RU2268885C1 - Method of recovering molybdenum form catalytic olefin epoxidation products - Google Patents

Abstract

FIELD: industrial organic synthesis.

SUBSTANCE: molybdenum is recovered from catalytic olefin epoxidation products using organic hydroperoxides. Method comprises treating heavy epoxidate fraction with alkali solution, treating resultant spent alkali stream with extractant, and subsequent precipitation of molybdenum trisulfide using sulfur-alkali effluents formed in production of olefins by pyrolysis of hydrocarbon feedstock.

EFFECT: increased molybdenum recovery degree and simplified operation.

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Description

The invention relates to the field of petrochemistry, specifically to a process for isolating a molybdenum-containing catalyst from the products of catalytic epoxidation of olefins with organic hydroperoxides.

A known method of separating molybdenum from the reaction mixture after epoxidation of olefins with organic peroxides by treating them with aqueous solutions of alkaline agents (US Patent No. 3523956, IPC B 01 J 23/92, publ. 1970).

The method has such disadvantages as large losses of the target products that are readily soluble in water, as well as their contamination of the aqueous phase containing molybdenum, which in turn complicates the regeneration of the catalyst.

A known method of separating a molybdenum catalyst from catalytic epoxidation products with a water-insoluble tertiary amine (US Patent No. 5,439,657, IPC B 01 D 11/00, publ. 08.08.95). Extraction of the molybdenum catalyst from the mixture of the epoxidation reaction is carried out by treatment with an aqueous solution of caustic soda. The spent alkaline stream is treated with acid (hydrochloric, sulfuric, phosphoric, formic, etc.) to a pH of 2 or lower. After phase separation, the organic layer is sent for processing, and the acid-water layer containing dissolved molybdenum and sodium is washed with an organic solvent and sent for extraction with tertiary amine (5% solution in ethylbenzene). The amount of molybdenum after extraction decreases from the initial content of more than 1000 ppm to 20 ppm and below. Next, the extract is sent to the stage of reextraction with an alkaline compound (aqueous solutions of alkali, sodium hydroxide, ammonium hydroxide, etc.). The extractant is regenerated with a 15% aqueous solution of sodium hydroxide and returned to the repeated cycle for repeated use. The degree of extraction of molybdenum is 97-99 wt.%.

The disadvantage of this method is the use of toxic, scarce, expensive imported extractant, as well as a multi-stage process.

A known method of acid treatment of the spent alkaline stream of the process for producing propylene oxide and styrene in order to remove sodium salts from the organic phase for its further use as fuel (US Patent No. 5,276,235, IPC C 07 C 1/20, publ. 04.01.94). Acid is used in such a molar concentration that allows the formation of sodium salts in solution above their solubility limit. Thus, salt products form a suspension with a large difference in densities between phases, which facilitates the separation of phases and improves the quality of the organic phase. The amount of water introduced with the acid should not be enough to completely dissolve the resulting sodium salts. Sodium salts precipitate as insoluble crystals in the lower aqueous layer. For acid treatment, preference is given to sulfuric acid, and its amount must be such that all sodium of the spent alkaline stream can bind, i.e. 0.5 mol of sulfuric acid per 1 mol of sodium. To form sodium bisulfate, it is recommended to take sulfuric acid in an amount of 1 mol per 1 mol of sodium. Typically, 93-96% sulfuric acid is used in industry, but 25% can be used to make the process cheaper. When using other acids, equivalent amounts are also taken.

In this patent, all attention is paid to the removal of sodium salts from the spent alkaline stream for the purpose of its further use and does not take into account that the presence of catalyst ions of the epoxidation process in the fuel is also unacceptable. This problem should be solved in a complex: 1) to receive an additional quantity of high-quality fuel, which can be used in the technological process; 2) remove the present metals from the organic part of the alkaline stream; 3) regenerate the epoxidation process catalyst.

A known method of extracting a molybdenum-containing catalyst for the epoxidation of olefins with organic hydroperoxides by treating the bottoms product with a water-alcohol mixture containing alcohol in an amount of 0.01-50 wt.% (AS USSR No. 485754, IPC B 01 J 11/02, publ. 30.09 .75). The bottoms product obtained by separating the products of the epoxidation of β-isoamylene with tertiary amyl hydroperoxide contained in oxidized isopentane contains 0.4 wt.% Molybdenum. The determination of molybdenum is carried out by the colorimetric method. Monohydric or polyhydric alcohols or mixtures thereof are used as the alcohol. The degree of extraction of molybdenum in a water-alcohol mixture is 90-95%. The resulting water-alcohol layer was evaporated. The residue is a dark brown viscous liquid that dissolves well in organic solvents and contains from 3.85 to 5.9 wt.% Molybdenum. The extraction time reaches from 4 minutes to 1 hour and the process temperature varies from 0 to 80 ° C. All these factors complicate the technology.

