RU2768163C1 - Method for producing coke with low sulfur content (embodiments) - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to the field of oil refining and coke chemistry, in particular, to the field of production of petroleum coke with low content of sulphur by preliminary oxidation of sulphur compounds contained in the raw material for coking, to the corresponding sulphones and can be used in oil refining and coke-chemical industry. Disclosed are embodiments of the method, each of which involves mixing a sulphur-containing hydrocarbon material with a catalyst and an oxidant, mixing the initial components, oxidation at high temperature, extraction of a product containing oxidised sulphur compounds and its coking to obtain a commercial product - coke. When mixing the initial components, a surfactant is additionally added - a quaternary ammonium salt, taken in amount of 0.1–4 wt. % with respect to the weight of the hydrocarbon material, in one embodiment, a gaseous oxidant is used as an oxidising agent, and in another embodiment, a liquid oxidant with an oxidant: sulphur ratio contained in the hydrocarbon feedstock of 2–30:1; catalyst is taken in amount of 0.05–1 wt. % with respect to hydrocarbon feedstock, mixing of initial components is carried out at a rate of not less than 600 rpm, oxidation of the obtained mixture is carried out at temperature of 40–200 °C, pressure of 1–20 atm for 1–6 hours, then cooling, in case of using a liquid oxidant, separation of the aqueous phase containing the spent oxidant and catalyst, and coking of the extracted product at temperature of 420–560 °C.

EFFECT: technical result of the declared group of inventions is the simplification and cheapening of the method of producing coke with low content of sulphur with the same or lower content of sulphur in the coke.

10 cl, 1 tbl, 29 ex

Description

The invention relates to the field of oil refining and coke chemistry, in particular to the field of obtaining petroleum coke with a reduced sulfur content by preliminary oxidation of sulfur compounds contained in the raw material for coking to the corresponding sulfones and can be used in the oil refining and coke industry.

Petroleum coke is widely used in industry, especially as the main component of carbon electrodes and in metallurgy. The largest proportion of petroleum coke currently available is from the delayed coking of residual oils and heavy residues. This coke is not pure carbon, but also contains heavy hydrocarbon compounds and other inorganic impurities. The sulfur content of petroleum coke often ranges from 4 to 8% sulfur or higher. Whereas for industrial purposes, suitable coke should contain sulfur below 2 wt. % and more preferably 1 wt. % or lower, which creates the need to find ways to reduce the sulfur content in commercial coke.

From the prior art there is a method for producing coke with a reduced sulfur content of coke desulfurization by preliminary oxidation of sulfur-containing coke (obtained by coking residual oil or tar) with an air stream or a mixture of oxygen and nitrogen at a temperature of at least 148°C, preferably 315-480°C (US 3369871 A , class IPC C01B 31/00, C10L 9/06, C10L 9/08, published 02/20/1968). After oxidation, the coke is held at a temperature of 871°C and then re-treated with an air flow at a temperature of 398°C, making it possible to obtain coke with a sulfur content of less than 0.2%.

The disadvantage of this approach is the use of elevated temperatures, as well as two-stage oxidation, which complicates the hardware design of the process and requires significant energy consumption.

A known method for producing coke with a reduced sulfur content in a two-stage process (US 3950503 A, class IPC C01B 17/04, C10L 9/00, publ. 13.04.1976). At the first stage, the coke is calcined under oxidizing conditions (in the presence of oxygen or air at a temperature of 537 to 1648°C), at the second stage, under reducing conditions at temperatures from 1093 to 2200°C. The result is coke with a reduced sulfur content (less than 2%), as well as elemental sulphur.

The disadvantage of this process is also the process at high temperatures, requiring significant energy consumption.

A known method for producing coke (US 9574143B2, class IPC C10G 17/00, C10G 17/02, published on February 21, 2017), according to which sulfur-containing compounds in hydrocarbon feedstock are pre-oxidized before coking. The resulting oxidized sulfur compounds are extracted from the raw material by extraction and then used for coking, obtaining coke with a sulfur content of less than 2%. The diesel fraction (150 - 400°C), as well as higher-boiling fractions, with a boiling point up to 700°C, can be used as hydrocarbon feedstock. Air, oxygen, ozone, hydroperoxides, organic peracids, etc. can be used as an oxidizing agent. The catalyst is oxides of transition metals (titanium, vanadium, chromium, molybdenum, tungsten). The oxidation temperature is about 20-150°C, the reaction time is from 30 minutes, the pressure is 1-10 atm.

