| HS Code | 699582 |
| Productname | Potassium Methoxide Liquid |
| Chemicalformula | CH3OK |
| Casnumber | 865-33-8 |
| Molecularweight | 70.13 g/mol |
| Appearance | Colorless to pale yellow liquid |
| Concentration | Typically 25-30% in methanol |
| Density | Approximately 0.95 g/cm³ at 20°C |
| Boilingpoint | Approximately 65°C for methanol solution |
| Flashpoint | Approximately 11°C for methanol solution |
| Solubility | Soluble in methanol; reacts with water |
| Ph | Strongly alkaline |
| Storageconditions | Store in cool, dry, well-ventilated area away from acids, moisture, and ignition sources |
| Hazardclass | Flammable liquid and corrosive |
| Mainapplication | Used as a strong base and catalyst in organic synthesis and biodiesel production |
As an accredited Potassium Methoxide Liquid factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Potassium Methoxide Liquid supplied in 200 L steel drums, sealed under nitrogen, with hazard labels and UN-approved packaging. |
| Container Loading (20′ FCL) | Potassium Methoxide Liquid loaded into a 20′ FCL container using approved packaging, secured stowage, and compliant hazardous materials handling procedures. |
| Shipping | Potassium Methoxide Liquid is classified as UN 3286, Flammable Liquid, Toxic, Corrosive, n.o.s. (Potassium Methoxide, Methanol), Class 3, Packing Group II, with subsidiary risks 6.1 and 8. Ship in UN-approved packaging with flammable, toxic, and corrosive labels; provide proper placards and documents. |
| Storage | Store Potassium Methoxide Liquid in a cool, dry, well-ventilated, flammable-liquid cabinet, away from heat, ignition sources, direct sunlight, water, acids, and oxidizers. Keep containers tightly closed, upright, labeled, and grounded/bonded. Use secondary containment and explosion-proof equipment. Protect from moisture; store under dry inert gas if recommended. Segregate from incompatible materials. Follow the SDS and local regulations. |
| Shelf Life | Potassium Methoxide Liquid shelf life is typically 12 months when stored sealed, cool, dry, protected from moisture and air. |
Potassium methoxide liquid is metered into a continuous transesterification train in which refined vegetable oil or tallow is mixed with anhydrous methanol. The liquid is supplied at a concentration of 25–32 wt% potassium methoxide in methanol, and the dosing system is configured to maintain a catalyst addition rate of 0.7–1.2 wt% of the oil feed. Methanol is maintained at a molar ratio of 6:1 methanol to triglyceride, and the reaction temperature is held at 60–65°C to avoid excessive methanol vapour generation while keeping the transesterification rate above the threshold required for economical conversion. In a continuous stirred-tank reactor with a residence time of 60–90 min, the methoxide-catalysed reaction generates methyl ester and glycerol, which are separated in a self-cleaning disc stack centrifuge operating at 0.2–0.5 bar back pressure. The methyl ester phase is washed with water, dehydrated under vacuum, and polished to remove residual catalyst; glycerol is drained from the centrifuge as a phase containing 80–88 wt% glycerol and must be stored above 35°C to prevent viscosity-driven pump cavitation.
The critical processing window is governed by water and free fatty acid content in the feedstock. If water exceeds 0.05 wt% or free fatty acid exceeds 0.5 wt%, potassium methoxide is consumed by hydrolysis and saponification reactions before the transesterification step, producing potassium soaps that increase interfacial tension between methyl ester and glycerol, slow phase separation, and can create stable emulsions in the centrifuge discharge. Feedstock is therefore vacuum-dried to <0.05 wt% water before entering the reactor. When the acid number of the feedstock is elevated, a stoichiometric pre-neutralisation with additional potassium methoxide is required before the catalytic dose is calculated; this pre-dose is determined by acid value measurement per EN 14104. The process is kinetically constrained by the boiling point of methanol at 64.7°C, so operation above 65°C requires a pressurised reactor. On production lines, excessive soap formation is controlled by reducing throughput rather than increasing temperature, because higher temperature accelerates methanol loss without resolving the phase-separation problem. Compliance is assessed against EN 14214 and ASTM D6751; EN 14103 defines the minimum ester content of 96.5 wt%, EN 14104 limits acid value to 0.5 mg KOH/g, EN 14105 limits total glycerol to 0.25 wt%, ISO 12937 limits water to 500 mg/kg, and EN 14108 plus EN 14109 limit sodium and potassium combined to 5 mg/kg in the finished fatty acid methyl ester.
