V. AT. IPATIEFF, G. S. MONROE, AND L. E. FISCHER Universal Oil P r o d u c t s Company, Riverside, 111. T h i s paper describes the conversion of mcthane and steam into hydrogen, carbon dioxide, and relatively small amounts of carbon monoxide over various catalysts within the temperature range of 470 O to 790 O C. The preparation of the different catalysts is described and the hydrogen yields and methane conversions are tabulated. Activity tests indicated that nickel-kieselgu hr was the most active low temperature catalyst prepared. A t atmospheric pressure [hourly gas space velocity (H.G.S.V.) of methane, 120; mole ratio of water to methane, 51 over a temperature range of 486 O to 640 O C., the hydrogen yield, based on the volume of methane charge, was 200 to 3407' and the
methane conversion was 52 to 91%. When the operating pressure was raised to 250 pounds per square inch gage and the steam-methane ratio was increased to 31 to 1, the hydrogen yields and methane conversions were about the same as those obtained at atmospheric pressure, but the carbon monoxide to carbon dioxide ratio was reduced as much as tenfold. Comparative life tests at atmospheric pressure and at 250 pounds per square inch gage indicated that the life of the catalyst was relatively short at the higher pressure. However, the addition of a promoter made the life comparable with that obtained at atmospheric pressure.
T
I n experiments at atmospheric pressure methane was metered through a met testmeter through the preheater coil into the preheater section of the reaction tube. In the pressure experiments, the methane ~1as discharged from pressure bottles by water displacement into the preheater coil by means of a variable cam hydraulic pump. The a m ~ n of t inethane charged, as well as the flow rate, could be determined from the amount of water pumped into the gas bottles. The ~1ater was pumped through a vaporizing coil into the preheater section of the reaction tube by a variable cam liquid feed pump. The reaction tube was 33 inches long, made from a/r-inch pipesize heavy stainless steel tubing. The upper section ( 7 1 / 8 inches from top), filled with porcelain beads or other inert material, served as a supplementary preheater zone. The middle section (11 inches) held the catalyst, 72 ml. The lower section (14l/* inches) contained a stainless steel filler (l/s-inch hole through the center) q7hich served as a support for the catalyst and a t the same time hastened the exit of the reaction products from the tube after leaving the catalyst zone. T W O '/sinch Pipe-size heavy stainless steel heating tubes extended upward between the inside wall of the furnace block and the reaction tube to the preheater section of the latter, one serving as a preheater for the methane and the other t o vaporize the water and preheat the steam. A stainless steel thermocouple well extended downward through the preheater section into the catalyst zone t o accommodate a sliding thermocouple. The furnace consisted of a cylindrical stainless steel block, 43/4inch outside diameter X 24 inches long with a hole in the center ( 2 inches) extending coaxially the length of the block to receive the catalyst tube* The was heated by external electric heating elements. An automatic electric switch, the operation of which depended on the differencebetween the thermal expansion of the block and a porcelain rod in an off-centered hole extending part way into the interior of the block, maintained the block temperature a t any desired level. The activity tests were made at progressively increased temperaturelevels (furnace range, 5000 to 806" c.; catalyst range, 481 to 801 ' C.) over the same batch of catalyst. This procedure after one to three experiments eliminated most of the catalyst preparations from further consideration. The life test experiments, likewise, were made at different temperature levels with the same hatch of catalyst over a furnace temperature range of 500" to 700' C. (catalyst range, about 480" t o 685" The results obtained on varying the temperature during the life test period should be an indication of the relative life of the catalyst a t the respective temperature levels.
HE increased use of hydrogen in the petroleum indurtry, together with the rapid growth of hydrogenatiorl processes in other fields, makes the problem of low-copt hydrogen production one of paramount importance The hydrogen needs of the petroleum industry are usually supplied by having steam react nrith natural gas or wit11 lorn molecular Tveight hydrocarbons such as methane, ethane, propane, etc., or mixtures of the rame. The process usually is carried out in two steps: CH,
+ HzO e CO + 3Hz;
co 4-H20 * cop 4- Hz ( 9 ) ; $- 2H20
coz
-I-4Hz ('1;
AH = 49,200 tal.
