Abstract: The present invention relates to a process for depolymerising polyethylene terephthalate (“PET”), in which method PET is reacted with sodium glycolate or potassium glycolate, which has been obtained by reactive distillation, to form a mixture M1 including Bis(2-hydroxyethyl) terephthalate (“BHET”). The process according to the invention is distinguished by the fact that BHET makes up a particularly high proportion of the decomposition products in the mixture M1. The process according to the invention thus provides a high yield of BHET that can be used directly for producing PET again. The present invention thus also relates to a process for recycling PET, in which the BHET obtained in the process for depolymerising PET is polymerised again to form PET, optionally after being further purified from M1.

Abstract: The invention relates to a method for depolymerising polyethylene terephthalate (“PET”), in which PET is reacted with electrolytically prepared alkali metal glycolate, in particular sodium or potassium glycolate, to form a mixture M1 comprising bis(2-hydroxyethyl) terephthalate (“BHET”). The method according to the invention is characterised in that BHET accounts for a particularly high proportion of the breakdown products in the mixture M1. As a result, the method according to the invention provides a high yield of BHET, which can be used directly for renewed PET production. The present invention also relates to a method for recycling PET, in which the BHET obtained in the method for depolymerising PET is polymerised again to PET, optionally after further purification from M1.

Abstract: The present invention relates to a method for the depolymerization of polyethylene terephthalate (PET), in which method PET is reacted with sodium glycolate or potassium glycolate which has been obtained via reactive distillation, to form a mixture M1 comprising bis(2-hydroxyethyl) terephthalate (BHET). The method according to the invention is characterized in that BHET forms a particularly high proportion of the cleavage products in the mixture M1. As a result, the method according to the invention provides a high yield of BHET, which can be used directly to produce PET again. The present invention therefore also relates to a method for recycling PET, in which method the BHET that is obtained in the method for the depolymerization of PET and, if necessary, has been further purified from M1, is repolymerized to form PET.

Abstract: A process can be used for electrochemical preparation of an alkali metal alkoxide solution. The process is performed in an electrolysis cell having three chambers, where the middle chamber is separated from the cathode chamber by a solid-state electrolyte permeable to cations, for example NaSICON, and from the anode chamber by a diffusion barrier, for example a membrane selective for cations or anions. The process solves a problem where a concentration gradient forms in the middle chamber of the electrolysis cell during the electrolysis, which leads to locally lowered pH values and damage to the solid-state electrolyte used. This is prevented where a gas is introduced into the middle chamber during the electrolysis, which results in better mixing of the electrolyte solution in the middle chamber and prevents the formation of a concentration gradient.

Abstract: The invention relates to a method for producing an alkali metal alcoholate solution L1 in an electrolysis cell E which comprises at least one cathode chamber KK, at least one anode chamber KA, and at least one central chamber KM lying therebetween. The interior IKK of the cathode chamber KK is separated from the interior IKM of the central chamber KM by a separating wall W comprising at least one alkali-cation-conductive solid ceramic electrolyte (=“AFK”) F (e.g. NaSICON). F has the surface OF. A part OA/MK of the surface OF directly contacts the interior IKM, and a part OKK of the surface OF directly contacts the interior IKK. The surface OA/MK and/or the surface OKK comprises at least one part of a surface OF?. OF? is produced from a pre-treatment step in which F is produced from an AFK F? comprising the surface OF?.

Abstract: The invention relates to a method for producing an alkali metal alcoholate solution L1 in an electrolysis cell E which comprises at least one cathode chamber KK, at least one anode chamber KA, and at least one central chamber KM lying therebetween. The interior IKK of the cathode chamber KK is separated from the interior IKM of the central chamber KM by a separating wall W comprising at least one alkali-cation-conductive solid ceramic electrolyte (=“AFK”) F (e.g. NaSICON). F has the surface OF. A part OA/MK of the surface OF directly contacts the interior IKM, and a part OKK of the surface OF directly contacts the interior IKK. The surface OA/MK and/or the surface OKK comprises at least one part of a surface OF?. OF? is produced from a pre-treatment step in which F is produced from an AFK F? comprising the surface OF?.

