Studies On The Separation Of Long-chain Olefin/Paraffin From F-T Synthetic Oil Mixture

Long-chain α-olefins are a kind of raw material,which are used to produce surfactant,oil field chemicals,olefin copolymer,plasticizing alcohol and lubricating oil.Fischer-Tropsch synthetic oil mixture has abundant long-chain α-olefins.Obtaining highly purified long-chain α-olefins from F-T oil not only improves the added value of long-chainα-olefins but also economic efficiency of F-T synthetic oil.Studies on the separation of F-T synthetic oil mixture are a demanding task.The methods of freezing,distillation,extraction and adsorption wered employed to separate the mixtures.Combining distillation andπ-complexation adsorption method was determined as the final solution to separate long-chain α-olefin/paraffin.The means of packed tower vacuum batch distillation was used to fractionate the F-T synthetic oil preliminarily.Different vacuum degrees and reflux ratios on the impact of fractional compositions were discussed;the temperature sections of single carbon mixtures were confirmed.A magnetic complex separation adsorbent—AgNO₃/MCM-41/NiFe₂O₄ was designed and synthesized via the incipient wetness impregnation.The samples were characterized and analyzed by scanning electron microscope（SEM）,transmission electron microscope（TEM）,powder X-ray diffraction analysis（XRD）,nitrogen adsorption-desorption analyses,Fourier transform infrared spectroscopy（FT-IR）,vibrating sample magnetometer（VSM）and etc.The tests showed that the obtained products were composed of NiFe₂O₄ with spinel structure and MCM-41 with hexagonal arrangement of unidimensional mesopores.When the loading amount of AgNO₃ was 0.2g/g magnetic carrier,AgNO₃ was finely dispersed in the channel.The specific surface area and most probable pore size were717.89m2/g,2.94 nm.For the C₁₁ α-olefin/C₁₁ paraffin mixtures,adsorption behaviours of C₁₁ α-olefin on magnetic adsorbent were investigated.Results showed that adsorbents have preferential adsorption for long-chain olefins.The one-stage equilibrium adsorption capacity and adsorption time were 2.14g/g,100 min respectively.The adsorption temperature and initialolefin concentration were studied.The optimal adsorption temperature was 20℃.When the mass percent of olefin was up to 60%,the adsorption capacity reached saturation.In the200℃,0.08 Mpa conditions,the adsorbent could be completely regenerated after 3h by vacuum heating.Adsorptive selectivity,adsorption and magnetic recovery of adsorbents after reuse ten times were investigated.The recovery was up to 98.9% and the selectivity and adsorption of olefin decreased slightly（1.93g/g）.But the changes still can satisfied requirements for olefin adsorbed selectively.