October 1955 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 2129

(13) Flumiani, G., 2. Elektrochem., 32, 221 (1926). (14) Gee, G., Trans. Faraday Soc., 34, 712 (1923). (15) Gregg, R. A., and Mayo, F. R., J. Am. Chem. SOC., 75, 3530

(16) Hayes, R. F., U. S. Patent 2,460,105 (Jan. 25, 1949). (17) Jeu, K., and Alyea, H. N., J . Am. Chem. SOC., 55, 575 (1933). (18) Joris, G. G., and Jungers, J. C., Bull. SOC. chim. Belg., 47, 135

(19) Jungers, J. C., and Taylor, H. S., J. Chem. Phys., 4, 94 (1936). (20) Jungers, J. C., and Yeddanopalli, L. M., Trans. Faraday Soc.,

(21) Kharasch, M. S., and Dannley, R. L., J. Org. Chem., 10, 406

(22) Kharasch, M. S., Jensen, E. V., and Urry, W. H., J. Am.

(23) Kharasch, M. S., Reinmuth, O., and Urry, W. H., Ibid., 69,

(24) Mathews, J. H., and Williamson, R. V., Ibid., 45, 2575 (1923). (25) Mayo, F. R., General Electric Co., private communication. (26) Melville, H. W., Trans. Faraday SOC., 32, 258 (1936). (27) Mosher; H. S., and Dykstra, J. S., 126th Meeting ACS, New

(28) Olson, A. R., and Meyers, C. H., J. Am. Chem. SOC., 48, 389

(29) Ibid., 49, 3131 (1927). (30) Oster, G., Nature, 173, 300 (1954). (31) Oster, G., Phot. Eng., 4, 173 (1953). (32) Owens, J. S., Heerema, J. H., and Stanton, G. W., U. S. Patent

(1953).

(1938).

36, 483 (1940).

(1945).

Chem. SOC., 69, 1100 (1947).

1105 (1947).

York, Abstracts of Papers, p. 55.

(1926).

2,344,781 (March 21, 1944).

(33) Pietrusza, E. W., Sommer, L. H., and Whitmore, F. C., J . Am.

(34) Pummerer, R., and Kehlen, H., Ber., 66, 1107 (1933). (35) Redington, L. E., J. Polymer Sci., 3, 503 (1948). (36) Renfrew, M. M., U. S. Patent 2,448,828 (Sept. 7, 1948). (37) Richards, L. M., Ibid., 2,460,105 (Jan. 25, 1949). (38) Robertson, A., and Waters, W. A., J. Chem. SOC., 1947, p. 492. (39) Roedel, M. J., U. S. Patent 2,484,529 (Oct. 11, 1949). (40) Rogers, D. C., Ibid., 2,480,752 (Aug. 30, 1949). (41) Rueggberg, W. H. C., Chernack, J., Rose, I. M., and Reid,

E. E., J . Am. Chem. Soc., 70, 2292 (1948). (42) Reuggberg, W. H. C., Cook, W. A., and Reid, E. E., J . Org.

Chem., 13, 110 (1948). (43) Sachs, C. S., and Bond, J., U. S. Patent 2,505,067 (April 25,

1950). (44) Ibid., 2,505,068. (45) Ibid., 2,579,095 (Dec. 18, 1951). (46) Ibid., 2,641,576 (June 9, 1953). (47) Taylor, H. S., and Emeleus, H. S., J. Am. Chem. Soc., 53, 562

(48) Taylor, H. S., and Hill, D. G., Ibid., 51, 2922 (1929). (49) Taylor, H. S., and Jungers, J. C., Trans. Faraday SOC., 33, 1353

(50) Toul, F., Collection Czechoslov. Chem. Communs., 6, 163 (1934). (51) Vauehan. W. E.. and Rust. F. F.. J. Ora. Chem., 7. 472 (1942).

Chem. Soc., 70, 484 (1948).

(1931).

(1937).

(52) WaGzonek, S., Nelson, M. F., and TheGn, P. J., i. Am.'Chem. SOC., 73, 2806 (1951).

