A method for preparing bio-based isoalkanes

Abstract

The invention discloses a method for preparing bio-based isoparaffins, and belongs to the technical field of organic chemical industry. The method is to convert bio-based lipid compounds into normal and isomeric mixed alkanes through hydrodeoxygenation and hydroisomerization reactions, and then obtain mixed alkanes with a carbon number of not less than 15 by normal pressure fractionation, and then separate normal and isoparaffins by molecular sieve adsorption and / or urea complexation. The obtained normal alkane is recycled back to the hydroisomerization unit for secondary hydroisomerization reaction, and the obtained high-purity isoparaffin is fractionated and / or rectified to obtain isoparaffin products of different fractions, which can be used as solvent oil, white oil, drilling fluid, aviation kerosene blending component, clean high cetane number diesel blending component, etc. The raw materials used in the present invention are renewable, and the prepared isoparaffin products are high in purity, high in yield, clean and environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of organic chemical industry, and specifically relates to a method for preparing bio-based isoalkane. Background Art

[0002] Isoalkanes have good low-temperature fluidity, stability, compatibility, spreadability and water retention. Low surface tension can ensure excellent wetting and surface diffusion. High-purity isoalkanes contain almost no harmful impurities, basically no odor, high chemical stability, long product shelf life, easy to recycle and reuse, good comfort and safety in use, and the flash point and volatility of narrow-fraction isoalkanes match, which has better application effect in professional fields. Isoalkanes are widely used in lubricants for various instruments, metalworking fluids, daily chemicals, polymerization reactants, oilfield drilling fluids, aviation kerosene blending components, clean high cetane number diesel blending components and many other fields. Isoalkanes prepared from bio-oils also have the advantages of renewable raw materials and green products.

[0003] CN 101921621 A discloses a method for preparing isoparaffin solvent oil by using a hydrogenation pre-refining-hydroisomerization process with petroleum-based distillate oil or deasphalted oil as raw materials. Since the petroleum-based raw oil contains a large amount of harmful compounds such as sulfur, nitrogen, and aromatics, which cannot be completely removed, the cleanliness of the product is affected.

[0004] Invention patents such as CN 111471488 A, CN 113980701 A, and CN 200410048351 disclose methods for separating and purifying normal alkanes in Fischer-Tropsch synthetic oil by molecular sieve adsorption, which can produce isoalkanes as by-products. A series and X series molecular sieves such as 3A, 5A, 10X, and 13X are used as adsorbents. The isoalkanes content in Fischer-Tropsch synthetic oil generally does not exceed 10%, and the pore size of the selected molecular sieve is not ideal for the adsorption selectivity of normal alkanes, resulting in low adsorption separation efficiency and low isoalkanes yield.

[0005] US 5866748 discloses a method for preparing isoparaffins. The method uses normal paraffins rich in carbon atoms of 8 to 20 in the liquid product of Fischer-Tropsch synthesis as raw materials, uses a catalyst with amorphous silicon aluminum as a carrier and a precious metal or non-precious metal as an active metal, and prepares isoparaffin solvent oil through a hydrogenation isomerization reaction under suitable process conditions. Since the irregular pore size carrier has poor selectivity for the reactants, the hydrogenation isomerization conversion rate and selectivity are reduced, the yield of the target product is low, and the purity of the isoparaffin is not more than 90%.

[0006] CN 108315051 B, CN 103897718 A, CN102464998 A, and US 8058492, US8198492, US 7232935B2, US 20100076238A1, US 20090163744A1 and US 20090163744A1, US20090031617A1, WO 2010053468 A1, WO 2006075057, WO 2009117337, etc. all disclose a method of using bio-oil as raw material, preparing normal alkanes by hydrogenation saturation and hydrodeoxygenation, and then preparing bio-jet fuel and biodiesel by hydrogenation isomerization reaction of normal alkanes. Due to the limitation of conversion rate and selectivity of hydroisomerization reaction, the purity of the obtained isoalkanes is not more than 90%.

