AU2017291058B2

AU2017291058B2 - Trapping mass consisting of an active phase in crystalline form

Info

Publication number: AU2017291058B2
Application number: AU2017291058A
Authority: AU
Inventors: Karin Barthelet; Nicolas Cadran; Antoine Hugon; Arnold Lambert; Anthony Tanguy
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 2016-06-30
Filing date: 2017-05-17
Publication date: 2022-07-21
Anticipated expiration: 2037-05-17
Also published as: WO2018001632A1; AU2017291058A1; FR3053260B1; FR3053260A1; MY189250A; CN109641171B; CN109641171A

Abstract

A trapping mass for trapping heavy metals, in particular mercury, contained in a gas or liquid feedstock, said mass comprising: - an active phase in the form of a crystalline phase, said active phase comprising at least one metal sulfide made from a metal M chosen from the group consisting of copper (Cu), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), and nickel (Ni); - an amorphous support comprising a material made from aluminium.

Description

CAPTURE MASS CONSTITUTED BY AN ACTIVE PHASE IN THE CRYSTALLINE FORM

Field of the invention

The present invention relates to the field of treating liquid or gaseous effluents containing heavy metals, in particular effluents of oil origin and their derivatives, such as gas of industrial origin, for example synthesis gas, natural gas and liquid hydrocarbons. More precisely, the invention concerns the capture of heavy metals, in particular mercury, present in a gaseous or liquid effluent.

Prior art

Mercury is a metallic contaminant which is found in gaseous or liquid hydrocarbons produced in many regions of the world such as the Gulf of Niger, South America, North Africa or the Asia-Pacific region.

The elimination of mercury from hydrocarbons is desirable from an industrial viewpoint for a number of reasons.

Firstly, the presence of mercury in those hydrocarbons is a risk to operators working in contact with these substances, because mercury is toxic. In its elemental form, mercury is volatile and runs severe risks of neurotoxicity by inhalation. In its organic form, mercury gives rise to risks which are similar to neurotoxicity by skin contact.

Secondly, the presence of mercury in hydrocarbons has a deleterious effect on conventional processing operations which are intended to upgrade those hydrocarbons. Conventionally, the hydrocarbons undergo catalytic reactions such as selective hydrogenation of the olefins produced by steam cracking or catalytic cracking of liquid hydrocarbons. However, the catalysts used, generally comprising noble metals such as platinum and palladium, can be deactivated by the mercury. In fact, mercury induces sintering of the catalysts by amalgamating with nanoparticles of the noble metals. The reduction in the specific surface area of the catalysts leads to a very substantial loss of their catalytic activity.

For these reasons and more, it is desirable to eliminate or at least reduce the concentration of mercury in gaseous or liquid hydrocarbon effluents.

Industrially, the elimination of mercury from gaseous or liquid effluents is carried out by moving the effluent to be treated through guard beds filled with adsorbent materials, otherwise known as capture masses. The impurity to be eliminated, in this case mercury, is then irreversibly retained, preferably by chemisorption, within or at the surface of the capture mass and the effluent evacuated from the bed of capture mass is then purified.

Mercury can be captured by reacting the mercury with an active phase based on elemental sulphur in a capture mass. In fact, elemental sulphur, S, reacts irreversibly with elemental mercury, Hg°, as follows:

Hg° (g/L) + S (s) -> HgS (s) (1)

The term "Hg° (g/L)" means that the mercury is dissolved in a gaseous (g) or liquid (I) fluid phase. In contrast, "(s)" denotes solid phases constituted by the active phase of the capture mass and by the reaction product.

Reaction (1) is spontaneous and has a negative free energy, AG (kJ/mole), over a wide temperature range, typically 0°C to 1500 C. The product formed, HgS, known as cinnabar or metacinnabar, is a chemically inert, mineral phase which is a solid over a vast range of temperatures. Thus, the mercury is trapped in the capture mass and the effluent to be treated is purified.

Conventionally, capture masses based on elemental sulphur are obtained by a method for impregnating elemental sulphur onto an activated charcoal type support.

However, capture masses based on elemental sulphur deposited on activated charcoal frequently suffer from stability problems when the effluent to be treated is liquid or when the effluent to be treated is gaseous and moist, because the active phase can be entrained by the water or another liquid. This phenomenon, linked to the low energetic interaction between the active phase and the surface of the activated charcoal and to the solubility of sulphur in these media, brings about a drastic drop in the service life of the capture masses.

In order to overcome these disadvantages, it is possible to use capture masses based on metal sulphides deposited on supports with a controlled porosity such as aluminas, for example. Copper sulphide is used in particular because of its stability and its low manufacturing costs. Patent document US 7 645 306 describes the fact that elemental mercury (Hg°) reduces copper sulphide, CuS, irreversibly in accordance with the following reaction:

Hg° (g/L) + 2 CuS (s) -> Cu2S (s) + HgS (s) (2).

This reaction is a gas/solid or liquid/solid reaction which is more favoured from the point of view of its kinetics as the specific surface area of the active phase, in this case CuS, is increased.

Capture masses based on metal sulphides are conventionally prepared by depositing a precursor of a metal in the oxide form, such as CuO, for example, onto a support, then by carrying out a sulphurization step in order to transform the metal oxide into metal sulphide. A capture mass containing a support and copper sulphide is described in the patent US 4 094 777.

However, using metal sulphides, and in particular of copper sulphides, cannot overcome all of the problems linked to the capture of heavy metals in gaseous or liquid effluents. It has in particular been shown that beyond a certain content, the retention capacity for heavy metals by the capture mass is not or is only slightly improved despite an increase in the metal sulphide content. In fact, Figure 5 of the article by W.R.A.M Robinson and J.C. Mol ("Characterization and Catalytic Activity of Copper/Alumina Methanol Synthesis Catalysts", Applied Catalysis, 44 (1988) 165-177) shows that, for contents of more than 8.5% by weight of copper with respect to the mass of CuO/Al203 catalyst, the specific surface area of copper per gram of catalyst reduces. This can be explained by the fact that beyond a certain quantity of active phase, the copper oxide crystallites have a tendency to agglomerate into coarser clusters. This could render a portion of the active phase inaccessible and also cause partial blockage of the pores, and hence a deterioration in material transfer. Thus, it is difficult to obtain capture masses with a large retention capacity for heavy metals.

