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Detergent-range alcohol alkoxylates via vicinal glycol additions to α-olefins
A~ .
APPLIED CATALYSIS A: GENEP~L
ELSEVIER
Applied Catalysis A: General 130 (1995) 79-88
Detergent-range alcohol alkoxylates via vicinal glycol additions to a-olefins John F. Knifton Austin Laboratories, Huntsman Corporation, Austin, TX 78761, USA
Received 20 February 1995; revised 5 April 1995; accepted 7 April 1995
Abstract
The synthesis of detergent-range, secondary alcohol alkoxylates via vicinal glycol addition to C8C,4 linear c~-olefins has been demonstrated using both homogeneous, heteropoly acids and solid strong-acid catalysis - - acidified montmorillonite clays. 1-Tetradecene reaction with ethylene glycol yields 2- (2-tetradecyloxy) ethanol as the principal glycol ether product. 1,2-Propylene glycol addition to typical linear a-olefins (e.g. 1-octene and 1-tetradecene) gives the corresponding secondary alkyl alcohol propoxylates. Both batch and continuous preparations of C8-C14 secondary alcohol 1-and 2alkoxylates are described. Keywords: a-Alkenes; Glycols; Heteropoly acids; Montmorillonite clays
I. Introduction Cs-C,8 Alcohol alkoxylates (alkyl polyglycol ethers) find wide commercial application as non-ionic detergents [ 1 ]. They are presently manufactured exclusively via the alkoxylation of a suitable fatty or oxo-alcohol hydrophobe with an oxirane hydrophile, principally ethylene oxide ((Eq. 1 )) [ 1,2]. However, it has become increasingly difficult to transport ethylene oxide (EO) to ethoxylation sites remote from the ethylene oxide sourcing due to the hazardous nature of EO [3,4]. O ROH + n CH2/
~
CH2 -....... >
RO-(-CH2CH20-)-H
.
(1)
An alternative approach to making alcohol ethoxylates would be the multiple addition of ethylene glycol (EG) to linear a-olefins ( (Eq. 2) ). The advantages to this approach are that both EG and a-olefins can be readily transported and the 0926-860X/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSDI O92 6 - 8 6 0 X ( 9 5 ) 0 0 0 9 0 - 9
J.F. Knifton / Applied Catalysis A: General 130 (1995) 79-88
80
alkyl alkoxylate products manufactured at locations separate from those generating the glycol and alkene. R-CH = CH, + n
HO-CH,-CH2-OH
---> R-CH-O-I,{ CH~CH_~O -)-H
I CH,
(2)
In this paper we describe our research into the addition of vicinal dihydric alcohols - - particularly ethylene glycol and 1,2-propylene glycol (PG) - - to C8C14 linear a-olefins using both homogeneous and solid, strong-acid, catalysis as a route to making secondary aliphatic alcohol alkoxylates. This research has been part of a more general study into the generation of value-added glycol ethers [ 58]. Continuous processing for the production of linear, secondary, aliphatic alcohol ethoxylates from long-chain a-olefins has been reported previously by Union Carbide workers using Nation ® H as catalyst [9]. Both sulfuric acid and benzenesulfonic acid have also been employed as strong acid catalysts for ethylene glycol additions to C8-C22 olefins [ 10]. Syntheses of secondary aliphatic alcohol alkoxylates via addition of vicinal dihydric alcohols to C8-Cj4 linear a-olefins have been demonstrated in this work using both homogeneous, heteropoly acid (12-tungstophosphoric acid) and solid strong acid catalysis - - acidified montmorillonite clays. Addition of 1-tetradecene to ethylene glycol yields 2-(2-tetradecyloxy)ethanol as the principal glycol ether product. An unexpected chemoselectivity has been discovered with 1,2-propylene glycol - - where PG addition is at the 2-C position of the linear a-olefin, then etherification involves the primary OH of the glycol, whereas addition to the 3-C olefin position is at the secondary OH of the glycol. Both batch and continuous preparations of a series of C8-C14 secondary alcohol 1-and 2-alkoxylates are described.
2. Experimental The ethylene glycol, 1,2-propylene glycol and C 8 - - - C 14 a-olefins starting materials were supplied either by Texaco Chemical Co., or by outside suppliers. 12-Tungstophosphoric acid was sourced from Alfa Products; the acidified montmorillonite clay, Grade F-24, was purchased from Engelhard Corp., these 20/60 mesh granules have a reported residual acidity of 16 mg K O H / g and a surface area of 350 m2/g. A typical batch synthesis procedure is as follows: To a 1450 c m 3 capacity, stainless steel, reactor ftted with a glass liner, was charged a mix of l-tetradecene (98.2 g, 0.5 mol), ethylene glycol (62.0 g, 1.0 mol), 1,4-dioxane ( 100 g) and 12tungstophosphoric acid (5.0 g). The mixture was flushed with nitrogen, pressurized to 14 bar, heated with mixing to 180°C, and held at temperature for four hours. Upon cooling, 253 g of a two-phase, light-brown, liquid product was recovered.
81
J.F. Knifton /Applied Catalysis A: General 130 (1995) 79-88 Table 1 Ethylene glycol addition to 1-tetradecene Ex.
Catalyst
Solvent
H3PO4" 12 WO3 H3POn ' 12 WO3 H3POn" 12 WO3 H3PO4"12 WO3
1
2 3 4
1,4-Dioxane 1,4-Dioxane None None
Tetradecyloxyethanols Conc. ( %)a
Temp. (°C)
180b 180b 180b 170c
A
B
C
D
19.1 19.2 5.2 2.1
4.4 3.0
1.9 1.8
0.5 0.2
a Tetradecyloxyethanol structures: A:
C~2H2~-C. I-I-CH3
!
B:
I
O - CH2-CH2OH C:
CnH23-CH-CH2-CH3
I O-CH~-CH2OH
C~2H25-CH-CH~ O-CH2-CH2-O-CH2-CH2OH
D.
C~H23-~H-CH2-CH3 O-CH2-CH2-O-CH2-CH2OH
b Run in autoclave, see Section 2 for details. Run in glassware, see Section 2 for details.
