Ruthenium tetroxide catalysed oxidation of illinois no.6 coal and some representative hydrocarbons

Short Communications

species, such as oxygen, are important linewidths in the coals.

in effecting the

ACKNOWLEDGEMENT The authors thank the Department of Energy, Mines and Resources for a grant under the Research Agreement Program No.184/2/81, which enabled this investigation to be carried out.

31

3

”

8

3

’ 4

a

8

13

”

“‘1

5 %

REFERENCES

6

Retcofsky, H. L., Stark, J. M. and Friedel, R. A. Anal. Chem. 1968,&J, 1699 Elofson, R. M. and Schultz, K. F. in ‘Spectrometry of Fuels’, (Ed. R. A. Friedel), Plenum Press, New York, 1970, 202 Retcofsky, H. L., Stark, J. M. and Friedel, R. A. Chem. Znd. (Ion&n) 1967, 1372 Toyoda, S., Sugawara, S. and Honda, H. J. Fuel Sot. Japan 1966,45, 876 Toyoda, S. and Honda, H. Carbon 1966,3,527 Retcofsky, H. L. in ‘Chemistry of Coal Utilization’, Second Supp. Vol., (Ed. M. A. Elliot), John Wiley, New York, 1981, 241

Hydrogen

Figure 2 Half-width of the free radical e.s.r. lines vs percentage of hydrogen in the coals, for the samples in the presence of air

hydrogen content, which is opposite to that expected for the effect of hydrogen. Hence, it appears that other atomic

Ruthenium tetroxide catalysed representative hydrocarbons

oxidation

of Illinois

No.6 coal and some

Leon M. Stock and Kwok-tuen Tse Department of Chemistry, The University of Chicago. Chicago, IL 60637, USA (Received 30 December 1982; revised 4 March 1983)

The use of ruthenium tetroxide for the catalytic oxidation of coal molecules under mild conditions has been examined. The selectivity of the reagent for aromatic nuclei has been assessed by a study of the oxidation of selected benzene, naphthalene and phenanthrene derivatives. The catalysed oxidation of Illinois No.6 coal has been studied. The preliminary results described in this report suggest that this oxidant is effective for the selective oxidation of the aromatic structures in this coal. (Keywords:

catalytic

oxidation,

selective

oxidation;

coal structure)

Hayatsu, Scott and Winans recently reviewed the methods suitable for the selective oxidation of coal’. They point out that a variety of reagents are useful for the oxidation of the aliphatic network of these substances, but only one procedure is available’for the oxidation of the aromatic structural components. In this reaction, coal is oxidized in a mixture of hydrogen peroxide and trifluoroacetic acid under refluxzp4. These rather severe conditions are not appropriate for the oxidation of many potentially interesting coal structures and the limitations of this method for the elucidation of the composition of coal have been discussed5T6.

Sharpless and his co-workers demonstrated that these deficiencies could be overcome by the use of a coordinating co-solvent, acetonitrile, for catalytic oxidation reactions*. This procedure has been adapted for the oxidation of coal. Preliminary experiments with Illinois No.6 coal established that it could be oxidized conveniently using a catalytic quantity of ruthenium(II1) chloride trihydrate in a mixture of water, acetonitrile and carbon tetrachloride at ambient temperature with excess sodium bromate, sodium periodate, periodic acid or sodium hypochlorite. The black reaction mixture acquired the appearance of pale green milk in -90 min.

USE OF RUTHENIUM

Tetroxide

TETROXIDE

An alternative method based upon ruthenium tetroxide is described in this report. While it has been known for some time that this oxidant is effective for the oxidation of aromatic structures, its usefulness has been limited by the low conversions realized in many reactions’. However, 0016236l/a3/oa0974-03S3.00 @ 1983 Butterworth & Co. (Publishers) Ltd 974

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and representative

compounds

Typically, the compound (10 mmol) was suspension of sodium periodate (160 mmol, ruthenium(II1) chloride trihydrate (0.1 mmol, a mixture of carbon tetrachloride (20 ml), (20 ml) and water (30 ml) and the mixture

added to a 34.2 g) and 26.1 mg) in acetonitrile was stirred

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vigorously for 12-16 h. Excess sodium periodate and sodium iodate were collected by filtration and the filtrate was either extracted with ether or concentrated to obtain the reaction products. These products were then methylated with diazomethane before analysis by chromatographic and spectroscopic methods. Experiments with aliphatic molecules such as decane, butyric acid, succinic acid and adipic acid and with aromatic carboxylic acids such as benzoic acid, 4-pentylbenzoic acid, phthalic acid and homophthalic acid established that more than 95% of each compound could be recovered unchanged from the oxidation reaction. The results for other more reactive molecules are summarized in Table 1.

