PL240269B1

PL240269B1 - Composite material in the form of solid particles with the construction of the core-coating-active phase type, method for obtaining of such composite material and its application

Info

Publication number: PL240269B1
Application number: PL423615A
Authority: PL
Inventors: Piotr KUŚTROWSKI; Piotr Kuśtrowski; Tomasz Kondratowicz; Kamil Machowski; Piotr NATKAŃSKI; Piotr Natkański
Original assignee: Univ Jagiellonski
Priority date: 2017-11-27
Filing date: 2017-11-27
Publication date: 2022-03-07
Also published as: DE102018129499A1; PL423615A1

Description

PL 240 269 B1

Description of the invention

The subject of the invention is a composite material in the form of solid particles having a core-shell-active phase structure, a method for obtaining such a composite material and its use for the elimination of volatile organic compounds.

The emission of volatile organic compounds (VOCs) to the atmosphere, both from natural and anthropogenic sources, is one of the most serious threats to the environment and human health. These substances, both directly and indirectly, interact with the components of the atmosphere, causing photochemical reactions, and often exhibit carcinogenic and mutagenic properties. The reduction of VOC emissions can be achieved by controlling industrial sources (including waste gases generated by paint factories, paint shops, pharmaceutical plants, bakeries, etc.) that produce nearly half of the total amount of VOC released by human activity. In addition to the primary methods aimed at reducing the level of emissions of organic compounds, a number of solutions have been developed consisting in catching (non-destructive techniques) or neutralizing (destructive techniques) VOC contained in the air. The most commonly used techniques are: thermal and catalytic oxidation, adsorption, condensation and membrane separation.

Adsorption of volatile organic compounds

Due to high efficiency, low operating costs of the necessary equipment and environmentally friendly nature, adsorption is the basic process of removing VOCs from low-emission sources. During the regeneration of used adsorbent, it is also possible to recover previously bound molecules and reuse them. Carbon materials based on activated carbon produced from fossil coal or biomass are the most widely used as VOC adsorbents. However, polymers (e.g. polyacrylonitrile, poly (vinyl chloride), poly (furfuryl alcohol), resole resins) are gaining more and more importance in the production of activated carbon. The advantage of using synthetic polymer raw materials is obtaining active carbons with a repeatable composition and low ash content. Activated carbons are obtained in the process of pyrolysis (carbonization) of the starting material carried out at high temperatures in an inert atmosphere with subsequent physical or chemical activation of the product obtained. The purpose of the first of these activation paths is to increase the porosity and specific surface area of activated carbon by removing non-carbon elements. The second method is used to generate appropriate surface properties. Water vapor or carbon dioxide is usually used for physical activation, while chemical activation is most often carried out in the presence of KOH, ZnCl2, or H3PO4. The activated carbons obtained in the above manner are microporous materials with a highly developed specific surface.

In recent years, intensive research has been carried out on porous carbon materials with spherical particles with diameters ranging from tens of nanometers to tens of micrometers, intended primarily for adsorptive, medical (drug carriers) and electrochemical (electrode materials) applications. These types of materials are mainly synthesized using: (i) the method of hydrothermal modification of saccharides and their copolymers (e.g. with phenol derivatives), (ii) the technique of mapping soft organic patterns, as well as (iii) the structural replication path of spherical silica materials. The synthesis of spherical carbon materials according to the first of these approaches consists in preliminary dehydration of the carbon precursor (e.g. glucose, xylose, fructose, xylose-phenol mixture) under hydrothermal conditions (140-210 ° C), optional activation (e.g. with KOH) followed by carbonization in the presence of an inert gas (e.g. argon or nitrogen) at temperatures in the range 600-1000 ° C. The materials obtained in this way have a specific surface area ranging from 13 (without activation) to approx. 1280 m ² / g (after KOH activation), mainly due to the presence of irregularly arranged micropores [M. Li, W. Li, S. Liu, Hydrothermal synthesis, characterization, and KOH activation of carbon spheres from glucose, Carbohydrate Research 346 (2011) 999-1004; J. Ryu, Y.-W. Suh, DJ Suh, DJ Ahn, Hydrothermal preparation of carbon microspheres from mono-saccharides and phenolic compounds, Carbon 48 (2010) 1990-1998; Q. Wang, H. Li, L. Chen, X. Huang, Monodispersed hard carbon spherules with uniform nanopores, Carbon 39 (2001) 2211-2214].

In contrast to the above-described technique, solutions using organic or inorganic structure-forming templates allow for obtaining carbon materials with an ordered system of pores of a controlled size, including mesoporous systems. The advantage of mesoporous activated carbons, obtained by means of pattern mapping methods, is the considerable width

The presence of uniform pores (with a specific surface area comparable to that of conventional activated carbons), which eliminates diffusion limitations in adsorption or catalytic applications. In the soft-template method, the surfactants are mainly block copolymers (e.g. Pluronic F127, Pluronic P123) or alkylammonium halides, forming matrices made of micelles on / in which the carbon precursor polymerizes (most often phenol-formaldehyde resins) [M. Li, J. Xue, Ordered mesoporous carbon nanoparticles with wellcontrolled morphologies from sphere to rod via a soft-template route, Journal of Colloid and Interface Science 377 (2012) 169-175; J. Liu, T. Yang, D. -W. Wang, G. Qing (Max) Lu, D. Zhao, SZ Qiao, A facile soft-template synthesis of mesoporous polymeric and carbonaceous nanospheres, Nature Communications 4 (2013) 2798]. The spherical shape of the particles obtained is obtained by using an appropriate amount of surfactant or co-surfactant. The formed polymer is thermally modified in the presence of an inert gas at temperatures in the range 400-800 ° C. Carbon materials obtained by this technique show the presence of ordered mesopores and are characterized by a specific surface area of ^460-1380 m2 / g.

