1234 INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. 22, No. 11

Table 111-Moisture Held within Various Pore Radii

1 LIGNITE 1 PEAT I BIRCH WOOD

Cm. I % % I % % X 10-7 Cm. X 10-7 I % 56 .73 10.31 6 . 2 0 4 . 6 5 3 . 9 3 2 . 6 0 1 . 6 5 1 . 3 5 0 . 9 7 0 . 6 7 0 . 5 7 0 . 4 5 0 . 3 2 0 .00

> 56 .73 10.31-56.73 6.20-10.31 4.65- 6 . 2 0 3.93- 4 . 6 5 2.60- 3 . 9 3 1.65- 2 . 6 0 1.35- 1 . 6 5 0 .97 - 1 . 3 5 0.67- 0 . 9 7 0.57- 0 . 6 7 0.45- 0 . 5 7 0.32- 0 . 4 6 0 . 0 - 0 . 3 2

14 .30 14 .30 24.75 39 .05

8 . 5 7 47 .62 6 . 2 6 53 .88 3 . 3 8 57 .26 7 . 5 64 .76 8 .34 73 .10 3 . 1 0 76 .20 6 . 2 6 82.46 4 . 4 5 86.91 2 . 4 3 89 .34 2 . 1 0 91 .44 3 . 8 1 9 5 . 2 5 4 . 7 6 100.00

German brown coal. The data for brown coal are taken from the work of Kreulin and Ongkiehong (1).

It is evident that, on the average, peat contains capillaries of larger radii than lignite and brown coal. I n terms of pore size we obtain the following classification: peat, birch wood, lignite, and brown coal, named in the order of decreasing pore size.

The classification of North American fuels has been a prob- lem of continuous discussion. The results of the present re- search indicate that a possible classification might be had in terms of pore size from sorption studies. It is the intention of the Division of Mines of the University of Korth Dakota to continue this study with the other ranks of coal, to obtain, if possible, such a classification.

Literature Cited a Bound water P E, where T = moisture in equilibrium at 100

per cent relative humidity, and E = equilibrium moisture in any other atmosphere.

(1) Kreulin and Ongkiehong, Brennslof-Chem., 10, 319 (1929). (2) Lavine and Gauger, IND. (3) Thompson, Phil. Mag., [4] 42, 448 (1871).

T CHEM., 221 1226 (lg30).

Effect of Copper and Lead Ions upon the Rate of Decomposition of Hydrogen Peroxide

at Various Acidities' Harry W. Rudel with Malcolm M. Haring

UNIVERSITY O F MARYLAND, COLLEGE P.4RK, MD.

S IS well known, hy- drogen peroxide tends to decompose s lowly

The rate of decomposition of 30 per cent hydrogen sition of c o n c e n t r a t e d hy- peroxide at varying acidities in the presence of varying drogen peroxide a t varying concentrations of copper and lead ions has been in- a c i d i t i e s , would be of in-

increasing pH. Copper ion has a marked catalytic Experimental Method ing to the equation:

effect on the decomposition, even in traces, while lead hiaas a n d ~ ~ t ~ h ~ ~ (18) ion has a slight inhibitory effect. Explanations for The gasometric m e t h o d

developed by Walton (21) claim that pure a q u e o u s the various curves are offered. solutions of hydrogen per- and Bohnson (2 ) was em- oxide in suitable containers will keep indefinitely. How- ployed in this study. Decomposition rates were measured ever, commercial peroxide is seldom absolutely pure, so by observing the volume of oxygen liberated from 2200 a study of the catalysts and inhibitors for this reaction is cc. of the peroxide while maintained a t constant tempera- very desirable. Many such studies have been made (1, ture. The mercury filled gas buret was connected to the 3, 4, 6, 8, 9, 10, 18, 20), usually with relatively large decomposition flask by means of capillary tubing. Pres- amounts of the catalyst in dilute solutions. The evi- sures were continually adjusted to atmospheric with the dence points to metallic ions, notably iron, as the active aid of a water manometer. The temperature of the thermo- catalyst and to the formation of unstable intermediate stat was 32" C. and decomposition rates were never ob- compounds as the mechanism, However, the work of served until the reaction mixtures had stood in the bath Elissafoff (7) on the rate of decomposition of hydrogen for 24 hours. All apparatus was scrupulously cleaned to peroxide in the presence of glass wool, both with and without prevent decomposition by unknown catalysts. traces of copper sulfate, seems t o show that, in this case a t The least, we are dealing with adsorption and not diffusion. mixtures were made up by adding the required amount of This view is supported also by the work of Rice (16). The catalyst solution to 2500 cc. of peroxide and then adjusting stability of hydrogen peroxide is likewise notably affected the acidity with normal sulfuric acid or sodium hydroxide. by its acidity, being least in alkaline solutions. Little Hydrogen-ion determinations were made with indicators. work has been done to obtain comparative data on the To guard against fictitious results in such strong oxidizing stability of hydrogen peroxide in solutions of varying acidity solutions, two different indicators were always used. in the presence of metallic ions. Furthermore, commercial hydrogen peroxide is now being made in a concentration of 30 per cent. Therefore, it was thought that a study of the effect of minute quantities of copper and lead ions, such as would be encountered in Dractice. uDon the decompo-

