201121640 六、發明說明： 【發明所屬之技術領域】 本發明係一種選擇性光催化還原氮氧化物之方法，該 發明制TiG2㈣光觸媒，並以^卜光作為㈣同時利用 氨作為還原劑’來對氧化物進行選擇性光催化還原反 應，將之還原成減與水’並達到減少氮氧化物排放之目 的。 本發明之方法可於低耗能的情况下，應用於處理燃料 燃燒（如火電廠、石油煉製業）、非燃料燃燒（如垃圾焚化 爐、露天燃燒）、工業製程等固定式污染源所排放之I氧 化物中。 【先前技術】 氮氧化物常見於工廠所排放之煙道氣體中，其主要污 染源係來自於燃燒化石能源，以及在產品製程中高溫燃燒 的副產物。隨著產業發展’對化石能源的需求持續成長， 進而使得高溫燃燒後NOx排放量亦持續升高，因此處理燃 燒後尾氣之放’將是空污防治的重大課題之一。繁 於氮氧化物生成方式之不同，氮氧化物控制技術發展亦漸 趨多元化，依氮氧化物之生成原理及處理階段，可將該等 處理技術分成三大類：燃燒前處理（燃料預先處理）、燃燒 中處理（製程控制、改善）與燃燒後處理（管末處理）。於燃 燒後處理中，一般常用乾式處理技術包含選擇性催化還原 技術（Selective Catalytic Reduction，SCR)、選擇性非催化 還原技術（Selective Non-catalytic Reduction，SNCR)、非選 201121640 擇丨生催化還原技術（Non-selective Catalytic Reduction， NSCR)等，比較上述處理技術可知，選擇性非催化還原技 術需在高溫下操作’而非選擇性催化還原技術則會有低選 ·.擇率的問題，因此一般ί業上常使用選擇性催化還原技術 . 來處理固疋式污染源所排放之氮氧化物。然而選擇性催化 〜 還原技術需將操作溫度升高至573Κ以上，以利氮氧化物之 還原。 . 選擇性催化還原技術（Selective Catalytic Reduction， • SCR) ’是指利用氮氧化物與還原劑於高溫流經觸媒時所進 -行之選擇性還原反應，來減少氣相氮氧化物的排放。197〇 -年代日本最早應用選擇性催化還原技術，來處理鍋爐所產 T ·生之氮氧化物。到1980年代歐洲及美國已廣泛將選擇性催 化還原技術用於固定式排放污染源（鍋爐及渦輪），以將所 排放之氮氧化物還原成氮氣，由於選擇性催化還原技術用 於移除固定排放汙染源中之氮氧化物的效果彰顯，該技術 也一直延用至今。固定污染源所排放之廢氣中—般常見硫 · 氧化物（S〇x)、鹵素以及氮氧化物(N0X)等，由於鹵素以及 • 硫氧化物容易毒化SCR所用觸媒（例如：V2〇5-W〇3/Ti〇24 ν2〇5-ΜοΟ/Π〇2)，故在設計廢氣處理程序時，常將去除 鹵素及硫氧化物之設備設置於SCR之上游，以在進行說氧 化物處理前，先將可能毒害SCR所用觸媒之_素及硫氧化 物去除。然而脫硫程序常於453K以下之溫度操作，若欲於 脫硫設備之下游進行該排放源氣體内所含之氡氧化物之還 原反應’則須將溫度升高至573K以上，以利SCR程序進行 去除亂乳化物之反應。故必須再次加溫進料氣體，使溫产 201121640 升高至SCR程序之反應蕰度，故將面臨耗費能源的問題。 近年來工業界除了持續改善SCR之效能外’也紛紛投 入低溫選擇性觸媒還原技術之研發工作，希望藉由改變 SCR程序以及觸媒製備的方式，來降低脫氮反應時所需之 環境溫度’以達到節省SCR升溫加熱所造成的成本負擔之 目的。 為了處理燃燒石化能源以及產品生產製程中高溫燃燒 所產生的氮氧化物’過去常見的方法包括以氮氧化物吸附 (台灣專利1302475 ;台灣專利422729)或還原（台灣專利 410170)的方式’來降低氮氧化物的排放量。然而使用氮 氧化物吸附的方式需要定期更換吸附劑，且以往使用氮氧 化物還原的方法必須在高溫下進行，仍有能源消耗的問 題。 另一方面，光化學反應一般可分成直接光解（direct photolysis)與間接光解(indirect photolysis)兩種。直接光解 係指物質吸收光能達到激發態後，物質本身繼續進行化學 反應而分解；間接光解則是反應系統中某一分子吸收光能 後，又與另一分子進行化學反應。此外，若在反應的進行 過程中，加入不參與反應但具有加速光反應作用的光觸媒 時，則此類光化學反應可稱為光催化反應 (photocatalysis)。在光催化反應的進行中需依賴觸媒的參 與，藉此降低反應分子的活化能，或提供足夠的表面活性 位置以增加觸媒表面反應濃度，並進而提高反應速率。一 般而言，具備光敏感性(photosensitive)的光觸媒皆屬金屬 半導體材料，利用半導體材料的特定光催化作用，即可進 201121640 .行異相催化反應。當光觸媒接受光能量照射時，若光源產 生之光子能量大於半導體能帶間隙(Eg)時，電子會由價電 帶（valance band)激發至導電帶（conduction band)而形成電 ‘ 子·電洞對，此時由於光子能量不斷輸入，電子電洞對會 因而持續產生，在碰撞機率提高之下，電子與電洞開始發 ' 生重組(recombination)的現象，以抵消輸入的光能量，或 是移動至半導體的表面與電.子提供者（electron donor)和電 子接受者(electron acceptor)發生氧化還原反應。 φ 就光催化還原反應而言，Teramura等人（2003)已在操 …: 作溫度323K下探討選擇性光催化觸媒還原反應之反應機 制，該研究係運用傅立葉轉換紅〜外線光譜儀（F〇urier Transform Infrared Spectroscopy，FT-IR)來偵測光催化還 原的過程中’ Ti〇2表面所生成之中間產物，藉以得知吸附 於Ti〇2表面之反應物以及光催化還原之關係，進而推測光 催化-SCR之反應機制。該研究指出反庳進行時會吸附 於Ti〇2之活性位置（Ti4+-〇-Ti)上，在經過紫外光催化後， .φ 於活性位置上形成ΝΗ2 ·自由基，該自由基易與>|〇反應形 成亞硝醯胺（nitrosamide) ’該中間產物（亞确醯胺）會進一 步轉換成氮氣和水’並從活性位置上脫附，最後，經過還 原的活性位置（Ti )會與氧氣進行氧化反應，經過氧化後 的活性位置會再二欠活化成Ti4+，以利後續反應的進行。此 文獻中雖已揭示利用光催化反應於常溫下進行氮氧化物之 還原，然此於文獻中所揭示使用300 W的高壓汞燈來進行 氤氧化物之還原處理，仍有能源耗費的問題。 雲於上述，本發明人對於如何以較低能源來處理氣氧 201121640 化物之製程進行廣泛研究，並發現藉由使用約而 光;kf來進彳了光催化反應，可以在低能_耗 、 虱，，物之處理效果，並發現將本發明之選擇性光1 ，氮氧化物之方法’應用於固定式污染源所排放之 ^的處理過財，可在較低溫、低耗能下進行燃燒煙道中 =乳化物㈣原，進而相減低能源之目的，因 本發明之新穎功效。 受成 【發明内容】 本發明爲達到上述目的所採用之技術手段，係 擇性觸媒還原程序之反應特 '、用選 率紫外光燈管，來作為光催化反應及:功 =氨作為還’《岐氡化物進行選擇化= 放之目的。 並精此達到減少眺化物排 依據本發明’係提供~~種選摆神杰 之方法，包括使_2作為==還原氣氧化物 以及利用氨作為還原劑下，於5_5G。、外光作為光源 3.73 mW/〇m^^^T , ' 2·37- 還原反應，將I氧化物還原錢氣與水仃選擇性光催化 依據本發明之方法，其中作為還 働ppmv，且=光之光源所使用之波=辰在产2 ^00nm之範圍内的料光，該紫外光波奶 最佳應用波長。 依據本發明之方法’其中紫外光之光源可使用紫外光 201121640 燈管，特別是在使用low左右的紫外光燈管即足以發揮本 發明之效果。 …依據本發明之方法，其可處理的氮氧化物濃度可高達 600 ppmv，因而可用於燃燒煙道中的氮氧化物之處理，該 發明之最佳氮氧化物處理濃度為2〇〇 ppmv至550ppmv。 • 依據本發明之方法，可於進料氣體中同時通入氧氣， 藉由氧氣對經還原之二氧化鈦進行氧化作用，而可再生二 氧化鈦之活性位置’以供下一循環之氮氧化物光催化還原 鲁 反應使用.。其中氧氣的漢度可落在1.0至3.0體積％之範圍 内。 ·— 本發明又與一種處理燃燒煙道中排放之廢氣之方法有 關，其包括下列步驟··（1)在180°C以下之溫度下，使廢氣 通過脫硫設備’去除排放廢氣中所含之齒素及硫氧化物； 及（2)使經過步驟（1)處理之氣體’以氨作為還原劑，而在 5-50°C之操作溫度及2.37-3.73 mW/cm2之光強度的操作條 件下，通過光催化反應器，使排放廢氣中之氮氧化物進行 -· 選擇性光催化還原反應，還原成氮氣與水；其中該光催^ •反應器包括有：一個内含圓管形石英管的環狀玻璃容器； 一可發射紫外光之燈管，該燈管係置於該圓管形石英管内 部，以及二氧化鈦觸媒，其係被覆於該圓管形石英管之外 部；藉此可利用該可發射紫外光之燈管朝該石英管外側照 射紫外光，進而激發被覆於該燈管外部的二氧化鈦觸媒了 而可在氮氧化物通過該光催化反應震置時，進行氮氧化 的還原反應。 本發明在應用於處理燃燒煙道中排放的廢氣之方法中 201121640 時，所運用之脫硫裝置為習知脫硫裝置，故於本發明中將 不再贅述。 藉由本發明之方法來對氮氧化物進行還原反應，不僅 能有效處理固定式污染源所排放之氮氧化物，更能在常溫 下進行氮氧化物之還原反應，以達到減少耗能以及節能減 碳的目的。 【實施方式】 依據本發明的選擇性光催化氮氧化物之方法及裝置， 主要係利用二氧化鈦作為光觸媒，以紫外光作為激發光 源，並以氨(NH3)作為還原劑，來對氮氧化物(NOx)進行還 原反應，以將NOx還原成氮氣及水。 依據本發明之方法，其所通入之作為還原劑的NH3， 將會吸附於Ti02之活性位置（Ti4+-0-Ti)上，於經過紫外光 催化後，於該活性位置上形成NH2 ·自由基並使Ti4+還原 成Ti3+，而該NH2 .自由基係易與NO反應而形成亞硝醯胺 (nitrosamide)，並進一步轉換成氮氣和水後，從活性位置 上脫附；最後，被還原的二氧化鈦活性位置（Ti3+)，將會 與氧氣進行氧化反應，再次被活化成Ti4+，而重複進行上 述的氮氧化物還原反應之循環。以本發明方法及裝置所進 行之氮氧化物的還原反應，可得到高達約50%的NO還原 效率及高達約90%的沁選擇率。 本發明將以下列實施例具體來說明本發明之方法及裝 置，惟該等實施例僅係用以例示說明之目的’而並非用於 侷限本發明之範圍。 