The solution for significantly increasing the quantity of active phase is to prepare what are known as bulk capture masses essentially constituted by copper sulphide as described, for example, in the patent W02008/020250. In that particular case, the adsorbent is obtained by co-granulation of one or more metal oxides or metal oxide precursors with a binder such as cement in order to ensure mechanical cohesion of the solid. The precursor obtained in this manner is then sulphurized in order to obtain the active capture mass. However, that type of material has a low porosity, which often brings about incomplete sulphurization and the presence of major limitations to diffusion, and a monomodal pore distribution constituted almost uniquely by large mesopores, and hence a slump in the mechanical behaviour of the solid, and thus the formation of fines as it is being charged and/or it is in use.

In this context, one of the aims of the present invention is to propose a capture -0 mass which does not have the disadvantages of the capture masses of the prior art, which has a large retention capacity for heavy metals, and which can be used to treat liquid and gaseous effluents, even those which are moist, which has a good service life while still having a substantially high pore volume.

The Applicant has discovered that, surprisingly, capture masses comprising an active phase in the form of a crystalline phase and an amorphous support can be used to obtain improved performances in terms of the adsorption of heavy metals, and in particular of mercury, and can advantageously be used to achieve the aims identified above.

SUMMARY OF THE INVENTION

According to one aspect, there is provided a process for the preparation of the capture mass for heavy metals, in particular mercury, contained in a gaseous or liquid feed, said mass comprising an active phase in the form of a crystalline phase, said active phase comprising at least one metal sulphide based on a metal M selected from the group constituted by copper (Cu), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) and nickel (Ni), and an amorphous support comprising a material based on aluminium, the process comprising the following steps:

a) preparing an aqueous solution containing at least one precursor of a material based on aluminium and at least one precursor of at least one metal sulphide based on a metal M selected from the group constituted by copper (Cu), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) and nickel (Ni);

b) carrying out a step for co-precipitation, in an aqueous reaction medium, by simultaneously adding the solution prepared in step a) containing said precursor of said material based on aluminium and said precursor of said metal sulphide based on a metal M to a base or an acid in a manner such as to obtain a precipitate;

c) filtering the precipitate obtained in step b), and washing said precipitate at least once;

d) drying the product obtained in step c) at a temperature in the range 700 C to 150 0C in order to obtain a powder;

e) shaping the powder obtained in step d) in order to obtain a green material;

f) calcining the green material obtained at the end of step e) in air at a temperature in the range 3000 C to 600°C;

g) sulphurizing the material obtained at the end of step f).

Disclosed herein is also a capture mass for heavy metals, in particular mercury, contained in a gaseous or liquid feed, said mass comprising:

- an active phase in the form of a crystalline phase, said active phase comprising at least one metal sulphide based on a metal M selected from the group constituted by copper (Cu), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) and nickel (Ni);

- an amorphous support comprising a material based on aluminium. Preferably, the amorphous support is constituted by a material based on aluminium.

In some embodiments, said capture mass contains at least 90% by weight of metal M in the form MxSy with respect to the total weight of metal M.

In some embodiments, the metal M is copper.

In some embodiments, the aluminium is present in a quantity of 1% to 48% by weight with respect to the total weight of said capture mass.

In some embodiments, the metal M is present in a quantity of 6% to 65% by weight with respect to the total weight of said capture mass.

In some embodiments, the sulphur is present in a quantity of 3% to 65% by weight with respect to the total weight of said capture mass.

In some embodiments, said capture mass has a total pore volume in the range 0.1 cm 3 .g-1 to 1.5 cm 3 .g-1 and a specific surface area in the range 40 m 2.g-1 to 400 m 2.g-1.

In some embodiments, said capture mass is in the form of a bead or an extrudate, preferably with a trilobal shape.

Disclosed herein is also a process for the preparation of the capture mass in accordance with the invention, comprising the following steps:

a) preparing an aqueous solution containing at least one precursor of a material based on aluminium and at least one precursor of at least one metal sulphide based on a metal M selected from the group constituted by copper (Cu), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) and nickel (Ni); b) carrying out a step for co-precipitation, in an aqueous reaction medium, by simultaneously adding the solution prepared in step a) containing said precursor of said material based on aluminium and said precursor of said metal sulphide based on a metal M to a base or an acid in a manner such as to obtain a precipitate; c) filtering the precipitate obtained in step b), and washing said precipitate at least once; d) drying the product obtained in step c) at a temperature in the range 700C to 1500C in order to obtain a powder; e) shaping the powder obtained in step d) in order to obtain the green material; f) calcining the green material obtained at the end of step e) in air at a temperature in the range 3000C to 600°C; g) sulphurizing the material obtained at the end of step f).

In some embodiments, the calcining step f) is carried out for a period in the range 2 to 10 h.

In some embodiments, the calcining step f) is carried out in air containing a relative humidity at 250C in the range 0% to 80%.

In some embodiments, the sulphurization step g) is carried out using a gaseous mixture of nitrogen and hydrogen sulphide the molar concentration of which is in the range 1000 ppm to 10%.

In some embodiments, the sulphurization step g) is carried out at a temperature in the range 100°C to 4000C.

According to another aspect, the invention is directed to the use of the capture mass prepared by the process described above in order to eliminate heavy metals, in particular mercury, contained in a gaseous or liquid feed.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

The textural and structural properties of the capture mass are determined by characterization methods which are known to the person skilled in the art.

