Study on reaction path and coke formation of decalin on acid catalyst
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摘要: 采用小型固定流化床装置(ACE Model C),研究了在反应温度460−540 ℃下,模型化合物十氢萘在Y分子筛催化剂上的裂化反应路径及生焦机理。结果表明,十氢萘裂化的初始阶段,H + 进攻十氢萘上与叔碳原子相连的C−H键和C−C键形成非经典五配位叔正碳离子是其最主要的引发反应;十氢萘裂化产物主要是丙烯、丙烷、异丁烷、异戊烷、甲基环戊烷、甲苯、二甲基苯等;产物的收率在催化剂上由大到小为,非芳烃、单环芳烃、双环芳烃;十氢萘催化生焦的机理是碳正离子机理,随反应温度和分子筛酸量的升高,双分子氢转移以及脱氢缩合能力增强,焦炭产率和转化率也随之升高。Abstract: A small fixed fluidized bed device (ACE Model C) was used to study the cracking reaction path and coke formation mechanism of model compound decaphthalene over Y molecular sieve catalyst at the reaction temperature of 460−540 ℃. The results show that in the initial stage of decalin cracking, H + attacking C−H bond and C−C bond with tertiary carbon atoms on decalin to form non-classical five-coordinated tertiary positive carbon ions is the most important initiation reaction. Decalin cracking products are mainly propylene, propane, isobutane, isopentane, methylcyclopentane, toluene, dimethyl benzene, etc. The yields of the products on the catalyst from large to small are: non-aromatic hydrocarbons, monocyclic aromatic hydrocarbons, bicyclic aromatic hydrocarbons. The catalytic coke formation mechanism of decalin is carbocation mechanism. With the increase of reaction temperature and molecular sieve acid content, the bilayer hydrogen transfer and dehydrogenation condensation ability are enhanced, and the coke yield and conversion are also increased.
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Key words:
- decalin /
- catalytic cracking /
- molecular sieve catalyst /
- coke /
- reaction
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表 1 两种分子筛催化剂的物化性质
Table 1 Main physicochemical properties of the two catalysts
Catalyst n(SiO2)/n(Al2O3) SBET/
(m2·g−1)v/
(mL·g−1)Smicro/
(m2· g−1)vmicro/
(mL·g−1)Acidity amount/
(µmol·g−1)USY-C 8.8 177.4 0.221 115.6 0.046 65.2 REY-C 4.8 160.3 0.193 109.8 0.044 102.1 表 2 老化后催化剂的吡啶红外表征
Table 2 Pyridine IR characteristics of the catalyst after aging
Catalyst Acidity(200 ℃)/
(µmol·g−1)Acidity(350 ℃)/
(µmol·g−1)L B L B USY-C 164 177 110 127 REY-C 256 642 175 358 表 3 H + 三种进攻反应的能垒
Table 3 Energy barrier of H + three attack reactions
Offensive position Energy barrier/(kJ·mol−1) C−H 203.7 C−C1 162.8 C−C2 238.5 表 4 十氢萘催化裂化的主要产物质量分数
Table 4 Mass fraction of main products of catalytic cracking of decalin
Catalyst w/% Catalyst w/% USY-C REY-C USY-C REY-C Hydrogen 0.026 0.021 methyl hexane 0.480 0.448 Methane 0.061 0.153 heptane 0.045 0.026 Ethane 0.041 0.182 heptene 0.100 0.062 Ethylene 0.394 0.775 methylcyclohexane 1.332 1.042 Propane 1.573 4.432 trimethylcyclopentane 0.182 0.191 Propylene 2.352 1.993 dimethylhexane 0.475 0.460 N-butane 1.338 3.200 toluene 2.077 7.214 Isobutane 7.111 10.409 methylheptane 0.065 0.047 1-butene 0.325 0.229 dimethylcyclohexane 0.176 0.135 Isobutylene 0.378 0.152 isopropylcyclopentane 0.028 0.020 Cis-2-butene 0.407 0.287 ethyl cyclohexane 0.033 0.030 Trans-2-butene 0.578 0.408 ethylbenzene 0.370 1.410 Isopentane 4.222 6.900 xylene 1.932 6.519 Pentane 0.236 0.475 propylbenzene 0.054 0.088 Cyclopentane 0.202 0.192 dimethyl octane 0.132 0.112 Methamene 0.719 0.462 methylethylbenzene 0.721 1.711 Trans-2-pentene 0.066 0.035 trimethylbenzene 1.611 2.545 1-pentene 0.038 0.034 methylnonane 0.488 0.254 Cis-2-pentene 0.040 0.036 n-decane 0.338 0.170 Cyclopentene 0.072 0.023 butylbenzene 0.163 0.073 Methyl pentene 1.076 0.942 methylpropylbenzene 2.322 2.347 Isomerhexene 2.282 2.913 indan 0.554 0.895 Cyclohexane 0.318 0.377 diethylbenzene 0.253 0.191 Malehexene 0.094 0.098 ethyl,dimethylbenzene 0.478 0.563 Hexane 1.035 2.091 methylindan 5.467 4.818 Methylpentane 0.477 0.760 tetramethyl benzene 3.312 5.148 Methylcyclopentane 4.217 3.866 n-undecane 0.027 0.032 Methylcyclohexane 0.284 0.275 methyl undecane 0.245 0.421 Benzene 0.971 2.337 naphthalene 2.865 2.672 Dimethylpentane 0.141 0.166 dimethylindan 0.334 0.322 Dimethylcyclopentane 1.584 1.321 coke 0.305 1.522 Cyclohexene 0.021 0.029 conversion/% 72.039 87.940 Conditions: mass ratio of catalyst to oil is 6, 8 h−1, 500 ℃ 表 5 十氢萘在不同反应温度下的生焦产率和转化率
Table 5 Coke yield and conversion of decalin at different reaction temperatures
CatalystCoke yield and conversion /% 460 ℃ 500 ℃ 540 ℃ coke conversion coke conversion coke conversion USY-C 0.29 66.96 0.31 72.04 0.34 75.82 REY-C 1.40 85.98 1.52 87.94 1.54 88.63 Conditions: mass ratio of catalyst to oil is 6, 8 h−1 -
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