Caustic Soda Supplier for Oil Refineries — Flakes, Pearls and Liquid from the UAE and Türkiye
Caustic soda in oil refining is sodium hydroxide (NaOH) used to strip acidic contaminants out of hydrocarbon streams: H₂S, mercaptans, phenols, naphthenic acids and acid carry-over. SUHA International Trading is a caustic soda export supplier to the petroleum industry, supplying refinery buyers, refinery chemical contractors, distributors and importers with caustic soda (sodium hydroxide) as 98% flakes, 99% pearls and liquid soda lye, loaded from our two origins at Jebel Ali (UAE) and Mersin (Türkiye).
Technical content and supply terms last reviewed by the SUHA International export desk.
What Is Caustic Soda Used for in Oil Refining?
In short — in oil refining, caustic soda is the main alkali for hydrocarbon treatment. Refineries use it to sweeten LPG and naphtha, scrub H₂S from gas streams, reduce chloride corrosion in the crude distillation unit, wash naphthenic acids and phenols out of distillates, neutralise acid carry-over from alkylation, free fixed ammonia in sour water strippers and adjust wastewater pH. It does this by reacting with acidic contaminants to form water-soluble sodium salts that leave with the aqueous phase.
What caustic treating does not do is remove total sulfur to ultra-low levels; that is the job of hydrotreating. Understanding that split, and where each caustic stream ends up as spent caustic, is what separates a well-run treating section from one that burns chemical and money. This guide covers the uses of caustic soda in oil refining unit by unit, the chemistry behind each one, spent caustic handling, safety, and what procurement teams should specify when they buy sodium hydroxide for petroleum refining.
- Chemical name
- Sodium hydroxide (NaOH)
- CAS number
- 1310-73-2
- HS code
- 2815.11 solid · 2815.12 solution
- UN number
- 1823 solid · 1824 solution
- Transport class
- IMDG Class 8, Packing Group II
- Forms supplied
- Flakes 98%, pearls 99%, liquid 32–50%
- Molar mass
- 39.997 g/mol
- Minimum order
- 1 FCL
- Loading ports
- Jebel Ali (UAE), Mersin (Türkiye)
What Does Caustic Soda Remove from Petroleum?
Crude oil and the streams made from it carry acidic compounds that corrode equipment, poison catalysts, cause odour and push products off specification. The role of sodium hydroxide in oil refining is to react with these acidic compounds and carry them out of the hydrocarbon as water-soluble sodium salts.
| Contaminant | Where it is found | Reaction with NaOH |
|---|---|---|
| Hydrogen sulfide, H₂S | Fuel gas, LPG, light naphtha, flare gas | H₂S + NaOH → NaHS + H₂O; with excess NaOH, NaHS + NaOH → Na₂S + H₂O |
| Mercaptans, RSH | LPG, naphtha, kerosene, FCC gasoline | RSH + NaOH ⇌ RSNa + H₂O |
| Naphthenic acids, RCOOH | Kerosene, jet, diesel from high-TAN crudes | RCOOH + NaOH → RCOONa + H₂O |
| Phenols and cresols | FCC and coker gasoline | ArOH + NaOH → ArONa + H₂O |
| Hydrogen chloride, HCl | Crude unit overhead, from hydrolysed MgCl₂ and CaCl₂ | Chlorides converted to stable NaCl before distillation |
| Carbon dioxide, CO₂ | Gas and LPG streams | CO₂ + 2 NaOH → Na₂CO₃ + H₂O (consumes caustic) |
| Sulfur dioxide, SO₂ | FCC regenerator and heater flue gas | SO₂ + 2 NaOH → Na₂SO₃ + H₂O in wet gas scrubbers |
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How Caustic Soda Is Used in Petroleum Refining
The applications of caustic soda in oil refining run from the crude unit to the wastewater plant. Each one below explains which stream is treated, what the caustic reacts with, and whether the caustic is consumed or regenerated.
1. Caustic soda for mercaptan removal: LPG, light naphtha and extraction Merox
Light streams are treated in two steps. A caustic prewash removes H₂S first, because H₂S would otherwise use up the treating caustic and foul the catalyst. The stream then goes to extraction Merox, where caustic extracts light mercaptans as sodium mercaptides. The mercaptide-rich caustic is oxidised with air over a cobalt phthalocyanine catalyst, which converts the mercaptides to disulfide oil and regenerates the caustic so it circulates back to the extractor:
The disulfide oil is separated and routed away from the treated LPG. This is the one major refinery caustic service where the sodium hydroxide is largely recovered rather than consumed.