The most frequently described technique for the synthesis of spherical grained coals in the scientific literature is the mapping of spherical silica templates (hard-template methods). A typical procedure for the synthesis of this type of carbon replica includes: (i) preparation of a mesoporous silica template with a spherical particle shape, (ii) deposition of the carbon precursor in the silica pore system, e.g. by impregnation, in situ polymerization or vapor deposition (CVD), ( iii) carbonization of the obtained material in an inert atmosphere at a temperature in the range of 800-1100 ° C to the form of a carbon-silica nanocomposite, and then (iv) removal of the silica template by etching with strong alkali (e.g. NaOH) or HF [M.-H. Kim, K.-B. Kim, SM. Park, KC Roh, Hierarchically structured activated carbon for ultracapacitors, Scientific Reports 6 (2016) 21182; M. Kim, SB Yoon, K. Sohn, JY Kim, C.-H. Shin, T. Hyeon, J.-S. Yu, Synthesis and characterization of spherical carbon and polymer capsules with hollow macroporous core and mesoporous shell structures, Microporous and Mesoporous Materials 63 (2003) 1-9; T.-W. Kim, P.-W. Chung, V S.-Y. Lin, Facile Synthesis of Monodisperse Spherical MCM-48 Mesoporous Silica Nanoparticles with Controlled Particle Size, Chemistry of. Materials 22 (2010) 5093-5104]. In this method, commercial spherical silica gels with disordered pore structure are often used as rigid matrices, as well as mesoporous ordered silica materials (e.g. SBA-15, SBA-16, MCM-41, MCM-48) formed by appropriate selection of surfactants to the form balls with a defined diameter. As carbon precursors, as in the previously discussed methods, resole resins, polyfuryl alcohol), polyacrylonitrile and disaccharides (e.g. sucrose) [Hl Melendez-Ortiz, LA Garcia-Cerda, Y. Olivares-Maldonado, G. Castruita, JA Mercado-Silva, YA Perera-Mercado, Preparation of spherical MCM-41 molecular sieve at room temperature: Influence of the synthesis conditions in the structural properties, Ceramics International 38 (2012) 6353-6358; T.-W. Kim, P.-W. Chung, V S.-Y. Lin, Facile Synthesis of Monodisperse Spherical MCM-48 Mesoporous Silica Nanoparticles with Controlled Particle Size, Chemistry of Materials 22 (2010) 5093-5104; MA Ballem, EM Johansson, JM Córdoba, M. Oden, Synthesis of hollow silica spheres SBA-16 with large-pore diameter, Materials Letters 65 (2011) 1066-1068; A. Katiyar, S. Yadav, PG Smirniotis, NG Pinto, Synthesis of ordered large pore SBA-15 spherical particles for adsorption of biomolecules, Journal of Chromatography A 1122 (2006) 13-20]. In order to improve the functional properties, the carbon materials obtained by the techniques described above can be subjected to subsequent physical or chemical activation, using methods analogous to those used for active carbons of natural origin, for example by partial gasification of the carbon material with a gas agent (e.g. steam, carbon dioxide). ), or chemical activation with a hydroxide solution (e.g. KOH, NaOH) or acid (e.g. H3PO4, HNO3).

Catalytic oxidation of volatile organic compounds

Apart from adsorption technologies, catalytic afterburning is a widely used method of removing VOCs from the gas phase. The catalysts used in this process usually contain small amounts of noble metals (eg Pt, Pd, Au or Rh), which as an active phase are characterized by very high efficiency, thermal stability and selectivity in obtaining the desired reaction products (mainly H2O and CO2). Due to the high production costs and susceptibility to poisoning, however, intensive research is carried out to find alternative catalytically active materials in the process of burning VOCs. An example of such systems are catalysts containing transition metal oxides and their mixtures (e.g. CuO, CosO4, MnO2, Fe2O3, CeO2), characterized by high resistance to poisoning (including compounds containing

Sulfur) and lower production costs compared to catalysts based on noble metals. Due to the beneficial effect of the expansion of the specific surface area on the activity of the catalyst, the active phase is applied to a support with appropriately selected porosity, and thus exposed surface (e.g. y-AbOs, TiO2, ZrO2, zeolites, natural aluminosilicates, porous silica gel) [R. Arroyo, G. Cordoba, J. Padilla, VH Lara, Influence of manganese ions on the anatase - rutile phase transition of TiO2 prepared by the sol-gel process. Materials Letters 54 (2002) 397-402; MR Moreles, BP Barbera, T. Lopez, LE Cadus, H. Moreng: Evoluantion and characterization of Mn-Cu mixed oxide catalyst supported on TiO2 and ZrO2 for ethanol total oxidation. Fuel 88 (2009) 2120-2129, A. Szegedi, M. Popova, K. Lazar, S. Klebert, E. Drotar, Impact of silica structure of copper and iron-containing SBA-15 and SBA-16 materials on toluene oxidation , Microporous and Mesoporous Materials 177 (2013) 97-104; A. Rokicińska, P. Natkański, B. Dudek, M. Drozdek, L. Litynska-Dobrzyńska, P. Kuśtrowski, Co3O4-pillared montmorillonite catalysts synthesized by hydrogel-assisted route for total oxidation of toluene, Applied Catalysis B: Environmental 195 ( 2016) 59-68]. It has been shown that the oxide systems deposited on the ZrO2 substrate with a tetragonal structure are distinguished by higher activity in total VOC oxidation than catalysts deposited on alumina, which is caused by the greater reactivity of oxygen present in the ZrO2 structure. In order to improve the catalytic properties, the supported materials are additionally modified with transition or noble metals [H.-J. Sedjame, C. Fontaine, G. Lafaye, J. Barbier Jr, On the promoting effect of the addition of ceria to platinum based alumina catalysts for VOCs oxidation, Applied Catalysis B: Environmental 144 (2014) 233-242; JC Rooke, T. Barakat, M. Franco Finol, P. Billemont, G. De Weireld, Y. Lie, R. Cousin, J.-M. Giraudon, S. Siffert, J.-F. Lamonier, BL Su, Influence of hierarchically porous niobium doped TiO2 supports in the total catalytic oxidation of model VOCs over noble metal nanoparticles, Applied Catalysis B: Environmental 142-143 (2013) 149-160].