[0007] In order to further improve the isomerization rate of the product, the method disclosed in US 20100000908A1 uses animal and vegetable oils as raw materials to prepare bio-jet fuel and biodiesel with good low temperature performance through hydrodeoxygenation and hydroisomerization reactions. + Compared with the one-pass process, this method has a high product isomerization rate, but the process of partial product recycling reduces production efficiency. In addition, the 200℃ of the one-pass hydrogenation isomerization product + The fraction is a mixture of normal alkanes and isoalkanes. When the isoalkanes therein undergo a second hydrogenation isomerization reaction, it is easy to cause an increase in hydrocracking side reactions and a decrease in the yield of the target product. Summary of the invention

[0008] In view of the above problems existing in the prior art, the technical problem to be solved by the present invention is to provide a method for preparing bio-based isoalkanes, which can simultaneously achieve high cleanliness, high purity and high yield of the product.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing bio-based isoparaffins, comprising the following steps:

[0011] (1) Bio-based lipid compounds are converted into normal alkanes through hydrodeoxygenation reaction;

[0012] (2) converting the normal alkane described in step (1) into normal-isomerized mixed alkanes through a hydrogenation isomerization reaction;

[0013] (3) separating the mixed alkanes described in step (2) into light and heavy fractions by atmospheric pressure fractionation to obtain light mixed alkanes (C 14 -) and heavy mixed alkanes with a carbon number of not less than 15 (C 15 + );

[0014] (4) C obtained in step (3) 14 - The light mixed alkanes are produced from the system as by-products;

[0015] (5) using urea complex separation and / or molecular sieve adsorption separation process to separate the C 15 + Mixed alkanes are used to separate normal alkanes from isoalkanes;

[0016] (6) C obtained in step (5) 15 + Normal alkanes (nC 15 + ) components are returned to step (2) for secondary hydrogenation isomerization reaction;

[0017] (7) C described in step (5) 15 + Isoalkanes (iC 15 + ) is directly extracted from the system as an isoparaffin product, or is fractionated to obtain light and heavy fraction isoparaffins, or is distilled to obtain narrow-fraction isoparaffin products, or the light fraction, heavy fraction and narrow-fraction isoparaffins obtained by fractionation and distillation are blended to obtain isoparaffin products with different carbon number distributions.

[0018] In the method for preparing bio-based isoparaffins, the bio-based lipid compounds are fatty acid glycerides obtained by refining and removing impurities from discarded or inedible animal and plant oils and fats, and / or fatty acid methyl esters obtained by transesterification and esterification of acidified oil, fatty acids and methanol.

[0019] The method for preparing bio-based isoparaffins comprises step (1) using alumina as a carrier for the catalyst for the hydrodeoxygenation reaction, using at least one of Ni, Co, Mo and W as a hydrogenation active metal component, and the content of the oxidized active metal is 5% to 25% of the carrier mass.

[0020] The method for preparing bio-based isoparaffins comprises step (1), wherein the hydrodeoxygenation reaction temperature is 300 to 400° C., the hydrogen partial pressure is 3 to 18 MPa, and the liquid hourly volume space velocity is 0.5 to 3.0 h -1 , hydrogen oil volume ratio 500~1500Nm 3 / m 3 .

[0021] The method for preparing bio-based isoparaffins, step (2), the catalyst for the hydroisomerization reaction uses at least one of ZSM-22, ZSM-23, ZSM-35, ZSM-48, SAPO-11, SAPO-31, SAPO-41 molecular sieves as a carrier, Pt and / or Pd as hydrogenation active metal components, and the active metal content in the form of a single substance is 0.2% to 1.0% of the carrier mass.

[0022] The preparation method of bio-based isoparaffins, step (2), the hydroisomerization reaction temperature is 280-400°C, the hydrogen partial pressure is 3-18MPa, and the liquid hourly volume space velocity is 0.5-3.0h -1 , hydrogen oil volume ratio 300~1000Nm 3 / m 3 .

[0023] In the method for preparing bio-based isoparaffins, in step (5), the molecular sieve is a 10-membered ring mesoporous molecular sieve, and the minor axis size of the elliptical pores of the molecular sieve is 0.4 to 0.52 nm, and the major axis size is 0.52 to 0.54 nm.

[0024] In the method for preparing bio-based isoparaffins, in step (5), the molecular sieve is any one of AlPO-41, UCSB-15GaGe, EU-1, ECNU-21, Laumontite, ZSM-23 or IST-1.

[0025] The method for preparing bio-based isoparaffins, step (5), using a urea solution with a mass ratio of urea: isopropanol: water of 30-45:35-40:15-30 as a complexing agent, a mass ratio of urea solution to alkane of 5:1-15:1, a complexing time of 2-10 hours, and a complexing temperature of 10-50°C.

