DE4420752A1 - Catalytic steam reformation process for methanol - Google Patents

Abstract

A process for the catalytic steam reformation of methanol. A steam/methanol mixture is supplied at a specified temperature. The process takes place in at least two steps. In at least a first step (1) the methanol is incompletely reacted at high temperature using an optimal heat transition process. In at least one later step (6) the methanol reaction is completed. Also claimed apparatus for carrying and the process.

Description

The invention relates to a method and an apparatus for Catalytic steam reforming of methanol according to the Preamble of the main claim.

From JP-AB 63-166701 is a plate-shaped device for Methanol reforming known by the arrangement of Alternating plates with spacers in between Reaction and boiler rooms are formed. The reaction rooms are filled with a catalyst material, with the help of which introduced methanol is reformed with the supply of heat.

The object of the invention is a method and Reduced methanol reforming apparatus To create space.

The object is achieved by the characterizing Features of claim 1 solved.

The two-stage reform process makes it possible to get one provide compact reactor with sufficient yield. In the first stage, which optimizes the heat input is the required energy of the reaction as isothermal as possible fed. The yield is then in a second stage, the is optimized in terms of sales. Since the second stage also operated at somewhat lower temperatures it is also possible to reduce the proportion of CO in the reformed gas to reduce.

Further advantages and configurations result from the subclaims Chen and the description. The invention is as follows described in more detail with reference to a drawing, wherein

Fig. 1 shows the basic structure of a device according to the invention,

Fig. 2 shows an embodiment of a plate-shaped reactor

Fig. 3 shows another embodiment of a plate-shaped reactor, and

Fig. 4 shows an embodiment for a tubular reactor.

Catalytic steam reforming is a mixture from methanol and water vapor with the supply of heat to one suitable catalyst converted to hydrogen, wherein at the same time carbon dioxide is generated:

CH₃OH + H₂O → 3 H₂ + CO₂

This reaction can be divided into the strongly endothermic Pyrolysis

CH₃OH → 2 H₂ + CO

and into the weakly exothermic shift reaction:

CO + H₂O → CO₂ + H₂

In mobile applications, such as water vapor reform for fuel cells in motor vehicles, it is important that the required yield of hydrogen gas possible as little space and weight as possible can. Since the reaction only takes place with the addition of heat, it is However, the yield depends on the heat input. Therefore, the Reactor be designed so that an optimal heat transfer from a provided heat transfer medium on the reform gas and on the catalyst material is guaranteed. For this purpose, in generally a variety of elaborately designed heating channels  needed so that the proportion of the filled with catalyst Volume of the total volume reduced. Since the yield, however also depends on the amount of active catalyst, this means at the same time again a reduction in the yield. So is it is crucial to reform the methanol with regard to this optimize both factors.

Fig. 1 shows a two-stage device for reforming of methanol, comprising a first reactor 1 and second reactor 6. The methanol / water vapor mixture is fed to the first reactor 1 via a feed line 2 . Line via a first heater 3 to the reactor 1 is also fed to a heat transfer medium and removed again after flowing through the reactor 1 via a first discharge line. 4 After flowing through the reactor 1 , the gas mixture, which still contains portions of unreacted starting materials, is passed on to a second reactor 6 via a connecting line 5 . The product gas formed during the reforming, primarily a mixture of hydrogen and carbon dioxide, is then discharged via an outlet line 7 . The second reactor 6 can also be supplied via a second heating line 8 , a heat transfer medium, which is then discharged again via a second outflow line 9 . In principle, both liquid and gaseous heat transfer media can be used. In particular, the second reaction stage 6 can also be heated electrically. The exact structure of the two reactors 1 , 6 is described in more detail below with reference to FIGS. 2 to 4.

With the help of the arrangement described above, the reforming of the methanol / water vapor mixture is carried out in a two-stage process. The first stage, which takes place in the first reactor 1 , is optimized with regard to the heat transfer between the heat transfer medium and the catalyst material or the gas to be reformed. Here, the conversion of the methanol is carried out at a temperature of 250 ° -350 ° Celsius, the degree of conversion in this first stage preferably being less than 90%.

In the second stage, the conversion of methanol is then completed. For this purpose, this second stage 6 should have a favorable ratio of reactor mass to catalyst mass. In addition, the second stage 6 for reducing the CO content can be operated at slightly lower temperatures and only slightly heated or adiabatically. For the second stage 6 , a catalyst is also used, wherein in the two stages 1 , 6 different, optimized for the respective process catalysts can be used. In principle, it is also possible to integrate both stages in a common arrangement. The entire reaction is operated under pressure, preferably 1-15 bar.

