Production of High-Hydrogen Water Gas from Younger Coal Cokes Effects of Catalysts' R. E. BREWER
AND
L. H. RYERSON, University of Minnesota, Minneapolis, Minn.
The influence of fuel and water gas conversion catalysts upon the rate of hydrogen production from lignite char and steam a t 600', 700°, and 800' C. has been studied. Under similar operating conditions higher yields of water gas-with corresponding increases in hydrogen volumesper unit time were obtained from char treated with a fuel catalyst (potassium carbonate, sodium carbonate, or a 60 titanium dioxide40 cupric oxide mixture) than from untreated char. Equivalent weight per centages of these catalysts added to fresh char and used immediately showed nearly the same increased effects upon the yields. Prepared charges, which had stood for some time before using, and residual chars from previous water gas experiments, followed by sodium carbonate treatment, ex-
A
N EARLIER investigation ( 4 ) covering
wide ranges of temperature and steam input in the production of high-hydrogen water gas by the action of steam upon younger coal cokes established that: (a) Excess steam-up to a certain maximum for a given temperature-increases the yield of hydrogen; (a) higher volumetric percentage yields of hydrogen for a given steam input are obtained at the lower temperatures; and (c) larger volumetric yields of hydrogen per unit time for the same steam input result at the higher temperatures. These facts, a priori, would lead to the conclusion t h a t optimum conditions of operation for obtaining high yields of hydrogen should be the use of excess steam a t higher temperatures. Working under such conditions, especially in largescale practice, has certain important disadvantages. The advantage of increased yields of hydrogen per unit time a t higher temperatures is offset in large measure by (a t h e need of higher heat input, (b) greater losses due to radiation, and (c) greatly increased initial cost and depreciation of equipment required for the higher operating temperatures. For economical operation, therefore, especially on a large scale, consideration must be given t o conditions favoring reasonably high yields of hydrogen a t as low operating temperatures as are practicable. It has been known for a number of years t h a t water gas of satisfactory composition and yield per unit time can be produced at temperatures several hundred degrees lower than 1 Other papera in this series appeared in July, 1934, pages 734 to 740, and in September, 1934, pages 1002 to 1008.
hibited lower activity. The mechanisms of the action of the three fuel catalysts are considered. Water gas generated in the usual manner showed increased hydrogen content after passage through water gas conversion catalysts. Best results were obtained with a 67 magnesia-30 ferric oxide3 potassium dichromate catalyst used in M-cm. column length, as 3 4 mesh size, in a separate furnace a t 500' C. This catalyst retained its activity and ruggedness with repeated use. Study of the volumetric composition of the gas before and after catalytic treatment suggests:
CO
+ HzO = C02 + H2
as the main reaction which was induced b y the catalyst. the usual operating temperatures by the addition of certain catalysts t o the fuel. Publications by Marson and Cobb (Id), Logan ( I S ) , Neumann, Kroger, and Fingas ( I @ , Neumann and van Shlen ( I b ) ,and FJ'eiss and White (.2(?), covering the effects of added fuel catalysts upon the rate of gasification of carbon materials, give, in addition to their own valuable experimental work, an excellent survey of the investigations of other workers in this field. The present study was conducted with the view of establishing favorable operating conditions for a larger scale investigation now in progress. The main portion of the laboratory data presented here shows the increased yields of hydrogen that result when a number of catalysts are added directly to the lignite char or raw lignite, which was carbonized in situ, to increase the rate of gasification, or are used as water gas conversion catalysts to change the composition of formed water gas into gas of higher hydrogen content.
Apparatus Except for the series I1 experiments, Table 11, the water gas generator furnace used was of the same general design and dimensions as the longer (aO-inch, or 76.2-em.) sillimanite reaction tube furnace previously described (4): To economize in laboratory space, however, the furnace was mounted vertically, instead of horizontally, for the series I11 and I V and a part of the series I ex eriments, in the present work. Except for a small, but measurabg, contraction in char column due to settling during the longer runs in the vertical furnace, no essential differences in results under otherwise similar operating 1047
1048
VOL. 27, NO. 9
INDUSTRIAL AND ENGINEERING CHEMISTRY
conditions were noted for the two positions of furnace mounting. The top or gas exit end of the reaction tube in the vertically mounted generator furnace was provided with a well-insulakd three-way cock; one opening of the cock n-as joined to the reaction tube, a second served as the carbonization gas outlet, and the third served as the water gas outlet. h condensing system, similar to that used by the Bureau of Mines ( I Z ) , was joined to the carbonization gas outlet to take care of the products resulting from carbonizing raw lignite in situ to form char and from further heating of this or other char sample used directly until free of carbonization gas at the temperature selected for a water-gas run. The essential features of the furnace, together with necessary accessory apparatus are illustrated and described in the earlier paper ( 4 ) . The water gas conversion chamber used in the series I11 and IV experiments was a separate horizontally mounted sillimanite (?,'E i. d. X 20 inch, or 2.2 X 50.8 cm.) reaction tube furnace constructed as previously described (4). The tube was packed with a 48-cm. column of the Yater gas conversion catalyst. The connection between the gas entrance end of the conversion chamber and the water gas outlet of the vertically mounted generator furnace was made of such length that cooling by radiation reduced the temperature of the formed water gas t o about 500" C. before its entry into the conversion chamber. The water gas condensing, sampling, and measuring accessories were connected on the gas exit end of the conversion furnace in the usual manner (4). A separate sampling assembly was used ahead of t'he conversion chamber so that gas samples from that point could be collected for analysis. The chamber was maintained at 500" C. in all runs except experiment 62 in which the temperature was 300" C. This latter temperature was judged to be too low for best results with the catalyst used. For the series I1 experiments a single horizontally mounted sillimanite ( i / g i. d. X 26 inch, or 2.2 X 66 cm.) reaction tube furnace (4) served both as a generator and conversion furnace. The lignite char fuel column occupied about 21 em. of the middle portion of the reaction tube. An 8-cm. column of the water gas conversion catalyst selected for a given run mas packed next to the fuel column on the gas exit end. The remaining space in the two ends of the reaction tube was packed with broken porcelain. Other necessary accessories and the manner of assembling have been previously described ( 4 ) .
