Search

EP-4735388-A1 - ONE-STEP METHOD IN AN INTENSIFIED ROTATING PACKED BED DEVICE WITH PACKING MATERIAL FOR THE PRODUCTION OF HYDRO-MAGNETITE NANOPARTICLES

EP4735388A1EP 4735388 A1EP4735388 A1EP 4735388A1EP-4735388-A1

Abstract

The invention pertains to a method of producing hydromagnesite nanoparticles (Mg 5 (CO 3 )(OH) 2 ·4H 2 O). In its basic embodiment it is carried out in one step by a chemical reaction of magnesium oxide or magnesium hydroxide carbonation in which a) the carbon dioxide carrying stream is directed inside a rotating packed bed reactor (3); b) inside the reactor it is contacted in packing material and reacts with a suspension of magnesium oxide or magnesium hydroxide; c) the packing material rotates and a centrifugal field is developed inside it; d) the streams of carbon dioxide and magnesium oxide or magnesium hydroxide suspension interact either cocurrently or countercurrently. Their contact increases the reaction rate of carbonation of the magnesium oxide or magnesium hydroxide suspension and the nucleation of hydromagnesite, resulting in the crystallization of hydromagnesite.

Inventors

  • PAPADOPOULOS, ATHANASIOS
  • NESSI, PARASKEVI
  • SEFERLIS, PANAGIOTIS
  • VOUTETAKIS, SPYRIDON

Assignees

  • Centre for Research and Technology Hellas

Dates

Publication Date
20260506
Application Date
20231003

Claims (10)

  1. 1. A method of producing hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 • 4W 2 0) characterized by a one-step chemical reaction of carbonation of magnesium oxide or magnesium hydroxide whereby: a) a stream carrying carbon dioxide (CO 2 ) is mixed and reacts with a suspension of magnesium oxide or magnesium hydroxide; b) the mixture of the carbon dioxide stream and the magnesium oxide or magnesium hydroxide suspension is in contact with packing material contained in a reactor and is rotated inside the packing material of the said reactor, where a centrifugal field is developed; c) the carbon dioxide and magnesium oxide or magnesium hydroxide suspension streams interact either cocurrently or countercurrently, and their contact promotes and increases the speed of the chemical reaction of carbonation of the magnesium oxide or magnesium hydroxide suspension and the nucleation of hydromagnesite, resulting in the crystallization of hydromagnesite.
  2. 2. A method according to claim 1, characterized in that the feedstock is a hydrated suspension of magnesium oxide (MgO) or magnesium hydroxide (M^(0/f) 2 ) and CO 2 irrespectively of its source.
  3. 3. A method according to the preceding claims, characterized in that the minimum concentration of the aqueous MgO suspension is higher than the solubility limit of pure MgO in water (8.6 mg/l) at 25 °C or, respectively, the concentration of magnesium hydroxide is higher than the solubility limit of pure Mg(0ff) 2 in water (6.54 mg/l) at 25 °C.
  4. 4. A method according to the preceding claims, characterized in that the minimum temperature for the reaction is 40 °C.
  5. 5. A method according to the preceding claims, characterized in that the minimum rotational speed of the reactor bed is 10 rpm.
  6. 6. A method according to the preceding claims, characterized in that the minimum liquid volumetric flow rate/volumetric CO 2 flow rate ratio is 0.01.
  7. 7. A method according to the preceding claims, characterized in that it results in the attainment of monodispersity, up to 100% purity in the hydromagnesite crystal structure and repeatable and consistently regular nanoparticle thickness distributions with small standard deviations.
  8. 8. A method according to the preceding claims, characterized in that the method can be performed in batch or continuous operation.
  9. 9. A method according to any of the preceding claims, wherein the reaction can be achieved in multiple reactors arranged either in series or in parallel with multiple combinations.
  10. 10. A system, used to perform the method of the preceding claims, comprising a CO 2 source (1); a gas flow regulator (2); a reactor (3), a reactant vessel (4); a product vessel (5); a product vessel outlet pump (6); a reactant vessel outlet pump (7); a gas flow meter (8); a three-way valve at the outlet stream of the reactor (9); a three-way valve at the outlet stream of the product vessel (10); a three-way valve at the outlet stream of the reactant vessel (11); a reactant vessel temperature gauge (12); a product vessel temperature gauge (13); a sampling point from the outlet stream of the reactant vessel (14); sampling point from the reactor outlet stream (15) after the three-way valve (arrow direction from the valve to the vessel) or loading the vessel 5 through the three-way valve with fresh suspension (arrow direction from the vessel to the valve); a sampling point from the outlet stream of the product vessel (16); and characterized in that the reactor (3) has a rotating bed with packing material (96) or (105).

