632
Energy & Fuels 1991,5,632-637
data on a triangle graph clearly show a common pathway for the high-volatile bituminous coals used in this study. In the initial stage, as the conversion increases there is a parallel increase in the A + P yields. The 0 + G yields remain fairly constant in this initial dissolution stage. Upon reaching a maximum coal conversion, the A + P yield also reaches a maximum and the pathway changes direction. In this second stage of the pathway, conversion remains relatively constant and the 0 + G yields increase at the expense of the A + P yields. At severe process conditions (high temperatures and long residence times), the pathway again changes. In this region of the pathway, total conversion decreases and lower yields of 0 + G and A + P are obtained. Retrogressive reactions are the primary reactions taking place in this section of the pathway. The utilization of supported, oil based, and acid catalysts has no major effect on the pathway observed for these coals. The catalyst therefore only increases the rate of reaction and does not significantly change the selectivity. The quality of the liquefaction solvent has no major effect on the thermal or catalytic pathway. The primary difference in the observed pathway for the different liquefaction solvents is the magnitude of the maximum
conversion obtained for the coals. The better the donor ability, the higher the maximum conversion obtained by the coal. The absence of a liquefaction solvent in the catalytic hydrogenation of a Westem Kentucky No. 6 coal changed the pathway. In this experiment, the 0 + G yields increased with increasing coal conversion in the initial section of the pathway; the A + P yields marginally increased. This is opposite to the trend in liquefaction with a solvent. Similar to the pathway observed in the presence of a liquefaction solvent, when the coal conversion reaches a maximum, the pathway changes. Upon reaching the maximum coal conversion, the pathway indicates retrogressive reactions are occurring. The coal conversion and A + P yields decrease in this region of the pathway; however, the 0 + G is comparable to those obtained in the presence of a solvent vehicle.
Acknowledgment. This work was supported by the Commonwealth of Kentucky and DOE Contract No. DEFC22-88PC8806 as part of the Consortium for Fossil Fuel Liquefaction Science (administered by the University of Kentucky).
Determination of Atomic Groups of Hydrocarbons in Coal-Derived Liquids by High Performance Liquid Chromatography and Nuclear Magnetic Resonance? Masaaki Satou,* Hirofumi Nemoto, Susumu Yokoyama, and Yuzo Sanada Metals Research Institute, Faculty of Engineering, Hokkaido University, N-13 W-8, Kita-ku, Sapporo, 060 Japan Received January 23, 1991. Revised Manuscript Received June 17, 1991
A systematic atomic group determination by high performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR) is proposed for the estimation of physical properties of hydrocarbons in a coal-derived liquid. HPLC has been used for the separation of hydrocarbons into compound classes according to the number of aromatic rings. The structural analyses of these compound classes were performed by using 'H and I3C NMR. The chemical structures of the compound classes are characterized by seven atomic groups. The numbers of these atomic groups in an average molecule for each fraction were calculated based on the resulta from this method. The physical properties of coal-derived liquids will be estimated from the chemical structure of the hydrocarbons by the method proposed here. Introduction Extensive data about the physical properties of coalderived liquid are necessary for the optimum design and operation of coal liquefaction and upgrading processes. However, the data are generally available only for low molecular weight hydrocarbons. They are more scarce especially for hydroaromatic and polyaromatic hydrocarbons, which exist in significant amounts in coal-derived liquids. Determination of all required data is usually not convenient experimentally. Even if possible, the wide variety of physical properties that are commonly measured -
~~
~
'Presented at the Symposium on Analyticd-Chemistry of Heavy Oile/Reside, 197th National Meeting of the American Chemical Society, Dallas, TX, April 9-14, 1989.
generally dictates a wide range of testing procedures, many of which can be quite tedious. Hence, a correlation is needed to estimate the values or to extend or extrapolate the limited available data. In general, the physical properties are closely related to the chemical structures of a given heavy hydrocarbon molecule.' One of the most common approaches to physical property prediction has been a group contribution method in which one assumes that the physical properties of a molecule are determined by the number and types of chemical groups p r e ~ e n t . ~ sThis method for the coal(1) Benron, 5.W. Thermochemical Kinetice, 2nd ed.; Wiley: New
York, 1976.
