Graphene-based PPB level sulfur detector in fuels
Inventors
Lock, Evgeniya H. • Perkins, F. Keith • Boyd, Anthony K. • Myers-Ward, Rachael L. • Gaskill, David Kurt • Nath, Anindya
Assignees
Publication Number
US-10976297-B2
Publication Date
2021-04-13
Expiration Date
2038-06-20
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Abstract
A sensitive and selective, in-line method to measure and validate the sulfur content at ppb levels in both the liquid and gas phase of fuel. The method includes etching graphene, for example to form a mesa structure comprising horizontal or vertical lines or an array of multidentate star features; functionalizing the etched graphene and attaching metal oxide nanoparticles to the functionalized graphene to form a device; exposing the device to a fuel in the gas or liquid phase; detecting a change in conductivity when sulfur is present in the fuel; and recovering the device for future use. Also disclosed is the related in-line graphene-based ppb level sulfur detector for fuels.
Core Innovation
The invention provides a sensitive and selective in-line method and device for measuring and validating sulfur content at parts per billion (ppb) levels in fuels, including both liquid and gas phases. This method involves etching graphene to create specific structures such as mesa structures with horizontal or vertical lines or arrays of multidentate star features. The graphene is then functionalized and metal oxide nanoparticles are attached using a chemical linking molecule activated by UV light to form a sensing device. The device is exposed to fuel, and changes in conductivity indicate the presence of sulfur compounds, with the device being capable of recovery for repeated use.
The problem being solved addresses a significant challenge in fuel cell applications, especially in military contexts where fuel cells operate on aviation fuels like JP-8 containing sulfur compounds. Sulfur poisons catalysts in fuel cells even at very low concentrations, causing rapid degradation and failure. Existing desulfurization technologies lack inexpensive, reproducible, and real-time methods to detect sulfur breakthrough, leading to operational inefficiencies or risks of damage due to undetected sulfur presence. Existing sensors either analyze sulfur after fuel combustion or lack the sensitivity and selectivity needed for intact fuel detection at ppb levels.
Graphene is an ideal sensing material given its surface-only atomic structure, high surface area, exceptional electronic properties, and sensitivity to molecular adsorption effects on conductivity. However, pristine graphene lacks selectivity due to absence of dangling bonds, necessitating functionalization for targeted detection. Metal oxide nanoparticles are incorporated to enhance sensitivity and selectivity towards sulfur-containing analytes, leveraging their high crystallinity, large surface-to-volume ratio, and stability. The invention realizes a hybrid graphene/metal oxide nanoparticle sensor with tailored device geometries and functionalization methods to deliver fast, selective, and sensitive detection of sulfur compounds in fuels at ppb levels.
Claims Coverage
The patent includes two independent claims defining a method and a detector device for in-line ppb level sulfur detection in fuels, each encompassing several inventive features related to graphene etching, functionalization, nanoparticle attachment, exposure to fuel, detection, and recovery.
Method for ppb level in-line detection of sulfur in fuel
A method comprising: etching graphene; functionalizing the etched graphene and attaching metal oxide nanoparticles through UV-activated chemical functionalization using a chemical linking molecule; exposing the device to fuel in gas or liquid phase; detecting a conductivity change when sulfur is present; and recovering the device for future use.
Chemical linking molecule for nanoparticle attachment
The chemical linking molecule used in functionalization is N-ethylamino-4-azidotetrafluorobenzoate (TFPA-NH2), enabling effective attachment of metal oxide nanoparticles to graphene.
Use of specific metal oxide nanoparticles
Metal oxide nanoparticles selected from ZnO, CuO, indium tin oxide (ITO), Fe2O3, or combinations thereof are attached to functionalized graphene to enhance sensing characteristics.
Graphene etching to form mesa structures
Graphene is etched to form mesa structures comprising horizontal or vertical strips, optimizing device performance.
Methods for device recovery
Recovery of the sensing device is achieved either by rinsing with isopropanol or by heating, enabling repeated use.
Detector device for ppb level sulfur detection
A detector made by etching graphene and functionalizing it with metal oxide nanoparticles via UV-activated chemical functionalization using a chemical linker, where exposure to fuel in gas or liquid phase causes detectable conductivity changes indicative of sulfur presence, with recoverability for future use.
The claims collectively define a novel method and device system incorporating UV-activated graphene functionalization, specific metal oxide nanoparticle attachment, engineered graphene structures, and practical recovery procedures to achieve sensitive, selective, and reusable in-line detection of ppb level sulfur in fuels.
Stated Advantages
Fast sensor response times of 30 seconds for gas-phase and 3 minutes for liquid-phase sensing.
Device selectivity towards common sulfur compounds such as thiophene, octanethiol, and benzothiophene in synthetic fuel mixtures.
Reactivity to aviation fuels (JP8) containing 20 ppm and 600 ppm sulfur in both gas and liquid phases.
Faster response kinetics at elevated temperatures, with response times reduced to about 10 seconds.
Device recovery facilitated by external heating to 125° C. or by rinsing with isopropanol.
High sensitivity with detection limits of approximately 4 ppb for benzothiophene, 6 ppb for octanethiol, and 5 ppm for thiophene, with predicted limits in the low ppt regime.
Low power consumption in the microwatt range.
Ability to differentiate sulfur-containing compounds through device geometry and functionalization variations.
Documented Applications
Fuel cell power generation assets requiring sulfur contamination monitoring.
Portable fuel sensors for rapid identification of sulfur content to distinguish between 'good' and 'bad' fuel in sulfur-sensitive applications.
Portable tools for the oil and gas industry for sulfur detection.
Fuel cell laboratory test equipment.
Use in automotive fuel cell vehicles for on-line sulfur monitoring.
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