Methylmagnesium bromide in 2-MeTHF by semi-batch Grignard reaction with methyl bromide gas dosing (4400 t/a)

A batch plant: methyl bromide gas is dosed into magnesium in dry 2-MeTHF at 318 K, 5 % first and a hold for the initiation; ethane and unabsorbed methyl bromide leave by the vent, and the 35 wt% solution is filtered from the excess magnesium. Concept stage, 5000 kg every 9.0 h on a dedicated train, initiation and accumulation screened, preliminary LCI.

Calculation maturity: not assessedDesign maturity: Concept (research)Not independently reviewedInorganic chemicalsReport a problem with this process
Research outputNot engineering advice and not an approved design: do not use it for construction, operation or safety decisions. What this means

Magnesium turnings (5 % above the methyl bromide) and dry 2-MeTHF are charged into a 6.3 m3 stainless-steel reactor under nitrogen, activated with a little iodine and warmed to 318 K. Methyl bromide, evaporated from its liquefied store, is dosed below the surface as a gas: 5 % in 15 min, a 30 min hold until the reaction has started, then the rest over 5 h, the rate set by the reactor's brine jacket. The product is the titrated solution, 35 wt% methylmagnesium bromide in 2-MeTHF (about 3.2 M), the grade of the Albemarle data sheet 10000303; it is filtered from the excess magnesium in a pressure Nutsche and filled under nitrogen. No isolation.

The batch is modelled with cheme-as-code's semi-batch reactor with a vent and a partly absorbed gas dose (reactor: semibatch, batch.vent, dosing.absorbed; core ADRs 0050 and 0054), magnesium as a solid reactant of the liquid model, and the batch recipe (process/recipe.yaml, core ADRs 0051, 0052 and 0057: one vessel over the charge and reaction steps, the warm-up from the jacket, the filtration time from Ruth's equation). The reaction releases 291 kJ per mol on the gas basis (Holm 1981 via the NIST WebBook), an adiabatic rise of the whole batch of 548 K against the solvent's boiling point of 356 K at the reactor's 120 kPa(a) (351 K at atmospheric pressure). With the ASSUMED fast rate the accumulated methyl bromide stays at 0.6 % and the cooling-failure temperature at 321.5 K; a reaction 10 times slower gives 4.3 % and 341.5 K, 100 times slower (a sluggish initiation) 21 % and 434 K, far above the boiling point. An uninitiated 5 % charge alone would take the charge to 349.5 K, just below the atmospheric boiling point. Yield 96.7 % on methyl bromide (1 % passes through the liquid, 1.7 % couples to ethane). See DESIGN.md for every assumption.

Capacity
4398 t/a of 35 wt% solution (1539 t/a MeMgBr): 879.5 batches/a of 5000 kg in 7920 h on a dedicated train (555.3 kg/h year average), ASSUMED (DESIGN.md D-002, D-003, D-013)
Operation
7,920 h/a
Location
generic fine-chemicals site with a thermal oxidiser for halogenated vents (not chosen)
Engineering gates
Concept and feasibility (no results yet)
Maintainers
Artur Schweidtmann
Design basis and assumptions (6)
  • Route: Mg + CH3Br -> CH3MgBr in 2-MeTHF (HSDB via PubChem CID 6349; the product of the Albemarle TDS 10000303), methyl bromide gas dosed into magnesium turnings at 318 K under nitrogen (D-001).
  • ASSUMED: 1.05 mol magnesium per mol methyl bromide, 5 % of the methyl bromide dosed first and a 30 min hold for the initiation, 99 % of the dosed gas absorbed (D-004).
  • Heat of reaction from Holm (1981) via the NIST WebBook, -291.1 kJ/mol on the gas basis (D-005).
  • ASSUMED fast effective rate laws, the Grignard formation first order in methyl bromide and of order 2/3 in the magnesium, the Wurtz coupling first order in the Grignard reagent and in methyl bromide (D-005): no open kinetics; the low accumulation follows from them.
  • ASSUMED jacket: U 400 W/(m2 K), chilled brine at 263 K; the main dosing time (5 h) is set by it (D-010).
  • All flows are year averages of the recipe (D-003); duties and power concept estimates (D-009); accuracy +/-30 % not demonstrated.