(2) Reid, R. C.; Prauanitz, J. M.; Sherwood, T. K. The Propertiee of Gases and Liquids, 3rd ed.; McGraw-Hill: New York, 1977.
0 1991 American Chemical Society
Energy & Fuels, Vol. 5, No. 5, 1991 633
Determination of Atomic Groups of Hydrocarbons Table I. C H N
Table 11. Results of Narrow-Cut Distillation
Ultimate Analysis of Middle Distillatea 87.09 S 0.04 8.68 0 (diff) 3.80 0.39
"Based on wt % daf.
derived liquids is one of the most useful methods for estimation of physical proper tie^.^^^ For this method, the principal task is to determine the atomic groups by which the chemical structures are present in the liquid and to calculate their number. Furthermore, characterizing the structures of coal-derived liquids is an important step in developing an understanding of the chemistry of coal reactions. Recently, by use of lH and 13C nuclear magnetic resonance (NMR), elemental analysis, and infrared spectroscopy, methods of structural analyses for estimation of the concentrations of atomic groups in the sample have been proposed and applied to the characterization of fossil fuels.The concentrations of atomic groups by these analyses were obtained mathematicallyas the solutions of a set of linear stoichiometric equations. Haw et al. have developed a structural analysis for a middle distillate of petroleum fuel by using high performance liquid chromatography (HPLC) and lH NMR.l0 Samples were separated into some chemically homologous fractions by HPLC. Detailed information on the various hydrogen types of hydrocarbons was obtained from lH NMR spectra of these fractions, and the numbers of the atomic groups in various hydrocarbons were calculated. This method might be applicable for the characterization of hydrocarbons in a coal-derived liquid." However, it is limited by some assumptions as follows. First, no branching of an alkyl side chain exists beyond the a position from aromatic ring. Second, few cycloalkanes are contained in a HPLC fraction, because cycloalkane protons produce signals inconsistent with the CH3, CH2,and CH spectral regions characteristic of normal and branched alkanes. Finally, the diaromatic fraction is composed exclusively of alkylnaphthalenes and acenaphthene. These assumptions might be reasonable for light oils such as aviation fuels. However, for characterization of coal-derived liquids containing a heavy fraction, this method is not always accurate in its representation of the structure of a hydrocarbon. The purpose of this study is to develop an analytical method of the chemical structures in a coal-derived liquid for not only the characterization but also its physical property estimation.
Experimental Section The middle distillate (boiling range of 473-723 K) of Wandoan coal-derived liquid was supplied from a coal liquefaction plant of 1 t / d (Sumitomo Metal Co., Ltd., Japan) and its ultimate analysis is listed in Table 1. The distillate was furthermore (3) Hoehino, D.; Nagahama, K.; Hirata, M.J. Jpn. Pet. Imt. 1979,22, 32. (4) Le,T. T.; Allen, D. T. Fuel 1986,64, 1754. (6) Allen, D. T.; Behmanesh, N.; Eatough, D. J.; White, C. M.Fuel 1988,67, 127. (6) Petrakis, L.; Allen, D. T.; Gavalas, G. R.; Gates, B. C. Anal. Chem. 1983,55, 1577. (7) Allen, D. T.; Petrakis, L.; Grandy, D. W.; Gavalas, G. R.; Gates, B. C. Fuel 1984,63,803. (8) Khorasheh, F.; Gray, M.R.; Dalla Lana, I. G. Fuel 1987,66,505. (9) Egiebor, N. 0.; Jacobson, J. M.;Gray, M.R.; Lee, L. K. Fuel Sci. Technol. Int. 1989, 7, 251. (10) Haw, J. F.; Glass, T. E.; Dom, H. C. Anal. Chem. 1983,55,22. (11) Yokoyama, S.; Uchino, H.; Satou, M.; Sanada, Y. J. Chem. SOC. Jpn. 1987,705.
