August, 1946
INDUSTRIAL AND ENGINEERING CHEMISTRY
growth when stretched. ('omparatirc tests showed that the rubbers from vinyl linseed esters (batch 46) possessed this property to the highest degree, although many vinyl esters of unsaturated fatty acids also gave tear resistance t o cured compositions. Nore than 10% vinyl fatt,y esters results in decreased strength (Table 111). S o advantage is apparent from using larger amounts unless greater softness is desired. Table I V shows the result of swelling tests in comparison tTith one of the most oil-resistant, commercial, acrylonitrile polymers. The degree of axelling is apparently measured by the acrylnnitrilp content, and these copolymers containing 40% acrylonitrile resi.+t Pn.t.lling in oils t o the same fl+>grwas the more resistant o i 1111 I I I ~ , W I : I ~I ;iijhc.rr.
839
ACKYOWLEDGMENT
The experimental viork in this paper on the preparation of the rubbers was largely done by IC. H. Weber and his assistants, and the compounding and testing were carried out under the supervision of T . W, Elkin and S. W. Eby. LITERATURE CITED
(1) Hersberger. A. B., Reid. J . C.. and H e i l i g n ~ a n n ,K . G.. I N D . KNG. CHEM.,37, 1073 (1945). 12) P a l m e r . R. C., Ibid..34, 10Bb (1942). '3) Reppe, W.. U. 9. P a t e n t 2,066,075 ( 1 9 3 6 ) . PRESESTBD tiefore t h e Division of Riihoer Chemistry nt t h e 109th SIPetinu nf t h o h\rmrc.4.v C H e w c A L SOCIETY, ;\tlsntic c i t y , s,1.
Some Physical Properties of
Activated Bauxite HEISZ HEISEAIAiVIU, IC. A. KRIEGER', .AND IT. S. R . 3IcC4RTER Porocel Corporation, Phikidelphin, Z'n,
Data are presented on the bulk, apparent and true densities, corresponding void and pore volumes, and surface areas and equivalent pore diameters of several bauxite ores activated at various temperatures. Bulk density and void volume depend upon granule size. The other physical properties are altered by changes in structure produced by increasing activation temperatures. It appears that bauxite granules possess a degree of rigidity sufficient to prevent collapse of the framework even under the action of forces associated with major chemical changes.
T
HERbL4LLT activated bauxite is used for the adsorbent, refining of lubricating oils and waxes (10) and of sugar liquors and sirups (I.$), as a desiccant (4, 15), as a catalyst support (6, If), and as a catalyst for desulfurization ( 1 7 ) ,defluorination (7, 11), cracking (3,11, 18), dehydrogenation (19), and dehydration ( 8 ) reactions. In all of these applications the bauxite is generally used as a granular material of appropriate mesh size (1). For each specific use there appears to be an optimum activation temperature which produces the desired adsorbent or catalytic properties in the bauxite. Since these properties develop as a result of structure chmges, it is of interest to follow the effect of heating on certain physical properties. The properties of granular porous solids are characterized in part by true density, surface area, void volume, and volume and diameter of the pores. From these a number of other quantities of practical interest can be derived. Although the true density, surface area, and void volume can be determined directly, the other two quantities are not easily measurable by direct methods. EXPERIMENTAL METHODS
The total or bulk volume, rb, occupied by a poroub solid is composed of three parts: the volume occupied by the solid and adsorbed material, VI, that occupied by pores within the granules, V p ,and that occupied by the voids between the granules, I
Harrison Laboratory TJnlveraty of Pennsylvania, Phi!adelphia, Pa.
+
1.6. In this work Vb, I-*,and (Vt V p ) ,the appaicnt volume, were determined with apparatus similar to that described by Washburn and Bunting @ I ) , using mercury under 25 cm. pressure as the displaced fluid. These quantities are related t o a set of densities so that, for one gram of solid,
1 T', = -
Dt
where D., DI, arid Db are apparent, true, and bulk densities, respectively. De was calculated from Equations 2 and 3 and Db from Equation 1. DI was measured with helium by the method of Howard and Hulett (9), using apparatus described by Iirieger (IS),and V , was calculated from Equation 3. Surface a i m was measured directly with nitrogen by the method of Brunauer, Emmett, and Teller (d), using the data of Livingston (26) and apparatus described by Krieger ( 1 2 ) . Equivalent pore diameter was calculated as follows (5): Assuming that one gram of solid contains N open-ended cylindrical pores of equivalent diameter d and length L, the total surface area S,neglecting the extt.rnal surface of the granules, is given by S = dL.Y
The pore volume is given hy l',
50
= Td2L.Y
4
