Section
| HS Code | 487372 |
| Product Name | Succinic Acid |
| Iupac Name | Butanedioic acid |
| Molecular Formula | C4H6O4 |
| Molecular Weight | 118.09 g/mol |
| Cas Number | 110-15-6 |
| Ec Number | 203-740-4 |
| Appearance | White crystalline solid |
| Odor | Odorless |
| Melting Point | 184-186 °C |
| Boiling Point | 235 °C |
| Density | 1.56 g/cm³ at 20 °C |
| Solubility In Water | 58 g/L at 20 °C |
| Pka1 | 4.21 |
| Pka2 | 5.64 |
| Chemical Class | Dicarboxylic acid |
| Synonyms | Butanedioic acid; Amber acid |
As an accredited Succinic Acid factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Succinic Acid is packaged in 25 kg net polyethylene-lined multiwall paper bags, sealed to protect against moisture and contamination. |
| Container Loading (20′ FCL) | Succinic Acid is loaded in a 20-foot FCL container, palletized and secured under dry conditions for ocean freight. |
| Shipping | Succinic acid is typically shipped as a non-hazardous solid in moisture-resistant bags, fiber drums, or bulk sacks. Keep containers closed, dry, and protected from heat and moisture. No UN hazard class is normally assigned; follow the SDS and applicable transport regulations. |
| Storage | Store Succinic Acid in a cool, dry, well-ventilated, secure area away from heat, ignition sources, and direct sunlight. Keep containers tightly closed to prevent moisture absorption and contamination. Segregate from strong oxidizers, bases, and incompatible materials. Avoid dust generation, use secondary containment where appropriate, and maintain clear labeling. Follow local chemical storage regulations and inspect containers regularly. |
| Shelf Life | Succinic acid typically has a shelf life of about two years when kept dry, tightly sealed, and stored in a cool place. |
In the melt polycondensation train preceding polybutylene succinate pelletization, succinic acid is charged into a jacketed esterification vessel together with 1,4-butanediol at a molar feed ratio typically maintained between 1:1.05 and 1:1.20 to compensate for diol losses in the distillation overheads. The esterification stage is held at 170–210 °C under atmospheric or slightly reduced pressure while water is removed through a packed column, followed by polycondensation at 230–250 °C and pressures below 0.5 kPa to shift equilibrium toward high molecular weight. Industry compliance for compostable end articles made from the resulting polybutylene succinate resin is assessed under EN 13432:2000 or ASTM D6400-23, with aerobic biodegradation testing performed according to ISO 14855-1:2012. Food-contact grades additionally require verification against Commission Regulation (EU) No 10/2011 Annex I Table 1 migration limits before commercialization in the EU. Downstream conversion of succinic acid-based polybutylene succinate into finished goods involves twin-screw compounding at barrel temperatures of 150–180 °C, moisture content held below 200 ppm prior to extrusion, and subsequent blown film extrusion or injection molding on 30:1 to 40:1 L/D screw configurations. Terminal products derived from this route include agricultural mulch films, compostable shopping bags, thermoformed trays, and injection-molded cutlery. Published data for the melt strength and die pressure profile of succinic acid-based polybutylene succinate grades on specific twin-screw lines is limited, so compounding trials should be performed with a torque-controlled extruder to establish the allowable processing window for each machine configuration.
In beverage concentrate formulation, succinic acid functions primarily as a dibasic acidulant; its pKa values of 4.21 and 5.64 create a buffering plateau that differs from citric acid and suppresses sourness without requiring sodium citrate buffering salts. Compliance for this food-use application is governed in the United States by FDA 21 CFR 184.1091, which lists succinic acid as a generally recognized as safe substance, and in the European Union by Commission Regulation (EU) No 1129/2011 Annex II Part B where it is designated E 363 for permitted food additive use; finished beverage bottlers additionally require FCC grade assay of at least 99.5% and heavy metal limits per the current Food Chemicals Codex monograph. Formula addition in beverage syrups is typically kept between 0.05 wt% and 0.20 wt% of finished concentrate, because higher levels depress pH below 3.10 and alter the dissociation equilibrium of preservatives such as benzoic acid. The downstream production process is integrated into hot or cold batching systems: succinic acid is dissolved in deionized water at 15–25 °C, blended with citric acid or malic acid in a high-shear mixer, and the syrup is then flash pasteurized at 90–95 °C for 15–30 s before dilution and carbonation for cold-fill lines. Finished product types include electrolyte-reduced sports drinks, dry-mix beverage powders, and fermented fruit-flavored refreshments where succinic acid contributes a slightly umami saline note rather than the sharp finish of citric acid. Published data for the specific taste threshold of succinic acid in carbonated matrices remain limited, and sensory panels must be calibrated for each flavor system before commercial formula lock.
