200307575 Π) 玖、發明說明 【發明所屬之技術領域】 本發明係關於一種雜多酸觸媒再活化的方法，其係在 以異丁烯醛進行氣相觸媒氧化反應產製甲基丙烯酸時所使 用的觸媒。 【先前技術】 使異丁烯醛進行使用雜多酸觸媒之氣相觸媒氧化反應 的方法係迄今已知的其中一種產製甲基丙烯酸的方法。在 該反應中，觸媒活性經常隨反應時間流逝而逐漸下降。因 此，爲了延長觸媒壽命，故已硏究經由再活化法恢復觸媒 活性。例如，日本專利特許公開申請案第（JP-A-)58-15635 1號係揭示一種在含有至少10體積％之水蒸汽的氣 流下以從70 °C至240 °C之溫度的熱處理觸媒的方法，其係 含有自由磷鉬酸或自由磷釩鉬酸及已在會使其活性減低的 上述反應中用過的觸媒。而且，JP-A-6-7 6 85係揭示一種 在含有至少0.1體積％之分子氧的氣流下以從300t至410 °C之溫度的熱處理觸媒的方法，其係含有磷、鉬和釩及已 在會使其活性減低的上述反應中用過的觸媒。 但是這些慣用的方法可能未必展現滿意的觸媒活性恢 復效應，並在一些情況中，不可能獲得具有預期活性的再 活化觸媒。 【發明內容】 -6- (2) (2)200307575 本發明的一個目的係提供一種用於產製甲基丙燒酸之 觸媒再活化的方法，該方法具有比慣用的方法更卓越的再 活化之觸媒活性。 在用心的硏究之後，本發明者發現在組合分子氧與水 蒸汽濃度之氣流中及用於再活化之溫度範圍的特殊條件下 以熱處理在上述反應中用過的觸媒可以達成以上的目的， 因此本發明者已完成本發明。 換言之，本發明係提供一種含有磷、鉬和釩及已在產 製甲基丙烯酸之異丁烯醛之氣相觸媒氧化反應中用過的雜 多酸觸媒再活化的方法，該方法包含在含有至少3體積％ 之分子氧及至少3體積％之水蒸汽的氣流下以從290t至 4〇〇°C之溫度的熱處理觸媒的步驟。 在本發明再活化的觸媒係含有磷、鉬和釩之雜多酸觸 媒。可在以異丁烯醛之氣相觸媒氧化反應進行甲基丙烯酸 的產製作用中使用該觸媒。觸媒可以包含自由雜多酸或可 以包含雜多酸的鹽。已提出許多關於產製甲基丙烯酸之雜 多酸觸媒的組成物、物性及製備方法的報告（參閱例如JP -A·59-12758 、 JP-A-60-239439 、 JP-A-5-96172 、 JP-A-8- 10621及 JP-A- 1 1-22641 1)。可以根據在報告中揭示的方 法獲得在本發明再活化的觸媒，但是不應該將該方法解釋 成對本發明範圍的限制。 以氣體原料（即異丁烯醛）與分子氧或水蒸汽一起供應 -7 - (3) (3)200307575 至以觸媒裝塡的固定床反應器中，可以進行使用雜多酸觸 媒的異丁烯醛之氣相觸媒氧化反應。在其工業產製作用中 ，可以使用多管型反應器作爲反應器。氣體原料可以包括 從1體積％至10體積％之異丁烯醛量、從3體積％至20 體積％之分子氧量、從5體積％至30體積％之水蒸汽量、 惰性氣體（如氮及二氧化碳）及類似物。可以使用空氣作爲 分子氧來源及可以使用蒸汽作爲水蒸汽來源。關於反應條 件，氣體原料的供應速度可以空間速度的名義從5 00至 5 000小時以標準狀態爲基準；以下同上），即以每1公 升觸媒計之氣體原料的供應速度（公升/小時），以及反應溫 度可以從25 0至350 °C。可將在濃縮或與其包括的水分離 之後的反應產物氣體（包括所獲得的甲基丙烯酸）進行分離 及純化操作。可將回收的未反應之異丁烯醛作爲原料再循 環。可將若必要在燃燒之後的廢氣作爲上述的惰性氣體來 源再循環。 以異丁烯或特丁醇進行使用含有鉬、鉍和鐵之氧化物 觸媒的氣相觸媒氧化反應可以適當地產製作爲上述原料使 用的異丁烯醛。經由兩階段氣相觸媒氧化反應可以產製甲 基丙烯酸，其包含作爲第一階段反應的異丁烯或特丁醇的 氣相觸媒氧化反應及作爲第二階段反應的上述使用所生成 之異丁烯醛作爲原料的氣相觸媒氧化反應。以異丁烯或特 丁醇與分子氧一起供應至以觸媒塡充的固定床反應器中， 可以進行第一階段反應。在工業產製作用中，可以使用多 管型反應器作爲反應器。用於第一階段反應的氣體原料可 -8 - (4) (4)200307575 以包括從2至1 0體積％之異丁烯或特丁醇、從3體積％至 20體積％之分子氧量、從0體積％至30體積％之水蒸汽量 、惰性氣體（如氮及二氧化碳）及類似物。可以使用空氣作 爲分子氧來源及可以使用蒸汽作爲水蒸汽來源。有可能使 用若必要在燃燒之後自第二階段反應回收的廢氣作爲惰性 氣體來源。關於第一階段反應的條件，氣體原料的供應速 度可以空間速度的名義從500至5000小時"及反應溫度 可以從300至400°C。可將在第一階段反應所獲得的異丁 烯醛進行第二階段反應的模式大致分成兩種型式；第一種 係分離模式，其中將第一階段反應產物氣體進行分離操作 ，以獲得具有相當高純度之異丁烯醛，接著將其進行第二 階段反應；以及第二種係直接組合模式，其中將含有異丁 烯醛的第一階段反應產物氣體直接進行第二階段反應，不 進行分離操作[參閱例如”Petrochemical process”（由 The Japan Petroleum Institute 編輯，由 Kodansha Scientific Ltd.於 20 01 年發表），第 174-175 頁]。 當異丁烯醛以上述方式進行在雜多酸觸媒存在下的氣 相觸媒氧化反應時，則經常使副產物牢固地黏在觸媒上或 使觸媒隨反應時間流逝而受到熱破壞，因此使觸媒活性逐 漸下降。在本發明中，在分別含有濃度不低於指定値之分 子氧及水蒸汽的氣流下以指定的溫度範圍的熱處理在上述 反應中用過的觸媒，以進行觸媒的再活化作用。 在用於觸媒熱處理的上述氣體中，分子氧濃度可以係 至少3體積％，並以10%體積％或更高較佳。當分子氧濃 -9 - (5) (5)200307575 度太低時，則再活化之觸媒活性可能夠不滿意。未特別限 制分子氧濃度的上限。但是，分子氧濃度可以高達約20 體積％，因爲方便使用空氣作爲分子氧來源。 而且，在用於觸媒熱處理的上述氣體中，水蒸汽濃度 可以係至少3體積％，並以8%體積％或更高較佳。當水蒸 汽濃度太低時，則再活化之觸媒活性可能不夠滿意。另一 方面’再活化之觸媒活性傾向於隨著水蒸汽濃度的增加而 增加。但是，在水蒸汽濃度達到超過30體積％時，則也 傾向於達到幾乎飽和的活性等級。因此，水蒸汽濃度的上 限可以高達3 0體積％。可以使用蒸汽作爲水蒸汽來源。 上述氣體的流速可以空間速度的名義從10至2000小 時_1，並以從100至1000小時〃較佳。除了分子氧及水蒸 汽之外，用於觸媒熱處理的上述氣體可以包括惰性氣體， 如氮及二氧化碳。用於再活化之氣體可以不含異丁烯醛。 上述熱處理的溫度可以係290°C或更高，並以320°C 或更高較佳。反之，溫度可以係400°C或更低，並以370 °C或更低較佳。不僅在溫度太低，並也在溫度太高時，所 得的處裡之觸媒可能具有不夠充份的活性。用於上述熱處 理的時間期限係依據其它條件而定，並可以從0.5至20 小時。 以自其中的觸媒已用過的反應器取出觸媒，將觸媒裝 入單獨準備的再活化容器中及接著將觸媒以熱處理的這種 方式可以進行觸媒的再活化處理，或者另一選擇係使觸媒 維持在反應器中及不自反應器取出的方式處理。但是，以 -10 - (6) (6)200307575 在反應與觸媒再活化作用之間轉換的可操作性觀點而言， 最好以後者的模式在反應器內進行再活化處理。 在上述的雜多酸觸媒之中，在本發明欲處理的觸媒係 以含有雜多酸之鹽的觸媒較佳，並以雜多酸之酸性鹽（部 份中和的鹽）最佳。 本發明的再活化法可以適合作爲在兩階段氣相觸媒氧 化反應中用於第二階段反應之觸媒再活化的方法使用，該 兩階段氣相觸媒氧化反應包含作爲第一階段反應的上述異 丁烯或特丁醇之氣相氧化反應及作爲第二階段反應的所得 異丁烯醛之氣相氧化反應。如以上所述，兩階段氣相氧化 反應可以包括分離模式（其中將異丁烯醛與具有相當高純 度的第一階段反應產物氣體分離及接著進行第二階段反應 )及直接組合模式（其中將含有異丁烯醛的第一階段反應產 物氣體直接進行第二階段反應，不進行分離操作）。本發 明的再活化法可以適用於在那些上述任何模式中的第二階 段反應之觸媒。本發明的再活化法在後者的直接組合模式 中特別展示明顯的觸媒活性恢復效應，因爲在該模式中， 幾乎將全部未反應的原料及包括在第一階段反應產物氣體 中的副產物引入第一階段反應器中，其容易造成減低第二 階段反應之觸媒活性。 在上述的兩階段氣相觸媒氧化反應中，不僅使第二階 段反應之觸媒，並也使第一階段反應之觸媒可能隨反應時 間流逝而逐漸喪失其觸媒活性。因此，在直接組合模式的 兩階段氣相觸媒氧化反應中，特別希望同時進行用於第一 -11 - (7) (7)200307575 階段反應之觸媒的再活化作用與用於第二階段反應之觸媒 的再活化作用。在含有至少3體積％之分子氧（以從1 〇至 20體積％較佳）的氣流下以從360。(：至45(TC之溫度（以從 3 60至4〇0°C較佳）的熱處理觸媒，可以適合進行用於第一 階段反應之觸媒的再活化作用。用於第一階段反應之觸媒 的再活化作用所使用的氣體可以包括水蒸汽，但不是必然 的。除了分子氧或水蒸汽之外，氣體可以包括惰性氣體， 如氮或二氧化碳。 以自其中的觸媒已用過的反應器取出觸媒，將觸媒裝 入單獨準備的再活化容器中及接著將觸媒以熱處理的這種 方式也可以進行用於第一階段反應之觸媒的再活化作用， 或者另一選擇係使觸媒維持在反應器中及不自反應器取出 的方式處理。但是，以在反應與觸媒再活化作用之間轉換 的可操作性觀點而言，最好以後者的模式在反應器內進行 再活化處理。 在直接組合模式的兩階段氣相觸媒氧化反應中，有可 能一起進行用於第一階段反應之觸媒的再活化作用與用於 第二階段反應之觸媒的再活化作用，其具有好的可操作性 及同時將觸媒維持在反應器中，因爲氣體容易以該次序流 經連續的第一階段反應器及第二階段反應器。例如，以其 中允許含有預定濃度之分子氧及水蒸汽的氣體流經連續的 第一階段反應器及第二階段反應器，而且使在每一個反應 器中的每一個觸媒層溫度維持在預定溫度的方法可以進行 用於第一及第二階段反應之觸媒的再活化作用。另一選擇 -12- (8) (8)200307575 係以宜中允許含有預定濃度之分子氧的氣體流經連纟賈的第 一階段反應器及第二階段反應器’而且使在每一個反應器 中的每一個觸媒層溫度維持在預定溫度，以及同時將含有 預定濃度之水蒸汽的氣體加在第二階段反應器A D的方法 可以進行觸媒的再活化作用。以含有分子氧之氣體引入連 續的第一階段反應器及第1階段反應器的方式進行ϋ種角蜀 媒再活化作用有可能同時進行固體物質的去除’如可在從 第一階段反應器出口延伸至第二階段反應器入口的管道中 固化的含碳物質。 在以異丁烯或特丁醇與分子氧及水蒸汽一起供應至第 一階段反應器的方式進行直接組合模式的兩階段氣相觸媒 氧化反應時，則有可能將反應平順地轉換成觸媒再活化作 用，其係藉由在進行特定的反應時間之後終止異丁烯或特 丁醇的供應及接著在若必要時調整在供應的氣體中的分子 氧及水蒸汽濃度和調整在每一個反應器中的觸媒層溫度。 