JP4963616B2 - Adsorbent for removing trace components in hydrocarbon oil and method for producing the same - Google Patents

Description

  The present invention relates to an adsorbent that adsorbs and removes trace components in hydrocarbon oil, such as sulfur compounds and polycyclic aromatic compounds, and a method for producing the same. Furthermore, the present invention relates to a method for removing trace components in hydrocarbon oil using the adsorbent, and a fuel cell system using the adsorbent.

In the 21st century, and environmentally friendly both in terms of the reduction of automobile exhaust gas emissions such as reduction and NO _X in the CO ₂ gas is greenhouse gas, further reducing the sulfur content in the fuel It is requested to do. In the near future, the sulfur content in gasoline and light oil is expected to be regulated to 10 ppm or less. In addition, with the spread of fuel cells such as automobiles equipped with on-board reforming fuel cells, there is a possibility that petroleum liquid fuel oil having a lower sulfur content is required. Therefore, desulfurization technology necessary for obtaining an ultra-low sulfur petroleum-based liquid fuel oil is currently being actively researched.

  Conventionally, a hydrodesulfurization method is a method mainly used as a desulfurization technique for light oil. However, in order to desulfurize light oil to a low sulfur concentration of 15 ppm or less using the hydrodesulfurization method, it is necessary to increase the reaction temperature, and raising the reaction temperature causes a problem that the hue of the product light oil deteriorates. As a method for improving the hue problem of light oil, there has been proposed a method in which a gas oil fraction having deteriorated hue is brought into contact with activated carbon (Patent Documents 1 and 2). There is also a method of decolorizing light oil by performing a hydrogenation treatment in the presence of a crystalline aluminate-containing inorganic oxide catalyst or activated carbon catalyst supporting either or both of Group VI metal and Group VIII metal. It has been proposed (Patent Document 3). In addition, various process developments have been made with respect to desulfurization techniques other than hydrodesulfurization methods, for example, sulfur in which a copper component is supported on an alumina carrier in order to remove trace amounts of sulfur compounds contained in hydrocarbon oils. There is an example using a compound adsorbent (Patent Document 4).

  By the way, by the hydrodesulfurization method, it is possible to remove difficult desulfurization compounds such as 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) remaining in the light oil fraction, and to remove sulfur content. An enormous amount of catalyst and hydrogen are required to reduce the carbon content to 15 ppm or less. In particular, hydrogen is expensive and affects the price of refined gas oil. In addition, various processes for desulfurization of difficult-to-desulfurize compounds have been studied, but at present, there is no choice but to deal with an additional reactor. Therefore, in order to reduce the sulfur content of the gas oil fraction, there is a demand for innovative technology that can be desulfurized with simple equipment and low operating costs.

  Recently, a technique for reducing polycyclic aromatic compounds (PAH's) contained in exhaust gas from diesel engines is also required. That is, diesel oil with extremely low sulfur content and PAH's has the potential to make a significant contribution to society in terms of preventing air pollution in large cities and protecting the global environment.

  On the other hand, for desulfurization of kerosene used in stationary fuel cells for home use and the like, a chemisorption desulfurization method using a nickel-based desulfurization agent at around 200 ° C. has been studied, but it consumes energy for heating. In addition, it takes time to start up, and it is necessary to carry out under pressurized conditions in order to prevent the vaporization of kerosene, resulting in a complicated system. The nickel-based desulfurizing agent to which copper is added has a certain activity even at a lower temperature of about 150 ° C., but has not yet solved the above problem. In addition, nickel-based desulfurization agents need to be subjected to a reduction treatment in advance, and a sudden exothermic reaction occurs due to contact with oxygen, resulting in a decrease in activity. There is. Furthermore, since nickel compounds are toxic, there is also a problem that the management method must be strict when they are spread to ordinary households. (Patent Literature 5, Patent Literature 6, Patent Literature 7, Patent Literature 8)

  Copper oxide desulfurization agents are used for desulfurization of naphtha fractions containing sulfur compounds such as mercaptans at a relatively low temperature of around 120 ° C. (Patent Document 4). However, benzothiophenes and dibenzothiophenes are used. There was no copper oxide-based desulfurization agent having sufficient performance for desulfurization such as kerosene containing bismuth and light oil containing dibenzothiophenes.

  On the other hand, a physical adsorption desulfurization method using zeolite, activated carbon or the like at around room temperature has been studied (Patent Document 9 and Patent Document 10), but carbonization of kerosene, light oil, etc. containing aromatic compounds that are competitively adsorbed with sulfur compounds. The desulfurization of hydrogen oil is not practical because there is no physical adsorbent with high performance and a very large amount of physical adsorbent is required to obtain the desired effect.

The types of sulfur compounds contained in kerosene are mostly benzothiophenes and dibenzothiophenes, and the ratio of benzothiophenes is particularly large. The ratio of benzothiophenes to the total sulfur compounds is 70% or more as the sulfur content. There are many cases. About removal of benzothiophenes, it can remove comparatively easily by using desulfurization agents, such as activated carbon with which the solid acid catalyst and / or transition metal oxide which the inventor proposed previously were supported. (Patent Document 11). However, it is difficult to remove dibenzothiophenes having a small content, and it is particularly difficult to remove alkyldibenzothiophenes having a large number of alkyl groups. The present inventor previously proposed activated carbon having a specific pore structure, particularly fibrous activated carbon, having high removal performance with respect to dibenzothiophenes contained in light oil and kerosene (Patent Document 12). However, fibrous activated carbon is cotton-like and the packing density cannot be increased, so the adsorption performance per unit volume cannot be increased, and the manufacturing process is complicated and the manufacturing cost is high. Expected not economical.
Therefore, a desulfurizing agent that can efficiently and economically remove dibenzothiophenes at a temperature from room temperature to about 150 ° C. that does not require reduction treatment or hydrogen and that does not require pressurization, and its production There is a need for a method.
JP-A-6-136370 JP 2000-192054 A JP 2000-282059 A Japanese Patent No. 3324746 Japanese Examined Patent Publication No. 6-65602 Japanese Patent Publication No.7-115842 Japanese Patent No. 3410147 Japanese Patent No. 3261192 JP 2003-49172 A JP 2005-2317 A WO2005-073348 WO2003-077771

  An object of the present invention is to provide an adsorbent that efficiently and economically removes sulfur compounds, polycyclic aromatic compounds, and the like contained in hydrocarbon oils such as kerosene and light oil, and a method for producing the same. It is an object to provide an adsorbent having a high adsorption performance per unit volume because the packing density can be increased, and an adsorbent production method for producing the adsorbent at a low production cost without complicated production processes And Moreover, this invention makes it a subject to provide the removal method of the trace component in hydrocarbon oil using this adsorption agent, especially a sulfur compound, and also to provide the fuel cell system equipped with the said adsorption agent.

  As a result of diligent research to solve the above-mentioned problems, the present inventor, as an adsorbent composed of activated carbon produced by a specific production method using rice husk obtained from plant biomass, particularly rice, is a hydrocarbon oil. In addition to excellent adsorption removal performance per unit weight of sulfur compounds and polycyclic aromatic compounds contained in the product, the packing density can be increased, so the adsorption performance per unit volume is also high, and the manufacturing process is not complicated It has been found that it has a special effect that the manufacturing cost is low, and has arrived at the present invention.

That is, the present invention provides a method for producing an adsorbent described below, an adsorbent produced by the method, a method for removing trace components in hydrocarbon oil using the adsorbent, and a fuel cell system equipped with the adsorbent. About.
(1) Further activation after carbonizing (A) plant biomass at 300-900 ° C under reduced pressure or (B) carbonizing at 200-900 ° C under reduced pressure and / or inert atmosphere By processing, after obtaining a carbonized product or activated product having a specific surface area of 200 m ² / g or more and an average pore diameter of 20 mm or more, an adsorbent is produced using the carbonized product or activated product. A method for producing an adsorbent for removing trace components in a hydrocarbon oil.

(2) The method for producing an adsorbent according to (1), wherein the carbonization treatment of (A) is performed at 300 to 500 ° C, and the carbonization treatment of (B) is performed at 200 to 500 ° C.
(3) The method for producing an adsorbent according to (1) or (2), wherein the activation treatment is performed at 800 to 900 ° C. for 0.1 to 4 hours in a carbon dioxide atmosphere.
(4) The adsorbent according to any one of (1) to (3), wherein the carbonized product obtained by the carbonization treatment is molded by adding a binder composed of a saccharide, and then the obtained molded product is activated. Manufacturing method.
(5) The method for producing an adsorbent according to any one of (1) to (4), wherein the plant biomass is rice husk or cedar.
(6) The method for producing an adsorbent according to any one of (1) to (5), further including a step of mixing and supporting a metal and / or a metal oxide.

