A process for removing oxygenates from a fischer-tropsch synthesis oil

Abstract

This invention discloses a method for removing oxygen-containing compounds from Fischer-Tropsch synthetic petroleum products, belonging to the field of coal chemical technology. It solves the problems of high energy consumption, complex processes, and incomplete removal of oxygen-containing compounds in existing methods. The method includes the following steps: Step S1, mixing Fischer-Tropsch synthetic petroleum products, water, carbides, and a catalyst, and stirring the mixture under inert gas protection to obtain a reaction solution; Step S2, filtering the reaction solution from Step S1 to obtain a filtrate, and then treating the filtrate with a chromatography column to remove alcohols, thereby obtaining Fischer-Tropsch synthetic petroleum products free of oxygen-containing compounds. The method of this invention is simple, easy to operate, and effectively removes oxygen-containing compounds such as alcohols, aldehydes, acids, ketones, and esters from Fischer-Tropsch synthetic petroleum products, achieving a high oil recovery rate.

Description

Technical Field

[0001] This invention belongs to the field of coal chemical technology, specifically relating to a method for removing oxygen-containing compounds from Fischer-Tropsch synthesis oils. Background Technology

[0002] Fischer-Tropsch synthesis is an indirect coal liquefaction technology and an important component of coal-to-oil conversion. It involves the production of straight-chain alkanes, olefins, and oxygen-containing compounds with carbon chains ranging from 1 to over 100 carbons from syngas (CO and H2) under appropriate reaction conditions using iron-based and cobalt-based catalysts. The olefins are predominantly α-olefins, comprising 50%–70% of the product, while the oxygen-containing compounds comprise 5%–15%, primarily including alcohols, aldehydes, acids, ketones, and esters. The presence of organic acids in Fischer-Tropsch synthesized oils can severely corrode equipment, hindering further processing. Alcohols, aldehydes, acids, and ketones can undergo complexation or substitution reactions with Lewis acid catalysts, leading to partial catalyst poisoning and deactivation. The presence of oxygen-containing compounds also affects the odor, color, and oxidation stability of the base oil in the oil to varying degrees.

[0003] In existing technologies, hydrogenation is the primary industrial method for removing oxygen-containing compounds. However, hydrogenation is accompanied by the hydrogenation saturation reaction of olefins, affecting the α-olefin content in Fischer-Tropsch synthesis oils, making the separation of additives from the oil difficult, and resulting in low α-olefin recovery rates. Another method uses adsorbents with porous structures, such as silica gel, to remove oxygen-containing compounds. However, due to the dynamic equilibrium of adsorption and the different polar selectivity of adsorbents for oxygen-containing compounds, the removal rate does not reach the ideal value. Adsorbents are less effective at removing carbonyl groups than hydroxyl groups, especially ester groups, making it impossible to completely remove oxygen-containing compounds from Fischer-Tropsch synthesis oils. Extraction utilizes the different solubilities of oxygen-containing compounds to achieve separation from the oil. The main problems are the large amount of extractant required, low oxygen-containing compound removal rates, complex solvent recovery and purification processes, high energy consumption, and low oil recovery rates. Chemical removal methods have high deoxygenation efficiency, but the selection of catalysts is demanding; unsuitable catalysts can introduce impurities or result in incomplete removal of oxygen-containing compounds. Summary of the Invention

[0004] The purpose of this invention is to provide a method for removing oxygen-containing compounds from Fischer-Tropsch synthetic oils, which solves the problems of high energy consumption, complex processes, and incomplete removal of oxygen-containing compounds in existing methods.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: a method for removing oxygen-containing compounds from Fischer-Tropsch synthetic oils, comprising the following steps:

[0006] Step S1: Mix Fischer-Tropsch synthesis oil, water, carbide and catalyst, and stir the mixture under inert gas protection to obtain a reaction solution;

[0007] Step S2: Filter the reaction solution obtained in step S1 to obtain a filtrate, and perform a dealcoholization treatment on the filtrate to obtain a Fischer-Tropsch synthetic oil product with oxygen-containing compounds removed.

