A method for extracting Fischer-Tropsch wax from Fischer-Tropsch synthetic residue wax

Abstract

This invention provides a method for extracting Fischer-Tropsch wax from Fischer-Tropsch synthesis residue wax. Using this method, Fischer-Tropsch wax can be extracted and separated from Fischer-Tropsch synthesis residue wax, resulting in Fischer-Tropsch wax with a low ash content while maintaining a relatively high Fischer-Tropsch wax recovery rate. The method includes the following steps: 1) mixing the Fischer-Tropsch synthesis residue wax with a depolymerizing agent and heating to dissolve it to obtain a residue wax liquid, wherein the depolymerizing agent is naphtha from the 90-130°C fraction, and the oxygen content of the naphtha is less than 0.1 wt%; preferably, the heating and dissolving is carried out at 80-100°C; 2) performing solid-liquid separation on the residue wax liquid to obtain a wax-containing liquid phase.

Description

Technical Field

[0001] This invention relates to a method for extracting Fischer-Tropsch wax from Fischer-Tropsch synthesis residue wax. Background Technology

[0002] In the prior art, there have been some process studies in the field on how to extract and separate wax from slag wax (or wax slag), especially Fischer-Tropsch slag wax. For example, a variety of different extraction and separation processes are reported in the following patent documents.

[0003] CN109321274 B discloses a process for recovering paraffin wax and simultaneously passivating and deactivating catalysts from Fischer-Tropsch wax residue. The process involves mixing the Fischer-Tropsch wax residue with a compound solvent containing hydrocarbon solvents, water, and a demulsifier to achieve paraffin wax recovery in a one-step process, achieving a recovery rate of 99%. Simultaneously, it increases the ignition point temperature of the solid residue catalyst, enabling safe landfill disposal after passivation and deactivation. While this method offers high paraffin wax recovery and a simple procedure, the demulsifier used is an alkali / alkaline earth metal oxide, which generates a large amount of alkaline wastewater, detrimental to environmental protection.

[0004] CN113528185 A discloses a method for extracting paraffin from wax residue. First, pretreated wax residue is wrapped in filter paper to form a wax residue package. Then, the wax residue package is mixed with an organic solvent and ultrasonically dissolved. The paraffin dissolves, yielding a mixture of organic solvent and paraffin. After heating and drying, the recovered paraffin product is obtained. This method, using filter paper to wrap the wax residue, can solve the problem of filter residue leakage during extraction. However, the ultrasonic dissolution of paraffin takes a long time, and the wrapping process of the filter paper requires high precision, making industrial-scale production difficult.

[0005] CN 113980693 A discloses a method for processing Fischer-Tropsch synthesis residue wax. The processing steps include thermal cracking, gas-liquid separation, gas treatment, liquid oil treatment, and high-temperature residue treatment. The wax residue is fed into a rotary kiln for cracking to obtain cracked oil and gas and high-temperature residue. The cracked oil and gas are dusted and cooled before gas-liquid separation. The gas is used as fuel for combustion, and the liquid is pumped to the stripping tower of the synthesis unit via an intermediate oil pump. Part of the high-temperature residue is returned to the rotary kiln, and the other part is mixed with cold air and then enters a cyclone separator. This invention has the advantages of low energy consumption and high recovery rate, but high-temperature cracking converts wax into low-grade gaseous hydrocarbons, which is economically unfeasible and poses certain safety risks and resource waste.

[0006] CN1029925 C discloses a method for recovering ceresin from ceresin bleaching clay residue. The method involves mixing the ceresin bleaching clay residue, an alkaline substance (or ammonium carbonate, hydrofluoric acid), and a solvent water to remove some of the bleaching clay from the residue. The remaining bleaching clay is then combined with the wax raw material from the ceresin bleaching clay residue for adsorption and refining to obtain the product, ceresin. This invention has a simple process and high processing capacity, but the resulting ceresin product has a high ash content, requiring further adsorption and refining to obtain a refined wax product that meets requirements. Furthermore, it generates alkaline wastewater, which is detrimental to environmental protection.

[0007] CN108546566 B discloses a supercritical extraction method for the continuous recovery and refining of Fischer-Tropsch slag wax. The method involves preheating an emulsion made from Fischer-Tropsch slag wax and injecting it into a high-pressure extraction device heated to a specific temperature. A preheated solvent is then injected into the high-pressure extraction device for rapid extraction. Temperature and pressure are adjusted to bring the solvent to a predetermined supercritical state, achieving supercritical extraction of the slag wax. The resulting wax recovery rate is between 90% and 93%, with an ash content of approximately 90 ppm. This method recovers Fischer-Tropsch wax with low ash content and allows for continuous production. However, this process requires operation under specific temperature and pressure conditions, resulting in high reaction pressure and significant equipment investment.