(7) produced by carbonizing plant biomass at (A) 300-900 ° C. under reduced pressure, or (B) carbonized at 200-900 ° C. under reduced pressure and / or inert atmosphere. A trace amount in a hydrocarbon oil, characterized by comprising a carbonized product or an activated product having a specific surface area of 200 m ² / g or more and an average pore diameter of 20 mm or more, which is produced by performing an activation treatment later. An adsorbent that removes components.
(8) The adsorbent according to (7), wherein the carbonization treatment of (A) is performed at 300 to 500 ° C, and the carbonization treatment of (B) is performed at 200 to 500 ° C.
(9) The adsorbent according to (7) or (8), wherein the activation treatment is performed at 800 to 900 ° C. for 0.1 to 4 hours in a carbon dioxide atmosphere.
(10) In any one of (7) to (9), the carbonized product obtained by carbonization treatment is molded by adding a saccharide binder, and then the resulting molded product is activated. The adsorbent described.
(11) The adsorbent according to any one of (7) to (10), wherein the plant biomass is rice husk or cedar.
(12) The adsorbent according to any one of (7) to (11), wherein the adsorbent further supports a metal and / or a metal oxide.

(13) A hydrocarbon characterized by adsorbing and removing sulfur compounds and / or polycyclic aromatic compounds contained in hydrocarbon oil using the adsorbent according to any one of (7) to (12). A method for removing trace components in oil.
(14) The removal method according to (13), wherein the hydrocarbon oil is kerosene or light oil.
(15) The removal method according to (13) or (14), wherein the sulfur compound in kerosene is adsorbed and removed at a temperature of 150 ° C. or lower.
(16) A fuel cell system equipped with an adsorbent that removes trace components in the hydrocarbon oil according to any one of (7) to (12).

  According to the adsorbent of the present invention, since it is an adsorbent made of activated carbon obtained by carbonizing and further activating rice husk obtained from plant biomass, particularly rice, as hydrocarbon oil, particularly as a sulfur compound Contact with hydrocarbon oils such as kerosene and light oil containing dibenzothiophenes or polycyclic aromatic compounds at room temperature to about 150 ° C without liquid reduction or hydrogenation. Thus, the sulfur compound and / or polycyclic aromatic compound can be adsorbed and removed efficiently and economically. Therefore, when the sulfur compound and / or polycyclic aromatic compound contained in kerosene or light oil is removed by adsorption, it can be removed with a more compact facility and at a lower cost. Furthermore, when applied to desulfurization of kerosene or the like, which is the raw fuel of the fuel cell, startup and maintenance are relatively easy, and the fuel cell system can be simplified.

  Examples of the hydrocarbon oil to which the adsorbent of the present invention is applied include hydrocarbon oils containing 5 to 20 carbon atoms containing dibenzothiophenes as sulfur compounds or containing polycyclic aromatic compounds. These hydrocarbon oils may contain any kind of sulfur compounds such as thiophenes, mercaptans (thiols), sulfides, disulfides, carbon disulfide, etc. In particular, it exhibits a remarkable effect on hydrocarbon oils containing sulfur compounds such as dibenzothiophenes that are extremely difficult to desulfurize. For example, the ratio of dibenzothiophenes to the total sulfur compounds is about 30% for kerosene and almost 100% for light oil. Hydrocarbon oils such as kerosene and light oil are preferred hydrocarbon oils for application of the adsorbent of the present invention. is there. Of course, the application target of the adsorbent of the present invention is not limited to kerosene or light oil. A polycyclic aromatic compound is a compound having two or more benzene rings and may contain heteroatoms other than carbon and hydrogen, but all the carbons forming the two benzene rings are in the same plane. The one located above has a stronger π-electron interaction with the adsorbent of the present invention, and the effects of the present invention can be remarkably obtained.

  When removing sulfur and polycyclic aromatic compounds from hydrocarbon oil with the adsorbent of the present invention, if the content is too large, a large amount of adsorbent will be required. Since the purification method is more efficient, the sulfur content is 20 mass ppm or less, preferably 10 mass ppm or less, more preferably 1 mass ppm or less, and the polycyclic aromatic compound content is 5 mass% or less, preferably Is 2% by mass or less, more preferably 0.5% by mass or less.

Kerosene, which is a preferred example of an object to be treated with the adsorbent of the present invention, is generally composed mainly of hydrocarbons having about 12 to 16 carbon atoms, and has a density (15 ° C.) of 0.790 to 0.850 g / cm. ³ , an oil having a boiling range of about 150 to 320 ° C., containing a large amount of paraffinic hydrocarbons as a main component, containing about 0 to 30% by volume of aromatic hydrocarbons, and 0 to 5 volumes of polycyclic aromatic compounds Including about%. Speaking of ordinary kerosene, it refers to No. 1 kerosene defined in Japanese Industrial Standard JIS K2203 as a fuel for lighting, heating, and kitchen. In JIS, the flash point is 40 ° C or higher, 95% distillation temperature 270 ° C or lower, sulfur content 0.008% by mass or lower, smoke point 23mm or higher (21mm or higher for cold weather), copper plate corrosion (50 ° C, 3 hours) 1 or less, color (Saebold) +25 or more. Usually, the sulfur content is about 6 ppm to 80 ppm and the nitrogen content is about several ppm to about 10 ppm.

The light oil which is another example suitable as the object to be treated with the adsorbent of the present invention is an oil mainly composed of hydrocarbons having about 16 to 20 carbon atoms, and has a density (15 ° C.) of 0.820 to 0.880 g / It contains cm ³ and a boiling point range of about 140 to 390 ° C. and contains a large amount of paraffinic hydrocarbons, but contains about 0 to 30% by volume of aromatic hydrocarbons and also contains about 0 to 10% by volume of polycyclic aromatic compounds. In general, JIS K2204 defines a standard property as “light oil” as fuel for automobile diesel engines.

  The main sulfur compounds contained in kerosene and light oil are benzothiophenes and dibenzothiophenes, but may include thiophenes, mercaptans (thiols), sulfides, disulfides, carbon disulfide, and the like. For qualitative and quantitative analysis of these sulfur compounds, Gas Chromatograph (GC) -Flame Photometric Detector (FPD), GC-Atomic Emission Detector (AED), GC- Sulfur Chemiluminescence Detector (SCD), GC-Inductively Coupled Plasma Mass Spectrometer (ICP-MS), etc. can be used, but GC-ICP is used for mass ppb level analysis. -MS is most preferred.

Dibenzothiophenes are heterocyclic compounds containing one or more sulfur atoms as heteroatoms, and the heterocycle is a penta- or hexa-atom ring and has aromaticity (two or more double bonds in the heterocycle). And a sulfur compound in which a heterocyclic ring is condensed with two benzene rings and derivatives thereof. Dibenzothiophene is also called diphenylene sulfide, biphenylene sulfide, or diphenylene sulfide, and is a sulfur compound having a molecular weight of 184 that can be represented by the molecular formula C ₁₂ H ₈ S. 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene are well known as difficult desulfurization compounds in hydrorefining. Other typical dibenzothiophenes include trimethyldibenzothiophene, tetramethyldibenzothiophene, pentamethyldibenzothiophene, hexamethyldibenzothiophene, heptamethyldibenzothiophene, octamethyldibenzothiophene, methylethyldibenzothiophene, dimethylethyldibenzothiophene, trimethyl Ethyl dibenzothiophene, tetramethylethyl dibenzothiophene, pentamethylethyl dibenzothiophene, hexamethylethyl dibenzothiophene, heptamethylethyl dibenzothiophene, methyldiethyldibenzothiophene, dimethyldiethyldibenzothiophene, trimethyldiethyldibenzothiophene, tetramethyldiethyldibenzothiophene, penta Methyldiethyldibenzothi Phen, hexamethyldiethyldibenzothiophene, heptamethyldiethyldibenzothiophene, methylpropyldibenzothiophene, dimethylpropyldibenzothiophene, trimethylpropyldibenzothiophene, tetramethylpropyldibenzothiophene, pentamethylpropyldibenzothiophene, hexamethylpropyldibenzothiophene, heptamethylpropyl Alkyl dibenzothiophenes such as dibenzothiophene, methylethylpropyldibenzothiophene, dimethylethylpropyldibenzothiophene, trimethylethylpropyldibenzothiophene, tetramethylethylpropyldibenzothiophene, pentamethylethylpropyldibenzothiophene, hexamethylethylpropyldibenzothiophene, thianthrene Diphenylene disulfide, molecular formula _C 12 _H 8 _{S 2,} molecular weight 216), thioxanthene (dibenzo thiopyran, diphenylmethane sulfide, molecular formula _C 13 _{H 10} S, include molecular weight 198) and derivatives thereof.

Benzothiophenes are heterocyclic compounds containing one or more sulfur atoms as heteroatoms, and the heterocycle is a penta- or hexa-atom ring and has aromaticity (two or more double bonds in the heterocycle). And a sulfur compound in which the heterocyclic ring is condensed with one benzene ring and derivatives thereof. Benzothiophene, also called thionaphthene or thiocoumarone, is a sulfur compound with a molecular weight of 134, which can be represented by the molecular formula C ₈ H ₆ S. Other representative benzothiophenes include methylbenzothiophene, dimethylbenzothiophene, trimethylbenzothiophene, tetramethylbenzothiophene, pentamethylbenzothiophene, hexamethylbenzothiophene, methylethylbenzothiophene, dimethylethylbenzothiophene, trimethylethylbenzo Thiophene, tetramethylethylbenzothiophene, pentamethylethylbenzothiophene, methyldiethylbenzothiophene, dimethyldiethylbenzothiophene, trimethyldiethylbenzothiophene, tetramethyldiethylbenzothiophene, methylpropylbenzothiophene, dimethylpropylbenzothiophene, trimethylpropylbenzothiophene, Tetramethylpropylbenzothiophene, pentame Le propyl benzothiophene, methyl ethyl propyl benzothiophene, dimethyl ethyl propyl benzothiophene, trimethyl ethylpropyl benzothiophene, alkyl benzothiophenes such as tetramethyl-ethylpropyl benzothiophene, Chiakuromen (Benzoa -γ- pyran, molecular formula C _{9 H} 8 _S, Molecular weight 148), dithiaphthalene (molecular formula C ₈ H ₆ S ₂ , molecular weight 166) and derivatives thereof.

