CA1182279A

CA1182279A - Process for the generation of hydrogen from carbon monoxide and water

Info

Publication number: CA1182279A
Application number: CA000370269A
Authority: CA
Inventors: Lothar Schanne; Matthias W. Haenel
Original assignee: Studiengesellschaft Kohle gGmbH
Current assignee: Studiengesellschaft Kohle gGmbH
Priority date: 1980-02-07
Filing date: 1981-02-06
Publication date: 1985-02-12
Also published as: JPS56125204A; EP0033949A1; DE3160447D1; DK50281A; IE51391B1; IE810229L; EP0033949B1; AU6697281A; ZA81801B; AU541814B2; ATE3841T1

Abstract

ABSTRACT of the DISCLOSURE

A process for the production of hydrogen by homogeneou catalized convertion of carbon monoxide and water into carbon dioxide and hydrogen with the aid of metal carbonyl compounds as catalysts, characterized in that carbon monoxide is reacted with water in the form of a mixture of a weakly aqueous base and a carbonyl compound of a metal selected from iron, cobalt, nickel, manganese, chromium, molybdenum and/or tungsten at temperatures above 180°C, preferably at 200 to 270°C, at a partial pressure of carbon monoxide between 1 and 500 bar, preferably between 20 and 100 bar.

Description

l ¦ The invention relates to a process which converts

2 ¦ carbon monoxide (C0) and water (ll20) into carbon dioxide (C02) ~ and hydrogen (H2) by homogenous catalysis and which on suitable 4 selection of the reaction parameters ~ives yields o 85 to 95 in short reaction times.
6 The conversion oE C0 according to 7 C0 -~ H20 _ C02 + ~l2 (1) 8 serves for the technical production of hydro~en from C0-rich C 9 gases produeed by gasifying coal or hydrocarbons. secause of the unfavorable equilibrium at hic3h temperatures reaction (I) ll has to be performed below 500 C. ~owever, the equilibrium 12 is e~tablished very slowly in this temperature re~ion, so that 13 hi~hly aetive catalysts are requirecl. For many years solid l~ catalysts based.on iron or copper have been utilized at 350 to 500 C (high temperature process, iron catalysts) anci at 210 lG to 270 C (low temperature process, copper contacts). DurincJ
~7 the last years several authors attemp-tcd to develop homocJellous la catalyst systems which would avoid the hi~h eneryy level of the 19 hi~h temperature process and the sensitivity to catalyst poison of the low temperature process in systems with minimal technical 21 difficulties. (Bibliography in C. ~ngermann, V. Landis, 22 S.A. Moya, H. Cohen, H. Walker, R.G. Pearson, R.G. Rinker and 23 P.C. Ford, J. Amer. Chem. Soc. 10l, 5922 (1979)).
2~ The main component of the hitherto known systems usually consists of a transltion metal carbonyl compound which 26 has been tested in ~ater containin~ solvents at C0-pressures 27 of 0.25 to 300 bar and temperatures of 80 to ca. 150 C.
28 The interestiny catalyst: systern deri~ed from iron pentacarbonyl - 2 - ~

~Z2~
:
~ ' l ~ (Fe(C0)5) and alkalines was already mentioned by W. Reppe in 2 ¦ 1953 (W. Reppe and coworkers~ Liebigs. Ann. Chem. 582, 121 (1953~))

3 ¦ and has been investigated by R.B. King (C.C. Frazier, R.M. Hanes~,

4 A.D. Kiny, Jr. and R.B~ King in Inorganic Compounds with Unusual

5 ¦ Properties (R.~ ing, editor), Vol. II, Chapter 9, pages 94 ff,

6 ¦ Aclvances in Chemistry Series 173, Am. Chem. Soc., Washington, .

7 ¦ D.C. and R.B. King et al, J. Amer. Chem. Soc. 100, 2925 (1g78))

