A method for removing oxides from Fischer-Tropsch heavy oil

Abstract

The present invention provides a method for removing oxides from Fischer-Tropsch heavy oil. The method comprises the following steps: deacidifying the Fischer-Tropsch heavy oil; extracting the deacidified Fischer-Tropsch heavy oil with a polar organic solvent; mixing the extracted Fischer-Tropsch heavy oil with an acid reactant to undergo an esterification reaction to obtain a mixed solution; and distilling the mixed solution to obtain the Fischer-Tropsch heavy oil after the oxides have been removed. Compared with the prior art mainly targeting the Fischer-Tropsch light oil fraction, the present invention fills the gap in the removal of oxides from Fischer-Tropsch heavy oil, and has low cost, excellent effect, and good market prospects.

Description

Technical Field

[0001] The present invention relates to a method for separating impurities in Fischer-Tropsch heavy oil, and in particular to a method for removing oxides in Fischer-Tropsch heavy oil. Background Art

[0002] As the raw material for the production of α-olefins, Fischer-Tropsch oil contains not only alkanes and olefins, but also oxygen-containing compounds such as alcohols, aldehydes, acids, and esters. These oxides seriously affect the processing and production of downstream products. Therefore, before separating and purifying α-olefins, Fischer-Tropsch oil needs to be pretreated, and oxides are generally removed by adsorption, extraction, distillation, etc. In order to increase the added value of products and promote the development of the downstream industrial chain, it is particularly important to refine and remove oxides from Fischer-Tropsch oil.

[0003] Patent CN109096033A proposes an efficient and energy-saving method and device for removing oxygen-containing compounds from the light narrow fraction of Fischer-Tropsch synthesis, which uses a bulkhead tower extraction or azeotropic distillation technology to replace the double tower structure of traditional extraction or azeotropic distillation. 12 After separation and purification by this process, C5-C 12 The mass content of the fraction products can reach more than 99%, and the recovery rate can reach more than 95%. 12 The applicable range of raw materials is narrow and it is not suitable for stable heavy oil fractions with high carbon number.

[0004] Patent CN109627137A proposes a method for separating coal-based Fischer-Tropsch olefins, comprising the following steps: 1) deacidifying the Fischer-Tropsch light distillate oil raw material; 2) adsorbing the deacidified distillate oil to remove carbonyl compounds. 3) The deacidified distillate oil enters a light-removing tower; the components with a carbon number less than n are separated from the top of the light-removing tower, and the components at the bottom enter a heavy-removing tower; the components with a carbon number greater than n are separated from the bottom of the heavy-removing tower, and the components with a carbon number of n are separated from the top of the heavy-removing tower; 4) The components with a carbon number of n enter an extractive distillation tower, and are in reverse contact with the extractant, and non-polar alkanes are separated from the top of the tower; 5) The target olefin is distilled from the top of the recovery tower, and the extractant is distilled from the bottom of the tower, and circulated into the extractive distillation tower. This process is mainly aimed at the refining of a single target carbon number (8≤n≤18) olefin in Fischer-Tropsch oil, and the raw material requirements are relatively strict (the oxide is not higher than 2wt%, and the acid value is not higher than 0.1mgKOH / 100ml), and the applicability is low.

[0005] Patent CN105272809A discloses a method for removing oxygenated compounds from coal-based α-olefins. The coal-based olefin raw material used is C3-C 13The invention combines chemical removal and solid adsorption. First, active alkaline earth metals are used to passivate oxygen-containing impurities containing active hydrogen atoms in coal-based α-olefins into alkoxy metal salts, which are then precipitated from the material and removed. Then, residual ketone compounds are removed by adsorption. This method is simple and efficient in removing oxygen-containing compound impurities in coal-based α-olefins, but is only applicable to light fractions of Fischer-Tropsch olefins (C3-C 13 Distillation section), this method is not ideal because the activity of oxygenates in heavy oil is reduced.

[0006] In summary, the prior art mainly removes oxides from the light fraction of Fischer-Tropsch oil, and the applicable fraction range of the raw material is relatively light. Currently, no process for removing oxides from Fischer-Tropsch heavy oil has been proposed. In view of this, the present invention is proposed. Summary of the invention

[0007] The main purpose of the present invention is to provide a method for removing oxides from Fischer-Tropsch heavy oil, so as to solve the problem that oxides in Fischer-Tropsch heavy oil are difficult to remove in the prior art.

