ТЕРМИЧЕСКАЯ ПЕРЕРАБОТКА ГОРЮЧЕГО СЛАНЦА И ЕГО СМЕСИ С МАЗУТОМ ДЛЯ ПОЛУЧЕНИЯ КОМПОНЕНТОВ МОТОРНЫХ ТОПЛИВ

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Introduction

In present-day conditions and in perspective, due to limited oil reserves (not more than 90 billion tons) and many times more significant oil shale reserves in the world, including Estonia, Russia and Kazakhstan, the issues of their chemical processing are still relevant [1-3]. Similar studies were carried out in Russia with respect to the Gdov and Volga oil shales [3-4]. The studies were conducted using high-ash oil shale under pressure up to 30 MPa, which is not very acceptable from the technical and economic points of view (increased erosion and wear of equipment, high price of the target products, etc.).

The organic mass of the shale self-associated multimer, by analogy with the multimer of low metamorphosed coals [5], is represented, apparently, by chemically weakly bound due to electron-donor-acceptor interactions (EDA interactions) associates, the main amount (up to 80%) of which easily passes into low-molecular liquid products under short-term exposure to a temperature of 350 380°C. The degradation of these compounds into distillate products under hydrogen pressure in the presence of catalysts proceeds at high rates, since the main type of chemical bonds in shale associates are oxygen-containing and saturated hydrocarbon bonds [6].

According to [7-9], the main amount of carbon in shale associates is in naphthenic cycles (50-75%) and paraffin chains (6-31%), and the share of carbon in aromatic cycles is 18-19%. Oxygen in OMOS is confined mainly to phenolic esters (up to 55%), carboxyl groups of phenolic character account for up to 30% of oxygen, carbonyl groups up to 16%. The organic mass of oil shale contains a considerable amount of hydrogen - more than 9%, which predetermines low hydrogen consumption during hydrogenation compared to coal hydrogenation (hydrogen content 5-6%) and more favorable economic indicators of processing.

Organic mass of oil shale can be used as additives (10-20%) in the hydrogenation of coal and heavy oil residues (HOR) to initiate its destruction due to the higher reactivity of OMOS [10]. This direction has recently attracted the attention of researchers in Germany, Russia, USA, Japan and other countries [10-12].

 

Experimental part

This article presents the results of research on hydrogenation of Kenderlyk oil shale and a mixture of oil shale and fuel oil to obtain components of motor fuels, assessment of the status and prospects of application of the method of hydrogenation under low hydrogen pressure for this purpose.

Samples of oil shale from the Kenderlyk oilfield were used as feedstock for hydrogenation.

The shale concentrates had a particle size of less than 0.1-0.2 mm and contained (wt.%): W^a-1.2-1.3; A^d-18-22 (including carbon dioxide 2.4-2.5); S^d-1.7-1.8. The elemental composition of the samples was as follows (% per daf): C-74.2-74.7; H-8.9-9.0; S-1.2-1.4; N-0.4-0.5; O-14.5-15.0. The heat of combustion of the oil shale O^daf was 31.5-33.4 kJ/kg. The composition of the mineral part, %: SiO₂-58.2; Al₂O₃+TiO₃-17.2; Fe₂O₃-7.3; CaO-2.3; MgO-1.0; SO₃-3.4; Na₂O+K₂O-0.3.

An oil shale paste consisting of 40 wt.% oil shale and 60 wt.% liquid oil shale product with a boiling point above 400-440⁰C obtained from the process itself and from pyrolysis of the liquefaction residue, was subjected to hydrogenation. The paste was added with 0.5-3.0 wt.% of catalysts, represented by appropriate polymetallic ores containing Fe, Ni, Ti.

The hydrogenation was carried out in a 2 L rotary autoclave and on a bench flow unit with a reactor volume of 0.8 L, and the processing of sludge (oil shale liquefaction residue) was carried out by pyrolysis in a flow unit with a moving downward layer of solid coolant.

 

RESULTS AND DISCUSSION

• Hydrogenation of oil shale

Experiments in the autoclave showed that 82-84% conversion of OMOS into liquid products and gas is achieved at the temperature of 410°C, pressure of 8 MPa for 15 min in the presence of iron-containing catalysts. Temperature has a significant influence on the degree of OMOS liquefaction and yield of liquid and gaseous products (Table 1). At temperature 420-440°С there is an increase in gas formation from 10.3 to 12.1 wt.% and hydrogen consumption from 0.8 to 1.5 wt.% as a result of degradation of fractions with boiling point above 320°С, the content of which decreases in hydrogenysate from 50 to 27.2 wt.%, respectively, and the content of gasoline and diesel fuel fractions increases. A similar effect on the process has an increase in the duration of the reaction up to 30-45 minutes.

