Catalysts for Oxidation of Ammonia t o Oxides of Nitrogen S. L. HANDFORTH . ~ N DJ. N. TILLEY, Eastern Laboratory of E. I. du Pont de Nemours &Company, Inc., Gibbstown, N. J.
C
ATALYTIC oxidation of a m m o n i a is commercially one of the most important reactions in heterogeneous catalysis, and the various materials suitable as catalysts have been the subject of extensive investigations. The stoichiometric equations are as follows :
together. As the reaction must be carried out a t a temperature above 600" C. (1112°F.) and under oxidizing conditions, only the few metals similar to platin u q will withstand the conditions and remain in m e t a l l i c form. P l a t i n u m is the outstanding metal of this group, The other catalysts are composed of various oxides. These 4NH3 502 = 4N0 6Hz0 (1) have been extensively investi4NH3 302 = 2x2 6Hz0 (2) gated by many w o r k e r s and There has been much theoriznearly all oxides and combinations that might be s u i t a b l e ing on the actual steps occurring in the reactions ( 1 , 2, 16), and have been tried. Except in one it is probable that the catalytic or two cases, the efficiency of surface actually takes active part such catalysts has been so low in some steps (16). The desiras to make their u s e u n e c o able catalyst, of course, is one nomical. During the World which will have extremely high War iron oxide c a t a l y s t s , activity for reaction 1, and a low activity with respect to reac- usually promoted with bismuth oxide (S), were used extion 2. Practically all surfaces catalyze both reactions to tensively in Germany. After the war, platinum again besome degree, and almost all conceivable materials have been came available there and almost entirely displaced oxide tried and patented (13). Most of these materials, however, catalysts. With possibly one exception (18) platinum or catalyze reaction 2 to such a degree as not to be commercially platinum alloy catalysts are used exclusively in this country. In view of these facts, the early work of the du Pont Comattractive. Two general types of commercial processes using air or pany was confined largely to the platinum catalysts. Tests oxygen-enriched air as the source of oxygen are in common on the oxide type catalyst indicated that even those reported use, I n one, the operation is carried out a t essentially at- in the literature as most promising were inferior to platinum. mospheric pressure; in the other, the operation is carried out Furthermore, the first results obtained on platinum-rhodium under increased pressure varying from 50 to 100 pounds per alloys ( 7 ) were so encouraging that most of the work theresquare inch. This higher pressure is used to increase the after was confined to the field of metallic catalysts. speed and efficiency of converting the oxides of nitrogen to The platinum catalysts lost weight and disintegrated nitric acid, and is well worth while (19) on account of the rapidly under the operating conditions first tried, but it was smaller equipment required and the higher final acid strength. known that all platinum metals oxidize and volatilize more or At these high pressures, however, i t is more difficult to obtain less rapidly a t high temperature in oxidizing atmospheres high efficiency in the oxidation of ammonia to oxides of (4, 5 , 6, 17). These investigators, however, indicated that nitrogen. Consequently, higher temperatures are used in there would be little or no volatilization of platinum below pressure oxidation in order to obtain good conversion effi- 900" C. (1652" F.). On the other hand, when used as a ciency. While the capacity is increased thereby, the de- catalyst in the ammonia oxidation process, platinum is volaterioration of the catalyst is more rapid. The results ob- tilized from the catalyst rapidly even at much lower temperatained with one catalyst operated under one pressure, there- tures. The surface of the metal becomes "etched" a t first, fore, cannot be compared with the results obtained with a and then covered with sprouts which continue to increase different catalyst a t any other pressure. until the original form of the metal is lost. This effect of a Even when operating under the same pressure, the ca- reaction greatly accelerating the loss of material from a pacity, efficiency, and life of a catalyst are interrelated and catalyst has also been noted with other reactions (20). It affected by so many factors that all must be taken into was found that this loss of metal did not depend on length of account in making any comparison. In general, the higher time or amount of platinum in service. Careful tests showed the temperature the greater is the