Carbon Materials
these chars and steam were used under similar operating conditions, when compared, proved that these three lots of lignite char may be considered to be equally representative. The proximate and ultimate analyses of the lot 1 char given in Table I1 of the earlier paper (4)may be taken as typical of the three fresh chars.
Composition of Lignite Ash Since the present work is concerned in part with the effects of inorganic fuel catalysts added to lignite char, it was desirable to know the composition of the original inorganic material (or ash) in the lignite char used. For this purpose and to correlate the present study with earlier (4) and planned future investigations, both chemical and spectrographical analyses were made upon ash samples of lot 1 Lehigh, S.Dak., lignite char (4) and of two other carbon materials-Colstrip, Mont., subbituminous coal and Acheson electrode graphite (4)-included for comparison. Table I gives a summary of the quantitative composition of the ash expressed as oxides in each of the three carbon materials. The analytical procedures used for the various determinations upon these ash samples were essentially those of Hillebrand and Lundell (11). Large stock samples of ash were obtained in the cases of char and coal by separately heating sufficient quantities of these carbon materials to constant weight within the limit's set by the A. S. T. ?VI.method for determining ash in coal and coke. Each ash sample, after thorough mixing, was then bottled until ready for use. The limited amount of electrode carbon TABLE
MATERIALS, IX
Constituenta Lose a t
800°C.
All carbon materials used in the present work were from stock lots (Xos. 1, 2, or 3 ) of Lehigh, N. Dak., lignit'e char produced in the Lehigh Briquetting Company plant or from char prepared for the particular experiment by laboratory carbonization in situ of freshly mined Lehigh, N. Dak., raw lignite: The carbon samples in each case were made ready by separately crushing the starting material to pass 3-mesh (6.73-mm.) and be retained on 4-mesh (4.76-mm.) screens. Screen analyses upon the char produced by laboratory Carbonization of 3-4 mesh raw lignite in situ showed but little change in particle size as a result of carbonization. Shrinkage in the fuel column, however, indicat,ed a closer packing effect in the vertically mounted generator furnace. All charges of lot l and 2 chars and all lignite samples were fresh materials and, except for experiments 12, 22, and 62, were used immediately after placing in the generator furnace. Charges 12 and 62, after preparation, were stored out of contact with air as indicated in column 13, Table 11. The prepared charge for experiment 22 first stood in partial contact with air for several days before being placed in the furnace. The mixture apparently absorbed additional water from the air as was evidenced by an accumulation of an appreciable amount of dark colored liquid in the bottom of the container. Some material was evidently extracted by the potassium carbonate solution from the lignite char. This liquid was drained off and the remaining material partially dried before being placed in the generator furnace. The char samples marked "used" in column 13, series I, Table 11, were originally lot 1 chars which had been employed without added fuel catalysts in earlier water gas runs Lot 3, a partially weathered char, was used in experiments 46-49, series 111. This char had a proximate analysis (in per cent) of 1.76 moisture, 15.83 ash, 28.20 volatile matter, and 54.21 fixed carbon. Some interesting variations in results from those obtained under similar operating conditions upon charges containing one of the three fresh chars-lot 1, lot 2, or char prepared by laboratory carbonization of raw lignite in situ-were observed in certain of the experiments using charges which had suffered some change in composition before use, such as those chars above described. The probable causes of these variations will be discussed later. Proximate analyses of the three fresh chars, as well as the composition of the water gas obtained when each of
I. CHEMICAL XNALYSES
Bi?Oa VlOj
Lignite Char Ashb
.Is
O F XSH IN CARBOS CENT BY WEIQHT
Subbituminous Coal Ash 8!.
received
Ignited
0.77 20,55 0.66 9.88 5.37 0.19 25.40 9.75 2.89 0.44 22.82 0,043 0.123 0.66 0.165c 0,025 0.05 Trace Absent -
PER
-
Summation 99.79 Less 0 0.03 for CI
received
Ignited
Electrode Carbon Ash hs received Ignited
10.31 20.71 0.67 9.96 5.41 0.19 25.60 9.82 2.91 0.44 23.00 0.043 0.124 0.67 0.166C 0.025 0.05 Trace Absent _
_
6.0
10.40 0.27 7.84 3.04 0.39 5s. 85 2.45 0.28 0.40 5.17 0.41 0.07 Trace
... ... ... ... ...
~
Absent
.. ..
Absent ~bsknt Trace
... , _
...
16.7 Trace 24.1 11.1 0.4 13.9 7.9
..
_
99.79
99.88
99.86
0.03
0.02
0.02
Trace _
_
75.7d
Trace .
74,ld
True total 99.76 99.76 99.86 99.84 a Spectrographic analyses checked the presence of all elements whost: oxides appear in the table: traces of Sr, Na, and B were also observed spectrographically in the electrode carbon ash sample. b Sought but not found: Pb, Hg, Cd, As, Sb, Ma, W , U, Cr, Zr, Be, Si, Co, Li. C Includes a trace of SrO. d Remainder is probably largely sO3.
available a t the time and the low ash content (0.761 per cent) in this material (4, correction) necessitated the use of smaller samples of this ash than are usually called for, in the various laboratory procedures. Furthermore, on account of continued appreciable loss in weight resulting upon ignition a t 800" C., the electrode carbon ash was ignited at 1100" C. The computed percentages of oxides in the electrode carbon ash recorded in Table I are, therefore, expressed to only one decimal place. Semi-quantitative tests for the elements listed in the footnotes for lignite ash were made in an attempt to identify the small amount of material not entirely accounted for in the recorded tabulated summary of the total oxides.
