Percolation Decolorization of a Lubricating Oil Fraction by Fuller's Earth W. T. GRANQUIST AND H. J. STREICH Floridin Co., Warren, Pa.
T
HIS paper presents the results of a study of the percolation
decolorization of steam-refined cylinder stock by fuller's earth, a hydrous aluminum magnesium silicate mineral found extensively in Gadsden County, Fla. The purpose of this study was dual in nature. Primarily, results reported elsewhere (57 ) concerning heat-induced changes in the general properties and adsorptive characteristics of fuller's earth suggested a n investigation of the effect of clay activation temperature on a n adsorption system of practical importance. Secondly, the general importance and applicability of the percolation technique described by FitzSimons, Amero, and Capell (4) made it advisable t o expand the work to include a general study of the nature of this process. The system employed is of necessity complex, because of the extremely complicated nature of the petroleum resins (8). The experimental technique, discussions, and conclusions are offered as an attack on the problem, and not as a complete solution. EXPERIMENTAL PROCEDURE
A Pennsylvania steam-refined cylinder stock mixed 40% by volume with a heavy naphtha (boiling range, 300" to 400' F.) served as the standard testing solution. The specifications of the cylinder stock are listed in the following table: Flash pt., O F. Fire pt., F. Viscosity,, SSU a t 210° F. API gravity Pour point, a F. Carbon residue, % '
For a study of the effect of activation temperature, the apparatus and technique described by FitzSimons et ul. (4) were used. I n this phase of the work, filter temperatures were held a t 134" F. (boiling acetone) and the flow rate was controlled a t 1.5 ml. per minute. Oil colors were measured by a method developed in this laboratory, involving the use of a Coleman Model 6A spectrophotometer set a t 600 mp using a sample of Stoddard solvent that had been percolated through fuller's earth as a reference. Optical densities were read directly from the scale. For the adsorption isotherm work reported later in this paper, these values were used directly; for the runs to a definite NPA (National Petroleum Association) color, special conversion curves were prepared. These curves are specific, in most cases, for a given batch of cylinder stock. The method, therefore, is not very flexible, but is convenient and very accurate where a large number of determinations are to be made on a particular oil. Samples of crude fuller's earth, Nos. 10648 and 11146, 30 t o 60 mesh [consisting of approximately 75% attapulgite,
560 630 155.2 25.4 40 2.48
I I4 -
10% montmorillonite, 5% free silica, and 10% calcite, dolomite, etc. (S)] were activated for 1 hour a t 800", 900", lOOO", l l O O o , 1200", 1300", 1400", and 1500' F. One hundred grams of each sample were charged t o the standard testing columns. The feed stock was then introduced and the run allowed to proceed until a composite filtrate of an equivalent 5 NPA color, corresponding to S P A light red, was obtained. The run was discontinued a t this point, the filters were drained and washed with 1 liter of cold naphtha t o remove the free solution (see later discussion), and the clay was removed from the filter and dried. Each clay sample was then extracted with C.P. benzene in a Soxhlet-type extractor, the benzene carefully removed by distillation, and the weight of resin determined. The molecular weight of each resin TTas determined by an ebullioscopic method using carefully purified and dried benzene as the solvent; the apparatus employed was that described by Barr and Anhorn ( I ) . Samples of the dried, saturated clay mere carefully ignited a t 1200' F.; corrections were applied for clay weight loss between the particular activatiori temperature and 1200" F.; and the weight loss caused by combustion and loss of resin was calculated. Plots were made relating volume yield to 5 KPA, molecular weight, total per cent weight loss, and per cent extractables t o the activation temperature of the clay. The same technique was applied to the percolation of a 9% solution by weight of reduced stock extract from a cylinder stock similar to the one used in this work (obtained from United Refining Co., Warren, Pa.) in a light naphtha (boiling range, 170"
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12 -
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COLUMN TEMP
9 m
ct 10 -
TOTAL k ADSORBED
134OF.
FLOW RATE I 5 ML/MIN
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in 0
n