[0008] CN110252765 A discloses a method and system for treating Fischer-Tropsch synthesis wax residue. The method involves first heating and melting the wax residue, followed by heat preservation and pressure filtration to achieve solid-liquid separation, yielding solid residue and molten wax. The solid residue is then subjected to hydrolysis to obtain molten wax and solid waste. The advantages of this method are short process cycle, simple steps, mild reaction conditions, and ease of industrialization. However, the recovered molten wax has a high ash content, and the solid residue has a high wax content.

[0009] While existing technologies offer various processes for separating Fischer-Tropsch wax from slag wax (or wax residue), particularly from Fischer-Tropsch synthetic slag wax, there is still much room for improvement. For example, there are drawbacks such as difficulty in industrialization and / or difficulty in balancing environmental protection and economics, or long process cycles and / or harsh process conditions, or difficulty in obtaining products with low ash content (e.g., difficulty in obtaining products with ash content below 10 ppm or lower), and / or difficulty in achieving high wax recovery rates. Summary of the Invention

[0010] In view of this, the present invention provides a method for extracting Fischer-Tropsch wax from Fischer-Tropsch synthetic residue wax. The method of the present invention can extract and separate Fischer-Tropsch wax from Fischer-Tropsch synthetic residue wax, and the method can effectively combine the advantages of environmental protection, economy and ease of industrial implementation.

[0011] To achieve its objective, the present invention provides the following technical solution:

[0012] This invention provides a method for extracting Fischer-Tropsch wax from Fischer-Tropsch synthesis residue wax, comprising the following steps:

[0013] 1) The Fischer-Tropsch synthesis residue wax is mixed with a depolymerizing agent and heated to dissolve to obtain a residue wax liquid, wherein the depolymerizing agent is naphtha in the 90-130°C fraction and the oxygen content of the naphtha is less than 0.1 wt%; preferably, the heating and dissolving is carried out at 80-100°C;

[0014] 2) The slag wax liquid is subjected to solid-liquid separation to obtain a wax-containing liquid phase.

[0015] In some embodiments, in step 1), the mass ratio of the Fischer-Tropsch slag wax to the depolymerizing agent is 1:1 to 5, preferably 1:2 to 1:5, and more preferably 1:2 to 1:4.

[0016] In some implementations, in step 2), the solid-liquid separation is performed by pressure filtration or centrifugation.

[0017] In some embodiments, the solid-liquid separation is performed by pressure filtration; the pressure filtration is carried out on a filter cloth coated with a coating material, the particle size of which is 100-400 mesh, preferably 200-400 mesh; the coating thickness of which on the filter cloth is 0.5-1.5 cm, preferably 0.7-1.5 cm.

[0018] Preferably, the pressure filtration is carried out at 80-100°C.

[0019] In some embodiments, the coating material is selected from one or more of gasification slag, fly ash, kaolin, bentonite, and diatomaceous earth, with gasification slag being preferred.

[0020] In some embodiments, the filtration is carried out under an inert atmosphere and pressurized conditions, preferably at a pressure ≤0.3 MPa;

[0021] Preferably, the pore size of the filter cloth is 5 to 12 μm.

[0022] Preferably, the coating material is wetted with an organic solvent and coated onto the filter cloth, and preferably the organic solvent is the same as the depolymerizing agent in step 1).

[0023] In some embodiments, after filtration, the filtrate is allowed to settle to form a lower sediment and an upper clear liquid, and the upper clear liquid is taken as the wax-containing liquid phase.

[0024] Preferably, the lower sediment is returned to step 1) for heating and dissolving.

[0025] In some embodiments, the settling is carried out at 80-100°C for 1-5 hours, preferably 2-5 hours;

[0026] Preferably, the supernatant is taken as 90-95% of the total mass of the filtrate.

[0027] In some embodiments, the filter cake obtained from filtration is dried and then burned as fuel to provide heat for the heating and dissolution in step 1); preferably, the solvent is recovered during the drying process of the filter cake, and the recovered solvent is returned to step 1) for use as a depolymerizing agent.

[0028] In some embodiments, in step 1), the mass ratio of the Fischer-Tropsch slag wax to the depolymerizing agent is 1:2-1:4;

[0029] In step 2), solid-liquid separation is performed by pressure filtration. The filtration is carried out on a filter cloth coated with a coating material, the particle size of which is 200-400 mesh, and the coating thickness of which is 0.7-1.5 cm on the filter cloth.

[0030] After the pressure filtration, the filtrate is allowed to settle, forming a lower sediment and an upper clear liquid. The upper clear liquid is taken as the wax-containing liquid phase, and the settling time is 2-5 hours. Preferably, the settling is carried out at 80-100°C, and the upper clear liquid accounts for 90-95% of the total mass of the filtrate.