(1)
AH = -9,800
(2)
*H = 39,400
i2,
The first reaction, highly endothermic, is run a t temperatures in excess of 800" C. over nickel catalysts and the second, exothermic, usually over promoted iron catalysts a t temperatures ranging from 3 7 5 ~to 5000 c. Running the two reactions concurrently in the sense of the over-all reaction, Reactions 1 Plus 2, has also been suggested. This proposal has merit but requires a catalyst that would catalyze Reactions 1 and 2 simultaneously, and the selection of operating conditions that give the conversions necessary to produce hydrogen of the required Purity after the removal of the carbon oxides. As previously stated, the first reaction is endothernlic and is favored, thermodynanlica]]y, by a n increase in temperature, and the second, exothermic, is favored by a decrease in temperature. For the two reactions to proceed together, a temperature between those which give optimum conversions for the ttvo separate reactions must be selected. This paper gives the results obtained with the over-dl reaction over different catalysts and the effect of various operating variables on conversion.
O
APPARATUS AND PROCEDURE
The apparatus consisted essentially of five parts: two gascharging systems for charging methane either at atmospheric pressure or at 250 pounds per square inch gage; a liquid feed pump for charging water into the system; a stainless steel reaction tube heated by a stainless steel block furnace with an automatic temperature regulator; a pressure controller (for pressure runs) attached to the exit end of the reaction tube, releasing the products to atmospheric pressure before condensation; and a water condenser and receiver (gas separator) to separate the liquid product (water) from the gas, the latter passing through a wet testmeter.
MATERIALS
The methane charge stock was grade with the composition of 95 t o 96% mole % methane a t 5 to 4 mole % nitrogen. 92
INDUSTRIAL AND ENGINEERING CHEMISTRY
January 1950
The precipitate was thoroughly washed, dried at 110' C., and HYDROGEN AND X '/8 inch pill pilled t o Hz Yield, size with rosin; the rosin was Moles Temperature, ~~l~ burned out with air a t 200" C., c. H.G.S.V.,, , . ; : :c $ is Composition :,"," Exit Gas CHI % and the pills were reduced Bloak Catalvst Pressure CH4 Hz0:Ckr % CHI COa CO ' Ht +Nn Total in hydrogen at 240" C. 67% AlzOi A. 33% CuO The nickel-kieselguhr cata1.8 0.0 9 . 0 89.2 100.0 3.9 16.5 Atm. 5.1 116 601 579 58.4 7 . 2 0 . 0 31.4 61.4 4.8 14.6 108 Atm. 679 700 100.0 lyst (3), D (composition before 121.0 8.8 5 . 2 51.8 34.2 3.5 21.0 124 Atm. 777 806 reduction, 76.9% by weight B. 5% CuO + 20% Fez08 75% Alto: nickel oxide f 23.1% kiesel2.8 96.6 100.0 Atm. 0.6 0.0 2.0 8.0 101 5.8 593 599 2.8 0.0 12.0 85.2 100.0 Atm. 5.1 20.5 101 5.3 691 702 guhr), was prepared by the 32.5 5.2 0.0 23.0 71.6 100.0 Atm. 4.6 8.1 115 788 804 precipitation of nickel carbonC. 10% COO + 57% CuO + 33% AhO: ate on kieselguhr by the ad100.0 5.8 23.2 4.8 0 . 0 19.6 75.6 Atm. 4.8 103 588 599 dition of sodium carbonate 131.9 12.0 2 . 8 58.6 26.6 100.0 Atm. 109 4.9 34.6 698 702 57.5 209.1 11.2 6.4 69.2 13.2 100.0 Atm. 115 4.7 8017 804 solution to nickel nitrate soluD. 76.9% NiO + 23.1% Kieselguhr tion containing the kieselguhr Atm. 5.0 54.2 210.0 15.0 2.2 67.8 15.0 100.0 121 486 in suspension. 8.7 Atm. 5.1 69.5 273.0 15.4 1 . 2 74.7 121 525 3 . 4 100.0 Atm. 5.2 86.7 323.0 15.0 5 . 8 75.8 122 581 The copper-nickel-kieselguhr 1.8 100.0 5 1 91.1 337.0 13.77 5 . 