CN103466546B - Intermediate temperate pressure swing adsorption method for using bifunctional adsorbent in adsorption enhanced type vapor reforming and water-vapor transformation reactions - Google Patents

Abstract

The invention discloses a medium-temperature pressure-swing adsorption method that applies a dual-function adsorbent to adsorption-enhanced steam reforming and water-gas shift reactions, which belongs to the technical field of clean energy. In the present invention, a dual-function adsorbent is added to the reactor, which has dual functions of catalytic reaction and decarburization and desulfurization. The process enables multi-step hydrogen production reactions to be carried out in the same reactor under medium temperature conditions, which reduces the investment in system equipment and simplifies the process flow; the temperature of the reforming reactor is lower, the requirement for steel is lowered, and the cost of equipment is reduced; it can be recycled directly Sensible heat of raw material gas improves the overall thermal efficiency of the system, reduces system heat exchange equipment, and reduces system cost; adsorbent adsorption/regeneration can be realized without temperature rise and fall, energy consumption is reduced, and the regeneration speed of adsorbent is fast, which can improve the pressure swing adsorption system. gas handling capacity.

Description

A Medium Temperature Pressure Swing Adsorption Method Using Dual Function Adsorbents for Adsorption Enhanced Steam Reforming and Water Gas Shift Reactions

technical field

The invention belongs to the technical field of clean energy, and specifically relates to a method for using a dual-function adsorbent to carry out adsorption-enhanced steam reforming, water-gas shift reaction and medium temperature pressure swing adsorption.

Background technique

With the increasingly prominent energy and environmental issues, H ₂ has attracted much attention as a clean and efficient fuel, and hydrogen is also an important raw material in the chemical industry. Methane steam reforming is the main way of traditional large-scale industrial hydrogen production. In addition, other hydrocarbon fuels can be steam reformed and coal gasification synthesis gas can also be produced by water gas shift reaction. Taking the steam reforming of methane as an example, in the traditional industrial route, the raw material gas needs to go through three process steps of reforming reactor, water gas shift reactor and purification device to finally produce high-purity hydrogen. Methane and water vapor first react in the reformer (1) to produce _H2 and CO, then enter the water gas shift reactor for reaction (2) further increase the _H2 yield, and finally remove the product gas through the purification device CO ₂ etc. to obtain high-purity H ₂ .

Reformation reaction:

Water gas shift reaction:

Both the reforming reaction and the water-gas shift reaction are reversible reactions, and it is difficult to achieve complete conversion of CH ₄ and CO. In addition, the reforming reaction is a strong endothermic reaction. In order to increase the conversion rate, it is necessary to use an external heat source for heating. Usually, it is necessary to maintain the operating temperature at 800-900 ° C and the pressure at 1.5-2 MPa. It is produced by the water-gas shift reaction The product gas temperature is usually between 200-450°C. However, the mature and applied CO ₂ /H ₂ separation process mainly includes normal temperature or low temperature wet decarburization technology (such as Selexol/NHD technology, active MDEA technology, low temperature methanol washing technology), and it is necessary to first clean the syngas after water gas shift. Perform cooling treatment to waste gas sensible heat.

Absorption (adsorption)-enhanced steam reforming (or syngas water-gas shift) adds a _CO2 absorption (adsorption) agent to a conventional reforming (or syngas water-gas shift) reactor. According to Le Chatelier's principle, when the CO ₂ generated by the reforming reaction and the water-gas shift reaction is absorbed, the reaction will proceed in the direction of increasing H ₂ , thereby significantly increasing the conversion rate of raw materials. Due to the enhancement of _CO2 absorption (adsorption), hydrogen production by steam reforming of hydrocarbon fuels can complete reforming reaction, water-gas shift reaction and _H2 purification in one reactor; coal gasification synthesis gas water-gas shift reaction and _H2 purification can also be done in one reactor.

