第31卷第2期齊齊哈爾大學(xué)學(xué)報VoL 31. No. 22015年3月Journal of Qiqihar UniversityMarch 2015KAg-SBA-15催化劑用于低溫苯甲醇?xì)庀噙x擇性氧化制苯甲醛項(xiàng)禮軍,賈麗華,郭祥峰(齊齊哈爾大學(xué)化學(xué)與化學(xué)工程學(xué)院,黑龍江齊齊哈爾161006)摘要:采用浸漬法制備KAg-SBA-15催化劑,并在低溫苯甲醇?xì)庀噙x擇性氧化制苯甲醛反應(yīng)中硏究其催化性能結(jié)果表明,對于0.5- K/Ag-SBA-15催化劑,在反應(yīng)溫度為240C時,苯甲醇的轉(zhuǎn)化率為96%,苯甲醛的選擇性為94%。通過XRD、XPS對催化劑進(jìn)行表征。由XRD結(jié)果發(fā)現(xiàn),隨著K,Ag摩爾比增加金屬Ag顆粒在SBA-15孔道內(nèi)的分散程度隨之增加。另外,XPS結(jié)果分析發(fā)現(xiàn),K2O可以使更多的電子富集在金屬Ag顆粒表面。關(guān)鍵詞:KAg-SBA-15;K2O;苯甲醇;苯甲醛中圖分類號:TQ2441文獻(xiàn)標(biāo)志碼:A文章編號:1007-984X(2015)02-0024-03近年來,苯甲醇?xì)庀噙x擇性氧化反應(yīng)的催化劑在發(fā)展高效和綠色的催化劑方面顯示出了巨大的潛力,然而這些催化劑的催化反應(yīng)溫度均在300cC以上,高出苯甲醇沸點(diǎn)(203C)100℃以上。對于高的反應(yīng)溫度,在反應(yīng)過程中往往需要消耗很高的能量,這就限制了催化劑的應(yīng)用。因此,開發(fā)低溫高效的催化劑是目前研究的重點(diǎn)。本研究采用浸漬法制備KAg-SBA-15催化劑,通過XRD,XPS對催化劑進(jìn)行表征,研究了不同K,Ag摩爾比的KAg-SBA-15催化劑在低反應(yīng)溫度下氣相催化氧化苯甲醇反應(yīng)的影響。1實(shí)驗(yàn)部分1.1K(Ag-SBA-15催化劑的制備浸漬法制備K,Ag摩爾比不同的K/Ag-SBA-15。合成過程如下:取1.500g新制SBA-15載體浸漬在50mL不同量的KNO3與0.142g的AgNO混合水溶液中,50℃下攪拌10h后,于80℃的烘箱中干燥12h,500Cc焙燒6h,既得K,Ag摩擎爾比不同的K/Ag-SBA-15催化劑。(記:x-K/Ag-SBA-15;x表示K,Ag摩爾比;x=0.3,0.5,0.8,1.0)12x-KAg-SBA-15催化劑的評價氣相催化氧化苯甲醇反應(yīng)采用常壓連續(xù)固定床反應(yīng)器(R=10mm,L=450mm)在N2和O體積比為3:7總流速為50m/min的條件下于500℃C活化2h,隨后通入載氣N2(35ml/min)、反應(yīng)物O2和苯甲醇,在反應(yīng)溫度240℃,重時空速WHSV為78h,n(O2):n( benzyl alcohol)=0.6的反應(yīng)條件下進(jìn)行反應(yīng),產(chǎn)物經(jīng)冰鹽浴(-10~-15C)冷卻后收集。產(chǎn)物在GC-9800氣相色譜儀上進(jìn)行定量分析。2結(jié)果與討論2.1x-KAg-SBA-15催化劑的XRD分析圖1中(a)為x-KAg-SBA-15催化劑小角x射線衍射圖,圖(b)為x-K/Ag-SBA-15催化劑的廣角x射線衍射圖,圖1(a)顯示在20=1.5°~20范圍內(nèi),所有樣品均出現(xiàn)兩個特征衍射峰分別歸屬于(110)和(200)晶面,說明樣品均保持了SBA-15分子篩的六方介孔結(jié)構(gòu),當(dāng)x=10時,特征衍射峰的強(qiáng)度明顯減弱,可能是由于過多的鉀物種的引人導(dǎo)致SBA-15結(jié)構(gòu)發(fā)生變化。圖4(b)顯示樣品(1)~(3)在20=384,44.0,收稿日期:2014-12-16基金項(xiàng)目:齊齊哈爾科技局項(xiàng)目(GYGG-201108)作者簡介:項(xiàng)禮軍(1988-),男,黑龍江鶴崗人,在讀碩士研究生,主要從事催化劑方面研究,xj945123@126.com。第2期K/Ag-SBA-15催化劑用于低溫苯甲醇?xì)庀噙x擇性氧化制苯甲酯643,77.5°出現(xiàn)特征衍射峰分別歸屬于金屬Ag的(111),(200),(220),(311)晶面,且隨著K,Ag摩爾比的增加金屬Ag的特征衍射峰逐漸減弱,表明金屬Ag顆粒在載體SBA-15表面的分散程度逐漸增加。(a)1.52025303540455030圖1x-K/Ag-SBA-15的XRD圖,(曲線(1)~(4):x=0.3,0.5.0.810)220.5- K/Ag-SBA-15催化劑的XPS分析圖2為0.5-KAg-SBA-15催化劑的XPS譜圖,其中圖2(a)為K2p的XPS譜圖,在結(jié)合能為2934eV處的峰歸屬于K2p;結(jié)合能為296.3cV處的峰歸屬于K2pi,說明在K/Ag-SBA-15催化劑中鉀物種以K3O的形式存在。圖2(b)是Ag3d的XPS譜圖,圖中電子結(jié)合能為3680eV和374.0eV的譜峰,分別歸屬于Ag3ds2和Ag3d,其中Ag3ds和Ag3dn的結(jié)合能差值4E=60eV,另外在圖2(b)中將Ag3ds峰分為兩個峰,其峰值分別在368.1eV和367.3eV,且分別對應(yīng)于Ag和Ag,這說明在催化劑表面Ag物種主要以金屬Ag存在這與XR的結(jié)果一致。與文獻(xiàn)結(jié)果5相比,催化劑中Ag的電子結(jié)合能值發(fā)生負(fù)偏移,表明K2O使金屬Ag的表面富集更多電子,這將有利于苯甲醇選擇性氧化300364366368370372374376378Binging Energy(ev)Binging Energy(ev)圖20.5-K/Ag-SBA-15催化劑的XPS圖23x-KAg-SBA-15催化性能測試圖3為K,Ag摩爾比對K/Ag-SBA-15催化100劑在苯甲醇?xì)庀噙x擇性氧化反應(yīng)中催化劑性能的影響圖。由圖3可知,隨著K,Ag摩爾比增加,催化劑活性明顯變化,其中K,Ag摩爾比為0.5時催化活性相對最好。