Succinic acid-derived esters—predominantly di-n-butyl succinate, diisobutyl succinate, and oligomeric succinate esters—are evaluated in flexible polyvinyl chloride as secondary plasticizers and viscosity depressants, but their low molecular weight relative to diisononyl phthalate or dioctyl terephthalate limits use in applications requiring low volatility. Regulatory data requirements for these compounds in industrial polymer compounding include REACH registration dossiers under EC No 1907/2006 and, where food contact is contemplated, the substance-specific migration limits of Commission Regulation (EU) No 10/2011 Annex I Table 1; in the United States, 21 CFR 178.3740 applies to plasticizer adjuvants in polymeric food-contact articles when the ester identity falls within the specified scope. Addition levels for succinate esters in PVC dry blends are generally confined to 5–20 phr when used as a secondary plasticizer; higher loadings increase melt flow but reduce Shore A hardness below 60 and raise volatile loss measured by ASTM D1203. The downstream production process uses a heated ribbon blender or Henschel mixer at 80–110 °C to absorb the ester into PVC resin, followed by twin-screw extrusion at 150–170 °C and pelletization; extruder vent vacuum is held above -0.08 MPa to strip residual water and low-boiling fractions from the melt. Terminal products include calendered PVC foils, flexible hoses, and decorative edge banding, but not high-temperature under-hood components where plasticizer volatility would exceed service limits. Published data for specific succinate ester compatibility with epoxidized soybean oil co-stabilizers in PVC at processing temperatures above 180 °C is limited, and migration testing under ISO 177:2016 is recommended before substitution in regulated food-contact compounds.
In high-solids alkyd systems, succinic acid is introduced as a renewable dibasic acid modifier at molar substitution levels of 10–25 mol% of the total polyacid fraction; the lower aromatic content reduces resin viscosity at a given solids level, but excessive substitution above 25 mol% degrades crosslink density and final film hardness due to the absence of the rigid phthalate ring. Applicable compliance testing for industrial baking enamels includes ASTM D4366 for pendulum hardness, ASTM D1640 for drying times at ambient or forced-air conditions, and ISO 4628-1:2016 for defect assessment after accelerated weathering; where the cured film contacts food, FDA 21 CFR 175.300 governs resinous and polymeric coatings and requires extraction testing with food-simulating solvents under the prescribed time-temperature conditions. The downstream production of succinic acid-modified alkyd resins is executed in a stainless steel reactor equipped with a distillation column and vacuum system, typically charged with tall oil fatty acids, glycerol or pentaerythritol, and succinic acid, then processed at 220–250 °C until the acid value falls below 10 mg KOH/g; xylene or azeotropic solvent is used to remove water of esterification. Terminal product types include direct-to-metal industrial primers, high-solids air-drying topcoats for machinery, and non-food metal furniture enamels; formulations intended for food-can internal linings additionally require confirmation of succinic acid migration under Commission Regulation (EU) No 10/2011 Annex I Table 1. Published comparative data for succinic acid-modified alkyds on continuous coil coating lines is limited, requiring pilot-scale cure response evaluations before commercial production.
Polyurethane polyester polyol synthesis from succinic acid and diethylene glycol uses a two-stage vacuum esterification protocol: succinic acid and excess glycol are first reacted at 180–200 °C under nitrogen until the acid number drops below 20 mg KOH/g, then the pressure is reduced to 1–3 kPa to drive oligomerization toward a hydroxyl number of 50–60 mg KOH/g. In this application, succinic acid content is defined by the ratio of dibasic acid to diol in the charge; succinic acid often constitutes 20–40 wt% of the total polyol solids to balance hardness and flexibility in the resulting polyurethane network. Regulatory compliance for polyols used in footwear and furniture foam includes REACH obligations under EC No 1907/2006 and residual monomer testing per customer specification, while polyurethane systems intended for food contact must follow Commission Regulation (EU) No 10/2011 Annex I Table 1 for migration of residual succinic acid and glycols. The downstream manufacturing process for these polyols includes charging succinic acid, diethylene glycol, and a tin(II) octoate catalyst at 0.01–0.05 wt% into a reactor, then preventing oxidation by sparging dry nitrogen at 0.2–0.4 m³/h; after endpoint verification, the polyester polyol is cooled and filtered through a 10 µm mesh before blending with isocyanate. Finished product types include flexible slabstock foam, rigid spray foam insulation, and cast elastomer components. Published data for specific load-bearing performance of succinic acid-based polyols in automotive seating foam is limited, so full-scale foam trials are required to determine indentation force deflection and resilience under production conditions.
