【作者】 邹秀晶；

【导师】 张文祥； 贾明君；

【作者基本信息】 吉林大学 ， 物理化学， 2009， 博士

【摘要】 邻羟基苯乙(甲)醚是香料、农业、医药、染料等工业中重要的中间体和原料,有着广泛的用途。以邻苯二酚和乙(甲)醇为原料、气相单醚化法合成邻羟基苯乙(甲)醚具有成本低、毒性和腐蚀性小等优点,是目前世界上最先进、最具竞争力的工艺路线之一。本论文以该反应为目标反应,重点围绕磷酸铝体系催化剂,通过改进和优化制备方法,制备出一系列具有不同孔结构和表面酸碱性质的催化剂,并对性能较好的催化剂进行了放大合成及催化剂成型研究。结合多种表征手段研究了催化剂的结构、表面酸碱性质与反应性能之间的关系,探讨了催化剂的活性中心性质及催化作用机制等问题。从磷铝两组分催化剂入手,通过筛选不同的磷源、调控各种制备参数(如:合成终点的pH值、P/Al比等),制备出具有高活性和高稳定性的磷酸铝催化剂。该方法制备过程简单、重现性好,经公斤级放大后,所制备催化剂的性能没有明显变化。对该催化剂进行挤出成型实验结果表明:添加一定量硝酸和硅胶作为粘结剂,可以得到机械强度和催化性能良好的催化剂。稳定性考察结果表明:催化剂在邻苯二酚和甲醇气相反应上连续进行480小时未见明显失活,在邻苯二酚和乙醇反应上累积寿命可达2000小时以上。考察了以柠檬酸作为有机添加剂制备的介孔磷酸铝催化剂上邻苯二酚分别与甲醇和乙醇反应的催化性能,系统地比较了两个反应在相同催化剂上邻苯二酚转化和产物分布的异同,结合催化剂表面酸碱性质探讨了催化剂的活性中心性质与反应性能之间的关系。结果表明:催化剂表面弱酸弱碱中心是邻苯二酚与乙(甲)醇O-烷基化反应的主要活性中心;与甲醇相比,乙醇与邻苯二酚选择合成邻羟基苯乙醚需要强度更弱的酸中心。采用溶剂热合成法制备了具有AFI结构的微孔AlPO-5材料并用于上述反应,结果表明这类催化剂上邻羟基苯甲醚的选择性均达到96%以上,显示出很高的目的产物选择性。此外,我们还考察了二氧化硅为载体的负载偏钨酸铵催化剂和以柠檬酸为添加剂制备的介孔钛硅材料的催化性能,结合材料表面酸碱性质进一步探讨了催化剂的活性中心本质和催化作用机制等问题。更多还原

