石脑油分离技术进展与应用前景探讨

直馏石脑油主要由正构烷烃、异构烷烃、环烷烃和芳香烃构成,其中正构烷烃是理想的乙烯裂解原料;异构烷烃是理想的清洁汽油调和组分;环烷烃和芳香烃是理想的催化重整原料。根据不同用途对石脑油烃族组成的需求,结合石脑油分离技术的发展现状,以及国内石脑油的性质和利用现状,分析了从石脑油中分离出正构烷烃的技术在国内的应用前景。通过对石脑油中的正构烷烃与非正构烷烃分离,把正构烷烃作为乙烯裂解原料,非正构烷烃作为重整原料,可大幅提高石脑油利用价值,以实现乙烯原料和重整原料的双目标优化,将进一步提升炼油化工一体化企业的整体竞争力。     

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。     

新疆原油基属及石脑油馏分裂解性能评价

以新疆土哈油田鲁克沁、三塘湖原油,克拉玛依油田陆梁、石南原油,塔里木油田塔中、柯克亚原油为研究对象,对这6种原油基属与其石脑油馏分的裂解性能进行了分析,综合分析原油基属、石脑油馏分的物性及其裂解性能。结果表明:柯克亚、三塘湖、石南和塔中原油所产的石脑油馏分中链烷烃含量较高,裂解得到的乙烯、双烯收率均较高,可作为乙烯原料;鲁克沁和陆梁原油,所产石脑油馏分中不易裂解的环烷烃和芳烃含量较高,裂解产物中乙烯收率较低,但丙烯、丁二烯的收率相对较高,若用作乙烯原料,需适当降低石脑油馏分的切割点,以提高石脑油馏分的裂解性能。     

采用BP神经网络预测石脑油裂解烯烃收率

在乙烯裂解工业装置的典型操作条件下,分别选取正构烷烃、异构烷烃、环烷烃、芳烃为裂解原料,考察了这些模型化合物的蒸汽裂解产物分布情况。结果表明,正构烷烃是优质的乙烯裂解原料,乙烯收率为36%~45%;异构烷烃的丙烯收率约为23%,明显高于正构烷烃;环烷烃裂解乙烯和丙烯收率较低,丁二烯收率则较高,为14%~15%;芳烃很难裂解生成烯烃。建立了包含2个隐层的级联前向BP神经网络,以模型化合物和石脑油样本裂解烯烃收率为依据对该神经网络进行训练,确定了模型参数,并对2种石脑油的裂解烯烃收率仿真数据与实验结果进行了对比。结果表明,二者的误差小于1个百分点,该模型可用于预测石脑油裂解的烯烃收率。     

不同烃类催化裂解生产低碳烯烃的性能

为了拓宽乙烯裂解原料并合理利用焦化石脑油资源,对比研究了烷烃、烯烃、环烷烃同系物及相同碳数不同结构烃在Cu改性ZSM-5分子筛及其与金属氧化物复合催化材料上的裂解性能。结果表明,同系物烃类裂解性能随着碳数增加,裂解生成低碳烯烃的性能增强,高碳数的烯烃和烷烃的转化率和低碳烯烃收率较高,是较好的催化裂解生成低碳烯烃原料。在相同条件下,烷烃和环烷烃的转化率明显低于相同碳数烯烃的转化率。复合催化材料A中的金属氧化物与Cu改性ZSM-5分子筛之间具有很好的协同作用,能够提高烷烃和环烷烃的裂解活性。     