Thiophenes are heterocyclic compounds containing one or more sulfur atoms as heteroatoms, and the heterocycle is a penta- or hexa-atom ring and has aromaticity (has two or more double bonds in the heterocycle). And a sulfur compound in which a heterocyclic ring is not condensed with a benzene ring and derivatives thereof. Also included are compounds in which heterocycles are fused together. Thiophene, also called thiofuran, is a sulfur compound with a molecular weight of 84.1 that can be represented by the molecular formula C ₄ H ₄ S. Other typical thiophenes include methylthiophene (thiotolene, molecular formula C ₅ H ₆ S, molecular weight 98.2), thiapyran (pentthiophene, molecular formula C ₅ H ₆ S, molecular weight 98.2), thiophene (molecular formula C ₆ H ₄ S ₂ , molecular weight 140), tetraphenylthiophene (thionesal, molecular formula C ₂₀ H ₂₀ S, molecular weight 388), dithienylmethane (molecular formula C ₉ H ₈ S ₂ , molecular weight 180) and derivatives thereof.

  Both thiophenes and benzothiophenes are highly reactive with heterocycles containing sulfur atoms as heteroatoms, and in the presence of a solid acid desulfurizing agent, the heterocycles can be cleaved or the heterocycles react with or decompose with aromatic rings. It happens easily. Dibenzothiophenes are less reactive than thiophenes and benzothiophenes because benzene rings are bonded to both sides of the thiophene ring. Dibenzothiophenes having many alkyl groups such as trimethyldibenzothiophene, tetramethyldibenzothiophene, and pentamethyldibenzothiophene are particularly difficult to remove with a solid acid desulfurization agent.

  Further, mercaptans are sulfur compounds RSH (R is a hydrocarbon group such as an alkyl group or an aryl group) having a mercapto group (—SH), and are also called thiols or thioalcohols. Mercapto groups are highly reactive and react particularly easily with metals. Typical mercaptans include methyl mercaptan, ethyl mercaptan, propyl mercaptan (including isomers), butyl mercaptan (including isomers such as tertiary butyl mercaptan), pentyl mercaptan, hexyl mercaptan, heptyl mercaptan, octyl mercaptan, nonyl Examples include mercaptans, decyl mercaptans, and thiophenols Ar-SH (Ar is an aryl group).

Sulfides, also called thioethers, are a generic term for alkyl sulfides and aryl sulfides, and are sulfur compounds represented by the general formula R—S—R ′ (R and R ′ are hydrocarbon groups such as alkyl groups and aryl groups). is there. This is a compound in which two hydrogen atoms of hydrogen sulfide are substituted with an alkyl group or the like. Sulfides are classified into chain sulfides and cyclic sulfides. The chain sulfides are sulfur compounds that do not have a heterocyclic ring containing a sulfur atom as a heteroatom among the sulfides. Typical chain sulfides include dimethyl sulfide, methyl ethyl sulfide, methyl propyl sulfide, diethyl sulfide, methyl butyl sulfide, ethyl propyl sulfide, methyl pentyl sulfide, ethyl butyl sulfide, dipropyl sulfide, methyl hexyl sulfide, ethyl pentyl sulfide. Propyl butyl sulfide, methyl heptyl sulfide, ethyl hexyl sulfide, propyl pentyl sulfide, dibutyl sulfide and the like. Cyclic sulfides have a heterocyclic ring containing at least one sulfur atom as a heteroatom among the sulfides and have no aromaticity (a penta- or hexa-atom ring and two or more double bonds). It is a sulfur compound that does not have a heterocyclic ring. Typical cyclic sulfides include tetrahydrothiophene (tetramethylene sulfide, molecular formula C ₄ H ₈ S, molecular weight 88.1), methyltetrathiophene, and the like.

  Disulfides are disulfides. It is a general term for alkyl disulfide and aryl disulfide, and is a sulfur compound represented by the general formula R—S—S—R ′ (R and R ′ are hydrocarbon groups such as alkyl groups). The sum of the carbon number of the hydrocarbon group constituting R and R ′ is preferably 2 to 8, specifically, dimethyl disulfide, methyl ethyl disulfide, methyl propyl disulfide, diethyl disulfide, methyl butyl disulfide, ethyl propyl disulfide, Examples thereof include chain disulfides such as methylpentyl disulfide, ethylbutyl disulfide, dipropyl disulfide, methylhexyl disulfide, ethylpentyl disulfide, propylbutyl disulfide, methylheptyl disulfide, ethylhexyl disulfide, propylpentyl disulfide, and dibutyl disulfide.

  When kerosene or light oil is used as the raw fuel of the fuel cell, the sulfur contained in kerosene or light oil is a catalyst poison of the reforming catalyst in the hydrogen production process, so it is necessary to remove it strictly. The sulfur content after desulfurization needs to be 50 mass ppb or less, preferably 20 mass ppb or less, and more preferably 5 mass ppb or less.

  The adsorbent of the present invention is particularly effective when adsorbing and removing sulfur compounds and / or polycyclic aromatic compounds that are difficult to desulfurize such as dibenzothiophenes contained in kerosene or light oil. It is also useful to combine a method for removing another sulfur compound or polycyclic aromatic compound before and / or after applying the method for removing adsorbing of the present invention, and in particular, to remove sulfur contained in kerosene or light oil. In that case, it is possible to desulfurize to very low values. Specifically, when combined with adsorption desulfurization of benzothiophenes using a solid acid desulfurization agent, a greater effect can be obtained. In addition, if the polycyclic aromatic compound is adsorbed and removed by the adsorbent of the present invention before performing high-temperature desulfurization at around 200 ° C. with a nickel-based desulfurizing agent, etc., carbon deposition due to the nickel-based desulfurizing agent is reduced. And the life of the desulfurizing agent can be extended.

The adsorbent of the present invention was produced by carbonizing plant biomass at (A) 300-900 ° C under reduced pressure, or (B) 200-900 ° C under reduced pressure and / or inert atmosphere. It is an adsorbent comprising a carbonized product or an activated product having a specific surface area of 200 m ² / g or more and an average pore diameter of 20 mm or more produced by further activation treatment after carbonization treatment in a hydrocarbon oil. Can be removed.

  The carbonized product or activated product is a pore structure substantially made of carbon produced by carbonizing a plant-based organic substance (carbonaceous material) which is plant-based biomass, and further activating the carbon-based material as necessary. A carbonaceous material that has been developed and is generally referred to as activated carbon (hereinafter, the carbonized product and the activated product may be simply referred to as activated carbon).

  In general, many carbonaceous materials are considered as raw materials for activated carbon, and the production conditions of activated carbon differ depending on the type of raw material. Activated carbon raw materials include plant biomass such as wood, sawdust, coconut husk, rice husk, and pulp waste liquid, and coal, heavy petroleum oil, or fossil fuel-based raw materials such as pitch and coke obtained by pyrolyzing them. . Activated carbon is classified into powdered activated carbon, granular activated carbon, and fibrous activated carbon depending on the shape. Powdered activated carbon is powdered activated carbon smaller than 100 mesh, and is usually manufactured from sawdust, wood chips, charcoal, grass charcoal and the like. Granular activated carbon is granular having a size of about 1 to 3 mm, and is manufactured from charcoal, coconut shell charcoal, coal, petroleum coke, or the like. Fibrous activated carbon is generally produced by activating an expensive carbon fiber starting from a fiber obtained by spinning a synthetic polymer, tar pitch or petroleum pitch.

The activated carbon used in the adsorbent of the present invention is preferably obtained from plant-based biomass, particularly wood activated carbon raw materials such as rice husk and / or cedar, and is a sulfur compound and / or polycyclic aromatic compound contained in hydrocarbon oil. Demonstrates excellent removal performance.
Plant biomass, especially wood such as rice husk and / or cedar, has developed water passages such as conduits, and even when activated carbon is formed, mesopores and macropores derived from the conduits are formed. The conduit is a main component of the vascular bundle of angiosperms, and is a passage of moisture absorbed from the roots in a vertically connected tissue in which the upper and lower partition walls of the tubular cells (conduit cells) disappear. The cell wall is partially thickened and produces various patterns. Further, in the case of rice husks, the inorganic components such as silica contained form mesopores and macropores.

