CS217164B1 - A method of complex processing of pyrolysis oils - Google Patents

Abstract

The invention relates to a complex processing of pyrolysis oils as heavy and light pyrolysis oil, in which heavy pyrolysis oil with a distillation range of 245 to 500 °C, optionally in a mixture with other hydrocarbon raw materials in a similar distillation range, is subjected to partial oxidation with a mixture of oxygen and water vapor, and the resulting hydrogen, or/and hydrogen produced by conversion of the partial oxidation product, is used to hydrogenate light pyrolysis oil with a distillation range of 120 to 360 °C into components of motor fuels. Hydrogenation takes place on carrier catalysts containing metal oxides of groups IV and VIII of the periodic table at a pressure of 3 to 20 MPa, a temperature of 200 to 430 °C and a vol. rate of 0.5 to 5 h_1.

Description

The invention relates to the complex processing of heavy and light pyrolysis oil.

The term pyrolysis oils refers to heavy liquid fractions resulting from the production of ethylene by pyrolysis of various petroleum fractions. The composition, properties, quantity and division of pyrolysis oils are always directly related to the actual olefin production technology and the raw material used for pyrolysis.

Pyrolysis oils are a mixture of various identifiable and unidentifiable compounds, the representation of which is diverse and dependent on both the origin of the raw material and the reaction conditions of pyrolysis.

With the development of olefin production and also due to the pyrolysis of heavier raw materials with a higher average boiling point, such as kerosene and gas oil, the amount of pyrolysis oils is increasing. For example, a unit with a capacity of 200,000 t ethylene/year pyrolyzing gasoline with a distillation range of 40 to 170 °C will produce about 25 to 30,000 t of pyrolysis oils per year. When processing gas oil, a unit with the same capacity will produce 113,000 t of pyrolysis oils per year.

Until recently, pyrolysis oils were a waste product used only as a low-sulfur fuel for industrial furnaces. Ensuring the combustion of pyrolysis oils is difficult because it requires higher temperatures in their storage and in the fuel oil piping loop before the burner for combustion. Boilers fired with pyrolysis oil must be designed with special attention to reducing emissions, and combustion requires preheated air and a specially designed burner.

As a result of the increasing production of pyrolysis oils, interest in their chemical use is increasing and pyrolysis oils are becoming a new raw material base. A number of methods for the use of pyrolysis oils are described in the literature and some of them are already used today. However, most of them still involve the processing of pyrolysis oil as a whole. In modern processes, which process heavier oil fractions, however, the so-called primary column, in which the pyrogas is divided into kven

Ϊ' oil treatment, to divide the pyrolysis oil into two parts, into a lighter, so-called gas oil and a heavier, so-called heating, pyrolysis oil, which after further stripping with steam leave the production as finished final products. The methods of processing pyrolysis oils listed below and still used are based on a mixture of both pyrolysis oils and hardly take advantage of the fact that in modern pyrolysis processes pyrolysis oils are already separated into two basic fractions. The fractions usually have the following composition:

Light pyrolysis oil

calorific value, about 41 MJ/kg density at 20 °G 965 to 985 kg/m^ flash point, usually higher than 70°C sulfur content, about 0.6% by weight BMCI index 95 to 115 water, usually lower than 0.3% by weight mechanical impurities, usually lower than 0.2% by weight ash, usually lower than 0.1% by weight Conradson test (ΟΚδ), usually lower than 0.5% by weight ASTM distillation vol. % temperature range (°C) z. d. 130 to 210 ,0 203 to 223 20 212 to 232 50 223 to 243 80 245 to 265

ir

90 k. d. remainder 0.5 vol. % 259 to 279 293 to 313 Heavy pyrolysis oil calorific value about 39 MJ/kg density 20 °C 1,116 to 1,125 kg/year flash point, usually higher than 140°C freezing point 35 to 55°C sulfur content, depends on the sulfur content of v raw material, about 1.4% by weight BMCI index 110 to 130 asphaltans 12 to 24% by weight water, usually lower than 0.1% wt. mechanical impurities, usually below than 0.1% by weight ash, usually lower than 0.1% by weight. Conrads Test (CKC) about 20% ASTM distillation Vol. % temperature range (°C) z. d. 265 to 285 10 299 to 319 20 312 to 332 50 445 to 465

the rest 50% vol.

