Determination of the Hydrogen-Donating Ability of Industrial Distillate

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Determination of Hydrogen-donating Ability of Industrial Distillate Narrow Fractions Qiang Sheng, Gang Wang, Mengchao Duan, Ailin Ren, Libo Yao, Miao Hu, and Jinsen Gao Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.6b02288 • Publication Date (Web): 01 Nov 2016 Downloaded from http://pubs.acs.org on November 13, 2016

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Determination of Hydrogen-donating Ability of Industrial Distillate Narrow Fractions Qiang Sheng, Gang Wang*, Mengchao Duan, Ailin Ren, Libo Yao, Miao Hu, Jinsen Gao ABSTRACT The hydrogen-donating ability of the narrow fractions of coker gas oil (CGO), FCC slurry (FCCS), and furfural extract oil (FEO) was investigated in an autoclave reactor. Anthracene was selected as hydrogen acceptor probe for accepting hydrogen released by the hydrogen donor. Hydrogen nuclear magnetic resonance (1H-NMR) was employed to identify different categories of hydrogen of the mixture. Based on the 1H-NMR data, a method for calculating hydrogen-donating ability (HDA) was developed to characterize the hydrogen donating-properties of selected industrial distillate narrow fractions (IDNF). The reliability of the proposed method was verified by the average molecular structure and hydrocarbon composition of narrow fractions. The HDA of the narrow fractions follows the order of FEO > FCCS > CGO, and that of the key components of IDNF is FEO-5 > FCCS-6 > CGO-4. FEO-5 is the optimal candidate for acting as industrial distillate hydrogen donor. The average molecular structure indicated the parameters of average molecular structure have a relationship with the HDA. RN/RA values closer to 1 indicate high HDA. Analysis of the hydrocarbon composition demonstrated that the total percentage of naphthenoaromatics including naphthenebenzenes, dinaphthenebenzenes, and naphthenephenanthrenes in the narrow fractions influenced the HDA of IDNF. Key words: hydrogen donor; hydrogen-donating ability; industrial distillate narrow 1

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fractions; 1H-NMR 1. INTRODUCTION Effective conversion of inferior heavy oil has become a worldwide problem1, 2; asphaltene conversion is of great important for converting inferior heavy oil3. However, many serious problems occurred when asphaltene was processed in the traditional heavy oil processes2-4, such as delayed coking5-7, residue fluid catalytic cracking, hydrocracking, hydrotreating8. In these processes, the heavy oil colloidal system is destroyed by decomposition of the solvation layer, leading to aggregation of asphaltene and condensation to coke according to the phase-separation mechanism5-7, 9-11. Hydrogen donor is one kind of compound with the naphthenoaromatic structure12-15, which not only enhances the stability of heavy oil colloidal system by providing a solvation layer for asphaltene16, but also reduces the coke formation15 by quenching the macromolecular radicals17 with active hydrogen atoms released by hydrogen donor. Therefore hydrogen donor can be favorably used for conversion of inferior heavy oil with minimal coke formation. A typical hydrogen donor tetralin is widely used in coal liquefaction12, 18, residue visbreaking17, and heavy oil hydroprocessing13-15 to reduce coke formation and increase liquid product yield19, 20. However, tetralin is expensive for refineries; hence, low-cost petroleum distillates, which contain abundant aromatic compounds, have been applied as hydrogen donors in heavy oil processes. Chen et al.21 used coker gas oil (CGO) narrow fractions (350 °C–420 °C) as hydrogen donor for visbreaking Karamay VR. Wang et al.17 2


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employed Venezuelan synthetic crude oil with true boiling point less than 420 °C as hydrogen donor for visbreaking Venezuelan vacuum residue. Guo et al.22 used FCC slurry (FCCS) as hydrogen donor for thermal cracking of vacuum residues under mild conditions. These studies suggest that using industrial distillates not only significantly improves the conversion of heavy oil, but also inhibits coke formation by donating hydrogen to heavy oil. Moreover, industrial distillates are cheap and can be readily obtained from refineries. Therefore, a systematic research must be performed on industrial distillates. Currently, industrial distillate hydrogen donors are usually full-range cuts or wide-range cuts. If the full-range cut or wide-range cut of industrial distillates is employed as hydrogen donor, the hydrogen donating properties may be weakened because of the presence of hydrocarbons without hydrogen donating properties. Industrial distillate narrow fractions (IDNF) with good hydrogen donating properties must be discovered to improve heavy oil conversion. The structure of model hydrogen donors has been studied by some scholars in the past years. Yokono et al.23 used force field method to calculate the precise geometry of hydroaromatic compounds including decalin, tetralin, 1,2-dihydronaphthalene, and 1,4dihydronaphthalene; the binding energies of the model compounds and their radicals were also calculated from approximate theory by Intermediate Neglect of Differential Overlap (INDO) method and were correlated to the transferable hydrogen of the donor compounds. Obara et al.24 studied the relationships between hydrogen donating ability (HDA) and the chemical structure of model compounds through gas chromatography, 1H-NMR, and computing calculation methods. Yang et al.25 estimated the HDA by calculating the energy 3


