Benzyl chloroformate by semi-batch phosgenation of benzyl alcohol at reduced pressure (1000 t/a, batch)

A batch plant: phosgene gas (phosgene-1) is dosed over 10 h into neat benzyl alcohol at 278 K and 50 kPa(a), the HCl vented as it forms; the crude is degassed in the same vessel and leaves neat, the off-gas to a caustic scrubber. Concept stage, 1770 kg per batch every 14.0 h, 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

Benzyl alcohol is charged to an enamelled 2.5 m3 reactor, cooled to 278 K, and phosgene from the site's phosgene unit (1.27 mol per mol of alcohol, the ratio of US 6 696 590 B2 Ex. 3) is evaporated and dosed into it as a gas over 10 h at 50 kPa(a), without base or solvent. The alcohol reacts to benzyl chloroformate and HCl; HCl leaves the liquid as it forms (95 % of it, the rest dissolved), 5 % of the dosed phosgene passes straight to the vent, and two side reactions make the impurities the patent reports (benzyl chloride with CO2, dibenzyl carbonate). The crude, holding about 11 wt% dissolved phosgene, is degassed in the same vessel at 20 kPa(a) to 0.05 mol% phosgene and leaves as the product: 99.2 wt% benzyl chloroformate, 0.51 wt% benzyl chloride, 0.26 wt% dibenzyl carbonate, 98.9 % yield on the alcohol. It is not distilled (the chloroformate decomposes on heating). The reactor's vent and the degassing gas pass the vacuum pump to a caustic scrubber that absorbs the HCl and destroys the phosgene; the spent liquor (NaCl, Na2CO3) goes to wastewater treatment. No HCl or phosgene is recovered.

The batch is modelled with cheme-as-code's semi-batch reactor with a vent and a partly absorbed gas dose (core ADR 0050, 0054), a batch still for the degassing (ADR 0055) and the batch recipe over three steps of one vessel (ADR 0051, 0052, 0057): the dosing, post-reaction and degassing times come from the models, the reactor is the bottleneck (cycle 14.0 h, 565 batches a year on a dedicated train), the recipe sizes the vessel and checks its jacket, and gives the vent's peak gas rate and the scrubber's load per batch (429 kg of vent gas, 233 kg of degassing gas). The kinetics are ASSUMED (no open data): a fast second-order reaction, dosing-controlled; the phosgene's heat of solution is the dose's (core ADR 0063), the heats of reaction on the dissolved basis. Thermal screening: dT_ad 494 K (the side reaction to benzyl chloride run on all the alcohol, with the dose's heat of solution; 323.4 K for the main reaction alone), accumulation at most 17 % (the deliberate phosgene excess, at the end of the dosing), MTSR 357 K (set by the side reaction to dibenzyl carbonate, counted on purpose; 294.1 K for the main reaction alone) against an MTT of 281 K (the boiling point of phosgene, which the excess would boil off). The gas a cooling failure releases at the MTSR, 3219 m3/h by the screening, is 18.6 times what the vacuum pump vents (173 m3/h), and 21.9 times (3788 m3/h, phosgene vapour 0.15 of it) with the liquid's vapour on a trial with core 1.10.0's vent vapour: a design finding for a dosing interlock and an emergency relief to the scrubber. The vent and scrubber are the safety-critical path; no class without a TD24. See DESIGN.md for every assumption.

Capacity
1000 t/a neat benzyl chloroformate: 565 batches/a of 1770 kg in 7920 h on a dedicated train (126.3 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 captive phosgene unit (not chosen)
Engineering gates
Concept and feasibility (no results yet)
Maintainers
Artur Schweidtmann
Design basis and assumptions (6)
  • ASSUMED route: phosgene gas dosed into neat benzyl alcohol at 278 K and 50 kPa(a), no base, no solvent (D-001), the reduced-pressure batch route of US 6 696 590 B2 Ex. 3.
  • ASSUMED rate laws (second order) and the side reactions' constants set to Ex. 3's impurities; the heats of PHOSG and CLBN from formation enthalpies, CARB's ASSUMED (D-005).
  • ASSUMED 95 % of the dosed phosgene taken up by the liquid and 95 % of the HCl leaving as it forms (D-005).
  • ASSUMED degassing at 20 kPa(a) and 278 K with constant relative volatilities to 0.05 mol% phosgene (D-006).
  • ASSUMED caustic scrubber destroying the HCl and phosgene, 99.99 % (D-007); no phosgene or HCl recovery.
  • 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

