The invention relates to a method for producing syngas by means of solar radiation, in which the reactor of a receiver-reactor is periodically heated via an aperture provided in the same for solar radiation by means of the solar radiation to an upper reduction temperature for a reduction process and subsequently cooled to a lower oxidation temperature for an oxidation process in the presence of an oxidation gas, wherein the sunlight is guided through an absorption chamber onto an absorber configured as a reactor, which includes a reducible/oxidizable material, and wherein a gas that absorbs the black-body radiation of the absorber is guided through the absorption chamber and the absorption chamber is configured so that the back radiation of the absorber through the aperture is essentially absorbed by the gas. Radiation losses caused by back radiation of the black-body radiation exiting the optical aperture are thus avoided in accordance with the invention. The heat of the back radiation, however, can be utilized directly in the heat-transporting fluid and is available for a flexible usage. The receiver-reactor has a simple design and is suitable as a low-cost receiver-reactor.

A two-step thermochemical reactor and method are disclosed. The reactor includes a housing and a reactor cavity formed within, and surrounded by, thermal insulation within the housing. The reactor cavity includes at least one unit cell, each cell having an electric heat source and a reactive material. The reactor also includes a feedstock inlet and a product outlet in fluid communication with the reactor cavity. The reactor also includes a reducing configuration, with the inlet being closed and the electric heat source of each unit cell being driven to thermally reduce the reactive material at a first temperature, releasing oxygen into the cavity. The reactor also has a splitting configuration where the reactive material is at a second temperature that is lower than the first, the feedstock inlet open and introducing feedstock gas into the cavity to reoxidize the reactive material and split into a product gas.

A method for producing hydrogen of the present invention includes thermally reducing a reaction medium in which CeO.sub.2 is doped with a metal other than Ce and bringing the thermally reduced reaction medium into contact with water to oxidize the reaction medium and to generate the hydrogen. When a reaction temperature in the thermally reducing the reaction medium is defined as T1 [° C.] and a reaction temperature in the bringing the thermally reduced reaction medium into contact with the water is defined as T2 [° C.], a relation of T1−T2≤150 is satisfied. It is preferred that a series of processes including the thermally reducing the reaction medium and the bringing the thermally reduced reaction medium into contact with the water is repeated.

Methods for controlling or operating solar thermochemical reactions process that maximize the two-step thermochemical energy cycle efficiency by a combination of pressure and temperature swing are disclosed.

The present disclosure is directed to the integration of direct air capture of carbon dioxide with thermochemical water splitting, the latter optionally driven by solar energy. The disclosure is also directed to a process comprising extracting carbon dioxide from an air stream by contacting the air-stream with an alkali metal ion-transition metal oxide of empirical formula A.sub.xMO.sub.2 (0.1<x1), where A represents the alkali metal ion comprising sodium ion, potassium ion, or a combination thereof and M comprises iron, manganese, or a combination thereof to form a transition metal composition comprising an oxidized ion extracted-transition metal oxide.

Disclosed is a system for producing hydrogen from a byproduct gas generated during a steelmaking process or a coal chemistry process, including a reformer for reforming the byproduct gas using steam (H.sub.2O), a separator for separating a reformed gas supplied from the reformer into a reduction gas and hydrogen gas (H.sub.2), a first reactor for reducing ferric oxide (Fe.sub.2O.sub.3) into ferrous oxide (FeO) using the reduction gas supplied from the separator, and a second reactor for producing ferrous-ferric oxide (Fe.sub.3O.sub.4) and hydrogen gas (H.sub.2) by mixing the ferrous oxide (FeO) supplied from the first reactor with steam (H.sub.2O), wherein the concentration of hydrogen gas (H.sub.2) in the reformed gas discharged from the reformer is higher than the concentration of hydrogen gas (H.sub.2) in the byproduct gas.

The present invention relates to a process for performing a chemical reaction consisting of at least two sequential reversible steps characterized by being performed in a cycle, and to a reactor for performing such process.

A two-step thermochemical reactor and method are disclosed. The reactor includes a housing and a reactor cavity formed within, and surrounded by, thermal insulation within the housing. The reactor cavity includes at least one unit cell, each cell having an electric heat source and a reactive material. The reactor also includes a feedstock inlet and a product outlet in fluid communication with the reactor cavity. The reactor also includes a reducing configuration, with the inlet being closed and the electric heat source of each unit cell being driven to thermally reduce the reactive material at a first temperature, releasing oxygen into the cavity. The reactor also has a splitting configuration where the reactive material is at a second temperature that is lower than the first, the feedstock inlet open and introducing feedstock gas into the cavity to reoxidize the reactive material and split into a product gas.

The present invention relates to a thermochemical reactor system for a temperature swing cyclic process with integrated heat recovery comprising at least two modules, wherein each module comprises at least one chemical reaction zone (CRZ) and at least one thermal energy storage unit (TES), wherein the at least two modules are operationally connected for at least one heat transfer fluid (HTF) for transporting heat between the two modules, wherein each chemical reaction zone (CRZ) comprises at least one reacting material that undergoes in a reversible manner an endothermic reaction at temperature T.sub.endo and an exothermic reaction at temperature T.sub.exo, wherein T.sub.endo and T.sub.exo differ from each other, wherein the at least one reacting material is provided in at least one encapsulation within each of the chemical reaction zones (CRZ) such that a contact of the reacting material and the at least one heat transfer fluid is avoided. The present invention relates further to a method for operating such a reactor system.

A method for producing hydrogen of the present invention includes thermally reducing a reaction medium in which CeO.sub.2 is doped with a metal other than Ce and bringing the thermally reduced reaction medium into contact with water to oxidize the reaction medium and to generate the hydrogen. When a reaction temperature in the thermally reducing the reaction medium is defined as T1 [ C.] and a reaction temperature in the bringing the thermally reduced reaction medium into contact with the water is defined as T2 [ C.], a relation of T1T2150 is satisfied. It is preferred that a series of processes including the thermally reducing the reaction medium and the bringing the thermally reduced reaction medium into contact with the water is repeated.