with carbon monoxide. A typical treatment was carried out at 1000' F. and 400-p.s i.g. hydrogen pressure, followed by carbon monoxide at 800 p.s.i.g. and 300' F. This resulted in removal of 53% nickel and 24% iron. Promoters such as HyS and NH3 bvere found to increase the carbonylation rate. Carbonylation may be combined with chlorination, the latter for vanadium removal. Conclusion
depend upon the contaminants present and other individual features of each cracking operation. Acknowledgment
'The authors express their appreciation for the significant contributions to this work of data and suggestions by J. P. Gallagher, A. D. Anderson, and L. L. Simantel. Literature Cited
This discussion of demetalization has summarized some of the chemistry related to demetalization and pointed out the importance of the pretreatment steps in obtaining significant removal of metals. The practical aspect of demetalization should not be overlooked and an indication of typical improvement in catalyst selectivity, using two of the methods discussed, is shown in Table 11. These yields were obtained on a small scale pilot plant fluid cracking unit. An increase in gasoline yield and decreases in coke and dry gas result from catalyst demetalization. Data on commercial application of demetalization and the associated economics of the process have been presented (7. 6). The specific process applied will
(1) Adams, N. R., Sterba, M. J.: A.1.Ch.E. Meeting, March 1963. (2) Donaldson, R. E., Rice, T., Murphy, J. R., 2nd. Eng. Chem. 53, 721 (1961). (3) Duffy, B. J., Hart, H. M., Chem. Eng. Progr. 48, 344 (1952). (4) Flinn, R. -4,, Beuther, H., IND.ENG. CHEM.PRODUCT RES. DEVELOP. 2, 53 (1963). (5) Gossett, E. C., Petrol. Rejiner 39, 177 (1960). (6) Sanford, R. A,, Erickson: H., Burk, E. H., Gossett, E. C., Van Petten, S.L., Ibid., 41, 103 (1962). RECEIVED for review August 28, 1963 .ACCEPTED September 2, 1963 Division of Petroleum Chemistry, 145th Meeting, ACS, New York, N.Y . , September 1963.
H I G H - T E M P E R A T U R E HYDRAULIC F L U I D S FROM PETROLEUM E.
E . K L A U S , E . J . T E W K S B U R Y , AND M .
R. F E N S K E
Department of Chemical Engineering, Pennsyloania State Cninieersity, University Park, Pa.
A series of superrefined mineral oils has been developed to meet aerospace requirements as high-temperature hydraulic fluids. The high quality of products obtained in the laboratory research and development phase has been maintained through the transition to commercial production. The continuous range of fluid properties and excellent storage stability are shown to b e outstanding features of hydrocarbon fluids. Thermal stability, lubricity, viscosity-temperature characteristics, oxygen tolerance, and oxidation inhibitor response of the paraffinic and naphthenic hydrocarbons are compared. Additional separational techniques and stock selection are discussed as a means of upgrading the viscosity properties of super-refined mineral oils. Several methods of preparing synthetic hydrocarbons competitive in physical and chemical properties with the fluids separated physically from mineral oils are discussed.
HE FIRST of the \vide temperature range aircraft hydraulic Tfluids, Spec. MIL-H-5606 (ZO), was developed about 20 years ago to meet a temperature range of -40' to fl6O' F. This same fluid, mithin a decade of its development, was being used over the range of -65' to +300° F. In the last decade. demands for still higher temperatures led to the development of tailor-made synthetic hydraulic fluids and lubricants for the to +400° F. In hydraulics, this era was range of -65' accompanied by the development of the closed system to control fluid loss. cleanliness. and oxidative deterioration. The rapid development of aerospace hardware has placed still more demands on the hydraulic fluid. The t\vo most exacting requirements are operability to temperatures in the range of 550' to 700' F. and excellent storage stability in the hardware for a period of 5 to 10 years. These requirements
332
I & E C P R O D U C T RESEARCH A N D D E V E L O P M E N T
must be met without seriously compromising the low-temperature properties, lubricity, or over-all stability. The pertinent properties of several chemical classes showing promise as high-temperature fluids are compared in Table I. The mineral oils used in this comparison are super-refined. The silicones, poly(pheny1 ethers), and super-refined mineral oils show the best over-all balance of properties for hydraulic fluid application at high temperatures. These three fluid types also exhibit deficiencies in certain properties requiring special mechanical design features in the hardware. The silicone fluid, for example, exhibits a substantially higher viscosity a t high temperature but poor boundary lubrication. Therefore, equipment design emphasizes hydrodynamic lubrication. The phenyl ether exhibits a high pour point which requires a mechanical device to allow cold starting.