capacity of a given catalyst, the loss a t a given temperature and with a given alloy to be but unfortunately the more rapid is the deterioration. At a proportional to the weight of oxygen in the reacting gas given capacity almost every catalyst has a maximum tempera- mixture passed over the catalyst, regardless of volume. In ture for highest conversion efficiency (9,14). the operation of large commercial plants, it has been found The catalysts for ammonia oxidation may be divided into that the rate of weakening and breaking of gauze catalysts is two broad classes, as they are different in both their chemical directly proportional to the loss of metal, provided mechanical nature and mechanical arrangement. Rletallic catalysts such damage is avoided. Within the limits of gas mixtures ordias platinum or platinum alloys are usually made up in the narily encountered, this loss is for practical purposes proporform of fine wire gauzes, several layers of which are placed tional to the ammonia used. Since the amount of ammonia is 1287
+ +
+ +
I n determining the economic value of a catalyst, it is necessary to consider all factors-namely, loss of metal, conversion eficiency, and capacityunder the actual conditions of commercial operation. Thus a n alloy which shows extremely high conversion eficiency may be entirely aneconomical because of the high loss of metal which is incurred under the conditions necessary to obtain high conversion eficiency. Platinum-rhodium alloys, howecer, hate been found to give a low loss of metal and high capacity under the operating conditions required f o r the maintenance of high conversion eficiency. Consequently, the pure platinum-rhodium alloys containing 5 to 10 per cent rhodium are the most advantageous and economictrl of any thus f a r proposed.
I N DUSTR IA L
1288
A N D E N G I N E E R I N G C H E 1% I S T R Y
always the known factor, t h e losses which limit t h e useful life have been reported in terms of amount of ammonia used, or troy lost per ~OO,OOO pounds of ammonia treated. As t h e Usefulness Of a catalyst is measured b y t h e amount of ammonia converted, t h e life of a catalyst m u s t be measured i n terms of ammonia oxidized per unit xveight of catalyst a n d
Vol. 26, Yo. 12
pressure plant converters entered the side. The catalyst holder was held between the bottom flange of the tee and the outlet pipe. m7here additional preheating was necessary, the gas was passed through a length of 1-inch nickel pipe heated externally by Nichrome heating elements, The flom was measured by means of an orifice and controlled by a needle valve. The pressure was controlled by a high-chrome iron needle valve in the outlet pipe arranged so that the gas could be released to the atmosphere when n o t b y time i n service. operating a t low pressure, or t o one of the high-pressure absorbers In determining t h e efiCiencJT of cOnverSiOn Of ammonia t o !Then operating a t increased pressure. Some of the oxides of nitrogen, it has been found that e r e n minute tracecatalysts were in the form of small cylinders in the shane of an ” inverted high hat with of some materials are the bottom end closed. such serious poisons These were 1.25 inches for platinum catalysts in diameter and 1.75 that e x t r e m e c a r e inches deep. In other cases small flat pads of must b e t a k e n t o fouror more layerswere eliminate t h e m comu s e d . M o s t of the pletely. T h e purest catalysts tested were in metals available were the form of gauzes of 0.003 inch d i a m e t e r used in t h e present inwire of 80 meshes per vestigation. Modern lineal inch, but tests developments in t h e were also made on both refining of metals a n d finer and coarser gauzes a n d on p e r f o r a t e d the p r e p a r a t i o n of plates. catalysts have overAll converters were c o m e m a n y of the e q u i p p e d with samdifficulties formerly pling pipes a short dise n c o u n t e red Imtance in front of and behind the c a t a1y s t , p u r i t i e s in t h e amConversion efficiency m o n i a occasionally determinations w e r e caused trouble but in m a d e b y a modified recent years there has Gaillard method (11). G a s s a m p l e s , from been n o d i f f i c u l t y in front of and behind f r o m t h i s source. t h e c a t a l y s t , were D u s t y air a n d pipetaken slowly and simulline scale m a y poison taneously into weighed FIGURE1. UNITED ALKALICOUVERTER glass globes fitted with or damage the cataremovable stopcocks. lyst and must b e After weighing, the ammonia samples were titrated directly, neuscrupulously avoided. In t h e following tests all conditions tralized hydrogen peroxide was added to the samples