RU2652991C1 - Method of hydroameliorative triglycerides of fatty acids in the mixture with oil fractions - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to methods for joint hydroblasting of fatty acid triglycerides and straight-run diesel fraction on sulfide catalysts in order to obtain low-sulfur hydrocarbon fractions and it can be used in the petroleum industry. Resulting hydrocarbon fractions can be directly used as diesel fuel, or can be further processed, if necessary, during the isomerization process in order to improve the low temperature properties. Method for hydrotreating triglycerides of fatty acids (TLC) in a mixture with petroleum fractions at an elevated temperature and pressure of hydrogen on sulfide catalysts MoS₂/Al₂O₃ and NiMo/Al₂O₃ in two stages is proposed, where in the first stage hydrotreating the straight-run diesel fraction in the presence of sulphide NiMo/Al₂O₃ catalyst, then the obtained mixture of hydrocarbons, hydrogen and hydrogen sulfide is mixed with fatty acid triglycerides and a hydrodeoxygenation reaction is carried out in the presence of a sulfide catalyst MoS₂/Al₂O₃.

EFFECT: high efficiency of the process of joint hydrotreating of diesel fractions and triglycerides of fatty acids.

1 cl, 1 tbl, 4 ex

Description

The invention relates to methods for joint hydrofining of fatty acid triglycerides and straight-run diesel fraction on sulfide catalysts in order to obtain low-sulfur hydrocarbon fractions. The resulting hydrocarbon fractions can be directly used as diesel fuel or, if necessary, can be further processed in the isomerization process in order to improve low-temperature properties.

In recent decades, one of the trends has been the use of renewable resources for the production of environmentally friendly motor fuels, which is caused, on the one hand, by a decrease in reserves and a deterioration in the quality of hydrocarbons, and on the other hand, by the need to reduce greenhouse gas emissions, mainly carbon dioxide, to slow down global temperature rise and climate change. Hydrofinishing of triglycerides of fatty acids (TFA) is one of the most promising approaches, since the result is a mixture of alkanes. This product does not contain oxygen, is characterized by a high cetane index and stability, is mixed with traditional diesel fuel in any proportions, which allows you to use the existing infrastructure for its transportation and storage and does not require the adaptation of automobile engines. A wide range of non-edible vegetable oils (canola, camelina, palm, etc.), used edible oils, animal fats, tall oils, etc. can be used as raw materials. [J.K. Satyarthi, T. Chiranjeevi, D.T. Gokak, P.S. Viswanathan, An overview of catalytic conversion of vegetable oils / fats into middle distillates, Catalysis Science & Technology, 3 (2013) 70-80; M. Al-Sabawi, J.W. Chen, Hydroprocessing of Biomass-Derived Oils and Their Blends with Petroleum Feedstocks: A Review, Energy & Fuels, 26 (2012) 5373-5399].

In industrial processes, conventional sulfide CoMo / Al ₂ O ₃ and NiMo / Al ₂ O ₃ hydrotreating catalysts are used to process fatty acid triglycerides [D. Kubicka, V. Tukac, Hydrotreating of Triglyceride-Based Feedstocks in Refineries, Advances in Chemical Engineering, V. 42, 2013, Pages 141-194.]. Fatty acid triglycerides, unlike petroleum feedstocks, do not contain sulfur, therefore, to maintain the catalysts in the active sulfide state, it is necessary to constantly add a sulfurizing agent, most often dimethyl disulfide, to the reaction mixture [Kubicka, D., Horacek J., De-activation of HDS catalysts in deoxygenation of vegetable oils // Applied Catalysis A, 394 (2011) 9-17.].

Known methods for hydrofining TFA on sulfide catalysts in a mixture with petroleum distillates, as described in patents (EP 2428548, C10G 3/00, 03/14/12) and (US 9556387, C10G 49/04, 01/31/2017). The hydrofining of TFA in a mixture with petroleum fractions allows the use of sulfur-containing compounds of petroleum distillates, which, when reacted with hydrogen, are converted to hydrogen sulfide to maintain the active component in a sulfide state. At the same time, the joint processing of triglycerides in a mixture with petroleum fractions leads to an improvement in the consumer properties of motor fuels: an increase in the cetane number and a decrease in the density and content of nitrogen and aromatic compounds.