Table 1.
Mineral oil (super-refined) Phenyl ether Silicone (improved lubricity) Siloxanes Esters Aromatic hydrocarbons
Comparison of Several Materials as High-Temperature Hydraulic Fluids
Storage Sta bill ty
ViscosityTemperature
LowTemperature Behavior
Thermal Stability
Boundary Lubricity
Oxygen Tolerance
Excellent Good Fair Good Poor Good
Good Fair Excellent Very good Very good Poor
Good Poor Excellent Very good Good Fair
Very good Excellent Very good Fair Poor Very good
Very good Fair Poor Poor Good Good
Very good Fair Poor Fair Good Fair
'The super-refined mineral oil shows a relatively low viscosity at high temperature but good boundary lubrication. The silicone and hydrocarbon fluids can be prepared to meet any viscosity level from a continuous spectrum of viscosity values. This provides the versatility needed to dovetail lubricant properties kvith specific hardware. Super-refining is the additional processing of conventionally refined mineral oils to optimize the chemical and physical properties of the mineral oil. The specific steps used in the laboratory for super-refining include additional distillation, hydrogenation, acid extraction, and deep dewaxing. These steps have been discussed previously (72, 7 3 ) . The base stocks used in those preliminary studies ranged from naphthenic stocks having a viscosity index (V.I.) of about 80 to paraffinic stocksof100to 110V.I. Formulations
Commercial Products. Two grades of super-refined mineral oils have received attention for aerospace hydraulic
10,300 8,000 6,000
7 + / / / /
/
i
/
/
i
i !
101 I
400
applications. These fluids have been distributed under the designations of h l L 0 7277 (or M L O 7243) and MLO 7557 (or h4LO 60-294). Both fluids are now being prepared commercially using the special processing steps from the laboratory development studies. T h e commercial fluids are of the same high quality as those prepared in the laboratory. The commercial MLO 7277 fluid is prepared to provide a liquid range from -25' to greater than 700' F.: with an ' to 700' F. operational range in hydraulic equipment of 0 This fluid is commercially available as 7277B from the Oronite Chemical Co. and as F S 3158 from the Humble Oil and Refining Co. The commercial MLO 60-294 fluid has been prepared \vith a liquid range from -75' to greater than 700' F. and a uscful range in hydraulic equipment of -65' to +700° F. This fluid is commercially available as FN 3160 from the Humble Oil and Refining Co. Typical physical and chemical properties of these two fluids are shown in Tables I1 and I11 (4, 79). Fluid Preparations. Preliminary studies established that the super-refined base stocks show excellent additive response. This includes respcnse to oxidation inhibitors. A comparison of the effectiveness of oxidation inhibitors in super-refined mineral oil base stocks is shown in Figure 1. These data show stable life as a function of temperature. Stable life decreases to values of 1 hour or less at 500 " F. for all of the additive types tested. I t is primarily for this reason that high-temperature hydraulic systems are made inert. In the range of 500" to 700" F., essentially all of the available oxygen will be assimilated by the fluid. The way to obtain good fluid life in the high temperature hydraulic system, therefore, is to eliminate or severely limit the availability of oxygen. Oxidation studies with mineral oils have shown that the oxygen tolerance of a fluid is best for the fluid \vithout additives. However, a super-refined mineral oil is devoid of natural inhibitors and vulnerable to oxidative deterioration unless protected. The real need in aerospace hydraulic fluids is for storage stability for 5 to 10 years under moderate temperatures. All of the inhibitors studied afford good protection against oxidation at lower temperatures. Storage life of more than 10 years is predicted for all of the inhibitor types a t 150' F. or less with the super-refined base stocks. These values of storage life have been confirmed experimentally by a study of storage samples of Spec. MIL-H-5606 fluids. High quality Spec. MIL-H-5606 fluids have shown good storage stability for 20 years under storage in unheated facilities. Excellent storage stability has been shown in a sample of this fluid taken from the "Lady Be Good," a World War I1 bomber, 16 years after it had crash-landed in the Libyan desert (74). These data suggest that any of the additive packages will remain stable in storage and, therefore, the inhibitor should be chosen on the basis of its other properties. The dithiocarbamate additive shows the best oxidation properties u p to 500' F. At temperatures exceeding 500' F.,
!