Current methods of processing mixtures of these pyrolysis oils are based on several procedures, the most well-known of which is the distillation (atmospheric, vacuum distillation) of pyrolysis oil and the subsequent processing of individual fractions, namely the naphthalene fraction as a raw material for the production of naphthalene, the methylnaphthalene fraction for a high-quality high-boiling aromatic solvent, the aromatic fraction as a raw material for the production of carbon black and pyrolysis pitch, i.e. the residue of atmospheric distillation, both as a raw material for the production of coke mass similar to pitch coke, and also by co-carbonization with black coal, and the final pyrolysis pitch, i.e. the residue of vacuum distillation for a filler in plastics, coking to electrode coke and as a raw material for silicon carbide.

Pyrolysis oils are further processed by coking to electrode coke, so-called needle coke, and by isolating resins from pyrolysis oil by precipitation with paraffinic hydrocarbon fractions. Pyrolysis oil can also be used directly in the regeneration of old rubber. Oxidation of pyrolysis oil yields an aromatic fraction and heavy pyrolysis resin.

The processing of pyrolysis oils according to the methods used so far presents certain problems related to the chemical nature and instability of pyrolysis oils, manifested by the formation of polymers and rubbers. These problems are particularly noticeable during storage and transportation, which is usually necessary because pyrolysis oils cannot usually be processed directly in petrochemical plants, and in the case of pyrolysis oils being processed on site, the overall processing by distillation is difficult for the same reasons. In addition, such processing requires special equipment, e.g. a vacuum film evaporator equipped with a rotor with Teflon wipers, which are not common in oil processing.

It has now been found that the above problems and difficulties can be avoided and that it is expedient to process pyrolysis oils comprehensively and to take advantage of the fact that in new processes pyrolysis oils are already removed from the olefin unit in two fractions, i.e. lighter and heavier. For some cases, it is advantageous to take advantage of the fact that heavy pyrolysis oil has a distillation start of 260 to 280 °C and that only 10% distils at 310 °C. The separation of these light fractions from heavy pyrolysis oil does not pose such difficulties as distillation processing into individual fractions and can be managed by conventional means. These light fractions are then added to the light pyrolysis oil.

The method of complex processing of pyrolysis oils, such as heavy and light pyrolysis oil, consists, according to the invention, in that heavy pyrolysis oil with a distillation range of 245 to 500 °C, as it is discarded from the production of olefins by pyrolysis of petroleum fractions or in a mixture with not more than 75% by weight of fuel oil, or not more than 85% by weight of vacuum residue, or not more than 50% by weight of distillation residue from brown coal tar from low-temperature carbonization, is subjected to partial oxidation with a mixture of oxygen and water vapor at a pressure of 2.0 to 20.0 MPa, preferably 3.0 to 10.0 MPa and at a temperature of 1,300 to 1,600 °C to form a mixture of hydrogen, carbon monoxide, carbon dioxide and other components depending on the composition of the raw material and reaction conditions, which is processed by commonly known processes to hydrogen or a mixture of hydrogen and carbon monoxide, and the hydrogen thus formed is hydrogenated to untreated light pyrolysis oil with a distillation range of 150 to 310 °C, as it is discarded from production, or in a mixture with light portions of heavy pyrolysis oil to components of light heating oils and motor fuels, or the hydrogen or mixture of hydrogen and carbon monoxide is used for hydrogenation processes or syntheses Light pyrolysis oil is hydrogenated in the presence of catalysts containing oxides of metals from Group XV, e.g. W, Mo, -preferably Mo in an amount of 2 to 20 wt. %, preferably 8 to 12 wt. % MoO^, promoted by an oxide of a metal from Group VIII, e.g. Co, Ni, preferably Ni in an amount of 1 to 8 wt. %, preferably 2 to 6 wt. % NiO on a carrier, the essence of which is active alumina, preferably in gamma form, or a mixture of alumina with magnesium oxide, at a pressure of 3.0 to 20.0 MPa, preferably 3.4 to 6.8 MPa, a space velocity of 0.5 to 5.0 h ^-1 , preferably 1 to 3 h ^_1 , a hydrogen to raw material ratio of 200 to 1,200 m^/m^ and at a temperature of 200 to 430°C.