RECEIVED for review November 8, 1954. Contribution 1934, California Institute of Technology.

ACCEPTED June 13, 1955.

Catalytic Effects of and Vanadium Oxides on Steam

Cobalt, Iron, Nickel,

Carbon Reaction W. M. TUDDENHAM' AND GEORGE RICHARD HILL

Department of Fuel Technology, University of Utah, Salt Lake City, Utah

URING the past 33 years the catalytic effect of metal D oxides on the steam-carbon reaction has been investigated by a number of individuals (1 , 8, 6-9, 11-1 6).

I n general all the results have been in qualitative agreement al- though some disagreement has existed as to the effects of iron and aluminum oxides (6, 11, 18, 16). Iron was judged as a good catalyst by a number of workers (7, 18-14) but Taylor and Ne- ville (16) and Long and Sykes (11) judged i t to be ineffective in increasing carbon gasification.

Of the other catalysts chosen for this study cobalt was found effective by Kroger and Melhorn (7, 8) when mixed with potas- sium carbonate and cupric oxide or lithium oxide and potassium oxide, and nickel was found effective by Kroger and Melhorn (7) and by Milner, Spivey, and Cobb (IS). While vanadium would be expected t o show catalytic activity i t was not specifically studied in any of the aforementioned work.

By and large previous experimenters have worked with rela- tively high catalyst concentrations and have given only frag- mentary information as to temperature dependence. The pur- pose of this investigation was to compare carefully the catal-ytic effects of cobalt, iron, nickel, and vanadium oxides on the steam- carbon reaction in a temperature range from the lowest tempera- tures practical to make measurements with the apparatus to its upper limit, 1140' C. Catalyst concentrations as low as 0.013'% are effective in increasing the reactivity of the carbon. Some results that have a bearing on the kinetics of the system are re- ported.

1 Present address. Western Division Research, Kennecott Copper Corp., Salt Lake City, Utah.

EXPERIMENTAL

Apparatus and Procedure. The primary features and the arrangement of the apparatus are shown schematically in Figure 1. The steam generator, A, was heated by the constant tem- perature bath, B, t o produce steam at the desired pressure. The nonsubmerged portions of the steam generator were main- tained at an elevated temperature b y means of heating coils. The steam then passed into the preheating chamber, C, and thence through the jet, D, impinging on the hot carbon, E, which was clamped in water cooled copper contacts. The temperature of the carbon was controlled by a variable trans- former and was measured with an optical pyrometer. Some of the lower temperatures were measured with a thermocouple inserted through the sample. The reaction chamber was im- mersed in a circulating water bath. The excess steam was then frozen in the cold trap, F, which was cooled with a dry ice- petroleum ether freezing mixture. The products of the reaction were collected in the weather balloon inside the bell jar, G, the pressure in the balloon being measured b y a Dubrovin gage. Test runs made by passing steam over cold carbon and , through the freezing chamber showed no measureable pressure build up in G due to steam alone. Before each run the preheat- ing and reaction chamber as well as the balloon, bell jar, and glass tubing were evacuated to a few tenths of a micron of mercury pressure as measured by a thermocouple gage.

At the completion of a run the weather balloon was collapsed, and the gas was forced into an evacuated sample bulb. Residual gas was transferred by means of the Toepler pump. The gas in

2130 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 47, No. 10

the sample bulb was analyzed for carbon monoxide and carbon dioxide using a Fisher Precision gas analysis unit,

In performing these experiments, since the conditions for a critical orifice (2) were fulfilled, the steam velocity was controlled by the pressure in the steam generator.

samples were heated to 200" to 400" C. with evacuation to aid in evaporation of the remaining water. After evacuation was com- plete the temperature was raised to 11W0 C. for 25 minutes after which time it was lowered for 5 minutes, The sample was then ready for use. Estimates of the amounts deposited were ob-

(To Toepler pump and sample bulb

To power supply

Figure 1. Schematic diagram of apparatus A = Steamgenerator B = Constant temperature bath C = Preheating chamber D = Jet E - &bon sample F = Cold trap G = Bell jar containing balloon

Three velocities were used in these experiments. Expressed as the number of moles of steam per second issuing from the orifice, 1.0 X 10-8 sq. cm., the values were 7.2 X 10-6 moles per second, 2.6 X 10-6 moles per second, and 0.52 X 1 0 - b moles per second, respectively. The linear velocities were of the order of lo4 cm. per second.

