N-Propanol Manufacturer and Supplier for Global Industrial Use
Industrial-grade n-propanol (IUPAC propan-1-ol, CAS 71-23-8, EC 200-746-9) enters global supply chains primarily from integrated oxo-alcohol complexes in which ethylene, carbon monoxide, and hydrogen are converted to propionaldehyde and then hydrogenated in a subsequent fixed-bed step. The molecule has a molecular weight of 60.10 g/mol, a boiling point at 101.3 kPa of 97.1 °C, a density at 20 °C of 0.8035 g/cm³ when measured by ASTM D4052, and a closed-cup flash point of approximately 22 °C when determined by ISO 2719. The lower flammable limit is approximately 2.1 vol% and the upper flammable limit is approximately 13.5 vol%; the autoignition temperature is approximately 371 °C. The vapor pressure at 20 °C is approximately 1.99 kPa. The solvent is hygroscopic and fully miscible with water, ethanol, toluene, and common ketones, but its polar and hydrogen-bonding solubility parameters create specific downstream advantages in printing inks, pharmaceutical crystallization, and esterification. Publicly available capacity data for individual plants is limited; the principal merchant supply routes are oxo-derived n-propanol from low-pressure rhodium-catalyzed hydroformylation followed by vapor-phase or liquid-phase propanal hydrogenation, with integrated distillation trains removing water, propionaldehyde, and higher-boiling condensation byproducts. Bulk cargoes are moved in stainless steel ISO tank containers and marine tankers under a nitrogen blanket because the material is a flammable liquid and oxygen uptake accelerates acid formation.
Why Does Carbon Monoxide Partial Pressure Dictate Propionaldehyde Selectivity in Rhodium-Catalyzed Ethylene Hydroformylation?
Process data from continuous low-pressure ethylene hydroformylation units indicate that propionaldehyde selectivity is controlled by the partial pressure ratio of carbon monoxide to hydrogen, reactor temperature, residence time, and ligand-to-rhodium molar ratio in the catalyst solution. The catalytically active species is a triphenylphosphine-modified rhodium carbonyl complex; excess triphenylphosphine ligand is maintained at a molar ligand-to-rhodium ratio between 50:1 and 150:1 because low ligand levels increase alkene isomerization and aldol condensation, while high ligand levels suppress carbonylation activity. The hydroformylation reaction C2H4 + CO + H2 → CH3CH2CHO is exothermic, and the heat release requires pumped-loop cooling with shell-and-tube exchangers engineered for a temperature rise of less than 15 °C across the catalytic zone. Reactor temperatures are typically held between 85 °C and 110 °C, with total syngas pressure between 1.5 MPa and 3.0 MPa; liquid hourly space velocity through the gas-liquid contactor is typically maintained between 1.0 h⁻¹ and 3.0 h⁻¹. Ethylene conversion is generally above 95 mol%, and propionaldehyde selectivity in the crude oxo product is reported in process licensor literature to exceed 97 mol%, with n-propanol co-product and trace C4 aldehydes arising from consecutive aldol condensation and hydrogenation. Carbon monoxide partial pressure is the primary kinetic control variable: too low a CO partial pressure accelerates ethylene hydrogenation to ethane, while too high a CO partial pressure suppresses the migratory insertion step and reduces volumetric productivity. The off-gas from the hydroformylation reactor is scrubbed, compressed, and recycled; online gas chromatography with thermal conductivity detection monitors CO, H2, and CH4 content at the recycle compressor suction, and the H2:CO ratio is trimmed to 1.00:1.0 to 1.05:1.0 after accounting for purge losses.
The degassed propionaldehyde stream is hydrogenated over a fixed-bed nickel or copper-chromite catalyst at temperatures between 90 °C and 150 °C and pressures between 1.0 MPa and 4.0 MPa. Hydrogenation selectivity to n-propanol exceeds 99 mol% when the aldehyde feed is kept dry and free of dissolved carbon monoxide; residual carbon monoxide can adsorb on nickel active sites and produce methane, consuming hydrogen and raising pressure drop across the catalyst bed. Reactor operators monitor the temperature profile across the bed in multiple axial thermowells, and the maximum exotherm is controlled to less than 30 °C per bed section to avoid sintering of the metal crystallites. Aldehyde breakthrough at the reactor outlet is measured by GC-FID or titration, and values above 0.05 wt% in the crude hydrogenation product trigger a reduction in feed rate or a rise in hydrogen partial pressure. The hydrogenation catalyst is regenerated by oxidative burn-off at 350 °C to 400 °C in a controlled air-nitrogen mixture, followed by hydrogen reduction at 250 °C to 300 °C, when pressure drop or aldehyde slip reaches the upper operating limit; published data for this specific catalyst configuration is limited for proprietary systems.
