INDUSTRIAL AND ENGINEERING CHEMISTRY
276
Vol. 20, No. 3
Factors Influencing Char Filtration-11' E. W. Rice and G. W. Murray, Jr. NATIONAL SUGAR RBFINBRY, YONKERS, N. Y.
INCE the presentation of the previous paper under this title2 explanations of some of the results have been asked; therefore, data covering these points will first be presented. The figures on the adsorption of invert sugar showed an apparent selective adsorption of levulose by the bone char, and it was thought that this might be due to a chemical combination of the levulose with free ammonia and a subsequent greater adsorption. Ammonia is known to be present in appreciable quantity in reactivated bone char. Therefore, the following experiment was tried: A portion of bone char was washed for 3 days with distilled water and, after drying, a solution of invert sugar was percolated upward through this char and simultaneously through a sample of unwashed char. The filtered material was collected in 50-ml. portions and polarized and the invert sugar determined by copper precipitation. The results show no appreciable difference in the solution from the two chars, although again the large differences in polarization are not borne out by the amounts of invert determined by copper precipitation. This experiment was purposely made on a more concentrated solution to determine if the same tendency to change in polarization would persist. The results are presented in Table I.
S
e
Table I-Invert
Sugar in Successive Portions of Solutions Treated with Bone Char (50-ml. portions analyzed) ORIGINAL SOLUTION 1
2
3
4
-2.0 -2.1
-2.2 -2.3
-2.3 -2.5
POLARIZATION
Off washed char Off unwashed char
-3.1 -3.1
-1.5 -1.5
GRAQMETRIC
Off washed char Off unwashed char
2.98 2.98
2.55 2.60
2.87 2.99
2.93 2.95
2.95 2.93
Since many calcium salts are more soluble in cold than in hot solvents, it was thought likely that the large adsorption of CaH4(PO& which was originally indicated might have been due to a precipitation during the passage through the hot filter. In making up solutions of CaHd(P04)Z it was observed that when the solutions were heated a slight precipitate was formedm3The precipitate was slight with the first bottle of salt purchased, but a succeeding bottle gave a much heavier precipitate. Solutions of Ca%(PO& were found to be strongly acid to phenolphthalein and upon addition of calcium carbonate to a pH of 7.0 a very heavy precipitate was formed. Since there is from 2 to 5 per cent of calcium carbonate in bone char, it was decided that the adsorption of CaH4(P0& could not be reliably determined under the conditions of the experiments and further work with this salt was discontinued. Effect of Varying Strength of Solution
As a continuation of the previous paper it was determined to try varying strengths of solutions to learn some of the Presented before the Division of Sugar Chemistry at the 74th Meeting of the American Chemical Society, Detroit, Mich., September 5 to 10, 1927. 2 Ind. En& Chem., 19, 214 (1927). 8 Watts, Dictionary of Chemistry, Vol. IV, P. 109; "UP to 1 part in 200 a clear solution is found." Solubility given in the Handbook published by Chemical Rubber Publishing Co.: 1.8 parts = 1.0 parts PzOa in 100 of Hz0 at 30' C.; and Van Nostrand Chemical Annual, 1922, gives 4.0 parts in 100 at 15' C. = 2.2 parts PzOa.