fraction no. 1. 2 34 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
boiling range of distillate, K 50% convrtd to cutoff yield, obsd 101.3 kPaa point, K w t 9 ' 0 IBP-394 461 6.31 3.42 463 461-467 394-399 3.34 469 467471 399-403 474 3.16 471-476 403-407 479 476481 3.07 407-412 484 3.66 481-487 4 12-417 3.11 488 417-419 487-489 491 419-421 489-492 2.90 494 421-425 492-496 3.31 499 425-431 496502 3.37 505 502-507 3.66 431-435 3.41 510 507-5 12 435-439 514 512-515 2.54 439-442 518 515-521 3.82 442-448 4.22 523 521-524 448-450 2.666 406-425 522-545 534 3.63 546-554 550 3.70 425-433 558 3.80 433-439 554-561 4.81 561-570 566 439-446 574 3.80 570-578 446453 0.6666 421-433 585 3.91 578-592 598 3.99 433-441 592-603 609 3.24 441-451 603-614 4.59 0.4000 438-459 613-641 627 1.40 646 459-467 641-650
distih press., kPa 13.33
a
90.17
461450
total distillate residue loss
9.52 0.31
650-
Converted by ASTM D-2892. 100 h
8
80
5
60
-@ m
8
40
4
cl
6 20 n
"
5
7
11
15
17
19
21
23
Fraction Number Figure 1. Content distribution of compound classes in narrow-cut distillate by HPLC: P, alkanes; M, monoaromatics; D1, naphthalene type diaromatics; D2, biphenyl type diaromatics; T, trior tetraaromatics; PP, polyaromatics and polar compounds. separated into 26 fractions with narrow boiling point ranges of width 2-28 K, spanning 461-650 K, by a spinning band distillation apparatus (Model HSB-605E, Tokyo Kagaku Seiki Ltd.). Their boiling ranges, 50% cutoff points, and yields are listed in Table
11. Representative fractions of the narrow cut distillates were separated into chemically homologous compounds called "compound classes'' by using a HF'LC (TRI-ROTAR,JASCO Ltd.) equipped with a Zorbax BP-NH2column having 67.9 mm X 250 mm (Du Pont Ltd.) according to the number of aromatic rings. These are six hydrocarbon compound classes; alkanes (Fr-P), monoaromatics (Fr-M), naphthalene type diaromatics (Fr-Dl), biphenyl type diaromatics (Fr-D2),tri- and tetraaromatics (Fr-T), and poly-aromatic and polar compounds (Fr-PP). The detailed procedures have already been described elsewhere.12 Content distribution of compound classes was shown in Figure 1. Samples for the 13C NMR measurement were prepared by dissolving approximately 150 mg of each compound class in 1mL of chloroform-d (99.8 atom % D, Merck) with tetramethylsilane (12) Uchino, H.; Yokoyama, S.; Satou, M.;Sanada, Y. Fuel 1985,64, 842.
Satou et a1
634 Energy & Fuels, Vol. 5, No. 5, 1991 1
Table 111. List of Chemical Shifts on NMR Spectra (ppm from TMS) l8C NMR aromatic carbons 115-148 aliphatic carbons 13-53
'H NMR aromatic hydrogens aliphatic a-hydrogens to aromatic rings Fr-M Fr-D1, D2, T a-methyl hydrogens attached to the aromatic rings Fr-M Fr-D1 Fr-D2, T aliphatic hydrogens further from the aromatic rings than the @ position Fr-M Fr-DI, D2, T aliphatic terminal methyl hydrogens further from the aromatic rings than the y position and methyl hydrogens in alkanes
I
I
45
6.20-9.20
4
'4'
1.95-4.20 2.00-4.20
7
1.95-2.40 2.00-2.70 2.10-2.70 1.00-1.95 1.00-2.00 0.50-1.00