 

Table 1 - Influence of temperature on the results of hydrogenation of Kenderlyk oil shale (conditions: pressure - 8 MPa, τ = 15 minutes, catalyst - a mixture of water-soluble salts of two and trivalent Fe, autoclave).

 

Indicator	Temperature, 0C
	410	420	440
1. Degree of OMOS transformation, wt. % 2. Hydrogen for reaction, wt. % 3. Yield of liquid products, wt. %: total with boiling point up to 320°C with boiling point above 320°C 4. Gas, wt. % 5. Water, wt. % 6. Coke on mineral part of oil shale, wt. %	83.2 0.8   50.3 27.2 23.1 10.3 7.6 2.5	84.5 1.2   49.7 28.4 21.3 10.4 7.8 2.9	82.2 1.5   46.2 29.5 16.7 12.1 8.0 3.6

 

The influence of pressure on the process of hydrogenolysis of oil shale was studied at temperature of 420⁰C and pressure within the interval from 4.0 to 10.0 MPa (Table 2⁾.

 

Table 2 - Characteristics of hydrogenolysis of Kenderlyk oil shale depending on the process pressure (Conditions: ratio of oil shale:paste-forming agent 1:1.5; temperature-420⁰C; experiment duration-15 min; catalyst-mixture of water-soluble salts of two and trivalent Fe).

 

Process parameters	Hydrogen pressure in the reactor volume, MPa
	4.0	6.0	8.0	9.0	10.0
Degree of OMOS transformation, wt.%	64.1	76.3	83.2	84.1	83.1
Hydrogen for reaction, wt.%	0.4	0.6	0.8	1.1	1.0
Yield of liquid products, wt.%	40.2	47.1	50.3	50.3	49.9
With boiling point up to 3200C	18.4	19.3	27.2	27.4	26.9
Residue with boiling point above 3200C	21.8	27.8	23.1	22.9	23.0
Gas, wt.%	6.8	8.9	10.3	11.0	10.5
Water, wt.%	5.7	6.8	7.6	7.8	7.8
Coke on mineral part, wt.%	1.8	2.1	2.5	2.5	2.5

 

With the increase of hydrogen pressure in the range from 4.0 to 8.0 MPa the degree of transformation of organic mass of oil shale and the amount of hydrogen involved in the reaction increases by almost 20%, the yield of liquid products increases from 40.2 to 50.3 wt.%, gas from 6.8 to 10.3 wt.%, water from 5.7 wt.% to 7.6 wt.%, gas from 6.8 to 10.3 wt.%, water from 5.7 wt.% to 7.6 wt.%, i.e. the process of hydrogenolysis of Kenderlyk oil shale is intensified, the content of gasoline and diesel fuel increases. Hydrogen pressure above 8 MPa has no significant effect on the process parameters.

Gasoline fractions with boiling point up to 180°С contain 1.0-1.5% phenols, 3.5% neutral oxygen compounds, 35-37% unsaturated, 15-16% aromatic and 44-45% paraffinonaphthenic hydrocarbons, as well as impurities of organic acids and pyridine bases with sulfur content of 0.6-0.75% (Table 3).

Fractions of diesel fuel with boiling point of 180 320°C contain up to 9 % of phenols C_6-C₈, including ~3% of phenol, cresols and xylenols; 10% of neutral oxygen compounds; 20-25% of aromatic and 30-32% of unsaturated hydrocarbons; impurities (less than 1.0%) of organic acids and pyridine bases. These fractions can be used for separation of chemical products, and after hydrogenation purification - as components of motor fuels. Process water is enriched with water-soluble phenols (including two- and three-atom phenols) and are raw materials for their extraction (Table 3).

 

Table 3 - Characteristics of distillate products (Conditions: ratio of oil shale:paste-former 1:1.5; pressure - 8 MPa; temperature - 420⁰C; experiment duration - 15 minutes; catalyst-mixture of water-soluble salts of two and trivalent Fe)

 

Indicator	Fractions with boiling point, 0C
	up to 180	180-320
Content, vol. %: phenols neutral oxygen compounds pyridine compounds	1.0-1.5 35-37 0.6-0.75	up to 9 10 less than 1.0
Hydrocarbon group composition, wt. %: unsaturated aromatic paraffinonaphthenic	35-37 15-16 44-45	30-32 20-25 -

 

Due to the fact that oil shale liquefaction products contain mineral components of ash and catalyst, the residue after separation of part of liquid products by centrifugation was subjected to pyrolysis at 440°C on a solid moving heat carrier. The resulting coke was used for heating the heat carrier. The yield of liquid products was 91-93%, the rest was gas, water and coke.

 

2) Thermocatalytic destruction of Kenderlyk oil shale and fuel oil

In recent years, the world market of raw materials has seen relatively high prices for major energy carriers and, above all, for oil. In this connection, the problem of improvement of existing and development of new promising technologies of advanced oil refining is still acute for the domestic oil industry.