The CO ₂ removal process in the reforming (or water gas shift) reactor includes chemical absorption and pressure swing adsorption (Pressure Swing Adsorption, PSA). The chemical absorption method is represented by calcium-based adsorbent, and its principle is: after the calcium-based adsorbent reacts with _CO2 in the reforming (or water-gas shift) reactor, the _CO2 in the gas is removed, and the adsorbed saturated The adsorbent enters the regeneration reactor to be calcined to decompose CO ₂ , and the adsorption and regeneration are carried out alternately, so as to realize the separation and recovery of carbon dioxide. However, the regeneration temperature of calcium-based adsorbents is high, which consumes a lot of energy, and is easy to cause sintering of adsorbent particles, which affects the stability of the cycle.

The basic principle of PSA technology is to use the difference in the adsorption characteristics of gas components on solid porous adsorbents and the characteristics of the adsorption capacity changing with pressure changes, and realize the separation or purification of gases through periodic pressure change processes. According to the product to be separated is in adsorption or non-adsorption state in the adsorption bed, it can be divided into adsorption phase product and non-adsorption phase product. For example, the composition of syngas in hydrocarbon fuel and coal gasification, biomass gasification, petrochemical, natural gas and other industries varies with different raw materials, and its basic composition mainly includes: C _x H _y , CO ₂ , CO, O ₂ , N ₂ , H ₂ , H ₂ S, H ₂ O, etc. Among the above components, H ₂ O, CO ₂ , and H ₂ S are usually strong adsorption components, C _x H _y , and CO have intermediate adsorption capabilities, O ₂ and N ₂ are weak adsorption components, and H ₂ hardly adsorbs. Typically, in a PSA system, multiple adsorption columns packed with adsorbent are used. The raw material gas is introduced into each adsorption tower, and the target product gas is obtained by repeating the adsorption-enhanced hydrogen production process, the decompression process, the desorption process and the boosting process. The principle of obtaining the target gas is described as follows: If the pressure of the gas in the adsorption tower becomes higher, the partial pressure of the exhaust gas generated by the reaction of the raw material gas also becomes higher, and as a result, the exhaust gas components are adsorbed by the adsorbent filled in the adsorption tower ( That is to remove some gas components from the gas in the tower), improve the conversion efficiency of raw gas, and discharge the gas in the tower in this state, that is, to obtain the product gas with less gas components. After that, as the pressure in the adsorption tower decreases, or by non Adsorbed gas purging, desorption of gas components from the adsorbent (adsorbent regeneration), the desorbed components and other components become non-adsorptive target gases, and the regenerated adsorbent can be further used to remove from the newly introduced raw material gas reaction To exclude gas components, the adsorbent used in each adsorption tower should be selected according to the type of target gas or the type of gas to be removed. For example, if _CO2 is removed from the raw gas to obtain _H2 product gas, activated carbon and molecular sieve adsorbents are usually used .

At present, the PSA gas separation method has been widely used in the fields of natural gas, coal-fired boiler flue gas, synthetic ammonia shift gas, roasting tail gas in alumina production, and _CO removal and recovery in lime kiln gas. However, there are disadvantages such as complex operation, high energy consumption, high cost, and large equipment corrosion in decarburization and desulfurization. However, the traditional PSA adsorption separation process is limited by the adsorbent and equipment operating conditions, and often can only be operated at room temperature (such as 20-45°C). At the same time, common PSA adsorbents (such as molecular sieves) are also very sensitive to the presence of H ₂ O. When H ₂ O coexists with other gases, they will preferentially and selectively absorb H ₂ O. The reforming reaction or the water-gas shift reaction cannot be carried out simultaneously in the same reactor, and the product gas of the reforming reaction or the water-gas shift reaction needs to be cooled and dehydrated before passing through an independent PSA system to purify hydrogen. If the catalyst and adsorbent are directly mixed or used in combination, on the one hand, the catalytic reaction and the adsorption reaction are not coupled in situ, and the efficiency is low; on the other hand, the amount of catalyst and adsorbent required will increase, which will increase the volume of the reactor. Thereby increasing the equipment cost. In addition, some raw gas may also contain H ₂ S, and a desulfurization device needs to be installed, which increases the system complexity and investment cost.

