Heteroatom removals from aromatic hydrocarbons over a phosphoric acid-promoted Mn2O3–NiO catalyst

Applied Catalysis A: General 174 (1998) 41±50

Heteroatom removals from aromatic hydrocarbons over a phosphoric acid-promoted Mn2O3±NiO catalyst Mitsuyoshi Yamamoto, Okio Nishimura, Takeshi Kotanigawa* Hokkaido National Industrial Research Institute, AIST, MITI Higashi-Tsukisamu, Toyohira-ku, Sapporo 062-0052, Japan Received 21 November 1997; received in revised form 15 March 1998; accepted 30 April 1998

Abstract The main objective of this paper is to investigate possible ways to produce high-quality products for transportation fuels from coal-derived oils and heavy distillates including heteroatoms. H3PO4-promoted Mn2O3±NiO catalysts were found to be essentially good for this purpose. The catalysts showed TPR spectra though they are acidic. Through XPS, TPR and NH3-TPD measurements, it was found that the added phosphate played a role in reducing NiO of the catalysts in the presence of hydrogen. This ®nding was con®rmed by the nuclear hydrogenation of naphthalene and anthracene, and heteroatoms removal and ring-opening reaction of carbazole and dibenzothiophene over these catalysts. A Canadian Battle River coal-derived oil sample was used as an empirical sample to estimate the catalyst activity. Among them, the 0.12H3PO4/0.2Mn2O3±0.8NiO catalyst showed the best performance for this purpose; it yielded 30 mol % of HDN products from carbazole, 29 mol % of HDS products from dibenzothiophene, 40 mol % of HDO products and 59 mol % of dearomatization products from the coalderived oil. Furthermore, it yielded chained and cyclic hydrocarbons by the ring-opening reaction. For comparison, a commercial NiMo/Al2O3 catalyst, HDS-3, was tested; it yielded 6 mol % of HDN products from carbazole, 58 mol % of HDS products from dibenzothiophene and 29 mol % of dearomatization products from the coal-derived oil, but HDO products were insuf®cient. It was found through comparison that the present catalysts were suf®cient for this purpose. # 1998 Elsevier Science B.V. All rights reserved. Keywords: Phosphate-promoted oxide catalyst; HDN; HDS; HDO; Aromatic hydrocarbons

1. Introduction Heteroatom removals and ring-opening reactions of polycyclic aromatic hydrocarbons are vitally important for the upgrading of coal-derived oils and heavy fractions from petroleum [1,2]. In addition, regulations recently announced for transportation fuels specify have reduced N and S contents, as well as aromatics contents, requiring deep hydrogenation, *Corresponding author. Fax: +8-111-857-8986.

e.g., production of hydroaromatics and saturated hydrocarbons, especially with regard to highly aromatic coal-derived liquids. In this ®eld, Ni±-Mo/Al2O3 and CoMo/Al2O3 catalysts are well known as commercial catalysts and have been well studied [3,4]. These are basically the catalysts for hydrocracking reactions. One role of these catalysts is therefore to quench thermal radicals of aromatic hydrocarbons with activated hydrogen. It is thus thought that further studies on catalysts of heteroatom removal are required, especially

0926-860X/98/$ ± see front matter # 1998 Elsevier Science B.V. All rights reserved. PII: S0926-860X(98)00151-3

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M. Yamamoto et al. / Applied Catalysis A: General 174 (1998) 41±50