The principle of the complex processing of light and heavy pyrolysis oil according to the invention therefore consists in the fact that the heavy pyrolysis oil, as it is discarded, is subjected to partial oxidation, i.e. the action of oxygen and water vapor at higher pressures and temperatures, in order to produce a mixture of carbon monoxide and hydrogen. This mixture is further processed into hydrogen and technical hydrogen, with which the untreated light pyrolysis oil, as it is discarded from the olefin unit, is hydrogenated to the desired products. As is evident, the proposed complex processing does not require any or only minimal pre-treatment or processing of both raw materials. Such pre-treatment, as mentioned above, is usually associated with difficulties arising from the chemical nature of pyrolysis oils, the components of which are subject to polymerization, deposits are formed in them and are easily coked.

The method of complex processing of pyrolysis oils according to the invention can be used particularly advantageously in chemical plants, where in addition to ethylene production there is also refining of crude oil, because when it is applied, problems with transportation and storage of pyrolysis oils are eliminated, and the products of hydrogenation processing of light pyrolysis oil and excess hydrogen can be used appropriately. Another advantage is that the proposed processes are similar to refinery processes and it is possible to use typical equipment and in some cases even the free capacity of existing equipment.

The choice of the method of hydrotreating light pyrolysis oil depends on local conditions and the desired products. It is important that heavy pyrolysis oil provides a sufficient raw material base for hydrogen production for all variants of hydrotreating light pyrolysis oil.νβ. its hydrocracking to the lightest hydrocarbon fractions. If more heavy pyrolysis oil is processed by partial oxidation than corresponds to the need for hydrogen for hydrotreating light pyrolysis oil, this hydrogen or a mixture of CO + Hg can be used for other common purposes, such as hydrogenation, ammonia synthesis, methanol synthesis, oxo process, etc.

The method according to the invention does not require the direct inclusion of hydrogenation treatment in the production scheme. In the case where light pyrolysis oil can be used directly without its hydrogenation treatment, the method can be used only in the partial oxidation part of the heavy pyrolysis oil. Similarly, the method can be used only in the part of the hydrogenation treatment of light pyrolysis oil using any hydrogen source.

The method according to the invention includes the preparation of raw material for partial oxidation and the conduct of the partial oxidation process, as well as the process of hydrogenation treatment of light pyrolysis oil.

As experimentally proven, heavy pyrolysis oil is chemically very unstable. Its uncontrolled mixing with raw materials commonly used for partial oxidation with petroleum distillation residues, such as fuel oil, vacuum residue, etc., also causes problems, because unstable mixtures forming a two-phase system can be formed. A detailed study has shown that the instability is caused by the different chemical character of conventional petroleum residues and heavy pyrolysis oil. The paraffinic character of petroleum residues, such as fuel oil, is manifested in the precipitation of resins and asphaltenes contained in heavy pyrolysis oil. This precipitation, in the presence of excess fuel oil, is not prevented even by the relatively high content of aromatic hydrocarbons in heavy pyrolysis oil.