The literature describes examples of successful syntheses of spherical materials based on ZrO2, in which this component forms the core of the sphere ("core") or the shell ("shell"). In the first case, spherical porous zircon (IV) oxide particles are synthesized by the hydrothermal, sol-gel method or by mapping soft and hard structure-forming patterns [Y. Chang, C. Wang, T. Liang, C. Zhao, X. Luo, T. Guo, J. Gong, H. Wu, Solegel Synthesis of Mesoporous Spherical Zirconia, RSC Advances 5 (2015) 104629-104634]. On the other hand, to create spherical ZrO2 envelopes, the so-called shell materials, it is necessary to use a spherical core on the surface of which a layer of the ZrO2 precursor is deposited, e.g. by hydrolysis of zirconium or zirconium chloride alkoxides [H. Zhang, Z.-T. An, Q. Tang, W.-C. Li, Optimization design of novel spray reaction synthesis of mesoporous c-ZrO2 spherical particles, Journal of Computer-Aided Materials Design 14 (2007) 309-316]. Depending on the material used, the core may be removed by calcination (for polymer particles) or etching (for silica core) [Y. Jiang, S. Yang, X. Ding, Y. Guo, H. Bala, J. Zhao, K. Yu, Z. Wang, Synthesis and catalytic activity of stable hollow ZrO2-SiO2 spheres with mesopores in the shell wall, Journal of Materials Chemistry 15 (2005) 2041-2046; J. Yin, X. Qian, J. Yin, M. Shi, J. Zhang, G. Zhou, Preparation of polystyrene / zirconia core-shell microspheres and zirconia hollow shells, Inorganic Chemistry Communications 6 (2003) 942-945].

Composite materials with a core-shell structure are known from the patent literature, also with regard to the adsorption-catalytic function in the elimination of volatile organic compounds. For example, international application WO16069856A1 discloses non-noble metal catalysts for the removal of ozone, volatile organic compounds and other contaminants from an air stream. The catalyst comprises a shell, a solid support located inside the shell, and a catalyst layer located on the support. The catalyst layer comprises a first catalytically active base metal component, a second base metal component and a support material impregnated with at least one of these components. A preferred catalyst composition is a combination of manganese oxide and copper oxide.

WO09157434A1 describes a method of purifying an exhaust gas containing carbon dioxide by afterburning VOC and sulfur compounds in the presence of a catalyst containing one or more metal oxides selected from the group consisting of zirconium oxide, titanium oxide and silicon oxide and one or more noble metals selected from the group consisting of platinum, palladium and iridium.

PL 240 269 B1

US patent application US2015057149A discloses catalysts and methods for the preparation of catalysts for the oxidation of CO and / or volatile organic compounds. In one embodiment, the catalyst comprises a reduced noble metal metal in an amount greater than 30 wt%, and the catalyst oxidizes volatile organic compounds and / or CO at a temperature of 150 ° C or less. In another embodiment, there is disclosed a catalyst for the oxidation of formaldehyde, methanol, formic acid, and / or CO at a temperature of from about 20 ° C to about 45 ° C at atmospheric pressure, the catalyst comprising a reduced noble metal dispersed on a support selected from the group of consisting of CeO2, TO2, ZrO2, Al2O3, SO2 and combinations thereof.

The solution described in the Chinese patent CN103480369B concerns a composite catalyst with nanometric platinum, its preparation and application. Many active sites of the catalyst formed by the Pt nanoparticles are deposited on the support in the form of SO2 to form the SiO2 / Pt core structure. The outer surface of the SiO2 / Pt core is covered with a mesoporous zirconium dioxide layer, forming a core-shell SiO2 / Pt / ZrO2 structure. According to this invention, in the reactions of producing aniline by hydrogenation of nitrobenzene and oxidation of carbon monoxide, the described catalyst can be used continuously or cyclically for more than 20 cycles, and the activity of the catalyst remains essentially unchanged. The catalyst is characterized by high activity, stability, as well as the possibility of reuse and easy recovery. Additionally, it is suitable for use in high-temperature conditions thanks to the protective effect of the mesoporous zirconium dioxide coating.

The development of new composite materials containing components selected to ensure the appropriate functionality of the material is very desirable in the emerging technical field of materials engineering. The aim of the present invention is to construct functional materials of a new generation, intended both for adsorption and catalytic applications in the field of VOC elimination.

The present invention relates to a particulate composite material having a core-shell-active phase structure comprising a core of adsorptive material, at least one inorganic oxide and particles of a catalytically active phase, characterized in that

- the adsorption material is porous carbon,

- the inorganic oxide constituting the core coating and the catalytically active phase carrier is zirconium oxide,

- the catalytically active phase consists of nanoparticles or their agglomerates based on metals or metal oxides selected from the group consisting of Pt, Co3O4, CuO. Preferably, the solid particles of the composite material are spherical. Preferably, the carbon core is a mesoporous carbon material with a surface area in the range ^306-514 m2 / g ^and a pore volume in the range 0.24 to 0.61 cm3 / g. Preferably, the composite material is characterized in that the inorganic oxide is porous. Preferably, the composite material is characterized in that the catalytically active phase consists of metals or their oxides deposited on the oxide shell and the coating itself.

Preferably, the catalytically active phase nanoparticles are deposited on the surface of the inorganic oxide without contacting the carbon core. The invention also relates to a method for obtaining the composite material described above, comprising the following steps:

a) obtaining porous carbon particles,

b) applying an oxide coating to the core of porous carbon material, c) depositing particles of the catalytically active phase on the oxide coating.

The method of obtaining the material is preferably characterized in that step a) is carried out using rigid silica pattern mapping, where the carbon feedstock / precursor is introduced into the silica matrix by impregnation or in-situ polymerization.

Preferably, the carbon precursor is polymers obtained by in situ polymerization of monomers selected from the group consisting of furfuryl alcohol, phenol-formaldehyde mixture, acrylonitrile.

