EA045593B1 - GOLD-CONTAINING CATALYST, METHOD OF PRODUCTION AND APPLICATION - Google Patents

Description

Scope of the invention

The present invention relates to the production of an improved gold catalyst and a method for its production. In particular, but not exclusively, the present invention relates to increasing the stability and/or inhibiting the deactivation of gold catalysts by adding an additive selected from an inorganic oxide, hydroxide, oxo salt or hydroxy acid, and methods for their preparation, as well as their use in the production of vinyl chloride monomer (VCM).

Prerequisites for creating the invention

Known commercial processes for producing vinyl chloride monomer (VCM) can combine ethylene, hydrogen chloride (HCl) and oxygen in the presence of copper chloride to form ethylene dichloride, which decomposes at high temperature to form VCM and HCl. In an alternative commercial process, ethylene (acetylene) from the carbide is reacted with HCl over a mercury-based catalyst. This method is preferred where cheap ethylene is available using carbide from coal-rich resources. The mercury catalyst used in this process, typically 8-10% mercuric chloride on activated carbon, is highly toxic. This toxicity creates problems during handling of the catalyst during its production, as well as during loading of the catalyst and removal of the catalyst after the production campaign. A production campaign typically has a duration of six months. Deactivation of the mercury catalyst and loss of HgCl2 through sublimation or volatilization from the reactor used can cause significant problems. The ethylene method, using a mercury-based catalyst, requires lower capital costs than the ethylene method. If a non-volatile and less toxic catalyst can replace the mercury catalyst without requiring significant plant changes in existing plant designs, this would be a significant advantage.

WO 2013/008004, the teachings of which are incorporated herein by reference in their entirety, describes a catalyst with increased toxicity compared to earlier VCM catalysts that can be used in a catalyzed process for the production of VCM from ethylene. However, commercial consumption of such a catalyst has been difficult due to the cost of gold required to produce the active catalyst. The use of relatively low levels of gold (to avoid high production costs) is detrimental to the stability of the catalyst and catalytic activity is reduced. Moreover, it has been discovered that the production of such gold-containing catalysts typically produces gold nanoparticles, which can in turn lead to the formation of carbon nanotubes during use of the catalyst, which subsequently leads to dusting of the catalyst, accompanied by loss of gold and deactivation of the catalyst. Thus, there is a need to produce gold catalysts with relatively lower levels of expensive gold active material, but which do not exhibit an undesirable reduction in catalyst stability, activity or selectivity, and preferably in which the formation of gold nanoparticles is reduced or negligible to avoid the formation of carbon nanotubes during the process. applications.

Preferred embodiments of the present invention are directed to overcoming one or more of the above disadvantages of the prior art. In particular, preferred embodiments of the present invention are directed to the production of improved gold catalysts by the addition of an inorganic oxide, hydroxide, oxo salt or hydroxy acid and methods for producing such an improved catalyst and its use in a chemical process for the production of vinyl chloride monomer (VCM) from acetylene are described herein.

Summary of the invention

According to a first aspect of the invention, there is provided a catalyst comprising a gold complex with a sulfur-containing ligand and an additive selected from the group consisting of an inorganic oxide, hydroxide, oxo salt or hydroxy acid, on a support.

According to a second aspect of the invention, there is provided a method for producing said catalyst, wherein:

i) a gold solution is prepared, ii) a sulfur-containing ligand solution is prepared, iii) a solution of the additive or its precursor is prepared, iv) the gold solution is mixed with the sulfur-containing ligand solution to produce a gold complex impregnation solution, and

v) the catalyst support is impregnated with a gold complex impregnation solution followed by drying the impregnated support, and then impregnated with the solution obtained in step (iii), followed by drying of the impregnated support, or vi) the catalyst support is impregnated with the solution obtained in step (iii), after whereupon the impregnated carrier is dried, then impregnated with an impregnation solution containing a gold complex, after which

- 1 045593 whereupon the impregnated carrier is dried.

In accordance with the third aspect of the invention, an alternative method for producing said catalyst is provided, characterized in that:

i) obtain an impregnation solution containing a gold complex and an additive or its precursor;

ii) the catalyst support is impregnated with the solution obtained in step (i) to obtain an impregnated support, after which the impregnated support is dried.

In accordance with a fourth aspect of the invention, there is provided a process for hydrochlorination of an alkyne, comprising reacting said alkyne with HCl in the presence of a catalyst in accordance with the first aspect of the invention.

Unless otherwise stated, all % refer to percentage by weight of the total weight of the catalyst.

Detailed description

Catalyst

In the catalyst of the present invention, the active catalyst components contain gold (Au) in the positive oxidation state, preferably in the form of Au ³⁺ and Au ¹⁺ , although some gold present may be in the form of metallic gold (Au ⁰ ). In some embodiments, the catalysts can be considered to contain gold particles having a core containing metallic gold and a shell or surface layer containing higher oxidation state forms of gold, including Au ³⁺ . The shell does not have to be continuous, but it is preferable that all or substantially all of the exposed surface of the particle has surface forms of gold with a higher oxidation state; for example, if gold metal is partially surrounded by a carrier, the shell may only extend over the exposed surface of the particle. Au ³⁺ need not be the only higher oxidation state forms of gold present in the shell and, for example, Au ¹⁺ may also be present. Such higher oxidation state forms can be stabilized by halide, for example in prior art catalysts. It is widely believed in the prior art that the higher oxidation state forms of gold are the active forms for catalyzing the reaction of acetylene with HCl. It is believed that in the catalysts of the present invention, gold is stabilized in a higher oxidation state due to complexation with sulfur-containing ligands. The core of the particles typically contains gold metal (Au ⁰ ), but alternative forms of gold may also be present in the core.

As used herein, the term additive means an inorganic oxide, hydroxide, oxo salt or hydroxy acid. As used herein, the term inorganic means free of carbon. As used herein, the term additive precursor means a material that can be converted to an inorganic oxide, hydroxide, oxo salt or hydroxy acid, typically after hydrolysis and/or drying. Additive precursors may or may not contain carbon.

