Fibrous solids based on titanium dioxide

Abstract

The present invention relates to a solid with a specific surface area (SBET) greater than 100 m² / g comprising 75 to 95% by weight of titanium dioxide (TiO₂), and 1 to 20% by weight of a mineral compound in the form of fibers, including terminals, relative to the total weight of the anhydrous solid. The fibers comprise 70 to 100% by weight of silica and have a median diameter between 5 nm and 50 µm and an average length between 50 nm and 1000 µm. The invention also relates to a process for preparing said solid and its use as a support or catalyst, particularly in a process for the hydrolysis of sulfur or nitrogen compounds. Figure 1 to be published

Description

Title of the invention: Fibrous solids based on titanium dioxide technical field

[0001] The present invention relates to titanium dioxide-based solids useful as catalysts or as supports for the preparation of heterogeneous catalysts, and their implementation in processes for the conversion of H2S to sulfur, in particular the modified Claus process. In this process, large quantities of COS and CS2 can be formed, and the use of catalysts active towards their hydrolysis to H2S is therefore necessary to ensure sufficient sulfur yields and compliance with atmospheric emission standards for sulfur compounds. Titanium dioxide-based catalysts are among the catalysts conventionally used for these hydrolyses due to their very high performance.

[0002] These solids can also be used for the hydrolysis of COS and HCN in the processes of purifying synthesis gas from natural gas, petroleum, coal or biomass, but are also useful for the selective reduction of nitrogen oxides to nitrogen in the treatment of fumes from the combustion of nitrogen derivatives, for example during the production of nitric acid.

[0003] The invention also relates to the preparation of fibrous solids based on titanium dioxide. Previous technique

[0004] Existing catalysts offer only average performance, requiring long residence times and therefore large reactors to transform sulfur compounds such as COS or CS2, thereby limiting atmospheric emissions. Improving catalytic performance often involves adding elements that increase the price of the catalysts or reducing their dimensions, such as the catalyst diameter, but this significantly increases the pressure drop. Increasing catalyst porosity also improves catalytic performance, but the resulting mechanical strength becomes too low for loading in industrial units, particularly when the catalyst drop height becomes significant.

[0005] Prior art document EP 38741 describes titanium dioxide (TiO2)-based solids prepared by mixing TiO2 powder to obtain a paste, which is then shaped and finally heat-treated in air between 200 and 900°C. During the preparation of the solid, a shaping additive (up to 30% by weight) can be added during the mixing step. This additive can be selected from silica, alumina, clays, silicates, sulfate, etc. titanium, ceramic fibers. It is also disclosed that the following can also be used as shaping additives: cellulose, carboxymethylcellulose, carboxyethylcellulose, tall oil, xanthan gums, surfactants, flocculants such as polyacrylamides, carbon black, starches, stearic acid, polyacrylic acid, polyvinyl alcohol, biopolymers, glucose, polyethylene glycol.

[0006] The publication by Knapp et al. focuses on the synthesis of TiO2-sepiolite-based supports containing 30 to 95% TiO2, but sepiolite is described as decreasing the amount of titanium on the surface, and increasing the titanium content leads to a decrease in the BET surface area below 100 m2 / g, whether the shaping is carried out in water or in the presence of acid. These two aspects are indicated as detrimental to catalytic activity (Phase distribution in titania-sepiolite catalyst supports prepared by different methods - Knapp et al. J. Mater. Chem., 1997, 7(8), 1641-1645). Summary of the invention

[0007] Surprisingly, the Applicant noted that the implementation of titanium dioxide at a content of between 75 and 95% by weight, in a mixture with 1 to 20% of a fibrous mineral binder comprising 70 to 100% silica and fibers with a median diameter of between 5 and 50 pm and an average length of between 50 and 1000 pm, made it possible to obtain a solid material with an open porosity greater than known solids while maintaining optimal mechanical resistance, allowing its use as a catalyst, in particular in the Claus process, or as a heterogeneous catalyst support.

