Method for Producing Hydrocarbon

The present disclosure relates to a method for producing a hydrocarbon.

In domestic refineries in Japan, fluid catalytic cracking (FCC) units play a central role in the production of hydrocarbons (for example, Patent Literature 1).

is a flow chart illustrating an example of a conventional method for producing hydrocarbons from crude oil. In the conventional method for producing hydrocarbons, as shown in, for example, hydrocarbons are produced by using a desulfurized atmospheric residue and a desulfurized vacuum gas oil, which are obtained by treating an atmospheric residue in a residue desulfurization unit, as feedstocks and treating the feedstocks in a fluid catalytic cracking unit.

Furthermore, as environmental awareness is increasing, attention has been paid to FT synthetic oil having lower sulfur content and nitrogen content as compared with petroleum. FT synthetic oil is produced by Fischer-Tropsch synthesis from synthesis gas, which is a gas mixture of hydrogen gas and carbon monoxide gas. For example, Patent Literature 2 discloses a technology for producing hydrocarbons by treating the FT synthetic oil as a feedstock in a fluid catalytic cracking unit.

Coke produced from a feedstock in the course of fluid catalytic cracking adheres to the surface of catalysts. The fluid catalytic cracking unit regenerates catalysts and also utilizes the coke as its own heat source by sending coke-attached catalysts to a regenerator and combusting coke within the regenerator.

However, as a result of studies conducted by the inventors of the present invention, it was found that when FT synthetic oil is treated in a fluid catalytic cracking unit, the amount of coke produced during fluid catalytic cracking is small, and there is a possibility that the heat source of the fluid catalytic cracking unit may be insufficient as compared to the case of treating oil derived from petroleum. That is, it is difficult to maintain the heat balance of the fluid catalytic cracking unit, and there is room for improvement from the viewpoint of stable operation of the fluid catalytic cracking unit. When a fluid catalytic cracking unit cannot operate stably, the utilization rate of the fluid catalytic cracking unit decreases, which leads to an increase in the production cost for hydrocarbons.

Thus, an aspect of the present disclosure provides a method for producing a hydrocarbon, which method uses FT synthetic oil as a feedstock and allows stable operation.

An aspect of the present disclosure relates to a method for producing a hydrocarbon, the method including a step of treating a feedstock using a fluid catalytic cracking unit, in which the feedstock includes FT synthetic oil, and the feedstock has a % Cof 6 to 23.

According to an embodiment, the above-described method for producing a hydrocarbon may further include: a step of mixing the FT synthetic oil and a hydrocarbon oil having a higher % Cthan the FT synthetic oil to obtain the feedstock; and a step of feeding the feedstock into a reactor of the fluid catalytic cracking unit. According to an embodiment, the hydrocarbon oil may include a desulfurized atmospheric residue. According to an embodiment, the hydrocarbon oil may include clarified oil.

According to an aspect of the present disclosure, there is provided a method for producing a hydrocarbon, which method uses FT synthetic oil as a feedstock and enables stable operation.

Embodiments of the present disclosure will be described below with reference to the drawings. However, the present disclosure is not limited to the following embodiments and is indicated by the scope of claims, and it is intended that all changes in the meaning and the scope equivalent to the scope of claims are included. In each of the drawings, a portion of the configuration may be shown in an exaggerated or simplified manner for the convenience of explanation. In addition, the dimensional ratio of each part may be different in each of the drawings. In the following description of the drawings, the same or similar parts may be assigned with the same or similar reference numerals.

In the present specification, a synthetic oil produced by Fischer-Tropsch synthesis is referred to as “FT synthetic oil”. In the present specification, a wax component included in the FT synthetic oil is referred to as “FT wax”. In the present specification, an FT synthetic oil produced by Fischer-Tropsch synthesis and not subjected to distillation is referred to as “FT crude oil”. In the present specification, with regard to “ton”, not the yard-pound system but the metric system is adopted. That is, 1 ton is 1000 kg.