at room temperature accord- vestigated. The rate of decomposition increases with terest. A

2H202 = 2Hz0 + 01

The peroxide used was a pure 30 per cent product.

Effect of Acidity

Before a comparative study of the effect of metallic ions could be made, i t was necessary to determine the effect of

I -

varying concentrations of hydrogen ions upon the hydrogen 1 Received August 29, 1930. Abstracted from a thesis submitted by

Harry W. Rudel in partial fulfilment of the requirements for the degree of perolji* The Of this study are given in master of science in the Graduate School of the University of Maryland, 1 and F'lgUre 1.

November, 1930 ILVDCSTRIAL A S D ESGINEE'RIXG CH ELITISTRY 1235

Table I-Effect of Acidity on Rate of Decomposit ion of Hydrogen Peroxide

(pH us. cc. 02 per hour per 2200 cc. I1202 at 32' C.) VOLLXE PER 0 2 P E R 0 2 P E R

2200 cc. HOUR TEMP. PRESS. HOUR €IzOz PH ( C S C O R ) O F 0 2 O F 0 2 ( C O R ) cc. cc. C. Jlm. cc.

1 A' HiSOa 6 2 . 0 2 . 0 26 .0 --- i i D 1 . 8 1 2 6 4 . 7 2 6 . 0 - - - i i D 4 . 2 0 3 . 4 2 7 . 1 18.5 --- i i i 25.4

13' h-aOH 1 3 . 8 41 .7 18.5 777 39 .1

81.5 2 0 . 2 777 75 8 2 3 5 6 0 443 2 5 . 0 761 394 8 6 3 677 25 .0 761 601

11 6 . 5 827 26 .0 761 730 36 7 . 5 1122 2 6 . 0 770 991

$ 2 195 2 0 . 2 777 182

I 1 I I I P jOo l 1 EFFECT OF A N D I T Y UPON RAT€ OF DECOMP05lT/ON

GF 30 % n2 0,

2: - 3 0 4 0 5 0 60 ZO D H

The positive catalytic effect of (OH)- is best explained by a modification of Lemoine's theory (12) . Unstable (HOs)- is assumed to be formed, which then decomposes to liberate oxygen and regenerate (OH)-.

(OH)- + HzPOz + (H0z)- + Hz'O (HOJ- + (OH)- + ' / ~ 0 z O t

The cycle is repeated indefinitely, the greater the (OH)- the greater the rate of decomposition.

Taylor's (19) theory of negative catalysis offers a possible explanation for the inhibitory effect of sulfuric acid. Per- sulfuric acid may be considered to be formed as follows:

Hi02 + HzO + (0) 2HzS04 + (0) HnSz08 + Hz0

The peroxide is then regenerated as follows:

H&08 + 2H2O + 2HzS04 f HzOz

This mechanism receives some support from the statement of Mellor (1 4 ) :

Sulfur heptoxide combines with water with a hissing noise like sulfur trioxide, but the solution has not the same properties as if sulfur trioxide alone had been dissolved in the water. A similar solution can be obtained by mixing concentrated sul- furic acid with hydrogen peroxide in the cold* *.

However, i t seems more reasonable to postulate a simple mass-action effect, according to the following equation, to explain the inhibitory effect of H+:

(HO2)- - 2~ F-) 02' + Hf

(OH)- will facilitate this reaction and H- will inhibit i t . The decomposition becomes then in effect auto-inhibitory. A little consideration will reveal that this equation alone cannot explain the accelerating effect of (OH)-; 2500 cc. of 30 per cent H202, assuming NaH02 to be formed, would require no less than 33 liters of normal NaOH for complete neutralization. 1 mechanism postulating regeneration of (OH)-is necessary in this case.