[0008] Unless otherwise indicated, the percentage weight contents are expressed on an anhydrous basis, i.e. taking as a basis the weight of the material deprived of water.

[0009] The invention relates to a solid with a specific surface area SBET greater than 100 m² / g, preferably greater than 120 m² / g, comprising: - 75 to 95% by weight of titanium dioxide TiO2 including terminals, relative to the total weight of the anhydrous solid; - 1 to 20% by weight of a mineral compound in the form of fibers, including terminals, relative to the total weight of the anhydrous solid, said fibres comprising from 70 to 100% by weight of silica and said fibres having a median diameter between 5 nm and 50 pm and an average length between 50 nm and 1000 pm.

[0010] The solid according to the invention may comprise 80 to 90% by weight of titanium dioxide TiO2 included, relative to the total weight of the anhydrous solid.

[0011] The solid according to the invention may comprise from 2 to 10% by weight of a mineral compound in the form of fibers, terminals included, relative to the total weight of the anhydrous solid.

[0012] The solid according to the invention may comprise a total pore volume of pore diameters between 3.7 nm and 10 pm measured according to ASTM D4284-12 greater than 0.35 ml / g, preferably greater than 0.5 ml / g.

[0013] The mineral compound can be chosen from glass fiber and sepiolite.

[0014] Preferably, the mineral compound is sepiolite.

[0015] The solid according to the invention can exhibit a grain-to-grain EGG crush resistance greater than or equal to 1 daN / mm and a breakage rate generated after an impact against a steel plate of less than 15% by volume.

[0016] The invention also relates to a method for preparing a solid according to any one of the described variants comprising the following steps: (i) A titanium dioxide source comprising 90 to 100% by weight of titanium dioxide TiO2, a mineral compound in the form of fibers, an organic thickening compound and water are mixed in the presence of a base or an acid to obtain a paste, in the proportions required to obtain the solid described above; ii) The kneaded dough obtained in step i) is shaped, preferably by extrusion or granulation; iii) The dough shaped in step ii) is dried at a temperature between 100 and 200°C in order to obtain a dried product; iv) The dried product is calcined at a temperature between 300 and 600°C.

[0017] The thickening compound can be chosen from a polysaccharide compound such as, for example, starch, cellulose, carboxymethylcellulose, carboxyethylcellulose, agar-agar, or a polysaccharide compound obtained by bacterial or fungal fermentation, such as xanthan gum, succinoglycan gum, scleroglucan gum or S-194 heteropolysaccharides.

[0018] The titanium dioxide source can be introduced at a content of between 50 and 65% by weight, the mineral compound in the form of fibers can be introduced at a content of between 1 and 8% by weight, the thickening compound can be introduced at a content of between 0.5 and 2% by weight, relative to the total mass of the mixture in step i).

[0019] The invention also relates to a process for hydrolyzing sulfur or nitrogen compounds contained in a gaseous charge, preferably chosen from H2S, COS, CS2 and / or HCN, by contacting said gaseous charge with water and a solid according to any of the variants described or prepared according to the preparation process according to any of the variants described.

[0020] The gaseous charge can be a gaseous effluent from a Claus treatment process of H2S.

[0021] The gaseous charge can be a synthesis gas.

[0022] The invention also relates to the use of the solid according to any one of the variants described, or prepared according to the preparation process according to any one of the variants described, as a catalyst or as a heterogeneous catalyst support. List of figures

[0023] Figures 1 and 2 illustrate the invention by way of non-limiting example. [Fig 1]

[0024] Fig. 1 presents an image obtained by scanning electron microscopy of a catalyst according to Example 1 containing 90% titanium dioxide and 10% sepiolite clay in the form of very fine fibers (diameter of 10 nm for an average length of 300 nm). [Fig 2]

[0025] Fig. 2 presents an image obtained by scanning electron microscopy of a catalyst according to example 5 containing 85% titanium dioxide and 5% glass fibers (diameter of 14 pm for a length of 200 pm).

