FR2490615A1 - Prodn. of gases contg. hydrogen and carbon mon:oxide - by steam cracking of methanol - Google Patents

Abstract

Prodn. of gases contg. H2 and CO (balance CO2, CH4, H2O and opt. N2) is carried out by cracking mixts. having variable proportions of steam and methanol vapour at 130-950 deg.C and 1-100 atm. (absolute), opt. in the presence of N2 or air and/or recycle gases (after removal of certain components) and/or gases from an external source. Gases contg. varying amts. of H2 and CO can be produced by varying the feed compsn., the catalyst and the reaction conditions.

Description

METHANOL REFORMING PROCESS AND DEVICE FOR IMPLEMENTING THE SAME
The present invention relates to a process for reforming methanol and an implementation device.

 The cutting of methanol, either by a cracking or steam reforming process, can lead to gas mixtures with distinctly different compositions; and both the proper choice of catalysts and the operating conditions largely determine the composition of the resulting gas stream.

 The use of methanol as a source of hydrogen production, although well known, was considered to have obvious disadvantages, particularly from the economic point of view. However, the decreasing availability of hydrocarbons and the future conversion of other raw materials into methanol (coal gasification) tend to change this situation.

 An improvement and adaptation of the existing techniques has been sought in order to optimize the use of methanol as starting hydrocarbon for the manufacture of gas with various compositions.

 For the production of hydrogen, the steam reforming technique seems particularly well adapted, some of the introduced water being transferred to hydrogen; and under conditions of use at low temperature, it is necessary to use a catalyst which is devoid of activity with respect to methanation.

- vaporéformage du méthanol

- réaction de conversion à l'eau

- méthanisation

pour lesquelles les constantes d'équilibre peuvent être évaluées T0C K1 K, K3 K4 K5 150 3,02 x 10 2,34 g 103 7,76 x 102 1,29 x 1014 1 66 I 1011 350 2,24 x 104 4,57 x 105 2,04 x 10 4,17 x 105 2,04 x 104 550 2,69 x 106 1,17 x 107 3,471100 1,29 x 101 3,72 x 10 750 -- - 1,26 x 100 1,12 x 10-2 8,91 x 10 950 - - 6,46 x 10-1 2,63 x 10-4 4,07 x 10 4
 la vue de ces chiffres ainsi qu'en considérant la stoechic- métrie de la réaction, on remarque - que la réaction (2) est plus productive en hydrogène que (1); - que la réaction (3) peut être employée pour augmenter la quantité
d'hydrogène produit; en fait la réaction (2) n'est autre que lasom-
me de (1) et (3); - que les réactions (4) et (5) sont très favoriséespar l'équilibre à
basse température, bien que la présence d'eau inhibe la formation de
méthane.The reaction system can be described by the following reactions
- decomposition of methanol

- steam reforming of methanol

- conversion reaction to water

- anaerobic digestion

for which the equilibrium constants can be evaluated T0C K1 K, K3 K4 K5 150 3.02 x 10 2.34 g 103 7.76 x 102 1.29 x 1014 1 66 I 1011 350 2.24 x 104 4, 57 x 105 2.04 x 10 4.17 x 105 2.04 x 104 550 2.69 x 106 1.17 x 107 3.471100 1.29 x 101 3.72 x 10 750 - - 1.26 x 100 1.12 x 10-2 8.91 x 10 950 - - 6.46 x 10-1 2.63 x 10-4 4.07 x 10 4
In view of these figures, and considering the stoichiometry of the reaction, it may be remarked that reaction (2) is more productive in hydrogen than (1); - that reaction (3) can be used to increase the amount
hydrogen produced; in fact the reaction (2) is none other than lasom-
me from (1) and (3); - that the reactions (4) and (5) are very favored by the equilibrium
low temperature, although the presence of water inhibits the formation of
methane.

 It is known that the catalysts for accelerating the reaction (2) are often identical to the catalysts used in the reaction (3), since, if the reaction (3) occurs, it also promotes the progress of the reaction. (1) by the disappearance of CO.

