Reforming with Carbon Catalysts ROBERT A. SANFORD AND BERNARD S. FRIEIPMAfi Sinclair Research Laboratories, Znc., Harvey, I l l .
I
N RECENT years the octane requirement of motor fuels has
increased steadily, necessitating the development of processes capable of reforming straight-run naphthas to give maximum yields of high octane fuels. The demand for benzene and i b homologs for the chemical industry has further stimulated the development of processes for dehydrogenating naphthenes, dehydrocyclizing aliphatics, and isomerizing cycloparaffins t o cyclohexane derivatives. I n general, these demands have been met by the development of new catalytic procedures that are superior to known thermal methods. However, these catalytic processes operate a t moderately high pressures. They depend chiefly on aromatic formation and paraffin isomerization for octane improvement. Several years ago, a program was initiated in these laboratories with the objective of improving the octane value of straight-run naphthas through dehydrogenation and limited cracking. It was thought that increasing both the aromatic and olefin content in straight-run naphtha through catalytic dehydrogenation would give motor fuels with satisfactory octane values. As this type of conversion is highly endothermic, the introduction of sufficient process heat was a problem. This was solved by employing superheated steam as a diluent during processing, thus eliminating in a commercial operation the need for either a series of reactors with reheating betn-een reactors or special and costly tubes for indirect heating. Although a number of steam-insensitive dehydrogenation catalysts were tested for the reforming of naphthas, only activated carbon gave results of potential commercial value. Processing a t atmospheric pressure using steam dilution gave yield-octane results comparable to that generally reported for hydroforming. The literature has numerous references to the use of active carbons as cracking catalysts. Rlarisic ( 4 ) suspended activated carbon in hydrocarbon feed stocks and treated these mixtures a t temperatures betvieen 800" and 1000" F. Coarse carbon particles were separated from the reaction product and regenerated with steam a t about 1200" F. Greensfelder and associates ( 2 ) cracked cetane, cetene, wax. and several isomeric hexanes with activated charcoal a t 500" C. Their work showed that cracking over carbon surfaces is most readily explained by a free-radical mechanism. Apparently a free-radical formed a t the catalyst surface by removal of a hydrogen atom anywhere in the carbon chain, cracks a t the beta position to yield a normal alpha-olefin and a primary free-radical. The latter is rapidly saturated by the addition of a hydrogen atom at the surface of the catalyst to form a saturated paraffin which cracks no further unless i t is still of high molecular lqeight. References to the use of active carbon as a dehydrogenation or reforming catalyst are few. Johnson (3)passed aliphatic hydrocarbons over active charcoal a t 450" to 500" C. and reported large quantities of olefins. In 1952, Adams and Kimberlin ( 1 ) nere issued a patent covering the antiknock improvenient of naphtha, using active carbon as a catalyst a t about 1000" to 1060" F. and preferably a t pressures between 50 and 100 pounds per square inch gage. The catalyst was regenerated by passing steam a t 1400" F. through the catalyst bed in a direction opposite to the process flow. I n the tests made in these laboratories, good reforming activity was observed (5) with activated charcoal promoted with small amounts of sodium, potassium, and lithium bases or salts. Con-
siderable variation in effectiveness was observed with the promoters tested. These promoters appeared to suppress nonselective cracking-i.e., scission to form Ci to Ca fragments-and to improve the dehydrogenation activity of the catalyst. Steam was employed as a diluent and its use suggested the possibility of a continuous reforming operation, provided coke deposits could be removed or activated in place by the water-gas reaction. To explore this possibility, life tests were made with unpromoted charcoals using either a high steam dilution during processing or intermittent regeneration with steam a t 1300' F. EXPERIMENTAL PROCEDURE
CATALYSTS.Activated coconut charcoal was purchased from the Columbia Division of the Carbide & Carbon Chemicals Co. Activated carbon, Type B.P., was purchased from the Pittsburgh Coke and Chemical Co. Table I gives an analysis of these carbons. -
TABLE
Chemical composition, wt. Na
I. ACTIVATED CARBOXS Yo
K
CS Si02 Surface area, sq. xneter/g. (Langmuir
equation)
Apparent density, g./ml.