[0026] Description of embodiments Terminology

[0027] Throughout this text, groups of chemical elements are described according to the new IUP AC classification. For example, groups 9 or 10 correspond to the metals in columns 9 and 10 according to the IUP AC classification or to the last two columns of group VIIIB according to the CAS classification (CRC Handbook of Chemistry and Physics, CRC editor press, editor-in-chief DR Lide, 81st edition, 2000-2001). Similarly, group 6 corresponds to the metals in column 6 according to the IUP AC classification or to the metals in columns VIB according to the CAS classification.

[0028] Throughout this text, the total pore volume VPT is obtained by mercury intrusion porosimetry according to the ASTM D4284-12 method and expressed as the pore volume generated by pores of diameter 37 Å at 10 pm.

[0029] The specific surface SBET is a surface measured by the BET method, that is, the specific surface determined by nitrogen adsorption in accordance with ASTM D 3663-78 established from the BRUNAUER-EMMETT-TELLER method described in the periodical The Journal of the American Chemical Society, 6Q, 309 (1938).

[0030] By hourly volumetric velocity (WH), we mean the ratio between the volumetric flow rate of the feed at the reactor inlet in m3 / h at 0°C, 1 atm, divided by the volume of catalyst in m3 contained in the reactor.

[0031] The median diameter of mineral fibers, particularly glass or sepiolite fibers, is obtained by measuring the diameter of at least 10 fibers observed under a scanning electron microscope. The average length is obtained by measuring the length of at least 10 fibers also observed under a scanning electron microscope.

[0032] The grain-to-grain crushing (EGG) value is obtained via a standardized test (ASTM D4179-01) which consists of subjecting a millimeter-sized object, such as an extruded support in the case of the present invention, to a compressive force that causes it to break. This test is used to indirectly measure the material's strength. The analysis is repeated on a number of individual particles, typically between 50 and 200, preferably between 100 and 200. The average of the measured lateral crushing forces constitutes the average EGG, which, in the case of spheroidal particles, is expressed in units of force (N).

[0033] The breakage rate generated by impact is obtained using a dedicated installation that projects the extrudates against a steel plate. One liter of millimeter-sized extrudates is fed into a tube 30 mm in diameter and 50 mm long, subjected to 3 bars of compressed air, which projects the extrudates one by one against the plate located 220 mm from the tube's outlet. The sample is then collected, and the dimensions of the resulting objects are characterized by laser diffraction. The breakage rate generated by impact is then expressed as the volumetric rate of extrudates that were broken (whose diameter is smaller than that of the initial extrudates) by the impact against the steel plate.

[0034] Unless otherwise indicated, weight percentages (% weight) correspond to mass percentages expressed in relation to the total mass of the components of the formulation or the final solid. Detailed description of the invention

[0035] The present invention relates to a solid material comprising 75 to 95% by weight of titanium dioxide relative to the total weight of the anhydrous material and 1 to 20% by weight of a mineral compound preferably comprising 70 to 100% silica, the mineral compound being in the form of fibers, relative to the total weight of the anhydrous material. The fibers advantageously take the form of needles with a median diameter between 5 nm and 50 pm and an average length between 50 nm and 1000 pm. The solid according to the invention advantageously has a total pore volume greater than 0.35 ml / g (ASTM D 4284-12, pore volume with a diameter between 3.7 nm and 10 pm). The BET specific surface area (measured according to ASTM D3663-78) of the solid is at least 100 m2 / g, preferably at least 120 m2 / g.

[0036] The titanium dioxide used to manufacture the solid is preferably crystalline (anatase or rutile structure). "Poorly crystalline" titanium dioxide is defined as titanium dioxide having an X-ray spectrum with halos instead of the main lines of well-crystalline titanium dioxide. "Amorphous" titanium dioxide is defined as titanium dioxide whose X-ray spectrum shows no diffraction lines.

[0037] According to the invention, the mineral compound can advantageously be chosen from glass fiber, sepiolite, rock fiber, or asbestos fiber. Preferably, the mineral compound is sepiolite or glass fiber.