limits which might be anticipated when using char as an adsorber. Two series of filtrations were made using 1 and 4 per cent solutions of four of the salts which had been used previously. The results are set forth in Table 11. The amounts of salts present were determined by measuring their conductivity as described in the previous paper.2 The results of filtrations using 2 per cent of salts are those reported in the previous paper, but are again included for comparison. Table 11-Salts in Successive Portions of Solutions Treated with Bone Char (Figures indicate grams per 100 ml.; 50-ml. portions analyzed) ORIGINALSOLUTION1 2 3 4 5 Per cent SODIUM S U L F A T E
1.00 2.00 4.00
0.05 0.16 0.53
1.00 2.00 4.00
0.34 0.60 2.10
1.00 2.00 4.00
0.85 1.98 3.85
1.00 2.00 4.00
0.05
0.40 0.68 3.50
0.60 1.80 3.70
0.80 1.80 3.85
0.95 1.80 3.90
0.94 2.04 3.85
0.97 2.40 3.90
1.00 2.06 5.15
1.00 2.06 5.15
0.90 2.04 3.90
0.95 2.40 3.90
SODIUM CITRATE
0.73 1.80 3.75
0.84 1.98 3.80
SODIUM CHLORIDE
1.00 2.06 5.15
1.00 2.06 5.15
CALCIUM ACETATE
0.35 1.40 3.90
0.27 0.75
0.80 1.98 3.90
It will be noted that the minus adsorption with sodium chloride is very large in the 4 per cent run and apparently gives results which might be anticipated from the results from the other concentrations. The 2 per cent solutiqns of sodium citrate and calcium acetate are not followed by minus adsorptions in the 4 per cent run. This is perhaps due to the fact that the 2 per cent runs were made in filters of brass and copper and some metal may have been dissolved, while the 1 and 4 per cent runs were made after the filters had been coated on the inside with Bakelite lacquer. The first three portions in all cases appear to conform to an adsorption isotherm, although the figures are too few to indicate definitely. Table 111-Salts in Successive Portions of Bone Char Treated Solution with Varying Sugar Concentrations (Figures indicate grams salts per 100 ml.; 50-ml. portions analyzed) SODIUM S U L F A T E
SOLUTION O o Bx. Original 1 2 3 4 5
2.00 0.16 0.68 1.60 1.80 1.80
5' Bx. 2.00 0.06 0.68 1.60 1.76 1.84
Original 1 2 3 4 5
ODBx. 2.00 0.27 1.40 1.95 2.04 2.40
15OBx. 2.00 0.10 1.06 1.70 1.78 1.86
20° Bx.
2.00 0.11 0.62 1.38 1.72 2.00
31' Bx. 2.00 0.0s
0.50 1.16 1.66 1.86
51" Bx. 2.00 0.04 0.50 0.98 1.40 1.60
60' Bx. 2.00 0.08 0.50 0.96 1.24 1.50
CALCIUM ACETATE
20OBx. 2.00 0.11 1.04 1.67 1.76 1.86
29OBx. 2.00 0.32 1.06 1.64 1.80 1.92
40'Bx. 2.00 0.18 0.96 1.60 1.84 1.90
58'Bx. 2.00 0.22 0.86 1.30 1.54 1.62
Combinations of Salts with Sugar Solution
1
It was decided to use Of with sugar solution and in Table I11will be found results of ten filtrations using 2 grams of Na2SOcand Ca(CzH80& per 100 ml. in sugar so~utionsof varying densities as indicated. The 00 Brix "pied from the Original papera2 The figures show an increase in the adsorption of the salt as the per-
March, 1928
INDUSTRIAL AND ENGINEERING CHEMISTRY
centage of sugar increased. This is probably due t o a decrease of solubility of the salt as the amount of sugar increases in the solution. This indicates the reason for the known fact, in practice, that the ratio of sugar to salts decreases very rapidly, as the density drops, during the process of sweetening off char filters.
277
Conclusion
It appears from these experiments that in refining sugars the solutions should be kept as dense as possible where the maximum of ash is to be removed from the solutions by the use of bone char.
The Free Energies of Some Hydrocarbons’ Alfred W. Francis ARTHURD. LITTLE,INC., CAMBRIDGE, hlass.