Table 1 The results of representative oxidation reaction?

Compound

Conversion (%)

ruthenium

(VIII)

catalysed

Results Product distribution

1%)

I-Phenylpropane

76

Butyric acid, 95 Propiophenone, 5 Propionic acid, trace

2-Phenylbutane

76

2-Methylbutyric acid, 95 2-Phanyl-2-butanol, 1

1-Phenyltridecane

70

Tetradecanoic acid, 91 Tetradecanophenone, 9

Tetralin

100

Adipic acid, 75 1 -Tetralone, 8 Glutaric acid, 17

lndan

106

Glutaric acid, 77 1 -Indanone, 16 Succinic acid, 7

Bibenzyl

75

Succinic acid, 35 Hydrocinnamic acid, 63 Deoxybenzoin, trace Benzil, trace

Diphenylmethane

80

Benzoic acid, 4 Phenylacetic acid, 41 Benzophenone, 32

4-Pentylbiphenyl

74

Valerie acid, trace Caproic acid, 51 Benroic acid, 54 4-Pentylbenzoic acid, 38 (4-PhenylphenylIbutyI ketone, 3

I-Butylnaphthalene

90

Butyric acid, trace Valerie acid, 48 Phthalic acid, 49 3-Butylphthalic acid, 43

Phenanthrene

9,10-Dihydrophenanthrene

100

81

Phthalic acid, 5 Diphenic acid, 91 Phenanthrenequinone, 4 1,2-Naphthalenedicarboxylic acid, traceb Succinic acid, 2 Phthalic acid, 7 3-(2Carboxyphenyl)propionic acid, 32 Diphenic acid, 55

a All the reactions were performed as described in the text, and the products were identified by comparison of their properties with those of authentic samples b Tentative identification

RESULTS The results presented in Table 1 and previous observations’,’ indicate that aromatic compounds with activating hydroxy or methoxy groups are rapidly oxidized (CH&H,OH+CH,CO,H + CO, + H,O) and that alkylaromatic compounds such as 4pentylbiphenyl and lbutylnaphthalene are converted to alkanoic acids and alkylbenzoic acids. Substituent alkyl groups are not oxidized under the reaction conditions and compounds such as indan and tetralin are converted predominantly to the corresponding alkanedicarboxylic acids. Aromatic compounds with bridging methylene groups are oxidized to carbonyl compounds and arylacetic acids (ArCH,Ar -+ArCOAr + ArCH,CO,H). The pattern of reactivity is a relatively simple one from which rather secure structural information can be obtained. Illinois No.6 coal from the Peabody mine in Pawnee, Illinois [70.91%C, 5.18%H, 0.62%N, O.l4%Cl, 2.71% organic S, 0.82% pyritic S, 0.00% sulfate, 8.19% ash, and 11.43x0 (by difference)] was prepared for oxidation as described by Hayatsu, Winans, Scott and McBeth”. A sample (-325 mesh, 4.0 g) was oxidized as described in the previous paragraph to yield a pale green heterogeneous reaction mixture. The oxidation product was almost completely soluble in dilute sodium hydroxide, but only = 10% soluble in ether. In one experiment, the reaction mixture was worked up to provide samples of the volatile carboxylic acids. Acetic, propionic and butyric acids were the only simple carboxylic acids isolated from the reaction mixture. Preliminary quantitative data suggest that = 1% of the carbon atoms in this coal were converted to these three acids. In another experiment, the reaction mixture was treated with excess diazomethane providing 2.56 g of dichloromethane-soluble material and 0.25 g of insoluble material. In a third experiment, 3.3 g of carbon dioxide were collected following the acidification of the reaction mixture. Analytical data indicate that not less than 80% of the carbon atoms in the original coal have been accounted for in these products.

CONCLUSIONS The methylated reaction products have been studied by proton and carbon n.m.r. spectroscopy and by high resolution mass spectrometry. The initial results clearly establish that this oxidation method provides a manageable mixture of monobasic and dibasic aliphatic carboxylic acids and aromatic and heteroaromatic carboxylic acids some of which bear alkyl.groups. The quantitative results will be presented in a subsequent report. All of the information acquired in this preliminary study supports the view that the principal aliphatic structural components have been preserved in the reaction products. The suitability of the method for the oxidation of other coals and related materials is now under study.