| Feedstock parameter | Test method | Typical threshold | KOMe dosing consequence |
|---|---|---|---|
| Free fatty acid content | EN 14104 / ASTM D664 | < 0.5 wt% | Stoichiometric KOMe pre-dosing is required before catalytic addition |
| Water content | ISO 12937 | < 0.05 wt% | Water above threshold hydrolyses methyl esters and increases soap-phase viscosity |
| Sodium and potassium residue | EN 14108 / EN 14109 | < 5 mg/kg combined | Elevated residue requires additional water washing or ion-exchange polishing |
In pharmaceutical intermediate trains, potassium methoxide liquid serves as a strong base for deprotonation of weakly acidic carbon acids and for O-methylation of intermediates that contain halide or sulfonate leaving groups. The addition ratio is not catalytic; it is set at 1.0–1.1 mol equivalents relative to the target acidic proton, with exact dosing determined by substrate pKa and competing ester hydrolysis. A 6,300-L glass-lined reactor is inerted with nitrogen to <1 vol% oxygen, and the methoxide solution is added through a metering pump over 60–120 min, with the reaction mass held at 0–10°C during exothermic neutralisation. After completion, the reaction is quenched with acetic acid or aqueous ammonium chloride, the methanol is distilled under vacuum, and the product is extracted into ethyl acetate or dichloromethane. Manufacturing is conducted under ICH Q7 for active pharmaceutical ingredients and 21 CFR Part 210/211 for finished pharmaceuticals. Residual methanol in the isolated intermediate is controlled according to ICH Q3C, where methanol is a Class 2 solvent with a concentration limit of 3,000 ppm; this requires vacuum drying of the final intermediate. Batch-to-batch variance in colour and assay is controlled by limiting potassium methoxide storage temperature to <25°C and avoiding exposure to atmospheric carbon dioxide, which forms potassium carbonate and reduces base strength. Terminal products include sulfonamide-class API intermediates and vitamin precursors in which methoxide-mediated condensation replaces halogen or sulfonate leaving groups under anhydrous process conditions.
Within a 6,300-L glass-lined vessel, potassium methoxide solution is used as a stoichiometric base for thiol alkylation and enolate formation in organophosphate and pyrethroid precursor trains. The reaction solvent, typically toluene or dimethylformamide, is azeotropically dried to <0.1 wt% water before methoxide addition; potassium methoxide is then added at 1.0–1.2 mol equivalents relative to substrate, with the addition controlled to maintain the reaction mass at -10°C to 60°C depending on substrate thermal stability. After the alkylation or condensation step, the mass is quenched with dilute hydrochloric acid or acetic acid, the aqueous phase is split, and solvent is recovered by vacuum distillation. Compliance with FAO/WHO specifications for pesticide active ingredients, US EPA 40 CFR Part 158 product chemistry data requirements, and EU 1107/2009 where the intermediate is registered in the European Union is maintained through batch analysis of the isolated intermediate. The terminal products of this segment are insecticide, miticide, and herbicide precursors, including organophosphate ester and pyrethroid ester interbodies that are subsequently converted into formulated crop protection agents. Operational boundaries include exclusion of atmospheric moisture and carbon dioxide, because potassium bicarbonate and potassium carbonate formation reduce the effective base loading and can lead to incomplete conversion of the substrate.
Potassium methoxide liquid functions as an alkoxylation catalyst when a fatty alcohol or polyol starter is converted into a nonionic surfactant or polyether polyol. The catalyst is charged at 0.1–0.4 wt% of the starter alcohol after the starter is degassed at 110°C and dried to <0.05 wt% water; the methanol introduced with the catalyst is stripped under vacuum before ethylene oxide or propylene oxide is admitted. In a stirred autoclave or loop reactor, ethylene oxide is dosed at 130–170°C and 3–6 bar gauge, with the oxide addition rate controlled by reactor heat removal. Potassium methoxide initiates ring-opening polymerisation and remains in the product until neutralised with lactic acid or citric acid; the neutralisation salt is removed by filtration. Finished surfactants are assessed under EU Detergent Regulation (EC) No 648/2004 and OECD 301B for ready biodegradability; residual ethylene oxide and dioxane limits are applied according to annex limits. Terminal products include fatty alcohol ethoxylates, EO/PO block copolymers, and polyether polyols used in polyurethane foam formulations. The process boundary is defined by residual methanol in the starter; if methanol is not stripped, oxide consumption does not match the expected molar ratio and the final polyol may exhibit a broader molecular-weight distribution with reduced block specificity.