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Succinic acid, systematically named butanedioic acid (CAS 110-15-6), is a linear saturated C4 dicarboxylic acid with the formula C4H6O4, a molar mass of 118.09 g mol−1, a density of 1.56 g cm−3 at 20 °C, and dissociation constants pKa1 = 4.21 and pKa2 = 5.64. The crystalline solid melts at 185–187 °C and begins to dehydrate to succinic anhydride near its boiling point of 235 °C; open melt processing is therefore maintained below 190 °C unless water removal is an intended reaction step. Aqueous solubility at 20 °C is approximately 58 g L−1, which separates it from fumaric acid and adipic acid in wet processes. Commercial production follows either hydrogenation of maleic anhydride to petrochemical grade or anaerobic fermentation of glucose-derived substrates; fermentation grade carries a biobased carbon fraction greater than 99% when measured by ASTM D6866-22. Product designations are specified by purity and particle morphology: SA-99 for industrial use, SA-99.5 for polymer synthesis, SA-BIO for fermentation-derived material, and SA-M50 for micronized lots with D50 below 50 µm by laser diffraction ISO 13320.
Polymer-grade material for poly(butylene succinate) and polyester polyol synthesis is controlled primarily for monobasic acid content, salt residue, iron, and moisture because esterification catalysts are sensitive to these species. Hydrogenation catalysts used in 1,4-butanediol production impose additional limits on sulfur-bearing species and alkali cations. The release profile below applies to SA-99.5 and SA-BIO lots produced under ISO 9001:2015 batch records.
| Assay, dry basis | Acid–base titration per USP/NF butanedioic acid monograph | ≥ 99.5% |
| Moisture | Karl Fischer titration, ASTM E203-24 | ≤ 0.5% |
| Melting range | USP <741>, ASTM E324-23 | 185.0–187.0 °C |
| Sulfated ash | USP <281> | ≤ 0.05% |
| Heavy metals | ICP-MS, USP <231> | ≤ 10 mg kg−1 |
| Arsenic | Atomic absorption, USP <211> | ≤ 3 mg kg−1 |
| Iron | Atomic absorption | ≤ 10 mg kg−1 |
| Chloride | USP <221> | ≤ 0.005% |
| Sulfate | Ion chromatography, ASTM D4327 | ≤ 0.01% |
| Bulk density | ASTM D1895-96 Method A | 0.70–0.90 g cm−3 |
| Particle size D50 | Laser diffraction, ISO 13320:2020 | 150–500 µm crystalline; 20–50 µm micronized |
| Biobased carbon | ASTM D6866-22 | ≥ 99% for fermentation grade only |
Conversion of succinic acid to 1,4-butanediol, tetrahydrofuran, and γ-butyrolactone uses fixed-bed catalytic hydrogenation over copper- or noble-metal-containing systems. The reaction is carried out in trickle-phase or slurry-phase reactors at 120–160 °C and hydrogen partial pressures of 5.0–8.0 MPa. The practical conversion ceiling is not thermodynamic but kinetic and poisoning-related. Fermentation-derived succinic acid contains sulfate, phosphate, sodium, potassium, calcium, magnesium, and protein-derived organic nitrogen. These residues deposit on catalyst pores and reduce liquid hourly space velocity stability. Plant-scale fixed-bed runs indicate that sulfate above 10 mg kg−1 in the feed shortens catalyst time on stream from months to weeks. Published data for this specific catalyst configuration is limited; however, tolling operators specify electrodialysis and recrystallization polishing to hold combined alkali and alkaline-earth cations below 10 mg kg−1 and sulfur-bearing species below 5 mg kg−1. Exotherm control requires staged hydrogen injection and inter-bed cooling because the heat of hydrogenation can produce localized temperatures above 220 °C; above this threshold, succinic acid undergoes decarboxylation and forms propionic acid and carbon dioxide, reducing hydrogen efficiency. Fixed-bed reactors with internal diameter to bed-length ratios of 1:8 to 1:15 are used to maintain plug-flow behaviour and prevent channelling. Downstream distillation of the crude 1,4-butanediol/tetrahydrofuran/γ-butyrolactone mixture requires an anhydrous recovery train because succinic acid and its monoesters are corrosive to carbon steel at 150 °C in the presence of trace mineral acids.