of converter were carefilly controlled a n d checked i o limit t h e effect of product gas, and, after allowing sufficient time for oxidation, these were titrated. The conversion efficiency was calculated from these factors. the percentage by weight of combined nitrogen in the two samples taken simultaneously. At least duplicate tests were made for APPARATUSAND PROCEDURE each determination. In order to carry out t h e large number of tests at a miniThe temperature of the catalyst was determined by means of m u m of expense a n d still obtain results comparable with plant a disappearing-filament type optical pyrometer and was checked results, the tests at atmospheric pressure were made in a by means of a platinum and platinum-rhodium thermocouple commercial converter of the United Alkali type, using a flat attached directly t o the hack of the gauze. It was found that, when using catalysts of three or more layers of gauze instead of gauze having a n exposed area of 4 X 5.5 inches (Figure 1): only one (IO),the back layers close the openings in the front It consisted of a cast-iron heat exchanger completely enameled layers so that the holes radiate as cavities. Also, the metal surfaces become covered with “sprouts” so that the whole gauze on all surfaces coming in contact with the gases. The flat gauze, radiates essentially as a black body, and the only correction weighing 1 to 2 ounces, was held between flanges in the head of necessary to the reading of the optical pyrometer is that occathe heat exchanger. The ammonia-air mixture was obtained sioned by the sight glass. I n some early work the catalyst from a large plant unit so that a continuous supply of gas of temperature was reported as the temperature of a thermocouple constant composition could be obtained. In some cases the temperature of the catalyst was controlled by altering t’he com- a short distance behind the catalyst. Obviously this was not the catalyst temperature. At these temperatures radiation has a position of the gas entering the main converter, but usually it was controlled by piping part of the gas around the small heat ex- much larger effect on such a thermocouple than the gas temperachanger. All piping with which the ammoiiia-air mixture came ture. Consequently, such a thermocouple will not indicate the in contact was either enameled or of aluminum, and no decom- catalyst temperature, but some temperature intermediate between it and t,hat of the surrounding walls. By using an exposition of ammonia ahead of the catalyst could be detected. The flow of gas was measured by means of an orifice, and the tremely fine wire platinum and platinum-rhodium couple, atpreheat temperature was determined by means of a glass ther- tached directly to the catalyst, the tip of the couple reached the catalyst temperature as indicated by the color. Under these mometer in the line just before the gauze. I t T V ~ Sso shielded and conditions the optical pyrometer, the thermocouple, and theothe line so lagged that the effect of radiation mas reduced t o a retical calculations based on the preheat temperature, temperaminimum. The gas from this experimental converter went back t’othe plant system so that the tests could he run continuously for ture rise due to the reaction, and the loss of heat by radiation weeks a t a time. Catalysts found most promising in tests on from the catalyst, all checked very closely. All platinum metal catalysts were pickled in hydrochloric equipment of this size were later tried out in the main plant either in the form of large cylindrical gauzes, 14 inches or more in di- acid, washed in distilled water, cleaned with acetone, and dried before being weighed and placed in the converter. When reameter, or as large flat gauzes of many layers ( 1 2 ) . Some small-scale tests a t atmospheric pressures as well as the moved, they were first weighed, then cleaned in the same manner, tests on oxide type catalysts, and on metallic catalysts a t 100 and weighed again. The loss of platinum through this method of cleaning was found to be negligible. In order t o bring the catapounds per square inch pressure, were carried out in a small pipetype converter. Several different designs were used, but the one lysts up to temperature to start the reaction, they were “lighted” in which most work was done consisted essentially of a flanged 2- with a hydrogen flame. In most cases, it was necessary to start inch nickel pipe tee. A sight glass was fastened in a flange the reaction in only one spot and the reaction then spread comattached t o the top end. The mixed gas from one of the high- pletely over the catalyst within a few minutes. The catalyst was
.