Distillation Train Configuration Controls Water and Propionaldehyde to High-Purity Grade Limits
The hydrogenated crude n-propanol is a multi-component mixture whose separation is governed by the behavior of the n-propanol-water minimum-boiling azeotrope and the wide boiling-point gap between propionaldehyde (48 °C) and n-propanol (97.1 °C). A typical two-column purification sequence begins with a lights column operated at 101.3 kPa to 130 kPa with a reflux ratio between 3:1 and 5:1, where propionaldehyde, methanol, ethane, and dissolved carbon monoxide are taken overhead and the n-propanol-water mixture is withdrawn as the bottom stream. The lights column is equipped with structured packing or high-efficiency trays, and the overhead condenser vent is routed to a thermal oxidizer with a destruction efficiency of at least 99.9%. The bottoms are then dehydrated in a product column or an azeotropic/extractive dehydration unit, because the n-propanol-water azeotrope at atmospheric pressure limits simple rectification to an alcohol-rich composition near 70–75 wt% n-propanol. In the dehydration column, the overhead temperature is held at approximately 87 °C to 88 °C at 101.3 kPa, and the decanter or molecular-sieve guard bed breaks the azeotrope by selective water absorption or pressure-swing adsorption. Water content in the dried n-propanol is measured by ASTM D1364 using Karl Fischer coulometric titration, and the product column is adjusted to keep water below 0.1 wt% for standard industrial grade and below 0.05 wt% for high-purity pharmaceutical-grade material. Residual propionaldehyde in the final product is controlled to less than 0.01 wt% by GC-FID because aldehyde carbonyl groups initiate imine formation with amine functional additives and contribute to color body formation in heat-aged formulations. The distillation train also removes heavier condensation products such as 2-methyl-1-pentanol and 2-methyl-3-pentanone, which arise from aldol condensation of propionaldehyde; these heavy ends are purged from the bottom of the product column at a rate calculated from the propionaldehyde concentration in the crude feed and the residence time at elevated temperature.
Quality Specifications and Test Methodology for Bulk Shipments
The certificate of analysis for bulk n-propanol is built around a small group of consensus test methods that detect purity, water, acidity, color, distillation range, non-volatile residue, and density. The table below summarizes typical acceptance limits for industrial and high-purity grades; reported values are traceable to the stated test methods and to NIST-traceable reference materials where available.
| Parameter | Industrial Grade | High-Purity / Pharmaceutical | Test Method |
|---|---|---|---|
| Purity by GC-FID | ≥99.0% | ≥99.9% | ASTM D7515 |
| Distillation range at 101.3 kPa | 96.0 °C to 98.0 °C | 96.5 °C to 97.5 °C | ASTM D1078 |
| Water content | ≤0.10 wt% | ≤0.05 wt% | ASTM D1364 |
| Acidity as propionic acid | ≤0.005 wt% | ≤0.003 wt% | ASTM D1613 |
| Color, Pt-Co scale | ≤10 APHA | ≤5 APHA | ASTM D1209 |
| Non-volatile residue | ≤0.001 wt% | ≤0.0005 wt% | ASTM D1353 |
| Density at 20 °C | 0.803–0.805 g/cm³ | 0.8035–0.8050 g/cm³ | ASTM D4052 |
Bulk storage terminals handling oxo-derived n-propanol in volumes above 10,000 L require fixed-roof tanks with nitrogen blanketing, pressure-vacuum vents, and continuous oxygen analyzers because the solvent is a flammable liquid with a closed-cup flash point of approximately 22 °C and lower flammable limit of 2.1 vol%. Tanks are constructed from 316L stainless steel or carbon steel with an inorganic zinc silicate lining; copper, brass, and zinc-containing alloys are excluded from wetted components because trace metal ions accelerate aldehyde oxidation and form colored carboxylate residues. Transfer pumps use mechanical seals with perfluoroelastomer or PTFE secondary containment, and the nitrogen blanket is maintained at an oxygen content below 2 vol% with a positive pressure of 5 kPa to 10 kPa. Loading and unloading of ISO tank containers into marine vessels follows NFPA 30 spacing criteria, and the vapor return line is connected through a dry-break coupling to reduce diffuse emissions below the concentration limits of the local permit. The material is hygroscopic; repeated opening of drums or day tanks at ambient relative humidity above 60% can raise water content by 0.02 wt% to 0.05 wt% per exposure event, so process users install desiccant breathers or closed-loop transfer. Field experience on drum filling lines indicates that static discharge during high-velocity pumping through filter housings can generate surface potentials above 25 kV; bonding and grounding verification with a resistance threshold below 10⁶ Ω and a flow velocity below 1 m/s in non-conductive piping are standard controls. n-Propanol is not classified as a peroxide-forming solvent under common laboratory safety guidance, but propionaldehyde impurity can undergo oxidative degradation to propionic acid; acid content is monitored by ASTM D1613 and is typically held below 0.005 wt% as propionic acid.