simultaneous removal of heteroatoms and the ring-opening reaction of polycyclic aromatic hydrocarbons, focusing on the upgrading of highly aromatic liquids for the production of transportation fuels. For these reasons, we tried to develop a new type of catalyst for the simultaneous reaction of the heteroatom removal and the ring opening of highly aromatic hydrocarbons. Our concept to develop a new type of catalyst was based on the following ideas. We previously con®rmed the activity of the selective nuclear hydrogenation of condensed aromatic hydrocarbons on Ru supported on Mn2O3±NiO [5]. As the principal activity of this catalyst is the selective nuclear hydrogenation of aromatics, it is very poor for heteroatom removal and the ring-opening reaction of aromatics, so, the improvement of the catalyst was needed for the present purpose. In order to charge the activity for heteroatom removal and the ring-opening reaction, the addition of phosphoric acid to Mn2O3-NiO was attempted to change the chemical properties of the neutral support, Mn2O3±NiO. Through this concept, we successfully prepared the phosphoric acid-promoted Mn2O3±NiO catalysts. First, the catalysts were characterized by XRD measurement, NH3-TPD and TPR, as well as XPS measurements, and then tested to investigate their catalytic activities for the nuclear hydrogenation of naphthalene and anthracene, the HDS of dibenzothiophene, the HDN of carbazole and the HDO of Canadian Battle River coal-derived oil with b.p. 760 523±623 K. This study aims to elucidate the data on nuclear hydrogenation, heteroatom removals and ring-opening reactions of polycyclic aromatic hydrocarbons over phosphoric acidpromoted 0.2Mn2O3±0.8NiO catalysts. 2. Experimental 2.1. Materials Manganese nitrate (6H2O), nickel nitrate (6H2O) and sodium hydroxide were of analytical reagent grade. As authentic compounds, naphthalene, anthracene, carbazole and dibenzothiophene of analytical reagent grade were used without any treatment. The coal-derived oil employed was prepared by distillation of coal liquid obtained by the liquefaction of Canadian Battle River coal at 723 K under hydrogen at 17 MPa

with FeS2 as a catalyst. The coal oil was fractionated into the fraction (b.p.760 523±623 K). Elemental analysis of the coal-derived oil was performed using a Yanaco CHN corder, MT-3, for carbon, hydrogen and nitrogen, a Yanaco CHN corder, MT-5, for oxygen and a Horiba sulfur analyzer, EM1A-120, for sulfur. The results were C, 87.3; H, 9.82; O, 2.0; N, 0.52; and S, 0.36 wt.%. 2.2. Catalyst preparation Prescribed amounts of manganese and nickel nitrates were dissolved in deionized water to make a 5 wt.% aqueous solution after which prescribed amounts of phosphoric acid were mixed into the solution. The pH values of the resulting solutions changed from 3.4 to 2.2±3.0 with the addition of phosphoric acid. The solution was mixed with a 2.5 N NaOH aqueous solution at room temperature until a pH of 10.4±10.8 was achieved. The resulting slurry was stirred overnight. The coprecipitate prepared was then washed with 6 l of deionized water, ®ltered, dried at 383 K overnight and ®nally calcined at 773 K for 3 h in an electric oven. The calcined catalysts were crushed and sieved under 100 mesh particles to make PMN and MN catalysts. A commercial catalyst, HDS-3 (NiO; 3±4%, MoO3; 14.5± 16.0%), supplied by American Cyanamid, was used as reference. The HDS-3 catalyst was presul®ded in an autoclave with 5.6 mol % hydrogen sul®de in hydrogen gas at 6 MPa at 633 K for 2 h before the reaction. 2.3. Characterization of catalysts 2.3.1. XRD and fluorescent X-ray measurements The catalysts were characterized by X-ray diffraction (Rigaku-Denki, Geiger¯ex, Radiation Cu Ka, 35 kV, 25 mA) and the compositions of Mn2O3, NiO and H3PO4 in the catalysts were determined by ¯uorescent X-ray analysis (Seiko Instruments, SEA 2001, Si (Li) detector). The BET surface areas of the catalysts were measured by the conventional method. 2.3.2. TPR measurement The temperature-programmed desorption spectra of hydrogen (TPR) were measured with gas chromatography using a TCD detector (80 , 60 mA, at 373 K).

