(shí)驗(yàn)在德國(guó)BRUKER公司vertex-70型紅外光譜儀(含MCT檢測(cè)器和HYPERION高溫顯微紅外附件)上進(jìn)行,采用英國(guó)LinKam公司生產(chǎn)的高溫?zé)崤_(tái)控制樣品環(huán)境溫度,每次試驗(yàn)取適量的樣品粉末壓片后放入原位池的樣品臺(tái)內(nèi),分辨率為8cm-1,掃描次數(shù)32次,波數(shù)范圍為4000～600cm-1.文中所有光譜都已扣除相應(yīng)背景.

1.3 催化劑活性評(píng)價(jià)系統(tǒng)

催化劑性能評(píng)價(jià)系統(tǒng)如圖1所示,由供給配氣系統(tǒng)、催化反應(yīng)裝置、紅外測(cè)試儀器三個(gè)部分組成.反應(yīng)氣體通過(guò)NO/N2、NH3/N2、O2和N2標(biāo)準(zhǔn)鋼瓶經(jīng)減壓閥和質(zhì)量流量計(jì)調(diào)節(jié)傳輸?shù)脚錃庀?總氣體流量為100mL/min.氣體經(jīng)預(yù)熱器及恒溫管道(恒溫管道溫度根據(jù)實(shí)驗(yàn)溫度設(shè)置,最高可設(shè)150℃)通入立式管式爐反應(yīng)器,反應(yīng)器為耐高溫石英玻璃管,內(nèi)徑為8mm,反應(yīng)器溫度調(diào)節(jié)范圍為50～350℃,恒溫時(shí)間為180min,催化劑置于石英纖維棉托底的石英管中段.反應(yīng)后氣體經(jīng)過(guò)濾疏水器、高效粉塵過(guò)濾器進(jìn)入多組分紅外煙氣分析儀檢測(cè).

圖1 催化劑性能評(píng)價(jià)實(shí)驗(yàn)裝置

文中氣體濃度以體積分?jǐn)?shù)()形式表示(NO為500×10-6、NH3為500×10-6、O2為6vol%),實(shí)驗(yàn)GHSV均為30000h-1.NO轉(zhuǎn)化率()計(jì)算如式(1)所示.

式中:為NO轉(zhuǎn)化率,%;[NO]in、[NO]out分別為反應(yīng)器進(jìn)出口NO濃度,×10-6.

2 結(jié)果與討論

2.1 催化劑脫硝活性分析

由圖2可知,Mn的負(fù)載顯著提高了稀土尾礦催化劑的脫硝活性,隨溫度增加催化劑脫硝活性先升高再降低.在200～300℃范圍,6%Mn、9%Mn/稀土尾礦催化劑表現(xiàn)出了較好的脫硝活性,活性幾乎可達(dá)90%以上,后者脫硝活性略?xún)?yōu)于前者.考慮更寬泛的溫度窗口(100～300℃)和Mn負(fù)載量對(duì)催化劑脫硝活性的綜合影響,可以認(rèn)為負(fù)載6%Mn以提高稀土尾礦催化脫硝活性最為合理,Mn負(fù)載量的進(jìn)一步增加,其活性提升作用并不顯著亦不經(jīng)濟(jì).

通過(guò)購(gòu)置、自制、聯(lián)合開(kāi)發(fā)，學(xué)院先后建立了一系列專(zhuān)業(yè)綜合實(shí)訓(xùn)實(shí)驗(yàn)室：嵌入式系統(tǒng)實(shí)訓(xùn)實(shí)驗(yàn)室、DSP實(shí)訓(xùn)實(shí)驗(yàn)室、電力拖動(dòng)自動(dòng)控制系統(tǒng)實(shí)訓(xùn)實(shí)驗(yàn)室、電機(jī)控制系統(tǒng)實(shí)訓(xùn)實(shí)驗(yàn)室、電動(dòng)自行車(chē)實(shí)訓(xùn)實(shí)驗(yàn)室、電力系統(tǒng)綜合自動(dòng)化實(shí)訓(xùn)實(shí)驗(yàn)室、電力系統(tǒng)繼電保護(hù)實(shí)訓(xùn)室、110kV變電站監(jiān)控實(shí)訓(xùn)室。