There is also known a method of extracting a molybdenum catalyst contained in bottoms after epoxidation of olefins with organic hydroperoxides by extraction with an aqueous solution of an organic acid: acetic, formic, propionic, butyric with a concentration of 0.01-2 wt.% (AS USSR No. 491398, IPC B 01 J 11/02, publ. 15.11.75). The epoxidation catalyst contains a metal of variable valency and can be extracted from bottoms by various organic hydroperoxides containing from 3 to 100 wt.% Of the basic substance. The volumetric ratio of the bottom residue containing the molybdenum product to the extractant is from 10: 1 to 1:20. The extraction process is carried out at 10-80 ° C for a period of time from 1 minute to 1 hour. The resulting aqueous extract is evaporated, the resulting residue is a dark brown colored viscous liquid that dissolves in organic solvents and contains 5.5 wt. .% molybdenum. The molybdenum content is determined colorimetrically. The isolated molybdenum-containing product can be used as a recycle catalyst, or a metal-containing compound can be isolated.

However, not under all the above extraction conditions, a sufficiently complete extraction of the molybdenum-containing product occurs, it can be only 93%. In addition, the high volumetric ratio of the bottom residue to the extractant, the need to control the temperature, and the duration of the extraction process complicate the technology for the extraction of the catalyst.

Closest to the proposed one is a method for isolating a molybdenum catalyst from catalytic epoxidation products after removal of the desired epoxy compound and side-forming alcohol (corresponding hydroperoxide) from the epoxide, molybdenum is isolated in the form of a solid molybdenum-containing precipitate (US Patent No. 4317801, IPC C 01 G 39/06, publ. 1982). The bottoms containing molybdenum and high molecular weight organic compounds are subjected to liquid extraction with water. Spent catalyst and water-soluble organic compounds pass into the aqueous layer. After phase separation, the hydrogen sulfide or water-soluble sulfide salt (sodium, magnesium, potassium, calcium or ammonium sulfide) is added to the aqueous phase upon heating. Preference is given to sodium sulfide, which can be added in solid form or dissolved in water, hydrogen sulfide can be added directly to the mixture. The precipitation of molybdenum is achieved with a molar ratio of H ₂ S or Na ₂ S to Mo equal to 10: 1, at a temperature of 50 to 125 ° C, and a deposition time of up to 3 hours. The solid molybdenum precipitate is separated by filtration, centrifugation or decantation of the liquid. The degree of deposition of molybdenum when heated to 50 ° C for 1 hour at atmospheric pressure is 31.72%, when heated to 100 ° C for 1 hour under vacuum, it is 72.07%, at 25 ° C for 16 hours under vacuum is 52.76%.

The disadvantage of this method is the long deposition time of molybdenum with a low degree of extraction.

The objective of the invention is to increase the degree of extraction of molybdenum and simplify the process as a whole.

The problem is solved by the method of extracting molybdenum from the products of the catalytic epoxidation of olefins with organic hydroperoxides, including treating the heavy fraction of the epoxide with an alkali solution, treating the resulting spent alkaline stream with an extractant, followed by precipitation of molybdenum trisulfide, using sulphide-alkaline olefin production of sulfur molybdenum pyrolisol raw materials.

The products of the epoxidation of olefins with organic hydroperoxides are separated by distillation into light fractions and a heavy fraction containing molybdenum, as well as unreacted hydroperoxide and side reaction products. After washing the heavy fraction of the epoxide with a solution of caustic soda from by-products of oxidation and from the spent molybdenum catalyst, spent alkaline stream (waste) (SC) is formed. The resulting alkali oxide is a solution of a dark brown color, with a pungent odor, with a density of 1.11-1.18 g / cm ³ , is a complex mixture of sodium salts of organic acids, phenolates, tarry and other substances (up to 35%). Molybdenum in an amount of 0.1-0.3 wt.% Is presented in the form of organic complexes of unknown composition, the recycling of the molybdenum catalyst is impossible due to the inconstancy of the composition of the ions of molybdenum and sodium. Next, the alkali oxide is treated with an extractant, which is used as an aqueous solution of mineral acid (sulfuric, hydrochloric, nitric, phosphoric, etc.) with a concentration of 2-2.5 N. The treatment is carried out at a temperature of 50-100 ° C with a volume ratio of alkali oxide to the extractant from 1: 1.5 to 1: 2, after which molybdenum is precipitated from the aqueous phase. In addition to molybdenum ions, sodium ions are extracted into the aqueous phase, which do not interfere with the deposition of molybdenum. The organic phase, purified from metals, can be subjected to further processing in order to obtain a number of useful components.

