5A和ZSM-5分子筛吸附分离石脑油中烷烃组分的研究

为了提高石脑油生产乙烯和芳烃的利用效率，采用5A分子筛和ZSM-5分子筛对石脑油进行连续吸附分离研究，分别得到脱正构烷烃吸余油（简称脱正构油）和脱单甲基异构吸余油（简称脱烷烃油）；采用氮气对分子筛进行脱附得到富含烷烃组分油（简称脱附油）。试验结果表明：脱烷烃油中正构烷烃质量分数为0.1%，单甲基异构烷烃质量分数为3.8%，芳烃潜含量为53.4%，可作为优质的催化重整原料；脱附油的烷烃质量分数可达到84%以上，可作为裂解制乙烯的优质原料。     

5A和ZSM-5分子筛吸附分离石脑油中烷烃组分的研究

为了提高石脑油生产乙烯和芳烃的利用效率,采用5A分子筛和ZSM-5分子筛对石脑油进行连续吸附分离研究,分别得到脱正构烷烃吸余油（简称脱正构油）和脱单甲基异构吸余油（简称脱烷烃油）;采用氮气对分子筛进行脱附得到富含烷烃组分油（简称脱附油）。试验结果表明：脱烷烃油中正构烷烃质量分数为0.1%,单甲基异构烷烃质量分数为3.8%,芳烃潜含量为53.4%,可作为优质的催化重整原料;脱附油的烷烃质量分数可达到84%以上,可作为裂解制乙烯的优质原料。     

重整拔头油吸附分离工艺

采用吸附分离工艺,以5 A分子筛为吸附剂,氮气为脱附剂,将重整拔头油分离成高纯度的正构烷烃和异构烷烃。结果表明,在吸附温度为180~280℃,进料空速为25~150 h-1的条件下,温度越低,穿透吸附容量越大。吸附分离最佳操作条件为:温度220℃,原料气体空速50 h-1,进料时间25 min,脱附气体空速50 h-1,脱附时间25 min。吸余油中正构烷烃质量分数为3.90%,异戊烷和二甲基戊烷质量分数分别为24.65%,28.21%,辛烷值为91.0;脱附油中正构烷烃质量分数可以达到99.0%以上。     

基于分子管理的模拟移动床吸附分离石脑油中的正构烷烃

基于分子管理的理念,以5A分子筛为吸附剂,分离石脑油中的正构烷烃和非正构烃。考察了模拟移动床（SMB）中分子筛对正构烷烃的吸附分离规律以及循环比、分配比、脱附剂比等因素对分离效果的影响。在操作压力2.0 MPa、操作温度170 ℃、石脑油质量空速0.024 h-1、切换时间900 s的条件下,优化的模拟移动床操作条件为：循环比2.25、分配比3.00、脱附剂比4。对于正构烷烃质量分数为31.95%的石脑油,经SMB液相吸附分离后,脱附油中正构烷烃质量分数达到87.76%,吸余油中非正构烃质量分数达到97.83%。与石脑油原料相比,以脱附油作为裂解原料时的乙烯收率提高13.1百分点;吸余油研究法辛烷值提高19.2个单位,芳烃潜含量提高10.2百分点。     

基于分子管理的13X分子筛吸附分离石脑油中的芳烃

在5A分子筛吸附分离石脑油中正构烷烃的基础上,采用固定床吸附器对比考察了13X分子筛对石脑油及其脱正构油中芳烃的吸附分离性能。实验结果表明,13X分子筛吸附分离石脑油中芳烃的优化工艺条件为:吸附温度290℃,进料气态空速75 h~(-1),吸附时间30 min,N_2脱附气态空速150 h~(-1)时的适宜脱附时间为75 min;石脑油经5A分子筛和13X分子筛吸附分离后,正构烷烃和芳烃含量(w)分别由31.9%和12.8%降低到0.4%和1.7%,异构烷烃和环烷烃含量(w)分别由34.7%和20.6%增加到62.1%和35.8%;5A分子筛脱附油中正构烷烃含量达到94.8%(w),可作为优质的裂解制乙烯原料;13X分子筛脱附油中芳烃含量为85.1%(w),可直接作为芳烃抽提的原料。     

固定床双塔并联吸附分离石脑油中正构烷烃

在固定床单柱吸附分离研究的基础上,通过程序控制的5A分子筛固定床双塔并联吸附分离试验装置,对中国石化上海高桥分公司石脑油中正构烷烃吸附/脱附分离过程进行连续操作,考察了多周期运转的吸附分离效果,并对工艺条件进行考察。研究结果表明,吸余油中正构烷烃含量经过5个吸附/脱附周期后趋于稳定,优化的吸附分离操作条件为：石脑油原料体积空速153.4 h-1,吸附/脱附温度270 ℃,吸附/脱附切换时间30 min,脱附气体体积空速127.5 h-1,中间油切割时间2 min。在该工艺条件下,稳定操作的吸余油中正构烷烃质量分数小于3%,芳烃潜含量比石脑油提高12.31百分点;脱附油中正构烷烃质量分数大于95%,作蒸汽裂解制乙烯原料时,与石脑油相比,乙烯收率提高约14百分点。     

