Carbonization properties of hydrogenated aromatic hydrocarbons—III

Co&n Vol. 21, No. 6, pp. 535-M, Printed in Great Britain.

ooO8-6223/83 $3.00 + .oO C I983 Per&mm Press Ltd.

1983

~AR~~N~ZATION

PROPERTIES

AROMATIC

OF ~YDRU~~NATED

HYDROCARBONS-~11

MODIFYING ACTIVITIES OF HYDROGENATED PRYENE AND ITS OXIDIZED DERIVATIVES IN THE CO-CARBONIZATION OF COALS AND COAL LIQUIDS ISAOMOCHIDA, KAZUHIRO TAMARU, Yozo KORAI, HIROSHI Fumsu and KENJIRO TAKESHITA Research Institute of Industrial Sciences, Kyushu University, Kasuga 816, Fukuoka, Japan (Received 17 September

1982)

Ahstraet-The modifying activities of hydrogenated pyrene (HP) and its oxidized derivatives were examined in co-carbonization with solvent refined coal, solvent treated coal, a fusible and a non-fusible coal. The present additives all showed a significant activity, with HP oxidized at 150°C exhibiting the highest activity. The activity of the addjtive is discussed from its st~ctural indices and coke yield in relation to its dissolving and hydrogen donating abilities. The modifying su~pti~lity of the ~rboni~ng substance is rated in the order described above, being correlated with its single carbonization properties, such as fusibility and potential for anisotropic development. A consecutive treatment of partial hydrogenation and oxidation is emphasize as a useful t~hnj~ue for producing active additive and an excellent coking substance from the pitch material.

be an improved technology for preparing a pitch or a carbonaceous source of desirable quality.

I. ~RODU~ION

Co-carbonization has been recognized as an advanced technique to produce cokes of desired quality from given carbon sources[i-4]. The major task is how to derive, up-grade or synthesize a co~arboni~a~on additive which can e&ctively modify the carbonization behavior of the principal carbonizing substances@-71. The present authors have revealed that the modifying activity of an additive is intimately related to its coke yield and dissolving and hydrogen donating abilities[& 91. These properties should all be related to its structure. Above all, the molecular weight distribution, aromaticity Vu) and the number of naphthenic units (Rnus) of the additive are recognized as indicators for these properties [9]. The authors have reported the carbonization properties of pyrene in previous papers [ 10, 1i], which produced a significant amount of coke in atmospheric carbonizations only after considerable hydrogenation. The coke yield from hydrogenated pyrene was increased further by the oxidative pretreatment around lSO”C, still main~iuin~ the development of the flow texture in the resultant coke. Althou~ some oxygens were induced, some naphthenic hydrogens remained even after the oxidative pretreatment, favoring the development of the flow texture. In the present study, the modifying activities of hydrogenated pyrene and its oxidized derivatives in the co-carbonization of solvent refined coal(SRC), solvent treated coal (STC) and two coals (a fusible bituminous and a non-fusible subbitumionus coal) are examined, since their structures and carbonization properties suggest that they have a high modifying activity. It can thus be shown that the consecutive treatment of partial hydrogenation and oxidation can

SRC (prepared from Mike coal), STC (provided from Sum~tomo Sekitan Co.) and coals used as the principal carbonjzing substance in the present study are listed in Table 1 with some of their analyses and properties. hydrogenate pyrene (HP) and oxidized HP used as the coking additives are listed in Table 2 with some analytical data. Hydrogenated pyrene was prepared from pyrene (Tokyo Kasei Co.) using lithium and ethylenediamine[ IO,1 11.The oxidative pretreatment of hydrogenated pyrene was carried out in a Pyrex glass tube (40 mm length, 20mmdia.f exposed to air at temperatures of 150°C (OHP-150) and 200°C (OHP-200) for 24 hr under atmospheric pressure. During the pre~eatment, hydrogenated pyrene fused and a certain amount sublimed [I 11, the yields being described in Table 2. The pretreatment in N, brought about little increase in coke yield at 15O”C, indicating the effectives of the oxidation pretreatment.