以逐漸增加第一階段反應溫度及第二階段反應溫度可 以進行直接組合模式的兩階段氣相觸媒氧化反應，尤其係 第一階段反應器及第二階段反應器之加熱介質溫度，其係 依據由於隨反應時間流逝而去活化之觸媒而定，以便於維 持分別在第一階段反應及第二階段反應中預定的轉化率。 因此，在該方法中，在第一階段反應器之加熱介質溫度成 爲3 60 °C或更高及第二階段反應器之加熱介質溫度成爲 290 °C或更高時終止異丁烯或特丁醇的供應，可以非常平 順地進行從反應轉換成觸媒再活化處理，可以在同時使兩 -13- (9) (9)200307575 種觸媒達到再活化處理必要的溫度時。最好以定期從每半 年一次至每年一次的頻率進行觸煤再活化作用。 根據本發明，有可能充份恢復已在異丁烯醛之氣相觸 媒氧化反應中用過的含有磷、鉬和釩之雜多酸觸媒的活性 及獲得具有極佳活性的再活化觸媒。 顯然可以各種方式改變因此所述的本發明。將這些變 化視爲在本發明的精神及範圍內，熟悉本技藝的人可能明 白所有這些修改係在以下的申請專利範圍內。 將在2002年4月16日提出申請的日本專利申請案第 2002-1 13 081號的揭示全文（顯示專利說明書、申請專利範 圍及總結論）以其全文倂入本文以供參考。 【實施方式】 實例 以參考以下的實例更詳細說明本發明，不應該將其解 釋成對本發明範圍的限制。 參考實例1 (a)觸媒的製備作用 將38.2公斤硝酸鉋[CsN03]、10.2公斤硝酸銅三水合 物[Cu(N03)2 · 3H2〇]、24.2公斤之85重量％正磷酸及 25.2公斤之70重量％硝酸溶解在加熱至40°C之224公斤 離子交換水中，以獲得所生成之溶液（液體A)。另一方面 ，在將297公斤鉬酸銨四水合物[(ΝΗ4)6Μο7〇24· 4H20]溶 (10) (10)200307575 解在加熱至40 °C之3 3 0公斤離子交換水中之後’將8.19 公斤偏釩酸銨[NH4V03]懸浮在其中’以獲得所生成之懸 浮液（液體B)。將液體A滴入攪拌下的液體B中’將10.2 公斤三氧化鍊[Sb2〇3]加入其中及接者在密封的谷器中以 1 2 0 °C攪拌1 7小時，以獲得泥漿液。將泥漿液使用噴霧乾 燥器乾燥，以獲得觸媒前驅體粉末。將4份重量之陶瓷纖 維[由 Toshiba Monofrax有限公司製造的 FIBERFRAX RFC400SL]、8份重量之硝酸銨及10份重量之離子交換水 ® 加入1 〇〇份重量之粉末中、捏和及接著進行擠壓模塑，成 爲具有5毫米直徑及3毫米高度之圓筒形。在9 0 °C之溫 度及3 5 % RH之濕度下乾燥3小時之後，將模塑之物件在 2 20 °C之空氣流中煅燒22小時，在250 °C之空氣流中煅燒 1小時，在43 5 °C之氮氣流中煅燒3小時及接著在39(TC 之空氣流中煅燒3小時，以該次序獲得觸媒。觸媒係由含 有分別以1 · 5、1 2、0.5、0.5、0.3和1 · 4之原子比的磷、 鉬、釩、銻、銅和鉋之雜多酸的酸性鹽所組成的。 φ (b )製得的觸媒之活性試驗 將9公克以上獲得的觸媒塡入具有15微米內徑之玻 璃微反應器中。以混合異丁烯醛、空氣、蒸汽與氮所製備 的含有4體積％之異丁烯醛、12體積％之分子氧及17體 積％之水蒸汽的氣體原料以670小時〃之空間速度供應至 玻璃微反應器中，並以28(TC之烘箱溫度（其係用於加熱 微反應器之熔爐溫度，以下同上）進行活性試驗。在自開 -15- (11) (11)200307575 始反應起流逝1小時時’異丁烯醛之轉化率係9 6 %及對甲 基丙烯酸之選擇率係78%。 參考實例2 (a)使用觸媒的反應 將含有分別以1 2、1、2 · 5、7 · 5和〇 . 6之原子比的鋁 、鉍、鐵、鈷和鉋之氧化物的1 3 0 0毫升模塑觸媒塡入具 有25微米內徑之鋼反應管中，以其作爲第一階段反應器 使用。將與參考實例1 ( a)相同的方式製得的1 8 〇 〇毫升觸 媒塡入具有30微米內直徑之鋼反應管中，以其作爲第二 階段反應器使用。以混合異丁烯、空氣、蒸汽與氮所製備 的含有5體積％之異丁烯、12體積％之分子氧及7.5體積 %之水蒸汽的氣體原料以1 200小時·1之空間速度供應至第 一階段反應器中’以獲得所生成之第一階段反應產物氣體 ，接著將其與空及氮混合，成爲含有3.2體積％之異丁烯 醛、8.5體積％之分子氧及11體積％之水蒸汽的氣體，接 著將所生成之氣體以1〇〇〇小時〃之空間速度供應至第二 階段反應器中，以進行兩階段氣相觸媒氧化反應。分別控 制在該操作期間的第一階段反應器及第二階段反應器之加 熱介質溫度，使得在第一階段反應中的異丁烯轉化率成爲 約9 9 %及在第二階段反應中的異丁烯醛轉化率成爲7 2 %或 更高。因此，將開始反應時的第二階段反應器之加熱介質 溫度設定成275 °C ’並將自反應開始起流逝3000小時時 的溫度設定成293 °C。在此時終止反應，並自第二階段反 (12) (12)200307575 應器取出觸媒。以放在反應器入口起向內約1/3之部位上 的觸媒取樣。利用該樣品作爲在以下實例中用過的觸媒。 (b)用過的觸媒之活性試驗 以與參考實例1 (b )相同的方式進行以上所獲得的用過 的觸媒之活性試驗。異丁烯醛轉化率係2 1 %。用過的觸媒 具有0 · 6重量％之總碳量’反之，以參考實例i ( a )所製備 的觸媒具有0.0 %之總碳量。 實例1 以參考實例2(b)進行用過的觸媒之活性試驗之後，將 用過的觸媒以350°C之烘箱溫度的熱處理15小時，同時 將以混合空氣、蒸汽與氮所製備的含有1 2體積％之分子 氧及1 8體積％之水蒸汽的氣體以5 0 0小時·1之空間速度供 應至已塡入用過的觸媒之玻璃微反應器中。接著將熱處理 之後的觸媒進行與參考實例1 (b)相同方式的活性試驗。異 丁烯醛轉化率係9 1 %。在熱處理之後的觸媒具有〇 . 〇 %之 總碳量。 實例2至14及比較性實例1至4 將以參考實例2(a)所準備的用過的觸媒塡入具有15 微米內徑之玻璃微反應器中，接著將以混合空氣、蒸汽與 氮所製備的含有分子氧及水蒸汽（具有表1展示的濃度）的 氣體以5 00小時·1之空間速度供應至微反應器中，並接著 (13) 200307575 以表1展示的烘箱溫度進行以表1展示的時間期限之熱處 理。接著以與參考實例1(b)相同的方式進行在熱處理之後 的觸媒活性試驗。將結果（異丁烯醛轉化率）展示在表1中 表1 分子氧(體積％) 水蒸汽(體積％) 烘箱溫度Gc) 時間(小時) 轉化率(％) 實例2 12 9 290 15 45 實例3 12 9 310 15 58 實例4 12 9 330 15 73 實例5 12 9 350 15 87 實例6 12 9 370 15 93 實例7 12 9 390 15 86 比較性實例1 12 9 410 15 31 比較性實例2 21 0 330 15 43 比較性實例3 20 2.5 330 15 64 實例8 19 9 330 15 73 實例9 17 18 330 15 80 實例10 15 30 330 15 82 實例11 10 50 330 15 82 比較性實例4 0 18 330 15 46 實例12 12 18 350 2 90 實例13 12 18 350 15 91 實例14 12 18 350 60 89200307575 Π) Description of the invention [Technical field to which the invention belongs] The present invention relates to a method for the reactivation of heteropolyacid catalysts, which is used in the production of methacrylic acid by gas phase catalytic oxidation reaction with methacrylaldehyde Catalyst. [Prior art] A method for subjecting methacryl to a gas phase catalytic oxidation reaction using a heteropolyacid catalyst is one of the methods known to date for producing methacrylic acid. In this reaction, the catalyst activity often decreases gradually as the reaction time elapses. Therefore, in order to extend the life of the catalyst, it has been investigated to restore the catalyst activity by a reactivation method. For example, Japanese Patent Laid-Open Application No. (JP-A-) 58-15635 No. 1 discloses a heat treatment catalyst at a temperature of 70 ° C to 240 ° C under an air stream containing at least 10% by volume of water vapor. The method comprises a free phosphomolybdic acid or a free phosphorovanadomolybdic acid and a catalyst which has been used in the above reaction which will reduce its activity. Further, JP-A-6-7 6 85 series discloses a method for heat-treating a catalyst at a temperature of from 300t to 410 ° C under a gas flow containing at least 0.1% by volume of molecular oxygen, which contains phosphorus, molybdenum, and vanadium And catalysts that have been used in the above reactions that would reduce their activity. However, these conventional methods may not necessarily exhibit a satisfactory catalyst activity