JPH0235684B2 - METANOORUKARANOSUISOSEIZOHO - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing hydrogen from methanol,
In detail, using a multi-stage reactor, specify the methanol and steam supply ratio of the first stage reactor, and
By dividing and supplying steam at a specific ratio to the stage reactor and the second and subsequent stage reactors, the reaction can be carried out at low temperatures, improving the yield of hydrogen gas obtained and also increasing the amount of hydrogen gas necessary for the reaction. This invention relates to a method for producing hydrogen from methanol that can reduce energy consumption.

[Prior Art] Conventionally, as a method of obtaining hydrogen using methanol as a raw material, a steam reforming method of methanol is known. For example, the steam reforming method for methanol involves reacting methanol and steam as follows.

CH ₃ OH + H ₂ O → 3H ₂ + CO ₂ −11.86 kcal/mol ………(1) Various steam reforming methods are known, but for example, Japanese Patent Laid-Open No. 59-39701 describes Disclosed.

The steam reforming method disclosed in JP-A-59-39701 uses two reactors: an externally heated main reactor and an adiabatic side reactor, and a heating furnace for the main reactor and a preheater for the side reactor. This method is characterized in that the temperature of the side reactor is controlled by sharing the same.

However, in the conventionally known steam reforming methods for methanol, each method has the problems described below, so it is difficult to sufficiently improve the yield of hydrogen gas without increasing the amount of steam supplied or energy consumption. It is not possible.

[Problems to be solved by the invention] In the methanol steam reforming method, a method for improving the yield of hydrogen gas is to increase the amount of steam relative to the amount of methanol supplied when reacting methanol and steam. A method of carrying out the reaction by supplying excess amount, that is, the ratio of the total amount of steam supplied/total amount of methanol supplied (hereinafter referred to as S/
One possible method is to increase the M ratio. However, when carried out on an industrial scale, this method requires too much steam and is economically disadvantageous.

It is also known that the yield of hydrogen gas can be improved by carrying out the steam reforming reaction of methanol at low temperatures. However, if the reaction temperature is simply lowered using the commonly used S/M ratio, capillary condensation of steam will occur in the pores of the catalyst when the dew point is approached, making it difficult to lower the reaction temperature to the desired low temperature. I can't. For example, in the steam reforming method for methanol described in JP-A No. 59-39701, no consideration is given to carrying out the reaction at a particularly low temperature; for example, in the examples, the reaction is carried out at a high temperature of 300°C or higher. is being carried out. This method therefore requires a normal S/M ratio (e.g. 0.5
~7.0) and conduct the reaction at a low temperature of around 200°C, capillary condensation of steam occurs on the catalyst in the main reactor. If the S/M ratio is made smaller, the dew point will be lowered, but the amount of steam supplied will be reduced, and the yield of hydrogen gas will be reduced. Furthermore, the reaction can be carried out at low temperatures by using a special highly active catalyst, but this catalyst is generally expensive and therefore not suitable for industrial use.

Under the circumstances described above, when carrying out steam reforming of methanol on an industrial scale, a method is desired which allows the reaction to be carried out at low temperatures without particularly changing the S/M ratio.

The present invention has been made in view of the above-mentioned problems, and it improves the yield of hydrogen gas obtained by making it possible to carry out the reaction at low temperature without changing the S/M ratio, and also improves the yield of hydrogen gas necessary for the reaction. The purpose of this invention is to provide a method for producing hydrogen from methanol that can reduce energy consumption.

As a result of intensive research to achieve the above object, the present inventors installed reactors in multiple stages and determined that the amount of steam supplied to the first stage reactor/the amount of methanol supplied (hereinafter referred to as
The dew point in each reactor can be lowered by setting the S ₁ /M ₁ ratio in a specific range and supplying steam at a specific ratio to the first stage reactor and each reactor after the second stage. The present invention was achieved by discovering that this can be done.

[Means and effects for solving the problems] That is, the present invention is a method for producing hydrogen from methanol, in which hydrogen gas is produced from methanol using reactors provided in multiple stages, the first reactor having: Steam/methanol 1.0
Methanol and steam are supplied so that the amount of steam supplied to the first stage reactor/the amount of steam supplied to the second and subsequent reactors is less than 1.0 (mole ratio). This is a method for producing hydrogen from methanol, which is characterized by supplying steam in parts.

The present invention is characterized by lowering the dew point without changing the S/M ratio in the reactor, and for this purpose, the reactor is of a multistage type, and the S ₁ /M of the first stage reactor is ₁ ratio is specified, and steam is divided and supplied at a specific ratio to the first stage reactor and the second and subsequent stage reactors.