SEPTEMBER, 193.5
/
INDUSTRIAL ,4ND ENGINEERING CHEhlISTRY
/
1049
chromic oxide. This catalyst w a s s c r e e n e d before using to pass 3-mesh and be retained on 4-mesh sieves. Catalyst F C p was prepared by soaking 3-4 mesh pumice in a solution containing ferric nitrate and chromic n i t r a t e i n proper proportion to give 93 mole per cent of ferric oxide and 7 mole per cent of chromic oxide. The treated pumice, after draining free of liquid, was dried a t 130" C. This catalyst was used without further screening. Catalyst F C S consisted of 91.16 mole per (lent of ferric oxide, 6.84 mole per cent of chromic oxide, and 2.0 mole per cent of sodium aluminate. This mixture w a s p r e p a r e d from pure ferric and chromic oxide!: and from proper proportions of aluminum and sodium hydroxides, dried at 700" C. and used as 2-3 mesh. Catalyst RIFK was composed of 67 parte by weight of magnesia, 30 parts of ferric oxide, and 3 parts of potassium d i c h r o m a t e (the latter dissolved in 1%-ater). These chemicals were weighed, out directly, niixed to the desired consistency with water, spread on a glass plate, cross-hatched, and dried a t 105" C. The M F K catalyst wah used as 3 3 mesh. This catalyst is of the same composition as that given by Crittenden ( 5 ) except that flake graphite was not incorporated with the dried material in the present work.
I'
A 6
SERIES SERIES
IX Te
AFTER WATER GAS CATALYST 0EFORE WATER GAS C 4 T A L I S l
Procedure
The general method of carrying out the experimental work was quite similar to that previI 2 3 4 5 6 7 a ously described (4). The only added descripMOLES OF STEAM S U P P L I E D PER HOUR tion that need be given here is the manner of FIGURE 1 . Y I E L D OF HYDROGEN FROM LIGNITEC H A R S FOR VARIOUS R.4TES preparing the generator furnace charge-lignite OF STE.4hl char or raw lignite treated with a d d e d f u e l The difference betneen the bum of all the oxides found and catalyst-used in series I a n d IV. Uniform mixing of a 100 per cent is remarkably small, however, and may easily given fuel catalyst-K, S, or TC-n-ith the dry lignite char be attributed to experimental errors. for a furnace charge was accomplished by stirring the weighed proportions of the two materials with just enough distilled Catalysts water to obtain uniform distribution of the powdered catalyst upon the surface of the lignite char particleq. Thus, 40 For convenience 111 recording and discussion, the catalyst parts char, 10 parts potassium carbonate, and 7 parts water used will be designated by the initial letters of the formula gave the correct combination for the 20 per cent potasof the compounds comprising the final inorganic mixture. sium-carbonate-treated char (i. e., char with 20 K). I n exThe number preceding the initial letter, column 3 , Table 11, periments using raw lignite and added fuel catalyst, no added repreqents the weight percentage of the fuel catalyst added water was needed to effect adherence of the powdered dry All catalysts used were made from c. P. chemicals and distilled catalyst-K, S,or TC-to the raw lignite. A uniform water. mixture was obtained simply by qtirring the two materials FUELCATALYSTS.Three separate catalysts-4. e., antogether. hydrous potassium carbonate (I()and sodium carbonate (S) and a n oven-dried mixture of 60 per cent titanium dioxide Presentation of Data (99 per cent purity) and 40 per cent cupric oxide (TC)-were used. The cupric oxide was first prepared by the method of Table I1 gives a summary of the results of water gas runs Evans and Sewton (9) using cupric nitrate and ammonium using catalysts, arranged in order of increasing steam input hydroxide. The titanium oxide was then added and the two for the three temperatures-600°, 'iOO", and 800" C. [Comoxides were washed thoroughly and dried a t 150" (2. plete gas analyses for all runs in the present study compared Gas CONVERSION CATALYSTS.The general procedure of with those for water gas produced under similar conditions Evans and Sewton ( 9 ) , modified for this work by properly of steam inputs and temperatures (4) show, in general, about shaping the product before oven-drying to give the desired the same percentage composition. I n the interest of brevity, mesh size in the d r y catalyst, was used t o prepare these catathe gas analyses are not shown.] The series I experiments lysts. The mixed hydroxides were precipitated from the include the runs for various rates of steam supply with lignite appropriate nitrates by the use of ammonium hydroxide. char or lignite treated with fuel catalysts in the weight proThe well-washed precipitate, after kneading and filtering to portions shown. S o water gas conversion catalysts were used in this series. The yields of hydrogen expressed as remove excess liquid, was spread out on a glass plate. B y proper cross-hatching of a suitably thick layer, a given cataliters per hour are shown in column 8. Comparison experilyst, after oven-drying, remained for the most part in the ments using approximately similar rates of steam supply but desired mesh size. Catalyst FC, dried a t 155" C., consisted no added catalysts gave yields of hydrogen recorded in colof 93 mole per cent of ferric oxide and 7 mole per cent of umn 9. The increased yields of hydrogen due to the use of fuel
VOL. 21, NO. 9
INDUSTRIAL AND ENGINEERING CHEMISTRY
1050
TABLE 11. SUMMARY OF WATERGASRUNS 1
4
3
2
5
6
9
8
7
10
Comparison Expts., No Catalysts
% b y tot.
