Al2O3

Article pubs.acs.org/IECR

Kinetics of Phenanthrene Hydrogenation System over CoMo/Al2O3 Catalyst Huibin Yang,†,‡ Yachun Wang,† Hongbo Jiang,*,† Huixin Weng,† Feng Liu,‡ and Mingfeng Li‡ †

Research Institute of Petroleum Processing, East China University of Science and Technology, Shanghai 200237, China Research Institute of Petroleum Processing, SINOPEC, Beijing 100083, China

‡

ABSTRACT: With phenanthrene and hydrogen as raw materials, the hydrogenation of phenanthrene was tested over CoMo/ Al2O3 catalyst in a fixed-bed microreactor. Effects of temperature, pressure and space velocity on the reactions were systematically investigated. On the basis of the equilibrium constants calculated by thermodynamic method and kinetic equation derived by the adsorption theory of Langmuir−Hinshelwood−Hougen−Watson, the rate constants, activation energy, and adsorption constants were estimated by the Broyden−Fletcher−Goldfarb−Shanno optimization method, and the different reaction networks were compared and screened. In this study, the result showed the path from 9,10-dihydrophenathrene to tetrahydrophenathrene could be neglected, and the path from 9,10-dihydrophenathrene to 1,10-octahydrophenanthrene could not be excluded.

1. INTRODUCTION In recent years, with oil becoming heavier and degraded all over the world, there has been an increasing trend toward processing heavier oils.1 Such crudes typically contain a large number of undesirable aromatic compounds and are considerably more difficult to be converted into clean transportation fuels. The polycyclic aromatic hydrocarbons widely present in the heavy oil as a major kind of coke precursors, and aromatic hydrocarbons of two or more rings have a material adverse effect on product quality.2 For example, high aromatic hydrocarbon content in diesel oil will decrease its quality and cetane number, and aromatic hydrocarbon will reduce the smoke point of kerosene. So, the efficient conversion of polycyclic aromatic hydrocarbons has an important effect on making full use of heavy oil. As a typical polycyclic aromatic hydrocarbon, hydrogenation of phenanthrene has been extensively studied.3,4 However, there are still disagreements on the major reaction paths.4−6 In addition, although the results of phenanthrene hydrogenation on different reduced-state hydrogenation catalyst and sulfide hydrogenation catalyst have been reported, due to the large difference of experimental conditions, such as the difference between reactors, reaction pressure and reaction temperature, it is hard to get the difference between the effects of different catalysts on performance of phenanthrene hydrogenation under the same reaction conditions according to the experimental data disclosed in the literature. In this study, the experiment was taken for the purpose of investigating reaction path and selectivity of phenanthrene hydrogenation. And in the reaction system of phenanthrene hydrogenation, there is phenanthrene, 9,10-dihydrophenathrene, tetrahydrophenanthrene, 1,8-octahydrophenanthrene, 1,10-octahydrophenanthrene and hydrogen. On the basis of the results of kinetics experiments over a CoMo catalyst, the equilibrium constants calculated by thermodynamic method7 and kinetic equation derived by the adsorption theory of Langmuir−Hinshelwood−Hougen−Watson,8 the different reaction networks were compared and screened, and the reaction © 2014 American Chemical Society

rate constants, activation energy and adsorption constants were estimated by Broyden−Fletcher−Goldfarb−Shanno (BFGS) optimization (an iterative method of Quasi-Newton methods for solving unconstrained nonlinear optimization problems using rank-2 updates).9