Also preferably the precursor are sugars selected from the group of sucrose, glucose, xylose.

Preferably, the method for obtaining the composite material is characterized in that the silica templates are based on silica gel or mesoporous silica materials of the type SBA-15, SBA-16, MCM-41 and MCM-48 with spherical particle shape.

The method for obtaining the composite material is preferably characterized in that a carbon precursor is introduced into the pore system of the spherical silica material to obtain a composite material.

Polymer-silica oxide, which is then carbonized at a temperature in the range of 600-1000 ° C in an inert gas such as argon, nitrogen or helium to obtain a carbon-silica material, and then the silica is removed from the carbon composite by etching with a NaOH solution with a concentration ranging from 1 to 5 M or a HF solution with a concentration ranging from 1-10% at a temperature ranging from 25 to 90 ° C.

Preferably, the method for obtaining the composite material is characterized in that the removal of the silica is carried out before or after the deposition of the inorganic oxide coating.

Preferably, the oxide coating in the process is applied in step b) by hydrolysis and polycondensation of the metal alkoxide.

Preferably, the method for obtaining the composite material is characterized in that the reaction is carried out in an anhydrous alcohol solution in the presence of a surfactant.

Preferably, after process step b), the material is dried and carbonized at a temperature in the range 600-1000 ° C in an inert gas atmosphere for 1 to 48 hours, increasing the temperature at a rate of 0.1 to 50 ° C / min.

The method for obtaining the composite material is preferably characterized in that the nanoparticles of the catalytically active phase in step c) are applied to the inorganic oxide layer by the impregnation method from a solution of a readily soluble compound of the selected metal.

The invention also relates to the use of the composite material described above for the elimination of volatile organic compounds by adsorption in a core made of porous carbon and their subsequent catalytic oxidation through the catalytically active phase present in the coating.

Preferably, the volatile organic compounds adsorption takes place at a temperature in the range of 20-100 ° C, and the catalytic afterburning at a temperature above 150 ° C.

Preferably, the volatile organic compounds are selected from the group of aliphatic and aromatic hydrocarbons.

The term "composite material" means the composite material according to the invention.

The term "polymer-silica composite", for the purposes of this description, refers to a material composed of a silica skeleton and a carbon precursor polymer incorporated therein, and a "carbon-silica composite" or "carbon-silica material" is a polymer-silica composite after thermal modification. in which the polymer part has been carbonized.

The term "carbon replica" means carbon material obtained by removing a silica template from a carbon-silica composite.

Commercially available agents can be used to practice the invention, including, but not limited to, silica materials of the types SBA-15, SBA-16, MCM-41 and MCM-48, which can also be prepared according to synthetic procedures known to those skilled in the art.

Unless otherwise defined, all ingredient levels are given in this specification as percentage by weight (wt%).

Therefore, a new composite material was developed, in which a porous carbon part was connected, constituting a spherical core ("core"), the task of which is to ensure high sorption capacity against VOC in the adsorption phase of the process (operation at ambient temperature). By using various compounds to eliminate the silica matrix from the catalyst core precursor (including NaOH, HF), different concentrations of these compounds and different conditions (temperature, etching time of the silica template), it is possible to modify the surface of the carbon core formed in the form of nano-micrometric spheres providing the desired adsorption properties for that part of the composite material.

It is observed that depending on the application of the composite material, e.g. for the elimination of a specific group of VOC compounds, specific types of carbon core surface modification are desirable:

- for the elimination of polar and non-polar VOCs, it is advantageous to ensure the presence of highly hydrophilic groups (oxygen functional groups) on the surface of the carbon core, which is achieved by using NaOH as an etching agent for the silica matrix,

for the elimination of non-polar VOCs such as aliphatic and aromatic hydrocarbons, it is preferable to ensure the presence of a low content of oxygen functional groups on the surface of the carbon core, which is achieved by the use of HF during the removal of the silica matrix.

PL 240 269 B1

Contrary to other core-shell materials, where the core is based on porous carbon, the above-described modification is innovative for the present composite material and extremely important for the purpose of the invention, as it allows to control the amount of surface oxygen groups responsible for the high adsorption capacity of the carbon core in relation to polar pairs of volatile organic compounds. In addition, it allows you to adjust the properties of the composite material to eliminate specific groups of VOC compounds.

The nano-micrometric spherical carbon grains were surrounded by a thin layer of inorganic oxide ("shell"), which was to protect the carbon core during the work of the material during the catalytic afterburning of VOC in the desorption cycle (operating phase at elevated temperature). Additionally, in order to improve the catalytic properties of the material, the porous inorganic shell was modified by applying to it a catalytically active phase in the form of nanometric metal particles (e.g. Pt, Pd, Rh, Re, Ir, Au) or a transition metal oxide (e.g. CuO, CO3O4, Mn2O3, MnO2, Mn3O4, CeO2, Fe2O3) or mixtures of the listed components. It should be emphasized that the catalytically active phase present in the composite material according to the invention is not homogeneously distributed throughout the entire volume of the inorganic oxide coating, but remains mainly deposited on its surface. The transport of molecules between the internal and external part of the material is possible thanks to the use of a porous inorganic support from the group of ZrO2, Al2O3, TiO2, CeO2, in contrast to composite materials from the state of the art, where the inorganic support is solid / non-porous, increasing the degree of dispersion of the active and filling phase the role of a separator of the carbon part and the catalytically active phase, the contact of which could lead to gradual gasification of the adsorbent.

The advantages of the present invention over the solutions disclosed in the prior art are therefore:

- covering three types of substances with different characteristics in one composite material;

- obtaining the multifunctionality of the material through appropriate selection of its components, which can be simplified as follows: core - adsorption; inorganic oxide

- support and shield against inactivation (gasification) of the core; active phase - oxidation of adsorbed VOCs;

- reducing the disadvantageous deactivation of the porous carbon core by surface modification as described above;

- limiting the penetration of the catalytic phase particles into the inorganic oxide layer supporting the active phase and thus further limiting the unfavorable deactivation of the porous carbon and obtaining a high catalytic capacity by exposing the catalyst particles;

- use of the material for the elimination of volatile organic compounds in adsorption-catalytic cycles, carried out at low (20-100 ° C) and high temperatures (above 150 ° C), respectively;

- the ability to control the type and amount of surface functional groups of the carbon core, allowing for selective adsorption of polar or non-polar volatile organic compounds.

