A high-acidity saPO-11 molecular sieve, a preparation method and application thereof

Abstract

This invention belongs to the field of molecular sieve synthesis technology, and discloses a high-acid-content SAPO-11 molecular sieve, its preparation method, and its applications. The molecular sieve synthesized by this method has a total acid content greater than 1 mmol / g, with moderately strong acids accounting for more than 45% of the total acid content in molar ratio, and also exhibits a hierarchical pore size distribution and a specific surface area greater than 240 m². 2 / g, with an external specific surface area accounting for more than 50% of the total specific surface area. It can be used as the active component of a long-chain alkane hydroisomerization catalyst. The SAPO-11 molecular sieve synthesized in this invention has the characteristics of high crystallinity, low impurity content, and high medium-strong acid content. Moreover, the product has good reproducibility and high yield, which is conducive to industrial scale-up production and solves the problem of poor product stability in existing technologies.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve synthesis technology, specifically relating to a high-acidity SAPO-11 molecular sieve, its preparation method, and its application. Background Technology

[0002] SAPO-11 molecular sieve is an AEL topology molecular sieve with a pore size of 0.39 × 0.64 nm and one-dimensional ten-membered elliptical channels. This unique channel structure and tunable acidity give it excellent application potential in catalysis, especially in the hydroisomerization reaction of long-chain alkanes. The hydroisomerization process of long-chain alkanes is a key technology for improving the low-temperature flow properties of fuel oils and lubricating oils. Compared with straight-chain alkanes, the isomerization products, branched alkanes, have lower melting and boiling points and better low-temperature flow properties, which can significantly improve oil quality to meet increasingly stringent environmental and usage standards. SAPO-11 molecular sieve, as the core acidic matrix of the bifunctional catalyst in this process, directly determines the activity, selectivity, and stability of the catalyst. The acidity of SAPO-11 molecular sieve originates from the substitution of phosphorus atoms in the framework by silicon atoms. Therefore, regulating the substitution of silicon atoms in the framework and increasing the number of medium-strong acid centers are the core objectives for optimizing the catalytic performance of SAPO-11 molecular sieves, which are directly related to the conversion rate, isomer selectivity, and single-branched isomer yield of long-chain alkane isomerization reactions.

[0003] Currently, the synthesis of SAPO-11 molecular sieves mostly employs the traditional hydrothermal method, using long-chain alkyl diamines as template agents, boehmite as the aluminum source, phosphoric acid as the phosphorus source, and ethyl silicate or silica sol as the silicon source. Crystallization at around 473 K for more than 24 hours yields the product. Chinese patent CN114380299A discloses a SAPO-11 molecular sieve and its preparation method, which effectively solves the problems of impurity crystal formation and the tendency for the crystal structure to transform into the Pna21 space group after calcination and template agent removal in existing SAPO-11 molecular sieve synthesis methods through a four-stage stepwise hydrothermal crystallization method, effectively improving the yield of SAPO-11 molecular sieves. Chinese patent CN113353954A discloses a green synthesis method for hierarchical porous SAPO-11 molecular sieves based on natural minerals, using inexpensive natural minerals as part of the raw materials to synthesize a highly crystallinity SAPO-11 molecular sieve with a large external specific surface area and hierarchical pores. Chinese patent CN107128944A discloses... A method for preparing SAPO-11 molecular sieve and its application is disclosed. A variable-speed stirring process is employed, where the stirring speed during the aging process of SAPO-11 molecular sieve is higher than that during the crystallization process. By optimizing the stirring speeds during the aging and crystallization processes, SAPO-11 molecular sieves with high crystallinity and uniform particle size are obtained, and the crystallization time is shortened. Chinese patent CN103241745A discloses a method for preparing small-particle-size SAPO-11 molecular sieves and its applications. This method involves functionalizing the molecular sieve precursor by adding alkylated organosilanes to a synthetic gel to synthesize a hydrophobic SAPO-11 seed precursor, which is then dispersed in an organic solvent medium for crystallization to obtain small-crystal SAPO-11 molecular sieves.