The total pore volume and the pore distribution are determined by mercury porosimetry (see Rouquerol F.; Rouquerol J.; Singh K. "Adsorption by Powders & Porous Solids: Principle, methodology and applications", Academic Press, 1999). More particularly, the total pore volume is measured by mercury porosimetry in accordance with the standard ASTM D4284-92 with a wetting angle of 140, for example using an Autopore ITM model instrument made by Microm6ritics TM .

In the present description, and in accordance with the IUPAC convention, the term "micropores" means pores with a diameter of less than 2 nm (0.002 pm), the term "mesopores" means pores with a diameter in the range 2 nm (0.002 pm) to 50 nm (0.05 pm), and "macropores" means pores with a diameter of more than 50 nm (0.05 pm).

In the disclosure of the invention below, the term "specific surface area" means the BET specific surface area determined by nitrogen adsorption in accordance with the standard ASTM D 3663-78 based on the BRUNAUER-EMMETT TELLER method described in the periodical "The Journal of American Society", 60, 309, (1938).

In the present invention, the expression "active phase in the form of a crystalline phase" means an active phase which leads to the presence of diffraction peaks in the X ray diffraction diagram.

The term "amorphous support" means a support characterized by the absence of a significant diffraction peak on the diffraction diagram.

DESCRIPTION

The invention concerns a capture mass for heavy metals, in particular mercury, contained in a gaseous or liquid feed, said mass comprising:

- an amorphous support comprising a material based on aluminium.

In fact, in accordance with an essential aspect of the invention, the support comprising a material based on aluminium is not crystalline, and is thus in an amorphous form. Surprisingly, the Applicant has discovered that a capture mass in accordance with the invention has a better sulphurization ratio compared with capture masses in accordance with the prior art, and also has a better capacity for the adsorption of heavy metals, in particular for mercury.

Advantageously, said capture mass in accordance with the invention contains at least 90% by weight of metal M in the form MxSy with respect to the total weight of the metal M. The fraction of metal contained in the sulphide form MxSy constituting the active phase preferably satisfies 0 < x 2, more preferably 0 < x : 1, and highly preferably x = 1. The fraction of sulphur contained in the sulphide form MxSy preferably satisfies 0 < y 5 2. When the metal is copper, the fraction of sulphur contained in the sulphide form MxSy preferably satisfies 0 < y 5 2, more preferably 0 < y 5 1, and highly preferably y = 1. More advantageously, when the metal is copper, the capture mass in accordance with the invention is such that the fraction of copper and the fraction of sulphur in the sulphide form satisfy the equations x = 1 and y = 1.

The molar ratio of the aluminium atoms to those for the metal selected for the capture mass may be in the range 0.05 to 20, preferably in the range 0.1 to 10, and more preferably in the range 0.5 to 5.

The total percentage by weight of the aluminium, expressed with respect to the total weight of the capture mass, may be in the range 1% to 48% of aluminium, preferably in the range 3% to 45%, and more preferably in the range 11% to 39%.

The total percentage by weight of the metal M, expressed with respect to the total weight of the capture mass, may be in the range 6% to 65%, preferably in the range 10% to 63%, and more preferably in the range 18% to 52%.

The percentage by weight of sulphur, expressed as the ratio of the weight of the capture mass, may be in the range 3% to 65%, preferably in the range 5% to 64%, more preferably in the range 7% to 53%, even more preferably in the range 8% to 33%, and yet more preferably in the range 9% to 26%.

The metal sulphide is preferably distributed homogeneously throughout the capture mass. It thus preferably forms only a shell at the surface of the capture mass.

The capture mass may have a total pore volume in the range 0.1 cm 3.g-1 to 1.5 cm3 .g-1 , preferably in the range 0.1 cm 3.g-1 to 1.3 cm 3.g- 1, preferably in the range 0.2 cm 3 .g-1 to 1.0 cm 3.g-1.

The capture mass may have a specific surface area in the range 40 m 2.g-1 to 400 m 2 .g-1 , preferably in the range 60 m 2 .g-1 to 350 m 2.g- 1, more preferably in the range 70 m 2 .g-1 to 320 m 2 .g- 1, and yet more preferably in the range 70 m 2.g-1 to 300 m 2.g-1.

The capture mass may be in a variety of forms, in particular in the divided form. Advantageously, the solid support may be in the form of a plurality of elements, each element being in the shape of a bead, cylinder, multi-lobed extrudate, cartwheel, hollow cylinder or any other geometrical shape used by the person skilled in the art.

In accordance with one embodiment, the capture mass may be in the form of a plurality of beads with a diameter which is in the range 0.4 mm to 20 mm, preferably in the range 0.5 mm to 15 mm, and more preferably in the range 0.5 mm to 10 mm, or in the form of a plurality of trilobal extrudates with a diameter and a length in the range 0.4 mm to 20 mm, preferably in the range 0.5 mm to 15 mm, and more preferably in the range 0.5 mm to 10 mm.

Advantageously, the metal M is copper. In the context of the present invention, the expression "copper sulphide" designates chemical compounds of the type CuxSy, in which x 2 0.5; 0< y:5 2, and preferably x = 1 and y = 1. Preferably, the expression "copper sulphide" designates CuS.

The present invention also concerns the process for the preparation of the capture mass described above.

The capture mass in accordance with the invention may be prepared using different embodiments for synthesis known to the person skilled in the art. Preferably, the preparation of this capture mass involves the preparation of a material comprising metal oxides, then sulphurization of that material in order to transform the metal oxides into metal sulphides.

The process for the preparation of the capture mass in accordance with the invention consists of preparing a material containing aluminium, oxygen and at least one metal M selected from the group constituted by copper (Cu), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) and nickel (Ni). Preferably, the metal M is copper. The process for the preparation of the capture mass may be carried out using conventional methods which are known to the person skilled in the art, in particular in the field of catalyst preparation. In particular, the material may be prepared by co-precipitation of several oxides including that of the metal M desired in the capture mass, in an acidic or basic medium. Preferably, the co-precipitation is carried out in a basic medium and at a constant pH.