M. Yamamoto et al. / Applied Catalysis A: General 174 (1998) 41±50

In each case, 200 mg of the catalyst, charged into a Utube reactor (3 mm I.D.), were pretreated in a stream of oxygen (25 ml/min) for 30 min and then with hydrogen gas at 533 K for 1 h. The TPR spectra were measured by heating the catalysts up to 773 K in a stream of Ar, followed by hydrogen treatment in a stream of a mixed gas of 5% hydrogen in Ar at elevated temperatures for 2 h. The ¯ow rate of the gas and the heating rate of the reactor were 25 ml/min and 10 K/min, respectively, in all cases. Ammonia TPD measurements: The temperature-programmed desorption spectra of ammonia (NH3-TPD) were measured with a multi-task T.P.D. (BEL Japan Inc. Q-mass detector). In each case, 500 mg of the supports, charged into a sample tube (3 mm ID), were pretreated in a stream of helium (50 ml/min) at 10 K/min up to 673 K for 2 h. The NH3-TPD spectra were measured by heating the supports up to 773 K in a stream of helium (10 ml/min), followed by NH3 gas treatment at 303 K for 30 min. At the same time, the acidity of the catalysts was determined as the relative values in comparison with a standard sample (JRC-Z5-25H, H-ZSM-5: Si/Alˆ12.5, 0.99 mmol/g) supplied by the Catalysis Society of Japan. 2.3.3. XPS measurements X-ray photoelectron spectroscopy was performed on an Escalab 200i-XL. The normal operating pressure in the analyzer chamber was 510ÿ9 mbar (of the order of 10ÿ9 Pa). The specimens were irradiated with a beam of Mg Ka (15 KV, 20 mA, 300 W, mean energy: 1253.6 eV). 2.4. Catalytic activity and analysis of products 2.4.1. Catalytic activity Catalytic activities were examined in an autoclave test (70 ml) with a magnetic stirrer (600 rpm). In each test, 6 g of the reactant was introduced with 0.3 g of each catalyst into the autoclave. Hydrogen at 10 MPa initial pressure was charged at room temperature and then heated to 703 K at 2.5 K/min. When the temperature reached 703 K, the autoclave was immediately cooled by an electric fan to quench the reaction. 2.4.2. Analysis of products The contents in the autoclave were dissolved in n-propyl benzene and all the components were

43

identi®ed by gas chromatography-mass spectrometry (Shimadzu, QP 5000, EI detector 70 eV, 523 K) and FTIR spectrometry (Shimadzu 8000 M). The products were analyzed by gas chromatography after adding p-xylene as an internal standard for quantitative analysis. The hydrogenated products from the coalderived oil were analyzed by 1H-NMR (JEOL a-500, 500 MHz, 16 scans). Uncondensable products were also analyzed by gas chromatography (molecular Ê for H2, N2, CO, CO2, 2 m, Ar 46 ml/min; sieve 5 A Polapak Q‡N for C2H4, C3H6, 3 m, He 16 ml/min; Sebaconitrile for C3H6±C5H12, 6 m, He 21 ml/min). 3. Results and discussion 3.1. Characterization of the catalysts The catalysts were characterized by ¯uorescent X-ray analysis, XRD analysis and BET measurement. The compositions of the catalysts were determined by ¯uorescent X-ray analysis and relationships between the quantities of feedstocks in catalyst preparations and catalyst components prepared are shown in Table 1. It was found that the present coprecipitation method resulted in stoichiometrical compositions of PMN catalysts because it was con®rmed that the molar ratio of Mn2O3/NiO was 0.260.1 among all PMN catalysts. However, the maximum amount of phosphoric acid analyzed in the catalysts was approximately 17 mol %, as seen in the 17PMN and 20PMN catalysts. The BET surface areas of the catalysts, which increased as P-contents increased are also summarized in Table 1. Fig. 1 shows XRD patterns of the catalysts. The XRD pattern of the MN catalyst exhibited diffraction lines of both crystalline NiMnO3, NiO and a trace of the diffraction line of Mn2O3 (2 2 2) at 338 (2) because of a large excess of NiO. All PMN catalysts exhibited only the diffraction lines of crystalline NiO. No traces of crystalline NiMO3 or Mn2O3 were present. Fig. 2 shows the effects of P-addition on the surface areas of the catalysts. These results indicate that an increase of the phosphoric acid added to the catalysts led to a broadening of the diffraction lines of NiO and to increases in the surface areas of the PMN catalysts. In order to reveal the effects of P-addition on the MN catalyst, the XPS spectra of the MN and 12PMN

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M. Yamamoto et al. / Applied Catalysis A: General 174 (1998) 41±50

Table 1 The relationship between feedstocks and molar composition of PMN (H3PO4/Mn2O3-NiO) catalysts Catalyst No.

MN 7PMN 8PMN 9PMN 11PMN 12PMN 14PMN 17PMN 20PMN

Feedstocks (g)

BET (m2/g)

Composition (mol %)

