aqueous organic chemistry. 6. reactivity of hydroxynaphthalenes

Energy & Fuels 1993, 7, 589-597 589

Aqueous Organic Chemistry. 6. Reactivity of Hydroxynaphthalenes

Michael Siskin," Glen Brons, and Stephen N. Vaughn

Corporate Research Science Laboratory, Exxon Research and Engineering Company, Annandale, New Jersey 08801

Alan R. Katritzky,' Marudai Balasubramanian, and John V. Greenhill

Department of Chemistry, University of Florida, Gainesville, Florida 3261 1-2046

Received March 18, 1993. Revised Manuscript Received May 26, 1993

Hydroxyaromatics are abundant in lignite and subbituminous coals. Cleavage of ethers in coals generates additional hydroxyaromatics. Reduction of the carbonyl intermediates of these hydroxyaromatics in 15 % formic acid or 15 % sodium formate provides hydrogenated species which can act as hydrogen donors during coal liquefaction. At 315 "C over a period of 3 days, 1- and 2-hydroxynaphthalenes showed little change under simple thermolytic or aquathermolytic conditions. These compounds underwent reduction to a small extent on aquathermolysis in 15% formic acid and to a larger extent in 15% sodium formate. 1,2-, 1,3-, 1,4-, and 2,3-Dihydroxynaphthalenes were all highly reactive at 315 "C in all four systems (cyclohexane, water, 15% formic acid, and 15% HCOzNa). The major products resulted from dehydroxylation or decarbonylation followed by ring opening, and self-condensation. In the presence of reducing agents (HCOzH or HCOZNa), large amounts of indane, tetralin, naphthalene, and methylated hydroxynaphthalenes resulted. 1,4- Dimethoxynaphthalene underwent ether cleavage and was transformed into various mono- and dihydroxynaphthalenes. Some of the hydroxynaphthalene products had been C-methylated. In the presence of HCOZNa, large amounts of reduction products were obtained.

Introduction

The relationship of coal liquefaction behavior to coal structure has been a subject of study for several years, particularly with respect to loss of oxygen.14 Most common liquefaction media employ an H-donor compo- nent such as tetralin, which transfers hydrogen to the coal. In such a medium, the coal is depolymerized and reduced to yield a more soluble, lower molecular weight product with a higher H/C atomic ratio. Thermal treatments of coal in H-donor media always yield the product contam- inated with the solvent through chemical incorporation. Conversions conducted in a carbon monoxide/ water system circumvent this problem because the medium is totally inorganic and yields an organic product which is derived solely from the coal.

The results of several studies show that conversions in CO/HzO systems generally decrease with decreasing oxygen content of the starting goal. Appell et al.,5 using synthesis gas (Hz and CO) and water, found that lignite underwent higher conversion when compared to a bituminous coal. Ouchi and Takemura,G using a CO/HzO system and a cobalt-molybdenum catalyst, found that

(1) Szladow, A. J.; Given, P. H. Prep. Pap.-Am. Chem. SOC., Diu. Fuel Chem. 1978,23, 161.

(2) Youtcheff, J. S.; Given, P. H. Fuel 1982, 61, 980. (3) Youtcheff, J. S.; Given, P. H. Prep. Pap.-Am. Chem. SOC., Diu.

Fuel Chem. 1984,29, 1. (4) Whitehunt, D. D. In Organic Chemistry of Coal; Larsen, J. W.,

Ed.;ACSSymposiumSeries 71;AmericanChemicalSociety Washington, DC, 1978; pp 10-35.

(5) Appell, H. R.;.Miller, R. D.; Illig, E. G.; Moroni, E. G.; Steffgen, F. W. 'Coal Liquefaction in Synthesis Gas"; U S . Department of Energy Representative PETCITR-79, Technology Information Center, U.S. Department of Energy, Washington, DC.

(6) Ouchi, K.; Takemura, Y. Fuel 1983,62,1133.

Q887-0624/93/25Q7-Q589$Q4.Q0/Q

conversion decreased with increasing carbon content for a series of coals ranging from 50% to 90% carbon. Oelert and Siekmann7 found that conversion increased with increasing O/C ratio of the starting material. These results, taken together, suggest that oxygen functionalities strongly influence the conversion behavior of the coal. It was found' that roughly 40% of the oxygen in coal was phenolic. The remaining 60 % , referred to as unaccounted oxygen, was assumed to be etheric. I t was noted that the main oxygen loss during conversion was from this "unaccounted oxygen" pool, with considerably smaller losses of phenolic oxygen.

Graff and Brandesa found that steam pretreatment of an Illinois No. 6 bituminous coal between 320 and 360 "C dramatically improves the yield of liquids obtained on subsequent conversion or solvent extraction. The steam modified coals also swelled more in water and contained twice as many hydroxyl groups as the raw coal, leading to the hypothesis that steam reacts with ether linkages in coal forming hydroxyl groups and thereby substantially hydrolyzing an important covalent cross-link in the coal s t r u ~ t u r e . ~ Model compound studies on aryl ether reactivity in hot water to form hydroxyaromatics are consistent with these conclusions.10Jl The concentration of hydroxyaromatics, especially in lower rank coals, is high, and this level is increased by aqueous treatment.

(7) Oelert, H.; Siekmann, R. Fuel 1976,55, 39. (8) Graff, R. A.; Brandes, S. D. Energy Fuels 1987, I , 84. (9) Brandes, S. D.; Graff, R. A.; Gorbaty, M. L.; Siskin, M. Energy

(10) Siskin, M.; Brons, G.; Vaughn, S. N.; Katritzky, A. R.; Balasubra-

(11) Siskin, M.; Katritzky, A. R.; Balasubramanian, M. Energy Fuels

Fuels 1989,3,494.

manian, M. Energy Fuels 1990,4,488.

1991, 5, 770.