recovery effect, and in some cases, it is impossible to obtain a reactivated catalyst having a desired activity. [Summary of the Invention] -6- (2) (2) 200307575 An object of the present invention is to provide a method for reactivating a catalyst for producing methylpropionic acid, which method has a superior reactivation than a conventional method. Activated catalyst activity. After careful study, the inventors have found that the catalyst used in the above-mentioned reaction can be achieved by heat treatment in a gas stream combining molecular oxygen and water vapor concentrations and under special conditions in the temperature range for reactivation. Therefore, the present inventors have completed the present invention. In other words, the present invention provides a method for reactivating a heteropolyacid catalyst containing phosphorus, molybdenum, and vanadium, and a heteropolyacid catalyst that has been used in a gas-phase catalyst oxidation reaction for producing methacrylic acid to form methacryl. The method comprises A step of thermally treating the catalyst under a flow of at least 3% by volume of molecular oxygen and at least 3% by volume of water vapor at a temperature of from 290 t to 400 ° C. The catalyst reactivated in the present invention contains heteropolyacid catalysts of phosphorus, molybdenum and vanadium. This catalyst can be used in the production of methacrylic acid by a gas phase catalyst oxidation reaction of methacryl. The catalyst may contain free heteropolyacids or may contain salts of heteropolyacids. Many reports on the composition, physical properties and preparation methods of heteropolyacid catalysts for producing methacrylic acid have been made (see, for example, JP-A · 59-12758, JP-A-60-239439, JP-A-5- 96172, JP-A-8- 10621 and JP-A-1 1-22641 1). The catalyst reactivated in the present invention can be obtained according to the method disclosed in the report, but the method should not be construed as limiting the scope of the present invention. Gas raw material (ie, methacryl) is supplied together with molecular oxygen or water vapor. -7-(3) (3) 200307575 In a catalyst-fixed fixed-bed reactor, methacryl using heteropoly acid catalyst can be used. Gas-phase catalytic oxidation reaction. In its industrial production, a multi-tubular reactor can be used as a reactor. The gas feedstock may include the amount of methacryl from 1 to 10% by volume, the amount of molecular oxygen from 3 to 20% by volume, the amount of water vapor from 5 to 30% by volume, and inert gases such as nitrogen and carbon dioxide. ) And the like. Air can be used as a source of molecular oxygen and steam can be used as a source of water vapor. Regarding the reaction conditions, the supply rate of the gas raw materials can be from 5000 to 5000 hours in the name of space velocity based on the standard state; the same as above), that is, the supply rate of the gas raw materials per liter of catalyst (liters / hour) , And the reaction temperature can be from 25 0 to 350 ° C. The reaction product gas (including the methacrylic acid obtained) after concentration or separation from the water it contains can be separated and purified. The recovered unreacted methacryl can be recycled as a raw material. The exhaust gas after combustion may be recycled as the above-mentioned inert gas source if necessary. The vapor phase catalytic oxidation reaction using an oxide catalyst containing molybdenum, bismuth and iron with isobutylene or tert-butanol can be appropriately produced as the isobutylene aldehyde used as the above raw material. Methacrylic acid can be produced through a two-stage gas-phase catalytic oxidation reaction, which comprises a gas-phase catalytic oxidation reaction of isobutylene or tert-butanol as the first-stage reaction and the isobutenal generated by the above-mentioned use as the second-stage reaction. Gas-phase catalytic oxidation reaction as a raw material. The first-stage reaction can be performed by supplying isobutene or tert-butanol together with molecular oxygen to a fixed-bed reactor filled with a catalyst. For industrial production, a multi-tubular reactor can be used as the reactor. The gaseous feedstock used for the first stage reaction may be -8-(4) (4) 200307575 to include from 2 to 10% by volume of isobutene or tert-butanol, from 3% to 20% by volume of molecular oxygen, from 0 to 30% by volume of water vapor, inert gases (such as nitrogen and carbon dioxide) and the like. Air can be used as a source of molecular oxygen and steam can be used as a source of water vapor. It is possible to use the exhaust gas recovered from the