The process for the preparation of the capture mass in accordance with the invention comprises the following steps:

c) filtering the precipitate obtained in step b), and washing said precipitate at least once, preferably with water;

d) drying the product obtained in step c) at a temperature in the range 700C to 1500C, preferably in the range 1000C to 1300C, more preferably at 1200C, in order to obtain a powder;

e) shaping the powder obtained in step d) in order to obtain the green material;

f) calcining the green material obtained at the end of step e) in air at a temperature in the range 3000C to 6000C, preferably in the range 3500C to 550°C;

g) sulphurizing the material obtained at the end of step f).

The process for the preparation of the capture mass is carried out in a manner such that the active phase is introduced into a material which is obtained by carrying out a step for co-precipitation of an aqueous solution of a precursor of a material based on aluminium with a precursor of a metal sulphide based on a metal M. In contrast to the process for the preparation of a capture mass conventionally used in the prior art, it is not necessary to impregnate the aqueous solution comprising the precursor of the metal sulphide based on the metal M onto a support which has already been shaped. The advantage of such a preparation is that more active phase can be introduced than when using conventional impregnation, and thus the mercury capture capacity can be significantly improved.

Step a) for preparation of the solution

Step a) is generally carried out at a temperature in the range 5C to 95C, preferably in the range 20 0C to 80 0 C, and more preferably in the range 400 C to 600C.

The precursors of the material based on aluminium and said metal sulphide based on the metal M selected from the group constituted by copper (Cu), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) and nickel (Ni) may be any metallic salt which is soluble in water. The precursors of the metals may in particular be selected from the group constituted by metal acetates, metal nitrates, metal hydroxides, metal carbonates, metal sulphides and mixtures thereof. Preferably, the precursors of the metals are metal nitrates.

The quantities of the precursors of the material based on aluminium and said metal sulphide based on the metal M selected from the group constituted by copper (Cu), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) and nickel (Ni) are selected in a manner such that the molar ratio of aluminium to the selected metal M is in the range 0.05 to 20 in the final capture mass, preferably in the range 0.1 to 10, and more preferably in the range 0.5 to 5.

Co-precipitation step b)

Preferably, the reaction medium is water.

Step b) is carried out at a controlled pH. The pH of the reaction medium for step b) is kept constant in the range varying from 4 to 10, preferably in the range 6 to 9, and more preferably in the range 7.5 to 8.5, by adjusting the flow rate of the precursor solutions and the base or acid.

Step b) is carried out by adding a base if the solution obtained from step a) is acidic, and by adding an acid if the solution obtained from step a) is basic.

In the case of co-precipitation with an acid, an aqueous solution of sulphuric acid, hydrochloric acid, nitric acid, alone or as mixtures, may be used. Preferably, nitric acid in aqueous solution is used.

In the case of co-precipitation with a base, an aqueous solution of ammonium hydroxide, sodium hydroxide or potassium hydroxide, alone or as a mixture, may be used. Preferably, a solution of sodium hydroxide is used.

Step b) is generally carried out at a temperature in the range 50C to 950C, preferably in the range 200C to 800C, and more preferably in the range 400C to 600C.

Preferably, the co-precipitation step b) is carried out for a period in the range 5 to 60 minutes, preferably in the range 20 to 40 minutes.

Step c) for filtration and washing

In accordance with the invention, the process for the preparation of the capture mass in accordance with the invention also comprises a step c) for filtration of the suspension obtained at the end of step b), followed by at least one washing step. Said filtration step is carried out in accordance with methods known to the person skilled in the art.

Said filtration step is advantageously followed by at least one step for washing with water, preferably deionized water. Advantageously, one to three washing steps are carried out with a quantity of water equal to the quantity of filtered precipitate.

Step d) for drying

The drying step is advantageously carried out at a temperature in the range 700C to 1500C, preferably in the range 1000C to 1300C, more preferably at 1200C, in order to obtain a powder.

The drying step is advantageously carried out for a period in the range 30 minutes to 48 h, preferably in the range 1 to 24 h, and more preferably in the range 2 to 12 h.

Said drying step may be carried out in a closed and ventilated oven, by atomisation, or by any other method for evaporating the water not eliminated by filtration.

Step e) for shaping

In accordance with the invention, the powder obtained at the end of the drying step d) is shaped in a step e) in order to obtain a green material.

The term "green material" means the shaped material which has not undergone steps for heat treatment at a temperature of more than 1500C.

Preferably, said shaping step e) is carried out by mixing-extrusion, by rotary plate granulation, by atomisation or by any method which is known to the person skilled in the art.

Highly preferably, said shaping step e) is carried out by mixing-extrusion.

In a particular embodiment of the invention, the drying step d) and the shaping step e) are carried out simultaneously. In this embodiment, drying and shaping are carried out by atomisation.

Step f) for heat treatment

In accordance with the invention, the green material obtained at the end of the shaping step e) then undergoes a step f) for heat treatment at a temperature in the range 3000C to 6000C, preferably in the range 3500C to 550C.

Preferably, during step f), the material is calcined in air containing a relative humidity at 250C in the range 0% to 80%, preferably in the range 15% to 50%.

Preferably, said heat treatment step f) is operated over a period in the range 2 h to 10 h.

Step g) for sulphurization

The sulphurization step g) may be carried out using any method which is known to the person skilled in the art that leads to the formation of at least one metal sulphide which is reactive as regards heavy metals, and in particular mercury. The sulphur is generally supplied with the aid of hydrogen sulphide, elemental sulphur or with the aid of an organo-sulphur precursor that is known to the person skilled in the art. The sulphurization step g) may be carried out in the gas phase or in the liquid phase, depending on the type of sulphur precursor used.

The sulphurization step g) may advantageously be carried out in the gas phase with the aid of a gas containing hydrogen sulphide. In particular, it is possible to use a gaseous mixture of nitrogen and hydrogen sulphide for which the molar concentration of hydrogen sulphide may be in the range 1000 ppm to 10%, preferably in the range 0.5% to 6%, at a temperature which may be in the range 100°C to 4000C, and preferably in the range 1200C to 2500C.

