Modification Of ZSM-5 Molecular Sieve And Its Catalytic Synthesis Of Methylene

In this thesis, nanosized ZSM-5 zeolites were used in isomerization of p-DCB to m-DCB, the activation conditions, reaction temperature, reaction pressure and space velocity were investigated over nanosized ZSM-5 zeolite.The results indicated that the optimized conditions were as follows:activation temperature 500℃, activation time 1h, reaction temperature, pressure and space velocity respectively were 450℃,4.0 MPa and 1 h-.ZSM-5 zeolite was modified by acid treatment and alkali treatment. Their physicochemical properties were characterized by XRD、SEM、XRF、NH3-TPD、Py-IR and N2 adsorption. The catalytic performance of the samples obtained from different methods was investigated with isomerization of p-dichlorobenzene with methanol as the probe reaction.ZSM-5 zeolite was modified by different concentration of acid and alkali solution,their physicochemical properties were characterized by XRD、SEM、XRF、 NH3-TPD、Py-IR and N2 adsorption, and their catalytic performance was investigated. The result indicated that modifization had a obvious influence on ZSM-5 zeolite. Sample had less acid site and more mesoporous after HCl modified, result in the conversion of p-DCB decreased but the selectivity of m-DCB increased. Meanwhile, sample had more acid amount and stronger acid strength after citric acid modified, result in both conversion of p-DCB and selectivity of m-DCB increased.The sample modified by lmol/L citric acid showed the best catalytic performance in the tank reactor and tubular reactor, when the conversion of p-DCB was 47.4%, the selectivity of m-DCB was reaching 96.4% in the tank reactor, when the conversion of p-DCB was 65.0%, the selectivity of m-DCB was reaching 80.1% in the tubular reactor.The inactivation of sample was decreasing after modified by weak alkali, and the sample modified by 0.1 mol/L NaOH solution showed the best catalytic performance, when the reaction time was 6 h, the conversion ofp-DCB was only decresing 15%.The performance for reuse of ZSM-5 getted from tank reactor was investigated, the reaction was took in tank reator, and the reactivation process was carried in static air atmosphere and flowing air atmosphere.The result indicated that the method of reactivation had a obvious influence on its physicochemical properties. Compare the sample reactivated in static air atmosphere to the parent sample, it had less acid site and poor catalytic activation.However the sample reactivated in flowing air atmosphere had almost the same acid site and catalytic perforence with parent sample, the conversion of p-DCB was only decresing 2%.