ZrCl_(4)对催化裂化柴油中杂原子化合物的脱除规律及机理分析

Removal Rules and Mechanism Analysis of Heteroatomic Compounds in FCC Diesel by ZrCl_(4)

催化裂化柴油中杂原子化合物的脱除一般采用高温高压下的加氢脱除。通过四氯化锆(ZrCl_(4))络合法在较为温和的条件下对催化裂化柴油中的杂原子化合物进行脱除。在90℃、常压、环己烷为反应溶剂的条件下,采用ZrCl_(4)与催化裂化柴油进行络合反应,可以得到富集氮化物和氧化物等杂原子化合物的组分,对ZrCl_(4)富集组分进一步进行固相萃取(SPE)分离,采用气相色谱-氮化学发光检测器(GC-NCD)和气相色谱-质谱联用仪(GC-MS)对催化裂化柴油原始样、ZrCl_(4)富集组分、SPE分离组分进行分析表征,并采用量化计算的方法对络合脱除机理进行初步研究。结果表明,ZrCl_(4)络合法对催化裂化柴油中总氮、碱性氮和非碱性氮的脱除率分别为75.9%、83.1%和75.1%。该方法对苯胺等碱性氮化物、咔唑等非碱性氮化物、萘嵌苯酮等氧化物均有较好的脱除效果,对噻吩类硫化物基本上无脱除效果。其脱除机理为:ZrCl_(4)可以与碱性氮、非碱性氮、酮等杂原子化合物发生选择性的络合反应,形成溶解度较差的络合物沉淀而从柴油体系中分离出来。该脱除杂原子的方法具有杂原子脱除率高、柴油收率高、反应条件温和、操作步骤简单等优势。

Heteroatomic compounds in fluid catalytic cracking(FCC)diesel are generally removed by hydrogenation at high temperature and high pressure.In this study,zirconium tetrachloride(ZrCl_(4))based complexation was used to remove heteroatomic compounds from FCC diesel under mild conditions.Under the conditions of 90℃,atmospheric pressure,and cyclohexane as the reaction solvent,ZrCl_(4)was used to complex with FCC diesel to obtain the fractions of heteroatomic compounds such as nitrogen and oxygen compounds.Then the ZrCl_(4)enriched fractions were further separated by solid phase extraction(SPE)and subdivided into SPE separated fractions.Gas chromatography-nitrogen chemiluminescence detector(GC-NCD)and gas chromatography-mass spectrometry(GC-MS)were used to analyze and characterize the FCC diesel,ZrCl_(4)enriched fractions,and SPE separated fractions.Further,quantum chemistry calculation was employed to study the mechanism of heteroatomic compounds removal by complexation.The results show that the removal rates of total nitrogen,basic nitrogen,and non-basic nitrogen in FCC diesel by complexation with ZrCl_(4)are 75.9%,83.1%and 75.1%,respectively.This method has a good removal effect on basic nitrogen compounds such as anilines,non-basic nitrogen compounds such as carbazoles,and oxygen compounds such as perinaphthenone in FCC diesel,and almost no removal effect on thiophene compounds.The removal mechanism is that ZrCl_(4)undergoes selective complexation reactions with heteroatomic compounds such as basic nitrogen,non-basic nitrogen,and ketone,thus forming complexation precipitates with poor solubility to be separated from the diesel system.This method for removing heteroatoms has the advantages of high heteroatom removal ratio,high diesel yield,mild reaction conditions,and simple operation steps.