EP-4741055-A1 - PRODUCTION OF METAL ION-EXCHANGED MOLECULAR SIEVE

EP4741055A1EP 4741055 A1EP4741055 A1EP 4741055A1EP-4741055-A1

Abstract

A method of quantifying a content of an insoluble metal compound in an aqueous suspension comprising an insoluble metal compound and a metal ion-exchanged molecular sieve is disclosed, The method comprises: treating the aqueous suspension of the insoluble metal compound and the metal ion-exchanged molecular sieve with a selective solubilising agent for the insoluble metal compound, thus producing a treated mixture comprising a metal solution comprising a dissolved metal from the insoluble metal compound and undissolved metal ion-exchanged molecular sieve; and quantifying a dissolved metal content of the treated mixture using a suitable analytical technique.

Inventors

FAIRALL, Charlotte
HOTCHKISS, Thomas

Assignees

Johnson Matthey Public Limited Company

Dates

Publication Date: 20260513
Application Date: 20241112

Claims (14)

A method of quantifying a content of an insoluble metal compound in an aqueous suspension comprising an insoluble metal compound and a metal ion-exchanged molecular sieve, the method comprising the steps of: treating the aqueous suspension of the insoluble metal compound and the metal ion-exchanged molecular sieve with a selective solubilising agent for the insoluble metal compound, thus producing a treated mixture comprising a metal solution comprising a dissolved metal from the insoluble metal compound and undissolved metal ion-exchanged molecular sieve; and quantifying a dissolved metal content of the treated mixture using a suitable analytical technique.
The method according to claim 1, wherein the metal ion-exchanged molecular sieve is a reaction product between the insoluble metal compound and a metal-free molecular sieve.
The method according to any one of claims 1 to 2, wherein the metal is a transition metal selected from the group consisting of copper, iron, manganese, and mixtures thereof.
The method according to any one of claims 1 to 3, wherein the insoluble metal compound is selected from the group consisting of metal carbonates, metal hydroxides, metal oxides, and mixtures thereof,
The method according to any one of claims 1 to 4, wherein the insoluble metal compound is alkaline copper carbonate (CuCO 3 .Cu(OH) 2 ).
The method according to any one of claims 1 to 5, wherein the molecular sieve is selected from the group consisting of a zeolitic molecular sieve, a non-zeolitic molecular sieve, and a mixture thereof.
The method according to any one of claims 1 to 6, wherein the selective solubilising agent is a polycarboxylic acid or an aminopolycarboxylic acid or a salt thereof, more preferably ethylenediaminetetraacetic acid (EDTA) or a salt thereof.
The method according to any one of claims 1 to 7, wherein the selective solubilising agent is ethylenediaminetetraacetic acid (EDTA) or a salt thereof.
The method according to any one of claims 1 to 8, wherein treating the aqueous suspension with the selective solubilising agent includes adjusting the pH of the aqueous suspension to greater than 7.
The method according to claim 9, wherein adjusting the pH of the aqueous suspension includes treating the aqueous suspension with a base selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, tetraethylammonium hydroxide, and mixtures thereof.
The method according to claim 9, wherein: the aqueous suspension is treated with the base simultaneously with the treatment of the aqueous suspension with the selective solubilising agent, either in an admixture with the selective solubilising agent or separately of the selective solubilising agent, or the aqueous suspension is treated with the base before treating the aqueous suspension with the selective solubilising agent, or the aqueous suspension is treated with the base after treating the aqueous suspension with the selective solubilising agent.
The method according to any one of claims 1 to 11, wherein suitable analytical techniques include inductively coupled plasma (ICP) spectroscopy, nuclear magnetic resonance (NMR) water relaxometry, ultraviolet-visible (UV-vis) spectroscopy, spectrophotometry, and gravimetry.
The method according to any one of claims 1 to 12, wherein the metal solution is a supernatant of the aqueous suspension after treatment with the selective solubilising agent.
A method of producing a metal ion-exchanged molecular sieve, the method comprising: forming an aqueous suspension of a molecular sieve and an insoluble metal compound such that the molecular sieve and the insoluble metal compound undergo ion-exchange in the aqueous suspension, thus forming a metal ion-exchanged molecular sieve; and, after expiry of a predetermined time period, or at predetermined time intervals, or at random time intervals, quantifying a dissolved metal content of the aqueous suspension in accordance with the method of claims 1-13.