Contents of the invention

The object of the present invention is to provide a medium-temperature pressure swing adsorption method that applies a dual-functional adsorbent to an adsorption-enhanced steam reforming reaction and a water-gas shift reaction.

A medium-temperature pressure-swing adsorption method that applies dual-functional adsorbents to adsorption-enhanced steam reforming and water-gas shift reactions. The dual-functional adsorbents are packed in the adsorption tower, which can make steam reforming reactions and water-gas shift reactions The reaction and medium-temperature pressure swing adsorption purification of hydrogen are completed in the same reactor, and the reaction temperature is 200-500°C; the dual-function adsorbent has dual functions of catalyzing steam reforming, water-gas shift reaction and decarbonization and desulfurization. The above-mentioned dual-function adsorbent is a medium-temperature adsorbent or a mixture of a medium-temperature adsorbent and a low-temperature adsorbent, and the medium-temperature adsorbent in the mixture accounts for more than 2% and less than 100% of the total mass of the adsorbent; the specific process is to pass the feed gas through two The product gas is obtained after one or more adsorption towers, and pressure filling, adsorption-enhanced hydrogen production reaction, product gas recovery, pressure equalization and pressure reduction, forward pressure release, reverse pressure release, and steam desorption are completed in each adsorption tower. , flushing, pressure equalization boost and final charge steps.

The above-mentioned dual-functional adsorbent not only has the functions of decarbonization and desulfurization, but also has weak adsorption to H ₂ O, so it can be directly applied to the purification of steam reforming and water-gas shift product gas. Moreover, the dual-functional adsorbent also has the functions of catalyzing steam reforming reaction and water-gas shift reaction, and has good activity at 200-500°C. Therefore, using this dual-functional adsorbent, the steam reforming reaction, the water-gas shift reaction and the medium-temperature pressure swing adsorption process can be carried out in the same reactor, which solves the problem that the PSA system cannot be integrated with the above two-step reactions in the same reaction. Defects carried out in the reactor and the shortcomings of the composite catalyst.

Each of the above-mentioned adsorption towers includes the following specific steps in a cycle:

(1) Pressure charging

Use raw material gas or product gas at a temperature of 200-500°C to increase the pressure of the adsorption tower until the adsorption pressure is 0.01-30MPa;

(2) Adsorption-enhanced hydrogen production reaction

The feed gas is sent into the adsorption tower from the bottom of the adsorption tower, and the steam reforming and water-gas shift reactions occur under the catalytic action of the adsorbent. At the same time, the easily adsorbed components CO ₂ and H ₂ S generated by the reaction are selectively adsorbed by the adsorbent, and the gases H ₂ , H ₂ O and N ₂ that are not easily adsorbed pass through the entire bed layer of the adsorption tower and are discharged from the outlet; When the leading edge moves to a certain position in the bed, the adsorption operation is stopped;

(3) Product gas recovery

The product gas is discharged from the product gas end. With the continuous discharge of the product gas, the pressure in the tower continues to drop. When the front of the adsorbed gas advances to a certain position, the recovery of the product is stopped;

(4) Pressure equalization and step-down

After the recovery of product gas is stopped, the product end of the adsorption tower continues to discharge gas, but this part of the gas is used to boost the pressure of another adsorption tower that completes the desorption process. This step can be changed according to the number of adsorption towers, which can be 1-6 times ;

(5) Release pressure in the forward direction

After equalizing and reducing the pressure, the gas will continue to be released along the direction of adsorption and return to the raw gas system. If the recovery volume of the product gas recovery step is large, and the pressure in the tower has dropped to the low pressure of the pressure swing adsorption system after the process of pressure equalization and pressure reduction is completed, this step is cancelled;

(6) Reverse pressure release

Release the gas in the adsorption tower along the opposite direction of adsorption, reduce the pressure, and this part of the gas can be returned to the raw gas system, or directly enter another adsorption tower that has completed the regeneration of the adsorbent;