9 78.6 Atm: 120 640 catalysts, E and F, were made 206.0 30.8 51.4 15.8 0 . 2 69.2 14.8 100.0 250 lb./sq. In. gage 108 471 7.4 100.0 304.0 1 7 . 2 0.4 75.0 31.8 76.5 250 Ib./sq. in. gaga 113 517 by t h e procedure followed 4.0 100,o 332.0 17.0 0 . 8 78.2 31.2 84.0 250 lb. /sq. in. gage 116 671 4 . 0 100.0 31.9 88.5 351.0 17.0 0.6 77.8 250 lb./sq. in. gaga 114 629 for t h e nickel-kieselguhr catalyst, D, using the required E. 7.7% CuO + 69.2% NiO + 23.1% Xiesdguhr 112 55.0 215.0 amounts of copper and nickel 13.0 1 . 2 77.2 13.6 100.0 5.7 Atm. 481 6.6 100.0 15.0 2.6 75.8 112 73.0 281.0 5.4 Atm. 533 sulfates t o give the composi307.0 4.8 100.0 14.2 3 . 2 77.8 117 80.4 5.1 Atm. 555 Atm. 1 4 . 0 2.4 8 0 . 0 3 . 6 100.0 317.0 5.1 123 82.3 . . 576 tions specified. 2 . 6 100.0 122 12.4 6 . 4 78.6 340.0 5.0 92.9 Atm. 629 The copper-nickel-magnesia 6 . 8 100.0 320.0 114 1 6 . 8 1.1 75.3 31.4 81.3 250 lb./sq. in. gage 57 1 2 . 3 100.0 340.0 31.1 16.5 1 . 4 79.8 115 86.6 250 lb./sq. in. gage 626 catalyst, G, was prepared by 1.9 100.0 16.2 1.8 80.1 361.0 31.6 113 92.5 250 lb./sq. in. gage 688 precipitating at 70" C. magF. 15.4% CuO + 61.5% NiO + 23.1% Kieselguhr nesium carbonate from a solu47.0 186.0 17.1 1.0 66.2 15.7 100.0 Atm. 120 5.1 482 502 8 . 5 100.0 16.0 2 . 8 72.7 Atm. 117 5.1 67.8 261.0 650 529 tion of the nitrate by the 3 . 4 100.0 Atm. 118 5.2 88.2 333.0 14.6 4 . 8 77.2 601 582 addition of sodium carbonate 9 . 2 100.0 32.5 74.8 294.0 16.2 1 . 2 73.6 250 lb./sq. in. gage 112 600 582 7.6 100.0 80.3 316.0 15.0 1 . 6 75.8 32.1 2501b./sq. in. gage 112 637 650 solution. After the precipitaG. 7.6% CuO + 6Q.3% NiO + 23.1% MgO tion of the magnesium car14.5 0 . 9 68.7 15.9 100.0 32.0 56.1 220.0 578 2501bJsq. in. gage 113 600 bonate, copper and nickel 76.6 100.0 2 . 8 0.9 20.6 32.0 6.5 26.0 2501b./sq. in. gage 113 586 600 5 . 7 93.3 100.0 sulfate in the required amounts 32.0 8.0 0.4 0 . 6 2.3 2501bJsq. in. gage 113 64 1 650 were dissolved in the precipi23.1% AlzOa H. 79.6% NiO tation mass and sodium car250 Ib./sq. in. gage 113 32.0 3.4 12.0 0.4 0.4 7 . 6 91.6 100.0 600 685 bonate solution again was I. 7.7% CuO + 69.2% NiO + 23.1% AlnOa added t o coprecipitate the 250 lb./sa. in. eaee 113 32.0 3.2 13.0 0.6 0.0 10.2 89.2 100.0 600 588 copper and nickel as carbonates 0 Compositions of catalysts are given on unreduced basis. on the suspended magnesium b H.G.S.V., volume gas (5.T.P) charged per unit volume of catalyst per hour. carbonate. The precipitate was filtered, dried, the carbonates decomposed in a stream of PREPARATION OF CATALYSTS X inch nitrogen at 538" C., pilled with 4'3, graphite t o pill size, and reduced in hydrogen at 538" C. The copper-alumina catalyst, A (composition before reduction, The nickel-alumina and copper-nickel-alumina catalysts, %yoby weight cupric oxide 67y0by weight aluminum oxide), H and I were prepared in the same manner as were the nickelwas prepared by the precipitation of copper carbonate a t 60" C. kieselguhr, D, and the copper-nickel-kieselguhr catalyst, E, on alumina (hydroxide calcined at 350" C.) by the addition of substituting alumina (calcined a t 350" C.) for the kieselguhr. ammonium carbonate solution to copper nitmte solution containing the alumina held in suspension by vigorous agitation. The washed precipitate was dried to 240" C., ground to 40 mesh, ANALYTICAL METHODS mixed with 4% rosin, and pilled t.0 '/a X l / inch ~ size (cylindrical). The composition of the