December, 1934
INDUSTRIAL AND ENGINEERING CHEMISTRY
then operated under carefully controlled conditions. Conversion tests were made from 1t o 24 hours after the catalyst was started, and the operation continued until constant efficiency was obtained under the given conditions. Where tests were made of the loss of catalytic material, the catalyst was operated under the specified conditions for periods of 4 t o 7 days, all conditions being maintained constant; hourly readings being taken by the plant operators t o assure this. I n practically all cases, two tests, or at least 2 weeks, were required to determine one loss-of-weight figure.
RESULTS O F EXPERIMENTS I n the early work pure platinum was used extensively. However, some alloying elements were required to improve the mechanical properties of the gauze. Small additions of iridium were tried, but the iridium alloys were not satis-
ii$p;vy/ v1
$
3.40%fLA1TINUM-lO%RHOD/LIM
* 004 9,. 802
720
760
805 840 880 723 GA UZL r m m w w r , "6.
460
FIGURE 2. EFFECTOF TEMPERATURE ON Loss O F RlETAL factory under the conditions of operation of the ammonia oxidation catalyst. Rhodium was then tried, as it was known that the platinum-rhodium alloys also had good mechanical properties. The first results with these alloys as catalysts were surprisingly good. Consequently, a complete investigation of platinumrhodium alloys (7) containing from 0.5 to 50 per cent rhodium was made. Table I shows the loss of weight from platinum and platinum-rhodium catalysts, and Table I1 the conversion efficiency. Figure 2 shows graphically the effect of temperature on the loss of metal from pure platinum and some platinum-rhodium alloys. At the higher temperatures, particularly above 900" C. (1652" F.), the loss increases
TABLEI.
LOSS OF
CATALYST FOR PL.4TISUM RHODIUM ALLOYS
4SD
PLATINUM-
RATEOF NH3
CATALYST PRECOMPOSITION
Platinum
99.5% Pt-0.5% Rh 99.0% Pt-1.0% Rh 98.5% Pt-1.5% Rh 98.0% Pt-2.0% Rh 90.0% Pt-lO.O'%
DAY Pounds 98 125 140 102 101 52 100 105 103 106 110 108 102 109 107 93 04 97 245 93 145 135 49 100 110 100 102 100 100 109 62 104 45 114
PER
Rh
85.0% Pt-15.0% Rh 80.0% Pt-20.0% Rh
50.0% Pt-50,070 Rh
rapidly for all materials, the loss a t 920" C. (1688" F.) being about double that a t 840" C. (1544' F.). But in all cases the addition of rhodium to the alloy reduced the loss, eo that the
b
/
2 3 4 5 6 7 8 9 /0/520
REAT
C. 275 200 200 170 125
...
220 185 240 250 190 250 240 220 140 275 235 240 300 210 270 190
...
.
.
I
240
...
340 330 318 270 310 280 135 315
m3B Y VOL. I N MIX
% 11.0 11.3 11.1 11.0 11.0 10.4 10.8 11.3 11.1 10.8 11.2 10.8 10.4 11.4 11.5 10.5 11.0 11.0 10.0 10.5 9.9 10.0 10.1 9.5 10.9 9.5 9.9 9.9 9.9 10.8 10.5 10.0 9.9 10.0
GAUZE
TEMP.
c.
FIGURE 3. EFFECTOF RHODIUM ON Loss
920 900 900 870 810 720 900 900 900 900 900 900 900 900 854 925 900 900 895 875 870 815 720 900 900 89 1 930 918 915 900 900 865 750 900
LB.
NH3
1.076 0.776 0,892 1.061 0.892 0.708 0.879 0.766 0.522 0.914 0.486 0.596 0.544 0.373 0.444 0.206 0.177 0.631 0.608 0.570 1.067 0.595 0.662
0.579 0.627 0.595 0.177 0.563
50
40
OF
METAL
loss from the 2 per cent rhodium alloy is about 90 per cent and from the 10 per cent alloy about 50 per cent of that from pure platinum. Figure 3 shows graphically the effect of the addition of rhodium on the loss for two temperatures; the loss decreases regularly with increase in rhodium content to nearly 10 per cent. The conversion efficiency increases rapidly with the first additions of rhodium and then more slowly until a content of about 10 per cent rhodium is reached, as shown graphically in Figure 4. The effect of temperature on the conversion efficiency is shown in Figure 5 for three representative alloys. Consistent results with alloys containing 15 per cent and more of rhodium were hard to obtain, probably because of their extreme hardness and brittleness. Table I11 shorn the results obtained on a gauze of finer wire and mesh. TABLE 11. CONVERSION EFFICIESCYFOR PLATINUM AND PL-4TIKUM-RHODIUM ALLOYS (80-mesh gauze; 0 003-inch wire; atmospheric RATEOF NH3
pressure)
PER T R O Y 08.