Rice is an annual plant of the grass family native to Southeast Asia. Around 1 meter in height, the leaves are linear and alternate. From summer to autumn, a flower spike consisting of many spikelets is attached to the top of the stem. Rice husk is the outer shell that wraps rice and is the shell of rice. About 5 to 10% by mass of water is contained, and about 50% by mass is volatilized by heating to 400 ° C. in an oxygen-free atmosphere. Further, when heated to 800 ° C., about 60 to 70% by mass is volatilized. The composition of the carbonized rice husk after heating at 800 ° C. is 30 to 40% by mass of carbon, about 1% by mass of hydrogen, about 1% by mass of nitrogen, and the remaining 60 to 70% by mass are inorganic components. Among the inorganic components, 90% by mass or more is SiO ₂ , and the rest is K ₂ O, P ₂ O ₅ , CaO and the like. These compositions are affected by soil and climate, and vary depending on the production area. As a raw material for the activated carbon, rice husk having a high carbon content to form micropores is preferable, that is, it is preferable that there are few inorganic components.

  Cedar is an evergreen Takagi of the cedar family and is planted in various places with Japanese special species. The trunk is upright, and needle-like leaves are closely attached in a spiral shape to the branches. Some have long lives and become giant trees with a height of 50 meters or more and a diameter of 5 meters or more. The material is aromatic and has a good grain texture, and it is light and soft, so it is often used for construction, furniture, and equipment. Any form of cedar that makes activated carbon can be used, but sawwood, wood chips, etc. are preferred. The use of cedar thinning is also effective from the viewpoint of effective use of resources. preferable.

Carbonization is a series of carbon enrichment, resulting in carbonaceous solid products, such as bond breakage caused by heat changes in organic matter and decomposition, polycondensation, aromatic cyclization, etc. It is a general term for a wide variety of chemical reactions. The raw material can be carbonized with high heat to obtain coke and char. At the same time, water, carbon oxide and light hydrocarbons volatilize and liquid is distilled off during this carbonization reaction process. The pore structure that greatly affects the adsorption characteristics of activated carbon varies depending on the carbonization temperature. In the present invention, carbonization is performed in a temperature range of 200 to 900 ° C. If the activation treatment is not performed after the carbonization treatment, the carbonization treatment is performed at 300 to 900 ° C.
Since the temperature of carbonization uses plant-based biomass as a raw material, it is preferable that the high temperature side is lower in any of the above temperature ranges, specifically 600 ° C. or lower is preferable, 500 ° C. or lower is more preferable, and particularly preferable. Is 400 ° C. or lower.

  Further, the carbonization treatment is performed under reduced pressure or in an inert atmosphere. It can also be performed under reduced pressure and in an inert atmosphere. The reduced pressure refers to a pressure in the range of 50 to 500 hPa, and more preferably 100 to 300 hPa. When the decompression is insufficient, the carbon component reacts with oxygen in the air and disappears. On the other hand, when carbonization is performed under a vacuum in which the pressure reduction has proceeded excessively, the carbonization process is not performed, and therefore a separate activation process is required. Here, the vacuum refers to a state where the atmospheric pressure is less than 50 hPa.

  When the carbonization treatment is performed in an inert atmosphere, it is preferably performed in an atmosphere of an inert gas such as nitrogen or argon, and it is particularly economical and preferable to perform in a nitrogen gas flow. The reason why the inert atmosphere is used is to prevent reaction with oxygen in the air, and any pressure that prevents the mixing of oxygen may be used. 0.05 to 0.2 MPa (absolute pressure) around atmospheric pressure Is preferred. If the pressure is reduced to 0.05 MPa (500 hPa) or less, there is no need for an inert atmosphere because oxygen is sufficiently small. Further, if the pressure is increased to 0.2 MPa or more, the equipment becomes expensive and pressure adjustment is required, which is not economical. When performing a carbonization process in nitrogen atmosphere, it is performed at 200-600 degreeC for 1-3 hours. Thereafter, when an activation treatment is performed at 800 to 900 ° C. for 1 to 3 hours in a carbon dioxide atmosphere, activated carbon having a large specific surface area and a large pore volume is obtained. Moreover, even if it carbonizes at 800-950 degreeC under reduced pressure for 1-3 hours, activated carbon with a large specific surface area and pore volume can be obtained.

  The method of activation treatment after carbonization treatment in the production of activated carbon used in the present invention is not particularly limited, and examples include conventional activation methods that are generally used, such as gas activation methods and chemical activation methods. Can do. In Japan, the gas activation method using water vapor is the mainstream, but the chemical activation method using zinc chloride is still used in the production of powdered activated carbon. In recent years, an alkali activation method, which is a new chemical activation method, has also been reported.

  Among these, the gas activation method is a more preferable method, which is also referred to as physical activation. The carbon material is heated at a high temperature, for example, at 800 to 900 ° C. with a gas such as water vapor, carbon dioxide, oxygen, and the like for a certain period of time, preferably 0.8. A fine porous activated carbon having good performance can be produced by contact reaction for 1 to 4 hours. The activation process is thought to proceed in two stages, and in the first heating process, the carbon in the unorganized portion where carbon crystallization has not progressed so much is selectively decomposed and consumed into carbon monoxide and carbon dioxide. Then, the closed fine pores between the carbon crystals are opened, and the specific surface area is rapidly increased. In the second stage gasification reaction process, carbon such as carbon crystals is consumed by reaction to carbon monoxide and carbon dioxide, and mesopores and macropores are formed.

  The chemical activation method is a method for producing fine porous activated carbon by dehydration and oxidation reaction of chemicals by impregnating raw materials evenly with an activation chemical and heating and baking in an inert gas atmosphere. Activating chemicals are zinc chloride, sulfuric acid, boric acid, nitric acid, hydrochloric acid, phosphoric acid, sodium phosphate, calcium chloride, potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, calcium carbonate, potassium sulfate, sodium sulfate, sodium sulfate Dehydrated, oxidized, and erodible chemicals such as potassium nitrate, potassium chloride, potassium permanganate, potassium sulfide, and potassium thiocyanate are used. In the chemical activation, the mass ratio of the chemical to be impregnated with respect to the carbonaceous raw material is an important measure of activation, and specifically, the mass ratio is preferably about 0.5 to 2.0. When the mass ratio is small, micropores are generated, and as the mass ratio increases, pores having a large pore diameter are developed and the pore volume increases.

  Plant-based biomass develops conduits for transporting water and tends to form mesopores and macropores. In addition, in the case of rice husk, the silica component further forms mesopores and macropores by including the silica component, so that it is easier to form mesopores and macropores than wood not containing the silica component. Therefore, since plant biomass, especially rice husks, can easily form mesopores and macropores, a chemical activation method for forming mesopores and macropores is not always necessary. A gas activation method using carbon is simple and preferable.

  The adsorption characteristics by activated carbon are essentially determined by the contact between the surface of the activated carbon and adsorbate molecules and the in-situ interaction energy. Therefore, the relationship between the pore distribution and the adsorbate molecular diameter affects the contact, and the structure and physical properties of the adsorbate molecule affect the strength of the interaction. That is, when the adsorbate is a relatively large sulfur compound such as dibenzothiophenes, not only the micropores that are the adsorption sites of activated carbon have developed, but also mesopores and macropores that serve as a passage to the micropores. Need to be well developed. Also, due to the interaction between the π-electron orbitals of polycyclic aromatic molecular assemblies (also called graphite structures) partially present on the surface of activated carbon and the π-electron orbitals of benzene rings of dibenzothiophenes and polycyclic aromatics It is considered that dibenzothiophenes are adsorbed on activated carbon. Furthermore, in many cases, liquid phase adsorption is multi-component competitive adsorption, and is complicated by the interaction between the solvent and the solute molecule and the adsorption force of the solvent or solute molecule to the adsorbent. The present inventor has found that the adsorption capacity of sulfur compounds is not simply proportional to the specific surface area.

  The fibrous activated carbon having a relatively small specific surface area has a larger adsorption capacity than the powdered activated carbon having a large specific surface area. Although various causes are considered, it is thought that the pore structure of the above-mentioned activated carbon has a great influence. Compared with granular activated carbon, fibrous activated carbon generally has advantages such as a very high adsorption rate, a high adsorption amount at a low concentration, and processing into various shapes such as felt. However, as mentioned above, it is an expensive product produced by activating carbon fibers starting from fibers that are spun from synthetic polymers or petroleum pitches, so it is used in large quantities for desulfurization of kerosene and light oil. It is not economical to do. The activated carbon used in the adsorbent of the present invention can be obtained by a relatively inexpensive method of carbonizing and activating plant biomass such as rice husk and cedar, and the plant biomass such as rice husk is fibrous. In addition, activated carbon made from rice husk and the like has the same effect as fibrous activated carbon.