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barrier and reaction heat of C–H bond dissociation in α-position of tetralin (a typical hydrogen donor) through molecular simulation based on density function theory. These studies show that the structure of model compounds is correlated with their HDA. However, the narrow fractions of industrial distillates have not been systematically studied and the average molecular structure of the narrow fraction has not been correlated with HDA. In the present study, industrial distillates were selected as hydrogen donor and the effectiveness of their hydrogen donating properties were predicted. This paper aims to assess the HDA of industrial distillate narrow fraction and correlate HDA with the average molecular structure parameters of IDNF. Three industrial distillates including CGO, FCCS, and furfural extract oil (FEO) were selected and cut into narrower fractions. HDA was determined using a developed brief computational formula based on 1

H-NMR data. The average molecular structures of the narrow fractions were studied using

modified Brown–Ladner (B–L) method. The hydrocarbon composition of narrow fractions were also studied by GC-MS analysis. 2. EXPERIMENTAL SECTION 2.1. Materials. CGO and FCCS obtained from Sinopec Refinery, and FEO acquired from China National Petroleum Corporation were used as feeds. These distillates were cut into several narrow fractions by true boiling point (TBP) distillation (ASTM D-1160). The detailed number and properties of the narrow fractions were listed in Tables 1 and 2, respectively. 4


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Anthracene (99%), supplied by Acros Organics BVBA, was used as hydrogen acceptor probe26, 27. 2.2. Equipment and Procedure. All hydrogen-donating experiments were performed in a batch reactor (Figure 1). For a typical experiment the reactor was filled with approximately 5 g of IDNF as hydrogen donor and approximately 5 g of the hydrogen acceptor probe (anthracene). The reactor was filled with the reactants, closed, and tested for leakage at 8 MPa with nitrogen. After confirming that the reactors were leak free, they were pressurized by nitrogen to 5 MPa and vented to the atmosphere three times to ensure an inert atmosphere. An appropriate amount of nitrogen was added into the reactor to obtain a final pressure of 7 MPa at reaction temperature. This pressure was set to ensure that most of the narrow fractions were in liquid phase under reaction conditions. The reactions were carried out at 380 °C for 8 min28. This temperature was achieved and maintained by submerging the reactor in a fluidized sand bath heater. After reaction, the reactor was cooled by submersion in cold water. When the temperature decreased to room temperature, the reactor was opened and the products were collected. The reactor was thoroughly cleaned and reused. 2.3. Analysis. 1

H-NMR. The samples were determined by 1H-NMR in a 500 MHz Bruker AVANCE

III HD spectrometer. The samples were dissolved by CDCl3 and tetramethylsilane (TMS) 5


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as internal standard reference. Spectra were recorded at room temperature and the NMR parameters were as follows: 20 ppm spectral width, 1 s relaxation, 30° pulse width, 64 scans and 3.28 s acquisition time. The phase and baseline were manually adjusted and corrected. GC-MS Analysis. The narrow cuts were divided into saturate and aromatic hydrocarbon fractions by a silica gel column. The composition of saturate and aromatic compounds was analyzed by a Thermo-Finnigan Trace DSQ GC-MS coupled with a HP5MS column (30 m × 0.25 mm × 0.25 μm). The GC oven was maintained at 35 °C for 1 min, then increased to 300 °C at 2 °C /min, and kept at 300 °C for 10 min. The sample was injected at 300 °C. The electron impact ionization source was operated under 12 and 70 eV ionization energies, respectively. The mass range was set to 35–500 Da at a 1 s scanning period. The ion source temperature was 200 °C, and the ion current was 250 μA. 3. TESTING METHOD OF HYDROGEN DONATING ABILITY As a typical hydrogen acceptor probe, anthracene can be easily hydrogenated by active hydrogen atoms, when mixed with industrial distillate hydrogen donor at 380 °C for 8 min. Anthracene was converted to 9,10-dihydroanthracene (DHN) by hydrogenation. Figure 2 shows the three kinds of hydrogen in anthracene and DHN molecules. 1

H-NMR is an effective tool used to identify different types of hydrogen in organic

chemistry; in this study, 1H-NMR was employed to identify different types of hydrogen in the products. The typical peaks at chemical shifts of 8.4 and 3.9 ppm in 1H-NMR spectra 6


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represent the hydrogen in positions c of anthracene (Figure 2A) and c′ of DHN (Figure 2B), respectively27, 28. A typical 1H-NMR spectra of the mixtures after the hydrogen donating reaction was shown in Figure 3. Hence, the amounts of anthracene and DHN in the product can be calculated using the peak areas at chemical shifts of 8.4 and 3.9 ppm, respectively. The ratio of DHN (A) generated after anthracene hydrogenation was shown in Equation 1, in addition, the mass of DHN (B) generated from anthracene and the mass of active hydrogen (C) released by industrial distillate hydrogen donor were shown in Equations 2 and 3, respectively. Furthermore, the mass of active hydrogen accepted by anthracene is equal to the mass released by the industrial distillate hydrogen donor, so the HDA of industrial distillate hydrogen donor can be expressed as Equation 4. A

1 S3.9 2

1 S3.9  S8.4 2

(1)

B  m1  A (2)

C

HDA 

B 2M H 1000 (3) M DHN 1 S3.9 2

C m  11.1 1  (4) m2 m2 1 S  S 3.9 8.4 2

Where S3.9 and S8.4 are the peak areas of chemical shift at 3.9 and 8.4 ppm, respectively. m1 and m 2 are the masses of anthracene and industrial distillate hydrogen donor, respectively. M H and M DHN are the molecular weights of hydrogen atom and 7


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DHN, respectively.