0 1993 American Chemical Society

590 Energy &Fuels, Vol. 7, No. 5, 1993

The hydroxyaromatic-keto equilibrium provides carbonyl groups in the coal and coal liquids at low, steady- state levels. McMillenI2 has proposed keto structures as intermediates in the hydrogenolysis of hydroxydiphenyl methanes and ethers in tetralin. Ross13 suggested that the mechanism of coal reduction begins with phenol-keto equilibrium followed by reduction of the carbonyl intermediates by a hydroaromatic structure (free radical) or by hydride ion transfer from formate ion in CO/water (ionic).

Our previous studies11J4 of the aquathermolytic chemistry of diary1 ethers demonstrated that hydroxyaromatics are formed from the ether cleavage reaction and these react via a reductive dehydroxylation mechanism to form polycyclic aromatic hydrocarbons in the presence of 15 % HC02Na. The present paper deals with the aquathermolysis chemistry of various hydroxynaphthalenes in an attempt to sort out the reductive dehydroxylation mechanism. We believe that this pathway represents the underlying mechanism for increasing the H/C atomic ratio during water/carbon monoxide treatments of coals and other low-rank resource materials. In coals, the molecules generated are capable of donating hydrogen during liquefaction.161B It should also be applicable to water/ carbon monoxide treatments of hydroxylated wastewater streams, removal of aromatics from diesel fuel, etc. The model compounds selected for this investigation were l-hydroxynaphthalene (15),2-hydroxynaphthalene (161, 1,2-dihydroxynaphthalene (23), 1,3-dihydroxynaphthalene (27),1,4-dihydroxynaphthalene (13),2,3-dihydroxynaphthalene (25), and 1,4-dimethoxynaphthalene (22). Each was heated (1 g of compound/6 g of solution) at 315 "C under four sets of conditions: (i) in cyclohexane, (ii) in water alone, (iii) in 15 % aqueous formic acid, and (iv) in 15 % aqueous sodium formate. Aquathermolyses under conditions ii-iv were compared with the purely thermal reactions of condition i.

Siskin et al.

with Table IB are available as supplementary material (see paragraph at end of paper regarding supplementary material). The reactions were conducted as previously described21 and the results are collected in Tables III-IX. The major products from all of the reactions are summarized in Tables X and XI.

Experimental Section

1,4Dimethoxynaphthalene (22) was prepared according to the literature procedure (methylation of 1,4-dihydroxynaphthalene using dimethyl sulfate).M The other compounds were obtained from commercial sources. All the starting materials were found by gas chromatography to be of suitable purity (>99 %) and were used without further purification. The gas chromatographic behavior of all the compounds employed for this study (starting materials and products) is summarized in Table I. Table IA (supplementary material) records the source and mass spectral fragmentation patterns of the authentic compounds used, either as starting materials or for the identification of products. Tables IB (supplementary material) and I1 record the mass spectral fragmentation patterns of products for which authentic samples were not available and which were identified by comparison with literature mass spectral data (Table IB), or by deduction (Table 11). Tables IA and IB and mass spectral assignments associated

(12) McMillen, D. F.; Ogier, W. C.; Ross, D. S. J. Org. Chem. 1981,46, 3322.

(13) Ross, D. S. In Coal Science; Gorbaty, M. L., Ed.; Academic Press:

(14) Part 5 of this series: Siskin, M.;Katritzky, A. R.; Balasubramanian, New York, 1984; Vol. 3, pp 329-331.

M. Fuel, in press. (15) Stuntz, G. F.; Culross, C.; Reynolds, S. D. U.S. Patent 5,026,475

(June 25, 1991). (16) Culross, C.; Reynolds, S. D. U.S. Patent 5,071,540 (Dec. 10,1991). (17) Culross, C.; Reynolds, S. D. U.S. Patent 5,110,450 (May 5,1991). (18) Vaughn, S. N.; Siskin, M.; Katritzky, A. R.; Brons, G.; Reynolds,

S. D.; Culross, C.; Neskora, D. R. U.S. Patent 5,151,173 (Sept. 29,1992). (19)Neskora, D. R.; Vaughn, S. N.; Mitchell, W. N.; Culross, C.;

Reynolds, S. D.; Effron, E. U.S. Patent 5,200,063 (April 6, 1993). (20) Sha, P. P. T. Recl. Trau. Chim. 1940,59,1029.

Results and Discussion

The reactions are summarized in eqs 1-16. In the equations, numbers 1100 are used for intermediates which are not detected by the GC-MS system.

l-Hydroxynaphthalene (15) (Table 111). At 315 "C l-hydroxynaphthalene (15) has low thermal reactivity. After 3 days in cyclohexane it showed only 7.3% thermal conversion to give 1,l'-dinaphthyl ether (42) as the only product. Aquathermolysis of 15 for 3 days showed only 9.3% conversion with the major product again 1,l'- dinaphthyl ether (8.0 % ). Byproducts were l-tetralone (10) (1.0%) and traces of tetralin (8) and naphthalene (9). In 15 % HC02H there was still only 10 % conversion with 1,l'-dinaphthyl ether (2.9%), tetralin (2.8%), and l-tetralone (2.0%) prevalent. There were also significant amounts of naphthalene (9, 1.2% ), 1,l'-bisnaphthalene (34,0.2 %),and the ring-methylated hydroxynaphthalenes 19 and 21. In the presence of 15% HCOZNa, the reactivity of 15 was enhanced resulting in 81 % conversion, the major products being naphthalene (38.8% ), tetralin (23.7 96 ), and 1,l'-dinaphthylether (42) (8.5% 1. Theother above-named products were all present in trace amounts along with l-methylnaphthalene (11,2.2% ). The much higher conversion in the presence of the formate salt is consistent with the reduction products observed since the formate ion is known to be a better hydride donor than free formic acid.