10 201121640 於本發明之下列實施例中，對於反應進料之溫度與濕 度條件’乃透過溫度控制單元與濕度控制單元等製程裝置 來加以控制’並依據NO還原之實際需要而加以控制，並 調整光觸媒催化反應裝置之光強度。在本發明之選擇性光 催化還原氮氧化物之實施例中，經由光催化還原方法來還 ' 原NO所生成之產物’係經由氣相層析儀7895 及NOx分析儀（Eco以州·％ CLD62)加以量測並記錄，以作 為NO還原反應效率及N2生成之參考指標。 • 在本發明之下列實施例中，其所用裝置主要係由流動 式環狀光反應器、可變電壓器、穩壓器、循環式恒溫水 槽、氣體供應單元、濕度控制單元、NOx、N2及NW分析 檢測裝置以及流量監控設備組合而成。此光反應器農置可 以用於光觸媒催化還原NOx反應。該光反應器裝置包括— 内含圓管形石英管之環狀玻璃容器；一置於該圓管形石英 管内部的可發射紫外光之燈管；以及一被覆於該圓管形石 英管之外部的二氡化鈦觸媒，藉此可利用該可發射紫外光 -·之燈管來朝玻璃管容器外側照射紫外光，進而激發被覆於 .該燈管外部的二氡化鈦觸媒，以在氮氧化物通過該光催化 反應裝置時’進行氮氧化物的還原反應。 實施例1 本發明之此實施例的選擇性光催化還原氤氧化物之方 法如下.將光觸媒被覆於該圓管形石英玻璃管外部，並調 整光源以對準該光觸媒表面’以乾淨He通入該光反應器 中，以測漏液檢測各閥件接口及反應器接縫處及進出口間 有無漏氣後，打開溫度控制系統、氣相層析儀及N〇x分析 201121640 儀待儀器系統達平衡，再通入實驗所用之進料氣體 、ΝΑ、〇2)，並於反應開始前將反應器溫度控制在^ C，將壓力維持在常壓，並調整濕度。反應前先進行三次 取樣=析’以氣密針每次取出反應氣體，以氣相層析儀及 Ν0Χ刀析儀，偵測各項反應物的初始濃度並計算其平均 值。實驗開始時打開實驗所用之燈源，約每5分=光催化 ，以氣密針自取樣σ取樣，注人氣相層析儀及肌分析儀 來分析反應氣體及產物之濃度餘平均值，韻反應是否 達：二若未達平衡則待一段時間後持續對出口端氣體進 仃濃度里測，直至各反應物之出口濃度達到 錄该貫驗所得數據。待反應完成後，通 ^ „ , _ 〜不含揮發性有機 物的南濕度氣體’以清除吸附於觸媒表面的殘存物質。 =實^例中，以波長365隱之紫外光關作為 直接先解貫,社光源，從職以得的ν〇氣體濃 度皆十分穩定，故N(m體受紫外光光解的㈣可予以忽 略。本發縣要係湘紫外规在不同操 進行 匕觸媒還原反應’並顯示N〇還原效率細 ^光強度以外的反應條件維持固 度(5〇〇Ppmv)、NH3濃度(550ppmv)、氧氣濃 進：氣體濕度(〇，、反應滯留時間(1.9‘^ 被覆罝(0.47g))，並以N〇x分析儀以及氣相 糸 Ν2^Ν2〇之㈣4 \ 下的選擇性光催化觸媒還原氮氧化物之方$ ν 隨時間之濃度變化如圖1所示，由實驗社坦中’ Ν0及2 、、’Q果可知，光反應 12 201121640 器中NO濃度會隨著反應時間增加而下降，此時被反應掉 的NO會於該程序中被轉換成^]，因此n2的濃度會隨著反 應時間的增加而上升，在反應時間約為六分鐘時，NO以 及A的濃度會逐漸穩定趨向固定值。圖2為在不同光強度 下選擇性進行光催化觸媒還原氮氧化物之方法中NO、 N〇2、N2以及N2〇之濃度變化，當光強度從2.37mW/cm2提 昇至:3.73 m\V/cm2時’ NO殘存濃度會從290.30ppmv下降至 225.27ppmv ’所反應之no氣體會於該方法中轉化成]^2以 及少量的>1〇2及1^2〇’隨著光強度(2.37111〜/(：1112上升至3.73 mW/cm2)上升而可生成 166.23ppmv至 229.98ppmv 之 N2， N〇2及N2〇則會分別由3 j2ppmv及15.04ppmv增加至 、6.96ppmv及24.52ppmv。由此實驗結果可知，在光催化還 原NO的過程中所產生之氣體包含有no、n〇2、n2以及 N2〇 ’然而大部分的NO會於光催化的過程中轉化成n2，以 達到降低NO排放量的目的。 ^將圖3中之數據進—步計算後，可得入射紫外光強度 ，應對NO去除效率及n2選擇率之影響如圖3所示。從圖中 賢驗，果得知’光催化還原NO之轉化率會隨著入射光強 ^的提高而呈線性的增加趨勢，而N2選擇率在各種光強度 t射下皆大約維持在9〇%左右。而造成NO去除效率隨光強 α ~加而上升的原因是’當提高紫外線光強度時可使光觸 媒叉光照射激發的程度變大’並造成電子_電洞對生成速 度加快’進而加速光觸媒表面氧化還原的速度。此外由本 貫驗之線性結果發現，本反應在較高光強度之下的反應行 為’並不會受到明顯之電子-電洞再結合現象的抑制，推 13 201121640 測可能與光觸媒的表面更新率有關；因為連續式反應器在 操作的過程中不斷地提供反應物，進而使得有^碰^機率 提高後，電子與電洞的再結合機率即可能因此而降低。因 此，推測該反應程序應可承受較高的紫外光強度照射。整 體而言2當選擇性光僅化觸媒還原反應之光強度二”昇至3二 . mW/cm2時’將可達到5〇%_〇去除率，且反應生成的 選擇率亦可維持在9〇% ’相較之下本發明之方法所耗費之 能量係遠低於以往在高溫下所進行之NO還原程序，此一 結果足以證明以本發明之方法處理NO效果相當優異。 根據貫驗之結果顯示，若在進料中含有過量氧氣的情籲 況下，光催化還原方法中之速率決定步驟為亞_胺轉^ 成氮氣及水的過程，若進料中之氧氣含量低於2%，反應 速率決定步驟則為光觸媒活性位置之活化速率。選擇性^ 催化觸媒還原程序在不同氧氣進料濃度下之^^〇去除效率 係如圖4所示，由圖中可知當氧氣濃度低於丨體積％時， NO的還原效率會隨著氧氣濃度增加而增加；若氧氣濃度 高於1體積％時’ NO還原效率則趨於平緩；因此在以本^ 明之方法進行氮氧化物還原反應時，應將氧氣濃度控制^ 1體積％以上，以重新氧化並再生二氧化鈦活性位置，以 . 利後續反應之進行。 圖5和圖6分別為不同NH3&N〇進料濃度下之N〇去除 速率，根據上述所描述之反應機制可知，本發明方法主要 是藉由NO與吸附於Ti〇2活性位置上之Μ%反應來生成， 因此反應速率主要由NH3於活性位置上之吸附量而定；由 圖5可知NO還原速率會隨著^^%初始濃度上升而上升，這 14 201121640 是由於通入反應器中NH3濃度越高，將會使得較多ΝΑ分 子吸附於活性位置上，經光催化後提昇N〇還原反應·，然 ，而當NH3初始濃度高於300ppmv時，NO還原速率將不再隨 . 著ΝΑ濃度增加而顯著的上升，該上升幅度反而逐漸趨於 平緩，這是由於NH3吸附量除了會受NH3濃度影響外，亦 會受限於Ti〇2的活性位置數量，當通aNh3氣體度高於 -300ppmv時’ Ti〇2表面之活性位置已不足以吸附該濃度下 之NH3，因此無法進一步提昇NO還原速率。圖6為]SiO進料 # 濃度對NO去除效率之影響，NO去除效率會隨著NO進料濃 度上升而升高，並逐漸趨於平緩，這是由於在mNO濃度 · 時，該反應之反應速率主要受限於NO氣體分子質傳至觸 媒表面速率’因此當NO進料濃度提昇時，氣體分子質傳 至觸媒表面之速率提昇，使得NO還原效率亦隨之上升； 而當進料NO濃度高於500ppmv時，NO分子質傳至觸媒表 面之速率已不再影響還原速率，因此NO還原速率不再隨 著NO濃度增加而上升。 41 由上述試驗結果可知’依據本發明之選擇性光催化還 原氮氧化物之方法可於低溫且低耗能下，有效地使氣體中 之氮氧化物還原成氮氣及水，極具有產業上利用價值。 [發明功效] 依據本發明之選擇性光催化還原氮氧化物之方法，可 被應用於燃燒煙道中’並於廢氣處理程序中的去除廢氣中 之鹵素及硫氧化物的步驟之後進行。由於依據本發明的選 擇性光催化還原氮氧化物之方法’可於低耗能之條件下， 進行氮氧化物之還原’故在應用於處理燃料燃燒（如火力 15 201121640 發電廠、石油煉製廠）、非燃料燃燒（例如垃圾焚化爐、露 天燃燒）、工業製程等固定式污染源所排放之氮氧化物 時，除了可降低氮氧化物排放量以外，亦可以降低能源的 使用量進而降低因能源消耗所產生之二氧化碳排放等問 題，其對於環保及節能減碳具有相當效益。201121640 VI. Description of the Invention: [Technical Field] The present invention is a method for selectively photocatalytic reduction of nitrogen oxides, which comprises a TiG2 (four) photocatalyst, and uses (b) as a reducing agent The oxide undergoes a selective photocatalytic reduction reaction, which is reduced to reduce water and achieve the purpose of reducing nitrogen oxide emissions. The method of the invention can be applied to the treatment of fuel burning (such as thermal power plant, petroleum refining industry), non-fuel combustion (such as waste incinerator, open burning), industrial process and other fixed pollution sources under low energy consumption. In the I oxide. [Prior Art] Nitrogen oxides are commonly found in flue gases emitted by factories. The main sources of pollution come from burning fossil energy sources and by-products of high temperature combustion in product processes. With the development of the industry, the demand for fossil energy