Temp. O C.
Abs. Pressure Mm.
Char Char Char Char Lignite Lignite Lignite Char Lignite Lignite Lignite Char
20 K 20 K 19.4 N 20 K 4.2 TC 4.6 N 4.2 TC 20 N 5.0 K 4.6 K 5.0 K 20 K
505 608 600 608 604 599 603 600 604 603 606 601
740 738 749 738 725 750 740 743 734 750 734 741
19 20 21 22
Char Lignite Char Char Char Char Char Char Char Char
18.8 K 5.0 K 20 K 20 N 20 K 16.7 K 18.7 N 15.5 N 20 K 20 K
599 701 704 701 703 697 699 701 702 805
750 754 735 735 733 747 731 748 749 743
23 24 25 26 27 28
Char Char Char Char Char Char
11.1 K 20 K 20 PI18.8 K 18.8 N 11.1 K
804 800 802 793 800 802
739 729 738 747 742 739
29 30 31 32
Series 11. Untreated Char None Char None Char None Char None
33 34
Char Char
Expt.
1
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Added Catalyst
Fuel
.
Steam per hr. Moles
----
Steam per hr. -Liters"Moles Series I. Char Treated with Fuel Catalysts 0.875 0.630 0.041 .. 0.149 2.595 1.282 1.243 o:i& 0.591 2.654 1.239 .... 0.825 4.777 2.670 2.186 0:835 3.482 2.406 0.885 0.935 5.607 3.900 2.406 0.885 0,952 6.019 2.406 0.885 3.770 0.973 6.434 0.885 5.730 2.406 9.394 1.083 0.885 1.143 10.317 6.582 2.406 1,917 2.037 11.270 7.292 4.234 2.067 2.065 13.295 8.482 5.165 .... 2.827 4.203 6.823
gii
Hydrogen Hydrogen
..
0,922 1.056 1.456 2.903 3.300 3.409 5,167 0.879
12.919 17.506 16.583 25,160 33.360 37.640 32.757 31.957 37.123 33.713
7.997 10.381 9.917 14.165 18.815 22.320 20.244 18.951 23.055 17.902
0.978 0.978 1.056 2.810 3.144 5.868
32.010 37.692 40.178 70,114 69.296 99.540
16.037 18.658 20.812 38.913 38.113 55.941
3.481 0.868
...
3.1
...
22.1 44.7 62,l 56.7 134.0 173.6 72.2 64.2
... ... ...
., .
... ...
.. . .., ...
0.736 0.905 0.905 1.233
42.5 3.6 47.9 57.2
11,480
....
3:804
65.1
14.210
0:906
26.0
15.333 15.333
0.945 0.945
4.6 21.7
... . . ...
3:478
40:s
... ..,
7.283 9.578 9.578 11.968
....
. .. .
.
..
...
, , , .,
27.061
.. . .
...
13
12 Yield of HydroYield gen of InHvdrocrease gen (Both InCatacrease lysts) -% b y uolume11
...
... ...
...
...
... , . , . . .. .
Remarks
1st lot char 1st lot cbar 1st lot char, "used" 1st lot char Raw lignite R a w lignite Raw lignite 2nd lot char Raw lignite Raw lignite Raw lignite 2nd lot char, dry charge stood several months 1st lot char, used" Raw lignite 1st lot char Zndlotchar 2nd lot char 1st lot char, "used" 1st lot char, "used" l s t l o t char, "used" 1st lot char 1st lot char, wet charge stood several days, exposed to air 2 n d l o t char 2 n d l o t char 2nd lot char 1st lot char, "used" 1st lot char, "used" 2nd lot char
~
Series 111.
35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 67
Lignite Lignite Lignite Lignite Lignite Lignite Lignite Lignite Lignite Lignite Lignite Char Char Char Char Lignite Lignite Lignite Lignite Lignite Lignite Lignite Lignite
None None
a
Lignite Lignite Lignite
.
704 800
752 733
0.988 0.871
18.689 26.277
Untreated Raw Lignite, Carbonized t o Char, M F K After water gas catalyst 604 733 0.172 2.906 None 4.007 600 761 0.806 None 0.836 4.287 605 738 None 4.457 743 0.878 None 605 1.872 5.517 None 600 748 6.638 747 1.917 None 599 8.696 733 2.067 None 605 3.166 None 699 746 0.103 4.631 739 0.179 None 700 0.736 12.179 741 None 702 0.777 12.632 None 698 734 0.791 14.959 None 704 751 1.047 17.841 None 701 749 1.906 30.009 None 703 740 31.269 743 2.302 None 694 22.068 738 3.805 696 None 8.583 26.523 702 731 None 735 0.088 2.933 None 800 None 800 728 0.172 5.450 739 0.861 22.455 None 801 2.094 38.038 796 752 ?one 3.478 45.326 743 hone 797 57.450 744 8.263 None 793
Series IV. Raw Lignite Treated 58 Lignite 4.2 T C 59 Lignite 4.6 N 60 Lignite 4.6 N 61 Lignite 4.2 TC 62 Lignite 5.0 K 63 64 65
Char, Various Water Gas Catalysts Used Once (8-Cm. Catalyst Column in Same Furnace and a t Temp. of Run) 601 746 0.976 2.442 1.179 .. . ... ... ,, FC. 3-4 mesh 603 742 0.934 2.507 1.331 ... ,, , RlFK 3-4 mesh ... M F K ' 3 - 4 m e s h 2Og. 702 732 0.907 15.946 9.615 9:578 0:905 0.4 706 726 0.931 16.25'1 9.405 9.578 0.905 -1.8 .., FCN,' 2-3 mesh: 27.5 g., black
4.6 K 5.0 K 6.0K
with TC, K , or 604 725 757 602 599 750 603 740 604 734 603 606 701
A t normal temperature and pressure.