4. RESULTS AND DISCUSSION 4.1. Hydrogen Donating Ability. In this part the HDA of industrial distillate hydrogen donor narrow fractions including CGO, FCCS, FEO, and model compound THN were tested using the method proposed above; in addition, the average molecular structure of part of narrow cuts were also studied to correlate the parameters of average molecular structure with the HDA of narrow fraction. 4.1.1. Hydrogen Donating Ability of CGO Narrow Fractions. The HDA of five narrow fractions of CGO (CGO-1–CGO-5) were tested, and the results are shown in Figure 4. The HDA of CGO narrow fractions is about 0.45 mg/g, and the HDA between each narrow fraction changes little. However, the maximum HDA is 0.56 mg/g obtained at CGO-3, furthermore, the HDA of the rest of the narrow fractions increased from 0.43 to 0.49 mg/g with increasing boiling point of narrow fractions. Model compounds of tetralin and decahydronaphthalene were used as examples to illustrate the principle of active hydrogen easily released by naphthenoarmatics. Figure 5A illustrates the C–H bond energies of tetralin. The C–H bond energies in the benzene ring are about 450 kJ/mol while that in the naphthenic ring are lower than 390 kJ/mol25, indicating that the C–H bonds on the benzene ring are much more stable than that of naphthenic ring, so it is harder to break. For the C–H bonds on the naphthenic ring, bond

8


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energy of C–H bond adjacent to the benzene ring (α-position) is 334.0 kJ/mol, while that of C–H bond far from benzene ring (β-position) is 389.8 kJ/mol25, indicating that C–H bond in α-position is easier to break than that in the β-position. From Table 3, the energy barrier and reaction heat of tetralin in I-position (or α-position) is 368.88 and 367.37 kJ/mol29, respectively. While in decahydronaphthalene, the energy barrier and reaction heat in II-position is 430.90 and 429.88 kJ/mol29, respectively, which are higher than that of tetralin, implying that the C–H bond in α-position of tetralin is much more unstable than that of decahydronaphthalene. Hence, tetralin releases hydrogen easily. The active hydrogen easily released by naphthenoaromatics is due to the naphthenic ring being activated by the benzene ring. The average molecule structure parameters of CGO-1, CGO-2, and CGO-4, whose HDA increased from 0.43 to 0.48 mg/g, were studied using modified B-L method and the results are listed in Table 4. According to Table 4, in CGO narrow fractions naphthenic rings (RN) is about 1.4 to 3.1 times as many as aromatic rings (RA). The value of RN/RA decreases with increasing cuts number, which leads to the increase of the interaction force between the π orbital of the benzene ring and σ orbital of the naphthenic ring attached to the benzene ring. The electron cloud density is therefore lowered with increasing the cuts number; hence, the C–H bond at the α-position of the naphthenic ring connected to the benzene ring was easily broken and released active hydrogen atom, ultimately leading to the increased HDA with icreasing boiling point of CGO narrow fraction.

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4.1.2. Hydrogen Donating Ability of FCCS Narrow Fractions. The HDA of seven narrow fractions of FCCS (FCCS-1–FCCS-7) were tested, and the results are given in Figure 6. As detailed, the HDA of FCCS narrow fractions changes between 0.51 and 0.68 mg/g. As the narrow fraction gets heavier, the value of HDA first increases to the maximum and then decreases to the minimum and goes up again. The average molecular structure parameters of three FCCS narrow fractions (FCCS2, FCCS-6, and FCCS-7) were studied, and the results are listed in Table 5. From Table 5, it can be seen from structural parameters of FCCS that the amount of its aromatic rings is higher than naphthenic rings, but the HDA decreases. The activated degree of naphthenic rings should be higher with the increase of the aromatic ring and the active hydrogen should be easily released, but the HDA of FCCS-2, FCCS-6, and FCCS-7 decreases with the aromatic ring increasing. To explain this phenomenon, the model compound is first studied. When an extra aromatic ring is connected to the tetralin structure, there will exist four different structures as shown in Figure 5 C, D, E, and F. For convenience, the C–H bond in the α-position was numbered and the energy barrier and reaction heat29 of the C–H bond dissociation in the α-position of tetralin and hydroaromatic hydrocarbons containing two aromatic rings are listed in Table 3. The data show that except for DHN, the energy barrier and reaction heat of C–H bond dissociation in the α-position of other hydroaromatic hydrocarbons are closer to tetralin, indicating the tendency of breaking C–H bond in the αposition is similar to tetralin. However, the energy barrier and reaction heat of the C–H 10