Detailed research has found the limiting ratios of fuel oil, vacuum residue and distillation residue from brown coal tar from low-temperature carbonization (hereinafter DZHD) to heavy pyrolysis oil, at which the aromaticity of heavy fuel pyrolysis oil is still sufficient to maintain a single-phase system. Various pressure and temperature conditions have been studied with regard to storage and injection into the partial oxidation reactor. The specific miscibility possibilities depend on the chemical nature of the distillation residues, such as petroleum fuel oil, petroleum vacuum residue, DZHD and heavy pyrolysis oil. The following maximum ratios (by mass) of distillation residues to heavy pyrolysis oil (hereinafter TPO) have been found:

Fuel oil / TPO Vacuum residue/TPO DZHD / TPO ₍ 3:1 5:1 1:1

Injection of the mixture of distillation residue and heavy pyrolysis oil in the above-mentioned proportions can be carried out similarly to, for example, the partial oxidation of pure fuel oil. It is advantageous to inject heavy pyrolysis oil into the stream of distillation residue, e.g. fuel oil, in the above-mentioned proportions at various locations, e.g. into the storage tank, in front of the partial oxidation reactor, into the screw mixer for soot remix.

The reaction conditions of partial oxidation of, for example, a mixture of fuel oil and heavy pyrolysis oil in the given ratios do not differ substantially from the reaction conditions of gasification of pure fuel oil, although in some parameters it is necessary to take into account the chemical character of heavy pyrolysis oil. It is possible to work under the following conditions:

temperature in the reactor: 1,300 to 1,500 °C pressure in the reactor: 3.0 to 5.0 MPa, preferably 3.4 to 4.0 MPa

The above partial oxidation conditions are based on a specific partial oxidation process, however, it is clear that other partial oxidation processes can be adapted for the processing of heavy pyrolysis oil.

As already mentioned above, the process according to the invention also includes a process of hydrogenation treatment of light pyrolysis oil. By hydrogenation treatment of light pyrolysis oil, high-quality components of motor fuels can be prepared.

Catalytic hydrogenation is carried out in a reactor with a fixed bed of catalyst in the form of particles, where the hydrogenation of unsaturated fractions, partial hydrogenation of polynuclear aromatics, or even hydrocracking into lighter fractions, and simultaneously desulfurization and denitrogenation of the raw material take place. Hydrogenation treatment of light pyrolysis oil can be carried out in the presence of catalysts containing metal oxide from group 17, e.g. Mo, W promoted by metal oxide from group VIII, e.g. Co, Ni on a carrier, the essence of which is active alumina, synthetic or natural aluminosilicates, mixtures of alumina with magnesia, etc.

Preferably, a nickel-molybdenum or nickel-cobalt-molybdenum catalyst based on active alumina can be used for this purpose, which in the sulfide form is characterized by high resistance to coking and poisoning by nitrogenous substances and at the same time allows the hydrogenation of polynuclear aromatics. The catalyst contains 5 to 20 wt. % MoO^, preferably 8 to 12 wt. % and 1 6Ž 8 5Í wt. % NiO, preferably 2 to 6 wt. %.

The hydrogenation treatment of light pyrolysis oil is carried out at a pressure of 3.0 to 20 MPa, preferably 3.4 to 6.8 MPa, a volume rate of 0.5 to 5 h\ preferably 1 to 3 h ^- ', a hydrogen to raw material ratio of 200 to 1,200 m^/m^, preferably 300 to 600 m^/m^ and at a temperature of 200 to 430 °C depending on the focus of the process.

The catalyst is sulfurized with a mixture of Hg-HgS (10%') or another model sulfur compound, e.g. lower boiling mercaptans or sulfides, or a primary petroleum fraction containing sulfur compounds, before use in the process. The catalyst can be used in several operating cycles.

During its lifetime, 2 to 4 oxidative regenerations can be performed, in which carbon deposits are removed using a mixture of steam and air, or nitrogen.

Hydrogen from partial oxidation of heavy pyrolysis oil or any gas with a hydrogen content above 70% vol., preferably above 85% vol., can be used for hydrogenation.

Figure 1 shows a simplified technological scheme for the hydrogenation treatment of light pyrolysis oil. Light pyrolysis oil supplied through inlet 1 together with hydrogen supplied through inlet 2 first passes through heat exchangers J and then enters the preheater í, in which it is preheated to the reaction temperature at which it enters the upper part of the reactor £.