Suggested reaction pathways are shown in eqs 1-4 (Scheme I). The methylated hydroxynaphthalenes 19 and 21 probably arise from reductions of intermediate aldehydes 100 and 102 (eq 1). The aldehydes result from the ortho and para formylation of 15 by formic acid. The higher percentage of methylated products in the sodium formate runs indicates the presence of a small proportion of naphthalate anion in the more basic medium. The tautomerism (15 - 103 - 104) is important in several of the transformations. Hydride reduction of the carbonyl group leads via the alcohol 101 and subsequent easy dehydration to naphthalene (9) (eq 2). Reduction of the conjugated double bond of 104 gives the l-tetralone (10) (eq 2). Further reduction gives the alcohol 107 which undergoes acid catalyzed elimination to 112 and a find reduction step to tetralin (8) (eq 2). Equations 3 and 4 also contain suggestions for the formation of the dinaphthyl deriyatives 42 and 34 via nucleophilic attack by the activated carbon at position 4, or the oxygen atom of l-naphthol on tautomer 103.

2-Hydroxynaphthalene (16) (Table IV). 2-Hydrox- ynaphthalene is less reactive than the l-hydroxynaphthalene (15) under both thermal and aquathermal conditions. In cyclohexane over 72 h, at 315 "C, 16 showed <1% conversion to the only product 2-hydroxy-l,l'-bis- (naphthalene) (37) (0.8% ), In general, the aquathermolysis of 2-hydroxynaphthalene was similar to that of

(21) Part 1 of the series: Aqueous High Temperature Chemistry of Carbo- and Heterocycles. Katritzky, A. R.; Lapucha, A. R.; Murugan, R.; Luxem, F. J.; Siskin, M.; Brons, G. Energy Fuels 1990, 4, 493.

(22) Littlewood, A. B. Gas Chromatography (Principles, Techniques and Applications); Academic Press: New York, 1962; p 401.

(23) Alberti Ann. 1926,450, 304. (24) Selman, S.; Eastham, J. F. Q. Rev. Chem. SOC. 1960,14, 221.

Reactivity of Hydroxynaphthalenes Energy & Fuels, Vol. 7, No. 5, 1993 591

Table I. Structure and Identification of Starting Materials and Products ~~ ~ ~ ~~ ~

no. tR,min structure mol w t eq w t identifn basisa response factor 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

5.35 5.85 5.90 6.30 6.50 6.63 6.80 7.00 7.20 7.60 8.12 8.50 8.85 9.30 9.62 9.69 9.72

10.06 10.35 10.53 10.55 10.95 11.08 11.25 11.45 11.59 11.60 12.14 12.24 13.42 13.70 13.82 13.88 13.96 14.45 14.70 14.91 15.18 15.84 15.89 16.03 16.77 16.89

propylbenzene indane indene l-methylindane l-methylindene

l-indanone tetralin naphthalene l-tetralone l-methylnaphthalene 2-tetralone 1,4-dihydroxynaphthalene l-methoxynaphthalene l-hydroxynaphthalene 2-hydroxynaphthalene 2-methyl-l,4-dihydroxynaphthalene l-methoxy-4-methylnaphthalene l-hydroxy-2-methylnaphthalene 2-hydroxy-l-methylnaphthalene l-hydroxy-4-methylnaphthalene 1,4-dimethoxynaphthalene 1,2-dihydroxynaphthalene 1- hydroxy-4-methoxynaphthalene 2,3-dihydroxynaphthalene 1,Gnaphthoquinone 1,3-dihydroxynaphthalene

1,l’- bis(indane) 2-methyl-l,4-naphthoquinone 2-cyclohexyl-l-hydroxynaphthalene 4-cyclohexyl-l-hydroxynaphthalene 1,l’-bis(naphthalene) l-indanyl-l-naphthalene 4-cyclohexyl-l,2-dihydroxynaphthalene 2-hydroxy- 1 , 1’-bis(naphthalene) 2,2’-bia(l,4-dimethoxynaphthalene) 4-hydroxy-l,l’-bis(naphthalene) 4,4’-dihydroxy-l,l’-bis(naphthalene) 2-hydroxy-l-indanylnaphthalene 1,l‘-dinaphthyl ether 2-( 1,3-dihydroxy-2-naphthyl)-l-phenyl-l-pr1

PhCHzCOCHs

PhCOCH(CHs)CH2Ph PhCH(Et)CH(CHs)CHzPh

Table IA and IB are supplementary material.

l-hydroxynaphthalene. Compound 16 showed just 1.3 % conversion (3 days) into naphthalene (9) (0.2%), 2-tetralone (12) (0.3%), and 2-hydroxy-l,2’-bis(naphthalene) (37) (0.8%). After3daysin15% HCOzH, 16showed8.0% conversion to tetralin (1.9%), naphthalene (2.8% 1, 2-tetralone , (1.9 % ) , 2-hydroxy- 1,l’- bis(naphtha1ene) (37) (l.O%),and 2-hydroxy-l-methylnaphthalene (20) (0.4%). Initially formed 2-tetralone evidently undergoes further reduction to naphthalene and tetralin in a way similar to the reactions of eq 2. In the presence of 15% HC02Na, 2-hydroxynaphthalene showed high reactivity (73.6 % conversion) and the major products were again tetralin (28.0%) and naphthalene (33.0%). In addition to small amounts of the other products mentioned above, 0.5% indane (2) was found.

Equations 5 and 6 summarize the main reaction pathways proposed (Scheme 11). The self-condensation probably involves tautomerism (16 - 113) and follows the route shown through 117 and 118 to 37 (eq 5). The routes to 2-hydroxy-l-methylnaphthalene (20) (via formylation/ reduction) and to 2-tetralone (12), tetralin (81, and naphthalene (9) (via tautomer 113) are deduced by analogy with the reactions of eqs 1 and 2. Tautomerism of 111 to 1 10 gives a l,&dione vulnerable to base-catalyzed hydro- lytic ring opening. The intermediate 112 could decar- boxylate, ring close and decarbonylate to indane (2) (eq 6).

