N-Methylmorpholine CAS 109-02-4

What is N-Methylmorpholine?

N-Methylmorpholine is morpholine with a methyl group on the nitrogen — a tertiary cyclic amine containing a ring oxygen, C₅H₁₁NO. That single methyl group changes a great deal, and most of what makes NMM commercially distinct follows from it.

Having no N-H bond, it cannot be acylated or alkylated into a product, so it works as a catalyst and a base rather than as a building block. Just as importantly, it cannot form a nitrosamine — a growing consideration in rubber, personal care and pharmaceutical work, and one that increasingly drives substitution away from secondary amines.

It is a clear, colourless liquid boiling at about 115 °C with a flash point near 13 °C and complete miscibility with water. The ring oxygen keeps it a relatively weak base, with a conjugate acid pK_a around 7.4, and it is notably less pungent than triethylamine — a practical advantage in a plant that most chemists notice immediately.

Commercially, NMM has two main markets and one quietly important one. It is a tertiary amine catalyst for polyurethane foam. It is a mild, low-odour acid scavenger used widely in pharmaceutical and peptide synthesis. And it is the precursor to N-methylmorpholine N-oxide, the direct solvent for cellulose that makes Lyocell fibre possible.

Why N-methylmorpholine specifically

• No N-H, so no nitrosamine. As a tertiary amine it cannot form a nitrosamine, which is increasingly the reason formulators move to it from morpholine or other secondary amines.
• Mild base, low odour. Weaker than triethylamine and markedly less pungent, which makes it the civilised choice for an acid scavenger in a plant where people have to work.
• Soluble hydrochloride. Its hydrochloride salt is more water-soluble than triethylamine hydrochloride, which changes the work-up — sometimes helpfully, sometimes not, but always deliberately.
• The route to NMMO. Oxidised to N-methylmorpholine N-oxide, the only commercially viable direct solvent for cellulose and the basis of the Lyocell fibre process.

How NMM is Manufactured

N-Methylmorpholine is made by methylating morpholine. The route is straightforward, and what varies between producers is how cleanly the methylation runs and how much unconverted morpholine is left.

• Methylation. Morpholine is methylated, most commonly with methanol over a catalyst at elevated temperature, or by reductive methylation with formaldehyde and hydrogen. Both convert the secondary amine to the tertiary one in a single operation.
• Conversion control. Because the starting material and the product are both amines with similar boiling points, pushing conversion high is more economical than separating a poorly converted mixture. Conversion is therefore where producers differ.
• Separation. The crude product is resolved by fractional distillation. Residual morpholine is the impurity of record, and the water azeotrope means drying is a distinct step.
• Finishing. The product is dried to specification and filled into drums, IBCs or tanks, with nitrogen blanketing where colour and water matter. Pharmaceutical and NMMO-feedstock grades receive tighter control.

Typical Commercial Specification

Figures below are representative of standard commercial grade. Pharmaceutical grades and NMMO-feedstock grades with tighter morpholine, water and metals limits are available — send us the specification you work to and we will quote against it.

Physical & Chemical Properties

Reactivity in practice

With no N-H bond, NMM acts on reactions rather than joining them. Four roles cover nearly all of its use:

• Polyurethane catalysis. As a tertiary amine it catalyses the isocyanate-polyol reaction, with a balance between gelling and blowing that suits flexible and rigid foam systems.
• Acid scavenging. Neutralises hydrogen chloride released in acylation, sulphonylation and mixed-anhydride coupling, with lower odour and milder basicity than triethylamine.
• Oxidation to the N-oxide. Oxidised with hydrogen peroxide to N-methylmorpholine N-oxide, the direct cellulose solvent behind Lyocell fibre.
• Quaternisation and salt formation. Alkylates to quaternary ammonium salts; forms salts with acids that are notably more water-soluble than the corresponding triethylamine salts.

N-Methylmorpholine vs Morpholine, Piperidine and Piperazine

The saturated six-membered nitrogen heterocycles are easy to confuse and behave quite differently. What separates them is what else is in the ring: a second nitrogen makes the molecule difunctional and solid, an oxygen pulls electron density away and weakens the base, and methylating the nitrogen removes the N-H altogether.

Stated plainly: piperidine is the strongest base of the four and the most nucleophilic; piperazine is the only difunctional one and the only solid; morpholine's ring oxygen makes it roughly a thousand times less basic than piperidine, which is exactly why it works as a mild neutralising amine; and N-methylmorpholine, having no N-H at all, acts as a catalyst and base rather than a building block — and cannot form a nitrosamine, which matters increasingly in rubber and personal care. They substitute for one another only rarely.

Industries We Supply NMM To

The same molecule leaves our warehouse for very different factories. What changes between them is not the CAS number but the grade — particularly residual morpholine and water — and the documentation each sector expects.

Where NMM is Used

NMM splits between bulk catalyst use and high-value synthesis use. These are the end uses our customers buy it for, roughly in order of volume.