COMPOBITION
Platinum
EXPOSED NH3 B Y PRE- V O L
CATALYST PER DAY
Pounds 100 100
99.5% Pt-0.5% Rh 99.0% Pt-1.0% Rh
LTT. P E R 100,000 Troy 01. 1.385 0.829 0.903 0.633 0.546 0.177
30
%PHOD/UM IN PL A TINUM- ,Q,YODIUM A1 L 0 Y
LOSS OF
TROY EXPOSED
PER
02.
1289
98.5% Pt-1.5% Rh
98.0% Pt-2.0% Rh
100 100 150 150 150 50 100 50 50 60 50 100 100 100 50
50 50 100 100 100 50 50 50 100 100 150
I50 90.0% Pt-lO.O% Rh
50 50 100 100 100 100 150 150
150 85.0% Pt-15.0% Rh
80.0% Pt-ZO.O% Rh
50.0% Pt-50.0% Rh
150 100 110 100 100 150 140 150 150 65 70 100 100 100 100 150
HE4T
c.
375 315 270 225 200 275 280 190 172 324 273 202 106 250 168 124 288 183 lo0 295 158 101 309 235 110 280 247 234 150 220 170 300 352 360 180 350 305 270 190 320 240
...
. .
310 340 28.5 260 275 280 340 325 290 315
...
IN M I X
% 9.5 9.5 9.6 9.6 10.4 9.6 9.1 11.2 11.0 10.7 10.9 10.9 10.9 10.8 10.8 10.9 10.6 10.8 10.9 10.9 10.9 10.9 10.8 10.8 11.0 11.2 10.8 10.9 10.9 10.8 10.8 10.7 8.2 8.0 10.7 10.0 9.2 9.9 10.0 10.2 10.9 9.5 9.5 10.1 9.5 10.2 10.1 10.0 10.0 9.9 9.9 10.6 10.0 8.2
GAUZE TEMP.
c. 920 900 870 810 918 900 877 900 904 906 866 82 1 797 902 838 809 863 816 780 900 860 810 876 827 779 900 844 886 845 830 800 900 870 840 810 920 901 880 810 920 900 900 891 928 908 897 880 870 850 930 916 900 900 945
COWER.
BION EFFICIENCY
% 97.5 96.1 94.6 92.5 96.4 94.6 93.6 99.0 95.5 98.3 95.5 94.2 89.9 97.2 95.5 91.9 98.5 97.3 95.8 97.1 96.6 93.8 98.2 97.4 94.2 98.3 95.9 95.8 94.9 99.0 97.9 99.3 97.6 97.2 97.0 98.0 97.7 96.0 95.0 99.6 99.6 98.3 98.3 99.7 98.1 96.1 94.9 99.3 97.9 98.6 98.7 99.0 97.0 98.8
INDUSTRIAL AND ENGINEERING CHEMISTRY
1290
TABLE 111. CONVERSION EFFICIENCY WITH FINER GAUZE (150-mesh gauze; 0.0016-inch wire; atmospheric pressure) RATEOF NHJ PER TROY08. "I O F CATALYST B Y VOL. I N GAUZE CONVERSION PER DAY PREHEAT lMIX TEMP. EFFICIENCY Pounds c. % c. % PLATINUM
50 50 50 50 50
170 10.5 130 10.0 95 10.6 55 9.8 46 9.4 225 10.5 200 10.1 150 9.7 so% PLATINUM-~O% 140 10.6 11.2 111 56 10.6 56 10.0 50 9.6 11.3 11.1 10.7 10.7
100 100 100 50 50 50 50 50 100 100 100 100
745 703 670 638 614
96.4 94.3 91.7 88.3 86.3 95.6 93.8 93.6
810 764 72 1
I n addition to platinum and rhodium, only palladium and iridium of the platinum metals will withstand the oxidizing conditions and temperature required by the reaction. Palladium has been tried repeatedly. While it is a fair catalyst, i t becomes brittle after short service and may even crumble to powder when touched. The economic advantages to be gained if i t could be used, however, prompted its investigation. Table V summarizes the results on the palladium alloys. All samples failed mechanically in so short a time as to be worthless.