There are three possibilities for the combination of the two stages 1 , 6 , whereby in principle the first stage 1 is optimized in terms of heat input and the second stage 6 is optimized in terms of sales. The first possibility is to carry out steam reforming at 250 ° -350 ° C in both stages 1 , 6 . Furthermore, the second stage 6 can also be operated at temperatures of 150 ° to 250 ° C., the CO shift reaction preferably taking place here. In the third possibility, only the pyrolysis is carried out at 250 ° -350 ° C in the first stage 1 , the CO shift reaction at 150 ° -250 ° C being carried out in the second stage 6 .

The basic structure of a plate-shaped reactor 16 will now be described in more detail with reference to FIGS. 2 and 3, only one single cell being shown in each case. The entire plate reactor 16 can be constructed from a large number of such individual cells. In the exemplary embodiment according to FIG. 2, the plate reactor 16 consists of several partition plates 10 , through which reaction channels 11 and heating channels 12 are alternately formed. In the reaction channel 11 , to which the methanol / water vapor mixture is fed via the feed line 2 , a catalyst bed 13 is introduced. Between the partition plates 10 , which form the heating channel 12 , a support or flow guide structure 14 is also introduced. The heating channels 12 are supplied with the heat transfer medium via the heating line 3 , 8 .

FIG. 3 shows a further exemplary embodiment, the same parts being identified with the same reference numerals as in FIG. 2. In contrast to FIG. 2, no catalyst bed 13 is used here, but rather the inner sides of the separating plates 10 facing the reaction channels 11 are coated with a suitable catalyst material 13 . In order to ensure the stability of the device and to distribute the gas flow, in this arrangement a support or flow guide structure 14 is also introduced in the reaction channels 11 , which can also be coated with catalyst material 13 . It is also possible to integrate the support or flow guide structure 14 for the heating channels 12 and / or the reaction channels 11 directly into the separating plates 10 . Instead of coating the partition plates 10 with catalyst material 13 , it is also possible to insert one or more catalyst mats 13 between the partition plates 10 . The reaction channels 11 are then either formed via separate supports or flow guide structures 14 or are worked directly into the catalyst mats 13, for example by stamping or rolling.

If both stages 1 , 6 are formed as a plate-shaped reactor, these can also be arranged between common end plates to further reduce the weight.

Fig. 4 shows a second stage to be used as tubular reactor 17, which is designed as a simple bulk reactor. The cylindrical housing 18 of the tubular reactor 17 is connected at the end faces to the connecting line 5 and the outlet line 7 . Within the housing 18 , a plurality of parallel deflecting structures 19 are provided , each of which is arranged perpendicular to the longitudinal axis of the housing. The deflecting structures 19 can be formed, for example, by circular plates, the circumferences of which each abut the housing and in which a circular section is recessed on opposite sides. This results in a meandering flow pattern for the gas mixture. To supply thermal energy, one or more heating devices 15 can additionally be provided, which consist of a tube coil through which the heat transfer medium flows or an adequate electrical heater. This tube reactor 17 can be formed with a large diameter, so that a favorable ratio of reactor mass to catalyst mass is achieved.

Claims (9)

1. A process for the catalytic steam reforming of methanol, the steam / methanol mixture is maintained by supplying heat energy at a predetermined temperature, characterized in that at least two reforming stages (1, 6) are provided, wherein in the at least one first stage (1) the methanol is incompletely converted in a heat transfer-optimized process at a higher temperature, and a reaction which completes the methanol conversion is carried out in the at least one downstream stage ( 6 ). 2. The method according to claim 1, characterized in that the first stage ( 1 ) is operated at a temperature of 250 ° -350 ° C. 3. The method according to claim 1, characterized in that in the at least one first stage ( 1 ) preferably the pyrolytic cleavage of the methanol is carried out. 4. The method according to claim 1, characterized in that in the at least one second stage ( 6 ) preferably a CO shift reaction is carried out at a temperature of 150 ° -250 ° C. 5. The method according to claim 1, characterized in that in the first and second stage ( 1 , 6 ) different, optimized for the respective reaction catalysts ( 13 ) are used. 6. Apparatus for performing the method according to claim 1, characterized in that as a first stage ( 1 ) a plate-shaped reformer ( 16 ) and as a second stage ( 6 ) a plate-shaped reformer ( 16 ) or a reformer ( 17 ) in tube or Tube bundle arrangement is used. 7. The device according to claim 6, characterized in that a tubular reactor ( 17 ) is used as the second stage ( 6 ), in the cylindrical housing ( 18 ) perpendicular to the longitudinal axis deflecting structures ( 19 ) are arranged such that there is a meandering flow pattern. 8. The device according to claim 6, characterized in that a plate-shaped reformer ( 16 ) is used as the first and second stage ( 1 , 6 ), wherein both stages ( 1 , 6 ) are arranged between common end plates. 9. The device according to claim 6, characterized in that the required thermal energy is supplied via a heat transfer medium or via an electrical resistance heater ( 15 ).