Coconut Charcoal 0.10 0 66 0.21 None 1320 0.5
Active Carbon, T y p e B.P. 0.08 0.10
0.29 5.52 1so2 0.5
The promoted carbons were prepared by impregnation of the carbon (about 8- to 14-mesh) with an aqueous solution of the promoter. The carbon was treated for 30 minutes with hot dilute hydrochloric acid (10 parts of water to 1 part of concentrated acid) washed with hot water until the wash water was neutral, and dried a t 1000" F. in a nitrogen atmosphere. This drying step removed the last traces of adsorbed hydrochloric acid, leaving a carbon free of surface promoters. After the carbon had been evacuated under 20 mm. of mercury pressure, the aqueous solution of promoter was added. Sufficient solution wa6 introduced just to saturate the carbon, the required amount being determined in advance. The promoted carbon was dried for 8 hours in an oven a t 230" F. Before use in reforming experiments, each catalyst charge was slowly warmed to 900" F. in an atmosphere of nitrogen. HYDROCARBON FEEDS. Naphthas. Characteristics of the naphthas employed as feed stocks in the reforming tests are given in Table 11. Pure Hydrocarbons. Methylcyclohexane, n-heptane, and methylcyclopentane wcre purchased from the Phillips Petroleum Co. They were found to be at least 99% pure by mass spectrograph analysis. APPARATUS.The reforming tests were made in a vertical Vycor tube reactor (26 mm. in inside diameter, 30 mm. in outside diameter), the top 10 inches of which contained packing for preheating the reactants. This was followed by a section 15 incher long, usually containing 150 ml. of catalyst. The reaction tube was heated with a three-element furnace and the temperature of the cataly-st bed was measured with a searching thermocouple in a quartz thermowell evtending through the catalyst bed. Both the water and hydrocarbon feed were introduced into the reaction zone by means of constant-feed pumps (UOP bellows-type). The effluent from the reactor was cooled with a water condenser and the gasoline collected in a receiver. Gaseous products were passed through receivers cooled with dry ice t o condense C, and additional gasoline. The effluent "dry" gas was sampled continuously by displacement of mercury and the total volume measured with a wet-test meter. PRODUCT ANALYSIS.All condensable liquid products from each reforming test were combined a t -80" C., and stabilized on a
2568
December 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE 11. NAPHTHA FEED STOCKS Naphthas Type API a t 60' F. Initial 10 30 50 70 90 EP Residue Loss S %
P: %
% pu', % A, %
0.
A
Mid-Continent 57.1
B
Mid-Continent 49.5
228 237 249 258 . 271 294 335 0.9 1.1
311 323 333 340 347 363 413 0.4 0.6
0,015 61.6 0.0 31.8 6.6
, . .
48.8 0.0 35.3 15.9
Octane No. 42.0 RM5 43.3 MMb a Research method C F R 1 method) b Motor method (C$.R:-Z'ðod).
30 33
fractionating column to a '5 C. overhead. This gave a Ca-free gasoline which was later adjusted (calculated) to a 10-pound Reid vapor pressure (RVP) basis with the addition of butane-butylene fraction (product plus necessary outside requirements). The stabilizer overhead gas and the dry gas samples were analyzed with a mass spectrograph. At the end of the process period the catalyst was flushed with steam and then with nitrogen. Coke deposited on the catalyst was then measured by weighing the catalyst before and after the test in a nitrogen atmosphere at about 25' C . All yields reported in this paper are based on 100% recovery. EXPERIMENTAL RESULTS AND DISCUSSION
ALKALI-TYPE PROMOTERS. Table 111 shows the results with naphtha B as feed. Operating conditions were: temperature 1040' F., atmospheric pressure, 1.33 liquid hourly space velocity (LHSV), and steam-hydrocarbon mole ratio of 2.7. Although the RM octane number of the reformate was 87.6 in the case of the neutral charcoal, compared to 80.6 for the sodium
2569
