JPH0513882B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing hydrogen for fuel cells by steam reforming of hydrocarbon fractions including kerosene fractions, which uses low-cost raw material oil for steam reforming. The present invention relates to a method for producing hydrogen for fuel cells, which is characterized by using a hydrocarbon fraction that is easily available, is suitable for steam reforming reactions, and allows production of hydrogen through a simple process.

Background of the Invention Fuel cells have high energy conversion efficiency and do not cause much environmental damage, so demonstration plants are being tested as power generation devices for civilian or industrial use, and there are various concerns regarding the completion of the technology. is expected. Although various substances are used as fuel for fuel cells, it is thought that the practical use of fuel cells that use hydrogen as the fuel, especially fuel cells that use phosphoric acid as the electrolyte, is considered to be the closest.

Hydrogen used for fuel cells is mainly produced by reforming liquefied natural gas (LNG), which mainly consists of methane, or city gas, which mainly consists of methane, with steam, or by reforming methanol. Research is being conducted on methods of manufacturing by decomposing or decomposing.

However, if you plan to install fuel cells in a distributed manner, including in evacuation areas (distributed fuel cells),
Fuel cells using LNG or city gas can only be installed within supply areas with pipes, and their use is extremely limited within the area. Furthermore, in the case of a large-scale disaster such as an earthquake, it will take a long time to restore the gas supply due to a break in the city gas pipe. Furthermore, methods for obtaining hydrogen by reforming or decomposing methanol currently have the disadvantage that they are considerably more expensive per unit of hydrogen than LNG.

It is also possible to use naphtha as a reforming raw material, but naphtha has a low boiling point and high vapor pressure.
Because it is volatile, it is highly flammable, highly dangerous, and difficult to handle.

On the other hand, if it becomes possible to use kerosene or its equivalent distillate, which is heavier, less flammable, less dangerous, and easier to handle than naphtha, as a raw material to obtain hydrogen for fuel cells, efficiency will increase. This will greatly contribute to the spread of fuel cells with high fuel efficiency. Furthermore, even in the event of a major earthquake, roads can be easily restored and supply by lorry can be resumed immediately, so as long as hydrogen production equipment and fuel cell equipment are operational, power generation outages can be kept to a minimum.

In addition, kerosene has a lower hydrogen production cost than LNG,
Another advantage is that power generation costs are low.

Problems to be solved by conventional technology and invention Conventionally, in hydrogen production plants using the steam reforming method using petroleum as raw materials, off-gas,
It is believed that everything from light hydrocarbons such as LNG to LPG and naphtha can be used as raw materials, and it has been difficult to use heavier oils as raw materials. The main reason for this is that, for example, when kerosene is used, the decomposition rate of the reforming catalysts used so far is low and carbon content is deposited.

However, especially with recent advances in technology, nickel catalysts that have a sufficient decomposition rate even when using kerosene and have little carbon content are being revealed, and steam reforming of oil with a boiling point range similar to that of kerosene has been discovered. It became possible to use it as a quality raw material.

However, even this catalyst is sensitive to sulfur,
As a raw material for reforming, it must be desulfurized to an extremely high level, with sulfur content of 1wtppm or less. However, for the purpose of using kerosene for heating equipment, which is a general use of kerosene, it is not necessary to reduce the sulfur content in kerosene to this high level. JIS (K2203) No. 1 kerosene has an upper limit of sulfur content of 150 ppm, and generally 10 to 100 ppm.
Currently, kerosene with a concentration of 150 ppm, usually around 20 to 60 ppm, is commercially available, and JIS No. 1 kerosene cannot be used as it is as a raw material for steam reforming.

It is not technically impossible to reduce the sulfur content to 1 wtppm or less by direct hydrodeflowing of such relatively high sulfur-containing kerosene. However, in this case, high-temperature and high-pressure conditions of 50 kg/cm ² G or higher in the presence of hydrogen and a temperature of 300°C or higher are required, and such equipment is installed upstream of each fuel cell steam reformer. The advantages of using kerosene as a raw material, which is cheaper than LNG, naphtha, or methanol, will be lost.

The present inventors have considered the many merits of kerosene fraction as a raw material for producing a hydrogen source for fuel cells.In addition, it is economically superior to LNG, methanol, etc., and it also simplifies the hydrogen production process. We conducted extensive research on possible raw materials for hydrogen production.