Mn-nitrate

Ni-nitrate

H3PO4

Mn2O3

NiO

H3PO4

25.9 20.2 17.0 17.0 17.0 20.0 17.0 17.0 16.5

52.4 40.4 34.5 34.5 34.5 40.4 34.5 34.5 33.5

Ð 1.70 1.22 1.76 3.57 7.70 7.30 14.80 44.50

21.0 20.0 19.0 19.0 19.0 19.0 18.0 17.0 16.0

79.0 73.0 73.0 72.0 70.0 69.0 68.0 66.0 64.0

Ð 7.0 8.0 9.0 11.0 12.0 14.0 17.0 20.0

catalysts were measured. Table 2 summarizes the binding energies for the electron levels of Mn 2p, Ni 2p, O 1s and P 2p, and atomic ratios of the catalysts. The binding energy of P 2p3/2 of the catalysts agreed with that of pyrophosphate [6]. On the other hand, there was a particular ®nding in Table 2. The atomic ratio of oxygen of the PMN catalyst increased in comparison with the MN catalyst. For an explanation, the atomic ratio of oxygen of the 12PMN catalyst was calculated from the molar ratio shown in Table 1 and found to be 59.4%: i.e., P,

Fig. 1. XRD patterns of PMN catalysts.

48.7 105.5 102.3 103.6 130.2 146.9 150.5 140.7 173.3

Table 2 Binding energies and atomic ratios of Mn 2p, Ni 2p, O 1s and P 2p measured for PMN catalysts Catalysts MN 12PMN a

Binding energies (eV)a/atomic ratios (%) Mn 2p3/2

Ni 2p3/2

O 1s

P 2p3/2

641.6/14.2 641.9/10.6

854.6/29.3 855.5/20.0

529.9/56.5 530.1/65.7

Ð 133.1/3.7

Eb (C 1s); 284.8 eV.

Fig. 2. Effects of P-addition on surface properties of PMN catalysts.

M. Yamamoto et al. / Applied Catalysis A: General 174 (1998) 41±50

45

Fig. 3. A comparison of binding energies (O 1s) of PMN catalyst with MN catalyst.

4.1%: Mn, 13.0%: Ni, 23.5% and O, 59.4%. In general, it was understood that atoms which sat on the surface and stayed in the bulk could be determined by XPS and XRD measurements, respectively. Therefore, the value of oxygen calculated above indicated the presence of more oxygen on the surface than in the bulk of the 12PMN catalyst (surface O/bulk O; 65.7% in Table 2/59.4% calculated). Fig. 3 shows a comparison of the XPS spectra of O 1s of the 12PMN catalyst with the MN catalyst. In the XPS spectrum of the 12PMN catalyst, a broad shoulder peak appeared at 531.7 eV, which was 1.6 eV higher than the binding energy of the MN catalyst. This was identi®ed as the oxygen created by the P-addition to the MN catalyst. The area of shoulder peak at 531.7 eV was separately measured and calculated to be 10.5 atom % of the total O 1s, whereas the atom % of P was 3.7, as shown in Table 2. Therefore, a chemical formula of the phosphate of the PMN catalysts was identi®ed by the atomic ratio of O/P. The value of O/P (ˆ2.8) was close to the atomic ratio (O/P) of P2O5. Therefore, the chemical formula of the phosphate of PMN catalysts in Fig. 4 was concluded to be P2O5. The catalysts were also characterized by NH3-TPD and TPR measurements to determine their acidities and activities of hydrogen activation, respectively.

Fig. 4. NH3±TPD spectra of PMN catalysts.

Figs. 4 and 5 show the NH3-TPD and the TPR spectra of the catalysts. From Fig. 4, it can be seen that the MN catalyst showed almost neutral property and the P-addition to the MN catalyst changed the catalytic property making it acidic. In the NH3-TPD measurements, the NH3TPD temperatures were 381 K for 11PMN, and 377 K for 7PMN and 17PMN. These temperatures were not varied by the amounts of P-additions. However, the TPR spectra of the 7PMN, 11PMN, and 17PMN catalysts exhibited peaks at 451, 467, and 453 K, respectively, and these were much higher than the peak of the MN catalyst. A very interesting result in Fig. 5 was the appearance of the TPR spectra of the catalysts, accompanied by an increase of acidity of the catalysts, though the TPR temperatures were signi®cantly changed by the amounts of P-additions. It was not thought that the PMN catalysts, which are acidic, were able to activate the hydrogen molecules. However, it was believed through the TPR measurements that the P-addition to the MN catalyst caused the creation of active sites for hydrogen molecules on the PMN catalysts. It seemed reasonable that the phosphate of the catalysts created an easily reducible