A methanol reforming process has been found to obtain gases containing varying concentrations of hydrogen,
of carbon dioxide, the balance of the gas being composed of carbon dioxide, methane, water vapor and optionally nitrogen, according to which a cracking operation is carried out on mixtures of variable proportions of water vapor and methanol vapor, optionally in the presence of nitrogen, or air and recycled gas, after possible separation of certain components, and gas from outside the unit.The cracking operation is carried out between 130 and 9500C, and at pressures between 1 and 100 bar
In this process at least two types of catalysts are used, the first one more specifically intended for cracking of methanol, the second and following being suitable for transforming the gases produced in the cracking reaction into gaseous products such as hydrocarbons, carbon, carbon monoxide, reducing or synthesis gases, and hydrogen.

 The catalysts make it possible to work at molar rates of water vapor / methanol and carbon dioxide / methanol of 0.2 to 10.

 The first catalyst contains zinc and chromium as the active constituents, to which at least one metal selected from the group consisting of copper, cobalt, platinum, palladium, rhodium, nickel, manganese, molybdenum. The second and subsequent catalysts are of a type adapted to the type of gas chosen.

 The first catalyst may also contain nickel and chromium as the main active constituents, to which at least one metal selected from the group may be added by zinc, cobalt, platinum, palladium, rhodium, nickel, manganese, magnesium and molybdenum; the second and possibly subsequent catalysts being of a type adapted to the type or composition of the chosen outlet gas, and therefore of variable nature.

 The catalysts can be loaded in the form of metal oxides without any need for pre-reduction inside the plant before starting.

 All the catalysts can be contained in a tubular reactor, and the process results in a sequence adapted to the composition of the selected exit gas.

 The supply of heat during the steam reforming operation, that is to say to the tubular reactor is done by direct combustion or by an intermediate agent or heat transfer fluid, heated by the combustion of a fraction of the gas produced, to make the process autonomous in heating. Said fraction of the product gas may be the waste gas of a purification, such as a molecular sieve purification of the gas leaving the reactor to obtain pure hydrogen One of the advantages of the invention is its independence when the combination of methanol steam reforming and molecular sieve purification is integrated into hydrogen production.

 The catalysts may also be contained in an adiabatic reactor, the process being carried out in a sequence adapted to the heat consumption for the reactions in question as well as to the composition of the chosen outlet gas.

 The catalysts can also be contained in two separate reactors.

 In order to obtain gases with a high carbon monoxide content, it is advantageous to add carbon dioxide in the gaseous mixture to be treated. The process can be implemented with carbon dioxide recycling, direct addition of this gas or combination of the two modes of introduction.

 He was found. that an initial start of the unit can ensure a reduction of metal oxides without use of external hydrogen while Bn conferring a better activity to the catalyst thus treated. This initial start-up is carried out by introducing into the reactor water vapor initially containing small quantities of methanol which are progressively increased until the composition of the normal operation is reached, this operation being carried out at temperatures above dew and below 400 ° C and under any pressure.

 The reaction can be carried out in a reactor in which the heat input for the reactions is made in the first part of the reactor either by direct heating or by a heat-carrying fluid flowing cocurrently with the process fluids contained in the tubes of said reactor.

 The arrangement of the catalysts is such that the heat generated by one of the reactions is used to provide the heat necessary for the other reaction.

 The steam reforming of methanol can be conducted in an installation of the type shown in the attached figure.

 This installation essentially comprises a tubular reactor, in which the steam reforming is carried out, interposed between a vaporizer of the reaction mixture, and a heat exchanger between the outgoing gases and the feed liquid, a condenser and a purification unit, the installation further comprises a purification gas combustion furnace.

 The feed liquids methanol and water respectively introduced in (1) and (2) are heated and partially evaporated in the heat exchanger (3) by heat exchange with the gas leaving the reactor (5), said exiting wet gas is then cooled in the condenser (6) before entering the purification unit (11), the purified gas leaving the installation at 10.The cooler (6) collects available calories from the water refrigeration leaving the conduit (12). the waste gas leaves the purification plant through the pipe (13) is accumulated in the buffer tank (7), before circulating to the combustion furnace (8), to be burned, the fumes escape into ( 9) while the heat is recovered by a coolant circulating between the reactor (5) the combustion furnace (9) and the vaporizer (4). This heat transfer fluid provides the necessary calories to the reaction mixture in the vaporizer (4) and in the reactor (5).

 Examples are given below which illustrate the invention in a non-limiting manner.

