本文關(guān)鍵詞：穩(wěn)定于具有亞5nm窗口的立方介孔氧化硅的金納米顆粒及其優(yōu)異的醇氧化活性（英文）　出處：《催化學(xué)報》2017年03期 　論文類型：期刊論文

  更多相關(guān)文章： 金納米顆粒 立方介孔氧化硅 窗口尺寸 抗燒結(jié)性能 醇氧化

【摘要】：金納米顆粒在烯烴加氫、水氣轉(zhuǎn)化、過氧化氫直接合成和醇類選擇性氧化等反應(yīng)中表現(xiàn)出獨特的催化性能,引起了人們廣泛關(guān)注.通常,金納米顆粒的催化活性受到尺寸、原子堆積形式、暴露晶面及其與載體的相互作用所影響.而金納米顆粒的燒結(jié)往往導(dǎo)致其催化效率迅速下降.為了解決金顆粒燒結(jié)問題,提高其使用壽命,必須控制高溫處理時顆粒和原子的遷移.盡管已有很多工作見諸報道,然而到目前為止,仍未完全解決金顆粒燒結(jié)問題.本文通過調(diào)整有機模板劑和反應(yīng)溫度成功地合成了不同窗口尺寸的立方介孔氧化硅材料(FDU-12),并將預(yù)先合成的3nm金顆粒負載于其上,考察了窗口尺寸對金顆粒燒結(jié)的影響.首先,采用小角X射線散射、氮氣吸附-脫附、透射電鏡和掃描電鏡等手段證實成功合成了具有亞5 nm窗口的FDU-12材料,同時以3 nm金顆粒為探針,進一步區(qū)分了具有3 nm和3 5nm窗口的FDU-12樣品.在抗燒結(jié)實驗中發(fā)現(xiàn),具有3 5 nm窗口尺寸的FDU-12能夠在一個較寬的金負載量(1.0 8.3 wt%)下穩(wěn)定金納米顆粒.在550 ℃空氣中焙燒5 h后,金顆粒的平均尺寸維持在4.5 5.0 nm.更小的窗口尺寸則會導(dǎo)致3 nm金顆粒無法進入FDU-12孔道,從而帶來低的負載能力和差的抗燒結(jié)性能.另一方面,具有7 nm窗口尺寸的FDU-12則只在高的金顆粒負載量(9 wt%)下才表現(xiàn)出較好的抗燒結(jié)性能,低負載量時燒結(jié)嚴重(2.1 wt%,14.2±5.5 nm).我們推測,合適的窗口尺寸(3 5 nm)恰好能允許3 nm金顆粒進入FDU-12的孔道,在高溫處理過程中,當金顆粒長大到5nm左右時,窗口極大地限制了金顆粒的移動,導(dǎo)致其不能在孔與孔之間自由遷移.此外,該FDU-12材料的孔徑為18 nm,這使得封裝在各個孔內(nèi)部的金顆粒與其他金顆粒距離較遠,不利于其通過原子遷移而發(fā)生燒結(jié).因此,擁有3 5 nm窗口尺寸的FDU-12在一個寬的金負載量下表現(xiàn)出良好的抗燒結(jié)能力.而對于具有7 nm窗口尺寸的FDU-12,在高的金負載量下,它可通過自聚焦效應(yīng)抑制原子遷移,從而具有優(yōu)良的抗燒結(jié)性能.但在低負載量時,介孔氧化硅的絕大部分孔內(nèi)并不包含多個金顆粒,自聚焦效應(yīng)無法發(fā)揮作用,在高溫焙燒時金顆�？梢酝ㄟ^大的窗口尺寸相互融合導(dǎo)致燒結(jié).我們將具有不同金尺寸的Au NP/FDU-12催化劑用于環(huán)己醇選擇性氧化反應(yīng)中.結(jié)果表明,4.5 nm的金催化劑表現(xiàn)出最好的活性(1544 mmol g_(Au)~(-1)h~(-1))和大于99%的選擇性(230 ℃),大大超過了先前報道的基于Ag和Mn為活性中心的催化劑.另外,與負載在商用γ-Al_2O_3上相比,Au NP/FDU-12體系表現(xiàn)出了很好的選擇性,直接脫水產(chǎn)物小于1%.同時可以保持100 h內(nèi)金顆粒不發(fā)生燒結(jié),活性不明顯下降.
[Abstract]:Gold nanoparticles exhibit unique catalytic properties in olefin hydrogenation, water-gas conversion, direct synthesis of hydrogen peroxide and selective oxidation of alcohols. The catalytic activity of gold nanoparticles depends on the size, atomic stacking form. In order to solve the problem of sintering gold particles and improve their service life, the sintering of gold nanoparticles often leads to a rapid decline in catalytic efficiency. It is necessary to control the migration of particles and atoms during high temperature treatment. Although a lot of work has been reported, so far. The problem of gold particle sintering has not been completely solved. In this paper, cubic mesoporous silicon oxide materials with different window sizes have been successfully synthesized by adjusting the organic template and reaction temperature. The effect of window size on the sintering of gold particles was investigated by loading the pre-synthesized 3nm gold particles on it. Firstly, small angle X-ray scattering and nitrogen adsorption-desorption were used. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that FDU-12 materials with sub-5 nm window were successfully synthesized, and 3nm gold particles were used as probes. The FDU-12 samples with 3 nm and 3 5 nm windows were further distinguished. The FDU-12 with a window size of 3 ~ 5 nm is capable of being measured at a wide gold load of 1. 0 ~ 8. 3 wts. The gold nanoparticles were calcined at 550 鈩，

本文編號：1430319