Abstract: The invention relates to a method for producing an alkali metal alcoholate solution L1 in an electrolysis cell E which comprises at least one cathode chamber KK, at least one anode chamber KA, and at least one central chamber KM lying therebetween. The interior IKK of the cathode chamber KK is separated from the interior IKM of the central chamber KM by a separating wall W comprising at least one alkali-cation-conductive solid ceramic electrolyte (=“AFK”) F (e.g. NaSICON). F has the surface OF. A part OA/MK of the surface OF directly contacts the interior IKM, and a part OKK of the surface OF directly contacts the interior IKK. The surface OA/MK and/or the surface OKK comprises at least one part of a surface OF?. OF? is produced from a pre-treatment step in which F is produced from an AFK F? comprising the surface OF?.

Abstract: The present invention relates, in a first aspect, to a dividing wall W suitable for use in an electrolysis cell E. The dividing wall W comprises a frame element R that forms an edge element RR and a separating element RT. The frame element R comprises two opposite parts R1 and R2, with at least two alkali metal cation-conducting solid-state electrolyte ceramics FA and FB disposed therebetween. The separating element RT lies between alkali metal cation-conducting solid-state electrolyte ceramics encompassed by the dividing wall W and separates these from one another. It is a feature of the invention that the two parts R1 and R2 are secured to one another by at least one securing element BR at the edge element RR and at least one securing element BT at the separating element RT.

Abstract: The present invention relates, in a first aspect, to an electrolysis cell E comprising a dividing wall W suitable for use in an electrolysis cell E. The dividing wall W encompasses at least two alkali metal cation-conducting solid-state electrolyte ceramics FA and FB separated from one another by at least one separating element T. Compared to the cases according to the prior art in which the dividing wall W encompasses the solid-state electrolyte in one piece, this arrangement is more flexible and the individual ceramics have more degrees of freedom available in order to react to fluctuations in temperature, for example by shrinkage or expansion. This increases stability with respect to mechanical stresses in the ceramic. The electrolysis cell E encompasses a cathode chamber KK divided by the dividing wall W from the adjacent chamber, which is a middle chamber KM of the electrolysis cell E.

Abstract: The present invention relates, in a first aspect, to an electrolysis cell having three chambers, wherein the middle chamber is separated from the cathode chamber by a solid-state electrolyte permeable to cations, for example NaSICON, and from the anode chamber by a diffusion barrier. The invention is characterized in that the middle chamber comprises internals. The electrolysis cell according to the invention solves the problem that a concentration gradient forms in the middle chamber of the electrolysis cell during the electrolysis, which leads to locally lowered pH values and hence to damage to the solid-state electrolyte. The internals result in vortexing of the electrolyte solution as it flows through the middle chamber during the electrolysis, which prevents the formation of a pH gradient. In a second aspect, the present invention relates to a process for producing an alkali metal alkoxide solution in the electrolysis cell according to the invention.

Abstract: The present invention relates, in a first aspect, to an electrolysis cell having three chambers, wherein the middle chamber is separated from the cathode chamber by a solid-state electrolyte permeable to cations, for example NaSICON, and from the anode chamber by a diffusion barrier, for example a membrane selective for cations or anions. The invention is characterized in that the middle chamber comprises a mechanical stirring device. The electrolysis cell according to the invention solves the problem that a concentration gradient forms in the middle chamber of the electrolysis cell during the electrolysis, which leads to locally lowered pH values and hence to damage to the solid-state electrolyte. With the aid of the mechanical stirring device, it is possible to stir the electrolyte solution in the middle chamber during the electrolysis. This leads to mixing of the electrolyte solution in the middle chamber, which prevents the formation of a pH gradient.

Abstract: The invention relates to a method for producing shaped heat storage bodies comprising a thermochemical substance, which bodies comprise a curved surface, the method comprising providing a powder comprising the thermochemical substance and optionally one or more further components, in particular one or more compressing aids; and compressing the powder into the shaped bodies, using a die or a mould, preferably by direct compression. The invention further relates to shaped heat storage bodies comprising a thermochemical substance, which bodies comprise a curved surface and to a thermochemical energy storage system, comprising said heat storage bodies.