When n-Propanol Replaces Isopropanol in Flexographic Ink Formulations, Evaporation Rate and Polymer Solubility Require Rebalancing
In flexographic ink plants that replace isopropanol with n-propanol, the formulation change is not a one-for-one substitution because the two solvents differ in boiling point, evaporation rate, Hansen solubility parameters, and hydrogen-bonding capacity. Isopropanol boils at 82.4 °C at 101.3 kPa, while n-propanol boils at 97.1 °C; the lower volatility of n-propanol extends open time on the anilox roll and frequently requires a reduction in slow solvent add-back or an increase in dryer temperature of 5 °C to 10 °C to maintain the same print speed. The Hansen solubility parameters for n-propanol are dispersive 16.0 MPa⁰·⁵, polar 6.8 MPa⁰·⁵, and hydrogen-bonding 17.4 MPa⁰·⁵, compared with isopropanol values of dispersive 15.8 MPa⁰·⁵, polar 6.1 MPa⁰·⁵, and hydrogen-bonding 16.4 MPa⁰·⁵. The higher hydrogen-bonding component increases the solubility of nitrocellulose and polyamide resins in solvent blends, but it also raises the solution viscosity at equal solids content. Viscosity measurements by ASTM D1200 with a Ford cup must be carried out at 25 °C and corrected for density by ASTM D4052 because n-propanol is denser than isopropanol. Production-scale trials on central-impression flexographic presses with chambered doctor blades have shown that anilox cell release can be maintained when the n-propanol content is blended with n-propyl acetate in a ratio between 80:20 and 70:30, but published data for this specific configuration is limited because press speed, plate durometer, and substrate surface energy interact with evaporation rate. Formulators also monitor retained solvent profiles by headspace gas chromatography; retained solvent values above 0.5 mg/m² on printed film typically indicate insufficient dryer residence time or excessive film thickness.
Downstream conversion of high-purity n-propanol to n-propyl acetate, propylamines, and agricultural intermediates requires a consistently low carbonyl and water content because protic impurities interfere with catalyst bed activity and esterification equilibrium. In n-propyl acetate production, n-propanol is reacted with acetic acid in the presence of sulfuric acid or a sulfonic acid resin at reflux; the equilibrium is shifted by continuous removal of water as a ternary azeotrope, and the final ester is washed, neutralized, and rectified to a purity above 99.5 wt%. For propylamine synthesis, n-propanol and ammonia are fed over a nickel- or cobalt-based amination catalyst at temperatures between 180 °C and 220 °C and pressures between 1.0 MPa and 3.0 MPa; the selectivity to mono-, di-, and tripropylamine is adjusted through the ammonia-to-propanol molar ratio and the degree of recycle. Pharmaceutical users of n-propanol as a crystallization and extraction solvent apply the ICH Q3C residual solvent classification, which lists n-propanol as a Class 3 solvent with a permitted daily exposure of 50 mg/day, and residual solvent analysis is performed by headspace gas chromatography according to USP <467> or Ph. Eur. 2.4.24. The same high-purity grade is used in high-solids coatings and in electrolyte formulations where water above 0.05 wt% interferes with lithium salt stability; in these applications, the final package is dried with molecular sieves and shipped under 99.5% nitrogen.
Supplier qualification for global n-propanol contracts includes a documented quality management system under ISO 9001:2015 clause 8.4 for control of externally provided processes and products, and environmental compliance under ISO 14001:2015. Batch-to-batch variance on high-purity n-propanol from oxo units is influenced by catalyst age, distillation reflux ratio, and storage tank heel management; production-scale data from integrated oxo-alcohol sites indicate that water content can drift by 0.01 wt% to 0.03 wt% as distillation column reboiler fouling increases over a run length of 12 to 24 months. When pharmaceutical-grade material is required, additional testing includes UV absorbance at 220 nm, 250 nm, and 275 nm against a water blank, and elemental impurities by ICP-MS according to USP <232> and USP <233> limits. Incompatibilities include strong oxidizing agents, acid anhydrides, and alkali metals; contact with aluminum metal should be avoided in closed systems where alkoxide formation and hydrogen evolution may occur.