750 734 754
0.905 0.903
11.8 15.0
... ...
...,AY "" n U r l
...-
Pl"z/I ' Y I l
F&p, 3 - 4 mesh. 5.3 g. RIFK, 3-4 mesh, 20 g
10,709 14.505
9.578 12.659
Water Gas After water gas catalyst 2.028 2.628 2.414 No anal. 3.553 4.256 5.406 1.912 2.848 2.770 ,.958 8.781 10.383 16.475 18.480 14.168 17.266 1.493 2.709 13.585 23.622
Catalyst (48-Cm. Catalyst Column in Separate Furnace a t 500' C.) Before water gas M F K catalyst history catalyst 1.109 0.172 18.7 .., Fresh catalyst (5) 7.4 ... 6th run on catalyst (1) 2.448 0.806 15.0 ... Fresh catalyst (1) 2.186 0.836 ... . ., 2nd run on catalyst (1) No anal. 0 . 8 7 8 3.4 .., 7th run on catalyst (1) 3.437 1.872 1.917 1.2 ... 15th run on catalyst (1) 4.208 6.4 ... 6th run on catalyst (4) 5.165 2.067 12.5 ... Fresh catalyst (2) 1.700 0.103 5.1 .., 10th run on catalyst (1) 2. i o 9 0.179 6.8 .,. 13th run on catalyst (1) 7.283 0.736 5.9 .., 5th run on catalyst (1) 7.516 0.777 4 t h r u n on catalyst (5) 0.791 12.0 ... 7.839 7.8 ... 3 r d r u n o n catalyst (5) 9.634 1.047 2 n d r u n o n c a t a l y s t (5) 1.906 3.4 ... 15.935 2.302 11.3 ... Freshcatalyst (5) 16.604 4.6 ... 14th run on catalyst (1) 3.805 13.550 5 t h r u n o n c a t a l y s t (2) 8.583 3.3 ... 16.709 1.4 .., 11th run on catalyst (1) 0.088 1.472 7th run on catalyst (4) 0.172 7.1 . .. 2.529 0.861 7.3 ... 4 t h r u n oncatalyst (1) 12.665 2nd run on catalyst (2) 2.094 6.7 ... 22.138 6.5 , .. 12th run on catalyst (1) 3.478 27.020 3 r d r u n o n c a t a l y s t (2) 8.263 4.4 .., 35.217
28,782
36.768
N, Carbonized t o Char, M F K Water Gas Catalyst (48-Cm. Catalyst Column in Separate Furnace a t 500" C.) Fresh catalyst 4) 3.2 49.4 0.935 3.482 5.607 3.594 0.935 73.1 6 t h r u n o n o a t & s t (4) 6.8 3.901 0.952 5.993 4.165 0.952 70.6 4 t h r u n o n c a t a l y s t (4) 5 . 3 0.952 4.105 3.900 0.952 6.019 74.6 Z n d r u n o n c a t a l y s t (4) 0,973 11.4 3.770 6.434 4.201 0.973 1.143 10.317 7.005 6.582 1.143 6.4 191.2 Fresh catalyst (3). charge stood 18 hr. in generator furnace 72.7 3rdrunoncatalye.t (4) 0.3 7.292 2.037 7.314 2.037 11,270 71.9 Z n d r u n o n c a t a l y s t (3) 3.6 8.881 8.482 2.065 2.065 13.295 49.7 3 r d r u n o n catalyst (3) 0.868 5.1 10.381 17.506 10.906 0.868
SEPTEMBER, 1935
INDUSTRIlL AND ENGINEERING CHEMISTRY
catalysts are expreswd in percentages by volume in column 1 1 4 . e., (column 8 - column 9) 100/column 9. The marked advantage of the ube of added fuel catalysts in increasing the rate of hydrogen production is well illustrated. As may be observed, the yields of hydrogen, columns 8 and 9, are not strictly comparable in all cases, since the corresponding experimental values of moles of steam added per hour (columns 6 and 10) show rather wide divergence in some instances. A better comparison of‘ hydrogen yields is afforded by reference to Figure 1. Here the perpendicular distance between any point on a I11 curve (experiments using no fuel catalysts) for a definite temperature and rate of steam supply and the corresponding point on an IF curve (experiments using added fuel catalysts) for the same conditions gives directly the increased yield of hydrogen in liters per hour. A careful study of the data of series I, Table 11,and the IF and 111curves of Figure 1 shows that the amounts of the various fuel catalysts added were sufficient in all cases to increase definitely the rate of gasification with consequent volume increase of hydrogen per unit time. Experiment 12, an old charge of char and potassium carbonate, and experiments 3,19, 20, and 27 made with “used” chars treated with sodium carbonate, however, showed lower yields than similar experimentsmade upon charges of fresh char and added fuel catalyst or upon “used” char treated with potassium carbonate. These lower yields must be due to differences in composition of the old and “used” chars as compared with fresh chars and the larger combining effect of sodium carbonate with silica in the “used” chars. This point and the relative effectiveness of the three fuel catalysts will be considered later. The series I1 experiments consisted of water gas runs upon lignite char employing no fuel catalyst but with various water gas conversion catalysts. These runs, carried out in a single horizontally mounted furnace, necessitated the use of a short catalyst column and a catalyst temperature approximating that of the given experiment. In this series similar rates of steam supply and a fresh catalyst, as shown in column 13, Table 11, were used for the several experiments. The physical condition of each of the various catalysts seemed unchanged after a single run except in experiment 32 I n this run the sized catalyst F C N disintegrated to a fine powder during use, possibly because it had been heated to 700” C. in its preparation. Comparison of the relative effectiveness of the several water gas conversion catalysts used under the conditions of the experiments in this series indicated that the M F K catalyst was the most effective. This catalyst was therefore used in all of the experiments in series 111and IV. The series I11 experiments include the work with no added fuel catalyst but with the M F K water gas conversion catalyst. Lignite char, formed in situ from raw lignite for each run (except for experiments 46-49 which used lot 3 char) and maintained a t the temperature selected for the given water gas run until free of carbonization gas, was then treated with steam. The resulting water gas was passed through the water gas conversion furnace whose reaction tube was completely filled (48-cm. column length) with M F K catalyst. The yields of hydrogen expressedin liters per hours before and after passing through the conversion catalyst are shown in column9 9 and 8, respectively. The values in column 9 were calculated from the volumes of dry gas (column 7 ) and the percentages of hydrogen in the gas samples taken ahead of the gas conversion chamber upon the assumption that the total gas volume did not change in passing through the conversion catalyst. These values may be in slight error when based upon this assumption and will be considered later. The increased yields of hydrogen, due to the use of the water gas conversion catalyst MFK, expressed in per cent by volume, are shown in column 11. Column 13 shows the history of the MFK catalyst for the individual experiments. Thus, for ex-
1051
