New Solid Acid Applied in Vapor Beckmann Rearrangement

己内酰胺是一种重要的有机化工原料。采用环己酮肟的气相Beckmann重排的方法制己内酰胺可以解决传统的液相工艺中存在的副产硫酸胺、腐蚀设备和污染环境等问题。本研究的目的是开发出适合环己酮肟的气相Beckmann重排的固体酸催化新工艺。 首先，本工作用同位素标记的方法研究了Beckmann重排在固体酸B2O3/γ-Al2O3和TS-1上的反应机理。同位素标记后的产品采用质谱测量。通过与H218O交换氧，发现环己酮肟与H218O的交换在B2O3/γ-Al2O3和TS-1只能进行到一定程度，这暗示固体酸上腈中间体的解离不如经典的机理完全。提出了解离度(α)的概念，其定义为解离了中间体腈与总中间体腈之比。通过拟合实验数据和同位素标记的产品的计算公式，获得了B2O3/γ-Al2O3和TS-1上α 值分别为0.199和0.806的结果。 其次，采用对氧化铝表面合适氟化的方法，对氟化的氧化铝的性能进行研究。发现氧化铝表面氟化可以改善Beckmann重排的性能。氧化铝表面氟化可以消除其表面碱性位，说明了催化剂表面碱性位不利于Beckmann重排。而完全氟化的氧化铝的选择性不如某些固体酸如负载B2O3和Silicalite-1，暗示着表面酸强度也影响催化剂的选择性。同时，我们对适合气相Beckmann重排的催化剂进行了简单的筛选。发现一种稀土焦磷酸盐有可能是适合此反应的催化剂。 再次，研究了稀土焦磷酸盐催化剂上气相Beckmann重排。通过对一些稀土磷酸进行XRD,FT-IR,NH3-TPD和水接触角等表征，发现这类催化剂上表面的弱酸位以及合适的表面疏水是它们具有较好性能的原因。 再次，对焦磷酸铈催化剂的合成以及反应氛围进行了优化。发现优化的反应氛围为催化剂在pH在3~4时沉淀，在500~550度焙烧，在~350度反应，载气~80ml/min，空速在0.43h-1时反应，能保持转化率在98％以上，选择性在70％以上，8小时不失活。 最后，采用P123作为模板剂合成了一种新型的中孔稀土磷酸盐，这种稀土磷酸盐具有无序的虫洞形结构。应用这种新型的中孔稀土磷酸盐于酚类甲醇氧烷基化获得了较好的结果。与不加表面活性剂的材料相比，这种中孔稀土磷酸盐在低温下具有更大的活性并且其选择性不受损失。认为这种中孔的形态对催化性能具有好的影响。Caprolactam is an important organic chemical industrial raw material. Vapor Beckmann rearrangement of cyclohexanone oxime into caprolactam is a green process, which can avoid the problems such as by-production of ammonium sulfide, corrosion and pollution of environment in conventional liquid process. The aim of this study is to exploit a new process of Beckmann rearrangement of cyclohexanone oxime catalyzed by solid acids. First, the reaction mechanism of the Beckmann rearrangement over B2O3/γ-Al2O3 and TS-1 in the gas phase has been investigated by isotope labeling approach. The isotopic labeled products were measured by mass spectrometry method. By exchanging oxygen with H218O in the rearrangement step, it was found that the exchange reaction between cyclohexanone oxime and H218O over B2O3/γ-Al2O3 and TS-1 could only be carried out in some extent. It suggested that the dissociation of nitrilium over solid acids be not completely free as the classical mechanism. A concept of the dissociation degree (α) that is defined as the ratio of the dissociated intermediate nitrilium to the total intermediate nitrilium has been proposed. By fitting the experimental values with the calculation equation of isotopic labeled products, it is obtained that α values for B2O3/γ-Al2O3 and TS-1 are 0.199 and 0.806 at the reaction conditions, respectively. Second, the appropriate fluorinated alumina was investigated in vapor Beckmann rearrangement. It was found that the performance of alumina was improved by the fluorination method. The surface alkaline sites were diminished by fluorination method, so, it is believed that the alkaline sites of catalysts were not good for Beckmann rearrangement. However, the completely fluorinated alumina was not as good as some prior catalysts such as support boric oxide and silicalite-1, it suggest that the strength of acid sites of catalysts also play an important role in Beckmann rearrangement. At the same time, we screened materials for vapor Beckmann rearrangement. It is found that rare earth pyrophosphates are potential solid acids catalysts for this reaction. Third, a new application of rare earth pyrophosphates in vapor phase Beckmann rearrangement of cyclohexanone oxime was investigated. The rare earth phosphates were characterized by means of XRD, FT-IR, NH3-TPD and water contact angle measurement. It was found that the weak surface acidity and appropriate surface hydrophobicity should be two key factors in the excellent performance of these catalysts. Fourth, the synthesis of Cerium(III) pyrophosphate and Beckman rearrangement reaction condition were optimized. It was found that under an optimized condition that the catalyst was precipitate at pH 3~4, calcined at 500~550℃, reacted at 350℃, carrying gas N2 in ~80ml/min, WHSV in 0.43h-1, the conversion of oxime was higher than 98%, the selectivity of CPL was higher than 70%, the lifetime was longer than 8h. Last, a novel kind of mesoporous rare earth phosphates were synthesized by using P123 as structure direction agent. The rare earth phosphates possess a worm-like mesostructure. Wonderful results were obtained over these catalysts for O-alkylation of phenol and catechol with methanol. Compared with the materials without adding P123, these mesoporous materials show higher conversion at lower temperature without decreasing selectivity. It was assumed that the mesoporous structure play an important role in good catalytic performance