In the present specification, the term % Cmeans an n-d-m method value (aromatic content). Specifically, % Cis calculated by the following procedure. That is, the specific gravity (d) and the refractive index (n) of the feedstock at 70° C. are measured. x is calculated by substituting the measured values into the following Formula (A1). With regard to the calculated x, a value determined by substituting x into the following Formula (A2) in a case where x is more than 0, and into the following Formula (A3) in a case where x is less than 0, is the % Cof the feedstock. The following Formulas (A1) to (A3) are defined with reference to the standard “ASTM D3238”. In Formulas (A2) and (A3), M represents the average molecular weight.

A method for producing a hydrocarbon according to an embodiment will be described below. The method for producing a hydrocarbon of the present embodiment includes a step of treating a feedstock using a fluid catalytic cracking unit. The feedstock includes FT synthetic oil, and the feedstock has a % Cof 6 to 23.

First, an outline of a method for producing FT synthetic oil that is used in the method for producing a hydrocarbon according to the present embodiment will be described. FT synthetic oil is produced by Fischer-Tropsch synthesis, for example, using carbon monoxide and hydrogen gas as feedstocks. The method for producing the FT synthetic oil is not particularly limited, and a known method can be employed. The reaction unit for producing the FT synthetic oil is preferably a fixed bed reaction unit or a slurry fluidized bed reaction unit. In addition, it is preferable to perform the reaction under the conditions in which the conversion rate of carbon monoxide, which is a feedstock, is set to be 50% or more, and even more preferably in the range of 70 to 90%.

As the slurry fluidized bed reaction unit, for example, a bubbling column type fluidized bed reaction unit can be used. A bubbling column type fluidized bed reaction unit has a reactor that performs Fischer-Tropsch synthesis. Inside the reactor of the bubbling column type fluidized bed reaction unit, liquid hydrocarbons that are liquid at the reaction temperature are accommodated. A catalyst for FT synthesis is dispersed in the liquid hydrocarbons, and the liquid hydrocarbons are in a slurry state. Synthesis gas, which is a gas mixture of carbon monoxide gas and hydrogen gas, is introduced into the liquid hydrocarbons from the lower part of the reactor. The synthesis gas dissolves in the liquid hydrocarbons while rising in the liquid hydrocarbons after becoming bubbles, and comes into contact with the catalyst for FT synthesis. The FT synthetic oil is produced from the synthesis gas by the function of the catalyst for FT synthesis.

The reaction temperature can be determined depending on the target carbon monoxide conversion rate; however, the reaction temperature is preferably 150 to 300° C., and more preferably 170 to 250° C.

The reaction pressure is preferably 0.5 to 5.0 MPa, and more preferably 2.0 to 4.0 MPa. When the reaction pressure is 0.5 MPa or more, there is a tendency that the carbon monoxide conversion rate is likely to be 50% or higher, and when the reaction pressure is 5.0 MPa or less, there is a tendency that the occurrence of local heat generation can be suppressed.

Synthesis gas is obtained by, for example, reforming of hydrocarbons such as natural gas. Synthesis gas only needs to include carbon monoxide gas and hydrogen gas and may be a gas other than a gas obtained by reforming of natural gas or the like.

The hydrogen/carbon monoxide ratio (molar ratio) in the synthesis gas is preferably 0.5 to 4.0, and more preferably 1.0 to 2.5. When this molar ratio is 0.5 or higher, the reaction temperature does not increase too high while deactivation of the catalyst tends to be suppressed, and when the molar ratio is 4.0 or lower, there is a tendency that production of methane, which is an undesirable byproduct, can be suppressed.

The gas space velocity of the synthesis gas is preferably 500 to 5000 h, and more preferably 1000 to 2500 h. When this gas space velocity is 500 hor more, higher productivity is obtained with the same amount of catalyst, and when the gas space velocity is 5000 hor less, there is a tendency that the conversion rate of carbon monoxide is likely to be 50% or higher.