[0031] The technical solution provided by this invention has the following beneficial effects:

[0032] The method for extracting and separating Fischer-Tropsch wax from Fischer-Tropsch synthesis residue wax provided by this invention has advantages such as short process flow, simple process operation, environmental protection, and economy, while also being able to obtain Fischer-Tropsch wax with low ash content. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the Fischer-Tropsch synthesis residue wax treatment process in one embodiment. Detailed Implementation

[0034] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The term "and / or" may be used herein to include any and all combinations of one or more of the associated listed items.

[0036] This invention provides a method for extracting Fischer-Tropsch wax from Fischer-Tropsch synthesis residue wax, the method mainly comprising the following steps:

[0037] 1) The Fischer-Tropsch synthesis residue wax is mixed with a depolymerizing agent and heated to dissolve to obtain a residue wax liquid, wherein the depolymerizing agent is naphtha in the 90-130℃ distillation range and the oxygen content of the naphtha is less than 0.1wt%.

[0038] 2) The slag wax liquid is subjected to solid-liquid separation to obtain a wax-containing liquid phase.

[0039] The method for extracting Fischer-Tropsch wax from Fischer-Tropsch synthesis residue wax provided by this invention is simple to operate and has a short process flow. It uses naphtha with a 90-130℃ distillation range and an oxygen content of less than 0.1 wt% as the solvent for extracting Fischer-Tropsch wax. This solvent allows for efficient separation of Fischer-Tropsch wax from Fischer-Tropsch synthesis residue wax using a simple and mild process, resulting in Fischer-Tropsch wax with low ash content. Furthermore, the separated wax-containing liquid phase does not require solvent recovery, simplifying the processing flow. The obtained wax-containing liquid can be directly fed into the subsequent processing unit of the indirect liquefaction process, for example, into the qualified wax stream for subsequent hydrorefining to produce diesel, naphtha, liquefied petroleum gas, etc. The specific naphtha added as a depolymerizing agent in this invention can serve as an inert solvent in the subsequent hydrorefining unit. In contrast, traditional Fischer-Tropsch wax processing methods using other solvents (such as petroleum ether, n-heptane, etc.) as depolymerizing agents require subsequent solvent removal, i.e., an additional solvent removal and recovery step is necessary. The inventors have discovered that using naphtha with a distillation temperature of 90–130°C and an oxygen content of less than 0.1 wt% for Fischer-Tropsch synthesis residue wax separation can play a role in solvent depolymerization. This not only effectively reduces the viscosity of the residue wax liquid, which is beneficial for subsequent solid-liquid separation and improves the efficiency of solid-liquid separation, but also protects the color of the wax product throughout the entire process.

[0040] In some embodiments, naphtha from the 90–130°C fraction with an oxygen content of less than 0.1 wt% can be directly obtained by hydrorefining and separating the oil products produced by the Fischer-Tropsch synthesis unit.

[0041] In step 1), the heating and dissolving process can be carried out at a temperature that allows the wax to fully melt. Preferably, the heating and dissolving process is carried out at 80-100°C. In some embodiments, in step 1), the heating and dissolving process is carried out with stirring, preferably for 15-40 minutes, for example, 15-30 minutes.

[0042] In some embodiments, in step 1), the mass ratio of the Fischer-Tropsch synthesis residue wax to the depolymerizing agent is 1:1 to 5, preferably 1:2 to 1:5. More preferably, the mass ratio is 1:2 to 1:4. The inventors have found that using the preferred amount of depolymerizing agent not only saves solvent and reduces solvent waste, but also achieves better extraction results, which is beneficial for obtaining Fischer-Tropsch wax with lower ash content.

[0043] In some implementations, in step 2), the solid-liquid separation is performed by pressure filtration or centrifugation.

[0044] In some preferred embodiments, the solid-liquid separation is performed by pressure filtration, and the filtration is carried out on a filter cloth coated with a coating material having a particle size of 100-400 mesh; the coating thickness of the coating material on the filter cloth is 0.5-1.5 cm. The inventors have found that by using this filtration method, with a coating material of a specific particle size coated on the filter cloth to form a coating layer of a specific thickness for solid-liquid separation of the mixture obtained in step 1), the ash content of the resulting wax-containing liquid phase can be significantly reduced, while maintaining a high product recovery rate and a low wax content in the solid residue. The inventors have also found that, compared with traditional centrifugal separation, this method of solid-liquid separation can significantly improve the product recovery rate and reduce the wax content in the solid residue. More preferably, the particle size of the coating material is 200-400 mesh, and the coating thickness of the coating material on the filter cloth is 0.7-1.5 cm, which can further significantly reduce the ash content of the resulting wax-containing liquid phase while maintaining a low wax content in the solid residue. Preferably, the filtration is carried out at 80-100°C.