>pen

120 118 116 132 130 134 132 132 128 146 142 146 160 158 144 144 174 172 158 158 158 188 160 174 160 158 160 224 238 234 172 226 226 254 244 242 270 374 270 286 260 270

le 276

120 118 116 132 130 134 132 132 128 146 142 146 160 158 144 144 174 172 158 158 158 188 160 174 160 158 160 224 238 234 172 226 226 127 122 242 135 187 135 143 130 135 133

Table IA Table IA Table IA Table IB Table IB Table IB Table IA Table IA Table IA Table IA Table IA Table IA Table IA Table IA Table IA Table IA Table IB Table IB Table IB Table IB Table IB Table IA Table IA Table IB Table IA Table IA Table IA Table I1 Table I1 Table I1 Table IB Table I1 Table I1 Table IB Table I1 Table I1 Table I1 Table I1 Table I1 Table I1 Table I1 Table IB Table I1

Dihydroxynaphthalenes. All

0.95 0.95 0.95 0.95 0.95 0.78 0.77 0.95 0.95 0.77 0.95 0.77 0.59 0.75 0.77 0.77 0.58 0.74 0.76 0.76 0.76 0.55 0.59 0.57 0.59 0.60 0.59 0.74 0.91 0.91 0.60 0.74 0.74 0.89 0.89 0.61 0.72 0.10 0.72 0.54 0.71 0.70 0.72

the dihydroxynaph- . -

thalenes investigated were much more reactive than the monohydroxynaphthalenes, so that all reactions were conducted at 315 OC for only 2 h. Reference to Tables I11 and IV shows that monohydroxynaphthalenes are virtually unchanged by 2 h heating at 315 O C . Thus, the consid- erable quantities of 1- and 2-hydroxynaphthalenes produced from the various dihydroxynaphthalenes are final products and cannot be indicated as intermediates for the formation of other products.

l&Dihydroxynaphthalene (23) (Table V) (Eqs 7-9). Compound 23 showed moderate reactivity (19.0% conversion) under aqueous conditions but was more reactive thermally (83.2% conversion). The main products from the cyclohexane reaction were l-hydroxynaphthalene (15) (17.2%) and 2-hydroxynaphthalene (16) (51.8%). By reaction with the solvent, 2-cyclohexyl-l-hydroxynaphthalene (32) (3.0 % ), 4-cyclohexyl-l-hydroxynaphthalene (33) (3.7 % ), and 4-cyclohexyl-1,2-dihydroxynaphthalene (36) (4.4 % ) were produced. Finally, self-condensation of l-naphthol gave 1,l’-dinaphthyl ether (42) (3.0% 1. In water, 23 gave mainly 2-hydroxynaphthalene (15) (14.5% ) and there were trace amounts of l-hydroxynaphthalene (16) (1.9%), l-tetralone (10) (l.l%), 2-tetralone (12) (0.5%), and l-indanone (7) (1.0%).

With 15 % formic acid, 23 showed 100% conversion, the major product being 2-hydroxynaphthalene (16) (90.1 9%)

592 Energy & Fuels, Vol. 7, No. 5, 1993 Siskin et al.

Table 11. Identification of Products from Mass Swctral Fragmentation Pattern

no. compound fragmentation pattern m/z

(% relative intensity, structure of fragment ion) MW 28 PhCOCH(CH&H2Ph

29 PhCH(Et)CH(Me)CHzPh

30 1,l’-bis(indane)

32 2-cyclohexyl-1-hydroxynaphthalene

33 4-cyclohexyl-1-hydroxynaphthalene

35 1-indanyl-1-naphthalene

36 4-cyclohexyl-l,2-dihydroxynaphthalene

37 2-hydroxy-l,l’-bis(naphthalene)

38 2,2’-bis(l,4-dimethoxynaphthalene)

39 4-hydroxy-l,l’-bis(naphthalene)

40 4,4’-dihydroxy-l,l’-bis(naphthalene)

41 1-indanyl-2-hydroxy-naphthalene

43 2-(1,3-dihydroxy-2-naphthyl)-l-phenyl-l-propene

224

238

234

226

226

244

242

270

374

270

286

260

276

224 (25, M); 119 (100, M-PhCO); 105 (50, M-CeHii); 104 (30, C a s ) ;

238 (40, M); 133 (5, M-C&); 105 (15, C&); 92 (85, PhCHa); 91 (15, C7H7+); 77 (30, Ph); 65 (25)

91 (100, C,H,+); 77 (15, Ph+); 65 (10) 234 (30, M); 117 (100, CgHg+); 116 (20, CgHB); 115 (30, CgH,+);

91 (15, C,H,+): 77 (20, Ph): 65 (10) 226 (100,’M); 208 (5, M-H20j; 183 (40, M-CsH7); 165 (20), 157 (80,183-CzHz);

156 (10); 144 (15, M-CeHio); 115 (20,144-CHO); 102 (10, CeHB); 77 (5, Ph) 226 (100, M); 197 (5, M-CzHs); 183 (45, M-CaH7); 157 (50,183-CzHz);

144 (10, M-C&iO); 115 (25,144-CHO) 102 (5, C h ) ; 77 (10, Ph)

128 (15, M-CgHe); 116 (60, CeHB) 115 (40, C9H7); 103 (5); 102 (5); 91 (15, C7H7); 64 (10); 63 (5)

242 (100, M); 160 (25, M-CeHio); 144 (30,160-0); 131 (10,160-CHO); 115 (25,144-CHO); 114 (5,144-CHz0); 103 (5, Ca7) ; 77 (5, CeH5); 76 (20, CeHd

244 (100, M); 229 (40, M-CH3); 228 (15,229-H); 202 (10,228-CzHd;

270 (100, M); 269 (50, M-H); 241 (35, M-CHO); 240 (15, M-CHzO); 239 (35,240-H); 237 (10); 215 (15); 187 (5); 163 (5); 126 (5, C&); 119 (10); 94 (5)

298 (20,313-CHs); 270 (10,298-CO) 187 (10, M-Ci2Hii02); 172 (20, 187-CH3); 76 (10, CeH4)

239 (40,240-H); 215 (5); 119 (10)

374 (100, M); 359 (25, M-CHs); 328 (95,359-OCHd; 313 (50,328-CHd;

270 (100, M); 269 (20, M-H); 241 (30, M-CHO); 240 (15, M-CH20);