As will be further described below, in the methods of the present invention, the catalyst is prepared by impregnating the catalyst support with an additive or additive precursor. Without being limited by any theory, it is believed that the additive or additive precursor forms at least a partial layer around the gold particles. After hydrolysis and/or drying, the result is typically an inorganic oxide layer around the gold complex particles, although this layer may include one or more of an inorganic oxide, hydroxide, oxo salt or hydroxy acid depending on the method of preparation. It is believed that the presence of this layer prevents the deactivation of gold particles.

Accordingly, the catalyst contains from 10 to 0.01% additive, preferably from 10 to 0.1% additive, preferably from 5 to 0.1%, more preferably from 3 to 0.5%. Low additive levels are preferred to avoid the additive level negatively affecting catalyst activity, however sufficient additive must be present to ensure improved catalyst stability. A level of 5 to 0.1% has been found to provide the best balance of these two requirements, although different amounts of additive may be preferred depending on the salt or acid selected and the individual operating parameters of any process in which the catalyst is used. The additive may include a mixture of one or more of an inorganic oxide, hydroxide, oxo salt or hydroxy acid.

As used herein, an oxo salt is a salt containing an anion of the formula [M _x O _y ] ^z- , where M is an element other than carbon or oxygen. Examples include metasilicate [SiO3] ^2- , orthosilicate [SiO4] ^4- , tetraborate [B4O7] ^2- and phosphate [PO4] ^3- . The hydroxy acid is the corresponding protonated form, for example [PO4] ^3- and _H3PO4 , which in some cases can depolymerize, for example [ _B4O7 ] ^2- and B(OH) ₃ . Preferred M elements include Zr, Ce, La, Y, Ti, Bi, Zn, Al, V, Cr, Mn, Mo, W, Re, B, N, Si, P, S, Ge, As, Se, Sn, Sb, Te, Cl, Br and I. More preferred M elements include Zr, Ce, La, B, Si, P and S.

In preferred embodiments, the additive is:

- 2 045593 (i) an oxide or hydroxide of a metallic, metalloid or non-metallic element, or (ii) an oxo-salt or hydroxy acid of a metalloid or non-metallic element.

Herein, the metalloid element is selected from B, Si, Ge, As, Sb and Te; preferred metalloids are B and Si, especially Si. The preferred nonmetals are S and P, especially P.

In a preferred embodiment, the additive is an oxide, hydroxide, oxo salt or hydroxy acid of boron, silicon, sulfur or phosphorus, more preferably boron, silicon or phosphorus, more preferably boron or silicon. A typical boron, silicon, sulfur or phosphorus content will be 0.01-10 wt%, for example 0.1-10 wt%, for example 0.5-10 wt%, or 0.5-5 wt%, based on the total mass of the catalyst. The content of these elements can be measured using techniques known to those skilled in the art, such as inductively coupled plasma (ICP) techniques, which include inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectrometry (ICP-MS), coupled plasma (ICP-AES) and inductively coupled plasma optical emission spectrometry (ICP-OES).

In a preferred embodiment, the additive is a silicon oxide, hydroxide, oxo salt or hydroxy acid. The catalyst may include one or more types of silicon, such as silica, silicates, metasilicates, and the like. A typical silicon content is 0.01-10% by weight, eg 0.1-10% by weight, eg 0.5-10% by weight, or 0.5-5% by weight, based on the total weight of the catalyst. Silicon content can be measured using techniques known to those skilled in the art, such as inductively coupled plasma (ICP) techniques, which include ICP-MS, ICP-AES and ICP-OES.

Advantageously, the additive should be a stable, relatively refractory or non-reducing/oxidizing oxide, hydroxide, oxo salt or hydroxy acid of a metalloid or non-metallic element. In some embodiments, the additive or additive precursor is an alkali, alkaline earth, or rare earth metal salt. Preferred counterions include ammonium or alkali metals, such as ammonium silicate, ammonium borate, ammonium sulfate, ammonium phosphate, sodium silicate, sodium borate, sodium sulfate or sodium phosphate.

Particularly suitable inorganic hydroxy acids are boric acids, phosphoric acid, silicic acids or sulfuric acid. Boric acid (B(OH) ₃ ) is a particularly preferred boron hydroxy acid.

More specifically, the following additives have been found to be particularly suitable: sodium metasilicate pentahydrate, sodium tetraborate, boric acid and trisodium orthophosphate. In particular, the additive is preferably a sodium silicate salt and most preferably is sodium metasilicate pentahydrate.

In some embodiments, the additive may be a product derived from an additive precursor that forms a non-reducible inorganic oxide upon conversion (typically by thermal or chemical decomposition and suitable hydrolysis) after deposition onto a catalyst support; preferred inorganic oxides that can be formed in this manner include SiO2, _Al2O3 , TiO2, ZrO2, _La2O3 , CeO2 suboxides thereof, or mixtures thereof. The additive precursor may be inorganic or organic. Suitable inorganic and organic precursors will be apparent to one skilled in the art and include alkoxides of the above elements, for example tetraethylorthosilicate (TEOS), titanium isopropoxide, and the like. Alternative precursors include metal salts such as metal chlorides or metal nitrates, which are converted by hydrolysis to the corresponding hydroxides and oxides.

Typically, the catalyst contains less than 1% gold. The catalyst preferably contains less than 0.5% gold. The catalyst preferably contains less than 0.1% gold. More preferably, the catalyst contains no more than 0.075% gold, and most preferably, the catalyst contains no more than 0.05% gold. In some applications, the catalyst can contain no more than 0.025% gold without loss of commercially acceptable catalytic activity. At gold levels of less than 0.1 wt.% of the catalyst, the catalysts can be considered low gold and atypical catalysts. The use of lower levels of gold is attractive due to the corresponding reduction in the cost of producing the catalyst, since gold will typically be the most expensive component of the catalyst. However, to date the ability to use these relatively low levels of gold (especially at levels as low as 0.05%) has been limited due to loss of stability of the catalytic product resulting in unacceptably low levels of catalytic activity, which is observed as unacceptably low levels of product conversion. The inclusion of an additive in the catalyst overcomes the disadvantages associated with the use of relatively low levels of gold (no more than 0.05%). Surprisingly, it has been found that adding an additive to the gold catalysts of the present invention is advantageous.

