JP5277364B2 - Process for producing hydrocarbons by reduction of carbon monoxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing hydrocarbons improved in selectivity of intermediate distillation fractions useful as a clean fuel, in FT (Fisher Tropsh) synthetic reaction. <P>SOLUTION: The method for producing hydrocarbons is characterized in that a paraffin-based solvent mainly existing as a liquid phase and an &alpha;-olefin coexist together with a raw material synthetic gas under a reaction condition, in the FT synthesis using synthetic gases comprising hydrogen and carbon monoxide as main ingredients, as raw materials. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a method for producing hydrocarbons from a synthesis gas mainly composed of hydrogen and carbon monoxide.

In recent years, the need for environmental conservation has been demanded, and the demand for clean liquid fuels with low contents of sulfur and aromatic hydrocarbons has rapidly increased. In addition, the development of energy sources that can replace oil has been desired due to the necessity of effectively using crude oil resources with limited reserves. As a technology that meets the above demands, ATL (Asphalt to Liquid), which produces liquid fuel containing almost no sulfur and aromatic hydrocarbons, using asphalt that is expected to decline in demand in the future as a raw material. GTL (Gas to Liquid) using natural gas as a raw material has been attracting more and more attention.
Production of liquid fuel by ATL and GTL includes reforming process for producing hydrogen and carbon monoxide from asphalt or natural gas, Fischer-Tropsch synthesis for producing high-grade paraffin using synthetic gas consisting of hydrogen and carbon monoxide FT synthesis) step, and more generally, a method of producing a product through a hydrotreatment step in which decomposition and isomerization are performed using FT synthesis product oil as a raw material is generally known.

  When liquid fuel is produced by ATL and GTL, it is desired to increase production of middle distillates such as kerosene and light oil that are particularly useful as clean fuel. In order to increase production of middle distillates, a method for increasing the selectivity of middle distillates in the FT synthesis process and a selectivity for wax in the FT synthesis process are produced, and the middle distillate is produced in the subsequent hydrocracking process. Methods are widely known and research has been focused on the industry in the past.

  The oil produced by FT synthesis is generally produced according to a Schulz-Flory distribution. Therefore, in the case of increasing the selectivity of middle distillate in the FT synthesis step, there is a problem that a large amount of undesired light hydrocarbon by-products such as methane is generated. In addition, when the wax selectivity is increased, the CO conversion rate and the wax yield tend to be traded off, so that it is necessary to operate under reaction conditions with a low CO conversion rate in order to increase the wax yield. is there.

Under such circumstances, Fujimoto et al. Of Kitakyushu City University reported that the addition of olefins showed high wax selectivity in the FT synthesis reaction performed in the presence of a supercritical solvent. (See Non-Patent Document 1). However, performing the reaction under conditions as severe as the supercritical state has a problem in terms of economy such as plant cost, and has not been put into practical use. In addition, Iglesia et al. Attempted to add a light olefin under a gas phase reaction condition in which no solvent coexists, but the effect of the olefin addition was not clearly shown under the gas phase reaction condition (Non-patent Document 2). reference).
Jun Fujimoto et al., “Journal of Petroleum Society”, 1995, Vol. 38, No. 2, p. 71 E. Iglesia et.al., “Adv. Catal.”, 1993, Vol. 39, p. 221

  An object of the present invention is to reduce the liquid fuel production cost by providing a process for improving the selectivity of middle distillate useful as a clean fuel in the FT synthesis reaction.

As a result of intensive studies, the present inventors have added the paraffinic solvent and α-olefin, which are mainly present as a liquid phase under the reaction conditions, to the reaction field, and conducted the reaction in a trickle bed reactor. The present inventors have found that this can be solved and have completed the present invention.
That is, the present invention is characterized in that a paraffinic solvent and an α-olefin existing as a liquid phase under reaction conditions coexist in FT synthesis using a raw material composed of synthesis gas mainly composed of hydrogen and carbon monoxide. The present invention relates to a method for producing hydrocarbons.

  According to the method of the present invention, in the FT synthesis, the production of light fractions such as gas and naphtha can be suppressed, and the middle fraction yield can be increased.

The present invention is described in detail below.
The reaction conditions for FT synthesis when carrying out the present invention are shown below. The raw material is not particularly limited as long as it is a synthesis gas mainly composed of hydrogen and carbon monoxide, but usually the hydrogen / carbon monoxide molar ratio is preferably in the range of 1.5 to 2.5, more preferably. Is preferably in the range of 1.8 to 2.2. The present invention can be applied to a fixed bed among processes conventionally known as reaction processes for FT synthesis. There is no restriction | limiting in particular in the reaction conditions at the time of using a fixed bed, It can carry out on well-known conditions. Usually, the reaction can be carried out in the range of 180 to 280 ° C. as the reaction temperature, 1.5 to 4.0 MPa as the reaction pressure, and h ⁻¹ of 1000 to 3000 as the gas space velocity.