Analyses by gas-liquid chromatography (GLC), gas chromatography-infrared spectroscopy (GC-IR) and gas chromatography-mass spectrometry (GC-MS) of the lighter phase ( 170 g) shows the presence of tetradecenes ( 61% ), tetradecyloxyethanols (21%), tetradecyloxyethoxyethanols (5 %), and 1,4-dioxane (4%). Further identification of the tetradecyloxyethanol and tetradecyloxyethoxyethanol fractions show them to comprise four principal components, where one and two molar ethoxylation has taken place at both the 2-C and 3-C portions of the tetradecene substrate, as illustrated in Table 1 and (Eq. 3). Identification of the tetradecyloxyethanol structures A and C, as well as the tetradecyloxyethoxyethanol structures B and D were as follows: A, GC-MS m/z principal ions 45, 89, 197,213 and 243, GC-IR v(cm - t ) 1110 (C-O-C), 1060 (CH2-OH); B, GC-MS m/z principal ions 45, 61, 75, 89, 133, 197, and 213, GC-IR v(cm -1) 1130 (C-O-C), 1060 (CH2-OH); C, GC-MS m/z principal ions 45,103, 197, and 229, D, GC-MS m/z principal ions 45, 89, 147, and 273. The heavier product phase ( 80 g) comprised 1,4-dioxane (32%), ethylene glycol (30%), diethylene glycol (18%), plus higher MW glycol homologues. Similar experiments with 1-tetradecene plus 1,2-propylene glycol yielded tetradecyloxypropanol structures E and F as the major products (see Table 5 and (Eq. 4) ). Identification of these adducts were as follows: E, GC-MS m/z principal ions 59, 75, 103, 197,213, and 257, GC-IR v(cm -1) 1130 (C-O--C), 1090 (CHOH); F, GC-MS m/z principal ions 45, 103, 197, and 241, GC-IR v (cm-~), 1130 (C-O-C), 1050 (CH2-OH). Related addition of 1-octene to 1,2-propylene glycol likewise gave octyloxypropanol structure G, identified as follows: GC-MS, m/z principal ions 45, 59, 75,
82
J.F. Knifton /Applied Catalysis A: General 130 (1995) 79-88
103, 113, 129 and 173, GC-IR ~(cm-~), 1130 (C-O-C), 1090 (CH-OH). Batch syntheses in glassware were typically conducted as follows: To a 250 c m 3 flask, fitted with a mechanical stirrer and condenser, was charged a mix of 1tetradecene (98.2 g, 0.5 mol), ethylene glycol (62.0 g, 1.0 mol), and Engelhard clay Grade F-24 granules (20/60 mesh, 5.0 g). The mixture was flushed with nitrogen, heated to reflux (ca. 175°C) and held at temperature for four hours. Upon cooling, the two-phase liquid product ( 130 ml lighter phase, 50 ml heavier phase) was separated and each phase analyzed by GLC, GC-IR and GC-MS techniques as described above. The lighter phase comprised 95% unreacted tetradecenes and 1.4% 2- (2-tetradecyloxy) ethanol ( structure A, (Eq. 3) ). The heavier phase comprised 94% ethylene glycol and 6% diethylene glycol. Continuous syntheses were conducted using a 50 c m 3 capacity, upflow reactor, fitted with temperature, pressure, and flow controls. A single-phase, homogeneous liquid feed comprising ethylene glycol (200 g, 3.2 mol), 1-dodecene (200 g, 1.2 mol), tripropylene glycol monomethyl ether (1000 g) plus 12-tungstophosphoric acid (60.0 g) was fed to the unit at rates of 0.4-0.8 LHSV. Pressure was maintained at 21 bar, reaction was allowed to proceed at a series of temperatures (150-180°C). After reaching equilibrium at each temperature, samples of product effluent were collected and analyzed by GLC and GC-IR. 3. Results and discussion
Batchwise addition of ethylene glycol (EG) to 1-tetradecene (1-C~) in the presence of a typical, soluble, heteropoly acid catalyst - - 12-tungstophosphoric a c i d - gives rise to 2-(tetradecyloxy) ethanol as the major product. Experiments using neat reactants yielded two-phase liquid products. The inclusion of a suitable solvent (e.g. 1,4-dioxane), however, does provide better phase mixing and consequently a sizable increase in concentration of the desired glycol ether adducts ( see Table 1). A typical experimental procedure may be found in Section 2. Data for duplicate batch autoclave runs made with 1,4-dioxane as added solvent are detailed in Table 1, ex. 1-2. In both cases sizable quantities of desired tetradecyloxyethanols and tetradecyloxyethoxyethanols were generated. The structures of the four major glycol ether adducts, with their concentrations in parentheses, are illustrated in (Eq. 3). CI2H~5~H-CH3
+ CH:2H~sCH-CH3
OCH~CH2OH (A, 19.1%)
I
O(CH2CH20)~H (B, 4.4%)
C,2H~sCH=CHT+HOCH2CH2OFI ~ ,~ C,jH23~H-CHz-CH; + O-CH2CH2OH
(c_, t.9~)
C.H23~H-CH2-CH3 O(CH2CH20)TH
(D, 0.5~)
(3)
J.F. Knifion / Applied Catalysis A: General 130 (1995) 79-88
83
Table 2 Ethylene glycol addition to 1-tetradecene Ex.
5 6
Catalyst
Clay F-24 Nation®
Solvent
None None
Temp.
C~4 conv.
Tetradecyloxyethanols conc. ( %)a
(°C)
(%)
h
a
175 b 160b
5 6
1.4 3.1
0.1 < 1
Tetradecyloxyethanol structures as identified in Table 1. b Run in glassware, see Section 2 for details.
