Method for hydroisomerization of industrial diesel fuel to improve its low-temperature properties

Abstract

FIELD: isomerization.SUBSTANCE: invention relates to a method for hydroisomerization of diesel fuel to improve its low-temperature properties, which includes carrying out the process in the presence of a granulated catalyst based on platinum-comprising 0.5% by weight. Pt silicoaluminophosphate molecular sieve SAPO-11, at a pressure of 3.0 MPa, a space velocity of 2.0 h-1 and a hydrogen / feed ratio of 800 Nm³ / m³. The method is characterized by the fact that granulated nanocrystalline silicoaluminophosphate SAPO-11 without binders with a crystal size of 80-100 nm is used as a catalyst, whereas the hydroisomerization process is carried out at a temperature of 280-350 °C.EFFECT: deep isomerization of long-chain n-paraffins to produce arctic fuel with improved low-temperature characteristics and a higher yield of the target product.3 cl, 2 tbl, 5 ex

Description

[0001] The invention relates to the field of petrochemical synthesis, namely to a method for hydroisomerization of industrial diesel fuel using a nanocrystalline catalyst based on granulated binder-free silicoaluminophosphate SAPO-11 promoted with platinum, for producing arctic diesel fuel with improved low-temperature properties.

[0002] At present, hydroisomerization of n-paraffins C 16+is one of the most promising technologies for producing low-pour point diesel fuels and Group III oils [Akhmedov VM, Al-Khowaiter SH Recent Advances and Future Aspects in the Selective Isomerization of High n-Alkanes / / Catalysis Reviews. 2007. V. 49:1. P. 33-139]. This technology became possible thanks to the development of bifunctional catalysts based on molecular sieves with a one-dimensional channel structure and a pore size of ~5 Å (10R-1D), promoted by noble metals [Yadav R., Sakthivel A. Silicoaluminophosphate molecular sieves as potential catalysts for hydroisomerization of alkanes and alkenes / / Appl. Catal. A Gen. 2014. V.481. P.143–160].

[0003] In the work [Kondrashev, D.O., Kleimenov, A.V., Gulyaeva, L.A. et al. Studying the efficiency of the diesel fuel isodewaxing process on a zeolite-containing nickel–molybdenum catalyst. Catal. Ind. 9, 128–135 (2017)], a method for producing winter diesel fuel under the action of the GIP-14 catalyst based on Ni–Mo–W supported on a mixture of zeolites is proposed, with a yield of 92–93% (300–310 °C, feed space velocity (w) 3 h -1 ) and a maximum filter plugging point (MPP) of –38 °C.

[0004] A similar approach was used in the work [Grudanova, AI, Gulyaeva, LA, Krasilnikova, LA, Shmelkova, OI, & Boldushevskii, RE (2017). Jet fuel and arctic diesel fuel production by isodewaxing of waxy middle distillate fractions. Fuel, 193, 485–487] under the action of a NiMo / ZSM-11 / mordenite catalyst, which made it possible to obtain fuel with a yield of 92% and a PTF of -49 °C.

[0005] Patents [Patent RU 2549617] and [Patent RU 2662934] describe methods of hydroisomerization using a mixture of high-silica zeolites (USY, ZSM-12 / ZSM-22, TsVN / ZSM-11), with hydrogenating metals (Ni, W, Mo), promoters (B2O3, P2O5) and an Al2O3 binder. In an improved version [Patent RU 2662934 C1], copper oxide (0.3–1.5%) is additionally introduced. The yield of the diesel fraction is 92–94% (250–400 °C, 2–5 MPa, w= 2–4 h -1 ), PTF up to –44 °C.

[0006] The patent [Patent RU 2612134 C1] describes a method for hydroisodewaxing middle distillate fractions using a catalyst containing a mixture of zeolites (CVN and mordenite / β-zeolite), Ni, Mo, a promoter (B2O3-La2O3), and a binder (γ-Al2O3). The yield of diesel fuel with a PTF equal to – 45°C is 53%.

[0007] The patent [Patent AU2016379179] describes a method of hydroisomerization in the presence of a (Ni-Mo / W)ZSM-11 / Al2O3 catalyst. The fuel yield is 78% (270–400 °C, 1–20 MPa, w=0.5–1.0 h -1, H2 / raw material ratio = 200–1000 nl / l), PTF is –20°C

[0008] The general disadvantage of these methods is low activity and selectivity, which does not allow achieving the characteristics of arctic fuels (PTF is -50°C and below) at high yield.