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M. Yamamoto et al. / Applied Catalysis A: General 174 (1998) 41±50

catalysts in the presence of hydrogen. Brenner et al. reported that Ni-metal was separated out by the reduction of nickel salts with NaH2PO2 [7,8]. Recently Atanasova and Agudo proved by infrared studies of nitric oxide adsorption that reducibility of Ni of the P±Ni±Mo/Al2O3 catalysts increased by in¯uence of the phosphorous concentration [9]. If these results were applicable to the explanation of the present phenomenon caused by the P-addition, it could be concluded that Ni-metal was separated out on the PMN catalysts by the reduction of NiO with the phosphate in the presence of hydrogen and consequently caused the appearance of the TPR spectra. Based on these observations, it was thought that the PMN catalysts would behave as the metallic catalysts in the presence of hydrogen and show suf®cient activity for hydrogenation of the aromatics. 3.2. Activities of the catalysts 3.2.1. Nuclear hydrogenation activity The hydrogenations of naphthalene and anthracene were carried out as the activity tests of the catalysts. Table 3 and Fig. 6 show the results of the hydrogenation of naphthalene and anthracene, respectively. A very interesting ®nding on the catalytic activities was that no gaseous products other than unreacted hydrogen were detected. The yield of liquid was therefore close to 100 wt.%, as shown in Table 3. This was related to the high selectivity of the catalysts for nuclear hydrogenation of the aromatics. On the other

Fig. 5. TPD spectra of PMN catalysts.

property or metallic portion on the PMN catalysts under the hydrogen atmosphere. The role of the Paddition to the MN catalysts was believed to be the promotion of the reduction of oxides of the PMN

Table 3 The results of the catalytic hydrogenation of naphthalence over the PMN catalysts Catalyst No. MN 7PMN 8PMN 9PMN 11PMN 12PMN 14PMN 17PMN 20PMN HDS-3 a

Conv.

Yield of liq.a

Yields (mol %)

(mol %)

(wt.%)

DMCyHb

Et-Bc

Tert-Decd

Cis-dece

Tetf

Othersg

0.00 0.00 0.16 0.34 0.31 0.52 0.49 0.26 0.00 0.00

0.80 0.67 0.64 0.48 0.45 0.27 0.30 0.53 0.76 0.00

9.8 28.1 32.8 39.7 40.5 31.9 45.5 29.3 21.2 19.4

3.9 10.8 13.4 20.8 24.0 79.8 29.5 23.3 8.4 8.6

83.7 54.8 48.5 35.1 30.9 16.8 21.8 42.7 64.8 61.7

0.66 0.61 0.50 0.41 0.46 0.43 0.41 0.62 1.50 4.10

94.8 94.4 99.1 96.4 96.2 97.4 97.5 96.1 95.1 93.8

98.2 97.7 97.7 99.1 98.9 96.1 100 100 99.2 90.0

Yields of liquid product, b Dimethyl cyclohexane, c Ethylbenzene, d Tert-Decaline, e Cis-Decaline, f Tetraline, g Unidentified products with m/e ˆ 138.

M. Yamamoto et al. / Applied Catalysis A: General 174 (1998) 41±50

Fig. 6. Catalytic activity of the PMN catalysts for selective nuclear hydrogenation of anthracene.

hand, the reference catalyst showed high activity, but it produced many unknown products and gaseous products. Therefore, the selectivity for the nuclear hydrogenation became no more than 90%. It was, therefore, considered that the acidity of the support, Al2O3, of the reference catalyst promoted the side reactions to produce unknown liquid products and hydrocarbon gases. The PMN catalysts were made acidic by the Paddition to the MN catalyst, as seen in Fig. 3, but the catalysts did not proceed onto acidic catalysis such as hydocracking. This was a clear piece of evidence for the formation of the metallic sites on the PMN catalysts, followed by the disappearance of the acidity of the PMN catalysts. Another effect of the P-addition was found to be an increase of the BET-surface area, as plotted in Fig. 2. This was expected in terms of the broadening of diffraction lines in the XRD measurements of the PMN catalysts. Thus, the P-addition to the oxides was of great interest with respect to a new modi®cation of the catalyst. 3.2.2. Hydrodesulfuration (HDS) activity Fig. 7 shows a comparison of HDS activity of dibenzothiophene on the MNP catalysts with the

47

Fig. 7. Effect of P-addition on HDS of dibenzothiophene (DBT).