圖2 摻雜不同比例Mn/稀土尾礦催化劑的脫硝性能

由圖3可知,在150～300℃范圍,6%Mn1%Zr/稀土尾礦催化劑脫硝活性均達(dá)到90%以上,200℃時(shí)脫硝活性最高可達(dá)96%.說(shuō)明Zr的添加在Mn負(fù)載拓寬脫硝溫度窗口的基礎(chǔ)上進(jìn)一步提升了催化劑活性.其原因可能是Mn、Zr的添加使其在稀土尾礦表面具有更高的錳氧化物分散度,催化劑具有更好的氧化還原性能和更弱的吸附氧種類(lèi)[18].

為明確Mn、Zr在稀土尾礦脫硝催化劑中的作用,對(duì)稀土尾礦、6%Mn/稀土尾礦和6%Mn1%Zr/稀土尾礦催化劑進(jìn)行NH3-SCR理化特性研究.

圖3 摻雜不同比例Mn/Zr/稀土尾礦催化劑的脫硝性能

2.2 催化劑氧化還原性能分析

催化劑氧化還原性能(H2-TPR)如圖4所示.從圖中可以看出,在400～450℃催化劑出現(xiàn)了MnO2向Mn2O3的氧化還原峰,675℃對(duì)應(yīng)的峰可能為Fe2O3向Fe3O4的轉(zhuǎn)化,704℃對(duì)應(yīng)的峰可能是FeO向Fe的還原,761℃處的峰可能是Fe3O4向FeO的轉(zhuǎn)化[19-20]. 6%Mn1%Zr/尾礦催化劑的還原峰面積增加更為明顯,氧化還原物種明顯增多,說(shuō)明Mn、Zr改性后稀土尾礦催化劑更強(qiáng)的氧化還原性能對(duì)于提高催化脫硝活性起到了顯著作用.

圖4 催化劑氧化還原性能

2.3 催化劑吸附性能和酸性位分析

圖5展示了催化劑表面酸性位和NH3吸附.由圖可知,在100～200℃范圍Mn、Mn/Zr改性催化劑都出現(xiàn)了弱酸性位點(diǎn)的脫附峰,歸屬為Bronsted酸性位;200～600℃范圍三種催化劑的脫附峰可以劃分為物理吸附在中強(qiáng)酸位點(diǎn)(200～400℃)和強(qiáng)酸位點(diǎn)(400～600℃)上對(duì)氨的連續(xù)解吸,其熱穩(wěn)定性較強(qiáng),稀土尾礦催化劑脫附峰更大,說(shuō)明該催化劑存在更多的Lewis酸性位[21].結(jié)合圖2和圖3可認(rèn)為低溫下催化劑在B酸性位的NH3吸附物種更多的參與到NO還原過(guò)程,L酸性位的吸附態(tài)NH3物種數(shù)量增加對(duì)催化脫硝過(guò)程貢獻(xiàn)較小.

圖5 催化劑表面酸性位和吸附性能

2.4 催化劑物相組成分析

圖6 催化劑XRD圖譜

由圖6可知,三種催化劑均出現(xiàn)了CaF2、SiO2、Fe2O3、CaMgxFex(CO3)、BaSO4、FeS2、CeCO3F、云母和長(zhǎng)石的衍射峰,Fe2O3與CeCO3F、FeS2與BaSO4的衍射峰相鄰或重合可能是由于礦物天然共伴生形成的固溶體所致.ZrO2、錳氧化物衍射峰未檢出是由于其在催化劑表面高度分散或其以非晶態(tài)[18-19]形式所存在所導(dǎo)致,錳氧化物高度分散可增加氧空位數(shù)量,有利于低溫NH3-SCR反應(yīng)的進(jìn)行[22].

2.5 催化劑NH3-SCR脫硝機(jī)理分析

選擇6%Mn1%Zr/稀土尾礦催化劑,分析催化劑NH3-SCR催化脫硝機(jī)理.