[0026] In the method for preparing bio-based isoparaffins, a multi-stage series connection method is adopted when separating normal paraffins from isoparaffins.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) In addition to using waste edible animal and vegetable oils and fats after refining and removing impurities, fatty acid methyl esters obtained by transesterification and esterification of acidified oils, fatty acids and methanol are also used as raw materials, so that the raw materials are fully purified, meeting the various restrictions on colloid, metal, sulfur, nitrogen, chlorine and other impurities in the hydrorefining catalyst, hydroisomerization catalyst and equipment, and broadening the range of raw materials;

[0029] (2) Most of the normal alkanes are converted into isoalkanes through the hydroisomerization reaction, and then the normal and isoalkanes are separated through molecular sieve adsorption and / or urea complexation, so that high-purity isoalkanes can be prepared with high yield. Compared with the method of producing isoalkanes as by-products during the purification of normal alkanes, the method used in the present invention has high efficiency and high yield; compared with the method of increasing the severity of the hydroisomerization reaction, the method used in the present invention has fewer side reactions. Moreover, the present invention uses a method of secondary isomerization of the normal alkanes obtained by separating the normal and isoalkanes, which improves the conversion rate of normal alkanes and further improves the yield of isoalkanes. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with specific examples. In the examples, except for the oxygen-containing raw material, the substances described in each calculation formula refer to liquid hydrocarbons with a carbon number of not less than 5. The liquid hydrocarbon yield (Y HDO ) Liquid hydrocarbon yield of hydroisomerization reaction (Y ISO ), the isoparaffin yield of normal isoparaffin separation (X ISO ) Purity of isoparaffins produced by hydroisomerization reaction (P ISO ), calculated by the following formula:

[0031] Y HDO (%) = total weight of hydrocarbon products ÷ total weight of oxygen-containing feedstock × 100%;

[0032] Y ISO (%) = total weight of hydrocarbon products ÷ total weight of hydrocarbon feedstock × 100%;

[0033] X ISO (%) = total weight of isoparaffin products ÷ total weight of hydrocarbon feedstock × 100%;

[0034] P ISO (%) = weight of isoparaffins in hydrocarbon products ÷ total weight of hydrocarbon products × 100%.

[0035] Fatty acid composition analysis method in Table 1:

[0036] Methylation method: weigh about 0.2g of waste oil, put it in a test tube, add 2mL of petroleum ether, and shake to completely dissolve the oil. Then add 2mL of KOH-methanol solution (0.4mol / L), heat and reflux for 30min, then add 10mL of deionized water, let it stand and take the supernatant for chromatographic analysis. Chromatographic analysis conditions: quartz capillary column, 3cm×0.25mm; column temperature 50℃ for 5min, then increase to 230℃ at a heating rate of 10℃ / min and keep for 20min; detection port FID 270℃; injection port temperature 250℃.

[0037] Analysis of alkane composition in Tables 2 to 4: First, qualitative analysis was performed by Agilent 5973MS, and then detection was performed by Varian CP-3800GC. The chromatographic column used was a 50m x 200μm x 0.5μm PONA column, FID detector, injection volume 0.2μL, split ratio 150:1, column box temperature 60℃, injection port temperature 300℃, and the temperature was increased to 180℃ at a rate of 5℃ / min, and then increased to 220℃ at a rate of 2℃ / min.

[0038] Example 1

[0039] A method for preparing bio-based isoparaffins, comprising the following steps:

[0040] (1) Fatty acid methyl esters prepared by esterification of soybean oil with methanol were used as raw materials. The fatty acid composition of the esters is shown in Table 1. 200 ml of 5% NiO-20% MoO3 / Al2O3 catalyst was used. The reaction temperature was 360°C, the hydrogen partial pressure was 8 MPa, and the liquid hourly volume space velocity was 1.0 h -1 、Hydrogen oil volume ratio 800Nm 3 / m 3 The hydrodeoxygenation reaction was carried out under the process conditions of , and liquid normal alkanes were obtained after gas-liquid separation and oil-water separation by thermal high fractionation. The carbon number distribution and liquid hydrocarbon yield are shown in Table 2;

[0041] (2) Using the liquid normal alkane obtained by hydrodeoxygenation as the raw material, 200 ml of 0.5% Pt / SAPO-11 hydroisomerization catalyst was used at a reaction temperature of 360°C, a hydrogen partial pressure of 8.0 MPa, and a liquid hourly volume space velocity of 1.0 h -1 、Hydrogen oil volume ratio 500Nm 3 / m 3 Under the process conditions, more than 60% of normal alkanes are converted into isoalkanes, and liquid normal and isomeric mixed alkanes are obtained after gas-liquid separation by cold high fractionation. The composition and liquid hydrocarbon yield are shown in Table 3.