[0045] In some embodiments, the coating material is selected from one or more of gasification slag, fly ash, kaolin, bentonite, and diatomaceous earth. Using these components as coating materials reduces costs and allows for the valuable utilization of solid wastes such as gasification slag and fly ash. Furthermore, using these components with specific particle sizes (100-400 mesh, preferably 200-400 mesh) as coating materials in the process of this invention achieves excellent filtration results and effectively intercepts solid residues in the mixed liquid. Simultaneously, the resulting filter cake can be burned, providing energy for upstream steps, reducing overall energy consumption, improving resource utilization, and being environmentally friendly. Preferably, the coating material is gasification slag. The inventors have found that using gasification slag as the coating material not only achieves excellent filtration results but also allows the resulting filter cake to be burned as fuel, providing heat and resulting in more complete combustion.

[0046] Preferably, the filtration is carried out under an inert atmosphere and pressurized conditions, with a pressure preferably ≤0.3MPa; preferably, the pore size of the filter cloth is 5-12μm, specifically, the filter cloth can be, but is not limited to, polytetrafluoroethylene filter cloth. In some specific embodiments, the filtration is carried out in a filter press. The filtration in step 2) is carried out under an inert atmosphere, specifically, an inert gas such as nitrogen can be used to provide the inert atmosphere.

[0047] Preferably, the coating material is wetted with an organic solvent and coated onto the filter cloth, and preferably the organic solvent is the same as the depolymerizing agent in step 1).

[0048] In some preferred embodiments, when performing solid-liquid separation by filtration, it is preferable to allow the filtrate to settle after filtration, forming a lower sediment and an upper clear liquid, and take the upper clear liquid as the wax-containing liquid phase; this can further significantly reduce the ash content in the obtained wax-containing liquid phase. In some embodiments, the sedimentation is carried out at 80-100°C for 1-5 hours. Using these sedimentation conditions can achieve good sedimentation results and promote the reduction of product ash content; preferably, the sedimentation time is 2-5 hours, which is beneficial for further reducing product ash content. Preferably, the lower sediment is returned to step 1) for heating and dissolving. Preferably, the upper clear liquid accounts for 90-95% of the total mass of the filtrate, with only a small amount entering the lower sediment.

[0049] In a preferred embodiment, the gasified slag is used as the coating material, and the filtered cake, after drying, can be used as fuel for combustion to provide heat for the heating and dissolution process in step 1). This further reduces the energy consumption of the entire method and facilitates cost reduction. The drying process may include, for example, spray drying, flash drying, or drum drying. Preferably, the solvent is recovered during the drying process of the filter cake, and the recovered solvent is returned to step 1) as a depolymerizing agent.

[0050] In some preferred embodiments, in step 1), the mass ratio of the Fischer-Tropsch slag wax to the depolymerizing agent is 1:2-1:4; in step 2), solid-liquid separation is performed by pressure filtration on a filter cloth coated with a material having a particle size of 200-400 mesh and a coating thickness of 0.7-1.5 cm; after pressure filtration, the filtrate is allowed to settle, forming a lower sediment and an upper clear liquid, which is taken as the wax-containing liquid phase, and the settling time is 2-5 hours; preferably, the settling is carried out at 80-100°C, and the upper clear liquid accounts for 90-95% of the total mass of the filtrate. Using the above preferred embodiments for the extraction and separation of Fischer-Tropsch slag wax can achieve extremely low product ash content (below 10 ppm) while maintaining a low wax content in the solid residue.

[0051] The method provided by this invention has a simple process, does not involve the use of toxic reagents, does not cause environmental pollution, and has low operating costs, combining the advantages of environmental protection, economy, and ease of industrial implementation. Furthermore, using this method to separate Fischer-Tropsch synthesis residue wax from Fischer-Tropsch wax can achieve a low product ash content. Using this method to treat waste residue wax can realize the resource utilization and harmless treatment of the residue wax, alleviating resource scarcity and environmental pollution problems. The Fischer-Tropsch synthesis residue wax mentioned in this invention can be, for example, the waste filter cake generated during the periodic replacement of activated clay in the Fischer-Tropsch wax refining process, or the catalyst containing Fischer-Tropsch wax generated during the periodic removal of catalyst in the reactor, etc.

[0052] The present invention will be further illustrated by the following examples.

[0053] The parameters in Table 1 below are explained as follows:

[0054] A sample was taken from the supernatant obtained after solid-liquid separation (filtrate in Example 7) to analyze the ash content of the product wax. The processing method was as follows: the sample was distilled using a rotary evaporator, and the obtained distillate was dried in a drying oven to constant weight to obtain the recovered Fischer-Tropsch wax product, which was used for ash content determination.

[0055] The ash content (i.e., product ash content) in the obtained Fischer-Tropsch wax product was determined by inductively coupled plasma optical emission spectrometry (ICP-OES) with reference standard GB / T 30902-2014. The test results are shown in Table 1.