SPECIMENS

The two graphitized carbons used in these experiments were AGKS spectroscopic carbon electrodes, hereafter called Type A, and AGKSP special spectroscopic graphite electrodes, hereafter called Type B, supplied by National Carbon Co.

The special spectroscopic graphite electrodes use petroleum coke flour as a raw material, and the spectroscopic carbon electrodes use a lamp black derived from coal tar oil. These raw materials are mixed with a coal tar pitch binder which carbonized during baking. The electrodes attained full graphitizing tem- peratures approaching 3000" C. for a sufficiently long time t o achieve the maximum crystallization possible a t that temperature with the respective starting materials (17). X-ray diffraction patterns indicated that the degrees of graphitization were similar for the two sample types.

The ash content of a typical sample of Type B carbon is 0.005% as compared with 0.02% for a typical Type A carbon sample.

Spectrographic examination of the Type A material show cal- cium, iron, magnesium, and silicon as the major impurities while aluminum, boron, chromium, copper, and manganese are present in trace amounts. Emission lines of these impurities are either missing or only faintly visible in spectrograms of the Type B

In preparing the samples for use, 38-mm. lengths of 6-mm. carbon rod were held in a jig and two sides were carefully flat- tened by shaving them with a clean knife edge. These samples were then either used or treated with catalysts immediately.

The catalysts were applied by soaking Type B samples in solu- tions of ammonium metavanadate, cobaltous nitrate, ferric nitrate, or nickelous nitrate for two or more days. Excess solution waa removed by blotting with filter paper jugt before use. The

v

8 carbon.

T o gc

uurn

w c u u m 1 w

tained by ashing the samples. Measurement of the ash contents showed that the amount of catalyst deposited was directly proportional to the concentration of the solution. The ash con- tents of Type B samples which had been treated with 0.1M solutions of the cobalt, iron, or nickel nitrates were about o.14y0. Treatment with 0.025M ammonium metavanadate produce sam- ples with ash contents of about o.0370.

GENERAL RESULTS . The basic data obtained from an experimental

run were the collecting pressure a t any given time and the analysis of the collected gases for carbon monoxide and carbon dioxide. For the purpose of analyzing the data, the net reactions represented by Equations 1, 2, and 3 were as- sumed to be the major contributors to reaction.

( 2 )

(3)

CO + HzO COz + HP

c + coz % 2co

Under the& circumstances the rate of gasification is propor- tional to the sum of the partial pressures of carbon monoxide and carbon dioxide [P(co + co,)]. The rate of gasification of carbon may be represented by plotting P(c0 + coI) versus time.

I .O 1

0.8

- 1 c 0.6

8 - h(

0

a- 0.4

0.2

0 0 40 80 I20 160 200

T I M E I M I N . 1

Figure 2. Gasification curves of untreated carbon samples at 1800" c.

0 s Type A carbon 0 = Type B carbon

I n Figure 2, such plots are given for Type A and Type B carbon samples a t 1080O C. The rates of gasification so measured were not constant during the run but increased with time. I n order to determine the gasification rate a t any given time it was neces- sary to draw a tangent to the curve a t the point in question and to determine the slope of the tangent. Inasmuch as the com-

October 1955 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 2131

pilations of data obtained in this study are quite voluminous, only the general results are recorded, and the reader is referred to the original work for a more detailed picture.