Preferably, the sulphurization step g) may be carried out at atmospheric pressure.

The sulphurization step g) may be carried out ex situ or in situ, i.e. outside or inside the heavy metal capture device containing the capture mass which will be used to capture the heavy metals from an effluent. Preferably, the sulphurization step g) is carried out in the gas phase and ex situ.

The sulphurization step g) may be characterized in that it can transform at least 80%, preferably at least 90%, and more preferably at least 95% of the metal oxide of the material obtained at the end of step f) into metal sulphide.

X ray diffraction on the sulphurized capture masses was carried out using conventional powder methods with the aid of a diffractometer. Surprisingly, at the end of this series of steps, the capture mass contains only the characteristic peaks of the metal sulphide and possibly those of its oxide precursor.

Scherrer's formula is a formula used in the X ray diffraction of polycrystalline powders or samples that links the width at half height of the diffraction peaks to crystallite dimension. It is described in detail in the reference: Appl. Cryst. (1978). 11, 102-113, Scherrer after sixty years: A survey and some new results in the determination of crystallite size, J.|. Langford and A. J. C.Wilson.

The capture mass in accordance with the invention, which may have been prepared as described above, may advantageously be used as a capture mass for heavy metals. The present invention also concerns a process for capturing heavy metals in a gaseous or liquid effluent with the aid of the capture mass as described above.

The gaseous or liquid effluent to be treated may contain heavy metals, for example mercury, arsenic or lead, in various forms. As an example, mercury may be found in the form known as Hg°, corresponding to elemental or atomic mercury, in the molecular form and/or in the ionic form, for example Hg2 and its complexes. The concentration of heavy metals in the gaseous or liquid effluent to be treated may vary. The gaseous effluent to be treated may preferably contain between 10 ng and 1 g of mercury per Nm 3 of gas. The liquid effluent to be treated may preferably contain between 10 ng and 1 g of mercury per m 3 of liquid. Further, this gaseous or liquid effluent to be treated may contain arsenic and/or lead in different forms. The quantity of lead in the effluent may be in the range 1 ppt (parts per trillion, i.e. 10-12) by weight to 100 ppm (parts per million, i.e. 10-6) by weight, and the quantity of arsenic may be in the range 100 ppt by weight to 100 ppb (parts per billion, i.e. 10-9) by weight. These heavy metals are a nuisance for safety reasons and for reasons of the efficiency of the treatments for these effluents, and so advantageously they have to be eliminated using the capture mass in accordance with the invention, or at least their quantities have to be reduced. Finally, the effluent to be treated may contain other elements such as sulphur and nitrogen in various forms. In particular, the sulphur may be present in the form of mercaptans, organic sulphur or indeed, thiophene. The sulphur content of the effluent may be in the range 1 ppt by weight to 1000 ppm by weight, and the nitrogen content may be in the range 1 ppt by weight to 100 ppm by weight. Advantageously, neither the nitrogen nor the sulphur which may be present in the effluent to be treated causes drops in the performance of the capture masses of the invention.

In contrast to the materials described in the prior art, the capture mass in accordance with the present invention can be used to treat both liquid and gaseous effluents. Further, the effluent may be a moist gas or a gas containing vapours of condensable compounds without notably reducing the service life of the capture mass. The hygrometry ratio of the gaseous effluent, defined as the ratio of the partial pressure of water to the saturated vapour pressure of water at a given temperature, may be in the range 0 to 100%, preferably in the range 1% to 95%, and more preferably in the range 2% to 90%.

The use of the capture mass in accordance with the invention is particularly suited to the treatment of liquid or gaseous effluents of oil origin and their derivatives. Such effluents routinely contain heavy metals. The gaseous or liquid effluent to be treated in the process in accordance with the invention may advantageously be selected from the group constituted by combustion fumes, synthesis gas, natural gas, natural gas condensates, petroleum, liquid or gaseous oil cuts, petrochemical intermediates and mixtures thereof. Preferably, the gaseous or liquid effluent to be treated in the process of the invention is advantageously selected from the group constituted by combustion fumes, synthesis gas, natural gas, natural gas condensates, crude oil and liquid hydrocarbon cuts from the refinery or from a petrochemicals plant.

Combustion fumes are in particular produced by the combustion of hydrocarbons, biogas and coal in a boiler or by a combustion gas turbine, for example with the intention of producing electricity. The temperature of these fumes is generally in the range 200 C to 600 C, with a pressure generally in the range 0.1 MPa (1 bar) to 0.5 MPa (5 bar) and may comprise, by volume, between 50% and 80% of nitrogen, between 5% and 40% of carbon dioxide, between 1% and 20% of oxygen, and impurities such as SOx and NOx, if these impurities have not been eliminated downstream by a deacidification process.

Synthesis gas is a gas containing carbon monoxide CO, hydrogen H2 in a molar H2/CO ratio which is generally equal to approximately 2, steam, generally saturated, and carbon dioxide C02 which generally has a content of approximately 10% by volume. The pressure of the synthesis gases which are -0 most frequently encountered in the industry is generally in the range 2 MPa (20 bar) to 3 MPa (30 bar), but it may reach 7 MPa (70 bar). In addition, synthesis gas may contain sulphur-containing impurities (H2S, COS etc), nitrogen-containing impurities (NH3, HCN etc) and halogen-containing impurities.

Natural gas is primarily constituted by gaseous hydrocarbons, but it may contain some of the following acidic compounds: carbon dioxide C02, hydrogen sulphide H2S, mercaptans, carbon oxysulphide COS and carbon disulphide CS2. The quantity of these acidic compounds in natural gas can vary widely and may be up to 40% by volume for C02 and H2S. The temperature of the natural gas which is most frequently employed in the industry may be in the range 200C to 1000C, and its pressure may be in the range 1 MPa (10 bar) to 20 MPa (200 bar).

Natural gas condensates are constituted by liquid hydrocarbons the production of which is associated with the production of natural gas. These complex liquid mixtures are very similar to crude oils.

