A method for separating oxygenated compounds from Fischer-Tropsch synthetic oil

Abstract

The present invention discloses a method for separating oxygenates from Fischer-Tropsch oil. A gaseous boron halide is introduced into the Fischer-Tropsch oil to cause the boron halide to undergo a complexation reaction with the oxygenates in the Fischer-Tropsch oil, thereby forming a heterogeneous system of the oxygenate complex and the Fischer-Tropsch oil. The heterogeneous system is then separated to obtain a deoxygenated Fischer-Tropsch oil phase and an oxygenate complex phase. The boron halide pressure in the system is 0.05 to 1 MPa. By controlling the amount of boron halide added, the boron halide can be complexed with the oxygenates in the Fischer-Tropsch oil to separate the oxygenates from the oil, while preventing the boron halide from causing polymerization of olefins in the oil.

Description

Technical Field

[0001] The invention belongs to the field of oil processing, and in particular relates to a method for separating oxygen-containing compounds from Fischer-Tropsch synthetic oil. Background Art

[0002] my country is a country rich in coal but short of oil, and coal occupies a crucial position in its energy structure. At the same time, the contradiction between supply and demand of petroleum energy in my country is becoming increasingly prominent, and fluctuations in international crude oil prices can severely constrain the operation of my country's energy economy. Therefore, coal liquefaction, replacing crude oil products, has become a key strategic approach for achieving oil self-sufficiency and maintaining a stable economic operation in my country. Coal liquefaction includes direct liquefaction and indirect liquefaction, with indirect coal liquefaction being a key development direction in the coal chemical industry. Fischer-Tropsch synthetic oil, a product of indirect coal liquefaction, offers advantages such as low sulfur and nitrogen content, making it a good alternative to petroleum products.

[0003] The Fischer-Tropsch synthesis (FTS) process can be categorized as either low-temperature or high-temperature, depending on the reaction temperature. Low-temperature FTS products have a broad carbon number distribution, primarily consisting of solid waxes. The group composition is linear alkanes, linear α-olefins, and oxygenates, with low levels of aromatics and cycloalkanes. High-temperature FTS products have a narrow carbon number distribution, primarily producing liquid synthetic oils. The group composition is linear α-olefins, linear alkanes, oxygenates, and aromatics. FTS products are characterized by a continuous carbon number distribution, primarily consisting of linear alkanes and α-olefins. The oxygenates present in the products are complex, typically ranging from 5% to 15%, and include alcohols, aldehydes, ketones, and acids of varying chain lengths. However, the presence of oxygenates in the FTS product can severely impact its quality and hinder further processing of the FTS oil. Therefore, developing a comprehensive, economical, and efficient method for separating oxygenates is crucial for the subsequent processing and high-value utilization of FTS products.

[0004] CN105272809A discloses a method for removing oxygenates from coal-based α-olefins. Active alkaline earth metals are used to passivate oxygenates containing active hydrogen atoms in α-olefins into alkoxy metal salts, which are then precipitated and removed from the material. Residual ketone compounds are then removed by adsorption using a fixed adsorption bed. However, this technology uses large amounts of alkaline earth metals and solid adsorbents, generating significant amounts of waste residue.

[0005] CN1764619A discloses a method for separating oxygenates from the fractionated hydrocarbon condensate of a Fischer-Tropsch reaction. Using methanol and water as extractants, the method effectively separates oxygenates when the water content in the methanol exceeds 3 wt%, while also achieving a high recovery rate for the desired product. However, this method lacks sufficient separation depth, and the separated product still contains a certain amount of oxygenates, making it unsuitable for subsequent use as a high-quality raw material.

[0006] CN105777467A discloses a method for separating oxygenates from Fischer-Tropsch oil products. Two extractant feeds are used to remove oxygenates in an extraction column, yielding an oxygenate-rich stream. A third extractant is then used to further remove the remaining oxygenates. However, this technology suffers from lengthy processes, high energy consumption, and high equipment costs. Summary of the Invention

[0007] The object of the present invention is to provide a method for separating oxygenated compounds from Fischer-Tropsch oil, so as to solve the problems in the prior art of insufficient removal depth of oxygenated compounds from Fischer-Tropsch oil and a long process.