The invention has been illustrated by means of embodiments which, however, are not intended to limit the scope of protection. It will be apparent to those skilled in the art that it is possible to substitute the measures indicated in the examples to adapt the process conditions to obtain a material comprising alternative embodiments of the invention including the components listed in the claims.

The following is a description of the figures that are described in detail in the examples.

F ig. 1 illustrates nitrogen adsorption-desorption isotherms for the MCM-48 / CMK-1 @ ZrO2 composite material before and after removal of the silica template with 1 M NaOH at 25 ° C (CMK-1 @ ZrO2_1 M_25 ° C sample) and 3 M NaOH in 50 ° C (CMK-1 @ ZrO2_3M_50 ° C).

F ig. 2 illustrates the results of the adsorption tests carried out on carbon replicas obtained by extracting the structure-forming template with 5% HF and 1 M NaOH.

F ig. 3 illustrates the results of catalytic tests of 1% Pt-CMK1 @ ZrO2 materials (Example 1) and 10% CuO-sC @ ZrO2 and 10% Co3O4-sC @ ZrO2 materials (Example 2). The signatures of the materials will be deciphered in the examples section below.

Examples

The examples use the following designations for specific materials:

PL 240 269 B1

MCM-48 / CMK-1 @ ZrO2 - carbon-silica composite with a carbon core designated CMK-1, MCM-48 silica and a layer of zirconium oxide,

CMK-1 @ ZrO2 - CMK-1 carbon replica with a layer of ZrO2 zirconium oxide, after removing the silica structure-forming template from the MCM-48 / CMK-1 @ ZrO2 composite (marking generally used without specifying the conditions for removing the silica matrix)

CMK-1 @ ZrO2_1M_25 ° C - CMK-1 carbon replica with a layer of ZrO2 zirconium oxide, after removing the silica structure-forming template at 25 C using 1 M NaOH

10% Co3O4 - sC @ ZrO2 - carbon replica made on the basis of spherical silica gel with a layer of ZrO2 zirconium oxide and deposited active phase Co3O4 in the amount of 10% by weight Co in relation to the mass of inorganic oxide (ZrO2 envelope).

sC - spherical carbon replica obtained on the basis of commercial spherical silica gel. Other, analogous markings should be deciphered on the basis of the above markings.

Example 1

The method of obtaining the composite material according to the invention is presented below.

Synthesis of MCM-48 spherical mesoporous silica material

67.0 mL of distilled water, 105.0 mL of methanol (99.8%, Aldrich), 30.0 mL of ammonia water (25% aqueous solution, POCH), 16.0 mL of hexadecyltrimethylammonium chloride were introduced into a 500 mL round bottom flask. (25% aqueous solution, Aldrich). The solution was stirred with a magnetic stirrer (400 rpm) at room temperature for 15 min. Then 15.0 mL of tetraethoxysilane (TEOS, 98%, Aldrich) was added dropwise at a dosing rate of approx. 2-3 drops per second while stirring continuously. After dropwise addition of TEOS, stirring was continued for 2 h. The resulting suspension was filtered on a Buchner funnel, washing with distilled water (5 x 250 mL). The obtained product was dried overnight at 90 ° C, and then calcined in air at 550 ° C for 6 hours with a temperature increase of 1 ° C / min.

Synthesis of MCM-48 silica-based spherical polymer-silica composite and its thermal modification

The polymer-silica composite was prepared by solvent-precipitation polycondensation of furfuryl alcohol (FA) in an aqueous suspension of MCM-48 silica support. 100.0 mL of distilled water, 2.00 g of mesoporous silica and 2.5 g of furfuryl alcohol were introduced into a 250 mL round-bottom flask placed in an oil bath on a magnetic stirrer with a heating plate, equipped with a thermometer and reflux condenser. The resulting slurry was stirred for 30 min (400 rpm) after which an acidic polycondensation catalyst (HCl, 35-38%, POCH) was added in an amount corresponding to a molar ratio FA: HCl = 1: 6. The reaction mixture was then heated to reflux and continued with stirring polycondensation was carried out for 6 h. The product was filtered on a Buchner funnel, washing with distilled water (3 x 100 mL) and dried overnight at 90 ° C. The obtained polymer-silica composite was placed in a quartz boat and subjected to carbonization in a tube furnace using isothermal annealing conditions for 4 hours at 850 ° C (temperature increase 1 ° C / min) under nitrogen flow (40 mL / min). As a result of thermal modification, a carbon-silica composite was obtained, which was the precursor to the core of the final catalyst.

Application of the ZrO2 layer

The spherical carbon-silica composite was dispersed in a 250 mL round bottom flask containing 100 g of anhydrous ethyl alcohol. The vessel was then placed on a magnetic stirrer and heated to 30 ° C. 0.5 mL of an aqueous solution of Lutensol AO5 non-ionic surfactant (3.76 wt.%) Was added. After an hour, 1.8 mL of zirconium butoxide (80 wt% in butanol) was added dropwise and the reaction was carried out for 15 hours. In the next stage, the material obtained was centrifuged and washed several times with distilled water. The synthesized intermediate was aged in water for 3 days in order to completely hydrolyze the substrate, then the preparation was centrifuged, dried and heated in an inert gas flow for 2 h at 900 ° C with a temperature increase of 2 ° C / min.