Particular examples of liquid refinery hydrocarbons which may be cited are LPG (C3-C4 cut), naphthas (C5-C8 cut), kerosenes and diesels.

Liquid hydrocarbons from petrochemicals plants which may in particular be cited are LPG (C3-C4 cut) and cracked gasolines (or "pyrolysis gasoline", also known as "PyGas").

In the process for capturing heavy metals in a gaseous or liquid effluent in accordance with the invention, said effluent is brought into contact with the capture mass in accordance with the invention. This contact may preferably be carried out by injecting the effluent to be treated into a reactor containing the capture mass in the form of a fixed bed.

This contact of the effluent to be treated with the capture mass in the process in accordance with the invention may be carried out at a temperature in the range -500C to 1150C, preferably in the range 0C to 1100C, and more preferably in the range 200C to 1000C. Further, it can be carried out at an absolute pressure in the range 0.01 MPa (0.1 bar) to 20 MPa (200 bar), preferably in the range 0.1 MPa (1 bar) to 15 MPa (150 bar), and more preferably in the range 0.1 MPa (1 bar) to 12 MPa (120 bar).

In addition, this step for bringing the effluent to be treated into contact with the capture mass may be carried out with an HSV in the range 0.1 h 1 to 50000 h 1 .

The term "HSV" means the hourly space velocity of the gaseous or liquid effluent, i.e. the volume of gaseous or liquid effluent per unit volume of reactor and per hour. For a gaseous effluent to be treated, the HSV may preferably be in the range 50 h 1 to 500 h 1 . For a liquid effluent to be treated, the HSV may be in the range 0.1 h 1 to 50 h 1 .

Prior to bringing the liquid or gaseous effluent to be treated into contact with the capture mass, said gaseous or liquid effluent may be pre-treated. This pre treatment may consist of heating or cooling, pressurizing or depressurizing, and/or a purification treatment for eliminating or reducing the content of an effluent that is deemed to be unwanted. As an example, the pre-treatment may comprise a step for reducing the relative humidity of a gaseous effluent. The reduction in the relative humidity of a gaseous effluent may be obtained using any means known to the skilled person, in particular a capture mass for water, for example a molecular sieve based on zeolite, a glycol process as described, for example, in the document WO 2005/047438, a step for heating the effluent in a heat exchanger in order to raise its temperature, for example by 30C to 100C, or a step for cooling the effluent.

Contact with the capture mass may advantageously be used to capture heavy metals contained in the effluent to be treated and to obtain an effluent with a heavy metal content which is reduced with respect to the initial effluent content, or in fact to completely eliminate the heavy metals from the effluent.

Advantageously, the reduction in the total weight content of the heavy metals between the gaseous or liquid effluent before treatment of the effluent and the effluent obtained after treatment with the capture mass in accordance with the -0 invention may represent at least 90%, preferably at least 95%, and more preferably at least 99%.

Other characteristics and advantages of the invention will become apparent from the following non-limiting examples given purely by way of illustration.

EXAMPLES

Four capture masses (Ml, M2, M3, M4) were prepared using different implementations in accordance with the invention or not in accordance with the invention. For the masses M1, M2 and M4, the envisaged copper content on the oxide precursors of the capture masses was 35% by weight with respect to the total weight of the oxide precursor of the capture mass. For the mass M3, prepared by impregnation, the support was dry impregnated using a saturated solution of the precursor of the active phase in a manner such as to prepare the mass with as large a charge as possible of active phase.

Example 1 (in accordance with the invention): Preparation of a capture mass M1 in accordance with the invention

Approximately 40 grams of mass M1 in accordance with the invention was prepared as follows:

A solution of aluminium nitrate obtained by dissolving 228.7 g of aluminium nitrate in 400 mL of water was mixed with a solution of copper nitrate obtained by dissolving 70.7 g of copper nitrate in 300 mL of distilled water at ambient temperature. At the same time, with the aid of peristaltic pumps, the above solution of precursors and 450 mL of a 30% solution of sodium hydroxide was added to a 280 mL starter quantity of water at 500C in a mechanically stirred reactor. The time over which the solutions were added was 30 minutes, the flow rate of the sodium hydroxide was adapted in order to keep the pH at 8, and the temperature of the mixture was maintained at 500 C. It was immediately filtered, then the precipitate obtained was washed with 3 x 1.5 L of distilled water. The filtration cake was oven dried at 1200 C for 12 h.

An acid mixing step was carried out using a Z arm mixer in order to produce a paste, then extrusion was carried out by passing the paste through a die provided with a 1.6 mm diameter orifice in a trilobal shape. Drying was carried out at 1200C for 24 h. Calcining was carried out in a muffle furnace at 4500C in air for 2 h (ramp-up at 5/min). Sulphurization was carried out at atmospheric pressure and in a stream containing 5% molar H2S diluted in nitrogen at a temperature of 2500C.

The Cu content measured on the oxide precursor was 33.6% by weight, which corresponded to 31.0% by weight of Cu on the sulphurized capture mass.

Example 2 (comparative): Preparation of a capture mass M2 by co precipitation with calcining temperature = 8000 C

Approximately 40 grams of mass M2, not in accordance with the invention, was prepared as follows:

A solution of aluminium nitrate obtained by dissolving 228.9 g of aluminium nitrate in 400 mL of water was mixed with a solution of copper nitrate obtained by dissolving 70.5 g of copper nitrate in 300 mL of distilled water at ambient temperature. At the same time, with the aid of peristaltic pumps, the above solution of precursors and 450 mL of a 30% solution of sodium hydroxide was added to a 280 mL starter quantity of water at 500 C in a mechanically stirred reactor. The time over which the solutions were added was 30 minutes, the flow rate of the sodium hydroxide was adapted in order to keep the pH at 8, and the temperature of the mixture was maintained at 500C. It was immediately filtered, then the precipitate obtained was washed with 3 x 1.5 L of distilled water. The filtration cake was oven dried at 1200C for 12 h. An acid mixing step was carried out using a Z arm mixer in order to produce a paste, then extrusion was carried out by passing the paste through a die provided with a 1.6 mm diameter orifice in a trilobal shape. Drying was carried out at 1200C for 24 h. Calcining was carried out in a muffle furnace at 4500C in air for 2 h (ramp-up at 50 /min). Sulphurization was carried out at atmospheric pressure and in a stream containing 5% molar of H2S diluted in nitrogen at a temperature of 2500C.