In the present invention, the synthesis gas is characterized by coexisting a paraffinic solvent and an α-olefin which exist mainly as a liquid phase under the reaction conditions.
The paraffinic solvent that mainly exists as a liquid phase under the reaction conditions used in the present invention preferably has 8 or more carbon atoms, more preferably 8 to 16 carbon atoms, more preferably 10 to 14 carbon atoms. Is a paraffinic solvent having a main component. Here, the main component indicates 80 mol% or more. When the number of carbon atoms is 7 or less, the solvent does not easily exist as a liquid phase, and thus the effect of the present invention cannot be obtained. Although there is no restriction | limiting in particular in the amount of solvent, Preferably it is 10-200 ml / g-cat * h, More preferably, it uses in the range of 50-100 ml / g-cat * h. If the amount of solvent is less than 10 ml / g-cat · h, the effect of the present invention is low. On the other hand, if it exceeds 200 ml / g-cat · h, the effect of the present invention reaches its peak and no further improvement is observed.

  The α-olefin that mainly exists as a liquid phase under the reaction conditions used in the present invention is preferably an α-olefin having 8 or more carbon atoms, and an α-olefin having 8 to 16 carbon atoms is particularly preferably used. . When the number of carbon atoms is 7 or less, the α-olefin is unlikely to exist as a liquid phase, so the effect of the present invention cannot be obtained. The amount of α-olefin added is not particularly limited, but the α-olefin / solvent volume ratio is preferably 0.001 to 1 ml / ml, more preferably 0.01 to 0.5 ml / ml. It is done.

As a catalyst used for FT synthesis in the present invention, a catalyst in which an active metal is supported on a carrier is used.
The active metal is not particularly limited as long as it has FT synthesis activity. For example, a metal conventionally known for FT synthesis activity such as iron, cobalt, nickel, ruthenium, and the like can be used. Among these, iron, cobalt, and nickel can be mentioned as a preferable metal, iron and cobalt can be mentioned as a particularly preferable metal, and cobalt can be mentioned as the most preferable metal. The active metal component is usually supported as a metal oxide on the support after impregnating the support with a solution containing the precursor compound of the metal, followed by steps such as drying and firing. The amount of the active metal to be supported is not particularly limited, but it is preferably 5 to 50% by mass, more preferably 10 to 30% by mass with respect to the support.

The catalyst carrier used in the present invention is not particularly limited, but preferred supports include silica, alumina, zirconia, titania and the like. Particularly preferred supports are silica and alumina, and most preferred supports. Silica can be mentioned. There is no restriction | limiting in particular about the shape of the support | carrier to be used, The shape suitable for the process to be used can be selected from various shape products, such as a spherical product, a crushing product, and a cylindrical molded product. The average particle size of the carrier is not particularly limited, but those having a particle size of usually 10 μm to 10 mm, preferably 50 μm to 5 mm can be appropriately selected according to the process. Further, the specific surface area of the carrier is not particularly limited, but is usually 100 to 400 m ² / g, preferably 200 to 350 m ² / g.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these.

Example 1
As the catalyst, a 20% by mass cobalt-supported silica catalyst in terms of metal per carrier was used. Cobalt nitrate hexahydrate was used as the cobalt precursor, and silica (CaliACT Q-15, manufactured by Fuji Silysia Chemical Ltd.) was used as the carrier. The catalyst was supported by the Incipient Wetness method, dried at 120 ° C. overnight, and then calcined at 250 ° C. for 2 hours in a muffle furnace to prepare a catalyst.
The reaction was performed using a fixed bed reactor. The reaction pressure was 2.1 MPa, the reaction temperature was 230 ° C., GHSV 2600 h ⁻¹ , CO / H ₂ = 1/2 (molar ratio), n-dodecane (82.8 ml / g-cat · h) was passed as a solvent, α− The reaction was carried out under the condition that 1-dodecene (2.4 ml / g-cat · h) was added as an olefin. The results are shown in Table 1.

(Example 2)
The same catalyst as in Example 1 was used, and the reaction was performed under the same conditions as in Example 1 except that 1-hexadecene was used as the α-olefin. The results are shown in Table 1.

(Comparative Example 1)
The reaction was carried out under the same conditions as in Example 1, except that the same catalyst as in Example 1 was used and no solvent and α-olefin were used. The results are shown in Table 1.

(Comparative Example 2)
The same catalyst as in Example 1 was used, and the reaction was carried out under the same conditions as in Example 1 except that no α-olefin was added. The results are shown in Table 1.

(Comparative Example 3)
The same catalyst as in Example 1 was used, and the reaction was carried out under the same conditions as in Example 1 except that no solvent was passed. The results are shown in Table 1.

Claims (5)

In the Fischer-Tropsch synthesis using a synthesis gas mainly composed of hydrogen and carbon monoxide and using a fixed bed reactor, a paraffinic solvent and α mainly present as a liquid phase under the reaction conditions together with the raw material synthesis gas -Adding olefins to the reaction field in amounts of 10 to 200 ml / g-cat · h and α-olefin / paraffinic solvent volume ratios of 0.001 to 1 ml / ml as the amount of paraffinic solvent, respectively. A method for producing hydrocarbons.   The production method according to claim 1, wherein the α-olefin has 8 to 16 carbon atoms.   The production method according to claim 1 or 2, wherein the paraffinic solvent has 8 to 16 carbon atoms as a main component.   The production according to any one of claims 1 to 3, wherein the reaction is carried out in the presence of a catalyst formed by supporting one or more metals selected from cobalt, iron, ruthenium and nickel on a support. Method.   5. The production method according to claim 4, wherein the carrier is made of an inorganic oxide mainly composed of alumina, silica, zirconia or titania.