吸附富集裂解原料中的正构烷烃蒸汽裂解制乙烯效果研究

研究了直馏石脑油、加氢焦化石脑油和天然气凝析油三种裂解制乙烯原料及其通过分子筛吸附分离后相应的富含正构烷烃脱附油的裂解乙烯收率,并考察了裂解反应条件对不同裂解原料的裂解性能的影响。在工业装置典型操作条件下,直馏石脑油及其吸附分离吸余油和脱附油的乙烯收率分别为29.9%,23.0%,41.1%,脱附油的乙烯收率比直馏石脑油增加11.2个百分点,脱附油的三烯总收率比石脑油增加8.6个百分点;对于加氢焦化石脑油和凝析油,其相应脱附油的裂解乙烯收率分别提高11.1和6.5个百分点。石脑油和脱附油裂解乙烯收率和丁二烯收率均随裂解出口温度的升高而增加,丙烯收率基本不随裂解出口温度的变化而改变。     

烃分子结构对其催化裂解反应性能的影响

采用脉冲微型反应器和小型固定流化床催化裂解装置,研究了直馏石脑油中不同结构烃分子的裂解反应性能,考察了链烷烃与环烷烃的相互作用,以及催化材料对烃分子裂解性能的影响。结果表明：随着烷烃分子支链度的增加,C8烷烃的反应性能降低,丙烯选择性提高;链烷烃和具有烷基侧链的环烷烃是丙烯的主要来源,双环环烷烃对丙烯也有部分贡献,而芳香烃不易生成低碳烯烃;环烷烃的竞争吸附抑制了链烷烃的转化,而链烷烃在催化裂解过程中生成的碳正离子或烯烃提高了环烷烃的反应性能;与Beta分子筛相比,ZRP分子筛具有较狭窄孔道和较多的Brønsted酸中心,有利于正辛烷的质子化裂解,裂解产物中乙烯和丙烯产率高。     

不同烃类催化裂解生产低碳烯烃的性能

 为了拓宽乙烯裂解原料并合理利用焦化石脑油资源,对比研究了烷烃、烯烃、环烷烃同系物及相同碳数不同结构烃在Cu改性ZSM-5分子筛及其与金属氧化物复合催化材料上的裂解性能。结果表明,同系物烃类裂解性能随着碳数增加,裂解生成低碳烯烃的性能增强,高碳数的烯烃和烷烃的转化率和低碳烯烃收率较高,是较好的催化裂解生成低碳烯烃原料。在相同条件下,烷烃和环烷烃的转化率明显低于相同碳数烯烃的转化率。复合催化材料A中的金属氧化物与Cu改性ZSM-5分子筛之间具有很好的协同作用,能够提高烷烃和环烷烃的裂解活性。     

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     

强化直馏石脑油催化裂解过程中链烷烃选择性催化裂解反应研究

在直馏石脑油催化裂解(SNCC)技术开发过程中,发现原料中链烷烃转化率始终难以大幅提高,仅保持在52.58%~77.07%,对低碳烯烃产率存在较明显的限制。本研究采用基于密度泛函理论的分子模拟计算方法,构建了正辛烷、2-甲基庚烷和2,5-二甲基己烷3种直馏石脑油馏分链烷烃模型化合物的催化裂解反应网络,并分别提出了正构烷烃和异构烷烃理想的链反应引发途径和反应方向,发现反应体系中存在的高供氢活性的环烷烃等烃类会通过负氢离子转移反应抑制链烷烃转化,从而导致链烷烃转化率较低。通过引入新型有特定孔道结构的IM-5分子筛催化剂,可有效强化SNCC过程中链烷烃的选择性催化裂解。     

优化裂解原料的初步研究

利用芳烃抽提、分子筛脱蜡等方法改进裂解原料,并对F-T合成馏分油的裂解性能进行了初步研究。采用芳烃抽提方法处理原料,提高了原料中烷烃的含量,在裂解条件和乙烯产量相同的条件下,可以节省裂解原料16%以上;而采用5A分子筛对原料进行脱蜡处理,可以使原料中正构烷烃的含量大大提高,在更为缓和的裂解条件下,乙烯产量相同时,可节省裂解原料50%以上。F-T合成馏分油以正构烷烃为主,是一种很好的裂解原料。F-T合成馏分油与常规裂解原料相比,在更为缓和的裂解条件下,可以得到更高的乙烯、丙烯和丁二烯收率。     

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.     

