化工学报 ›› 2020, Vol. 71 ›› Issue (S1): 38-45.doi: 10.11949/0438-1157.20190694

• 热力学 • 上一篇    下一篇

费托蜡催化裂化反应生产清洁汽油的热力学分析

韩建年(),王刚(),杨梅,刘美佳,高成地,高金森   

  1. 中国石油大学(北京)重质油国家重点实验室,北京 102249
  • 收稿日期:2019-06-20 修回日期:2019-09-16 出版日期:2020-04-25 发布日期:2020-05-22
  • 通讯作者: 王刚 E-mail:2018213559@student.cup.edu.cn;wanggang@cup.edu.cn
  • 作者简介:韩建年(1992—),男,硕士研究生,2018213559@student.cup.edu.cn
  • 基金资助:
    国家重点研发计划项目(2017YFB0602504)

Thermodynamic study on fluid catalytic cracking of Fischer-Tropsch wax to produce clean gasoline

Jiannian HAN(),Gang WANG(),Mei YANG,Meijia LIU,Chengdi GAO,Jinsen GAO   

  1. State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China
  • Received:2019-06-20 Revised:2019-09-16 Online:2020-04-25 Published:2020-05-22
  • Contact: Gang WANG E-mail:2018213559@student.cup.edu.cn;wanggang@cup.edu.cn

摘要:

费托蜡主要由链烷烃组成,不含硫、氮等杂原子,是生产清洁汽油的优质原料。由于缺少芳烃和环烷烃,费托蜡催化裂化过程需要强化异构化、芳构化反应以实现降低汽油馏分烯烃含量、保持高辛烷值的目标。对费托蜡为原料的催化裂化反应体系进行热力学分析,重点计算了不同温度下生成汽油馏分主要烃类的反应焓变和反应平衡常数。研究结果表明,以大分子链烷烃为主的费托蜡,其裂化吸热反应焓变约为80 kJ/mol,反应平衡常数随温度的升高而增大,高温有利于一次裂化反应。对于异构化反应,主要是大分子链烷烃裂化为烯烃,再由烯烃分子转化为异构烷烃,因此对于异构化反应,可以通过优化反应器促进汽油烯烃的转化。在考察温度范围内,烯烃环化反应平衡常数随温度升高而减小,环烷烃脱氢芳构化反应平衡常数随温度升高而增大,所以适宜的反应温度是制约进一步增加汽油中芳烃的重要因素。

关键词: 费托蜡, 催化裂化, 焓, 异构化, 芳构化, 燃料, 烷烃

Abstract:

Fischer-Tropsch (F-T) wax is mainly composed of long-chain paraffin without any sulfur or nitrogen and is well suited for producing clean gasoline. The contents of naphthenic and aromatic species of F-T wax are exceptionally low, a high gasoline fraction with a high-quality motor octane number and low olefin fraction is still problematic. Thus, the solution aims at enhancing isomerization and aromatization reactions in the fluid catalytic cracking (FCC) process. This paper shows that the thermodynamic analysis of the catalytic cracking reactions of F-T wax. Emphasis was given to the enthalpy change and equilibrium constant of the reaction to produce gasoline fraction at different temperatures. The results of the calculation indicate that the cracking of highly paraffinic F-T wax is endothermic (enthalpy change on reaction is about 80 kJ/mol), and the equilibrium constant and the equilibrium conversion from reactant to products increase with increasing temperature.In the case of isomerization, the equilibrium constant of n-paraffin in isomerization is extremely lower than olefin. It s speculated that olefin cracked from n-paraffin isoforms further to i-paraffin, reasonably. Therefore, a zoned reactor can be designed to promote the conversion of olefin. The equilibrium constant of n-paraffin cyclization is low at different temperatures and then occurrence of reaction is difficult. On the other hand, the value of the equilibrium constant of aromatization of naphthenic is high, as a consequence, suitable reaction temperature is the key to increase the aromatics in gasoline further.

Key words: Fischer-Tropsch wax, FCC, enthalpy, isomerization, aromatization, fuel, alkane

中图分类号: 

  • TE 626

图1

费托蜡1H NMR谱图"

图2

正三十一烷催化裂化反应产品分布"

表1

正三十一烷催化裂化反应产物烃组成分析"

柴油馏分质量分数/%汽油馏分质量分数/%气体组分质量分数/%
链烷烃57.70正构烷烃6.27碳一0.49
总环烷烃6.20异构烷烃41.94碳二2.72
单环芳烃17.70烯烃36.59碳三39.19
双环芳烃17.00环烷烃1.36碳四52.18
三环芳烃1.40芳烃13.84碳五5.42
总计100.00总计100.00总计100.00

图3

正三十一烷催化裂化生成汽油、液化气产品的主要反应网络"

表2

正三十一烷催化裂化产物组分?Hf?、?Gf?与温度T关联式"

