EP2265695A1

EP2265695A1 - Method for removing mercury from hydrocarbon streams

Info

Publication number: EP2265695A1
Application number: EP09720628A
Authority: EP
Inventors: Peter Rudolf; Michael Bender
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2008-03-10
Filing date: 2009-03-09
Publication date: 2010-12-29
Also published as: KR20100133394A; CN101970614A; US20110005975A1; WO2009112440A1; JP2011513565A; JP5455939B2

Abstract

The invention relates to a method for removing mercury from a mercury-containing hydrocarbon stream, the hydrocarbon stream being contacted with an absorbent containing copper on a carrier substance. The method according to the invention is characterized in that the hydrocarbon stream is contacted with the absorbent in the presence of hydrogen.

Description

Process for the separation of mercury from hydrocarbon streams

The invention relates to a process for the separation of mercury and / or arsenic from a mercury-containing hydrocarbon stream.

Mercury is present as an impurity in numerous streams that are produced or processed in the chemical or petrochemical industry. Often, these are material flows that occur in the processing or thermal utilization of fossil fuels such as oil, natural gas or coal, as well as the recycling of waste, as these raw materials or waste contain traces of mercury in elemental form or chemically bound. Also, mercury contaminant streams fall into processes in which mercury or mercury-containing substances are used as the reagent or catalyst. An example of this is the electrolysis hydrogen produced in the chlorine production by the A-malgam process. Because of the high toxicity of mercury, it is necessary in most cases to separate these metal or metal-containing compounds from the streams occurring in the processes in question. Furthermore, mercury has the property of attacking aluminum-based apparatus by amalgamation, destroying the surface oxide layer of the aluminum, so that streams passing through aluminum apparatus or containers must be virtually free of mercury. Furthermore, noble metal-containing catalysts, such as those used in petrochemical processes, are poisoned by traces of mercury.

J.H. Pavlish et al. in Fuel Processing Technology 82 (2003), pp. 89-165 give an overview of methods for removing mercury from the exhaust gas streams produced in coal-fired power plants. S.M. Wilhelm gives in Hydrocarbon Processing, 1999, p. 61 ff. A review of methods for the removal of mercury from liquid hydrocarbon streams. An overview of the removal of mercury in olefin plants is given by Steve Coleman et al .: Feedstock Contaminants at Ethylene Plants, 2005 Spring National Meeting Atlanta, GA, April 10-14, 2005.

When metallic mercury is liquid in streams, mercury removal is often accomplished by mechanical means utilizing the high surface tension or high specific gravity of mercury by decantation, coalescing, activated carbon precoat or the like. EP-A-0 761 830 discloses a simple, purely mechanical process in which finely divided mercury is collected by coalescence into larger mercury droplets which are easily separable. WO 2004/048624 describes a process for the removal of mercury by filtration on electrographite.

For the removal of mercury, methods are also often used in which the mercury is bound to an adsorbent. Thus, DE-A 26 43 478 describes the separation of mercury from liquids by adsorption on activated carbon having a specific surface area of at least 250 m ² / g. To remove mercury from streams, inter alia, carbon-supported adsorbents are used, as described in US Pat. No. 3,755,989. No. 4,500,327 describes sulfur-impregnated activated carbon for the separation of mercury from gaseous streams, while JP 52-53793 describes the separation of iodide-containing activated carbon for the separation of mercury from liquid streams. US Pat. No. 4,909,926 and US Pat. No. 4,094,777 describe active compositions for removing mercury from streams which contain CuS or CuO or Ag ₂ S on support materials such as aluminum oxide. EP-A 0 385 742 describes a process for the removal of mercury from liquid hydrocarbon streams of hydrocarbons having up to 8 C atoms by contacting with metallic copper or copper compounds present on a support.

Often, the formation of solid amalgams is also used to remove mercury. Most suitable for this purpose are the metals of the 1st group of the periodic table (Cu, Ag, Au), which are usually used in the form of an absorption mass in which the metal is finely distributed on a support. Thus, DE-A 21 02 039 discloses a method for separating mercury from gases, in which the mercury-containing gases are brought into contact with a mass containing copper on a porous alumina support. US 4,230,486 discloses a process for separating mercury from liquids by passing the liquids over an absorbent containing metallic silver on a porous support such as activated carbon or a ceramic support. DE-A 42 21 207 teaches a method for the separation of mercury from alkali or alkali koholatlösung by passing the solutions over silver-coated fibers. DE-A 41 16 890 discloses absorbents for the removal of mercury, which in particular Cu, Ag, Fe and Bi, but also Au, Sn, Zn and Pd and mixtures of said metals in metallic or oxidic or sulphidic form on an activated carbon support with a BET Surface of 300 to 1000 m ² / g.