From process/design-basis.yaml.

Engineering model

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Snapshot of a3c52e4, cheme-as-code 1.6.0.

What goes in and out

In

  • MagnesiumFeedstockMagnesium turnings (merchant), 0.0775 kg/kg solution, 1.05 mol per mol of methyl bromide
  • Bromomethane (methyl bromide)FeedstockLiquefied methyl bromide (merchant), evaporated and dosed as a gas, 0.288 kg/kg solution
  • 2-MethyltetrahydrofuranFeedstockDry 2-MeTHF (merchant), 0.648 kg/kg solution, the solvent of the product
  • IodineFeedstockIodine activator (iodine-1), 0.4 kg per batch, 0.08 g/kg solution (ASSUMED)
  • NitrogenFeedstockNitrogen (asu-1) for inerting, pressing and blowing the cake, 37.5 kg per batch, 7.5 g/kg solution (ASSUMED)

Out

Utilities: Electricity (0.0095 kWh/kg solution: agitators of R-101 and F-101 (ASSUMED)), Steam (0.028 kWh/kg solution of LP steam 350 kPa(a): the charge's warm-up and the methyl bromide vaporiser), Chilled water (0.241 kWh/kg solution removed by brine at 263 K: the heat of the Grignard reaction (the registry has chilled water, not brine: closest entry))

Show in the process graph

Reactions

IdAs writtenReactionOther processes
GRIGMg + CH3Br → CH3MgBr · Grignard formation from magnesium and methyl bromideMg+CH3BrCH3BrMg
WURTZCH3MgBr + CH3Br → C2H6 + MgBr2 · Wurtz coupling of the Grignard reagent with methyl bromideCH3BrMg+CH3BrC2H6+MgBr2

Each reaction's page has the conversion, heat of reaction, catalyst and sources this process states, next to those of other processes with the same reaction. All reactions

Life cycle assessment

–kg CO2-eqPreliminarypartial, 10 data gaps

Climate change per 1 kg Methylmagnesium bromide 35 wt% in 2-MeTHF, cradle-to-gate

No factors. No contribution is characterised, so no factor stands behind any number.

Main contributors
    Method and data
    Goal
    Preliminary gate-to-gate life cycle inventory of methylmagnesium bromide, sold as a 35 wt% solution in 2-MeTHF, made by the semi-batch Grignard reaction of magnesium turnings with methyl bromide gas and filtered from the excess magnesium, at the concept stage: which raw materials, utilities and wastes the batch plant exchanges per kg of solution, as the foreground for a later cradle-to-gate study. No impact results: most backgrounds are not mapped yet (D-012).
    Functional unit
    1 kg Methylmagnesium bromide 35 wt% in 2-MeTHF (1 kg methylmagnesium bromide)
    Boundary
    cradle-to-gate
    Characterisation
    Factors kept with the process · GWP100
    Data quality
    No factors
    Result
    partial screening carbon footprint · 10 data gaps
    ScenarioClimate change (kg CO2-eq)
    baselineno total (data gaps)

    Inventory per 1 kg Methylmagnesium bromide 35 wt% in 2-MeTHF (11 flows)