分离石脑油馏分组成优化乙烯原料

为了改进乙烯原料,提高乙烯收率,分别选取正构烷烃、异构烷烃、环烷烃和芳烃为裂解原料,考察模型化合物的蒸汽裂解产物分布,并分别采用分子筛吸附分离和溶剂萃取两种工艺,提出了可以适应三种目的烯烃产品不同比例需求的裂解制乙烯原料分子生产路线。在典型的裂解工艺条件下石脑油中的正构烷烃对裂解产物中乙烯的贡献最大,异构烷烃是产生丙烯的主要来源,而环烷烃主要生成丁二烯,芳烃很难裂解生成烯烃。通过吸附分离工艺富集石脑油中的正构烷烃,富含正构烷烃的脱附油蒸汽裂解制乙烯收率与不富集石脑油原料相比可提高13%。通过溶剂萃取将芳烃和环烷烃从石脑油中萃出,萃余油蒸汽裂解制乙烯和丙烯收率与未萃取石脑油原料相比分别提高3.0%和1.5%。分子筛吸附分离和溶剂萃取工艺相结合可以显著提高裂解烯烃收率。     

石脑油中正构烷烃在无黏结剂5A分子筛床层中的吸附行为研究

在固定床吸附分离实验装置上对比研究了石脑油中正构烷烃在无黏结剂和有黏结剂5A分子筛床层中的吸附行为。结果表明,随着碳数的增加,各正构烷烃穿透床层的时间增加。与有黏结剂5A分子筛床层相比,无黏结剂5A分子筛床层具有更高的正构烷烃吸附容量,床层穿透时的油筛比更大。在吸附温度300 ℃、石脑油进料空速90 h-1的条件下,无黏结剂5A分子筛对石脑油中正构烷烃的动态吸附容量较有黏结剂5A分子筛高34.5%。正构烷烃在无黏结剂5A分子筛床层中的传质段长度小于有黏结剂5A分子筛床层,无黏结剂5A分子筛床层的有效利用率更高。     

石脑油中正构烷烃在5A分子筛上液相吸附动力学特性

设计双阀门液相吸附动力学测定装置测定正构烷烃在5A分子筛上的液相吸附动力学数据,分别考察吸附温度、正构烷烃碳数以及正构烷烃初始浓度对石脑油中正构烷烃在5A分子筛上吸附速率的影响。结果表明：随着吸附温度和正构烷烃初始浓度的增加,正构烷烃在分子筛上的吸附速率变快;而随着正构烷烃碳数的变化,正构烷烃在分子筛上的吸附速率变化不明显。分别以异辛烷、甲基环己烷和甲苯为溶剂考察石脑油中不同非正构烷烃组分对正构烷烃在5A分子筛上吸附特性的影响。结果表明,石脑油中不同非正构烷烃类对正构烷烃在5A分子筛上吸附速率影响从大到小的顺序为：芳香烃类>环烷烃类>异构烃类。采用阿仑尼乌斯公式对实验数据拟合结果表明,以芳香烃化合物为溶剂时正构烷烃在5A分子筛上的扩散阻力最大。     

1.2Mt/a石脑油吸附分离装置运行状况分析

中国石化扬子石油化工有限公司1.2 Mt/a石脑油吸附分离装置于2013年1月23日一次开车成功。装置采用模拟移动床吸附分离技术，将石脑油中的正异构烷烃分离，正构烷烃用作蒸汽裂解原料，非正构烷烃用作催化重整原料。装置标定结果表明，以正构烷烃质量分数为26.25%的石脑油为吸附分离装置原料，抽出液产品正构烷烃质量分数达到94.83%，正构烷烃吸附收率达到87.02%。相比以石脑油作原料，抽出液作蒸汽裂解原料时乙烯收率提高14.10百分点，抽余液作重整装置原料时芳烃潜含量提升11.20百分点。对装置出现的抽余液塔周期性波动、解吸剂消耗量高和抽出液塔液泛等问题进行了原因分析，并提出了解决措施     

Research on Optimized Utilization of Naphtha Resources Based on Adsorptive Separation with Zeolite

By means of molecular scale management, the technology of separating normal paraffins from naphtha through adsorption using 5A molecular sieves was studied with the purpose of optimizing the utilization of naphtha. The raw materials used in steam cracking and catalytic reforming processes could be allocated properly. During the adsorption process, the separation efficiency of the normal paraffins was above 99.9% with the purity of normal paraffins in the desorption oil exceeding 98.2%. With the use of the desorption oil as the feedstock of steam cracking, the ethylene yield increased from 29.7%--35.0% to 41.4%-49.2% compared to that of the naphtha in the existing plant under similar operation conditions. The potential aromatic content of the raffinate oil rose from 30.6% to 43.5% compared to that in naphtha. The research octane number of the raffinate oil reached more than 85 with an increase of 20 units compared to that of naphtha, so the raffinate oil is more suitable for use as a blending component for high-octane clean gasoline.     