Example 1
A conventional catalyst of the low temperature conversion type is chosen with the following composition
CuO = 44% by weight
ZnO = 45% by weight
Al2O3 = 117 weight.

550 ml of this catalyst are loaded into a tubular reactor, with a diameter of less than 5 cm and a bed height of 25 cm, preceded by a preheating zone of 40 cm with inert filling. The catalyst is reduced with a mixture of 271of of H2 in N2 at 200 OC for 12 hours. Then the average temperature of the catalyst is raised to 29500 and a liquid mixture of molar ratio H 2 O / CH 3 OH = 5 is pumped at atmospheric pressure into the preheater so as to have a gaseous stream on the catalyst at a space velocity of 900 h. The leaving gas has a volumetric composition of 0.45% CO, 23S56% CO 2, 76.76% He, 0.02% CH 3 OH and inerts. The condensed liquid contains 0.10% by weight of CH 3 OH. These analyzes relate to 70 hours of walking.

It appears however that it is not possible to maintain this good conversion without rapidly increasing the temperature. After 214h, the average temperature of the reactor being 307 ° C., the liquid already contains 1.11% by weight of CH 3 OH, the compositions and flow rates at the inlet having not changed. Finally, after 492 h at an average temperature of 35000, the condensed liquid contains 1.00% by weight CH3OH and after 690 h at an average temperature of 3500C, the condensate titre 5.65% by weight
CH30H.

Example 2
Another catalyst is subjected to the same test under identical conditions. The composition is as follows
ZnO = 71% by weight
Cr2O3 = 22% weight
AI 203 = 7% by weight.

We note that it is necessary to rise at a higher temperature to obtain the same conversion. Thus, after 96 hours of operation, the condensate content 0.07% by weight of CH 3 OH, but at an average temperature of 3340 C.
However, this catalyst is characterized by a better stability as a function of time: after 478 h at an average temperature of 3490G, the CH3OH in the condensate is 0.84% and after 831 h at an average temperature of 3500C it is 0.53 ^ 7> weight.

Example 3
Considering that the conventional composition of the low temperature conversion catalyst is not suitable, that the zinc and chromium elements are catalytic by themselves, stable over time, but that the working temperature is higher, it is produced another catalyst with the next composition
ZnO = 57% by weight
Gr203 = 11% weight
CuO = 21% weight
AI 203 = 11% weight which is subjected to the test described in Examples I and 2. After 144h, at an average temperature of 3110C, there is no detectable CH3OH in the condensate. This catalyst is then subjected to more severe test conditions: higher pressure and lower H 2 O / CR 3 OH molar ratio. Thus, after 311 h, at an average temperature of 33 ° C., a pressure of 30 bar and a molar ratio H 2 O / EC 3 OH of 1, 5, the CH3OH in the condensate is only 0.25% by weight. Finally, after 3444 hours of operation, at an average temperature of 349 ° C., a pressure of 24 bar and an H 2 O / CH 3 OH molar ratio of 2.5, the CH 3 OH in the condensate is only 0.83% by weight.

 The critical examination of the 3 examples shows that zinc and chromium are the main elements of the catalyst composition but that the addition of copper makes it possible to work at a lower temperature. However, the disadvantage of using a catalyst reduction phase, which requires the use of hydrogen in the gas stream, or the use of a prereduced catalyst, makes handling more difficult.

 It is possible to envisage a starting method which does not have this disadvantage and which in addition confers a still lower temperature activity on the catalyst of Example 3.

Example 4
The catalyst of Example 3 is charged to the same reactor and the temperature is uniformized to 2000 C. Without any reduction, a liquid stream containing 1% CH 3 OH in H 2 O is pumped into the preheater system at atmospheric pressure. After 20 h, the amount of CH3OH is increased to 2 / and after 40h to 8 Vo. Then, the system is progressively enriched in methanol up to the conditions of Examples 1,2 and 3. Thus, after 192h, at an average temperature of 2680C, a pressure of 24 bar and an H 2 O / CH 3 OH molar ratio of 2.5, 0.89% by weight of CH 3 OH in the condensate. This good activity is maintained, since after 1665h, at an average temperature of 2930C, a pressure of 24bar and a molar ratio H 2 O / CH 3 OH of 1.9 CH 3 OH in the condensate is still only 0.52% weight.