Potassium methoxide is charged as a transesterification catalyst in polyol ester production, where trimethylolpropane or neopentyl glycol is reacted with C8–C10 fatty acids to form low-volatility ester base stocks. The catalyst addition is 0.05–0.3 wt% of the reaction mass, and the reaction is conducted at 180–220°C under 10–50 mbar absolute pressure to remove methanol and shift equilibrium toward the ester. A wiped-film evaporator is used when the residual acid value must be reduced below 0.05 mg KOH/g; after reaction, the catalyst is neutralised with citric acid, and the salt is removed by plate-and-frame filtration. The resulting ester is assessed by ASTM D7042 for kinematic viscosity and by ISO 6619 for acid number; when the ester is intended for hydraulic applications, ISO 15380 applies to readily biodegradable hydraulic fluids. Terminal products include ISO VG 32, 46, and 68 polyol ester base stocks for hydraulic fluids, refrigeration lubricants, and metalworking fluids. The high-temperature vacuum boundary is critical because prolonged exposure above 220°C accelerates decarboxylation and colour development; process control therefore couples thermocouple feedback with a vacuum pump capable of maintaining <20 mbar absolute during the final stripping stage.
Potassium methoxide solution is used in the synthesis of trimethyl orthoformate by the reaction of chloroform with methoxide ion; the addition ratio is stoichiometric at 3 mol methoxide per 1 mol chloroform, with the reagent supplied as a 25–32 wt% methanolic solution. The reaction is conducted in a continuous liquid-liquid reactor at 0–20°C, with the methanol feed dried to <0.1 wt% water as measured by ASTM D1364. Crude trimethyl orthoformate is purified by atmospheric or pressurised distillation; the byproduct potassium chloride is removed by filtration. Registration under REACH requires substance identity and compositional data for the orthoester product; production quality is managed under ISO 9001. Terminal products include trimethyl orthoformate and related orthoester intermediates used in pharmaceutical and agrochemical process chemistry. Published data for this specific potassium methoxide configuration is limited compared with sodium methoxide; therefore, commissioning trials typically verify chloroform conversion and salt settling time before continuous operation is authorised.
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Potassium methoxide liquid is supplied as a methanolic solution of potassium methanolate, formula CH3OK, CAS 865-33-8. Commercial designations commonly encode the nominal potassium methoxide concentration: KM-25 for 25 wt% potassium methoxide in methanol and KM-32 for 32 wt%, with the balance methanol. The product is a clear to pale-yellow alkaline liquid with density 0.90–0.95 g/cm³ at 20 °C when measured by ASTM D4052 and dynamic viscosity 1.0–2.5 mPa·s at 20 °C by ISO 3104. The closed-cup flash point is approximately 11 °C by ISO 3679, placing the solution in flammable liquid Class 3, Packing Group II. Water specification is normally ≤0.5 wt% by ASTM E203, and carbonate content is controlled below 0.5 wt% as potassium carbonate by acid titration. The liquid form is used in continuous metering systems because it eliminates the dust exposure and hygroscopic caking associated with solid potassium methoxide; however the methanol carrier requires closed-loop storage, nitrogen blanketing, and explosion-proof pumping equipment.
| Parameter | Specification | Test method |
|---|---|---|
| Potassium methoxide content | 25.0–32.0 wt% by grade | non-aqueous acid titration |
| Methanol balance | to 100 wt% | gas chromatography |
| Water | ≤0.5 wt% | ASTM E203 |
| Carbonate as K2CO3 | ≤0.5 wt% | acid titration after barium chloride precipitation |
| Density at 20 °C | 0.90–0.95 g/cm³ | ASTM D4052 |
| Dynamic viscosity at 20 °C | 1.0–2.5 mPa·s | ISO 3104 |
| Flash point, closed cup | 11–13 °C | ISO 3679 |
| Appearance | clear to pale yellow | visual inspection |
For KM-25, the lower viscosity at 20 °C supports metering through positive-displacement pumps with tungsten carbide rotors and PTFE seals. For KM-32, the higher dissolved-alkoxide concentration reduces methanol input per kilogram of active catalyst but narrows low-temperature handling margins because viscosity increases and the solution may become turbid after exposure to carbon dioxide. Both grades are miscible with methanol, ethanol, and tetrahydrofuran but react violently with water, strong acids, and oxidizing agents. Contact with zinc, aluminium, tin, or chlorinated solvents should be avoided because hydrogen evolution or metal-catalyzed decomposition can occur. The normal boiling range is governed by methanol at 64.7 °C at 101.325 kPa; the vapor pressure of the methanol component at 20 °C is approximately 12.8 kPa, requiring storage tank vent treatment.