Effect of Copper Ion

Three different concentrations of copper ion were used. The results are displayed The source was cupric sulfate.

in Table 11, and Figure 2 .

Table 11-Effect of Copper Ion on Rate of Decomposit ion of Hydrogen Peroxide

VOLUME PER 0 2 P E R 0 2 P E R 2200 cc HOLR TEMP PRESS HOUR O F H ? O n PH ( U V C O R ) OF 0 2 OF 0 1 ( C O R )

cc cc. O C Mm cc 0.04 MG. c U + + P E R LITER

1 N HnSOa 6 2 . 1 87.6 2 9 . 2 766 7 6 . 7 0 3 . 1 124 28.5 759 108

4 . 2 265 28 .5 759 230 3 5 . 0 405 28 .7 759 389 10 6 . 3 1015 28.7 759 882

1 Y NaOH

0.10 MG. Cu + PER LITER 1 A' H2SOd

6 2 . 1 122 27 .6 768 108 0 3 .3 134 27 .6 768 119

2 3 .8 304 25 .3 757 267 3 4 . 8 293 25.0 757 258 5 6 . 0 211 25 .0 757 186

10 6 . 6 438 2 4 . 0 762 391 20 7 . 2 699 2 4 . 0 762 624

1 S NaOH

0.40 MG. Cu + + PER LITER

6 2 . 1 218 2 5 . 4 757 192 0 3 . 0 202 25 .4 757 178

1 HzSO4

1 N NaOH 2 3 . 7 405 2 9 . 0 759 352 2 . 5 4 . 4 195 2 9 . 0 766 170 3 5 . 3 111 25.5 757 98 5 6 . 1 143 2 7 . 1 759 126

10 6 . 4 320 2 7 . 1 759 280 20 7 . 2 569 29 .0 759 494

I FIGURE 2

EFFECT OF COPPER #?Oh' RAT€ OF DECOMPOSITION

900

OF 30 % H 0 A T

800

700

I600

$ h 500 Zl OIOMG CUPEPLITEP 9 D4OMGCU PER.IIfPH2

d 8 ADO

300

200

IO0

I r l Z I 2 0 3 0 40 5 0 6 0 70

P H

The curves reveal that Cu++ has a very marked effect on the decomposition rate, usually increasing it but under certain conditions decreasing it. Solutions containing 0.4

VOl. 22, No. 11 1236 INDUSTRIAL A N D ENGINEERING CHEMISTRY

700

600

mg. of Cu++ per liter show different colors depending on the pH. Thus, below 3.8 the solution is colorless, above 4.4 it is grass green, and between these two values there is a marked yellow turbidity. These colors correspond to those of Cu02, HzO, and colloidal Cu(OH)2, which may be obtained by treating Cu(OH)2 with HzOz. Osborne (15) obtained the yellow color with a small excess of Cu(0H)z and the green with a large excess. This agrees with Robertson's (17) spectroscopic proof of the existence of an unstable cupric acid, CuOz. H20. He postulated the following mecha- nism for the catalysis:

yn

I / I / . I I I

Increasing the C u + - should increase the rate of decompo- sition, and this is observed. However, other effects are superimposed which produce the maxima and minima observed in curves I11 and IV of Figure 2. Increasing the copper sulfate also increases the sulfuric acid, according to Equations 1 and 4. This tends to inhibit the reaction

1 F I G U R E 3

EFFECT OF LEAD UPON RATE OF DECDMPOSITIOU

OF 30% HzO, AT VARYING ACIDITIES

B O O

600

I B L A N K B 0,04MG?BP€PIITER Y O 2 m 0.40 MG PB PERLITEQ H 0

100 MG.PB?ERLITER li:O:

by thz mechanism already pcstulated and also by reversal of Reactions 1 and 4. These effects apparently balance in the neighborhood of pH 4.0. Hence there is an increase in catalytic effect with increasing Cu++, although not so great as might be expected. As the pH increases the tend- ency to precipitate C u f f as colloidal cupric hydroxide increases, and this effect should be greater the greater the Cu'-. Accordingly we find curve IV, except a t low pH values, lying below curve 111. The great increase in de- composition rate observed a t pH values above 6 is, of course, due to the marked catalytic effect of (OH)-. At very low concentrations of Cu++ the copper probably remains in the ionic state throughout-i. e., the solubility product is never exceeded by the ion product-and so curve I1 exhibits no maximum or minimum.