As the catalyst for FT synthesis, a catalyst in which an active metal is supported on an inorganic carrier is used. Examples of the inorganic carrier include porous oxides such as silica, alumina, titania, magnesia, and zirconia. Examples of the active metal include cobalt, ruthenium, iron, and nickel. Furthermore, in the catalyst, a compound including a metal element such as zirconium, titanium, hafnium, sodium, lithium, or magnesium may also be supported, in addition to the above-described active metals. These components improve the catalytic activity and contribute to the control of the number of carbon atoms and the distribution thereof in the FT synthetic oil.

The FT synthetic oil is, for example, a mixture of straight-chained hydrocarbons (normal paraffins) having 5 to 100 carbon atoms. The FT synthetic oil may be a synthetic oil produced by Fischer-Tropsch synthesis and may include straight-chained hydrocarbons having more than 100 carbon atoms. The FT synthetic oil includes almost none of aromatic hydrocarbons, naphthene, and isoparaffin. The FT synthetic oil has, for example, a % Cof 0. Incidentally, the FT synthetic oil may have a % Cof more than 0, for example, in a case where aromatic hydrocarbons are included.

The FT synthetic oil may include an FT wax having a boiling point of higher than 330° C. The FT wax is, for example, a mixture of straight-chained hydrocarbons (normal paraffins) having 17 or more carbon atoms. The percentage content of the FT wax in the FT synthetic oil may be 30% by mass or more, 50% by mass or more, 70% by mass or more, 90% by mass or more, or 95% by mass or more and may be 100% by mass. The percentage content of the FT wax in the FT synthetic oil can be easily controlled by appropriately adjusting the above-described reaction conditions.

Next, an outline of the method for producing a hydrocarbon according to the present embodiment will be described. Hydrocarbons can be produced by treating a feedstock including FT synthetic oil in a fluid catalytic cracking unit.

The % Cof the feedstock is 6 or more, and from the viewpoint of the amount of coke production, the % Cis preferably 7 or more, and more preferably 8 or more. The % Cof the feedstock is 23 or less and may be 22 or less, or may be 21 or less.

The FT synthetic oil included in the feedstock may be an oil produced by Fischer-Tropsch synthesis and is not particularly limited. The FT synthetic oil included in the feedstock may be, for example, an FT crude oil, may be an oil obtained by distilling FT crude oil, may be an FT wax, or may be a mixture of these.

The feedstock may further include a hydrocarbon oil having a higher % Cthan the FT synthetic oil.

The above-described hydrocarbon oil is obtained from, for example, refining. Examples of the above-described hydrocarbon oil include RDS-BTM, DS-VGO, and CLO. As shown in, RDS-BTM is a desulfurized atmospheric residue obtained by treating an atmospheric residue in a residue desulfurization unit. The atmospheric residue is obtained by treating crude oil in an atmospheric distillation unit. As shown in, DS-VGO is, for example, a desulfurized vacuum gas oil obtained by treating an atmospheric residue in a vacuum gas oil desulfurization unit. RDS-BTM may or may not include a solvent deasphalted vacuum residual oil as a feedstock thereof. As shown in, CLO (CLarified Oil) is, for example, a product obtained by removing catalyst from a slurry oil, which is a residual oil obtained by treating RDS-BTM or DS-VGO in a fluid catalytic cracking unit to obtain an oil and further treating the obtained oil in an atmospheric distillation unit. CLO may or may not include FT synthetic oil as a feedstock thereof.

In a case where the feedstock includes the above-described hydrocarbon oil, the method for producing a hydrocarbon according to the present embodiment may further include: a step of mixing FT synthetic oil and a hydrocarbon oil to obtain a feedstock; and a step of feeding the feedstock into the reactor of the fluid catalytic cracking unit. As a result, the oil constituting the feedstock becomes more uniform as compared to the case where the feedstock is obtained in the reactor of the fluid catalytic cracking unit. Therefore, the fluid catalytic cracking reaction in the reactor tends to be more stable.

In a case where the feedstock includes the above-described hydrocarbon oil, the method for producing a hydrocarbon according to the present embodiment may further include a step of feeding FT synthetic oil into the reactor of the fluid catalytic cracking unit while at the same time, feeding a hydrocarbon oil into the reactor of the fluid catalytic cracking unit, and obtaining a feedstock in the reactor of the fluid catalytic cracking unit.