- 3 045593

In a further or alternative embodiment, even low gold catalysts having relatively high gold levels (ie, greater than 0.05%) experience improvements in catalyst properties. More specifically, nanotube formation was preferentially inhibited. Thus, adding the additive to gold catalysts having relatively high levels of gold (ie, greater than 0.05%) provides surprising benefits. The formation of nanotubes leads to catalyst deactivation, and therefore it has been found that the addition of an additive inhibits the deactivation of gold catalysts. The process of catalyst deactivation through the formation of nanotubes occurs mainly due to the reduction of oxidized gold in the catalyst and the growth of gold particles to form relatively large (>200 nm) gold nanoparticles. It is believed that nanoparticles can also act as nuclei for the formation of carbon nanotubes. Nanotube formation appears as a yellow, easily powdered deposit on the catalyst granules, resulting in dust formation and loss of gold contained in the powder, causing deactivation of the catalyst.

Without being limited by any theory, it is possible that a thin film of additive or additive precursor forms around the gold particles, preventing sintering and nucleation for the nanotubes. The additive precursor may undergo hydrolysis or partial hydrolysis to form the corresponding non-reducible oxide or suboxide around the gold particles; this may prevent migration and sintering of catalyst gold particles after/during use or act as a barrier between the carbon carrier and the metal particle.

Taking into account the above paragraphs, one skilled in the art will appreciate that the benefits of including the additive in the gold catalyst according to the present invention are twofold: first, the stability of catalysts with low gold content (up to 0.05%) is improved and the loss of activity is negligible is small, and secondly, inhibition of deactivation of gold-containing catalysts is essentially achieved by limiting the formation of nanotubes on the surface of the catalyst.

Any known catalyst support can be used to prepare the catalyst of the present invention. Typical metal oxide supports such as alumina, silica, zeolite, aluminosilicate, titanium dioxide or zirconia and composites thereof can be used.

Most preferably, the catalyst support is made from carbon, including carbon supports derived from natural sources (peat, wood, graphitic carbon, etc., or combinations thereof) or synthetic carbons. The carbon is preferably activated carbon, activated, for example, by steam, acid or otherwise chemically activated. Preferred carbon supports include high surface area activated carbon, preferably greater than 800 m ² /g, such as 1300 m ² /g carbon extrudate. Carbon extrudates are commercially available in high purity or ultra-high purity grades, and such grades are typically acid washed to remove impurities. A combination of metal oxide and carbon can also be used as a catalyst support.

The catalyst carrier may be in the form of powders, granules or particles molded into various shapes (molded elements). Preferred molded elements include spheres, tablets, cylinders, multi-lobed cylinders, rings, minilites, and the like. or a massive catalytic unit such as a monolith. In an alternative embodiment, the catalyst in powder form may be included in a coating composition and applied to the reactor wall or a molded substrate, such as a monolith. One preferred catalyst support form comprises a plurality of cylinder, sphere or lobed cylinder moldings, each having a diameter of 0.1-10 mm, or more preferably a diameter in the range of 1-3 mm. In the case of a cross-sectional shape having an uneven diameter, such as a lobed cylinder, the diameter is the average diameter. Such catalyst support forms are commercially available and can be prepared by extrusion, tabletting, or other methods.

Sulfur may be present in the catalyst in the form of a sulfur compound containing sulfur in a reduced or oxidized state or a combination of reduced and oxidized states, for example, as in the thiosulfate ion. More specifically, the sulfur is present in a sulfur-containing compound that is a ligand capable of complexing with gold particles or that complexes with gold particles. More preferably, the sulfur-containing ligand is capable of stabilizing gold in a positive oxidation state. Suitable sulfur-containing ligands are oxidizing ligands, in particular oxygen donor ligands containing sulfur in a positive oxidation state, or sulfur donor ligands. Preferred sulfur-containing compounds include sulfates, sulfonates, thiosulfates, thiocyanates, thioureas, thiols and thionyl chloride. Preferred thioureas include thiourea itself or substituted thioureas. Preferred thiols include thiopropionic

- 4 045593 acid and thiomalic acid.

In a preferred embodiment, the sulfur-containing compound is a ligand capable of complexing with gold particles via a sulfur atom or complexing with gold compounds via a sulfur atom. In this embodiment, the ligand includes one or more sulfur atoms, at least one of which is a sulfur donor. Preferred sulfur donor ligands include thiosulfates, thiocyanates, thioureas, thiols and thionyl chloride. Preferred thioureas include thiourea itself or substituted thioureas. Preferred thiols include thiopropionic acid and thiomalic acid.

The amount of sulfur in the fresh catalyst is preferably in the range from about 0.005 to 15 wt.%, more preferably from 0.03 to 7 wt.%, in a dry catalyst, in particular up to about 5 wt.%. In one embodiment of the invention in which the gold complex is a gold-thiosulfate complex, the molar ratio of S to Au in the complex is preferably in the range of about 3:1 to about 8:1. In such an embodiment, containing a preferred amount of gold, the amount of sulfur in the catalyst may be in the range of 0.03-1.50 wt.%. Some sulfur, originating from sources other than the S-containing complex, may also be present in the catalyst, for example included in the support material.