using Type B.P. activated carbon impregnated with various amounts of these bases. All tests were made with naphtha B a t atmospheric pressure, using a steam mole ratio of 2.75. Impregnation with sodium hydroxide produced a catalyst which had greater reforming activity, formed much less coke, and produced a reformate with a much higher spread between R M and MM (C.F.R-1 and C.F.R-2 methods) octane values than did a similar catalyst promoted with potassium hydroxide. The larger amount of coke deposited on the potassium-containing catalyst is in keeping with the higher hydrogen production observed, the latter possibly resulting from a greater formation of coke precursors through h ydrogen-transfer reactions. Impregnation with a 1 to 3 mixture of potassium hydroxide and sodium hydroxide gave a catalyst which produced more coke and yielded a gasoline with a lower octane spread than would be expected on the basis of proportions of each alkali used. It t h e r e fore seemR that the potassium hydroxide is capable of suppressing the sodium promotion, even though the latter is present in sufficiently high concentrations. For this reason, all carbons used as catalysts were first leached with dilute hydrochloric acid as previously described, to remove any potassium hydroxide which might be present initially. Several sodium and potassium salts were evaluated in reforming naphtha A at 1100" F., atmospheric pressure, 2.0 LHSV, and a steam ratio of 10. Results of these tests are shown in Table V. These data show that sodium silicate, sodium phosphate, potassium phosphate, and Eodium carbonate give comparable performances as measured by a reformate octane level (RM) of 85 t o 86. With potassium carbonate the reformate octane level was only 74. The low activity observed with potassium carbonate may be a characteristic of potassium oxide, formed directly by the dissociation of the carbonate on the carbon surface. With potassium phosphate, the formation of potassium oxide would be more difficult, depending upon the hydrolysis of the phosphate with dry steam, and this did not appear to be substantial in view of the high octane product. On the basis of coke deposition per octane increase, potassium carbonate is much inferior to potassium phosphate, which in turn is inferior to the sodium salts. PUREHYDROCARBONS. Several tests were made with pure hydrocarbons using B.P. carbon promoted with 3.64% sodium carbonate. The purpose of these tests was to study the dehydrogenation, dehydrocyclization, and naphthene isomerization activity of a typical carbon catalyst. Processing conditions were atmospheric pressure, 2.0 LHSV, and steam mole ratio of 2.75. These results appear in Table VI.
carbonate-impregnated charcoal, the liquid yield was considerably lower and the dry gas make more pronounced. It is also apparent from the relative amounts of hydrogen and methane produced, that the alkali impregnant decreased the cracking activity and increased the dehydrogenation activity of the charcoal catalyst. Lithium carbonate, however, was not so effective as sodium carbonate in controlling the selectivity of the catalyst. In fact, a lithium carbonate-promoted catalyst gave results comparabie to that obtained with the neutral carbon. TABLE 111. EFFECTOF ALKALIPROMOTERS The catalysts were regenerated with 207-52 248-6 steam after 5 hours processing. The Run No* Neutral 0.2% NaOH+ regeneration data in Table I11 show that Charcoal Catalyst (HCI-washed) 3,G4% NazCOs Product distribution, wt. % on feed impregnation with alkali is particularly 10 lb. R V P gasoiine 74.4 87.4 desirable, as the impregnated catalysts Excess C4 3.4 -2.1 Dry gas, CJ20.1 12.4 can be regenerated approximately five Coke deposit 2.3 2.1 times more rapidly a t 1300" to 1400" F. 100.0 100.0 than the neutral catalyst. The high carnaphtha 0.17 0.56 Hz bon monoxide-carbon dioxide ratio in the CHI 0.36 0.20 coz 0.0088 0.0052 regeneration effluent shows that with a i o lb. RVP gasoline Feed Octane No. neutral carbon, coke removal is chiefly RM 30 87.6 80.6 by the water-gas reaction. However, in MM 33 76.1 72.0 Spread -3 11.5 8.6 the case of the alkali-promoted catalysts Regenerabion with steam (1 liter HlO/liter the low carbon monoxide-carbon dioxide catalyst/hr.) Rate of gas make, literslliter catalyst/hr. ratios indicate that removal of coke is acA t 1300O F. 17 100 companied by the shift reaction. A t 1400° F. 48 324 A pronounced variation was observed Gas composition, % HZ 62.2 62.0 between catalysts impregnated with co 26.8 2.5 ,sodium hydroxide and potassium hycon 6.2 28.5 droxide. Table IV show-s the results ~
.