  • Benzyl alcoholFeedstockDry benzyl alcohol (benzyl-alcohol-1, reagent grade at least 99.8 wt%, linked as a proxy for the dry alcohol), 0.636 kg/kg BCF
  • PhosgeneFeedstockLiquid phosgene (phosgene-1, captive), evaporated and dosed as a gas, 0.738 kg/kg BCF (1.27 mol per mol of alcohol)
  • Sodium hydroxideFeedstockCaustic soda 50 wt% (chlor-alkali-1) for the off-gas scrubber, 1.086 kg/kg BCF, counted by mass of the solution
  • WaterFeedstockProcess water diluting the scrubber's caustic to 10 wt%, 4.34 kg/kg BCF
  • NitrogenFeedstockNitrogen (asu-1) for inerting R-101, breaking its vacuum and padding the transfer, 15 kg per batch, 8.5 g/kg BCF (ASSUMED)

Out

  • Benzyl chloroformateMain productNeat benzyl chloroformate, 99.2 wt%, degassed and not distilled, to cold storage
  • WastewaterWasteSpent scrubber liquor, 5.80 kg/kg BCF: 9.1 wt% NaCl, 3.0 wt% Na2CO3, 0.85 wt% NaOH, to treatment

Utilities: Electricity (0.051 kWh/kg BCF: R-101 agitator, vacuum pump, scrubber pump (ASSUMED)), Steam (0.069 kWh/kg BCF of LP steam to the tempered water of the phosgene evaporator and the degassing), Chilled water (0.163 kWh/kg BCF removed by brine at 248 K: the charge's cool-down (Q1) and the heat of phosgenation with the heat of absorption of the dosed phosgene (Q2, the semi-batch model's, core ADR 0063) (the registry has chilled water, not brine: closest entry)), Cooling water (0.354 kWh/kg BCF: the scrubber's heat of neutralisation and phosgene destruction (ASSUMED heats))

Show in the process graph

Reactions

IdAs writtenReactionOther processes
CARBC8H7ClO2 + C7H8O → C15H14O3 + HCl · Dibenzyl carbonate from the chloroformate and the alcoholC8H7ClO2+C7H8OC15H14O3+HCl
CLBNC7H8O + COCl2 → C7H7Cl + CO2 + HCl · Benzyl chloride and CO2 (net of the alcohol's chlorination by HCl and the water's phosgene hydrolysis)C7H8O+COCl2C7H7Cl+CO2+HCl
NEUT_CO2CO2 + 2 NaOH → Na2CO3 + H2O · CO2 absorbed in caustic sodaCO2+2NaOHNa2CO3+H2O3 other processes
NEUT_HCLHCl + NaOH → NaCl + H2O · HCl absorbed in caustic sodaHCl+NaOHNaCl+H2O4 other processes
NEUT_PHOSCOCl2 + 4 NaOH → Na2CO3 + 2 NaCl + 2 H2O · Phosgene destroyed in caustic sodaCOCl2+4NaOHNa2CO3+2NaCl+2H2O2 other processes
PHOSGC7H8O + COCl2 → C8H7ClO2 + HCl · Phosgenation of benzyl alcohol to benzyl chloroformateC7H8O+COCl2C8H7ClO2+HCl

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 Benzyl chloroformate (neat), 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 benzyl chloroformate made by the semi-batch phosgenation of benzyl alcohol at reduced pressure, degassed and not distilled, with the HCl and the excess phosgene destroyed in a caustic scrubber, at the concept stage: which raw materials, utilities and wastes the batch plant exchanges per kg of product, 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 Benzyl chloroformate (neat) (1 kg benzyl chloroformate)
    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 Benzyl chloroformate (neat) (11 flows)

    FlowPhaseDirectionQuantityUnitProvenance
    Benzyl alcohol (merchant)operationinput0.6356kgassumed
    Liquid phosgene (phosgene-1)operationinput0.7384kgassumed
    Caustic soda 50 wt% (chlor-alkali-1)operationinput1.086kgassumed
    Process water (caustic dilution)operationinput4.343kgassumed
    Electric poweroperationinput0.05147kWhassumed
    LP steam 350 kPa(a) (to the tempered-water circuits of the phosgene evaporator and the degassing)operationinput0.06902kWhassumed
    Benzyl chloroformate (neat) to cold storageoperationoutput1kgcalculated
    Spent scrubber liquor to wastewater treatmentoperationoutput5.802kgcalculated
    Chilled brine return (253 K)operationoutput0.163kWhassumed
    Cooling water returnoperationoutput0.3535kWhassumed
    Nitrogen for inerting R-101, breaking its vacuum and padding the transferoperationinput0.008477kgassumed