The catalyst may further comprise a metal other than gold or any metal forming a support compound. Known promoters for use with gold catalysts used for hydrochlorination reactions include cobalt, copper or lanthanum compounds, and such metals may be present in the catalysts of the present invention or in the catalysts used in the process of the present invention. Group 1 and Group 2 metals may also advantageously be included in the catalysts of the present invention. Thus, the catalyst may contain, in addition to gold, a metal or metal compound selected from the group consisting of cobalt, copper, lanthanum, cerium, lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium and barium. The additional metal may be present as a promoter or may serve another function in the catalyst or in its preparation. For example, certain metals, such as calcium, are believed to inhibit the formation of carbon deposits on catalysts and, therefore, can be used to help maintain catalyst activity over a period of time. Thus, even if the presence of a metal does not increase the activity of a catalyst in the short term, it may be considered a promoter if it reduces the tendency of the catalyst to deactivate during its use in a reaction or has another beneficial effect on the practical use of the catalyst.

Catalyst production

According to a second aspect of the present invention, there is provided a method for producing a catalyst in accordance with the first aspect of the invention, wherein:

i) a gold solution is prepared, ii) a sulfur-containing ligand solution is prepared, iii) a solution of the additive or its precursor is prepared, iv) the gold solution is mixed with the sulfur-containing ligand solution to produce a gold complex impregnation solution, and

v) the catalyst support is impregnated with a gold complex impregnation solution followed by drying the impregnated support, and then impregnated with the solution obtained in step (iii), followed by drying of the impregnated support, or vi) the catalyst support is impregnated with the solution obtained in step (iii), after which is dried, then impregnated with an impregnation solution containing a gold complex, after which the impregnated carrier is dried.

In general, it is preferable to follow the impregnation order specified in step v).

In accordance with the third aspect of the invention, there is provided an alternative method for producing the catalyst in accordance with the first aspect of the invention, in which:

i) obtain an impregnation solution containing a gold complex and an additive or its precursor;

ii) the catalyst support is impregnated with the solution obtained in step (i) to obtain an impregnated support, after which the impregnated support is dried.

This alternative process is advantageous because it requires only a single impregnation and drying step, providing a simpler and less expensive method of preparing the catalyst.

In a preferred embodiment in accordance with the third aspect of the invention:

i) a gold solution is prepared, ii) a sulfur-containing ligand solution is prepared, iii) the additive or its precursor is added to either the gold solution or the sulfur-containing ligand solution before step iv), iv) the gold solution is mixed with the sulfur-containing ligand solution, the gold solution or

- 5 045593 sulfur-containing ligand also contains an additive or its precursor, to obtain a solution for impregnation,

v) the catalyst carrier is impregnated with the impregnation solution, after which the impregnated carrier is dried.

As provided by the method in accordance with the third aspect of the invention, the additive or additive precursor can be added to either the gold solution or the sulfur-containing ligand solution. An additive or additive precursor is preferably added to the sulfur-containing ligand solution if it may cause gold to precipitate out of solution when added to the gold solution, and in an alternative embodiment, the additive or additive precursor is added to the gold solution if it may cause adverse reactions with the ligand when added into a solution containing the ligand.

In some embodiments, it is preferable that the pH of the gold solution (before gold complexation) is neither too acidic nor too alkaline. In strongly acidic environments, some sulfur-containing ligands are unstable, which negatively affects the formation of the gold complex and leads to undesirable impurities in the impregnation solution. For example, thiosulfate is known to form the tetrathionate ion ([S4O6] ² ' in acidic environments. In highly alkaline environments, gold solution can form a colloid, which also negatively affects gold complex formation. The preferred pH range for gold solution is pH 5-8, preferably pH 5.57.5 In a preferred embodiment, the gold solution is prepared by adjusting an aqueous solution of HAuCl ₄ using a base such as NaOH or KOH.

According to a further and alternative embodiment of the present invention, there is provided a method for producing said catalyst, wherein the step of impregnating a catalyst support with an additive is carried out by obtaining an additive precursor and converting the precursor into an inorganic oxide, hydroxide, oxo salt or hydroxy acid, whereby the catalyst support is impregnated with the desired additive, After which, if necessary, drying can be done. In this case, the catalyst support is impregnated with the additive precursor and then the precursor is converted into the additive, preferably through thermal or chemical decomposition. This will cause the catalyst carrier to become saturated with the selected additive.

In a process according to the second aspect of the invention involving sequential impregnations with a gold complex followed by an additive precursor, it is sometimes preferable to use a strongly alkaline solution of the gold complex in the first impregnation step if the additive precursor is resistant to hydrolysis in neutral or moderately alkaline environments. In this embodiment, the pH of the impregnation solution containing the gold complex is preferably 9 or higher, preferably 10 or higher, more preferably 11 or higher. The appropriate pH value can be obtained by adding a base such as NaOH or KOH after gold complexation. Without being limited by any theory, it is believed that the alkaline gold complex solution used to impregnate the catalyst support alkalizes the support and thereby preconditions the support for hydrolysis of the additive precursor in the subsequent impregnation step. This is particularly preferred when hydrolysis of the precursor is necessary to form the corresponding oxide, for example when the inorganic precursor is a metal nitrate or chloride.

The catalysts can be prepared using various catalyst preparation methods known per se in the art, for example by impregnation, preferably using moisture impregnation methods or sputtering/deposition methods. In the catalyst production methods of the invention, the catalyst is preferably prepared by impregnating a support with a solution of a gold complex with a sulfur-containing ligand to form a gold complex in combination with an additive or additive precursor.

Preferred gold complexes are soluble in readily available solvents that pose little environmental hazard. The preferred solvent is an organic solvent, water, or a mixture thereof. The solvent is preferably water. Preferred impregnation solutions include aqueous solutions of gold sulfates, sulfonates, thiosulfates, thiocyanates, thiourea, thionyl chloride, thiopropionic acid and thiomalic acid.

In one preferred embodiment, the method of the present invention comprises impregnating a particulate carbon support with an aqueous solution containing a complex comprising a gold compound and a thiosulfate ion containing compound with an additive or additive precursor, then separating the excess solution if necessary and then drying impregnated material.