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bond dissociation in the α-position of DHN are much lower than tetralin, implying that it is easier to be broken than tetralin. This is mainly because the σ orbital of the C–H bond in the α-position could form two σ-π hyperconjugations with the benzene ring, leading to a lower electron cloud density compared with that of tetralin. Although the C–H bond in the α-position of DHN is much easier to be broken than tetralin their hydrogen donating amount is equal as shown in Table 6. Moreover, the molecular weight of DHN is far heavier than tetralin, hence the HDA of tetralin is higher than that of DHN. In terms of other hydroaromatic hydrocarbons containing two aromatic rings, although the energy barrier and reaction heat of the C–H bond dissociation in the α-position are closer to tetralin and the hydrogen donating amount is equal to tetralin, due to the growing molecular weight caused by increased aromaticity, the HDA is therefore weakened. Hence if the hydrogen donating amount is identical, molecular weight determines the HDA. Therefore, although with the growth of the distillation range of FCCS, RA and RN increase separately, the value of RN/RA increases first and then decreases. Just as mentioned above, although the hydrogen in the α-position of the naphthenic ring attached to the aromatic ring could be well activated by a large number of benzene rings and easily releases active hydrogen, however, due to the aromatic ring being heavier than the naphthenic ring, the amount of active hydrogen released by per unit mass of FCCS narrow fraction is limited. In addition, comparing FCCS-2, FCCS-6, and FCCS-7, it can be seen that the tendency of the increases of RA is obviously faster than RN, hence the order of HDA is FCCS-2 > FCCS-6 > FCCS-7. Additionally, there is little variation of RN/RA value between FCCS-6 and FCCS-7, so the 11


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HDA of FCCS-6 and FCCS-7 is almost identical. 4.1.3. Hydrogen Donating Ability of FEO Narrow Fractions. The HDA of eight FEO narrow fractions (FEO-1–FEO-8) were tested, and the results are shown in Figure 7. It can be seen that the HDA of FEO narrow fractions first increases from 0.90 mg/g to the maximum of 1.18 mg/g then gradually decreases to the minimum of 0.53 mg/g with the increase of the distillation range. The average structure parameter of FEO-2, FEO-4, FEO-6, and FEO-7 were studied, and the results are shown in Table 7. From Table 7, it can be seen that in FEO narrow fractions the amount of RA is slightly higher than RN. The values of RN/RA are less than 1 but closer to 1 compared with FCCS narrow fractions. Hence, it can be concluded that the hydrogen in the α-position of the naphthenic ring attached to the aromatic ring is fully activated; therefore comparing with FCCS and CGO narrow fractions, the hydrogen in the α-position is more easily released. With the increasing of distillation range, the value of RN/RA decreases, resulting in the decrease of the amount of naphthenic ring attached to per unit aromatic ring, hence the HDA of FEO-2, FEO-4, FEO-6, and FEO-7 decreases progressively. 4.1.4. Comparison of HDA Among CGO, FCCS, FEO Narrow Fractions, and THN. The HDA of the model compound hydrogen donor THN was also studied using the same HDA testing method and its HDA was compared with narrow fractions of FEO, FCCS, and CGO; the results are plotted in Figure 8. As can be seen from Figure 8 the HDA of 12


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THN is 1.94 mg/g which is higher than any IDNF. As a whole, comparing the HDA of different kinds of industrial fractions, CGO owns the minimum HDA value, FEO owns the maximum HDA value, and the HDA value of FCCS lies between CGO and FEO. According to Table 1, the statistics show that CGO-4, FCCS-6, and FEO-5 account for 32.00 wt%, 21.78 wt%, and 44.58 wt%, respectively. Hence, CGO-4, FCCS-6, and FEO-5 are the key components of CGO, FCCS, and FEO, respectively. The sequence of HDA of key components in CGO, FCCS, and FEO order is given: CGO-4 < FCCS-6 < FEO-5. Moreover, the percentage of FEO-5 in FEO is 44.58% which is higher than that of CGO-4 and FCCS-6, therefore FEO-5 can be selected as a suitable candidate for acting as an industrial distillate hydrogen donor. Just as discussed above CGO-4, FCCS-6, and FEO-5 are the key components of CGO and FCCS, and FEO, respectively, and THN is the most popular hydrogen donor. The HDA and the value of RN/RA of those hydrogen donors are listed in Table 8. THN HDA is 1.94 mg/g, which is obviously higher than the selected industrial distillate hydrogen donor. But the order of RN/RA values is as follows: FCCS-6 < FEO-5 < THN = 1 < CGO-4. The RN/RA value of THN is equal to 1, namely, one aromatic ring is connected to one naphthenic ring, which is higher than FCCS-6 and FEO-5, but less than CGO-4. The hydrogen atoms in the α-position of the naphthenic ring attached to the aromatic ring is sufficiently activated by the π bond of benzene ring than other narrow fractions, so active hydrogen atoms in the THN molecule are easily released, resulting in the HDA of THN being higher than other hydrogen donors. 13