A tetradecyloxyethanol distillate fraction was subsequently isolated from the crude product mix of ex. 1, the majority (93%) of this cut was 2-(2-tetradecyloxy)ethanol (A in (Eq. 3)). A higher boiling fraction comprised tetradecyloxyethoxyethanols in 88% purity. The major competing reactions to (Eq. 3) (ex. 14) are double bond isomerization to internal tetradecenes, plus glycol oligomerization to diethylene glycol (DEG) etc. Some 2- and 3-tetradecanols have also been detected. Solid acid clays generally appear less effective for reaction (2), the desired etherification is illustrated in Table 2 both for an acidified montmorillonite clay (Engelhard's clay Grade F-24, granules, acidity 16 mg KOH/g) and for a perfluorosulfonated resin (Nation ® NR50, beads, 10/35 mesh, Aldrich Chemical). Continuous syntheses of the same secondary, aliphatic alcohol ethoxylates have been demonstrated using solubilized heteropoly acids ( 12-tungstophosphoric acid and 12-molybdophosphoric acid) as the acid catalysts and tripropylene glycol monomethyl ether as the compatibilizing solvent. Feeding ethylene glycol plus 1dodecene ( 1-C ~, 2.5 molar ratio) to a continuous, upflow reactor as a single-phase, homogeneous liquid mix, syntheses of the dodecyloxyethanols was demonstrated over a range of temperatures (150-180°C) and feed rates. The results are summarized in Table 3; the procedure is detailed in Section 2. Slightly higher temperatures (200°C) are necessary to achieve the same effluent concentrations of dodecyloxyethanols when employing the acidified montmorillonite clay catalyst - - clay Grade F-24 (cf. Table 4). In all three experimental series, the principal competing reactions are dodecene double bond isomerization to internal isomers and ethylene glycol oligomerization to DEG, TEG, etc. Both 2-and 3-dodecanols were also identified. No substantial improvement in glycol ether productivity was realized when the clay catalyst and reactants were rigorously dried prior to use. Generally, as depicted in Table 1 and (Eq. 3), the individual product distributions are each consistent with four parallel, consecutive reactions (see Scheme 1) involving: EG addition to the 2-C position of the linear a-olefin substrate to give the principal glycol ether product A. The addition of 2 mol of glycol to the a-olefin to yield adduct B.
J.F. Knifion /Applied Catalysis A: General 130 (1995) 79-88
84
Table 3 Continuous addition of ethylene glycol to l-dodecene via heteropoly acid catalysis Ex. Catalyst
7
8
Solvent Temp. (°C)
HsPO4 " 12WO~
H3PO4 • 12MOOb
TPGM
TPGM
LHSV Sample Effluent sample composition ( % )" EG I-Cj2
~vCI2 TPGM DDOE 1- DDOE2-
23.2 6.7 18.3 17.9 14.4 13.4
27.4 23.2 24.5 24.3 28.4 26.3
54.7 26.6 44.1 42.5 N.D5 N.D.
t.2 54.3 2.5 2.5 2.7 2.3
1.2 0.1 0.2 0.3 0.4
26.0 25.8 22.8 22.7 18.8 18.7 15.7
28.5 28.4 26.5 26.4 24.4 24.3 22.6
57.7 57.9 43.5 53.5 44.7 44.7 N.D.
0.3 0.4 1.2 1.2 2.0 2.0 2.9
0.1 0.1 0.2 0.2 0.3
150
0.8
1
165
0.8
180
0.8
3 4 5 6
6.6 2 5.4 5.2 3.3 4.1
150
0.8
165
0.8
180
0.8
180
0.4
1 2 3 4 5 6 7
7.5 7.4 6.7 6.7 5.4 5.3 3.9
Abbreviations as follows: total dodecene isomers (XC~2), tripropylene glycol monomethyl ether (TPGM), dodecyl alcohol mono and diethoxylates (DDOE 1-, 2-). b Run in 50 cm 3 capacity continuous reactor, see Section 2 for details. " N.D., not determined. Table 4 Continuous addition of ethylene glycol to l-dodecene via clay catalysis Ex. Catalyst
Solvent Temp.
LHSV Sample Effluent sample composition (%)a
(°c)
9
Clay F-24 b TPGM
150
1.0
165
1.0
180
1.0
200
1.0
1 2 3 4 5 6 7
EG
1-C~
9.6 9.2 7.6 7.7 4.9 4.8 5.9
28.8 29.3 29.4 29.4 24.9 23.8 16.2
XC~
TPGM DDOE 1- DDOE2-
29.9 29.1 23.8
56.2 55.8 52.7 52.6 N.D. N.D. N.D.
0.2 0.1 0.5 0.5 1.8 1.8 2.3
a Abbreviations as in Table 3. b Run in 50 cm 3 capacity continuous reactor, see Section 2 for details. EG R-CH~-CH-CH3 ............... > R-CH2-CH-CH3
R-CH~-CH= CH2
Y E ~ R
I
I
O-CH~CH_,OH
EG -~H-CH2-CH3 ............... >
O-(-CH2CH20)2H
R-CH-CH~-CHs
I O-CH_~CH2OH
O-(-CH2CHzO)~H
Scheme 1. Ethylene glycol addition to linear a-olefins.
0.2 0.2 0.5
85
J.F. Knifton / Applied Catalysis A: General 130 (1995) 79-88
5 1,2-Propyleneglycol
Table
Ex.
addition to l-tetradecene
Catalyst
10 11 12 13
Solvent
H3PO4"I2WO~ Clay F-24 Clay F-24 Clay F-24
Temp.
IA-Dioxane IA-Dioxane 1,4-Dioxane 1,4-Dioxane
Tetradecyloxypropanols conc. ( %) a
(°C)
180 180 150 120
E
F
1.6
0.8 0.4 0.1
0.9 0.2 <0.1
~Tetradecyloxypropanol structures: E:
CI2H2~-CH-CH ~ ! O-CH,-CHOH I CH~
F:
Cull2-CH-CH,-CHa
I
O-CH-CI-I~OH I CH~
The addition of either 1 or 2 tool of ethylene glycol at the 3-C position of the o~-olefin coreactant to give products C and D. A similar, but more complex, regioselectivity is observed when 1,2-propylene glycol is added to 1-tetradecene. Etherifications catalyzed by both the soluble 12tungstophosphoric acid and with the clay Grade F-24, at 120-180°C, using an initial olefin:glycol molar ratio of ca. 1:2, provide the two major secondary alkyl alcohol propoxylates depicted in (Eq. 4). Experimental run data are summarized in Table 5, ex. 10-13. C,2H~Cp-CH~ f
O-CH~-CHOH I CH~
I~
+ /
/
OH OH
C. H23CH-CH~_-CH~ I O-CH-CH~OH
I
c.,
(4)
Here we find an unexpected chemoselectivity with respect to the position of 1,2propylene glycol addition, viz.: When PG addition is at the 2-C position of the olefin, then etherification involves the primary OH of the glycol to give ether adducts of type E in (Eq. 3). This is major product fraction. Where the addition occurs at the 3-C position of the olefin, however, the etherification now involves the secondary OH of the glycol to give monoethers of type F.
