【摘要】：苯甲醛是一種重要的化工原料,也是一種重要的有機(jī)合成中間體,普遍用于香料、塑料合成和染料行業(yè)中。傳統(tǒng)的合成苯甲醛方法是甲苯鹵代水解法,該工藝是通過甲苯甲苯氯代反應(yīng)、皂化反應(yīng),制得苯甲醛。該方法不僅污染環(huán)境且苯甲醛的收率低下,產(chǎn)品中含有鹵素離子,使其應(yīng)用受到限制。因此,尋求一種高效、清潔的苯甲醛合成路線具有十分重要的意義。本文通過可控合成,制備一系列對(duì)甲苯選擇氧化合成苯甲醛具有高活性和高選擇性的催化劑,探討催化劑結(jié)構(gòu)與性能的關(guān)系,為甲苯選擇氧化合成苯甲醛新技術(shù)的開發(fā),提供基礎(chǔ)數(shù)據(jù)與關(guān)鍵技術(shù)。本研究通過可控固相合成,制備了Mo O_3-Mo V_2O_8催化劑和Mo O_3-Fe_2(Mo O_4)_3-Mo V_2O_8催化劑,并引入Fe_3O_4磁核,制備了Mo O_3-Mo V_2O_8@Fe_3O_4磁性催化劑�？紤]石墨型氮化碳g-C_3N_4材料的特殊空間結(jié)構(gòu)和電子分布特性,組裝了Mo V_2O_8/g-C_3N_4催化劑。采用雙氧水為氧化劑,甲苯選擇性氧化反應(yīng)為探針反應(yīng),對(duì)上述催化劑的活性與苯甲醛的選擇性進(jìn)行了評(píng)價(jià)。采用XPS、SEM、TG-DSC、XRD、TPR等系列現(xiàn)代分析表征方法,對(duì)催化劑結(jié)構(gòu)進(jìn)行了深入分析,并關(guān)聯(lián)催化劑的催化性能,揭示催化劑的構(gòu)效關(guān)系,為選擇氧化反應(yīng)催化劑的設(shè)計(jì)與組裝提供重要的基礎(chǔ)數(shù)據(jù)。研究表明,當(dāng)釩鉬比為1:1時(shí),通過溶膠凝膠法制備的前驅(qū)物在550℃下的高溫固相反應(yīng),制備出Mo O_3-Mo V_2O_8催化劑。該催化劑在80℃下催化甲苯氧化反應(yīng)中,當(dāng)反應(yīng)8小時(shí),甲苯轉(zhuǎn)化率為36.0%,苯甲醛選擇性為53.2%。為了進(jìn)一步提高催化劑的性能,通過摻雜Co、Cr、Ce、La和Fe對(duì)Mo O_3-Mo V_2O_8催化劑進(jìn)行了改性研究。研究表明,Co、Cr、Ce、La和Fe對(duì)催化劑都有改性作用,其中以Fe對(duì)催化劑的改性較大,當(dāng)原子比V:Mo:Fe=6:7:1時(shí),甲苯轉(zhuǎn)化率為40.3%,苯甲醛選擇性為84.5%。XRD分析表明,催化劑中存在Fe_2(Mo O_4)_3物相,XPS分析表明,鐵的摻入,使得催化劑中鉬物種的電子云密度增加,提高了催化劑的活性。為了便于快速回收液相反應(yīng)中的催化劑粉體,引入了磁性材料Fe_3O_4,并以此為核,在Fe_3O_4表面自組裝Mo O_3-Mo V_2O_8催化劑殼層,組裝成具有核殼結(jié)構(gòu)的Mo O_3-Mo V_2O_8@Fe_3O_4磁性催化劑。研究表明,在Fe_3O_4表面散亂分布的釩鉬復(fù)合氧化物,在550℃下可自組裝為Mo O_3-Mo V_2O_8晶相。甲苯在該催化劑上的轉(zhuǎn)化率為36.6%,苯甲醛的選擇性為79.8%。反應(yīng)后,通過附加外部磁場,催化劑可快速聚集回收�；谑偷糶-C_3N_4特殊的空間結(jié)構(gòu)和在催化中呈現(xiàn)的優(yōu)異催化性能,通過高溫固相反應(yīng),在g-C_3N_4表面自組裝了Mo V_2O_8催化劑,考察了制備過程對(duì)Mo V_2O_8/g-C_3N_4催化劑結(jié)構(gòu)與性能的影響。研究表明,甲苯在該催化劑上的甲苯轉(zhuǎn)化率和苯甲醛選擇性分別為43.5%和72%,苯甲醛收率可達(dá)31.3%。
[Abstract]:Benzaldehyde is an important chemical raw material and an important intermediate of organic synthesis. It is widely used in perfume, plastics synthesis and dye industry. The traditional method of synthesizing benzaldehyde is the hydrolysis of toluene halogenation. The process is to produce benzaldehyde by chlorination of toluene and saponification. The method not only pollutes the environment, but also has a low yield of benzaldehyde and halogen ions in the product, so its application is limited. Therefore, it is of great significance to seek an efficient and clean synthetic route for benzaldehyde. In this paper, a series of catalysts with high activity and selectivity for the selective oxidation of toluene to benzaldehyde were prepared by controllable synthesis. The relationship between the structure and the performance of the catalyst was discussed, and the new technology of selective oxidation of toluene to benzaldehyde was developed. Provide basic data and key technologies. In this study, Mo O_3-Mo V_2O_8 catalyst and Mo O_3-Fe_2 (Mo Oste4) _ 3-Mo V_2O_8 catalyst were prepared by controllable solid-state synthesis, and Fe_3O_4 magnetic nuclei were introduced. Mo O_3-Mo V_2O_8@Fe_3O_4 magnetic catalyst was prepared. Considering the special space structure and electron distribution of graphite type carbon nitride (g-C_3N_4), the Mo V_2O_8/g-C_3N_4 catalyst was assembled. The activity of the catalyst and the selectivity of benzaldehyde were evaluated by hydrogen peroxide as oxidant and toluene selective oxidation as probe reaction. A series of modern analysis and characterization methods, such as XPS,SEM,TG-DSC,XRD,TPR and so on, were used to analyze the structure of the catalyst, and related the catalytic performance of the catalyst to reveal the structure-activity relationship of the catalyst. It provides important basic data for the design and assembly of catalyst for selective oxidation reaction. The results show that when the vanadium molybdenum ratio is 1:1, the Mo O_3-Mo V_2O_8 catalyst is prepared by solid state reaction of the precursor prepared by sol-gel method at 550 鈩，

本文編號(hào)：2303822