As a result, the present inventors discovered that conventionally it was mixed with JIS No. 1 kerosene and used only as a heating fuel for home heaters and industrial use, and that when used as a raw material for steam reforming, steam reforming could be performed stably for a certain period of time. Fractions that have not previously been considered as to whether they can proceed, i.e. fractions contained in crude oil and/or
Or, it is a fraction obtained by cracking the fraction contained in crude oil, which has undergone hydrorefining treatment using a catalyst and hydrogen, and has a sulfur content of 1wtppm or less, and some of the fractions have boiling points. Distillate between 150 and 260℃
First, a hydrocarbon fraction containing 70wt% or more is produced,
Next, straight-chain hydrocarbons are separated and removed from the hydrocarbon fraction by an adsorption method using synthetic zeolite and/or a urea adduct method. It was found that it has suitability for modified raw materials.

The distillate referred to in the present invention is, for example, the residue (ruffinate) obtained by collecting and separating relatively expensive linear hydrocarbons, which are raw materials for synthetic detergents with good biodegradability, and has not been effectively utilized in the past. be. If this fraction is used as a raw material for steam reforming to obtain a hydrogen source for fuel cells, it will be possible to effectively utilize a fraction that could only exhibit the same value as JIS No. 1 kerosene.
Additionally, if JIS No. 1 kerosene is used as the raw material for steam reforming, steam reforming can be performed without the need for expensive deflow equipment to carry out the strict desulfurization reaction that reduces the sulfur content to 1wtppm or less. We have completed the present invention by discovering that it is possible to reduce the cost of the total fuel cell system and downsize the facility, making it possible to produce hydrogen at an unprecedented cost for fuel cells.

Means for Solving the Problems The raw material for steam reforming used in the method for producing hydrogen for fuel cells of the present invention is obtained as follows. That is, appropriate fractions in crude oil separated by distillation of crude oil and/or fractions contained in crude oil are subjected to thermal cracking or catalytic cracking in the presence of a catalyst and/or hydrogen, for example at temperatures above 300°C. The fraction having a boiling point of 150 to 260°C, which is contained in the decomposition product fraction obtained by decomposition in whole or in part or a mixture thereof, at a temperature of
The hydrocarbon fraction containing 70wt% or more is the basic component of the hydrocarbon compound. Further, the component is subjected to hydrorefining treatment in the presence of a catalyst and hydrogen to reduce the sulfur content to 1 wtppm or less before or after obtaining the above-mentioned fraction, or at one or more stages of the process. Here, the fraction having a boiling point of 150 to 260°C is a so-called kerosene fraction, and if the content of this kerosene fraction is less than 70 wt%, it is not desirable from the viewpoint of utilizing the convenience of kerosene as a raw material for steam reforming.
Further, hydrocarbons having a boiling point of 260° C. or higher are difficult to steam reform, so the smaller the amount, the better. Hydrocarbons with a boiling point of 150° C. or lower do not pose a problem in steam reforming, but if the amount of hydrocarbons with a low boiling point is too large, the flash point will decrease when used as a reforming raw material, which is undesirable. Further, if the fraction having a boiling point other than 150 to 260° C. is too large, there will be a problem that the economic efficiency of the process for separating highly valuable linear hydrocarbons will be lowered, so it is preferable that the fraction is not too large. In addition, if the sulfur content exceeds 1wtppm, it will be harmful in the separation process of linear hydrocarbons, which will be described later.
The sulfur content must be 1wtppm or less.

The catalyst used in the hydrorefining treatment is
Inorganic solids such as bauxite, activated carbon, diatomaceous earth, zeolite, silica, alumina or silica-alumina are used as carriers to prepare Group B, Group or group metals of the periodic table in the form of oxides, sulfides, composites or mixtures thereof. It is something that is carried in form. Group B, group and group metals include:
Cobalt, nickel, molybdenum and tungsten are preferred. In the present invention, a catalyst obtained by presulfiding a combination of two or more of nickel oxide, cobalt oxide, molybdenum oxide, and tungsten oxide supported on an alumina carrier is particularly preferably used. The reaction temperature in the hydrogenation treatment is usually 230-400°C, preferably 260-360°C. Below 230°C, the degree of purification is low, and above 400°C, side reactions such as decomposition and dehydrogenation occur. The reaction pressure is usually 20-150Kg/ ^cm2・G, preferably 25-120Kg/
cm ²・G. Also, hydrogen is 100 ~
10,000Nm ³ preferably 200 to 1,000Nm ³ ,
The LHSV used is 0.2 to 5 hr ^-1 , preferably 0.5 to 4 hr ^-1 .

The kerosene-equivalent fraction thus hydrorefined is then separated into linear hydrocarbons and other fractions by an adsorption separation method using synthetic zeolite or a separation method by a urea adduct method.

