CH630402A5 - Process for generating a fuel gas by catalytic reaction of methanol with steam - Google Patents

Description

The invention relates to a method for producing a methane-containing heating gas by reacting methanol with steam under increased pressure on a nickel-containing catalyst.

Known methods for producing city gas or also for heating gas exchangeable with natural gas work with high efficiency and produce a gas of excellent quality for distribution in the corresponding natural gas or city gas networks. It is also known to increase the capacity of naphtha cracking plants for generating hot gas for periods of peak demand by adding methanol. Evaporated methanol is added to the steam-containing cracking gas at about 400 ° C. The mixture is converted catalytically into a gas with a high calorific value on a catalyst suitable for CO conversion. This can increase the performance of existing slitting lines by around 25 to 30%.

The use of methanol as the sole raw material for the production of high-calorific gas is problematic for a base load coverage because of the high cost of Mathanol. Basically, however, methanol is well suited for gas production because it can be transported and stored in a simple manner. In a supply network, peak demand is therefore preferably covered, e.g. in winter, in question.

In a known process, heating gas for peak demand is generated from methanol by catalytic conversion with water vapor. Methanol is reacted together with water vapor and air at an inlet temperature of about 350 ° C. on a nickel-rich catalyst with an aluminum oxide support. The addition of air primarily sets the calorific value of the gas in the desired manner, but the disadvantage here is that the density of the gas is increased too much, so that considerable amounts of CO2 have to be washed out of the product gas. The addition of air also leads to a high outlet temperature of the product gas from the cracking reactor, which in turn leads to undesirably high amounts of CO in the product gas. The carbon monoxide must be converted in a downstream conversion stage. The high reaction temperatures achieved in the known process also place a heavy burden on the catalyst material and make it unusable after a relatively short time.

The invention has for its object to carry out the method of the type mentioned in such a way that work can be carried out without air supply and a product gas is formed which is as low in carbon monoxide as possible. According to the invention, this is achieved in that water vapor is reacted with methanol in a weight ratio of 0.5 to 1.5 at an inlet temperature of 300 to 500CC in an adiabatic reactor at a pressure in the range from 10 to 40 bar and that the product gas , which leaves the reactor at a temperature of 500 to 700 ° C, is then cooled.

According to this process, the product gas contains a carbon monoxide content of typically less than 5% by volume, based on dry gas. After sufficient cooling and condensation of water vapor, the gas can be used as town gas without further conversion of gas components.

For stagnant city gas qualities with an upper calorific value of 4000 to 5000 kcal / Nm3, the process according to the invention is expediently carried out in such a way that the product gas is drawn off from the reactor at a temperature of 580 to 700 ° C., cooled and, depending on the desired city gas density, partly from carbon dioxide is released.

If a gas that can be exchanged with natural gas and has a methane content of more than 90 vol.% (Calculated dry), the hot product gas from the catalytic methanol cleavage can be cooled to 250 to 350 ° C and reacted with steam on nickel-containing catalyst material in at least one methanation stage and methanized Excess carbon dioxide gas is washed out. Process conditions known per se can be observed for the methanation.

A further significant improvement in the inventive catalytic conversion of methanol with steam is achieved by a special type of catalyst. This type of catalyst expediently has a nickel content of 25 to 50% by weight and additionally contains molten alumina cement. The content of this cement is e.g. at 5 to 40% by weight. In addition to these main components, the support material of the catalyst can also contain zirconium dioxide and / or titanium dioxide. If one of the two oxidic components is present in the catalyst, its proportion is advantageously at least 5% by weight.

A first embodiment of an advantageous catalyst is described below. This catalyst contains the compounds NisMgAh09 and ZrCh in a weight ratio of 13: 1 and an alumina cement that makes up 30% of the total catalyst weight. (Composition of the alumina cement in wt .-%: 26.4 CaO; 71.9 Al2O3; 0.2 Fe2C> 3; 0.2 MgO; 0.4 Na20; 0.07 SÌO2 and traces K, Cr, Cu, Mn , Ni and Pb.) The production of this first embodiment of the advantageous catalyst takes place, for example as follows:

Solution II is added to suspension I within 15 minutes. The composition of the suspension or solution is as follows:

Suspension I: 1250 g of soda in 61 water with 37.5 g of ZrCh

Solution II: 250 g Mg (NC> 3) 2 • 6 H2O

1280 g Ni (N03> 2 • 6 H2O 690 g A1 (N03) 3 • 9 H2O in 61 water.