~
207-64 0.2% LiOH+ 2.77% LizCOs 74.0 -1.4 25.1 2.3 100.0
0.33 0.35 0.0072 87.1 77.7 9.4
41
253
64.1 2.5 28.5
INDUSTRIAL AND ENGINEERING CHEMISTRY
2570
TABLE
OF IMPREGSATIOS T I T H POTASSIUM HYDROXIDE AND 1br. EFFECT HYDROXIDE 207-63 KOH
R u n No Impregnating Solution
2.\
LHSV (naphtha) Temp., F, Coke, wt 7,on feed
1.35 1075 1.8
SODIEM
207-81 2 S KOH
207-82 0 5.Y KOH 1 5 S NaOH
207-71 1NNaOH
207-74 2 V XaOH
2.0 925 0.94
2.0 980 0.74
2.0 9 80 0.80
2.0 945 0.43
Vol. 46, No. 12
It is evident in Table V I 1 that when superatmospheric pressures are used in reforming naphtha B with carbon catalysts, coke deposition is sharply increased and a much lower octane reformate is produced. E F F E C T OF F E E D R.4TE B S D TEllI'ER.4-
Naphtha A was processed over unpromoted B.P. cat,alyst at atmospheric .. _. . - n _ _-..-.pressure with 14 moles of eteam. The % (100% recorerv) 93 3 102.2 100.4 88.2 97.0 results of variations in temperatures and space velocities are given in Table 1'111. The data show that even with high steam dilution, temperatures above TABLE v. EV.4LCATIOiY OF SODIC11 BND POT.4SSIUhf SALTS AS PROMOTERS 1100° F. result in poor liquid yields. 270-68 270-71 270-72 270-69 270-53 Run No. Coke deposit,ion is higher and the rate of 5% XazSiOs 5 % NaaPOa 3.5% Pu'aiCOa 5Y0 &PO? 6.57, KzC03 Promoter" nonselective cracking is increased. Best Product distribution, wt. 70 on feed 10 lb. R V P gasoline 80.3 84.9 82.26 81.5 94.7 results appear obtainable at temperatures Excess Ca 0.i -2.2 1.0 1.1 -2.0 of 1000" t o 1100" F. when space veloci19.4 16.5 16,5 15.9 5.8 D r y gas Ca1.5 Coke deposit 0.2 0.8 0.3 __ 1.5 ___ ties of 0.5 to 2.0 are used. 100 0 100 0 100.0 100 0 100.0 EFFECT OF DILGEST. I n Table I S SIole/niole naphtha hydrogen and steam are compared as Hz C Ha diluents in processing napht,ha B over COZ B.P. carbon at atmospheric unpromoted 10 lb. R V P easoline Feed pressure. Octane No 32 0 85 5 86 1 84 9 d Rbl 85 8 74 0 I n tests 214-45 and 214-46 a com74 5 76 3 73 7 76 5 69 1 hIhI 53 3 parison of the product distributions Impregnated on Type B.P. carbon. b Products contain following weight percentages based on feed: Cz=/Cz; 2.3313.14; Ca-/Ca: 4.81/ shows that steam is somewhat more 4.20; Ca-/Ca; 3.92/2.9. Conversion of,90% of C I - and CI- to polymer gasoline would increase yield t o desirable as a diluent than hydrogen. 89.7 vol. % of 86 O.N. (3.3 vol. % outside C4 required). c Questionable, large amount of air in sample. This is probably true even though the exd riromatics 28.857,,olefins 33.3%. cess Cq produced might be comidered an offset to the lower liquid recovery- observed with hydrogen. From the point Test, conditions employed were mild, as it was felt, t,hat,specific of view of equipment and operating costs, however, dilution catalyst functions might be shadoJYed by secondary reactions if with steam would seem t o be more economical because of the small volume of tail gas. experimental conditions were too severe. About 15% of the methylcyclohesane was converted to aromatics and 3.5'3& to COKTIKCOUS REGENERATIOS. A reforming process d i i c h could be operated on a continuous basis would have a decided adolefins. This is understandable, as it is generally accepted that the resonance stabilization in the benzene ring facilitates the coinvantage over intermittent processing with periodic catalyst replete dehydrogenation of the cyclic olefin to the corresponding generation. T o determine if continuous opcration was possible, a life test rras made with unpromoted Type B.P. carbon employing aromatic. With n-heptane, dehydrocyclization amounted t o about 8%. a steam mole ratio of 14. Unpromoted carbon was used as a hnother 12y0 was converted to olefins either by dehydrogenation catalyst, because some of the alkaline promotere tended t o or through cracking. It was noticeably more difficult (higher temmigrate under process conditions, causing a change in both the perature required) to reform n-heptane than methylcyclohexane. concentration and distribution of ,promoter in the catalyst bed. The required temperature was determined by using the rate of dry Control of this factor by injection of make-up alkali would be less of a problem in a conimercial plant than 111 the laboratory gas make as a criterion. ieactor The test with methglcyclopentane is interesting because i t s h o m the inability of carbon catalysts to isomerize cyclopentyl rings t o cyclohexane isom The ability of methylcyclopentanes to form coke is evident even in this mild test. TABLE 1711. EFFECT OF PRESSURE As one would expect in a dehyEFFECT OF TOTAL PRESSURE. Test KO. 214-1 214-2 drogenation process, total preswr? greatly affects both the extent Act. Coconut Charcoal Catals s t , and type of conversions observed. 3.ti3LTc SazCOa Temp.. P. 1000 1000 TURE.