[0056] The ash content of the raw material residue wax was determined according to standard SH / T 0422-2000. The formula for calculating the ash content ω% is as follows:

[0057] ω%=100(m3-m1) / (m2-m1)

[0058] In the formula, m1 is the mass of the crucible, in grams.

[0059] m2 — Mass of the crucible and raw material residue / wax sample, in grams

[0060] m3 — Mass of crucible and ash, in grams

[0061] The recovery rate of Fischer-Tropsch wax (i.e., product recovery rate) = 100 × mass of Fischer-Tropsch wax product / (mass of raw material residue wax × (1-ω%)); where the mass of Fischer-Tropsch wax product is obtained by distilling the supernatant obtained from solid-liquid separation (filtrate in Example 7) using a rotary evaporator, drying it in a drying oven to constant weight, and weighing it to obtain the mass of Fischer-Tropsch wax product.

[0062] The wax content of the solid residue is calculated as 100 × (1 - 100 × mass of ash content in solid residue / mass of solid residue), where the method for determining the ash content of the solid residue is also performed according to standard SH / T 0422-2000. In Examples and Comparative Examples 1-8, a portion of the upper layer of the filter cake obtained from filtration, excluding coating material, was taken, dried to obtain the mass of solid residue, and then the mass of ash content in the solid residue was determined. The wax content of the solid residue was then determined according to the above formula. In Example 14, the wax content of the solid residue was determined by referring to the above method using the sediment obtained from centrifugation.

[0063] The raw material slag wax used in the following examples comes from Fischer-Tropsch synthesis slag wax produced in a coal indirect liquefaction unit in a certain workshop.

[0064] In Examples 1-14 below, the naphtha used was naphtha from the Fischer-Tropsch synthesis unit, obtained through hydrorefining and separation, with a 90-130°C fraction and an oxygen content of less than 0.1 wt%. The naphtha used in Comparative Example 1 was naphtha from the Fischer-Tropsch synthesis unit that had not undergone hydrorefining and separation, and had an oxygen content of approximately 2 wt%.

[0065] Example 1

[0066] 1) Mix 100g of raw material residue wax with 200g of naphtha (90-130℃ fraction, oxygen content less than 0.1wt%), place in an oil bath at 80℃ and heat, mechanically stir for 15min to obtain a uniformly mixed residue wax liquid.

[0067] 2) Filter the slag wax liquid under heat and pressure:

[0068] Prepare a pressure filtration device. The filter cloth of the pressure filtration device is pre-coated with a 1 cm thick layer of gasified fine residue. The particle size of the gasified fine residue is 200-300 mesh. The gasified fine residue is wetted with naphtha from step 1) as a solvent. The filter cloth used is made of polytetrafluoroethylene with a pore size of 12 μm. The filtration pressure is 0.3 MPa, the nitrogen atmosphere is used, and the filtration temperature is 80℃. After filtration, the solid-liquid separation is completed, and filtrate and solid residue (i.e., filter cake) are obtained.

[0069] 3) The filtrate was kept at 80℃ in an oven for 4 hours to allow it to settle, resulting in a lower sediment and an upper clear liquid.

[0070] 4) Separate the supernatant and the sediment. Take out the supernatant (accounting for 95% of the filtrate mass), and the remaining material is the sediment. Take out a portion of the supernatant for ash content analysis. The experimental results are shown in Table 1.

[0071] Example 2

[0072] The experiment was conducted according to the method of Example 1, except that the 1 cm thick gasification slag was replaced with an equal mass of fly ash (particle size 200-300 mesh). The experimental results are shown in Table 1.

[0073] Example 3

[0074] The method of Example 1 was followed, except that the 1 cm thick gasification slag was replaced with equal mass of fly ash and gasification slag, both with a particle size of 200-300 mesh and a mass ratio of 1:1. The experimental results are shown in Table 1.

[0075] Example 4

[0076] The method of Example 1 was followed, except that the amount of naphtha (90-130℃ fraction, oxygen content less than 0.1wt%) was adjusted from 200g to 400g. The experimental results are shown in Table 1.

[0077] Example 5

[0078] The method was carried out according to Example 1, except that the settling time was changed from 4 hours to 2 hours. The experimental results are shown in Table 1.

[0079] Example 6

[0080] 1) Mix 100g of raw material residue wax with 200g of naphtha (90-130℃ fraction, oxygen content less than 0.1wt%), place in an oil bath at 100℃ and heat, mechanically stir for 15min to obtain a uniformly mixed residue wax liquid.