(7) Vacuum pressure reduction

When the pressure of the adsorption bed is close to the atmospheric pressure, the adsorption tower is vacuumed and depressurized;

(8) Steam desorption

Steam is introduced into the adsorption tower to further reduce the partial pressure of the adsorbed gas and realize the regeneration of the adsorbent;

(9) rinse

The pressure of the adsorption tower is reduced to normal pressure by reverse pressure release. In order to further reduce the partial pressure of the impurity components, the method of flushing the adsorbent with the degassing is adopted to further reduce the partial pressure of the impurities in the adsorption tower and complete the regeneration of the adsorbent;

(10) Equalizing and boosting

The pressure of the adsorption tower that has completed regeneration is increased by adopting a pairwise pressure averaging method with the adsorption tower that has completed the adsorption process;

(11) Final charge

Pressure equalization can only increase the pressure of the adsorption tower to a certain extent, and there is still a certain difference between it and the pressure of the entire system. This part of the difference is finally charged with product gas to raise the pressure of the adsorption tower to the system pressure.

The above raw material gas contains C _x H _y , CO ₂ , CO, O ₂ , N ₂ , H ₂ , H ₂ S and H ₂ O, where x and y are both integers, 1≤x≤20, 4≤y≤42 ; The above-mentioned product gas is mainly H ₂ .

The above preferred C _x H _y , wherein both x and y are integers, 1≤x≤12, 4≤y≤26.

The above medium temperature adsorbent is hydrotalcite, hydrotalcite-like, modified hydrotalcite, modified hydrotalcite-like, Na ₂ O modified Al ₂ O ₃ , modified or unmodified double salt adsorbent or other A substance that realizes the adsorption and desorption of CO ₂ and H ₂ S under the condition of ℃; the low-temperature adsorbent is molecular sieve or activated carbon.

The above-mentioned modified or unmodified hydrotalcite or hydrotalcite-like adsorption material is a compound of the following general formula:

[M ² _1-x M ³ _x (OH) ₂ ][A] _2-x yH ₂ O zM ¹ _2(1-w )M ³ _w B

Among them, M ¹ is Li ⁺ , Na ⁺ , K ⁺ , Cr ⁺ , Rb ⁺ and other monovalent cations or their mixtures; M ² is Mg ²⁺ , Ca ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Zn ²⁺ and other divalent cations or their mixtures; M ³ is Al ³⁺ , Cr ³⁺ , Mn ³⁺ , Co ³⁺ , Ni ³⁺ , La ³⁺ and other trivalent cations or their mixtures. [A] is NO ₃ ^- , SO ₄ ^2- , CO ₃ ^2- , Cl ^- , Br ^- , F ^- , I ^- , C _x H _y O _z ^n- ; B is O ^2- or CO ₃ ^2- ; n=1 or 2; x=0-1; y=0-4; z=0-7, w=0-1. A further preferred modified hydrotalcite adsorption material is a potassium-modified hydrotalcite or a potassium-modified hydrotalcite-like material.

The above modified or unmodified double salt adsorbent is a salt composed of two or more cations and one anion. Wherein, the cation is selected from the above-mentioned M ¹ , M ² or M ³ , and the anion is selected from the above-mentioned [A], O ^2- or CO ₃ ^2- . A further preferred double salt adsorbent is MgO-K ₂ O double salt.

Beneficial effects of the present invention: a dual-function adsorbent is added to the reactor, the adsorbent has dual functions of catalytic reaction and decarburization and desulfurization, the multi-step hydrogen production reaction can be carried out in the same reactor under medium temperature conditions, and the hydrogen purification equipment is eliminated It can reduce costs, simplify the process, and have high catalytic efficiency and feed gas conversion rate; it can recover the sensible heat of feed gas, improve the overall thermal efficiency of the system, and reduce heat exchange equipment, further reducing costs; adsorption can be realized without heating and cooling The adsorption/regeneration process of the agent, and the regeneration speed of the adsorbent is fast, which can improve the gas treatment capacity of the PSA system; it can realize the common removal of CO ₂ and H ₂ S components in the gas, which can reduce the desulfurization equipment and system complexity. When there is only CO ₂ in the feed gas, it is also possible to remove CO ₂ alone.