Results a n d Discussion Calculation of t h e Concentrations of Atomic Groups from NMR Analyses. As coal-derived liquids were separated by HPLC according to the number of aromatic rings, as a hydrocarbon compound class, prior to the 13C and 'H NMR measurements, detailed information about the distributions of various bonding types of carbons and hydrogens were obtained.13-18 13C NMR enables the classification of carbon into two groups, that is, aromatic and aliphatic. 'H NMR enables the classification of hydrogen atoms into five bonding groups: aromatic hydrogens, a-methyl hydrogens attached to the aromatic rings, aliphatic a-hydrogens to aromatic rings, aliphatic hydrogens further from the aromatic rings than the /3 position, and aliphatic terminal methyl hydrogens further from the aromatic rings than the y position and methyl hydrogens in alkanes. The ranges of chemical shifts of the various bonding typea of carbons and hydrogens are listed in Table III. The concentrations of each carbon and hydrogen were obtained from the peak area percentage of the NMR spectra. Assuming that aliphatic quaternary carbons and olefinic double bonds are absent in the chemical structures of coal-derived liquids, the structures of hydrocarbons are represented by seven atomic groups as shown in Figure 2: aliphatic methyl groups, aliphatic methylene groups, aliphatic methine groups, aromatic protonated carbons, aromatic substituted carbons, aromatic conjunction carbons, and naphthenic rings. Let us consider an example as follows. Components in Fr-D1 have a condensed aromatic ring system such as naphthalenes and 1,2,3,4tetrahydrophenanthrenes,while those in Fr-D2 have a separated aromatic ring system such as biphenyls, fluorenes, and 9,lO-dihydrophenanthrenes. To distinguish (13) B d e , K. D.; Martin,T. G.; Williams, D. F. Chem. Ind. 1976,313. (14) Pugmire,R.J.; Grant, D. M.; Zilm, K. W.; Anderson, L. L.; Oblad, A. G.; Wood, R. E.Fuel 1977,56,296. (15) Bartle, K. D.; Smith, J. A. S.Fuel 1967, 46, 29. (16) Bade, K. D.; Jones, D. W.Fuel 1969,48, 21.
'2'
1 : Aliphatic Methyl Groups 2
(TMS, 1 vol %) as internal standard. For the 'H NMR measurement, -20 mg of the sample was dissolved in 0.3 mL of chloroform-a' with TMS. Both spectra were obtained with a Varian XL-200spectrometer. 13C NMR spectra were obtained by using a pulse width of 16 s, total of 3000 transients, a pulse delay of 15 a, and gated decoupling to ensure quantitative results. Elemental analyses were carried out with a CHN analyzer. Molecular weight measurements were made with a KNAUER vapor pressure osmometer for Fr-P and T.
A+;
Aliphatic Methylene Groups
:
3 : Aliphatic Methine Groups 4 : Aromatic Protonated Carbons
5
:
Aromatic Substituted Carbons
6
:
Aromatic Conjunction Carbons
7 : Naphthenic Rings
Figure 2. Atomic groups in CB-phenylnaphthenonaphthalene. Table IV. Definitions of Reeresentative Symbols 13C NMR peak area percentage for aromatic carbons C,/C I3C NMR peak area percentage for aliphatic carbons HJH 'H NMR peak area percentage for aromatic hydrogens H,,.cH,/H *HNMR peak area percentage for a-methyl hydrogens attached to the aromatic rings H,/H 'H NMR peak area percentage for aliphatic a-hydrogens to aromatic rings H,/H 'H NMR peak area percentage for aliphatic hydrogens further from the aromatic rings than the @ position HJH 'H NMR peak area percentage for aliphatic terminal methyl hydrogens further from the aromatic rings than the y position and methyl hydrogens in alkanes H number of hydrogens per average molecule C number of carbons per average molecule H/C atomic ratio of hydrogen and carbon C,/C
between the various structures, aromatic bridgehead carbons were defined as the aromatic conjunction carbons in Fr-D1 and as the aromatic substituted carbons in Fr-D2, as shown in Figure 2. The molar fractions n* of compound classes can be calculated by eqs 1-19 from NMR and elemental analyses. Symbols in equations are listed in Table IV. The molar fractions of aliphatic methyl groups (n*cb), aromatic protonated carbons ( R * ~ )aromatic , substituted carbons (n*m),and aromatic conjunction carbons (n**c) are expressed as in eqs 1-11, where Y should be precisely n*CH3 n*CH,