continues to grow, and the NOx emissions continue to rise after high-temperature combustion. Therefore, the treatment of exhaust gas after combustion will be one of the major issues in the prevention and control of air pollution. Due to the different ways of nitrogen oxides generation, the development of nitrogen oxides control technology has become more diversified. According to the formation principle and processing stage of nitrogen oxides, these treatment technologies can be divided into three categories: pre-combustion treatment (fuel pre-treatment). ), combustion treatment (process control, improvement) and post-combustion treatment (end treatment). In post-combustion treatment, commonly used dry treatment technologies include Selective Catalytic Reduction (SCR), Selective Non-catalytic Reduction (SNCR), and non-selective 201121640 (Non-selective Catalytic Reduction, NSCR), etc., comparing the above treatment techniques, it can be seen that selective non-catalytic reduction technology needs to be operated at high temperature. Instead of selective catalytic reduction technology, there is a problem of low selectivity and selectivity. The selective catalytic reduction technology is often used in the industry to treat nitrogen oxides emitted by solid waste sources. However, the selective catalysis ~ reduction technique requires an increase in operating temperature above 573 , to facilitate the reduction of nitrogen oxides. Selective Catalytic Reduction (SCR) is a selective reduction reaction that uses nitrogen oxides and reducing agents to flow through a catalyst at high temperatures to reduce NOx emissions. . 197 〇 - The first application of selective catalytic reduction technology in Japan to treat nitrogen oxides produced by boilers. By the 1980s, selective catalytic reduction technology was widely used in Europe and the United States for stationary emission sources (boilers and turbines) to reduce the emitted nitrogen oxides to nitrogen, due to the selective catalytic reduction technology used to remove fixed emissions. The effect of nitrogen oxides in pollution sources is evident, and the technology has been extended to this day. Among the exhaust gases emitted by fixed sources, sulfur, oxides (S〇x), halogens, and nitrogen oxides (N0X) are commonly used. Due to halogens and sulfur oxides, it is easy to poison the catalyst used in SCR (for example, V2〇5- W〇3/Ti〇24 ν2〇5-ΜοΟ/Π〇2), so when designing the exhaust gas treatment program, the equipment for removing halogens and sulfur oxides is often placed upstream of the SCR to perform the oxide treatment. First, remove the catalyst and sulfur oxides that may be harmful to the SCR. However, the desulfurization procedure is usually operated at a temperature below 453 K. If the reduction reaction of niobium oxide contained in the source gas is to be carried out downstream of the desulfurization equipment, the temperature must be raised above 573 K to facilitate the SCR procedure. The reaction for removing the emulsified emulsion is carried out. Therefore, it is necessary to warm the feed gas again, so that the temperature production 201121640 rises to the reaction temperature of the SCR program, so it will face the problem of energy consumption. In recent years, in addition to continuously improving the performance of SCR, the industry has also invested in the research and development of low-temperature selective catalyst reduction technology. It is hoped that by changing the SCR program and the way of catalyst preparation, the ambient temperature required for the denitrification reaction can be reduced. 'To achieve the purpose of saving the cost burden caused by SCR heating. In order to deal with the combustion of petrochemical energy and the production of nitrogen oxides from high-temperature combustion in the production process, the common methods used in the past include the reduction of nitrogen oxides (Taiwan Patent 1302475; Taiwan Patent 422729) or reduction (Taiwan Patent 410170). Nitrogen oxide emissions. However, the method of adsorbing nitrogen oxides requires regular replacement of the adsorbent, and the conventional method of reducing nitrogen oxides must be carried out at a high temperature, and there is still a problem of energy consumption. On the other hand, photochemical reactions can generally be divided into direct photolysis and indirect photolysis. Direct