periment 36, the expression “6th run on catalyst (1)” means the first filling of the conversion chamber with h l F K catalyst and the sixth run on this filling. Experiments 4-9, run directly upon a slightly weathered char, lot 3, indicate a higher reactivity than is shown by char prepared in situ from raw lignite. This increased rate in gasification is apparently due to this particular char (which contains more ash). From other observations no appreciable differences are noted in the rates of gas generation from fresh char samples, whether previously prepared or made from raw lignite carbonized in situ for the particular run. The yields of hydrogen expressed in liters per hour (columns 9 and 8) plotted against the moles of steam supplied per hour (column 6) are shown for the hydrogen volumes before and after catalytic treatment as curves I11 and IIIG, respectively, for the three temperatures 600°, 700 ”, and 800” C. in Figure 1. It is seen from the percentage values in column 11, Table 11,and from a comparison of curves 111aiid curves IIIG that the yield of hydrogen per unit time is appreciably increased by passing water gas through the MFK catalyst a t 500” Series IV experiments give the results of using both the water gas conversion catalyst RIFK, used as described above for series I11 experiments, and an added fuel catalyst-TC, IC, or K-added to raw lignite which was then carbonized in situ to form char for the particular experiment, A new fuel charge was used in each run. The increase in hydrogen yield, column 11, series IV, due to the water gas conversion catalyst alone, is of the same order of magnitude as in the experiments of series 111. The data of experiments 58, 60-65, series IV, are retabulated as experiments 5-7, 9-11, and 14, series I, respectively, to show the increased yield of hydrogen due to the separate effect of the added fuel catalyst. The percentage by volume increase in liters of hydrogen for these numbered experiments above that for the corresponding comparison experiments using untreated lignite is shown in column 11, series I. An approximate estimate of the total increase in yield of hydrogen due to the influence of both fuel and water gas conversion catalysts based on these same comparison experiments is expressed in per cent by volume in column 12, series IV. These total increased yields of hydrogen in liters per hour for like steam inputs are best seen in Figure 1 by comparing the lengths of the ordinates, The perpendicular distance between the A plotted points and the corresponding points on the 6111 curve give the increase in hydrogen directly. It is seen from this plotted data or from the values in column 12, series IV, that the increase in hydrogen yield due to the use of both kinds of catalyst is quite marked. The history of the use of the water gas conversion catalyst is given in column 13. series IV.
H
c.
Mechanisms The data in the paper by Weiss and White (20) and in an earlier publication by Fox and White (10) furnish strong support for the mechanism suggested by White and his co-workers for the catalytic action of sodium carbonate upon carbon (graphite) a t temperatures above and below 800” C. These authors believe that a t temperatures above 800” C. alternate reduction of sodium carbonate and reoxidation of the products to reform sodium carbonate occur. Neumann, Kroger, and Fingas (16) used potassium carbonate instead of sodium carbonate and offered a like mechanism. For temperatures below 800” C. Weiss and White (20) suggest the mechanism:
+ +
+
Na2COs C = XazO 2CO 2co 02 = 2c02 Na20 COZ = NazCOs
+
(1) (2) (3)
While it has not been proved that these reactions-suggested for this low-temperature mechanism-actually take place as
INDUSTRIAL AND ENGIKEERING CHEMISTRY
1052
written, thermodynamic considerations indicate their probability. Previous investigators have found and the present work has corroborated that water gas produced in the presence of added alkali carbonate fuel catalysts is not essentially different in composition from that formed under similar conditions except for added carbonates. The low-temperature mechanism suggested by Weiss and White ($0) affords a reasonable explanation for the increased rate of mater gas generat,ion obtained with additions of potassium carbonate or sodium carbonate as fuel catalysts in the temperature range, 600" to 800" C., of the present work. Weiss and White (61))found that impregnation of graphite with 0.1 per cent of sodium carbonate seemed to be adequate for maximum catalytic effect. The rate of reaction was not, increased with further addition of sodium carbonate. For foundry coke, however, impregnated with 1 per cent sodium carbonate, hardly any increased effect over untreated coke was not'ed. With 5 per cent addition of sodium carbonate, however, the expected increase was quite noticeable. The increased effect of 5 per cent over 1 per cent additions of sodium carbonate mas attributed to the supposition that the ash of the coke was combining with a certain amount of the sodium carbonat'e, thus fixing the sodium as a silkatme,while with 5 per cent addition some sodium carbonate was left uncombined to react according to the above mechanisms. Similar results with varying percentages of added carbonate-for example, sodium carbonate a t 600" C. (experiments 6 and 8) and potassium carbonate a t 800" C. (experiments 23 and 24)-were noted in the present work. The present study indicates also greater combination of sodium carbonate with "used" chars. More extensive work using smaller percentages of carbonates is being continued in this laboratory. At the outset of the present study it was believed that titanium dioxide might be a contributing factor in the greater activity shown by younger coal cokes above that of bituminous cokes in water gas generatmion. The lignite ash analysis indicates that the small amount of titanium dioxide present should play but little part. The work of Neumann, Kroger, and Fingas (16) has shown that cupric oxide is a less effect,ive catalyst than an equivalent weight percentage of potassium carbonate. I n the present work, since the additions of equivalent weight percentages of 60 titanium dioxide-40 cupric oxide, potassium carbonate, or sodium carbonate showed comparable catalytic effects in increasing the rate of gasification of carbon for the additions studied, it seems reasonable to believe that the t'itanium dioxide has a promoting effect upon the cupric oxide. The mechanism for the action of cupric oxide upon carbon offered by h'eumann, Kroger, and Fingas (16) is: 2CuO 4CuO
+ C = 2Cu + CO, + 22.5 kg-cal. + C = 2Cuz0 + COz + 30 kg-cal.