  The adsorbent of the present invention can be used for adsorbing and removing sulfur compounds and / or polycyclic aromatic compounds contained in kerosene or light oil, such as powdered, particulate, or molded products such as spherical, disk-shaped, cylindrical, etc. It can be used in the form of When used in powder or particulate form, the activated carbon is pulverized with a known appropriate pulverizer and then classified with a known appropriate classifier to obtain a powder or average particle having an average particle diameter of about 0.5 μm to 0.1 mm. The activated carbon can be appropriately used according to use conditions by sieving it into particulate activated carbon having a diameter of about 0.1 to 5 mm. In the case where the adsorbent is continuously used and regenerated repeatedly, it is preferable to use activated carbon as a molded product. As the shape of the molded product, in order to increase the concentration gradient of trace components to be removed, such as sulfur compounds, in the case of flow-through type, the shape is small, especially spherical, so long as the differential pressure before and after the container filled with the adsorbent does not increase. Is preferred. In the case of a spherical shape, the size is preferably 0.1 to 5 mm, particularly 0.3 to 3 mm. In the case of a columnar shape, the diameter is preferably 0.1 to 4 mm, particularly 0.12 to 2 mm, and the length is preferably 0.5 to 5 times, particularly 1 to 2 times the diameter. The molded article preferably has a breaking strength of 0.5 kg / pellet or more, particularly 1.0 kg / pellet or more so as not to crack during use as an adsorbent. The breaking strength is measured by a compressive strength measuring device such as a Kiya-type tablet breaking strength measuring device (manufactured by Toyama Sangyo Co., Ltd., TH-203MP).

When used as a molded product, (1) the raw material may be molded and then carbonized and then activated, or (2) the raw material may be carbonized and then molded and activated. (3) The raw material may be formed after carbonization treatment and activation treatment, dried and fired. Since most of the raw material is a volatile component, the strength of the activated carbon obtained by molding before carbonization treatment does not increase, the mixing with the binder component can be made more uniform after carbonization than the raw material, Since the carbonization treatment and the activation treatment can be performed at the same time, the process can be shortened. Therefore, it is particularly preferable that the raw material (2) is molded after the carbonization treatment and then activated.
The raw material and / or carbonized product is particularly preferable when it is pulverized before mixing with the binder component because it can be uniformly mixed with the binder component.

  When molding, a binder (binding agent) can be used as necessary. Examples of the binder include tar pitch, tar-compatible resin, expanded graphite, lignin, sodium alginate, carboxymethyl cellulose (CMC), synthetic polymer compounds such as phenol resin and polyvinyl alcohol, molasses, starch, sugar beet juice, brown sugar, Examples include natural organic binders composed of sugars such as sugar cane juice and oligosaccharides, and inorganic binders such as alumina, smectite, and water glass. Activated carbon from plant-based biomass, which is a raw material, has the best mixability with sugars, and the strength of the obtained activated carbon is also increased. Further, as a carbon source, there is an effect of improving the specific surface area. Of these, starch and sugar beet are more preferable.

Starch is a kind of polysaccharide and is a polymer of glucose (D-glucose). About 20% by mass is composed of linear polymer amylose, and about 80% by mass is composed of amylopectin having many branches. Side dish is another name for sugar beet and beat. For use as a binder, sugar beet juice can be used as it is, but it is preferably boiled and concentrated to increase viscosity.
These binders may be used to such an extent that they can be molded, and are not particularly limited, but are usually about 0.05 to 200% by mass, particularly preferably 20 to 100% by mass based on the raw material. The When it is less than 0.05% by mass, the strength of the obtained activated carbon is lowered. On the other hand, when the amount is more than 200% by mass, the pore structure, which is a feature of rice husks, etc. cannot be obtained sufficiently. In the case of a natural organic binder containing an unspecified amount of moisture, the amount of the binder used is based on the remaining amount excluding moisture (dry basis).
Since there is no caking property in the dry state, water of the same weight is added to the sufficiently dried powdery saccharide, and it is heated at about 100 ° C. As time elapses, the water evaporates and becomes a fluid liquid (syrupy saccharide). In this state, it is used as a binder.
When adding saccharides as a carbon source for improving the specific surface area, powdered saccharides can be dissolved in 1 to 20 times the weight of water at about 60 ° C. and impregnated with carbide as an aqueous saccharide solution. good.

  The activated carbon of the present invention is carbonized in order to improve the adsorption performance of sulfur compounds, etc., on which activated carbon is difficult to adsorb, and / or to increase the diffusion rate of sulfur compounds, etc. by increasing the abundance of mesopores and macropores. You may mix inorganic substances, such as a silica, an alumina, and a zeolite, in the middle of processing, shaping | molding, and an activation process. Also, by combining with metals and / or metal oxides such as silver, mercury, copper, cadmium, lead, molybdenum, zinc, cobalt, manganese, nickel, platinum, palladium, iron, etc., that is, by supporting these metals The adsorption performance can also be improved. From the viewpoint of safety and economy, the oxides of copper, silver, manganese, zinc, and nickel are preferable. Among these, copper is inexpensive and has excellent performance for adsorption of sulfur compounds in a wide temperature range from near room temperature to about 300 ° C., in the state of copper oxide without reduction treatment, and in the absence of hydrogen. This is particularly preferable. The preferred amount of metal supported is not particularly limited, and varies depending on the type of metal, but is 0.1 to 20% by mass, particularly 0.5 to 5% in the case of a noble metal, based on the metal simple substance relative to the finished adsorbent. It is preferable to carry by mass%. If it is less than 0.1% by mass, the supporting effect is small, and if it is more than 20% by mass, it is not economical. In the case of copper and other metals, it is preferable to carry 0.1 to 60 mass%, particularly 3 to 20 mass%. If the amount is less than 0.1% by mass, the supporting effect is small. If the amount is more than 60% by mass, the amount of the metal having a weak bond with the activated carbon that is the carrier increases, so that the metal component may be detached. When the amount of metal supported is large, the adsorption performance of sulfur compounds such as thiophenes and benzothiophenes that are difficult to adsorb activated carbon can be further improved.

  The adsorbent is preferably dried at about 100 to 200 ° C. in an oxidizing atmosphere such as air in order to remove a small amount of water adsorbed on the adsorbent as a pretreatment. If it exceeds 200 ° C., it reacts with oxygen and the weight of the adsorbent decreases, which is not preferable. On the other hand, the adsorbent is preferably dried at about 100 to 800 ° C. in a non-oxidizing atmosphere such as nitrogen. In particular, heat treatment of the adsorbent at 400 to 800 ° C. in a non-oxidizing atmosphere is more preferable because organic substances and contained oxygen are removed and the adsorption performance is improved.

  A larger specific surface area is preferable in terms of increasing the number of sites where sulfur compounds and the like are adsorbed, but the specific surface area is correlated with the amount of micropores, and the larger the specific surface area, the more micropores. However, if there are not enough mesopores and macropores that are paths to the micropores, adsorbates such as sulfur compounds cannot be smoothly diffused into the micropores. If all of the micropores and macropores are increased, the adsorbent becomes extremely low in strength and the shape of the activated carbon cannot be maintained. Therefore, the balance between the micropores, mesopores and macropores is important. Therefore, even if the specific surface area is increased unnecessarily, that is, the number of micropores is increased, the large specific surface area cannot be fully utilized unless the number of mesopores and macropores is sufficiently large.

Since the specific surface area of the adsorbent of the present invention greatly affects adsorption such as desulfurization performance, it is preferably 200 to 4,000 m ² / g, more preferably 300 to 3,000 m ² / g, particularly 450 to 2,000 m. ² / g is preferred. The average pore diameter is proportional to the pore volume and inversely proportional to the specific surface area. If the average pore diameter is too large, the pore volume is too large to obtain a sufficient density, and the adsorption capacity per unit volume becomes low. On the other hand, if the average pore diameter is too large, the specific surface area is too small to obtain sufficient adsorption sites, and the adsorption capacity is also lowered. The average pore diameter of the adsorbent of the present invention is preferably 20 to 40 mm, more preferably 20 to 35 mm, and particularly preferably 20 to 30 mm.

  The pore volume is related to the specific surface area, but is preferably 0.10 ml / g or more, more preferably 0.20 ml / g or more, and particularly preferably 0.25 ml / g or more. The pore volume having a pore diameter of less than 10 mm is preferably 0.05 ml / g or more, particularly preferably 0.10 ml / g or more in order to increase the adsorption capacity of sulfur compounds and the like. In addition, the pore volume having a pore diameter of 10 mm or more and less than 0.1 μm is 0.01 ml / g or more, further 0.02 ml / g or more, particularly 0 in order to increase the diffusion rate of sulfur compounds in the pores. It is preferable to set it as 0.03 ml / g or more. The pore volume having a pore diameter of 0.1 μm or more is preferably 0.3 ml / g or less, particularly preferably 0.25 ml / g or less, in order to increase the mechanical strength of the molded article. In general, the specific surface area and the total pore volume are measured by a nitrogen adsorption method, and the macropore volume is measured by a mercury intrusion method. The nitrogen adsorption method is simple and commonly used, and is described in various documents. For example, Kazuhiro Hagio: Shimazu review 48 (1) 35-49 (1991), ASTM (American Society for Testing and Materials) Standard Test Method D 4365-95.