[0038] The addition of a mineral binder in the form of fibers to a catalyst or support manufacturing process consisting mainly of titanium dioxide and involving the use of an organic thickening additive unexpectedly leads to a significant improvement in the catalytic performance of the product. This gain is possible because the resulting product has a large porosity without negatively impacting its mechanical resistance to crushing or impact breakage. Preparation process

[0039] The catalyst can be manufactured from a titanium dioxide source mixed with a mineral binder in the form of fibers, advantageously in the form of needles, containing between 70 and 100% silica. The manufacturing process notably includes forming a paste by mixing the titanium dioxide source and the mineral binder in fiber form, to which an acidic or basic solution and a thickening organic compound additive such as xanthan gum are added. The solid is shaped by any technique known to those skilled in the art, then dried and calcined to form a support. Preferably, the solid is shaped by extrusion or granulation.

[0040] Advantageously, the substrate preparation process according to the invention may comprise the following steps: - a step i) of preparing a paste from a mixture comprising water, 50 to 65 wt% of a titanium dioxide source containing 90 to 100 wt% of TiO2, 1 to 8 wt% of the mineral compound in the form of fibers, preferably sepiolite clay or glass fiber and 0.5 to 2 wt% of a thickening organic compound, such as xanthan gum, in the presence of an acid preferably (HCl, HNO3, H2SO4, organic acid (acetic acid, citric maleic acid...,) or a base (KOH, NaOH, Ca(OH)2 Mg(OH)2, tetraethyl ammonium hydroxide); - a step ii) of shaping the dough, for example by extrusion or granulation of said dough; - a step iii) of drying between 100 and 200°C, preferably for 1 to 24 hours; - a step iv) of calcination between 300 and 600°C preferably for 1 to 24h and preferably under air and possibly humid.

[0041] The preparation of the paste can be carried out in either an acidic or a basic medium, preferably the pH of the suspension in step i) is less than 3 or greater than 11.

[0042] The organic thickening compound is preferably a polysaccharide compound such as, for example, starch, cellulose, carboxymethylcellulose, carboxyethylcellulose, agar-agar, or a polysaccharide compound obtained by bacterial or fungal fermentation. Suitable polysaccharide compounds obtained by bacterial fermentation for the invention include xanthan gums, succinoglycan gums, or the S-194 heteropolysaccharide described in particular in patent EP 77680.

[0043] Xanthan gums are obtained by fermentation of a carbohydrate under the action of microorganisms and more particularly of bacteria belonging to the genus Xanthomonas, such as those described in Bergey's manual of determinative bacteriology (8th edition - 1974 - Williams N. Wilkins C degrees Baltimore) (Xanthomonas begoniae, Xanthomonas campestris, Xanthomonas carotae, Xanthomonas hederae, Xanthomonas incanae, Xanthomonas malvacearum, Xanthomonas papavericola, Xanthomonas phaseoli, Xanthomonas pisi, Xanthomonas vasculorum, Xanthomonas vesicatoria, Xanthomonas vitians, Xanthomonas pelargonii).Other microorganisms capable of producing polysaccharides include bacteria belonging to the genus Arthrobacterium, particularly the species Arthrobacter stabilis and Arthrobacter viscosus; to the genus Erwinia; to the genus Azotobacter, particularly the species Azotobacter indiens; to the genus Agrobacterium, particularly the species Agrobacterium radiobacter, Agrobacterium rhizogenes, and Agrobacterium tumefaciens.

[0044] As suitable polysaccharide compounds obtained by fungal fermentation, scleroglucan gums synthesized by fermentation of a carbohydrate using fungi belonging to the genus Sclerotium and more particularly to the species Sclerotium glucancium, and Sclerotium rolfsii.