2. EXPERIMENTAL SECTION 2.1. Preparation of Catalyst. In this study, a commercial Al2O3 carrier was chosen that the water absorption is 0.85 mL/ g. Commercial cobalt nitrate and ammonium molybdate as precursors were dissolved together in a saturated solution of ammonium hydroxide, and then diluted to 85 mL to impregnate 100 g of carrier. The CoMo/Al2O3 catalyst was obtained after being dried at 120 °C and calcined at 420 °C for 4 h. The metal quality contents of the prepared catalyst were the following: CoO 2.4%, and MoO 12%. The superficial area of the CoMo catalyst was 155 m2/g, the pore volume was 0.39 mL/g, and the crushing strength was 36.0 N/m2. The materials for manufacturing catalyst are shown in Table 1. Table 1. Manufacturers and Purity of Catalyst Materials name

manufacturer

ammonium paramolybdate cobalt nitrate n-decane phenanthrene carbon disulfide cyclohexane

Received: Revised: Accepted: Published: 12264

purity (%)

Tianjin Sifang Chemical Co., Ltd.

>98

Beijing Yili Fine Chemicals Co., Ltd. Tianjin Kemiou Chemical Reagent Co., Ltd. Alfa Aesar, a Johnson Matthey Company Tianjin Jindong Tianzheng Fine Chemical Industry Beijing Yili Fine Chemicals Co., Ltd.

>99 >99 >97 >99 >99

April 3, 2014 June 23, 2014 July 14, 2014 July 14, 2014 dx.doi.org/10.1021/ie501397n | Ind. Eng. Chem. Res. 2014, 53, 12264−12269

Industrial & Engineering Chemistry Research

Article

2.2. Stability of the Catalyst Activity. The purpose of the experiment was to get the concentration distributions of the phenanthrene hydrogenation products. So, in order to ensure all data was measured at the same level of catalyst activity under different conditions, it was necessary to investigate the stability of the catalyst activity. Through the experiment, it was found that the catalyst activity decreased during the first 10 h, and then stabilized relatively. So, the catalyst of each experiment was investigated in the activity stable region. 2.3. Diffusion Exclusion. 2.3.1. Exclusion of External Diffusion. The influence of external diffusion on the reaction rate of phenanthrene hydrogenation was investigated by changing the linear velocity of the reaction oil through the catalytic bed under the same space velocity. The experimental results showed the changes of the concentration distributions of the phenanthrene hydrogenation products were quite small when the linear velocity was greater than or equal to 1.02 cm/ min, and the influence of external diffusion on the activity on the CoMo catalyst can be excluded. 2.3.2. Exclusion of Internal Diffusion. The influence of internal diffusion on the catalyst activity was investigated by changing the particle size of catalyst under the same space velocity. The experimental results indicated that when the particle size was less than or equal to 40 mesh, the influence of internal diffusion on the catalyst activity was insignificant and could be excluded. So the particle size was determined by 40 to 60 mesh under the reaction conditions. 2.4. Performance Evaluation of the Catalyst. The inner diameter of the fixed-bed microreactor was 8 mm and the height of the constant temperature district was 6 cm. The oil for reaction was the n-decane solution with 2% mass content of phenanthrene (CS2 was added as sulfide in order to ensure the state of vulcanization of the catalyst, the mass content of sulfur of raw material was 0.1%), and the hydrogenation reactions was carried out on the catalyst. The size of the catalyst was 40−60 mesh, the particle density was 0.72 g/mL, and its loading amount was 0.118 g when the space velocity was 40 h−1 (catalyst loading amount was adjusted to the change of space velocity and the position of catalyst was within the constant temperature zone of the reactor). Before the reaction, the fresh catalyst was presulfided with cyclohexane solution containing 5% CS2 in each experiment. In the vulcanization process, the temperature was 360 °C, the pressure was 4.0 MPa, the hydrogen flow rate was 120 mL/min, and the oil flow rate was 0.2 mL/min. After the vulcanization, the vulcanized oil was switched to reaction oil, and the catalyst was passivated for 3 h at 280 °C and 4 MPa, with the same hydrogen flow rate and oil flow rate as before. Then the reaction conditions were adjusted to experimental conditions and the condensate was collected after stabilization of reaction conditions. The product compositions were analyzed by gas chromatography−mass spectrometry (GC−MS). The repeating experiment showed the relative error of experimental data was within 1%. The flowchart of the microreactor evaluating device is shown in Figure 1. The chromatographic type was GC 7890-MS 5975C produced by Agilent company, whose chromatographic column was HP-5MS 5% phenyl methyl silox 30 m × 250 μm × 0.25 μm and the carrier gas was He. The temperature programming of the chromatographic column was that the starting temperature was 50 °C for 5 min, with heating up to 160 °C at a rate of 1 °C/min, over a total duration of 115 min. 2.5. Kinetic Experimental Design. In this study, effects of space velocity, reaction pressure, hydrogenation oil rate, and