RESULTS WITH UNTREATED SAMPLES

Rate Law. In nearly all runs with both Type A and Type B samples, the gasification rate is a linear function of P(c0 + ~ 0 % ) to 0.5 mm. of Hg pressure or more. This linearity is demon- strated in Figure 3. If one considers that as the reaction pro- ceed:, the surface roughness, and thus the number of readily attacked sites, increases, it is possible to relate the rate a t which P(c0 + coz) changes to the rate a t which the concentration of active centera increases. Thus, if c = the number of active sites a t any given time in thb area affected by the steam jet,

C 20 40 00 80 100 120 140 160

I l o4 I ~ ~ / ~ ~ ~ . 1 d P ( C 0 + C O Z )

c = ( a + b p ) (4) d i

where a = the original number of sites available

p = pressure of the carbon gasified, P(CO + coz) b = proportionality constant

bp = additional number formed by gasification

Assuming that in the beginning, under a given set of conditions, the rate of gasification is proportional to the concentration of active sites

9 = kc = k ( a + b p ) (5) dt

Aceording to Equation 5, a plot of dp/dt versus p should result in a straight line with slope equal to kb, b times the specific rate constant, and intercept equal to ka. This corresponds with the results observed for the untreated samples of Type A and Type B carbon, and has been interpreted to mean that the gasification rate of the untreated samples was first order with respect t o the concentration of available active sites in the presence of excess carbon.

Table I contains values of ka, kb, and b / a obtained for the two types of carbon a t various temperatures. It was not possible to get absolute values of a or b from the experimental data.

Table I. Experimental Values of kb, ka, and b/a for Untreated Carbon Samples

Carbon c. kb Ra b/ a Temperature,

A A A A A A A B B B

1110" 1095 1080 1065 1050 1035 1020

0.027 0.050 0.026 0.023 0.017 0.012 0.0091

2.9 7.5 4.9 6.0 3.2 3.5 2.5

1140 0.018 0.0012 15 1110 0.014 0.0012 12 1080 0.011 0.0011 10

This run was apparently out of control.

HEATS OF ACTIVATION

If one assumes that the b term is not temperature dependent, the slope of a plot of log k b / T versus 1 / T should be equal to

- AH"/2.303R

Analyzing the experimental data in this manner for the two types of carbon gave heats of activation of 72 kcal. per mole for the Type A and 36 kcal. per mole for the Type B carbon.

Carbon Monoxide: Carbon Dioxide Ratio. The level of carbon dioxide in the products obtained using Type A samples was generally higher than was obtained with Type B samples. Previous workers ( 4 ) have pointed out that the reaction

( 2 ) is catalyzed by impurities such as were present in relatively large amounts in the Type A carbon samples.

CO + HzO F? COz + H B

Figure 3. Gasification pressure versus gasification rate for Type B carbon

Dashed lines indicate deviations from linearity beyond P(cO+ 001) = 0.5 - 1080' C. 3 X 10-6 moles steam/sec. 8 = 1140O C. 0.5 X 10-6 moles steam/sec.

0 = 1140' C. 3 X 10-b moles steam/sec.

TREATED GRAPHITE SAMPLES

Rate Curves. I n Figure 4 are shown curves of P(co + cos) versus time for treated graphite samples a t 1100' C. The gasification of the sample treated with ammonium metavanadate (NHIVO~) proceeded a t a constant rate whereas with iron, cobalt, and nickel, the rates increased with time in a manner somewhat similar to that of the untreated Type B carbon. Further investigation showed that the changes in gasification rate exhibited by the treated samples were not linear functions O f P ( C 0 + cod.

I

1 0 1 I " I ' ' I l

Figure 4. Gasification curves of treated Type B samples at 1100' C.

0 2 A 6 8 I O i z 1 6 >6 18 LC r i M E i v i N I

1 = Iron treated, 0.14% ash 2 = Cobalt treated. 0.14% ash 3 - Nickel treated, 0.14% ash 4 = Vanadium treated, 0.3% ash

I n experimental runs a t lower temperatures, both iron and vanadium treated samples showed evidence of having been poisoned, probably by adsorption of one or more of the reaction products. No such phenomenon was noted for cobalt and nickel. Judging from the observations of previous investigators, the adsorbed product was probably hydrogen. This poisoning effect was shown to be reversible by repeating the experiments with the same sample after re-evacuating the apparatus while heating the carbon t o the temperature in question.

The effect is shown in Figure 5 for vanadium.

