# Patent

## Title
Reagent for decomposing fluorocarbons

## Abstract

This is a continuation-in-part of patent application Ser. No. 09/156,744, filed on Sep. 17, 1998, now abandoned.

## Background
Heat transfer fluids, sometimes referred to as heat transfer media, are heat transfer agents which are used in cooling and heating circuits and in heat recovery units. There may be other uses for such fluids and as such, they are required or expected to have a high heat transfer capacity, high thermal loading capacity and adequate thermal stability for the operating range. It is also desirable to have fluids which can stand very high heat and yet have a low freezing point while being inert.

There have been prior art heat transfer fluids which have some of the proper characteristics at high temperatures and at low temperatures and are chemically inert. The eutectic mixture of 73% diphenyl oxide and 27% biphenyl commonly known as DowthermA, is currently one of the largest volume heat transfer fluids sold worldwide. Other widely used fluids are a mixture of hydrogenated terphenyl and quatraphenyl and dibenzyl toluene.

It has, however, become desirable to get away from the available heat transfer fluids which have previously been used for a number of reasons, one of which is the current requirements of the EPA as to reportable spill quantity for biphenyl. It is also desirable to provide a heat transfer fluid which has a higher resistance to heat and a lower freezing capability, or a combination of both.

It is the object of the present invention to overcome any disadvantages of the prior art heat transfer fluids and to eliminate the use of biphenyls to obviate the need for spill reportage under the EPA regulations. It is also an object of the present invention to provide a more useful heat transfer fluid insofar as heat levels and freezing points are concerned and to additionally create heat transfer fluids having better stability under various conditions.

To achieve the objects of this invention, therefore, it has been discovered that a mixture in broad proportions of diphenyl oxide (DPO) sometimes referred to as diphenyl ether, which has a structural formula of C.sub.6 H.sub.5 OC.sub.6 H.sub.5 and 1,1 diphenyl ethane (DPE) having a structural formula of CH.sub.3 CH(C.sub.6 H.sub.5).sub.2 in varying amounts but generally a larger amount of either diphenyl oxide or 1,1 diphenyl ethane to substantially equal amounts of diphenyl oxide and 1,1 diphenyl ethane. In other words, fluid with an excess of 1,1 diphenyl ethane over diphenyl oxide and vice versa provides a useful heat transfer fluid. However, the preferred ratios of about 5 to 50% 1,1 diphenyl ethane to 95-50% diphenyl oxide provides a heat transfer fluid with remarkable improvements over the prior art fluids, i.e., higher heat transfer coefficients and lower freezing points as well as greater thermal stability. The composition recited above though similar to the prior art compositions already mentioned, is not shown in the prior art, has not been used, and as previously stated, is remarkably better than the prior art compositions so much so that it may be considered that the performance of this material is unexpected and even synergistic.

Although a mixture of 1,1 diphenyl ethane and diphenyl oxide, as outlined above, is the preferred embodiment of the invention, it is known to one of ordinary skill in the art that certain impurities and/or isomers can be added in small quantities to this preferred heat transfer mixture without affecting the performance characteristics of the invention, as discussed more fully below. In particular, it is known that XCELTHERM XT, a commercially available product consisting essentially of a mixture of 92-95% 1,1 diphenyl ethane, 7-4% 1,2 diphenyl ethane, and 1% diphenyl methane can be substituted for the pure 1,1 diphenyl ethane material of the preferred heat transfer mixture without essentially affecting the overall heat transfer characteristics of the resultant mixture when compared to the expected performance characteristics of the preferred embodiment of the invention. The XCELTHERM XT product is processed by the assignee of this patent, Radco Industries, Inc. of LaFox, Ill. Accordingly, it is known that a material consisting essentially of 1,1 diphenyl ethane and smaller amounts of other impurities and/or isomers can be substituted for the pure 1,1 diphenyl ethane of the preferred composition.

Thermal stability tests of mixtures of 1,1 diphenyl ethane and diphenyl oxide alone have been conducted. However, in view of all of the materials that have been used prior to the development of the heat transfer fluid of this invention, it has been decided to run confirmatory tests as to the novelty and unexpected improvement provided by the heat transfer fluid combination of this invention, namely, diphenyl ether and 1,1 diphenyl ethane. The combinations that have been tested are terphenyls, dibenzyl toluene, the diphenyl oxide-biphenyl mixture and the compositions of the invention to determine which fluid provides the best heat transfer results. It should be noted here that the terms "diphenyl ether," "diphenyl oxide" and "DPO" will be used throughout this specification as indicating the same chemical component while "DPE" will be used as indicating 1,1 diphenyl/ethane.