[0045] The catalyst or support according to the invention can advantageously be in all known conventional forms: powder, beads, extruded and crushed materials. Beads and extruded materials are preferred. The size of the beads is advantageously between 0.5 and 10 mm, preferably between 0.7 and 8 mm. The extruded materials They can be cylindrical or polylobed in shape, solid or hollow; their size is advantageously between 0.5 and 6 mm, preferably between 2 and 5 mm.

[0046] The product thus obtained has a total pore volume greater than 0.35 ml / g, preferably greater than 0.5 ml / g (ASTM D 4284-12), a specific surface area BET (ASTM D 3663-78) greater than 100 m2 / g, preferably greater than 120 m2 / g, most preferably between 120 and 150 m2 / g, a catalytic activity 50% greater than the prior art and a resistance to breakage by impact at least equivalent to the prior art.

[0047] In addition to the aforementioned components, the final solid may include possible impurities introduced by the preparation process, in particular by the titanium dioxide source, for example impurities selected from: aluminum oxide or sulfate, iron oxide or sulfate, niobium oxide or sulfate, other aluminum, ferric, ferrous, or niobic impurities.

[0048] The final solid advantageously exhibits a loss on ignition (LOI, expressed as a percentage by weight relative to the total weight of the solid) of between 0.5 and 5% by weight. Applications

[0049] The solid according to the invention is advantageously used as a catalyst for the hydrolysis of COS and CS2 contained in the gases treated in the Claus processes, the composition of which is generally that indicated in Table 1 below:

[0050] [Tables 1] Component Concentration H2S (vol%) 0.5-15 SO2 (vol%) 0.25-7.5 H2O (vol%) 20-40 CO2 (vol%) 1-20 CO (vol%) 0-3 N2 (vol%) Complement to 100% COS (ppmv) 100-1000 CS2 (ppmv) 10-500

[0051] In the case of the hydrolysis of COS and HCN for the purification of synthesis gas, for example obtained by gasification or pyrolysis of biomass, the composition is typically that indicated in Table 2 below:

[0052] [Tables2] Components Concentration CO 30-65 vol% h2 25-40 vol% co2 1-11 vol% h2o 1-20 vol% h2s 0.3-1.5 vol% n2 0.5-5 vol% ch4 1000-1000 ppmv cos 100-1000 ppmv HCN 100-500 ppmv nh3 100-500 ppmv

[0053] The hydrolysis of the compounds COS, CS2 and HCN with the solid according to the invention is generally carried out at a pressure of between 0.1 and 5 MPa (preferably between 0.5 and 3 MPa), at a temperature of between 100 and 400°C (preferably between 150 and 250°C), and with a WH (ratio between the volumetric flow rate of the feed at the reactor inlet in m³ / h at 0°C, 1 atm and the volume of catalyst in m³ contained in the reactor) of between 1000 and 8000 h⁻¹ (preferably between 500 and 8000 h⁻¹), most preferably between 1000 and 6000 h⁻¹. The hydrolysis is carried out in the presence of water, the content of which is generally between 5 and 50% by volume relative to the volume of gas to be treated. Advantages of the invention

[0054] The solid according to the invention exhibits greater open porosity than the prior art and greater resistance to breakage upon impact against a protected metal plate. In fact, the solid according to the invention exhibits superior catalytic activity for the conversion of sulfur or nitrogen compounds such as CS2, COS, and HCN compared to the prior art. Examples Example A (comparative)

[0055] Comparative example A is a catalyst comprising 90 wt% TiO2 in the form of anatase. This catalyst is made by preparing a paste in a Z-arm mixer from water, nitric acid, and an anatase powder such as Tronox G2, which contains 10 wt% calcium sulfate and 90 wt% TiO2 on a dry basis. The paste thus obtained contains 8 wt% nitric acid and its loss on ignition is 43.5%.

[0056] The paste is extruded through a die with cylindrical holes 4 mm in diameter. The extrudates are then dried for two hours in an oven at 140°C and then calcined for 2 hours at a temperature of 450°C under humid air containing 40 g of water per kg of dry air.

