Methanol-to-Jet (MtJ)

Methanol-to-Jet, often abbreviated MtJ, is the family of synthesis processes that converts methanol into a kerosene-range hydrocarbon product suitable, after appropriate finishing, for use as jet fuel. It is one of several SAF pathways within the ASTM D7566 framework or in active certification at the time of writing, alongside hydroprocessed esters and fatty acids (HEFA), Fischer-Tropsch synthetic paraffinic kerosene (FT-SPK), alcohol-to-jet (ATJ) from ethanol or isobutanol, catalytic hydrothermolysis, and others at earlier stages of qualification.

The pathway as it is usually configured is not a single conversion step. It is a sequence: methanol is first converted to a mixture of light olefins or aromatics, the intermediate is oligomerised and rearranged to longer-chain hydrocarbons, the oligomerised product is hydrogenated, and a kerosene-range cut is isolated by fractionation and finished to meet jet fuel specification. Each step in this sequence is well-established chemistry. Methanol-to-olefins is operated industrially in China at coal-to-chemicals scale. Olefin oligomerisation underpins much of the modern petrochemical industry. Hydrogenation and fractionation are oil-refining basics. The MtJ proposition is the integration of these mature chemistries into a single process train optimised for a kerosene slate, rather than the discovery of any individual new chemistry.

The pathway is sometimes described as a long way around. A defender of Fischer-Tropsch synthesis will note that FT goes directly from syngas to a hydrocarbon slate that includes kerosene, in one principal reaction step, and ask why an MtJ developer would choose to go through methanol as an intermediate at all. The honest answer is principally about decoupling. Methanol is a stable, transportable, room-temperature liquid that can be produced at one location and shipped to another for upgrading, in a way that syngas cannot. The MtJ pathway lets the front end of the production system, the methanol synthesis itself, sit anywhere with cheap renewable energy, including in regions where the produced fuel will not be consumed. The back end, the upgrading to jet, can then sit closer to refining infrastructure or to demand markets. The case for MtJ is therefore a logistical and infrastructural case as much as a chemical one, and it is best understood in that light.

A second, related, argument for MtJ is the alignment with the rapidly scaling green methanol industry. Green methanol production capacity is currently being built primarily to serve maritime shipping decarbonisation, which has both hard regulatory pressure (FuelEU Maritime, the IMO mid-term measures) and commercial engine availability (dual-fuel methanol engines from MAN Energy Solutions and Wärtsilä are mature products). The methanol pipeline being built for shipping is, in principle, an immediately accessible feedstock pool for MtJ. The aviation industry, by contrast, has been slower to commit to a specific SAF molecule beyond HEFA. MtJ allows aviation to draw on infrastructure built for another sector rather than building its own from scratch.

This framing, that MtJ is fundamentally a coupling technology between green methanol and SAF demand rather than a primary fuel technology in its own right, is the most analytically useful way to understand the pathway and the right way to assess its commercial position. The viability of an MtJ project depends, more than on anything in the conversion train, on the viability of the green methanol industry that feeds it.

The MtJ process train is a sequence of four principal reaction stages, each well-established in isolation. The integration of these stages into a single jet-optimised plant is where the engineering work lives.

Methanol-to-olefins (MTO) or methanol-to-aromatics (MTA). The first reactor converts methanol into a hydrocarbon intermediate over a shape-selective zeolite catalyst. SAPO-34 is the workhorse for ethylene-and-propylene-targeted MTO operation, and ZSM-5 is the alternative for a broader olefin slate or for MTA configurations. The reaction is exothermic, with operation around 400 to 500 °C, and hot-spot management is the principal reactor engineering challenge. Catalyst lifetime is limited by coke deposition on the zeolite framework, and the catalyst is regenerated by air burn-off on a continuous or semi-continuous basis, depending on the process licensor's choice. For MtJ, the desired intermediate slate is C3 and C4 rich rather than ethylene-rich, since longer olefins are easier to oligomerise to jet-range chains. The catalyst formulation and operating conditions are tuned for this preference, sometimes at the cost of catalyst lifetime or selectivity. The fork between MTO and MTA configurations is a process-design choice with real consequences for the jet product: an MTA-routed product contains more aromatics, which raises density and shifts freeze-point and combustion characteristics. ASTM D7566 has specific aromatic content requirements that interact with this choice.

Olefin oligomerisation. The light olefin or olefin-plus-aromatic mixture is then linked together over a second catalyst (typically a different zeolite, often ZSM-5 in a different configuration, or a homogeneous nickel-based system in some process variants) at moderate temperatures (200 to 300 °C) and pressures (10 to 50 bar). The reaction is exothermic, and again the selectivity question dominates: the target is the C8 to C16 range relevant to jet fuel, with light gases and very heavy products as losses. Reactor design for oligomerisation has matured significantly over the past decade, driven in part by oil-refining interest in dimerisation and trimerisation for petrochemical applications, and the technology is now considered industrially robust at the scales relevant to SAF.

Hydrotreatment. The oligomerised stream is olefinic and somewhat unsaturated, and needs to be hydrogenated to produce paraffins of the correct molecular structure for jet fuel. Hydrotreatment is the standard refining operation, well-established at the relevant scales, with the only project-specific question being the hydrogen supply. The hydrogen demand at this step is real, typically a few percent of the carbon flow on a mass basis, and is a meaningful cost contributor. For an integrated green hydrogen project with on-site electrolysis, the hydrogen comes from the same electrolyser fleet that produces the methanol, and the cost is internalised. For a project drawing on imported methanol, the hydrogen has to be supplied locally, and the local hydrogen cost can dominate the integration economics.