[0081] 2) Filter the slag wax liquid under heat and pressure:

[0082] Prepare a pressure filtration device. The filter cloth of the pressure filtration device is pre-coated with a 1 cm thick layer of gasified fine residue. The particle size of the gasified fine residue is 200-300 mesh. The gasified fine residue is wetted with naphtha from step 1) as a solvent. The filter cloth used is made of polytetrafluoroethylene with a pore size of 12 μm. The filtration pressure is 0.3 MPa, the nitrogen atmosphere is used, and the filtration temperature is 100℃. After filtration, the solid-liquid separation is completed, and filtrate and solid residue (i.e., filter cake) are obtained.

[0083] 3) The filtrate was kept at 100℃ in an oven for 4 hours to allow it to settle, resulting in a lower sediment and an upper clear liquid.

[0084] 4) Separate the supernatant and the lower sediment. Take out the supernatant (accounting for 95% of the filtrate mass), and the remaining material is the lower sediment. Distill the supernatant using a rotary evaporator. Place the distilled substrate in a drying oven and dry it to constant weight to obtain the recovered Fischer-Tropsch wax product. The experimental results are shown in Table 1.

[0085] Comparative Example 1 (different naphtha)

[0086] 1) Mix 100g of raw material residue wax with 200g of naphtha (from the Fischer-Tropsch synthesis unit and without hydrorefining and separation, with an oxygen content of about 2wt%) solution, place in an oil bath at 100℃ and heat, mechanically stir for 15min to obtain a uniformly mixed residue wax liquid.

[0087] 2) Filter the slag wax liquid under heat and pressure:

[0088] Prepare a pressure filtration device. The filter cloth of the pressure filtration device is pre-coated with a 1 cm thick layer of gasified fine residue with a particle size of 200-300 mesh. The naphtha from step 1) is used as a solvent to wet the gasified fine residue. The filter cloth used is made of polytetrafluoroethylene with a pore size of 12 μm. The filtration pressure is 0.3 MPa, the nitrogen atmosphere is used, and the filtration temperature is 100℃. After filtration, solid and liquid are separated to obtain filtrate and solid residue (i.e., filter cake).

[0089] 3) The filtrate was kept at 100℃ in an oven for 4 hours to allow it to settle, resulting in a lower sediment and an upper clear liquid.

[0090] 4) Separate the supernatant and the sediment. Take out the supernatant (accounting for 95% of the filtrate mass), and the remaining material is the sediment. Take out a portion of the supernatant for ash content analysis. The experimental results are shown in Table 1.

[0091] Example 7 (settlement without insulation)

[0092] 1) Mix 100g of raw material residue wax with 200g of naphtha (90-130℃ fraction, oxygen content less than 0.1wt%), place in an oil bath at 80℃ and heat, mechanically stir for 15min to obtain a uniformly mixed residue wax liquid.

[0093] 2) Filter the slag wax liquid under heat and pressure:

[0094] A pressure filtration device was prepared. The filter cloth of the pressure filtration device was pre-coated with a 1 cm thick layer of gasified fine residue. The naphtha from step 1) was used as a solvent to wet the gasified fine residue. The particle size of the gasified fine residue was 200-300 mesh. The filter cloth used was made of polytetrafluoroethylene material with a pore size of 12 μm. The filtration pressure was 0.3 MPa, the nitrogen atmosphere was used, and the filtration temperature was 80℃. After filtration, solid and liquid were separated to obtain filtrate and solid residue (i.e., filter cake). A portion of the filtrate was taken out for ash content analysis. The experimental results are shown in Table 1.

[0095] Example 8 (no coating material was applied to the filter cloth)

[0096] 1) Mix 100g of raw material residue wax with 200g of naphtha (90-130℃ fraction, oxygen content less than 0.1%), place in an oil bath at 80℃ and heat, mechanically stir for 15 minutes to obtain a uniformly mixed residue wax liquid.

[0097] 2) Filter the slag wax liquid under heat and pressure:

[0098] The filtration temperature is 80℃, the filter cloth used is made of polytetrafluoroethylene with a pore size of 12μm, the filtration pressure is 0.3MPa, and the atmosphere is nitrogen; after filtration, solid-liquid separation is completed, and filtrate and solid residue are obtained.

[0099] 3) The filtrate was kept at 80℃ in an oven for 4 hours to allow it to settle, resulting in a lower sediment and an upper clear liquid.

[0100] 4) Separate the supernatant and the sediment. Take out the supernatant (accounting for 95% of the filtrate mass), and the remaining material is the sediment. Take out a portion of the supernatant for ash content analysis. The experimental results are shown in Table 1.

[0101] Example 9

[0102] The method of Example 1 was followed, except that the coating thickness was 0.5 cm, and the results are shown in Table 1.

[0103] Example 10

[0104] The method was carried out according to Example 1, except that the heat preservation and settling time was 1 hour, and the results are shown in Table 1.

[0105] Example 11

[0106] The method of Example 1 was followed, except that the particle size of the gasified fine slag of the coating material was 100-200 mesh, and the results are shown in Table 1.