Figure 1. Experimental scheme

temperature on the distribution of phenanthrene hydrogenation products were investigated, and the specific reaction conditions are shown in Table 2. Table 2. Reaction Conditions of Phenanthrene Hydrogenationa reaction conditions T (°C) P (MPa) space velocity (h−1) hydrogen/oil ratio catalyst loading amount (g) reaction conditions T (°C) P (MPa) space velocity (h−1) hydrogen/oil ratio catalyst loading amount (g)

SV1

SV2

SV3

SV4

280 4 20

280 4 24

280 4 30

280 4 40

280 4 60

SV5

280 4 120

SV6

600

600

600

600

600

600

0.236

0.197

0.157

0.118

0.0787

0.0393

P1

P2

P3

T1

T2

T3

280 2 40

280 4 40

280 6 40

220 4 40

250 4 40

280 4 40

600 0.118

600 0.118

600 0.118

600 0.118

600 0.118

600 0.118

a Note: SV refers to space velocity, P refers to the reaction pressure, and T is the reaction temperature. The hydrogen/oil ratio refers to the feed volumetric flow rate ratio of hydrogen to oil.

3. EXPERIMENTAL RESULTS 3.1. Influence of Space Velocity on Reactions. The changes in space velocity affected the contact time of each molecule with the catalyst, and the mole fraction of each molecule in reaction products at 280 °C, P = 4 MPa is shown in Figure 2. It showed that as the contact time increased, the content of phenanthrene in the mixture of the reactor outlet gradually decreased, while the other molecules increased. And as the contact time increased, the conversion of phenathrene as well as the selectivity of 1,8-octahydrophenanthrene and 1,10octahydrophenanthrene increased, while the selectivity of 9,10dihydrophenathrene and tetrahydrophenanthrene decreased. 3.2. Influence of Pressure on Reactions. At T = 280 °C, SV = 40 h−1, the pressure of reaction system was changed, and 12265

dx.doi.org/10.1021/ie501397n | Ind. Eng. Chem. Res. 2014, 53, 12264−12269


Article

Figure 2. Influence of space velocity on products distribution and selectivity. Note: A is phenanthrene, C is 9,10-dihydrophenathrene, D is tetrahydrophenanthrene, E is 1,8-octahydrophenanthrene, and F is 1,10-octahydrophenanthrene.

Figure 3. Influence of pressure on products distribution and selectivity. Note: A is phenanthrene, C is 9,10-dihydrophenathrene, D is tetrahydrophenanthrene, E is 1,8-octahydrophenanthrene, and F is 1,10-octahydrophenanthrene.

Figure 4. Influence of temperature on products distribution and selectivity. Note: A is phenanthrene, C is 9,10-dihydrophenathrene, D is tetrahydrophenanthrene, E is 1,8-octahydrophenanthrene, and F is 1,10-octahydrophenanthrene.

