Electrochemical hydrogen sensor
A sensor for hydrogen in a fluid medium has a chamber for electrolyte with a window which is selectively permeable to hydrogen to allow hydrogen to pass from the fluid medium under test into the electrolyte in the chamber. A plurality of electrodes in contact with the ionic liquid electrolyte are used to observe hydrogen concentration by voltammetry. The electrolyte is an ionic liquid. Applications where such a sensor may be used include a wellbore tool for measuring the content of hydrogen in a subterranean fluid, monitoring of fiber-optic cables for damage by hydrogen, corrosion monitoring, and small-scale process plant where hydrogen is part of a gas stream.
1. A process for measuring a content of hydrogen in a subterranean fluid, the process comprising:
contacting the subterranean fluid with a sensor, the sensor comprising a housing enclosing a chamber containing a quantity of electrolyte which is an ionic liquid, a window which is permeable to hydrogen positioned in an opening in the housing, a plurality of electrodes in contact with the ionic liquid electrolyte in the chamber, and a combined temperature and pressure sensor enclosed within the chamber;
allowing hydrogen to pass through the window from the subterranean fluid into the electrolyte;
heating the sensor;
applying electrical potential to the electrodes;
determining a temperature and a pressure of the subterranean fluid with the combined temperature and pressure sensor; and
measuring current flow.
2. The process according to claim 1 , wherein the window comprises a hydrogen permeable metal membrane that is selectively permeable to hydrogen.
3. The process according to claim 1 , wherein the window comprises a hydrogen permeable membrane on a porous support, the membrane comprising a sheet of metal that is selectively permeable to hydrogen.
4. The process according to claim 3 , wherein the sheet of metal that is selectively permeable to hydrogen is not more than 200 μm thick.
5. The process according to claim 3 , wherein the sheet of metal that is selectively permeable to hydrogen is overlaid with a protective layer.
6. The process according to claim 1 , wherein the window comprises a hydrogen permeable membrane on a porous support, the membrane comprising a polymer film and a layer of metal that is selectively permeable to hydrogen deposited on the polymer film.
7. The process according to claim 6 , wherein the layer of metal that is selectively permeable to hydrogen is overlaid with a protective layer.
8. The process according to claim 1 , wherein the ionic liquid fills the chamber and the concentration of water in the ionic liquid is not more than 1% by weight.
9. The process according to claim 1 , wherein an electrode of the plurality of electrodes comprises palladium nanoparticles.
10. The process according to claim 1 , wherein the sensor is part of a downhole tool.
11. The process according to claim 1 , wherein the sensor is connected to a protective enclosure containing a fiber-optic cable.
12. The process according to claim 1 , wherein the subterranean fluid is a flow stream which is a feedstock, product, intermediate product or exhaust of at least one chemical reaction which consumes or generates hydrogen.
13. The process according to claim 12 , wherein the chemical reaction is any one of:
partial oxidation of methane to syngas,
Fischer-Tropsch conversion of syngas to alkanes and water,
methanol synthesis,
hydrocracking of hydrocarbons,
water gas shift reaction, and
hydrodesulfurisation.
14. The process according to claim 1 , wherein the process is carried out in a well that is equipped for carrying out upgrading of hydrocarbon by reaction with hydrogen at a downhole location, and wherein the subterranean fluid is a flow stream which is a feedstock to the well or produced therefrom.