[0008] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a method for removing oxides from Fischer-Tropsch heavy oil is provided, characterized in that the method comprises the following steps: step S1, deacidifying the Fischer-Tropsch heavy oil to obtain deacidified Fischer-Tropsch heavy oil; step S2, extracting the deacidified Fischer-Tropsch heavy oil with a polar organic solvent to obtain extracted Fischer-Tropsch heavy oil; step S3, mixing the extracted Fischer-Tropsch heavy oil with an acid reactant, causing an esterification reaction, and obtaining a mixed solution; step S4, distilling the mixed solution to obtain the Fischer-Tropsch heavy oil from which oxides have been removed.

[0009] Furthermore, in step S4, the distillation treatment includes a first distillation treatment and a second distillation treatment performed sequentially; wherein the first distillation treatment is atmospheric distillation for removing unreacted excess acid reactant in the mixed solution; and the second distillation is reduced pressure distillation for separating the Fischer-Tropsch heavy oil after the oxide is removed.

[0010] Further, step S1 comprises: treating the Fischer-Tropsch heavy oil with a deacidifying agent; wherein the deacidifying agent is an inorganic alkali aqueous solution; wherein the alkali in the inorganic alkali aqueous solution is one or more of sodium hydroxide, potassium hydroxide and potassium carbonate.

[0011] Furthermore, the mass concentration of the inorganic alkali aqueous solution is 0.01 to 10%, preferably 0.05 to 5%; the volume ratio of the inorganic alkali aqueous solution to the Fischer-Tropsch heavy oil is (0.2:1) to (6:1), preferably (0.5:1) to (3:1).

[0012] Furthermore, in step S2, the deacidified Fischer-Tropsch heavy oil is extracted with a polar organic solvent to remove carbonyl oxides and some alcohol oxides therein; in the extracted Fischer-Tropsch heavy oil, the carbonyl oxide content is ≤100 ppm.

[0013] Furthermore, the polar organic solvent is a sulfone or alcohol organic solvent; preferably one or more of sulfolane, dimethyl sulfoxide, propylene glycol, ethylene glycol, methanol, and ethanol.

[0014] Furthermore, the volume ratio of the polar organic solvent to the deacidified Fischer-Tropsch heavy oil is (0.2:1) to (12:1), preferably (2:1) to (8:1).

[0015] Further, the acid reactant is an organic carboxylic acid; preferably, the organic carboxylic acid is one or a mixture in any proportion of formic acid, acetic acid, oxalic acid, propionic acid, malonic acid, butyric acid, succinic acid, valeric acid, isovaleric acid, and isononanoic acid; more preferably, the organic carboxylic acid is one or more of formic acid, acetic acid, or propionic acid.

[0016] Furthermore, the acid-alcohol molar ratio of the acid reactant to the alcohol oxide that has not been removed is (1:1) to (12:1); preferably, the acid-alcohol molar ratio of the acid reactant to the alcohol oxide that has not been removed is (3:1) to (6:1).

[0017] Furthermore, the reaction temperature of the esterification reaction is 50 to 240° C., preferably 80 to 150° C.; the reaction time of the esterification reaction is 1 to 10 hours, preferably 2 to 6 hours; the molar ratio of the catalyst of the esterification reaction to the alcohol oxide that has not been removed is (1:1) to (1:30), preferably (1:1) to (1:10).

[0018] The technical solution of the present invention can be used to simply and efficiently remove oxides from Fischer-Tropsch heavy oil. The solution uses a new process flow to remove oxides from Fischer-Tropsch heavy oil to obtain a Fischer-Tropsch heavy oil raw material that meets downstream processing requirements. Compared with the existing technology that mainly targets Fischer-Tropsch light oil fractions, the technical solution of the present invention fills the gap in the removal of oxides from Fischer-Tropsch heavy oil, and the technical solution provided by the present invention is low-cost, has excellent effects, and has good market prospects. DETAILED DESCRIPTION

[0019] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0020] In order to solve the technical problems mentioned above, the present invention provides a method for removing oxides from Fischer-Tropsch heavy oil, which comprises the following steps: step S1, deacidifying the Fischer-Tropsch heavy oil to obtain deacidified Fischer-Tropsch heavy oil; step S2, extracting the deacidified Fischer-Tropsch heavy oil with a polar organic solvent to obtain extracted Fischer-Tropsch heavy oil; step S3, mixing the extracted Fischer-Tropsch heavy oil with an acid reactant to undergo an esterification reaction to obtain a mixed solution; step S4, distilling the mixed solution to obtain the Fischer-Tropsch heavy oil after the oxides are removed. The technical solution of the present invention can be used to simply and efficiently remove oxides from Fischer-Tropsch heavy oil. The solution uses a new process flow to remove oxides from Fischer-Tropsch heavy oil to obtain a Fischer-Tropsch heavy oil raw material that meets downstream processing requirements. Compared with the prior art mainly targeting Fischer-Tropsch light oil fractions, the technical solution of the present invention fills the gap in the removal of oxides from Fischer-Tropsch heavy oil, and the technical solution provided by the present invention is low in cost, excellent in effect, and has a good market prospect.

[0021] In order to better remove impurities from the Fischer-Tropsch heavy oil, in a preferred embodiment, in the above step S4, the distillation treatment includes a first distillation treatment and a second distillation treatment performed in sequence; wherein the first distillation treatment is atmospheric distillation, which is used to remove the unreacted excess acid reactant in the mixed solution; and the second distillation is a reduced pressure distillation, which is used to separate the Fischer-Tropsch heavy oil after the oxide is removed. Among them, the acid reactant has a low boiling point, so it can be removed under atmospheric distillation. The boiling point of the Fischer-Tropsch heavy oil is slightly higher, and it is necessary to use reduced pressure distillation to separate it from the esterified product with a high boiling point generated in the esterification reaction in the above step S3.

[0022] In order to better reduce the acid value of the Fischer-Tropsch heavy oil and facilitate subsequent processing, in a preferred embodiment, the above step S1 includes: treating the Fischer-Tropsch heavy oil with a deacidifying agent; wherein the deacidifying agent is an inorganic alkali aqueous solution; wherein the alkali in the inorganic alkali aqueous solution is one or more of sodium hydroxide, potassium hydroxide, and potassium carbonate.

[0023] In order to further improve the deacidification effect, in a preferred embodiment, the mass concentration of the inorganic alkali aqueous solution is 0.01-10%, preferably 0.05-5%; the volume ratio of the inorganic alkali aqueous solution to the Fischer-Tropsch heavy oil is (0.2:1)-(6:1), preferably (0.5:1)-(3:1).

[0024] Under the above preferred deacidification process parameters, the Fischer-Tropsch heavy oil can be deacidified more effectively to remove the acid and water-soluble oxides therein. After the deacidification treatment, the acid value of the Fischer-Tropsch heavy oil can be reduced to below 0.05 mgKOH / g.

[0025] In order to further remove the deacidified Fischer-Tropsch heavy oil, in a preferred embodiment, the above method further includes: in step S2, the deacidified Fischer-Tropsch heavy oil is extracted with a polar organic solvent to remove carbonyl oxides and some alcohol oxides therein; in the extracted Fischer-Tropsch heavy oil, the carbonyl oxide content is ≤100ppm. After the extraction treatment, the impurity content in the Fischer-Tropsch heavy oil is further reduced, which is more convenient for subsequent separation. In actual operation, the content of alcohol oxides can be detected by analytical methods such as OFID or carbon number distribution and normal alcohol distribution analysis as a basis for subsequent addition of reagents.

[0026] In order to further improve the extraction effect, in a preferred embodiment, the polar organic solvent is a sulfone or alcohol organic solvent; preferably one or more of sulfolane, dimethyl sulfoxide, propylene glycol, ethylene glycol, methanol, and ethanol.

[0027] In a preferred embodiment, the volume ratio of the polar organic solvent to the deacidified Fischer-Tropsch heavy oil is (0.2:1) to (12:1), preferably (2:1) to (8:1). Under the above preferred dosage, the alcohol oxides and carbonyl oxides with higher polarity, such as aldehydes and ketones, in the Fischer-Tropsch heavy oil can be better removed.

[0028] For the purpose of further removing the remaining alcohol and acid in the Fischer-Tropsch heavy oil after extraction, in a preferred embodiment, the acid reactant is an organic carboxylic acid; preferably, the organic carboxylic acid is one or more of formic acid, acetic acid, oxalic acid, propionic acid, malonic acid, butyric acid, succinic acid, valeric acid, isovaleric acid, and isononanoic acid; more preferably, the organic carboxylic acid is one or more of formic acid, acetic acid, or propionic acid. The above-mentioned acid reactant can undergo an esterification reaction with the remaining alcohol and acid to generate a high-boiling esterified product, which is beneficial for subsequent separation. In actual operation, preferably, the above-mentioned esterification reaction is carried out in a kettle reactor.

[0029] In order to fully convert the unremoved alcohol oxides into esters, preferably, the acid-alcohol molar ratio of the acid reactant to the unremoved alcohol oxides is (1:1) to (12:1); preferably, the acid-alcohol molar ratio of the acid reactant to the unremoved alcohol oxides is (3:1) to (6:1). The above molar ratio is preferred, and the excess acid reactant can fully convert the alcohol oxides, and the excess acid reactant can also be separated from the mixed solution by distillation due to its low boiling point.

[0030] In order to further enable the esterification reaction to occur fully, in a preferred embodiment, the reaction temperature of the esterification reaction is 50-240°C, preferably 80-150°C; the reaction time of the esterification reaction is 1-10h, preferably 2-6h; the molar ratio of the catalyst of the esterification reaction to the alcohol oxide that has not been removed is (1:1)-(1:30), preferably (1:1)-(1:10).

[0031] In actual operation, the catalyst for the esterification reaction can be selected conventionally in the art, such as one or more of a strong acid resin catalyst, a molecular sieve catalyst, a heteropolyacid catalyst, and an ionic liquid catalyst.

[0032] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0033] Embodiment 1:

[0034] A method for removing oxides from Fischer-Tropsch heavy oil, wherein the selected raw material is a low-temperature Fischer-Tropsch stable heavy oil C14-C16 fraction containing 5.73wt% oxides, and the specific operation is as follows:

[0035] Step S1, weighing a KOH aqueous solution with a mass concentration of 0.5% and a Fischer-Tropsch heavy oil in a volume ratio of 2:1, respectively, and performing a deacidification treatment to obtain a deacidified Fischer-Tropsch heavy oil;

[0036] Step S2, extracting the deacidified Fischer-Tropsch heavy oil with dimethyl sulfoxide, wherein the volume ratio of dimethyl sulfoxide to the deacidified Fischer-Tropsch heavy oil is 8:1, to obtain extracted Fischer-Tropsch heavy oil;

[0037] Step S3, mixing the extracted Fischer-Tropsch heavy oil with acetic acid in an alcohol-acid molar ratio of 1:2 to cause an esterification reaction, the esterification reaction temperature is 95° C., the esterification reaction time is 2.5 h, the catalyst is a resin catalyst, and the catalyst-alcohol ratio (w / w) is 1:5.

[0038] After separation, the oxygen-containing compound content of the obtained product is 0.51wt%

[0039] Embodiment 2:

[0040] A method for removing oxides from Fischer-Tropsch heavy oil, wherein the selected raw material is a low-temperature Fischer-Tropsch stable heavy oil C14-C16 fraction containing 5.73 wt% of oxides, comprising the following steps:

[0041] Step S1, weighing a 10% potassium carbonate aqueous solution and a Fischer-Tropsch heavy oil at a volume ratio of 0.5:1, respectively, and performing a deacidification treatment to obtain a deacidified Fischer-Tropsch heavy oil;

[0042] Step S2, extracting the deacidified Fischer-Tropsch heavy oil with propylene glycol, wherein the volume ratio of propylene glycol to the deacidified Fischer-Tropsch heavy oil is 3:1, to obtain extracted Fischer-Tropsch heavy oil;

[0043] Step S3, mixing the extracted Fischer-Tropsch heavy oil with formic acid in an alcohol-acid molar ratio of 1:1 to cause an esterification reaction, the esterification reaction temperature is 80° C., the esterification reaction time is 10 hours, the catalyst is a resin catalyst, and the catalyst-to-alcohol ratio is 1:3.

[0044] After separation, the oxygen-containing compound content of the obtained product is 0.67wt%

[0045] Embodiment 3:

[0046] A method for removing oxides from Fischer-Tropsch heavy oil, wherein the selected raw material is a low-temperature Fischer-Tropsch stable heavy oil C14-C16 fraction containing 5.73 wt% of oxides, comprising the following steps:

[0047] Step S1, weighing a sodium hydroxide aqueous solution with a mass concentration of 0.01% and a Fischer-Tropsch heavy oil in a volume ratio of 6:1, respectively, and performing a deacidification treatment to obtain a deacidified Fischer-Tropsch heavy oil;

[0048] Step S2, extracting the deacidified Fischer-Tropsch heavy oil with ethanol, wherein the volume ratio of ethanol to the deacidified Fischer-Tropsch heavy oil is 6:1, to obtain extracted Fischer-Tropsch heavy oil;

[0049] Step S3, mixing the extracted Fischer-Tropsch heavy oil with propionic acid in an alcohol-acid molar ratio of 1:4 to cause an esterification reaction, the esterification reaction temperature is 110° C., the esterification reaction time is 4 hours, the catalyst is a resin catalyst, and the catalyst-alcohol ratio is 1:30.