In other words, methanol and steam supplied to the first stage reactor have an S ₁ /M ₁ ratio of less than 1.0 (molar ratio).
The steam supply amount to the first stage reactor/the steam supply amount to the second and subsequent reactors (hereinafter referred to as steam supply ratio) should be 1.0 (molar ratio) or less. necessary and preferably
It is 0.5 (molar ratio) or less. The reasons for limiting the S ₁ /M ₁ ratio and the steam supply ratio are as follows.

When hydrogen is produced from methanol, the decomposition reaction of formula (2) and the CO shift reaction of formula (3) coexist in the steam reforming of methanol, resulting in the reforming reaction of formula (1) described above. Also, without steam reforming
It is also possible to carry out the decomposition reaction of formula (2) and the CO shift reaction of formula (3) separately.

CH ₃ OH→CO+2H ₂ −21.7kcal/mol ………(2) CO＋H ₂ O→CO ₂ H ₂ +9.84kcal/mol ………(3) Regarding this reaction, consider a process using two reactors. do. Assuming that a total of a mole of steam is added to react with 1 mole of methanol, x moles of the a mole of steam are added to the first stage reactor, and (ax) moles of steam are divided into the second and subsequent reactors. We will supply it.

First, the reaction in the first stage reactor occurs as follows.

xCH ₃ OH + xH ₂ O → xCO ₂ +3xH ₂ (1-x) CH ₃ OH → (1-x) CO + 2 (1x) H ₂ In other words, x moles of added steam are completely consumed in the reaction of equation (1), Remaining methanol (1-x)
Moles are decomposed by the reaction of equation (2). Strictly speaking, since a chemical equilibrium exists, the reaction does not proceed completely to the right, but it is practically negligible. In addition, x
When is 0, only the decomposition reaction of equation (2) will occur. At this time, if x is 1.0 or more, it is similar to the conventional method with excessive steam, and the dew point in the first reactor cannot be lowered. Therefore, in the present invention, S ₁ /
It is necessary that the M ₁ ratio is less than 1.0.

The reactors from the second stage onwards are equipped with divided steam (a-
x) moles and the outlet gas of the first stage reactor will be supplied, but since the outlet gas of the first stage reactor is (3+x) moles, the fraction of steam in the second stage reactor will be The pressure will be lower and the dew point will also be lower.

Further, assuming that the total pressure is π, the partial pressure of steam in the first stage reactor is xπ/(1+x), and that in the second and subsequent stage reactors is (ax)π/(3+a). Here, the danger of steam condensation and the
The dew point of both can be lowered most efficiently when the steam is distributed equally to the reactors after the stage, so the steam normally supplied to a is calculated as xπ/(1+x)=(a-x)π/(3+a). By substituting the quantities, the optimal value of x can be calculated. From this equation, in the general S/M ratio range of 0.5 to 7.0 in steam reforming of methanol, it is desirable to set the steam supply ratio to 1.0 or less, preferably 0.5 or less.

In the present invention, the entire amount of steam can be supplied to the second and subsequent stage reactors without supplying any steam to the first stage reactor. In this case, the first
In the stage reactor, only the above-mentioned decomposition reaction of formula (2) occurs, and in the second and subsequent stage reactors, the CO decomposition reaction of formula (3) occurs.
A shift reaction will occur. Therefore, the outlet gas of the first stage reactor is used in the second and subsequent stage reactors.
Since CO and hydrogen gas are supplied, even if the entire amount of steam is injected, the partial pressure of steam can be lowered, and the dew point can be lowered.

Hereinafter, the present invention will be specifically explained based on the drawings.

FIG. 1 is a process sheet showing one embodiment of the present invention. In the figure, raw methanol is supplied to a first stage reactor 3 through a methanol supply line 1. In this case, as shown by the dotted line,
Methanol may be supplied in portions to the second stage reactor. On the other hand, steam is dividedly supplied to a first stage reactor 3 and a second stage reactor 4 through a steam supply line 2. A heat medium circulation line 7 is provided between the first stage reactor 3 and the heating furnace 5 via a pump 6, and the inside of the first stage reactor 3 is kept at a predetermined temperature. The capillary condensation of steam mentioned above starts at a temperature approximately 10°C higher than the dew point temperature, so in the present invention, the reaction is carried out at a temperature 10 to 50°C higher than the dew point temperature in the reactor.
It is necessary to carry out the process at a temperature higher than 10°C. In the present invention, by appropriately adjusting the _S1 / _M1 ratio and the steam supply ratio, the dew point can be lowered to around 80℃ even when raw materials are supplied with the same S/M ratio as before. be able to. Therefore, in the present invention, the reaction can be carried out at a low temperature of 190 to 300°C, preferably 190 to 250°C. Note that the reaction takes place at a pressure of 0.
~50 Kg/cm ² ·G, preferably carried out in the presence of a copper-based catalyst.