A ground principal carbonizing substance (passing 100 U.S. mesh screen) or a mixture with a cocarbonization additive was heated in a pyrex glass tube (300 mm fength, 30 mmdia.) in a vertical furnace under a nitrogen flow. The additive was mixed with a mortar and a pestle. The heating rate, soaking temperature and time were 600”C/hr, 600°C and 2 hr, respectively. The semi-coke thus produced in the tube was weighed to calculate the coke yield. The coke was 535

I. MOCHIDA er al.

536

Table 1. Analyses of principal carbonizing substances Elemental analyses(wtb)') c 865 86:4 82.6

SRC STC Akabira (fusible) 76.6 Wandoan (non-fusible)

H 56 6:3 6.1

N 15 2:l 2.0

s 0.5

6.3

1.1

0.4

Coke Ash(s) Yield (8) trace 57 2.5 56 9.2 64 9.8

Optical*' texture MC Mf I

53

I

1) day, ash free basis 2) See Table 3

Table 2. Analyses of hydropyrene and its oxidized derivatives Elemental C HPl)

analyses H

N

(wt%) Proton distribution (rr4)py6)m7) . . H/C

Har

Ha

Hg

H

fa')(wtl)

I

. . (wta)

91.67

6.72

0.16

0.88

43.9

40.5

15.6

0.0

0.71

-

OHP 150*) 92.17

6.52

0.12

0.85

37.8

40.0

22.2

0.0

0.74

95

29

OHP 2003) 91.86 5.72 0.08 1) hydrogenated pyrene

0.75

39.3

37.4

16.8

6.5

0.77

92

36

16

2) HP oxidized at 15OV 3) HP oxidized at 2OOV 4) defined by 'H-NMR according to Ouchi's method (refer to 17) Har: 6-10 ppm

Ha: 2-4 ppm

He: 1.1-2 ppm

IiT: 0.3-1.1 ppm

5) Carbon aromaticity (refer' to 17) 6) P.Y.: Pitch Yield, Pitch yield after oxidation 7) C.Y.: Coke Yield

mounted in a resin and was examined with an optical microscope (Nikon POH) to qualify the optical anisotropy developed in the coke after conventional polishing[l2]. The classification of anisotropic texture which is designed to distinguish the units appearing in the coke from the coals, and the coal/pitch mixtures was made according to Table 3[8,9]. 3. RESULTS Photomicrographs of coke produced in the cocarbonization of SRC with HP and OHP-150 are shown in Fig. 1, where the mixing ratios were 9/l and 4/l (SRC/additive by weight). The SRC always produced a coke of medium mosaic texture (Fig. la). The additives of HP and OHP-150 modified the optical texture in the resultant cokes, providing the coarse mosaic texture with a partial flow texture at 9/l (Fig. 1b and c). The size of anisotropic unit and area of the

flow texture developed at 9/l were definitely larger in the coke produced with OHP-150 than with HP. The cokes produced at the mixing ratio of 4/l with both additives were essentially of flow texture, the length and width of the flow unit being even larger with OHP-150. Photomicrographs of cokes from STC and its blend with HP and OHP-150 are shown in Fig. 2, where the mixing ratios were 4/l and 2/l. STC produced a coke of fine mosaic texture when it was singly carbonized. Co-carbonization with HP and OHP-150 increased the size of the anisotropic unit at 4/l. Although the texture was still classified as a fine mosaic, the size of the anisotropic unit in the coke with OHP-150 was definitely larger. An increase in the amount of additive further increased the size, producing a medium mosaic texture on co-carbonization

Table 3. Description of size and shaue of oDtica1 texture Optical texture Isotropy AnisotropiGSpherical unit ultrafine mozaic very-fine mozaic fine mozaic medium aozaic coar'se mozaic small domain domain Elongated unit elongated mozaic flow flow domain

Abbreviation I

Size (pm)

UMF


Mvf Mf Mm

0.5-1.0 1.0-2.5 2.5-5.0 5.0-10.0 10.0-60.0 >60

MC

SD D EM P ID

10-20 20-60 >60.0

Carbonization

properties of hydrocarbons-III

Fig. 1. Photomicrographs of cokes obtained by the cocarbonization of SRC with HP or OHP 150 at variable mixing ratios (under crossed-polars). Cocarbonization: 6OOT-2 hr, (a) SRC, (b) SRC/HP = 9/l, (c) SRCjOHPlSO = 9/l, (d) SRC/HP =4/l, (e) SRCjOHPl50 = 4/l.