Description of drawings

Figure 1 is a schematic diagram of a medium-temperature pressure swing adsorption system for adsorption-enhanced hydrogen production with four towers;

Figure 2 is a schematic diagram of a medium-temperature pressure swing adsorption system for adsorption-enhanced hydrogen production with two tower configurations;

In the figure, A, B, C, D, 1 and 2 each represent an adsorption tower.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1:

This example adopts four adsorption tower configurations, as shown in Figure 1. The raw material gas is transported from the raw material gas buffer tank through the insulation pipeline, through the high temperature resistant program-controlled valve, to the adsorption tower; Steps of pressure release in direction, reverse pressure release, flushing, 2 pressure equalizations and final charge.

The composition of raw gas is as follows:

Raw gas pressure: 5MPa

Raw gas temperature: 400-450°C

The pressure of the four adsorption _towers is adjustable, and the adsorption tower is equipped with an adsorbent, which is composed of Mg-Al hydrotalcite modified by _K2CO3 , molecular sieve and activated carbon _, and Mg-Al hydrotalcite modified by _K2CO3 Accounting for 50% of the total mass of the adsorbent.

After the raw material gas enters the adsorption tower, it undergoes steam reforming and water-gas shift reaction under the catalysis of the dual-function adsorbent, and easily adsorbable gases such as CO ₂ and H ₂ S produced by the reaction are adsorbed by the adsorbent filled in the adsorber. The hydrogen flows out of the adsorption tower; when the adsorption capacity of the adsorbent reaches 60% of its saturated adsorption capacity, the adsorption towers will automatically switch between them, and the previously working adsorption tower will enter the depressurization regeneration state. After increasing the pressure to the working pressure, it enters the adsorption state.

The regeneration of the adsorption tower is mainly based on the principle that the adsorption capacity of the adsorbate on the mixed packing is different according to the pressure. When the pressure of the adsorption tower is reduced, the impurities adsorbed on the mixed packing will be desorbed automatically, and will be excluded from the adsorption tower. The filler is regenerated. The regeneration of the adsorption tower includes three states of pressure equalization and depressurization, reverse depressurization and steam flushing. Pressure equalization and depressurization means that the adsorption tower in the depressurization regeneration state distributes the gas in the adsorption tower to the adsorption tower in the pre-boost state and lower pressure, so that the residual gas in the adsorption tower can be effectively used and the gas in the adsorption tower can be avoided. Discharging the system will cause waste and improve the recovery rate; reverse depressurization refers to the adsorption tower in the decompression regeneration state. When its pressure is the lowest pressure among all adsorption towers, a part of this part of the remaining gas is collected through the reflux gas.

The following are the specific operation steps of the above-mentioned pressure swing adsorption enhanced hydrogen production process:

a. Adsorption enhanced hydrogen production reaction

The raw gas enters from the bottom of the adsorption tower, undergoes steam reforming and water-gas shift reaction, and the impurity components in the gas are selectively adsorbed by various adsorbents. Unadsorbed hydrogen is used as product gas. Through this step, qualified product gas is obtained.

b. Desorption

① Average pressure drop

The adsorbent that completes the adsorption process contains a large amount of impurity components. Using the characteristics of large adsorption capacity of the adsorbent at high pressure and low temperature, and small adsorption capacity at low pressure and high temperature, the operating pressure of the adsorbent is reduced by equalizing the pressure between the adsorption towers. The adsorbed impurities are partially desorbed.

② Release pressure in the forward direction

After a pressure equalization process is completed, a part of the gas with a high concentration of hydrogen is released along the direction of adsorption, which is used as the gas source of another adsorption tower in the flushing step to reduce the impurity partial pressure in the flushing tower, so that the flushing tower can be regenerated. And through releasing the pressure in the forward direction, the self-generated pressure of the adsorption tower is reduced, and the impurities are partially desorbed.