[0008] To achieve the above-mentioned purpose, the present invention provides a method for separating oxygen-containing compounds from Fischer-Tropsch oil, wherein gaseous boron halide is introduced into the Fischer-Tropsch oil to cause the boron halide to undergo a complex reaction with the oxygen-containing compounds in the Fischer-Tropsch oil to form a heterogeneous system of oxygen-containing complexes and Fischer-Tropsch oil, and the heterogeneous system is separated to obtain a deoxygenated Fischer-Tropsch oil phase and an oxygen-containing complex phase, wherein the boron halide pressure in the system is 0.05 to 1 MPa.

[0009] In the method for separating oxygen-containing compounds from Fischer-Tropsch synthetic oil of the present invention, the boron halide is one or more of BF3, BCl3 and BBr3.

[0010] In the method for separating oxygen-containing compounds from Fischer-Tropsch synthetic oil of the present invention, the temperature of the complexation reaction is 0-50°C.

[0011] The method for separating oxygen-containing compounds from Fischer-Tropsch synthetic oil of the present invention further comprises the step of removing residual boron halide from the deoxygenated Fischer-Tropsch oil phase.

[0012] The method for separating oxygen-containing compounds from Fischer-Tropsch synthetic oil of the present invention adopts a stripping process to remove residual boron halide, and the gas used for stripping is nitrogen with a flow rate of 0.1 to 2 Nm 3 / h, temperature is 80~180℃.

[0013] The method for separating oxygen-containing compounds from Fischer-Tropsch synthetic oil of the present invention further comprises the step of recovering boron halide from the oxygen-containing complex phase.

[0014] The method for separating oxygen-containing compounds from Fischer-Tropsch synthetic oil of the present invention comprises thermally cracking the oxygen-containing complex phase to recover boron halide and oxygen-containing compounds.

[0015] The method for separating oxygenated compounds from Fischer-Tropsch synthetic oil of the present invention separates the heterogeneous system by natural sedimentation centrifugation.

[0016] Beneficial effects of the present invention:

[0017] Through extensive experimentation and exploration, the inventors surprisingly discovered that gaseous boron halide exhibits suitable complexing activity with oxygenates in Fischer-Tropsch oil. By controlling the amount of boron halide added, complexing with oxygenates in the oil can be achieved, thereby separating the oxygenates from the oil while preventing boron halide-induced polymerization of olefins in the oil. The present invention boasts high separation efficiency and can deeply remove oxygenates from Fischer-Tropsch oil. The resulting product has an oxygen content of less than 100 ppm and a deoxygenation rate of 98% or higher, providing high-quality raw materials for the subsequent high-value utilization of Fischer-Tropsch oil.

[0018] The process is short and easy to operate. This separation method requires only two steps: complexation and sedimentation to quickly separate oxygenates from Fischer-Tropsch oil. The separated complexes are then thermally cracked to produce boron halides and oxygenates. The boron halides can be recovered and reused, while the oxygenates can be further processed and utilized as by-products, thus reducing separation costs and the generation of three wastes. DETAILED DESCRIPTION

[0019] The present invention is described in detail below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Those skilled in the art may make some non-essential improvements and adjustments to the present invention based on the above disclosure.

[0020] Evaluation and analysis method: Use inductively coupled plasma atomic emission spectrometry (ICP-AES) to determine the content of B, F, Cl, and Br elements in the oil to obtain the residual BF3, BCl3, and BBr3 contents; use oxygen element analysis to analyze the oxygen content; and use chromatographic analysis to analyze the olefin content.

[0021] Example 1

[0022] A high-temperature Fischer-Tropsch synthetic oil C7-C30 mixed hydrocarbon fraction was selected, with an olefin content of 66% and an oxygen content of 12000ppm. 1L of mixed hydrocarbon fraction was added to a 2L reactor, and BF3 was introduced into the reactor at 30°C and fully reacted at 0.05Mpa for 2h. The system after the reaction was fully settled to obtain an upper Fischer-Tropsch oil phase and a lower oxygen-containing complex flow. The upper Fischer-Tropsch oil phase was transferred to a stripping tower and heated at 2Nm 3 Nitrogen was introduced at a flow rate of 1 / h and stripped at 80°C for 3 hours to separate the residual BF3 dissolved in the Fischer-Tropsch oil phase, yielding a Fischer-Tropsch oil free of oxygenated compounds. Elemental analysis revealed that the resulting medium Fischer-Tropsch oil contained ≤1 ppm of BF3, 696 ppm of oxygen, and a deoxygenation efficiency of 94.2%.