It is well known that improvement of heavy oil residue refining methods helps to improve a number of environmental indicators, reduce the burden on the oil industry and save resources. For domestic refineries, deep oil refining complexes developed by such leading world engineering companies as UOP, Shell, Axens, Texaco and others remain extremely expensive projects even if the state has a significant stabilization fund, so the development and implementation of relatively inexpensive domestic processes that meet modern requirements of the industry are still relevant [13-14].

We have developed a process of thermochemical processing of heavy oil residues of native and destructive origin (fuel oil, tar, heavy pyrolysis resins) in the presence of activating additives (Kenderlyk oil shale), which has no analogues abroad and is carried out at a pressure of 0.5-2 MPa, temperature 400-430°C without hydrogen [15-22].

It was found that the organic and mineral parts of oil shale have an activating effect on the thermal transformation of heavy petroleum products. Thus, in the temperature range of 370-420°C during the destruction of the organic mass of oil shale (kerogen) various compounds with hydrogen donor properties are formed. These compounds actively promote hydrogenation reactions of unsaturated compounds formed during cracking of oil residues (fuel oil) and prevent intensive coke formation.

On the other hand, the mineral part of oil shale containing aluminosilicates, oxides of iron, molybdenum, cobalt, nickel and other catalytically active metals also contributes to the intensification of cracking and hydrogenation reactions. When used as activating additives oil shale in the amount of 5-25% and containing 15-70% of kerogen can regulate the process of thermal cracking of oil residues, carried out in the temperature range of 390-450°C, with a yield of light distillates up to 70% without pelletization and coking, not exceeding 5%.

The process of thermal destruction of oil residues in the presence of organomineral activators (oil shale) proceeds by the carbonium-ion mechanism, and the mineral part of oil shale plays the role of a coke carrier and to some extent has a catalytic effect, so we decided to intensify the process through the use of zeolites, which are solid Bransted acids.

As raw materials we used straight-run fuel oil of Pavlodar oil refinery (Table 4).

 

 

Table 4 - Physical and chemical properties of fuel oils

 

Fuel oil type	Density, kg/m3	Fractional composition, vol. %			Conditional viscosity at 80 °C, VU	Content, wt. %
		Initial boiling point,  °C	Initial boiling point, 360 °C	boils out before reaching 450°C		waters	asphalt tenens	sulphur	Mechanical impurities
Straight fuel oil from Pavlodar refinery	937	252	12.4	45.8	10.5	0	1.9	2.2	0

 

Natural zeolite of clinoptilolite structure of Shankanai deposit of Kazakhstan (W^a- 4.3%, A^d- 81.2%, SiO₂/Al₂O₃=7,5, density - 2500 kg/m³, clinoptilolite content 65%, SiO₂- 67.5%, A₂O₃-15.8%, Fe₂O₃-4.6%) was studied as a catalyst.

In order to optimize the conditions of fuel oil thermolysis, a study was carried out with the use of oil shale from the Kenderlyk deposit as an activating additive. The influence of oil shale concentration, temperature and reaction time on the yield of products of thermocatalytic processing of fuel oil and oil shale was studied (Table 5).

The results of the study of the influence of oil shale concentration on thermal cracking of fuel oil show that the increase in oil shale concentration leads to an increase in the yield of gasoline fraction (from 6.7 to 17.2 wt.%) and diesel fraction (from 22.3 to 41.8 wt.%), and the yield of middle distillates decreases from 60.1 to 32.3 wt.%. It should be noted that coke yield at thermochemical processing of fuel oil without shale is noticeably higher than at optimal concentrations in the feedstock. Increase of oil shale concentration leads to increase of light distillates yield from 29.4 to 59.0 wt.%.

From the data of Table 5 it follows that dependence of fuel oil the yield of light distillate fractions on the temperature of thermal cracking is 45.3-54.8 wt.%. At that, the yield of gasoline fraction with boiling point up to 180⁰C increases from 8.2 wt.% at 300⁰C to 25.9 wt.% at 435⁰C, and the yield of diesel fraction with boiling point of 180-300⁰C is 37.2-28.9 wt.%, respectively. At the temperature above 360⁰C, the coke formation is 3.0-9.0 wt.%.

The results of influence of thermal cracking time on the main results of the process (Table 5) show that change of the reaction time from 10 to 60 minutes leads to increased yield of gasoline fraction (from 7.5 to 14.2 wt.%) and diesel fraction (from 22,6 to 42,0 wt.%), and the decreased yield of middle distillates from 67.5 to 38.0 wt.%.