~
T ~ B LTI E
REFORMISG PUREHEDROCARBOSS
Test Yo Feed
207-75 Slethgleyclohexane 91 6
207-76 n-Heptane
+
98.5
C3 -
1.5
100.0
so.; 10. I 9.2 0.0 100.0
4.6 0.4 __ 100.0
81.4 3.5 15.1
75.7 14.7 9.0
7Q.8 20.2 0.0
Temp., ' F. Product distribution, wt.Yo CS
c: d
Coke Composition Cs+,wt. Yo Paraffin 7 naphthene Olefin Aromatic
0.0 __
s7n
207-77 Alethylcyclopentane 970 95.0
.. .
Pressure, atn1.Q LHST Mole ratio steam/HC P . P . of HC o>'er catalyst atin. Product distribution, wt. R on feed Stabilized reformate (Toaromatirs) (4°C olefins) Stabilizer overhead UT.^ gas Coke 10 lb. R V P gasoline Octnne N o . Rhl 11R l Yield, vol. %
.
a
Conducted in stainless steel flow reactor.
34.0 1.3 2.1 11.0
75.5 (32 . 9 ) (29,3) 8.6 11.8 3.1 15Ei
67.8 132.3 84.6
1.0
1.4 2.3
0 3
~
7s.z ( 3 3 0) (30.9) 12.4 I1 . 0 1.4 ~ 100.0
77.3 70.8 83 1
INDUSTRIAL AND ENGINEERING CHEMISTRY
December 1954
TABLE VIII. EFFECT OF FEEDRATEAND TEMPERATURE Test No. Conditions Temp., F. LHSV Product distribution, wt.% on feed Stabilized reformate 'Stabilizer overhead D r y gas Coke Total, agprox.
270-30
270-34
270-8
270-16
1175 1.0
1175 3.0
1100 1.0
1000 0.5
63.6 13.5 20.0 2.9
70.3 11.2 18.0 0.5
1oo.o
loo.0
1.38 4.92 0.70
0.66 3.80 0.55
Mole/mole naphtha Hz c HI
coz
10 Ib. R V P gasoline Octane NO.
R ih4
MM Yields, vol. Yo gasoline Outside C4 required Excess C4 produced
92.3 79.6 67.1
88.6 76.5 75.1
8:s
4:0
84.3 8.1 7.6 0.02
82.7 10.3 6.9 0.09
0.38 1.75 0.04
0.47 1.75 0.19
1oo.o loo.0
76.5 69.7 93.0 4.0
80.2 72.9 90.5 1.2
..
..
TABLE 13. HYDROGEX us. STEAMAS DILUEXT Test No. Conditions Temp., F.
LHSV
Diluent hlole ratio diluent/HC Product distribution, wt. % on feed Stabilized reformate Stabilizer overhead D r y gas Coke
214-45
214-46
1020 2.05 Hz0 2.41
1020 1 95 HZ 2 37
77.4 13.4 9.0 0.2100.0
10 lb. RVP gasoline Octane SO. RM
MM
Yields, ,vel. % gasoline Excess C P produced
72 6 21 - 00 100
~
3 7 0 0
81.6 72.4
81.6 72.3
86.7 0.8
81.4 5.7
Naphtha A was used in a life test conducted a t 1000" F., atmospheric pressure, and 0.5 LHSV. The data for 115 hours of processing are tabulated in Table X. It is apparent that the original activity of unprornoted B.P. carbon cannot be maintained during continuous processing with high steam dilution a t 1000" F. In 115 hours, the yield-octane relationship changed from an original 90.5% of 80.2 (RM) to 95.8% of 73.5 (RM). Hydrogen make decreased gradually, showing lessened dehydrogenation activity. The data also indicate some depreciation in cracking activity over the period of the test (Ca-make). In spite of theseresults, it might have been possible to maintain the activity of the catalyst had it been promoted with active water-gas catalvsts-e.g., cobalt oxides sodium carbonate, etc. Such water-gas promoters might inoie effectively balance coke deposition with coke activation.