3.3. Influence of Temperature on Reactions. At P = 4 MPa, SV = 40 h−1, the reaction was studied at different temperatures, and the molar fraction of each molecule in reaction products is shown in Figure 4. As the temperature increased, the content of phenantherene decreased, while other molecules increased, which indicated that it was conducive to the reactions with the increase of temperature. Also, with the increase of temperature, the conversion of phenathrene as well as the selectivity of 9,10-dihydrophenathrene and 1,10octahydrophenanthrene increased, the selectivity of tetrahy-

the molar fraction of each molecule in reaction products is shown in Figure 3. As seen from Figure 3, with the increase of pressure, the content of phenanthrene in the mixture of reactor outlet was on a declining trend, while the contents of other molecules were on an increasing trend. This indicated that the increase of pressure was conducive to the reaction. And with the increase of pressure, the conversion of phenathrene as well as the selectivity of 1,8-octahydrophenanthrene and 1,10octahydrophenanthrene increased, while the selectivity of 9, 10dihydrophenathrene and tetrahydrophenanthrene decreased slightly. 12266



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Table 3. Basic Data of Raw Material under the Reaction Conditionsa Vaporization ratios (%) reaction conditions

ndecane

phenanthrene

hydrogen partial pressure (MPa)

SV1 SV2 SV3 SV4 SV5 SV6 P1 P2 P3 T1 T2 T3

98.74 98.74 98.74 98.74 98.74 98.74 100.0 98.74 72.03 35.54 65.38 98.74

81.35 81.35 81.35 81.35 81.35 81.35 100.0 81.35 14.56 2.07 8.82 81.35

3.32 3.32 3.32 3.32 3.32 3.32 1.66 3.32 5.22 3.72 3.52 3.32

total volumetric flow rate(L·s−1) 6.03 6.03 6.03 6.03 6.03 6.03 1.21 6.03 3.88 4.90 5.43 6.03

× × × × × × × × × × × ×

10−05 10−05 10−05 10−05 10−05 10−05 10−04 10−05 10−05 10−05 10−05 10−05

space time (kgcat·s·L−1)

reaction concentration of phenanthrene (mol·L−1)

3.91 3.26 2.61 1.96 1.31 0.65 0.98 1.96 3.04 2.41 2.17 1.96

0.00244 0.00244 0.00244 0.00244 0.00244 0.00244 0.00122 0.00244 0.00379 0.00300 0.00271 0.00244

Note: C is the reaction concentration of phenanthrene, it follows that C = Q/F, where Q is the molar flow rate (mol/L) and F is the total volumetric flow rate (L/s), including the volumetric flow rate of hydrogen and vaporized reactants as well as the volumetric flow rate of liquid phase reactants under the reaction conditions. The space time is expressed as τ, where τ = W/F, where W is the mass of catalyst (kg). a

Figure 5. Reaction network of phenanthrene hydrogenation system. Note: A is phenanthrene, B is hydrogen, C is 9,10-dihydrophenathrene, D is tetrahydrophenanthrene, E is 1,8-octahydrophenanthrene, and F is 1,10-octahydrophenanthrene.

pass through the liquid film before reaching the catalyst surface. So, this study assumed that the reaction of phenanthrene hydrogenation was mainly a liquid−solid catalytic reaction under the reaction condition and the concentration of compounds was calculated based on total volumetric flow rate. And the flowing state in reactor was assumed as plug flow.

drophenanthrene decreased, and the selectivity of 1,8octahydrophenanthrene increased first, then decreased.

4. MODEL ASSUMPTION The critical temperature of hydrogen is −239.9 °C, and its critical pressure is 1.297 MPa, so it was in supercritical state under the reaction conditions of the study. The critical temperature of n-decane is 344.6 °C, and its critical pressure is 2.11 MPa, and the boiling point is 174.2 °C; the critical temperature of phenanthrene is 595.9 °C, its critical pressure is 2.9 MPa, and the boiling point is 340 °C, so the saturated vapor pressures of n-decane and phenanthrene were 0.829 and 0.029 MPa, respectively, at 280 °C according to the Riedel−Plank− Miller equation.10 The vaporization ratios of n-decane and phenanthrene were calculated with Aspen Plus software with the Uniquac method, as shown in Table 3; both phenanthrene and n-decane were partially vaporized under the reaction conditions of the present study. Normally, it is easy for liquid reactants to form a liquid film on the catalyst surface, and the reactants in gas phase must