As a polyurethane catalyst

Tertiary amines catalyse the reaction between isocyanate and polyol, and the choice of amine controls the balance between the gelling reaction that builds polymer and the blowing reaction that generates gas. NMM sits in a useful part of that space and is used in flexible slabstock, moulded and rigid foam catalyst packages, often in blends. Its relatively low odour compared with the alkyl amines is a genuine advantage in a foam plant and in the finished article.

As a mild acid scavenger

In acylation and sulphonylation the liberated hydrogen chloride has to be neutralised, and triethylamine is the default. NMM is chosen instead where its milder basicity avoids side reactions, where its lower odour matters, or where the greater water solubility of its hydrochloride salt simplifies the work-up. It is particularly established in peptide chemistry, where mixed-anhydride and active-ester couplings are sensitive to base strength and a stronger base promotes racemisation at the activated centre.

In Lyocell fibre production

This is the quietly important application. Cellulose is extremely difficult to dissolve without chemically derivatising it, which is why the viscose process exists and why it is so chemically intensive. N-methylmorpholine N-oxide — made by oxidising NMM with hydrogen peroxide — dissolves cellulose directly, allowing fibre to be spun from solution and the solvent to be recovered and recycled at very high rates. That makes NMM the upstream feedstock for the whole Lyocell fibre industry. Feedstock grades are specified tightly on morpholine, metals and peroxide behaviour, because the oxidation step and the solvent recycle loop are both sensitive.

As a nitrosamine-free alternative

Increasingly, NMM is specified not for what it does but for what it cannot do. Having no N-H bond, it cannot be nitrosated, so formulators facing nitrosamine limits in rubber, personal care or pharmaceutical products move to it from morpholine and other secondary amines. Where that is the reason for the switch, residual morpholine in the NMM is the specification that actually matters — carry-over of the starting material reintroduces precisely the liability being designed out.

Quality Control & Testing

Every lot is released against a batch-specific Certificate of Analysis. The methods behind the numbers are standard across the industry, and we are happy to share them or to work to your own in-house test protocol.

• Assay and residual morpholine — gas chromatography. The morpholine figure should be reported explicitly on the batch certificate, since it is the specification most customers actually care about.
• Water content — Karl Fischer titration, which matters in acid-chloride chemistry and in NMMO manufacture.
• Colour — APHA / Hazen against a standard. Colour drift signals air ingress, peroxide formation or metal contamination.
• Peroxide value — relevant for NMMO feedstock and for long-stored material, since amines with ether oxygens can form peroxides on prolonged air exposure.
• Distillation range — a fast, revealing check for morpholine and moisture carry-over.
• Metals and residue — iron and evaporation residue, both of which matter in pharmaceutical and NMMO service.

Common Process Problems & Likely Causes

When N-methylmorpholine misbehaves in a plant, the cause is usually one of a short list of things. This table is the shortcut our technical desk works through before anyone opens a complaint file.

Packaging, Storage & Shipping

• Standard packing. 180 kg net in lined steel or HDPE drums, with 1000 L IBCs for larger users.
• Bulk packing. Road tankers and ISO tank containers for foam system houses and fibre producers.
• Inert blanketing. Nitrogen-blanketed at fill where colour, water or peroxide behaviour matters — particularly for NMMO feedstock.
• Storage. Cool, dry, well-ventilated and bunded area away from heat, ignition sources, oxidisers and acids, with containers kept tightly closed.
• Materials of construction. Stainless steel, carbon steel or suitable lined vessels. Avoid copper, brass, bronze, aluminium and mercury, all of which are attacked by amines.
• Shelf life. Typically 12 months in unopened original packing under those conditions. Beyond that, re-test rather than assume.
• Peroxide awareness. Like other amines containing an ether oxygen, NMM can form peroxides on prolonged exposure to air. Keep containers closed and blanketed, rotate stock, and check peroxide value on long-stored material rather than assuming it is unchanged.
• Fire precautions. The flash point is near 13 °C, so the vapour space above the liquid is in the flammable range at ordinary room temperature. Bonding, earthing and explosion-proof fittings, and the storage area zoned accordingly.
• Transport classification. UN 2535, 4-Methylmorpholine, Class 3 flammable liquid with subsidiary risk 8 corrosive, Packing Group II — shipped with full dangerous-goods documentation.

Hazards & Safe Handling

N-Methylmorpholine is highly flammable and corrosive, and must be handled by trained personnel under a proper risk assessment. The classifications below are indicative — the current SDS supplied with your consignment is the governing document.