2132 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 41, No, 10

Rate Law. The order of reaction with respect to the amount of carbon gasified is zero for vanadium-treated samples up to those pressures a t which poisoning sets in. For samples treated with cobalt, 'iron, or nickel, the order appears to change in an undetermined manner, tending toward zero order as reaction proceeds in a number of cases.

"O %

T l Y E l Y l N I

Figure 5. Gasification curves for vanadium catalyzed samples at various temperatures

0 11000 c W 1050° C:} Run 1 0 9750 c. 0 975O C. Run 2 0 975OC. R u n 3

Arrhenius Plots. In addition to notable increases in gasifica- tion rates of treated Type B samples, plots of log rate versus the reciprocal of the absolute temperature gave indication of differences in the reaction mechanisms under the influence of four catalytic agents. As is shown in Figure 6, in the tempera- ture range studied, the experimental activation energies of all but the vanadium treated samples go from positive values, through zero to negative values as the temperature increases. This demonstrates changes in the rate controlling steps.

Table I1 contains the relative gasification rates obtained with treated Type B samples a t 1100"

Figure 6 shows that these relative gasification rates are highly dependent on temperature, and except for the results with vanadium treated samples, would be even higher a t lower tem- peratures. Notable increases in reactivity are noted with vana- dium-treated samples having ash contents as low as 0.013% and with iron and cobalt treated sample with ash contents of 0.03%.

Relative Gasification Rates.

Table 11. Relative Gasification Rates Obtained with Treated Type B Carbon Samples

Temperature - 1100' C. P(C0 + Con) - 0.5 mm.

Steam moles/sec.: 0.52 X 10-6 Relative Gaei- fication Rate Treatment Ash, %

0.005 0.14 0.14 0.14 0.03

1 27 32 19 22.

Carbon Monoxide: Carbon Dioxide Ratio, The effect of sample treatment on the carbon monoxide : carbon dioxide ratio varied considerably with the catalyst used (Table 111). With samples treated with cobalt, nickel, or vanadium, the carbon monoxide : carbon dioxide values increase quite regularly with in-

Table 111. Carbon Monoxide: Carbon Dioxide Values with Treated and Untreated Type B Carbon Samples

Temperature CO: C o t Values Treatment Range, O C. Average Range -

Untreated 1080-1 140 57 14-91 0.1M Co(NO8): 555-1100 39 236-62 0 1M Fe NO:): 590-1100 240 78-512 0.02M NHtVO: 975-1100 94 41-160 0:1M NifNO:)r 580-1100 4 <1-10

creasing temperature. Iron treated samples, however, give de- creasing values of carbon monoxide: carbon dioxide as the tem- perature was increased beyond 770" C. The inflection point corresponds roughly to the temperature below which reaction seems to be inhibited by poisoning by adsorption of the products of reaction.

4 I I 1 I I

L -I

- < .j

P .06

L

H 8

8 + . 0 4

$- .02

010

008

006

7 8 9 1 0 I. I 1 2

UT x 103

Figure 6. Log rate versuB 1 / T for cobalt-, piron-, nickel-, and vanadium-treated samples,

and untreated Type B samples Rates measured at P(CO + COI) - 0.5 mm. except initial rate

for vanadium 0 - Iron treated, 0.14% ash 0 Cobalt treated 0.14 % ash 0 - Nickel treateh, 0.14% ash 0 - Vanadium treated, 0.03 % ash 0 - Untreated, 0.005 % ash

COKC LU SION Very small quantities of the catalysts studied are effective in

causing considerable increases in reactivity. This emphasizes the necessity of caution in interpreting results with pure carbon samples as being free from catalytic effect. The tendency of the catalyzed reactions to approach zero order with respect to the amount of carbon gasified indicates that diffusion probably be- comes rate controlling as reaction proceeds under these conditions.

ACJLNO W LEDGM ENT

This investigation was supported in part by the University of Utah Research Committee and in part by the United States Air Force under Contract No. AF 33(038)-20839, monitored by the Office of Scientific Research and Development Command.

REFERENCES

(1) Dent, F. J., and Cobb, J. W., J. Chenz. SOC., 1929, pp. 1903-12. (2) Dodge, B. F., "Chemical Engineering Thermodynamics," p.