286 (100, M); 287 (20, M-H); 268 (15, M-H20); 257 (25, M-CHO); 239 (15,268-CHO); 228 (15) 202 (10); 143 (5, M-Cid70); 128 (10, CloHe); 115 (10, CgH7); 89 (5); 63 (15); 72 (5)

116 (90, M-CioHBO); 115 (50, CgH7); 89 (10); 63 (5)

91 (50, C7H7); 65 (10, CSHS); 63 (5)

260 (100, M); 245 (20, M-CHs); 231 (10, M-C2Hs); 144 (25, M-Cgh);

276 (20, M); 157 (10, M-CgHii); 119 (100, CgHii); 118 (10, C9Hio);

Table 111. Products of Aauathermolysis of 1-HydroxunaDhthalene (15) at 315 “C

no. structure

solvent cyclohexane water 15% HCOzH 15% HCOzNa

2 h 72 h 2 h 72 h 2 h 72 h 2 h 72 h 8 9

10 11 15 19 21 34 42

tetralin naphthalene 1-tetralone 1-methylnaphthalene 1-hydroxynaphthalene 1-hydroxy-2-methylnaphthalene 1-hydroxy-4-methylnaphthalene 1 , 1’-bis (naphthalene) 1,l’-dinaphthyl ether

- 0.2 0.2 0.2 0.1 0.2 0.3 1.0 0.6

98.3 90.7 99.0 - - - - - - - - - - - - 1.2 8.0 -

2.8 1.2 2.0

90.0 0.4 0.5 0.2 2.9

-

Table IV. Products of Aquathermolysis of 2-Hydroxynaphthalene (16) at 315 O C

3.0 4.0 1.0

90.0 - - - - 2.0

23.7 38.8 2.5 2.2

19.0 1.6 3.1 0.6 8.5

solvent ~ ~~ ~

cyclohexane water 15% HCOnH 15% HCOaNa ~~

no. structure 2 h 72 h 2 h 72 h 2 h 72 h 2 h 72 h 2 indane - - 8 tetralin - - 9 naphthalene - -

12 2-tetralone - - 16 2-hydroxynaphthalene 99.6 99.2 20 2-hydroxy-1-methylnaphthalene - - 37 2-hydroxy-l,l’-bis(naphthalene) 0.4 0.8

and minor products 1-hydroxynaphthalene, 1- and 2-te- tralones, naphthalene, tetralin, indane, and indene. In the presence of 15 5% HC02Na, 23 showed 96.3 % conversion to give a long slate of products, foremost among which were the 1- and 2-hydroxynaphthalenes (8.1 and 42.6% respectively), tetralin (19%)) naphthalene (11.2%), and indene (7.7 ’% 1.

The most important reaction is dehydroxylation. Under all conditions, more 2-hydroxynaphthalene (16) is produced than 1-hydroxynaphthalene (15). The ratio is probably controlled by the reduction of an intermediate tautomeric form of the dihydroxy derivative: one possi- bility is shown (eq 7 ) (Scheme 111). The reducing agent

- - - - - 0.5 0.1 1.9 2.0 28.0

0.2 0.2 2.8 0.8 33.0 0.3 0.2 1.9 0.9 0.5

99.9 98.7 99.0 92.0 95.7 36.4 0.5 0.4 0.8

0.1 0.8 1.0 0.6 0.8

- - - -

- - - -

is formic acid or formate anion, or in their absence, another molecule of 23. a-Tetralone (lo), tetralin (8), and naphthalene (9) evidently arise from a distinct but probably similar path we suggest reduction of the intermediate dione (119).

The methyl derivatives 1-hydroxy-2-methylnaphthalene (19) and 1-hydroxy-4-methylnaphthalene (21) undoubtedly arise by initial formylation and reduction of the formyl group to methyl. The route to bis(a-naphthyl) ether 42 is unknown.

The generation of the cyclohexyl-substituted hydroxynaphthalenes 32,33, and 36 depends upon the production of the cyclohexyl radical. It is likely that the semiquinone

Reactivity of Hydroxynaphthalenes Energy & Fuels, Vol. 7, No. 5, 1993 593

Table V. Products of Aquathermolysis of If-Dihydroxynaphthalene (23) at 315 OC for 2 h solvent

no. structure cyclohexane water 15% HCOzH 15% HCO2Na - - 2 indane 0.4 0.1

3 indene 0.1 7.7 4 1-methylindane 0.3 7 1-indanone 1.0 0.2 8 tetralin 1.0 19.0 9 naphthalene 0.5 11.2 10 1-tetralone 1.1 3.4 0.3 12 2-tetralone 0.5 2.0 2.6 15 1- hydroxynaphthalene 17.2 1.9 2.5 8.1 16 2-hydroxynaphthalene 51.8 14.5 90.1 42.6

1.0 21 1-hydroxy-4-methylnaphthalene 0.5

- - - - - - - - - - - - -

- - 19 1-hydroxy-2-methylnaphthalene -

23 1,2-dihydroxynaphthalene 16.8 81.0 3.7 32 2-cyclohexyl-1-hydroxynaphthalene 3.0 - - - 33 4-cyclohexyl-1-hydroxynaphthalene 3.7 - - - 36 4-cyclohexyl-1,2-dihydroxynaphthalene 4.4 - - -

- - - -

- - 42 1 , 1’-dinaphthyl ether 3.0 2.6

Table VI. Products of Aquathermolysis of 1,3-Dihydroxynaphthalene (27) at 315 OC for 2 h

no. structure solvent

cyclohexane water 15% HCOiH 15% HCOPNa 1 5 6 8 9 10 15 16 19 21 27 28 29 43

propylbenzene 1-methylindene

tetralin naphthalene 1-tetralone 1-hydroxynaphthalene 2- hydroxynaphthalene 1- hydroxy-2-methylnaphthalene 1-hydroxy-4-methylnaphthalene 1,3-dihydroxynaphthalene PhCOCH(Me)CHaPh PhCH(Et)CH(Me)CHzPh 24 1,3-dihydroxy-2-naphthyl)-l-phenyl-l-propene