J.F. Knifton/Applied Catalysis A." General 130 (1995) 79-88
86
Table 6 1,2-Propylene glycol addition to I-octene Catalyst
Ex.
14 15 16 17
Clay Clay Clay Clay
Solvent
None None None None
F-24 F-24 F-24 F-24
CJPG
Temp.
C~ conv.
Octyloxypropanols conc. (%)"
molar ratio
( °C )
(%)
G
It
1:2 1:2 1:8 1:0.25
150 120 150 150
4 < 1 37 2
0.6 <0.1 7.5 <0.1
0.4 4.6
Octyloxypropanol structures: G:
C6H~CH-CH~
H:
CsHHCH-CH~-CH~
[
I
O-CH2-CHOH
O-CH-CH2OH
I
I
CH~
CH~
Generally, an etherification temperature of greater than 120°C is needed in order to generate significant quantities of desired propylene glycol ethers (see Table 5, ex. 11-13), even in the presence of added 1,4-dioxane. No ethylene glycol or bisethylene glycol ether adducts were identified in these liquid products, indicating that the 1,4-dioxane is not significantly involved in the etherification process and is not, for example, a major source of (-OCH2CH2OCHzCH2OH) type linkages. 1,2-Propylene glycol coupling with 1-octene can, likewise, give rise to a similar pattern of chemoselective derivatives. At 150°C, in the presence of the solid acid catalyst, clay Grade F-24 granules, but using a 1:8 molar mix of 1-octene plus 1,2propylene glycol, yields two major propylene glycol octyl ethers (See Table 6, ex. 16) of structures depicted in (Eq. 5 ). Again it is apparent that where the propylene glycol addition is to the 2-C position of the starting olefin, then etherification will involve the primary OH group of the diol, whereas addition to the 3-C position involves the secondary OH of the glycol molecule. Addition at the 2-C position predominates. C6H~3CH-CH3
I
O-CHT-CHOH
I
CH~ C 6 H [ 3 C H ~ C H ~ Ca 3 - e u ' e u 2
/ / OH OH
CsHt,C[H-CH2-CH; H O-CH-CH2OH
I
CH3
(5)
When 1,4-dioxane is added as solvent, similar experiments using clay Grade F24 and 12-tungstophosphoric acid as catalysts each yielded these same C~t ethers
J.F. Knifton / Applied Catalysis A: General 130 (1995) 79-88
87
Table 7 1,2-Propylene glycol addition to l-octene Ex.
18 19 20 21
Catalyst
Clay F-24 Clay F-24 H3PO4" 12WO3 H3PO4 12WO 3
Solvent
1,4-Dioxane 1,4-Dioxane 1,4-Dioxane 1,4-Dioxane
C8-/PG
Temp.
Octyloxypropanols conc. (%)a
molar ratio
(°C)
G
H
1:2 1:2 1:2 1:2
150 180 150 180
3.5 0.9 3.5 < 0.1
2.6 0.4 1.3
Octyloxypropanol structures as identified in Table 6.
as the major products (Table 7). Internal octene isomers and propylene glycol homologues (DPG, etc.) are once again the major by-products. Generally, higher operating temperatures ( > 180°C) result in a loss of glycol ether formation, irrespective of whether the catalyst is a soluble heteropoly acid, or a solid acidic clay (cf. ex. 18 versus 19 and ex. 20 versus 21 ). Somewhat surprisingly, the regioselectivity of olefin addition leading to products E and F, as well as G and H, is not substantially altered by whether the acid catalyst is a soluble heteropoly acid or a more hindered, layered montmorillonite clay (cf. Table 5 and Table 7).
4. Conclusions In conclusion, the feasibility of generating detergent-range alcohol alkoxylates through addition of vicinal glycols to linear a-olefins via either heteropoly acid or solid acid clay catalysis has been demonstrated. At this stage of technology development, however, it is evident that (a) all major glycol ether adducts (Tables 17) have the secondary alkyl alcohol alkoxylate structure, comprising only one or two alkoxy groups added to the C8-C~4 alkyl chains (Eqs. 1-5), and (b) the rates of glycol addition to C8-C14linear a-olefins are extremely slow in comparison to both oxirane addition rates to detergent-range alcohol [ 11-13] and the rates of vicinal glycol additions to branched olefins capable of forming tertiary carbocations [14]. Nevertheless, the unexpected chemoselectivity seen here, particularly in reactions (4) and (5), suggests that further developments of this chemistry could lead to unique and commercially viable products.
Acknowledgements Thanks are due to Huntsman Corporation for permission to publish this paper, Robert L. Burke and R.E. Baldwin for GC-MS and GC-IR identifications, and Messers. P. Lopez and C.A. Armstrong for technical assistance.
88
J.F. Knifton /Applied Catalysis A: General 130 (1995) 79-88
References [ 1 ] Nonionic Surfactants - - Primary Alcohol-Based, Chem Systems Report Number 83-4, Chem Systems Inc., July 1984. [ 2] M. Am6, Nonionic Surfactants, Stanford Research Institute Report No. 168, SRI International, March 1984. [3] Chem. Market. Report., (9 Nov. 1992) 7. [4] Chem. Eng. News, (30 Sept. 1985) 11. [5] J.F. Knifton, US Patent 5 146 041 (1992). [6] J.F. Knifton, US Patent 5 177 301 (1993). [7] J.F. Knifton, US Patent 5 349 110 (1994). [8] J.F. Knifton, Applied Catal. A, 109 (1994) 247. [9] R.J. Knopf, European Patent Appl., 0 310 194 (1989). [ 10] T.E. Paxson, L. Kim and A.B. Van Aken, US Patent 4 371 716 (1983). [ 11 ] E. Santacesari, M. DiSerio, R. Garaffa and G. Addino, Ind. Eng. Chem. Res., 31 (1992) 2413. [ 12] G. Gee, W.C.E. Higginson, P. Levesley and K.J. Taylor, J. Chem. Soc., (1959) 1338. [ 13 ] N.G. Gaylord (Editor), Polyethers Part I. Polyalkylene Oxides and Other Polyethers, Interscience, New York, 1963. [ 14] J.F. Knifton, ChemTech, 24 (May 1994) 43.