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Comparing CGO-4 with FCCS-6, the RN/RA value of CGO-4 is 1.46. The number of aromatic rings is apparently less than the naphthenic rings, so the hydrogen in the αposition of the naphthenic ring attached to the aromatic ring could not be fully activated, leading to poor active hydrogen amount. However, the RN/RA value of FCCS-6 is 0.44. The number of aromatic rings is greater than the naphthenic rings, so in FCCS-6 the hydrogen in the α-position of the naphthenic ring attached to the aromatic ring could be fully activated compared with CGO-4. Hence, the HDA of FCCS-6 is higher than CGO-4. However, comparing FCCS-6 with THN, although hydrogen in the α-position of the naphthenic ring are both fully activated as discussed above, due to the high density and high molecular weight of FCCS-6, FCCS-6 provides lower amount of active hydrogen than THN. Hence FCCS-6 presents poorer HDA than THN. Comparing FEO-5 with FCCS-6, the HDA and RN/RA value of FEO-5 are both higher than FCCS-6, moreover, the RN/RA value of FEO-5 is much closer to 1, that means the average molecular structure of FEO-5 is much similar to the ideal molecular structure like THN, therefore the HDA of FEO-5 is higher than FCCS-6. To conclude, the RN/RA value, obtained through modified B–L method of industrial distillate hydrogen donor, is a key parameter for representing the HDA of hydrogen donors. The average molecular structure parameters have a certain relationship with narrow fraction HDA. The closer the RN/RA value is to 1, the higher the HDA possessed by IDNF hydrogen donors.

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4.2. Hydrocarbon Composition of FCCS-6, FEO-5, and FEO-2. In order to confirm which kinds of hydrocarbons plays a key role of donating hydrogen in distillate narrow fraction, FCCS-6, FEO-5, and FEO-2, with the HDA increased, were analyzed by GC-MS and the results are presented in Figure 9. It can be seen from the GC-MS results that FCCS-6, FEO-5, and FEO-2 contain small amounts of paraffins and the content has no obvious change. In FEO-5 and FEO-2, the percentage of naphthenes is apparently higher than FCCS-6; the content of monoaromatics in FEO-5 is about half of FEO-2, but obviously higher than FCCS-6. Moreover, the ratio of diaromatics is FEO-2 > FEO-5 > FCCS-6. FEO-2 possesses the largest proportion of monoaromatics and diaromatics, with FEO-5 and FCCS-6 taking second and third place; while FEO-5 has the greatest triaromatics content and FCCS-6 claims a large proportion of tetra- and pentaaromatics among the three narrow fractions. It is also noteworthy that the content of thiophenes, unidentified aromatics, and resins account for more than 20% of FCCS-6, which is much greater than that in FEO-2 and FEO-5. Among the three categories, thiophenes and unidentified aromatics contents increase in the sequence of FEO-2, FEO-5 and FCCS-6, while there is little change among the fractions in terms of resin content. By analyzing the GC-MS result of these three narrow fractions, it can be concluded that FCCS-6 mainly consists of aromatics with four rings and above, but FEO-2 and FEO5 are mainly composed of naphthenes and aromatics with no more than three rings. Hydrocarbons with a special structure of the naphthenic ring attached to the aromatic rings 15


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have the ability to donate its active hydrogen30, 31. Monoaromatics consist of alkylbenzenes, naphthenebenzenes and dinaphthenebenzenes. Among them, naphthenebenzenes and dinaphthenebenzenes have stronger HDA. Additionally, diaromatics are composed of naphthalenes, acenaphthenes plus dibenzofurans, and fluorenes, which have no HDA. Furthermore, triaromatics mainly consist of phenanthrenes and naphthenephenanthrenes, and only naphthenephenanthrenes have a certain HDA. In addition, multi-aromatics that have more than three rings have little HDA. Aromatics with the ability of donating hydrogen are mainly concentrated on monoaromatics and triaromatics, especially monoaromatics. Based on the results of GC-MS analysis, the amounts of naphthenebenzenes, dinaphthenebenzenes and naphthenephenanthrenes in FCCS-6, FEO5, and FEO-2 are plotted in Figure 10. It can be observed that the contents of the three multi-aromatics increase. These results are in good agreement with the HDA results and verify the testing method of HDA once again. It can concluded that within the scope of the study, naphthenebenzenes, dinaphthenebenzenes, and naphthenephenanthrenes play a dominant role of donating active hydrogen. Therefore, narrow fraction, which contains high naphthenebenzenes, dinaphthenebenzenes, and naphthenephenanthrenes content, shows high HDA. 5. CONCLUSIONS The HDA of IDNF narrow fractions including CGO, FCCS, and FEO were investigated in an autoclave reactor. Anthracene was selected as hydrogen acceptor probe 16


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and 1H-NMR was employed to identify different categories of hydrogen of the mixture. Based on the 1H-NMR data, a calculation method of HDA was developed to characterize the hydrogen donating properties of the selected IDNF, and the calculation method was verified by average molecular structure and hydrogen composition of IDNF. The narrow fractions HDA followed the order: CGO < FCCS < FEO. CGO-4, FCCS-6, and FEO-5 are the key components of CGO, FCCS, and FEO, respectively, FEO-5 owns the highest HDA and proportion of full distillate range. As IDNF, FEO-5 is the optimal candidate for acting as an industrial distillate hydrogen donor. The average molecular structure of IDNF was studied using modified B–L method. The RN/RA value of CGO narrow fractions is greater than 1, but for FCCS and FEO the RN/RA values are less than 1. The RN/RA value of IDNF can reflect HDA, and the closer the RN/RA value is to 1, the higher the HDA. The hydrocarbon compositions of FEO-2, FEO-5, and FCCS-6, with declining HDA, were analyzed using GC-MS. FCCS-6 mainly consists of aromatics with four rings and above, but FEO-2 and FEO-5 are mainly composed of naphthenes and aromatics with no more

than

three

rings.