This mechanism is based upon the work of T~~~~~~~~ and Sworykin (19) who give also the reactions: CuO 2CuO
+ C --f Cu + CO - 8.2 kg-cal. + C +Cu20 + CO - 4.6 kg-cal.
VOL. 27, NO. 9
(16) affords valuable supporting evidence to previous investigations upon the relative effectiveness of different inorganic additions to cokes and the proposed mechanisms explaining these effects. The mechanism of the action of the water gas conversion catalyst, MFK, is rather difficult to formulate accurately. The main chemical change observed appears to be:
CO
+ H20 = Hz + CO2
This change is evidenced by the decreases in the content of carbon monoxide and water and the increases in hydrogen and carbon dioxide in the water gas upon passage through the AIFK catalyst column. Reinders (17) in his excellent discussion of t'he thermodynamic requirements in the water gas reactions has shown that the theoretical methane content in t'he equilibrium gas for 1 atmosphere and the temperatures 600°, TOO", and 809" C. can reach only the maximum percentages of 8.6, 4.0, and 1.8, respectively. For practical purposes, therefore, the small methane content before and after the catalytic treatment of technical mater gas may be neglected. The general effects caused by catalytic treatment in the present work appear to be a decrease in methane content for the 600" C. runs and the lower steam input runs a t 700" C. and an increase (or variation) in methane content for the higher steam input runs a t 700" C. and for the 800' C. runs. The formation of such small amounts of methane in mater gas and the problem of obtaining an accurate analysis of methane in the gas make difficult any clear interpretation of possible changes caused by catalytic agents. The reaction CO H20 = H? C 0 2 is known to be largely surface-catalyzed and does not require a very specific catalyst. Armstrong and Hilditch ( 1 ) investigated the action of solid surfaces upon this reaction. They found that in the presence of copper the reaction began a t 220" C. and proceeded actively up to 300". For ferric oxide the initial temperature of the reaction was 250" C. and t'he reaction mas active u p to temperatures below 400" C. At temperatures above 600" C. the ferric oxide gave better results than were obtained with copper. As stated previously, the best of the water gas conversion catalyst under the experimental conditions of the present work appeared to be the 67-30-3 mixture of magnesia-ferric oxide-potassium dichromate, or LIFK catalyst. This catalyst, prepared as already described in 3-4 mesh size, retained its physical ruggedness and activity for many runs. The function of so large a proportion of magnesia deierres some comment. Armstrong and Hilditch (2) believe that magnesia acts as a catalyst "support" because of mechaiiical development of large surfaces, so that the other constituents of magnesia-bearing catalysts can function more effectively. Schotz (18) explains the promoter action of magnesia as being due to the removal of catalyst poisons by this oxide or by regeneration of the active metallic catalyst by alternate oxidations and reductions. This viewpoint is held also by Emmett (6) whose large experience with many types of water gas conversion catalysts of varied composition adds considerable weight. The exact mechanisms exdaining all the Dossible reactions under experimental conditions similar to those in the present work can be established with certainty only by further careful study. It was found that with the fuel catalysts used, the rate of water gas generation is increased without any appreciable change in the gas composition; it is believed, therefore, that, since carbonates are also found in appreciable amounts in the lignite ash, these carbonates contribute to the increased activity of lignite chars compared to the usual bituminous cokes. It was found, moreover, that the main reaction taking place in the water gas conversion chamber through the influence of the MFK catalyst was CO H20 = Hz CO?. The present work is being continued on both laboratory
+
+
0
The mechanism of the action of titanium dioxide as a fuel catalyst a t lower temperatures has apparently not been studied. Brantley and Beckman ( 3 ) studied the reaction, Ti02
+ 3C = Tic + 2CO
over the temperature range 1005O to 1155" C. The 60 titanium dioxide40 cupric oxide mixture has been used for oxidation of carbon monoxide a t 300" and 150" C. by Engelder and Miller ( 8 ) . Further examination of this catalyst showed it to be unsatisfactory for this purpose a t higher temperatures ( 7 ) . The recent paper of h'eumann and van Ahlen
+
+
SEPTERIBER, 1933
INDUSTRIAL AND ENGINEERING CHEMISTRY
and larger scale over the same temperature range using the more promising fuel and water gas conversion catalysts.
