CN1233584A

CN1233584A - Method for prodn. of hydrogen from methyl alcohol

Info

Publication number: CN1233584A
Application number: CN 98108113
Authority: CN
Inventors: 李玉柱; 张立功
Original assignee: Shanxi Institute of Coal Chemistry of CAS
Current assignee: Shanxi Institute of Coal Chemistry of CAS
Priority date: 1998-04-27
Filing date: 1998-04-27
Publication date: 1999-11-03
Anticipated expiration: 2018-04-27
Also published as: CN1085186C

Abstract

A prodn. method of hydrogen from methanel is composed of methanol catalytic cracking and alloy composite inorganic membrane sopn., only methanol and without water is used as raw material, the yield can be up to higher than 85% and the purity of product is higher than 99.5%, it is simple in process, less in equipment, and small in investment.

Description

Production method for producing hydrogen from methanol

The invention relates to a hydrogen production method by taking methanol as a raw material.

Hydrocarbon processing (6.1986) "chemical industrial production of carbon" (1990) discloses a method for preparing hydrogen by using methanol as a raw material, which comprises the following two steps: reforming with methanol and distilled water Then obtaining H through Pressure Swing Adsorption (PSA)₂. The method has the disadvantages that the raw material needs excessive distilled water besides methanol, a distilled water generating device is additionally arranged, a vaporizer, a heat exchanger, a gas-liquid separation tower and the like are also needed, and pressure swing adsorption is adoptedto separate H₂And CO₂Besides, it also needs several adsorption towers and pressure-stabilizing tanks, 10-20 electromagnetic valves and pneumatic valves and programming controller, etc. after drying, it has large floor area, high one-time investment and high H₂The yield was low (about 75%).

The invention aims to develop a production method for preparing hydrogen from methanol, which has the advantages of simple process, low investment and high hydrogen yield.

The method of the invention comprises two steps: firstly, methanol is catalyzed and cracked to obtain CO + H₂Secondly, the generated gas passes through an alloy composite inorganic membrane to convert CO and H₂And (4) separating.

"electric furnace" in the second phase (70 th phase overall) of 1986, page 23, describes a "methanol low-temperature catalytic cracking machine", using CH₃OH is used as raw material, the reaction temperature is 230-450 ℃, the pressure is 0.8-1MPa, and the liquid space velocity is 0.3-1hr^-1The product gas comprises the following components: h₂66-70％,CO 30-33％,CO₂+CH₄≤1.5％。

The catalyst adopted by the invention is a commercial product and can be purchased from Shanxi coal chemical of Chinese academy of sciences, and the weight percentage is as follows: which is as follows: 25-50% of CuO, 20-40% of ZnO and Al₂O₃10-30％,K₂CO₂1-4% of graphite and 3-10% of graphite; the second is as follows: 25-50% of CuO, 20-40% of ZnO and Cr₂O₂10-30％,K₂CO₂1-4% of graphite and 3-10% of graphite; the third is: ZnO 30-50%, Cr₂O₂20-65％,K₂CO₂2-2.5% and 3-10% of graphite.

The inorganic membrane separation technique of alloy adopted by the invention has been introduced in "chemical development" in 1994, 6 th volume, 6 nd phase 2. The alloy composite inorganic membrane of the invention takes ceramic as a framework, the wall thickness of the ceramic tube is 1mm, the ceramic tube has a uniform microporous structure, palladium and nickel are deposited on the outer side of the ceramic tube by applying a chemical vapor deposition method to form a 2-5 mu m thin film, the membrane is characterized in that only H2 is used as a penetrating phase, the working temperature is 300-400 ℃, the pressure is 0.8-1MPa, and the recovery rate of hydrogen is up to more than 85%. Product gas CO + H of methanol cracking₂And introducing the hydrogen into a membrane separator, dissolving the adsorbed surface hydrogen in a bulk phase, diffusing the dissolved hydrogen to the other side of the membrane in the bulk phase under the pushing of concentration difference, and desorbing the hydrogen on the inner surface of the membrane by diffusion to obtain the product hydrogen on the inner side of the membrane tube. The selectivity of the membrane tube to hydrogen is 100%, so the purity of the product hydrogen can reach 99.5%.

The embodiments of the invention are described below with reference to the accompanying drawings:

FIG. 1 is a process flow diagram of the present invention.

As shown in the figure: 1 is CH₃OH storage tank, 2 metering pump, 3 heat exchanger and 4 vaporizer5 is a cracking reactor, 6 is a heater, and 7 is a membrane separator.

The dynamic process is as follows: methanol is metered into a heat exchanger 3 from a tank 1 through a pump 2, the waste heat of the product gas is recovered, the methanol is heated and then is led into a vaporizer 4, and CH is removed₃OH steam is introduced into the reactor 5 for methanol cracking to obtain CO + H₂After heat exchange, CO + H₂Introducing into a heater 6, heating to above 320 deg.C, introducing into a membrane separator 7, and separating H₂And CO, the yield of the product hydrogen is up to more than 85%, and the purity is up to more than 99.5%.