APPLIED CATALYSIS A: GENEP~L
ELSEVIER
Applied Catalysis A: General 130 (1995) 79-88
Detergent-range alcohol alkoxylates via vicinal glycol additions to a-olefins John F. Knifton Austin Laboratories, Huntsman Corporation, Austin, TX 78761, USA
Received 20 February 1995; revised 5 April 1995; accepted 7 April 1995
Abstract
The synthesis of detergent-range, secondary alcohol alkoxylates via vicinal glycol addition to C8C,4 linear c~-olefins has been demonstrated using both homogeneous, heteropoly acids and solid strong-acid catalysis - - acidified montmorillonite clays. 1-Tetradecene reaction with ethylene glycol yields 2- (2-tetradecyloxy) ethanol as the principal glycol ether product. 1,2-Propylene glycol addition to typical linear a-olefins (e.g. 1-octene and 1-tetradecene) gives the corresponding secondary alkyl alcohol propoxylates. Both batch and continuous preparations of C8-C14 secondary alcohol 1-and 2alkoxylates are described. Keywords: a-Alkenes; Glycols; Heteropoly acids; Montmorillonite clays
I. Introduction Cs-C,8 Alcohol alkoxylates (alkyl polyglycol ethers) find wide commercial application as non-ionic detergents [ 1 ]. They are presently manufactured exclusively via the alkoxylation of a suitable fatty or oxo-alcohol hydrophobe with an oxirane hydrophile, principally ethylene oxide ((Eq. 1 )) [ 1,2]. However, it has become increasingly difficult to transport ethylene oxide (EO) to ethoxylation sites remote from the ethylene oxide sourcing due to the hazardous nature of EO [3,4]. O ROH + n CH2/
~
CH2 -....... >
RO-(-CH2CH20-)-H
.
(1)
An alternative approach to making alcohol ethoxylates would be the multiple addition of ethylene glycol (EG) to linear a-olefins ( (Eq. 2) ). The advantages to this approach are that both EG and a-olefins can be readily transported and the 0926-860X/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSDI O92 6 - 8 6 0 X ( 9 5 ) 0 0 0 9 0 - 9
J.F. Knifton / Applied Catalysis A: General 130 (1995) 79-88
80
alkyl alkoxylate products manufactured at locations separate from those generating the glycol and alkene. R-CH = CH, + n
HO-CH,-CH2-OH
---> R-CH-O-I,{ CH~CH_~O -)-H
I CH,
(2)
In this paper we describe our research into the addition of vicinal dihydric alcohols - - particularly ethylene glycol and 1,2-propylene glycol (PG) - - to C8C14 linear a-olefins using both homogeneous and solid, strong-acid, catalysis as a route to making secondary aliphatic alcohol alkoxylates. This research has been part of a more general study into the generation of value-added glycol ethers [ 58]. Continuous processing for the production of linear, secondary, aliphatic alcohol ethoxylates from long-chain a-olefins has been reported previously by Union Carbide workers using Nation ® H as catalyst [9]. Both sulfuric acid and benzenesulfonic acid have also been employed as strong acid catalysts for ethylene glycol additions to C8-C22 olefins [ 10]. Syntheses of secondary aliphatic alcohol alkoxylates via addition of vicinal dihydric alcohols to C8-Cj4 linear a-olefins have been demonstrated in this work using both homogeneous, heteropoly acid (12-tungstophosphoric acid) and solid strong acid catalysis - - acidified montmorillonite clays. Addition of 1-tetradecene to ethylene glycol yields 2-(2-tetradecyloxy)ethanol as the principal glycol ether product. An unexpected chemoselectivity has been discovered with 1,2-propylene glycol - - where PG addition is at the 2-C position of the linear a-olefin, then etherification involves the primary OH of the glycol, whereas addition to the 3-C olefin position is at the secondary OH of the glycol. Both batch and continuous preparations of a series of C8-C14 secondary alcohol 1-and 2-alkoxylates are described.
2. Experimental The ethylene glycol, 1,2-propylene glycol and C 8 - - - C 14 a-olefins starting materials were supplied either by Texaco Chemical Co., or by outside suppliers. 12-Tungstophosphoric acid was sourced from Alfa Products; the acidified montmorillonite clay, Grade F-24, was purchased from Engelhard Corp., these 20/60 mesh granules have a reported residual acidity of 16 mg K O H / g and a surface area of 350 m2/g. A typical batch synthesis procedure is as follows: To a 1450 c m 3 capacity, stainless steel, reactor ftted with a glass liner, was charged a mix of l-tetradecene (98.2 g, 0.5 mol), ethylene glycol (62.0 g, 1.0 mol), 1,4-dioxane ( 100 g) and 12tungstophosphoric acid (5.0 g). The mixture was flushed with nitrogen, pressurized to 14 bar, heated with mixing to 180°C, and held at temperature for four hours. Upon cooling, 253 g of a two-phase, light-brown, liquid product was recovered.
81
J.F. Knifton /Applied Catalysis A: General 130 (1995) 79-88 Table 1 Ethylene glycol addition to 1-tetradecene Ex.
Catalyst
Solvent
H3PO4" 12 WO3 H3POn ' 12 WO3 H3POn" 12 WO3 H3PO4"12 WO3
1
2 3 4
1,4-Dioxane 1,4-Dioxane None None
Tetradecyloxyethanols Conc. ( %)a
Temp. (°C)
180b 180b 180b 170c
A
B
C
D
19.1 19.2 5.2 2.1
4.4 3.0
1.9 1.8
0.5 0.2
a Tetradecyloxyethanol structures: A:
C~2H2~-C. I-I-CH3
!
B:
I
O - CH2-CH2OH C:
CnH23-CH-CH2-CH3
I O-CH~-CH2OH
C~2H25-CH-CH~ O-CH2-CH2-O-CH2-CH2OH
D.
C~H23-~H-CH2-CH3 O-CH2-CH2-O-CH2-CH2OH
b Run in autoclave, see Section 2 for details. Run in glassware, see Section 2 for details.