reference catalyst. The yields of the HDS and hydrogenated dibenzothiopnene (DBT) in Fig. 7 were the sum of HDS products such as benzene, cyclohexane, hexylbenzene, hexylcyclohexane, cyclohexylbenzene, bicyclohexyl and biphenyl, and the sum of tetrahydro DBT and hexahydro DBT. The others were unidenti®ed products with a mass number of (m/e) 190. In the HDS activity, the reference catalyst, HDS-3, demonstrated excellent results. In contrast with the reference catalyst, the MNP catalysts showed much lower activity, but it was con®rmed that the P-addition to the MN catalyst promoted the activities; not only for the hydrogenation, but also for the HDS reaction of dibenzothiophene. 3.2.3. HDN activity of catalysts Fig. 8 shows a comparison of HDN activity of carbazole on MNP catalysts with the reference catalyst. The yields of the HDN and hydrogenated carbazole were the sum of benzene, cyclohexane, hexylbenzene, hexylcyclohexane, cyclohexylbenzene and bicyclohexyl, and dodecahydrocarbazole, octahydrocarbazole, hexahydrocarbazole and tetrahydrocarbazole. The others were unidenti®ed products with the

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M. Yamamoto et al. / Applied Catalysis A: General 174 (1998) 41±50

There is a big question why the in¯uence of the P-addition to the PMN catalysts is so different for the HDS and HDN activities. Craig et al. studied the formation of new catalytic sites for heteroatom removal with direct participation of phosphorous in Ni±Mo/Al2O3 catalysts and pointed out that Ni-phosphate had a low activity for HDS, but a high activity in HDN [10]. It was considered that the activities for HDS and HDN of the PMN catalysts followed their indication.

Fig. 8. Effect of P-addition on HDN of carbazole.

sum of mass numbers of (m/e) 160 and 177. On the contrary, the HDS-3 catalyst showed very poor activity for the HDN reaction in comparison with the PMN catalysts. The yields of the HDN and the nuclear hydrogenation, in particular, were remarkably low. It is known that a lowering of the HDN activity of the HDS-3 catalyst is caused by neutralization of the acidity of Al2O3 support with the ammonia formed during the reaction. On the contrary, the MNP catalysts, though they had acidity, showed excellent activity for the HDN reaction, as well as the nuclear hydrogenation of carbazole. If the PMN catalysts were actually acidic even under the working conditions, the catalysts would not show such high HDN activity. In other words, this was the experimental proof of the fact that the acidity given to the PMN catalysts did not behave as the acidic sites under the working state, as already explained above. In the HDN reaction of carbazole over the PMN catalysts, the ring-opening reaction was also carried out together with the HDN reaction. The simultaneous reaction with the HDN and the ring-opening reaction is essential for the upgrading of heavy distillates.

3.2.4. Hydrotreatment of coal-derived oil In the hydrotreatment of coal-derived oils and heavy distillates, the HDO reaction is another important target because they include a large amount of oxygenated compounds and produce water as the product of HDO reaction of the compounds. Therefore, in the hydrotreatment of coal-derived oils and heavy distillates, catalysts are required to have activities for the HDO as well as the HDS, the HDN and the ring-opening reaction. For further evaluation of the activity of the PMN catalysts, the same kinds of catalysts were applied for the hydrotreatment of the coal-derived oil. Since the coal-derived oil includes a large amount of heteroatoms (O, 2.0; N, 0.52 and S, 0.36 wt.%), this was an empirical test reaction for the PMN catalysts to evaluate the activities for heteroatom removal and the ring-opening reaction. Also, the coalderived oil was a good sample to evaluate the HDO activity of the PMN catalysts. For the evaluation of the activity of the catalysts, the reaction products were subjected to 1H-NMR analysis. Song and Nomura [11] summarized the results of the assignments of hydrogen types of the coal-derived oils determined by 1 H-NMR spectroscopy. The spectra were separated into the aromatic (9.20±6.00 ppm) and aliphatic (5.00±0.20 ppm) hydrogen resonance; the aliphatic region was further divided into six subgroups because the aliphatic region of the spectrum provided highly characteristic structural data regarding coal-derived oil. Based on the assignments, the products obtained by the hydrotreatment of the coal-derived oil were analyzed. Compared with the hydrogen distribution of the original coal-derived oil, the production of alkylated hydroaromatics was con®rmed, as shown in Fig. 9. The 12MNP catalyst showed the best performance in terms of the highest yield of H as well as the lowest

M. Yamamoto et al. / Applied Catalysis A: General 174 (1998) 41±50

49

Fig. 10. Effect of P-addition on HDO of coal-derived oil.