Many industrial production processes require the use of a heat transfer fluid in the temperature range of 600.degree. F.-700.degree. F. The heat transfer fluids used in this temperature range fall into two broad classifications: transfer occurring in the liquid phase. heat transfer occurring in the liquid or vapor phase.

Three distinct chemistries, all aromatic, define the most widely used fluids worldwide in this temperature classification.

The primary factors which define a fluid's use range are:

The primary factor which defines its effectiveness within it's operating range is: heat/unit time-area at a given temperature.

A major factor in a fluid's use is its environmental impact--whether it is regulated as a hazardous chemical. Since these fluids may from time-to-time leak from the system or be subject to the over-the-road spillage, those fluids regarded as "hazardous" by the EPA incur additional potential liabilities, and therefore expense, in their use.

Disadvantages of the various types of fluids: especially in colder climates. 100 lbs. of biphenyl.

The objective is to provide a single fluid that will operate in either the liquid/vapor phase with acceptable thermal stability to 700.degree. F. offering a sufficiently low pour/crystallizing point, high heat transfer coefficient, and minimal environmental exposure.

The heat transfer coefficient is a primary measure of the ability of a heat transfer medium to transfer heat. Therefore, a fluid having a higher heat transfer coefficient at a given temperature may be expected to transfer more heat/unit heat exchange surface area than another with a lower heat transfer coefficient at the same temperature. As such, a higher production rate or a decrease in production time is possible with the fluid having the higher heat transfer coefficient.

Table 1 represents a comparison of the heat transfer coefficients of the common types of heat transfer fluids with the heat transfer coefficients of this invention when the DPO is in excess of or equal to the DPE. __________________________________________________________________________ Comparison of Heat Transfer Coefficients HEAT TRANSFER COEFFICIENTS Schedule 40 2' pipe (2.066' ID) @ 7 ft/sec flow rate 73/27 95/5 85/15 75/25 50/50 TEMP (.degree. F.) Terphenyl.sup.1 DBT.sup.2 DPO/BIP DPO/DPE DPO/DPE DPO/DPE DPO/DPE __________________________________________________________________________ 600   360.66 369.86 445.65 452.16 447.24 443.79 442.23 625   365.46 377.52 444.77 454.05 449.45 445.47 444.73 650   369.05 385.29 442.68 455.37 450.36 447.53 445.68 675   N/A.sup.1 N/A.sup.2 438.85 457.06 451.31 447.83 444.83 700   N/A.sup.1 N/A.sup.2 433.68 456.35 450.49 448.16 441.46 __________________________________________________________________________ .sup.1 Maximum use temperature recommended by fluid supplier is 650.degree. F. .sup.2 Maximum use temperature recommended by fluid supplier is 66.degree F. Heat transfer coefficient is a measure of the ability of a fluid to uptake, transport, and download BTU. The higher the heat transfer coefficient relative to another product the greater the ability of the fluid with the higher heat transfer coefficient to transfer heat per unit area of heat exchange surface.

Table 2 represents a comparison of the heat transfer coefficients of the common types of heat transfer fluids with the heat transfer coefficients of this invention when DPE is in excess of DPO. __________________________________________________________________________ Comparison of Heat Transfer Coefficients HEAT TRANSFER COEFFICIENTS Schedule 40 2' pipe (2.066' ID) @ 7 ft/sec flow rate 73/27 95/5  85/15 75/25 TEMP (.degree. F.) Terphenyl.sup.1 DBT.sup.2 DPO/BIP DPE/DPO DPE/DPO DPE/DPO __________________________________________________________________________ 600   360.66 369.86 445.65 415.17 419.11 423.08 625   365.46 377.52 444.77 416.55 420.55 424.59 650   369.05 385.29 442.65 441.21 450.14 447.67 __________________________________________________________________________ .sup.1 Maximum use temperature recommended by fluid supplier is 650.degree. F. .sup.2 Maximum use temperature recommended by fluid supplier is 660 .degree. F. Heat transfer coefficient is a measure of the ability of a fluid to uptake, transport, and download BTU. The higher the heat transfer coefficient relative to another product the greater the ability of the fluid with the higher beat transfer coefficient to transfer beat per unit area of heat exchange surface.