[0009] The patent [Patent RU 2826904 C1] describes a method of hydroisodewaxing under the action of a catalyst containing amorphous aluminosilicate (5-15%), zeolites MFI or TSVN (10-20%), MTT or MEL (20-30%) and aluminum oxide, providing a diesel fuel yield of 91.6-94.6% (320-380°C, 3.0-5.0 MPa) with PTF down to -46°C.

[0010] The patent [Pat. RU 2 789 593 C1] describes a method for producing arctic diesel fuel grades A-44 and A-48 (PTF is -44°C and -48°C, respectively) with a fuel yield of 92-94% under the influence of a binary mixture of zeolites: ZSM-5 / LaHY and Al2O3, promoted with NiO (5.0-10.0%), B2O3 (1.0-4.0%).

[0011] Patent [Patent RU 2827816 C1] describes a method of hydroisomerization in the presence of a catalyst containing a complex carrier composition: USY zeolite (0.01-15%), amorphous aluminosilicate (5-15%), MFI or TsVN zeolite (5-45%), MTT zeolite (0.01-30.0%), MEL zeolite (5-30%) and γ-alumina. Active metals are nickel oxides (1.0-5.0%) and molybdenum oxides (3.0-11.5%). The yield of diesel fraction is 90.4-94.8% (280-380 °C; 2.0-5.0 MPa), PTF up to -52 °C.

[0012] A method is known [Patent RU 2183505] for producing diesel fuel with a pour point (PP) of minus 35°C under the action of a catalyst containing tungsten and / or molybdenum, nickel or cobalt, on an aluminosilicate carrier with zeolites β, Y, ZSM-5.

[0013] The disadvantage of these methods is the technological complexity of preparing catalysts due to the large number of components, and the low-temperature properties of the resulting diesel fuel do not meet the requirements for Arctic grades.

[0014] The patent [Pat. RU 2225433] describes a method for hydroisomerization of diesel fuel under the action of zeolites β, Y, ZSM-5, modified Ni / Mo, to obtain fuel with a TD down to –35°C (240–380°C, 3 MPa, w=1.0–2.0 h -1 and the H2 / raw material ratio of 400–1500 nm 3 / m 3 ).

[0015] Catalytic systems based on noble metals make it possible to produce diesel fuel with improved low-temperature characteristics. Thus, the patent [Patent RU 2739566 C1] describes a method of hydroisomerization under the action of Pt / EU-2 or Pt / ZSM-23 catalysts with Al2O, providing an isomer yield of 89-98 wt.% (350–360 °C; 8.0 MPa; w=2.7 h -1 ) with low PTF (up to -44°C).

[0016] The patent [Patent RU 2 758 847 C1] describes a method for producing winter and arctic diesel fuels under the action of a Pt / EU-2 / Al2O3 catalyst with a yield of 98 wt.% (345–390 °C; 6.0–10.0 MPa; 1.0–3.0 h -1 , H2 / raw material 200–700 nl / l), having a PTF from –26 to –49 °C.

[0017] A method of hydroisomerization under the action of Pt–Pd / EU-2 / Al2O3 [Patent RU 2 758 846 C1] is proposed, which makes it possible to obtain fuel with PTF down to -44°C.

[0018] The patent [Patent RU2560157] proposes a method for hydroisomerization of diesel fractions under the action of granulated zeolite Pt / ZSM-23 / Al2O3. The yield of isomers is 72.0-97.5 wt.% (4.0–5.5 MPa, 250–420 °C, w=1.0–4.0 h -1 and H2 / raw material ratio of 350–700 nl / nl) with PTF down to –45°C.

[0019] The patent [Patent RU 2536585] describes a method of hydroisomerization in the presence of a Pd / B / ZSM-23 / Al2O3 catalyst. The yield of diesel fuel with a temperature of up to –42°C reaches 90.6% (320–340°C, 2.5–6.5 MPa, w=2–6 h) -1 and an H2 / raw material ratio of 200–600 nm 3 / m 3 ).

[0020] A common drawback of the catalytic systems considered is the use of binders during catalyst formation, which leads to partial blocking of pores, an increase in diffusion limitations and, as a consequence, a decrease in the availability of active centers for long-chain alkane molecules.

[0021] A method is known for producing low-freezing diesel fuel [Patent CN 113976171 A] under the action of zeolites ZSM-22, ZSM-23, ZSM-48 or ZSM-35 (50–80% by weight), promoted with platinum (150–350°C, 3–10 MPa and w=0.5–3 h -1 , H2 / feedstock ratio = 200:1–1000:1). The method allows for the production of diesel fuel with a temperature range down to –45 °C.