2. Kerosene and jet fuel: sweetening Merox
Heavier mercaptans in kerosene and jet fuel do not extract well into caustic. In sweetening Merox they are oxidised in place to disulfides in an alkaline environment, usually over a fixed catalyst bed wetted with caustic, after a caustic prewash for H₂S and naphthenic acids:
Sweetening does not lower total sulfur. The disulfides stay in the fuel. Sweetening fixes odour, corrosivity, copper strip and doctor test results; the total sulfur limit is met upstream by hydrotreating.
3. Caustic soda for acid gas removal: H₂S scrubbing
Caustic scrubbers polish fuel gas, flare recovery gas and small off-gas streams after amine treating, or treat small streams where an amine unit is not justified. Caustic reaches very low residual H₂S with simple equipment, but in this service it is non-regenerative: every tonne of H₂S removed consumes caustic and becomes sulfidic spent caustic. Any CO₂ in the gas also consumes caustic by forming sodium carbonate, which is often the largest hidden cost in a caustic scrubber.
4. Crude distillation unit: chloride corrosion control
Magnesium and calcium chlorides that survive the desalter hydrolyse when the crude is heated, magnesium chloride from about 120 °C and calcium chloride to a much smaller extent, releasing HCl into the overhead system:
A small, controlled injection of dilute caustic into the desalted crude converts part of these chlorides to sodium chloride, which does not hydrolyse under distillation conditions, so less HCl reaches the overhead. Overhead pH itself is controlled separately, with neutralising amines or ammonia and wash water injected into the overhead line.
Injection is kept low because the sodium goes to the atmospheric and vacuum residue. Too much sodium poisons FCC, resid FCC and hydrocracking catalysts, increases furnace and exchanger fouling and harms coke quality. Hot concentrated caustic can also cause caustic stress corrosion cracking of carbon steel at the injection point, so injection points are designed with quills, dilution and inspection in mind.
5. Naphthenic acid removal from distillates
Naphthenic acids are measured as Total Acid Number (TAN, mg KOH/g); crudes above about 0.5 are generally treated as high-TAN, and naphthenic acid corrosion is most severe roughly between 220 and 400 °C. At whole-crude level refineries manage high-TAN crude mainly by blending, upgraded metallurgy and corrosion inhibitors rather than caustic, because sodium naphthenates form emulsions and carry sodium into the residue. Where caustic is used routinely is caustic washing of kerosene, jet and diesel to bring the acidity of the finished distillate within specification, producing naphthenic spent caustic.
6. FCC and coker gasoline treating
Cracked gasolines contain H₂S, mercaptans, phenols and cresols. Caustic treating removes them to improve odour, colour and oxidation stability, and the spent caustic from this service is cresylic (phenolic). Cresylic acids can be recovered from it by acid neutralisation and sold.
7. Alkylation units
In sulfuric acid alkylation, the reactor effluent carries traces of acid and acid esters that are neutralised in a caustic wash followed by a water wash. Hydrofluoric acid alkylation units use caustic or potassium hydroxide scrubbing to neutralise acid-bearing vent and relief streams.
8. Sour water strippers
Sour water contains ammonia bound as ammonium salts that steam stripping alone cannot release. Caustic is added to the stripper, typically in the lower section, to raise pH and free this fixed ammonia so it strips out. Raising pH has the opposite effect on H₂S, so caustic addition is placed where the H₂S has already been stripped.
9. Flue gas and wastewater
Wet gas scrubbers on FCC regenerator and heater flue gas use caustic to absorb SO₂ and particulates. In the wastewater plant, caustic adjusts pH ahead of biological treatment and precipitates dissolved metals as hydroxides.
| Unit or service | Main target | Caustic consumed or regenerated | Spent caustic type |
|---|---|---|---|
| Caustic prewash | H₂S | Consumed | Sulfidic |
| Extraction Merox (LPG, naphtha) | Light mercaptans | Mostly regenerated | Small sulfidic purge |
| Sweetening Merox (kerosene, jet) | Mercaptans to disulfides | Slow consumption | Naphthenic and sulfidic |
| Gas scrubbers | H₂S, CO₂ | Consumed | Sulfidic, carbonate |
| Crude unit injection | Chloride hydrolysis | Consumed, very low rate | None; sodium goes to residue |
| Distillate caustic wash | Naphthenic acids | Consumed | Naphthenic |
| FCC gasoline treating | Phenols, mercaptans | Consumed | Cresylic |
| Alkylation effluent wash | Acid carry-over | Consumed | Neutral salts |
| Sour water stripper | Fixed ammonia | Consumed | Leaves with stripped water |
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Is Caustic Soda Used to Remove Sulfur from Petroleum?
