Acetyl chloride by semi-batch reaction of acetic acid with PCl3, phase split and batch distillation (2000 t/a)

A batch plant: PCl3 is dosed over 2 h into acetic acid at 313 K, the mixture settles into an upper acetyl chloride and a lower crude phosphorous acid phase, and the upper phase is distilled. Concept stage, 1460 kg per batch every 5.78 h on a dedicated train, thermal screening with a rate-constant sensitivity, preliminary gate-to-gate LCI.

Calculation maturity: not assessedDesign maturity: Concept (research)Not independently reviewedChlorinated organicsReport 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

Glacial acetic acid (acetic-acid-1, 691 ppm water) is charged to an enamelled reactor and warmed to 313 K; phosphorus trichloride (1 mol per 3 mol of acid) is dosed into it over 2 h and held 0.5 h, 3 CH3COOH + PCl3 -> 3 CH3COCl + H3PO3, the batch route of CS 272 248 B2 (Nitrokemia, Example 1: below 40 C, then 30 min at 40-50 C). The water of the acid hydrolyses some PCl3; its HCl leaves by the vent through a brine condenser, which returns the acetyl chloride vapour, to a water scrubber. The mixture settles: the lower phase, 87.5 wt% phosphorous acid with acetic acid and acetyl chloride, leaves as a crude phosphorous acid co-product (0.41 kg per kg); the upper phase is distilled in a batch still with a column of about 10 stages at reflux 1. Product 99.43 wt% acetyl chloride with 0.57 wt% PCl3 (specification at least 99.0 wt%), which a column hardly separates (US 4 209 460 A); the PCl3-rich still residue (46 g per kg) goes to incineration. Yield 92.1 % of theory on the acetic acid and the PCl3: a model result, not a sourced one (no open source states a yield for this route).

The batch is modelled with cheme-as-code's semi-batch reactor with a gas vent (reactor: semibatch, batch.vent, core ADRs 0050 and 0054), its batch still with a rectifying column (still: with column, ADRs 0055 and 0061) and the batch recipe (process/recipe.yaml with units over several steps, ADRs 0051, 0052, 0057): the dosing, post-reaction, warming and distillation times come from the models, the reactor is the bottleneck (cycle 5.78 h, 1370 batches a year), the recipe sizes the reactor (2.5 m3) and checks its jacket, and the flowsheet's flows are the recipe's year averages. The semi-batch and the still write their own duties (ADR 0059), the still's reboiler with its reflux and charge's heat-up and its column's condenser (ADRs 0061, 0063), and the screening compares the gas a cooling failure releases with R-101's vent (ADR 0058). The phase split is a specified split until core has a liquid-liquid model for these liquids. The conversion and the phase split are calibrated to the source's lower phase; the kinetics are ASSUMED: the PCl3 accumulates to 11.7 % at the end of the dosing and the cooling-failure temperature stays 8.4 K below the boiling point of acetyl chloride; a 100 times slower reaction would exceed it. The vent, sized for 50 m3/h, passes every cooling failure the screening covers, but not the boiling and water-ingress cases, which need a relief study. See DESIGN.md for every assumption.

Capacity
2000 t/a distilled acetyl chloride: 1370.0 batches/a of 1459.9 kg in 7920 h on a dedicated train (252.52 kg/h year average), ASSUMED (DESIGN.md D-002, D-003, D-013)
Operation
7,920 h/a
Location
generic fine-chemicals site with PCl3 and acetic acid supply (not chosen)
Engineering gates
Concept and feasibility (no results yet)
Maintainers
Artur Schweidtmann
Design basis and assumptions (5)
  • Route of CS 272 248 B2 (Nitrokemia, 1991), Example 1: PCl3 dosed into acetic acid (1 mol on 3 mol) below 40 C, held at 40-50 C; the mixture settles into an upper acetyl chloride and a lower phosphorous acid phase (D-001, D-004).
  • ASSUMED second-order rate law, k 5.5e-4 m3/(kmol s) at 313 K, Ea 50 kJ/mol, sized to the source's 30 min hold; heat of reaction -10.5 kJ/mol derived from CRC formation enthalpies with crystalline H3PO3 (+2.3 with the liquid): the sign is uncertain (D-005).
  • ASSUMED conversion of the PCl3 0.95 and the phase split of D101, both calibrated to the lower phase of CS 272 248 B2, Example 1 (D-005, D-006); all HCl leaves the liquid as it forms (batch.vent fraction 1).
  • Still: a batch still with a column of 10 theoretical stages at a constant reflux ratio of 1 (US 4 209 460 A, Example 1: a 2 m packed column at 1:1; the stages ASSUMED), core's batch rectification (ADR 0061) at 101.325 kPa(a) on Raoult's law with NIST Antoine constants (an ideal liquid, ASSUMED), to 50 mol% acetyl chloride in the residue (D-007, D-008, D-015).
  • All flows are year averages of the recipe (D-003); the duties and power concept estimates (scripts/balance.py, D-006, 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