5. KINETICS 5.1. Reaction System Model. The hydrogenation of phenanthrene has been extensively studied by foreign scholars as early as the 1970s,5,11,12 and it is found that all the reactions in the system of phenanthrene hydrogenation are reversible reactions. This study assumed that the phenanthrene hydrogenation reaction network proposed by Beltramone et al. as reaction network 1,4 the reaction network proposed by Korre et al. as reaction network 2,5 and the reaction network proposed by Qian et al. as reaction network 3.6 And all the reaction networks are shown in Figure 5. 5.2. Kinetic Equation. Referencing to the results of previous studies,5 the adsorption theory of Langmuir−Hinshel12267



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wood−Hougen−Watson8 was used to deduce kinetic equations. The (L−H)-type assumes a reaction on the surface governs the rate, with one of the elementary steps in the reaction sequence constituting a rate-determining step, thus all the adsorption/desorption steps are quasi-equilibrated and a Langmuir isotherm can be used to relate surface concentrations to bulk concentrations or partial pressures, and the (H−W)type is broader because it also allows for an adsorption step or a desorption step to be a rate-determining step, but Langmuir isotherms are again used, when appropriate, to relate surface and bulk concentrations. In this study, the CoMo hydrogenation catalyst is a monofunction catalyst, and the hydrogenation reactions on the surface of catalyst were regarded as rate controlling steps. The rate expression was as follows: rij =

Table 5. Reaction Rate Constants of All Reactions for Phenanthrene Hydrogenation System (280°C) reaction rate constant (L·kgcat−1 s−1) reactions A+B⇌C A + 2B ⇌ D C+B⇌D C + 3B ⇌ F D + 2B ⇌ E D + 2B ⇌ F

× PH2

(1)

n

(2)

where rij is the rate of conversion of compound i to compound j (mol/kgcat·s), kij is the rate constant of compound i to compound j (L/kgcat·s), Ci, Cj, Cm are the concentration of compound i, compound j, or compound m (mol/L), Km is the adsorption constants of individual compounds (L/mol), Kij is the equilibrium molar ratio of compound i to compound j (mol j/mol i), Kijeq is the hydrogenation equilibrium constant, n is the reaction stoichiometry with respect to hydrogen, and PH2 is the Hydrogen partial pressure (atm). 5.3. Equilibrium Constants of Hydrogenation Reaction at Different Temperatures. The equilibrium constants of liquid phase hydrogenation reactions at different temperatures could be calculated by a thermodynamic method7 as shown in Table 4.

reaction equilibrium constants reactions

220 °C 0.328 1.235 3.765 1.329 1.055 0.353 0.557 1.665

0.2075 0.0593

0.1962 0.0696

0.0358 0.1934 0.0047

0.1861 0.1358

0.2082 0.0595 0.00008 0.0357 0.1009 0.0046

atm−1 atm−2 atm−1 atm−3 atm−2 atm−2 atm−3 atm−3

250 °C

280 °C

0.139 atm−1 0.200 atm−2 1.435 atm−1 0.0873 atm−3 0.170 atm−2 0.0609 atm−2 0.0391 atm−3 0.109 atm−3

0.0644 atm−1 0.0389 atm−2 0.605 atm−1 0.00764 atm−3 0.0329 atm−2 0.0126 atm−2 0.00364 atm−3 0.00947 atm−3