In reactor 2, in the presence of a catalyst in the form of particles, hydrotreating, hydrogenation and/or hydrocracking reactions take place, depending on the process focus. Since these reactions are accompanied by significant heat development, the catalyst in the reactor is divided into several layers, between which the reaction products are cooled. Cooling can be carried out in the exchanger 2 or by supplying cold circulating gas and/or by supplying liquid product between two catalyst layers. A combination of the above cooling methods is also possible. The cooling arrangement is such that the temperature increase after passing through an individual catalyst layer does not exceed 10 to 12 °C.

In the separator 6, gas is separated from the liquid product, which is mixed again with light pyrolysis oil, supplied by inlet 2, after the addition of fresh hydrogen. A smaller part of the gas is discharged from the system together with the other off-gases. The liquid product from the separator 6 is freed from dissolved gases and light liquid hydrocarbons in the stabilization column 1. In the case of hydrocracking of light pyrolysis oil, the product is conventionally separated by distillation into the desired fractions, e.g. hydrocarbon gases, gasoline, kerosene, diesel fuel, etc.

Fig. 2 shows a general diagram of the pyrolysis oil processing method. From the olefin unit 2, heavy pyrolysis oil ^is discharged through the pipe 15 to the partial oxidation reactors J_0, where, with the addition of oxygen supplied through the inlet 11 and water vapor supplied through the inlet 12, a mixture of hydrogen, carbon monoxide, carbon dioxide and other substances is formed, depending on the composition of the raw material and the reaction conditions, which is discharged through the pipe 14 to the device for cleaning and processing the reaction products of partial oxidation 16. where this mixture is processed by commonly known procedures into hydrogen or a mixture of hydrogen and carbon monoxide, while simultaneously discharging through the pipe 18 waste gases formed primarily by CO ₂ and HgS. The hydrogen thus formed is discharged through the pipe 2 to the hydrogenation unit 13. where light pyrolysis oil is also supplied from the ethylene unit 2 through the inlet. The hydrogenation unit processes

Ί the supplied raw materials according to the scheme in Fig. 1 and in the case of hydrocracking, the product from this unit 13 is discharged through the pipe 17 to the distillation column 8, where it is divided into the desired products.

The following examples illustrate the method of complex processing of pyrolysis oils according to the invention and demonstrate its effects.

Example 1

Heavy pyrolysis oil mixed with fuel oil, the analyses of which are given in Table 1, was subjected to partial oxidation under the following reaction conditions:

temperature in the reactor: 1,350 to 1,450 °C pressure in the reactor: 3.6 MPa

Raw material consumption and yields of individual products are shown in Table 2.

Table No. I

Heavy fuel oil (heavy pyrolysis oil)

density at 20 °C 952.0 kg/ ^m3 1,120.0 kg/ ^m3 sulfur content 2.0% by weight 1.2% by weight asphaltans 3.95% by weight 14.5% by weight Conradson test (CKC) · 9.73% by weight 12.3% by weight ASTM distillation (vol. %) z. d. 240°C 270°C 10 350°C 305°C 20 412°C 318°C 50 501°C 450°C

Table No. 2

Fuel oil

Fuel oil/TPO

3:1

TPO

Raw material consumption kg/ 1,000 m ³ CO + H2 Steam consumption t/t raw material Oxygen consumption 1,000 m ³ /t raw material Soot formation kg/t raw material Gas composition CO + H2 (vol. 56)

H,S mg/mh ₂ /co

333

0.35

0.52

99.4

920

335

0.437

0.55

99.4

800

0.87

338

0.400

0.59

4,

99.3

430

0.8

Example 2

Light pyrolysis oil, the analysis of which is given in Table 3, was hydrogenated in an experimental device containing 200 ml of nickel-molybdenum catalyst at a pressure of 6.8 MPa, a vol. rate of

217164 8

2.5 h’, at a hydrogen to raw material ratio of 500 1/1. The catalyst contained 3.1 wt. % NiO and 12.3 wt. % MoOj on an active gamma-form alumina support. The catalyst was dried in a nitrogen stream at 400 °C in the reactor before the actual experiment. The catalyst was sulfurized at 280 °C with a Hg-HgS mixture (3 vol. % HgŠ).