  • Acetic acidFeedstockGlacial acetic acid (acetic-acid-1, 691 ppm water), 0.826 kg/kg acetyl chloride (stoichiometric 0.765)
  • Phosphorus trichlorideFeedstockPhosphorus trichloride (no exported library process; proxy P4 + 6 Cl2 recorded, D-012), 0.629 kg/kg acetyl chloride (stoichiometric 0.583)
  • WaterFeedstockProcess water to the vent scrubber, 0.213 kg/kg
  • NitrogenFeedstockNitrogen (asu-1) for inerting R-101, the still and the receivers, 10 kg per batch, 6.85 g/kg (ASSUMED)

Out

  • Acetyl chlorideMain productDistilled acetyl chloride, modelled 99.43 wt% with 0.57 wt% PCl3 (about 1290 ppm P) against a specification of at least 99.0 wt% (US 4 209 460 A), to storage under nitrogen; no source states a purity for this route
  • Phosphorous acid (phosphonic acid)Co-productCrude phosphorous acid (the lower phase), 0.406 kg/kg: 87.5 wt% H3PO3, 10.1 wt% acetic acid, 2.0 wt% acetyl chloride; mass allocation, 28.9 % of the burdens (DESIGN.md D-012)
  • WastewaterWasteScrubber bleed, 0.217 kg/kg: 1 wt% HCl, 0.8 wt% acetic acid, to neutralisation

Utilities: Electricity (0.021 kWh/kg: agitators of R-101 and C-101, reflux pump, scrubber pump and fan (ASSUMED)), Steam (0.224 kWh/kg of LP steam 350 kPa(a): R-101's tempered-water loop and the still's reboiler at a reflux ratio of 1 with the charge's heat-up (core's still model with its column)), Cooling water (0.232 kWh/kg removed by cooling water: R-101's jacket (from core's semi-batch model), the column's condenser (from core's still model), the product cooler, the residue's cooling), Chilled water (0.0014 kWh/kg removed by brine at 258 K: the vent condenser E-103 (the registry has chilled water, not brine: closest entry))

Show in the process graph

Reactions

IdAs writtenReactionOther processes
ACCL3 C2H4O2 + PCl3 → 3 C2H3ClO + H3PO3 · Acetic acid and phosphorus trichloride to acetyl chloride and phosphorous acid3C2H4O2+PCl33C2H3ClO+H3O3P
AHYDC2H3ClO + H2O → C2H4O2 + HCl · Hydrolysis of the acetyl chloride vapour that passes the vent condenser, in the scrubberC2H3ClO+H2OC2H4O2+HCl
HYDPCl3 + 3 H2O → H3PO3 + 3 HCl · Hydrolysis of phosphorus trichloride by the water of the acetic acidPCl3+3H2OH3O3P+3HCl

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 Acetyl chloride, 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 acetyl chloride made by dosing phosphorus trichloride into acetic acid in a semi-batch reactor, settling the crude phosphorous acid off as a lower phase and distilling the acetyl chloride at atmospheric pressure, at the concept stage: which raw materials, utilities and wastes the batch plant exchanges per kg of acetyl chloride, 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 Acetyl chloride (1 kg acetyl chloride)
    Boundary
    cradle-to-gate
    Allocation
    shares
    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 Acetyl chloride (12 flows)

    FlowPhaseDirectionQuantityUnitProvenance
    Acetic acid (acetic-acid-1)operationinput0.5875kgassumed
    Phosphorus trichloride (no library process)operationinput0.4476kgassumed
    Process water (vent scrubber)operationinput0.1517kgassumed
    Electric poweroperationinput0.01461kWhassumed
    LP steam 350 kPa(a)operationinput0.1595kWhassumed
    Acetyl chloride to storageoperationoutput1kgcalculated
    Crude phosphorous acid (lower phase; co-product)operationoutput0.406kgassumed
    Still residue (PCl3 and acetyl chloride) to hazardous-waste incinerationoperationoutput0.03303kgcalculated
    Scrubber liquor (dilute hydrochloric acid) to neutralisationoperationoutput0.1541kgcalculated
    Cooling water returnoperationoutput0.1651kWhassumed
    Chilled brine return (263 K)operationoutput0.0009809kWhassumed
    Nitrogen for inerting R-101, the still and the receiversoperationinput0.00487kgassumed