[0057] This catalyst is conventionally used in the first converter of the Claus process to convert by hydrolysis CS2 and COS into H2S and possibly HCN. Example 1 (according to the invention)#:

[0058] A titanium dioxide-based catalyst is prepared by mixing a paste in a Z-arm mixer from water, nitric acid, xanthan gum, sepiolite clay, and anatase M211 powder, marketed by Venator, which contains at least 98% TiO2 by weight on a dry basis. The paste is obtained by mixing the powders and an acidified solution in the following proportions: - 0.88% by weight xanthan gum - 2.76% by weight nitric acid - 52.23% by weight anatase M211 powder - 6.32% by weight sepiolite clay - The remainder is water

[0059] The loss on ignition of the paste is then 48.5%. The loss on ignition (LOI) is measured as the weight loss corresponding to the ratio: LOI (%) = (Po-Pi)ZPo, Po = Initial weight of the raw material Pi = Weight of this raw material after calcination for 2 hours at 1000°C and cooling to room temperature in an anhydrous chamber

[0060] The quantity of sepiolite clay is targeted to obtain 10% by weight of sepiolite clay relative to the weight of the final product. The sepiolite clay is in the form of very fine needle-like fibers with a median diameter of approximately 10 nm and an average length of approximately 300 nm.

[0061] The paste is extruded through a die with cylindrical holes of 4 mm diameter. The extrudates are then dried for two hours in an oven at 140°C, then calcined for 2 hours at a temperature of 450°C under humid air containing 40 g of water per kg of dry air. Example 2 (according to the invention)

[0062] A titanium dioxide-based catalyst is prepared by mixing a paste in a Z-arm mixer from water, nitric acid, xanthan gum, sepiolite clay (fibers with a median diameter of 10 nm and an average length of approximately 300 nm), and anatase G2 powder from Tronox, which contains 10 wt% calcium sulfate and 90 wt% TiO2 on a dry basis. The paste is obtained by mixing the powders and an acidified solution in the following proportions: - 0.94% by weight of xanthan gum - 3.15% by weight of nitric acid - 56.31% by weight of anatase G2 powder - 6.50% sepiolite clay by weight - the rest water

[0063] The quantity of sepiolite clay is targeted to obtain 10% sepiolite clay by weight relative to the weight of the final product. The loss on ignition of the paste is then 46.8%.

[0064] The paste is extruded through a die with cylindrical holes of 4 mm diameter. The extrudates are then dried for two hours in an oven at 140°C and then calcined for 2 hours at a temperature of 450°C under humid air containing 40 g of water per kg of dry air. Example 3 (according to the invention)

[0065] A titanium dioxide-based catalyst is prepared by mixing a paste in a Z-arm mixer from water, nitric acid, xanthan gum, needle-shaped glass fibers with a median diameter of 14 pm and an average length of 200 pm, and anatase G2 powder commercially available from Tronox. The paste is obtained by mixing an aqueous solution containing, by weight of the mixture: - 0.93% by weight of xanthan gum - 3.29% by weight of nitric acid - 58.50% by weight of anatase G2 powder - 3.20% fiberglass by weight - the rest is water

[0066] The quantity of glass fibers is targeted to obtain 5% by weight of glass fibers relative to the weight of the final product. The loss on ignition of the paste is then 47.7%.

[0067] The paste is extruded through a die with cylindrical holes of 4 mm diameter. The extrudates are then dried for two hours in an oven at 140°C and then calcined for 2 hours at a temperature of 450°C under humid air containing 40 g of water per kg of dry air. Example 4 (according to the invention)

[0068] A titanium dioxide-based catalyst is produced by preparing a paste in a Z-arm type mixer from water, nitric acid, xanthan gum, sepiolite clay in the form of a needle with a median diameter of 10 nm and an average length of approximately 300 pm) and anatase G2 powder from the Tronox company.