photolysis means that after the absorbed light energy reaches the excited state, the substance itself continues to undergo chemical reaction and decomposes; indirect photolysis is the reaction of one molecule in the reaction system with another molecule. Further, if a photocatalyst which does not participate in the reaction but has an accelerated photoreaction is added during the progress of the reaction, such a photochemical reaction may be referred to as photocatalysis. In the progress of the photocatalytic reaction, it is necessary to rely on the participation of the catalyst, thereby reducing the activation energy of the reaction molecule, or providing a sufficient surface active site to increase the reaction concentration on the surface of the catalyst and thereby increase the reaction rate. In general, photosensitized photocatalysts are metal semiconductor materials, and the specific photocatalysis of semiconductor materials can be used to enter heterogeneously catalyzed reactions. When the photocatalyst is irradiated with light energy, if the photon energy generated by the light source is greater than the semiconductor energy band gap (Eg), the electron is excited by a valance band to a conduction band to form an electric hole. Yes, at this time, due to the continuous input of photon energy, the electron hole pair will continue to be generated. Under the collision probability, the electrons and holes begin to undergo recombination to offset the input light energy, or The surface moved to the semiconductor undergoes a redox reaction with an electron donor and an electron acceptor. φ In terms of photocatalytic reduction, Teramura et al. (2003) have investigated the reaction mechanism of selective photocatalytic catalyst reduction reaction at a temperature of 323 K. This study uses a Fourier transform red-outer line spectrometer (F〇 Urier Transform Infrared Spectroscopy (FT-IR) is used to detect the intermediate products formed on the surface of Ti〇2 during photocatalytic reduction, so as to know the relationship between the reactants adsorbed on the surface of Ti〇2 and photocatalytic reduction, and then speculate Photocatalytic-SCR reaction mechanism. The study indicated that the ruthenium was adsorbed on the active site of Ti〇2 (Ti4+-〇-Ti), and after UV catalysis, .φ formed ΝΗ2 at the active site, and the free radical was easy to > 〇 reaction to form nitrosamide 'The intermediate product (arsamine) is further converted to nitrogen and water' and desorbed from the active site, and finally, the reduced active site (Ti) will Oxygen undergoes an oxidation reaction, and the oxidized active site is further deactivated to form Ti4+ for subsequent reaction. Although the reduction of nitrogen oxides at room temperature by photocatalytic reaction has been disclosed in this document, it has been disclosed in the literature that the use of a 300 W high-pressure mercury lamp for the reduction treatment of cerium oxide still has a problem of energy consumption. In the above, the inventors conducted extensive research on how to process the gas-oxygen 201121640 compound with a lower energy source, and found that by using the light; kf to carry out the photocatalytic reaction, it can be in low energy consumption, 虱, the treatment effect of the object, and found that the method of the selective light 1 and the nitrogen oxide of the present invention is applied to the treatment of the discharge of the fixed pollution source, and the combustion smoke can be performed at a lower temperature and a lower energy consumption. In the middle of the road = the emulsion (four) original, and thus the purpose of reducing energy, due to the novel effect of the present invention. According to the technical means adopted by the present invention for achieving the above object, the reaction of the selective catalyst reduction procedure is selected as a photocatalytic reaction and the work is as follows: 'The selection of bismuth compounds = the purpose of the release. In order to achieve the reduction of the bismuth sulphate according to the present invention, the method of providing ～ 种 摆 , , , , , , , , , , , , 作为 作为 作为 作为 作为 作为 作为 作为 作为 作为 作为 作为 作为 作为 作为 作为 作为 作为, external light as a light source 3.73 mW / 〇m ^ ^ ^ T, ' 2 · 37 - reduction reaction, I oxide reduction of money and water hydrazine selective photocatalysis according to the method of the present