The following Tables 1A-1E and 2A-2C are derived from heat transfer coefficients in Tables 1 and 2. (+)% shows the percentage increase in heat transfer coefficient of DPO/DPE-DPE/DPO relative to the indicated product. (-)% shows the percentage decrease in heat transfer coefficient of DPO/DPE-DPE/DPO relative to the indicated product. ______________________________________ % COMPARISON OF HEAT TRANSFER COEFFICIENTS 600.degree. F. 95/5     85/15      75/25  50/50 Product  DPO/DPE  DPO/DPE    DPO/DPE DPO/DPE ______________________________________ Terphenyl +25.37   +24.01     +23.05 +22.62 Dibenzyl +22.25   +20.92     +19.99 +19.57 Toluene 73/27     +1.46    +0.36      -0.42  -0.77 DPO/BIP ______________________________________ ______________________________________ % COMPARISON OF HEAT TRANSFER COEFFICIENTS 625.degree. F. 95/5     85/15      75/25  50/50 Product  DPO/DPE  DPO/DPE    DPO/DPE DPO/DPE ______________________________________ Terphenyl +24.24   +22.98     +21.89 +21.69 Dibenzyl +20.27   +19.05     +18.00 +17.80 Toluene 73/27     +2.09    +1.05      +0.16  -0.01 DPO/BIP ______________________________________ ______________________________________ % COMPARISON OF HEAT TRANSFER COEFFICIENTS 650.degree. F. 95/5     85/15      75/25  50/50 Product  DPO/DPE  DPO/DPE    DPO/DPE DPO/DPE ______________________________________ Terphenyl +23.39   +22.03     +21.27 +20.76 Dibenzyl +18.19   +16.89     +16.15 +15.67 Toluene 73/27     +2.87    +1.73      +1.11  +0.68 DPO/BIP ______________________________________ ______________________________________ % COMPARISON OF HEAT TRANSFER COEFFICIENTS 675.degree. F. 95/5     85/15      75/25  50/50 Product  DPO/DPE  DPO/DPE    DPO/DPE DPO/DPE ______________________________________ Terphenyl N/A.sup.1 N/A        N/A    N/A Dibenzyl N/A.sup.2 N/A        N/A    N/A Toluene 73/27    +4.15    +2.84      +2.05  +3.36 DPO/BIP ______________________________________ .sup.1 Manufacturer recommends highest use temperature of 650.degree. F. .sup.2 Manufacturer recommends highest use temperature of 660 .degree. F. ______________________________________ % COMPARISON OF HEAT TRANSFER COEFFICIENTS 700.degree. F. 95/5     85/15      75/25  50/50 Product  DPO/DPE  DPO/DPE    DPO/DPE DPO/DPE ______________________________________ Terphenyl N/A.sup.1 N/A        N/A    N/A Dibenzyl N/A.sup.2 N/A        N/A    N/A Toluene 73/27    +5.23    +3.88      +3.35  +1.79 DPO/BIP ______________________________________ .sup.1 Manufacturer recommends highest use temperature of 650 .degree. F. .sup.2 Manufacturer recommends highest use temperature of 660.degree. F. ______________________________________ % COMPARISON OF HEAT TRANSFER COEFFICIENTS 600.degree. F. 95/5         85/15    75/25 Product   DPE/DPO      DPE/DPO  DPE/DPO ______________________________________ Terphenyl.sup.1 +15.11       +16.20   +17.31 Dibenzyl.sup.2 +12.25       +13.32   +14.39 Toluene 73/27      -7.34        -6.33    -5.06 DPO/BIP ______________________________________ .sup.1 Manufacturer recommends highest use temperature of 650.degree. F. .sup.2 Manufacturer recommends highest use temperature of 660 .degree. F. ______________________________________ % COMPARISON OF HEAT TRANSFER COEFFICIENTS 625.degree. F. 95/5         85/15    75/25 Product   DPE/DPO      DPE/DPO  DPE/DPO ______________________________________ Terphenyl.sup.1 +13.98       +15.07   +16.18 Dibenzyl.sup.2 +10.34       +11.40   +12.47 Toluene 73/27      -6.77        -5.76    -4.75 DPO/BIP ______________________________________ .sup.1 Manufacturer recommends highest use temperature of 650.degree. F. .sup.2 Manufacturer recommends highest use temperature of 660.degree. F. ______________________________________ % COMPARISON OF HEAT TRANSFER COEFFICIENTS 650.degree. F. 95/5         85/15    75/25 Product   DPE/DPO      DPE/DPO  DPE/DPO ______________________________________ Terphenyl.sup.1 +19.55       +21.97   +21.30 Dibenzyl.sup.2 +14.51       +16.83   +16.19 Toluene 73/27      -0.33        +1.68    +1.12 DPO/BIP ______________________________________ .sup.1 Manufacturer recommends highest use temperature of 650 .degree. F. .sup.2 Manufacturer recommends highest use temperature of 660 .degree. F.