③Reverse pressure release

After the pressure equalization process is completed, the adsorption tower generally still has a certain pressure. At this time, the adsorption tower is filled with desorbed impurity components, and this part of impurities is released from the adsorption tower against the direction of adsorption, and the pressure of the adsorption tower is close to normal pressure through the reverse pressure prevention process.

④Vacuum pressure reduction

After the pressure of the adsorption tower is reduced to close to normal pressure by reverse pressure release, the adsorption tower is continuously vacuumed and depressurized.

⑤Steam flushing

In order to further reduce the partial pressure of impurity components, the method of steam flushing the adsorbent is used to reduce the partial pressure of impurities in the adsorption tower and regenerate the adsorbent to the specified requirements.

Through the joint action of the above three methods, the regeneration of the adsorbent is completed.

c. Adsorption preparation

The adsorption preparation process is mainly to restore the pressure of the adsorption tower to the system pressure, and the recovery process is generally divided into:

① Average pressure rise

The pressure of the adsorption tower that has completed regeneration is increased by means of two-two pressure averaging with the adsorption tower that has completed the adsorption process. This process is not only a process of boosting pressure, but also a process of recovering effective components in the dead space of other adsorption towers.

② Final charge

The pressure equalization can only increase the pressure of the adsorption tower to a certain extent, and there is still a certain difference between it and the pressure of the whole system. This part of the difference is finally charged with product gas to raise the pressure of the adsorption tower to the system pressure.

So far, a single adsorption tower has completed a complete adsorption-desorption cycle after going through the above process, and can start a new cycle of adsorption process. The same is true for the other three adsorption towers, but the time steps are staggered from each other. The cycle of a cycle is 30 minutes. The temperature of the whole process is controlled between 400-450°C, the whole set of equipment is made of corrosion-resistant and pressure-resistant materials, and all equipment has insulation measures.

The carbon conversion rate in the feed gas is >90%, the H ₂ S removal rate is >95%, the product hydrogen purity is >90% (after drying), and the recovered product CO ₂ purity is >90% (after drying).

Example 2:

This example uses a four-tower configuration, as shown in Figure 1. The raw material gas is transported from the raw material gas buffer tank through the insulated pipeline, through the high temperature resistant program-controlled valve, to the adsorption tower.

The composition of raw gas is as follows:

Raw gas pressure: 3MPa

Raw gas temperature: 200-300°C

The pressure of the four adsorption towers is adjustable, and the adsorption tower is equipped with an adsorbent, which is composed of Na-modified Zn-Al hydrotalcite, molecular sieve, and activated carbon, and NaNO3 _- modified Zn-Al hydrotalcite accounts for the total mass of the adsorbent. 70% of.

The specific operation steps are the same as in Example 1, and the changes are as follows: when the adsorption capacity of the adsorbent reaches 60% of the saturated adsorption capacity, the adsorption towers are automatically switched, and the previously working adsorption towers are depressurized and enter the depressurized regeneration state, and the regeneration is good. The adsorption tower enters the adsorption state after pre-boosting to the working pressure; the temperature of the whole process is controlled between 200-300 °C. The entire device is made of corrosion-resistant and pressure-resistant materials, and all equipment has insulation measures.

The carbon conversion rate in the feed gas is >90%, the H ₂ S removal rate is >95%, the product hydrogen purity is >90% (after drying), and the recovered product CO ₂ purity is >90% (after drying).

Example 3:

This example adopts the configuration of 2 adsorption towers, as shown in Figure 2. The raw material gas is transported from the raw material gas buffer tank through the insulated pipeline, through the high temperature resistant program-controlled valve, to the adsorption tower. The steps experienced by each adsorption tower include four steps of pressure charging, adsorption, pressure release and purging.