invention, wherein as a 働ppmv, and = The light used by the light source is the light source in the range of 2 ^ 00 nm, and the UV light wave is the best application wavelength. According to the method of the present invention, the ultraviolet light source can use the ultraviolet light 201121640 lamp, and particularly, the use of a low-about ultraviolet lamp is sufficient to exert the effects of the present invention. ... according to the method of the present invention, the processable nitrogen oxide concentration can be as high as 600 ppmv, and thus can be used for the treatment of nitrogen oxides in the flue. The optimum nitrogen oxide treatment concentration of the invention is 2 〇〇 ppmv to 550 ppmv. . • According to the method of the present invention, oxygen can be simultaneously introduced into the feed gas, and the reduced titanium dioxide can be oxidized by oxygen to regenerate the active site of the titanium dioxide for photocatalytic reduction of nitrogen oxides in the next cycle. Lu reaction use. The degree of oxygen may fall within the range of 1.0 to 3.0% by volume. The present invention is further related to a method for treating exhaust gas discharged from a combustion flue, which comprises the following steps: (1) passing the exhaust gas through a desulfurization device at a temperature below 180 ° C to remove the exhaust gas And acene oxides; and (2) operating conditions of the gas treated in step (1) using ammonia as a reducing agent at an operating temperature of 5-50 ° C and a light intensity of 2.37-3.73 mW/cm 2 Next, through the photocatalytic reactor, the nitrogen oxides in the exhaust gas are subjected to a selective photocatalytic reduction reaction to be reduced to nitrogen and water; wherein the photocatalyst comprises: a tubular quartz containing An annular glass container of a tube; a lamp tube capable of emitting ultraviolet light, the lamp tube being disposed inside the circular tubular quartz tube, and a titanium dioxide catalyst coated on the outside of the circular tubular quartz tube; The ultraviolet light can be irradiated to the outside of the quartz tube to excite the titanium dioxide catalyst coated on the outside of the tube, and the nitrogen oxide can be oxidized when the nitrogen oxide is shaken by the photocatalytic reaction. Reduction reaction. The present invention is applied to a method for treating exhaust gas discharged from a combustion flue in 201121640, and the desulfurization device used is a conventional desulfurization device, and thus will not be described in detail in the present invention. The reduction reaction of nitrogen oxides by the method of the invention can not only effectively treat the nitrogen oxides emitted by the stationary pollution source, but also reduce the nitrogen oxides at normal temperature to reduce energy consumption and save energy and reduce carbon. the goal of. [Embodiment] The method and apparatus for selectively photocatalyzing NOx according to the present invention mainly utilizes titanium dioxide as a photocatalyst, ultraviolet light as an excitation light source, and ammonia (NH3) as a reducing agent to treat nitrogen oxides ( NOx) undergoes a reduction reaction to reduce NOx to nitrogen and water. According to the method of the present invention, NH3 as a reducing agent, which is introduced as a reducing agent, will be adsorbed on the active site of Ti02 (Ti4+-0-Ti), and after catalysis by ultraviolet light, NH2 is formed at the active site. And the Ti2+ is reduced to Ti3+, and the NH2 radical is easily reacted with NO to form nitrosamide, and further converted into nitrogen and water, and then desorbed from the active site; finally, reduced The titanium dioxide active site (Ti3+) will be oxidized with oxygen and activated again to form Ti4+, and the above-described cycle of nitrogen oxide reduction reaction is repeated. The reduction of nitrogen oxides by the process and apparatus of the present invention provides up to about 50% NO reduction efficiency and up to about 90% ruthenium selectivity. The present invention will be described in detail by the following examples of the invention, which are not intended to limit the scope of the invention. 