gaseous product was determined by After the rosin was burned out with air at 220" C., the pills were combustion and absorption methods. reduced in hydrogen at 250 " C. The copper-iron-alumina catalyst, B (composition before HYDROGEN YIELDS AND METHANE CONVERSIONS reduction, 5% by weight cupric oxide 20% by weight ferric oxide + 75y0 by weight aluminum oxide), WYLLS made by heating The hydrogen yields were determined from expansion data. a mixture of copper and ferrir nitrates with activated alumina to The hydrogen yield (moles hydrogen produced per 100 moles 470 'C. and subsequently reducing in hydrogen at 500 " C. methane charged) equals the per cent expansion. The cobalt-copper-alumina catalvst, C (comuosition before reduction, 10% weight cobalto& oxide 57% by weight A Volume x 100 cupric oxide 33y0 by weight aluminum oxide), was prepared Volume CHI by the coprecipitation of cobalt and copper carbonates on alumina (hydroxide calcined a t 350' c.) by t h e addition of The methane conversion was calculated by the formula: ammonium carbonate solution t o the mixed nitratresolution con% methane converted = ?& expansion/ taining the alumina held in suspension by vigorous agitation.
TABLE I. EFFECTO F CATALYST COMPOSITION"
CONVERSION O F METHANE AND CARBON OXIDESOVER VARIOUS CATALYSTS ON
2:::
+
+
~~
+
i
93
+
+
+
by
'+
STEAM INTO
INDUSTRIAL AND ENGINEERING CHEMISTRY
94
DISCUSSION OF RESULTS
In the quest for an active low tpmperature catalyst for the conversion of methane and steam into hydrogen and carbon dioxide, catalysts of various compositions were investigated. Activity tests were made with some of these catalysts a t atmospheric pressure, with others a t 260 pounds per square inch gage, and the most active was tested under both pressure conditions.
MOLE RATIO
- H=O/CH~
Vol. 42, No. 1
SPACEVCLOCITY. The effect of change in the methane space velocity on hydrogen yield a t the two mole ratios of water to methane at 5 to 1 and 11 to 1 is shown in Figure 1, curves 1 and 2. At the lower mole ratio (5 to 1) the hydrogen yield remained virtually constant a t about 200'30 when the methane space velocity varied over a range of 112 to 600. On further increase in the space velocity to 1010, the hydrogen yield dropped to 168%. When the mole ratio of water to methane was 11 t o 1, the hydrogen yield, though higher than a t the lower mole ratio of 5 to 1, dropped continuously from 300 to 229% on increase in the space velocity from 115 t o 600. MOLLRATIO(WATERTO ~ICTI-IANE). The effect of change in the mole ratio (u ater to methane) was investigated a t atmospheric pressure and a t 250 pounds per square inch gage (Figure 1, curves 3 and 4). At atmospheric pressure and the relatively low catalyst temperature of 480" C., increase in the mole ratio from 1.4 to 1 to 15.2 to 1 raised the hydrogen yield from 78 to 328%, and it is probable that a t 600" t o 650" C. the conversion of methane would be almost complete, possibly at a mole ratio less than 15 to 1. At 250 pounds per square inch gage, because of the adverse effect of pressure on the reaction, the effect of increase in the mole ratio of water to methane was not so pronounced. CARBON FORMATION. Carbon deposition n as low (less than 0.57' by weight of the catalyst) in most runs. Several tests were usually made with the same catalyst without intermediate regenuation.
HOURLY GAS SPACE VELOCITY-CH4
Figure 1. Hydrogen Yield a t 480' Catalyst D 1. 2.
3. 4.
Ha yield
US.
HZyield
US.