second stage reaction if necessary after combustion as a source of inert gas. Regarding the conditions of the first-stage reaction, the supply rate of the gaseous raw materials may be from 500 to 5000 hours in the name of space velocity, and the reaction temperature may be from 300 to 400 ° C. The mode of the second-stage reaction of the methacrolein obtained in the first-stage reaction can be roughly divided into two types; the first is a separation mode in which the reaction product gas of the first-stage reaction is separated to obtain a relatively high purity Isobutenal, which is then subjected to a second-stage reaction; and the second system is a direct combination mode in which the first-stage reaction product gas containing isobutenal is directly subjected to a second-stage reaction without separation operation [see, for example, "Petrochemical process "(edited by The Japan Petroleum Institute and published by Kodansha Scientific Ltd. in 2001), pp. 174-175]. When methacrylaldehyde undergoes a gas-phase catalyst oxidation reaction in the presence of a heteropolyacid catalyst in the above manner, by-products are often firmly adhered to the catalyst or the catalyst is thermally damaged as the reaction time elapses. The catalyst activity gradually decreases. In the present invention, the catalyst used in the above-mentioned reaction is subjected to a heat treatment in a specified temperature range under an air stream containing a molecular oxygen and water vapor at a concentration not lower than the specified gadolinium to reactivate the catalyst. In the above-mentioned gas used for the catalyst heat treatment, the molecular oxygen concentration may be at least 3% by volume, and preferably 10% by volume or more. When the molecular oxygen concentration -9-(5) (5) 200307575 is too low, the catalytic activity of the reactivation may not be satisfactory. The upper limit of the molecular oxygen concentration is not particularly limited. However, the molecular oxygen concentration can be as high as about 20% by volume because it is convenient to use air as a source of molecular oxygen. Further, in the above-mentioned gas used for the catalyst heat treatment, the water vapor concentration may be at least 3% by volume, and preferably 8% by volume or more. When the water vapor concentration is too low, the reactivation catalyst activity may not be satisfactory. On the other hand, the reactivation catalyst activity tends to increase as the water vapor concentration increases. However, when the water vapor concentration exceeds 30% by volume, it tends to reach an almost saturated activity level. Therefore, the upper limit of the water vapor concentration can be as high as 30% by volume. Steam can be used as a source of water vapor. The flow velocity of the above-mentioned gas may be from 10 to 2000 hours_1 in the name of space velocity, and preferably from 100 to 1000 hours. In addition to molecular oxygen and water vapor, the above-mentioned gases for catalyst heat treatment may include inert gases such as nitrogen and carbon dioxide. The gas used for reactivation may be free of methacryl. The temperature of the above heat treatment may be 290 ° C or higher, and preferably 320 ° C or higher. Conversely, the temperature may be 400 ° C or lower, and preferably 370 ° C or lower. Not only is the temperature too low, but also the temperature is too high, the resulting catalyst may have insufficient activity. The time period used for the above heat treatment is dependent on other conditions and can be from 0.5 to 20 hours. The catalyst can be reactivated by taking out the catalyst from the reactor in which the catalyst has been used, filling the catalyst into a separately prepared reactivation container, and then heat treating the catalyst by heat treatment. One option is to keep the catalyst in the reactor and not to remove it from the reactor. However, from the viewpoint of operability of -10-(6) (6) 200307575 to switch between reaction and catalyst reactivation, it is preferable to perform the reactivation treatment in the reactor in the latter mode. Among the heteropoly acid catalysts mentioned above, the catalyst to be treated in the present invention is preferably a catalyst containing a salt of a heteropoly acid, and the acid salt (partially neutralized salt) of the heteropoly acid is the most preferable. good. The reactivation method of the present invention can be suitably used as a method for reactivating a catalyst for a second-stage reaction in a two-stage gas-phase catalytic oxidation reaction. The two-stage gas-phase catalytic oxidation reaction includes