10 201121640 In the following examples of the present invention, the temperature and humidity conditions of the reaction feed are controlled by a process unit such as a temperature control unit and a humidity control unit, and are controlled and adjusted according to the actual needs of NO reduction. The photocatalyst catalyzes the light intensity of the reaction device. In the embodiment of the selective photocatalytic reduction of nitrogen oxides of the present invention, the product of the original NO is also passed through the gas chromatograph 7895 and the NOx analyzer via the photocatalytic reduction method (Eco is in the state·%) CLD62) was measured and recorded as a reference for NO reduction reaction efficiency and N2 generation. • In the following embodiments of the present invention, the apparatus used is mainly a flow type annular photoreactor, a variable voltage regulator, a voltage regulator, a circulating constant temperature water tank, a gas supply unit, a humidity control unit, NOx, N2, and The NW analysis and detection device and the flow monitoring device are combined. The photoreactor farm can be used for photocatalytic catalytic reduction of NOx. The photoreactor device comprises: an annular glass container containing a circular tubular quartz tube; a fluorescent tube capable of emitting ultraviolet light inside the circular tubular quartz tube; and a covering of the circular tubular quartz tube An external titanium dioxide catalyst, whereby the ultraviolet light-emitting tube can be used to irradiate ultraviolet light to the outside of the glass tube container, thereby exciting the titanium dioxide catalyst coated on the outside of the tube. The reduction reaction of nitrogen oxides is carried out when the nitrogen oxides pass through the photocatalytic reaction device. Embodiment 1 A method of selectively photocatalyzing a ruthenium oxide according to this embodiment of the present invention is as follows: a photocatalyst is coated on the outside of the circular tubular quartz glass tube, and a light source is adjusted to align the surface of the photocatalyst to clean He In the photoreactor, after detecting the leakage of the valve member and the joint between the valve and the inlet and outlet of the reactor, the temperature control system, the gas chromatograph and the N〇x analysis 201121640 are used for the instrument system. Once the balance is reached, the feed gas, helium and neon 2) used in the experiment are passed, and the reactor temperature is controlled to ^ C before the reaction starts, the pressure is maintained at normal pressure, and the humidity is adjusted. Three samples were taken before the reaction, and the reaction gas was taken out with a gas-tight needle. The initial concentration of each reactant was measured by a gas chromatograph and a krypton analyzer, and the average value was calculated. At the beginning of the experiment, the light source used in the experiment was turned on, about every 5 minutes = photocatalysis, and the sample was sampled by gas-tight needle σ. The gas chromatograph and the muscle analyzer were used to analyze the residual concentration of the reaction gas and the product. Whether the reaction reaches: If the balance is not reached, the concentration of the gas at the outlet end is continuously measured after a period of time until the outlet concentration of each reactant reaches the data obtained by the test. After the reaction is completed, pass the „, _~ the volatile moisture-free southern humidity gas' to remove the residual material adsorbed on the surface of the catalyst. In the case of the example, the ultraviolet light at the wavelength 365 is used as the direct first solution. Through, the social light source, the concentration of ν〇 gas obtained from the job is very stable, so N (m) can be neglected by ultraviolet photolysis (4). The county should be responsible for the reduction of catalyst in different operations. Reaction 'and shows N〇 reduction efficiency fineness> Reaction conditions other than light intensity Maintaining solidity (5〇〇Ppmv), NH3 concentration (550ppmv), oxygen enrichment: gas humidity (〇, reaction residence time (1.9'^ coating)罝(0.47g)), and the concentration of NOx reduced with time by the N〇x analyzer and the selective photocatalytic catalyst under the gas phase 糸Ν2^Ν2〇(4)4 \ It can be seen from the experimental community's 'Ν0 and 2', 'Q fruit, the NO concentration in the photoreaction 12 201121640 will decrease with the increase of the reaction time, and the NO that is reacted will be converted into the