[0023] Example 2

[0024] A high-temperature Fischer-Tropsch synthetic oil C16-C24 mixed hydrocarbon fraction was selected, with an olefin content of 63% and an oxygen content of 9500ppm. 1L of mixed hydrocarbon fraction was added to a 2L reactor, and BCl3 was introduced into the reactor at 40°C and fully reacted under 0.2Mpa for 1.5h. The system after the reaction was fully settled to obtain an upper Fischer-Tropsch oil phase and a lower oxygen-containing complex flow. The upper Fischer-Tropsch oil phase was transferred to a stripping tower and heated at 1.5Nm 3 Nitrogen was introduced at a flow rate of 100°C / hour and stripped at 150°C for 3 hours to separate the residual BCl₃ dissolved in the Fischer-Tropsch oil phase, yielding a Fischer-Tropsch oil free of oxygenated compounds. Elemental analysis revealed that the resulting medium Fischer-Tropsch oil contained ≤1 ppm of BCl₃, 247 ppm of oxygen, and a deoxygenation efficiency of 97.4%.

[0025] Example 3

[0026] A high-temperature Fischer-Tropsch synthetic oil C8-C12 mixed hydrocarbon fraction was selected, with an olefin content of 72% and an oxygen content of 7200ppm. 1L of mixed hydrocarbon fraction was added to a 2L reactor, and BBr3 was introduced into the reactor at 50°C and fully reacted under 0.4Mpa for 1h. The system after the reaction was fully settled to obtain an upper Fischer-Tropsch oil phase and a lower oxygen-containing complex flow. The upper Fischer-Tropsch oil phase was transferred to a stripping tower and heated to 1Nm 3 Nitrogen was introduced at a flow rate of 100°C / hour for 3 hours to separate the residual BBr3 dissolved in the Fischer-Tropsch oil phase, yielding a Fischer-Tropsch oil free of oxygenated compounds. Elemental analysis revealed a BBr3 content of ≤1 ppm, an oxygen content of 94 ppm, and a deoxygenation efficiency of 98.7%.

[0027] Example 4

[0028] A low-temperature Fischer-Tropsch synthetic oil C7-C30 mixed hydrocarbon fraction was selected, with an olefin content of 50%, and the oxygen content was measured to be 8000ppm. 1L of mixed hydrocarbon fraction was added to a 2L reactor, and BF3 was introduced into the reactor at 0°C and fully reacted at 0.1Mpa for 2h. After the reaction, the system was fully settled to obtain an upper Fischer-Tropsch oil phase and a lower oxygen-containing complex flow. The upper Fischer-Tropsch oil phase was transferred to a stripping tower and heated at 1Nm 3 Nitrogen was introduced at a flow rate of 1 / h and stripped at 80°C for 3 hours to separate the residual BF3 dissolved in the Fischer-Tropsch oil phase, yielding a Fischer-Tropsch oil free of oxygenated compounds. Elemental analysis revealed that the resulting medium Fischer-Tropsch oil contained ≤1 ppm of BF3, 248 ppm of oxygen, and a deoxygenation efficiency of 96.9%.

[0029] Example 5

[0030] A low-temperature Fischer-Tropsch synthetic oil C12-C24 mixed hydrocarbon fraction was selected, with an olefin content of 52% and an oxygen content of 5600ppm. 1L of mixed hydrocarbon fraction was added to a 2L reactor, and BF3 was introduced into the reactor at 10°C and fully reacted under 0.3Mpa for 1.5h. The system after the reaction was fully settled to obtain an upper Fischer-Tropsch oil phase and a lower oxygen-containing complex flow. The upper Fischer-Tropsch oil phase was transferred to a stripping tower and heated at 0.5Nm 3 Nitrogen was introduced at a flow rate of 1 / h and stripped at 180°C for 3 hours to separate the residual BF3 dissolved in the Fischer-Tropsch oil phase, yielding a Fischer-Tropsch oil free of oxygenated compounds. Elemental analysis revealed that the resulting medium Fischer-Tropsch oil contained ≤1 ppm of BF3, 67 ppm of oxygen, and a deoxygenation efficiency of 98.8%.