Silica removal from carbon-silica composite with ZrO2 (MCM-48 / CMK-1 @ ZrO2)

Extraction of the MCM-48 core was performed using sodium base. For this purpose, the carbon-silica MCM-48 / CMK-1 @ ZrO2 composite was divided into two equal portions and flooded with 1 and 3 M NaOH solution, and then the system was heated to 25 and 50 ° C, respectively. After

After 2 hours, the precipitate was filtered off, washed thoroughly with distilled water to remove Na ⁺ cations and dried. The results confirm that matrix removal can be accomplished under various conditions.

The results of digestion of the MCM-48 matrix with 1 or 3 M NaOH solution at 25 or 50 ° C, respectively, are described in Example 3.

Application of the active phase Pt with nanometric dimensions

Pt nanoparticles were obtained by reducing PtCl4 with NaOH in anhydrous ethylene glycol solution. For this purpose, 0.018 g of PtCl4 was dissolved in a solution containing 0.016 g of NaOH in 5 mL of ethylene glycol. After 30 minutes, the solution was heated to 160 ° C and held for a further 3 hours, then cooled to room temperature. The obtained Pt nanoparticles were applied to the surface of the inorganic shell using 1 g of a carbon carrier with CMK-1 @ ZrO2 zirconium oxide. For this purpose, the support was poured with the solution obtained and left on a magnetic stirrer for overnight. The material was then washed with distilled water and dried.

Example 2 ^{1 1}

Synthesis of spherical mesoporous carbon material based on commercial spherical silica with a particle size of 40-75 μm

Commercial silica with 40-75 μm spherical grain size (Sigma-Aldrich) was used as a hard template to synthesize the spherical carbon materials. In the first step, a low pH sugar solution was prepared by dissolving 1.25 g of sucrose in 5.0 mL of water acidified with 0.14 g of concentrated sulfuric acid (VI). A previously dried (100 ° C, 1 h) silica gel was impregnated with a sucrose solution using the incipient wetness technique. The thus modified silica was baked in an air atmosphere, initially at 100 ° C for 6 h, and then for 6 h at 160 ° C. The finished brown-colored preparation was gently ground in a porcelain mortar and subjected to the impregnation procedure again. The black material obtained was ground in a porcelain mortar and placed in a tube furnace, annealing for 4 h at 850 ° C with a temperature ramp of 1 ° C / min under nitrogen flow (40 mL / min) to produce a carbon-silica composite. From the synthesized carbon-silica composite, the silica template was removed by washing twice with 5% hydrofluoric acid solution at room temperature, using 30 mL of HF solution per 1 g of composite. Carbon material, isolated from the solution by filtration through a fluted filter, washed with water (3 × 100 mL) and ethanol (1 × 100 mL) to remove excess water. The obtained replica was then dried at the temperature of 80 ° C for 12 h.

Application of the ZrO2 layer

Spherical porous sC carbon (0.5 g) was dispersed in 5 mL of anhydrous ethyl alcohol. The suspension was placed in a round bottom flask and 0.1 mL of distilled water and Brij 30 surfactant (0.1 mL) were added. The flask was placed on a magnetic stirrer and its contents stirred for 30 minutes. Then 0.2 mL of zirconium butoxide (80 wt% in butanol) was added dropwise. The hydrolysis reaction was carried out for 8 hours. The material obtained was centrifuged and washed copiously with distilled water. The isolated product was aged in water for 12 hours at room temperature to ensure complete condensation of the ZrO2 precursor. After this time, the preparation was dried at a temperature of 75 ° C for 24 h and annealed in a flow of inert gas for 2 h at a temperature of 850 ° C with a temperature increase of 2 ° C / min.

Application of the active phase using incipient wetness impregnation

In the first step, the sorption capacity of the catalytically active element carrier (in this case sC @ ZrO2) in relation to water was determined. Using an automatic pipette, distilled water was dropped in small portions (20 μL each) until the glass transition appeared. The sorption capacity of the carrier was 700 μL / g. Based on this value, samples of 1 g of the carrier were impregnated with a volume of solutions with the concentrations of a given metal salt (copper (II) nitrate (V) or cobalt (II) nitrate (V)) necessary to introduce 2.5, 5.0, 7, % 5, 10.0 and 15.0 wt. Cu and Co in relation to the weight of the zirconium oxide. After impregnation, the materials were dried and then calcined at a temperature of 500 ° C in an air atmosphere with a temperature increase of 5 ° C / min and maintaining the set temperature for 3 hours.

Example 3

Comparison of the porosity of the materials according to the invention obtained by a method of removing a silica template other than in Examples 1 and 2.

The process of the textural evolution of the core-shell materials obtained according to Example 1 was tested by low-temperature nitrogen adsorption. Chemical composition of the obtained preparations

PL 240 269 Β1 was determined by the XRF method. Measurements of low-temperature nitrogen sorption were carried out using the ASAP 2020 sorptomat (Micromeritics) using about 200 mg of the sample. Before the measurement, the materials were degassed at 150 ° C for 6 h. Chemical composition analyzes were performed on a Thermo Scientific EDXRF Quant'x Arl spectrometer equipped with a Rh source. About 200 mg of the sample was used each time, placed in a holder on a polypropylene film.

The thermal stability of the manufactured materials was tested using the TA Instruments SDT Q600 thermogravimeter. The experiments were performed for approx. 10 mg of the sample in the air flow (100 ml / min) in the range of 30-100 ° C, with the temperature increase of 20 ° C / min.

Fig. 1 demonstrates nitrogen adsorption-desorption isotherms for the MCM-48 / CMK-1 @ ZrO2 composite material and after removal of the silica template with 1 M NaOH at 25 ° C (CMK-1 @ ZrO ₂ _1M_25 ° C sample) and 3 M NaOH at 50 ° C (CMK-1 @ ZrO ₂ _3M_50 ° C).