The disadvantage of this method is the presence of an additional extraction step. It is important to note that organic extractants are used to isolate the oxidation products, which then need to be regenerated by distillation. In this case, organic solvents in the form of alcohols, chloroform, nitrogen-containing compounds are often used as extractants, which often extract a significant amount of hydrocarbon components. The need for the stage of extraction and regeneration of the extractant by distillation leads to the appearance of additional stages that complicate the process, which should be attributed to the main disadvantage of this method.

The closest to the declared set of essential features and the achieved technical result is a method for producing low-sulfur coke (SU 1407949 A1, class IPC S10V 55/00, publ. 07/07/1988), including mixing the residue of sour oils (tar) with a catalyst - molybdenum pentachloride in the amount of 0.1-0.2% wt. from the feedstock, heating to 100°C, stirring for 2-3 hours, adding an oxidizing agent - cumene hydroperoxide, deasphalting by treatment with saturated hydrocarbons (light gasoline) at 150-185°C, separation from the deasphalting product by distillation of the solvent and conversion products , and coking of the deasphalted oil.

Get coke with a sulfur content of 1.1-1.38% wt.

The disadvantage of the known technical solution is the complexity and multi-stage nature of the described method, associated with the need for deasphalting, separating products for further coking by distillation of the solvent used and, as a result, the use of additional hardware. Also among the disadvantages should be noted the use of a corrosive chlorine-containing catalyst, which is unstable in the presence of traces of water present in oil.

Thus, the known methods for reducing the sulfur content in coke using the oxidation method have a number of disadvantages, in particular, the oxidation of sulfur compounds in coke, which requires significant energy consumption, or the use of an extraction stage after the oxidation of hydrocarbon feedstock, which complicates the process hardware.

The objective of the present invention is to develop a simpler and more economical, in terms of instrumentation, method for producing coke with a reduced sulfur content.

To solve this problem, a method for producing coke with a reduced sulfur content is proposed, including mixing sulfur-containing hydrocarbon raw materials with a catalyst and an oxidizer, mixing the initial components, oxidizing at elevated temperature, separating a product containing oxidized sulfur compounds, and coking it to obtain a commercial product - coke, in which, when mixing the initial components, a surfactant is additionally added - a quaternary ammonium salt, taken in an amount of 0.1-4% wt. in relation to the mass of hydrocarbon raw materials, as an oxidizing agent, a gaseous oxidizing agent is used at a ratio of oxidizing agent: sulfur contained in the hydrocarbon raw material, equal to 2-30:1; the catalyst is taken in the amount of 0.05-1% wt. in relation to the hydrocarbon feedstock, the mixing of the initial components is carried out at a speed of at least 600 rpm, the oxidation of the resulting mixture is carried out at a temperature of 40-200 ° C, a pressure of 1-20 atm for 1-6 hours, then cooling and coking of the isolated product at temperature 420-560°C.

Oxygen or air is used as the gaseous oxidizer.

According to the second option, to solve the problem, a method for producing coke with a reduced sulfur content is proposed, including mixing sulfur-containing hydrocarbon raw materials with a catalyst and an oxidizer, mixing the initial components, oxidizing at an elevated temperature, separating a product containing oxidized sulfur compounds, and coking it to obtain a commercial product - coke, in which, when mixing the initial components, I additionally add a surfactant - a quaternary ammonium salt, taken in an amount of 0.1-4% wt. in relation to the mass of hydrocarbon feedstock at a ratio of oxidizing agent: sulfur contained in the hydrocarbon feedstock, equal to 2-30:1; the catalyst is taken in the amount of 0.05-1% wt. in relation to the hydrocarbon feedstock, the mixing of the initial components is carried out at a speed of at least 600 rpm, the oxidation of the resulting mixture is carried out at a temperature of 40-200 ° C, a pressure of 1-20 atm for 1-6 hours, then cooling, separation of the aqueous phase, containing spent oxidant and catalyst, and coking the selected product at a temperature of 420-560°C.