However, the reactions of hydrogenation and hydrolysis of triglycerides, hydrodeoxygenation of oxygen-containing compounds proceed with the release of a large amount of heat, which causes local overheating in the frontal layer of the reactor and leads to the formation of carbon deposits and deactivation of the catalyst. To improve temperature control in the reactor during the processing of mixtures of TFA with oil fractions, it is proposed to use a low-active sulfide catalyst in the first layer, which contains only MoS ₂ phase (not promoted with Co or Ni), and in the second layer - traditional NiMo, CoMo or NiW systems deposited on alumina, silica, titanium dioxide or a combination thereof (RU 2495 082, C10G 3/00, 10/10/2013). Stage hydrodeoxygenation is carried out at a temperature of 50-350 ° C, a hydrogen pressure of 1-200 bar, a space velocity of 0.1-10 h ^-1, and the subsequent hydrotreating step - at temperatures 200-500 ° C and a hydrogen pressure up to 200 bar (a the example shows a space velocity of 0.95 hour ^-1 ). To improve low-temperature properties, if necessary, an isomerization step is additionally used on bifunctional catalysts containing noble metals or sulfide nanoparticles deposited on a zeolite-containing carrier. According to the text of the patent, the MoS ₂ phase-based catalyst, due to the lower activity compared to NiMo CoMo catalysts in the hydrodeoxygenation reaction, provides a gradual conversion of oxygen-containing raw materials and avoids local overheating, thereby reducing deactivation. The disadvantage of this method is the formation of large amounts of water in the first stage, which can reduce the effectiveness of the hydrotreating and hydroisomerization catalysts in the subsequent stages due to the inhibitory effect, and also lead to irreversible deactivation and reduce the life of the catalysts as a result of prolonged contact with water vapor at elevated temperatures. In addition, the authors allow the incomplete conversion of TFA in the first catalyst bed, which will lead to the formation of carbon oxides, which are also inhibitors of hydrodesulfurization and hydroisomerization reactions, when TFA comes in contact with traditional NiMo and CoMo hydrotreating catalysts.

It is well known that TFA hydrodeoxygenation reactions in the presence of traditional NiMo and CoMo catalysts proceed along two routes: by removing oxygen in the form of water or by cleaving CO / CO ₂ molecules [Furimsky E., Hydroprocessing challenges in biofuels production // Catalysis Today, 217 ( 2013) 13-56]. The carbon oxides formed as a result of the reaction can be hydrogenated, which leads to an additional consumption of hydrogen, and carbon dioxide in the presence of water causes corrosion of the equipment. The removal of gases (carbon monoxide and methane) generated during the hydrodeoxygenation of triglycerides requires additional costs for the implementation of technologies for purification of circulating hydrogen. Otherwise, the accumulation of methane and CO in the circulating gas will lead to a decrease in the partial pressure of hydrogen, the purity of which, as you know, is one of the critical parameters for the production of environmentally friendly motor fuels (<10 ppm sulfur) from oil fractions [A. Stanislaus, A. Marafi, M.S. Rana Recent advances in the science and technology of ultra-low sulfur diesel (ULSD) production // Catalysis Today. - 2010. - V. 153. - P. 1-68].

It is known that the conversion of oxygen-containing compounds on a supported or bulk MoS ₂ catalyst proceeds along the direct hydrodeoxygenation route while maintaining the number of carbon atoms, i.e. without the formation of carbon oxides [MR de Brimont, S. Dupont, A. Daudin, S. Geantet, P. Raybaud, Deoxygenation mechanisms on Ni-promoted MoS ₂ bulk catalysts: A combined experimental and theoretical study, Journal of Catalysis, 286 (2012 ) 153-164; D. Kubicka, L. Kaluza, Deoxygenation of vegetable oils over sulfided Ni, Mo and NiMo catalysts, Applied Catalysis A-General, 372 (2010) 199-208]. It turned out that TFA hydrodeoxygenation proceeds without the formation of carbon oxides in the presence of a MoS ₂ / Al ₂ O ₃ catalyst (US 8546626, B01J 21/02, 01/10/2013) or in the presence of a Ni-MoS ₂ / Al ₂ O ₃ catalyst with a controlled Ni ratio / Mo in the range of 0-0.095, preferably in the range of 0-0.03 (US 8552235, C07C 1/24, 08/10/2013).