The composition of raw gas is as follows:

Raw gas pressure: 3MPa

Raw gas temperature: 200-300°C

The pressure of the two _adsorption towers is adjustable, and the adsorption tower is equipped with an adsorbent, which is composed of _Na2CO3 -modified Mg-Al hydrotalcite and activated carbon, and the Na-modified Mg-Al hydrotalcite accounts for the total mass of the adsorbent 20% of.

The specific operation steps are the same as in Example 1, and the changes are as follows: when the adsorption capacity of the adsorbent reaches 40% of the saturated adsorption capacity, the adsorption towers are automatically switched, and the previously working adsorption towers are depressurized and enter the depressurized regeneration state, and the regeneration is good. The adsorption tower enters the adsorption state after pre-boosting to the working pressure; the temperature of the whole process is controlled between 200-300 °C. The entire device is made of corrosion-resistant and pressure-resistant materials, and all equipment has insulation measures.

The carbon conversion rate in the feed gas is >90%, the H ₂ S removal rate is >95%, the product hydrogen purity is >90% (after drying), and the recovered product CO ₂ purity is >90% (after drying).

Claims (3)

1. bifunctional adsorbent is applied to the method for sorption enhance steam reforming and water gas shift reaction and middle temperature pressure-variable adsorption by one kind, it is characterized in that, bifunctional adsorbent is seated in adsorption tower, steam reforming reaction, water gas shift reaction and middle temperature Pressure Swing Adsorption hydrogen are completed in same reactor, and temperature of reaction is 200-500 DEG C; Described bifunctional adsorbent has the dual-use function that catalyzed aqueous vapour is reformed with water gas shift reaction and decarbonization, desulfuration, described bifunctional adsorbent is the mixture of middle temperature sorbent material or middle temperature sorbent material and low temperature adsorbent, and the middle temperature sorbent material in this mixture accounts for more than 2% of sorbent material total mass and is less than 100%; Detailed process for by unstripped gas successively by obtaining gas product after two or more adsorption tower, in each adsorption tower, complete pressurising, sorption enhance hydrogen production reaction, gas product recoverys, drop pressure, forward bleed off pressure, reversely to bleed off pressure, steam desorb, flushing, boost pressure and fill step end;

Described unstripped gas comprises C _xh _y, CO ₂, CO, O ₂, N ₂, H ₂, H ₂s and H ₂o, wherein x and y is integer, 1 < x≤20,4 < y≤42; Described gas product is mainly H ₂;

Described middle temperature sorbent material is hydrotalcite, houghite, the hydrotalcite of modification, the houghite of modification; Described low temperature adsorbent is molecular sieve or gac;

Described modification or unmodified hydrotalcite or houghite sorbing material are following general formula compound:

[M ² _1-xM ³ _x(OH) ₂][A] _2-x·yH ₂O·zM ¹ _2(1-w)M ³ _wB

Wherein, M ¹for Li ⁺, Na ⁺, K ⁺, Cr ⁺, Rb ⁺; M ²for Mg ²⁺, Ca ²⁺, Mn ²⁺, Zn ²⁺divalent cation or its mixture; M ³for Cr ³⁺, Mn ³⁺, La ³⁺tricationic or its mixture; [A] is NO ^3-, SO ₄ ^2-, CO ₃ ^2-, Cl ^-, Br ^-, F ^-, I ^-, C _xh _yo _z ^n-; B is O ^2-or CO ₃ ^2-; N=1 or 2; X=0-1; Y=0-4; Z=0-7, w=0-1.

2. a kind of method bifunctional adsorbent being applied to sorption enhance steam reforming and water gas shift reaction and middle temperature pressure-variable adsorption according to claim 1, is characterized in that, described C _xh _yin x and y be integer, 1 < x≤12,4 < y≤26.

3. a kind of method bifunctional adsorbent being applied to sorption enhance steam reforming and water gas shift reaction and middle temperature pressure-variable adsorption according to claim 1, is characterized in that, described middle temperature sorbent material is the houghite that the hydrotalcite modified of potassium or potassium are modified.