Chemistry of hydrocarbon compounds – Product blend – e.g. – composition – etc. – or blending process... – Fluent dielectric
Reexamination Certificate
2000-01-06
2001-05-29
Wood, Elizabeth D. (Department: 1755)
Chemistry of hydrocarbon compounds
Product blend, e.g., composition, etc., or blending process...
Fluent dielectric
C585S001000, C252S073000, C252S570000
Reexamination Certificate
active
06239320
ABSTRACT:
This invention relates to high temperature heat transfer fluids, and more particularly to heat transfer fluids comprising blends of 1,2,3,4-tetrahydro(1-phenylethyl)-naphthalene with other fluids, especially dibenzyl toluene.
Thermal fluids or heat transfer fluids are widely used, for example, to control processing temperatures in chemical plants. The ability of a fluid to resist degradation at elevated temperatures is called thermal stability. Typically, as a heat transfer fluid degrades, volatile, light boiling materials as well as other heavier components are formed. These heavy components increase the fluid's viscosity leading to an increase in film temperature, which results in higher degradation. Further, polymers formed through the degradation of the fluids tend to darken the fluid and ultimately deposit on surfaces in the system thereby decreasing the system efficiency and potentially leading to more serious system failure. Thus, significantly degraded fluid must be replaced with fresh fluid, or it must be periodically recycled.
The long-standing importance of findings fluids exhibiting improved thermal stability is evidenced, for example, by Matsumoto et al., Ind. Eng. Chem., Prod. Res. Dev., Vol. 15, no. 3, 1976, p. 215-218, which is herein incorporated by reference. Matsumoto tested the thermal stability of 1-phenyl-1-tetrahydronaphthylethane (PTE, also called 1,2,3,4-tetrahydro(1-phenylethyl)naphthalene which is abbreviated as ST-THN) and compared the results with thermal fluids such as dibenzyl benzenes and partially hydrogenated terphenyls which are well-established fluids in the industry. Matsumoto's results showed ST-THN to have favorable properties for a high boiling point thermal fluid. Matsumoto also identified the degradation products from ST-THN. Although ST-THN was found to have favorable properties alone, its compatibility with other fluids was not investigated.
In industrial applications, the ability to mix different thermal fluids without the detrimental effects described above can be advantageous. Therefore, a cost effective heat transfer fluid blend having favorable thermal stability properties would be desirable.
This invention is a heat transfer fluid which comprises a mixture of 1,2,3,4-tetrahydro(1-phenylethyl)naphthalene (ST-THN) and dibenzyl toluene as the second fluid. It has been discovered, surprisingly, that mixing ST-THN with specific second fluids significantly improves the thermal stability of the second fluid, better than the weight average of the two fluids. The resulting fluid mixture had thermal stability comparable to the thermal stability of ST-THN alone.
The heat transfer fluid can be beneficially admixed from 1,2,3,4-tetrahydro(1-phenylethyl)naphthalene; and a second fluid characterized as an aromatic component having alkyl, cyclohexyl, or cyclopentyl linkages; preferably, alkyl linkages. The second fluid is preferably other than a degradation product of 1,2,3,4-tetrahydro(1-phenylethyl)naphthalene.
More specifically, the heat transfer fluid can be admixed from: 1,2,3,4-tetrahydro(1-phenylethyl)naphthalene; and a second fluid selected from the group consisting of dibenzyl toluene, partially hydrogenated terphenyl, dibenzyl benzene, xylyl toluene, dixylyl toluene, xylyl xylene, dixylyl xylene, diethylbenzene, 1,1-diphenylethane, benzene alkylates, alkylnaphthalenes, alkylbiphenyls, diphenylmethane, cyclohexyldiphenyl ether, alkyldiphenylethers, triphenylmethane, tritolylmethane, and mixtures thereof.
Another embodiment of the present invention is a method for preparing the heat transfer fluid. The method comprises admixing 1,2,3,4-tetrahydro(1-phenylethyl)-naphthalene with a second fluid as described above. The 1,2,3,4-tetrahydro(1-phenylethyl)naphthalene component preferably constitutes at least twenty-five percent by weight of the total heat transfer fluid.
A further embodiment of the present invention is a method of controlling the temperature of a system. The method comprises adding to the system 1,2,3,4-tetrahydro(1-phenylethyl)naphthalene and a second fluid as described above. The 1,2,3,4-tetrahydro(1-phenylethyl)-naphthalene and the second fluid may be added to the system separately or admixed together prior to addition to the system.
REFERENCES:
patent: 5017733 (1991-05-01), Sato et al.
Benjamin, Ben M. et al., Thermal cleavage of chemical bonds in selected coal-related structures, Fuel, 1978, vol. 57, May, pp. 269-272.
Commandeur, R. et al., A New Family of High Performance Thermal Fluids, Informations Chimie, vol. 33, No. 376, 1996-03, pp. 93-96 (translation).
Galasso, P.J. et al., Syntrel 350 Un nuovo fluido diatermico sintetico per alte prestazioni, Pitture Vernici, 1986, vol. 62, 10, pp. 103-107 —English language sections. (Considered only English Summary).
Matsumoto, Tadashi et al., Thermal; Transfer Fluid: 1-Phenyl-1-tetrahydronaphthylethane, Ind. Eng. Chem., Prod. Res. Dev., Vol. 15, No. 3, 1976, presented at the Division of Industrial and Engineering Chemistry, Centennial Meeting of the American Chemical Society, New York, N.Y., Apr. 1976, pp. 215-218.
Syntrel 350 heat transfer fluid, Exxon Chemicals, May 1988.
Cuthbert John B.
Mendoza Abel
Schultz Dale H.
The Dow Chemical Company
Wood Elizabeth D.
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