Fig. 9. Effect of P-addition on hydrotreatment of coal-derived oil.

H-arom, which means the saturation of aromatic rings. A particular result obtained in the present work was that no hydrogen assigned to a-CH2 to two aromatic rings, Ar±(CH2)±Ar, as described in the previous paper [5] was produced. This suggests that the path of nuclear hydrogenation was carried out via the edged aromatic rings. Also, no production of gaseous products indicates no activity for dealkylation and hydrocracking of the products. In principle, this statement was almost the same as that concerning the results in the previous paper [5]. This was also of great interest because it was con®rmed that the reaction over the non-metallic catalysts (PMN catalysts) was conducted under the same mechanism as over the ruthenium supported on the 0.2Mn2O3±0.8NiO catalyst. This was also the direct evidence of the formation of the metallic portion on the PMN catalysts by the P-addition to the MN catalyst. By comparing the activity of the HDS-3 catalyst with the results in Fig. 9, the HDS-3 catalyst provided results of H-arom (18.1 mol %), H (23.7 mol %), H

(40.1 mol %) and H (18.1 mol %). These results were very close to those for the MN catalyst. Fig. 10 shows the effects of the P-addition to the MN catalyst on the HDO reaction of the coal-derived oil. In this case, the 12PMN catalyst showed the best performance. The ef®ciency of the HDO reaction in the hydrotreatment of the coal-derived oil was found to be 40% over 12PMN catalyst. On the other hand, the HDS-3 catalyst showed a very low activity in comparison with the activities seen for the PMN catalysts. The reason why the HDS-3 catalyst showed such poor HDO activity was not clear, but it could be considered to be contamination of the HDS-3 catalyst with the ammonia and water produced during the reaction in the closed system, such as the autoclave. Nevertheless, the hydrotreatment of the coal-derived oil over the PMN catalysts was carried out in the same autoclave system, but the PMN catalysts showed remarkable HDO activity. This was again some direct evidence of the formation of the metallic portion on the PMN catalysts by the P-addition to the MN catalyst, as seen in Fig. 10. This activity is also essential for the upgrading of coal-derived oils into transportation fuels.

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4. Conclusions

References

1. The phosphoric acid addition to the 0.2Mn2O3± 0.8NiO catalyst causes the creation of the active sites on the catalysts for hydrogen molecules. 2. The phosphoric acid addition to the 0.2Mn2O3± 0.8NiO catalyst plays a role in promoting the reduction of NiO of the catalysts in the presence of hydrogen. 3. The phosphate-promoted 0.2Mn2O3±0.8NiO catalysts simultaneously promote the nuclear hydrogenation, the HDN, the HDS, the HDO and the ring-opening reactions, though the activity of the HDS is not as effective as the commercial HDS-3 catalyst. 4. Phosphate-promoted 0.2Mn2O3±0.8NiO catalysts are essentially good for the upgrading of coalderived oils and heavy distillates into transportation fuels.

[1] R.F. Sullivan (Ed.), Upgrading of Coal Liquids, vol. 139, Am. Chem. Soc. Sym. Ser., 1981, 39 pp. [2] I. Mochida, K. Sakanishi, Y. Korai, H. Fujitsu, Fuel 65 (1986) 1090. [3] C. Song, K. Hanaoka, T. Ono, M. Nomura, Bull. Chem. Soc. Japan 61 (1988) 3788. [4] K. Sakanishi, M. Ohira, I. Mochida, H. Okazaki, M. Soeda, Bull. Chem. Soc. Japan 62 (1989) 3994. [5] T. Kotanigawa, M. Yamamoto, T. Yoshida, Appl. Catal. A. 164 (1997) 323. [6] J. Chastain (Ed.), Handbook of X-ray Photoelectron Spectrometry, Perkin-Elmer Corp., 1992. [7] A. Brenner, E. Grace, J. Res. Nat. Bur. Standards, 37 (1946) 1. [8] A. Brenner, E. Grace, J. Res. Nat. Bur. Standards, 37 (1947) 385. [9] P. Atanasova, A. Lopez Agudo, Appl. Catal. 5 (1995) 329. [10] M.W.J. Craje, V.H.J. de Beer, A.M. van der Kraan, Catal. Today 10 (1991) 337. [11] C. Song, M. Nomura, Bull. Chem. Soc. Japan 59 (1986) 3643.