Equations have been derived for the free energies of formation of methane, ethane, octane, ethylene, acetylene, benzene, toluene, naphthalene, and cyclohexane as functions of temperature. These equations have been plotted with the ordinates reduced to free energy of formation per carbon atom to show the true stability relations between various hydrocarbons. The equations have been simplified to linear equations for cracking temperatures, 427-727’ C. By suitable interpolations similar equations for the other paraffin, olefin, acetylene, and naphthene hydrocarbons have been estimated. The equations have been tested and found consistent with several known reactions. Some predic-
tions as to the possibility of other desirable reactions have been made. The direct production of higher paraffin hydrocarbons from lower ones is shown to be impossible except with simultaneous production of still lower ones in a t least equivalent amounts. The catalytic formation of acetylene in more t h a n traces is likewise impossible. The direct removal of hydrogen from a paraffin to form an olefin with the same number of carbon atoms is possible only a t high temperatures and to a very limited extent. The synthesis of gasoline from water gas can take place only below about 450’ C. The isomerization of olefins to naphthenes requires temperatures below about 430’ C., while the production of aromatics requires 550-900’ C.
.... H E recent interest in synthetic gasoline makes it desirable to have reliable free-energy values for the pure hydrocarbons involved.2 Such data tvould throw light also upon the chemistry of cracking and other reactions involving hydrocarbons. From the free-energy change of a proposed reaction predictions may be made as to its possibility and the conditions of temperature and pressure required. Some of the data assumed in the present calculations are only approximate, but in many cases this fact does not introduce the error which it seems to do. An error in the specific-heat equation of a substance, for example, makes a tremendous difference in the chemical constant, Z, but because of compensating errors, the resulting free energy is almost unchanged. The values of free energy calculated will be tested by several known reactions. Consistency with them will increase the reliability of the results. The figures are offered only as estimates, which can be revised when more data become available, but they are believed to be sufficiently accurate for any prediction that is made from them. The symbols used throughout conform to the system of‘ Lewis and Randall.3 Methane
C, = 1.1 0.0048T - 0.0512Tz (3) (except in the case of methane, (3) will be simplified to c, = 1.1 0.004T) (4) Combining ( l ) ,(2), and (3) AC, = - 11.83 0.0169T - 0.0j3T2 (5) Then AHZgl = Ho - 11.83T -I-0.00845T2 - 0.051T3 = -18,300 (6) from which
Methane is the only hydrocarbon with sufficient stability for accurate data on equilibrium with its elements, and even with this compound the numerous calculations which have been made are not very consistent because some of them are based upon equilibria with “amorphous carbon,” which is not a definite chemical individual, and which is converted
Employing the same equilibrium data as given by Lewis and Randall,S the value of Z is found to be -52.07 * 0.17, with slightly better agreement than that found by them. Then, for C 2H2 *CH4 A F = -18,500 -I- 11.83TlnT - 0.00845T2
T
1 Presented before the Division of Petroleum Chemistry at the 74th Meeting of the American Chemical Society, Detroit, Mich., September 5 to 10,1927. 2 Since this paper was written, calculations for a few of these hydrocarbons have been published b y Srmth, I n d . Eng. Chem., 19, 801 (1927); but the present paper is much more comprehensive, and different methods have been used in the calculations. * “Thermodynamics,” McGraw-Hill Book Co., New York, 1923, (hereinafter abbreviated “L. and R.”).
gradually to graphite during the experiments. For this reason graphite is taken as the standard form of carbon in this paper. The heat of formation of methane from graphite and hydrogen is given by Lewis and Randall4 as AHzsl = -18,300. The specific-heat data employed by them were admittedly by a rough estimate, and should be replaced by those of Dixon, Campbell, and Parker5as calculated by Partington and Shilling. C p = 2.57 4- 0.0231T- 0.0542T2 (1) Similarly for hydrogen6 C,
and for graphite’
=
+ 0.0007T
6.65
(2)
+
+
+
AH0 = -15,500
(’7)
+
+ 0.065T3 - 52.07T
AFzss
-11,670
(8) (9)
This is intermediate between the value of Lewis and Randall, 4 5 6
1 8
L.and R., pp. 80, 571. Proc. Roy. SOC.(London), A100, 1 (1921). “Specific Heats of Gases,” p. 206, Ernest Benn, Ltd., London, 1924. I,. and R., p. 569. L.and R., p. 572.