Aclinow-ledgment The authors deqire to exprev their appreciation of the services of Robert 11. lliller for aid in the experimental work. Grateful acknonledgnient iz made also to Vernon A. Stenger for hi3 pain-taking work in the ash analyses Literature Cited (1) Amistronr, E. F.. and H i l d i t c h , T. P., Proc. Roil. Suc. ( L o n d o n ) . 697,265-73 (1920!. ( 2 ) Ihid., -1103, 586-97 ( 1 9 2 3 ) . (3) Brantley, L . R., a n d Becknian, -1.O., J . A m . Chenz. Soc., 52, 3956-62 (1930).
(4) Brewer. R . E., and Reyerson, L . H . , IXD.ESG. CHEM.,26, 734-40, 892 (correctioni 11934).
( 5 ) C r i t t e n d e n , E. D., C a n a d i a n P a t e n t 318.433 (Dei,. 29, 1931). (6) E m m e t t , P H . p r l r a t e communlcatlon. ( 7 ) Engelder, c'. J., a n d Bliimer, >I., J . P h y s . Chern., 36, 1353 (1932). IS) Engelder. C . ,J., a n d Miller. L. E.,I b i d . , 36, 1345-62 (1932).
1053
M.,a n d N e w t o n , IT. L.. ISD. ESG. ('HEM., 18, 514 (1926). (10) Fox, D. A , a n d W h i t e , A. H . , Ihid., 23, 259-66 (1981). (11) Hillebrand, W.F.. a n d Lundell, G. E. F., "Applied Inorganic .&nalysis," P a r t 111,?Jew T o r k , J o h n Wiley & Sons, 1929. (12) Horne, J. W., a n d B a u e r , .1.D., Bur. Mines, RE&. Incesfigations 2832 (1927). (13) Logan, L.. Am. Gas d s s o c . Proc., 14, 976-1015 (1932). (14) Marson, C. B., and Cobb, J. IT., Gas J . , 171,:39-46 (1925). (15) N e u m a n n , B., a n d .Ihlen, A. v a n , Brennsto,f-Chern., 15, 6 - 4 (9) E v a n s . R .
(1934). (16) Neurnann, R., Kroger, C., and Finpas, E., Z . anorg. allgem. Chem., 197, 321-35 (1931). (17) Reinders, IT-.,Z . p h y s . Chem., 130,405-14 (1927). (18) Schotz, S. P., "Synthetic Organic C o m p o u n d s , " p. 84, Sexv Tork, D. Van S o s t r a n d Co., 1925. (19) T a n i m a n n , G., a n d Sxvorykin, .I.. Z . anorg. aZ2gern. Chern., 170, 62-70 (1925). (20) Weiss, C. B., a n d W h i t e , .1.H., ISD.ESG. CHEX.,26, 83-7
(1934'1.
RECEIVED 3Zarch 13, 1935. Presented before the Division of Gas and Fuel Chemietry a t the 89th Xeeting of the .Imerican Chemical Society, Cleveland. Ohio, September 10 to 1 4 , 1934.
Canned Meats Effect of pH on the Formation of Ferrous Sulfide V. R. RUPP, Kingan and Company, Indianapolis. Ind.
@A
N O S G canned meat products, tripe ii: notably subject to iron sulfide discoloration. One of the common methods used in preventing this discoloration is to dip the tripe in a vinegar solution before canning. Lowering the pH of the tripe in this nianiier represses the ionization of the hydrogen sulfide formed during the processing. If the ionization of hydrogen sulfide i; repre.sed to a degree where the product of the sulfide-ion and the ferrous-ion concentrations is less than the solubility product of ferrous sulfide, precipitation will not occur. The effect of the hydrogen-ion concentration on the ionization of hydrogen sulfide can be calculated from the following equations:
If the concentration of sulfides and the pH are known, the concent'rationof sulfide ion can be calculated from Equation 5 . From Equation 6, (F-+) (S-) = L where
L
=
the concent'ration of ferrous ions necessary to produce precipitation with a given concentration of d f i d e ions can lie calculated. L as determined by Bruner and Zawadski is 3.7 x 10-19 ($1. Similarly, if the iron concentration is determined, the pH a t which precipitation of ferrous sulfide mill occur can be calculated. By substituting in Equation 6 the value of (S--)as obtained in Equation 5 , we have:
+ 9.1 X
(H+)
(H+)2 ahere c
of sulfides p r e s e n t first, i o n i z a t i o n c o n s t a n t of h y d r o g e n sulfide (given b y Auerbach, 3) = 9.1 X = s e c o n d i o n i z a t i o n c o n s t a n t of h y d r o g e n sulfide ( g i v e n by K n o x , 5 ) = 1 . 2 X
+ 10.9 X
=
1 0 . 9 X 10-*8 (c)
= molal concn.
k1 = I:?
(6)
solubility p r o d u c t of ferrous sulfide
(Fc-7)
3.7 X
-
(7)
This equation can be simplified without a material change in the exactness of the expression to
From Equations 1and 3 we obtain: (H') = 1.7 X
10-2
\/m - 4.5 X IO-'
(8)
Experiments with Tripe Substituting Equation 4 in Equation 2:
Equation 8 waq checked experinientally over a limited range of pH which is commonly encountered in vinegardipped tripe. Owing to the unequal distribution of iron in canned tripe, solutions of ferrous chloride and hydrogen sulfide containing no protein were used for the purpose:
