Method for removing oxygen-containing compounds from fischer-tropsch light distillates by means of catalytic distillation

Abstract

Disclosed in the present application is a method for removing oxygen-containing compounds from Fischer-Tropsch light distillates by means of catalytic distillation. In the present invention, oxygen-containing compounds in Fischer-Tropsch light distillates are initially removed by means of a catalytic distillation column; a crude deoxygenated product is extracted from the top of the catalytic distillation column and enters a fixed-bed adsorption column to undergo deep removal, so as to obtain a product having an oxide content of less than 1 μg / g; and the bottom liquid of the catalytic distillation column is recycled and intermittently regenerated. In the present invention, oxygen-containing compounds in Fischer-Tropsch light distillates are converted, by means of the coupling of reaction and separation, into components having boiling points largely different from those of alkanes and olefins, thereby achieving the aim of separating alkanes and olefins from the oxygen-containing compounds, and also reducing energy consumption and equipment costs.

Description

A method for removing oxygen-containing compounds from Fischer-Tropsch light distillate oil by catalytic distillation Technical Field

[0001] This application relates to the fields of chemical engineering and technology, and in particular to a method for removing oxygen-containing compounds from Fischer-Tropsch light distillate oil by catalytic distillation. Background Technology

[0002] Fischer-Tropsch oil contains a large amount of α-olefins and is an important raw material for the synthesis of high-end chemicals. However, the oxygen-containing compound impurities present in Fischer-Tropsch oil can significantly affect the quality of downstream products and are difficult to remove, usually requiring complex process technologies to achieve deep removal.

[0003] Existing technologies also document the removal of oxygen-containing impurities from Fischer-Tropsch oils. For example, Chinese invention patent application CN112126458A discloses a method for removing oxygen-containing compounds from Fischer-Tropsch synthetic oils with different carbon numbers. Different molecular sieves are used to adsorb and remove oxygen-containing compounds for Fischer-Tropsch oils with different carbon numbers. However, molecular sieves have a small deoxygenation adsorption capacity, generally between 5% and 10%, resulting in low throughput and making them unsuitable for treating Fischer-Tropsch oils with an oxygen-containing compound concentration ≥1%.

[0004] For example, Chinese invention patent application CN113684056A discloses a continuous process for removing oxygen-containing compounds from Fischer-Tropsch oil. The process uses a coupled process of alkaline washing and extractive distillation. The extractive distillation uses two-stage extraction with sulfoxides and propylene carbonate, which is complex, introduces more new substances, and is not conducive to subsequent separation work.

[0005] For example, Chinese invention patent CN100413824C discloses the use of methanol and water as extractants to remove oxygen-containing compounds from Fischer-Tropsch oil. However, the boiling points of methanol, ethanol, and isopropanol are within the distillation range of Fischer-Tropsch synthetic oil, making them impossible to remove by distillation, which causes difficulties in separation. Summary of the Invention

[0006] This application aims to address the problems of complex processes, low separation efficiency, and low deoxygenation depth in existing methods for removing oxygen-containing impurities from Fischer-Tropsch oil. It provides a method for removing oxygen-containing compounds from Fischer-Tropsch light distillate oil by catalytic distillation, which features a simple process flow, high deoxygenation depth, and high deoxygenation efficiency.

[0007] The present invention is achieved by the following technical solution.

[0008] A method for removing oxygen-containing compounds from Fischer-Tropsch light distillate oil by catalytic distillation includes the following steps:

[0009] S1. The Fischer-Tropsch light distillate feedstock and reactant are fed into a catalytic distillation column for reaction under the action of a catalyst to initially remove oxygen-containing compounds. After the reaction, the Fischer-Tropsch light distillate product at the top of the column contains oxides with a concentration of <100 μg / g. The reactant is a mixture of liquid acid catalyst and alkanes, with alkanes accounting for 70% to 100% of the total mass of the mixture, preferably 85% to 100%.

[0010] S2. The top product of the catalytic distillation column enters the fixed bed adsorption column for deep removal of oxygen-containing compounds. After treatment, the oxygen-containing compounds in the Fischer-Tropsch light distillate oil are <1μg / g.

[0011] S3. The bottom liquid of the catalytic distillation column is recycled and fresh reactants are added. When the content of heavy components with boiling point >250℃ in the bottom liquid is ≥10%, the bottom liquid enters the regeneration column for reactant regeneration. The regenerated reactants are then reintroduced into the catalytic distillation column.

[0012] Furthermore, the catalytic distillation column comprises a rectification section, a reaction section, and a stripping section. The rectification section has 5-45 theoretical plates, preferably 10-30 theoretical plates; the reaction section has 10-50 theoretical plates, preferably 20-40 theoretical plates; and the stripping section has 5-45 theoretical plates, preferably 10-30 theoretical plates. The residence time of the material in the reaction section is 5-60 min, preferably 10-40 min. The top pressure of the column is 0.1-5 atm, preferably 0.2-1 atm. The molar reflux ratio is 0.1-10, preferably 0.5-5. The Fischer-Tropsch light distillate feedstock enters from the stripping section, and the reactant enters from the rectification section. The mass ratio of the reactant to the Fischer-Tropsch light distillate feedstock is 0.05-1, preferably 0.1-0.6.

[0013] Furthermore, the catalyst for the catalytic distillation column is a solid catalyst; the solid catalyst is selected from one or a combination of macroporous sulfonic acid resin, ZSM-5 molecular sieve, ZSM-23 molecular sieve, Y molecular sieve, silica gel, and alumina, and the amount of solid catalyst added is 0.1% to 5% of the mass flow rate of Fischer-Tropsch light distillate oil feedstock, preferably 0.5% to 2%.

[0014] Furthermore, the boiling point of the liquid acid catalyst in the reactant is 195–255°C, preferably 200–230°C; the boiling point of the alkane is 195–255°C, preferably 200–230°C.

[0015] Furthermore, the theoretical plate number of the regeneration tower is 50-100, preferably 65-85; the feed position is 30-60, preferably 40-50; the tower top pressure is 0.05-0.5 atm, preferably 0.1-0.3 atm; and the molar reflux ratio is 1-15, preferably 3-10.

[0016] Furthermore, the number of fixed-bed adsorption towers is 2 to 6, preferably 2 to 4, and the connection method is a series-parallel hybrid; the operating temperature of the adsorption towers is 25 to 60°C, preferably 35 to 45°C; and the feed space velocity is 0.1 to 3 h⁻¹. -1 Preferably 0.5 to 2 hours -1 The pressure of the adsorption tower is 0.2 to 1.0 MPaG, preferably 0.4 to 0.6 MPaG.

[0017] Furthermore, the adsorbent in the fixed-bed adsorption tower is packed in a graded manner. The adsorbent includes a dehydrating adsorbent and a de-alcoholizing adsorbent. The dehydrating adsorbent is placed in the upper part, and the de-alcoholizing adsorbent is placed in the lower part. The dehydrating adsorbent accounts for 10% to 30% of the total mass of the adsorbent. The dehydrating adsorbent is selected from one or more of type A molecular sieve, silica gel, and type X molecular sieve; the de-alcoholizing adsorbent is selected from one or more of type X molecular sieve, type Y molecular sieve, and activated carbon.

[0018] Furthermore, the Fischer-Tropsch light distillate feedstock has a distillation range of 30°C to 180°C and an oxide content of 0.5% to 10%.

[0019] This application has the following beneficial effects.

[0020] (1) The process of this invention is simple, with low investment and high economic benefits;

[0021] (2) The present invention introduces a reaction between the reactant and the light Fischer-Tropsch oil oxide, and the heavy components and raw materials have a large boiling point difference, making them easy to separate;

[0022] (3) The present invention has a deep deoxygenation degree and can remove oxygen-containing compounds in Fischer-Tropsch oil to below 1 μg / g. Attached Figure Description

[0023] Figure 1 is a flowchart of the method for removing oxygen-containing compounds from Fischer-Tropsch light distillate oil by catalytic distillation according to the present invention.

[0024] Among them, 1. catalytic distillation column; 2. regeneration column; 3. fixed bed adsorption column. Detailed Implementation

[0025] The present patent application will be further described below with reference to the embodiments.

[0026] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials and reagents used in the following preparation examples and examples are commercially available unless otherwise specified.

[0027] As shown in Figure 1, the Fischer-Tropsch light distillate feedstock is fed into catalytic distillation column 1. After reaction separation, the overhead product enters fixed-bed adsorption column 3 for deep removal of oxygen-containing compounds via adsorption separation, resulting in an oxygen-free light Fischer-Tropsch oil product. The bottom product of the catalytic distillation column is recycled. When the content of heavy components with a boiling point >250℃ in the bottom product is ≥10%, the bottom product enters regeneration column 2 for regeneration. The overhead reactant product of the regeneration column is recycled, while the bottom product is treated as an impurity.

[0028] The formula for calculating the Fischer-Tropsch oil yield in the following examples is as follows:

[0029] Fischer-Tropsch oil yield = (Light Fischer-Tropsch oil product mass flow rate / Feed light Fischer-Tropsch oil mass flow rate) × 100%

[0030] Example 1

[0031] A method for removing oxygen-containing compounds from Fischer-Tropsch light distillate oil by catalytic distillation includes the following steps:

[0032] (1) The Fischer-Tropsch oil feedstock is C5-C9 Fischer-Tropsch synthetic oil with an oxide content of 1.5%. The main components are shown in Table 1. The reactant is 100% dodecane, and the catalyst is ZSM-5 molecular sieve. The addition amount is 0.5% of the Fischer-Tropsch oil feedstock mass flow rate.

[0033] (2) The catalytic distillation column has 12 theoretical plates in the rectification section, 25 theoretical plates in the reaction section, and 15 theoretical plates in the stripping section; the material residence time in the reaction section is 12 min; the pressure at the top of the column is 0.2 atm, and the molar reflux ratio is 1.1; the feed enters from the 40th theoretical plate, and the reactant enters from the 10th theoretical plate; the mass ratio of the reactant to the Fischer-Tropsch feed is 0.15.

[0034] (3) The regeneration tower has 65 theoretical plates, 40 theoretical plates at the feed position, a top pressure of 0.3 atm, and a molar reflux ratio of 4.0.

[0035] (4) The number of fixed-bed adsorption towers is 2, and the connection method is a series-parallel hybrid connection; the operating temperature of the adsorption towers is 35℃, and the space velocity is 1.0h. -1 The pressure in the adsorption tower is 0.5 MPaG.

[0036] (5) The adsorbent in the fixed bed includes 20% dehydration adsorbent and 80% de-alcoholization adsorbent. The dehydration adsorbent uses 3A molecular sieve; the de-alcoholization adsorbent uses activated carbon. The dehydration adsorbent is placed in the upper part and the de-alcoholization adsorbent is placed in the lower part.

[0037] The oxide content in the top product of the catalytic distillation column was 30 μg / g, which was reduced to 0 after deep deoxygenation, and the Fischer-Tropsch oil yield was 98.5%.

[0038] Example 2

[0039] A method for removing oxygen-containing compounds from Fischer-Tropsch light distillate oil by catalytic distillation includes the following steps:

[0040] (1) The Fischer-Tropsch oil feedstock is C5-C9 Fischer-Tropsch synthetic oil with an oxide content of 6.8%. The main components are shown in Table 1. The reactant is 90% dodecane + 10% isoheptane, and the catalyst is macroporous sulfonic acid resin. The catalyst addition amount is 0.5% of the Fischer-Tropsch oil feedstock mass flow rate.

[0041] (2) The catalytic distillation column has 15 theoretical plates in the rectification section, 35 theoretical plates in the reaction section, and 20 theoretical plates in the stripping section; the material residence time in the reaction section is 15 min; the pressure at the top of the column is 0.2 atm, and the molar reflux ratio is 1.4; the feed enters from the 55th theoretical plate, and the reactant enters from the 15th theoretical plate; the mass ratio of the reactant to the Fischer-Tropsch feed is 0.2.

[0042] (3) The regeneration tower has 70 theoretical plates, 45 theoretical plates at the feed position, 0.18 atm at the top of the tower, and a molar reflux ratio of 4.5.

[0043] (4) The number of fixed-bed adsorption towers is 2, and the connection method is a series-parallel hybrid connection; the operating temperature of the adsorption towers is 35℃, and the space velocity is 1.0h. -1 The pressure in the adsorption tower is 0.5 MPaG.

[0044] (5) The adsorbent in the fixed bed includes 10% dehydration adsorbent and 90% de-alcoholization adsorbent. The dehydration adsorbent uses 5A molecular sieve; the de-alcoholization adsorbent uses 13X molecular sieve. The dehydration adsorbent is placed in the upper part and the de-alcoholization adsorbent is placed in the lower part.

[0045] The oxide content in the top product of the catalytic distillation column was 85 μg / g, which was reduced to 0 after deep deoxygenation, and the Fischer-Tropsch oil yield was 95.8%.

[0046] Example 3

[0047] A method for removing oxygen-containing compounds from Fischer-Tropsch light distillate oil by catalytic distillation includes the following steps:

[0048] (1) The Fischer-Tropsch oil feedstock is C8-C10 Fischer-Tropsch synthetic oil with an oxide content of 4.5%. The main components are shown in Table 1. The reactant is 80% dodecane + 20% isononanoic acid. The catalyst is macroporous sulfonic acid resin. The catalyst addition amount is 0.4% of the Fischer-Tropsch oil feedstock mass flow rate.

[0049] (2) The catalytic distillation column has 20 theoretical plates in the rectification section, 40 theoretical plates in the reaction section, and 25 theoretical plates in the stripping section; the material residence time in the reaction section is 14 min; the pressure at the top of the column is 0.3 atm, and the molar reflux ratio is 1.7; the feed enters from the 60th theoretical plate, and the reactant enters from the 20th theoretical plate; the mass ratio of the reactant to the Fischer-Tropsch feed is 0.3.

[0050] (3) The regeneration tower has 60 theoretical plates, 35 theoretical plates at the feed position, 0.1 atm at the top of the tower, and a molar reflux ratio of 3.1.

[0051] (4) The number of fixed-bed adsorption towers is 3, and the connection method is a series-parallel hybrid connection; the operating temperature of the adsorption towers is 30℃, and the space velocity is 0.5h. -1 The pressure in the adsorption tower is 0.5 MPaG.

[0052] (5) The adsorbent in the fixed bed includes 5% dehydration adsorbent and 95% de-alcoholization adsorbent. The dehydration adsorbent uses 4A molecular sieve; the de-alcoholization adsorbent uses Y molecular sieve. The dehydration adsorbent is placed in the upper part and the de-alcoholization adsorbent is placed in the lower part.

[0053] The oxide content in the top product of the catalytic distillation column was 64 μg / g, which was reduced to 0 after deep deoxygenation, and the Fischer-Tropsch oil yield was 96.9%.

[0054] Example 4

[0055] A method for removing oxygen-containing compounds from Fischer-Tropsch light distillate oil by catalytic distillation includes the following steps:

[0056] (1) The Fischer-Tropsch oil feedstock is C6-C8 Fischer-Tropsch synthetic oil with an oxide content of 3.0%. The main components are shown in Table 1. The reactant is 85% 2-methylundecane + 15% hexanoic acid. The catalyst is silica gel. The catalyst addition amount is 0.8% of the Fischer-Tropsch oil feedstock mass flow rate.