[0008] In some embodiments, in step S1, the content of oxygenated compounds in the Fischer-Tropsch synthetic oil is ≥2000ppm, and the carbon number n of the Fischer-Tropsch synthetic oil is 4≤n≤20.

[0009] In some embodiments, in step S1, the carbide is ionic, and the carbide is one or more of calcium carbide, zinc carbide, lithium carbide, or aluminum carbide.

[0010] In some embodiments, in step S1, the amount of carbide added is 0.05% to 10% of the mass of the Fischer-Tropsch synthetic oil.

[0011] In some embodiments, in step S1, the catalyst is one or more of potassium fluoride, sodium fluoride, rubidium fluoride, cesium fluoride, or francium fluoride.

[0012] In some embodiments, the amount of catalyst added is 0.005% to 5% of the mass of the Fischer-Tropsch synthetic oil.

[0013] In some embodiments, in step S1, the water content is 10 to 50,000 ppm.

[0014] In some embodiments, in step S1, the reaction temperature is 30–200°C, the reaction time is 1–24 h, and the reaction pressure is 0.1–2 MPa.

[0015] In some embodiments, in step S2, the filtrate is subjected to de-alcoholization treatment by passing it through a chromatography column from bottom to top.

[0016] In some embodiments, the chromatography column is a chromatography column packed with an alkali metal aluminosilicate molecular sieve.

[0017] Compared with existing technologies, this invention employs a chemical heterogeneous method to convert the carbonyl groups of oxygen-containing compounds in Fischer-Tropsch synthetic oils into hydroxyl groups, followed by physical adsorption to remove alcohols, resulting in oxygen-free Fischer-Tropsch synthetic oils. In this invention, carbonyl groups are more reactive than hydroxyl groups, making chemical reactions easier. The products are alkynyl alcohols and hydroxides, which are converted into highly polar alcohols, making them easier to remove using physical adsorption. Furthermore, the carbides are solid, facilitating separation from the oil. The oxygen-containing compound removal rate reaches over 98%, meeting industrial production needs. This invention's method is simple, easy to operate, and effectively removes oxygen-containing compounds such as alcohols, aldehydes, acids, ketones, and esters from Fischer-Tropsch synthetic oils. The carbonyl content in the deoxygenated Fischer-Tropsch synthetic oil can be reduced to below 10 ppm, and the alcohol content to below 1 mg KOH / g, with a high oil recovery rate. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] The method for removing oxygen-containing compounds from Fischer-Tropsch synthetic oils according to the present invention includes the following steps:

[0020] Step S1: Add oxygen-containing Fischer-Tropsch synthesis oil, water, carbides, and catalyst to a reaction vessel, and stir the reaction at 30–200°C under inert gas protection to obtain a reaction solution. The reaction time is 1–24 h, and the reaction pressure is 0.1–2 MPa. Oxygen-containing compounds such as ketones, aldehydes, acids, and esters are converted into alcohols.

[0021] Step S2: After the reaction solution in step S1 is allowed to stand and undergoes solid-liquid separation, the lower layer of ionic carbides is removed and filtered to obtain a filtrate. The carbonyl value of the filtrate is detected. The filtrate is then passed through a chromatography column packed with a specially treated alkali metal aluminosilicate molecular sieve for alcohol removal to obtain Fischer-Tropsch synthetic oil with oxygen-containing compounds removed. The hydroxyl value is then detected.

[0022] Example 1

[0023] The reaction conditions for the chemical decarbonylation of the Fischer-Tropsch synthetic oil in Example 1 are shown in Table 1.

[0024] Table 1. Reaction conditions for decarbonylation of Fischer-Tropsch synthetic oils using chemical decoupling in Example 1.

[0025]

[0026] Example 2

[0027] The reaction conditions for the chemical decarbonylation of the Fischer-Tropsch synthetic oil in Example 2 are shown in Table 2.