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The resulting precipitate of NisMg (OH) i6 • CO3 • 4H2O on zirconium dioxide is filtered off, washed free of alkali, dried at 110 ° C. for 12 hours and then calcined at 400 ° C. for 4 hours. The roasted mass obtained in this way thus contains nickel oxide and magnesium oxide, aluminum oxide and zirconium dioxide as carrier components. 350 g of the toasted mixture are dry mixed with 150 g of alumina cement, mixed with 60 g of water, compressed to 3 x 3 mm tablets, then briefly soaked and then fully cured for 6 days at 40 ° C in a closed system stored in a moist condition. After that, the tablets reach an end compressive strength of 464 kg / cm2 and a bulk density of 1.57 kg / 1. The nickel content, based on the oxidic state, is 28.7% by weight. Before use, the catalyst is reduced, which can be done with hydrogen or other reducing gases.

A second embodiment of an advantageous catalyst contains the compounds NisMgAkO, ZrCh and a-AhCb in a weight ratio of 12: 1: 2 and, in addition, the already explained alumina cement. This cement accounts for 15% of the total catalyst weight. This second form of catalyst can be made in the following ways:

Solutions I and II are continuously combined in suspension III at a temperature of 60 ° C. in such a way that the pH of the solution does not drop below 8.5. The composition of the solutions or the suspension is as follows:

Solution I: 1250 g soda in 61 water

Solution II: 255 g Mg (N03) 2 • 6 H2O 1280 g Ni (NCb) 2 • 6 H2O 690 g AI (N03) 3 • 9 H2O in 61 water

Suspension III: 43.2 g zirconium dioxide and 74.0 g (X-Al2O3 in 31 water.

The resulting precipitate is filtered off, washed, the filter cake is dried at 110 ° C. for 12 hours and then calcined at 400 ° C. for 4 hours.

425 g of the roasted mass produced in this way are mixed dry with 75 g of alumina cement, mixed with 75 g of water and compressed to form 3 × 3 mm tablets. The finished catalyst is briefly soaked and then dried at 110 ° C for 12 hours. Then the catalytic converter achieves an end compressive strength of 453 kg / cm2 and a bulk density of 1.52 kg / 1. The nickel content, based on the oxidic state, is 30.3% by weight. The catalyst is reduced before use.

A third embodiment of an advantageous catalyst contains the compounds NÌ6AI2O9 and TÌO2 in a weight ratio of 7: 2 and, in addition, alumina cement (20% of the total catalyst weight). The production happens e.g. as follows:

First solutions I and II and suspension III are prepared. Its components are as follows:

Solution I: 1909 kg soda in 61 water

Solution II: 1745 kg Ni (N03> • 6 H2O

750 kg A1 (N03) 2 • 9 H2O in 61 water

Suspension III: 57 g TÌO2 in 31 water.

Solutions I and II are combined in suspension III at 60 ° C. and a pH of not less than 8. The resulting precipitate is filtered off, washed free of alkali, dried at 110 ° C. for 12 hours and then calcined at 400 ° C. for 4 hours.

400 g of the roasted mass produced in this way are dry mixed with 100 g of alumina cement, 150 g of water are added and then compressed into 3 x 3 mm tablets. The tablets are briefly soaked and treated at 110 ° C for 12 hours. Then the catalytic converter achieves an end compressive strength of 463 kp / cm2 and a bulk density of 1.53 kg / 1. The nickel content, based on the oxidic state, is 41.3% by weight. A reduction follows.

The example of a process scheme shown in the drawing is explained as follows:

The methanol to be split is fed into line 1, pressed into line 3 by pump 2 and from there passed into the shaft reactor 4 via several heating stages. The heating takes place first in the heat exchanger 5, from where the methanol is passed through line 6 to a further heat exchanger 7 and evaporated there. The methanol vapor then flows in line 8 to a heater 9 and finally in line 10 to reactor 4.

The water vapor required for the catalytic reaction in the reactor 4 is added to the methanol through line 11; this water vapor comes from the steam collector 12. In the reactor 4, the catalyst material is arranged in a fixed bed. The reaction in the reactor 4 takes place under autothermal adiabatic conditions. The water vapor-containing product gas leaves the reactor 4 through the line 13 and has a temperature in the range from 500 to 700 ° C. This higher temperature compared to the inlet temperature of the material to be converted results from the exothermic nature of the reaction in the reactor.

A first cooling of the product gas of line 13 takes place in a waste heat boiler 14, then the product gas is led in line 15 to heat exchanger 7 and through line 16 to a feed water preheater 17. Further cooling stages for the product gas are the heat exchanger 5, the fresh water preheater 18 and an air cooler 19. The cooled product gas present in the line 20 can already be used directly as town gas.

For certain city gas qualities, the gas in line 20 is passed to a washing device known per se for removing excess carbon dioxide. If the gas is to be further processed into gas that can be exchanged with natural gas, the product gas is passed to a one- or multi-stage methanation. The C02 washout takes place before or after the last methanation stage.