[0069] The paste is obtained by mixing an aqueous solution which contains, relative to the weight of the mixture: - 0.92% by weight of xanthan gum - 3.38% by weight of nitric acid - 60.0% by weight of anatase G2 powder - 1.60% by weight of sepiolite clay - the rest in water

[0070] The quantity of sepiolite clay is targeted to obtain 2.5% by weight of sepiolite clay relative to the weight of the final product. The loss on ignition of the paste is then 47.7%.

[0071] The paste is extruded through a die with cylindrical holes of 4 mm diameter. The extrudates are then dried for two hours in an oven at 140°C, then calcined for 2 hours at a temperature of 450°C under humid air containing 40 g of water per kg of dry air. Example 5 (according to the invention)

[0072] A titanium dioxide-based catalyst is produced by preparing a paste in a Z-arm type mixer from water, nitric acid, agar-agar, glass fibers in needle form (median diameter of 14 pm and average length of 200 pm) and anatase G2 powder from the company Tronox.

[0073] The paste is obtained by mixing an aqueous solution which contains, relative to the weight of the mixture: - 0.92% by weight of agar-agar - 3.26% by weight of nitric acid - 58.0% by weight of anatase G2 powder - 3.17% fiberglass weight - the rest in water

[0074] The quantity of glass fibers is targeted to obtain 5% by weight of glass fibers relative to the weight of the final product. The loss on ignition of the paste is then 48.2%.

[0075] The paste is extruded through a die with cylindrical holes of 4 mm diameter. The extrudates are then dried for two hours in an oven at 140°C and then calcined for 2 hours at a temperature of 450°C under humid air containing 40 g of water per kg of dry air.

[0076] The characteristics of the extruded catalysts obtained are summarized in Table 3 below:

[0077] [Tables3] Example: Content of fibrous mineral binder CaSO4 (anhydrous base) Content of TiO2 (anhydrous base) Specific Surface Area (S BET) Total Pore Volume (TPV) EGG Fractures generated after impact % weight % weight % weight m2 / g ml / g daN / mm % volume Comparison A - 10 90 120 0.385 1.4 10.9 1 10% Sepio Lite 0 90 140 0.529 1.2 10.8 2 10% Sepio Lite 9.3 80.7 149 0.503 1.3 12.4 3 5% Fiberglass 9.5 85.5 130 0.477 1 7.1 4 2.5% Sepio Lite 9.8 87.7 135 0.465 1.1 7.5 5 5% Fiberglass 9.5 85.5 132 0.47 1 2.3

[0078] The catalysts of the invention therefore have open porosities (in particular total porous volume VPT) measured by mercury intrusion significantly higher than conventional catalyst A while maintaining sufficient mechanical strengths with an EGG > 1 daN / mm and a breakage rate generated after an impact of less than 15% by volume. Example 6

[0079] The present example illustrates the application of the catalysts of the invention for the hydrolytic conversion of CS2 under conditions simulating the first converter of the Claus process. This reaction is considered a model for evaluating the performance of a catalyst under these conditions, since the reaction rate is much lower than that of COS hydrolysis:

[0080] [Chem.l] 02 E 2020 ~ CO2 at 2O2S

[0081] The following gas mixture is sent into a reactor maintained at 320°C: - 3% vol H2S - 2% vol SO2 - 1000 ppmv CS2 - 30% vol H2O - Balance (complement to 100% vol) N2

[0082] The reactor contains 30 g of the catalysts according to the invention. The total gas flow rate is adjusted to achieve WH values ​​of 4000 and 6000 h⁻¹ relative to the catalyst volume in the reactor. The WH values ​​in this example are deliberately chosen to be very high. superior to the WH values ​​of industrial Claus processes to discriminate the activity of catalysts to convert CS2.

[0083] The CS2 conversions recorded during the implementation of the extruded catalysts obtained are summarized in Table 4 below:

[0084] [Tables4] Example: Mineral binder content (fibrous) TiO2 content CS2 conversion by hydrolysis at 320°C % by weight % by weight % at VVH=6000 h⁻¹ % at VVH=4000 h⁻¹ Comparison A - 90 45 51 1 10% sepiolite 90 51 67 2 10% sepiolite 85 57 72 3 5% glass fibers 85 75 83 4 2.5% sepiolite 87.5 58 73 5 5% Glass fibers 85 76 84

[0085] It therefore appears that the catalysts of the invention, thanks to a much higher open porosity, can achieve CS2 conversions under conditions simulating the first converter of the Claus process that are much higher than those observed on conventional catalysts such as that of comparative example A.