Temperature of operation is not an economic factor, but only conversion efficiency, catalyst life, or loss of weight, and capacity. The rela\IO0 tion between conv e r s i o n efficiency
(Perforated plate cylinders) RATEOF 3" "a cox-
ALLOY 99.9% Pd0.1% Co 99.9% Pd0.1% Rh
GAQE PER byVERSION PRES- TROYoz. VOL. GAUZE EFFISURE PER DAY I N MIX ~ E M P . CIENCY Lb./sq. in. Lb. % C. % .Atm. 100 11.3 928 83.2 Atm. 100 9.8 901 97.0 Atm. 100 11.2 870 94.1 Atm. 200 10.8 900 96.2 Atm. 200 10.8 840 91.0 100 200 9.4 790 77.8
99.9% Pd0.1% Ru
...
...
..
...
..
99.9% Pd0 . 1 % Au 99.9% Pd0 . 1 % Cu
90
200
11.5
770
87.9
Atm. Atm. Atm. 100 100 Atm. 100 100
100 100
10.2 9.9 10.0 10.4 10.7 8.3 8.3 8.3 7.0 9.4 6.6 9.6 9.2 9.4 8.9 8.9 8.7 8.2 8.0 8.2 10.1 10.0 10.0 10.1 10.0 10.0 8.6 8.8 8.4
928 902 870 875 875 901 910 880 830 880 750
98.2 98.3 96.9 83.2 81.9 98.5 80.5 86.6 81.0 99.3 40.4
shown graphically in 99.9% Pd-
Table
IV
O.l'%Ir
shows
creased p r e s s u r e 1; Io with platinum and 2 RHODIUM IMPLA TINUM-RHODIUM AL L o Y plat inum-rh odium FIGURE 4. EFFECTOF RHODIUM ON alloys. HighercataCONVERSION EFFICIENCY lyst temperatures are necessary to obtain satisfactory efficiency under increased pressure and consequently higher losses result, but with properly arranged catalysts much higher capacities can be obtained. 91
;
3 45
7
9
TABLEIV. CONVERSION EFFICIENCYUNDER PRESSURE
RESULTS WITH PALLADIUM ALLOYS
TABLE V.
RHODIUM
98.3 95.5 92.8 92.0 88.5 100.0 97.5 96.8 95.6
Vol. 26, No. 12
100
100 100 100
100 100
100
99.9% PdO.l%Ag 25% Pd75% Pt
100 150 150
4tm. 90 Atm. .4tm. Atm. Atm. Atm. Atm. 95 95 95 80 80 80 80 80 SO -4tm. 85 85
90% Pd10% Rh
10% Pd90% Pt 90% PdINCREASED 10% Ag
50 80 100 150 60 100 100 150 150
REMARKS Meltedin2 hr. Very brittle in 7 hr. Melted before test could be made llIeltedin2hr. Conditionfairafter 7 hr.
Brittleafter6hr.
Brittle after 5 hr.