 In Examples 1 to 4, the product gas has always been of relatively constant composition, and corresponding to the reaction (2) namely 3 parts of H2 to 1 part of CO 2. CO and methane are not important. If, after removal of CO 2 by known methods, the gas is thus substantially pure hydrogen, it is very possible to make other compositions by choosing other catalysts or with the catalyst of Examples 3 and 4 of other reaction and feeding conditions. This makes it possible to vary the composition of the gases obtained.

Example 5
The catalyst described in Example 3 is charged to the reactor and starts up by the method according to the invention and described in Example 4.

After this initial phase, the following conditions are imposed and the results are shown in the table below.
p Dry gas time R20 / CH30H bar cat VVE CO C02 H2 C114
5 33 350 1000 0.8 24.4 74.7 0.1
1.2 25 380 1000 7.4 19.4 72.9 0.3
2 25 380 1000 3.9 22.0 74.0 0.1
5 33 350 700 0.8 24.9 74.6 0.1
1.5 33 350 700 4.5 21.6 73.7 0.2
1.5 33 300 700 2.5 23.6 73.6 0.2
2 25 300 1000 1.7 23.7 74.5 0.1
3 25 300 500 0.9 24.3 74.7 0.1
3 25 330 500 1.3 23.9 74.6 0.2
1.0 30 300 500 6.0 20.5 73.0 0.2
Example 6
A catalyst of the following composition is charged
NiO = 14 ffi
Al2 3 86% and proceeds to methanol steam reforming test at a reactor outlet temperature of about 8000C, the mixture entering the reaction zone at 4000C. CO 2 was also added to the inlet gas to shift the equilibria to promote CO formation.

H20 C02 PT output VVH Dry gas CH3OH CH3OH bar OC ~~~~ CO C02 H2 CH4
1 1.6 1 890 2500 31.8 29.4 38.8 0
0.8 0.8 1 870 300G 31.2 18.1 50.6 0
0.5 2.4 1 910 1700 41.0 33.9 25.1 O
O 1.2 1 900 2700 40.8 14.2 37.0 0
The process of the invention can be made particularly interesting by the combination of a molecular sieve purification. This purification process, known per se, is advantageous in combination with steam reforming of methanol not only for the production of highly hydrogen pure, but in addition that the purge gas of this purification can be directly used to provide all the calories necessary for the operation of the process.

One aspect of the invention is therefore the thermal independence of the process if the combination of methanol steam reforming and molecular sieve purification is integrated into hydrogen production.

Example 7
The reaction of the steam reforming of methanol is carried out in an installation illustrated in the single appended figure.

A mass and thermal balance makes it possible to prove the thermal autonomy of the system. The operating conditions chosen are H 2 O / CH 3 OH = 2 in molar ratio, outlet temperature of the reactor 300 C, pressure 25 bar. The facility is expected to produce 250 Nm3 / h of purified H2, resulting in 347 Nm3 / h of H2 at the reactor outlet based on the normal figure of 72> / in recovery. Hydrogen to the molecular sieve purification system. Taking as a basis the analytical composition of the dry gas leaving the reactor obtained in Example 5 at the same operating conditions, it follows by mass balance a flow rate of 172 kg / h of CH 3 OH at the inlet (1) of the installation and 193 kg / h of H2O at the inlet (2) thereof at a temperature of 250 ° C.

The gas exiting the reactor (5) at 3000 ° C. and 25 bar has a volumetric wet composition of 1.33 ° C., 18.55% CO 2, 58.14% H 2, 0.778% CH 0.15% CH 3 OH and 21.753% H 2 O, flow rate of 597 Nm3 / h.

To heat the feed mixture to its boiling point of 2030C, it is necessary to supply 55.600Kcal / h, to vaporize 111.400Kcal / h to overheat it up to 3000C it still needs 15.200 Kcal / h, a total of 182,200 Kcal / h to be supplied before entering the reactor (5).

The heat of reaction to reach the conversion at this mass flow
that amounts to a total of 79.300 Koal / h.

