ICCT study finds hydrotreating an inexpensive approach to remove naphthalenes from petroleum jet fuel for contrail abatement
A study by MathPro Inc., prepared for the International Council on Clean Transportation (ICCT), has found that hydrotreating is an inexpensive approach to produce near-zero naphthalenes petroleum jet fuel (PJF) for contrail abatement. The report estimates an incremental cost of 0.09 to 0.12 USD/gallon (~€0.03/L) to hydrotreat fossil jet fuel at the conversion refineries that produce the bulk of aviation jet fuel worldwide.
That incremental cost represents a 4 to 5% increase from today’s jet fuel prices, compared to the 2 to 5x cost premium typically quoted for sustainable aviation fuels (SAF).
Further, new aviation fuels such as SAF, require years of rigorous testing and certification by various national and international regulatory bodies before they can be placed in commercial service.
Aircraft consume fuels and emit a range of emissions, including carbon dioxide and water vapor in the form of condensation trails (contrails). Recent studies have indicated that contrails likely contribute to global radiative forcing at a level that is roughly equivalent to that of the CO2 emissions from the entire aviation sector, which is estimated to be about 2% of total global CO2 emissions.
The US ARPA-E recently issued a funding opportunity to explore developing contrail predictive systems. (Earlier post.)
The ice crystals in condensation trails form by the condensation of water vapor on small particulate matter (e.g., soot) present in the engine exhaust. Recent research indicates that a particular class of aromatics compounds—naphthalenes—constituting a small portion (∼2 vol%) of PJF, account for a disproportionately large share of the particulate matter in engine exhaust.
As a result, there is interest in either reducing the volume fraction of aromatics or essentially eliminating naphthalenes from PJF. The MathPro study for the ICCT aims to (1) delineate the type of processes and process modifications that refineries would have to undertake to reduce the naphthalenes content of PJF, and (2) provide a preliminary, first-order assessment of the technical and economic feasibility of these process routes.
The study considered two refining technologies: hydrotreating and extractive distillation.
Hydrotreating, which is widely used in the refining industry in numerous applications, would remove the naphthalenes by converting them to other aromatics and other hydrocarbons.
Extractive distillation would remove the naphthalenes by employing a solvent (not yet in the marketplace) to extract virtually all the aromatics and naphthalenes from the straight run (SR) kerosene stream. The extracted aromatics would be separated from the naphthalenes and sent to the PJF pool.
Although both processes could remove most of the naphthalenes in PJF by processing only straight run kerosene—the PJF component in which most of the naphthalenes reside—the study found that hydrotreating is the most cost-effective for conversion refineries, which are the dominant suppliers of PJF in most regions of the world.