According to both embodiments of the proposed method, heavy fractions with a boiling point of 200-560 ° C are used as sulfur-containing hydrocarbon raw materials from oil distillation or thermal cracking of gasoline, or catalytic cracking of gasoline, or pyrolysis of gasoline, or thermal cracking of gas oil, or catalytic cracking of gas oil, or pyrolysis gas oil.

As a catalyst in both cases, compounds selected from the series are used: ammonium molybdate - (NH ₄ ) ₂ MoO ₄ , molybdenum oxide VI, ammonium paramolybdate - (NH ₄ ) ₆ MoO ₂₄ , phosphomolybdic acid - H ₃ PMo ₁₂ O ₄₀ , tungstate ammonium - (NH ₄ ) ₂ WO ₄ , phosphotungstic acid - H ₃ PW ₁₂ O ₄₀ , tungsten oxide VI.

In both variants of the proposed method, compounds selected from the following series are used as quaternary ammonium salts: cetyltrimethylammonium bromide, didodecyldimethyl ammonium bromide, dodecyltrimethyl ammonium bromide, tetrabutyl ammonium bromide.

When mixing the mixture at a speed of less than 600 rpm, a sufficient degree of homogenization of the mixture and a uniform distribution of the catalyst, surfactant and liquid oxidizer over the volume of the raw material are not ensured. The higher the RPM, the better the homogenization.

At a pressure above 20 atm, during oxidation, strong overoxidation and resinification of the raw material is possible.

At temperatures below 40°C, the oxidation reaction does not proceed, and at temperatures above 200°C, decomposition of the oxidizing agent begins, or strong overoxidation and resinification occur.

When the coking temperature is below 420°C or above 560°C, the quality of the coke decreases, namely, the sulfur content in the coke increases.

The technical result of the invention is the simplification of the technological scheme in comparison with known analogues. This result is achieved due to the fact that the products of oxidation of sulfur compounds - sulfones, decompose at temperatures above 350-400°C with the release of sulfur dioxide. Thus, the oxidized sulfur compounds can be decomposed during the coking process to remove sulfur dioxide together with coke oven gases and obtain coke with a reduced sulfur content. Thus, there is no need to use an additional extraction step, as well as organic solvents.

General methodology for the process.

The content of total sulfur in the feedstock for coking is preliminarily analyzed by the X-ray fluorescence method on the ASE-2 instrument.

The calculated amount of oxidizer, catalyst and surfactant is added to the initial sulfur-containing hydrocarbon feedstock, the order of addition can be arbitrary. The molar ratio of oxidizer : sulfur varies in the range of 2-30:1, the mass fraction of the catalyst in relation to the feedstock varies in the range of 0.05-1% wt., the mass fraction of surfactant in relation to the feedstock varies in the range of 0.1-4%.

Next, sulfur-containing compounds are oxidized, for this the resulting mixture is stirred at a speed of at least 600 rpm at a temperature of 40-200°C for 1-6 hours and a pressure of 1-20 atm.

After the reaction, an aqueous phase is separated containing the spent oxidant and catalyst (in the case of using liquid oxidizers).

Next, the remaining mass containing oxidized sulfur compounds is subjected to coking at a temperature of 420-560°C for 90-200 minutes and a pressure of 1-2 atm.

At the end of coking analyze the sulfur content in the coke according to GOST 1437-75.

The results obtained are shown in the table.

Thus, the proposed method allows to obtain coke in a simpler and more economical way, compared with the prototype, and, in some cases, with the same sulfur in coke, and in most cases with a lower sulfur content: up to 1% wt. %.