the The above-mentioned vapor-phase oxidation reaction of isobutylene or tert-butanol and the vapor-phase oxidation reaction of the obtained isobutenal as the second-stage reaction. As mentioned above, the two-stage gas-phase oxidation reaction can include a separation mode (in which isobutenal is separated from the first-stage reaction product gas with a relatively high purity and then a second-stage reaction) and a direct combination mode (in which isobutene will be contained The first-stage reaction product gas of the aldehyde is directly subjected to the second-stage reaction without separation operation). The reactivation method of the present invention can be applied to a catalyst for a second-stage reaction in any of those modes. The reactivation method of the present invention particularly exhibits a significant catalyst activity recovery effect in the latter direct combination mode, because in this mode, almost all unreacted raw materials and by-products included in the first-stage reaction product gas are introduced. In the first-stage reactor, it is easy to reduce the catalytic activity of the second-stage reaction. In the above-mentioned two-phase gas-phase catalyst oxidation reaction, not only the catalyst in the second-stage reaction, but also the catalyst in the first-stage reaction may gradually lose its catalytic activity as the reaction time elapses. Therefore, in the two-stage gas-phase catalyst oxidation reaction in the direct combination mode, it is particularly desirable to simultaneously perform the reactivation of the catalyst used in the first-11-(7) (7) 200307575 stage reaction and the second stage Reactivation of reaction catalyst. Under a gas flow containing at least 3% by volume of molecular oxygen (preferably from 10 to 20% by volume) from 360. (: To 45 (TC temperature (preferably from 3 60 to 400 ° C)) heat treatment catalyst can be suitable for the reactivation of the catalyst used in the first-stage reaction. For the first-stage reaction The gas used for the reactivation of the catalyst may include water vapor, but it is not necessary. In addition to molecular oxygen or water vapor, the gas may include an inert gas such as nitrogen or carbon dioxide. The catalyst from which it has been used has been used The catalyst is taken out from the reactor, and the catalyst is packed into a separately prepared reactivation container and the catalyst is then heat-treated. This method can also perform the reactivation of the catalyst for the first stage reaction, or another The choice is to keep the catalyst in the reactor and not remove it from the reactor. However, from the viewpoint of operability of switching between reaction and catalyst reactivation, it is best to use the latter mode in the reaction In the two-stage gas-phase catalyst oxidation reaction of the direct combination mode, it is possible to perform the reactivation of the catalyst for the first-stage reaction and the contact for the second-stage reaction together. Reactivation, which has good operability and maintains the catalyst in the reactor at the same time, because the gas easily flows through the continuous first-stage reactor and second-stage reactor in this order. For example, it allows A method in which a gas containing a predetermined concentration of molecular oxygen and water vapor flows through the continuous first-stage reactor and the second-stage reactor, and the temperature of each catalyst layer in each reactor is maintained at a predetermined temperature can be performed. Reactivation of the catalyst for the first and second stage reactions. Another option is -12- (8) (8) 200307575, which is suitable for allowing gases containing molecular oxygen of a predetermined concentration to flow through the The first-stage reactor and the second-stage reactor 'and also maintain the temperature of each catalyst layer in each reactor at a predetermined temperature, and simultaneously add a gas containing a predetermined concentration of water vapor to the second-stage reactor AD The method can be used to reactivate the catalyst. The reactivation of the horned seeds is carried out by introducing the gas containing molecular oxygen into the continuous first-stage reactor and the first-stage reactor. It is possible to carry out the removal of solid matter simultaneously, such as carbonaceous matter that can be solidified in a pipe extending from the outlet of the first stage reactor to the inlet of the second stage reactor. In isobutene or tert-butanol with molecular oxygen and water vapor When the two-stage gas phase catalyst oxidation reaction in the direct