Routine release testing includes potassium methoxide content by non-aqueous acid titration, water by ASTM E203, density by ASTM D4052, carbonate content by titration with barium chloride precipitation, and appearance. The titration is performed under nitrogen using an automatic titrator with a solvotrode electrode; a sample is dissolved in anhydrous methanol and titrated with 0.1 mol/L hydrochloric acid in isopropanol. Water content above specification signals tank blanketing failure or solvent impurity; carbonate content above specification indicates carbon dioxide ingress. Viscosity by ISO 3104 is measured with a capillary viscometer at 20 °C to verify pumpability and lot-to-lot consistency. Because the material is hygroscopic and alkaline, sampling must use sealed syringes or dip tubes under nitrogen purge.
Compared with sodium methoxide solution, the potassium analogue provides the same methoxide anion but carries a larger cation. The ionic radii are 138 pm for K+ and 102 pm for Na+; in methanolic solution the larger potassium cation is more weakly coordinated to the methoxide oxygen, resulting in higher free methoxide activity. The molecular weight of CH3OK is 70.13 g/mol, versus 54.02 g/mol for CH3ONa. At a nominal 30 wt% concentration, the molar methoxide content is 4.28 mol/kg for the potassium grade and 5.56 mol/kg for the sodium grade. Consequently, direct mass-for-mass substitution is not stoichiometrically equivalent; dosage must be corrected by molecular weight and target catalyst molarity.
In transesterification, comparative kinetic data in public literature are not uniformly normalized to ion activity; published direct rate constants for the potassium grade may be higher under identical alkali molar loading, but the magnitude is feedstock-specific. A numeric ratio for continuous stirred-tank methyl ester conversion is not well established for all configurations and should be verified on retained feedstock. The K+ cation also changes the solubility and morphology of soaps formed when water or free fatty acids exceed process limits. Potassium soaps tend to be softer and may separate more readily in settling vessels, but this effect does not replace upstream drying or acid neutralization.
| Parameter | Potassium methoxide liquid | Sodium methoxide solution |
|---|---|---|
| CAS number | 865-33-8 | 124-41-4 |
| Molecular formula | CH3OK | CH3ONa |
| Molecular weight | 70.13 g/mol | 54.02 g/mol |
| Typical concentration | 25–32 wt% in methanol | 25–30 wt% in methanol |
| Density at 20 °C | 0.90–0.95 g/cm³ | 0.94–0.97 g/cm³ |
| Flash point, closed cup | ≈11 °C | ≈11 °C |
| Water content | ≤0.5 wt% | ≤0.5 wt% |
| Physical form at 20 °C | clear liquid | clear liquid |
Compared with potassium hydroxide, potassium methoxide liquid introduces no water when the methanol is dry, which is critical in transesterification and water-sensitive condensations. Potassium hydroxide is typically supplied as a solid or aqueous solution and generates water upon neutralization. The methoxide alcohol solution is more readily miscible with non-aqueous reactor charges than aqueous KOH, but it is more costly per mole of base and carries flammability. The choice between the two is governed by the water tolerance of the process and the need for methoxide as a leaving group in the reaction.
In a continuous biodiesel unit processing degummed rapeseed oil with water content below 0.1 wt% by ASTM E203, potassium methoxide liquid is injected at a rate corresponding to 0.8–1.2 wt% of the oil charge. The reactor is operated at 55–60 °C; the upper boundary is the methanol bubble point at approximately 64.7 °C at atmospheric pressure, and the lower boundary is imposed by reduced mass transfer and slower transesterification kinetics. A processing window of ±5 °C can be required for feedstocks carrying residual phosphatides because emulsion-forming soaps increase below 50 °C and methanol vaporization reduces liquid-phase methoxide above 62 °C. After the reactor, residual methanol is removed in a flash drum at 80 °C under vacuum, and the glycerol phase is separated by settling or decanter centrifuges. The ester phase is washed with acidulated water to remove residual soap and catalyst; final product must meet EN 14214:2012+A2:2019 limits for total group I metals (Na+K) ≤5 mg/kg, water ≤500 mg/kg, total glycerol ≤0.25 wt%, and monoglycerides ≤0.70 wt%. Under ASTM D6751-20, total glycerol is limited to 0.240 wt% and free glycerin to 0.020 wt% for B100.
In a plug-flow reactor, the methoxide-oil dispersion is generated with static mixers having 3–7 elements and an internal Reynolds number above 2000 in the methanol-oil two-phase zone. Incomplete dispersion causes localized methoxide depletion at the oil-methanol interface, forming diglyceride-rich intermediates that do not fully convert under the same residence time. A two-stage reactor cascade with interval glycerol separation is used when target total glycerol below 0.20 wt% must be reached without a final vacuum distillation. Published data for this specific configuration are limited to specific feedstocks; standard practice is to validate residence time distribution by tracer studies using sodium chloride or potassium chloride pulses and conductivity probes. Because potassium methoxide liquid contains no sodium, a potassium-specific ion-selective probe can monitor the aqueous phase after acidulation to confirm catalyst carryover below detection limits.