In the adsorbent of the present invention, the micropore specific surface area S _micro [m ² / g], the micropore external pore volume V _ext [cm ³ / g], and the micropore external specific surface area of the carbon material used for the adsorbent are used. It is preferable that S _ext [m ² / g] satisfies the following formula (1).
S _micro × 2 × V _ext / S _ext > 0.7 (1)

The carbon material used for the adsorbent of the present invention preferably has a mesopore having a large specific surface area and a pore diameter of about 20 to 500 mm. Parameters such as specific surface area, pore diameter, and pore volume used in the analysis of carbon materials are generally measured by gas adsorption methods using physical adsorption based on intermolecular forces acting between gas molecules and solid surfaces, especially nitrogen. An adsorption method is used. Since many carbon materials have an average pore diameter of 20 mm or less, care must be taken in their analysis. A commonly used BET (Brunouer-Emmett-Teller) method is a method for obtaining the specific surface area of a carbon material based on the following formula (2).
x / V / (1-x) = 1 / V _m / C _B + (C _B −1) x / V _m / C _B (2)
Here, x is the relative pressure, V is the adsorption amount when the relative pressure is x, V _m is the monomolecular layer adsorption amount, and _CB is a constant (> 0). That is, the constant C _B is the BET method needs a positive value, not suitable if negative. When the constant C _B <0, the relative pressure used for the calculation may be lowered to 0.05 to 0.1, for example, or parameters such as specific surface area, pore diameter, pore volume may be obtained by the Langmuir method. Many. In the Langmuir method, the specific surface area of the carbon material is obtained based on the following formula (3).
_{x / V = x / V m} + 1 / V m / C L ··· (3)
Here, x is the relative pressure, V is the adsorption amount when the relative pressure is x, V _m is the monomolecular layer adsorption amount, and _CL is a constant (> 0). Therefore, it not appropriate if the constant C _L is negative in Langmuir method. When the constant C _B <0 and the constant C _L <0, remeasurement or the like is necessary.

In addition, micropores can be quantified by the t plot method. In the t plot method, the horizontal axis represents the adsorption layer thickness t (function of relative pressure), and the vertical axis represents the adsorption amount, and the change in the adsorption amount of the carbon material with respect to the adsorption layer thickness t is plotted. In the plotted characteristics, there exists an adsorption layer thickness region t _{B in} which the slope of the t plot continuously decreases. In the area t _B, with the progress of the multi-molecule layer adsorption, the fine pore (micropore) is met adsorbed gas (nitrogen), it does not contribute as a surface. Since this phenomenon is caused by the filling of the micropores in the adsorption layer thickness region t _B , in the region where the adsorption layer thickness t is smaller and larger than the region t _B , the gas molecule micro- Since no pore filling or capillary condensation has occurred, the slope of the t plot is constant. Therefore, the thickness t is larger than the area t _B region of the adsorption layer, i.e. draw a straight line in the region where the filling of the micropores of the gas molecules is completed, the contribution from the slope as the surface other than the micropores of the carbon material The specific surface area (external specific surface area) is determined. Further, if the value of the intercept on the vertical axis of the straight line drawn in the region where the thickness t of the adsorption layer is larger than the region tB is converted into liquid, the micropore volume can be obtained. In summary, the adsorption amount V of the carbon material, the micropore external specific surface area S _ext [m ² / g], the micropore specific surface area S _micro [m ² / g], the micropore volume V _micro [cm ³ / g] and micropore external pore volume V _ext [cm ³ / g] are obtained by the following formulas (4) to (8).
V = αt + β (t> t _B ) (4)
S _ext = α × 10 ³ × D (5)
V _micro = β × D (6)
_{S micro = S a -S ext ···} (7)
V _ext = V _a −V _micro (8)
Here, α [cm ³ (STP: 1 atm, 0 ° C.) / G / nm] is the slope of the straight line of the t plot in the region where the thickness t of the adsorption layer is larger than the region t _B , and β [cm ³ (STP) / g] (0.001547 when the nitrogen used as a ^gas) intercept of the straight line and the longitudinal axis of the t plot in the region greater than the thickness t of the region _{t B} of the adsorption layer, D is the density conversion coefficients are ^[cm 3 liq / Cm ³ (STP)], S _a is the total specific surface area [m ² / g], and V _a is the total pore volume [cm ³ / g]. However, S _a is the total specific surface area determined by such aforementioned BET method or Langmuir method. V _a can be defined as a value obtained by converting the amount of adsorbed gas at a pressure close to the saturated vapor pressure into a liquid. For example, the adsorbed amount [cm ³ (STP) / g] when the relative pressure is 0.95. Is the value of D multiplied by D.

Many of the carbon materials are mainly micropores, and there are almost no mesopores outside the micropores. However, it has been found through a verification experiment by the present inventors that a very small amount of mesopores existing outside the micropores greatly affects the adsorption of sulfur compounds. The present inventor has found that a value of 2 × Vext / Sex is suitable as an index representing the influence of mesopores. Since the value 2 × V _a / S _a represents the average pore radius (D _a / 2) or the distance between the walls of the plate-like pores assuming that the pores are cylindrical, 2 × V _ext / S _ext is an index representing a value close to the average pore radius (D _ext / 2) of the mesopores or the distance between the walls. Furthermore, the present inventor has previously proposed an activated carbon having a specific pore structure, particularly a fibrous activated carbon, having high removal performance with respect to dibenzothiophenes contained in light oil and kerosene. Regarding the adsorption of sulfur compounds, it is preferable that the micropore specific surface area and the mesopore average pore radius (or the wall-to-wall distance) of the carbon material are large, and in particular, the product of both (S _micro × 2 × V _ext / S _ext ) has a value. It has been found that the larger the value, the better the adsorption performance of the carbon material. _{Specifically,} the value of _{S micro × 2 × V ext /} S ext 0.7cm 3 / g or more, more preferably 3.0 cm ³ / g or more, the carbon and even more preferably at 5.0 cm ³ / g or more It was found that the material adsorption performance is improved. The cause of this is not clear, but the adsorption performance of the carbon material does not simply depend on the amount of mesopores, and in order to improve the adsorption performance of the carbon material, a sufficient diameter that does not clog due to adsorption of sulfur compounds. It is thought that this represents the need for other mesopores.

In order to remove sulfur contained in light oil to a low concentration by using the adsorbent of the present invention for desulfurization, for example, to make it 15 ppm or less, the packing density of the carbon material used for the adsorbent is sufficiently high. It is desirable to do. Specifically, the packing density C [g-adsorbent / ml-adsorbent] of the carbon material and the adsorption capacity A [g-S per unit weight of the carbon material when the sulfur concentration of the gas oil in the liquid phase is 15 ppm. / G-adsorbent] and the density B [g / ml] of the light oil must satisfy at least the following formula (9).
C> B × k ÷ A (9)
Here, k = 0.000015 [g-S / g]. When the sulfur concentration of the light oil in the liquid phase is 15 ppm, the adsorption capacity A per unit weight of the carbon material can be obtained from the adsorption isotherm at the temperature of the adsorption desulfurization process.

The above-mentioned carbon materials have excellent adsorption performance for thiophenes, benzothiophenes, and dibenzothiophenes, and are superior in adsorption performance for benzothiophenes and dibenzothiophenes, especially dibenzothiophenes, compared to zeolite-based adsorbents. In addition, although polycyclic aromatic compounds are adsorbed, there is little influence on aromatic content.
On the other hand, the zeolite component is superior in adsorption performance for mercaptans, chain sulfides, and cyclic sulfides as compared with carbon materials. Therefore, depending on the type and amount of sulfur compounds contained in petroleum fractions, it is possible to efficiently remove sulfur compounds contained in petroleum fractions by using a combination of zeolite components and carbon materials as adsorbents. It becomes. Examples of the type of zeolite include X-type zeolite, Y-type zeolite, L-type zeolite, mordenite, ferrierite, and β-zeolite.

The method of bringing the adsorbent of the present invention into contact with hydrocarbon oil may be a batch type (batch type) or a flow type, but a flow type in which hydrocarbon oil is circulated in a container filled with the adsorbent of a molded product is more preferable. .
For flow-through, as a condition for contacting the pressure is atmospheric pressure to 50 kg / ^cm 2 G, is more preferably from atmospheric pressure to 10 kg / cm ² G, particularly 0.1~3kg / cm ² G preferable. The flow rate is preferably 0.01 to 100 hr ⁻¹ , particularly 0.05 to 20 hr ⁻¹ in LHSV. The temperature for performing the desulfurization treatment is preferably 10 to 150 ° C, particularly 30 to 100 ° C.

  When the adsorbent of the present invention is used in a fuel cell system, the adsorbent of the present invention may be used in combination with another adsorbent. Since the adsorbent of the present invention is particularly excellent in removal performance of dibenzothiophenes, other adsorbents excellent in removal performance of other types of sulfur compounds such as benzothiophenes, mercaptans, or sulfides, For example, for the removal of benzothiophenes, the present invention has previously proposed the removal of desulfurization agents such as activated carbon on which a solid acid catalyst and / or transition metal oxide is supported, and mercaptans, which the present inventor previously proposed. A combination with zeolite or the like is preferable for removing copper oxide-supported alumina and sulfides.