[0042] (3) C in the liquid normal-isoalkane mixture obtained by hydroisomerization reaction is fractionated by atmospheric pressure 14 - With C 15 + Component separation;

[0043] (4)C 14 - Extracted from the system as a by-product;

[0044] (5)C 15 +The components are separated by adsorption of normal and iso-alkanes through two fixed-bed adsorption separation reactors filled with ZSM-23 molecular sieves in series. The ZSM-23 molecular sieve is a one-dimensional 10-membered ring molecular sieve with an elliptical pore whose short axis size is 4.5 nm and long axis size is 5.2 nm. Adsorption separation and purification are carried out under the conditions of an adsorption tower temperature of 200°C and a hydrogen pressure of 2.5 MPa. The iso-alkanes are not adsorbed by the molecular sieve, and the normal alkanes are adsorbed on the molecular sieve. A mixture of normal pentane and isoheptane with a mass ratio of 2.5:1 is used as a desorbent. Under the conditions of a hydrogen flow rate of 0.025 m / s, a desorption temperature of 360°C and a desorption pressure of 0.1 MPa, the normal alkanes adsorbed on the molecular sieve are desorbed, and the desorbent is removed by fractionation to obtain normal alkanes.

[0045] (6) n-alkanes obtained by molecular sieve adsorption separation 15 + The components are returned to step (2) for secondary hydroisomerization reaction;

[0046] (7) Using vacuum distillation to separate the C 15 + Isoalkanes undergo C 15 ~C 17 With C 18 + Component separation, under the conditions of 40 plates, 0.02 MPa operating pressure, 222 ° C tower top temperature, 256 ° C tower bottom temperature, and 12 reflux ratio, C 15 ~C 17 and C 18 + The purity and yield of two narrow-fraction high-purity isoparaffins are shown in Table 4.

[0047] Example 2

[0048] A method for preparing bio-based isoparaffins, comprising the following steps:

[0049] (1) Jatropha oil was used as raw material, and its fatty acid composition is shown in Table 1. 5% NiO-20% MoO3 / Al2O3 catalyst 200ml, reaction temperature 360℃, hydrogen partial pressure 8MPa, liquid hourly volume space velocity 1.0h -1 、Hydrogen oil volume ratio 800Nm 3 / m 3 The hydrodeoxygenation reaction was carried out under the process conditions of , and liquid normal alkanes were obtained after gas-liquid separation and oil-water separation by thermal high fractionation. The carbon number distribution of the product and the yield of liquid hydrocarbons are shown in Table 2;

[0050] (2) Using the liquid normal alkane obtained by hydrodeoxygenation reaction as the raw material, 200 ml of 0.5% Pt / ZSM-22 hydroisomerization catalyst was used at a reaction temperature of 320°C, a hydrogen partial pressure of 8.0 MPa, and a liquid hourly volume space velocity of 1.0 h -1 、Hydrogen oil volume ratio 500Nm 3 / m 3 Under the process conditions of , more than 60% of normal alkanes are converted into isoalkanes by hydroisomerization reaction, and liquid normal and isomeric mixed alkanes are obtained after gas-liquid separation by cold high fractionation. The analysis results and the liquid hydrocarbon yield of hydroisomerization reaction are shown in Table 3;

[0051] (3) C in the liquid normal-isoalkane mixture obtained by hydroisomerization reaction is fractionated by atmospheric pressure 14 - With C 15 + Component separation;

[0052] (4)C 14 - Extracted from the system as a by-product;

[0053] (5)C 15 + The normal and isomeric mixed alkanes are separated by urea complexation; the mass ratio of urea complexing agent is urea: isopropanol: water = 40: 40: 20, the mass ratio of urea complexing agent to alkane is 8: 1, the complexation temperature is 35 ° C, and the complexation reaction time is 2 hours, C 15 + High-purity iso-alkanes and high-purity normal-alkanes;

[0054] (6) The normal alkane nC obtained by urea complexation separation in step (5) 15 + The components are returned to step (2) for secondary hydroisomerization reaction;

[0055] (7) Using distillation to separate the C 15 + High-purity isoparaffins were separated into narrow fractions. Under the conditions of 40 plates, 0.02 MPa operating pressure, 222°C tower top temperature, 256°C tower bottom temperature, and 12 reflux ratio, C 15 ~C 17 and C 18 + The purity and yield of two narrow-fraction high-purity isoparaffins are shown in Table 4.