compounds

reaction network 1

reaction network 2

reaction network 3

A C D E F

32.45 7.06 7.56 5.31 6.31

32.06 7.07 7.95 6.30 6.21

32.31 7.04 7.18 5.32 5.40

average deviation was 0.75%. And all the calculation values and experimental values of three networks were analyzed with paired-sample t-test by statistics software that showed that the correlations of three networks were the same, 0.996. And the two-tailed test probabilities of three networks were greater than 0.05, which indicated that there were no significant differences between calculation values and experimental values. The confidence intervals of three networks were −0.1172 to +0.1269, −0.1094 to +0.1297, and −0.1146 to +0.1333, respectively. Though all the calculation values of different networks were close to the experimental values, but comparing the rate constants of different phenanthrene hydrogenation systems, it was clear that the rate constant of the path from 9,10dihydrophenathrene to tetrahydrophenathrene was much smaller than that of other reactions. And the actual reaction rate was equal to the rate constant times the hydrogen partial pressure, considering the influence of hydrogen partial pressure, the difference of reaction rate became larger as the pressure increased, so this path may not exist, but the reaction possibility from the 9,10-dihydrophenathrene to 1,10-octahydrophenanthrene could not be excluded. 6.2. Activation Energy. The influence of temperature on reactions was investigated by changing the reaction temperature, and the activation energy was estimated. The specific reaction conditions are shown in Table 1. According to the Arrhenius equation:

Table 4. Equilibrium Constants of Hydrogenation Reaction at Different Temperatures

A+B⇌C A + 2B ⇌ D C+B⇌D C+ 3B⇌F D + 2B ⇌ E D + 2B ⇌ F E + 3B ⇌ G F + 3B ⇌ G

reaction network 3

adsorption constant (L·mol−1)

1 + ∑m K m × Cm

in which K ij =

reaction network 2

Table 6. Adsorption Constants of Individual Compounds over CoMo Catalyst (280°C)

k ij × (Ci − Cj/K ij)

K ijeq

reaction network 1

6. RESULT AND ANALYSIS 6.1. Reaction Rate Constants. The reaction rate constants of all reactions for phenanthere hydrogenation system were estimated with the BFGS optimization method as shown in Table 5, and the adsorption constants of individual compounds over the CoMo catalyst are shown in Table 6.3 Comparing calculation values with experimental values, the maximum deviation of reaction network 1 was 1.17%, the average deviation was 0.73%; the maximum deviation of reaction network 2 was 1.22%, the average deviation was 0.77%; the maximum deviation of reaction network 3 was 1.24%, the

k = A exp( − Ea/RT )

(3)

where k is the rate constant (mol/kgcat·s), Ea is the activation energy (j/mol), T is the reaction temperature (K). The rate constants of other temperatures could be derived with 280 °C as the reference temperature: ⎛ Ea ⎞ × (1/T1 − 1/T0)⎟ k = k 0 × exp⎜ − ⎝ R ⎠

(4)

where k0 is the rate constant of 280 °C, T1 is other reaction temperatures (K), T0 = 553.15 K. 12268



■

Though the temperature will influence the adsorption constants of organic molecules over the NiMo catalyst, but the ratio between adsorption constants changed little in the range of reaction temperature investigated, so the influence of temperature on the adsorption constants was neglected during the estimation of activation energy, and the result is shown in Table 7.