Low-temperature nitrogen sorption isotherms and the textural parameters calculated on their basis illustrate the influence of the conditions of extraction of the structure-forming template (MCM-48) on the porosity of the formed materials. The starting material MCM-48 / CMK-1 @ ZrO ₂ shows a high silica content, i.e. 48.3% (XRF tests). Extraction of SiO ₂ at a temperature of 25 ° C leads to its significant elimination, and thus opens the porous structure in the tested preparation. Increasing the temperature of the process to 50 ° C and the concentration of NaOH solution to 3 M caused a further increase in porosity. This effect is observed in the course of N ₂ adsorption-desorption isotherms, by a significant increase in the volume absorbed at low relative pressure p / po, which is related to the appearance of micro- and mesopores. The values of Vmicro and Vmeso presented in Table 1 support this thesis. The formation of new pores affects the specific surface area of the Sbet, which increased from 306 to 514 m2 / g for the material with the SiO ² core removed most efficiently _.

Table 1 summarizes the determined textural parameters and the chemical composition of the materials depending on the conditions for the extraction of the SiO ₂ core.

Table 1. Results of physicochemical characterization of selected materials

A sample TG XRF Low-temperature N ₂ sorption Organic content [%] SiO ₂ [%] ZrO ₂ [%] Sbet ³ [m7g] Vtotal ^b km7g] V micro ¹ [cm7g] V meso ^d [cm7g] V macro ⁶ [cm7gl MCM-48 / CMKl @ ZrO ₂ 25.0 48.3 26.7 306 0.24 0.06 0.13 0.06 CMKl @ ZrO ₂ _lM_25 ° C 50.4 13.3 36.3 421 0.60 0.06 0.40 0.14 CMKl @ ZrO ₂ _3M_50 ° C 53.4 8.5 38.1 514 0.61 0.10 0.40 0.11

^a S _BET - specific surface area (BET | ^h V _a iK - total pore volume (single point method) ^c V _micro - micropore volume (t-Plot method) ^d V mesopore volume (BJH method) ^e _Ymata - macropore volume ((V , _ota | - (V _neso + V _micro ))

Example 4

Comparison of the adsorption properties of the carbon cores of the composite material.

Synthesis of a spherical carbon replica based on a wide porous silica gel (grain size 40-75 µm and 75-200 µm) and the influence of the method of removing the structure forming pattern on the absorption properties.

5 g of spherical silica gel was placed in a porcelain crucible, which was impregnated with the incipient wetness method with concentrated sulfuric acid (VI), and then heated in an oven at 150 ° C for 3 hours. After cooling, the mixture was transferred to a beaker containing approx. 200 mL distilled water and sedimented under static conditions. The remaining clear solution was decanted, the precipitate was dispersed in a new portion of distilled water and filtered, washing with distilled water until the filtrate was completely neutralized, and then dried.

PL 240 269 Β1 for 2 h at 120 ° C. Furfuryl alcohol, being a carbon precursor, was introduced into the pore system of sulfonated silica by incipient moisture impregnation, followed by static polycondensation in a closed container at a temperature of 100 ° C for 24 hours. The resulting polymer-silica nanocomposite was carbonated under nitrogen flow (40 mL / min) at the temperature of 850 ° C for 4 hours with a temperature increase of 1 ° C / min.

Before etching the silica, the obtained material was divided into two parts, which differed in the method of removing the silica. The inorganic pattern from the first part was etched with a 5% aqueous hydrofluoric acid solution. For this, the material was dispersed in acid in an amount of 30 mL / g and left under static conditions for 1 h. The second batch was subjected to digestion with 1M NaOH solution. As in the previous case, the solution used was in the amount of 30 mL / g. Digestion was performed twice in static conditions for 24 h. The resulting carbon replicas were then filtered on a fluted filter, washing with distilled water until neutralization of the filtrate, then with ethanol (2 x 20 mL) and dried overnight at 90 ° C.

The obtained materials were marked as s-CR_40-75_z and s-CR_75-200_z, where: z - means the etching agent (HF or NaOH).

Fig. 2 shows the results of the adsorption tests carried out on carbon replicas obtained by extracting the structure-forming template with 5% HF and 1 M NaOH.

The obtained results confirm that the carbon replicas constituting the core of the composite material described in the invention are characterized by high sorption capacity in relation to all tested VOC representatives. It has been proved that an important parameter influencing the hydrophilicity of the carbon material surface is the selection of a silica matrix etching agent. The use of a sodium base solution allows to obtain a material of high hydrophilicity, which has a similar affinity for both polar and non-polar adsorbates. On the other hand, removing the template with hydrofluoric acid results in obtaining a material with a lower content of oxygen surface groups, which causes a significant reduction in its hydrophilicity and, consequently, a much lower affinity for polar adsorbates. The sorption capacity in terms of toluene vapor is also reduced, while in the case of n-heptane its slight increase was noted.

Example 5

Comparison of the adsorption-desorption properties of a carbon core, a carbon core with a ZrO2 shell and a carbon core with a ZrO2 and Pt shell with respect to toluene vapors.

The adsorption properties of the materials were tested in the toluene vapor dynamic adsorption-desorption process with the QMS mass spectrometer detector. A carrier gas stream (nitrogen or air, 100 mL / min) saturated with toluene vapor (toluene content in the carrier gas equal to 0.1 vol.%) Was directed to a flow-through reactor with a stationary bed of the adsorbent (50 mg). The reactor was kept at a temperature of 68 ° C, the toluene vapor pressure p / po = 0.25. Sorption was carried out for 1.5 h from the moment of opening the valve, after which the system was switched to the desorption mode (the flow of pure carrier gas was 100 mL / min).

Table 2. Results of dynamic adsorption-desorption tests of toluene vapors - physically adsorbed forms

Sample Replica CMK-1 CMK-l / ZrO ₂ Pt-CMK-l / ZrO ₂ Capacity [mg / g] Carrier gas - nitrogen 48.9 38.6 42.4 Carrier gas - air - 27.1 27.3

Claims

PL 240 269 Β1

Table 3. Results of dynamic adsorption-desorption tests of toluene vapors - total amount of adsorbed

Sample Replica CMK-1 CMK-l / ZrOi Pt-CMK-l / ZrO ₂

Capacity [mg / g]

Carrier gas - nitrogen 168.9 158.8 103.8

Carrier gas - air - 51.7 75.8

The results of the experiments confirmed the high sorption capacity of the materials according to the invention. Although the modification of the carbon surface reduced the adsorption capacity of the materials in relation to the carbon precursor, the ZrO2 coating increased the thermal stability of the carbon core in an oxidizing atmosphere compared to the exemplary CMK-1 mesoporous carbon. The ZrO2 coating isolates the carbon core of the catalyst from the oxidizing atmosphere in which the catalytic VOC afterburning process is carried out, protecting it against combustion. The application of the active phase increased the sorption capacity in relation to CMK-1 / ZrO2.