[0022] A separate group consists of two-stage and multi-layer catalytic processes aimed at the combined improvement of low-temperature and environmental characteristics of diesel fuel.

[0023] The patent [Patent WO 2009 / 088454A1] proposes a two-stage process comprising hydrotreating with Ni-Mo, Co-Mo, or Ni-W on Al3O3 and catalytic hydroisomerization of diesel fuel on ZSM-48, ZSM-23, or Beta zeolites promoted with Pt or Pd. An effective reduction in the cloud point (CP) of the feedstock from -5 °C to -65 °C is demonstrated. However, the process is highly complex to control and, more importantly, the hydroisomerization catalyst is extremely sensitive to residual impurities, especially sulfur and ammonia. The latter causes its rapid deactivation and requires frequent replacement.

[0024] Patent WO 2013 / 085533 A1 describes a method for producing low-pour point diesel fuels under the action of a zeolite-containing catalyst (ZSM-48, ZSM-23, ZSM-35, SSZ-32) promoted with Pt / Pd or Ni / W / Mo (2.1–20.6 MPa, 260–425 °C, w=0.2–10 h) -1 ). The cloud point of the product (CP) is –30...–10 °C.

[0025] A method for producing low-freezing diesel fuel is known [Patent CN 105087063 A] under the action of a composite catalyst FDW-3 (6.0–20.0 MPa, 270–460 °C, w=0.1–10.0 h -1 , H2 / feedstock ratio = 200:1–1500:1). The method allows for the production of diesel fuel with a TD of –42°C, but the product yield does not exceed 79.6%.

[0026] Silicoaluminophosphates SAPO-n exhibit the highest selectivity in the hydroisomerization of long-chain n-alkanes [Barthomeuf D. Topological model for the compared acidity of SAPOs and SiAl zeolites / / Zeolites. 1994. V.14. P.394–401]. The activity and selectivity of these systems are determined by the acidic properties, the texture of the support (specific surface area, mesopore volume, crystal size), and the dispersion of the metal component.

[0027] High efficiency of SAPO-based catalysts in the hydroisomerization reaction of model n-alkanes (n-C 16 , n-S 10) [Miller SJ / / Micropor. Mater. 1994. V. 2 (5). P. 439–449; Yu, G., Qiu, M., Wang, T., Ge, L., Chen, X., & Wei, W. Optimization of the pore structure and acidity of SAPO-11 for highly efficient hydroisomerization on the long-chain alkane / / Microporous and Mesoporous Materials. – 2021. – T. 320. – P. 111076; Serebrennikov, DV, Filippova, NA, Fayzullina, ZR, Mescheryakova, ES, Kutepov, BI, Sabirov, DS, Agliullin, MR Hydroisomerization of n-Hexadecane over Pt / SAPO-11 and Pt / SAPO-41 Molecular Sieves: Differing in Crystal Morphology and Size / / Petroleum Chemistry. – 2025. – Pp. 1-9] demonstrates their significant potential for solving a practical problem – hydroisomerization of diesel fuel to improve its low-temperature properties.

[0028] The authors of [Patent US4960504] proposed a method for the catalytic hydroisomerization of hydrocarbon feedstock fractions using silicoaluminophosphate molecular sieves (SAPO), which makes it possible to reduce the TZ of products to -40°C with minimal feedstock conversion (15%) into low-boiling fractions. The catalyst is SAPO-11, SAPO-31, SAPO-41 molecular sieves promoted with Pt, Pd, Ni, W, Mo, supported on a matrix of inorganic oxide (Al2O3, SiO2, SiO2-Al2O3, etc.) in an amount of 10–99% of the catalyst weight.

[0029] The patent [Patent RU2560157] proposes a method for hydroisomerization of diesel fractions using a Pt / SAPO-41 / Al2O3 molecular sieve granulated with a binder. The hydroisomerization process is carried out at a pressure of 4.0–5.5 MPa, a temperature of 250–420 °C, and a space velocity of 1.0–4.0 h -1 and an H2 / feedstock ratio of 350–700 nL / nL. The yield of fuel isomers is 81.3–97.5%, and PTF down to –40°C.

