WO3/Al2O3-TiO2催化劑的制備及其在甘油氣相脫水制備丙烯醛中的應(yīng)用

劉 濤, 王奐祎, 賀站鋒, 王 丹, 蔣 毅

(1. 中國(guó)科學(xué)院 成都有機(jī)化學(xué)研究所，四川 成都 610041； 2. 中國(guó)科學(xué)院大學(xué)，北京 100049)

近年來(lái)，生物柴油在全球的迅猛發(fā)展[1]致使副產(chǎn)物甘油的大量過(guò)剩，如何有效利用過(guò)剩的甘油成為一個(gè)重要的研究課題。比較有效的解決方式是將甘油通過(guò)化學(xué)法，如選擇性氧化、脫水、氫解、鹵化、酯化和醚化、蒸汽重整等途徑[2,3]轉(zhuǎn)化成附加值更高的化工產(chǎn)品。在這些轉(zhuǎn)化途徑中，甘油脫水制備丙烯醛[4]具有較大的發(fā)展?jié)摿Α?/p>

目前，用于甘油脫水制備丙烯醛的固體酸催化劑主要有四大類：氧化物[5～8]、雜多酸[9～11]、分子篩[12～14]和磷酸鹽[15～17]。其中含有WO3的催化劑具有較大的應(yīng)用潛力。Arda Ulgen等報(bào)道WO3/ZrO2[5]或WO3/TiO2[8]催化甘油脫水制備丙烯醛，收率均在70%以上；Lauriol-Garbey P等[7]用SiO2修飾WO3/ZrO2為催化劑，反應(yīng)150 h，轉(zhuǎn)化率達(dá)80%，丙烯醛選擇性>70%；Kraleva E等[18]報(bào)道W-SBA-15催化劑在280 ℃以下反應(yīng)，轉(zhuǎn)化率達(dá)90%，丙烯醛選擇性>70%；Suprun W等[17]使用過(guò)渡金屬修飾鋁磷酸鹽為催化劑，其對(duì)丙烯醛的選擇性順序?yàn)椋篧>Mo>Cu>V～Fe>Cr>Mn>Ce。以上催化劑，雖然在甘油脫水制備丙烯醛的反應(yīng)中，具有較佳的催化活性，但還難以實(shí)現(xiàn)商業(yè)化應(yīng)用，新催化劑的開(kāi)發(fā)仍是甘油脫水研究的熱點(diǎn)。工業(yè)Al2O3(含5 wt%TiO2)是一種廣泛使用的載體，而WO3/Al2O3-TiO2催化劑應(yīng)用于甘油脫水高選擇性制備丙烯醛的相關(guān)研究還未見(jiàn)文獻(xiàn)報(bào)道。

Scheme1

1 實(shí)驗(yàn)部分

1．1 儀器與試劑

NOVA 2200e型氮吸附儀；Rigaku D/max-2500/PC型X-射線衍射儀(XRD)；SC-200型和SC3000-B型氣相色譜儀[HP-INNOWAX毛細(xì)管柱(30 m×0.32 mm×0.25 μm)；載氣：高純N2；FID檢測(cè)器；1,2-丙二醇為內(nèi)標(biāo)]；STA449C型熱重分析儀(TGA)；自行組裝的TCD-GC裝置(內(nèi)徑9 mm,長(zhǎng)度35.0 cm)。

鎢酸銨(H40N10O41W12·xH2O),分析純，國(guó)藥集團(tuán)化學(xué)試劑有限公司；30%過(guò)氧化氫，分析純，廣東光華化學(xué)廠有限公司；工業(yè)Al2O3(含5 wt%TiO2)，江蘇三劑實(shí)業(yè)有限公司，使用前于750 ℃焙燒2 h，研磨至40 目～60 目后備用。

在反應(yīng)瓶中加入鎢酸銨2.94 g(0.97 mmol)和水10 mL，攪拌使其溶解；加入Al2O3載體10 g，攪拌均勻，于室溫浸漬24 h；于110 ℃干燥10 h制得Cat20[w(WO3)=20%]。

改變鎢酸銨用量，用類似方法制得Catw(表1)。

表 1 制備的實(shí)驗(yàn)條件Table 1 Conditions of preparing

*w(WO3)=m(WO3)/[m(WO3)+m(Al2O3-TiO2)]×100%; T：焙燒溫度

1．3 甘油脫水制備丙烯醛反應(yīng)

2 結(jié)果與討論

2.1 表征

2θ/(°)圖的XRD譜圖

Temperature/℃圖2 Cat20的TGA曲線Figure 2 TGA curvesl of Cat20

2.2 載體與催化劑的織構(gòu)性質(zhì)

表 2 載體和催化劑的織構(gòu)性質(zhì)Table 2 Textural properties of the support and catalysts

w/%圖3 w對(duì)脫水反應(yīng)的影響*Figure 3 Effect of w on dehydration of glycerol over

Calcination temperature/℃圖4 焙燒溫度對(duì)脫水反應(yīng)的影響Figure 4 Effect of calcination temperature on dehydration of glycerol over

Reaction temperature/℃圖5 反應(yīng)溫度對(duì)脫水反應(yīng)的影響Figure 5 Effect of reaction temperature on dehydration of glycerol over

(1)w

(2)焙燒溫度

2.4 反應(yīng)溫度對(duì)反應(yīng)的影響

2.5 催化劑的NH3-TPD

Temperature/℃圖的NH3-TPDFigure 6 NH3-TPD prfiles of

w/%圖總酸量與w(a)或焙燒溫度(b)的關(guān)系Figure 7 Effect of w(a) or calcination temperature(b) on the total amount of acid of

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