Solubilitv of Gases in and Microcrvstalline
ar
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T. P. RIDENOUR, W. D. WEATHERFORD, JR., AND R. 6. CAPELL .dlultipIe Fellowship of Gulf Research & Development Go.. Mellon Institute of Industrial Research, Pittsburgh, Pa. LTHOUGH others have reported the solubility of oxygen, nitrogen, and other gases in a variety of petroleum products such as solid paraffin ( S ) , medicinal white oils (14),petroleum ether ( 7 ) , gasolines (f7), lubricating oils (1, I f ) , lrerosine and iso-octane (I, 4),and aircraft and Diesel fuels ( 1 , & , 1 8 ) ,no published data are available on rhe solubility of gases in molten paraffin or microcrystjalline waxes from petroleum. KnoJi-ledge of the solubilit~iesof gases in petroleum waxes is important for several reasons. Dissolved gases and occluded gases have a st,ronginfluence on the ext,entof penetration of waxes int,opaper and fabrics of all types while they are being coated with inolten ~vax. For example, wax coatings t h a t are applied with degassed waxes, or under vacuum, penet,rate more deeply than coatings applied under atniospheric pressure. Information concerning the role of gas solubilit,y in this process of wax coating is, therefore, of iniport,ance. The “mottling” of waxes on solidification is thought to be due to dissolved air which comes out of solution. Dat,a on the solubility of gases in liquid and solid wax indicate the magnitude of this effect. Data on the solubility of gases in molten n-ax may lead to a better understanding of the thermal stability and oxidation characteristics of waxes as starting materials for chemical manufacture. For example, when oxygen is consumed by chemical reaction in waxes a t high temperatures, it is desirable to know the relative proportion of the total oxygen take-up resulting from solubilit,yalone. This paper presents data on the solubility of gases in tvaxes and a method for predicting or extending such data.
for each gas is given in Table I. The waxes which were used in this st,udy are described in Table 11. The solubility values rpported in Table I11 could be in error by around 0.001 cc. per gram x i t h a possible maximum error of 0,003 cc. per gram. These errors are due t o the following factors: 1. The temperature of t,hc circulat,ing system used in calculating solubilit,iee could be o f f by at least 2’ C. This could affect the Bolubility value to the extent of 0.0006 to 0.0013 cc. per gram, depending on the pressure. 2. Pressure readings may be in error by 0.2 mm., which would change solubility values by 0.00003 t o 0.00018 cc. per gram.
A change of 0.001 cc. per gram in qolubility produces a change of around 0.004 in the Bunsen coefficient in the l o x pressure range, d i i k the (Bhange is about 0.001 for the higher pressure region.
Kitrogen
0.2
Carbon dioxide Methane
0.1
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.,,
.,.
.,
..
... ..,
,.
Air Reduction Co., Pittsburgh, Pa. KhInO? .. . 99.8 . , . , . Ohio Cheniical Co., d- ZIfg. c o . , Pittsbrirgh, Pa. 0 . 1 . . . 9 6 . 4 . , . 3 . 4 NaHCOd . . . . . . . . . 9 7 . S . , Ohio Chemical Co. 0.04
1.1 97.8
0.1
,
a Balance of 2 2 % , consisted of heavier hydrocarbons.
EXPERIMEYTAL TABLE
The apparatus used for this investigation, illustrated in Figure 1, is similar to the equilibrium adsorption apparatus described by Brunauer, Emmett, and Teller (2) for measurement of the suiface areas of solid catalysts. The mercur3 diffusion pump was used to evacuate the system t o a pressuie of 1 micron or less as determined b y the McLeod gage. The inanomcter was used to measure the pressure of the gas in the system. The two calibrated burets supplied measured amounts of gas to the sample container by displacement with mercury. The wax sample container, n i t h its circulating system, appears a t the right of the gas burets. SOLUBILITY &IF,~ S U R E M E N T S . -2 v,-eighed amount of F a x was placed in the tyax chamber, which v a s attached t o the solubility apparatus. B y filling one or more bulbs of the buretswithmercury, ta o or more pressure readings could be obtained, and the volume of gas in the buret-capillary system could be calculated from the ideal gas law, For each volume setting of the burets, 20 minutes to 1 hour was allowed for the system to reach equilibrium For each gas, three or more readings, covering a range of about 250 to 760 mni. of mercury or higher, were taken. Desorption data were obtained t o serve as a check OII the absorption data. I n most cases, both sets of values agreed very well. Desorption data for methane did not check the absorption values in all cases. However, the discrepancies were probably caused b y contaminants in the methane (Table I). Gases used in this solubility study were argon, nityogen, oxygen, carbon dioxide, and methane. The source and analysis
99.96
Oxygen Argon
TI.
PEIYSICAI,
PROPERTIES
OF
PARAFFIN
I’ETROKAX X
ax
AND
I’araffin TTax Petrowax A 12&2 (-4SThI D 87.- 189.6 fAST\I 22) D 127-30) Xeedle penetration (77’ F . , 150 30 20 g , , 5 see.) 350 7 50 hIolecular weight Density, g . / c c ~ 0.7716 a t 68.3’ C. 0.8039atB2.4° C. 0.7662 a t T6.S0 C. 0.7910a i 97.O0 C. Estd. pseudo critical temp., I