[0028] Table 2. Reaction conditions for decarbonylation of Fischer-Tropsch synthetic oils using chemical decoupling in Example 2.

[0029]

[0030] Example 3

[0031] The reaction conditions for the chemical decarbonylation of the Fischer-Tropsch synthetic oil in Example 3 are shown in Table 3.

[0032] Table 3. Reaction conditions for decarbonylation of Fischer-Tropsch synthetic oils using chemical decarbonylation in Example 3.

[0033]

[0034] Example 4

[0035] The reaction conditions for the chemical decarbonylation of the Fischer-Tropsch synthetic oil in Example 4 are shown in Table 4.

[0036] Table 4. Reaction conditions for decarbonylation of Fischer-Tropsch synthetic oils using chemical decarbonylation in Example 4.

[0037]

[0038] Example 5

[0039] The reaction conditions for the chemical decarbonylation of the Fischer-Tropsch synthetic oil in Example 5 are shown in Table 5.

[0040] Table 5. Reaction conditions for decarbonylation of Fischer-Tropsch synthetic oils using chemical decoupling in Example 5.

[0041]

[0042] Comparative Example 1

[0043] The reaction conditions for the chemical decarbonylation of the Fischer-Tropsch synthetic oil in Comparative Example 1 are shown in Table 6.

[0044] Table 6 shows the reaction conditions for the chemical decarbonylation of Fischer-Tropsch synthetic oils in Comparative Example 1.

[0045]

[0046] Comparative Example 2

[0047] The reaction conditions for the chemical decarbonylation of the Fischer-Tropsch synthetic oil in Comparative Example 2 are shown in Table 7.

[0048] Table 7. Reaction conditions for decarbonylation of Fischer-Tropsch synthetic oils in Comparative Example 2 using chemical decarbonylation.

[0049]

[0050]

[0051] The carbonyl and hydroxyl content of the Fischer-Tropsch synthetic oils in Examples 1-5 and Comparative Examples 1-2 is shown in Table 8.

[0052] Table 8. Carbonyl and hydroxyl content in Fischer-Tropsch synthetic oils from Examples 1-5 and Comparative Examples 1-2.

[0053] Carbonyl content (ppm) Hydroxyl group content (mgKOH / g) Example 1 8.6 0.58 Example 2 8.3 0.37 Example 3 9.2 0.76 Example 4 0.3 0.25 Example 5 0.1 0.18 Comparative Example 1 715.3 20.75 Comparative Example 2 632.1 15.46

[0054] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for removing oxygen-containing compounds from Fischer-Tropsch synthetic oils, characterized in that, Includes the following steps: Step S1: Mix Fischer-Tropsch synthetic oil, water, carbide, and catalyst, and stir under inert gas protection to obtain a reaction solution; the content of oxygenated compounds in the Fischer-Tropsch synthetic oil is ≥2000 ppm, the carbon number n of the Fischer-Tropsch synthetic oil is 4≤n≤20; the carbide is ionic, and the carbide is one or more of calcium carbide, zinc carbide, or lithium carbide; the amount of carbide added is 0.05%~10% of the mass of the Fischer-Tropsch synthetic oil; the catalyst is one or more of potassium fluoride, sodium fluoride, rubidium fluoride, cesium fluoride, or francium fluoride; the amount of catalyst added is 0.005%~5% of the mass of the Fischer-Tropsch synthetic oil; the water content is 10~50000 ppm; the reaction temperature is 30~200℃, the reaction time is 1~24h, and the reaction pressure is 0.1~2 MPa; Step S2: Filter the reaction solution obtained in step S1 to obtain a filtrate, and perform a dealcoholization treatment on the filtrate to obtain a Fischer-Tropsch synthetic oil with oxygen-containing compounds removed; the filtrate is passed through a chromatography column from bottom to top for dealcoholization treatment; the chromatography column is a chromatography column packed with alkali metal aluminosilicate molecular sieves.

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