  When the present adsorbent is used in a refinery or the like, it is preferable to install two or more adsorption tanks (or adsorption towers) filled with the adsorbent. First, the hydrocarbon oil that adsorbs and removes sulfur compounds and polycyclic aromatic compounds is circulated in one adsorption tank. When the removal performance of the adsorbent is reduced and sufficient removal performance cannot be obtained, another adsorption is performed. Switch to the tank. The separated adsorption tank is replaced with a new adsorbent, or the deteriorated adsorbent is desorbed and regenerated to prepare for switching to the adsorption tank during the adsorption process. Furthermore, two or more adsorption tanks are connected in series, and when the removal performance of the adsorption tank on the most upstream side is completely lost or significantly reduced, the use of the adsorption tank is stopped and a new adsorption is most downstream. A method in which an adsorption tank filled with an agent or desorbed and regenerated is always connected is particularly preferable.

  Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.

  Akitakomachi from Ogata Village, Akita Prefecture (2002 harvest), Akitakomachi from Nishikimura, Akita Prefecture (2003 harvest), Akitakomachi from Ogatsu-gun, Akita Prefecture (2003 harvest), Hitomebori from Yurihonjo, Akita Prefecture (2003 harvest), Akita Prefecture Rice husks from Yokote City Akitakomachi (harvested in 2003) and Toyooka village in Shizuoka Prefecture (harvested in 2004) and cedar produced in Akita Prefecture were carbonized and activated under the conditions shown in Table 1. The carbonization treatment was performed in a range of 400 to 900 ° C. for 1 to 3 hours under vacuum (5 hPa), reduced pressure of 200 hPa, or normal pressure and under a nitrogen atmosphere. Furthermore, about a part of sample, the activation process was implemented in the range of 800-900 degreeC and 0.25-5 hours in the carbon dioxide atmosphere.

Specific surface area, pore volume and average pore diameter, micropore external specific surface area S _ext , micropore volume, micropore specific surface area S _micro , micro of each activated carbon obtained by performing carbonization treatment and activation treatment described in Table 1 Tables 2 and 3 show the pore average pore diameter D _micro , micropore external pore volume V _ext , external average pore diameter D _ext , micropore specific surface area × external average pore diameter / 2 (S _micro × D _ext / 2). Show. The average pore diameter [Å] was determined by the following formula (10).
Average pore size [Å]
= 4 × pore volume [ml / g] / specific surface area [m ² / g] × 10 ⁴ (10)

  When carbonization treatment is performed at 400 to 600 ° C. for 1 to 3 hours in a nitrogen atmosphere and then activation treatment is performed at 800 to 900 ° C. for 1 to 3 hours in a carbon dioxide atmosphere, or carbonization treatment is performed at 900 ° C. for 1 hour under reduced pressure. It can be seen that activated carbon having a large specific surface area and a large pore volume can be obtained. It can also be seen that the physical properties differ depending on the rice husk producing area even in the same carbonization treatment and activation treatment. Furthermore, comparing rice husk and cedar, it can be seen that cedar has a larger specific surface area but a smaller average pore diameter. The optimum activation treatment temperature differs depending on the raw material. When rice husk was used as the raw material, the activation treatment temperature was 850 ° C. in a carbon dioxide atmosphere. However, when cedar was used as the raw material, the activation treatment temperature was carbon dioxide. When the temperature was 850 ° C. or higher in the atmosphere, the yield was remarkably lowered.

The activated carbons of Examples 1 to 20 and Comparative Examples 1 to 10 prepared as described above were used as adsorbents, and immersion adsorption experiments with kerosene were performed. The prepared activated carbon was previously dried at 150 ° C. for 3 hours. Even after the activation treatment, the rice husk maintained the raw material shape such as the shape of the rice husk, but was not pulverized. The ratio (weight) of kerosene to the adsorbent was set to 8 or 30, and the adsorbent was immersed in kerosene and allowed to stand at 10 ° C. for 4 days, and then the sulfur content of kerosene was analyzed. From the value of the sulfur content before and after the immersion, the ratio of the sulfur content adsorbed and removed by the following formula (11) was calculated as the desulfurization rate [%]. The results are shown in Table 4.
Desulfurization rate [%] = 100 × (S ₁ −S ₂ ) / S ₁ (11)
In the formula, S ₁ and S ₂ represent the sulfur content before and after immersion, respectively.

  In the above immersion type adsorption experiment, kerosene manufactured by Japan Energy Co., Ltd. was used. Its properties are the boiling range 158.5 to 270.0 ° C, 5% distillation point 170.5 ° C, 10% distillation point 175.0 ° C, 20% distillation point 181.5 ° C, 30% distillation point. 188.0 ° C, 40% distillation point 194.5 ° C, 50% distillation point 202.5 ° C, 60% distillation point 211.0 ° C, 70% distillation point 221.0 ° C, 80% distillation point 232.0 ° C, 90% distillation point 245.5 ° C, 95% distillation point 256.5 ° C, 97% distillation point 263.5 ° C, density (15 ° C) 0.7982 g / ml, aromatic content 17 0.5% by volume, 82.5% by volume of saturation, 13.6 mass ppm of sulfur, 16 mass ppb of sulfur derived from light sulfur compound (lighter sulfur compound than benzothiophene), benzothiophenes (benzothiophene, And heavier than benzothiophene and lighter than dibenzothiophene) Coming sulfur content 9.6 mass ppm, sulfur content 4.0 mass ppm derived from dibenzothiophenes (dibenzothiophene and sulfur compounds heavier than dibenzothiophene) (ratio 29 mass% in the total sulfur content), The nitrogen content was 1 mass ppm or less and the polycyclic aromatic content (the total of the contents of the 2-ring, 2.5-ring and 3-ring aromatic) was 0.29 mass%. The sulfur content was measured using a fuel oxidation-ultraviolet fluorescence sulfur analyzer, the sulfur compound type was gas chromatograph-inductively coupled plasma mass spectrometer (GC-ICP-MS), and the polycyclic aromatic quantitative analysis was performed by the British Petroleum Institute (The Institute of Petroleum) standard IP standard method 391/95 (analysis of aromatic hydrocarbons in middle distillate by high performance liquid chromatograph using refractive index detector).

Activated carbon produced by carbonization treatment at 400 to 600 ° C. for 1 hour under a nitrogen atmosphere and then activation treatment at 800 to 900 ° C. for 1 to 3 hours under a carbon dioxide atmosphere or carbonization treatment at 900 ° C. for 1 hour under reduced pressure. Shows that the desulfurization rate is high. In addition, comparing rice husk and cedar, it can be seen that cedar can obtain a higher desulfurization rate even though cedar has a larger specific surface area.
In addition, since activated carbon mainly removes dibenzothiophenes selectively, the content of dibenzothiophenes contained in kerosene is about 30% with respect to the entire sulfur content, so the desulfurization rate is about 30%. It is difficult to obtain a higher desulfurization rate.
The polycyclic aromatic content of kerosene after desulfurization, which was subjected to an adsorption test under the condition of kerosene / adsorbent ratio: 8/1 with the activated carbon of Example 2, was 0.23% by mass. It can be seen that the adsorbent of the present invention can adsorb and remove polycyclic aromatic compounds in the same manner as sulfur compounds.

(reference)
Kerosene after desulfurization, which was subjected to an adsorption test with the activated carbon of Example 2 under the condition of kerosene / adsorbent ratio: 8/1, was further treated with tungstic acid / alumina (specific surface area 102 m ² / g, pore volume 0.316 ml / g, The same immersion type adsorption experiment was performed with a median pore diameter of 101 mm, tungstic acid 20 mass%, zirconia 53 mass%, and alumina 25 mass%. The ratio (weight) of kerosene to tungstic acid / alumina was 4. The sulfur content of the kerosene after the experiment was 20 mass ppb or less.

(Example 22)
Manufacture of molded adsorbent Akitakomachi rice husk from Ogatamura was carbonized at 400 ° C. for 1 hour in a nitrogen atmosphere to obtain carbonized rice husk. Also, after adding water of the same weight to fully dried powdered saccharides (sugar beet, brown sugar and sugarcane), heat at about 100 ° C. to gradually evaporate the water, and a fluid liquid (syrupy saccharides) ) A paste was prepared by mixing 0.7 g (dry basis) of syrup sugars with 1.0 g of carbonized rice husk. The paste was pressed at a pressure of 1 ton / cm ² for 1 minute to form a disk having a diameter of 15 mm and a thickness of 5.0 to 7.3 mm. Thereafter, the disk-shaped molded product was subjected to activation treatment at 850 ° C. for 1 to 2 hours in a carbon dioxide atmosphere. Table 5 shows the properties and the like of the activated product obtained as a result. It can be seen that the disk shape is maintained even after the activation treatment, and the specific surface area is high as in the case where the molding is not performed, and the molding can be performed by using a saccharide as a binder.