Analyses by gas-liquid chromatography (GLC), gas chromatography-infrared spectroscopy (GC-IR) and gas chromatography-mass spectrometry (GC-MS) of the lighter phase ( 170 g) shows the presence of tetradecenes ( 61% ), tetradecyloxyethanols (21%), tetradecyloxyethoxyethanols (5 %), and 1,4-dioxane (4%). Further identification of the tetradecyloxyethanol and tetradecyloxyethoxyethanol fractions show them to comprise four principal components, where one and two molar ethoxylation has taken place at both the 2-C and 3-C portions of the tetradecene substrate, as illustrated in Table 1 and (Eq. 3). Identification of the tetradecyloxyethanol structures A and C, as well as the tetradecyloxyethoxyethanol structures B and D were as follows: A, GC-MS m/z principal ions 45, 89, 197,213 and 243, GC-IR v(cm - t ) 1110 (C-O-C), 1060 (CH2-OH); B, GC-MS m/z principal ions 45, 61, 75, 89, 133, 197, and 213, GC-IR v(cm -1) 1130 (C-O-C), 1060 (CH2-OH); C, GC-MS m/z principal ions 45,103, 197, and 229, D, GC-MS m/z principal ions 45, 89, 147, and 273. The heavier product phase ( 80 g) comprised 1,4-dioxane (32%), ethylene glycol (30%), diethylene glycol (18%), plus higher MW glycol homologues. Similar experiments with 1-tetradecene plus 1,2-propylene glycol yielded tetradecyloxypropanol structures E and F as the major products (see Table 5 and (Eq. 4) ). Identification of these adducts were as follows: E, GC-MS m/z principal ions 59, 75, 103, 197,213, and 257, GC-IR v(cm -1) 1130 (C-O--C), 1090 (CHOH); F, GC-MS m/z principal ions 45, 103, 197, and 241, GC-IR v (cm-~), 1130 (C-O-C), 1050 (CH2-OH). Related addition of 1-octene to 1,2-propylene glycol likewise gave octyloxypropanol structure G, identified as follows: GC-MS, m/z principal ions 45, 59, 75,
82
J.F. Knifton /Applied Catalysis A: General 130 (1995) 79-88
103, 113, 129 and 173, GC-IR ~(cm-~), 1130 (C-O-C), 1090 (CH-OH). Batch syntheses in glassware were typically conducted as follows: To a 250 c m 3 flask, fitted with a mechanical stirrer and condenser, was charged a mix of 1tetradecene (98.2 g, 0.5 mol), ethylene glycol (62.0 g, 1.0 mol), and Engelhard clay Grade F-24 granules (20/60 mesh, 5.0 g). The mixture was flushed with nitrogen, heated to reflux (ca. 175°C) and held at temperature for four hours. Upon cooling, the two-phase liquid product ( 130 ml lighter phase, 50 ml heavier phase) was separated and each phase analyzed by GLC, GC-IR and GC-MS techniques as described above. The lighter phase comprised 95% unreacted tetradecenes and 1.4% 2- (2-tetradecyloxy) ethanol ( structure A, (Eq. 3) ). The heavier phase comprised 94% ethylene glycol and 6% diethylene glycol. Continuous syntheses were conducted using a 50 c m 3 capacity, upflow reactor, fitted with temperature, pressure, and flow controls. A single-phase, homogeneous liquid feed comprising ethylene glycol (200 g, 3.2 mol), 1-dodecene (200 g, 1.2 mol), tripropylene glycol monomethyl ether (1000 g) plus 12-tungstophosphoric acid (60.0 g) was fed to the unit at rates of 0.4-0.8 LHSV. Pressure was maintained at 21 bar, reaction was allowed to proceed at a series of temperatures (150-180°C). After reaching equilibrium at each temperature, samples of product effluent were collected and analyzed by GLC and GC-IR. 3. Results and discussion
Batchwise addition of ethylene glycol (EG) to 1-tetradecene (1-C~) in the presence of a typical, soluble, heteropoly acid catalyst - - 12-tungstophosphoric a c i d - gives rise to 2-(tetradecyloxy) ethanol as the major product. Experiments using neat reactants yielded two-phase liquid products. The inclusion of a suitable solvent (e.g. 1,4-dioxane), however, does provide better phase mixing and consequently a sizable increase in concentration of the desired glycol ether adducts ( see Table 1). A typical experimental procedure may be found in Section 2. Data for duplicate batch autoclave runs made with 1,4-dioxane as added solvent are detailed in Table 1, ex. 1-2. In both cases sizable quantities of desired tetradecyloxyethanols and tetradecyloxyethoxyethanols were generated. The structures of the four major glycol ether adducts, with their concentrations in parentheses, are illustrated in (Eq. 3). CI2H~5~H-CH3
+ CH:2H~sCH-CH3
OCH~CH2OH (A, 19.1%)
I
O(CH2CH20)~H (B, 4.4%)
C,2H~sCH=CHT+HOCH2CH2OFI ~ ,~ C,jH23~H-CHz-CH; + O-CH2CH2OH
(c_, t.9~)
C.H23~H-CH2-CH3 O(CH2CH20)TH
(D, 0.5~)
(3)
J.F. Knifion / Applied Catalysis A: General 130 (1995) 79-88
83
Table 2 Ethylene glycol addition to 1-tetradecene Ex.
5 6
Catalyst
Clay F-24 Nation®
Solvent
None None
Temp.
C~4 conv.
Tetradecyloxyethanols conc. ( %)a
(°C)
(%)
h
a
175 b 160b
5 6
1.4 3.1
0.1 < 1
Tetradecyloxyethanol structures as identified in Table 1. b Run in glassware, see Section 2 for details.