PhCH2COCHa

5.5

9.5 - - - -

20.5

14.1

50.9

- -

- - -

0.5 1.1

41.3 - - 0.1

11.4

1.5

34.3

- - - - 9.5

___

2.5

40.4

0.3 0.5

18.3 4.0 0.2 1.2

21.2 1.4 1.0 8.8

- -

3.3

53.6 1.5 0.2

11.5 0.8 3.0

21.2

1.0 3.8

-

-

-

-

Table VII. Products of Aquathermolysis of 1,4-Dihydroxynaphthalene (13) at 315 OC for 2 h solvent

no. structure cyclohexane water 15% HCOzH 15% HCOgNa 2 indane - 3 indene - 5 1-methylindene - 7 1-indanone - 8 ktralin - 9 naphthalene - 10 1-tetralone 13 1,4-dihydroxynaphthalene 55.5 15 1-hydroxynaphthalene 32.4 19 1-hydroxy-2-methylnaphthalene - 21 1-hydroxy4methylnaphthalene - 26 1,4-naphthoquinone 12.1 39 4-hydroxy-l,l’-bia(naphthalene) - 40 4,4’-dihydroxyl,l’-bis(naphthalene) -

-

radical (127) would form readily under the conditions employed and that exchange with the solvent would convert some C6H12 into C&1*. This attacks the various hydroxynaphthalenes at the most electron-rich positions

The formation of 1-methylindane (4) probably occurs after a benzoin-type rearrangement 119 - 123 and the formation of 1-indanone (7) after a benzilic acid rear- rangement13 119 - 129. Further reduction of 7 and then dehydration leads successively to 1-hydroxyindane and indene (eq 9). 1,3-Dihydroxynaphthalene (27) (Table VI) (eqs 10

and 11). 27 was also very reactive under all conditions and we report reactions run for 2 h at 315 OC. In general, 1,3-dihydroxynaphthalene displayed two major reaction types, conversion to 1-hydroxynaphthalene (15) and ring opening to 2-phenylpropanone (6) and propylbenzene (1).

(eq 8).

0.7 2.6

14.2 - - - -

10.1 70.2 - - 2.0 - -

- - - - 0.9 0.8 3.5 3.4

83.6 0.7 0.7 3.0 1.7 1.7

6.8 0.8 0.7

9.0 14.3 1.0

49.7 1.4 1.3 8.4 5.2 1.4

-

-

In cyclohexane (49% conversion), the only other product was 2-methyl-1-hydroxynaphthalene (19) (14.1 %). In water (65.7% conversion), the same products were obtained plus dimeric product 43 (9.5 % ) and two other compounds. In 15 9% HCOOH there was 78.8 9% conversion to the same slate of products with some further minor products including ring-opened compounds notably the 2-substituted derivative 43 (8.8%). The sodium formate product slate (100% conversion) was similar to the formic acid result, but 43 was absent. Our suggested reaction pathways are given in eqs 10

and 11 (Scheme IV). Conversion to 1-hydroxy- (15) and 2-hydroxynaphthalene (16) probably occurs by reduction of dione tautomer 130 (eq 10): the 3-keto group in 130 is expected to be more easily reduced than the 1-keto group which explains the predominance of 15 over 16. The formation of tetralin (81, naphthalene (91, and 1-tetralone

594 Energy & Fuels, Vol. 7, No. 5, 1993 Siskin et al.

Table VIII. Products of Aauathermolvsis of 2.3-Dihvdroxunaehthalene (25) at 315 OC for 2 h ~ ~ ~~~~

solvent no. structure cyclohexane water 15% HCOzH 15% HC02Na

- - 2 indane 0.3 14.8 3 indene 0.2 8.9

tetralin 0.7 9 naphthalene - - - 9.7 8

12 2-tetralone 1.0 16 2-hydroxynaphthalene 43.1 24.5 70.2 52.6 20 2-hydroxy-1-methylnaphthalene 0.5 1.1 25 2,3-dihydroxynaphthalene 56.9 75.5 27.3 7.8

1 , 1’-bis (indane) 1.0 35 1-indanyl-1-naphthalene - - - 1.0 30

37 2-hydroxy-l,l’-bis(naphthalene) 0.4 - 41 1-indanyl-2-hydroxynaphthalene 2.4

- - - - -

- - -

- -

- - - - - - - -

Table IX. Products of Aquathermolysis of 1,4-Dimethoxynaphthalene (22) at 315 OC for 2 h solvent

no. structure cyclohexane water 15% HCOzH 15% HCOzNa - - - 2 indane 13.9

7 1-indanone 0.5 4.3 8 tetralin 0.3 2.5 9 naphthalene 1.5 14.2 10 1-tetralone 0.9 4.6 13 1,4-dihydroxynaphthalene 7.6 5.8 4.1

- - - - - - - - - - 14 1-methoxynaphthalene 5.3 11.2 -

15 1- hydroxynaphthalene 0.2 4.6 33.3 9.8

18 1-methoxy-4-methylnaphthalene 0.2 - 21 1-hydroxy-4-methylnaphthalene 0.6 0.5 0.8 2.1 22 1,4-dimethoxynaphthalene 93.3 22.0 28.8 18.0 24 1-hydroxy-4-methoxynaphthalene 3.6 9.1 12.9 7.8 26 l,4-naphthoguinone 3.4 - - 31 2-methyl-l,4-naphthoquinone 1.2 - - -

- 17 2-methyl-l,4-dihydroxynaphthalene 4.2 2.3 6.2

19 1-hydroxy-2-methylnaphthalene 2.3 0.7 12.4 - - -

-

- 38 2,2’-bis(l,4-dimethoxynaphthalene) 37.0 - - 40 4,4’-dihydroxy-l,l’-bis(naphthalene) 1.0 3.5 1.3 - Table X. Conversion Summary of Naphthol Systems under Thermolysis and Aquathermolysis Conditions at 315 O C

major reduction productsasb total conversion medium 2 h 72 h 2 h 72 h

1-Hydroxynaphthalene cyclohexane 0.0 0.0 0.0 7.3 water 0.5 1.3 1.7 9.3 15% formic acid 1.0 1.0 1.0 10.0 15% sodium formate 8.0 65.0 10.0 81.0

2-Hydroxynaphthalene cyclohexane 0.0 0.0 0.4 0.8 water 0.0 0.5 0.1 1.3 15 % formic acid 0.5 6.6 1.0 8.0 15% sodium formate 3.7 61.5 4.3 63.6

0 Major reduction products include 1-tetralone, tetralin, naphthalene, indene, indane, and indanone. Naphthalene is unreactive under all these conditions.