Preferably, impregnation is carried out using a moisture-holding or pore-filling protocol, in which the amount of solution used is calculated so that it only fills the pores of the carrier. Accordingly, the gold compound and the compound containing the thiosulfate ion together form a gold-thiosulfate complex, and the additive has a stabilizing effect on the formed gold-containing complex. Typically, when using the moisture-based impregnation method, the volume of impregnation solution used is 100% ± to about 20% of the measured (or calculated) pore volume of the carrier. The carrier is typically mixed with the impregnation solution by rotating in a drum, or the impregnation solution can be added, for example dropwise or by spraying, to the agitated carrier layer over a period of time. In an alternative embodiment, the catalyst support can be impregnated with an impregnation solution containing a gold complex and an additive or additive precursor using an excess volume of the impregnation solution such that the gold and/or sulfur compound is deposited on the catalyst support by absorption or ionic reactions. exchange. One skilled in the art of catalyst production is aware of such methods for producing catalysts by impregnating support materials with a solution of active metal compounds.

The amount of gold, sulfur and additive or additive precursor in the impregnation solution is calculated to provide the required amount of gold, sulfur and additive in the finished catalyst.

The impregnation solution containing the gold complex may include an additional metal compound, for example including a metal compound selected from the group consisting of cobalt, copper, lanthanum, cerium, lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium and barium. In an alternative embodiment, additional metal, if present, can be added to the catalyst in a separate step, for example by impregnating the gold-containing catalyst particle with a solution of the additional metal compound or by impregnating the support material with such a solution before adding the gold complex solution to the catalyst.

In an alternative, although less preferred production method, the catalyst can be prepared by known solid-state process methods, for example by mixing dry support, gold, ligand and additive or additive precursor components. In this case, the ligand-gold complex can be preformed at the initial stage. Ball milling is a particularly suitable solid-state process method, but more uniform application of the active components to the catalyst support can be achieved using the support impregnation methods described herein.

As stated above, the catalyst support is preferably carbon and can be subjected to acid washing, preferably using hydrochloric acid, nitric acid, phosphoric acid or sulfuric acid, which can preferably be carried out before impregnation with an impregnation solution containing a gold complex. This can be achieved, for example, by dispersing the carbon in hydrochloric acid, optionally heating it, possibly to boiling, draining, rinsing with distilled or deionized water and air drying. As an alternative to using an acid wash procedure in preparing the catalyst, a pretreated or acid washed support can be obtained from a carbon support manufacturer as a commercial material if it is desired to use an acid washed form of the carbon support.

The catalyst may not necessarily require an activation step before being used in a chemical process. In such cases, it may be more appropriate to consider the dried, impregnated catalyst support as a catalyst precursor, but for simplicity, such materials are considered herein to be catalysts, whether or not they require activation (or pre-activation) to achieve full catalytic activity.

Catalyst Application

The catalysts of the present invention are expected to be useful in any chemical process for which gold-containing catalysts are known to find practical application. However, a preferred chemical process of the present invention provides a process for producing vinyl chloride (also called vinyl chloride monomer or VCM) by hydrochlorination of acetylene, comprising reacting acetylene with hydrogen chloride (HCl) in the presence of a catalyst containing a gold complex with a sulfur-containing ligand and a supported additive. The catalyst is preferably a catalyst in accordance with the invention and/or obtained using the method of the present invention. The process is carried out at elevated temperature, typically from about 100 to 250°C, more preferably <200°C. HCl and acetylene are preferably premixed and also preferably preheated to reaction temperature. HCl is usually present in an amount greater than that required for a stoichiometric reaction. The catalyst may be present in the reactor in the form of a fixed bed of catalyst particles arranged such that the feed gases pass over or through the catalyst bed. Alternative reactor designs may be used, including fluidized bed or other moving bed designs. In an alternative embodiment, the catalyst may be provided in the form of a monolith or applied to the wall of the reactor vessel. The catalyst bed may be provided with temperature control to avoid overheating due to an exothermic reaction or to increase the temperature if necessary. May be preferable

- 7 045593 treat the catalyst with HCl before use in the method. This treatment is typically accomplished by passing HCl through the catalyst for at least an hour at a temperature of at least 50°C, more particularly >100°C. This pre-treatment can occur in a reactor operating with an acetylene-free HCl stream at a suitable temperature.

It should be understood that elements described in connection with one aspect of the invention are equally applicable to another aspect of the invention. For example, the features described in relation to the catalyst of the present invention may be equally applicable to the catalyst obtained by the production method of the present invention, and vice versa.

The invention will now be described in the following examples with reference to the accompanying drawings, in which: FIG. 1 shows an SEM image of a fresh, untreated catalyst surface containing 0.1% gold;

in fig. 2 shows an SEM image of a fresh catalyst surface treated with 1% boric acid containing 0.1% gold;

in fig. 3 shows an SEM image of the formation of nanotubes on the used untreated surface of a catalyst containing 0.1% gold;

in fig. 4 is an SEM image of a used 1% boric acid treated catalyst containing 0.1% gold without the formation of nanocarbon tubes;

in fig. 5 shows the relative VCM conversions obtained for the untreated 0.1 and 0.05% gold catalysts compared to the treated 0.05% gold catalyst with sodium silicate addition;

in fig. 6 shows the significant increase in conversion to VCM obtained with a catalyst containing 0.05% gold with the addition of a silicate salt, compared to the gold catalyst in the absence of such silicate salt.

Examples

Example 1 (comparative). Preparation of thiosulfate catalyst with 0.1% Au according to the prior art

0.142 g of HAuCl ₄ solution containing 41% Au was diluted in 24 ml of water. Separately, 0.186 g of anhydrous sodium thiosulfate was dissolved in 24 ml of water. The gold containing solution was then added with stirring to the thiosulfate solution to produce a pale yellow mixed solution of the finished gold complex. 4.8 ml of this gold complex solution was then added with stirring to 5.8 g of commercially available activated carbon granules. The carbon absorbed all the liquid within about 5 minutes. After leaving the product to air dry for about one hour, the material was then dried at 120° C. overnight to obtain a catalyst containing approximately 0.1% Au. In fig. Figure 1 shows an SEM image of this as-prepared untreated catalyst.