I
I
350 300 TEST TEMPERATURE, F.
250
j 200
Figure 1. Effect of temperature on oxidation stability of deep-dewaxed super-refined mineral oil Test procedures and techniques in accordance with Spec. MIL-L7808 ( 2 I ) . Test temperature and time as indicated; a i r r a t e = 5 f 0.5 liter/haur; test fluid charged = 100 ml. of MLO 7557 ( a d e e p - d e w a x e d super-refined mineral oil); catalysts = 1 -inch square each of copper, steel, aluminum, and magnesium Additives: V Dithiocarbamate 0 Phenyl-wnaphthylamine (PAN) 2,6-Di-ferf-butyl-4-methylphenol A 5-Ethyl-1 0,lO-diphenylphenazasiline PAN
+
VOL 2
NO. 4 D E C E M B E R 1 9 6 3
333
the dithiocarbamates decompose thermally to form an insoluble metal sulfide. This deposit could not be tolerated in the close clearances existing in aerospace hydraulic hardware. Phenyl-a-naphthylamine (PAN) shows excellent effectiveness with super-refined stocks. PAN exhibits poor light stability which results in darkening of the fluid and the formation of traces of insoluble material. Oxidation in the liquid phase, even within the fluid stable life, produces a trace of oil-insoluble sludge. This behavior is typical of oxidation inhibitors containing nitrogen.
Table II. Properties of Commercially Available Superrefined Mineral Oil Hydraulic Fluid Formulations"
Fluid Grade MLO 7557 M L O 7277
Property
Kinematic viscosity, cs., at 500' F. 210' F. 100' F. 0' F. -40' F. -65' F. Viscosity index rlSTM slope Boiling range (ASTM),' F. 5% 50% 95% Evaporation loss (6.5 hr., 400" F.), 70 Flash point, F. Fire uoint. ' F. clou;l point, F. Pour point, ' F. Neutralization No. Precipitation No. Aniline point, O F. \$rater content, % Color, Saybolt * Mass spectrometer analysis,
%
Isoparaffins 1-ring naphthenes 2-ring naphthenes 3+-ring naphthenes Molecular wt. (calcd. from b.p.) Thermal decomposition point, ' F. Autogenous ignition temp., O F. Thermal stability in stainless steel bomb (N2; 6 hr.: 700' F.)d Wt. change, mg. /sq. cm. 52-100 steel M-10 steel Naval bronze Viscosity increase, % Total acid No. increase Pressure increase, p.s.i:g. Corrosion-oxidation stability [Spec. MIL-L-7808 ( 2 7 ) ; 72 hr.; 347" F.] Catalyst wt. change, ma./ sq. cm. Viscosity increase, yG Total acid No. increase Shell four-ball wear test (75' C.; 620 r.p.m.; 1 hr.; 52-100 balls) '\Year scar diam., mm. At 1 kg. At 10 kg. At 40 kg. I
0.71 3.20 14.35 310 3,210 22,900 94 0.786
696 712 740 59.2 390 425 -70 -75