【Abstract】 Guathol and guaiacol are important synthetic intermediate in fine chemical production. They are widely used in the production of flavouring agents, fragrances, agricultural chemicals and pharmaceuticals. Traditionally, guathol and guaiacol were synthesized by homogeneous phase and batch processes, which had complicated technological process and were corrosive, toxic and environmental hazardous. Recently, vapour-phase alkylation of catechol with methanol and ethanol for the synthesis of guaiacol and guathol has received more attention, since this route is more economical and more environmentally friendly for industrial applications. This process will be the main direction of scientific research and industrial production in future.Some heterogeneous catalysts have been tested in the vapour-phase alkylation of catechol with ethanol (methanol) early. However, a common problem is that most of the tested catalysts exhibited unsatisfactory activity and/or unfavourable rapid deactivation. These drawbacks restrict the application of this route to produce guathol(guaiacol). Recently, our research team found that Al-P-Ti and Al-P-Ti-Si showed high catalytic activity and stability in the vapour-phase of catechol and ethanol (methanol), which indicates a good prospect. However, from the perspective of industrial applications, the preparation process of the catalysts is relative complexity and the shaping technics need to study systemically. Otherwise, the relationship between the acid-base properties of the catalysts and their catalytic performance for the reaction needs to study further.Base on preliminary work, we focus on preparing the Al-P-O catalysts with different texture and acid-base properties by improving and optimizing the preparation method. The vapour-phase O-methylation of catechol with ethanol (methanol) has been investigated over these catalysts. Magnifying and shaping of the catalysts which showed better catalytic performance are also studied. The relationship between the texture, acid-base properties and the catalytic performance of catalysts were studied by different characterization means of XRD, BET, TPD, SEM and FTIR of pyridine and ammonia adsorption etc. Meanwhile, the nature of active center and the reaction mechanism were also discussed.TFirstly, Al-P-O catalysts were prepared with a simple precipitation method. The catalytic properties of Al-P-O samples synthesized with different P sources, pH and P/Al ratio in the vapour-phase O-ethylation of catechol with ethanol were investigated. Al1P1.1 prepared with NH4H2PO4 and shows higher activity. With the incresacing of pH, the activity of the reaction increase and the catalyst prepared with 7 showed the highest activity. Magnifying, repeatability and shaping of the catalysts were also studied. Samples prepared with different batchs give higer activity and yield of guathol (above 80%), so this preparation method shows good repeatability. Silica gel, nitric acid and sesbania gum powder as shaping additives were attempted to shape the catalyst. With the increasing amount of silica gel and nitric acid, the mechanical strength of shaped catalysts increase and the conversion of catechol decrease gradually. When the amount of silica gel were 0-10% and nitric acid were 8.7-17.4%, the mechanical strength of shaped catalysts and the conversion of catechol were comparatively higher. The shaped catalysts were satisfied with amplificatory reaction.The catalyst shows the excellent durability. The stability of the catalysts is investigated for the vapour-phase alkylation of catechol with methanol and the vapour-phase alkylation of catechol with ethanol. The catalyst can keep high stability for more than 450h and 2000h respectively. Mesoporous aluminophosphate materials have been synthesized in the presence of citric acid. The results of characterization showed that P/Al molar ratio could adjust the acidic-basic property. The vapour-phase selective O-methylation of catechol with methanol reaction and catechol with ethanol reaction are carried out separately to investigate the catalytic performances of AlPO materials with different P/Al ratios. The conversion of catechol and the production distribution were compared in these two reactions systemically. Among AlPO materials with different P/Al ratios, AlP1.1O shows the highest activity and the highest yield of the main product in the two reactions. The conversion of catechol and the production distribution on AlP0.9O、AlP1.0O and AlP1.05O samples have distinct difference bewteen the two reactions. When catechol reacted with methanol, the conversion of catechol increased with the increasing P/Al ratios and the selectivity of guaiacol are all above 60%. When catechol reacted with ethanol, catechol is nearly reacted to produce C-alkylation productions. It supposes that ethanol produce carbenium ions easily on these catalysts, so the carbenium ions are probability to attack the atom of the catechol and produce C-alkylation productions. Meanwile, the conversion of catechol is very high. On AlP1.1O and AlP1.15O samples,there have no difference of catechol conversion and the production distribution. The conversion of catechol are both above 85% of the two reactions, and the yield of guaiacol and guathol are 73.8% and 64.1% respectively. According to the characterization results, weak acid-base sites are the active centers of O-methylation of catechol with methanol and ethanol. The weaker acid-base centers are required of the latter reaction than that of the former reaction.AlPO-5 molecular sieve prepared by solvothermal method was investigated on the vapour-phase O-methylation of catechol with methanol. AlPO-5 was highly selectivity of the main product guaiacol (96%), but the conversion of catechol was lowly (38%). Different hydroxy-carboxylic compounds (citric acid, glucose and polyethylene glycol) were attempted to modify AlPO-5. The samples synthesized with polyethylene glycol was the highest conversion of catechol(68%) and the selectivity of guaiacol was highly (94%).Other weak acid-base catalysts were investigated in the vapour-phase O-methylation of catechol and methanol. AMT impregnated C, TiO2 and SiO2 catalysts were highly active and selective for the vapour-phase O-methylation of catechol with methanol. The activity of AMT impregnated C and TiO2 decreased obviously in 24h, no obviously activity loss occurs with the running term of 47h on AMT/ SiO2 sample. With further increasing reaction time, the activity of the catalyst decreased gradually, which may be mainly caused by the coke formation on the surface of the catalysts. In order to remove the carbon deposition, the used catalyst was calcined at higher temperature. The conversion of catechol increased slightly, but the stability decreaed. This result is consistent with the performance of catechol and methanol over the catalyst calcined at higer temperature. According to the result of CO2-TPD and NH3-TPD, the catalyst calcined at higer temperature present a certain amount of relatively stronger acid-base centers. These results further suggest that weak acid-base sites are acitive centers for the vapour-phase of catechol and methanol to produce guaiacol. Ti-Si samples possessed weak acid-base sites were also investigated in the vapour-phase O-methylation of catechol and methanol. Reaction activity decreased significantly within 6h, may be due to the sample surface on the Lewis acid sites caused by coke formation. Bronsted acid site of the materials with weak acid-base is active center in the O-methylation of catechol with methanol.更多还原