Example 2 Carbon Nanotube Formation Test The catalyst prepared as described in Example 1 was loaded into a stainless steel tube with a diameter of 2 cm, and the formed layer at both ends was protected with a quartz wool packing. The tube was then placed in a tube furnace. A mixture of HCl and _C2H2 (molar ratio 1.2:1) was passed through _the catalyst at a flow rate of 240 ml/min at a temperature of 220°C. Initial conversion to VCM was about 90%, falling to 65% after 48 hours. After 48 hours, the catalyst was purged with nitrogen, cooled, and then removed from the furnace. Optical examination showed the presence of carbon nanotubes on carbon granules. The degree of nanotube formation was assessed as follows: 0=no nanotubes; 1=nanotubes are present on some particles; 2=nanotubes are present on many particles; 3=nanotubes are present on most particles.

SEM examination revealed that the coating consists of a mass of carbon nanotubes, each formed by an active site on a gold particle, as shown in FIG. 3. The degree of nanotube formation in this example was 3.

Example 3 Preparation of a catalyst according to the present invention

The catalyst was prepared as described in Example 1, except that 0.58 g of an additive in the form of sodium metasilicate pentahydrate was dissolved in the HAuCU solution. After this, the procedure was the same as in example 1.

Example 4 Preparation of a catalyst according to the present invention

The catalyst was prepared as described in example 1, except that 0.58 g of an additive in the form of sodium tetraborate was dissolved in a solution of HAuCl ₄ . After this, the procedure was the same as in example 1.

Example 5 Preparation of a catalyst according to the present invention

The catalyst was prepared as described in example 1, except that 0.58 g of boric acid was dissolved in the HAuCl4 solution. After this, the procedure was the same as in Example 1. In FIG. Figure 2 shows an SEM image of this fresh catalyst treated with boric acid.

- 8 045593

Example 6. Preparation of a catalyst in accordance with the invention

The catalyst was prepared as described in example 1, except that 0.58 g of trisodium orthophosphate was dissolved in the HAuCl ₄ solution. After this, the procedure was the same as in example 1.

Example 7. Testing catalysts in accordance with the invention for the formation of nanotubes

The catalysts prepared as described in Examples 3-6 were tested for nanotube formation in accordance with the method presented in Example 2 for periods ranging from two to five days. In all cases, carbon nanotube formation is either completely prevented (nanotube formation rate=0) or present only in a few microscopic areas of the granules (nanotube formation rate=1). In fig. 4 is an SEM image of the boric acid treated catalyst of Example 5 after testing according to the method of Example 2; in this case, one can see an increase in the size of gold particles, but no noticeable growth of nanoparticles. The degree of nanotube formation in this example was 0.

Example 8 (comparative). Preparation of catalyst with 0.05% Au according to prior art

The catalyst was prepared as described in Example 1, except that 0.071 g of HAuCl ₄ solution containing 41% Au was used to obtain a dilute HAuCl ₄ solution; and 0.093 g of sodium thiosulfate was used to prepare a sodium thiosulfate solution. The resulting catalyst contained approximately 0.05% Au.

Example 9 Preparation of a 0.05% Au Catalyst According to the Present Invention

The catalyst was prepared as described in Example 8, except that 0.58 g of sodium metasilicate pentahydrate was dissolved in the HAuCl ₄ solution. After this, the procedure was the same as in example 8.

Example 10 Testing the 0.05% Au Catalyst of the Present Invention for Enhanced Activity

The silicate-doped 0.05% Au catalyst of Example 9 was subjected to the conversion test described in Example 2. The conversion rates are shown in FIG. 6, where it can be seen that a significant increase in conversion to VCM was achieved with the silicate containing catalyst compared to the silicate free catalyst. In the case of the material obtained in Example 9, there was no formation of nanotubes after six days, as shown in FIG. 5.

In fig. 5 shows the conversion to VCM at 220° C. in accordance with Example 2, but over a longer period of time (up to 6 days as opposed to 48 hours) for two untreated catalysts, one containing 0.1% Au and the other containing 0.05% Au, compared to a 0.05% Au catalyst treated with sodium silicate as described above. In fig. 5 it can be clearly seen that the addition of sodium silicate allows the lower gold content 0.05% Au catalyst to achieve selectivity comparable to that of the higher gold content 0.1% Au catalyst (but untreated).

The improvement in conversion demonstrated in Example 10 for the 0.05% Au silicate catalyst does not appear to occur for the 0.1% Au catalyst, although nanotube formation is predominantly inhibited. Thus, the present invention is particularly suitable and desirable for catalysts containing less than 0.1% gold.

Examples 11-17.

A HAuCl ₄ solution containing 0.100 g Au was diluted with the indicated amount of demineralized water (DI). Separately, solutions of the sulfur-containing ligand and additive were prepared with the indicated amount of demineralized water (DI). The solutions were mixed in the specified order to obtain a gold-containing solution for impregnation. This solution was then added, with stirring, to 100 g (dry weight) of commercially available activated carbon granules using the water-capacity impregnation method. The impregnated material was left at rest for approximately 30 minutes, during which time all the added solution was adsorbed. The material was then dried at 105° C. overnight to obtain a catalyst containing approximately 0.1% Au.

In the case of example 17, pH adjustment was carried out as follows. A HAuCl4 solution containing 0.100 g Au was diluted with 30 ml demineralized water. An approximately 5% KOH solution was prepared by dissolving 5 g NaOH in 100 ml demineralized water. Approximately 1 ml of KOH solution was added dropwise to the gold-containing solution to obtain a solution having a pH of approximately 6.8. Separately, 0.336 g of ammonium thiosulfate was dissolved in 30 ml of demineralized water. The gold-containing solution was then added with stirring to the ammonium thiosulfate solution to obtain a mixed solution of the finished gold complex. Next, the resulting solution was used in the moisture-capacity impregnation method according to the procedure described above.

XPS analysis of examples 11-16 showed the presence of SiO ₂ in the material formed after drying at 105°C overnight.

The catalysts were tested for the formation of carbon nanotubes according to the procedure

- 9 045593 described in example 2.