Pour Point/Crystallizine Point Was Determined For The Various Fluids Utilizing ASTM D97. ______________________________________ Comparison of Pour Points/Crystallizing Points of the various fluids POUR/CRYSTALLIZING POINTS Product         Temp .degree. F. ______________________________________ Terphenyl       -15 Dibenzyl Toluene -50 73/27 DPO/BIP    54 95/5 DPO/DPE     54 85/15 DPO/DPE    40 75/25 DPO/DPE    27 50/50 DPO/DPB    10 95/5 DPE/DPO    -30 85/15 DPE/DPO   -21 75/25 DPE/DPO   -13 ______________________________________ .sup.1 ASTM D97 Testing Method

Thermal stability may be defined as the resistance of chemical bonds to thermal cracking. A fluid exhibiting greater thermal stability relative to another at any given temperature will provide increased fluid life and a decreased potential for system fouling caused by thermal degradation by products.

The Thermal stability tests were conducted using the Ampule Test Procedure.

The Ampule Test is generally accepted as an industry standard for the testing of relative thermal stability between heat transfer fluids Although there is no standard ASTM-type Ampule Test defined, the data generated by such testing has proven reliable over the course of many years. Variations between methods exist as to the composition and diameter of the ampules, the method by which the oxygen is removed from the ampule, the sample size, and the temperature run. However, with the exception of those methods which do not properly provide for oxygen removal, the relative results are reliable as long as uniform temperatures are maintained across the oven. The data serves to define the thermal stability performance differences between fluids in any given system.

The procedure for the Ampule Test is as follows:

Purpose: To determine relative thermal stability by measuring the thermal decomposition of heat transfer fluids under like conditions in the absence of oxygen.

A. SAMPLE PREPARATION sufficient number for two samples of each fluid to be tested. and allow to dry.

B. SAMPLE PREPARATION Ampule marked 1A, 5 ml into Ampule marked 1B, etc.) and note the product name of the sample and its designated Ampule. samples on either side of the rack.

C. OXYGEN REMOVAL

Tube Sparging Procedure instructions. each tube for 1 minute.

D. THERMAL STRESS the selected temperature at .+-.1.degree. F. and with no more than .+-.1/2.degree. F. temperature gradient across the oven. under the parameters defined above the 336 hrs. (Two Weeks). cool for 24 hours undisturbed.

E. ANALYSIS samples utilizing using ASTMD2997 Simdis Gas Chromatography Methodology. sample

The results of the Thermal Stability Test are as follows:

Thermal Stability--Resistance of chemical bonds to thermal cracking at any given temperature DPO is in excess of or equal to DPE. __________________________________________________________________________ Comparison of Thermal Stability 336 Hour Ampule Test % THERMAL DECOMPOSITION 73/27 95/5 85/15 80/20 75/25 50/50 TEMP (.degree. F.) Terphenyl.sup.1 DBT.sup.2 DPO/BIP DPO/DPE DPO/DPE DPO/DPE DPO/DPE DPO/DPE __________________________________________________________________________ 600   0.87  0.59 0.004 0.002 0.002 0.01 0.01 0.004 625   1.36  0.99 0.01 0.01 0.01 0.02 0.03 0.03 650   3.50  2.29 0.04 0.03 0.06 0.12 0.15 0.22 675   N/A.sup.1 N/A.sup.2 0.11 0.13 0.37 0.60 0.88 1.60 700   N/A.sup.1 N/A.sup.2 0.49 0.48 1.67 2.89 4.50 7.42 __________________________________________________________________________ .sup.1 Maximum use temperature recommended by fluid supplier is 650.degree. F. .sup.2 Maximum use temperature recommended by fluid supplier is 660.degree. F. .sup.3 Maximum use temperature recommended by fluid supplier is 750.degree. F. .sup.4 Sample analysis by ASTM D2997