The Cu content measured on the oxide precursor was 31.7% by weight, which corresponded to 29.4% by weight of Cu on the sulphurized capture mass.

Example 3 (comparative): Preparation of a capture mass M3 by dry impregnation onto a porous support

The capture mass was prepared using the protocol described in the document FR 2 980 722.

Approximately 40 grams of mass M3, not in accordance with the invention, was prepared as follows:

A step was carried out for precipitating boehmite by mixing aluminium sulphate, A12(SO4)3, containing 101 g/L of A1203, with sodium aluminate, NaAIO2, containing 152 g/L of A1203, at a temperature of 600C, at a pH of 9, for 60 minutes. It was oven dried overnight at 1200 C. A mixing step was carried out using a Z arm mixer in order to produce a paste, and an extrusion step was carried out by passing the paste through a die provided with a 1.6 mm diameter orifice in a trilobal shape. Drying of the extrudates was carried out at 1500C. The extrudates obtained were calcined in a muffle furnace at 5000C in air for 2 h (ramp-up at 5/min); the extrudates were dry impregnated at a temperature of 200C using a saturated solution of copper nitrate (impregnation in which the volume of the impregnation solution corresponds exactly to the water take-up volume of the support, i.e. to the accessible pore volume of the solid):

• preparation of the impregnation solution by dissolving 28.47 g of Cu(N03)2. 3H20 in 21.63 g of water; • impregnation by slowly irrigating the support; • maturation in a closed cup for 3 h at ambient temperature; 3-0 • drying at 900C for 3 h; • calcining at 4500C in a moist atmosphere for 45 minutes in a tube furnace.

Sulphurization was carried out at atmospheric pressure and in a stream containing 5% molar of H2S diluted in nitrogen at a temperature of 2500C.

The quantity of Cu which was deposited was 18.3% by weight of the oxide precursor of the capture mass, which corresponds to 17.5% by weight of Cu in the capture mass in the sulphurized form.

Example 4 (comparative): Preparation of a capture mass M4, not in accordance with the invention

In order to obtain approximately 40 grams of the bulk capture mass M4 not in accordance with the invention, the following procedure was carried out:

27.52 g of basic copper carbonate and 10.02 g of alumina trihydrate were intimately mixed with two binders, calcium aluminate (1.64 g) and attapulgite (2.01 g), in the presence of a little water in order to form beads in a bead granulator.

The granules obtained in this manner were dried for 2 h at ambient temperature, then at 1050C for 16 h in air.

Sulphurization was carried out at atmospheric pressure and in a stream containing 5% molar of H2S diluted in nitrogen at a temperature of 500C.

The Cu content measured for the oxide precursor was 34.2% by weight, which corresponds to 31.5% by weight of Cu for the sulphurized capture mass.

Example 5: Determination of crystalline phases of capture masses M1 to M4

The X ray diffraction diagrams provided us with information regarding the nature of the crystalline phases that were present. The nature of the crystalline phases, the pore volumes, the mean sizes of the pores and the specific surface areas of the capture masses are reported in Table 1 below.

The total pore volume and the pore distribution were determined by mercury porosimetry (see Rouquerol F.; Rouquerol J.; Singh K. "Adsorption by Powders & Porous Solids: Principle, methodology and applications", Academic Press, 1999). More particularly, the total pore volume is measured by mercury porosimetry in accordance with the standard ASTM D4284-92 with a wetting angle of 1400, for example using an Autopore 11ITM model instrument made by Microm6ritics TM .

In accordance with the invention, the term "specific surface area" means the BET specific surface area determined by nitrogen adsorption in accordance with the standard ASTM D 3663-78 based on the BRUNAUER-EMMETT TELLER method described in the periodical "The Journal of American Society", 60, 309, (1938).

Table 1 - Nature of the crystalline phases and structural characteristics of M1 to M4

Mean Nature of SBET Vpore pore crystalline phases (m 2 .g- (mL.g- diameter

Mass M1,in CuS 234 0.84 6.4 accordance with

Cu MassM2,notS 55 0.17 14. in accordance 5 Cu Mass M3, not in 199 0.49 12. accordance with 8 Cu Mass M4, not in 27 0.21 62. accordance with 0 the invention Cu2(CO3)(OH)

The capture masses were analysed by X ray diffraction. Figure 1 represents the diffraction spectra measured respectively for masses M1 to M4. The figure shows the angle "2-theta" of the X rays along the abscissa and the intensity "Lin" of the diffracted X rays up the ordinate. The vertical black lines indicate the position of the characteristic peaks of CuS.

For the capture mass M1, all of the peaks coincide with those that are characteristic of CuS and no supplemental peaks are seen, which means that the clear conclusion can be drawn that only a CuS crystalline phase is present.

For the other capture masses, the following was observed:

- for the capture mass M2, the supplemental presence of peaks at 20 angles of 31.5; 37; 45; 56; 59.5 and 65.8 means it can be concluded that a CuA1204 crystalline phase is present, and peaks at angles 15.5; 16.1; 17.2; 19; 21; 22.5; 24; 25; 26; 33.4; 33.6; 35; 40.2; 50 mean that it can be concluded that a Cu(S04)2.5H20 crystalline phase is present in addition to the CuS phase;

- for the capture mass M3, the supplemental presence of broad peaks at angles 37; 46 and 66.50 means it can be concluded that a crystalline phase A1203 is present in addition to the CuS phase;

- for the capture mass M4, the supplemental presence of peaks at angles 17.5; 14.5; 18.5; 20.5; 24; 26.5; 32.5; 37; 36; 42; 48.5; 53.5 and 600 means it can be concluded that the crystalline phases Cu2(CO3)(OH)2 and A(OH)3 are present in addition to the CuS phase.