(10) could all occur by variations in the reduction of dione tautomer 130 (see previous discussion).

Ring opening (reverse Claisen) of the dione tautomer 130 leads to the intermediate keto acid 131 which undergoes decarboxylation to yield 2-phenylpropanone (6). Compound 6 can undergo self-condensation to give olefin 132 from which 28 and 29 are derived by reduction. Dione 130 reacts with ketone (6) in an aldol condensation to yield the dimer olefin which tautomerizes to form 2-(1,3- dihydroxy-2-naphthyl)-l-phenyl-l-propene (43). Further reduction of 6 forms n-propylbenzene (1) (eq 11).

Methylated derivatives 19 and 21 are, as before, formed by formylation of 27 at the 2- and 4-positions followed by the removal of the 3-hydroxy group. The appreciable amounts of 19 and 21 formed are explained by the high reactivity of 27 to formylation. 1,4-Dihydroxynaphthalene (13) (Table VII) (Eqs

12 and 13). 1,4-Dihydroxynaphthalene was more reactive

in water (89.9% conversion) than in cyclohexane (44.5% conversion). Under thermal conditions 13 gave only two products: reductive loss of one hydroxyl group to l-hydroxynaphthalene (32.4%) and oxidation to l,.l-naphthoquinone (26) (12.1%). In water (90% conversion), 1-hydroxynaphthalene was the main product (70.2% 1, but indanone (7) (14.2%) and trace amounts of three other compounds were also identified. With 15% formic acid, 13 showed 96.6% conversion to the major product l-hydroxynaphthalene (83.6 % ), together with 1-tetralone (3.5%), tetralin (0.9%), and the dimeric products 4,4’- dihydroxy-1,l’-birdnaphthalene) (40) (1.7 % ) and 4-hydroxy-1,l’-bis(naphthalene) (39) (1.7 % 1. In 15% HC02- Na, 13 showed complete conversion to the same slate of products plus indane (6.8%) and traces of indene (3) and 1-methylindene (5).

The ease of oxidation of 1,4-dihydroxynaphthalene (13) to the quinone (26) is well-known: the simultaneous

Reactivity of Hydroxynaphthalenes Energy & Fuels, Vol. 7, No. 5,1993 595

Table XI. Conversion Summary of Dihydroxynaphthalene Systems under Thermolysis and Aquathermolysis Conditions at 315 OC for 2 h

medium major reduction productaalb 1- and 2-hydroxynaphthalenes total conversion

cyclohexane water 15 % formic acid 15 % sodium formate


cyclohexane water 15% formic acid 15% sodium formate


1,2-Dihydroxynaphthalene 0.0 69.0 2.1 16.4 5.4 92.6

38.5 50.7

0.0 0.1 0.8 1.7

0.0 17.5 5.2

32.6

0.0 0.0 1.5

34.1

1,3-Dihydroxynaphthalene 20.5 11.4 22.3 12.3

32.4 70.2 83.6 49.7

43.1 24.5 70.2 52.6

1,4-Dihydroxynaphthalene

2,3-Dihydroxynaphthalene

83.2 19.0

100.0 96.3

49.1 65.7 78.8

100.0

44.5 89.9 96.6

100.0

43.1 24.5 72.7 92.2

Maior reduction Droducta include 1-tetralone, tetralin, naphthalene, indene, indane, and indanone. Naphthalene is unreactive under all these c&ditions.

Scheme I

HCOOH

2 1 CH, 102

J H IO8 CH3

101

0

- w

106

ow

109 3 4

103

reduction of 13 to 1-hydroxynaphthalene (15) probably occurs via the tautomer 138 and intermediate 139 (eq 12) (Scheme V). Minor variations in the oxidation-reduction

Scheme I1

CHO

0" - - OH HQH - I 6 111

10

pathways on tautomer 138, account for the formation of tetralin (8), naphthalene (9), and 1-tetralone (10). Ad- dition of hydroxide ion to quinone 26 yields 142 which rearranges to produce 1-indanone-3-carboxylic acid 143 and hence by loss of C02 to 1-indanone (7) (eq 13). Reduction of 7 to the alcohol and further reduction or elimination would then give indane (2) and indene (3). 1-Methylindene (5) could be derived as shown through intermediates 143, 144, and 146 (eq 13).

Addition of 1-hydroxynaphthalene to quinone 26 could provide a plausible source for the formation of bis- (naphthalenes) 39 and 40. The hydroxymethylnaphtha- lenes 19 and 21 are undoubtedly formed by formylation of 13 at the 2- and 1-positions, respectively, followed by reduction. 2,3-Dihydroxynaphthalene (25) (Table VIII) (Eq

14). Under both thermolytic and aquathermolytic conditions, 2,3-dihydroxynaphthalene (25) readily lost one hydroxyl group to give 2-hydroxynaphthalene (43.1 and 24.5%, respectively) as the only product detected. With 15% HC02H, 25 showed 72.7 % conversion and again the major product was 2-hydroxynaphthalene (70.2 % ) with some 2-hydroxy-2,2'-bisnaphthalene (37) (0.4% ) and several minor products. 2,3-Dihydroxynaphthalene showed high conversion (92.2%) with 15% HCOzNa, the major products being 2-hydroxynaphthalene (52.6% 1, naphthalene (9.7%), indene (8.9%), and indane (14.8%).