Naphthenebenzenes,

dinaphthenebenzenes,

and

naphthenephenanthrenes are the components that really possess the ability of donating hydrogen in IDNF. The total percentage of naphthenebenzenes, dinaphthenebenzenes, and naphthenephenanthrenes in hydrogen donor is in good agreement with the HDA, which verified the developed method of testing HDA of hydrogen donor again. AUTHOR INFORMATION 17


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Corresponding Author *Gang Wang, Tel.: 8610-8973-3085. E-mail: [email protected] NOTES The authors declare no competing financial interest. ACKNOWLEDGEMENTS The authors acknowledge the financial support provided by the State Key Program of National Natural Science Foundation of China (21336011), National Natural Science Foundation of China (21476259). REFERENCES (1) Speight, J. G. The chemistry and technology of petroleum. CRC press: 2014. (2) Gray, R. M. Upgrading petroleum residues and heavy oils. CRC press: 1994. (3) Rana, M. S.; Samano, V.; Ancheyta, J.; Diaz, J. A review of recent advances on process technologies for upgrading of heavy oils and residua. Fuel 2007, 86, (9), 1216-1231. (4) Le Page, J.-F.; Chatila, S. G.; Davidson, M. Resid and heavy oil processing. 1992. (5) Gonçalves, M. L. A.; Ribeiro, D. A.; Teixeira, A. M. R.; Teixeira, M. A. G. Influence of asphaltenes on coke formation during the thermal cracking of different Brazilian distillation residues. Fuel 2007, 86, (4), 619-623. (6) Wu, J.; Liu, Q.; Wang, R.; He, W.; Shi, L.; Guo, X.; Chen, Z.; Ji, L.; Liu, Z. Coke formation during thermal reaction of tar from pyrolysis of a subbituminous coal. Fuel Processing Technology 2016. (7) Ebrahimi, S.; Moghaddas, J.; Aghjeh, M. R. Study on thermal cracking behavior of 18


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petroleum residue. Fuel 2008, 87, (8), 1623-1627. (8) Kohli, K.; Prajapati, R.; Maity, S.; Sau, M.; Garg, M. Deactivation of hydrotreating catalyst by metals in resin and asphaltene parts of heavy oil and residues. Fuel 2016, 175, 264-273. (9) Wang, J.; Anthony, E. J. A study of thermal-cracking behavior of asphaltenes. Chemical engineering science 2003, 58, (1), 157-162. (10) Jin, N.; Wang, G.; Han, S.; Meng, Y.; Xu, C.; Gao, J. Hydroconversion Behavior of Asphaltenes under Liquid-Phase Hydrogenation Conditions. Energy & Fuels 2016, 30, (4), 2594-2603. (11) Wiehe, I. A. A phase-separation kinetic model for coke formation. Industrial & engineering chemistry research 1993, 32, (11), 2447-2454. (12) Whitehurst, D. D.; Mitchell, T. O.; Farcasiu, M. Coal liquefaction: the chemistry and technology of thermal processes. New York, Academic Press, Inc., 1980. 390 p. 1980, 1. (13) Aaarts, J. J.; Ternan, M.; Parsons, B. I. Catalytic desulphurization of Athabasca bitumen using hydrogen donors. Fuel 1978, 57, (8), 473-478. (14) Kubo, J.; Higashi, H.; Ohmoto, Y.; Arao, H. Heavy oil hydroprocessing with the addition of hydrogen-donating hydrocarbons derived from petroleum. Energy & fuels 1996, 10, (2), 474-481. (15) Vilcáez, J.; Watanabe, M.; Watanabe, N.; Kishita, A.; Adschiri, T. Hydrothermal extractive upgrading of bitumen without coke formation. Fuel 2012, 102, 379-385. (16)Alemán-Vázquez, L. O.; Domínguez, J. L. C.; García-Gutiérrez, J. L. Effect of Tetralin, 19


