FCC催化剂氢气还原活化脱镍研究

我国的FCC催化剂在使用中镍污染较为严重, 镍不仅会破坏催化剂的结构, 而且还会影响反应产物的分布, 增加企业的生产成本. 本研究提出了氢气还原活化＋稀硝酸洗涤的脱镍新方法, 具有良好的效果. 镍在FCC催化剂上以NiAl₂O₄和Ni₂SiO₄的形式存在, 这些物种在700 ℃以下就可以被氢气还原, 并且随着温度的升高, 不仅催化剂表面的镍能够被还原, 而且催化剂体相中的镍也可以迁移到表面从而被还原, 但这种迁移受到平衡的限制. 还原后生成的金属镍可以溶于稀硝酸, 因而可以洗涤除去. 在适宜的条件下, 经过一次还原＋酸洗处理, 脱镍率可达到50%以上; 经过两次处理, 脱镍率可达75%以上. 脱镍后催化剂的微反活性可以得到大幅度提高.

Removal of Ni on FCC Catalyst Reduced by Hydrogen

Ni deposited on the FCC catalyst could not only destroy the structure of the catalyst, but also deteriorate the product distribution. Almost all the Ni on the catalyst existed in the forms of NiAl₂O₄ and Ni₂SiO₄, which can be reduced by H₂ even below 700 ℃. Here a new Ni-removal procedure, reducing activation by H₂ plus washing by dilute nitric acid was suggested. If the catalyst containing 2.13 wt% Ni was treated only once under appropriate conditions, then more than 50% Ni could be removed, and the micro-activity of the catalyst improved markedly. At high temperature, the Ni species in the bulk of the catalyst moved out to the surface during reducing, but the movement might be limited by equilibriums, so repeat of the treating steps was helpful to Ni-removal.