Reduction of 25, presumably on the keto tautomeric form, gave 2-hydroxynaphthalene (16) as in eqs 7,10, and

596 Energy & Fuels, Vol. 7, No. 5, 1993

Scheme I11

Siskin et al.

OH OH

(7) OH

==== . H,O

16 23 119 121

,?. 111

116

03 Scheme IV

OH

2 7 I10 16

130

K / .YO

Scheme V

I39 13

131

C". CWO I

12. The formation of large quantities of 16 in the absence of any added reducing agent suggests that 2,3-naphtha- lenequinone (149) is formed simultaneously and that this polymerizes. Reductive pathways similar to those mentioned for preceding compounds afford tetralin (8) and 2-tetralone (12).

The tautomeric form of 25 undergoes benzilic acid rearrangement and the resulting a-hydroxyacid 147 loses water and COZ to give indene (3), reduction of which affords indane (2). Addition of 2,3-dihydroxynaphthalene (25)

to l-indene (3) gave intermediate 163. The tautomeric form 148 of 153 can now undergo reduction to yield 41, double reduction to give 35, or benzilic acid rearrangement to afford 30 (eq 14) (Scheme VI). Addition of 25 to quinone 149 yields an intermediate which undergoes reduction to bis(naphthalene) 37. 2,3-Dihydroxy-l-formylnaphthalene 151 is the intermediate for the formation of l-methyl-2- hydroxynaphthalene (20). 1,4-Dimethoxynaphthalene (22) (Table IX) (Eqs 15

and 16). In cyclohexane, 1,4-dimethoxynaphthalene showed 6.7 % conversion, and the major reaction was ether cleavage to give l-hydroxy-4-methoxynaphthalene (24) (3.6%). 2-Methyl-l,4-naphthoquinone (31) (1.2%),4,4'- dihydroxy- 1,l'-bis(naphthalene) (40) (1 .O % 1, l-hydroxy- 4-methylnaphthalene (21) (0.6% ), and l-hydroxynaphthalene (15) (0.2%) were also detected.

In water, 22 showed 78% conversion to give 2,2'-bis- (1,4-dimethoxynaphthalene) (38) (37.0% 1, l-hydroxy-4- methoxynaphthalene (24) (9.1 % ),1,4-dihydroxynaphthalene (13) (7.6%), l-methoxynaphthalene (14) (5.3%), l-hydroxynaphthalene (4.6 % ), and 1,4-naphthoquinone (26) (3.4%). 1,4-Dimethoxynaphthalene (22) showed 71.2 5% conver-

sion in 15 9% formic acid and 82 % conversion in 15 5% HC02- Na to give products similar to those described above except that no dimer 38 was formed. In formic acid there were also trace amounts of several other products, and in sodium formate, 22 yielded substantial amounts of indane (2) (13.9%), l-indanone (7) (4.3%), tetralin (2.5%), l-tetralone (10) (4.6%), and naphthalene (14.2%).

The overall reaction pathways are outlined in eqs 15 and 16 (Scheme VII). Under aquathermolysis condition, 1,4-dimethoxynaphthalene (22) shows a strong tendency to both oxidation and reduction. The major product of oxidation is dimer 38 which is probably formed by electron addition and dimerization followed by H+ ion loss (eq 15). Another oxidation product is naphthoquinone 26. The main reduction products are l-methoxy- (14) and l-hydroxynaphthalene (15), methyl naphthols 19 and 21, and reduced dimer 40. Their formation is exemplified by the route shown for 22 - 155 - 14 (eq 15) and 154 - 156 - 157 - 40 (eq 15). Hydroxyl groups in 1P-dihydroxynaphthalene (13), l-naphthol (15), 2-methyl-l,4dihy- droxynaphthalene (17), 1-hydroxy-4-methoxynaphthalene (24), and 4,4'-dihydroxy- 1,l'-bis(naphthalene) (40) are obtained by loss of methanol and/or by methyl cation transfer, which is reduced for the formation of the C-methyl products 17, 19, and 21.

Reactivity of Hydroxynaphthalenes

Scheme VI1

Energy & Fuels, Vol. 7, No. 5, 1993 697

low levels of reduction products are evident in water (Table X). Conversion in formic acid, which simulates a water- carbon monoxide system, is significantly higher due to the formation of reduced products. This trend is dramatically reinforced in the sodium formate system because of stabilization of the formate ion as the sodium salt. Dihydroxynaphthalenes are significantly more reactive thannaphthols (Table XI). Dehydroxylationto anaphthol is a major pathway. In the case of 1,3-dihydroxynaphthalene, ring opening was also observed. Again, more reduction products are generally formed in water than in cyclohexane. The addition of formic acid or sodium formate to the aquathermolytic mixtures generally increased reaction rates and produced more reduction products, but the overall pattern of reaction remained the same.

It is clear that, under reducing conditions, polyhydrox- ylated aromatics, as would be present in lignite and subbituminous coals and formed by cleavage of ethers during conversion, would be reactive and generate reduced products capable of acting as hydrogen donors during liquefaction.

I "" I57 OMe 4Q 1 5 6

M I "V.

In the presence of formic acid, more of the dimer 38 is formed. The same type of reaction products are produced, but the mechanism of their formation is probably by hydride ion transfer from the formate ion. Appreciable amounts of tetralin (a), naphthalene (S), and l-tetralone (10) appear, presumably by pathways similar to those found for 1,4-dihydroxynaphthalene. A still greater shift to the more completely reduced products is formed in the presence of sodium formate.

Conclusions

Overall thermal and aquathermal reactivities over 3 days at 315 O C are comparably low for naphthols, except that

Supplementary Material Available: Tables LA and IB listing the properties (IA) and mass spectral fragmentation patterns (IA, IB and list of mass spectral assignmenta for Table IB) of the compounds in this paper (7 pages). Ordering information is given on any current masthead page.

aqueous organic chemistry. 6. reactivity of hydroxynaphthalenes

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