8 and R. Pettit (R. Pettit, K. Cann, T. Cole, C.~. Mauldin and

9 ! w. Slegeir in Inorganic Copounds with Unusual Properties (R.B.
lO ¦¦ King, editor) Vol. II, Chapter 11, pages 121 ff, Advances in ll Chemistry Series 173, Am. Chem. Soc. Washington, D.C. 1979).
12 The conversion rates so far observed are, however, too small 13 for technical application. Furthermore, the main disadvantage l~ ,j is caused by the fact that under these conditions even aEter 15 ll longer reaction times the reaction (1) does not establish the 16 ¦ thermodynamic equilibrium of more than 95 % hydrogen yield, 17 1l but stops below 40 % hydrogen yield depending on the experimental 18 1I parameters in an unclear manner.
19 1 These low hydrogen yields do not permit an economic application of the Fe(C0)5-base-system.
21 C.C. Frazier et al show on page '~7 of the above mentio-22 I ned reference in Table II the effect of pressure and temperature 23 l on the reactivity of the iron pentacarbonyl-catalized water 2~ 1l gas shift reaction. The iron pentacarbonyl catalyst is used in 25 ~I butanol as solvent which contains the necessary amount of water.
2~ According to this publication temperatures between 140 and 160C
27 ~ are preferred. Runs 4 and 5 of Table II show temperatures of 28 ~l 181 C and 183 C respectively. The turnover numbers (mole 1~ 3 _ i 2~
~ ., l hydrogen/mole me-tal per 6 hours) are given in the las-t column 2 ¦ of Table II. It is stated on page 96, lines 26 - 28 -that the 3 ¦ turnover numbers represent only the turnover in an early stage 4 ¦ of the reaction. In a further reference (A.D. King, Jr., R.s. I
5 ¦ King and D.B. Yang, J. Am. Chem. Soc 102, p. 1028 e-t seq. (1980)l) 6 ¦ Kinq et al are discussing the homogeneous catalysis of -the water 7 ¦ ~as shiE-t reaction using iron pentacarbonyl in a mainly methano 8 lic solution. From Fig. 4 on page 1003 follows that the -turn-9 ! over number is not constan-t over the whole reaction time (the lO ¦ turnover number is propo~ional to the slope of the partial ll ¦ pressure of hydrogen versus -time-curve). Therefore, -the -turn-12 over numbers of Table II of Frazier e-t al canno-t be used to 13 , estimate the expected hydrogell yields. Run 6 (161~ and run 9 l~ l (163 C) of Table II of -the Frazier et al reference are des-15 I cribed in more detail and evalua-ted in form oE Fig. I and 16 ~¦ Fi~. II on pages 98 and 99 respectively. From the last 17 ll measured points of these Figures one can calculate that in run 18 !1 6 after 25 hours less than 40 ~ conversion and ln run 9 after 19 1 6 hours less than 2~ ~ conversion are measured. On page 100, 20 ~ second paragraph, it is stated that the rate of hydrogen 21 1 production increases as the reaction tempera~ure is raised. I
22 1 In thereafter following Figure 3, same page, it is only demon-23 strated that the rate of the very early stage of the reaction 2~ is raised by increasing temperature when the partial pressure 25 ~l of the carbon dioxide formed during the reaction is neglectable.
2~ 1l However, this does not permit to deduct tha-t the ob-tainable 27 1I hydrogen yields at the end of the reaction are also increased 28 l by raising temperature.
I -- 3a -l ~ Frazier et al and King et al are using alcoholic so-2 lutions of the catalysts which solutions contain water in a small ~ amount. King et al state in their publication on page 1030, 4 left column, last paragraph, that the use oE water should be 5 1 avoided because it is stated in line 5 "pure water is seen to 6 be a very poor choice of solvent.". In this connection, Fig. 3 7 ¦ in the SAme column, lowest curve, has to be considered from 8 which follows that at 140 C after 70 hours less than 10 %
9 ll conversion is obtained. As explanation for these results -the lO ~ low solubility of carbon monoxide in water and -the decomposition ll ¦ of the catalyst system which is connec-ted therewith is given 12 on page 1032, left column, last paragraph by King et al..
13 It follows from the above discussion tha-t the state of l~ l¦ the art until immediately before -the priority date of -the 15 ll instant application has dissuaded the ar-tisan -to use high 16 ~ temperatures and water as solvent :Eor the water gas shift 17 ~; reaction of carbon monoxide and water to carbon dioxi.de and l~ h~drogen.
19 1 The process presented here is based on the surprisi.ng, 20 1 not foreseeable observation that at temperatures above 220 C

21 ! wea~ly basic aqueous solutions of Fe(C0)5 do convert C0 and E-l20' 22 l! into C02 and H2 with yields up to 95 ~. Reaction rates high 23 enough for an application are achieved only above 180 C.