=
(Hy/H)(H/C)/3for Fr-P + Hy)/H)(H/C)/3
=
((HaCH,
(1)
for Fr-M, D1, D2, T (2) n*AH
n*AH
R*AS
=0
(H,/H)(H/C)
for Fr-P (3) for Fr-M, D1, D2,T (4)
n*As= 0 for Fr-P = (C,/C) - ( H , / H ) ( H / C ) for Fr-M, D2
AS = (4/5)(C,/C) - ( H , / H ) ( H / C ) n*AS = (((HaCH3/H)/3) +
(5)
(6)
for Fr-D1 (7)
(l/V((Ha - Ha~~,)/H))(H/C) for Fr-T (8) n*AC ~ * A c=
=0
for Fr-P, M, D2 for Fr-D1
(1/5)(Ca/C)
(9)
(10)
Determination of Atomic Groups of Hydrocarbons ~ * A=C(C,/C)
- (H,/H)(H/C) - n*1\5
Energy & Fuels, Vol. 5, No.5,1991 635
for Fr-T (11)
the average number of aliphatic a-hydrogens per a-carbon except for a-methyl groups. Because Y can not be exactly calculated in the analyses, it is assumed that Y is approximately equal to the average number of hydrogens of the alkyl chains per carbon of alkyl chains except for methyl groups, which is hereafter denoted as X. It is worth noting that the equations oft^*^ and n*Ac for Fr-T have unique formats compared with those of other atomic groups. In Fr-T, since the number of aromatic rings could not be determined precisely except that it had the value of three or above by HPLC separation with an amine column, it is not possible to qualify the chemical structure in as much detail as for Fr-P, M, D1, and D2. For example, the total aromatic carbon and aromatic bridgehead carbon numbers could not be precisely determined, so the assumption here is that n*AS in Fr-T is equal to that of aliphatic a-carbons. This has the fault, however, that the values of n*u involve an error in some compounds having a separate ring system. That is, for example, in 11,12dihydrochrysene, the carbons at the positions 4a and 4b are distinguished not as the aromatic substituted carbons but as the aromatic conjunction carbons because of the absence of aliphatic a-carbons between them, while those at 10b and 12a are the aromatic substituted carbons as defined, because of the presence of aliphatic a-carbons at the positions of 11and 12. Furthermore, in fluoranthene, the value of X is zero, and the calculation of n*+ is impossible by this equation. At the present time, it is better to assume that, if compounds having a separate ring system are present in Fr-T, they are compounds such as 5,12dihydronaphthacene with aliphatic a-carbons. The molar fractions of aliphatic methylene groups (n*cH1) and aliphatic methine groups (n*CH) are derived by using the following relations. 2C+Z=H (12) Cn*CHB= Cn*cH + Z (for Fr-P) (13)
c,/c = n*CH + n*CH* + n*CH$ x = (n*CH + 2n*CH2)/(n*CH + n*CH1)
(14)
The Z number indicates hydrogen deficiency compared with the paraffin of the same carbon number. X is defined as the average number of hydrogens of the alkyl chains per carbon of alkyl chains, except for methyl groups. n*CHI = (C,/C) - (n*cH + n*CH3) for Fr-P (16) n*cHZ= (C,/C - n*CH3)(X- 1)
for Fr-M, D1, D2, T (17) + 2 for Fr-P (18) ~ * C H~ Z * C-H(H/C) ~
n*CH =
((c,/c)- N*CH3)(2- x)
for Fr-M, D1, D2, T (19) The molar fractions of the six atomic groups obtained in this study are one of the average structure parameters, which characterize the chemical structures of compound classes in coal-derived liquids, and are listed in Table V. Calculation of the Numbers of Atomic Groups in an Average Molecule of Fr-M, D1,and D2 for the Estimation of the Physical Properties by the Group Contribution Method. Estimation of the physical properties by the group contribution method requires the data set of the numbers of atomic groups, ni, in an average