combination mode is carried out by supplying to the first-stage reactor together, it is possible to smoothly convert the reaction into a catalyst reactivation effect by performing a specific reaction time Thereafter, the supply of isobutene or tert-butanol is terminated and then, if necessary, the concentration of molecular oxygen and water vapor in the supplied gas and the temperature of the catalyst layer in each reactor are adjusted to gradually increase the reaction temperature in the first stage And the second-stage reaction temperature can carry out the two-stage gas-phase catalytic oxidation reaction in direct combination mode, especially the heating medium temperature of the first-stage reactor and the second-stage reactor, which is based on deactivation due to the reaction time passing It depends on the catalyst in order to maintain the predetermined conversion rates in the first-stage reaction and the second-stage reaction, respectively. Therefore, in this method, the isobutene or tert-butanol is terminated when the heating medium temperature of the first-stage reactor becomes 3 60 ° C or higher and the heating medium temperature of the second-stage reactor becomes 290 ° C or higher. The supply can be smoothly converted from the reaction to the catalyst reactivation treatment, and at the same time when two -13- (9) (9) 200307575 catalysts are reached to the temperature necessary for the reactivation treatment. The reactivation of coal contact is best carried out at a frequency from once every half year to once a year. According to the present invention, it is possible to sufficiently restore the activity of a heteropolyacid catalyst containing phosphorus, molybdenum, and vanadium, which has been used in a gas phase catalyst oxidation reaction of methacrylaldehyde, and to obtain a reactivated catalyst having excellent activity. Obviously the invention thus described can be changed in various ways. These changes are considered to be within the spirit and scope of the present invention, and those skilled in the art may understand that all these modifications are within the scope of the following patent applications. The full disclosure of Japanese Patent Application No. 2002-1 13 081 filed on April 16, 2002 (showing the patent specification, scope of patent applications, and general conclusions) is incorporated herein by reference in its entirety. [Embodiment] Examples The present invention will be described in more detail with reference to the following examples, which should not be construed as limiting the scope of the present invention. Reference Example 1 (a) Preparation of catalyst 38.2 kg of nitric acid planer [CsN03], 10.2 kg of copper nitrate trihydrate [Cu (N03) 2 · 3H2〇], 24.2 kg of 85% by weight orthophosphoric acid, and 25.2 kg of 70% by weight of nitric acid was dissolved in 224 kg of ion-exchanged water heated to 40 ° C to obtain the resulting solution (Liquid A). On the other hand, after dissolving 297 kg of ammonium molybdate tetrahydrate [(ΝΗ4) 6Mο7〇24 · 4H20] in (10) (10) 200307575, the solution was heated to 3 30 kg of ion-exchanged water heated to 40 ° C. 8.19 kg of ammonium metavanadate [NH4V03] was suspended in it 'to obtain the resulting suspension (Liquid B). Liquid A was dropped into liquid B under stirring 'and 10.2 kg of trioxide chain [Sb2 03] was added thereto and stirred in a sealed trough at 120 ° C for 17 hours to obtain a slurry. The slurry was dried using a spray dryer to obtain a catalyst precursor powder. 4 parts by weight of ceramic fiber [FIBERFRAX RFC400SL manufactured by Toshiba Monofrax Co., Ltd.], 8 parts by weight of ammonium nitrate and 10 parts by weight of ion-exchanged water® are added to 1,000 parts by weight of the powder, kneaded and then extruded Compression molded into a cylindrical shape with a diameter of 5 mm and a height of 3 mm. After drying for 3 hours at a temperature of 90 ° C and a humidity of 35% RH, the molded article is calcined in an air flow at 2 20 ° C for 22 hours, and calcined in an air flow at 250 ° C for 1 hour. The catalysts were obtained in this order by calcining in a nitrogen stream at 43 5 ° C for 3 hours and then in an air stream at 39 ° C for 3 hours. The catalysts consisted of Consisting of acidic salts of phosphorus, molybdenum, vanadium, antimony, copper and planed heteropolyacids with atomic ratios of 0.3, 1.4 and 1.4. Φ (b) The test of the activity of the catalyst prepared by φ (b) The catalyst was poured into a glass microreactor with an inner diameter of 15 micrometers. 