24 1I Completely unexpected is the temperature behaviour of 25 1l the system: Between 180 and 250 C a~ in some cases between 180 2~ and 220 C the reaction (1) does not give complete corlversion, 27 1l l~ ~ 3b -I
1~ ~

but depending on the temperature a cer-tain, no-t to be exceeded, maximal yield is found which is around 40 % at 180C and can be raised to 95 % by increasing the temperature. This surprising behaviour will be demonstrated by means of the attached drawings in which Figure 1 is a pressure-temperature-diagram; and Figure 2 is a pressure-reactiontime-diagram.
In figure 1 curve a d~scribes the theoretical pressure-temperature-dependence of an inactive system (no conversion, hydrogen yield 0 %) calculated by addition of the ideal CO-pressure (gas law) and the respective steam pressure of the excessive aqueous phase.
Curve b is obtained in a similar manner for complete conversion (hydrogen yield 100 ~ corresponds to a twofold amount of gas).
The experimentally measured points of table 1 marked by (o) show that in a typical run (initial CO pressure ~8 bar) heating the autoclave rapidly and continuous~y to 222C the reac-tion starts noticably above ca. 180C and proceeds to high conversions on approaching the final temperature. Figure 2 shows the coxrespondiny pressure-time-dependence, whereby the continuous line between the experimental points represents the isothermal pressure development when the final temperature of 222C was reached. ~hen the system was only heated to 181C (experimental points (x) of table 2) the conversion reached a final reaction pressure of 115 bar asymptotically after 5 - 7 hours (figure 2) which according to figure 1 corresponds to a yield of about 40 ~.

? ~ 2 ~

On further heating to 198~C the reaction started again until after 3 to 4 hours another limiting value of about 70% yield was obtained. Raising the temperature once more to 217C
finally gave the pressure corresponding to a practically complete conversion. This observed temperature behaviour clearly indicates that despite of a low catalytic activi-ty of the Fe(CO)5-alkali water-system higher yields than about 40~ are in principle not to be attained below 180C. Temperatures of only 220C and more lead to hydrogen yields which are interest-ing with regard to a technical application.
Mixtures o-E water, alkali and carbonyl compounds of the metals Cr, ~o, W, Co, Ni, and Mn give results similar to the Fe(CO)5 system.
In the conversion using metal carbonyl catalysts hydrido-metal carbonyl complexes, among others, are apparently involved, ie. metal compounds having hydrogen bonded directly on the metal. Therefore, a catalytically active phase can be prepared using a metal carbonyl compound itself or precursors which give the metal carbonyl or the hydrido-metal carbonyl in a preceeding process or under the reaction conditions themselves. For instance Fe(CO)5 is formed directly from metallic iron, iron(II) compounds or polynuclear iron carbonyls (or instance Fe2(CO)g, Fe3(CO)12)by reaction with CO.
Accordingly Fe(CO)5 might be replaced by these substances.
Similarly polynuclear anionic iron complexes react to the hydrido-tetracarbonyl ferrat anion (HFe(CO)4 ) with CO, as for instance Fe2(CO)8 and HFe3(CO)13 . Therefore, the application of such compounds - with or without an additional base -~ 7~

1 ¦ similarly leads to catalytically active mixtures. Tllese 2 ¦ examples shall illustrate that each compound or mixtures of 3 ¦ those compounds are sui-table to prepare the catalyst solution 4 ¦ which either form metal carbonyls or hydrido-metal carbonyl 5 ¦ compounds and higher analogs, having hydrogen bonded directly 6 ¦ on the metal or establish e~uilibria with those species.
7 ¦ A11 compounds which form hydroxyl ions, under circum-8 stances only under the reaction conditions, are suitable bases, C ¦ preferably the alkali and earth alkali metal hydroxides, 1~ ¦ carbonates, and hydrogencarbonates, especially sodium carbonate 11 ¦ and sodium hydrogencarbonate.
12 ¦ Generally the process is carried out by intimately 13 ¦ mixiny the aqueous phase containing the catalyst component(s) 14 ¦ and the gas phase of C0 or C0-rich gases in a pressure vessel 15 ¦ at temperatures of 190 to 300 C, preferably 200 to 270 C, 16 ¦ and at carbon monoxide partial pressures of 1 - 500 bar, 17 ¦ preEerably 20 to 100 bar. The concentration oE the metal la ¦ component and the base which has to be applied is dependent 1~ ¦ on the kind of components and the reaction parameters pressure 20 ¦ and temperature. The carbon monoxide partial pressure can be 21 ¦ varied in broad limits, but should not fall below the C0-22 decomposition pressure of the metal carbonyls. Addition of 23 ¦ organic solvents like ether or alcohols is sometimes advan-2~ ¦ tageous.
25 1 Definition of some terms used hereafter:
26 1 1.) Composition of the product gas 27 XH = molar fraction of hydrogen in the product gas 28 XcO and XcO are defined in analogy , , . -~

