Crosslinking Modification Of Polyimide Nanofiltration Membrane For Lubricating Oil Solvent Recovery Research

Solvent dewaxing process is an important step in base oil production. Nowadays, traditional solvent recovery process is low efficiency and consumes large amounts of energy. While, the method of membrane separation process is a simple process with high efficiency and no phase transition. Solvent-resistant nanofiltration is a recently emerging separation process, which can be used for organic system. Therefore, the application will expand to lubricating oil solvent recovery with great prospect.In this thesis, asymmetric nanofiltration membrane was prepared with polyimide(PI) made by our own lab via the method of phase inversion. Then it was applied to recovery ketone-benzol solvent from dewaxing organic system. The effects of volatizing temperature, volatizing time, coagulation bath temperature and the content of inorganic salt on the membrane structure and separation performance were investigated. Then the membrane with better performance was selected and was conducted crosslinking modification. The effects of different modifying method such as the immersion time and the concentration of crosslinking reagent on membrane performance were studied. The flux, rejection rate and swelling ratio were measured to determine the membrane with good separation performance and solvent resistance. According to the SEM photographs of PI membrane with or without inorganic salt, the effect of inorganic salt on the mechanism of phase transition was explained.The experimental result indicates:with the volatizing time growing, the rejection rate firstly rises then drops and the flux drops gradually; when the volatizing temperature is32℃, the coagulating bath temperature is30℃, and the content of inorganic salt is0.5%, the performance of PI/inorganic salt is good. In the process of crosslinking modification process, with the immersion time increase, the rejection rate grows, while the flux drops. Similarly, along with the concentration of crosslinking agent increases, the rejection rate firstly rises then drops, the flux assumes the opposite trend. In addition, it is favorable for the enhancement of solvent resistant property to modify the membrane with a range of immersion time or concentration of crosslinking agent.