A tetradecyloxyethanol distillate fraction was subsequently isolated from the crude product mix of ex. 1, the majority (93%) of this cut was 2-(2-tetradecyloxy)ethanol (A in (Eq. 3)). A higher boiling fraction comprised tetradecyloxyethoxyethanols in 88% purity. The major competing reactions to (Eq. 3) (ex. 14) are double bond isomerization to internal tetradecenes, plus glycol oligomerization to diethylene glycol (DEG) etc. Some 2- and 3-tetradecanols have also been detected. Solid acid clays generally appear less effective for reaction (2), the desired etherification is illustrated in Table 2 both for an acidified montmorillonite clay (Engelhard's clay Grade F-24, granules, acidity 16 mg KOH/g) and for a perfluorosulfonated resin (Nation ® NR50, beads, 10/35 mesh, Aldrich Chemical). Continuous syntheses of the same secondary, aliphatic alcohol ethoxylates have been demonstrated using solubilized heteropoly acids ( 12-tungstophosphoric acid and 12-molybdophosphoric acid) as the acid catalysts and tripropylene glycol monomethyl ether as the compatibilizing solvent. Feeding ethylene glycol plus 1dodecene ( 1-C ~, 2.5 molar ratio) to a continuous, upflow reactor as a single-phase, homogeneous liquid mix, syntheses of the dodecyloxyethanols was demonstrated over a range of temperatures (150-180°C) and feed rates. The results are summarized in Table 3; the procedure is detailed in Section 2. Slightly higher temperatures (200°C) are necessary to achieve the same effluent concentrations of dodecyloxyethanols when employing the acidified montmorillonite clay catalyst - - clay Grade F-24 (cf. Table 4). In all three experimental series, the principal competing reactions are dodecene double bond isomerization to internal isomers and ethylene glycol oligomerization to DEG, TEG, etc. Both 2-and 3-dodecanols were also identified. No substantial improvement in glycol ether productivity was realized when the clay catalyst and reactants were rigorously dried prior to use. Generally, as depicted in Table 1 and (Eq. 3), the individual product distributions are each consistent with four parallel, consecutive reactions (see Scheme 1) involving: EG addition to the 2-C position of the linear a-olefin substrate to give the principal glycol ether product A. The addition of 2 mol of glycol to the a-olefin to yield adduct B.
J.F. Knifion /Applied Catalysis A: General 130 (1995) 79-88
84
Table 3 Continuous addition of ethylene glycol to l-dodecene via heteropoly acid catalysis Ex. Catalyst
7
8
Solvent Temp. (°C)
HsPO4 " 12WO~
H3PO4 • 12MOOb
TPGM
TPGM
LHSV Sample Effluent sample composition ( % )" EG I-Cj2
~vCI2 TPGM DDOE 1- DDOE2-
23.2 6.7 18.3 17.9 14.4 13.4
27.4 23.2 24.5 24.3 28.4 26.3
54.7 26.6 44.1 42.5 N.D5 N.D.
t.2 54.3 2.5 2.5 2.7 2.3
1.2 0.1 0.2 0.3 0.4
26.0 25.8 22.8 22.7 18.8 18.7 15.7
28.5 28.4 26.5 26.4 24.4 24.3 22.6
57.7 57.9 43.5 53.5 44.7 44.7 N.D.
0.3 0.4 1.2 1.2 2.0 2.0 2.9
0.1 0.1 0.2 0.2 0.3
150
0.8
1
165
0.8
180
0.8
3 4 5 6
6.6 2 5.4 5.2 3.3 4.1
150
0.8
165
0.8
180
0.8
180
0.4
1 2 3 4 5 6 7
7.5 7.4 6.7 6.7 5.4 5.3 3.9
Abbreviations as follows: total dodecene isomers (XC~2), tripropylene glycol monomethyl ether (TPGM), dodecyl alcohol mono and diethoxylates (DDOE 1-, 2-). b Run in 50 cm 3 capacity continuous reactor, see Section 2 for details. " N.D., not determined. Table 4 Continuous addition of ethylene glycol to l-dodecene via clay catalysis Ex. Catalyst
Solvent Temp.
LHSV Sample Effluent sample composition (%)a
(°c)
9
Clay F-24 b TPGM
150
1.0
165
1.0
180
1.0
200
1.0
1 2 3 4 5 6 7
EG
1-C~
9.6 9.2 7.6 7.7 4.9 4.8 5.9
28.8 29.3 29.4 29.4 24.9 23.8 16.2
XC~
TPGM DDOE 1- DDOE2-
29.9 29.1 23.8
56.2 55.8 52.7 52.6 N.D. N.D. N.D.
0.2 0.1 0.5 0.5 1.8 1.8 2.3
a Abbreviations as in Table 3. b Run in 50 cm 3 capacity continuous reactor, see Section 2 for details. EG R-CH~-CH-CH3 ............... > R-CH2-CH-CH3
R-CH~-CH= CH2
Y E ~ R
I
I
O-CH~CH_,OH
EG -~H-CH2-CH3 ............... >
O-(-CH2CH20)2H
R-CH-CH~-CHs
I O-CH_~CH2OH
O-(-CH2CHzO)~H
Scheme 1. Ethylene glycol addition to linear a-olefins.
0.2 0.2 0.5
85
J.F. Knifton / Applied Catalysis A: General 130 (1995) 79-88
5 1,2-Propyleneglycol
Table
Ex.
addition to l-tetradecene
Catalyst
10 11 12 13
Solvent
H3PO4"I2WO~ Clay F-24 Clay F-24 Clay F-24
Temp.
IA-Dioxane IA-Dioxane 1,4-Dioxane 1,4-Dioxane
Tetradecyloxypropanols conc. ( %) a
(°C)
180 180 150 120
E
F
1.6
0.8 0.4 0.1
0.9 0.2 <0.1
~Tetradecyloxypropanol structures: E:
CI2H2~-CH-CH ~ ! O-CH,-CHOH I CH~
F:
Cull2-CH-CH,-CHa
I
O-CH-CI-I~OH I CH~
The addition of either 1 or 2 tool of ethylene glycol at the 3-C position of the o~-olefin coreactant to give products C and D. A similar, but more complex, regioselectivity is observed when 1,2-propylene glycol is added to 1-tetradecene. Etherifications catalyzed by both the soluble 12tungstophosphoric acid and with the clay Grade F-24, at 120-180°C, using an initial olefin:glycol molar ratio of ca. 1:2, provide the two major secondary alkyl alcohol propoxylates depicted in (Eq. 4). Experimental run data are summarized in Table 5, ex. 10-13. C,2H~Cp-CH~ f
O-CH~-CHOH I CH~
I~
+ /
/
OH OH
C. H23CH-CH~_-CH~ I O-CH-CH~OH
I
c.,
(4)
Here we find an unexpected chemoselectivity with respect to the position of 1,2propylene glycol addition, viz.: When PG addition is at the 2-C position of the olefin, then etherification involves the primary OH of the glycol to give ether adducts of type E in (Eq. 3). This is major product fraction. Where the addition occurs at the 3-C position of the olefin, however, the etherification now involves the secondary OH of the glycol to give monoethers of type F.