Feedstock quality is the limiting constraint. Free fatty acid content above 0.5 mg KOH/g acid value consumes catalyst stoichiometrically to form potassium carboxylates, and water above 0.1 wt% hydrolyzes methoxide to hydroxide, producing soaps and reducing methyl ester yield. Typical pretreatment includes acid degumming and vacuum drying at 90–100 °C under 5–10 kPa absolute. When water exceeds 0.3 wt%, pre-drying with 3A molecular sieves or wiped-film evaporators is preferred over increasing catalyst load because soap breakthrough into the ester phase becomes difficult to reverse.
In fine-chemical synthesis, potassium methoxide liquid is used in Williamson etherifications, Claisen condensations, transesterifications, and deprotonation of active methylene compounds where a strong base and methoxide nucleophile are required. For deprotonation at 0–20 °C in tetrahydrofuran/methanol mixed solvents, the reagent is normally charged at 1.0–1.2 molar equivalents; the exotherm is controlled by jacketed reactors with coolant at −10 °C, and addition rate is limited to maintain internal temperature below 10 °C. The methoxide concentration and residual water are critical because water hydrolyzes the reagent to potassium hydroxide, which can alter selectivity and increase byproduct formation. Residual methanol in the final active pharmaceutical ingredient is regulated under ICH Q3C as a Class 2 solvent with a permitted daily exposure of 30 mg/day and a concentration limit of 3000 ppm. Equipment for pharmaceutical use generally includes glass-lined or 316L stainless steel reactors with PTFE-lined seals, and additions are performed under nitrogen to exclude carbon dioxide. The liquid form allows automated mass-flow dosing with Coriolis meters, which is an operational advantage over solid potassium methoxide in low-humidity solids charging. However, the methanol carrier can be a limitation when the substrate is sensitive to methoxide attack; in such cases solid potassium tert-butoxide is normally selected instead.
During storage, potassium methoxide liquid should be held below 25 °C in 316L stainless steel or high-density polyethylene containers with nitrogen blanketing. Moisture ingress above 0.5 wt% causes partial hydrolysis to potassium hydroxide, and carbon dioxide absorption forms potassium methyl carbonate; both increase turbidity and reduce functional methoxide concentration. Transfer lines should be stainless steel with conductive PTFE or graphite-filled PTFE seals; EPDM or FFKM elastomer O-rings are preferred over nitrile rubber because nitrile can degrade under strongly alkaline conditions. The material is corrosive to aluminum, zinc, tin, brass, and galvanized surfaces, and can generate hydrogen gas with aluminum. Spill control must account for methanol flammability: vapor density is greater than air, and electrical equipment in storage and processing areas should conform to ATEX Zone 1 or NFPA 70/NEC Class I Division 1 requirements. Eye and skin contact with the liquid requires immediate rinsing with water for at least 15 minutes; acid neutralization should not be attempted on skin. Because methanol is absorbed through skin, impervious butyl rubber or nitrile gloves are used only when verified against alkaline methanol permeation data, and glove breakthrough time should exceed the maximum expected contact period.
Changeover requires a mass-balance review rather than a simple volumetric swap. For equivalent active methoxide molar dosing, the required mass flow of 25 wt% potassium methoxide liquid is higher than that of 25 wt% sodium methoxide solution because the molecular weight of CH3OK is 70.13 g/mol versus 54.02 g/mol for CH3ONa. For a catalyst dose of 1.0 wt% sodium methoxide based on oil charge, the molar equivalent potassium methoxide dose at the same concentration is 1.30 wt%. This increases the liquid volume introduced but may reduce the total alkali molar requirement in optimized operation. Metering pumps must be recalibrated; positive-displacement pumps with stroke adjustment are generally suitable, but the higher viscosity of 32 wt% potassium methoxide may require larger suction line diameter or low-speed gear pumps to avoid cavitation. Cleaning between the two grades is usually carried out with dry methanol recirculation until sodium or potassium content is below the acceptable residue limit specified in the downstream product specification. If the product is biodiesel, residual sodium and potassium are both counted in the EN 14214 group I metals limit of ≤5 mg/kg, so cross-contamination is analytically visible by inductively coupled plasma spectroscopy. Published data for direct changeover economics in this specific configuration are limited; laboratory verification of methyl ester yield, soap content, and phase separation should be performed on retained oil batches before full plant conversion.