Closest to the proposed technical solution is the application (US 2012/0216450, C10L 1/00, 08/30/2011), which describes a method of hydrofining oil distillates together with TFA, designed to produce hydrocarbon fractions with a sulfur content of less than 10 ppm (mg / kg ) The prototype method includes two stages: the first stage of hydrofining, in which a pre-prepared mixture of petroleum feedstocks with TFA together with hydrogen passes through a catalyst comprising at least one element from group VI B (mainly Mo) and may include one element from group VIII ( predominantly Ni) with a ratio of the listed elements 0-0.095, on which the hydrodeoxygenation of TFA occurs selectively without the formation of carbon oxides. In the second stage, the stream from the first stage passes through the NiMo / Al ₂ O ₃ hydrotreating catalyst (Ni / Mo-0.4), where the reactions of hydrodesulfurization, hydrodeazotization and hydrogenation of aromatic compounds occur. According to the invention, preferred for hydrofining is a mixture containing 70-99 wt. % oil distillates and 1-30 wt. % renewable raw materials, including animal and vegetable fats, as well as mixtures thereof; hydrodeoxygenation is recommended at a temperature of 120-450 ° C (preferably 180-310 ° C), a pressure of 1-10 MPa (preferably 1-6 MPa), a space velocity of 0.1-10 hour ^-1 (preferably 0.2-5 hours ^-1 ), the ratio of hydrogen / raw materials is 50-3000 Nm ³ / m ³ (preferably 150-1500 Nm ³ / m ³ ). Hydrotreated products obtained in the first step is carried out in the presence of NiMo / Al ₂ O ₃ catalyst at a temperature sulphide 250-450 ° C (preferably 300-400 ° C), a pressure of 0.5-30 MPa (preferably 1-25 MPa) a space velocity of 0.1-20 hour ^-1 (preferably 0.2-4 hour ^-1 ), the ratio of hydrogen / feed 50-2000 Nm ³ / m ³ .

The disadvantage of the above method is the presence of a large amount of water in the hydrodeoxygenation products entering the hydrotreatment stage, which can lead to irreversible deactivation and reduce the service life of the second stage catalysts as a result of prolonged contact with water vapor at elevated temperature. In addition, the hydrodeoxygenation of vegetable oils is accompanied by a significant consumption of hydrogen, which leads to a decrease in the partial pressure of hydrogen at the stage of hydrotreatment and a decrease in the activity of NiMo / Al ₂ O ₃ catalyst in the process of hydrodesulfurization. Another disadvantage of the proposed approach is the low activity of Mo / Al ₂ O ₃ catalyst hydrodeoxygenation reaction conversion of sulfur compounds, especially at low temperatures, its operation, which may lead to hydrogen sulfide deficiency required to maintain the catalyst in the sulfide state in frontal layer hydrodeoxygenation catalyst and to its gradual decontamination due to loss of sulfur. And, finally, during prolonged operation, the frontal layer of the catalyst can gradually become contaminated with Ni and Fe compounds that come with the feed, which will lead to the formation of nickel and iron sulfides active in decarbonylation and decarboxylation reactions and increase the formation of carbon oxides.

The technical task of this invention is to develop a more effective method for hydrofining triglycerides of fatty acids mixed with petroleum fractions into low-sulfur hydrocarbon fractions, which avoids the problems described above, including the formation of carbon oxides in the process of TFA hydrodeoxygenation.

The problem is solved by providing a method for hydroforming TFAs by using stratified catalyst loading and twin feed raw materials to the reactor (or reactors): the first layer is fed hydrogen and straight-run diesel fraction, where it is hydrotreating in the presence of sulphide Ni-MoS ₂ / Al ₂ O ₃ a catalyst obtained by any of the known methods; after that, the hydrotreated diesel fraction in a mixture with hydrogen and the resulting hydrogen sulfide enters the second layer (reactor) together with the TFA stream, where the selective hydrodeoxygenation of plant materials occurs in the presence of a MoS ₂ / Al ₂ O ₃ catalyst.

Distinctive features of the proposed method of hydrofining TFA in a mixture with oil fractions are:

1. The arrangement of the Ni-MoS ₂ / Al ₂ O ₃ hydrotreatment catalyst and the MoS ₂ / Al ₂ O ₃ hydrodeoxygenation catalyst.