~ 27g~

l ¦ 2.) hydrogen yield - XH (X~l2 + Xco) 2 ¦ 3 ~ ZM~ ~B = number of catalytic cycles relative to metal 3 ¦ and base, respectively, expressed by mole hydrogen 4 ¦ per mole metal or base 5 ¦ ZM = yleldH mole (C0) mole (metal) 1 6 ¦ Z~ = yieldH '.mole (C0) . mole (base) 1 81 . "

f 9 ¦ E.Yample 1 I
lO ¦ A 500 ml shaking autoclave with fittings, both made ll ¦ from stainless steel (DIN 1.4571), was charged with 1;96 g 12 ¦ (0.01 mole) Fe(C0)5, 1.06 g (0.01 mole~ water-free sodium l3 ¦ carbonate (Na2C03) and 100 g (5.56 mole) wa-ter, pressurized l4 ¦ initially with 48 bar (0.8 mole) carbon monoxide under exclusion 15 ¦ of oxygen and heated to 222 C with shaking. During the whole 16 experiment the internal temperature and the pressure were 17 measured by an iron constan-tan thermocouple and a pressure l8 gauge, respectively. Table 1 shows the experimental data of 19 pressure,`temperature and reaction time.
Composition of the product gas: Xl~ 0~493, XcO 0.414, 21 XcO 0 093~ ZM 67~ ZB 67, yield~l 84.1 ~-23 Table 1 24 Reaction Time Temperature Pressure 2S (h) (C) (bar) ,"l ~.3 130 72 :'ll 0,7 .1f~5 ~1 I . ~ .

z~

Reaction Time TemperaturePressure (h) . (c) (bar) 1.0 200 109 1.3 210 125 1.5 217 1~2 1.9 219 15~
2.1 220 162 2.8 221 172 3.3 222 178 3.4 222 180 4.1 222 18~
4.4 222 184 Example 2 The autoclave was charged in the same manner as in Example 1 and heated stepwise first to 181C, then to 198C and finally to 217 C. The experimental data are given in table 2 XH0 494~ XcO 0.427, XCoO-079, YieldH 86.2~, ZM 69, ZB69 Table 2 Reaction Time TemperaturePressure (h) (C) ~bar) 0.5 176 87 0.7 183 90 0.8 178 90 llffZZ79 l ~Reaction Time Temperature Pressure 2 ¦ (h) (C) (~ar) 3 ¦ 1.0 178 92 4 ¦ 1.5 ~ 181 9B
5 ¦ 2.0 -. 185 104 6 ¦ 3.0 181 .107 7 ¦ 4.0 181 111 8 ¦ 5.0 181 113 5.5 181 114 lO ¦ 6.0 181 115 ll ¦ 6.4 185 117 12 ¦ 6.9 190 122 13 ¦ 7.3 - 193 124 l~ ¦ 7.8 . 196 129 15 ¦ 8.0 198 137 16 I 8.9 198 1~1 17 10.0 198 145 18 11.0 198 146 19 ¦ 1~.0 198 147 20 ¦ 12.2 205 150 21 ¦ 12.9 215 168 2Z ¦ 13.4 217 - 174 23 ¦ 13.8 . . 217 177 24 ¦ 14.7 217 179 Z6 ¦ Example 3 27 4.9 g (0.025 mole) Fe~C035 were dissolved in 100 (3 1 m po~as-28 sium hydroxide by stirrin~3 the mixture 6 h at 60 C with l exclusion of oxygen ~aryon atmosphcre). The brown-yellow 2 solution of potassi,um hydrido-tetracarbonyl ferrat (K~ e(C0~9) 3 and 46 bar initial pressure of carbon monoxide (0.77 mole) 4 was heated to 260 C in.the 500 ml shaking autoclave. AEter 5.5 h (1.5 h heating time, 4 h isothermally a-t 260 C final 6 pressure 210 bar) a gas sample had -the followiny compositi.on:
7 ~I2 ' C02 0-452, XcO 0.060, yield~I 89.1 %, Z 27

10 1 ll ¦ Examples4 to 14 12 ¦ The examples 4 to 14 were carried ou-t similarly to l3 ¦ Exampl 1. The parameters and res~llts are given in Table 3.