Thermal Stability-Resistance of chemical boards to thermal cracking at any given temperature when DPE is in excess of DPO. __________________________________________________________________________ Comparison of Thermal Stability 336 Hour Ampule Test % THERMAL DECOMPOSITION 73/27 95/5  85/15 75/25 TEMP (.degree. F.) Terphenyl.sup.1 DBT.sup.2 DPO/BIP DPE/DPO DPE/DPO DPE/DPO __________________________________________________________________________ 600    0.87  0.59 0.004 0.09  0.01 0.01 625    1.36  0.99 0.01 0.27  0.15 0.09 650    3.50  2.29 0.04 1.40  1.02 0.85 __________________________________________________________________________ .sup.1 Maximum use temperature recommended by fluid supplier is 650.degree. F. .sup.2 Maximum use temperature recommended by fluid supplier is 660.degree. F. .sup.3 Maximum use temperature recommended by fluid supplier is 750.degree. F. .sup.4 Sample analysis by ASTM D2997

Thus, the tests ofthese various chemical compositions demonstrate that the diphenyl ether or oxide/1,1 diphenyl ethane mixture is superior insofar as heat transfer co-efficient and thermal stability is concerned with respect to terphenyl and dibenzyl toluene and equivalent or superior in heat transfer coefficient to the eutectic mixture of diphenyl oxide and biphenyl while providing lower point and lastly, avoids the use of biphenyl which is now important in the industry.

Various features of the invention have been particularly shown and described in connection with the illustrated embodiments of the invention, however, it must be understood that these particular arrangements merely illustrate and that the invention is to be given its fullest interpretation within the terms of the appended claims.

## Claims

1. A biphenyl-free heat transfer fluid comprising a mixture of diphenyl oxide and 1,1 diphenyl ethane.

2. The heat transfer fluid of claim 1 wherein said 1,1 diphenyl ethane is comprised of a mixture of 1,1 diphenyl ethane and one or more impurities.

3. The heat transfer fluid of claim 2 wherein said one or more impurities can be selected from the group consisting of diphenyl methane and 1,2 diphenyl ethane.

4. The heat transfer fluid of claim 1 wherein said 1,1 diphenyl ethane consists essentially of a mixture of 1,1 diphenyl ethane, 1,2 diphenyl ethane and diphenyl methane.

5. The heat transfer fluid of claim 4 wherein said 1,1 diphenyl ethane is about 92 to 95 weight percent of said mixture, said 1,2 diphenyl ethane is about 7 to 4 weight percent of said mixture, and said diphenyl methane is about 1 weight percent of said mixture.

6. The heat transfer fluid of claim 1 wherein the amount of said 1,1 diphenyl ethane ranges from an excess to equal to said diphenyl oxide.

7. The heat transfer fluid of claim 1 wherein the amount of said diphenyl oxide ranges from an excess to equal to said 1,1 diphenyl ethane.

8. The heat transfer fluid of claim 1 wherein said diphenyl oxide is present from 95-5% by weight of said mixture and said 1,1 diphenyl ethane is present from 5-50% by weight of said mixture.

9. The heat transfer fluid of claim 8 wherein said diphenyl oxide is present in about 95% by weight of said mixture and said 1,1 diphenyl ethane is present in about 5% by weight of said mixture.

10. The heat transfer fluid of claim 8 wherein said diphenyl oxide is present in about 85% by weight of said imxture and said 1,1 diphenyl ethane is present in about 15% by weight of said mixture.

11. The heat transfer fluid of claim 8 wherein said diphenyl oxide is present in about 75% by weight of said mixture and said 1,1 diphenyl ethane is present in about 25% by weight of said mixture.

12. The heat transfer fluid of claim 8 wherein said diphenyl oxide is present in about 50% by weight of said mixture and said 1,1 diphenyl ethane is present in about 50% by weight of sald mixture.