Table No. 3

Pointer

Raw material

Product hydrogenation temperature 300 °C 360 °C

20 Specific gravity, h ASTM distillation (°C) (kg/ ^m3 ) 967 905 880 z. d. 130 125 112 10% vol. 203 198 169 20% vol. 212 210 202 50% vol. 250 245 233 80% vol. 260 252 240 k. distillation 313 299 283 dist. rest of vol. ) 0, ,5 - - sulfur content (% wt.) 0, .6 0.005 0 freezing point (°C) -22 -45 Jttan. number 40-50 Consumption H ₂ m ³ /m ³ - 224 278

The hydrogenation product listed in Table 3 can be used as a component of heating or diesel fuel, which will improve its combustion characteristics (cetane number 40 - 50) and low-temperature behavior.

As mentioned above, light pyrolysis oil can be processed without the mentioned catalyst by coarser hydrogenation to a jet fuel component or by hydrocracking to the considered light fractions. »

The examples given confirm the advantage of the method of complex processing of light and heavy pyrolysis oil according to the invention. Pyrolysis oils represent, as already mentioned, waste from olefin units that is difficult to process. The benefit of the invention is the full use of pyrolysis oils by processing them into valuable products, which will improve the economic balance of olefin production by pyrolysis of petroleum fractions and contribute to eliminating the shortage of high-quality components of motor fuels. A further benefit is that for plants producing hydrogen by partial oxidation of petroleum distillation residues, part of these raw materials can be replaced with heavy pyrolysis oil and the obtained raw material can be used to increase hydrogen production, or for other suitable purposes.

In the method of processing pyrolysis oils according to the invention, it is important that it is a comprehensive processing of the entire amount of waste pyrolysis oils, procedures based on untreated raw pyrolysis oils and therefore not requiring any preliminary treatment of the processed pyrolysis oils, thereby eliminating the dangers and difficulties associated with such processing. At the same time, it is a simple procedure consisting of two partial processes, allowing the entire amount of pyrolysis oils to be easily utilized even from large-capacity units.

Claims (2)

Process for the complex treatment of pyrolysis oils as a heavy and light pyrolysis oil, characterized in that heavy pyrolysis oil having a distillation range of 245 to 500 ° C as it is obtained from olefin production by pyrolysis of petroleum fractions or in a mixture with not more than 75% by weight. % oil, optionally with a maximum of 85 wt. % of the vacuum residue, or at most 50 wt. distillation residue from brown coal tar from low-temperature carbonization, subjected to a pressure of 2 to 20 MPa, preferably 3 to 10 MPa and at a temperature of 1300 to 1600 ° C, partial oxidation of oxygen and water vapor mixtures to form a mixture of hydrogen, carbon monoxide, carbon dioxide and other components depending on the composition of the feedstock and the reaction conditions to be treated Untreated light pyrolysis oil with a distillation range of 120 to 360 ° C, as is removed from the above production into motor fuel components, or in a mixture with light proportions of heavy pyrolysis oil. 2. Process according to claim 1, characterized in that the light pyrolysis oil is hydrogenated in the presence of a catalyst containing metal oxides from IV. W, Mo, preferably Mo, 2 to 20 wt.%, preferably 8 to 12 wt. MoO 2; promoted by metal oxide VIII. %, e.g., Co, Ni, preferably Ni, in an amount of 1 to 8 wt.%, preferably 2 to 8 wt. NiO on a support based on active alumina, preferably in gammaforra; mixture of alumina with magnesium oxide, at a pressure of 3.0 to 20 MPa, preferably 3.4 to 6.8 MPa, at a rate of 0.5 to 5.0 h -1, preferably 1 to 3 h ^-1 , a hydrogen ratio to a feedstock of 200 to 1200 nP / nP at a temperature of 200 to 430 ° C.