[0107] Example 12 (Fischer-Tropsch synthetic residue wax and naphtha in a mass ratio of 1:1)

[0108] 1) Mix 100g of raw material residue wax with 100g of naphtha (90-130℃ fraction, oxygen content less than 0.1wt%), place in an oil bath at 80℃ and heat, mechanically stir for 15min to obtain a uniformly mixed residue wax liquid.

[0109] 2) Filter the slag wax liquid under heat and pressure:

[0110] Prepare a pressure filtration device. The filter cloth of the pressure filtration device is pre-coated with a 1 cm thick layer of gasified fine residue. The particle size of the gasified fine residue is 200-300 mesh. The gasified fine residue is wetted with naphtha from step 1) as a solvent. The filter cloth used is made of polytetrafluoroethylene with a pore size of 12 μm. The filtration pressure is 0.3 MPa, the nitrogen atmosphere is used, and the filtration temperature is 80℃. After filtration, the solid-liquid separation is completed, and filtrate and solid residue (i.e., filter cake) are obtained.

[0111] 3) The filtrate was kept at 80℃ in an oven for 4 hours to allow it to settle, resulting in a lower sediment and an upper clear liquid.

[0112] 4) Separate the supernatant and the sediment. Take out the supernatant (accounting for 95% of the filtrate mass), and the remaining material is the sediment. Take out a portion of the supernatant for ash content analysis. The experimental results are shown in Table 1.

[0113] Example 13 (Fischer-Tropsch synthetic residue wax and naphtha in a mass ratio of 1:5)

[0114] 1) Mix 100g of raw material residue wax with 500g of naphtha (90-130℃ fraction, oxygen content less than 0.1wt%), place in an oil bath at 80℃ and heat, mechanically stir for 15min to obtain a uniformly mixed residue wax liquid.

[0115] 2) Filter the slag wax liquid under heat and pressure:

[0116] Prepare a pressure filtration device. The filter cloth of the pressure filtration device is pre-coated with a 1 cm thick layer of gasified fine residue. The particle size of the gasified fine residue is 200-300 mesh. The gasified fine residue is wetted with naphtha from step 1) as a solvent. The filter cloth used is made of polytetrafluoroethylene with a pore size of 12 μm. The filtration pressure is 0.3 MPa, the nitrogen atmosphere is used, and the filtration temperature is 80℃. After filtration, the solid-liquid separation is completed, and filtrate and solid residue (i.e., filter cake) are obtained.

[0117] 3) The filtrate was kept at 80℃ in an oven for 4 hours to allow it to settle, resulting in a lower sediment and an upper clear liquid.

[0118] 4) Separate the supernatant and the sediment. Take out the supernatant (accounting for 95% of the filtrate mass) and use the remaining material as the sediment. Take out a portion of the supernatant for ash content analysis. The experimental results are shown in Table 1.

[0119] Example 14 (Centrifugal Separation)

[0120] 1) Mix 100g of raw material residue wax with 200g of naphtha (90-130℃ fraction, oxygen content less than 0.1wt%), place in an oil bath at 80℃ and heat, mechanically stir for 15min to obtain a uniformly mixed residue wax liquid.

[0121] 2) Centrifuge the residue and wax liquid from step (1) to obtain the supernatant and sediment;

[0122] The experimental results are shown in Table 1.

[0123] Table 1

[0124]

[0125]

[0126] The experimental results above show that the extraction and separation of Fischer-Tropsch wax from slag wax using the method of the present invention, with naphtha containing less than 0.1 wt% oxygen in the 90-130°C fraction as the depolymerizing agent, unexpectedly and significantly reduces the wax ash content of the product compared to Comparative Example 1, which uses naphtha that does not meet the specific requirements of the present invention. Furthermore, under the same conditions, the solid slag obtained by treating slag wax with the specific naphtha of the present invention also has a significantly lower wax content. The inventors found that, in the above examples and comparative examples, compared to Comparative Example 1 which uses other naphtha, the examples using naphtha containing less than 0.1 wt% oxygen in the 90-130°C fraction as the depolymerizing agent did not show any color change in Fischer-Tropsch wax during treatment and achieved faster solid-liquid separation. In contrast, Comparative Example 1, which used other naphtha, showed a significant color change in Fischer-Tropsch wax during treatment, and the filtration speed was significantly slower.