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Decalin and Naphthalene as Hydrogen Donors in the Upgrading of Heavy Oils. Procedia Engineering 2012, 42, 532-539. (17) Wang, Q.; Guo, L.; Wang, Z.; Mu, B.; Guo, A.; Liu, H. Hydrogen donor visbreaking of Venezuelan vacuum residue. Journal of Fuel Chemistry and Technology 2012, 40, (11), 1317-1322. (18) Barraza, J.; Coley-Silva, E.; Piñeres, J. Effect of temperature, solvent/coal ratio and beneficiation on conversion and product distribution from direct coal liquefaction. Fuel 2016, 172, 153-159. (19) Carlson, C.; Langer, A.; Stewart, J.; Hill, R. Thermal hydrogenation. Transfer of hydrogen from tetralin to cracked residua. Industrial & Engineering Chemistry 1958, 50, (7), 1067-1070. (20) Langer, A.; Stewart, J.; Thompson, C.; White, H.; Hill, R. Thermal hydrogenation of crude residua. Industrial & Engineering Chemistry 1961, 53, (1), 27-30. (21) Chen, Q.; Gao, Y.; Wang, Z.; Guo, A. Application of Coker Gas Oil Used as Industrial Hydrogen Donors in Visbreaking. Petroleum Science and Technology 2014, 32, (20), 25062511. (22) Guo, A.; Wang, Z.; Zhang, H.; Wang, Z. Fundamental study on mild thermal cracking of vacuum residue with industrial hydrogen donors. Journal of Fuel Chemistry and Technology 2007, 35, (6), 667-672. (23) Yokono, T.; Obara, T.; Sanada, Y.; Shirahama, H.; Ōsawa, E. Chemical structure and kinetic properties of hydroaromatic compounds. Journal of the Chemical Society, Perkin 20


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Transactions 2 1982, (8), 979-982. (24) Obara, T.; Yokono, T.; Sanada, Y. Relationships between hydrogen donor abilities and chemical structure of aromatic compounds in terms of coal liquefaction. Fuel 1983, 62, (7), 813-816. (25) Yang, Z.; Zong, S.; Long, J. Quantum mechanical studies on the micro-struture of tetrahydro-naphthalene. Computers and Applied Chemistry 2012, 29, (4), 465-468. (26) Obara, T.; Yokono, T.; Miyazawa, K.; Sanada, Y. Carbonization behavior of hydrogenated ethylene tar pitch. Carbon 1981, 19, (4), 263-267. (27) Iyama, S.; Yokono, T.; Sanada, Y. Development of anisotropic texture in cocarbonization of low rank coal with pitch-evaluation from hydrogen donor and acceptor abilities of coal and pitch. Carbon 1986, 24, (4), 423-428. (28) Liu, H.; Chen, K.; Wang, Z.; Guo, A. Evaluation of relative hydrogen-donating abilities of different heavy oils during mild thermal conversion by 1H-NMR. Journal of Fuel Chemistry and Technology 2013, 41, (10), 1191-1198. (29) Jiang, X.; Zong, S.; Li, X.; Zhao, Y. Molecular Simulation of the Hydrogen Doanting Ability of Hydrocarbon Molecule. Acta Petrolei Sinica (Petroleum Processing Section) 2012, 28, (2), 254-259. (30) Zhang, H.; Deng, W.; Que, G. Study on thermal reaction characteristics of Shenli vacuum residue with hydrogen donor and solvent. Acta Petrolei Sinica (Petroleum Processing Section) 1997, 13, (2), 17-22. (31) Wang, Z.; Wang, Z. Roles of hydrogen donor in visbreaking of vacuum residue. 21


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Journal of Fuel Chemistry and Technology 2006, 34, (6), 745-748.

22


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Table 1. Detailed number and cutting temperature of narrow fractions Material

Narrow fraction number

Cutting temperature/°C

Proportion /wt%

CGO

CGO-0 CGO-1 CGO-2 CGO-3 CGO-4 CGO-5 CGO-end

450

3.97 2.94 8.26 21.29 32.00 15.47 16.07

FCCS

FCCS-0 FCCS-1 FCCS-2 FCCS-3 FCCS-4 FCCS-5 FCCS-6 FCCS-7 FCCS-end

490

4.69 4.16 4.87 6.83 6.40 15.57 21.78 15.65 20.05

FEO

FEO-0 FEO-1 FEO-2 FEO-3 FEO-4 FEO-5 FEO-6 FEO-7 FEO-8 FEO-end

510

0.65 0.90 0.58 0.56 7.00 44.58 23.90 9.94 3.16 8.74

23


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Table 2． Properties of parts narrow fractions Elemental composition/wt%

Item

Density (20 °C)/g/cm3

Kinetic viscosity （80 °C）/mm2/s

C

H

S

N

H/C

CGO-4 FCCS-6 FEO-2 FEO-5

0.9529 1.0593 0.9849 0.9976

22.64 120.06 9.28 88.31

86.64 90.22 88.48 88.18

11.67 8.08 10.88 11.24

1.26 1.34 0.17 0.24

0.47 0.34 0.47 0.35

1.62 1.08 1.48 1.53

Table 3. Energy barrier and reaction heat of C–H bonds dissociation Number of C–H bond I II III IV V VI

Energy barrier /(kJ.mol−1)

Reaction heat /(kJ.mol−1)

368.88 430.90 331.33 364.62 372.09 365.13

367.37 429.88 324.23 360.37 369.70 364.53

Table 4. Average structure parameters of parts CGO narrow fractions Item

CGO-1 (350–370 °C)

CGO-2 (370–390 °C)