2. The procedure for introducing the feedstock into the hydrotreating reactor: the diesel fraction enters the first layer (or reactor), which is subjected to hydrodesulfurization in the absence of oxygen-containing inhibitors on the Ni-MoS ₂ / Al ₂ O ₃ catalyst; and the TFA stream is fed into the second catalyst layer, where it is mixed with the stream from the first layer (reactor) and undergoes hydrodeoxygenation in the presence of MoS ₂ / Al ₂ O ₃ catalyst.

The method described above will improve the efficiency of hydrofining triglycerides of fatty acids in a mixture with petroleum fractions. In the proposed method, in contrast to the prototype, the hydrotreating catalyst is not exposed to water vapor and is operated under more favorable conditions (at a higher partial pressure of hydrogen and in the absence of water vapor). At the same time, hydrogen sulfide formed in the first stage (hydrotreating stage of petroleum feedstock) ensures that the active phase of the MoS ₂ / Al ₂ O ₃ catalyst is maintained in the sulfide state. The proposed sequence of arrangement of the layers of hydrotreating and hydrodeoxygenation catalysts and the order of introduction of the feedstock prevents the danger of increasing the selectivity of TFA conversion along the decarbonylation route in the presence of Ni, Fe sulfides that accumulate in the frontal layer of the catalyst during its operation.

- 134. Непромотированный катализатор Мо/Al₂O₃ готовили методом пропитки гранул алюмооксидного носителя водным раствором, содержащим рассчитанные количества оксида молибдена(VI), ортофосфорной Н₃РО₄ и лимонной кислоты С₆Н₈О₇×Н₂О. Для приготовления NiMo/Al₂O₃ катализатора в раствор предшественника активного компонента добавляли необходимое количество никеля(II) углекислого основного (водного) NiCO₃⋅Ni(OH)₂⋅xH₂O. Катализаторы использовали после сушки в потоке азота при комнатной температуре и в сушильном шкафу («Binder», Германия) при температуре (110±10)°С в течение 4 часов. Содержание активных компонентов определяли после прокаливания в муфеле при температуре 550°С в течение 4 ч, содержание активных компонентов в Мо/Al₂O₃ катализаторе составляет, мас. %: MoO₃ - 18,6; в NiMo/Al₂O₃, мас. %: МоО₃ - 18,1, NiO - 4,7.To illustrate the invention, the catalysts described in the method prepared below were used. A granular alumina support was obtained by mixing powders of aluminum oxide and hydroxide, followed by molding through a laboratory syringe with a die having a trefoil hole of 1.2 ± 0.1 mm in size. The formed granules were dried at a temperature of (110 ± 10) ° С in an oven (Binder, Germany) for 12 hours. The dried carrier granules were calcined in a flow reactor in a stream of nitrogen at a temperature of (550 ± 10) ° C for 4 hours. The texture characteristics of the obtained carrier: S _yd , m ² / g - 235; pore volume, cm ³ / g - 0.79; average pore diameter

- 134. An unpromoted Mo / Al ₂ O ₃ catalyst was prepared by impregnating the alumina carrier granules with an aqueous solution containing the calculated amounts of molybdenum (VI) oxide, phosphoric N ₃ PO ₄ and citric acid C ₆ H ₈ O ₇ × H ₂ O. For preparation The required amount of nickel (II) carbon dioxide basic (aqueous) NiCO ₃ ⋅ Ni (OH) ₂ ⋅ xH ₂ O was added to the solution of the active component precursor of NiMo / Al ₂ O ₃ catalyst. The catalysts were used after drying in a stream of nitrogen at room temperature and in a drying oven cabinet ("Binder", Germany) at a temperature (110 ± 10) ° С for 4 hours. The content of the active ingredients was determined after calcining in a muffle at 550 ° C for 4 hours, the content of active components in the Mo / Al ₂ O ₃ catalyst is, by weight. %: MoO ₃ - 18.6; in NiMo / Al ₂ O ₃ , wt. %: MoO ₃ - 18.1, NiO - 4.7.