液化气作裂解料的技术经济评估

根据重整液化气和加氢裂化液化气的模拟评价单程裂解收率，利用PIMS生产优化模型对两种饱和液化气作乙烯裂解料的综合收率和经济效益进行了评估。结果表明，在给定条件下．重整液化气和加氢裂化液化气裂解双烯收率都超过了加氢裂化轻石脑油和焦化加氢石脑油。在裂解经济性方面，两种液化气的裂解边际贡献在给定条件下低于两种石脑油。因此重整液化气和加氢裂化液化气在石脑油资源供应不足和液化气市场价格低于石脑油的情况下，可以作为乙烯企业尤其是炼化一体化企业的裂解原料。     

常压化学气相沉积法制备SiO_2涂层及其抗结焦性能

以正硅酸乙酯为硅源物质、空气为载气和稀释气,采用常压化学气相沉积法在HP40钢表面制备了SiO2涂层;采用扫描电子显微镜和能量色散能谱表征了SiO2涂层的组织结构和表面形貌;考察了在乙烯裂解的工艺条件下SiO2涂层的结焦抑制能力。实验结果表明,所制备的SiO2涂层具有表面平整、均匀致密的特点,粒径均在1μm以下,且与基体具有一定的结合强度;在乙烯裂解的工艺条件下,SiO2涂层具有良好的抑制结焦能力,当裂解温度为830℃、水蒸气与石脑油的质量比为0.67时,SiO2涂层的结焦抑制率为75%左右,大大提高了HP40钢的抗结焦能力。     

提高蒸汽热裂解三烯收率最佳操作条件的模拟计算

采用反应管入口总摩尔流率不变的汽/烃质量比调节方法,用管式裂解炉二维工艺数学模型在较宽的操作条件范围内对大庆石脑油蒸汽热裂解制乙烯、丙烯、丁二烯和三烯总收率进行了模拟计算,并对结果进行了正交分析。结果表明,汽/烃质量比调节方法可确保各个操作条件间无交互作用,说明了各调节参数的独立性和本模拟计算结果的可靠性。不同目的产物具有不同的最佳操作条件,以乙烯、丙烯、丁二烯和三烯总收率最大为目标时最佳裂解温度分别为1143、1103、1133和1143 K。裂解深度主要取决于裂解温度,在裂解温度较低时停留时间和汽/烃质量比的作用较大,而在达到或大于最佳裂解温度后,两者的影响较小,应以高温、短停留时间来提高裂解反应的反应深度,汽/烃质量比的变化对提高目的产物的影响较小。     

Molecular reconstruction of naphtha by maximum information entropy method

Naphtha is the feedstock for steam cracking and catalytic reforming of aromatics. Based on the molecular library and 42 groups of practical data including the properties of density, potential aromatic content, the weight fractions of PNA and carbon number distribution, a molecular reconstruction model for naphtha was established by maximum information entropy method. The content of 451 components for naphtha were estimated. The molecular composition generated by the simulation is in good agreement with the practical data. The model can provide the referential value for the steam cracking and catalytic reforming of aromatics processes at molecular level.     

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.     

The Use of ANN and the Mathematical Model for Prediction of the Main Product Yields in the Thermal Cracking of Naphtha

Thermal cracking of naphtha has such numerous reaction routes that the detailed reaction mechanism has not yet been determined. In this regard, a model of artificial neural networks (ANNs), using back propagation (BP), is developed for modeling thermal cracking of naphtha. The optimum structure of the neural network was determined by a trial-and-error method. Different structures were tried with several neurons in the hidden layer. The model investigates the influence of the coil outlet temperature, the pressure of the reactor, the steam ratio (H2O/naphtha), and the residence time on the pyrolysis product yields. A good agreement was found between model results and experimental data. A comparison between the results of the mathematical model and the designed ANN was also conducted and the relative absolute error was calculated. Performance of the ANN model was better than the mathematical model.