Table V. Molar Fractions of Atomic Groups and H/C for Each Compound Class atomic groups fraction name CH1 CHI CH AH AS AC HIC 5P 0.235 0.600 0.165 O.OO0 O.OO0 O.OO0 2.07 11 P 0.178 0.695 0.127 O.OO0 O.OO0 O.OO0 2.05 15 P 0.185 0.640 0.175 O.OO0 O.OO0 O.OO0 2.01 17 P 0.170 0.676 0.154 0.OOO O.OO0 O.OO0 2.02 0.083 0.858 0.059 O.OO0 O.OO0 O.OO0 2.03 19 P 21 P 0.142 0.781 0.077 O.OO0 O.OO0 O.OO0 2.07 23 P 0.106 0.867 0.027 O.OO0 O.OO0 O.OO0 2.08 5 M 0.095 0.377 0.040 0.302 0.186 O.OO0 1.38 11 M 0.101 0.461 0.001 0.232 0.205 O.OO0 1.46 15 M 0.108 0.469 0.044 0.183 0.196 O.OO0 1.49 17 M 0.106 0.435 0.097 0.162 0.200 O.OO0 1.45 19 M 0.086 0.470 0.101 0.151 0.192 O.OO0 1.45 21 M 0.099 0.416 0.142 0.170 0.173 0.OOO 1.44 23 M 0.119 0.419 0.114 0.129 0.219 O.OO0 1.44 5 D1 0.025 0.070 0.021 0.697 0.010 0.177 0.84 11 D1 0.078 0.048 0.022 0.667 0.015 0.170 1.02 15 D1 0.088 0.157 0.028 0.473 0.109 0.145 1.08 17 D1 0.078 0.196 0.023 0.417 0.145 0.141 1.06 19 D1 0.087 0.190 0.082 0.347 0.166 0.128 1.07 21 D1 0.075 0.259 0.025 0.342 0.171 0.128 1.11 23 D1 0.070 0.262 0.067 0.289 0.192 0.120 1.09 15 D2 0.042 0.086 0.010 0.553 0.309 O.OO0 0.86 0.027 0.098 0.077 0.493 0.305 0.OOO 0.85 17 D2 0.056 0.156 0.004 0.451 0.333 O.OO0 0.94 19 D2 21 D2 0.082 0.138 0.030 0.417 0.333 O.OO0 0.97 23 D2 0.065 0.085 0.033 0.467 0.350 O.OO0 0.87 19 T 0.031 0.026 0.005 0.630 0.002 0.306 0.91 21 T 0.037 0.008 0.008 0.656 0.016 0.275 0.75
molecule of each fraction. They are calculated with their molar fractions and total carbon numbers Ct. ni = n*ic, (20) C,, the numbers of aromatic carbons, C,, and molar fractions of aromatic parta, that is, n*m, n*M, and n*Acin a average molecule, are related to each other as follows. n*AH + n*As + n*Ac = C,/Ct (21) By use of HPLC with an amine column, the values of Ca in Fr-M, D1, and D2 were limited; that is, they were 6,lO and 12, respectively. Next, the average molecular weights M, of each fraction are calculated by the following equation. M , = C,(12 + H/C) (22) Consequently, the values of C,,M,, and ni are calculated from the data set of n*AH,n*As,n*Ac,and C,. However, for Fr-P and T, the values of C, cannot be calculated by equation because C, are zero and unclear, respectively. Thus, the values of ni and C,for Fr-P and T are calculated from the average molecular weights measured by VPO. In this study, information on the naphthenic ring structure was not directly obtained from NMR spectra data. Still, the numbers of naphthenic rings, nNR,in an average hydrocarbon molecule are mathematically related with those of some atomic groups as follows. nNR = (nCH - nCHB)/2 + 1 for Fr-P (23) ~ N = R
AS + ~
~ N =: R
-
for Fr-M, D1, T (24) AS + nCH - n c ~ , ) / 2- 1 for Fr-D2 (25) C H ncH3)/2
The sole disadvantage is that it cannot be clarified how many and what kind of aliphatic groups the naphthenic rings are formed from. Therefore, naphthenic rings are not primary atomic groups but secondary ones. The numbers of seven atomic groups, total carbon numbers, and average molecular weights in an average molecule of
Satou et a1
636 Energy & Fuels, Vol. 5, No. 5, 1991
Table VI. Number of Atomic Groups, Total Carbon Numbers (Ct), Average Molecular Weights (M,)in an Average Molecule of Each Fraction atomic groups CHS