Partly. Caustic soda for sulfur removal works on H₂S and light mercaptans, which it extracts, but not on the thiophenes and heavier sulfur compounds that make up most of the sulfur in fuels. Modern fuel specifications set total sulfur at levels that only hydrotreating can reach. Caustic treating is still needed alongside it, for the streams and properties hydrotreating does not address: LPG, H₂S in gas, mercaptan odour and corrosivity.
| Regulation | Region | Sulfur limit |
|---|---|---|
| EPA Tier 3 | United States | 10 ppm gasoline, annual average |
| Fuel Quality Directive 2009/30/EC (EN 228, EN 590) | European Union | 10 ppm gasoline and diesel |
| Bharat Stage VI | India | 10 ppm |
| China VI | China | 10 ppm |
| IMO 2020 (MARPOL Annex VI) | Global marine fuel | 0.50% m/m; 0.10% m/m inside Emission Control Areas |
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Spent Caustic: Types and Treatment
Every tonne of caustic soda in oil refining that is not regenerated leaves the unit as spent caustic, one of the most difficult refinery effluents: strongly alkaline, high in COD and, when sulfidic, odorous and toxic. How it is segregated at source decides which treatment options are open.
| Type | Main contaminants | Typical source | Common handling |
|---|---|---|---|
| Sulfidic | NaHS, Na₂S, mercaptides | Caustic prewash, gas scrubbers, LPG treating | Wet air oxidation; sale to kraft pulp mills where quality allows |
| Cresylic (phenolic) | Sodium phenolates and cresylates | FCC and coker gasoline treating | Acid neutralisation to recover cresylic acids; wet air oxidation |
| Naphthenic | Sodium naphthenates | Kerosene, jet and diesel washing | Acid springing to recover naphthenic acids; wet air oxidation |
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Treatment technologies
Wet air oxidation (WAO) is the most widely used treatment. It oxidises sulfides with air at elevated temperature and pressure; low-temperature units mainly convert sulfide to thiosulfate, while higher-temperature units carry the oxidation through to sulfate and also destroy much of the organic load:
Neutralisation and acid springing lowers pH to release H₂S (sent to the sulfur recovery unit) and to separate cresylic or naphthenic acids as saleable oils. Biological treatment can follow oxidation or dilution. Reuse of suitable sulfidic spent caustic as sodium make-up in kraft pulp mills turns a waste into a by-product. Under US RCRA, spent caustic is typically corrosive waste (D002) and sulfidic spent caustic may also be reactive (D003).
Sulfidic spent caustic is chemically related to sodium sulfide, which is why some grades can replace purchased sulfide in pulping and mineral processing.
Caustic Soda vs Alternative Treating Chemicals
| Chemical | Typical refinery use | Strength vs NaOH | Limitation |
|---|---|---|---|
| Amines: MEA, DEA, MDEA | Bulk H₂S and CO₂ removal | Regenerated, low chemical consumption | Higher capital cost; does not reach the lowest residual H₂S alone |
| Neutralising amines | Crude unit overhead pH control | Volatile, protects the condensing zone | Can form amine hydrochloride salts if misapplied |
| Potassium hydroxide, KOH | HF alkylation, specialty treating | Potassium salts more soluble | Considerably more expensive per unit of alkalinity |
| Soda ash, Na₂CO₃ | Mild neutralisation, some scrubbers | Easier to handle, not corrosive-class | Too weak for mercaptan extraction |
| Solid H₂S scavengers | Small fixed-bed gas polishing | No liquid effluent | Non-regenerable, batch replacement |
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Caustic Soda Dilution Calculator
Refineries buy 50% liquid or 98% flakes and dilute them to the treater's design strength. Enter the batch you need; the calculator uses a mass balance and published density data for NaOH solutions at 20 °C.
How much caustic do I need?
Handling Caustic Soda in a Refinery
Sodium hydroxide is classified Skin Corr. 1A (H314), Eye Dam. 1 (H318) and Met. Corr. 1 (H290). Burns can be deep and painless at first, and eye contact can cause permanent damage. This is orientation only; the Safety Data Sheet supplied with every shipment governs.