這是由于粒徑變小的Ag顆粒易吸附氧,而吸附的氧會在富電子-a-Conversion of benzyl alcohol的金屬Ag表面與金屬Ag表面的電子相互作用-o- Selectivity of benzaldehyde形成親核氧物種,過多的親核氧物種會通過氧溢流過程遷移到SBA-15表面并與吸附在The molar ratio of K to agSBA-15表面的苯甲醇分子發(fā)生氧化反應(yīng),從圖3K,Ag摩爾比對 K/Ag-SBA15催化劑的催化性能影響圖而使催化活性隨K,Ag摩爾比增加而提高了。26齊齊哈爾大學(xué)學(xué)報但當(dāng)K,Ag摩爾比大于0.5時催化活性下降,這可能是過多的K2O與Ag顆粒以及載體之間相互作用導(dǎo)致催化劑結(jié)構(gòu)的變化所致。3結(jié)束語通過浸漬法制備的x-K/Ag-SBA-15催化劑,在低反應(yīng)溫度(240℃)下完成了苯甲醇?xì)庀噙x擇性氧化反應(yīng),且0.5-K/Ag-SBA-15的催化劑獲得了相對較好的催化活性。另外,從催化劑表征結(jié)果發(fā)現(xiàn)增加K,Ag摩爾比的量可以增加Ag顆粒的在SBA-15表面分散程度;K2O可以使Ag顆粒表面富集更多的電子。參考文獻(xiàn)[1 Mao J, Deng M Xue Q et al. Thin-Sheet Ag/Ni-Fiber Catalyst for Gas-Phase Selective Oxidation of Benzyl Alcohol with MolecularOxygen [J Catal. Commun., 2009, 10(10): 1376-1379[2] Jia L, Zhang S,Gu F, et al. Highly Selective Gas-Phase Oxidation of Benzyl Alcohol to Benzaldehyde over Silver-ContainingHexagonal Mesoporous Silica[J]. Microporous Mesoporous Mater. 2012, 149(1 ): 158-165[3] Yamamoto RSawayama Y, Shibahara H, et al. Promoted Partial Oxidation Activity of Supported Ag Catalysts in the Gas-PhaseCatalytic Oxidationzyl Alcohol(J- J Catal., 2005, 234(2): 308-317[4] Deng M, Zhao G, Xue Q, et al. Microfibroug-Structured Silver Catalyst for Low-Temperature Gas-Phase Selective Oxidation of BenzylAlcohol[J). Appl. Catal. B: Environ., 2010. 99(1-2): 222-228[5] Mao J, Deng M, Chen L, et al. Novel Microfibrous-Structured Silver Catalyst for High Efficiency Gas-Phase Oxidation of Alcohols[JIAIChE J.20091545-155616 Liu J, Liu Y, Yang W, et al. A Novel and Simple Strategy for the Direct Synthesis Bimetallic Mesoporous Materials Zr-La-SBA-15[J]. Mater. Lett., 2014, 128: 15-18[7] Yang M Ling Q, Yang H,et al. Enhanced Catalytic Activity of K-Birnessite MnO, Confined in Carbon Nanotubes for SelectiveOxidation of Benzyl Alcohol[J]. Catal. Commun., 2014, 46: 238-241[8] Reshetnikov S I Mathematical Modeling of Toluene Oxidation with a Periodic Reactor Operation [J]. Reaction Kinetics, Mech. Catal2010,99:23-219] Pajonk G M Contribution of Spillover Effects to Heterogeneous Catalysis[J].Appl. Catal. A: Gen, 2000, 202: 157-169K/Ag-SBA-15 catalysts in the selective oxidation of benzyl alcohol to benzaldehydeXIANG Li-jun, JIA Li-hua, GUO Xiang-fengCollege of Chemistry and Chemical Engineering, Qiqihar University, Heilongjiang Qiqihar 161006, ChinaAbstract: K/Ag-SBA-15 catalysts was prepared by an impregnation method. Their catalytic performance wasInvestigated in the gas-phase selective oxidation of benzyl alcohol to benzaldehyde. It was found that the0.5-K/Ag-SBA-15 catalyst gave 96% conversion of benzyl alcohol and 94 %o selectivity of benzaldehyde at 240CThe catalysts were characterized by Xrd and XPS. The results showed that increasing the amount of K,0 couldpromote the metallic Ag particles disperse in the channel of SBA-15. XPS analysis found thatK20 make more electron rich on Metallic Ag surfaceKey words: K/Ag-SBA-15; K20; benzyl alcohol; benzaldehyde