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The apparatus is consisting of a vertical arranged reaction tube of 1,3 litre content (2000 mm length, 28 mm inner diameter) which is heated by oil circulating around the tube, a fur-ther tube mounted thereon which is heated in the same manner and has a capacity of 1.7 1 (670 mm length, 56 mm inner diameter) which served for the sepa-ration of gaseous phase and liquid, and a reflux condenser (620 mm length, 56 mm inner diameter) which was water-cooled. An aqueous sodium carbonate solution (o.l~, 1%
and 10~ respectively) was pumped through a metering pump into the lower end of the reaction tube at the beginning of the runs. The filling height was adjusted with an overflow valve mounted at the upper end of the reaction tube. The water consumed was supplemented through the pump when necessary. Carbon monoxide was pressed into the lower end of the reactor by means of a compressor operating isobaric at the pressure side through a pressure vessel (700 ml content, 250 ml iron penta carbonyl) filled with iron pentacarbonyl and through an oil-heated preheater.
The thermostatisation of the pressure vessel and the down-stream capilar leading to the pre-heater permitted the adjustment of a defined partial pressure of iron penta-carbonyl. The withdrawal of gas was controlled by means of a release valve on the top of the cooler and recorded by a flowmeter. The gas analysis was performed with the aid of a gas analyzing apparatus (Orsat) in defined time inter-vals. -The temperature was measured in the upper third of the reaction tube.

The process parameters, results of measuring and the there-from calculated data of examples 15 - 28 are given in Table 4 and defined as follows:
(Na ) concentration of sodium ions in mol/l in the aqueous phase P total pressure in bax measured at the top of the reactor T reactor temperature in C
T

e( )5 temperature of the iron penta carbonyl in C

,~t~, 27~

Fe(CO)5 partial pressure of iron carbonyl in bar output gas gas withdrawn in l/h (related to 20C
and atmospherlc pressure) input CO carbon monoxide calculated from output gas and hydroyen yield - input in l/h (related to 20C
and atmospheric pressure) input Fe(CO)5 iron pentacarbonyl calculated from input CO
(related to the actual process parameter TF (CO
and P) and Fe(cO)5 P

C/Fe(C)5 calculated molar carbon monoxide iron pentacarb ratio at the reactor entrance output H2 productlon rate of hydrogen calculated from output gas and hydrogen yield in l/h (related to 20C and atmospheric pressure).

Temperature, pressure, partial pressure of iron penta-carbonyl and throughput o~ carbon monoxide varied in examples 15 - 23 whereby conversions (=hydrogen yield) up to 70%
were obtained when carbon monoxide was passed once through the liquid phase. As it can be seen from examples 21 and 23 respectively on one side and 18 and 22 respectively on the other side, the temperature is the decisive process para-meter which allows high conversions. I~ the reaction tube is charged with fi:Llers (cylindric wire nets Erom V2A, 6 mm diameter, examples 24 - 28) thi.s results in higher throughputs at the same yields. Pumping of a 10% instead oE a 1~ aqueous sodium carbonate solution has no signi icant influence, however the activity o~ a 0.1-percent solution decreases remarkably (examples 27 and 28).

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the production of hydrogen by homo-geneous catalized conversion of carbon monoxide and water into carbon dioxide and hydrogen with the aid of metal carbonyl compounds as catalysts, characterized in that carbon monoxide is reacted with water in the form of a mixture of a weakly aqueous base and a carbonyl compound of a metal selected from iron, cobalt, nickel, manganese, chromium, molybdenum and/or tungsten at temperatures above 181°C at a partial pressure of carbon monoxide between 1 and 500 bar.

2. A process as claimed in claim 1 wherein the reaction is carried out at a temperature of from 200 to 270°C and at a partial pressure of carbon monoxide between 20 and 100 bar.

3. A process according to claim 1, characterized in that the reaction is carried out at temperatures between 190 and 300°C.

4. A process as claimed in claim 1 or claim 3, characterized in that the reaction is carried out at pressures of 50 bar or above.

5. A process as claimed in claim 1, claim 2 or claim 3, characterized in that the reaction is carried out at 50 to 100 bar.

6. A process as claimed in claim 1, claim 2 or claim 3, characterized in that the weak base is selected from hydroxides, carbonates and hydrogen carbonates of the alkali metals and earth alkali metals.

7. A process as claimed in claim 1, claim 2 or claim 3, characterized in that the weak base is sodium carbonate.

8. A process as claimed in claim 1, claim 2 or claim 3, characterized in that the carbonyl compound is iron pentacarbonyl.

9. A process as claimed in claim 1, claim 2 or claim 3, characterized in that the molar ratio between weak base and metal carbonyl compound is between 1 and 3 : 1.