[0004] However, existing synthesis techniques suffer from numerous bottlenecks, making it difficult to meet the industrial catalytic demand for high-acid SAPO-11 molecular sieves. For example, conventional hydrothermal synthesis produces products with poor reproducibility, uneven distribution of silicon atoms in the framework, and a tendency to form numerous silicon regions without acid sites, resulting in insufficient medium-strong acid content, limited catalytic activity and selectivity, and hindering industrial scale-up production. Furthermore, traditional processes yield molecular sieves with larger crystal sizes, limited specific surface areas, and high pore diffusion resistance, which not only reduces the accessibility of active sites but also easily triggers side reactions such as cracking, further affecting the selectivity of isomerization.

[0005] Existing research has improved the acid properties and pore structure of SAPO-11 molecular sieves through modification treatments, but post-treatment methods such as etching are complex and can easily damage the framework structure.

[0006] Therefore, developing a method for preparing SAPO-11 molecular sieves that is simple to synthesize, has good reproducibility, is cost-controllable, and has high to medium acid content is of great practical significance and industrial application value for breaking through existing technological bottlenecks and promoting the efficient development of long-chain alkane hydrogenation isomerization processes. Summary of the Invention

[0007] To address the existing technical problems of insufficient acid content, uneven silicon distribution, and poor catalytic performance of SAPO-11 molecular sieves, the present invention aims to provide a high-acid-content SAPO-11 molecular sieve, its preparation method, and its applications. The molecular sieve synthesized by this method has a total acid content greater than 1 mmol / g, with a molar ratio of moderately strong acids greater than 45% of the total acid content. It also exhibits a multi-level pore size distribution and a specific surface area greater than 240 m². 2 / g, with the external specific surface area accounting for more than 50% of the total specific surface area. It solves problems such as uneven silicon distribution, insufficient medium-strong acid content, many impurities, and poor reproducibility, and obtains SAPO-11 molecular sieve with high acid content, multi-level pore size, and high specific surface area. At the same time, it simplifies the synthesis process, reduces costs, and is conducive to industrial-scale production.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A high-acidity SAPO-11 molecular sieve, wherein the molecular sieve is prepared from a composite template agent, additives and other excipients; The composite template agent is composed of a main template agent and an auxiliary template agent in a mass ratio of 5 to 10:1. The main template agent is a dialkylamine organic compound; The auxiliary template agent is a hydroxyalkylamine; The auxiliary agent is a quaternary ammonium salt; The molar ratio of the primary template agent, auxiliary template agent, and adjuvant in the composite template agent is: n R1:n R2:n S = (1~1.5):(0.05~0.15):(0.03~0.10), where R1 is the main template agent, R2 is the auxiliary template agent, and S is the adjuvant. The molecular sieve has a total acid content >1 mmol / g, a molar ratio of moderately strong acids to total acid content >45%, and a specific surface area >240 m². 2 / g, the external specific surface area accounts for more than 50% of the total specific surface area.

[0009] Preferably, the composite template agent is composed of a main template agent and an auxiliary template agent in a mass ratio of 7 to 9:1. The main template agent is one or a combination of di-n-propylamine and diisopropylamine; The auxiliary template agent is triethanolamine; The auxiliary agent is dodecyltrimethylammonium bromide; The molar ratio of the primary template agent, auxiliary template agent, and quaternary ammonium salt adjuvant in the composite template agent is: n R1:n R2:n S = (1.1~1.3):(0.08~0.12):(0.04~0.06), where R1 is the main template agent, R2 is the auxiliary template agent, and S is the adjuvant.

[0010] Preferably, the other excipients include acidic silica sol as a silicon source; macroporous boehmite with a particle size <10μm and a pore volume >1.1mL / g as an aluminum source; phosphoric acid as a phosphorus source; and ammonia water as an alkali source. The raw materials are calculated in molar ratio as follows: n Al2O3: n P2O5: n SiO2: n H2O = 1: (0.8~1.3): (0.2~0.5): (40~80).

[0011] Preferably, the raw materials are calculated in the following molar ratio: nAl2O3:nP2O5:nSiO2:nH2O = 1:(0.9~1.1):(0.3~0.5):(50~60).