Description

DESCRIPTION ONE-STEP METHOD IN AN INTENSIFIED ROTATING PACKED BED DEVICE WITH PACKING MATERIAL FOR THE PRODUCTION OF HYDRO-MAGNETITE NANOPARTICLES [0001] The invention relates to the production of nanoparticle-sized hydromagnesite. Specifically, existing methods involve two-step carbonation (two reactions are required) and the majority of them are done in continuous stirred tank reactors (CSTR) (See "state of the art"). Hydromagnesite exists in nature as a mineral, in mixtures with other substances. Its separation requires a large amount of energy consumption, thus synthetic methods of production are preferred, especially when it can be produced directly in nanoparticle form (its extraction from minerals requires significant further processing and becomes even more difficult and expensive to achieve its production in nanoparticle size). Its use in nanoparticle form is desirable in many applications such as its use as a combustion retardant (e.g., in polymers), as an additive in cement, in drug release methods, tissue engineering, etc. [0002] The production of hydromagnesite from industrial flue gases, e.g., using carbon dioxide (CO2), is a method of using CO2. It allows the conversion of the latter into a useful product that can be profitable and provide incentives for the installation of capture plants in a variety of industrial applications, contributing significantly to the reduction of greenhouse gas emissions. The production of the hydromagnesite by the present invention using a rotating packed bed (RPB) reactor allows for very rapid scale-up of the process, as it is an intensified reactor of small size, easy to build and handle. The RPB reactor significantly increases the mass transfer from the gas to the liquid phase. This is due to the high rotational speed which leads to the formation of a thin liquid film which exerts little resistance to mass transfer in the liquid. The present invention could be applied to the production of all carbonated substances wherein a positively charged ion of the general form M+f M2+ , or M3+ reacts with CO2l wherein M can be lithium, sodium, potassium, rubidium, caesium, francium, strontium, barium, radium, manganese, iron, aluminium, zinc, copper, nickel, silver, cadmium, platinum, lead, and in general any element belonging to alkalis, alkaline earths, transition elements, posttransition elements and metalloids. It could also be used directly and easily in industries producing oxides of the above substances and also magnesium oxide and/or magnesium hydroxide as they could avail these products as raw materials and combine them with the utilization of the CO2 produced by the process. In particular, general applications of hydromagnesite and magnesium carbonate salts include the following, in addition to those previously mentioned: - Feedstock in plastics, polymers, fertilizers and building materials. - Use in magnesium-ion batteries, which are likely to replace lithium-ion batteries as they have much higher energy density, less environmental impact and can withstand much lower temperatures. - Use in alloys in the vehicle and aircraft industry, as the use of magnesium carbonates increases their strength and reduces their weight. - Additional applications are reported in the cosmetics and pharmaceuticals and paper industries. - In general, the commercial price of carbonate salt nanoparticles can be very high, depending on their purity and crystal characteristics, providing a great commercial incentive for their production. State of the art [0003] There are only two patents (CN110573458A, AU2018222897) which mention few features that are relevant to this invention, and many features that have no similarity, making the technology of this invention unique. The differences that do exist are commented upon and evaluated below based on specific, representative features of the technology to which the specific invention relates. The present invention is implemented based on the following reaction: SMgO + SH2O + SCO2 M^5(CO3)4(O//)2 • 4H2O + CO2 (1) It is further implemented based on the following reaction when the starting material is an aqueous suspension of magnesium hydroxide (Mg(0H)2), as follows: SMg(0H)2 + H2O + SCO2 M^5(CO3)4(O//)2 • 4H2O + CO2 + H2O (2) Patent CN110573458A does not disclose a reaction, however it refers to the production of salts of the type nMgC03 ■ Mg(0H)2 • mH20, where n and m are integers, and that it is a two-step carbonation (see also below for details). Patent AU2018222897 discloses the following reaction: For AU2018222897, it is obvious that it is a different production method compared to the technology of the present invention. [0004] The present invention is implemented in one carbonation step, without pre-treatment, as the precursor suspension comprises two components (CO2 and an aqueous suspension of MgO or Mg 0H')2). The Chinese patent CN110573458A relates to a carbonation process implemented in two stages, while the Australian patent appli