US Pat. No. 4.91 1, 825 describes the separation of mercury and arsenic from hydrocarbon streams, in which, in the presence of hydrogen, these are reacted in a first step with a catalyst comprising nickel and palladium on alumina and in a second Step comprising an absorbent containing sulfur or a metal sulfide, preferably copper sulfide or a combination of copper and silver sulfide, on a support. The process can also be carried out in one stage on a mixture of the catalyst and the absorbent. FR-A 2 310 795 describes the removal of mercury from a gaseous natural gas stream using an absorbent containing metallic gold, silver, copper or nickel on a support of silica, alumina or aluminosilicate having a BET surface area of 40 to 250 m ² / G. WO 91/15559 discloses a process for separating mercury from liquid hydrocarbon streams by contacting it with an absorbent obtained by mixing a powdery oxide, preferably selected from nickel oxide, copper oxide and cobalt oxide, with a porous support material, such as alumina, silica, zeolites or Toning, and subsequent reduction is made.

The object of the invention is to provide an improved process for the separation of mercury from a mercury-containing hydrocarbon stream.

The object is achieved by a method for separating mercury from a mercury-containing hydrocarbon stream in which the hydrocarbon stream is contacted with an absorbent containing copper on a porous oxidic support material, characterized in that the hydrocarbon stream in the presence of hydrogen with the absorbent in Contact is brought.

It has been found that in the presence of hydrogen with the copper-containing absorbers containing copper on a support and acting as hydrogenation catalysts, a much better separation of mercury from the hydrocarbon streams is effected than in the absence of hydrogen.

The absorbent used according to the invention contains copper, preferably in reduced form, on a porous support material. The absorbent used in the invention is effective as a hydrogenation catalyst. Suitable porous support materials are amorphous and crystalline aluminosilicates, alumina, silica, clays and metal oxides. Suitable clays are, for example, attapulgite, kaolin, bentonite, fuller earth. Suitable metal oxides are, for example, in addition to aluminum oxides and silicon dioxide, magnesium oxide, zirconium dioxide, titanium dioxide, zinc oxide, chromium (III) oxide, barium oxide and mixtures thereof. Preferred alumina is γ-alumina. - A -

In the process according to the invention, it is possible to use all conventional copper-containing hydrogenation catalysts in activated (reduced) form.

The copper-containing hydrogenation-active absorption agents used according to the invention are obtainable by mixing copper oxide with a support material and subsequent conversion of copper into the metallic form by reduction, preferably in a hydrogen stream. The absorbents used according to the invention can be further prepared by impregnating the support material with an aqueous solution of a copper salt, drying, optionally calcining, and converting the copper into the metallic form by reduction, preferably with a hydrogen-containing gas stream, but also with a reducing agent such as hydrazine.

Copper is generally reduced in the absorbent used in the invention, d. H. metallic (elemental) form finely dispersed on the support material before. In general, the absorbents used according to the invention contain from 10 to 50% by weight of copper on an oxidic support material. Examples of suitable compositions on the basis of which the absorbents used according to the invention are obtained are compositions comprising copper oxide, zinc oxide and aluminum oxide or compositions comprising copper oxide, magnesium oxide, barium oxide, chromium (III) oxide, zinc oxide and silicon dioxide. Particularly preferred is a mixture of 10 to 60 wt .-% copper oxide, 0 to 40 wt .-% zinc oxide, 0 to 20 wt .-% alumina, 5 to 25 wt .-% magnesium oxide, 10 to 40 wt .-% silica , 0 to 5 wt .-% chromium (III) oxide and 0 to 10 wt .-% barium oxide.

Hydrocarbon streams from which mercury can be separated according to the invention are any hydrocarbon streams which may be contaminated with mercury. These generally contain aliphatic, aromatic, alicyclic and / or heterocyclic hydrocarbons having 1 to 14 carbon atoms. Examples of hydrocarbon mixtures which can be freed from mercury according to the invention are LNG (Liquefied Natural Gas), LPG (Liquefied Petroleum Gas), Napththa and kerosene. Examples of pure hydrocarbons which can be purified according to the invention are ethylene and propylene and also aliphatic hydrocarbons.

The mercury content of the hydrocarbons or hydrocarbon mixtures before carrying out the process according to the invention can be up to 100 ppm, In general, it is up to 1 ppm Hg. Mercury is generally present in the form of organomercury compounds.

The process according to the invention can be carried out in suspension or fixed bed mode. If it is carried out in fixed bed mode, it can be carried out in sump or breeze mode. The mercury or arsenic-containing hydrocarbons or mixtures can be used in gaseous or liquid form. The hydrocarbons or hydrocarbon mixtures are preferably used in liquid form. Hydrogen is introduced together with the gaseous or liquid hydrocarbon or hydrocarbon mixture into a suitable reaction vessel and, generally in cocurrent, passed through the lumped absorbent arranged in a fixed bed. It can be worked in sump or trickle way. However, hydrogen and hydrocarbon or hydrocarbon mixture can also be passed in countercurrent over the absorbent bed. The absorbent may further be suspended in the hydrocarbon or hydrocarbon mixture. In general, the process is carried out at a temperature of 30 to 250 ^° C., preferably 60 to 180 ^° C., and a hydrogen pressure of 1 to 20 bar. The pressure is preferably chosen such that the hydrocarbon or the hydrocarbon mixture is present as a liquid. The amount of hydrogen introduced generally corresponds to a load of 10 to 650 Nl per kg of absorbent and hour.