Testing of the catalysts in the process of joint hydrofining of straight-run diesel fraction with PM was carried out on a 2-reactor pilot plant, the diameter of each reactor was 26 mm, and the length was 1300 mm. Raw materials were supplied using Gilson-305 liquid chromatographic pumps from tanks located on the balance, the consumption of raw materials was controlled by mass change. Hydrogen was dosed with automatic Bronkhorst dispensers, raw materials and hydrogen entered the reactor from top to bottom. The reactors are housed in tube furnaces with three independent heating zones, providing an isothermal zone in the central part of the reactor. Testing was carried out using granules of catalysts in the form of a trefoil with a diameter of 1.2 mm and a length of 4-6 mm. The required number of catalyst granules (4-6 mm long) was loaded into the reactor, diluting it with fine particles of silicon carbide (fraction 0.1-0.25 mm) in a volume ratio of 1: 4. In the study of a system similar to the prototype, 20 ml of MoS ₂ / Al ₂ O ₃ catalyst were placed in the first reactor, and 40 ml of Ni-MoS ₂ / Al ₂ O ₃ catalyst in the second reactor; tests were performed using a mixture of straight-run diesel fraction containing 30 wt. % rapeseed oil, which was mixed with hydrogen at the entrance to the first reactor.

Before the experiments, the catalysts were sulfidized by straight run diesel fraction (PDF) containing an additional 0.6 wt. % sulfur in the form of dimethyldisulfide (at a space velocity of 2 hours ^-1 , the ratio of hydrogen / raw materials - 300, hydrogen pressure - 3.5 MPa) in several stages: at a temperature of 240 ° C for 8 hours, at a temperature of 340 ° C for 6 hours, the rate of temperature increase between stages was 25 ° C per hour.

After sulfidation was completed, the catalyst was operated in the process of hydrotreating a straight-run diesel fraction for 3 days, after which the corresponding raw material was fed into the reactor. Testing of the catalysts was carried out under the conditions described in examples 1-4.

In the examples illustrating the invention, a Ni-MoS ₂ / Al ₂ O ₃ hydrotreating catalyst (40 ml) was placed in the first reactor, and a Hydrodeoxygenation catalyst (20 ml) in the second — MoS ₂ / Al ₂ O ₃ . The straight-run diesel fraction together with hydrogen was fed into the first reactor, and rapeseed oil into the second.

After the second reactor, the product enters the separator, where it is separated into a liquid and gas phase, the liquid phase is purged with nitrogen to remove the resulting hydrogen sulfide and ammonia. The resulting products are analyzed to determine the residual sulfur, oxygen and density. The total sulfur content (at a content of ≥50 μg / kg) was determined using a Lab-X 3500SCl energy dispersive X-ray fluorescence analyzer, the determination of trace amounts of nitrogen and sulfur was carried out using an ANTEK 9000NS sulfur / nitrogen analyzer in accordance with ASTM D 5762 and ASTM D 5453 respectively. The oxygen content was determined using a CHNSO elemental analyzer Vario EL Cube (Elementar Analysensysteme GmbH, Germany). The selectivity of the reaction along the decarbonylation route, calculated from the analysis of carbon oxides in the gas phase as the ratio of the amount of carbon oxides formed to the theoretically possible amount, does not exceed 3% in all experiments.

The essence of the invention is illustrated by the following examples, reflecting the dependence of the sulfur content in hydrocarbon fractions on the sequence of loading of the catalysts and process conditions. The test results are shown in table 1.

Example 1 According to the prototype

The catalytic properties of the system containing in the first reactor a sulfide MoS ₂ / Al ₂ O ₃ hydrodeoxygenation catalyst (20 ml), and in the second reactor, Ni-MoS ₂ / Al ₂ O ₃ (40 ml) hydrotreating catalyst, were studied during the joint hydrotreating of the mixture rapeseed oil and straight-run diesel fraction at a temperature of 340 ° C; hydrogen pressure - 4.0 MPa; the volume ratio of hydrogen / feed is 600 Nm ^{3 of} hydrogen / m ^{3 of} feedstock, the volumetric rate of feed (calculated as the ratio of the volume of the mixture to the volume of the catalyst) is 1.1 hour ^-1 . As a feedstock, a mixture containing 70 wt. % straight run diesel fraction and 30 wt. % rapeseed oil, with a sulfur content of 0.7 wt. %, oxygen content - 3.3 wt. %, Nitrogen content - 115 mg / kg Density - 0.866 g / cm ^3. This mixture is obtained by mixing straight-run diesel fraction and rapeseed oil, the properties of which are described in example 2.

