Study On The Chemical Deactivation Of Catalyst In The HPPO Process

Titanium silicalite/H₂O₂（TS/H₂O₂）system for catalytic oxidation of propylene to1,2-epoxypropane（HPPO）is the trend of green chemical technology for PO production.The study on the deactivation of titanosilicates catalyst and its regeneration method is one of the keys to the development of HPPO process technology.In this paper,the deactivation of Ti-MWW in the process of HPPO was studied.The effect of organics in the reaction system on the catalytic performance of Ti-MWW was systematically investigated.It was found that the chemical interaction between PO and catalyst was the source of Ti-MWW deactivation,the corresponding regeneration method is further developed.The study comprises the following two parts:1.Based on the reaction network diagram of HPPO,the influence of organics which include PO,propylene glycol（PG）,popylene alcohol ether（MME）and propylene（C₃⁼）in the reaction system of HPPO on the catalytic performance of Ti-MWW was investigated by impregnation method.The results show that PO is the key to decrease the activity of Ti-MWW.In combination with in-situ FT-IR,¹³C MAS NMR and XPS,it was found that deactivation mechanism was due to the acid sites in the zeolites initiated the binding of PO with Ti active sites,resulting in the formation of didentate propoxides,which resulted in a significant decrease in Ti-MWW activity.By designing Ti-MWW with different kinds of acid sites,the contribution of different acid sites to the decrease of activity was studied:Ti-OOH>Si-OH（B）>Si-OH（Ti）>Ti⁴⁺>Si-OH.By proper alkali metal ion exchange,the acid sites in the catalyst can be suppressed,and the intermediate Ti-OOH can be stabilized by introducing hydrogen-bonded acceptor,thus the service life of Ti-MWW in HPPO process can be increased significantly.2.The method of in situ regeneration of deactivated titanosilicates catalysts from methanol at high temperature was developed.The results showed that the regeneration effect of catalyst was good and the catalyst could run stably for 1800 h after regeneration.