固体催化剂的成型与热处理对其强度的影响
Impact of molding and heat treatment on strength of solid catalysts
针对挤条成型氧化铝催化剂机械强度的调控机制,系统考察了成型工艺与热处理参数对径向抗压强度的影响规律。实验表明,胶溶剂与助挤剂的添加量存在最优阈值,当添加质量分数为5%的柠檬酸与田菁粉时,颗粒径向强度分别达到27.43 N/mm和27.65 N/mm;粒性分析中,三叶草形颗粒因双接触线结构,其平均径向强度较圆柱形颗粒提升16.69%。热处理过程中,干燥升温速率从2℃/min提升至10℃/min可使强度增加9.96%;焙烧时,温度对强度具有显著调控作用,850℃焙烧样品较450℃样品强度提高72.76%,焙烧时间对机械强度的影响幅度相对有限,焙烧时间由4 h延长至24 h则强度提升16.2%。不同元素掺杂同样会对机械强度产生影响,实验发现含4% La2O3的氧化铝颗粒强度分布集中,优于其他掺杂体系。该研究揭示了胶溶-挤出协同作用及晶相转变对孔隙结构与应力分布的调控机制,为高机械强度催化剂的可控制备提供了工艺优化窗口。
With regard to the regulation mechanism for mechanical strength of extruded alumina catalysts,this study systematically investigates the influences of molding process and heat treatment parameters on the radial compressive strength of the catalysts.It is shown from the experiments that there is an optimal threshold for the addition of gum solvent and extrusion aid.The radial strength of the catalyst particles reaches 27.43 N·mm-1 and 27.65 N·mm-1,respectively when 5% citric acid and 5% sesbania powder are added independently.During the granularity comparison,the average radial strength of clover-shaped particles,due to their double-contact lines structure,is 16.69% higher than that of cylindrical particles.During the heat treatment process,the heating rate for drying increases from 2℃·min-1 to 10℃·min-1,which can increase the strength of catalyst particles by 9.96%.During the roasting process,the temperature has a significant role in regulating the strength of catalyst particles,and the strength of the sample roasted at 850℃ is 72.76% higher that of the sample roasted at 450℃.The roasting time has little impact on the mechanical strength of catalyst particles,which can be increased by 16.2% only when the roasting time prolongs from 4 h to 24 h.Doping with different elements also affects the mechanical strength of catalyst particles.It is found that alumina particles containing 4% La2O3 has a concentrated strength distribution,better than other doping systems.This study reveals the regulation mechanism of the pore structure and stress distribution by colloidal-extrusion synergism and crystalline phase transformation,which provides a process optimization window for the controllable preparation of the catalysts with high mechanical strength.
固体催化剂 / 径向强度 / 单颗粒压碎 / 成型 / 氧化铝
solid catalyst / radial strength / single particle crushing / molding / alumina
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