    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 Benzyl chloroformate (neat) to cold storage 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 1 unmapped exchange. 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:BCF 100 %
    Allocation findings
    none
    Change report
    Not available: this build has no change report against an earlier release.
    Dataset pages
    Benzyl chloroformate (neat) to cold storage Preliminary

    KPI benchmark positions

    KPIValueReference rangePosition
    Benzyl alcohol consumption per kg of benzyl chloroformate
    No open source with a plant's or a pilot's benzyl alcohol use per kg of benzyl chloroformate found (searched 2026-11-05: Google Patents US 6 696 590 B2 and US 3 966 786 A read, laboratory and continuous examples only; web search for benzyl chloroformate production yields and consumption). US 6 696 590 B2 Ex. 3 implies 0.79 kg/kg (217 g of alcohol for 275 g of product, an 81 % isolated laboratory yield), a single value and the dataset's own basis of conditions; the stoichiometric floor is 0.634 kg/kg.
    		– kg/kgnot availablenot evaluated
    Phosgene consumption per kg of benzyl chloroformate
    No open source with a plant's phosgene use per kg of benzyl chloroformate found (searched 2026-11-05 as for bcf-specific-benzyl-alcohol); US 6 696 590 B2 states a preferred excess of 1.5 to 2.5 mol per mol of alcohol and uses 1.27 in Ex. 3 (the dataset's ratio), no plant figure; the stoichiometric floor is 0.580 kg/kg.
    		– 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 7 steps within tolerance). Every stream is calculated by cheme process propagate from the feeds: the semi-batch R101 with its HCl vent and partly absorbed phosgene dose from its ASSUMED rate laws, the degassing T101 as a batch still with ASSUMED constant relative volatilities, the scrubber S101 as a conversion step; no balance script. The recipe's year-average rate of the product agrees with the flowsheet (cheme process recipe, no cheme.recipe-basis finding), and the jacket removes the model's peak duty (31.65 kW of 34.35 kW, with the phosgene's heat of solution). The duties of R101 (Q2, 19.88 kW) and T101 (Q4, 1.177 kW) are the models' year averages written by cheme process propagate (core ADR 0059); Q2 holds the heat of solution of the absorbed phosgene (the dose's heat_of_solution, assumed, with the heats of reaction on the dissolved basis, core ADR 0063; D-015). Thermal screening (cheme process reactor-hazards): dT_ad 494.0 K (with the dose's heat of solution, 102.6 K), accumulation 0.173, MTSR 357.1 K against an MTT of 280.65 K (phosgene's boiling point, hazard.mtt), all set by the side reactions, every reaction counted on purpose (hazard.reactions, CARB included as the conservative choice; CLBN's heat for the dT_ad, CARB for the MTSR); the main reaction PHOSG alone gives dT_ad 323.4 K (220.8 K without the heat of solution) and MTSR 294.1 K, still above the MTT (DESIGN.md D-011). The gas release at the MTSR, 3219 m3/h at 357.1 K and 50 kPa(a), is 18.6 times the vent capacity of 173 m3/h (the vacuum pump, hazard.vent_capacity, assumed); with the phosgene vapour (vent.vapour, core ADR 0062, on a scratch copy, not adopted) it is 3788 m3/h, 21.9 times, and the relief is to be sized on that (DESIGN.md D-014, D-015). The two warnings cheme.reactor-hazard-mtsr and -vent are design findings, kept (D-011, D-014); no criticality class without a TD24 from calorimetry. The kinetics are assumed: the accumulation rests on that assumption (k/10 and k/100 in DESIGN.md D-011). Preliminary gate-to-gate LCI with the nitrogen purges as a per-batch consumable; benzyl alcohol, phosgene, caustic soda and nitrogen linked to benzyl-alcohol-1, phosgene-1, chlor-alkali-1 and asu-1, 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 (the dose's heat_of_solution, ADR 0063; from 1.9 the model duties and energy_port, ADR 0059, hazard.reactions and vent_capacity, ADR 0058; and from 1.8 batch.vent, dosing.absorbed, still:, recipe units:, ADRs 0054, 0055, 0057).

    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/benzyl-chloroformate-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
    Benzyl chloroformate · 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: "Benzyl chloroformate by semi-batch phosgenation of benzyl alcohol at reduced pressure (1000 t/a, batch)", 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}
}