Alloy became brittle
902 857 889 896 880 880 900 875 875
75.8 74.5 76.6 75.0 85.6 85.5 98.5 90.1 89.5
Exceedingly brittle: cracked after short aervice Very brittle Brittle, melted
(Platinum and platinum-rhodium alloys; 90 pounds per square inch gage pressure) In an attempt still further to improve the efficiency of the RATEO F platinum-rhodium catalysts and reduce their deterioration, NHa PER TROY 02. NH3 B Y CONVERthe effect of various other alloying constituents was investiof CATALYSTPREVOL IN GAUZE SION COMPOSITION PER DAY HEAT MIX TEMP. EFFICIENCY gated. These tests were first made by alloying the additional Pounds C. % oc. % constituent with pure platinum rather than with the platiFOUR-LAYER CYLINDERS
Platinum
98% Pt-2% Rh
90% Pt-10% Rh
100 100 100 150 150 100
360 320 280 350 330
100 100 150 150 150 65 100 100 150 150 150
8.3 8.3 8.4 9.0 8.6 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.4 9.1 8.8 8.3 8.2
930 900 856 930 890
92.5 89.0 85.6 90.5 86.4
93.1 99.0 99.0 98.2 98.4 97.6 94.4
THIRTY-LAYER F L A T QAUZE
90% Pt-10% Rh
400
336
10.0
930
98.0
The figures indicated in the tables are not individual results, but are averages of a large number of tests made during some eight years of investigation. All scales of operation, including full plant size, are represented. The results indicate quite conclusively the effect of the addition of rhodium both as regards life of the catalyst and ability to obtain high conversion efficiency.
95
41'
'
800
I
820
840
860
880 900 GdffZE TfMPERATUPE, 2.
920
ON FIGURE 5. EFFECTOF GAUZETEWERATURE CONVERSION EFFICIENCY
num-rhodium alloy so as to investigate the effect of one factor a t a time. It was considered that anything which would benefit platinum would also benefit the platinum-rhodium alloy. Table V I shows the effect of various alloying constitu-
I N D U S T R I A L AIVD E N G I N E E R I N G C H E M I S T R Y
December, 1934
TABLEVII. CONVERSION EFFICIENCY FOR TERNARY ALLOYS
ents. A few of these, when first started, appeared promising, but, as the operation was continued, their conversion efficiency decreased and complete testing indicated that none added much to the value of the platinum. Some, however, had little or no deleterious effect. Those elements which were thought to be promising in spite of these results were further checked in platinum-rhodium alloys as shown in VI, and , VI1 Table VII. Comparison of results in Tables IT shows that some of the tests were made under atmospheric and some under greatly increased pressure. It should be stressed that in these tables comparison can be made between alloys only when tested under the same operat,ing conditions.
RATEOF "8
GAGE PER NHSBY PRES- TROY oz. VOL. GAUZE BCRE P E R DAY I N MIX T E M P . Lb./sq in. Lb. % C.
ALLOY
96% Pt-270 Rh-2% I r (4-layer flat gauze)
95% Pt-2.570 Rh-2,570 I r (4-layer cylinder) 80% Pt-10% Rh-10% Ag (12-layer flat gauze)
TABLEVI. CONVERSION EFFICIENCY FOR VARIOUSBINARY ALLOYS 85.72% Pt-9,52% Rh4.76% Co (4-layer cylinder)
RATEOF NH3
ALLOY 99% Pt-170 Au
GAGE PER S H B B Y VERSION PRES-TROYoz. VOL. GAUZE EFFIS U R E PER DAYI N MIX TEMP. CIENCY Lb./sq in. Lb. % C. % 80 80 80 80 80
95% Pt-5% 4U
...
95% Pt-5% co
80 80 90 90 90 90 90 80 82 79 82 80 .4tm. -4tm. 100 100 100 100 100 100 Atm. Atm. Atm. Atm. Atm. Atm. .\tm. Atm. Atm. 95 95 95 90 90 95 90 Atm. Atm. Atm. htm. Atm. 90 90 90 90 90 90 Atm. 95 95 90 95 95 90 92 95 Atni. Atm. Atm. Atm. Atm. Atm. ~ t m .
95% Pt-570 Ni
90% Pt10% Ag
97% Pt-3'1
M0
95% Pt-5% Re 98.1% Pt1 . 9 % TV
96.470 Pt3 6% 11-
9 6 . 6 % Pt4.4T0
w
97% Pt-3% Ru
90% Pt10% c u
CON-
;:295 95 95
50 100 100 150 150
...