Sulfur-alkaline effluents of olefin production by pyrolysis of hydrocarbon raw materials (SSS), for example, ethylene complex, which are a full-fledged substitute for pure sodium sulfide, are used as a precipitant of molybdenum trisulfide. Sulfur-alkaline effluents are fed for precipitation at a volume ratio to the aqueous phase of 0.19-1: 1, depending on the content of Na ₂ S.

The molybdenum content is determined by the photocolorimetric method based on the formation of colored compounds of molybdenum (V) with the thiocyanate ion.

The implementation of the method of extracting molybdenum from the products of catalytic epoxidation of olefins with organic hydroperoxides is illustrated by the following examples.

Example 1

In a thermostatically controlled funnel at a temperature of 70 ° C, 100 ml of alkaline waste, obtained by epoxidation of propylene with ethylbenzene hydroperoxide containing 0.21 wt.% Molybdenum and having a density of d ₄ ²⁰ = 1.1530, are added, 150 ml of 2.5 N sulfuric solution are added acid (123 g / l), mix for 5 minutes. The phase separation time is less than 1 minute. The aqueous phase is drained from below, the degree of extraction of molybdenum is 90.52 wt.%, The molybdenum content is 967 mg / l, pH 1.0.

To precipitate molybdenum trisulfide, a 20% excess of sodium sulfide is taken in sulfur-alkaline effluents from the production of olefins by pyrolysis of hydrocarbon feedstocks. To 100 ml of the aqueous phase, 18.3 ml of SCH are added until the pH of the solution is 1.95. The content of the total concentration of sodium compounds in the SHS is 63.25 g / l, the content of sodium sulfide is 20.66 g / l, the content of sodium hydroxide is 45.75 g / l. The volumetric ratio of the aqueous phase: WMS (V _in : V _WSS ) = 1: 0.19. The solution is boiled for 1-2 minutes for better coagulation of the precipitate, the flocculent brown precipitate of molybdenum trisulfide is filtered off. The molybdenum content in the filtrate is 48 mg / l, the degree of molybdenum precipitation is 95.22 wt.%.

Example 2

In 100 ml of the aqueous phase obtained after extraction of the alkaline waste with a solution of sulfuric acid, as in example 1, add 34.5 ml of sulfur-alkaline effluent from the production of olefins by pyrolysis of hydrocarbon feeds to a pH of 1.95. The content of the total concentration of sodium compounds in the SHS is 39.52 g / l, the content of sodium sulfide is 10.85 g / l, the content of sodium hydroxide is 28.68 g / l. The volumetric ratio of V _in : V _ccc = 1: 0.35. The excess sodium sulfide in relation to the amount required by the reaction is 20%.

The solution is boiled for 1-2 minutes for better coagulation of the precipitate, the flocculent brown precipitate of molybdenum trisulfide is filtered off. The molybdenum content in the filtrate is 46 mg / l, the degree of molybdenum precipitation is 94.56 wt.%.

Example 3

The method is carried out as described in example 1. To precipitate molybdenum trisulfide, 42.5 ml of alkaline sulphide effluents (analogous to Example 2) are added to 100 ml of the aqueous phase to a pH value of 2.5. The volume ratio of V _in : V _scc = 1: 0.43. The excess sodium sulfide in relation to the amount required by the reaction is 50%.

The solution is boiled for 1-2 minutes, the precipitate of molybdenum trisulfide is filtered off. The molybdenum content in the filtrate is 16 mg / l, the degree of molybdenum precipitation is 97.88 wt.%.

Example 4

The method is carried out as described in example 1. To precipitate molybdenum trisulfide, 100 ml of the aqueous phase is added 21.5 ml of sulfur-alkaline effluents (analogous to example 1) to a pH value of 2.4. The volumetric ratio of V _in : V _ccc = 1: 0.22. The excess sodium sulfide in relation to the amount required by the reaction is 40%.

The solution is boiled for 1-2 minutes, the precipitate of molybdenum trisulfide is filtered off. The molybdenum content in the filtrate is 27 mg / L, the degree of molybdenum precipitation is 97.06 wt.%.

Example 5

The method is carried out as described in example 1. To precipitate molybdenum trisulfide, 65 ml of alkaline sulphide effluents (analogous to Example 2) are added to 100 ml of the aqueous phase to a pH value of 7. Volume ratio V _in : V _ccc = 1: 0 , 65. The excess sodium sulfide in relation to the amount required by the reaction is 130%. It is then acidified to a pH of 2.2 by adding 1 ml of sulfuric acid.

The solution is boiled for 1-2 minutes, the precipitate of molybdenum trisulfide is filtered off. The molybdenum content in the filtrate is 7 mg / l, the degree of molybdenum precipitation is 99.06 wt.%.