Occupational exposure limits
| Body | Limit | Basis |
|---|---|---|
| OSHA PEL (United States) | 2 mg/m³ | 8-hour time-weighted average |
| NIOSH REL | 2 mg/m³ | Ceiling, not to be exceeded at any time |
| ACGIH TLV | 2 mg/m³ | Ceiling |
| NIOSH IDLH | 10 mg/m³ | Immediately dangerous to life or health |
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Storage of liquid caustic
50% caustic starts to crystallise at about 12 °C (54 °F), so tanks and lines are insulated and heat traced in cool climates, or the caustic is held at a lower strength. Carbon steel is the usual tank material at ambient temperature; at elevated temperature carbon steel is susceptible to caustic stress corrosion cracking, so hot service, steam-traced lines and welds are designed with post-weld heat treatment or upgraded to nickel alloys. Warehouse practice for solid caustic is covered in our guide on how to store caustic soda safely.
Caustic Soda in Edible (Vegetable) Oil Refining
"Oil refining" also means refining vegetable oils and fats, a separate industry that is a large caustic soda user. In chemical (alkali) refining, caustic soda neutralises the free fatty acids in crude oil, turning them into sodium soaps called soapstock that are removed by centrifugal separators before the oil is bleached and deodorised. Soapstock is then split with acid to recover fatty acids or used in soap making. Oils refined physically remove free fatty acids by distillation instead and use little or no caustic.
Edible oil refiners buy food-grade sodium hydroxide; see our page on caustic soda in food production for grade requirements.
Caustic Soda Supplier for Oil Refineries
As a caustic soda supplier for the petroleum industry, SUHA International Trading supplies bulk caustic soda for refinery use to refinery purchasing departments, refinery chemical contractors, distributors and importers. Every use of caustic soda in oil refining described above depends on product that arrives on specification and on time. Liquid caustic suits sites with tankage close to a port; flakes and pearls suit remote refineries and container imports, because solid caustic carries far more NaOH per container than liquid.
Liquid caustic soda for refineries
32% and 50% soda lye, ready to dilute with no dissolving step. The standard form for refineries with bulk tankage near the discharge port.
32–50% NaOH Liquid caustic soda specificationCaustic soda flakes for oil refining
98% NaOH, the lowest freight cost per tonne of NaOH for container imports. Dissolved on site to treater strength.
98% NaOH Caustic soda flakes specificationCaustic soda pearls for oil refining
Caustic soda 99% for refinery use: free-flowing, low dust, for automated dissolving systems and tighter impurity limits.
99% NaOH Caustic soda pearls specificationWhy refinery buyers work with SUHA
What refinery buyers should specify
Assay alone is not enough. Chloride and chlorate matter for stainless steel corrosion, iron for colour and fouling, carbonate for freshness and wasted alkalinity, and mercury where the refinery's permit or catalyst supplier restricts it. Ask for these limits in the contract and a batch certificate of analysis for each lot; our guide on how to check caustic soda quality explains which COA figures matter.
| Parameter | Typical result | Why a refinery cares |
|---|---|---|
| NaOH (assay) | 98 ± 1% | Sets dilution ratio and cost per tonne of alkalinity |
| Na₂CO₃ (carbonate) | 0.43% | Carbonate adds no treating capacity |
| NaCl (chloride) | 0.0085% | Chloride drives stainless steel pitting and SCC |
| Fe (iron) | 10 ppm | Colour and fouling in treated products |
| Heavy metals (as Pb) | max 2 ppm | Catalyst and effluent limits |
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Packing, loading and export terms
| Item | Detail |
|---|---|
| Minimum order | 1 FCL (one full container load) |
| Solid packing | 25 kg or 50 kg PP bags with PE liner; 1,000–1,250 kg lined jumbo bags |
| Liquid packing | IBCs, HDPE drums or ISO tanks, confirmed with the quotation |
| Loading ports | Jebel Ali (UAE) and Mersin (Türkiye) |
| Incoterms | FOB Jebel Ali or FOB Mersin; CFR or CIF to your port on request |
| Documents | Commercial invoice, packing list, bill of lading, certificate of origin, batch COA, TDS, SDS, IMDG dangerous goods declaration; third-party inspection on request |
| Classification | UN 1823 solid / UN 1824 solution, Class 8, PG II; HS 2815.11 / 2815.12 |
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Caustic Soda Refinery Supplier for the Middle East, Africa and Beyond
As a caustic soda international supplier with loading points in the UAE and Türkiye, we match each refinery market to the origin with the shorter, cheaper freight route.