2.5.1 催化劑吸附NH3性能分析 為進(jìn)一步明確催化劑表面酸性位點(diǎn),在50～300℃條件下進(jìn)行了6%Mn1%Zr/稀土尾礦催化劑表面NH3吸附熱穩(wěn)定性分析,結(jié)果如圖7所示.1309cm-1[23]處NH3物種脫氫而產(chǎn)生的-NH2物種和1579cm-1[24]處Lewis酸性位點(diǎn)吸附的NH3物種在150℃以下消失,而1326cm-1[25]處NH3物種脫氫產(chǎn)生的-NH2物種和1695cm-1[26]處Bronsted酸性位點(diǎn)吸附的NH4+物種在200℃左右消失.1488cm-1[27]處Bronsted酸性位點(diǎn)吸附的NH4+物種在275℃以下可穩(wěn)定存在.在250～300℃溫度范圍內(nèi),1302cm-1[23]可能是NH3物種脫氫而產(chǎn)生的-NH2,且隨著溫度的升高而消失, 1700cm-1[28]為Bronsted酸性位點(diǎn)上NH4+的N-H對(duì)稱(chēng)彎曲振動(dòng)且穩(wěn)定存在.說(shuō)明在150～300℃溫度范圍,可能參與SCR脫硝反應(yīng)的NH3吸附產(chǎn)物是NH4+物種、-NH2物種.

圖7 催化劑表面吸附NH3的熱穩(wěn)定性分析

從圖8可以看出,NH3通入5min后,催化劑表面出現(xiàn)的1270cm-1[29],1334cm-1[27]處吸附峰歸屬為L(zhǎng)ewis酸位點(diǎn)配位吸附NH3物種,1479cm-1[30]和1676cm-1[26]為Br?nsted酸位點(diǎn)吸附的NH4+物種.NH3通入20min后NH4+吸附峰的消失,說(shuō)明此處該物質(zhì)吸附并不穩(wěn)定.當(dāng)NH3通入40～50min后, 出現(xiàn)了1465cm-1處Br?nsted酸位點(diǎn)吸附NH4+[31]、1559cm-1處NH3物種由于脫氫反應(yīng)而生成的中間產(chǎn)物-NH2[32]和1620cm-1處L酸性位點(diǎn)吸附NH3[33]. 1620cm-1、1270cm-1和1334cm-1處吸附物種經(jīng)N2吹掃后依然存在或峰強(qiáng)變化較弱,說(shuō)明這些物種吸附較為牢固.

圖8 催化劑表面 NH3吸附的原位紅外光譜

2.5.2 催化劑吸附NO+O2性能分析 圖9為6%Mn1%Zr/稀土尾礦催化劑在50～300℃溫度區(qū)間內(nèi)NO+O2吸附的熱穩(wěn)定性原位紅外光譜圖.如圖所示,在50～150℃溫度范圍內(nèi),1380cm-1[34]處催化劑表面吸附的NO3-、1583cm-1[24]處橋式硝酸鹽和1349cm-1[35]單齒亞硝酸鹽物種隨溫度增加而逐漸消失.在175～250℃溫度范圍內(nèi),出現(xiàn)了1415cm-1[36]處單齒硝酸鹽、1489cm-1[26]處單齒亞硝酸鹽、1547cm-1[8]和1646cm-1[37]處雙齒硝酸鹽吸附峰,表明該溫度段三種物質(zhì)較為穩(wěn)定.在100℃以上,出現(xiàn)了1498cm-1[38]和1390cm-1[37]處的線性亞硝酸鹽吸附峰吸,說(shuō)明該物質(zhì)在相應(yīng)溫度段可穩(wěn)定存在.以上結(jié)果表明,在在150～300℃溫度范圍,可能參與SCR脫硝反應(yīng)的NO吸附產(chǎn)物是單齒硝酸鹽、單齒亞硝酸鹽、雙齒硝酸鹽和線性亞硝酸鹽類(lèi)物種.