[0057] (2) The catalytic distillation column has 20 theoretical plates in the rectification section, 30 theoretical plates in the reaction section, and 20 theoretical plates in the stripping section; the material residence time in the reaction section is 10 min; the pressure at the top of the column is 0.5 atm, and the molar reflux ratio is 1.5; the feed enters from the 50th theoretical plate, and the reactant enters from the 20th theoretical plate; the mass ratio of the reactant to the Fischer-Tropsch feed is 0.4.

[0058] (3) The regeneration tower has 70 theoretical plates, 50 theoretical plates at the feed position, 0.3 atm at the top of the tower, and a molar reflux ratio of 3.5.

[0059] (4) The number of fixed-bed adsorption towers is 2, and the connection method is a series-parallel hybrid connection; the operating temperature of the adsorption towers is 45℃, and the space velocity is 0.8h. -1 The pressure in the adsorption tower is 0.4 MPaG.

[0060] (5) The adsorbent in the fixed bed includes 15% dehydrating adsorbent and 85% de-alcoholizing adsorbent. The dehydrating adsorbent is made of silica gel; the de-alcoholizing adsorbent is made of 13X molecular sieve. The dehydrating adsorbent is placed in the upper part and the de-alcoholizing adsorbent is placed in the lower part.

[0061] The oxide content in the top product of the catalytic distillation column was 50 μg / g, which was reduced to 0 after deep deoxygenation, and the Fischer-Tropsch oil yield was 96.1%.

[0062] Comparative Example 1

[0063] A method for removing oxygen-containing compounds from Fischer-Tropsch light distillate oil by catalytic distillation includes the following steps:

[0064] (1) The Fischer-Tropsch oil feedstock is the same as that in Example 4.

[0065] (2) The reactant used is 85% 2-methylundecane + 15% hexanoic acid, and the catalyst used is X molecular sieve. The amount of catalyst added is 2% of the mass flow rate of Fischer-Tropsch oil feedstock.

[0066] (3) The catalytic distillation column has 20 theoretical plates in the rectification section, 30 theoretical plates in the reaction section, and 20 theoretical plates in the stripping section; the material residence time in the reaction section is 5 min; the pressure at the top of the column is 1 atm, and the molar reflux ratio is 1.5; the raw material enters from the 50th theoretical plate, and the reactant enters from the 20th theoretical plate; the mass ratio of the reactant to the Fischer-Tropsch oil raw material is 0.4.

[0067] (4) The regeneration tower has 70 theoretical plates, 50 theoretical plates at the feed position, a tower top pressure of 0.3 atm, and a molar reflux ratio of 3.5.

[0068] (5) The number of fixed-bed adsorption towers is 2, and the connection method is a series-parallel hybrid connection; the operating temperature of the adsorption towers is 45℃, and the space velocity is 0.8h. -1 The pressure in the adsorption tower is 0.4 MPaG.

[0069] (6) The adsorbent in the fixed bed includes 15% dehydration adsorbent and 85% de-alcoholization adsorbent. The dehydration adsorbent uses 5A molecular sieve; the de-alcoholization adsorbent uses 13X molecular sieve. The dehydration adsorbent is placed in the upper part and the de-alcoholization adsorbent is placed in the lower part.

[0070] The oxide content in the top product of the catalytic distillation column was 1%, which decreased to 0.1% after deep deoxygenation, and the Fischer-Tropsch oil yield was 81.2%.