Fractionation and finishing. The final stage separates the product slate into kerosene-range jet, naphtha, LPG, and small amounts of heavier material. Jet specification finishing includes hydrogenation of any residual unsaturation, removal of trace contaminants, and adjustment of properties (flash point, freeze point, density, aromatic content) to meet Jet A-1 and the relevant ASTM D7566 blend requirements. This is again standard refinery operation and is rarely the engineering bottleneck.

The yields of each stage compound. From methanol input to jet output, on a carbon-mass basis, typical reported yields are 50 to 65 percent jet, with the remainder distributed across naphtha (15 to 25 percent), LPG (10 to 15 percent), and minor heavier and lighter cuts. A higher jet yield is technically achievable but generally at the cost of total product yield, which is not usually a good trade. Realistic project economics treat the full product slate, with co-products sold into their respective markets, rather than treating naphtha and LPG as waste streams. The co-product valorisation question recurs in the engineering section below because it is one of the higher-leverage commercial decisions in an MtJ project.

ASTM D7566 is the standard governing synthetic aviation fuels approved for blending with conventional Jet A-1. The standard has multiple annexes, each covering a different production pathway and each carrying a specific blending limit and qualification dossier. MtJ pathways are progressing through ASTM qualification, with route-specific blending limits typically in the 50 percent range upon initial approval and subject to upward revision as in-service experience accumulates. Project developers should confirm the specific annex and current blending limit applicable to their chosen process configuration with the technology licensor and the certifying body, as the certification landscape is evolving on the timescale of months rather than years.

The blending limit matters in the near term because no commercial flight today operates on neat synthetic jet fuel. The current SAF supply is blended with conventional Jet A or A-1 at the airport. A 50 percent limit means that even at full SAF substitution intent, the fuel uplifted is half conventional. Pathway-by-pathway blending limits also create logistical complications when multiple SAF batches from different pathways are mixed in the same supply chain, because the resulting blend must respect all applicable limits simultaneously. The industry push for higher blending limits and for 100 percent neat SAF qualification is active, and several major engine and airframe manufacturers have completed neat-SAF flight tests in recent years. The expectation is that neat-SAF qualification will progressively be granted over the 2025 to 2030 period, pathway by pathway, but the timing is not guaranteed.

For MtJ projects specifically, the certification status is a moving target on at least seven dimensions that project developers need to track in parallel: the specific D7566 annex covering their process configuration; the current blending limit applicable to that annex; the ICAO CORSIA approval status for the same pathway; the RefuelEU and CORSIA-applicable lifecycle methodology; any country-specific qualification requirements (the UK Jet Zero framework, the US 45Z tax credit and the related SAF Grand Challenge, the various national implementations of RED III); the carbon intensity threshold under the applicable schemes; and the expected timing of blending-limit increases or neat-SAF qualification. A project that has not actively engaged with the certification process by the basic engineering design stage is a project that is taking unmodelled regulatory risk and exposing its investors and offtakers to that risk without their full awareness.

The next decade for Methanol-to-Jet will be shaped by four interacting forces.

First, the trajectory of green methanol supply. The pipeline of announced green methanol projects globally is in the order of 30 to 50 million tonnes per year of nameplate capacity targeting operation between 2025 and 2030. Realised capacity will be a fraction of this, in line with the realisation rate observed in other Power-to-X categories. The actual delivered green methanol price, and its certification status under the relevant schemes, will determine the addressable MtJ market more directly than any change in the conversion technology itself.

Second, the competing demand from maritime shipping. The shipping industry is the principal current advocate for green methanol, with dual-fuel methanol engines now standard offerings from major engine manufacturers and major shipping companies (Maersk, CMA CGM, Hapag-Lloyd, and others) committed to methanol-fuelled fleet renewal. Shipping demand is policy-supported by FuelEU Maritime, the IMO mid-term measures, and emerging port-side regulations. The green methanol pool will not allocate to MtJ if shipping prices clear higher, and shipping has both willingness to pay and regulatory urgency on its side.

Third, the certification framework maturation. The MtJ pathway is in the active certification process under multiple frameworks (ASTM D7566 annexes, ICAO CORSIA, RefuelEU, country-specific schemes including UK Jet Zero, US SAF Grand Challenge and 45Z). Each certification step opens or restricts the addressable market. The historical pace of SAF certification has been slow relative to industrial-build timelines, and whether certification accelerates to match the announced SAF demand is an open question that depends on regulatory bandwidth, on the willingness of certifiers to accept partial qualification data, and on the in-service experience accumulating from early commercial plants.

Fourth, the competitive dynamics with parallel SAF pathways. HEFA dominates today and will continue to dominate near-term volume because of its existing operational base and lower per-litre cost. FT-SPK has multiple announced projects but a track record of execution difficulty at commercial scale. ATJ has strong feedstock cases in specific regions but limited global applicability. MtJ's position will be relative to these alternatives, not absolute, and the SAF market is likely to be served by a portfolio of pathways rather than by any single one.

The honest assessment is that MtJ is a credible SAF pathway with a clear technical foundation and a real, if conditional, commercial logic. It is not the pathway. It is one of several, with a specific case (alignment with the green methanol industry) and specific risks (dependence on that industry's trajectory and on the certification environment). Projects that have understood this conditionality, and structured around it with long-term methanol offtake contracts, integrated hydrogen supply, and access to co-product markets, are well-positioned. Projects that have treated MtJ as a standalone fuel technology, independent of the upstream methanol market, are not.