332, MoGraw-Hill, New York, 1944.

October 1955 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 2133

(3) Fox, D. A., and White, A. H., IND. ENG. CHEM., 23, 259-66

(4) Johnstone, H. F., Chen, C. Y., Scott, D. R., Ibid. , 44, 1564-9

(5) Kroger, C., Angew. Chem., 52, 129-39 (1939). (6) Kroger, C., and Knothe, H., Brennstoff-Chem., 20, 373-8,

(7) Kroger, C., and hilelhorn, G., Ibid., 19, 157-69 (1938).

(9) Long, F. J. , and Sykes, K. W., J . chim. phys., 47, 361-78 (1950). (10) Long, F. J . , and Sykes, K. W., Proc. Roy. Soc., A 193, 377-99

(11) Ibid., A215, 100 (1952). (12) Marson, C. B., and Cobb, J. W., Gus. J., 175,882 (1920).

(1931).

(1 952).

388-91 (1939).

( 8 ) Ibid., pp. 257-62.

(1 948).

(13) Milner, G., Spivey, E., and Cobb, J. W., J . Chem. SOC., 1943, pp.

(14) Neumann, B., Kroger, C., and Fjngas E., Z. anorg. u. allgem.

(15) Sihvonen, V., Fuel, 19,35-8 (1940). (16) Taylor, H. S., and Neville, H. A., J . Am. Chem. SOC., 43,2065-70

(17) Young, D. C., Pacific District National Carbon Co. private

578-89.

Chem., 197, 321 (1931).

(1921).

communication, November 1952.

RECEIVED for review April 19, 1964. -4CCEPTED April 23, 1966. From a thesis submitted to the faculty of the Cniversity of Gtah in partial fulfillment of the requirements for the degree of doctor of philosophy March 1954. Presented a t Division of Gas and Fuel Chemistry, 124th Meeting, ACS, Chicago, Ill., September 1953.

Emulsified Fuels in Compression Ignition Engines .

I. CORNET AND W. E. NERO’ University of California, Berkeley, Calg.

HE object of this investigation was to determine experi- T mentally the effects of water emulsified in Diesel fuel on the performance of a Diesel engine.

The use of additives to improve the cetane number of Diesel fuels has been widely investigated. Acetone peroxide and alkyl nitrates are generally considered to be the most effective (4, 8, 9, 13, 22, 26), but are not completely soluble in Diesel fuel. I n classifying ignition accelerators, Bogen and Wilson (4) make the following rough generalization: “The more effective the igni- tion accelerator, the less soluble in Diesel fuel.” Mang water- soluble compounds which theoretically would be good additives are not soluble in Diesel fuel, but they may function as ignition accelerators. It would therefore be of interest to know how water, as a vehicle for these additives, would affect the fuel.

Emulsified fuels are the subject of numerous patents ( 1 , 2, 10-12, id-19, 21, 25,W) dating back over 50 years ( I d ) , but rela-

1 Present address, The Trane Co., Los Angeles, Calif.

tively little information on such fuels has appeared in the tech- nical literature (5 ) .

EQUIPMENT, MATERIALS, AND PROCEDURE

Description of Apparatus. ENGINE. The engine used, shown in Figure 1, was a General Motors series 2-71 Diesel, which is a two-stroke-cycle, two-cylinder engine employing a Roots-type blower supercharger and General Motors unit injectors, injecting solid fuel directly into the cylinder chamber.

I n a Diesel engine, the throttle controls the quantity of fuel injected. In order to have full control of the throttle position, the governor unit was rendered inoperative and replaced mith the mechanical throttle control lever shown in Figure 2.

Xormal injection timing (14” C. before TDS, top dead center) was used in all runs except four in TThich the effects of varying injection timing were determined.

DYNAMOMETER. The engine was connected to a Sprague dynamometer rated a t 122-pound load from 500 to 2000 r.p.m. on a torque arm of 1.3125 feet. The torque arm was connected to a balance scale, and the load read directly from the scale. The output from the dynamometer was absorbed in a series of cast-

Figure 1. Experiment station Figure 2. Throttle control lever