The mechanism suggested by Kiss and Lederer (11) for the catalytic decomposition of hydrogen peroxide by cupric ions does not seem quite so competent to explain all the observed facts as the foregoing. This mechanism is embodied in the following equations:

It is evident that an increase in pH will aid Reaction 1 and hinder Reaction 3. This makes it difficult to explain the maxima as well as the color changes observed. However, the data of this paper can scarcely be considered t o decide definitely between the two theories.

Effect of Lead Ion

Lead chloride solution was used as the source of Pb++. Three concentrations were studied-0.04, 0.4, and 1.0 mg. of Pb-+ per liter of solution. The data are given in Table 111, and Figure 3.

Table 111-Effect of Lead Ion on Rate of Decomposit ion of Hydrogen Peroxide

VOLUME PER 0 2 P E R 0 2 P E R 2200 cc H O U R TEMP. P R E S S . HOUR

OF 0 2 (COR.) OF HzOz P H ( U I C O R ) OF 0 2

cc. cc . c. M m . cc . 0 04 M G . Pb + + PER LITER

1 S H ~ S O I 6 2 . 1 51 3 20 3 765 4 7 . 0

1 N XaOH 3 4 . 1 133 2 5 . 5 774 120

4 . 4 167 2 5 . 5 767 149 5 321 2 5 . 5 767 287

10 6 . 6 711 2 7 . 3 767 630 3+ 6.0

20 7 . 2 835 2 7 . 3 767 740 0.4 XG. Pb + + P E R L I T E R

1 A; &Son 6 2 . 1 49 .9 2 5 . 0 768 4 4 . 8 0 3 . 5 5 8 . 8 2 5 . 0 768 52 .8

1 N9h7aOH 4 . 5 7 4 . 0 2 7 . 2 770 6 5 . 8

4 5 . 9 114 2 7 . 2 770 102 10 6 . 6 284 2 6 . 9 769 252 15 6 . 8 376 26 .9 769 334 20 7 . 2 583 2 6 . 3 142 502

1.0 MG. Pb + + P E R L I T E R 1 iv HzSOa

6 2 . 0 4 9 . 4 2 5 . 8 756 4 3 . 6 0 3 . 3 4 7 . 8 2 5 . 0 743 4 1 . 4

1N NaOH 3 5 . 5 123 25 .0 743 107 5 6 2 145 2 8 . 0 762 127

10 6 7 275 28 .0 762 241 20 7 . 2 494 2 5 . 3 743 427

It is evident that lead ion exerts an inhibitory effect, although there is a slight accelerating action, especially with the most dilute mixture. The catalytic effect may be explained on the basis of the chain reaction of Zotier (22) .

The inhibitory effect can be explained by assuming that the (OH)- removes HX, thereby facilitating Reaction 1 and hindering Reaction 2 . This will result in an increase in the amount of lead oxide and a decrease in P b + + a t high pH values. The decomposition in the presence of PbOz is probably mainly a surface effect. Bray and Livingstone ( 5 ) state that hydrogen peroxide is catalytically decomposed by lead oxide "in the intermediate ranges," high acid and high alkali yielding Pb -- and plumbates, respectively. If this view is correct, the rate of decomposition should be nearly independent of the P b - + which seems to be the case especially as exemplified in curves I11 and IV.

Acknowledgment

The writers wish to thank J. S. Reichert for his active interest in this research and the Roessler and Hasslacher Chemical Company for the use of their laboratories.

Literature Cited

(1) B e r t a l a n , Z . physzk. Chem., 96, 328 (1920). (2) Bohnson, J. Phys. Chew., 24, 677 (1920).

November. 1930 I,VDUSTRIAL AND ENGINEERING CHEMISTRY 1237

(3) Bohnson, J . Phys. Chem., 25, 19 (1921). (4) Bohnson and Robertson, J . .4m. Chem. Soc., 45, 2493, 2512 ( ( 5 ) Bray and Livingstone, Ibid., 45, 1255 (1923). (6) Hrode, Z. p h y s i k . Chem., 37, 237 (1901). (7) Elissafoff, Z. Illektrochem., 21, 352 (1915). (8) Fenton and Jackson, J . Chem. Soc., 75, 1 (1899). (9) Fenton and Jones, Ibid., 77, 69 (1900).

(10) Kastle and Loevenhart, Am. Chem. J . , 29, 397 (1903). (11) Kiss and Lederer, Rfc. Irav. chim., 46, 453 (1927). (12) Lemoine, Combt. r e n d . , 161, 47 (1915).