[0056] Table 1 Fatty acid composition of hydrodeoxygenated feedstock oil of Example 1 and Example 2

[0057] Fatty acid composition, % Example 1 Example 2 Hexadecanoic acid 11.32 14.25 Hexadecenoic acid 0.13 0.13 n-Octadecanoic acid 3.58 6.41 Octadecenoic acid 84.28 76.29 n-Eicosane / Eicosanoic acid and above 0.69 2.92

[0058] Table 2 Yield and composition of liquid hydrocarbon products from hydrodeoxygenation reaction

[0059]

[0060] Table 3 Yield and composition of liquid hydrocarbon products from hydroisomerization reaction

[0061]

[0062] Table 4 Purity and yield of narrow fraction isoparaffins obtained by molecular sieve adsorption and urea complex separation

[0063] project Example 1 Example 2 Method for separation of normal and iso-alkanes Molecular sieve adsorption Urea complex <![CDATA[C 15 ~C 17 Purity of component isoparaffin, %]]> 99.67 96.72 <![CDATA[C 15 ~C 17 Yield of component isoparaffins, %]]> 32.01 31.46 <![CDATA[C 18 + Purity of component isoparaffin, %]]> 99.42 97.53 <![CDATA[C 18 + Yield of component isoparaffins, %]]> 46.04 40.08

Claims

1. A method for preparing bio-based isoalkanes, characterized in that: The specific steps include: (1) Bio-based lipid compounds are converted into normal alkanes through hydrodeoxygenation reaction; bio-based lipid compounds are fatty acid glycerides obtained by refining and removing impurities from waste or inedible animal and vegetable oils and fats, and / or fatty acid methyl esters obtained by transesterification and esterification of acidified oils, fatty acids and methanol; (2) converting the normal alkanes described in step (1) into normal and isomeric mixed alkanes through a hydrogenation isomerization reaction; (3) separating the light and heavy fractions of the mixed alkane in step (2) by atmospheric pressure fractionation to obtain C 14 - Light mixed alkanes and C 15 + Heavy mixed alkanes; (4) C obtained in step (3) 14 - The light mixed alkanes are produced from the system as by-products; (5) using urea complex separation and / or molecular sieve adsorption separation process to separate the C 15 + Mixed alkanes are used to separate normal alkanes from isoalkanes; The molecular sieve is a 10-membered ring mesoporous molecular sieve, the minor axis size of the elliptical pore of the molecular sieve is 0.4-0.52 nm, and the major axis size is 0.52-0.54 nm; a urea solution with a mass ratio of urea: isopropanol: water of 30-45: 35-40: 15-30 is used as a complexing agent; (6) nC obtained in step (5) 15 + The components are returned to step (2) for secondary hydroisomerization reaction; (7) The IC described in step (5) 15 + It can be directly extracted from the system as an isoparaffin product, or obtained by fractionation to obtain light and heavy fraction isoparaffins, or by rectification to obtain narrow fraction isoparaffin products, or the light fraction, heavy fraction and narrow fraction isoparaffins obtained by fractionation and rectification can be blended to obtain isoparaffin products with different carbon number distributions.

2. The method for preparing bio-based isoalkanes according to claim 1, characterized in that: In step (1), the catalyst for the hydrodeoxygenation reaction uses alumina as a carrier, and at least one of Ni, Co, Mo, and W as a hydrogenation active metal component, and the content of the oxidized active metal is 5% to 25% of the carrier mass.

3. The method for preparing bio-based isoalkanes according to claim 1, characterized in that: Step (1), hydrodeoxygenation reaction temperature 300 ~ 400 ° C, hydrogen partial pressure 3 ~ 18MPa, liquid hourly volume space velocity 0.5 ~ 3.0h -1 , hydrogen oil volume ratio 500~1500Nm 3 / m 3 .

4. The method for preparing bio-based isoalkanes according to claim 1, characterized in that: In step (2), the catalyst for the hydroisomerization reaction uses at least one of ZSM-22, ZSM-23, ZSM-35, ZSM-48, SAPO-11, SAPO-31, and SAPO-41 molecular sieves as a carrier, uses Pt and / or Pd as hydrogenation active metal components, and the active metal content in the form of a single substance is 0.2% to 1.0% of the carrier mass.

5. The method for preparing bio-based isoalkanes according to claim 1, characterized in that: Step (2), the hydroisomerization reaction temperature is 280-400°C, the hydrogen partial pressure is 3-18 MPa, and the liquid hourly volume space velocity is 0.5-3.0 h -1 , hydrogen oil volume ratio 300~1000Nm 3 / m 3 .

6. The method for preparing bio-based isoalkanes according to claim 1, characterized in that: In step (5), the molecular sieve is any one of AlPO-41, EU-1, ECNU-21 or ZSM-23.

7. The method for preparing bio-based isoalkanes according to claim 1, characterized in that: In step (5), the mass ratio of urea solution to alkane is 5:1-15:1, the complexing time is 2-10 hours, and the complexing temperature is 10-50°C.

8. The method for preparing bio-based isoalkanes according to claim 1, characterized in that: In step (5), a multi-stage series connection method can be adopted to separate normal alkanes from isoalkanes.

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