program in this program. ^], so the concentration of n2 will increase as the reaction time increases, during the reaction time At six minutes, the concentrations of NO and A will gradually stabilize and tend to be fixed values. Figure 2 shows the NO, N〇2, N2, and N2 in the selective photocatalytic reduction of nitrogen oxides at different light intensities. The concentration changes, when the light intensity is increased from 2.37mW/cm2 to: 3.73 m\V/cm2, the residual concentration of NO will decrease from 290.30ppmv to 225.27ppmv. The gas reacted will be converted into ^^2 in this method. A small amount of >1〇2 and 1^2〇' can generate 166.23ppmv to 229.98ppmv of N2, N〇2 and N2〇 as the light intensity (2.37111~/(:1112 rises to 3.73 mW/cm2) rises). It will increase from 3 j2ppmv and 15.04ppmv to 6.96ppmv and 24.52ppmv respectively. From the experimental results, it can be seen that the gas generated during photocatalytic reduction of NO contains no, n〇2, n2 and N2〇' Part of the NO will be converted to n2 in the photocatalytic process to reduce the NO emission. ^ After the data in Figure 3 is calculated, the incident UV intensity can be obtained, and the NO removal efficiency and n2 selection can be obtained. The effect of the rate is shown in Figure 3. From the picture, the results show that 'photocatalytic reduction of NO The rate of linearization increases linearly with the increase of the incident light intensity, while the N2 selectivity is maintained at about 9〇% under various light intensity t shots, and the NO removal efficiency increases with the light intensity α~ The reason for the rise is that 'when the intensity of the ultraviolet light is increased, the degree of excitation by the photocatalyst fork light is increased, and the electron-hole generation speed is increased', thereby accelerating the rate of photocatalytic surface redox. In addition, it is found from the linear results of this test that the reaction behavior of the reaction under higher light intensity is not inhibited by the obvious electron-hole recombination phenomenon. The measurement may be related to the surface renewal rate of the photocatalyst; Since the continuous reactor continuously supplies reactants during the operation, and thus the probability of recombination is increased, the probability of recombination of electrons and holes may be reduced. Therefore, it is speculated that the reaction procedure should be able to withstand high ultraviolet light intensity. Overall, when the selective light only reduces the light intensity of the catalyst reduction reaction by two" to 3 2. mW/cm2, the removal rate of 5〇%_〇 can be achieved, and the selectivity of the reaction can be maintained. 9〇% 'Comparatively, the energy consumed by the method of the present invention is much lower than the NO reduction procedure previously performed at high temperatures, and this result is sufficient to demonstrate that the effect of treating NO by the method of the present invention is quite excellent. The results show that if the feed contains excess oxygen, the rate determining step in the photocatalytic reduction process is a process in which the amine is converted to nitrogen and water, and if the oxygen content in the feed is less than 2 %, the reaction rate determining step is the activation rate of the photocatalyst active site. Selective ^ Catalytic catalyst reduction procedure at different oxygen feed concentrations is shown in Figure 4, as shown in the figure, when the oxygen concentration Below 丨 vol%, the reduction efficiency of NO increases with increasing oxygen concentration; if the oxygen concentration is higher than 1 vol%, the reduction efficiency of NO tends to be flat; therefore, the reduction of nitrogen oxides is carried out by the method of the present invention. When reacting, it should be The oxygen concentration is controlled to be more than 1% by volume to reoxidize and regenerate the active site of the titanium dioxide to facilitate subsequent reaction. Figures 5 and 6 show the N〇 removal rates at different NH3 & N〇 feed concentrations, respectively. The reaction mechanism described shows that the method of the present invention is mainly produced by reacting NO with Μ% adsorbed on the active site of Ti〇2, so the reaction rate is mainly determined by the amount of adsorption of NH3 on the active site; It can be seen that the NO reduction rate will increase with the initial concentration of ^^%, which is due to the higher concentration of NH3 in the reactor, which will cause more ruthenium molecules to adsorb on the active site, and enhance N after photocatalysis. 