Claims (10)

1. A method for producing coke with a reduced sulfur content, including mixing sulfur-containing hydrocarbon raw materials with a catalyst and an oxidizing agent, mixing the initial components, oxidizing at an elevated temperature, separating a product containing oxidized sulfur compounds, and coking it to obtain a commercial product - coke, characterized in that that when mixing the initial components, a surfactant is additionally added - a quaternary ammonium salt, taken in an amount of 0.1-4 wt.% relative to the mass of hydrocarbon feedstock, a gaseous oxidizer is used as an oxidizing agent at a ratio of oxidizer: sulfur contained in hydrocarbon feedstock , equal to 2-30:1; the catalyst is taken in an amount of 0.05-1 wt.% relative to the hydrocarbon feedstock, the mixing of the initial components is carried out at a speed of at least 600 rpm, the oxidation of the resulting mixture is carried out at a temperature of 40-200 ° C, a pressure of 1-20 atm for 1-6 hours, then cooling and coking of the isolated product at a temperature of 420-560°C. 2. The method according to p. 1, characterized in that heavy fractions of oil distillation with a boiling point of 200-560 ° C, or thermal cracking of gasoline, or catalytic cracking of gasoline, or pyrolysis of gasoline, or thermal cracking of gas oil, are used as sulfur-containing hydrocarbon raw materials, or catalytic cracking of gas oil, or pyrolysis of gas oil. 3. The method according to p. 1, characterized in that air or oxygen is used as a gaseous oxidizer. 4. The method according to p. 1, characterized in that the catalyst used compounds selected from the series: ammonium molybdate - (NH ₄ ) ₂ MoO ₄ , molybdenum oxide VI, ammonium paramolybdate - (NH ₄ ) ₆ MoO ₂₄ , phosphomolybdic acid - H ₃ PMo ₁₂ O ₄₀ , ammonium tungstate - (NH ₄ ) ₂ WO ₄ , phosphotungstic acid - H ₃ PW ₁₂ O ₄₀ , tungsten oxide VI, sodium phosphomolybdate. 5. The method according to claim 1, characterized in that compounds selected from the following series are used as the quaternary ammonium salt: cetyltrimethylammonium bromide, didodecyldimethyl ammonium bromide, dodecyltrimethyl ammonium bromide, tetrabutyl ammonium bromide. 6. A method for producing coke with a reduced sulfur content, including mixing sulfur-containing hydrocarbon raw materials with a catalyst and an oxidizer, mixing the initial components, oxidizing at an elevated temperature, separating a product containing oxidized sulfur compounds, and coking it to obtain a commercial product - coke, characterized in that that when mixing the initial components, a surfactant is additionally added - a quaternary ammonium salt, taken in an amount of 0.1-4 wt.% relative to the mass of the hydrocarbon feedstock, at a ratio of liquid oxidizer: sulfur contained in the hydrocarbon feedstock equal to 2-30 :one; the catalyst is taken in an amount of 0.05-1 wt.% relative to the hydrocarbon feedstock, the mixing of the initial components is carried out at a speed of at least 600 rpm, the oxidation of the resulting mixture is carried out at a temperature of 40-200 ° C, a pressure of 1-20 atm for 1-6 hours, then cooling, separation of the aqueous phase containing spent oxidizer and catalyst, and coking of the isolated product at a temperature of 420-560°C. 7. The method according to p. 6, characterized in that heavy fractions with a boiling point of 200-560 ° C of oil distillation, or thermal cracking of gasoline, or catalytic cracking of gasoline, or pyrolysis of gasoline, or thermal cracking of gas oil, are used as sulfur-containing hydrocarbon raw materials, or catalytic cracking of gas oil, or pyrolysis of gas oil. 8. The method according to claim 6, characterized in that hydrogen peroxide or tert-butyl hydroperoxide or performic acid or peracetic acid is used as the oxidizing agent. 9. The method according to claim 6, characterized in that compounds selected from the series are used as a catalyst: ammonium molybdate - (NH ₄ ) ₂ MoO ₄ , molybdenum oxide VI, ammonium paramolybdate - (NH ₄ ) ₆ Mo ₇ O ₂₄ , phosphomolybdic acid - H ₃ PMo ₁₂ O ₄ O, ammonium tungstate - (NH ₄ ) ₂ WO ₄ , phosphotungstic acid - H ₃ PW ₁₂ O ₄₀ , tungsten oxide VI. 10. The method according to claim 6, characterized in that compounds selected from the following series are used as the quaternary ammonium salt: cetyltrimethylammonium bromide, didodecyldimethyl ammonium bromide, dodecyltrimethyl ammonium bromide, tetrabutyl ammonium bromide.