• Exposure control. Handle in a closed system or under local exhaust ventilation. The low flash point means the vapour space above the liquid is in the flammable range at ordinary temperature, and the lower odour relative to triethylamine means there is less warning of a leak, not less hazard.
• PPE. Chemical-resistant gloves, chemical goggles and face shield, chemical-resistant clothing, and respiratory protection suited to the task.
• Ignition control. Vapours are heavier than air, travel to a distant ignition source and flash back. Bonded, earthed and explosion-proof equipment, and no ignition sources in the zone.
• Peroxide formation. Containing an ether oxygen, NMM can form peroxides on prolonged air exposure. Do not distil material that has been stored open or for a long period without checking peroxide value first.
• Incompatibilities. Strong oxidising agents, strong acids, acid chlorides, isocyanates, and copper, brass, bronze and aluminium equipment.
• Spill response. Eliminate ignition sources and ventilate. Contain, absorb with inert non-combustible material and collect in a labelled closed container. Do not wash to drain.
• Fire. Highly flammable. Use alcohol-resistant foam, dry chemical or carbon dioxide; cool exposed containers with water spray. Decomposition releases nitrogen oxides — use self-contained breathing apparatus.
• First aid. Move to fresh air, remove contaminated clothing immediately, wash skin with plenty of water, flush eyes for at least 15 minutes, and seek medical attention with the SDS to hand.

Regulatory & Compliance Notes

N-Methylmorpholine is an established industrial chemical and is listed on the major national chemical inventories. Because obligations differ by territory, volume and use, the notes below are orientation rather than legal advice — confirm your own position with your regulatory adviser before importing.

• Inventory status. Listed on the principal chemical inventories in the major importing regions. Ask us for the inventory confirmation relevant to your destination country.
• Import registration. Several territories require the importer to hold a registration or notification before a consignment lands. Start that process early — it is the most common cause of delay at destination.
• Hazard communication. Supplied with an SDS compliant with the format applicable to your region, and labelled in line with the GHS classification for the product.
• Nitrosamine status. As a tertiary amine with no N-H bond, NMM cannot itself form a nitrosamine — which is frequently the reason it is specified. That advantage depends entirely on residual morpholine being controlled, so where a nitrosamine limit applies to your finished product, make the morpholine figure part of your incoming specification.
• Textile and fibre end use. Material destined for NMMO and Lyocell fibre production is bought against tighter feedstock specifications, and the fibre itself may carry its own certification requirements at destination. Flag the end use at enquiry.
• Dangerous goods. UN 2535, 4-Methylmorpholine, Class 3 with subsidiary risk 8, Packing Group II. Declarations prepared for IMDG (sea) or IATA (air) as appropriate to the mode.
• Workplace exposure. Occupational exposure limits apply in several jurisdictions. Note that the lower odour relative to other amines means smell is a poorer warning here — set controls against the limit, not the nose.

We Supply NMM Worldwide

Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship N-Methylmorpholine from India to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, dangerous-goods paperwork and freight so the material arrives ready to use.

• Incoterms. EXW, FOB, CIF, CFR and DAP quoted to suit your purchasing terms and freight arrangements.
• Ports. Regular shipments through Nhava Sheva (JNPT) and Mundra, with other Indian ports arranged where it suits the routing.
• Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and dangerous-goods declaration issued as a complete set.
• Flexible volumes. A single drum for laboratory qualification, through LCL consolidations, up to repeat full loads on a supply contract.
• Supply continuity. Because we are independent of any one producer, a plant turnaround or a shipping disruption at one source does not have to become your stock-out.

Buying NMM from Chelora

We are an independent sourcing and supply partner. For N-methylmorpholine that means establishing one thing before anything else: whether you are buying it as a catalyst, as a mild base, as NMMO feedstock, or specifically to avoid a nitrosamine — because the last answer makes residual morpholine the governing specification.

• Documentation on every lot. Batch-specific COA including residual morpholine, current SDS and TDS with the consignment.
• Samples before commitment. Trial quantities for process qualification ahead of a commercial order.
• Quantities. From a single 180 kg drum through to tank loads and ongoing contract supply.
• Export experience. Dangerous-goods documentation, packing and labelling handled for sea and road freight to any destination.
• Technical support. Direct access to people who know the chemistry, for questions on morpholine limits, peroxide behaviour or catalyst blending.
• Related intermediates. Morpholine, triethylamine, dimethylethanolamine, diethylethanolamine and the wider catalyst amine range from one supplier.

How ordering works

• Send the enquiry. Product, grade or specification, quantity, destination port and the Incoterm you buy on. If you have a spec sheet, attach it — it saves a round trip.
• We quote. Price, lead time, packing and a sample COA, normally within one working day.
• Sample and qualify. For first orders or critical applications, we send a trial quantity so your lab can sign off before you commit.
• Confirm the order. Proforma invoice issued; payment terms agreed against the volume and the relationship.
• Production and QC. Material allocated and released against a batch-specific COA, with a pre-shipment sample where the application calls for it.
• Ship and document. Packed, labelled and loaded with the full export and dangerous-goods document set, and tracked through to arrival.

Related Catalyst & Heterocyclic Amines

Buyers of N-methylmorpholine usually source several of these alongside it. Consolidating them on one order cuts freight cost and gives you a single point of contact for documentation.