The performance of the hydrofining process are shown in table 1.

Example 2

In the example according to the invention the two reactors are connected in series, the first reactor was placed Ni-MoS ₂ / Al ₂ O ₃ hydrotreating catalyst (40 ml), and the second - MoS ₂ / Al ₂ O ₃ catalyst hydrodeoxygenation (20 ml); straight run diesel fraction and hydrogen were fed into the first reactor, where hydrotreatment reactions proceeded. The mixture of hydrocarbons, hydrogen and hydrogen sulfide formed from the first reactor was mixed with rapeseed oil before entering the second reactor. The feed was supplied in such a quantity that the proportion of rapeseed oil in the feed was 30 wt. %, and the space velocity of the feed was equal to the space velocity used in the first example, 1.1 hour ^-1 . The hydrogen / feed ratio, calculated on the total amount of the diesel fraction and rapeseed oil, was 600 Nm ^{3 of} hydrogen / m ^{3 of} feedstock, the hydrogen pressure was 4.0 MPa. For testing the catalysts used straight run diesel fraction and rapeseed oil used to prepare the mixture of example 1. Straight run diesel fraction has the following characteristics: sulfur content - 1.03 wt. %, nitrogen content - 150 mg / kg, oxygen content - 680 mg / kg, density - 0.847 g / cm ³ . The total proportion of C ₁₈ acids (oleic, linoleic, linolenic and stearic) in the vegetable oil used in the work is 90.5% wt. %, oxygen content - 11.19 wt. %

The performance of the hydrofining process are shown in table 1.

Example 3

The method of joint hydrofining of diesel fractions and rapeseed oil according to example 2, characterized in that the ratio of hydrogen / raw materials, calculated on the total amount of diesel fraction and rapeseed oil, was 510 Nm ³ hydrogen / m ³ raw materials.

The performance of the hydrofining process are shown in table 1.

Example 4

Method joint hydrotreating of diesel fractions and rapeseed oil of Example 2, characterized in that the volumetric hourly space velocity of 1.25 h ^-1.

The performance of the hydrofining process are shown in table 1

As can be seen from the presented examples, the process of joint hydrofining of straight-run diesel fraction with triglycerides of fatty acids by the proposed method (example 2) provides a lower sulfur content in products compared to the prototype (example 1) under the same experimental conditions - at a temperature 340 ° C; hydrogen pressure - 4.0 MPa; the volumetric ratio of hydrogen / raw materials is 600 Nm ^{3 of} hydrogen / m ^{3 of} raw materials, the volumetric rate of raw materials is 1.1 hour ^-1 . In the example according to the prototype, the residual sulfur content is 10.9 ± 0.5 mg / kg, while the proposed method allows for deep hydrotreating with a lower hydrogen / feed ratio (example 3) and at a higher space velocity (example 4).

Thus, the proposed method allows to solve the problem of increasing the efficiency of the joint hydroforming fatty acid triglycerides and low-sulfur petroleum fractions in the hydrocarbon fraction using a Ni-MoS ₂ / Al ₂ O ₃ hydrotreating catalyst and MoS ₂ / Al ₂ O ₃ hydrodeoxygenation catalyst.

Claims (2)

1. The method of hydrofining triglycerides of fatty acids (TFA) in a mixture with oil fractions at elevated temperature and hydrogen pressure on sulfide catalysts MoS ₂ / Al ₂ O ₃ and NiMo / Al ₂ O ₃ in two stages, characterized in that the first stage is carried out hydrotreating a straight-run diesel fraction in the presence of a sulfide NiMo / Al ₂ O ₃ catalyst, then the resulting mixture of hydrocarbons, hydrogen and hydrogen sulfide is mixed with fatty acid triglycerides and a hydrodeoxygenation reaction is carried out in the presence of a MoS ₂ / Al ₂ O ₃ sulfide catalyst. 2. A method according to claim 1, characterized in that the feed hydrotreating is carried out at a temperature of 340 ° C, a hydrogen pressure of 4.0 MPa, volumetric feed flow rate -. 1.1-1.25 h ^-1, the total volume ratio of hydrogen / feed - 510-600 Nm ³ / m ³ .