In a case where the feedstock includes RDS-BTM, the proportion occupied by RDS-BTM in RDS-BTM and FT synthetic oil is 1% by mass or more based on the total mass of RDS-BTM and FT synthetic oil, and the proportion may be 15% by mass or more, may be 30% by mass or more, or may be 45% by mass or more.

The proportion occupied by RDS-BTM in RDS-BTM and FT synthetic oil is 98% by mass or less based on the total mass of RDS-BTM and FT synthetic oil, and the proportion may be 75% by mass or less, or may be 50% by mass or less.

The % Cof RDS-BTM is 5 or more and may be 10 or more, or may be 20 or more. The % Cof RDS-BTM is 99 or less and may be 80 or less, or may be 60 or less.

In a case where the feedstock includes DS-VGO, the proportion occupied by DS-VGO in DS-VGO and FT synthetic oil is 1% by mass or more based on the total mass of DS-VGO and FT synthetic oil, and the proportion may be 15% by mass or more, may be 30% by mass or more, or may be 45% by mass or more.

The proportion occupied by DS-VGO in DS-VGO and FT synthetic oil is 98% by mass or less based on the total mass of DS-VGO and FT synthetic oil, and the proportion may be 75% by mass or less or may be 50% by mass or less.

The % Cof DS-VGO is, for example, 1 or more and may be 5 or more, or may be 10 or more. The % Cof DS-VGO is 99 or less and may be 80 or less, or may be 60 or less.

In a case where the feedstock includes CLO, the proportion occupied by CLO in CLO and FT synthetic oil is 1% by mass or more based on the total mass of CLO and FT synthetic oil, and the proportion may be 15% by mass or more, may be 30% by mass or more, or may be 45% by mass or more.

The proportion occupied by CLO in CLO and FT synthetic oil is 98% by mass or less based on the total mass of CLO and FT synthetic oil, and the proportion may be 75% by mass or less or may be 50% by mass or less.

The % Cof CLO is, for example, 1 or more and may be 5 or more, may be 10 or more, or may be 20 or more. The % Cof CLO is 99 or less and may be 80 or less, or may be 60 or less.

RDS-BTM, DS-VGO, and CLO may be used in combination of two or more kinds such that the % Cof the feedstock is within the range of the above-mentioned upper limit value and lower limit value.

The fluid catalytic cracking unit used for fluid catalytic cracking of the feedstock is not particularly limited. Regarding the fluid catalytic cracking unit, a known fluid catalytic cracking unit can be used.is a schematic view illustrating an example of the fluid catalytic cracking unit used for the method for producing a hydrocarbon according to the present embodiment. A fluid catalytic cracking unit A includes: a reactor; a regenerator; a lineconnecting to the reactor; a lineconnecting the reactorand the regenerator; a lineconnecting the reactorand the regenerator; a lineconnecting the regeneratorand a boiler (not shown in the drawing); and a lineconnecting the reactorand a recovery unit (not shown in the drawing).

The reactoris a riser type. The reactorincludes a reaction zoneand a separation zone. The reactoris fed with a feedstock and innumerable catalyst particles (cracking catalyst). The feedstock is fed into the reaction zonethrough the line. In a case where the feedstock further includes a hydrocarbon oil having a higher % Cthan the FT synthetic oil, the feedstock may be obtained by mixing the FT synthetic oil and the hydrocarbon oil in the line. In this case, the linemay branch off from the middle. By feeding the FT synthetic oil through one branched line of the lineand feeding the hydrocarbon oil through the other line, the FT synthetic oil and the hydrocarbon oil are mixed at the confluence of the branched lines, and the feedstock is obtained. Furthermore, in a case where the feedstock further includes a hydrocarbon oil having a higher % Cthan the FT synthetic oil, a mixture obtained by mixing the FT synthetic oil and the hydrocarbon oil in advance may be fed as the feedstock to the reaction zonethrough the line.