    FlowPhaseDirectionQuantityUnitProvenance
    Magnesium turnings (merchant)operationinput0.07746kgassumed
    Dry 2-MeTHF (merchant)operationinput0.6483kgassumed
    Liquefied methyl bromide (merchant)operationinput0.2882kgassumed
    Electric poweroperationinput0.009544kWhassumed
    LP steam 350 kPa(a) (hot-water loop of R-101's jacket and the vaporiser E-101)operationinput0.0277kWhassumed
    Methylmagnesium bromide 35 wt% in 2-MeTHF to fillingoperationoutput1kgcalculated
    Magnesium cake with its liquor to quench and hazardous-waste treatmentoperationoutput0.01022kgcalculated
    Off-gas (ethane, methyl bromide) to the thermal oxidiseroperationoutput0.003653kgcalculated
    Chilled brine return (R-101's jacket)operationoutput0.2415kWhcalculated
    Nitrogen for inerting R-101, pressing the slurry to F-101 and blowing the cakeoperationinput0.007499kgassumed
    Iodine activator for the magnesiumoperationinput0.00007999kgassumed

    Computed by ChemE-as-Code from lca/README.md, lca/dataset.yaml, lca/factors.yaml, lca/gaps.csv, lca/inventory.csv, lca/lca.yaml, lca/mappings.yaml, lca/results.csv, lca/results.md.

    In the open LCI database (cheme-as-code-atlas-preview-a3c52e4) as Methylmagnesium bromide 35 wt% in 2-MeTHF to filling Preliminary.

    Download it for Brightway, openLCA and other tools.

    In the LCI database: system model, datasets and KPIs against the benchmarks

    In the LCI database

    Status
    Preliminary 6 unmapped exchanges. Some exchanges have no background mapping yet: they are exported unlinked and count no burden, so the inventory is incomplete.
    System model
    attributional, cut-off (methodology 1.1.0)
    Allocation
    mass (single-output, from default) · product:PROD 100 %
    Allocation findings
    none
    Change report
    Not available: this build has no change report against an earlier release.
    Dataset pages
    Methylmagnesium bromide 35 wt% in 2-MeTHF to filling Preliminary

    KPI benchmark positions

    KPIValueReference rangePosition
    Magnesium consumption per kg of methylmagnesium bromide solution (35 wt%)
    No open source with a plant's magnesium excess or use per kg of MeMgBr solution found (searched 2026-11-05 as for memgbr-specific-methyl-bromide). Only the stoichiometric floor, 0.071 kg/kg, is known.
    		– kg/kgnot availablenot evaluated
    Methyl bromide consumption per kg of methylmagnesium bromide solution (35 wt%)
    No open source with a plant's or a pilot's methyl bromide use per kg of MeMgBr solution found (searched 2026-11-05: the Albemarle TDS 10000303 gives the product, not the process; the Fraunhofer IMM flyer on continuous Grignard formation (2020) names no MeMgBr figures; am Ende et al., OPRD 1999, 3, 319 seen as an abstract only). Only the stoichiometric floor, 0.279 kg/kg, is known.
    		– kg/kgnot availablenot evaluated

    Maturity and review

    Design maturity Concept (claimed): An idea or first flowsheet; numbers are rough. Concept batch PFD with closed mass, component and element balances (cheme validate, cheme process streams: 2 blocks and 4 steps within tolerance). The charge mixer M101, the semi-batch R101 with its vent (from its ASSUMED rate laws, magnesium a solid reactant), the vaporiser E101 and the specified filter F101 are calculated by cheme process propagate; there is no balance script. The duties are year averages: Q1 from R101's semi-batch model (energy_port, core ADR 0059), the other duties by hand (DESIGN.md D-009). The recipe's year-average rate of the product agrees with the flowsheet (no cheme.recipe-basis finding); the recipe sizes R-101 (6.3 m3) and its jacket check passes at the 5 h main dosing. Thermal screening (cheme process reactor-hazards): dT_ad 548 K, accumulation 0.615 %, MTSR 321.5 K against the default MTT of 356.3 K (2-MeTHF at R-101's 120 kPa(a), Clausius-Clapeyron, core 1.9.0 ADR 0058); no criticality class without a TD24 from calorimetry. R-101's vent capacity, 20 m3/h ASSUMED, passes the base case's gas release at the MTSR (2.8 m3/h) but not that of a sluggish initiation (k/100: 49 m3/h of ethane), which the dosing interlocks and a separate emergency relief must meet (D-011). The low accumulation rests on the assumed kinetics; the k/10 and k/100 sensitivities are in DESIGN.md D-011, with the toxic methyl bromide a cooling failure releases (about 300 kg at k/100) and the warm-up's hot water above the solvent's normal boiling point 351.15 K (the MTT if the pad is lost), 3.2 K below the MTT at 120 kPa(a) (D-010); quenching the magnesium cake gives about 1 kmol of hydrogen per batch (D-007). Preliminary gate-to-gate LCI with the per-batch nitrogen and iodine; both linked to asu-1 and iodine-1, the other backgrounds gaps (magnesium, methyl bromide and 2-MeTHF have no library producer; their proxies are named, not linked). cheme maturity reaches no level (assumed feeds, kinetics and separations); the claim `maturity: concept` is the lowest value of the schema, not an evidenced level. Not reviewed. Needs cheme-as-code 1.9 (batch.vent, dosing.absorbed, recipe units and filtration since 1.8; energy_port, vent_capacity and the default MTT at the vessel's pressure since 1.9).