C. Using
H.G.S.V. (atmospheric pressure; HzO:CH4 = 5 =t 0.3) H.G.S.V. (atmospheric pressure; H?O:CH4 = 11 =I= 0.5) Hx yield U S . m o l e ratio (atmospheric pressure; H.G.S.V. = 114 =t 2) Hz yield US. m o l e ratio (250 lb./sq. i n o h gage; H.G.S.V. = 111 =I= 3)
EFFECTOF C A T l L Y S T CO&fPOSITIOX. The effect of catalyst composition on the methane conversion or hydrogen yield is shown in Table I. As indicated, the most active compositions consisted of nickel-kieselguhr, D, and copper-nickel-kieselguhr, E and F. At atmospheric pressure the nickel-kieselguhr catalyst, I), gave hydrogen yields ranging from 210 to 337% (methane conversion 54 to 91%) over a block temperature range of 505 O to 650 O C. (average catalyst 486' to 640 O C.) when the mole ratio of water to methane was 5 to 1and the hourly space velocity of the methane was 120. At 250 pounds per square inch gage and the mole ratio of water to methane a t 32 t o 1, the hydrogen yield was 206 to 351 (methane conversion 51.4 to 88%). The results obtained with copper-nickel-kieselguhr E (7.7% cupric oxide) and copper-nickel-kieselguhr catnyst F (15.401, cupric oxide) were of about the same order. In regard to catalyst activity it might be well to point out the important effect of the type of carrier used. Catalysts containing kieselguhr gave the highest activity whereas catalysts containing either alumina or magnesia as carriers were relatively inactive. As would be expected, increase EFFECTOF TEMPERATURE. in temperature increased the hydrogen yield and the ratio of carbon monoxide to carbon dioxide. EFFECT OF PRESSURE. Increase in pressure lowered the hydrogen yield or methane conversion as would be expected with a reaction proceeding with an increase in volume. However, by increasing the mole ratio of water to methane a t the higher pressures the adverse effect of pressure could be nullified (see Figure 1, curves 3 and 4). Increasing the pressure resulted in a decrease in the formation of.carbon monouide, the ratio of carbon monoxide to carbon dioxide being reduced as much as tenfold.
TABLE 11.
SUMX4RY O F
LIFE TESTS
T ~ ~0 c., ~ . , Catalyst D a Catalyst Ea Catalyst F Furnace Drop in Drop in Drop in Hr. H2 yield Hr. Nz yield Hr. Hz yield Block Atmospheric Pressure (Hz0:CIlr = 5 ; H.G.S.V., CH4 = 115) 500 78 217-194 h-0 life test made 600 65 316-314 650 28 326-328 36 340-340
!!
250 Lb./Sq. Inch Gage Pressure (HaO:CH4 = 32; H.G.S.V., CH4 = 115) 600 10 330-74 44 340-285 40 290-140 650 20 350-175 69 350-175 40 315-180 40 355-300 .. 700 .. ... ... Catalysts D and E regenerated t w o times with air 575O to 650° C., and subsequent reduction with hydrogen a t 535O to 555O C., during the life test runs a t atmospheric pressure.
LIFE TESTSAND EFFECT OF COPPER. B s indicated in Table I a11 catalyst preparations, exclusive of nickel-kieselguhr, D, and the two copper-nickel-kieselguhr combinations, E and F, had relatively low initial activities or, if having a high initial activity, suffered a rapid loss of the same in the course of two or three consecutive experiments (catalyst G). Life tests were made on the nickel-kieselguhr catalyst, D, and on the two copper-nickel-kieselguhr catalysts, E and F. The results of these tests are summarized in Table TI and indicate that the three catalysts stood in the following order of dcctrasing life: copper-nickel-kieselguhr E (7.7% cupric oxide), coppernickel-kieselguhr F (15.4% cupric oxide), and nickel-kieselguhr D (0% cupric oxide). The first mentioned was w r y susceptible to regeneration The results indicate the beneficial effect of copper and the probability of a critical amount in the region of 7%. LITERATURE CITED
(1) Ipatieff, T'. N., "Catalytic Reactions a t High Pressures a n d Temperatures," p. 231, Yew York, The Macmillan Go., 1936. (2) Ibid.,p. 238. ( 3 ) Ipatieff, V. N., and Corson, B. B., IND. ENG.CHEM.,30, 1039 (1938).
RECEIVED J u l y 1 , 1949