537

538

Fig. 2. Photomicrographs of cokes obtained by the cocarbonization of STC with HP or OHP150 at variable mixing ratios (under crossed-polars). Co-carbonization: 6WC-2 hr, (a) STC, (b) STC/HP = 4/l, (c) STCjOHPl50 =4/l, (d) STC/HP = 2/l, (e) STCjOHP = 2/l.

with OHP-150 at a mixing ratio of 2/l. The same amount of HP also enlarged the size, but the product was still classified as a fine mosaic. The optical micrographs of cokes produced from Akabira coal, a highly fusible coal, are shown in Fig. 3(a). The coal grains fused together to give an isotropic coke. Addition of HP developed a partial fine mosaic texture in the very fine mosaic texture with the mixing ratio of 3/l. It is difficult to distinguish the regions originating from the coal and the additive, indicating that there was excellent mixing in the co-carbonization process. The fine mosaic texture prevailed over all the coke when OHP-150 was added at the same ratio. The photomicrographs of cokes from Wandoan, an Australian non-fusible coal, are shown in Fig. 4. The coal was completely non-fusible, giving fine chars of optical isotropy without any adhesion. Addition of HP at a mixing ratio of 3/l slightly fused the coal grains which were still distinguishable, although they

were deformed and adhered each other through narrow bridges. The coke stayed completely isotropic. Addition of OHP-150 fused the coal grains so effectively that the were hardly distinguishable from each other. This produced a strong coke, although the coke was still isotropic. More addition of the additives up to a ratio of l/l produced anisotropy and fused the coal grains completely, providing a fine mosaic texture with HP and medium mosaic texture with OHP-150. In both cases well-bound cokes were formed. The modifying activity of OHP-200 (oxidized at 200°C) was examined. The micrographs of the cokes produced in the co-carbonization with Wandoan coal are illustrated in Fig. 5. At a mixing ratio of 3/l, the coal grains were deformed and bound each other. Some large grains were formed, probably through dissolution of the original coal grains at their outer surface. However narrow bridges were also observed. At a mixing ratio of l/l, the fine mosaic texture

Carbonization

properties of hydrocarbons-III

539

Fig. 3. Photomicrographs of cokes obtained by the co-carbonization of Akabira coal with HP or OHPlSO at variable mixing ratios (under crossed-polars). Co-carbonization: 6WC-2 hr, (a) Akabira coal, (b) Akabira/HP = 3/l, (c) Akabira/OHPISO = 3/l.

prevailed in a well-bound judged as being between 4.

coke. Such an activity was that of HP and OHP-150.

DISCUSSION

The co-carbonization of rather poor carbonizing substances with effective additives for the development of better anisotropic texture has been well documented [ 141. The present study revealed further examples with the co-carbonization of SRC, STC, a fusible and a non-fusible coal, with hydropyrene and its oxidized derivatives as the co-carbonizing additives. The co-carbonization susceptibility to the principal carbonizing substances[7] in the present study decreased in the above order; SRC which was most easily modified, exhibiting an excellent flow texture at a mixing ratio of 4/l with OHP-150. In contrast, Wandoan coal, which was the hardest to modify, required a ratio of l/l to produce a medium mosaic texture with the same additive. The co-carbonization susceptibility of the carbonaceous substances appears to be related to their carbonization properties such as fusibility and potentiality of anisotropic development in a single carbonization. Their H/C and O/C ratios may be analytical parameters which approximately describe such properties [7, 131.IR spectroscopy of the oxygen functionality may provide more a chemical basis[7, 141. Although the extent of modification performed by an additive may depend on the principal carbonizing substances as previously discussed [ 151, the aromaticity, naphthenic component, and coke yield of the additive have been key structural factors for its high activity[8,9]. Such factors are assumed to be CAR Vol. 21. No. hB

related to its dissolving and hydrogen transferring abilities, both of which may moderate the carbonization reactivity and keep the viscosity of cocarbonizing system low during the final stage of the carbonization [ 161. The coke yield is a direct measure of the amount remaining from the process. Partially hydrogenated pyrene, which has been previously found[lO, 1l] to give a significant amount of coke with a flow texture, has the above structural characteristics and may be expected to be an effective additive. The oxidative treatment can increase the coke yield considerably through the condensation via oxidative dehydrogenation and oxygenation at the sacrifice of the naphthenic hydrogen as indicated by the proton distribution shown in Table 2. However, not all of the hydrogen-donating ability is lost, since some stable naphthenic hydrogens, of which the chemical shifts in NMR are 2 and 3 ppm, remain even after the pretreatment [l 11. Some a position hydrogens are even produced by the treatment. Such hydrogens survive up to the co-carbonization temperature and are therefore expected to be effective in the modification through hydrogen transfer. OHP-150 exhibited the highest modifying activity of the present additives because of its appropriate extent of oxidation. OHP-200 is definitely inferior to OHP-150 in spite of a further increase in coke yield. High temperature oxidation may remove too much naphthenic hydrogens. The values offa, HB+JH and, coke yield of the additives summarized in Table 2, explain qualitatively the order of their modifying activity in a similar manner previously discussed[9]. In conclusion, a consecutive treatment of partial