(Example 23)
The rice husks from Koshihikari (harvested in 2004) from Toyooka Village, Shizuoka Prefecture were carbonized at 250 ° C. for 1 hour in a nitrogen atmosphere to obtain carbonized rice husks. Moreover, after adding water of the same weight to the sufficiently dried powdery side dish, the liquid was gradually evaporated by heating at about 100 ° C. to obtain a fluid liquid (syrupy side dish). A paste was prepared by mixing 0.7 g (dry basis) of syrupy sugar beet with 1.0 g of carbonized rice husk. The paste was pressed at a pressure of 3 ton / cm ² for 1 minute to form a disk having a diameter of 30 mm and a thickness of 2 mm. Carbonization was performed at 400 ° C. for 1 hour under a nitrogen atmosphere to obtain carbonized rice husk twice. After pulverizing the carbonized rice husk twice, a paste was prepared by mixing 0.3 g (dry basis) of syrupy sugar beet with 1.0 g of carbonized rice husk twice. The paste was pressed at a pressure of 3 ton / cm ² for 1 minute to form a disk having a diameter of 30 mm and a thickness of 2 mm. Thereafter, the disk-shaped product was subjected to activation treatment at 875 ° C. for 1 hour in a carbon dioxide atmosphere.

(Example 24)
The rice husks from Koshihikari (harvested in 2004) from Toyooka Village, Shizuoka Prefecture were carbonized at 250 ° C. for 1 hour in a nitrogen atmosphere to obtain carbonized rice husks. In addition, after adding 11 times the weight of water to a well-dried powdered side dish, the temperature was raised to about 60 ° C. while stirring at 200 rpm with a hot stirrer and held for 10 minutes to obtain a side dish solution It was. A sugar beet-impregnated carbonized rice husk was prepared by spraying 2.0 g (dry basis) of the sugar beet solution with 2.0 g (dry basis) of the carbonized rice husk. After standing for 18 hours, the sugar beet-impregnated rice husk was dried in an oven at 105 ° C. for 2 hours, and then carbonized at 400 ° C. for 1 hour in a nitrogen atmosphere to obtain carbonized rice husk twice. After pulverizing the carbonized rice husk twice, 0.6 g (dry basis) of the sugar beet solution was sprayed onto 1.4 g of the carbonized rice husk twice to prepare a carbonized rice husk twice impregnated with the sugar beet twice. After standing for 18 hours, the carbonized rice husks impregnated twice with the sugar beet twice were pressed at a pressure of 3 ton / cm ² for 1 minute to form a disk with a diameter of 30 mm and a thickness of 3 mm. After drying in an oven at 105 ° C. for 1 hour, the disk-shaped molded product was subjected to activation treatment at 875 ° C. for 1 hour in a carbon dioxide atmosphere.

(Example 25)
The rice husks from Koshihikari (harvested in 2004) from Toyooka Village, Shizuoka Prefecture were carbonized at 250 ° C. for 1 hour in a nitrogen atmosphere to obtain carbonized rice husks. Also, after adding 2.5 times the weight of water to the well-dried powdered side dish, the temperature was raised to about 60 ° C. while stirring at 200 rpm with a hot stirrer and held for 10 minutes to prepare a side dish solution Got. A sugar beet-impregnated carbonized rice husk was prepared by spraying 2.0 g (dry basis) of the sugar beet solution with 2.0 g (dry basis) of the carbonized rice husk. After standing for 18 hours, the sugar beet-impregnated rice husk was dried in an oven at 105 ° C. for 2 hours, and then carbonized at 400 ° C. for 1 hour in a nitrogen atmosphere to obtain carbonized rice husk twice. After pulverizing the carbonized rice husk twice, 0.6 g (dry basis) of the sugar beet solution was sprayed on 1.5 g of the carbonized rice husk twice to prepare a carbonized rice husk twice impregnated with the sugar beet twice. After standing for 18 hours, the carbonized rice husks impregnated twice with the sugar beet twice were pressed at a pressure of 3 ton / cm ² for 1 minute to form a disk with a diameter of 30 mm and a thickness of 3 mm. After drying in an oven at 105 ° C. for 1 hour, the disk-shaped molded product was subjected to activation treatment at 875 ° C. for 1 hour in a carbon dioxide atmosphere.

(Example 26)
Rice husks from Akitamachi (Nikki-mura, 2005) from Nishiki Village, Akita Prefecture were carbonized for 1 hour at 250 ° C. in a nitrogen atmosphere to obtain carbonized husks. Moreover, after adding water of the same weight to the sufficiently dried powdery side dish, the liquid was gradually evaporated by heating at about 100 ° C. to obtain a fluid liquid (syrupy side dish). A paste was prepared by mixing 0.7 g (dry basis) of syrupy sugar beet with 1.0 g of carbonized rice husk. The paste was pressed at a pressure of 3 ton / cm ² for 1 minute to form a disk having a diameter of 30 mm and a thickness of 2 mm. Carbonization was performed at 400 ° C. for 1 hour under a nitrogen atmosphere to obtain carbonized rice husk twice. After pulverizing the carbonized rice husk twice, 0.2 g (dry basis) of syrup-like sugar beet was mixed with 1.0 g of carbonized rice husk twice to prepare a paste. The paste was pressed at a pressure of 3 ton / cm ² for 1 minute to form a disk having a diameter of 30 mm and a thickness of 2 mm. Thereafter, the disk-shaped product was subjected to activation treatment at 875 ° C. for 1 hour in a carbon dioxide atmosphere.

(Example 27)
Rice husks from Akitamachi (Nikki-mura, 2005) from Nishiki Village, Akita Prefecture were carbonized for 1 hour at 250 ° C. in a nitrogen atmosphere to obtain carbonized husks. Moreover, after adding water of the same weight to the sufficiently dried powdery side dish, the liquid was gradually evaporated by heating at about 100 ° C. to obtain a fluid liquid (syrupy side dish). A sugar beet-attached carbonized rice husk was prepared by attaching 0.7 g (dry basis) of syrup-like sugar beet to 1.0 g of carbonized rice husk. The carbonized rice husk with attached sugar beet was carbonized at 400 ° C. for 1 hour under a nitrogen atmosphere to obtain carbonized rice husk twice. After pulverizing the carbonized rice husk twice, 0.2 g (dry basis) of syrup-like sugar beet was mixed with 1.0 g of carbonized rice husk twice to prepare a paste. The paste was pressed at a pressure of 3 ton / cm ² for 1 minute to form a disk having a diameter of 30 mm and a thickness of 2 mm. Thereafter, the disk-shaped product was subjected to activation treatment at 875 ° C. for 1 hour in a carbon dioxide atmosphere.

  Table 2 shows the specific surface area, pore volume, and average pore diameter of each of the activated carbons of Examples 23 to 27 prepared by carbonization at a relatively low temperature as described above. Moreover, the immersion type | mold adsorption experiment to kerosene was implemented similarly to the above. The prepared activated carbon (disc-shaped molded product) was dried in advance at 150 ° C. for 3 hours, and then the powder adsorbent was added to kerosene at a ratio (weight) of kerosene to 30 and stirred and immersed. . After standing at 10 ° C. for 7 days, the sulfur content of kerosene was analyzed. Table 4 shows the desulfurization rate [%] (kerosene / adsorbent ratio: 30/1) obtained from each result. From the values of Examples 23 to 27 in Tables 2 and 4, it can be seen that, by reducing the carbonization temperature, the specific surface area is increased and the desulfurization rate is improved without decreasing the average pore diameter.

(Example 28)
The disk-shaped molded products of Examples 23, 25 and 27 were pulverized and mixed in the same weight ratio to prepare an equal weight mixture. 2.0 g of the mixture was impregnated with an aqueous copper nitrate solution prepared by dissolving 0.35 g of copper (II) nitrate trihydrate in 6.8 g of ion-exchanged water. After standing overnight, it was calcined at 400 ° C. for 1 hour in a nitrogen atmosphere to prepare rice husk activated carbon carrying 4% by mass of copper oxide as metallic copper with respect to the finished adsorbent. The immersion adsorption experiment to kerosene was conducted in the same manner as above. Table 4 shows the desulfurization rate [%] (kerosene / adsorbent ratio: 30/1) obtained as a result. It can be seen that the desulfurization rate is greatly improved by supporting copper oxide. The “mixtures of Examples 23, 25 and 27” in Table 4 show the results of immersion adsorption experiments on kerosene of an equal weight mixture before supporting copper oxide.

Claims (6)

Further activation treatment after carbonizing plant biomass at (A) 300-900 ° C under reduced pressure or (B) 200-900 ° C under reduced pressure and / or inert atmosphere. The carbonized product or activation treatment product having a specific surface area of 200 m ² / g or more and an average pore diameter of 20 mm or more is obtained, and then an adsorbent is produced from the carbonization treatment product or the activation treatment product. A method for producing an adsorbent that removes trace components in hydrocarbon oil.   The method for producing an adsorbent according to claim 1, wherein the carbonization treatment (A) is performed at 300 to 500 ° C, and the carbonization treatment (B) is performed at 200 to 500 ° C.   The method for producing an adsorbent according to claim 1 or 2, wherein the activation treatment is performed at 800 to 900 ° C for 0.1 to 4 hours in a carbon dioxide atmosphere.   The method for producing an adsorbent according to any one of claims 1 to 3, wherein the carbonized product is molded by adding a binder composed of a saccharide, and then the obtained molded product is activated.   The method for producing an adsorbent according to any one of claims 1 to 4, wherein the plant biomass is rice husk or cedar. Furthermore, the manufacturing method of the adsorption agent in any one of Claims 1-5 including the process which mixes and carries | supports a metal and / or a metal oxide.