[0012] A method for preparing a high-acidity SAPO-11 molecular sieve includes the following steps: S1. Add phosphorus source to deionized water and stir evenly. Slowly add aluminum source and stir vigorously for 1-4 hours at a speed greater than 600 r / min to obtain mixture A. S2. Select the main template agent and auxiliary template agent according to the corresponding ratio, mix them evenly, and add them dropwise to the mixture A and stir for 0.3~1h to obtain the mixture B; S3. Dissolve the additive in deionized water and stir until uniform. Add it to mixture B and stir for 1-4 hours. Add the silicon source dropwise and stir for another 1-4 hours to obtain mixture C. S4. Add ammonia water dropwise to mixture C, adjust the pH value to 5-6, continue stirring for 0.3-1h, and then transfer to a hydrothermal reactor. S5. Static crystallize the hydrothermal reactor at 180~210℃ for 20~36h, and obtain the high acid content SAPO-11 molecular sieve after washing, filtering, drying and calcining.

[0013] Preferably, in S1, the phosphorus source is an aqueous solution of phosphoric acid with a phosphoric acid content of 85 wt%. The aluminum source is added slowly in batches in a constant temperature water bath at 35°C.

[0014] Preferably, in step S3, the silicon source is an acidic silica sol with a silica content of 25 wt%, and the silicon source is added dropwise with continuous stirring.

[0015] Preferably, in step S4, the molar concentration of ammonia is 0.5~2 mol / L.

[0016] Preferably, in step S5, the calcination temperature is 500~600℃ and the duration is 1.5~8h.

[0017] An application of a high-acidity SAPO-11 molecular sieve, in which the molecular sieve is used as the active component of a long-chain alkane hydroisomerization catalyst in a process for improving the low-temperature flow properties of fuel oil or lubricating oil.

[0018] Compared with the prior art, the present invention has at least the following technical effects: This invention provides a high-acid SAPO-11 molecular sieve, which features high acid content, high acid strength, low impurity content, and low cost.

[0019] When this high-acidity molecular sieve is used as the active component of a catalyst, it can effectively improve the conversion rate and isomer selectivity of the hydroisomerization reaction of long-chain alkanes, which is beneficial to improving the reaction conversion rate and selectivity of the catalyst. The product has low impurity crystal content, good experimental repeatability and high product yield, which is conducive to the industrial scale-up production of the product and solves the problem of poor product stability in existing technologies. The molecular sieve has a multi-level pore size distribution, a high external specific surface area ratio, low pore diffusion resistance and improved accessibility of active sites.

[0020] In the synthesis method of this high acid content SAPO-11 molecular sieve, (1) a composite system of main template agent and auxiliary template agent is adopted. Dialkylamine organic compounds are selected as the main template agent and a small amount of hydroxyl-containing alkylamine is added. The hydroxyl groups in its molecular structure can form hydrogen bonds with Si-OH and Al-OH in the gel, which enhances the directional guidance effect on the AEL topology and promotes the uniform embedding of silicon atoms into the phosphate skeleton, thereby increasing the medium-strong acid content. At the same time, the composite template agent system significantly reduces the total cost of the template agent and significantly improves the purity of SAPO-11 in the product, with no other impurities, and the experimental repeatability is good.

[0021] (2) Adding a small amount of quaternary ammonium salt to the molecular sieve precursor solution, the quaternary ammonium salt interacts with the silicon source species through intermolecular forces, breaks the aggregation tendency of silicon atoms, reduces the size and number of (4Si, 0Al) silicon islands, and at the same time increases the relative content of (nSi, (4-n)Al) and (0<n<4) coordination structures, so that silicon is more uniformly dispersed in the molecular sieve framework, avoids local silicon enrichment, and thus regulates the strength and distribution density of acidic sites, thereby improving the surface acidity of SAPO-11 molecular sieve. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the NH3-TPD experimental results for Example 1 and Comparative Examples 1 and 2; Figure 2 The XRD results are for Example 1 and Comparative Examples 1 and 2; Figure 3This is a schematic diagram of the physical adsorption results of Example 1. Detailed Implementation

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be briefly introduced below in conjunction with the accompanying drawings and descriptions of the embodiments or the prior art. Obviously, the following description of the structure of the accompanying drawings is only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.