After exhaustion of the absorbent, this can be thermally regenerated by this is heated in an inert gas or a hydrogen-containing gas stream, generally to temperatures of 180 to 400 ⁰ C, for example 200 to 220 ⁰ C, and evaporated mercury is condensed out.

The invention is further illustrated by the following examples.

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. In this solution, 1, 5 Nl / h of hydrogen were introduced with stirring. To this solution, 5 g of a non-reduced hydrogenation catalyst of 40 wt .-% CuO, 40 wt .-% ZnO and 20 wt .-% Al ₂ O ₃ in the form of 3 x 5 mm tablets (Absorbent A) was added. The solution was sampled after 2 hours and 24 hours, and the mercury content of the samples was determined. The results are shown in Table 1.

Comparative Example 2

A solution of diphenylmercury in 500 ml of octane, corresponding to 350 ppm of mercury, was heated to 60 ^° C. in a glass flask. To this solution, 5 g of the catalyst of 40 wt .-% CuO, 40 wt .-% ZnO and 20 wt .-% Al ₂ O ₃ , which had previously been reduced and activated at 180 ⁰ C by means of H ₂ (Absorbent B ), in the form of 3 x 5 mm tablets. Hydrogen was not introduced. The solution was stirred. After 2 h and 24 h, samples were taken and their mercury content was determined. The results are shown in Table 1.

example 1

The procedure was as in Comparative Example 2, but 1, 5 Nl / h of hydrogen were introduced. Samples were taken at regular intervals and their mercury content was determined. The results are shown in Table 1.

Example 2

The procedure was as in Example 1. However, the reduced catalyst was added in powder form (Absorbent C). Samples were taken at regular intervals and their mercury content determined. The results are shown in Table 1.

Table 1

Example 3

The procedure was as in Example 1, but the solution was heated to 25 ⁰ C. Samples were taken at regular intervals and their mercury content determined. The results are shown in Table 2.

Example 4

The procedure was as in Example 1. The temperature was thus 60 ^° C. Samples were taken at regular intervals and their mercury content was determined. The results are shown in Table 2.

Example 5

The procedure was as in Example 1, but was heated to 100 ⁰ C. Samples were taken at regular intervals and their mercury content was determined. The results are shown in Table 2.

Table 2

Example 6

The experiments were carried out in a monoline reactor with an internal diameter of 6 mm and a total length of 5 m. The reactor consisted of 4 segments connected by a capillary. The reactor was operated in trickle mode. The reactor segments were heated to 60 ⁰ C. In front of the reactor inlet, the liquid hydrocarbon feed was mixed with hydrogen. The reactor effluent was cooled by means of an intensive condenser and the gas phase separated from the liquid phase. The liquid phase was used to determine the mercury content, the gas phase was disposed of via a mercury Guardbed.

In the reactor were 80 g of a catalyst of 45 wt .-% CuO, 16 wt .-% MgO, 35 wt .-% SiO ₂ , 0.9 wt .-% Cr ₂ O ₃ , 1, 1 wt. % BaO and 0.6% by weight ZnO in the form of 3 × 5 mm tablets. Between the individual tablets was in each case a glass sphere of 2 mm diameter. The catalyst was first activated in a hydrogen stream at 180 to 220 ⁰ C. Subsequently, the reactor was cooled to 60 ^° C. in a hydrogen stream. The reactor was operated at atmospheric pressure.

The feed used was octane, which was saturated with an organomercury compound. As an organomercury compound, phenylmercuric acetate PhHgOAc was used in one part of the experiments and mercury acetate Hg (OAc) ₂ in another part of the experiments. In each case several batches with different mercury concentrations were used. 100 Nl / h of the mercury-containing octane and 2 Nl / h of hydrogen were added. The results of the experiments are summarized in Table 3.

Table 3

Claims

claims

A process for separating mercury from a mercury-containing hydrocarbon stream, wherein the hydrocarbon stream is contacted with an absorbent containing copper on a support material, characterized in that the hydrocarbon stream is contacted with the absorbent in the presence of hydrogen.

2. The method according to claim 1, characterized in that copper is present on a porous oxidic carrier material.

3. The method according to any one of claims 1 or 2, characterized in that the absorbent contains 10 to 60 wt .-% copper.

4. The method according to any one of claims 1 to 3, characterized in that the absorbent 10 to 60 wt .-% copper oxide, 0 to 40 wt .-% zinc oxide, 0 to 20 wt .-% alumina, 5 to 25 wt. % Magnesium oxide, 10 to 40 wt .-% silicon dioxide, 0 to 5 wt .-% chromium (III) oxide and 0 to 10 wt .-% barium oxide.

5. The method according to any one of claims 1 to 4, characterized in that the hydrocarbon stream is in liquid form.

6. The method according to any one of claims 1 to 5, characterized in that the absorbent is present as a fixed bed.

7. The method according to claim 6, characterized in that the hydrocarbon stream is brought into contact with the absorbent in sump or trickle mode.

8. The method according to claim 5, characterized in that the absorbent is suspended in the hydrocarbon stream.