圖9 催化劑表面吸附NO+O2的熱穩(wěn)定性分析

圖10 催化劑表面 NO+O2吸附的原位紅外光譜

圖10為200℃時(shí)6%Mn1%Zr稀土尾礦催化劑表面NO+O2吸附隨時(shí)間變化的原位紅外光譜圖,從圖中可以看出,通入NO+O25min后,出現(xiàn)了1403cm-1[25],1500cm-1[33],1605cm-1[39]的紅外吸附峰,其中1403cm-1為連二次硝酸鹽-N2O22-,且隨通入時(shí)間增加及N2吹掃后仍然穩(wěn)定存在,1500cm-1出現(xiàn)的單齒硝酸鹽物種和1605cm-1出現(xiàn)的雙齒硝酸鹽物種隨通入時(shí)間增加而逐漸消失.隨通入時(shí)間增加,出現(xiàn)了1665cm-1、1578cm-1[33]處雙齒硝酸鹽物種和1479cm-1[27]處NO2-物種并穩(wěn)定存在,在1609cm-1[40]處出現(xiàn)了較為不穩(wěn)定的氣態(tài)NO2分子.

2.5.3 催化劑脫硝機(jī)理 為進(jìn)一步明確6%Mn1%Zr/稀土尾礦催化劑在活性最高溫度200℃時(shí)的NH3-SCR催化脫硝機(jī)理,開(kāi)展了催化劑吸附NH3、NO+O2反應(yīng)的順序紅外實(shí)驗(yàn).

圖11是催化劑預(yù)吸附50min NO和O2后再通入NH3的原位紅外光譜.由圖可知,催化劑吸附NO和O2后,出現(xiàn)了橋式硝酸鹽(1265cm-1)[26]、單齒硝酸鹽(1356cm-1,1500cm-1)[33,37]和雙齒硝酸鹽(1693cm-1)[23].NH3通入后,1500cm-1處的單齒硝酸鹽、雙齒硝酸鹽峰和橋接硝酸鹽的消失說(shuō)明三個(gè)物種與NH3的吸附物種發(fā)生了反應(yīng).分析NH3通入后的吸附峰變化,與NO吸附產(chǎn)物發(fā)生反應(yīng)的NH3吸附物種應(yīng)該是:出現(xiàn)較晚的1706cm-1[41]、1455cm-1[31]處B酸性位吸附的NH4+、1559cm-1[32]處氨基物種脫氫所產(chǎn)生的-NH2物種以及逐漸減弱的1623cm-1[42]為L(zhǎng)酸性位點(diǎn)吸附的NH3.

由圖12可見(jiàn),催化劑預(yù)吸附50min NH3后, 1324cm-1[36]和1643cm-1[43]處吸附峰為B酸性位點(diǎn)吸附的NH4+物種,1559cm-1[32]處吸附峰為氨基物種脫氫所產(chǎn)生的-NH2物種,這兩類(lèi)物種在通入NO+O2后消失,表明其與NO/O2吸附物種發(fā)生了反應(yīng). 1421cm-1[36]處單齒硝酸鹽物種穩(wěn)定存在,表明該物種不與NH3吸附物質(zhì)反應(yīng).通入NO+O230min后,出現(xiàn)了1318cm-1[38]處氣態(tài)NO2不對(duì)稱(chēng)拉伸振動(dòng)和1524cm-1[44]處雙齒硝酸鹽峰,說(shuō)明這兩個(gè)物種是參與了和NH4+物種、-NH2物種的反應(yīng)后出現(xiàn)的,存在“快速SCR”反應(yīng).

圖12 催化劑吸附NH3-NO+O2的原位紅外光譜

綜合圖7至圖12分析結(jié)果,6%Mn1%Zr/稀土尾礦催化劑在200℃時(shí)NH3-SCR脫硝過(guò)程可歸納為NH3和NO在催化劑表面均有吸附和轉(zhuǎn)化產(chǎn)物,參與NH3還原NO過(guò)程的NH3吸附物種是大量的NH4+、少量的-NH2物種和吸附態(tài)NH3,與之反應(yīng)的NO吸附物種是部分單齒硝酸鹽、橋式硝酸鹽、雙齒硝酸鹽和氣態(tài)NO2,催化脫硝反應(yīng)過(guò)程遵循E-R機(jī)理和L-H機(jī)理共同作用.