100 150 50 65 95 100 150 50 50 100 100 150
52 52 94 94 50 100 100 100
200
150 250 330 320 360 380 475 560 720 44 44 55 55 75 84 80
g:;100 100 200
9.8 10.0 10.0 9.8 9.9
910 945 775 924 815
89.6 87.2 52.3 71.4 48.9
..
...
..
10.0 10.1 10.0 10.1 10 2 10 0 10.2 10.0 10.1 10 1 10.2 10.0 9.9 10.1 10.2 10.7 9.5 10.7 9.8 9.9 11.9 11.8 10.9 10.8 9.8 9.5 9.4 9.2 9.8 9.8 9.8 9.8 9.9 9.8 9.8 9.8 9.4 9.6 9.5 9.6 9.6 9.5 9.6 9.5 9.6 9.5 9.7 9.9 10.0 8.9 9.8 9.8 10.0 10.0 10.0 10.1 10.8 11.0 11.9 11.6 10.9 11 2 10.0 ~~
t,: 9.7 9.8 8.4
879 910 907 902 892 924 911 946 859 931 872 912 930 970 960 1000 930 960 955 970 870 835 898 857 862 870 835 780
880 870 796 897 814 870 922 895 814 913 870 879 955 977 900 950 960 980 977 985 990 882 820 918 860 900
88.3 82.3 78.8 71.6 60.8 67.1 52.0 87.9 87.8 84.9 83.9 84.3 85.2 84.1 84.7 83.6 82.7 80.9 82.1 78.7 91.7 88.3 96.6 88.8 92 1 96.3 92.2 93.0 91.4 88.0 84.2 87.7 87.0 88.8 81.0 78.1 95.5 88.2 95.5 89.2 86.8 90.4 90.3 88.3 88.1 82.0 83.7 92.5 84.4 81.6 87.0 86.1 85.5 86.5 87.0 85.6 87.5 76.1 94.3 85.5 94.7
REMARKS 4-layer cylinder
4-layer cylinder; could not be lighted 4-layer cylinder 4-layer cylinder; conversion t o NJ indicated
9 7 . 8 % Pt-1.6% Rh0 . 4 % Co (4-layer flat gauze) 85.72% Pt-9.52% Rh4.76% Cu (4-1ayer cylinder)
4-layer cylinder
12-layer flat gauze
4-layerflatgauze
4-layer cylinder
1291
85.72% Pt-9.52% Rh4.76% Ni (4-layer cylinder)
Atm. Atm. 4tm Atm. Atm. 80 81 81 79 Atm. Atm. 100 100 100 100 100 Atm. Atm. Atm. Atm. Atm. 90 90 90 90 90 90 90 Atm. Atm. Atm. Atm. Atm. Atm. Atm. Atm. 90 90 90 92 88 95 88 Atm. 90 90 90 90 90 88
51 49 49 94 98
50 100 100 100 115 316 188 260 335 528 695
90 109 105 110 107 100 100
I50
50 50 100 100 100 150 150 100 50 100 100 100 150 150
11.8 11.5 11.4 11.2 11.2 9.5 10.3 10.1 9.8 11.5 10.7 9.4 10.5 10.7 10.3 10.3 10.0 10.5 10.0 10.2 10.2 9.7 10.1 9.8 9.8 10.1 10.0 10.1 10.2 11.3 11.0 11.2 11.2 10.1 9.9 9.9 9.8 9.9 10.0 9.6 9.8 10.2 9.9 9.9 9.9 10.2 9.9 10.0 10.1 10.0
875 850 821 898 839 912 955 946 943 935 933 900 935 940 935 935
844 905 797 904 860 910 87 5 910 885 560 910 885 860 910 885 825 850 910 900 860 925 850
CONVERSION
EFFI-
CIENCY
% 98.5 96.1 97.0 98.7 94.9 73.0 75.2 74.3 73.9 89.2 95.2 92.1 95.7 93.6 93.8 92.6 94.4 93.7 95.5 91.4 91.4 86.5 93.0 91.1 89.8 94.2 91.4 88.1 98.9 98.4 90.8 96.0 94.0 91.2 88.7 87.5 92.1 87.3 92.8 94.4 91.4 90.1 89.1