J.F. Knifton/Applied Catalysis A." General 130 (1995) 79-88
86
Table 6 1,2-Propylene glycol addition to I-octene Catalyst
Ex.
14 15 16 17
Clay Clay Clay Clay
Solvent
None None None None
F-24 F-24 F-24 F-24
CJPG
Temp.
C~ conv.
Octyloxypropanols conc. (%)"
molar ratio
( °C )
(%)
G
It
1:2 1:2 1:8 1:0.25
150 120 150 150
4 < 1 37 2
0.6 <0.1 7.5 <0.1
0.4 4.6
Octyloxypropanol structures: G:
C6H~CH-CH~
H:
CsHHCH-CH~-CH~
[
I
O-CH2-CHOH
O-CH-CH2OH
I
I
CH~
CH~
Generally, an etherification temperature of greater than 120°C is needed in order to generate significant quantities of desired propylene glycol ethers (see Table 5, ex. 11-13), even in the presence of added 1,4-dioxane. No ethylene glycol or bisethylene glycol ether adducts were identified in these liquid products, indicating that the 1,4-dioxane is not significantly involved in the etherification process and is not, for example, a major source of (-OCH2CH2OCHzCH2OH) type linkages. 1,2-Propylene glycol coupling with 1-octene can, likewise, give rise to a similar pattern of chemoselective derivatives. At 150°C, in the presence of the solid acid catalyst, clay Grade F-24 granules, but using a 1:8 molar mix of 1-octene plus 1,2propylene glycol, yields two major propylene glycol octyl ethers (See Table 6, ex. 16) of structures depicted in (Eq. 5 ). Again it is apparent that where the propylene glycol addition is to the 2-C position of the starting olefin, then etherification will involve the primary OH group of the diol, whereas addition to the 3-C position involves the secondary OH of the glycol molecule. Addition at the 2-C position predominates. C6H~3CH-CH3
I
O-CHT-CHOH
I
CH~ C 6 H [ 3 C H ~ C H ~ Ca 3 - e u ' e u 2
/ / OH OH
CsHt,C[H-CH2-CH; H O-CH-CH2OH
I
CH3
(5)
When 1,4-dioxane is added as solvent, similar experiments using clay Grade F24 and 12-tungstophosphoric acid as catalysts each yielded these same C~t ethers
J.F. Knifton / Applied Catalysis A: General 130 (1995) 79-88
87
Table 7 1,2-Propylene glycol addition to l-octene Ex.
18 19 20 21
Catalyst
Clay F-24 Clay F-24 H3PO4" 12WO3 H3PO4 12WO 3
Solvent
1,4-Dioxane 1,4-Dioxane 1,4-Dioxane 1,4-Dioxane
C8-/PG
Temp.
Octyloxypropanols conc. (%)a
molar ratio
(°C)
G
H
1:2 1:2 1:2 1:2
150 180 150 180
3.5 0.9 3.5 < 0.1
2.6 0.4 1.3
Octyloxypropanol structures as identified in Table 6.
as the major products (Table 7). Internal octene isomers and propylene glycol homologues (DPG, etc.) are once again the major by-products. Generally, higher operating temperatures ( > 180°C) result in a loss of glycol ether formation, irrespective of whether the catalyst is a soluble heteropoly acid, or a solid acidic clay (cf. ex. 18 versus 19 and ex. 20 versus 21 ). Somewhat surprisingly, the regioselectivity of olefin addition leading to products E and F, as well as G and H, is not substantially altered by whether the acid catalyst is a soluble heteropoly acid or a more hindered, layered montmorillonite clay (cf. Table 5 and Table 7).
4. Conclusions In conclusion, the feasibility of generating detergent-range alcohol alkoxylates through addition of vicinal glycols to linear a-olefins via either heteropoly acid or solid acid clay catalysis has been demonstrated. At this stage of technology development, however, it is evident that (a) all major glycol ether adducts (Tables 17) have the secondary alkyl alcohol alkoxylate structure, comprising only one or two alkoxy groups added to the C8-C~4 alkyl chains (Eqs. 1-5), and (b) the rates of glycol addition to C8-C14linear a-olefins are extremely slow in comparison to both oxirane addition rates to detergent-range alcohol [ 11-13] and the rates of vicinal glycol additions to branched olefins capable of forming tertiary carbocations [14]. Nevertheless, the unexpected chemoselectivity seen here, particularly in reactions (4) and (5), suggests that further developments of this chemistry could lead to unique and commercially viable products.
Acknowledgements Thanks are due to Huntsman Corporation for permission to publish this paper, Robert L. Burke and R.E. Baldwin for GC-MS and GC-IR identifications, and Messers. P. Lopez and C.A. Armstrong for technical assistance.
88
J.F. Knifton /Applied Catalysis A: General 130 (1995) 79-88
References [ 1 ] Nonionic Surfactants - - Primary Alcohol-Based, Chem Systems Report Number 83-4, Chem Systems Inc., July 1984. [ 2] M. Am6, Nonionic Surfactants, Stanford Research Institute Report No. 168, SRI International, March 1984. [3] Chem. Market. Report., (9 Nov. 1992) 7. [4] Chem. Eng. News, (30 Sept. 1985) 11. [5] J.F. Knifton, US Patent 5 146 041 (1992). [6] J.F. Knifton, US Patent 5 177 301 (1993). [7] J.F. Knifton, US Patent 5 349 110 (1994). [8] J.F. Knifton, Applied Catal. A, 109 (1994) 247. [9] R.J. Knopf, European Patent Appl., 0 310 194 (1989). [ 10] T.E. Paxson, L. Kim and A.B. Van Aken, US Patent 4 371 716 (1983). [ 11 ] E. Santacesari, M. DiSerio, R. Garaffa and G. Addino, Ind. Eng. Chem. Res., 31 (1992) 2413. [ 12] G. Gee, W.C.E. Higginson, P. Levesley and K.J. Taylor, J. Chem. Soc., (1959) 1338. [ 13 ] N.G. Gaylord (Editor), Polyethers Part I. Polyalkylene Oxides and Other Polyethers, Interscience, New York, 1963. [ 14] J.F. Knifton, ChemTech, 24 (May 1994) 43.