本文選題：花狀鎢酸鉍 + 甲苯氧化�。� 參考：《催化學(xué)報(bào)》2017年03期

【摘要】：甲苯及其衍生物的選擇性氧化是化學(xué)工業(yè)中重要的一環(huán).氧化產(chǎn)物醛、酮和酸類(lèi)化合物是各種農(nóng)藥、染料、防腐劑、阻燃劑、香料、塑料的合成中間體.在傳統(tǒng)的化工過(guò)程中,通常在苛刻的條件下,如高溫、高壓以及酸性溶劑中進(jìn)行甲苯的選擇性氧化.光催化有機(jī)合成作為一種"綠色"的合成方法受到越來(lái)越多的關(guān)注.我們發(fā)現(xiàn)鎢酸鉍作為可見(jiàn)光響應(yīng)的光催化劑,可以利用氧氣作為氧化劑,對(duì)甲苯及其衍生物進(jìn)行催化氧化反應(yīng).通過(guò)調(diào)節(jié)水熱法合成鎢酸鉍的酸堿條件,控制其成核生長(zhǎng)過(guò)程,改變其形貌,發(fā)現(xiàn)在pH值為0.49時(shí),得到花狀鎢酸鉍粉末活性最高.X射線衍射、掃描電鏡、紫外可見(jiàn)吸收光譜和比表面測(cè)定結(jié)果發(fā)現(xiàn),花狀鎢酸鉍粉末表現(xiàn)出最佳的甲苯氧化活性很可能是與它最大的比表面積有關(guān)系.為了進(jìn)一步提高催化的活性,我們將助催化劑擔(dān)載在鎢酸鉍粉末上,發(fā)現(xiàn)Pd的擔(dān)載量為0.1wt%時(shí)甲苯氧化反應(yīng)活性最高.將鄰、間、對(duì)位甲基取代以及對(duì)位甲氧基和氯取代的甲苯衍生物進(jìn)行反應(yīng),發(fā)現(xiàn)均可高選擇性地得到目標(biāo)產(chǎn)物.在加入電子犧牲劑硝酸銀和空穴犧牲劑草酸銨到反應(yīng)體系后,發(fā)現(xiàn)反應(yīng)被完全禁阻,說(shuō)明在甲苯氧化反應(yīng)過(guò)程中電子和空穴都起到了相應(yīng)的作用.通過(guò)電化學(xué)測(cè)試發(fā)現(xiàn),鈀作為助催化劑擔(dān)載在鎢酸鉍表面后,產(chǎn)生更強(qiáng)的氧化和還原信號(hào),說(shuō)明其在電子和空穴發(fā)生反應(yīng)的過(guò)程中都起到了相應(yīng)的促進(jìn)作用.由此推測(cè),在甲苯的氧化反應(yīng)中,鎢酸鉍材料表面吸收可見(jiàn)光,產(chǎn)生光生電子和空穴,而鈀的擔(dān)載則促進(jìn)了電子和空穴進(jìn)行氧氣還原和甲苯氧化的過(guò)程.
[Abstract]:Selective oxidation of toluene and its derivatives is an important part of the chemical industry. Oxidation products aldehydes, ketones and acids are synthetic intermediates of pesticides, dyes, preservatives, flame retardants, spices and plastics. The selective oxidation of toluene in traditional chemical processes is usually carried out under harsh conditions, such as high temperature, high pressure and acid solvents. As a green synthetic method, photocatalytic organic synthesis has attracted more and more attention. It is found that bismuth tungstate can be used as a visible photocatalyst to catalyze the oxidation of toluene and its derivatives using oxygen as oxidant. By adjusting the acid-base conditions of hydrothermal synthesis of bismuth tungstate, the nucleation and growth process of bismuth tungstate was controlled and its morphology was changed. It was found that the highest activity of bismuth tungstate powder was obtained at pH 0.49. UV-Vis absorption spectra and specific surface measurements showed that the best toluene oxidation activity of bismuth tungstate powder was probably related to its largest specific surface area. In order to further improve the catalytic activity, the catalyst was supported on bismuth tungstate powder. It was found that the activity of toluene oxidation was the highest when the loading of PD was 0.1 wt%. The reaction of o-, m-, p-methyl-substituted, p-methoxy and chlorinated toluene derivatives shows that the target products can be obtained with high selectivity. After adding electron sacrificial silver nitrate and hole sacrificial ammonium oxalate to the reaction system, it was found that the reaction was completely blocked, indicating that both electrons and holes played a corresponding role in the oxidation of toluene. It was found by electrochemical measurement that palladium as a catalyst supported on the surface of bismuth tungstate produced stronger redox and reduction signals, which indicated that palladium played a corresponding role in the reaction between electrons and holes. It is inferred that in the oxidation of toluene the surface of bismuth tungstate absorbs visible light to produce photogenerated electrons and holes while the loading of palladium promotes the oxygen reduction of electrons and holes and the oxidation of toluene.
【作者單位】： 中國(guó)科學(xué)院大連化學(xué)物理研究所;中國(guó)科學(xué)院大學(xué);
【基金】：supported by the National Natural Science Foundation of China(21322202,21472187) the National Basic Research Program of China(2010CB833300)~~
【分類(lèi)號(hào)】：O643.36

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