Example 6: Evaluation of the performances of the various capture masses M1 to M4 for Hg capture

The sulphurization capability of the capture masses was estimated by calculating the atomic ratio between the sulphur and the copper present in the mass. This S/Cu ratio was calculated from the elemental sulphur and copper contents with respect to the capture masses and the molar masses. A ratio of close to 1 corresponds to a mass for which the copper is very well sulphurized because the formula approaches that of CuS; a ratio of well below 1 corresponds to a mass with low sulphurizability.

The mercury adsorption performances for the capture masses prepared as described above were tested in a reactor R1. A bead of liquid mercury of approximately 30 g was initially poured into a glass cup which was then deposited into the bottom of a reactor R1 with a volume of 1 L. A mass mm of capture mass was deposited in a metal lattice basket which was then introduced into the interior of the reactor R1. The reactor R1 was introduced into a heating chamber regulated at T = 70°C for a minimum of 1 week. The metal basket containing the capture mass was weighed at regular time intervals until saturation. The mass of the saturated capture mass was denoted, mm'. The difference in the mass of the capture mass from before and after contact with the mercury in the reactor R1 provided access to the quantity of mercury captured by the capture mass.

This quantity with respect to the mass of the capture mass produced the Effective Mass Capacity (EMC) for capture of mercury by the capture mass:

EMC = (mm'-mm) / mm x 100

Table 2 below provides information regarding the quantities of the elements (% by weight) of copper and sulphur, the degree of sulphurizability (S/Cu atomic ratio) and the mercury capture capacity for each of the capture masses studied (Ml to M4).

Table 2 - Evaluation of capture mass performances %Cu %S S/Cu EMC

30.9 12.9 0.83 39.4 Mass M1 (in accordance with the invention)

Mass M2 (not in 29.4 5.4 0.36 19.6 accordance with the

Mass M3 (not in 17.5 7.8 0.88 25.8 accordance with

Mass M4 (not in 36.1 12.7 0.70 29.1 accordance with

It will be observed that the capture mass M1 in accordance with the invention has a better sulphurizability (higher S/Cu atomic ratio) than the masses M2 and M4 (comparative). The mass M3 (comparative) has a comparable sulphurizability, but contains less active phase. The capture mass M1 thus has a higher sulphur content than masses M2, M3 and M4 (comparative). With a high sulphurizability and its high concentration of metal M (copper), the capture mass M1 in accordance with the invention also has an effective capture capacity (EMC) which is higher than for masses M2, M3 and M4 (comparative).

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or ";comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Claims

Claims

A process for the preparation of the capture mass for heavy metals, in particular mercury, contained in a gaseous or liquid feed, said mass comprising an active phase in the form of a crystalline phase, said active phase comprising at least one metal sulphide based on a metal M selected from the group constituted by copper (Cu), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) and nickel (Ni), and an amorphous support comprising a material based on aluminium, the process comprising the following steps:

a) preparing an aqueous solution containing at least one precursor of a material based on aluminium and at least one precursor of at least one metal sulphide based on a metal M selected from the group constituted by copper (Cu), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) and nickel (Ni);

b) carrying out a step for co-precipitation, in an aqueous reaction medium, by simultaneously adding the solution prepared in step a) containing said precursor of said material based on aluminium and said precursor of said metal sulphide based on a metal M to a base or an acid in a manner such as to obtain a precipitate;

c) filtering the precipitate obtained in step b), and washing said precipitate at least once;

d) drying the product obtained in step c) at a temperature in the range 700C to 1500C in order to obtain a powder;

e) shaping the powder obtained in step d) in order to obtain a green material;

f) calcining the green material obtained at the end of step e) in air at a temperature in the range 3000C to 600°C; g) sulphurizing the material obtained at the end of step f).
2. The process as claimed in claim 1, wherein the calcining step f) is carried out for a period in the range 2 to 10 h.
3. The process as claimed in claim 1 or claim 2, wherein the calcining step f) is carried out in air containing a relative humidity at 250 C in the range 0% to 80%.
4. The process as claimed in any one of claims 1 to 3, in which the sulphurization step g) is carried out using a gaseous mixture of nitrogen and hydrogen sulphide the molar concentration of which is in the range 1000 ppm to 10%.
5. The process as claimed in any one of claims 1 to 4, wherein the sulphurization step g) is carried out at a temperature in the range 100°C to 4000 C.
6. The process as claimed in any one of claims 1 to 5, wherein said capture mass contains at least 90% by weight of metal M in the form MxSy with respect to the total weight of metal M.
7. The process as claimed in any one of claims 1 to 6, wherein the metal M is copper.
8. The process as claimed in any one of claims 1 to 7, in which said capture mass comprises the aluminium in a quantity of 1% to 48% by weight with respect to the total weight of said capture mass.
9. The process as claimed in any one of claims 1 to 8, wherein said capture mass comprises the metal M in a quantity of 6% to 65% by weight with respect to the total weight of said capture mass.
10. The process as claimed in any one of claims 1 to 9, wherein said capture mass comprises sulphur in a quantity of 3% to 65% by weight with respect to the total weight of said capture mass.
11. The process as claimed in anyone of claims 1 to 10, wherein said capture mass presents a total pore volume in the range 0.1 cm 3.g-1 to 1.5 cm 3 .g-1 and a specific surface area in the range 40m 2 g-1 to 400m 2 g-1.
12. The process as claimed in any one of claims 1 to 11, wherein said capture mass is in the form of a bead or an extrudate.
13. The process as claimed in claim 12, wherein said capture mass is in the form of a trilobal extrudate.
14. Use of the capture mass prepared by a process as claimed in any one of claims 1 to 13, in order to eliminate heavy metals, in particular mercury, contained in a gaseous or liquid feed.