2571
INTERMITTENT REGENERATION. In view of the depreciation in catalyst activity observed with continuous regeneration, a short life test was made employing intermittent regeneration with high temperature steam. I n these experiments, naphtha B was reformed using B.P. carbon as a catalyst. I n the 41-hour aging test summarized in Table X, processing was conducted a t 1000° F. atmospheric pressure, 2 LHSV and a steam mole ratio of 2.6. After every 4-hour process period, cokr deposit (increment in catalyst weight) was removed from the catalyst by regeneration with steam (1 liter of water per liter of catalyst per hour) a t 1300" F. Coke removal was calculated on the basis of volume and composition of gas produced during regeneration. S o significant change in catalyst activity was observed throughout the aging test. However, liquid recoveries ultimatel: increased to some extent, octane values remaining nearly constant; the reverse is true for the intermediate runs. The data indicate no significant change in dehydrogenation (hydrogen production) or cracking (C, - make) activity. This maintenance of catalyst activity may be attributed to the method of regeneration CONCLUSIONS
Activated carbons, with and without promoters such as sodium salts and bases, are effectivecatalysts for naphtha reforming. Promotion with these agents retards cracking and promotes dehydrogenation. The product is high in olefins and aromatics. Other alkaline impregnants-e.g., potassium hydroxide and potassium carbonate-have adverse effects on the catalyst activity and selectivity, while lithium carbonate appears to have only a minor effect on product distribution. However, all of these impregnants greatly accelerate regeneration with steam. Best results are obtained with a process temperature between 1000" and l l O O o F., employing a space velocity (LHSV) of 0.5 to 1.0. Comparisons between hydrogen and steam as diluents in reforming over carbon catalysts show that a somewhat more favorable product distribution is obtained when steam is used. 411increase in total pressure adversely affects product distribution. Maintenance of original catalyst activity was realized in tests where hydrocarbon processing was periodically interrupted t o allow catalyst regeneration with high temperature (1300" F.) steam. Continuous processing was not possible using steam dilution with an unpromoted carbon catalyst. Catalysts promoted with active water-gas catalysts-e.g., sodium carbonate, cobalt oxides, &-might permit continuous processing if high steam-hydrocarbon ratios are employed. LITERATURE CITED
Adams, C. E., a n d K i m b e r lin, C. N., U. S. P a t e n t 2,587,425(Feb. 26, 1952). ( 2 ) Greensfelder, B. S.,and associates, IND. ENG.CHEM., 41, 2573 (1949).
(1) TABLE
x. CONDITIONS O F CONTINUOUS AND INTERMITTENT REGENERATION ___
Run F o Service time, hours Product distribution, yt, Yc on feed Ca C3 Coke Total, approx.
-
Hz
C Ha
cot
10 lb. R V P gasoline Octane S o . Rhl hl h% Yields, vol. % gasoline Outside C4 required Excess Cd produced a Sample lost.
270-16 0-5
Continuous Regeneration 270-18 270-22 270-31 270-39 5-15 25-35 65-75 105-115
89.0 10.9 0.1 ~. 100.0
88.9 90.6 11.0 9.3 0 . 0 5 0.05 -__ 100.0 100.0
0.47 1.74 0.19
__
0 38 1.74 0.12
0.31 1.37 0.24
90.5 9.5 0.0 __ 100.0 0.30 1.35 0.10
91 1 8 9
~~
0.002 100.0
79.8 71.6
77 8 69.9
74.5 68.7
73.5 67.9
90.5 1.2
89.8
91.3 1.6
96.6 6.0
95.8 3.6
i:2
..
..
ca.88 2 ...a
0.60
0.24 1.32 0.10
80.2 72.9
..
248-8 0-5
..
.
Intermittent Regeneration 248-12 248-13 248-18 248-20 5-9 9-13 29-33 37-41 87.9 11.8 0.3 100.0 0.20 1.65 0.02
73.3 68.0 91.4 ,.
87.9 11.9 0.2 100.0
0.22 1.93 0.02
88 2 11.0
0.2 100.0 0.22 1.89 0.02
88.8 11.0 0.2 100.0 0.19 3.10 0 02
75.3 70.2
76.7 71.0
74.1 89.8
74.2 G8 6
90.6 1.3
91.3 1.0
91.8 0.3
93.1 0.1
(3) J o h n s o n , J.
Y.,B r i t . Patent
301,402( J u n e 27, 1 9 2 7 ) . (4) Marisic, M. M., U. S.P a t e n t 2,428,715(Oct. 7 , 1947). ( 5 ) S a n f o r d , R. A , and P r i e d -
man, €3. S.,I b i d . , 2,592,603 (-4pril 15, 1952). RECEIVEDfor review July 16, 1953. ACCEPTED July 30, 1954. Presented before the Division of Petroleum Chemistry a t the 123rd Meeting Of the AbfERICAN CHEMICAL SOCIETY, Los Angeles, Calif.