3 結(jié)論

3.1 以白云鄂博稀土尾礦為原料,分析了溶膠凝膠法制備的Mn/Zr/稀土尾礦催化劑NH3-SCR脫硝活性,Mn、Zr負(fù)載顯著提高了稀土尾礦催化劑脫硝活性.在150～300℃溫度范圍內(nèi),6%Mn1%Zr/稀土尾礦催化劑脫硝活性可達(dá)90%以上,200℃脫硝活性為96%.

3.2 稀土尾礦負(fù)載Mn、Mn/Zr后,ZrO2、錳氧化物在催化劑表面的高度分散增加了表面氧空位,同時(shí)提高了表面B酸性位點(diǎn)及吸附物種數(shù)量,增強(qiáng)了催化劑氧化還原性能,有利于低溫下NH3-SCR脫硝反應(yīng)的進(jìn)行.

3.3 6%Mn1%Zr/稀土尾礦催化劑NH3-SCR脫硝過(guò)程主要由NH4+、-NH2物種、吸附態(tài)NH3和單齒硝酸鹽、橋式硝酸鹽、雙齒硝酸鹽、氣態(tài)NO2的反應(yīng)完成,該脫硝機(jī)理遵循E-R機(jī)理和L-H機(jī)理共同作用.

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A Study of Mn/Zr modification for NH3-SCR denitration mechanism of rare earth tailings.

JIAO Kun-ling1,2, JIAO Xiao-yun1, LIU Jia-jie1, LI Na1, HOU Li-min1, WU Wen-fei1,2*

(1.School of Energy and Environment, Inner Mongolia University of Science and Technology, Baotou 014010, China；2.Inner Mongolia Autonomous Region Key Laboratory of Efficient and Clean Combustion, Baotou 014010, China)., 2023,43(11)：5655～5662

Mn and Mn/Zr modified rare earth tailings-based NH3-SCR catalysts were prepared using the sol-gel method. The catalysts were characterized using a catalyst activity evaluation system, along with H2-TPR, NH3-TPD, XRD, and DRIFT techniques, to investigate the denitration process and reaction mechanism. The results showed that the denitration activity of the Mn and Mn/Zr modified rare earth tailings catalysts was significantly enhanced, with a denitration activity of 96% achieved at 200°C for the 6%Mn1%Zr/rare earth tailings catalyst. The modified catalysts exhibited increased oxygen vacancies and acidic sites on the surface, as well as a higher adsorption capacity. The increase in reducible surface area of the catalysts contributed to the improvement of their redox performances. The reaction between NH4+and gaseous NO2on the acidic sites of the catalysts followed the E-R mechanism, while the reactions between NH4+and monodentate and bidentate nitrate species followed the L-H mechanism.

rare earth tailings；Mn、Zr modified；catalysts；NH3-SCR；denitration mechanism

X511

A

1000-6923(2023)11-5655-08

焦坤靈(1984-),男,內(nèi)蒙古赤峰人,副教授,博士,主要從事燃煤煙氣污染控制和稀土尾礦脫硝催化劑研究.發(fā)表論文10余篇. jiaokunling@imust.cn.

焦坤靈,焦曉云,劉佳杰,等.Mn/Zr改性稀土尾礦催化劑NH3-SCR脫硝機(jī)理分析 [J]. 中國(guó)環(huán)境科學(xué), 2023,43(11):5655-5662.

Jiao K L, Jiao X Y, Liu J J, et al. A Study of Mn/Zr modification for NH3-SCR denitration mechanism of rare earth tailings [J]. China Environmental Science, 2023,43(11):5655-5662.

2023-03-13

內(nèi)蒙古自治區(qū)自然科學(xué)基金重大項(xiàng)目(2019ZD13);內(nèi)蒙古自治區(qū)高?；究蒲许?xiàng)目(2022098)

* 責(zé)任作者,教授,wwf@imust.edu.cn