CH2
CH
AH
AS
AC
NR
ct
M"
5P 11 P 15 P 17 P 19 P 21 P 23 P
3.00 2.43 2.85 2.65 1.46 2.60 2.42
7.65 9.52 9.87 10.53 14.99 14.31 19.77
2.11 1.75 2.70 2.40 1.03 1.41 0.62
0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.55 0.66 0.92 0.88 0.78 0.40 0.10
12.76 13.70 15.41 15.58 17.48 18.31 22.80
179.6 192.5 215.9 218.4 245.2 257.5 321.0
5M 11 M 15 M 17 M 19 M 21 M 23 M
1.16 1.39 1.71 1.76 1.51 1.74 2.05
4.64 6.33 7.43 7.21 8.22 7.28 7.22
0.49 0.01 0.69 1.61 1.77 2.48 1.97
3.72 3.19 2.90 2.69 2.64 2.97 2.22
2.28 2.81 3.10 3.31 3.36 3.03 3.78
0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.81 0.72 1.04 1.58 1.81 1.89 1.85
12.30 13.73 15.83 16.57 17.49 17.49 17.24
164.5 184.8 213.6 222.9 235.3 235.1 231.7
5 D1 11D1 15 D1 17 D1 19 D1 21 D1 23 D1 15 D2 17 D2 19 D2 21 D2 23 D2 19 T 21 T
0.29 0.92 1.21 1.10 1.36 1.17 1.17
0.79 0.56 2.16 2.78 2.96 4.04 4.36
0.23 0.26 0.38 0.32 1.28 0.39 1.11
7.88 7.83 6.51 5.92 5.41 5.33 4.81
0.11 0.17 1.49 2.08 2.59 2.67 3.19
2.00 2.00 2.00 2.00 2.00 2.00 2.00
0.03 0.01 0.33 0.65 1.25 0.94 1.57
11.32 11.74 13.76 14.20 15.60 15.60 16.64
145.3 152.8 179.9 185.6 203.9 204.5 217.8
0.59 0.41 0.86 1.32 0.96
1.20 1.48 2.39 2.21 1.24
0.14 1.15 0.06 0.47 0.49
7.70 7.41 6.90 6.67 6.86
4.30 4.59 5.10 5.33 5.14
0.00 0.00 0.00 0.00 0.00
0.92 1.67 1.15 1.24 1.33
13.93 15.04 15.31 16.00 14.69
179.1 193.2 198.0 207.5 189.0
0.43 0.53
0.36 0.11
0.07 0.11
8.74 9.43
0.03 0.23
4.24 3.96
0.00 0.00
13.87 14.37
179.0 183.2
fraction name
20 I
2
20
5 z
15
CH3
P
5
10
z CH2
I
CH2 C H ~ 10
0
ta
P
1
u
5
" 1 0 470
0
470
520 570 620 D i s t i l l a t i o n Temperature (K)
Figure 3. Distribution of atomic groups in Fr-Pwith distillation temperature: (CH) aliphatic methine group; (CH,) aliphatic methylene group; (CH,) aliphatic methyl group.
520 570 620 D i s t i l l a t i o n Temperature (K)
Figure 5. Distribution of atomic groups in Fr-D1 with distillation temperature: (AC) aromatic conjunction carbon; the others are same as in Figure 4.
a2 bl
$
15
; 7
10
0
a
2
0
f
5 0 470
a
u 520 570 620 D i s t i l l a t i o n Temperature (K)
Figure 4. Distribution of atomic groups in Fr-M with distillation temperature: (AH) aromatic protonated carbon; (AS) aromatic substituted carbon; others are same as in Figure 3.
each fraction obtained by this analysis are summarized in Table VI. These values will be useful for the estimation of some physical properties, such as density, reported in the following paper." (17) Calculation of Molar Volume of Hydrocarbons in Co$ Derived Liquids by a Group Contribution Method.Energy Fuels, follomg paper in this issue.
5
0 470
520 570 620 D i s t i l l a t i o n Temperature (K)
Figure 6. Distribution of atomic groups in Fr-D2 with distillation temperature. Screen area indicated same as in Figure 4.
Distributions of the Atomic Groups with Distillation Temperature for Each Compound Class Fraction. The changes in the distributions of the six primary atomic groups in Fr-P, M, D1,and D2 with distillation temperature are shown in Figures 3-6. In Fr-T, they are not shown due to lack of enough data. Generally, the total carbon numbers increase with the distillation temperature. The number of aromatic substituted carbons increases in
Determination of Atomic Groups of Hydrocarbons
470
490
510
530
550
570
590
610
Distillation Temperature ( K )
Figure 7. Changes of the naphthenic ring numbers with distillation temperature for each compound claas: (m) F’r-P (X) F’r-M, ( 0 )Fr-D1; (A)Fr-D2.