Description

Field of the Invention This invention relates to the production of a metal ion-exchanged molecular sieve. More specifically, the invention relates to quantifying the content of an insoluble metal compound in a metal ion-exchanged molecular sieve suspension to determine the progress of a metal ion-exchange reaction between the insoluble metal compound and the molecular sieve in the suspension in the context of the manufacture of the metal ion-exchanged molecular sieve. Background to the Invention Various analytical techniques are available to quantify the concentration of dissolved species in solutions, including spectroscopic techniques and gravimetric techniques. The quantification of the concentration or the content of such dissolved species, and particularly of dissolved metal species, finds prominent application in the manufacture of metal ion-exchanged molecular sieve by metal ion-exchange reactions between metal compounds and molecular sieves in a liquid medium, e.g., an aqueous medium. Quantifying the concentration of dissolved species, and particularly of dissolved metal species can help to determine the extent to which such dissolved metal species have been deposited onto or into the molecular sieve. One approach to the manufacture of metal ion-exchanged molecular sieve, in which such quantification finds application, is for a molecular sieve to be suspended in a liquid medium and for a metal to be deposited onto and/or into the molecular sieve through an ion-exchange reaction in the liquid medium between the molecular sieve and a metal compound. In many cases, the metal compound is soluble in the liquid medium. In such cases, quantifying the progress of the metal ion-exchange reaction may conveniently be performed using one or more of the abovementioned analytical techniques. However, there are also cases in which the metal compound is insoluble in the liquid medium. In such cases, quantifying the progress of the metal ion-exchange reaction is not possible using the abovementioned analytical techniques, due to the insolubility of the metal compound. WO2020/227333A1 discloses the manufacture of a selective catalytic reduction catalyst by metal ion-exchange using copper carbonate. WO2020/227333A1 discloses that the efficiency of metal ion-exchange may be determined by ammonia back-exchange and inductively coupled plasma-optical emission spectrometry (ICP-OES). In ammonia back-exchange, ion exchanged metal in the zeolitic material is removed, leaving un-exchanged residual metal in the form of the metal oxide. The amount of residual metal is determined by ICP-OES, and the difference in the metal concentration before and after the ammonia back-exchange is the amount of ion-exchanged metal. The back-exchange required by this approach is complicated and laborious. Summary of the Invention According to a first aspect of the invention, there is provided a method of quantifying a content of an insoluble metal compound in an aqueous suspension comprising an insoluble metal compound and a metal ion-exchanged molecular sieve, the method comprising the steps of: treating the aqueous suspension of the insoluble metal compound and the metal ion-exchanged molecular sieve with a selective solubilising agent for the insoluble metal compound, thus producing a treated mixture comprising a metal solution comprising a dissolved metal from the insoluble metal compound and undissolved metal ion-exchanged molecular sieve; andquantifying a dissolved metal content of the treated mixture using a suitable analytical technique. According to a second aspect of the invention, there is provided a method of producing a metal ion-exchanged molecular sieve, the method comprising: forming an aqueous suspension of a molecular sieve and an insoluble metal compound such that the molecular sieve and the insoluble metal compound undergo ion-exchange in the aqueous suspension, thus forming a metal ion-exchanged molecular sieve; andafter expiry of a predetermined time period, or at predetermined time intervals, or at random time intervals, quantifying a dissolved metal content of the aqueous suspension in accordance with the method of the first aspect of the invention. Detailed Description of the Invention The inventors of the present invention have found that the application of known analytical techniques may conveniently be enabled in quantifying the content of an insoluble metal compound that is present with a suspended metal ion-exchanged molecular sieve in an aqueous suspension, by treating the suspension with a selective solubilising agent for the insoluble metal compound. The selective solubilising agent added to the aqueous suspension comprising a metal-ion-exchanged molecular sieve and the insoluble metal compound reacts with the insoluble metal compound present in the suspension to form a soluble metal compound or compounds, which allows for conventional analytical techniques to be applied to quantify the dissolved metal content in