Table

Example Solution HAiC14 [HAuCU] Ligand solution [ligand] Additive solution [Additive] Addition procedure to obtain an impregnation solution pH regulation Degree of nanotube formation eleven 0.100 g HAuCU in 12 ml DI 0.373 g sodium thiosulfate in 24 ml DI 1.162 g sodium metasilicate pentahydrate in 24 ml DI [NLpS1 ₄ ] to [ligand], then add [additive] -No 0 12 0.100 g HAuCU in 12 ml DI 0.372 g sodium thiosulfate in 24 ml DI 1.161 g sodium metasilicate pentahydrate in 24 ml DI [HAuCU] to [add], then add [ligand] -No 0 13 (comparative) 0.100 g HAuCU in 30 ml DI - 1.160 g sodium metasilicate pentahydrate in 30 ml DI [HAuCU] to [addendum] No 3 14 0.100 g HAuCU in 12 ml DI 0.200 g sodium thiocyanate in 24 ml DI 1.162 g sodium metasilicate pentahydrate in 24 ml DI [HAuCU] to [ligand], then add [addition] No - 15 0.100 g HAuCU in 12 ml DI 0.200 g sodium thiocyanate in 24 ml DI 1.162 g sodium metasilicate pentahydrate in 24 ml DI [HAuCU] to [add], then add [ligand] No 3 16 0.100 g HAuCU in 12 ml DI 0.180 g thiourea in 24 ml DI 0.350 g silicic acid in 24 ml DI [HAuCU] to [ligand], then add [addition] No 1 17 (comparative) 0.100 g HAuCU in 30 ml DI 0.336 g ammonium thiosulfate in 30 ml DI - [HAuCU] to [ligand] [HAuCU] adjusted to pH 6.8s using 1 M KOH -

Precursors of Zr, Ce and La

Example 18 (comparative).

A HAuCl4 solution containing 0.100 g Au was diluted with 12 ml demineralized water. Approximately 1 M NaOH solution was prepared by dissolving 4 g of NaOH in 100 ml of demineralized water. 1.60 g of the resulting 1 M NaOH solution was added dropwise to the gold solution to obtain a solution having a pH of approximately 6.5. Separately, 0.336 g of sodium thiosulfate was dissolved in 12 ml of demineralized water. The gold-containing solution was then added with stirring to the sodium thiosulfate solution to obtain a mixed solution of the finished gold complex having a pH of approximately 11.2. An additional 12 ml of the previously prepared 1 M NaOH solution and 22 ml of demineralized water were added to the gold-containing solution to obtain a finished gold complex solution having a pH of approximately 12.3. The resulting gold-containing solution was then added with stirring to 100 g (dry weight) of commercially available activated carbon granules using the water-capacity impregnation method. The impregnated material was left at rest for approximately 30 minutes, during which time all the added solution was adsorbed. The material was then dried at 105°C overnight to obtain an Au/C catalyst containing approximately 0.1% Au. This catalyst was tested as described in example 2. The degree of formation of carbon nanotubes was 1.

Example 19.

A catalyst with 0.1% Au/C was prepared as described in Example 18. Separately, 1.467 g of zirconium oxynitrate dihydrate [ZrO(NO ₃ ) ₂ -2H ₂ O] was dissolved in 30 ml of demineralized water and this solution was added to 50 g of dried gold-containing coal granules using the moisture-capacity impregnation method. After leaving the material at rest for approximately 30 minutes, the material was dried at 105°C overnight to obtain a catalyst containing approximately 0.1% Au and 1% Zr.

Example 20.

A catalyst with 0.1% Au/C was prepared as described in example 18. Separately, 1.550 g of cerium nitrate hexahydrate [Ce(NO) ₃ ) ₃ 6H ₂ O] was dissolved in 30 ml of demineralized water and this solution was added to 50 g of dried gold-bearing coal granules using the moisture-capacity impregnation method. After leaving the material at rest for approximately 30 minutes, the material was dried at 105°C overnight to obtain a catalyst containing approximately 0.1% Au and 1% Ce. This catalyst was tested as described in example 2. The degree of formation of carbon nanotubes was 1.

Example 21.

A 0.1% Au/C catalyst was prepared as described in Example 18. Separately, 1.335 g of lanthanum chloride heptahydrate [LaCl ₃ .7H ₂ O] was dissolved in 30 ml of demineralized water and this solution was added to 50 g of dried gold-containing carbon granules using impregnation method based on moisture capacity. After leaving the material at rest for approximately 30 minutes, the material was dried at 105°C overnight to obtain a catalyst containing approximately 0.1% Au and 1% La.

Those skilled in the art will appreciate that the above embodiments are described by way of example only and not in any limiting sense, and that various changes and modifications are possible without departing from the scope of the invention as defined in the appended claims.

The invention also includes the following embodiments:

1. A catalyst containing a complex of gold with a sulfur-containing ligand and an inorganic salt

- 10 045593 or acid on a carrier.

2. The catalyst according to Embodiment 1, containing from 10 to 0.1% by weight of an inorganic salt or acid based on the total weight of the catalyst.

3. The catalyst according to Embodiment 1, containing from 5 to 0.1% by weight of an inorganic salt or acid based on the total weight of the catalyst.

4. The catalyst according to Embodiment 1, containing from 3 to 0.5% by weight of an inorganic salt or acid based on the total weight of the catalyst.

5. The catalyst according to any of the preceding embodiments, wherein the inorganic acid or salt is an inorganic acid selected from boric acid, phosphoric acid or sulfuric acid.

6. The catalyst according to any one of embodiments 1 to 4, wherein the inorganic acid or salt is an inorganic salt selected from ammonium, silicate, borate or phosphate salt.

7. The catalyst according to embodiment 6, wherein the inorganic salt is sodium silicate, sodium borate or sodium phosphate salt.

8. The catalyst according to embodiment 7, wherein the inorganic salt is selected from sodium metasilicate pentahydrate, sodium tetraborate, boric acid and trisodium orthophosphate.