The water vapor required for the reaction is generated in the following way: The feed water, e.g. also gas condensate, is guided in line 25 through the fresh water preheater 18 and is first collected in the feed water tank 26, which also serves for degassing. From there, the water is fed through line 27, pump 28 and line 29 to preheater 17 and from there through line 30 into steam collector 12. Condensate in the steam collector 12 flows through the line 31 and a branch line 32 through the heater 9, in which the evaporation takes place by means of a heater, not shown. The steam flows in lines 33 and 34 back into the collector 12. Another part of the condensate in line 31 is led through line 35 to the waste heat boiler 14, at least partially evaporated there and added to the return line 34 through line 36.

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Example 1 _

City gas is generated in a laboratory apparatus with a process according to the drawing. 1 kg of methanol per hour is fed via line 1 to pump 2 and brought to the operating pressure for gas generation of 24 bar. The methanol flows via line 3 to the heat exchanger 5, where it is preheated to 150 ° C. with cooling fission gas. The preheated methanol is then evaporated in the heat exchanger 7. The vaporized methanol in line 8 is admixed with 1 kg / h of process steam at saturated steam temperature from line 11 and the mixture is then brought to a temperature of 460 ° C. in the fired heater 9. At this temperature, the mixture enters the gap reactor 4, which is designed as a shaft reactor. The reactor contains the catalyst previously described as the first embodiment of a preferred catalyst.

1.29 Nm3 of product gas leave the reactor 4 per hour via line 13 at a temperature of 630 ° C. and a pressure of 20 bar and having the following composition:

no gas is fed to wet methanation with an inlet temperature of 260 ° C. For every Nm3 of product gas, 0.7 Nm3 of methanized gas at 480 ° C and the composition mentioned below leave the first methanation stage:

CO2 CO Ha CH4

24.6 vol.% 0.6 vol.%

22.1 vol.%

52.7 vol.%

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This gas also contains 1.665 Nm3 water vapor per Nm3 dry gas. After the gas has cooled in a waste heat boiler to 250 ° C, it is fed to a second wet methanation. 0.82 Nm3 of gas of the following composition are produced per Nm3 of gas from the first methanation stage:

CO2

CO less than 20 H2 CH4

25.0 vol.% 0.1 vol.% 5.0 vol.% 70.0 vol.%

CO2 CO H2 CH4

21.7% by volume 4.4% by volume 45.7% by volume 28.2% by volume

This gas also contains 1.03 Nm3 of water vapor per Nm3 of dry gas. The product gas is then cooled in several heat exchangers and is finally available in line 20 with the following values which are characteristic of a city gas:

Lower heating value: 4200 kcal / Nm3 density: 0.727 kg / Nm3

Density ratio, based on air: 0.562

The discharge pressure is 18 bar, the temperature is 40 ° C. The gas is saturated with water vapor under these conditions.

Example 2

To produce a gas that is exchangeable with natural gas, the product gas is dried after the heat exchanger 5 with the total water vapor content of 1.03 Nm3 per Nm3.

A known catalyst with 40% by weight of nickel on a Zr02-Ak03 support 25 is used in both methanation stages. The proportion of water vapor per Nm3 of gas from the second methanation stage is 2.14 Nm3. The gas leaves the second methanation stage at a temperature of 330 ° C and goes through another methanization stage after being previously cooled to 250 ° C. In this 30 stage, 0.97 Nm3 of gas of the following composition is produced per Nm3 of gas from the previous stage:

CO2

CO less than 35 H2 CH4

25.0% by volume 0.1% by volume 1.6% by volume 73.4% by volume

The third stage methanation catalyst is the same as for the previous stages. The product gas of the third methanation stage is treated with hot pot pocket to wash off excess CO 2. The scrubbed gas now contains 97% by volume CH4.2% by volume H2 and 1% by volume CO2; it is interchangeable with Erdags.

1 sheet of drawings

Claims (5)

630402 PATENT CLAIMS 1. A method for producing a methane-containing heating gas by reacting methanol with steam under increased pressure on a nickel-containing catalyst, characterized in that steam with methanol in a weight ratio of 0.5 to 1.5 at an inlet temperature of 300 to 500 ° C in one reacting adiabatically operating reactor at a pressure in the range of 10 to 40 bar and that the product gas which leaves the reactor at a temperature of 500 to 700 ° C is then cooled. 2. The method according to claim 1 for the production of town gas with an upper calorific value of 4000 to 5000 kcal / Nm3, characterized in that the product gas is withdrawn from the reactor at a temperature of 580 to 700 ° C, cooled and optionally partially freed from CO2 . 3. The method according to claim 1 for producing a gas exchangeable with natural gas with a methane content of over 90 vol.%, Characterized in that the product gas is cooled to 250 to 350 ° C, converted to nickel-containing catalyst material in at least one methanation stage and from the methanized gas CO2 is washed out. 4. The method according to any one of claims 1-3, characterized in that the catalyst has a nickel content of 25 to 50 wt .-%, and at least Contains 5 wt .-% alumina cement and at least 5 wt .-% zirconium dioxide or titanium dioxide.