[0050] After separation, the oxygen-containing compound content of the obtained product is 0.65wt%

[0051] Comparative Example 1:

[0052] A method for removing oxides from Fischer-Tropsch heavy oil, wherein the selected raw material is a low-temperature Fischer-Tropsch stable heavy oil C14-C16 fraction containing 5.73wt% oxides, and the oxides are removed only by extractive deoxidation, i.e., only step S2 is included, and other operations are the same as those in Example 1. The obtained intermediate product has an oxide content of 2.43wt%, and there is a problem of large loss of extractant.

[0053] Comparative Examples 2-3:

[0054] In Example 2 and Example 3, only step S2 is performed, and other operations are the same as in Examples 2 and 3. The oxide contents in the obtained intermediate products are 3.15wt% and 2.76wt%, respectively.

[0055] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0056] The technical solution of the present invention can be used to simply and efficiently remove oxides from Fischer-Tropsch heavy oil. The solution uses a new process flow to remove oxides from Fischer-Tropsch heavy oil to obtain a Fischer-Tropsch heavy oil raw material that meets downstream processing requirements. Compared with most existing technologies that mainly target Fischer-Tropsch light oil fractions, the technical solution of the present invention fills the gap in the removal of oxides from Fischer-Tropsch heavy oil, and the technical solution provided by the present invention is low-cost, has excellent effects, and has good market prospects.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for removing oxygenates from the C14-C16 fraction of Fischer-Tropsch heavy oil, characterized in that: The method comprises the following steps: Step S1, deacidifying the Fischer-Tropsch heavy oil C14-C16 fraction to obtain a deacidified Fischer-Tropsch heavy oil C14-C16 fraction; Step S2, extracting the deacidified Fischer-Tropsch heavy oil C14-C16 fraction with a polar organic solvent to obtain an extracted Fischer-Tropsch heavy oil C14-C16 fraction; Step S3, mixing the extracted Fischer-Tropsch heavy oil C14-C16 fraction with an acid reactant to undergo an esterification reaction to obtain a mixed solution; Step S4, distilling the mixed solution to obtain a C14-C16 fraction of Fischer-Tropsch heavy oil after the oxides are removed; The step S1 comprises: treating the Fischer-Tropsch heavy oil C14-C16 fraction with a deacidifying agent, wherein the deacidifying agent is an inorganic alkali aqueous solution; the mass concentration of the inorganic alkali aqueous solution is 0.05-5%; the volume ratio of the inorganic alkali aqueous solution to the Fischer-Tropsch heavy oil C14-C16 fraction is (0.5:1)-(3:1); the alkali in the inorganic alkali aqueous solution is one or more of sodium hydroxide, potassium hydroxide, and potassium carbonate; In the step S2, the deacidified Fischer-Tropsch heavy oil C14-C16 fraction is extracted with the polar organic solvent to remove carbonyl oxides and part of alcohol oxides therein; the polar organic solvent is one or more of dimethyl sulfoxide, propylene glycol, and ethanol; in the extracted Fischer-Tropsch heavy oil C14-C16 fraction, the carbonyl oxide content is ≤100ppm; In step S3, the acid reactant is an organic carboxylic acid, and the organic carboxylic acid is one or more of formic acid, acetic acid or propionic acid; In step S4, the distillation treatment includes a first distillation treatment and a second distillation treatment performed sequentially; wherein the first distillation treatment is atmospheric distillation for removing the unreacted excess acid reactant in the mixed solution; and the second distillation is reduced pressure distillation for separating the C14-C16 fraction of the Fischer-Tropsch heavy oil after the removal of oxides.

2. The method according to claim 1, characterized in that The volume ratio of the polar organic solvent to the deacidified Fischer-Tropsch heavy oil C14-C16 fraction is (0.2:1) to (12:1).

3. The method according to claim 1, characterized in that The volume ratio of the polar organic solvent to the deacidified Fischer-Tropsch heavy oil C14-C16 fraction is (2:1) to (8:1).

4. The method according to claim 1, characterized in that The acid-alcohol molar ratio of the acid reactant to the alcohol oxide that has not been removed is (1:1) to (12:1).

5. The method according to claim 4, characterized in that The acid-alcohol molar ratio of the acid reactant to the alcohol oxide that has not been removed is (3:1) to (6:1).

6. The method according to claim 1, characterized in that The reaction temperature of the esterification reaction is 50-240°C; The reaction time of the esterification reaction is 1 to 10 hours; The molar ratio of the catalyst for the esterification reaction to the alcohol oxide that has not been removed is (1:1) to (1:30).

7. The method according to claim 6, characterized in that The reaction temperature of the esterification reaction is 80-150°C; The reaction time of the esterification reaction is 2 to 6 hours; The molar ratio of the catalyst for the esterification reaction to the alcohol oxide that has not been removed is (1:1) to (1:10).