KR20100133394A - Method for removing mercury from hydrocarbon streams - Google Patents

Abstract

The present invention relates to a method for removing mercury from a mercury containing hydrocarbon stream, wherein the hydrocarbon stream is contacted with an absorbent comprising copper on a support material and the hydrocarbon stream is contacted with an absorbent in the presence of hydrogen.

Description

How to remove mercury from hydrocarbon streams {METHOD FOR REMOVING MERCURY FROM HYDROCARBON STREAMS}

The present invention relates to a method for removing mercury and / or arsenic from a mercury-containing hydrocarbon stream.

Mercury is present as impurities in numerous material streams obtained or processed in the chemical or petrochemical industries. Such streams are often streams obtained from the treatment or thermal use of fossil raw materials such as petroleum, natural gas or coal, and from the use of waste, which contain such traces of mercury in elemental or chemical bond form. Because. Streams containing mercury as impurities may also be obtained in processes in which mercury or mercury containing materials are used as reagents or catalysts. Examples that may be mentioned are the electrolytic hydrogens obtained in the production of chlorine by the amalgam process. Due to the high toxicity of mercury, in most cases it is necessary to separate off such metals or compounds containing such metals from the stream obtained in the relevant process. In addition, mercury has the property of attacking devices containing aluminum by forming amalgams with the destruction of the oxide layer on the aluminum surface, so that the stream passing through a device or vessel made of aluminum should be virtually free of mercury. In addition, catalysts containing precious metals, such as used in petrochemical processes, for example, are contaminated by trace amounts of mercury.

Fuel Processing Technology 82 (2003), pp. 89-165, J. H. Pavlish et al. Provide an overview of the method of removing mercury from off-gas streams obtained from coal-fired power stations. In Hydrocarbon Processing, 1999, p. 61 ff., S. M. Wilhelm provides an overview of the method for removing mercury from liquid hydrocarbon streams. An overview of mercury removal in olefin plants is provided by Steve Coleman et al .: Feeded Contaminants in Ethylene Plants, 2005 Spring National Meeting Atlanta, GA April 10-14, 2005.

Where metallic mercury is present in the liquid stream in the material stream, mercury is often used as a coalescence filter, activated carbon coated filter, by physical means utilizing the high surface tension or high specific gravity of mercury by decantation. And the like. EP-A 0 761 830 discloses a simple pure physical process in which finely divided mercury is collected by coalescence to form larger mercury droplets that are easy to separate and remove. WO 2004/048624 describes a method for removing mercury by filtration through electrographite.

In addition, the removal of mercury is often carried out using a method of binding mercury to the adsorbent. Accordingly, DE-A 26 43 478 describes the separation of mercury from liquid by adsorbing mercury on activated carbon having a specific surface area of at least 250 m ² / g. Carbon-based adsorbents are used to remove mercury from material streams, in particular as described in US Pat. No. 3,755,989. US 4,500,327 describes sulfur-impregnated activated carbon for removing mercury from gas streams, while JP 52-53793 describes the use of iodide containing activated carbon to remove mercury from liquid streams. US 4,909,926 and US 4,094,777 describe the use of active compositions comprising CuS or CuO or Ag ₂ S on a support material, such as aluminum oxide, for removing mercury from a material stream. EP-A 0 385 742 describes a method for removing mercury from a stream of liquid hydrocarbon comprising a hydrocarbon having up to 8 carbon atoms with a metallic copper or copper compound present on the support.

Formation of solid amalgam is also often used to remove mercury. The most suitable metal for this purpose is the metals of group XI (Cu, Ag, Au) of the periodic table, which is usually used in the form of an absorbent composition in which the metal is finely distributed on the support. Accordingly, DE-A 21 02 039 discloses a method for removing mercury from a gas in which the mercury containing gas is in contact with a composition comprising copper on a porous aluminum oxide support. US 4,230,486 discloses a method for removing mercury from a liquid by passing the liquid over an absorbent comprising metallic silver on a porous support such as activated carbon or a ceramic support. DE-A 42 21 207 teaches the removal of mercury from a solution by passing an alkali metal hydroxide solution or an alkali metal alkoxide solution onto the silver coated fibers. DE-A 41 16 890 discloses in the form of metals or oxides or sulfides on activated carbon supports having a BET surface area of 300 to 1000 m ² / g, in particular Cu, Ag, Fe and Bi, or else Au, Sn, Zn and Pd Absorbents for removing mercury are disclosed, including also mixtures of the mentioned metals.