〇Reduction reaction ·, However, when the initial concentration of NH3 is higher than 300ppmv, the NO reduction rate will not increase significantly with the increase of strontium concentration, but the increase will gradually become flat, which is due to the NH3 adsorption amount. It will be affected by the concentration of NH3, and will also be limited by the number of active sites of Ti〇2. When the aNh3 gas is higher than -300ppmv, the active position of the surface of Ti'2 is insufficient to adsorb the N at this concentration. H3, therefore, can not further increase the NO reduction rate. Figure 6 is the effect of SiO feed # concentration on NO removal efficiency, NO removal efficiency will increase with the increase of NO feed concentration, and gradually tend to be flat, which is due to At the mNO concentration, the reaction rate of the reaction is mainly limited by the rate at which the NO gas molecules are transferred to the catalyst surface. Therefore, when the NO feed concentration is increased, the rate at which the gas molecules are transferred to the catalyst surface is increased, so that the NO is reduced. The efficiency also increases. When the NO concentration of the feed is higher than 500ppmv, the rate at which the NO molecules pass to the catalyst surface no longer affects the reduction rate, so the NO reduction rate no longer increases as the NO concentration increases. 41 According to the above test results, the method for selective photocatalytic reduction of nitrogen oxides according to the present invention can effectively reduce nitrogen oxides in gases into nitrogen and water at low temperature and low energy consumption, and is highly industrially utilized. value. [Effect of the Invention] The selective photocatalytic reduction of nitrogen oxides according to the present invention can be carried out after the step of removing the halogen and sulfur oxides in the exhaust gas in the combustion flue and in the exhaust gas treatment process. Since the method for selectively photocatalytic reduction of nitrogen oxides according to the present invention can perform reduction of nitrogen oxides under conditions of low energy consumption, it is applied to processing fuel combustion (eg, fire power 15 201121640 power plant, petroleum refining) In addition to reducing nitrogen oxide emissions, it can also reduce the amount of nitrogen oxides emitted by stationary sources such as non-fuel combustion (such as waste incinerators, open burning) and industrial processes. Problems such as carbon dioxide emissions from energy consumption are quite effective for environmental protection and energy conservation and carbon reduction.
16 201121640 【圖式簡單說明】 圖1顯示於不同光強度下本發明的選擇性光催化還原 氮氧化物之方法中的no&n2隨時間之濃度變化。 圖2顯示於不同光強度下本發明的選擇性光催化還原 氮氧化物之方法中的NO、N02、N2以及N20之濃度變 化。 圖3顯示本發明的選擇性光催化還原氮氧化物之方 法，在不同光強度下之NO去除效率以及N2選擇率。 圖4顯示本發明的選擇性光催化還原氮氧化物之方 法，在不同氧氣進料濃度下之NO去除效率。 圖5顯示本發明的選擇性光催化還原氮氧化物之方 法，在不同NH3進料濃度下之NO去除速率。 圖6顯示本發明的選擇性光催化還原氮氧化物之方 法，在不同NO進料濃度下之NO去除速率。 【主要元件符號說明】 益 - t »»> 1716 201121640 BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows the change in concentration of no & n2 over time in the method of selective photocatalytic reduction of nitrogen oxides of the present invention under different light intensities. Figure 2 shows the concentration changes of NO, N02, N2 and N20 in the selective photocatalytic reduction of nitrogen oxides of the present invention at different light intensities. Figure 3 shows the method of selective photocatalytic reduction of nitrogen oxides of the present invention, NO removal efficiency and N2 selectivity at different light intensities. Figure 4 shows the NO removal efficiency of the selective photocatalytic reduction of nitrogen oxides of the present invention at different oxygen feed concentrations. Figure 5 shows the NO removal rate of the selective photocatalytic reduction of nitrogen oxides of the present invention at different NH3 feed concentrations. Figure 6 shows the method of selective photocatalytic reduction of nitrogen oxides of the present invention, the NO removal rate at different NO feed concentrations. [Main component symbol description] Benefit - t »»> 17