| Region | What refinery buyers usually take | Usual origin |
|---|---|---|
| Middle East and GCC | Flakes and pearls by container; liquid where tankage allows | Jebel Ali |
| East and West Africa | Flakes 98% by container for coastal and inland refineries | Jebel Ali or Mersin |
| North Africa and the Mediterranean | Flakes and pearls by container | Mersin |
| Türkiye, Black Sea and Central Asia | Flakes, pearls and liquid | Mersin |
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Buyers in the Gulf can use our caustic soda supplier UAE desk, African refineries and importers our caustic soda supplier Africa page, and buyers in Türkiye and the region our caustic soda supplier Turkey page.
Caustic Soda Price for Refineries and Minimum Order
Prices are quoted on request. Caustic soda re-prices with the chlor-alkali market, freight and form, so we quote against your enquiry. Send the grade, quantity, packing and destination port by WhatsApp on +971 50 720 9246 or by email to info@causticsodaco.com, and we reply with a dated FOB or CFR/CIF quotation.
Minimum order: 1 FCL. Repeat shipments, multi-container orders and annual supply schedules are quoted on request. For market context, see our caustic soda price and caustic soda flakes price pages.
| Driver | Effect on your landed cost |
|---|---|
| Form | Liquid looks cheaper per tonne of product but costs more per tonne of NaOH once freight on the water content is included |
| Chlor-alkali balance | Caustic is a co-product of chlorine, so chlorine and PVC demand move the caustic price |
| Impurity limits | Tighter chloride, chlorate, iron or mercury limits narrow the supply pool |
| Volume | Multi-container and contract volumes price better than a single FCL |
| Origin, freight and Incoterm | Jebel Ali versus Mersin, FOB versus CIF, and Class 8 freight acceptance on the route |
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How to Order Caustic Soda for a Refinery
| Line | Example |
|---|---|
| Form and grade | Caustic soda flakes 98%, or liquid 50% membrane grade |
| Quantity | 1 FCL, or annual volume for a supply schedule |
| Impurity limits | NaCl, NaClO₃, Fe, Na₂CO₃, Hg as required by the refinery |
| Packing | 25 kg bags, jumbo bags, IBC or ISO tank |
| Destination and Incoterm | FOB Jebel Ali, FOB Mersin, CFR or CIF your port |
| Documents | COA, SDS, DG declaration, origin, inspection |
| Shipment window | Required loading or arrival date |
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- Enquiry by WhatsApp or emailSend the lines above. You receive a dated quotation for your form, packing, port and Incoterm.
- DocumentsCurrent COA, TDS and SDS for the offered grade are sent with the quotation on request.
- Proforma invoiceIssued against the accepted quotation, fixing specification, packing, Incoterm, payment terms and shipment window.
- LoadingBatch allocated, COA issued, optional third-party inspection, container stuffed and sealed at Jebel Ali or Mersin.
- Documents and sailingInvoice, packing list, bill of lading, certificate of origin, COA, SDS and DG declaration released per the agreed payment terms.
Get a Price for Bulk Caustic Soda for Refinery Use
Send the form, quantity and destination port. We reply with a dated FOB or CFR/CIF quotation, packing options and a batch COA. Minimum order 1 FCL.
Caustic Soda in Oil Refining FAQ
What is caustic soda used for in oil refining?
What does caustic soda remove from petroleum?
Is caustic soda used for mercaptan removal?
What is caustic washing in a refinery?
How does the Merox process use caustic soda?
Is caustic soda used to remove sulfur from petroleum?
What is spent caustic?
How is spent caustic treated?
Why is caustic injected into crude oil before distillation?
What happens if too much caustic is injected into the crude unit?
Is caustic soda or amine better for H₂S removal?
What concentration of caustic soda is used in refineries?
Why does 50% caustic soda need heat tracing?
How is caustic soda used in edible oil refining?
Which caustic soda grade is used in oil refineries?
What is the OSHA exposure limit for sodium hydroxide?
Is caustic soda hazardous to ship?
How do I choose a caustic soda supplier for an oil refinery?
What is the minimum order and how do I get a price?
Ask for the Caustic Soda Price
Prices are sent by WhatsApp or email against your enquiry. A COA, TDS or SDS is supplied free of charge on request.
WhatsApp — fastest price reply+971 50 720 9246 ✉ Emailinfo@causticsodaco.com ☎ Phone+971 50 720 9246 📄 Enquiry formSend a full RFQ with specification and destination