    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 Acetyl chloride to storage Preliminary; Phosphorous acid (phosphonic acid), Crude phosphorous acid (lower phase; co-product) 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 3 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
    shares (deviation, from study) · product:ACCL 71.1 %, product:H3PO3P 28.9 %
    Allocation findings
    none
    Change report
    Not available: this build has no change report against an earlier release.
    Dataset pages
    Acetyl chloride to storage Preliminary · Phosphorous acid (phosphonic acid), Crude phosphorous acid (lower phase; co-product) Preliminary

    KPI benchmark positions

    KPIValueReference rangePosition
    Crude phosphorous acid (lower phase) per kg of acetyl chloride
    No open source independent of the dataset found (searched 2026-11-06 as for accl-specific-pcl3): CS 272 248 B2, Example 1, gives 96 g of lower phase per 1.0 mol PCl3 but no acetyl chloride mass, and the dataset's phase split is calibrated to that example, so it is not an independent reference.
    		– kg/kgnot availablenot evaluated
    Phosphorus trichloride consumption per kg of acetyl chloride (acetic acid route)
    No open source with a plant's or a pilot's PCl3 use per kg of acetyl chloride found (searched 2026-11-06: Google Patents CS 272 248 B2, the dataset's basis, gives charges and the lower phase but no acetyl chloride yield; US 4 209 460 A purifies a crude from another process; US 4 060 546 A names the 1:3 ratio as prior art without a yield; Ullmann's chapters not read, licensed). Only the stoichiometric floor, 0.583 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: 3 blocks and 8 steps within tolerance). The semi-batch R101 with its vent (from its ASSUMED rate laws), the batch still ST101 with its column (10 theoretical stages at a reflux ratio of 1, Diwekar's shortcut on Raoult's law with NIST Antoine constants, the ideal liquid ASSUMED; 99.43 wt% acetyl chloride at 98.19 % recovery, 19.2 % of the charge's PCl3 overhead), the scrubber's hydrolysis and the coolers are calculated by cheme process propagate; scripts/balance.py gives the feeds for 2000 t/a, the phase split D101 (calibrated to CS 272 248 B2), the scrubber water, the still's stream temperatures and the duties (no property package of core covers these liquids, no liquid-liquid model applies), except R101's duty and the still's reboiler and condenser, which core's models write (ADRs 0059, 0061, 0063). The vent's acetyl chloride and E-103's load stay script estimates: core 1.10.0's vent vapour carries only the HCl's (DESIGN.md D-015). The recipe's year-average rate of the product agrees with the flowsheet (no cheme.recipe-basis finding); the recipe sizes R-101 (2.5 m3), its jacket check passes against the log-mean cooling-water temperature, and the still's distillation time comes from its boil-up. Thermal screening (cheme process reactor-hazards): dT_ad 21.4 K, accumulation 11.7 %, MTSR 315.8 K against an MTT of 324.15 K (hazard.mtt: the boiling point of acetyl chloride); no criticality class without a TD24 (1 or 2 if the TD24 lies above the MTSR, 5 if below). With k/10 the MTSR is 321.1 K, with k/100 330.5 K, above the MTT (DESIGN.md D-011). At the MTSR a cooling failure releases 0.41 m3/h of gas, at most 31.2 m3/h over the batch (37.9 m3/h at k/100), within R-101's vent capacity of 50 m3/h (ASSUMED); the boiling cases (k/100 above the MTT, a failed warming loop) and water ingress are a design finding for the relief study (DESIGN.md D-014). The heat of reaction's sign is uncertain (D-005). Preliminary gate-to-gate LCI with the per-batch nitrogen, mass allocation to the crude phosphorous acid; the acetic acid linked to acetic-acid-1 and the nitrogen to asu-1, the PCl3 a gap with a recorded proxy, the other backgrounds gaps. 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 1.10.0.

    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/acetyl-chloride-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
    Acetyl chloride · cheme-as-code>=1.10
    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: "Acetyl chloride by semi-batch reaction of acetic acid with PCl3, phase split and batch distillation (2000 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}
}