contrast with the decrease of the aromatic protonated carbons, because the numbers of aromatic carbons and aromatic conjunction carbons have constant values throughout the above-mentionedHPLC separation. These facts indicate that the aliphatic substituted groups increase with the distillation temperature. Among aliphatic carbons, the numbers of aliphatic methyl groups are almost constant. On the other hand, the aliphatic methylene groups increase with the distillation temperature, except for Fr-D2. They are one of the constituent groups of naphthenic rings. Though the increase or decrease of naphthenic rings is due to the changes in aromatic substituted carbons, aliphatic methine groups and aliphatic methyl groups clarified from the eqs 23-25, it is believed that the numbers of naphthenic rings increase with the distillation temperature. Their variation with the distillation temperature are shown in Figure 7. In fact, although there is some scatter, the number of naphthenic rings increases with the distillation temperature, except for Fr-P. Fr-P are remarkably decreased in the high temperature range of distillate. This fact might indicate that the levels of normal paraffins in Fr-P are increased with the distillation temperature because the number of aliphatic methyl groups has constant values while the number of aliphatic methine groups has decreased.
Conclusion A systematic structural analysis by high performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR) was proposed to establish an atomic group analysis of a coal-derived liquid for the estimation of ita physical properties according to the contribution method. HPLC has been used for the separation of hydrocarbons into compound classes, according to the number of aromatic rings. The structural analyses of these compound classes were performed by using ‘H and 13C NMR. The chemical structures of the compound classes are characterized by seven atomic groups, that is, aliphatic methyl groups, aliphatic methylene groups, aliphatic methine groups, aromatic protonated carbons, aromatic substituted carbons, aromatic conjunction carbons, and naphthenic rings. The relationship between the chemical structure of components and their physical properties will facilitate the utilization of coal-derived liquids and the estimation of their physical and thermal properties. Acknowledgment. We are very grateful to the New Energy Development Organization (NEDO),Japan, for the supply of coal derived liquid for this study. Appendix The calculations of the numbers of some atomic groups are somewhat hard to understand. In this section, we describe the derivations of these equations briefly.
Energy & Fuels, Vol. 5, No. 5, 1991 637 Equations 1-11 are directly defined from the forms of aliphatic methyl groups, aromatic protonated carbons, aromatic substituted carbons, and aromatic conjunction carbons in a molecule. Equations 12, 14, and 15 are clarified by definition. Using the 2 number, the molecular formula of hydrocarbons is represented as C,H2n+z. Since the aromatic ring numbers of each compound class are limited by HPLC separation, the decrease of 2 number means the increase of naphthenic ring number (nm) in the absence of olefinic double bonds. In Fr-P, the relationship beheen 2 number and nNR is expressed as follows = 2(1 - nNR) (AI) The formation of naphthenic ring increases the number of aliphatic methine groups by 2, and the existence of an aliphatic methyl group in a branching chain also increases it by 1. Thus Cn*cH = 2 n m + (Cn*CHs - 2) (A2) Then eq 13 is derived from eqs A1 and A2. Equation 16 is obtained by the transposition of n*cH and ~*cH terms ~ in eq 14. Next, if both side of eq 14 are multiplied by n*CHz and rearranged
where
In the same way, if both side of eq 14 are multiplied by n*CH and rearranged
where n*CH1 + n*CH
..
n*CH* + n*CH =2-x n*CH = (c,/c - n*cHS)(2 -
x)
(19)
Equation 18 is derived by substituting eq 12 for (13) and rearranging. Finally, the number of naphthenic rings is obtained as follows. In Fr-P, eq 23 is derived from eq A2. In Fr-M,Dl and T, the formation of naphthenic ring increases the number of aromatic substituted carbons (nu) by 2, or the number of aliphatic methine groups (nCH)by 2, or the numbers of n u by 1and ~ c Hby 1. And the existence of aliphatic methyl group in a alkyl side chain also increases the number of AS, or nCH, by 1. Thus ~ N = R AS + ~ C H~ c H J / ~ (24) In Fr-D2, as shown in Figure 2, the aromatic bridgehead carbons were defined as the aromatic substituted carbons. So, even if the naphthenic ring is absent, there are two aromatic substituted carbons in Fr-D2. Consequently, in the calculation of nm,the number of aromatic substituted carbons should be decreased by 2. Thus nNR = ( n A S + nCH - nCH3)/2 - 1 (25)