[0031] Example 6

[0032] A low-temperature Fischer-Tropsch synthetic oil C8-C16 mixed hydrocarbon fraction was selected, with an olefin content of 56% and an oxygen content of 5000ppm. 1L of mixed hydrocarbon fraction was added to a 2L reactor, and BF3 was introduced into the reactor at 20°C and fully reacted under 0.5Mpa for 1h. The system after the reaction was fully settled to obtain an upper Fischer-Tropsch oil phase and a lower oxygen-containing complex flow. The upper Fischer-Tropsch oil phase was transferred to a stripping tower and heated at 0.2Nm 3 Nitrogen was introduced at a flow rate of 1 / h and stripped at 120°C for 3 hours to separate the residual BF3 dissolved in the Fischer-Tropsch oil phase, yielding a Fischer-Tropsch oil free of oxygenated compounds. Elemental analysis revealed that the resulting medium Fischer-Tropsch oil contained ≤1 ppm of BF3, 45 ppm of oxygen, and a deoxygenation efficiency of 99.1%.

[0033] Example 7

[0034] A high-temperature Fischer-Tropsch synthetic oil C16-C30 mixed hydrocarbon fraction was selected, with an olefin content of 62% and an oxygen content of 6200ppm. 1L of mixed hydrocarbon fraction was added to a 2L reactor, and BF3 was introduced into the reactor at 40°C and fully reacted under 1.0Mpa for 1h. The system after the reaction was fully settled to obtain an upper Fischer-Tropsch oil phase and a lower oxygen-containing complex flow. The upper Fischer-Tropsch oil phase was transferred to a stripping tower and heated at 2.0Nm 3 Nitrogen was introduced at a flow rate of 1 / h and stripped at 180°C for 3 hours to separate the residual BF3 dissolved in the Fischer-Tropsch oil phase, yielding a Fischer-Tropsch oil free of oxygenated compounds. Elemental analysis revealed that the resulting medium Fischer-Tropsch oil contained ≤1 ppm of BF3, 25 ppm of oxygen, and a deoxygenation efficiency of 99.6%.

[0035] Comparative Example 1

[0036] A high-temperature Fischer-Tropsch synthetic oil C8-C16 mixed hydrocarbon fraction was selected, with an olefin content of 69%, and the oxygen content was measured to be 7400ppm. 1L of the mixed hydrocarbon fraction was added to a 2L reactor, and 49.3g (370mmol) of AlCl3 was added to the reactor at 30°C and stirred for 1h. The system after the reaction was fully settled to obtain an upper Fischer-Tropsch oil phase and a lower oxygen-containing complex and unreacted AlCl3 deposit. The upper Fischer-Tropsch oil phase was filtered to obtain the Fischer-Tropsch oil after the oxygen-containing compounds were removed. Elemental analysis showed that the oxygen content of the final medium Fischer-Tropsch oil was 1976ppm, and the deoxygenation rate was 73.3%.

[0037] Comparative Example 2

[0038] A high-temperature Fischer-Tropsch synthetic oil C8-C12 mixed hydrocarbon fraction with an olefin content of 72% was selected, and the oxygen content was measured to be 7200ppm. 1L of the mixed hydrocarbon fraction was added to a 2L reactor, and 96.0g (360mmol) of AlBr3 was added to the reactor at 30°C and stirred for 1h. The system after the reaction was fully settled to obtain an upper Fischer-Tropsch oil phase and a lower oxygen-containing complex and unreacted AlBr3 deposit. The upper Fischer-Tropsch oil phase was filtered to obtain the Fischer-Tropsch oil after the oxygen-containing compounds were removed. Elemental analysis showed that the oxygen content of the final medium Fischer-Tropsch oil was 2680ppm, and the deoxygenation rate was 62.8%.

[0039] Comparative Example 3

[0040] A low-temperature Fischer-Tropsch synthetic oil C8-C20 mixed hydrocarbon fraction with an olefin content of 55% was selected, and the oxygen content was measured to be 550 mmol. 1 L of the mixed hydrocarbon fraction was added to a 2 L reactor, and 44.6 g (275 mmol) of FeCl3 was added to the reactor at 30 ° C and stirred for 1 hour. The system after the reaction was fully settled to obtain an upper Fischer-Tropsch oil phase and a lower oxygen-containing complex and unreacted FeCl3 deposit. The upper Fischer-Tropsch oil phase was filtered to obtain a Fischer-Tropsch oil after the oxygen-containing compounds were removed. Elemental analysis showed that the oxygen content of the final medium Fischer-Tropsch oil was 3672 ppm, and the deoxygenation rate was 33.2%.