The catalyst particles are fed into the reaction zonethrough the line. In the reaction zone, a fluidizing gas, which is steam, is blown from the lower part of a layer formed of the catalyst particles. The catalyst particles are fluidized by the fluidizing gas. The feedstock and the fluidized catalyst particles move up through the reaction zonetogether with the fluidizing gas. When the feedstock comes into contact with the catalyst particles in the reaction zone, catalytic cracking occurs, and hydrocarbons are produced from the feedstock. The hydrocarbons obtained by cracking the feedstock and the catalyst particles used for catalytic cracking are separated in the separation zone.

The separated hydrocarbons are fed into the recovery unit through the line. The hydrocarbons are separated into a plurality of components and recovered in the recovery unit. The recovery unit may include, for example, a plurality of distillation columns, absorbers, compressors, strippers, fractionators, splitters, and heat exchangers. The hydrocarbons are fractionated into, for example, gas components and hydrocarbon oil in the distillation column (atmospheric distillation column). The gas components include dry gas and LP gas (LPG). Examples of the hydrocarbon oil include a gasoline fraction (CCG), a gas oil fraction (LCO), a kerosene fraction, clarified oil (CLO), and coke. The recovered clarified oil (CLO) may be fed into the reactoras a feedstock.

The separated catalyst particles are fed into the regeneratorthrough the line. Coke generated during fluid catalytic cracking is attached to the surface of the catalyst particles fed into the regenerator, and the catalyst particles have deteriorated catalytic activity. In the regenerator, the catalyst particles used for catalytic cracking are regenerated. Airis supplied to the regeneratorfor the regeneration treatment. In the regenerator, by combusting the coke attached to the surface of the catalyst particles, the amount of coke attached to the surface of the catalyst particles is reduced, and at the same time, the temperature of the catalyst particles is increased. The catalyst particles after regeneration are fed into the reaction zoneagain through the line. That is, the catalyst particles circulate between the regeneratorand the reactor. High-temperature carbon monoxide gas and carbon dioxide gas generated in the course of the regeneration treatment are supplied to a boiler (not shown in the drawing) or a heat exchanger (not shown in the drawing) through the lineand serves as one of heat sources for the fluid catalytic cracking unit A. In a case where the carbon monoxide gas and carbon dioxide gas generated in the course of the regeneration treatment are supplied to a heat exchanger, the gases are utilized for increasing the temperature of the feedstock.

A value obtained by dividing the circulation rate (ton/h) of the catalyst circulating between the reactorand the regeneratorby the feed rate (ton/h) of the feedstock is a catalyst/oil ratio. The catalyst/oil ratio is 3 [mass/mass] or more and may be 4 [mass/mass] or more, may be 5 [mass/mass] or more, or may be 7.5 [mass/mass] or more. The catalyst/oil ratio is 50 [mass/mass] or less and may be 13 [mass/mass] or less, may be 12 [mass/mass] or less, 11 [mass/mass] or less, or may be 9 [mass/mass] or less.

The cracking catalyst used for fluid catalytic cracking may include, for example, an inorganic oxide (matrix component) and zeolite. The inorganic oxide may be, for example, at least one selected from the group consisting of kaolin, montmorinite, halloysite, bentonite, alumina, silica, boria, chromia, magnesia, zirconia, titania, and silica-alumina. The zeolite may be, for example, at least any of natural zeolite and synthetic zeolite. The natural zeolite may be at least one selected from the group consisting of gmelinite, chabazite, dachiardite, clinoptilolite, faujasite, keyite, heulandite, levynite, erionite, sodalite, cancrinite, ferrierite, brewsterite, offretite, natrolite, and mordenite. The synthetic zeolite may be at least one selected from the group consisting of X-type zeolite, Y-type zeolite, USY-type zeolite, A-type zeolite, L-type zeolite, ZK-4-type zeolite, B-type zeolite, E-type zeolite, F-type zeolite, H-type zeolite, J-type zeolite, M-type zeolite, Q-type zeolite, T-type zeolite, W-type zeolite, Z-type zeolite, α-type zeolite, β-type zeolite, ω-type zeolite, ZSM-5-type zeolite, SAPO-5-type zeolite, SAPO-11-type zeolite, and SAPO-34-type zeolite.