US 4,911,825 discloses contacting a hydrocarbon stream with a catalyst comprising nickel and palladium on aluminum oxide in the first step in the presence of hydrogen and in the second step the sulfur or metal sulfides, preferably copper sulfide, or copper sulfide and silver sulfide It is described to remove mercury and arsenic from the hydrocarbon stream by contacting with an absorbent comprising the combination. The process can also be carried out in a single step on a mixture of catalyst and absorbent. FR-A 2 310 795 has a gaseous nature using an absorbent comprising metallic gold, silver, copper or nickel on a support made of silicon dioxide, aluminum oxide or aluminosilicate having a BET surface area of 40 to 250 m ² / g. The removal of mercury from gas streams is described. WO 91/15559 contacts a liquid hydrocarbon stream with an absorbent prepared by mixing a fine powder oxide, preferably an oxide selected from nickel oxide, copper oxide and cobalt oxide with a porous support material such as aluminum oxide, silicon dioxide, zeolite or clay. A method of removing mercury from the liquid hydrocarbon stream by means of a reduction followed by a reduction treatment is disclosed.

It is an object of the present invention to provide an improved method for removing mercury from a mercury containing hydrocarbon stream.

Its purpose is to remove mercury from a mercury-containing hydrocarbon stream, wherein the hydrocarbon stream is contacted with an absorbent comprising copper on the porous oxide support material, and the hydrocarbon stream is contacted with the absorbent in the presence of hydrogen. Is realized.

It has been found that even better removal of mercury from hydrocarbon streams is realized in the presence of hydrogen using copper-containing absorbents that include copper on the support and are effective as hydrogenation catalysts than in the absence of hydrogen.

The absorbent used according to the invention comprises copper, preferably in reduced form, on the porous support material. Absorbents used according to the invention are effective as hydrogenation catalysts. Suitable porous support materials are amorphous and crystalline aluminosilicates, aluminum oxide, silicon dioxide, clays and metal oxides. Suitable clays are, for example, attapulgite, kaolin, bentonite, Fuller's earth. Suitable metal oxides are, for example, aluminum oxide and silicon dioxide, and also magnesium oxide, zirconium dioxide, titanium dioxide, zinc oxide, chromium (III) oxide, barium oxide and mixtures thereof. Preferred aluminum oxide is γ-aluminum oxide.

All conventional copper containing hydrogenation catalysts in active (reduced) form can be used in the process of the present invention.

The copper-comprising hydrogenated-active absorbent used according to the invention can be obtained by mixing copper oxide with the support material and preferably converting copper to the metal form by reduction in a hydrogen stream. The absorbent used according to the invention can also be impregnated with a support material in an aqueous copper salt solution, dried, calcined if appropriate, by reduction and also with a reducing agent such as hydrazine, but preferably with a hydrogen containing gas stream, It can also be produced by converting to a metal form.

In the absorbent used according to the invention, copper is generally present in reduced form, ie in the form of metals (elements), finely dispersed on the support material. In general, the absorbent used according to the invention comprises 10 to 50% by weight of copper on the oxidizing support material. Examples of suitable compositions based on obtaining the absorbent used according to the invention include compositions comprising copper oxide, zinc oxide and aluminum oxide, or copper oxide, magnesium oxide, barium oxide, chromium (III) oxide, zinc oxide and It is a composition containing silicon dioxide. 10 to 60 wt% copper oxide, 0 to 40 wt% zinc oxide, 0 to 20 wt% aluminum oxide, 5 to 25 wt% magnesium oxide, 10 to 40 wt% silicon dioxide, 0 to 5 wt% Particular preference is given to mixtures of chromium (III) oxide and 0-10% by weight of barium oxide.

The hydrocarbon stream from which mercury can be removed in accordance with the present invention is any hydrocarbon stream that can be contaminated with mercury. It generally includes aliphatic, aromatic, cycloaliphatic and / or heterocycle hydrocarbons having 1 to 14 carbon atoms. Examples of hydrocarbon mixtures capable of removing mercury in accordance with the present invention are LNG (liquefied natural gas), LPG (liquefied petroleum gas), naphtha and kerosene. Examples of pure hydrocarbons that can be purified according to the invention are ethylene and propylene, and also aliphatic hydrocarbons.

The mercury content of the hydrocarbons or hydrocarbon mixtures prior to carrying out the process of the invention may be up to 100 ppm, but is generally less than 1 ppm Hg. Mercury is generally present in the form of organic mercury compounds.

The process of the invention can be carried out in a suspension or fixed bed manner. When performed in a fixed bed method, it may be performed in an upflow or downflow method. Hydrocarbons or hydrocarbon mixtures comprising mercury or arsenic can be used in gaseous or liquid form. Hydrocarbons or hydrocarbon mixtures are preferably used in liquid form. Hydrogen is introduced into a suitable reaction vessel together with gas or liquid hydrocarbons or hydrocarbon mixtures and is usually passed in cocurrent over the particulate absorbent present in the fixed bed. This can be done in an upflow or downflow manner. However, hydrogen, and hydrocarbons or hydrocarbon mixtures may also be passed over the absorbent phase in countercurrent. The absorbent may also be present in suspension in the hydrocarbon or hydrocarbon mixture. In general, the process is carried out at a temperature of 30 to 250 ° C., preferably of 60 to 180 ° C. and a hydrogen pressure of 1 to 20 bar. The pressure is preferably selected such that the hydrocarbon or hydrocarbon mixture is present as a liquid. The amount of hydrogen introduced generally corresponds to the space velocity of 1 kg of absorbent and 10-650 standard I per hour.