Next, the outlet gas from the first stage reactor 3 is supplied to the second stage reactor 4 through the outlet gas line 8a, and the steam is supplied to the second stage reactor 4 through the steam supply line 2.
Supplied from. Further, methanol is supplied from the methanol supply line 1 if desired. In the second stage reactor 4, a Cu/Zn based catalyst is preferably used, and the conditions such as temperature and pressure are substantially the same as in the first stage reactor.

The outlet gas from the second stage reactor 4 contains H ₂ and CO ₂ as main components, and also contains small amounts of unreacted steam, unreacted methanol, and CO. This outlet gas passes through the outlet gas line 8b and passes through the cooler 10 and the gas-liquid separator 11.
Sent to PSA system 12. PSA system 1
In step 2, CO ₂ and residual CO are separated and removed,
Hydrogen gas is purified.

Next, a method of supplying the entire amount of steam to the second stage reactor without supplying steam to the first stage reactor will be explained.

Figure 2 shows that in the present invention, the total amount of steam is
It is a process sheet showing an example of feeding to a stage reactor. In the figure, methanol is supplied to a first stage reactor 3 through a methanol supply line 1. On the other hand, steam passes through the steam supply line 2 and is supplied only to the second stage reactor 4a via the heat exchanger 9 and the evaporator 13. Second stage reactor 4a
In this case, the CO shift reaction of equation (3) described above occurs, so it is necessary to remove the reaction heat. This reaction heat is removed by a water circulation line 14 provided between the evaporator 13 and the second stage reactor 4a. Other equipment is approximately the same as the process shown in FIG.

In FIG. 1 and FIG. 2, only two stages of reactors are provided, but in the present invention, three or more stages can also be provided. Further, in the present invention, the type of reactor is not particularly limited, but it is preferable that at least the first stage reactor is an external heating type. Furthermore, it is desirable that the second and subsequent stage reactors be adiabatic reactors from the viewpoint of cost. In this case, as described above, in order to utilize the reaction heat of methanol, it is preferable to supply a portion of the methanol in portions to the adiabatic reactors in the second and subsequent stages.

[Examples] The present invention will be described below based on Examples and Comparative Examples. Note that for Examples 1 and 2, reactions were carried out using substantially the same process as shown in FIG. 1, and for Examples 3 and 4, reactions were carried out using substantially the same process as shown in FIG. Furthermore, in Comparative Example 1, the reaction was carried out using only one stage reactor.

Example 1 Methanol 10Kg/hr and steam 2.81Kg/hr
is supplied to an externally heated first stage reactor filled with 30 kg of methanol reforming catalyst, and the reaction is carried out at a temperature of 195 to 200°C and a pressure of 15.5 kg/cm ² G. 14.01Kg/hr of H ₂ O was added to the gas and supplied to an externally heated second stage reactor filled with 60Kg of methanol reforming catalyst, and the mixture was heated at 195-200℃, 15.0Kg/cm ² .
The reaction was carried out while maintaining the temperature at G.

When the outlet gas of the second stage reactor was cooled and unreacted steam and unreacted methanol were condensed and removed, a gas with a composition of 74.8% by volume of H ₂ , 24.3% by volume of CO ₂ and 0.9% by volume of CO was produced at 27.7Nm ³ /hr was able to be obtained. This yield did not change even after 10 hours had passed after the start of the reaction. Furthermore, the dew point at the inlet of the first stage reactor is
The temperature was 155°C, and that at the second stage reactor inlet was 160°C.

Comparative example 1 Methanol 10Kg/hr and steam 1.687Kg/hr
hr was supplied to an externally heated reactor packed with 90 kg of methanol reforming catalyst at a temperature of 195-200℃ and a pressure of 15.0℃.
The reaction was carried out while maintaining the temperature at Kg/cm ² ·G.

When the outlet gas was cooled to condense and remove unreacted steam and unreacted methanol, a gas with a composition of 74.9% by volume of H ₂ , 24.9% by volume of CO ₂ and 0.2% by volume of CO was initially obtained at 20.2Nm ³ /hr. Ta. However, the yield gradually decreased and after 5 hours, almost no gas could be obtained.

After the experiment was completed, the catalyst inside the reactor was taken out and observed, and it was confirmed that water was capillary condensed in the pores. Note that the dew point at the inlet of the reactor was 187°C.

Example 2 Methanol 10Kg/hr and steam 2.81Kg/hr
is supplied to an externally heated first stage reactor filled with 30 kg of methanol reforming catalyst, and the reaction is carried out at a temperature of 195 to 200°C and a pressure of 15.5 kg/cm ² G. Methanol 3.6Kg/hr and
Methanol reforming catalyst 130 by adding H ₂ O20.12Kg/hr
Kg is supplied to an adiabatic second-stage reactor filled with 2 kg, and the reactor inlet temperature is set at 195-200°C and the pressure is set at 15.0 Kg/ ^cm2 .
The reaction was carried out while maintaining the temperature at G. At this time, the reactor outlet temperature was 195-200°C.