[0024] In all the following examples, the raw material mass corresponds to a molar ratio range: each raw material is expressed as a molar ratio as follows: The formula is: n Al2O3:n S:n P2O5:n SiO2:n R1:n R2:n H2O = 1:0.05:1:0.4:1.2:0.1:55. Where S is an auxiliary agent, R1 is the primary template agent, and R2 is the secondary template agent.

[0025] Example 1: A method for preparing a high-acidity SAPO-11 molecular sieve includes the following steps: In a constant temperature water bath at 35℃, 13.83g of phosphoric acid (85wt%) was weighed and added to 30g of deionized water. After stirring evenly, 8.37g of macroporous pseudoboehmite was slowly added to the liquid in batches and stirred vigorously for 2 hours. This mixture is recorded as mixture A. Weigh out 6.86g of di-n-propylamine and 0.86g of triethanolamine, mix them thoroughly, and then add them dropwise to mixture A. Stir for 0.5h and record this mixture as mixture B. Weigh 0.88g of dodecyltrimethylammonium bromide and dissolve it in 20g of deionized water. After stirring evenly, add it to mixture B and stir for 2 hours. Then, add 4.80g of acidic silica sol (silica content 25wt%) dropwise and stir for 2 hours. This mixture is called mixture C. Under stirring, 1 mol / L ammonia was added dropwise to the mixture C to adjust the pH to 5.5. After stirring for 0.5 h, the mixture was transferred to a hydrothermal reactor. The mixture was statically crystallized at 190 °C for 24 h, washed, filtered, dried, and calcined at 550 °C for 2 h to obtain the SAPO-11 molecular sieve SAPO-11-A1 of Example 1.

[0026] Example 2: A method for preparing a high-acidity SAPO-11 molecular sieve includes the following steps: In a constant temperature water bath at 35℃, 12.68g of phosphoric acid (85wt%) was weighed and added to 32g of deionized water. After stirring evenly, 8.37g of macroporous pseudoboehmite was slowly added to the liquid in batches and stirred vigorously for 2 hours. This mixture is recorded as mixture A. Weigh 7.03g of diisopropylamine and 1.00g of triethanolamine, mix them thoroughly, and then add them dropwise to mixture A. Stir for 0.5h and record this mixture as mixture B. Weigh 0.88g of dodecyltrimethylammonium bromide and dissolve it in 21g of deionized water. After stirring evenly, add it to mixture B and stir for 2 hours. Then, add 5.10g of acidic silica sol (silica content 25wt%) dropwise and stir for 2 hours. This mixture is called mixture C. Under stirring, 1 mol / L ammonia was added dropwise to the mixture C to adjust the pH to 5.5. After stirring for 0.5 h, the mixture was transferred to a hydrothermal reactor. The mixture was statically crystallized at 200 °C for 22 h, washed, filtered, dried, and calcined at 550 °C for 2 h to obtain SAPO-11 molecular sieve SAPO-11-A2 of Example 2.

[0027] Example 3: A method for preparing a high-acidity SAPO-11 molecular sieve includes the following steps: In a constant temperature water bath at 35℃, 14.15g of phosphoric acid (85wt%) was weighed and added to 30g of deionized water. After stirring evenly, 8.37g of macroporous pseudoboehmite was slowly added to the liquid in batches and stirred vigorously for 2 hours. This mixture is recorded as mixture A. Weigh out 2.69g of di-n-propylamine, 4.04g of diisopropylamine and 0.92g of triethanolamine, mix them thoroughly, and then add them dropwise to mixture A. Stir for 0.5h and record this mixture as mixture B. Weigh 0.79g of dodecyltrimethylammonium chloride and dissolve it in 25g of deionized water. After stirring evenly, add it to mixture B and stir for 2 hours. Then, add 4.80g of acidic silica sol (silica content 25wt%) dropwise and stir for 2 hours. This mixture is called mixture C. Under stirring, 1 mol / L ammonia was added dropwise to the mixture C to adjust the pH to 5.5. After stirring for 0.5 h, the mixture was transferred to a hydrothermal reactor. The mixture was statically crystallized at 190 °C for 24 h, washed, filtered, dried, and calcined at 550 °C for 2 h to obtain SAPO-11 molecular sieve SAPO-11-A3 of Example 3.