After the absorbent has been discharged, it can be thermally regenerated by heating in an inert gas stream or hydrogen containing gas stream and condensing vaporized mercury at a temperature generally between 180 and 400 ° C, such as between 200 and 220 ° C.

The invention is illustrated by the following examples.

Comparative Example 1

A solution of diphenylmercury (Ph ₂ Hg) in 500 ml of octane, corresponding to 350 ppm Hg, was heated to 60 ° C. in a glass flask. Into that solution, 1.5 standard I / h of hydrogen was passed with stirring. To this solution was added 5 g of an unreduced hydrogenation catalyst (absorbent A) comprising 40 wt% CuO, 40 wt% ZnO and 20 wt% Al ₂ O ₃ in the form of 3 × 5 mm pellets. Samples were taken from the solution after 2 and 24 hours and the mercury content of the samples was measured. The results are shown in Table 1 below.

Comparative Example 2

A solution of diphenylmercury in 500 ml octane, corresponding to 350 ppm mercury, was heated to 60 ° C. in a glass flask. In this solution a catalyst comprising 40 wt% CuO, 40 wt% ZnO and 20 wt% Al ₂ O ₃ in the form of 3 × 5 mm pellets, previously reduced and activated by H ₂ at 180 ° C. 5 g of absorbent B) was added. Hydrogen was not passed through. The solution was stirred. Samples were taken from the solution after 2 and 24 hours and their mercury content was measured. The results are shown in Table 1 below.

Example 1

The procedure of Comparative Example 2 was repeated but passed through 1.5 standard I / h of hydrogen. Samples were taken at regular intervals and their mercury content was measured. The results are shown in Table 1 below.

Example 2

The procedure of Example 1 was repeated, but the reduced catalyst was added in the form of fine powder (absorbent C). Samples were taken at regular intervals and their mercury content was measured. The results are shown in Table 1 below.

Example 3

The procedure of Example 1 was repeated but the solution was kept at 25 ° C. Samples were taken at regular intervals and their mercury content was measured. The results are shown in Table 2 below.

Example 4

The procedure of Example 1 was repeated. The temperature was 60 degreeC by this. Samples were taken at regular intervals and their mercury content was measured. The results are shown in Table 2 below.

Example 5

The procedure of Example 1 was repeated but the solution was heated to 100 ° C. Samples were taken at regular intervals and their mercury content was measured. The results are shown in Table 2 below.

Example 6

Experiments were performed in a monoline reactor with an internal diameter of 6 mm and a total length of 5 m. The reactor contained four segments connected to each other by capillaries. The reactor was operated in downflow mode. The reactor segment was maintained at 60 ° C. The liquid hydrocarbon feed was mixed with hydrogen before the reactor inlet. The reactor outlet was cooled by a cold condenser and the gas phase was separated from the liquid phase. Liquid phase was used to measure mercury content and gas phase was processed through a mercury guard bed.

45 wt% CuO, 16 wt% MgO, 35 wt% SiO ₂ , 0.9 wt% Cr ₂ O ₃ , 1.1 wt% BaO and 0.6 wt% ZnO in the form of 3 × 5 mm pellets 80 g of catalyst was present in the reaction. Glass spheres with a diameter of 2 mm were present between each individual pellet. The catalyst was first activated at 180-220 ° C. in a hydrogen stream. The reactor was then cooled to 60 ° C. in a hydrogen stream. The reactor was operated at atmospheric pressure.

As feed, saturated octane over organic mercury compounds was used. In some of the experiments, phenylmercury acetate PhHgOAc was used as the organic mercury compound, and in some of the experiments, mercury acetate Hg (OAc) ₂ was used as the organic mercury compound. Multiple batches with different mercury concentrations in each case were used. 100 standard I / h of mercury-containing octane and 2 standard I / h of hydrogen were metered in. The results of the experiment are summarized in Table 3 below.

Claims (8)

A method of removing mercury from a mercury-containing hydrocarbon stream, wherein the hydrocarbon stream is contacted with an absorbent comprising copper on the support material and the hydrocarbon stream is contacted with the absorbent in the presence of hydrogen. The method of claim 1, wherein the copper is present on the porous oxide support material. The method of claim 1 or 2, wherein the absorbent comprises 10 to 60 weight percent copper. The absorbent according to any one of claims 1 to 3, wherein the absorbent is 10 to 60 wt% copper oxide, 0 to 40 wt% zinc oxide, 0 to 20 wt% aluminum oxide, 5 to 25 wt% Magnesium oxide, 10-40% by weight of silicon dioxide, 0-5% by weight of chromium (III) oxide and 0-10% by weight of barium oxide. The process of claim 1, wherein the hydrocarbon stream is in liquid form. The method of claim 1, wherein the absorbent is present as a fixed bed. The method of claim 6, wherein the hydrocarbon stream is contacted with the absorbent in an upflow or downflow mode. The method of claim 5 wherein the absorbent is present in suspension in the hydrocarbon stream.