Example 6

Evaluation of the catalytic activity of the materials according to the invention.

The change in catalytic activity of the 1% Pt-CMK1 @ ZrO2 materials (Example 1) and the 10% CuO-sC @ ZrO2 and 10% Co3O4-sC @ ZrO2 materials (Example 2) as a function of temperature is shown in Fig. 3. Catalytic tests were carried out using a flow system equipped with an air-flow quartz microreactor (100 mL / min, toluene concentration 1000 ppm). A mass spectrometer equipped with a quadrupole mass detector was used to detect the amount of reactants / reaction products. The experiment was performed in the temperature range of 50-500 ° C, with a continuous increase of 1 ° C / min for a sample weighing 100 mg. Prior to the experiment, the sample was degassed under an inert gas flow (50 mL / min) at 200 ° C for 30 minutes.

The test results confirmed the high catalytic activity of the developed materials. The complete oxidation of the adsorbed toluene vapors took place at the temperature of 210 ° C for the 1% Pt-CMK1 @ ZrO2 material and at 400 ° C for the samples containing CuO or CO3O4 as the active phase. Such a low temperature of toluene oxidation combined with the high sorption capacity of the carbon core indicates the possibility of their potential use as bifunctional materials in the processes of adsorption and catalytic elimination of volatile organic compounds.

Patent claims

CLAIMS 1. A particulate composite material having a core-shell-active phase structure comprising a core of an adsorbent material, at least one inorganic oxide and particles of a catalytically active phase, characterized in that

- the adsorption material is porous carbon,

- the catalytically active phase consists of nanoparticles or their agglomerates based on metals or metal oxides selected from the group consisting of Pt, CO3O4, CuO.

2. The composite material according to claim 1 The process of claim 1, wherein the solids are spherical.

3. The composite material according to claim 1 The method of claim ¹ , wherein the carbon core is a mesoporous carbon material with a specific surface area in the range ^306-514 m2 / g and a pore volume in the range 0.24 to 0.61 cm3 / g.

4. The composite material according to claim 1 The method of claim 1, wherein the inorganic oxide is porous.

5. The composite material according to claim 1 2. The process of claim 1, wherein the catalytically active phase consists of metals or their oxides deposited on the oxide shell and the shell itself.

6. A composite material according to claim 1, characterized in that the catalytically active phase nanoparticles are deposited on the surface of the inorganic oxide without contact with the carbon core.

PL 240 269 B1

7. A method for obtaining a composite material according to claims 1-6, comprising the following steps:

a) obtaining porous carbon particles,

8. A method for obtaining a composite material according to claim 1. The method of claim 7, wherein step

a) is performed using rigid silica pattern imaging, where the carbon raw material / precursor is introduced into the silica matrix by impregnation or in-situ polymerization.

9. A method for obtaining a composite material according to claim 1 The process of claim 8, wherein the carbon precursor is polymers obtained by in situ polymerization of monomers selected from the group consisting of furfuryl alcohol, phenol-formaldehyde mixture, acrylonitrile.

A method for obtaining a composite material according to claim 1, The method of claim 8, wherein the precursor is sugars selected from the group of sucrose, glucose, xylose.

11. A method for obtaining a composite material according to claim 1. The method of claim 8, characterized in that the silica templates are based on silica gel or mesoporous silica materials of the type SBA-15, SBA-16, MCM-41 and MCM-48 with spherical particle shape.

12. A method for obtaining a composite material according to claim 1, 8. The process of claim 8, characterized in that the carbon precursor is introduced into the pore system of the spherical silica material to obtain a polymer-silica composite, which is then carbonized at a temperature in the range of 600-1000 ° C in an inert atmosphere such as argon, nitrogen or helium to obtain the material carbon-silica, and then the silica is removed from the carbon composite by etching with a NaOH solution ranging from 1 to 5 M or a HF solution ranging from 1-10% at a temperature ranging from 25 to 90 ° C.

13. A method for obtaining a composite material according to claim 1, 7. The process of claim 7, wherein removal of the silica is performed before or after deposition of the inorganic oxide coating.

14. A method for obtaining a composite material according to claim 1, The method of claim 7, wherein the oxide coating is applied in step b) by hydrolysis and polycondensation of the metal alkoxide.

15. A method for obtaining a composite material according to claim 1, 14. The process of claim 14, wherein the reaction is carried out in an anhydrous alcohol solution in the presence of a surfactant.

16. A method for obtaining a composite material according to claim 1, 7. The method of claim 7, characterized in that, after step b), the material is dried and carbonized at a temperature in the range of 600-1000 ° C in an inert gas atmosphere for 1 to 48 hours, increasing the temperature at a rate of 0.1 to 50 ° C / min.

17. A method for obtaining a composite material according to claim 1 8. Method according to claim 7, characterized in that the catalytically active phase nanoparticles in step c) are applied to the inorganic oxide layer by the impregnation method from a solution of a readily soluble compound of the selected metal.

18. Use of a composite material as defined in claim 1 1 for the elimination of volatile organic compounds by adsorption in a core formed of porous carbon and their subsequent catalytic oxidation through the active catalytic phase present in the coating.

19. Use of a composite material according to claim 1 18, characterized in that the volatile organic compounds adsorption takes place at a temperature in the range of 20-100 ° C, and catalytic afterburning at a temperature above 150 ° C.

20. Use of a composite material according to claim 1 18. The volatile organic compounds are selected from the group of aliphatic and aromatic hydrocarbons.