When the outlet gas of the second stage reactor was cooled and unreacted steam and unreacted methanol were condensed and removed, a gas with a composition of 74.9% by volume of H ₂ , 24.8% by volume of CO ₂ and 0.3% by volume of CO was produced at 38.0Nm ³ /hr was able to be obtained. This yield did not change even after 10 hours had passed after the start of the reaction. Furthermore, the dew point at the inlet of the first stage reactor is
The temperature at the second stage reactor inlet was 167°C.

Example 3 Methanol 10Kg/hr was mixed with methanol decomposition catalyst 60Kg/hr.
The gas is supplied to an externally heated first stage reactor filled with Kg, and the reaction is carried out at a temperature of 195 to 200℃ and a pressure of 15.5Kg/ ^cm2・G.
16.9Kg/hr of H ₂ O was added and supplied to an externally cooled second reactor filled with 60Kg of low-temperature shift catalyst.
The reaction was carried out while maintaining the temperature at 15.0°C/cm ² ·G.

When the outlet gas of the second stage reactor was cooled and unreacted steam and methanol were condensed and removed, H ₂ 74.9
It was possible to obtain 27.9 Nm ³ /hr of gas having a composition of 24.9 volume % CO ₂ and 0.2 volume % CO 2 . This yield did not change even after 10 hours had passed after the start of the reaction.

Example 4 Methanol 10Kg/hr was mixed with methanol decomposition catalyst 60Kg/hr.
The gas is supplied to an externally heated first stage reactor filled with Kg, and the reaction is carried out at a temperature of 195 to 200℃ and a pressure of 15.5Kg/ ^cm2・G.
Adiabatic type 2nd tank filled with 120Kg of low temperature shift catalyst with addition of 8.7Kg/hr of H ₂ O and 7Kg/hr of methanol.
Feed into the stage reactor and keep the reactor inlet temperature at 195-200
The reaction was carried out while maintaining the temperature and pressure at 15.0 Kg/cm ² ·G. At this time, the reactor outlet temperature was 200°C.

When the outlet gas of the second stage reactor was cooled and unreacted steam and unreacted methanol were condensed and removed, a gas with a composition of 74.9 volume % H ₂ , 24.9 volume % CO ₂ , and 0.2 volume % CO was produced at 47.5 Nm ³ /hr was able to be obtained. This yield did not change even after 10 hours had passed after the start of the reaction.

[Effects of the Invention] As explained above, by using two or more multi-stage reactors, the steam/methanol ratio (S ₁ /M ₁ ratio) of the first stage reactor and the steam supply amount / According to the method for producing hydrogen from methanol of the present invention in which the steam supply amount (steam supply ratio) of the second stage and subsequent reactors is set within a specific range, in particular, the total steam supply amount/total methanol supply amount (S/M ratio ) The dew point inside the reactor can be lowered without changing the temperature, and the reaction can be carried out at low temperatures. Therefore, the yield of hydrogen gas can be improved, and
Since the reaction temperature is low, energy consumption can be reduced compared to conventional methods.

Further, in the present invention, since it is only necessary to extend the steam supply line to the supply ports of the second stage and thereafter, the equipment does not need to be particularly expensive or large-sized, and has great industrial utility value.

For this reason, the present invention is suitably used as a method for producing hydrogen from methanol.

[Brief explanation of drawings]

FIG. 1 is a process sheet showing one embodiment of the invention, and FIG. 2 is a process sheet showing another embodiment of the invention. 1... Methanol supply line, 2... Steam supply line, 3... First stage reactor, 4, 4a...
Second stage reactor, 5... Heating furnace, 6... Pump, 7
... Heat medium circulation line, 8a, 8b ... Outlet gas line, 9 ... Heat exchanger, 10 ... Cooler, 1
1... Gas-liquid separator, 12... PSA system, 1
3...Evaporator, 14...Water circulation line.

Claims (1)

[Scope of Claims] 1. A method for producing hydrogen from methanol in which hydrogen gas is produced from methanol using reactors provided in multiple stages, wherein the first stage reactor has a ratio of steam/methanol of 1.0
Methanol and steam are supplied so that the amount of steam supplied to the first stage reactor/total amount of steam supplied to the second and subsequent reactors is less than 1.0 (mole ratio). A method for producing hydrogen from methanol, characterized by supplying steam in parts. 2 The reaction in each of the multi-stage reactors is below the dew point.
The method for producing hydrogen from methanol according to claim 1, which is carried out at a temperature 10 to 50°C higher.