The total calories to be supplied is 261,500 Kcal / h. The con
densification of the wet gas leaving the reactor (5) will provide 61,800 Kcal at the level of a heat exchanger (3), which will allow
heat and partially evaporate the feed liquid, its
temperature being raised from 250C to 2030 C. The moist gas, entering
300 C comes out of the exchanger to 132 at and is then cooled in a
condenser (6) up to 350C before entering the purifica unit
tion (11). The cooler (6A) still collects 51.200 Kcal / h which
however are only available in the proposed scheme with water
refrigerating outlet at 370C via the conduit (12).

After leaving the exchanger, it is necessary to provide the mixture
reaction 120.400 Kcal / h to bring it to the reaction conditions
and 79,300 Kcal / h for the actual reaction, a total of
of 199,700 Kcal / h.

These are provided by the combustion in a furnace (8) of the gas
waste from purification, from the purification unit
(11) through the conduit (13) and through a tam
pon (7). This gas with a composition of 44.5% 112, 3.6 Vo CO, 0.5 Vo
CH4 + CH30Hs 50.8% CO2 and 0.5 Vo 1120, is capable of providing 285,400
Kcal / h at combustion. By conferring an exit temperature of
fumes in (9) of 300au, heat recoverable by a heat fluid
carrier is 233,500 Kcal / h, which ultimately gives a surplus
in calories of 33,800 Kcal / h. The heat transfer fluid provides the
calories required to the reaction mixture in a vaporizer (4)
and in the reactor (5). The process is thus in thermal balance
with 13% excess calories.

Claims (10)

REVENM CATI0NS  1- Process for reforming methanol to obtain gases containing variable concentrations of hydrogen and carbon monoxide, the balance of the gas being composed of carbon dioxide, methane, water vapor and optionally nitrogen according to which is carried out a cracking operation of mixtures in variable proportions of water vapor and methanol vapor, optionally in the presence of nitrogen, air, recycled gas, and gas from outside of the unit, characterized in that the cracking operation is conducted between 130 and 9500C, at pressures of between 1 and 100 bar, in the presence of at least two types of catalysts, the first one more specifically intended for cracking the methanol, the second and subsequent ones being suitable for converting the gases produced in the cracking reaction into gaseous products such as hydrocarbons, carbon dioxide, carbon monoxide, reducing gases, synthesis gases and hydrogen. hydrogen, the molar ratios of water vapor / methanol and carbon dioxide / methanol being between 0.2 and 10.  2-process for reforming methanol according to claim 1, characterized in that the first catalyst contains as main active constituents zinc and chromium to which are optionally added at least one metal selected from the group consisting of copper, cobalt, platinum, palladium, rhodium, nickel, manganese, magnesium, molybdenum and that the second and following are adapted to the type of gas chosen.  3-process for reforming methanol according to claim 1, characterized in that the first catalyst contains as main active constituents nickel and chromium, to which are optionally added at least one metal selected from the group consisting of zinc, cobalt, platinum, palladium, rhodium, nickel, manganese, magnesium and molybdenum and that the second and following are adapted to the type of gas chosen.  4- Methanol reforming process according to claim 2 or 3, characterized in that the active metals are in the form of oxides.  5-reforming process according to any one of claims 1 to 4, characterized in that the heat input during the steam reforming operation is via a fluid, coolant flowing co-current fluids of the process, and of auffé by the combustion of a fraction of the gas produced, said fraction being the waste gas of a purification of said gas produced for the purpose of obtaining pure hydrogen.  6. Reforming process according to any one of claims 1 to 5, characterized in that the steam reforming reaction is conducted in the presence of carbon dioxide, by direct addition of this gas, recycling or combination of the two modes of introduction.  7- reforming process according to any one of claims 1 to 6, characterized in that the initial start of the process is carried out by introducing water vapor initially containing small amounts of methanol gradually increased to reach the composition normal operation, this operation being carried out at temperatures above the dew point and below 4000C,  8- Reactor for carrying out the methanol reforming process according to claim 1, characterized in that the catalysts are arranged in a tubular reactor in such a way that the heat released by one of the reactions is used to bring the heat necessary for the other reaction.  9- Installation for carrying out the methanol reforming process characterized in that it essentially comprises a tubular reactor (5) interposed between a vaporizer (4) of the reaction mixture and a heat exchanger (3) between the outgoing gases and the feed liquid, a condenser (6) and a purification unit (11).  10- Installation according to claim 9, characterized in that it further comprises a purifying waste gas combustion furnace (8).