Optimizing Naphtha Utilization Based on Molecular Scale Management

The technology of separating normal paraffins from naphtha through adsorption using 5A molecular sieves was studied. The separation efficiency of the normal paraffins was above 99.99%. Using the desorption oil as the feedstock of steam cracking, the ethylene yield increased from 29.7-35.0% to 41.4-49.2% compared to that of the naphtha. The research octane number of the raffinate oil reached more than 85 units with an increase of 20 units compared to that of naphtha.     

Optimizing Naphtha Utilization Based on Molecular Scale Management

Abstract

The technology of separating normal paraffins from naphtha through adsorption using 5A molecular sieves was studied. The separation efficiency of the normal paraffins was above 99.99%. Using the desorption oil as the feedstock of steam cracking, the ethylene yield increased from 29.7–35.0% to 41.4–49.2% compared to that of the naphtha. The research octane number of the raffinate oil reached more than 85 units with an increase of 20 units compared to that of naphtha.     

碱处理多级孔ZSM-5的酸性及吸附扩散性能研究

不同条件下用NaOH处理ZSM-5分子筛,得到了不同孔径分布的微-介孔多级ZSM-5分子筛,运用 XRD、N2吸附-脱附、SEM、NH3-TPD和Py-FTIR等方法对其进行表征。采用智能重量分析仪（IGA）等考察了改性后的分子筛与苯分子之间吸附扩散性能及其与酸量及吸附位的构效关系。结果表明,碱处理不会改变分子筛整体的晶相结构,但是碱处理会一定程度破坏分子筛的结晶度。碱改性会形成微-介多级孔分子筛,并能调变分子筛的酸量。调变后酸量相对大的多级孔ZSM-5分子筛有更多的吸附位,吸附量也会相应增大。此外,苯在多级孔ZSM-5上的传质性能不仅与多级孔ZSM-5分子筛的吸附位有关,还与孔结构有关。介孔含量越多,多级孔体系贯通性越好,苯的传质性能越好,越有利于多级孔ZSM-5活性位的吸附及其催化性能的提高。     

ZSM-5分子筛晶粒尺寸对石脑油催化裂解性能的影响

采用XRD、NH_3-TPD、N_2物理吸附、XRF和SEM等方法对两种ZSM-5分子筛(ZRP和FX分子筛)进行了表征,并在固定床反应器中于600℃下对其催化裂解石脑油的性能进行了评价。表征结果显示,ZRP和FX分子筛均具有ZSM-5分子筛的特征衍射峰,均为单晶条状晶粒,且具有几乎相同的硅铝比和酸量及酸分布,但两者的晶粒尺寸、BET比表面积和微孔比表面积有差异;ZRP分子筛的晶粒粒径为2～3μm,FX分子筛的晶粒粒径小于1μm;FX分子筛的BET比表面积和微孔比表面积大于ZRP分子筛。实验结果表明,ZSM-5分子筛对石脑油的催化裂解能力及乙烯与丙烯的总收率随晶粒尺寸的减小而增大,这与小晶粒分子筛的扩散路程短有关。     

Separating group compositions in naphtha by adsorption and solvent extraction to improve olefin yields of steam cracking process

In order to improve the steam cracking feeds, several model compounds including normal paraffins, iso-paraffins, cyclanes and aromatics were selected as the feeds of steam cracking process and the olefin yields were investigated. In the typical reaction conditions, the normal paraffins in the naphtha contribute most to the ethylene in the products; the iso-paraffins are the main sources of the propylene; the cyclanes mainly produce the butadiene and the aromatics can hardly produce olefins. According to this, the adsorption process and solvent extraction process were adopted to separate the group compositions in naphtha properly to optimize the cracking feeds. The n-paraffins in naphtha were gathered through adsorption process using 5A molecular sieves. The ethylene yield improved by 13% using the desorption oil rich in n-paraffins as the cracking feed. The aromatics and the cyclanes were extracted from the naphtha. Compared with the naphtha, the ethylene and propylene yields of the extraction raffinate oil were 3.0 and 1.5% higher respectively.