    Calculation maturity, from the checked evidenceNot assessed

    The process has no maturity report (cheme maturity, checks/maturity.json), so no calculation maturity is established.

    No level shownThe design maturity (Concept) is the manifest's claim, not evidence. A level appears here once the process's repository holds a current report from cheme maturity --write.

    Artifact completeness

    Which deliverables exist. They never raise a calculation maturity level: a drawing from unchecked numbers is still unchecked.

    Not reported without a maturity report.

    Independent review

    Not independently reviewed

    No independent engineering review yet. Automated checks passing is not a review.

    Set by people only. Reaching a calculation maturity level or passing automated checks is not an independent review or an approval.

    Where the evidence comes from
    Report
    processes/methylmagnesium-bromide-1/checks/maturity.json (not in the library)
    Design basis
    process/design-basis.yaml
    Method
    How ChemE-as-Code checks the levels (requirement by requirement)

    Open items

    0 open items · 0 closed

    New action itemNew engineering holdNew technical queryNew design changeAll issues

    Sources

    Engineering project
    Methylmagnesium bromide · cheme-as-code>=1.9
    Library version
    a3c52e4 (process last changed in a3c52e4)
    Drawings rendered by
    cheme 1.6.0 (pyDEXPI 2.1.0)
    Data
    Catalog record (JSON) · CC-BY-4.0
    Files
    View the files on GitHub · change history and authors

    References

    How to cite

    For the data, cite the Process Atlas paper; for the platform that builds and checks it, the ChemE-as-Code paper.

    Schweidtmann, A. M. & Weber, J. M. (2026, in preparation). Process Atlas: an open, git-native, reproducible library and life cycle inventory of chemical processes (working title).

    For this process: "Methylmagnesium bromide in 2-MeTHF by semi-batch Grignard reaction with methyl bromide gas dosing (4400 t/a)", ChemE-as-Code process library, version a3c52e4.

    BibTeX
    @unpublished{schweidtmann_process_atlas,
  author = {Schweidtmann, Artur M. and Weber, Jana M.},
  title = {{Process Atlas: an open, git-native, reproducible library and life cycle inventory of chemical processes (working title)}},
  year = {2026},
  url = {https://atlas.cheme-as-code.org},
  note = {in preparation}
}

    Schweidtmann, A. M. (2026). ChemE-as-Code: An Open-Source Platform for Agentic AI in Chemical Engineering. arXiv:2611.07947. https://doi.org/10.48550/arXiv.2611.07947

    BibTeX
    @misc{schweidtmann_cheme_as_code,
  author = {Schweidtmann, Artur M.},
  title = {{ChemE-as-Code: An Open-Source Platform for Agentic AI in Chemical Engineering}},
  year = {2026},
  eprint = {2611.07947},
  archivePrefix = {arXiv},
  doi = {10.48550/arXiv.2611.07947},
  url = {https://arxiv.org/abs/2611.07947}
}