From the above, the obvious advantages of the present invention are as follows:

1. the raw material only uses methanol without water, thereby reducing the energy consumption in the processes of heating, vaporizing and cooling water, simplifying the process, reducing equipment and saving the investment of methanol cracking.

2. The membrane separation is used to replace pressure swing adsorption, greatly simplifying the process and equipment and effectively reducing the investment.

3. The yield of the product hydrogen is up to more than 85 percent, and the purity is up to 99.5 percent.

The examples of the invention are as follows:

example 1

5Nm³Hydrogen production device from/hr methanol

The raw material methanol is fed into a heat exchanger by a plunger pump at the feeding amount of 6 liters/hr, and is introduced into a vaporizer after heat exchange with hot gas after reaction, and is vaporized and heated to 280 ℃ and then introduced into the reactor. 15Kg of catalyst is filled in a reactor, and under the action of the catalyst, 8.68Nm is generated at the reaction temperature of 285 ℃ and the pressure of 1MPa³Methanol cracking gas (H)/hr₂+ CO). Wherein: h₂67％,CO 32％ CO₂+CH₄1％。

The cracking gas is introduced into a heat exchanger and a heater, the temperature of the gas reaches 375 ℃, and the gas is introduced into a membrane separator, and 3 palladium-nickel alloy composite inorganic membrane tubes with the length of 600mm, the diameter of phi 20 and the membrane thickness of 5 mu m are arranged in the membrane separator. 5Nm is obtained at the gas production end of the membrane separator³Hydrogen gas (purity: 99.5%) per hr.

System pressure: 1MPa of

Hydrogen production pressure: 0.05MPa

Hydrogen recovery rate: 86 percent of the total weight

Purity of hydrogen: 99.5 percent

Example 2

10Nm³Hydrogen production device from/hr methanol

The raw material methanol is fed into a heat exchanger and a vaporizer by a plunger pump at the feeding amount of 15 liters/hr,methanol was vaporized in a vaporizer and heated to 250 ℃ and passed into the reactor. In the reactor, 30Kg of catalyst is filled, and under the action of the catalyst, the reaction temperature is 255 ℃ and the pressure is 1MPa, 20.5Nm is generated³Methanol cracking gas (H)/hr₂+ CO). Wherein: h₂66.5％,CO 32％ CO₂+CH₄1.5％。

The cracking gas is introduced into a heat exchanger and a heater, the temperature of the gas reaches 320 ℃, and the gas is introduced into a membrane separator, and 5 palladium-nickel alloy composite inorganic membrane tubes with the length of 600mm, the diameter of phi 20 and the membrane thickness of 5 mu m are arranged in the membrane separator. 11.8Nm is obtained at the gas production end of the membrane separator²Hydrogen gas (purity: 99.5%) per hr.

System pressure: 1MPa of

Hydrogen production pressure: 0.06MPa

Hydrogen recovery rate: 86.5 percent

Purity of hydrogen: 99.5 percent

Example 3

100Nm³Hydrogen production device from/hr methanol

Raw material methanol was fed by a plunger pump at a feed rate of 150 liters/hr into a heat exchanger and a vaporizer, and the methanol was vaporized and heated to 250 ℃ in the vaporizer and introduced into the reactor. 300Kg of catalyst is filled in the reactor, and 211Nm is generated under the action of the catalyst and the reaction temperature of 260 ℃ and the pressure of 1MPa³Methanol cracking gas (H)/hr₂+ CO). Wherein: h₂67％,CO 31.5 CO₂+CH₄1.5％。

To make thisIntroducing pyrolysis gas into a heat exchanger and a heater, wherein the temperature of the gas reaches 390 ℃, introducing the gas into a membrane separator, and 18 palladium-nickel alloy composite inorganic membrane tubes with the length of 600mm, the diameter of phi 20 and the membrane thickness of 5 mu m are arranged in the membrane separator. 120Nm is obtained at the gas production end of the membrane separator³Hydrogen gas (purity: 99.5%) per hr.

System pressure: 1MPa of

Hydrogen production pressure: 0.04MPa

Hydrogen recovery rate: 85 percent of

Purity of hydrogen: 99.5 percent

Claims

1. The production process of methanol to produce hydrogen features that methanol is first catalytically cracked and cracked gas CO + H is then produced₂Obtaining a product H by a membrane separator₂。

2. A process for producing hydrogen from methanol as claimed in claim 1, wherein the raw material is methanol alone and water is not present.

3. The method for producing hydrogen from methanol according to claim 1, characterized in that the process conditions of the methanol cracking gas are as follows: the reaction temperature is 230 ℃ and 450 ℃, the reaction pressure is 0.8-1.5MPa, and the liquid space velocity is 0.3-1hr^-1The catalyst is a commercial product.

4. The method of claim 1, 2 or 3, wherein the membrane separator is an alloy composite inorganic membrane separator with a ceramic skeleton.