Example 6

The method is carried out as described in example 1. To precipitate molybdenum trisulfide, 40 ml of sulfur-alkaline effluents (similar to example 1) are added to 100 ml of the aqueous phase to a pH value of 7.2. The volume ratio of V _in : V _ccc = 1: 0.4. The excess sodium sulfide in relation to the amount required by the reaction is 160%. It is then acidified to a pH of 2.2 by adding 1.25 ml of sulfuric acid.

The solution is boiled for 1-2 minutes, the precipitate of molybdenum trisulfide is filtered off. The molybdenum content in the filtrate is 8 mg / l, the degree of molybdenum precipitation is 98.97 wt.%.

Example 7

The method is carried out as described in example 1. To precipitate molybdenum trisulfide, 76.5 ml of alkaline sulphide effluents (analogous to Example 2) are added to 100 ml of the aqueous phase to a pH value of 9.0. The volumetric ratio of V _in : V _ccc = 1: 0.77. The excess sodium sulfide in relation to the amount required by the reaction is 170%. Then add 1.7 ml of sulfuric acid to a pH of 2.2.

Molybdenum is absent in the filtrate; molybdenum precipitation is complete.

Example 8

The method is carried out as described in example 1. To precipitate molybdenum trisulfide, 45.5 ml of sulfur-alkaline effluents (analogous to example 1) are added to 100 ml of the aqueous phase to a pH value of 9.0. The volumetric ratio of V _in : V _ccc = 1: 0.46. The excess sodium sulfide in relation to the amount required by the reaction is 200%. Then add 1.5 ml of sulfuric acid to a pH of 2.2.

Molybdenum is absent in the filtrate; molybdenum precipitation is complete.

Example 9

A temperature-controlled funnel at a temperature of 70 ° C is charged with 100 ml of alkaline waste obtained by washing with a solution of caustic soda of a heavy fraction of the process of epoxidation of cyclohexene with tert-butyl hydroperoxide. The molybdenum content in the alkaline waste is 0.24 wt.%. Pour 150 ml of 2.5 N sulfuric acid solution (123 g / l) and mix for 5 minutes. The phase separation time is less than 1 minute. The aqueous phase is discharged from below, the degree of extraction of molybdenum is 91.46 wt.%, The content of molybdenum in the aqueous phase is 984 g / l.

To precipitate molybdenum trisulfide, 48 ml of alkaline sulphide effluents (similar to Example 1) are added to 100 ml of the aqueous phase to a pH of 9.2. The volumetric ratio of V _in : V _ccc = 1: 0.48. The excess sodium sulfide relative to the amount required by the reaction is 190%. Then add 1.6 ml of sulfuric acid to a pH of 2.2.

Molybdenum is absent in the filtrate; molybdenum precipitation is complete.

Example 10

The method is carried out as described in example 9. To precipitate molybdenum trisulfide, 80 ml of sulfur-alkaline effluents (analogous to example 2) are added to 100 ml of the aqueous phase to a pH value of 9.0. The volumetric ratio of V _in : V _ccc = 1: 0.8. The excess sodium sulfide in relation to the amount required by the reaction is 180%. Then add 1.9 ml of sulfuric acid to a pH of 2.2.

Molybdenum is absent in the filtrate; molybdenum precipitation is complete.

Example 11

An olefin epoxidation catalyst is synthesized from the obtained molybdenum trisulfide: 0.44 g of molybdenum trisulfide is dissolved in 12.5 ml of 25% ethylbenzene hydroperoxide. The mixture is heated to 50 ° C. and 12.5 ml of ethyl alcohol are added. The oxidation is carried out for four hours at a temperature of 70 ° C, the content of dissolved molybdenum in the prepared catalyst is 0.61 wt.%. In parallel, an epoxidation catalyst based on metallic molybdenum with a dissolved molybdenum content of 0.6 wt.% Is prepared. The resulting catalyst solutions are tested in the process of epoxidation of octene-1. The conversion of hydroperoxide using a catalyst obtained from molybdenum metal is 94.6 wt.%, Using a catalyst obtained from molybdenum trisulfide, 97.2 wt.%. The selectivity of the formation of octene oxide is 92.8 and 93.8 wt.%, Respectively.

As can be seen from the above examples, the proposed method allows to achieve a high degree of extraction of molybdenum from the products of catalytic epoxidation of olefins with organic hydroperoxides.

Claims (1)

A method of extracting molybdenum from the products of the catalytic epoxidation of olefins with organic hydroperoxides, including treating the heavy fraction of the epoxide with an alkali solution, treating the resulting spent alkaline stream with an extractant, followed by precipitation of molybdenum trisulfide, characterized in that sulphide alkaline pyrolysis stocks of olefin production are used as a precipitant of molybdenum trisulfide .