9. The catalyst according to embodiment 6, wherein the inorganic salt is an ammonium salt.

10. The catalyst according to any of the preceding embodiments, containing less than 1.0 wt.% gold based on the total weight of the catalyst.

11. The catalyst according to any of the preceding embodiments, containing no more than 0.1% gold by weight based on the total weight of the catalyst.

12. The catalyst according to any of the preceding embodiments, containing no more than 0.05% gold by weight based on the total weight of the catalyst.

13. The catalyst according to any of the preceding embodiments, wherein said support contains carbon.

14. The catalyst according to any of the preceding embodiments, wherein said carrier is in the form of a powder, granulate or molded element.

15. The catalyst according to any of the preceding embodiments, wherein at least a portion of the gold has a positive oxidation state.

16. The catalyst according to any of the preceding embodiments, wherein said sulfur-containing ligand is an oxidizing ligand containing sulfur with a positive oxidation state.

17. The catalyst according to embodiment 16, wherein said sulfur-containing ligand is selected from the group consisting of sulfonate, thiosulfate, thiocyanate, thiourea, thionyl chloride, thiopropionic acid and thiomalic acid.

18. The catalyst according to any of the preceding embodiments, containing sulfur in the range of from about 0.005 to 15 wt.%, based on the total weight of the catalyst.

19. The catalyst according to any of the preceding embodiments, further comprising a metal or metal compound selected from the group consisting of cobalt, copper, lanthanum, cerium, lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium and barium .

20. A method for producing a catalyst in accordance with any one of embodiments 1-19, wherein:

i) a gold solution is prepared, ii) a sulfur-containing ligand solution is prepared, iii) an inorganic salt or acid solution is prepared, iv) the gold solution is mixed with the sulfur-containing ligand solution to obtain a gold complex impregnation solution,

v) the catalyst support is impregnated with a gold complex impregnation solution, after which the impregnated support is dried, vi) the catalyst support is impregnated with an inorganic salt or acid, after which the impregnated support is dried.

21. A method for producing a catalyst in accordance with any one of embodiments 1-19, characterized in that:

i) a gold solution is prepared, ii) a sulfur-containing ligand solution is prepared, iii) an inorganic salt or acid is added to either the gold solution or the sulfur-containing ligand solution before step iv), iv) the gold solution is mixed with the sulfur-containing ligand solution, the solution being either gold, or sulfur-containing ligand also contains an inorganic salt or acid, to obtain a solution

-

Claims (10)

impregnation agent containing a gold complex and an inorganic salt or acid, v) the catalyst support is impregnated with an impregnation solution containing a gold complex and an inorganic salt or acid, after which the impregnated support is dried. 22. The method according to embodiment 20 or 21, wherein the inorganic salt or acid is obtained from the converted precursor. 23. The method according to embodiment 22, wherein the precursor is converted by thermal or chemical decomposition. 24. The method in accordance with any one of embodiments 20-23, further comprising an activation step. 25. A chemical process comprising reacting at least one chemical substrate in the presence of a catalyst in accordance with any one of embodiments 1-19 or carried out by a method in accordance with embodiment 20 or 21. 26. The chemical method according to embodiment 23, comprising oxidizing said chemical substrate. 27. A method for hydrochlorinating an alkyne, comprising reacting said alkyne with hydrogen chloride in the presence of a catalyst in accordance with any one of embodiments 119. 28. The method for hydrochlorination of an alkyne in accordance with embodiment 25, comprising the step of treating said catalyst with hydrogen chloride in the absence of acetylene. CLAIM 1. A catalyst for the hydrochlorination of an alkyne containing a gold complex with a sulfur-containing ligand and an additive selected from the group consisting of silicon oxide, silicon hydroxide, silicon oxo salt or silicon oxyacid; on a carrier containing carbon; wherein the catalyst contains less than 0.5% gold. 2. The catalyst according to claim 1, in which the silicon content is 0.01-10 wt.%. 3. The catalyst according to claim 1 or 2, containing from 10 to 0.1% of the specified additive by weight based on the total weight of the catalyst. 4. The catalyst according to any one of claims 1-3, in which the additive is silicic acid. 5. The catalyst according to any one of claims 1-3, in which the additive is sodium metasilicate pentahydrate. 6. The catalyst according to any one of claims 1-5, containing no more than 0.1% gold by weight based on the total weight of the catalyst. 7. The catalyst according to any one of claims 1 to 6, containing no more than 0.05% gold by weight based on the total weight of the catalyst. 8. The catalyst according to any one of claims 1 to 7, wherein said sulfur-containing ligand is selected from the group consisting of sulfate, sulfonate, thiosulfate, thiocyanate, thiourea, thiol or thionyl chloride. 9. A method for producing a catalyst for the hydrochlorination of alkyne according to any one of claims 1 to 8, in which: i) a gold solution is prepared, ii) a solution of a sulfur-containing ligand is prepared, iii) a solution of an additive selected from the group consisting of silicon oxide, silicon hydroxide, a silicon oxo salt or a silicon hydroxy acid, or a precursor thereof is prepared, iv) a gold solution is mixed with a solution of a sulfur containing ligand to obtain a solution for impregnation with a complex of gold and v) the catalyst support containing carbon is impregnated with the gold complex impregnation solution, followed by drying the impregnated support, and then impregnated with the solution obtained in step (iii), followed by drying the impregnated support, or vi) the catalyst support containing carbon is impregnated with the solution obtained in step (iii), after which it is dried, then impregnated with a gold complex impregnation solution, after which the impregnated carrier is dried. 10. A method for producing a catalyst for the hydrochlorination of alkyne according to any one of claims 1 to 8, in which: i) prepare an impregnation solution containing a gold complex with a sulfur-containing ligand and an additive selected from the group consisting of silicon oxide, silicon hydroxide, silicon oxo salt or silicon oxy acid, or a precursor thereof; ii) the catalyst support containing carbon is impregnated with the solution obtained in step (i), -