Claims

Demands

1. Solid with a specific surface area SBET greater than 100 m2 / g comprising: - 75 to 95% by weight of titanium dioxide TiO2 including terminals, relative to the total weight of the anhydrous solid; - 1 to 20% by weight of a mineral compound in the form of fibres, including terminals, relative to the total weight of the anhydrous solid, said fibres comprising 70 to 100% by weight of silica and said fibres having a median diameter between 5 nm and 50 pm and an average length between 50 nm and 1000 pm - a total pore volume of pore diameters between 3.7 nm and 10 pm measured according to ASTM D4284-12 greater than 0.35 ml / g.

2. Solid according to claim 1 comprising 80 to 90% by weight of titanium dioxide TiO2bomes included, relative to the total weight of the anhydrous solid.

3. Solid according to any one of claims 1 or 2 comprising from 2 to 10% by weight of a mineral compound in the form of fibers, terminals included, relative to the total weight of the anhydrous solid.

4. Solid according to any one of claims 1 to 3 comprising a total pore volume of pore diameters between 3.7 nm and 10 pm measured according to ASTM D4284-12 greater than 0.5 ml / g.

5. Solid according to any one of claims 1 to 4 wherein the mineral compound is selected from glass fiber and sepiolite.

6. Solid according to claim 5 wherein the mineral compound is sepiolite.

7. Solid according to any one of the preceding claims having a grain-to-grain EGG crush resistance greater than or equal to 1 daN / mm and a breakage rate generated after impact against a steel plate of less than 15% by volume.

8. A process for preparing a solid according to any one of the preceding claims comprising the following steps: i) A titanium dioxide source comprising 90 to 100 wt% titanium dioxide TiO2 is mixed with a mineral compound in the form of fibers comprising 70 to 100 wt% silica, said fibers having a median diameter of between 5 nm and 50 pm and an average length of between 50 nm and 1000 pm, a compound organic thickener and water in the presence of a base or an acid to obtain a paste; ii) The kneaded paste obtained in step i) is shaped, preferably by extrusion or granulation; iii) The paste shaped in step ii) is dried at a temperature between 100 and 200°C to obtain a dried product; iv) The dried product is calcined at a temperature between 300 and 600°C.

9. A method for preparing a solid according to claim 8 wherein the thickening compound is selected from a polysaccharide compound such as, for example, starch, cellulose, carboxymethylcellulose, carboxyethylcellulose, agar-agar, or a polysaccharide compound obtained by bacterial or fungal fermentation, such as xanthan gum, succinoglycan gum, scleroglucan gum or S-194 heteropolysaccharides.

10. A process for preparing a solid according to claim 8 or 9 wherein the titanium dioxide source is introduced at a content of between 50 and 65 wt%, the mineral compound in the form of fibers is introduced at a content of between 1 and 8 wt%, the thickening compound is introduced at a content of between 0.5 and 2 wt%, relative to the total mass of the mixture in step i).

11. A process for hydrolyzing sulfur or nitrogen compounds contained in a gaseous feed, preferably selected from H2S, COS, CS2 and / or HCN, by contacting said gaseous feed with water and a solid according to any one of claims 1 to 7 or prepared according to any one of claims 8 to 10.

12. Hydrolysis process according to claim 11, wherein the gaseous feedstock is a gaseous effluent from a Claus treatment process of H2S.

13. Hydrolysis process according to claim 11, wherein the gaseous feedstock is a synthesis gas.

14. Use of the solid according to any one of claims 1 to 7 or prepared according to any one of claims 8 to 10 as a catalyst or as a heterogeneous catalyst support.

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