4 vol% of methacryl, 12 vol% of molecular oxygen, and 17 vol% of water vapor were prepared by mixing methacryl, air, steam, and nitrogen. The gaseous raw material was supplied to the glass microreactor at a space velocity of 670 hours, and an activity test was performed at 28 (TC oven temperature (which is the temperature of the furnace used to heat the microreactor, ibid below). In the self-opening- 15- (11) (11) 200307575 The conversion rate of 'isobutenal at 1 hour after the start of the reaction was 96% and The selectivity of methacrylic acid is 78%. Reference Example 2 (a) The reaction using a catalyst will contain aluminum, bismuth, iron at an atomic ratio of 1, 2, 1, 2, 5, 7, 5 and 0.6, respectively. 1,300 ml of the molded catalyst of cobalt, cobalt, and planed oxide was poured into a steel reaction tube having an inner diameter of 25 micrometers and used as a first-stage reactor. It will be the same as in Reference Example 1 (a) 18000 ml of catalyst prepared in this way was poured into a steel reaction tube with an internal diameter of 30 microns and used as a second-stage reactor. It was prepared by mixing isobutene, air, steam, and nitrogen and containing 5 vol% The gaseous raw materials of isobutene, molecular oxygen of 12% by volume, and water vapor of 7.5% by volume were supplied to the first-stage reactor at a space velocity of 1 200 hours · 1 'to obtain the first-stage reaction product gas generated, and then It is mixed with air and nitrogen to become a gas containing 3.2% by volume of methacrylaldehyde, 8.5% by volume of molecular oxygen, and 11% by volume of water vapor, and then the generated gas is supplied at a space velocity of 1,000 hours. Into the second stage reactor for two stages Gas-phase catalytic oxidation reaction. The temperature of the heating medium of the first-stage reactor and the second-stage reactor during the operation are controlled respectively, so that the isobutene conversion rate in the first-stage reaction becomes about 99% and in the second stage. The conversion rate of methacrylaldehyde in the step reaction became 72% or higher. Therefore, the temperature of the heating medium of the second-stage reactor at the start of the reaction was set to 275 ° C, and the temperature at which 3000 hours had passed since the start of the reaction Set to 293 ° C. At this point, stop the reaction and remove the catalyst from the second stage (12) (12) 200307575 reactor. Samples were taken with the catalyst placed about 1/3 inward from the reactor inlet. This sample was used as a catalyst used in the following examples. (b) Activity test of used catalyst The activity test of the used catalyst obtained above was performed in the same manner as in Reference Example 1 (b). The conversion rate of methacryl was 21%. The used catalyst has a total carbon content of 0.6% by weight ', and the catalyst prepared in Reference Example i (a) has a total carbon content of 0.0%. Example 1 After performing the activity test of the used catalyst in Reference Example 2 (b), the used catalyst was heat-treated at an oven temperature of 350 ° C for 15 hours. At the same time, the prepared catalyst was mixed with air, steam, and nitrogen. A gas containing 12% by volume of molecular oxygen and 18% by volume of water vapor is supplied at a space velocity of 500 hours · 1 into a glass microreactor that has been used for the catalyst. Next, the catalyst after the heat treatment was subjected to an activity test in the same manner as in Reference Example 1 (b). The conversion rate of methacryl was 91%. The catalyst after heat treatment has a total carbon content of 0.00%. Examples 2 to 14 and Comparative Examples 1 to 4 The used catalyst prepared in Reference Example 2 (a) was poured into a glass microreactor having an inner diameter of 15 μm, and then mixed with air, steam, and nitrogen The prepared gas containing molecular oxygen and water vapor (having the concentrations shown in Table 1) was supplied to the microreactor at a space velocity of 5000 hours · 1, and then (13) 200307575 was carried out at the oven temperature shown in Table 1 to Table 1 shows the heat treatment for the time periods. Then, the catalyst activity test after the heat treatment was performed in the same manner as in Reference Example 1 (b). The results (the conversion rate of methacryl) are shown in Table 1. Table 1 Molecular oxygen (vol.%) Water vapor (vol.%) Oven temperature Gc) Time (hours) Conversion (%) Example 2 12 9 290 15 45 Example 3 12 9 310 15 58 Example 4 12 9 330 15 73 Example 5 12 9 350 15 87 Example 6 12 9 370 15 93 Example 7 12 9 390 15 86 Comparative Example 1 12 9 410 15 31 Comparative Example 2 21 0 330 15 43 Comparative Example 3 20 2.5 330 15 64 Example 8 19 9 330 15 73 Example 9 17 18 330 15 80 Example 10 15 30 330 15 82 Example 11 10 50 330 15 82 Comparative Example 4 0 18 330 15 46 Example 12 12 18 350 2 90 Example 13 12 18 350 15 91 Example 14 12 18 350 60 89