[0028] Comparative Example 1: In a 35℃ constant temperature water bath, 16.47g of phosphoric acid (85wt%) was weighed and added to 50g of deionized water. After stirring evenly, 11.20g of pseudoboehmite was slowly added to the liquid in batches and stirred vigorously for 2h, which was recorded as mixture A. 7.23g of di-n-propylamine was weighed and added dropwise to mixture A and stirred for 0.5h, which was recorded as mixture B. 5.14g of acidic silica sol (silica content 25wt%) was weighed and added dropwise to mixture B and stirred for 2h, which was recorded as mixture C. Under stirring conditions, 1mol / L ammonia water was added dropwise to mixture C to adjust the pH to 5.5, and after stirring for another 0.5h, it was transferred to a hydrothermal reactor. Static crystallization was carried out at 190℃ for 24h, followed by washing, filtration, drying, and calcination at 550℃ for 2h to obtain SAPO-11 molecular sieve SAPO-11-B1 of Comparative Example 1.

[0029] Comparative Example 2: In a 35℃ constant temperature water bath, 16.47g of phosphoric acid (85wt%) was weighed and added to 50g of deionized water. After stirring evenly, 11.20g of pseudoboehmite was slowly added in batches to the liquid, and the mixture was stirred vigorously for 2 hours. This mixture was recorded as mixture A. 6.86g of di-n-propylamine and 0.92g of triethanolamine were weighed and added dropwise to mixture A, and the mixture was stirred for 0.5 hours. This mixture was recorded as mixture B. 5.14g of acidic silica sol (silica content 25wt%) was weighed and added dropwise to mixture B, and the mixture was stirred for 2 hours. This mixture was recorded as mixture C. Under stirring conditions, 1mol / L ammonia was added dropwise to mixture C to adjust the pH to 5.5. After stirring for another 0.5 hours, the mixture was transferred to a hydrothermal reactor. The mixture was statically crystallized at 190℃ for 24 hours, washed, filtered, dried, and calcined at 550℃ for 2 hours to obtain SAPO-11 molecular sieve SAPO-11-B2 of Comparative Example 2.

[0030] To demonstrate the effectiveness of the SAPO-11 molecular sieve provided in this application, the following analytical characterization experiments were conducted: The SAPO-11 molecular sieves synthesized in Example 1 and Comparative Examples 1-2 were analyzed by NH3-TPD, XRD and physical adsorption, and the results are as follows: like Figure 1 The diagram shown is a schematic diagram of the NH3-TPD experimental results of Example 1 and Comparative Examples 1 and 2.

[0031] Depend on Figure 1 The results show that, compared with Comparative Examples 1-2, the synthesis method in this application embodiment can obtain SAPO-11 molecular sieve with high acid content and high acid strength.

[0032] Table 1 below shows the comparison results of the acid content of the synthesized molecular sieves in Example 1 and Comparative Examples 1 and 2.

[0033]

[0034] As can be seen from the results in Table 1, compared with Comparative Examples 1-2, the synthesis method in the embodiments of this application can obtain SAPO-11 molecular sieves with a total acid content greater than 1 mmol / g and a molar ratio of moderately strong acid to total acid content greater than 45%.

[0035] Figure 2 The XRD results are for Example 1 and Comparative Examples 1 and 2.

[0036] Depend on Figure 2 The results show that, compared with Comparative Examples 1-2, the synthesis method in this application embodiment synthesizes SAPO-11 molecular sieve with high crystallinity and no impurities.

[0037] Figure 3 This is a schematic diagram of the physical adsorption results of Example 1.

[0038] Depend on Figure 3 The results show that the synthesis method in the embodiments of this application can produce a specific surface area greater than 240m². 2 SAPO-11 molecular sieves with an external specific surface area accounting for more than 50% of the total specific surface area.