*Hongbo Jiang. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

■

A+B⇌C A + 2B ⇌ D C+B⇌D C + 3B ⇌ F D + 2B ⇌ E D + 2B ⇌ F

reaction network 2

reaction network 3

132.5 104.1

129.3 108.9

104.8 100.5 192.7

99.4 191.8

133.0 102.7 30.9 99.6 100.1 189.6

REFERENCES

(1) Gembicki, V. A.; Cowan, T. M.; Brierley, G. R. Update processing operations to handle heavy feedstocks. Hydrocarbon Process. 2007, 86, 41. (2) Sun, Y.; Yang, C.; Shan, H.; Zhao, H.; Shen, B. Hydrotreating reaction performance of different residua. Pet. Process. Sect. 2011, 27, 32−36. (3) Korre, S. C.; Klein, M. T.; Neurock, M.; Klein, M. T.; Quann, R. J. Hydrogenation of polynuclear aromatic hydrocarbons 2. Quantitative structure/reactivity correlations. Chem. Eng. Sci. 1994, 49, 4191− 4210. (4) Beltramone, A. R.; Resasco, D. E.; Alvarez, W. E.; Choudhary, T. V. Simultaneous hydrogenation of multiring aromatic compounds over NiMo catalyst. Ind. Eng. Chem. Res. 2008, 47, 7161−7166. (5) Korre, S. C.; Klein, M. T.; Quann, R. J. Polynuclear aromatic hydrocarbons hydrogenation 1. Experimental reaction pathways and kinetics. Ind. Eng. Chem. Res. 1995, 34, 101−117. (6) Qian, W.; Yoda, Y.; Hirai, Y.; Ishihara, A.; Kabe, T. Hydrodesulfurization of dibenzothiophene and hydrogenation of phenanthrene on aluminha-supported Pt and Pd catalysts. Appl. Catal., A 1999, 184, 81−88. (7) Yang, H.; Chang, X.; Jiang, H.; Weng, H. Estimation of thermodynamics for phenanthrene hydrogenation system. Chem. React. Eng. Technol. 2012, 28, 499−505. (8) Vannice, M. A. Kinetics of Catalyst Reactions; Springer Science: New York, 2005. (9) Wang, K. The optimization methods; Science Press: Beijing, 2010. (10) Dong, X.; Fang, L.; Chen, L. Physical property estimation principle and computer calculation; Chemical Industry Press: Beijing, 2006. (11) Chareonpanich, M.; Zhang, Z. G.; Tomita, A. Hydrocracking of aromatic hydrocarbons over USY-zeolite. Energy Fuels 1996, 10, 927− 931. (12) Korre, S. C.; Klein, M. T.; Quann, R. J. Hydrocracking of polynuclear aromatic hydrocarbons: Development of rate laws through inhibition studies. Ind. Eng. Chem. Res. 1997, 36, 2041−2050.

activation energy (kJ·mol−1) reaction network 1

AUTHOR INFORMATION

Corresponding Author

Table 7. Activation Energy of All Reactions of Phenanthrene Hydrogenation System

reactions

Article

Comparing calculation values with experimental values, the maximum deviation of reaction network 1 was 0.42%, the average deviation was 0.30%; the maximum deviation of reaction network 2 was 0.46%, the average deviation was 0.33%; the maximum deviation of reaction network 3 was 0.43%, the average deviation was 0.31%. The deviation of all reaction networks was small, which means that neglecting the influence of temperature on the adsorption constants was acceptable. And all the calculation values and experimental values of three networks were analyzed with paired-sample t-test by statistics software that showed that the correlations of the three networks were greater than 0.998. And the two-tailed test probabilities of three networks were greater than 0.05, which indicated that there were no significant differences between calculation values and experimental values. The confidence intervals of three networks were −0.1284 to +0.1774, −0.0982 to +0.1713 and −0.1220 to +0.1821, respectively. Comparing three reaction networks, all the calculation values of different networks were close to the experimental values, but the rate constant of the path from 9,10-dihydrophenathrene to tetrahydrophenathrene was still much smaller than that of other reactions, so this path could be neglected and the path from 9,10-dihydrophenathrene to 1, 10-octahydrophenanthrene could not be excluded.

7. CONCLUSION (a) Under the conditions of the present study, the assumption that the reaction of phenanthrene hydrogenation was mainly a liquid−solid catalytic reaction and the concentration of compounds was based on total volumetric flow rate was reasonable. (b) The reaction rate constants, activation energy, and adsorption constants were estimated by the BFGS optimization method for the system of phenanthrene hydrogenation over the CoMo catalyst. Under the reaction conditions of this study, the result showed that the reaction path from 9,10-dihydrophenathrene to tetrahydrophenathrene could be neglected, and the path from 9,10-dihydrophenathrene to 1,10-octahydrophenanthrene could not be excluded. 12269


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