CGO-4 (410–430 °C)

NH/NC M fA fN fP RT RA RN RN/RA

1.66 241 0.23 0.34 0.43 1.92 0.46 1.45 3.15

1.65 261 0.25 0.28 0.47 1.95 0.66 1.29 1.95

1.62 306 0.26 0.25 0.49 2.36 0.96 1.41 1.46

24


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Table 5. Average structure parameters of parts FCCS narrow fractions Item

FCCS-2 (370–390 °C)

FCCS-6 (450–470 °C)

FCCS-7 (470–490 °C)


1.46 257 0.43 0.10 0.48 2.04 1.57 0.47 0.30

1.08 348 0.61 0.24 0.15 5.08 3.53 1.55 0.44

1.06 374 0.62 0.23 0.15 5.50 3.91 1.59 0.41

Table 6. H-donating amount, molecular weight, HDA and RN/RA of hydrocarbons Hydrocarbon

H-donating amount/(mol)

Molecular weight/(g/mol)

HDA/(mg/g)

RN/RA

A B C D E F

2 0 2 2 2 2

132 138 180 182 180 182

15.15 0 11.11 10.99 11.11 10.99

1 0 0.5 0.5 0.5 0.5

25


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Table 7. Average structure parameters of parts FEO narrow fractions Item

FEO-2 (370–390 °C)

FEO-4 (410–430 °C)

FEO-5 (430–50 °C)

FEO-6 (450–470 °C)

FEO-7 (470–490 °C)


1.48 258 0.34 0.26 0.40 2.74 1.50 1.24 0.83

1.49 303 0.32 0.25 0.43 3.12 1.71 1.41 0.82

1.53 327 0.30 0.22 0.48 3.07 1.73 1.34 0.77

1.53 355 0.30 0.21 0.50 3.26 1.91 1.35 0.71

1.52 383 0.31 0.18 0.52 3.44 2.20 1.24 0.56

Table 8. HDA and RN/RA value of parts narrow fractions Item

CGO-4

FCCS-6

FEO-5

THN

HDA, mg/g RN/RA

0.48 1.46

0.67 0.45

0.73 0.77

1.94 1.00

26


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Figure 1. Schematic diagram of the bathc reactor. P Valve 1

T

N2

Themocouple

Safty Valve

Reactor

Air Valve 2 Fluidized sand bath furnace

Gas sparger

Figure 2. Molecular structure of anthracene (A) and 9,10-dihydroanthracene (B).

27


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Figure 3. 1

H-NMR spectra of anthracene and industrial distillate hydrogen donor mixtures after

hydrogen donating reaction. 1.8 1.6

Peak intensity

1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 10

9

8

7

6

5

4

3

Chemical shift / ppm

28


2

1

0

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Figure 4. HDA of CGO narrow fractions. 0.6

0.5

HDA/mg/g

0.4

0.3

0.2

0.1

CG O5

CG O4

CG O3

CG O1

CG O2

0.0


Figure 5. C–H bond energiers of tetralin and C–H bond numbers of hydrocarbons. A

B

Ⅰ

C

H

Ⅲ

Ⅱ

E

D Ⅳ

F

Ⅴ

Ⅵ

29


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Figure 6. HDA of FCCS narrow fractions.

0.7 0.6

HDA/mg/g

0.5 0.4 0.3 0.2 0.1

FC CS -7

FC CS -6

FC CS -5

FC CS -4

FC CS -3

FC CS -2

FC CS -1

0.0


Figure 7. HDA of FEO narrow fractions.

1.2

HDA/mg/g

1.0

0.8

0.6

0.4

0.2


30


FE O8

FE O7

FE O6

FE O5

FE O4

FE O3

FE O2

FE O1

0.0

Page 31 of 32

Figure 8. HDA of THN and narrow fractions of CGO, FCCS, and FEO.

2.0 1.8 1.6

HDA / mg/g

1.4 1.2 1.0 0.8 0.6 0.4 0.2 N TH

CG C GO- 1 C GO- 2 C GO- 3 C GO- 4 O5 FC CS FC -1 C FC S-2 C FC S-3 C FC S-4 C FC S-5 C FC S-6 CS -7 FE OFE 1 O FE -2 O FE -3 O FE -4 O FE -5 O FE -6 O FE -7 O8

0.0


Figure 9. Hydrocarbon composition of narrow fractions. Narrow fraction number

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FEO-2 FEO-5 FCCS-6 0

20

40 60 Fraction, wt%

80

100

Paraffins /Alkanes

Naphthecenes

Monoaromatics

Diaromatics

Triaromatics

Tetraaromatics

Pentaaromatics

Thiophenes

Unidentified Aromatics

Resins

31


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Figure 10. Naphthenebenzenes, dinaphthenebenzenes, and naphthenephenanthrenes content of narrow fractions. 40 35 30 Fraction, wt%

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 32

Naphthenephenanthrenes Dinaphthenebenzenes Naphthenebenzenes

25 20 15 10 5 0 FCCS-6

FEO-5 Narrow fraction number

32


FEO-2

Determination of the Hydrogen-Donating Ability of Industrial Distillate

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