【摘要】 催化氧化苯甲醇是制备苯甲醛的一种简便高效的方法.以天然高分子黑荆树单宁(BWT)为两亲性稳定剂,制备水溶性钯纳米胶体催化剂,用于苯甲醇的氧化反应.采用透射电镜(TEM)、傅里叶变换红外光谱(FT-IR)等表征手段表征所制备催化剂的形貌,探讨制备条件对催化剂形貌的影响.TEM测试表明,单宁的用量对胶体中钯纳米粒子的粒径具有显著的影响,随着BWT用量从2 mg增加到60 mg,Pd粒子的粒径呈现减小趋势.FT-IR测试表明,BWT通过其结构中大量的酚羟基对Pd纳米粒子进行稳定和分散.系统考察单宁用量、反应温度、反应时间等因素对Pd纳米胶体在苯甲醇氧化反应中活性的影响,结果表明:当BWT用量为15 mg时制备的BWT15 mg-Pd胶体催化剂在50℃,空气气氛下8 h催化苯甲醇的转化率高达98.58%; BWT用量对催化剂重复使用性能也有显著的影响,BWT15 mg-Pd可以重复使用5次转化率仍然在90%以上,明显优于BWT5 mg-Pd和BWT60 mg-Pd.更多还原

【Abstract】 Catalytic oxidation of benzyl alcohol is an efficient synthesis method of benzaldehyde. In this paper,black wattle tannin( BWT) was used as amphiphilic stabilizer to prepare water soluble palladium nano-colloid catalyst for oxidation of benzyl alcohol. The morphology of the catalyst was characterized by Transmission Electron Microscopy( TEM) and Fourier Transform infrared spectrometer( FT-IR). The influence of preparation conditions on the morphology of the catalyst was discussed. TEM images showed that the particle size decreased with the increase of the amount of BWT from 2 mg to 60 mg. BWT amount had a significant effect on the size of palladium nanoparticles in the colloid. FT-IR results indicated that the Pd nanoparticles were stabilized and dispersed through a large number of phenolic hydroxyl groups in BWT structure. The effects of BWT amount,reaction temperature and time on the activity of as-prepared Pd nanoparticles in benzyl alcohol oxidation were investigated. When the BWT amount was 15 mg,the conversion rate was up to98.58% when the BWT-Pd colloid catalyst was used as catalyst at 50 ℃ in air for 8 hours. The amount of BWT also had a significant effect on the reusability of the catalyst. The conversion rate of BWT15 mg-Pd was above 90% after 5 cycles,which was obviously superior to that of BWT5 mg-Pd and BWT60 mg-Pd.更多还原