[0030] The closest to the proposed invention is the method of hydroisomerization of hydrotreated diesel fraction using a catalyst based on granular platinum-containing molecular sieve SAPO-11, described in the work [Yakovenko, RE, Agliullin, MR, Zubkov, IN et al. Diesel Fraction Isodewaxing in the Presence of Granular Platinum-Containing SAPO-11 and SAPO-41 Molecular Sieves. Catal. Ind. 2024, 16, 178–186]. According to this method, a catalyst prepared as follows is used: SAPO-11 powder is mixed with 30 wt.% boehmite as a binder, moistened, granules of 1.4-1.5 mm in diameter and 2-3 mm in length are formed by extrusion, dried at 100 °C and calcined at 600 °C for 6 hours. The granules are then impregnated with a solution of hexachloroplatinic acid to achieve a platinum content of 0.5 wt.%, after which they are dried again and calcined at 550 °C. The resulting catalyst provides at 280-350 °C, a pressure of 3 MPa, a space velocity of raw materials of 2.0 h-1 and the ratio H2 / raw material = 800 m 3 / m 3 production of winter diesel fuel with a yield of 89-98%, pour point (P) up to -44 °C, cloud point (CP) up to -38 °C.

[0031] However, this method has significant drawbacks: the use of a binder (boehmite) during catalyst synthesis leads to blocking of the micropores of the molecular sieve, reducing their volume by 50–70% and a threefold decrease in the concentration of acid sites; large granules (1.4–1.5 mm in size) create diffusion limitations; in addition, the technological process is complicated by the need for additional granulation and calcination stages.

[0032] The objective of the present invention is to develop an efficient and reproducible method for hydroisomerization of diesel fuel, ensuring deep isomerization of long-chain n-paraffins to produce arctic fuel with improved low-temperature characteristics and a higher yield of the target product and a simplified catalyst preparation technology.

[0033] The problem is solved by carrying out diesel fuel hydroisomerization in the presence of binder-free granulated nanocrystalline silicoaluminophosphate molecular sieve Pt / SAPO-11 (Pt content – ​​0.5 wt.%). A powdered sample of SAPO-11 is synthesized by the hydrothermal method from a reaction gel of the following composition: 1.0 Al2O3⋅1.0 P2O5⋅0.1 SiO2⋅1.0 DIPA⋅20H2O, followed by holding (90 °C, 24 h), crystallization (200 °C, 24 h), washing and centrifuging, drying (100 °C, 48 h), calcination (550-600 °C, 3-4 h). The resulting powdered sample of SAPO-11 with a crystal size of 80–100 nm is moistened with a 5% nitric acid solution, intensively mixed in a mixer to obtain a homogeneous mass, the mixture is formed using an extruder into granules with a diameter of 1.4–1.5 mm and a length of 2–3 mm, dried (100°C, 24 h), and calcined (600°C, 6 h).After calcination, the granules are crushed to a fraction of 0.25–0.5 mm and impregnated with an aqueous solution of hexachloroplatinic acid, dried (100 °C, 24 h) and activated (400 °C, 5 h) in a stream of hydrogen (30 ml / min).

[0034] The hydroisomerization process is carried out in a stainless steel flow reactor (inner diameter 16 mm) at 3.0 MPa, 280–350 °C, hydrogen / feedstock ratio of 800 nm 3 / m 3 , and the feed rate of raw materials is 2.0 h -1 .

[0035] Diesel fuel hydroisomerization is carried out according to the following procedure: a sample of Pt / SAPO-11 catalyst mixed with inert silicon carbide is loaded into a stainless steel tubular reactor, heated to a predetermined temperature, and the feedstock is added. The composition and quantity of the gas at the unit outlet are measured hourly. The products are analyzed by gas-liquid chromatography (GLC) on a Chromatec-Crystal 5000 chromatograph equipped with an Agilent HP-1 glass capillary column (50 m × 0.2 mm). The key performance properties of the obtained diesel fractions are determined using standard methods: cloud point (CP, ASTM D2500) and pour point (PP, ASTM D97 / D5949) on a Lintel Crystal-21 analyzer, maximum filterability point (MP, ASTM D6371) on a Lintel PTF-20 device, open crucible flash point (ASTM D92) on a Lintel ATVO-20 apparatus, and cetane number (ASTM D613) on a CFR unit.

[0036] The proposed method, compared with the prototype, provides the following advantages:

[0037] 1. Allows to obtain arctic diesel fuel with a yield of 98.3% with improved low-temperature properties (TP = -43°C, TPT =

[0038] -62°C, PTF = -50°C).

[0039] 2. The use of binder-free granulated nanocrystalline molecular sieve SAPO-11 with a crystal size of 80–100 nm improves the access of reagents to active sites and minimizes side reactions (hydrocracking, coke formation).

[0040] The proposed method is illustrated by the following examples.

[0041] Example 1.