[0127] A comparison of the experimental results of Examples 1 and 7 shows that the main difference in Example 7 is that no sedimentation step was performed after filtration, resulting in a significant increase in the ash content of the product. A comparison of the experimental results of Examples 1 and 8 shows that the main difference in Example 8 is that no coating material was applied to the filter cloth during filtration, resulting in a significant increase in the ash content of the product. A comparison of the experimental results of Examples 1 and 11 shows that Example 1 used a coating material within a preferred particle size range during filtration, resulting in a significantly lower ash content in the product. A comparison of the experimental results of Examples 1, 12, and 13 shows that using a preferred mass ratio of Fischer-Tropsch slag wax to depolymerizing agent for slag wax treatment can significantly reduce the ash content of the product. A comparison of Example 14 and Examples 1-13 shows that pressure filtration separation significantly reduces the wax content in the solid slag compared to centrifugal separation. Testing showed that the product recovery rate of Examples 1-13 all reached over 90%, with Example 6 achieving a recovery rate of 94.1%; while the product recovery rate of Example 14 was only 77.0%, thus pressure filtration separation is preferred.

[0128] As can be seen from the experimental results of Examples 1-14 above, Examples 1-6, compared with other examples, simultaneously meet the following conditions: the mass ratio of Fischer-Tropsch slag wax to depolymerizing agent is 1:2-1:4; solid-liquid separation is carried out by filtration on a filter cloth coated with a coating material, the particle size of which is 200-400 mesh; the coating thickness of which on the filter cloth is 0.7-1.5 cm; after filtration, the filtrate is allowed to settle, forming a lower sediment and an upper clear liquid, and the upper clear liquid is taken as the wax-containing liquid phase, the settling time being 2-5 hours; by processing Fischer-Tropsch slag wax in a manner that meets the above conditions, no large amount of naphtha is required, which not only yields an extremely low product ash content but also achieves a low solid slag wax content. In Example 13, the mass ratio of slag wax to depolymerizing agent was 1:5. Compared with Examples 1-6, the ash content of the final product and the wax content of the filter cake were different. Although more depolymerizing agent was used, there was no significant increase in efficiency. Therefore, a ratio of 1:2 to 1:4 is preferred.

[0129] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for extracting Fischer-Tropsch wax from Fischer-Tropsch synthesis residue wax, characterized in that, Includes the following steps: 1) The Fischer-Tropsch slag wax is mixed with a depolymerizing agent and heated to dissolve to obtain a slag wax liquid, wherein the depolymerizing agent is naphtha in the 90~130℃ distillation range and the oxygen content of the naphtha is less than 0.1wt%; the mass ratio of the Fischer-Tropsch slag wax to the depolymerizing agent is 1:1~5; 2) The slag wax liquid is subjected to solid-liquid separation to obtain a wax-containing liquid phase; the solid-liquid separation is carried out by pressure filtration; the pressure filtration is carried out on a filter cloth coated with a coating material, the particle size of the coating material is 100~400 mesh, and the coating thickness of the coating material on the filter cloth is 0.5-1.5cm; the coating material is selected from one or more of gasification fine slag, fly ash, kaolin, bentonite, and diatomaceous earth.

2. The method according to claim 1, characterized in that, The heating and dissolving process is carried out at 80-100°C.

3. The method according to claim 1, characterized in that, In step 1), the mass ratio of the Fischer-Tropsch synthesis slag wax to the depolymerizing agent is 1:2 to 1:

5.

4. The method according to claim 3, characterized in that, In step 1), the mass ratio of the Fischer-Tropsch synthesis slag wax to the depolymerizing agent is 1:2 to 1:

4.

5. The method according to claim 1, characterized in that, The particle size of the coating material is 200-400 mesh; the coating thickness of the coating material on the filter cloth is 0.7-1.5 cm.

6. The method according to claim 5, characterized in that, The pressure filtration is carried out at 80-100°C.

7. The method according to claim 1, characterized in that, The filtration is carried out under pressure in an inert atmosphere with a pressure ≤0.3MPa; The filter cloth has a pore size of 5~12μm.

8. The method according to claim 7, characterized in that, The coating material is wetted with an organic solvent and coated onto the filter cloth.

9. The method according to claim 8, characterized in that, The organic solvent is the same as the depolymerizing agent in step 1).

10. The method according to claim 1, characterized in that, After filtration, the filtrate is allowed to settle, forming a lower sediment and an upper clear liquid. The upper clear liquid is taken as the wax-containing liquid phase.

11. The method according to claim 10, characterized in that, The lower sediment is returned to step 1) for heating and dissolution.

12. The method according to claim 10, characterized in that, The settling is carried out at 80-100℃ for 1-5 hours.

13. The method according to claim 12, characterized in that, The settling time is 2-5 hours.

14. The method according to claim 12, characterized in that, The supernatant liquid obtained accounts for 90-95% of the total mass of the filtrate.

15. The method according to any one of claims 1, 4-11, characterized in that, The filtered cake is dried and then burned as fuel to provide heat for the heating and dissolution process in step 1).

16. The method according to claim 15, characterized in that, During the drying process of the filter cake, the solvent is recovered and returned to step 1) as a depolymerizing agent.

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