[0071] Table 1 Raw Material Composition

[0072] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A process for the catalytic rectification removal of oxygenates from Fischer-Tropsch light distillate oil, characterized in that: Includes the following steps: S1. The Fischer-Tropsch light distillate feedstock and reactant are fed into a catalytic distillation column (1) and reacted under the action of a catalyst to initially remove oxygen-containing compounds; the reactant is a mixture of liquid acid catalyst and alkanes, with alkanes accounting for 70% to 100% of the total mass of the mixture; S2. The top product of the catalytic distillation column (1) enters the fixed bed adsorption column (3) for deep removal of oxygen-containing compounds; S3. Catalytic distillation column (1) The bottom liquid of the column is recycled and fresh reactant is added. When the content of heavy components with boiling point > 250℃ in the bottom liquid is ≥ 10%, the bottom liquid enters the regeneration column (2) for reactant regeneration. The regenerated reactant re-enters the catalytic distillation column (1).

2. A process for the removal of oxygenates from Fischer-Tropsch light distillate by catalytic rectification according to claim 1, characterized in that: The catalytic distillation column (1) includes a rectification section, a reaction section and a stripping section. The rectification section has 5-45 theoretical plates, the reaction section has 10-50 theoretical plates, and the stripping section has 5-45 theoretical plates. The residence time of the material in the reaction section is 5-60 min. The top pressure of the column is 0.1-5 atm. The molar reflux ratio is 0.1-10. The Fischer-Tropsch light distillate feedstock enters from the stripping section, and the reactant enters from the rectification section. The mass ratio of the reactant to the Fischer-Tropsch light distillate feedstock is 0.05-1.

3. A process for the removal of oxygenates from Fischer-Tropsch light distillate by catalytic rectification according to claim 1, characterized in that: The catalyst used in the catalytic distillation column is a solid catalyst. The solid catalyst is selected from one or more of the following: macroporous sulfonic acid resin, ZSM-5 molecular sieve, ZSM-23 molecular sieve, Y molecular sieve, silica gel, and alumina. The amount of solid catalyst added is 0.1% to 5% of the mass flow rate of the Fischer-Tropsch light distillate feedstock.

4. A process for the removal of oxygenates from Fischer-Tropsch light distillate by catalytic rectification according to claim 1, characterized in that: The boiling point of the liquid acid catalyst in the reactants is 195–255 °C; the boiling point of the alkanes is 195–255 °C.

5. A process for the removal of oxygenates from Fischer-Tropsch light distillate by catalytic rectification as claimed in claim 1, wherein: The theoretical plate number of the regeneration tower (2) is 50 to 100; the feed position is 30 to 60; the pressure at the top of the tower is 0.05 to 0.5 atm; and the molar reflux ratio is 1 to 15.

6. A process for the removal of oxygenates from Fischer-Tropsch light distillate by catalytic rectification as claimed in claim 1, wherein: The number of fixed bed adsorption towers (3) is 2-6, and the connection mode is a combination of series and parallel connection; the operating temperature of the adsorption tower is 25-60℃, the feed speed is 0.1-3h -1 , and the pressure of the adsorption tower is 0.2-1.0MPaG.

7. A process for the removal of oxygenates from Fischer-Tropsch light distillate by catalytic rectification as claimed in claim 1, wherein: The adsorbent in the fixed-bed adsorption tower is packed in a graded manner. The adsorbent includes a dehydrating adsorbent and a de-alcoholizing adsorbent. The dehydrating adsorbent is placed in the upper part and the de-alcoholizing adsorbent is placed in the lower part. The dehydrating adsorbent accounts for 10% to 30% of the total mass of the adsorbent. The dehydrating adsorbent is selected from one or more of type A molecular sieve, silica gel, and type X molecular sieve. The de-alcoholizing adsorbent is selected from one or more of type X molecular sieve, type Y molecular sieve, and activated carbon.

8. A process for the removal of oxygenates from Fischer-Tropsch light distillate by catalytic rectification as claimed in claim 1, wherein: The Fischer-Tropsch light distillate feedstock has a distillation range of 30°C to 180°C and an oxide content of 0.5% to 10%.

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