[0041] Comparative Example 4

[0042] A high-temperature Fischer-Tropsch synthetic oil C7-C30 mixed hydrocarbon fraction was selected, with an olefin content of 66% and an oxygen content of 12000ppm. 1L of mixed hydrocarbon fraction was added to a 2L reactor, and BF3 was introduced into the reactor at 30°C and fully reacted at 0.03Mpa for 2h. The system after the reaction was fully settled to obtain an upper Fischer-Tropsch oil phase and a lower oxygen-containing complex flow. The upper Fischer-Tropsch oil phase was transferred to a stripping tower and heated at 2Nm 3Nitrogen was introduced at a flow rate of 1 / h and stripped at 80°C for 3 hours to separate the residual BF3 dissolved in the Fischer-Tropsch oil phase, yielding a Fischer-Tropsch oil free of oxygenated compounds. Elemental analysis revealed that the resulting medium Fischer-Tropsch oil contained ≤1 ppm of BF3, 1860 ppm of oxygen, and a deoxygenation efficiency of 84.5%.

[0043] Comparative Example 5

[0044] A high-temperature Fischer-Tropsch synthetic oil C16-C24 mixed hydrocarbon fraction was selected, with an olefin content of 63% and an oxygen content of 9500ppm. 1L of mixed hydrocarbon fraction was added to a 2L reactor, and BCl3 was introduced into the reactor at 40°C and fully reacted at 1.5Mpa for 1.5h. The system after the reaction was fully settled to obtain an upper Fischer-Tropsch oil phase and a lower oxygen-containing complex flow. The upper Fischer-Tropsch oil phase was transferred to a stripping tower and heated at 1.5Nm 3 Nitrogen was introduced at a flow rate of 100°C / hour and stripped at 150°C for 3 hours to separate the residual BCl₃ dissolved in the Fischer-Tropsch oil phase, yielding a Fischer-Tropsch oil free of oxygenated compounds. Elemental analysis revealed that the resulting medium Fischer-Tropsch oil contained ≤1 ppm of BCl₃ and 27 ppm of oxygen, with a deoxygenation efficiency of 99.7%.

[0045]

[0046]

[0047] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for separating oxygenated compounds from Fischer-Tropsch oil, characterized in that: Gaseous boron halide is introduced into Fischer-Tropsch oil to cause the boron halide to undergo a complex reaction with oxygen-containing compounds in the Fischer-Tropsch oil to form a heterogeneous system of oxygen-containing complexes and Fischer-Tropsch oil. The heterogeneous system is separated to obtain a deoxygenated Fischer-Tropsch oil phase and an oxygen-containing complex phase, wherein the boron halide pressure in the system is 0.05-1 MPa; and the olefin content in the Fischer-Tropsch oil is 50-75%.

2. The method for separating oxygenated compounds from Fischer-Tropsch synthetic oil according to claim 1, characterized in that: The boron halide is one or more of BF3, BCl3 and BBr3.

3. The method for separating oxygenated compounds from Fischer-Tropsch synthetic oil according to claim 1, characterized in that: The temperature of the complexation reaction is 0~50℃.

4. The method for separating oxygenated compounds from Fischer-Tropsch synthetic oil according to claim 1, characterized in that: The method further comprises the step of removing residual boron halide from the deoxygenated Fischer-Tropsch oil phase.

5. The method for separating oxygenated compounds from Fischer-Tropsch synthetic oil according to claim 4, characterized in that: The stripping process is used to remove the residual boron halide. The gas used for stripping is nitrogen with a flow rate of 0.1~2Nm 3 / h, temperature is 80~180℃.

6. The method for separating oxygenated compounds from Fischer-Tropsch synthetic oil according to claim 1, characterized in that: The method further comprises the step of recovering the boron halide from the oxygen-containing complex phase.

7. The method for separating oxygenated compounds from Fischer-Tropsch synthetic oil according to claim 6, characterized in that: The oxygen-containing complex phase is thermally cracked to recover boron halide and oxygen-containing compounds.

8. The method for separating oxygenated compounds from Fischer-Tropsch synthetic oil according to claim 1, characterized in that: Separate heterogeneous systems by natural sedimentation or centrifugation.

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