540

I. MOCHIDAet al.

Fig. 4. Photomicrographs of cokes obtained by the co-carbonization of Wandoan coal with HP or OHP150 at variable mixing ratios (under crossed-polars). Co-carbonization: 6OO’T-2 hr, (a) Wandoan coal, (b) Wandoan/HP = 3/l, (c) Wandoan/OHPlSO = 3/l, (d) Wandoan/HP = l/l, (e) Wandoan/OHPlSO = l/l.

Fig. 5. Photomicrographs variable mixing ratios

of cokes obtained by the co-carbonization of Wandoan coal with OHP200 at (under crossed-polars). Co-carbonization: 6OOT-2 hr, (a) Wandoan/ OHP200 = 3/ 1, (b) Wandoan/OHP200 = l/l.

Carbonization

properties of hydro~rbons-III

hydrogenation and oxidation on the carbonaceous material is a useful approach for preparing an active carbonization additive as well as an excellent carbonizing substance by enlarging the aromatic unit to increase the coke yield, while maintaining sufficient transferable hydrogens. The reactivity of hydrogen is carefully taken into account in both treatments. An application of the technique to practical substances such as coal tar is now under progress. REFERENCXS 1. H. Marsh and P. L. Walker, Jr., Chemistry and P&s&s of Carbon (Edited by P. L. Walker, Jr. and P. A. &rower), vol. 15, p.-247. Marcel Dekker, New York (1979). 2. H. Marsh, I. Macefield and J. Smith, 13th Co& on Carbon, American Carbon Society, Abstracts, p. 304 (1977). 3. I. Mochida, K. Amamoto, K. Maeda and K. Takeshita Fuel 56, 49 (1977).

4. I. Mochida and H. Marsh, Fuel 58, 7 (1979). 5. 1. Mochida, Y. Koria, H. Fujitsu, K. Takeshita, K. Mukai, W. Migitaka and Y. Suetsugu, Fuel 60, 405 (1981).

541

6. Y. Korai, H. Fujitsu, K. Takeshita and I. Mochida, Fuel 60, 1106 (1981). 7. I. Mochida, Y. Koria, K. Takeshita, K. Mukai, W. Migitaka and Y. Suetsugu, 15th Biennial Conf. on Carbon, Abstracts p. 138, Pennsylvania (1981). 8. I. Mochida, H. Matsuoka, Y. Korai, H. Fujitsu and K. Takeshita, Fuel 61, 587 (1982). 9. I. Mochida, H. Matsuoka, Y. Korai, H. Fujitsu and K. Takeshita, Fuel 61, 595 (1982). 10. I. Mochida, H. Matsuoka, H. Fujitsu, Y. Korai and K. Takeshita. Carbon 19. 213 (19811. il. I. Mochida, K. Tam&, Y: Kokai, H. Fujitsu and K. Takeshita, Carbon 20, 231 (1982). 12. H. Marsh and J. Smith, Anaiy~ic~l Method for CoalMtd Co& Products, Vol. 2 (Edited by Karr, Jr.), p. 373 Academic Press, New York (1978). 13. Y. Korai and Y. Yoshida. K. Takeshita and I. Mochida. Fuel 62, 649 (1983). 14. P. R. Solomon, Advances in Chemistry Series (Edited by M. L. Gorbaty and K. Ouchi), No. 192, p. 96. American Chemical Society (1981). 15. I. Mochida, H. Marsh and A. Grin& Fuel 58 803 (1979). 16. I. Mochida, T. Ando, K. Maeda and K. Takeshita, Carbon 18, 131 (1980). 17. K. Iwata, H. Itoh and K. Ouchi, Fuel Process Technol. 3, 25 (1980).