-18 - (14) (14)200307575 實例15 以與參考實例2 ( a)相同的方式再進行兩階段氣相觸媒 氧化反應。在自反應開始起流逝7 2小時時，將第一階段 反應器及第二階段反應器之加熱介質溫度分別設定成348 °C及2 7 5 °C，並在自反應開始起流逝6 0 0 0小時時，將第 一階段反應器及第二階段反應器之加熱介質溫度分別設定 成3 62°C及294°C。此時在第一階段反應中的異丁烯轉化 率係 9 9 · 0 %及在第二階段反應中的異丁烯醛轉化率係 7 3.2% 在該階段暫時終止反應，並進行用於第一階段反應之 觸媒及用於第二階段反應之觸媒的再活化作用。尤其將以 混合空氣、蒸汽與氮所製備的含有1 4體積％之分子氧及 1 8 :體積％之水蒸汽的氣體以使得在第一階段反應器中的空 間速度成爲690小時胃1及在第二階段反應器中的空間速度 成爲500小時胃1的方式流經連續的第一階段反應器及第二 階段反應器。接著將第一階段反應器及第二階段反應器的 加熱介質溫度分別緩慢增加至370°C及350t，並維持10 小時。 接著將第一階段反應器及第二階段反應器之加熱介質 溫度分別設定成3 5 0 °C及288°C，並在與那些參考實例2 相同的條件下重新開始兩階段氣相觸媒氧化反應。在自反 應重新開始起流逝2200小時時，將第一階段反應器及第 二階段反應器之加熱介質溫度分別設定成354°C及289t 。此時在第一階段反應中的異丁烯轉化率係99.2%及在第 (15) (15)200307575 二階段反應中的異丁烯醛轉化率係80.3%。 實例1 6 在進行參考實例2(a)的兩階段氣相觸媒氧化反應之後 ，將第一階段反應器中的觸媒保留其原來的樣子，並將在 第二階段反應器中的觸媒換成以參考實例1(a)所製備的新 鮮觸媒。接著在與那些參考實例2相同的條件下再進行兩 階段氣相觸媒氧化反應。在自反應重新開始起流逝4000 小時時，將第一階段反應器及第二階段反應器之加熱介質 溫度分別設定成363 °C及292 °C。此時在第一階段反應中 的異丁烯轉化率係98.9 %及在第二階段反應中的異丁烯醛 轉化率係7 2.6 %。 在此時只終止異丁烯的供應，並將第一階段反應器及 第二階段反應器之加熱介質溫度分別在3 63 °C及292°C下 維持2小時。 然後重新供應異丁烯，開始反應。在自反應重新開始 起流逝 20小時時，第一階段反應的異丁烯轉化率係 99· 7 %及第二階段反應的異丁烯醛轉化率係85.8%。-18-(14) (14) 200307575 Example 15 In the same manner as in Reference Example 2 (a), a two-stage gas phase catalytic oxidation reaction was performed. When 72 hours have elapsed from the start of the reaction, the heating medium temperatures of the first-stage reactor and the second-stage reactor have been set to 348 ° C and 2 75 ° C, respectively, and 6 0 0 has elapsed since the start of the reaction. At 0 hours, the temperature of the heating medium of the first stage reactor and the second stage reactor were set to 3 62 ° C and 294 ° C, respectively. At this time, the conversion rate of isobutene in the first-stage reaction was 99.0% and the conversion rate of isobutenal in the second-stage reaction was 73.2%. At this stage, the reaction was temporarily stopped, and the reaction for the first-stage reaction was performed. Reactivation of catalyst and catalyst used in the second-stage reaction. In particular, a gas containing 14 vol% molecular oxygen and 18: vol% water vapor prepared by mixing air, steam, and nitrogen is used so that the space velocity in the first-stage reactor becomes 690 hours. The space velocity in the second-stage reactor became 500 hours and the stomach 1 flowed through the continuous first-stage reactor and the second-stage reactor. The temperature of the heating medium in the first-stage reactor and the second-stage reactor was then slowly increased to 370 ° C and 350t, respectively, and maintained for 10 hours. Then set the heating medium temperature of the first-stage reactor and the second-stage reactor to 350 ° C and 288 ° C, respectively, and restart the two-stage gas-phase catalyst oxidation under the same conditions as those of Reference Example 2. reaction. When 2200 hours have passed since the reaction restarted, the heating medium temperatures of the first-stage reactor and the second-stage reactor were set to 354 ° C and 289t, respectively. At this time, the isobutene conversion rate in the first-stage reaction was 99.2% and the isobutenealdehyde conversion rate in the (15) (15) 200307575 second-stage reaction was 80.3%. Example 16 After performing the two-stage gas-phase catalyst oxidation reaction of Reference Example 2 (a), the catalyst in the first-stage reactor was left as it was, and the catalyst in the second-stage reactor was retained. Replace with fresh catalyst prepared in Reference Example 1 (a). Then, under the same conditions as those of Reference Example 2, a two-stage gas-phase catalytic oxidation reaction was performed. When 4000 hours have elapsed since the reaction restarted, the heating medium temperatures of the first-stage reactor and the second-stage reactor were set to 363 ° C and 292 ° C, respectively. At this time, the conversion rate of isobutylene in the first-stage reaction was 98.9%, and the conversion rate of isobutenealdehyde in the second-stage reaction was 72.6%. At this time, only the supply of isobutylene was terminated, and the heating medium temperatures of the first-stage reactor and the second-stage reactor were maintained at 3 63 ° C and 292 ° C, respectively, for 2 hours. Isobutene was then re-supplied and the reaction started. When 20 hours had elapsed since the reaction restarted, the isobutene conversion rate of the first-stage reaction was 99.7% and the isobutenealdehyde conversion rate of the second-stage reaction was 85.8%.