(13) Maas and Hatcher, J . Am. Chem. SOC., 42, 2368 (1920)

(15) Osborne, Am. J . Sci., 32, 334 (1886). (16) Rice, J . .4m. Chem. Soc., 43, 2099 (1926). (17) Robertson, Ibid., 47, 1299 (1925). (18) Spitalsky and Petin, Z. physik. Chem., 113, 161 (1924). (19) Taylor, J . Phys. Chem., 27, 322 (1923). (20) Thenard, A n n . chim. phys., 9, 441 (1818) (21) Walton, Z. physik. Cizem., 47, 185 (1904). (22) Zotier, B i d . SOC. chim., 21, 241 (1917).

19231. (14) Mellor, “Modern Inorganic Chemistry,” p. 543.

Cracking Value of Straight-Run and Cycle Gas Oil’ H. Sydnor and A. C. Patterson

TECHSICAL SERVICE DIVISION, STAXDARD OIL COMPANY OF S E W JERSEY, ELIZABETH, h-. J.

T HAS been appreciated for some time, in the oil industry, that the gas oils produced as by-products of the cracking process are less valuable as cracking stock than the

straight-run gas oils originally fed to the process. The term “straight-run gas oil” has been used to apply t o gas oils that have not been subjected to cracking conditions except in so far as incipient cracking may occur upon crude distillation. The gas oils produced as by-products of the cracking process are known as “cycle gas oils.” The cycle gas oils may be produced as by-products of the cracking of either straight- run gas oils or rrude residuums.

The Cracking Coil Cycle

Most modern cracking processes recycle to some extent- that is, they return a portion or all of the cycle gas oil pro- duced to the system as feed stock along with the incoming straight-run gas oil. I n such a system the total feed rate (straight-run plus cycle oils) is maintained constant and the amount of straight-run gas oil added per unit of time must be the equivalent of the gasoline, fuel oil, cycle gas oils, gas, and coke removed from the system. Cvcle gas oils may be re-

I

” -

moved from the system in several ways. They may be removed directly as cuts from the fractionating equipment. They may be removed by increasing the A. P. I. gravity of the fuel oil produced, in which case they are designated as fuel oil un- less subjected t o a redistillation process and recovered as overhead products. I n most low-pressure (atmospheric to 350 pounds) cracking equipment they are taken out to some extent along with the gasoline composing the product desig- nated as “distillate.” After removal of the gasoline, the remaining cycle gas oil is either returned to the cracking process or sold to the trade. Modern high-pres- sure (750 to 1000 pounds) cracking equip- ment is built with fractionating equip- ment that will permit all of the cycle gas oil to be retained within the system until completely converted to 400” F. end point specification gasoline, fixed gases, and fuel

coming straight-run gas oil decreases. Furthermore, since the unit is operating on a feed stock containing a higher percentage of straight-run gas oil in the total feed, the quantity of gasoline produced per unit of time increases as the quantity of cycle gas oil withdrawn is increased. I t has also been noted that the yield of fuel oil of a given gravity increases in proportion to the yield of gasoline as the quantity of cycle gas oil withdrawn from the system is diminished.

I n order more accurately to evaluate these factors, a study was made of the cracking value of the cycle gas oil produced by successive passes through a miniature cracking coil. The results of four successive passes through the equipment in which no recycling was inrolved were combined and com- pared with an operation on the same equipment when cur- rently recycling to produce the same yield of gasoline on the straight-run gas oil as was produced by the combined suc- cessive operations. I n the successive “once-through” opera- tions, the cycle gas oil produced in each pass served as the feed stock for the succeeding pass.

The history of the straight-run gas oil used in this work is

Fi‘ O&

Figure 1-Flow Diagram of Labora to ry E q u i p m e n t

oil of the gravity desired d6n-n to about 5” A. P. I. The percentage of incoming straight-run gas oil in the total

feed mill, of course, increase with increasing withdrawal of cycle gas oil from the system. It follows that, since de- composition of the cycle gas oil is necessary to obtain the ultimate yield of gasoline, the yield of gasoline based on in-

not definitely known, but it is believed t o be a wide gas oil cut from Midcontinent crude.

Description of Equipment

This work was carried out in laboratory equipment

Figure 1 is a flow diagram of the apparatus. is a miniature tube and tank cracking in all essentials,

1 Received October 16, 1930. Figure 2 is