响应面模型用于Beta分子筛催化剂蜂窝状整体式成型的研究

STUDY ON FORMATION OF BETA ZEOLITE HONEYCOMB MONOLITHS CATALYST BY USING RESPONSE SURFACE METHOD

Beta分子筛由于具有独特的三维十二元环孔道结构,可提供更多活性组分附着位点,是在实际应用中具有优异性能的工业催化剂。在工业使用中,蜂窝整体式催化剂具有通量高、流场均匀、压降小、不易堵塞的优点,是气固或者液固催化反应的最优解决方案。但由于Beta分子筛吸水率高,收缩率大,导致蜂窝成型困难,严重限制了Beta分子筛的工业应用。基于此,选择拟薄水铝石(SB粉)为黏结剂、硝酸为胶溶剂、田菁粉为助挤剂,在水粉比为0.6的条件下制备一系列蜂窝整体式成型Beta分子筛催化剂,基于响应面法,评价了各原料的配比对蜂窝整体式催化剂机械强度的影响,得到了催化剂的机械强度与3个因素(黏结剂用量、胶溶剂用量、助挤剂用量)之间关系的二阶多项式近似模型函数。将试验结果与预测值进行对比,证明了预测模型的可靠性,并利用该模型找到最优的Beta分子筛蜂窝成型条件为SB粉质量分数36.1%、硝酸质量分数8.4%、田菁粉质量分数4.7%。

Beta zeolite is an industrial catalyst with excellent performance in practical application due to its unique 3-D 12-membered ring channel structure,which can provide more active component adsorption sites.In industrial use,the honeycomb monolith catalyst has the advantages of high flux,uniform flow field,small pressure drop and non-clogging,which is the optimal solution for gas-solid or liquid-solid catalytic reactions.However,because of the high water absorption and shrinkage of Beta zeolite,it is difficult to form honeycomb,which greatly limits the industrial application of Beta zeolite.To solve the above problems,pseudoboehite(SB powder)was selected as binder,HNO 3 as solvent,and sesbania powder as extrusion-aid,and a series of Beta zeolite honeycomb monoliths catalyst were prepared at a water-to-powder ratio of 0.6.Based on the response surface method,the effect of the ratio of each raw material on the mechanical strength of the honeycomb monoliths was evaluated.The function of the second order polynomial approximation model of the relationship between the mechanical strength of the monoliths and the three variables was obtained.The reliability of the predicted model was proved by comparing the results with the predicted values.The optimal forming conditions of Beta zeolite honeycomb monoliths were found by using the model,which were the pseudo-boehmite mass fraction of 36.1%,the nitric acid mass fraction of 8.4%,and the cyanine powder mass fraction of 4.7%.