[0039] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high acid content SAPO-11 molecular sieve characterized in that, The molecular sieve is prepared from composite template agents, additives and other excipients; The composite template agent is composed of a main template agent and an auxiliary template agent in a mass ratio of 5 to 10:

1. The main template agent is a dialkylamine organic compound; The auxiliary template agent is a hydroxyalkylamine; The auxiliary agent is a quaternary ammonium salt; The molar ratio of the primary template agent, auxiliary template agent, and adjuvant in the composite template agent is: n R1:n R2:n S = (1~1.5):(0.05~0.15):(0.03~0.10), where R1 is the main template agent, R2 is the auxiliary template agent, and S is the adjuvant. The total acid amount of the molecular sieve is >1 mmol / g, the molar ratio of the medium-strong acid to the total acid amount is >45%, the specific surface area is >240 m 2 / g, and the proportion of the external specific surface area to the total specific surface area is >50%.

2. The high acid content SAPO-11 molecular sieve of claim 1, wherein, The composite template agent is composed of a main template agent and an auxiliary template agent in a mass ratio of 7 to 9:

1. The main template agent is one or a combination of di-n-propylamine and diisopropylamine; The auxiliary template agent is triethanolamine; The auxiliary agent is dodecyltrimethylammonium bromide; The molar ratio of the primary template agent, auxiliary template agent, and quaternary ammonium salt adjuvant in the composite template agent is: n R1:n R2:n S = (1.1~1.3):(0.08~0.12):(0.04~0.06), where R1 is the main template agent, R2 is the auxiliary template agent, and S is the adjuvant.

3. The high acid content SAPO-11 molecular sieve of claim 1, wherein, The other excipients include acidic silica sol as a silicon source; macroporous pseudoboehmite with a particle size <10μm and a pore volume >1.1mL / g as an aluminum source; phosphoric acid as a phosphorus source; and ammonia as an alkali source. The raw materials are calculated in molar ratio as follows: n Al2O3: n P2O5: n SiO2: n H2O = 1: (0.8~1.3): (0.2~0.5): (40~80).

4. The high-acidity SAPO-11 molecular sieve according to claim 3, characterized in that, The raw materials are calculated in molar ratio as follows: n Al2O3: n P2O5: n SiO2: n H2O = 1: (0.9~1.1): (0.3~0.5): (50~60).

5. A method for preparing a high-acidity SAPO-11 molecular sieve as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Add phosphorus source to deionized water and stir evenly. Slowly add aluminum source and stir vigorously for 1-4 hours at a speed greater than 600 r / min to obtain mixture A. S2. Select the main template agent and auxiliary template agent according to the corresponding ratio, mix them evenly, and add them dropwise to the mixture A and stir for 0.3~1h to obtain the mixture B; S3. Dissolve the additive in deionized water and stir until uniform. Add it to mixture B and stir for 1-4 hours. Add the silicon source dropwise and stir for another 1-4 hours to obtain mixture C. S4. Add ammonia water dropwise to mixture C, adjust the pH value to 5-6, continue stirring for 0.3-1h, and then transfer to a hydrothermal reactor. S5. Static crystallize the hydrothermal reactor at 180~210℃ for 20~36h, and obtain the high acid content SAPO-11 molecular sieve after washing, filtering, drying and calcining.

6. The method for preparing a high-acidity SAPO-11 molecular sieve according to claim 5, characterized in that, In S1, the phosphorus source is an aqueous solution of phosphoric acid, with a phosphoric acid content of 85 wt%. The aluminum source is added slowly in batches in a constant temperature water bath at 35°C.

7. The method of making a high acid SAPO-11 molecular sieve of claim 5, wherein, In step S3, the silicon source is an acidic silica sol with a silica content of 25 wt%, and the silicon source is added dropwise with continuous stirring.

8. The method of making a high acid SAPO-11 molecular sieve of claim 5, wherein, In S4, the molar concentration of ammonia water is 0.5~2 mol / L.

9. The method of making a high acid SAPO-11 molecular sieve of claim 5, wherein, In step S5, the calcination temperature is 500~600℃ and the duration is 1.5~8h.

10. Use of a high acid content SAPO-11 molecular sieve according to any one of claims 1 to 4, characterized in that, The molecular sieve is used as the active component of a long-chain alkane hydroisomerization catalyst in a process to improve the low-temperature flow properties of fuel oil or lubricating oil.

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