REFERENCES 1 2 3

R., Scott, R. G. and Winans, R. E. in Oxidation in Organic Chemistry, (Trahanovsky, W. S., Ed.), Academic Press, NY, Part D, 1982 Deno, N. C., Greigger, B. A. and Stroud, S. G. Fuel 1978,57,455 Deno, N. C., Curry, K. W., Greigger, B. A., Jones, A. D., Rakitsky, W. G., Smith, K. A., Wagner, K. and Minard, R. D. Fuel 1980,69, Hayatsu,

694

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Deno, N. C., Jones, A. D., Koch, C. C., Minard, R. D., Potter, T., Sherrard, R. S., Stroh, J. G. and Yevak, R. J. Fuel 1982,61,490 Liotta, R. and Hoff, W. S. J. Org. Chem. 1980, 45, 2887 Hessley, R. K., Benjamin, B. M. and Larsen, J. W. Fuel 1982,61, 1085 Lee, D. G. and van der Engh, M. in Oxidation in Organic Chemistry,(Trahanovsky, W. S., Ed), Academic Press, NY, Part

5 6 7

Thermodynamics the Bolles-Drago

B, 1973 and references therein Carlsen, P. H. J., Katsuki, T., Martin, V. S. and Sharpless, K. B. .I. Org. Chem. 1981,46, 3936 Spitzer, U. A. and Lee, D. G. J. Org. Chem.1974,39,2468 Hayatsu, R., Winans, R. E., Scott, R. G. and McBeth, R. L. Fuel

8 9 10

1981,66,

158

of hydrogen bonding in coal-derived approach applied to mixtures

Orville R. Weyrich, Jr. and John W. Larsen Department of Chemistry, University of Tennessee, Knoxville, TN 37996, (Received 17 June 1982; revised 13 October 1982)

liquids.

Failure

of

USA

The validity of using the Belles-Drago technique to calculate thermodynamic functions for the hydrogen bonding interactions of an acid with a pair of bases was tested by computer. Sets of ‘data’ were calculated for five cases having different enthalpies and free energies of association and these ‘data’ were used in the Belles-Drago treatment to recalculate the thermodynamic perameters. If the enthalpies and free energies of association of the acid with the two bases are different, the Belles-Drago treatment fails. (Keywords:

coal-derived

liquids; thermodynamics;

The association of the various molecular constituents of coal-derived liquids is important. Recently, a series of papers ’ -6 has appeared in which the thermodynamics (AG, AH, and AS) of hydrogen bonding in coal-derived mixtures was measured using a technique developed for 1:l interactions by Bolles and Drago’. It was assumed that for these mixtures the Bolles-Drago treatment would give values for the equilibrium constant, K, and the enthalpy, AH, that represented the ‘total interaction’ between the mixture and the added acid or base. While ‘total interaction’ was not defined, the discussion indicated that the number average values for K and AH were the anticipated result. A study was therefore made of the application of the Bolles-Drago treatment to complexes formed simultaneously between a single acid and a pair of bases: HA + B=B.. .HA

(1)

HA + D=D..

(2)

.HA

Except in very limited special cases, the treatment used does not result in an accurate thermodynamic description of this simple system and is also expected to fail for the more complex situations studied’ -6. The five cases shown in Table 1 were considered. For all

Table

1 AH and K values for 5 test cases

Case

K0

1

50 50 25 25 25

2 3 4 5

KD

AH9

50 50 75 75 75

-5.0 -2.5 -5.0 -2.5 -7.5

001~2361/83/08097&02$3.00 @ 1983 Butterworth & Co. (qublishers) Ltd 976

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A”D -5.0 -7.5 -5.0 -7.5 -2.5

hydrogen

bonding;

viscosity)

cases, the number average Kavg and AHa_ is K = 50.0mol-1dm-3andAH=-5.0kcalmol-‘.Acomputer program’ was written to calculate experimental data from the ‘results’ given in Table 1; these data then were used in the Bolles-Drago treatment in an attempt to regenerate the correct ‘results’. For each case 496 data pairs were considered. The rounded values for AH,,, and Kavg calculated from each of the 496 data pairs for each of the 5 cases are given in Tables 2 and 3. If the treatment works as is assumed’ -6, each data pair should yield Kavg= 50 and AHa_ = - 5. It is clear from the results that the Bolles-Drago approach works unfailingly only when the equilibrium constants for the two bases are identical. Its performance when the K values are different and AH is the same for both bases (case 3) is probably acceptable for AH, but fails for K. However, if both K and AH are different, as

Tab/e 2 Number of calculated rounded 496 data pairs for the five cases

values for

AHavs

from

AHavg

Case 1

Case 2

Case 3

Case 4

Case 5

-10 -9 -6 -7 -6 -5 -4 -3 -2 -1

0 0 0 0 0 494 0 0 0 0 0 0 0

0 0 0 0 0 494 0 0 0 0 0 0 0

0 0 0 0 0 494 3 4 0 0 2 0

0 5 36 21 111 247 17

1 0 3 1 19 227 118

a

44

7 9 9 0

2

2

12 0

26 0

8 4 30 1 40

0 >o

Complex roots Coincident lines

0