In the adsorption separation method, synthetic zeolite (called molecular sieve 5A) with a pore size of 5 Å is generally used as the adsorbent. This means that the diameter of the molecular cross section is approximately 4.9
Linear hydrocarbons (normal paraffins) with a diameter of 5 Å pass through the pores of synthetic zeolite and are adsorbed on the internal surface, but isoparaffins, naphthenes, and aromatic compounds with molecular cross-sectional diameters larger than 5 Å pass through the pores of the synthetic zeolite and are adsorbed on the internal surface. This makes it possible to separate linear hydrocarbons because they cannot pass through the water and exit the system without being adsorbed. Adsorbed linear hydrocarbons can be removed by increasing the temperature.
It can be desorbed from zeolite by lowering the pressure, blowing with inert gas, or replacing it with low molecular weight linear hydrocarbons.

As an industrial process, separation is carried out in the liquid phase.
Mo1ex method, sosiv method in gas phase, BP method and
There are methods such as the TSF method, and even if linear hydrocarbons are separated by any method, the residue (ruffinate) thereof can be used in the present invention.

In addition, in the urea adduct method, urea is used in a solvent (methylene dichloride, methanol, etc.) that has the ability to activate it.
This is a method to separate linear hydrocarbons from kerosene by applying the principle of producing linear hydrocarbons of _C7 or higher and urea adducts at room temperature in the presence of kerosene. Linear hydrocarbons are recovered by treating the produced adduct with urea or a solvent that dissolves linear hydrocarbons. Industrial methods include methods that use solid urea and methods that use a urea solution; methods that use solid urea include the Nurex method, and methods that use a urea solution include the Edeleane method.

Roughinate obtained by this method has a sulfur content,
Impurities such as nitrogen, oxygen, and metals are significantly reduced, and in particular, sulfur content is less than 1wtppm, which is permissible as a raw material for steam reforming using a nickel catalyst. Unexpectedly, the residue obtained by further separating linear hydrocarbons (roughinate) from the hydrorefining fraction obtained by the method of the present invention by adsorption separation method or urea adduct method. Compared to feedstock oils with similar properties that are finished using only the hydrorefining method, the rate of carbon precipitation is slower and the catalyst can be used for a longer period of time as a hydrogen source for steam reforming reactions using nickel-based catalysts. He showed excellent aptitude by showing trends. This tendency was significantly observed in the adsorption separation method. Although the cause of this is not clear, it is believed that some of the substances responsible for the decrease in the activity of the nickel-based reforming catalyst were removed by the adsorbent treatment method or the urea adduct method.

Roughinate obtained by the method of the present invention is added with water (steam) necessary for steam reforming, and then sent to a steam reformer filled with a nickel catalyst. The nickel catalyst used for steam reforming of kerosene contains 5 wt% or more of nickel, for example 5 to 50 wt%,
It preferably contains 10 to 35 wt%.

The nickel catalyst mentioned here is one that contains nickel in the form of a metal, oxide, or other compound, and most of it exists as nickel in a reduced state under normal reforming reaction conditions. is used.

Supports include alumina, magnesia, silica,
Calcia and magnesia-alumina spinel may be used alone or in combination, or a catalyst may be used in which 5 wt% or less of potassium oxide is added to these. Reaction conditions are reaction temperature 500
~1,000℃, reaction pressure 3Kg/ ^cm2・G or higher, steam/carbon (molar ratio) 2-6, LHSV 0.2-4
is preferably used.

The sulfur compounds contained in the hydrocarbon feedstock are known as active poisons for the nickel catalyst used in steam reforming, and the hydrogen sulfide produced when the sulfur compounds come into contact with the nickel catalyst is stoichiometric with the nickel catalyst. It reacts to form nickel sulfide and loses its activity.
Therefore, it is desirable that the sulfur content in the raw material to be subjected to the reforming reaction is as low as possible, but from an economic standpoint and industrially, it is preferable that the sulfur content in the raw material is 1 wtppm or less. It can be said that the steam reforming raw material used in the method for producing hydrogen for fuel cells of the present invention is suitable also in terms of this sulfur content concentration. Furthermore, if a steam reforming reaction is carried out using a nickel catalyst using a raw material with a sulfur content exceeding 1wtppm, the catalyst will be poisoned from near the entrance of the reaction tower, and the decomposed hydrocarbons will be released from the exit of the reaction tower in a short period of time. is detected, a hot spot is formed at the inlet of the reaction tube, and the ∆P of the reaction tube increases due to coking, making it necessary to stop operation in a short period of time and replace or regenerate the catalyst.

Next, the method of the present invention will be specifically explained using examples.