Judging by the yield of distillate fractions, the optimal reaction conditions can be considered as: temperature 415-425°C, processing time 60 min, and the amount of activating additive (oil shale) 10-12 wt.%. Thus the total yield of distillate fractions reaches 56-59 wt. %.

 

 

Table 5 - Influence of oil shale concentration, temperature and reaction time on yield (wt. %) of products of thermocatalytic processing of fuel oil and oil shale.

Thermolysis product	Amount of oil shale, wt. % (415°C, 60 min)						Temperature, °C (10% oil shale, 60 min)					Thermolysis time, min (415°C, 10% oil shale)
	0	3	5	8	10	12	300	400	415	425	435	10	20	30	45	60
Gas	8.1	4.9	5.2	5.4	5.8	7.8	3.0	4.5	5.8	7.4	9.0	2.0	2.8	3.7	5.2	5.8
Fraction <180°C	15.2	6.7	7.4	11.6	14.2	17.2	8.2	12.3	14.2	18.8	25.9	7.5	8.9	10.5	13.5	14.2
Fraction 180-360°C	14.2	28.3	29.9	36.2	42.0	41.8	37.1	38.9	42.0	36.2	28.9	22.6	28.3	33.1	36.9	42.0
Fraction > 360°C	62.5	60.1	57.5	46.8	38.0	32.3	51.7	44.5	38.0	38.0	36.2	67.5	60.0	52.7	44.4	38.0
Coke on solid phase	8.1	4.9	5.2	5.4	5.8	8.7	3.0	4.3	5.8	7.0	9.0	2.4	2.8	3.7	5.2	5.8
Total distillate yield	29.4	35.0	37.3	47.8	56.2	59.0	45.3	51.2	56.2	55.0	54.8	30.1	37.2	43.6	50.4	56.2
Note - No formation of pellets was observed

 

 

Conclusion

Thus, the paper shows the possibility of obtaining synthetic oil from oil shale by means of hydrogenation processing. In this case it is possible to extract more than 90% of the organic matter of oil shale. According to the obtained results, increasing the temperature of oil shale hydrogenation from 410 to 440⁰C at a pressure of 8.0 MPa leads to increase in gas formation from 10.3 to 12.1 wt.% and hydrogen consumption from 0.8 to 1.5 wt. %, and connection of gasoline and diesel fuel fractions.

Increasing the hydrogen pressure from 4.0 to 8.0 MPa increases the degree of conversion of organic matter of oil shale by 20% and increases the yield of liquid products (40.2 to 50.3 wt. %), gas (6.8 to 10.3 wt. %), water (5.7 to 7.6 wt. %). Hydrogen pressure above 8.0 MPa has no effect on the process parameters.

The results of the experimental studies unambiguously testify to the undoubted advantages of the new process of thermal cracking of fuel oil in a mixture with oil shale over industrial thermal cracking, as in case of one-stage processing under relatively mild conditions (8 MPa, 425⁰C, volumetric feed rate 1.0 h^-1) a deep destruction of fuel oil is achieved (yield of gasoline fraction with boiling point up to 180⁰C is 17.2 wt. %; middle distillates with boiling point of 180-360 ⁰C - 41.8 wt.; feedstock for catalytic cracking with boiling point above 360 ⁰C - 51,7 wt. %). The formed coke-like products and V and Ni containing in the feedstock are deposited on the mineral part of the oil shale and removed from the reaction zone with the liquid products of the process.

Об авторах

Indira Dzheldybaeva

Казахский национальный университет имени аль-Фараби

Автор, ответственный за переписку.
Email: indiko_87@mail.ru
ORCID iD: 0000-0002-1524-4046

PhD, Ведущий научный сотрудник, НИИ Новых химических технологий и материалов

Казахстан

Жаксынтай Каирбекович Каирбеков

Казахский национальный университет имени аль-Фараби

Email: zh_kairbekov@mail.ru
ORCID iD: 0000-0002-0255-2330
Scopus Author ID: 5591070520
ResearcherId: A-5389-2015

докт. хим. наук, профессор

Казахстан, Алматы

Маншук Зейнуллаевна Есеналиева

Казахский национальный университет имени аль-Фараби

Email: esenalieva@mail.ru
ORCID iD: 0000-0002-0817-2048
Scopus Author ID: 6507284187

канд. хим. наук, доцент

Казахстан, Алматы

Раушан Гайсиевна Сармурзина

KAZENERGY

Email: sarmurzina_r@mail.ru
ORCID iD: 0000-0002-9572-9712

докт. хим. наук, профессор

Казахстан, г. Астана

Салтанат Маликовна Суймбаева

Казахский национальный университет имени аль-Фараби

Email: saltanat_suimbayeva@mail.ru
ORCID iD: 0000-0003-3990-4974
Scopus Author ID: 57201691853
ResearcherId: EBK-0532-2022
Казахстан, Алматы

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