[0042] The catalytic hydroisomerization process of diesel fuel is carried out in a high-pressure flow-through unit with a fixed catalyst bed. A 10 cm3 stainless steel tubular reactor (internal diameter 16 mm) is loaded 3 catalyst (fraction 0.18–0.25 mm), diluted with 15 cm 3inert quartz to ensure isothermal conditions. Tests are conducted at 3.0 MPa, 340°C, and a liquid feed rate of 2.0 h -1 and a hydrogen / raw material ratio of 800 nm 3 / m 3 The reaction products were analyzed by gas-liquid chromatography using a Chromatec-Crystal 5000 chromatograph equipped with a thermal conductivity detector and an Agilent HP-1 glass capillary column (50 m × 0.2 mm). The analysis mode was temperature-programmed with a heating rate of 8°C / min.

[0043] The yield of the target fraction with boiling ranges of 180-360 °C is 98.3%. The cloud point (CP) is -43 °C, the limiting filter plugging point (LFPP) is -50 °C, and the pour point (PLP) is -62 °C.

[0044] Examples 2-5. Similar to example 1. The results are shown in Table 1.

[0045] Table 1 – Hydroisomerization of diesel fuel fraction with Tb = 180-360 °C in the presence of granulated binder-free nanocrystalline molecular sieve Pt / SAPO-11 Example T, °C Exit, % Low-temperature properties, °C TP, °C PTF, °C TPT, °C 1 340 98.3 -43 -50 -62 2 280 99.9 -16 -23 -27 3 300 98.8 -23 -28 -32 4 320 98.5 -31 -36 -42 5 350 96.1 -44 -51 -63 Prototype* 340 92.0 -38 Not a decree. -42

[0046] * Yakovenko, RE, Agliullin, MR, Zubkov, IN et al. Diesel Fraction Isodewaxing in the Presence of Granular Platinum-Containing SAPO-11 and SAPO-41 Molecular Sieves. Catal. Ind. 2024, 16, 178–186

[0047] Table 2 shows the performance properties of fuels obtained at 340°C

[0048] Table 2 - Performance properties of diesel fuel obtained after hydroisomerization on Pt / SAPO-11 catalyst at 340°C Name of the indicator Initial diesel fraction Hydroisomerization product Cetane number 53 51 Kinematic viscosity, mm2 / s 2,728 2,572 Flash point in open crucible, °C 56 54 Density at 15 °C, kg / m3 835 828 Filter plugging point (FPP), °C - 5 -50 Cloud point (CP), °C 0 - 43 Pour point (PP), °C -10 -61

Claims

1. A method for hydroisomerization of diesel fuel to improve its low-temperature properties, including carrying out the process in the presence of a granulated catalyst based on platinum-containing - 0.5% wt. Pt silicoaluminophosphate molecular sieve SAPO-11, at a pressure of 3.0 MPa, a space velocity of feedstock of 2.0 h -1 and a hydrogen / raw material ratio of 800 nm³ / m³, characterized in that granulated, binder-free nanocrystalline silicoaluminophosphate SAPO-11 with a crystal size of 80-100 nm is used as a catalyst, while the hydroisomerization process is carried out at a temperature of 280-350°C.

2. The method according to claim 1, characterized in that the granulated SAPO-11 catalyst without binders is obtained by preparing a reaction gel of the composition 1.0 Al₂O₃⋅1.0 P₂O₅⋅0.1 SiO₂⋅1.0 DIPA⋅20 H₂O; subsequent holding of the gel at 90°C for 24 hours; hydrothermal synthesis of powdered SAPO-11 at 200°C for 24 hours; washing and centrifuging; drying at 100°C for 48 hours, then calcining at 550-600°C for 3-4 hours; moistening the obtained powdered SAPO-11 with a 5% nitric acid solution; intensively mixing the mixture in a mixer to obtain a homogeneous mass; molding the mixture using an extruder into granules with a diameter of 1.4-1.5 mm and a length of 2-3 mm; drying the granules at 100°C for 24 hours, calcining at 600°C for 6 hours; grinding the granules to a fraction of 0.25-0.5 mm and impregnation with an aqueous solution of hexachloroplatinic acid; drying at 100°C for 24 hours, and activation at 400°C for 5 hours in a stream of hydrogen (30 ml / min).

3. The method according to paragraph 1, characterized in that the hydroisomerization process is carried out at a temperature of 340°C, ensuring a diesel fraction yield of 98.3% with a cloud point of minus 43°C, a maximum filterability temperature of minus 50°C, and a pour point of minus 62°C.