Substance?Hf?=a1+b1T+c1T2?Gf?=a2+b2T+c2T2
a1b1×103c1×106a2b2×103c2×107
propane-80.700-90.50042.104-105.600264.747325.001
hexane-129.110-150.13573.459-170.450554.166503.033
octane-160.340-190.25194.492-212.690747.742623.610
nonane-175.880-210.359105.006-233.830844.766684.506
undecane-207.110-250.454125.997-276.1101038.900804.055
tricosane-394.060-491.726252.484-529.5202202.7801526.540
hentriacontane-518.730-625.480336.728-698.4602978.6302008.990
2-methylpentane-137.110-147.07272.785-177.680563.031483.129
2-methyloctane-184.630-204.075101.981-240.800854.744662.894
cyclohexane-818.200-167.055928.304-127.920520.324447.064
propylcyclohexane-141.000-211.840118.098-199.500808.737561.762
cyclohexylhexane-187.020-272.040149.591-262.1801100.050740.705
propene37.330-65.19128.08519.410136.848257.471
1-hexene-9.810-125.04759.735-44.220427.345433.515
1-nonene-56.530-185.489914.790-107.580718.380614.413
1-undecene-87.790-225.438112.353-149.840912.363735.384
1-dodecene-103.270-245.814123.039-170.9101009.320796.543
1-tricosene-274.670-466.945238.969-403.3102076.6801458.700
1-octacosene-352.560-567.497291.679-508.9202561.7901760.070
benzene101.400-72.13632.87881.510152.823265.222
propylbenzene40.970-130.67563.4634.890429.374440.117
hexylbenzene-6.770-191.05095.123-59.460719.974621.722
1-ethylnaphthalene127.100-120.98561.10393.650431.031383.179

表3

不同温度下烃类裂化反应焓变"

Reaction?rHT?/(kJ/mol)
350℃400℃450℃500℃550℃
n-C3101-C28=+C3080.9280.4579.9779.4778.96
n-C3101-C23=+C8079.5479.0978.6378.1577.65
n-C23=1-C12=+1-C11=79.5479.0978.6278.1477.64
n-C2301-C12=+n-C11079.5179.0678.5978.1077.60
1-C12=1-C9=+C3=79.6979.2278.7378.2377.71
i-C90i-C60+C3=79.3278.8378.3577.8677.36
cyclohexylhexanepropylcyclohexane+C3=78.9278.4577.9677.4576.93
cyclohexylhexanecyclohexane+1-C6=84.0483.2382.4481.6680.89
hexylbenzenepropylbenzene+C3=80.6880.2179.7279.2178.68
hexylbenzenebenzene+1-C6=93.5693.0992.6192.1291.61

表4

不同温度下费托蜡裂化反应平衡常数"

ReactionKp?
350℃400℃450℃500℃550℃
n-C3101-C28=+C304.5114.3938.8891.68193.87
n-C3101-C23=+C807.9424.8065.88153.10319.66
n-C23=1-C12=+1-C11=8.6527.0471.76166.91348.49
n-C2301-C12=+n-C1108.2525.7668.29158.64330.87
1-C12=1-C9=+C3=7.3823.1061.37142.81298.30
i-C90i-C60+C3=8.2925.8268.32158.41329.75
cyclohexylhexanepropylcyclohexane+C3=8.5526.4569.56160.44332.42
cyclohexylhexanecyclohexane+1-C6=0.913.038.4620.4944.11
hexylbenzenepropylbenzene+C3=5.8018.4049.49116.41245.42
hexylbenzenebenzene+1-C6=0.090.331.062.856.79

表5

不同温度下生成C6异构烷烃反应焓变"

Reaction?rHT?/(kJ/mol)
350℃400℃450℃500℃550℃
i-C90i-C60+C3=79.3278.8378.3577.8677.36
n-C60i-C60-6.35-6.24-6.14-6.03-5.94
1-C6=i-C60-135.96-136.21-136.40-136.53-136.59
cyclohexanei-C60-50.62-50.92-51.32-51.82-52.42

表6

不同温度下生成C6异构烷烃反应平衡常数"

ReactionKp?
350℃400℃450℃500℃550℃
i-C90i-C60+C3=8.2925.8268.32158.41329.75
n-C60i-C601.611.471.361.281.21
1-C6=i-C608674.191242.48231.8853.5614.73
cyclohexanei-C6066.5231.8916.889.675.91

表7

不同温度下环化及芳构化反应焓变"

Reaction?rHT?/(kJ/mol)
350℃400℃450℃500℃550℃
1-C9=propylcyclohexane-90.55-90.15-89.61-88.93-88.12
n-C90propylcyclohexane39.0439.8240.6641.5642.53
i-C90propylcyclohexane45.0545.7146.4447.2648.16
propylcyclohexanepropylbenzene211.33211.85212.09212.06211.76
hexylbenzenepropylbenzene+C3=80.6880.2179.7279.2178.68
hexylbenzeneethylnaphthalene164.32165.62166.74167.70168.49