Example 1 <Hydrorefining treatment> A fraction with a boiling point of 190 to 260°C obtained by distillation from Sumatralite crude oil [specific gravity (15/4°C) 0.797,
Sulfur content 190wtppm, linear hydrocarbons 40.5wt%,
aromatic content of 10.2 vol.%] was placed in a reaction tower packed with a commercially available nickel-molybdenum catalyst at a reaction pressure of 85 kg/
^cm2・G, temperature 280℃, LHSV0.9, _H2 /Oil=400
I passed on the condition of /. The sulfur content of refined oil is
It decreased to less than 1wtppm, the aromatic content was 5.2vo%, and the nuclear hydrogenation rate was 51%.

<Adsorbent separation> Next, the hydrotreated oil is passed through a molecular sieve.
Insert into Molex device filled with 5A,
Straight chain hydrocarbons were separated to obtain roughinate. Roughinate has a boiling point of 191-260℃ and a specific gravity.
0.815, sulfur content 1wtppm or less, aromatic content 9.3vo%
It was hot.

〈Steam reforming〉 34wt% NiO and A ₂ O ₃ are used as raw materials without any further treatment of the roughinate.
Using a reaction tube filled with approximately 1 mm crushed pieces of steam reforming catalyst consisting of 12 wt% and 54 wt% MgO, the reaction pressure was 30 Kg/cm ² G, the reaction temperature at the inlet was 500°C,
Steam reforming was carried out under the following conditions: 800°C at the outlet, LHSV 1.5, and H ₂ O/C (raw material) 3.5 mol/mol. Even after 1,000 hours had passed since the start of the reaction, there was not much change in the temperature distribution in the reaction tube, and the gas composition at the outlet was close to the thermodynamic equilibrium value, indicating that the raffinate is suitable as a raw material for steam reforming. It was hot.

Example 2 <Hydrorefining treatment> A fraction with a boiling point of 161 to 256°C obtained by distillation from Arabian Light crude oil [specific gravity (15/4°C) 0.795,
Sulfur content 2200wtppm, linear hydrocarbons 26wt%,
Aromatic content 18.5 vol.%] using a commercially available nickel-tungsten catalyst at a reaction pressure of 50 Kg/cm ² G and temperature.
The treatment was performed at 320°C, LHSV2, and H ₂ /Oil = 250/. The sulfur content of refined oil is below 1wtppm, the aromatic content is reduced to 14.8ov%, and the nuclear hydrogenation rate is 20%.
It was %.

<Urea adduct method> Next, 1 part by weight of the hydrogenated refined oil was heated to 80°C.
It is mixed with 1 part by weight of a 76 wt% urea saturated aqueous solution and 2 parts by weight of methylene dichloride, and then cooled to 30°C to form an adduct of urea and linear hydrocarbons. Then, the adduct in the mixed solution was separated and removed to obtain ruffinate.

<Steam reforming> Using the roughinate as a raw material without any further treatment, a commercially available nickel-based steam reforming catalyst (22 wt% NiO, 26 wt% A ₂ O ₃ ,
A reaction was carried out in the same manner and under the same conditions as in Example 1 using 11 wt% MgO, 13 wt% CaO, 16 wt% SiO ₂ and 7 wt% K ₂ O crushed to about 1 mm. 500 hours after the start of the reaction, the point showing the highest temperature in the reaction tube moved slightly toward the outlet of the reaction tube, but the gas composition at the outlet was close to the thermodynamic equilibrium value at that temperature, indicating that the roughinate was steam reformed. It is clear that it is suitable as a raw material for quality production.

Comparative example 1 Commercially available JIS No. 1 kerosene (specific gravity 0.796, sulfur content
A steam reforming reaction was carried out in the same manner as in Example 1 using raw materials (35wtppm, linear hydrocarbons 24.5wt%, aromatics 17.0vol.%) as raw materials. As a result, the reaction progressed smoothly for the first hour, but after about 10 hours, end-reacted hydrocarbons were detected in the outlet gas, and commercially available JIS No. 1 kerosene was used as a raw material for steam reforming. It was inappropriate.

Claims (1)

[Claims] 1. A fraction contained in crude oil and/or a fraction obtained by cracking a fraction contained in crude oil, which has been subjected to hydrorefining treatment using a catalyst and hydrogen, and has a sulfur content of 1 wtppm or less. First, a hydrocarbon fraction containing 70wt% or more of a fraction with a boiling point of 150 to 260°C is produced, and then linear hydrocarbons are adsorbed from the hydrocarbon fraction by synthetic zeolite. The necessary amount of water is added to the fraction obtained by separation and removal using the urea adduct method and/or the urea adduct method, and a reforming reaction is performed using a steam reforming catalyst containing 5 wt% or more of nickel, resulting in a hydrogen source for use in fuel cells. A method for producing hydrogen for fuel cells.