Direct polyesterification of succinic acid with 1,4-butanediol under titanium catalysis produces poly(butylene succinate), commonly designated PBS. The esterification stage is run at 180–210 °C with a glycol-to-diacid molar ratio of 1.10–1.30:1; tetrabutyl titanate is added at 100–200 mg kg−1 titanium relative to the acid. Water and tetrahydrofuran are removed through a partial condenser, and esterification progress is judged by top-column temperature and acid value rather than by fixed residence time. Polycondensation is carried out at 230–250 °C under mechanical vacuum below 100 Pa in a wiped-film or rotating-disc reactor. Target number-average molar mass is 4×10⁴ to 1.5×10⁵ g mol−1 by gel permeation chromatography against polystyrene standards, ISO 16014-3. The melt must be pre-dried to moisture below 200 mg kg−1 before injection molding; otherwise hydrolysis reduces molecular weight during plastication. In twin-screw compounding with starch or talc, screw L/D ratios of 40:1 to 48:1 and barrel temperatures of 160–200 °C are typical to limit thermal degradation. Film grades are processed on cast-film lines at melt temperatures of 190–210 °C; higher temperatures increase formation of tetrahydrofuran and other low-molar-mass decomposition products. The resulting PBS exhibits a melt flow index of 4–20 g/10 min at 190 °C/2.16 kg under ISO 1133-1:2022, tensile strength of 30–45 MPa under ISO 527-2, and elongation at break of 200–400%. These values place PBS between polypropylene and low-density polyethylene in ductility, but with ester-linkage susceptibility to hydrolysis in composting environments. Succinic acid-based PBS degrades measurably under controlled composting conditions in ISO 14855-1 respirometric testing, whereas adipic acid-based copolymers degrade faster due to lower crystallinity.
In polyurethane casting systems, succinic acid is pre-reacted with diethylene glycol, 1,3-propanediol, or diethylene glycol/propylene glycol blends at 180–220 °C using p-toluenesulfonic acid or tetrabutyl titanate to produce linear polyester polyols with hydroxyl values between 50 mg KOH g−1 and 150 mg KOH g−1 according to ASTM D4274. The esterification is continued until acid value falls below 1 mg KOH g−1 to prevent catalyst interference in the subsequent isocyanate reaction. These succinate polyols impart higher modulus to cast elastomers than adipate polyols of equivalent molecular weight; Shore hardness increases by 5–10 A as measured by ASTM D2240. Operationally, succinate polyols require preheating to 60–80 °C before metering because their viscosity at 25 °C ranges from 10 Pa·s to 40 Pa·s, compared with 3–8 Pa·s for equivalent adipate polyols.
As a C4 diacid, succinic acid yields polyols with higher ester-group density and lower free volume than adipic acid, which is a C6 diacid. In polyester polyols for polyurethane elastomers, the shift from adipic acid to succinic acid increases glass transition temperature by roughly 10–20 °C at equivalent molecular weight and raises low-shear viscosity as described above. In plasticizer esters, dibutyl succinate has a molar mass of 230.30 g mol−1, substantially lower than dioctyl adipate at 370.57 g mol−1; migration and volatility are therefore higher. Dialkyl succinates are selected for low-temperature flexibility in nitrile rubber where volatility is acceptable, but not for long-service PVC wire insulation where oil extraction resistance is critical. The comparative data below show the structural and solubility differences that govern solvent- and melt-processing selection.
| Parameter | Succinic acid | Adipic acid | Fumaric acid | Citric acid |
| CAS number | 110-15-6 | 124-04-9 | 110-17-8 | 77-92-9 |
| Carbon chain | C4 saturated | C6 saturated | C4 unsaturated, trans | C6 hydroxy-tricarboxylic |
| Molar mass | 118.09 g mol−1 | 146.14 g mol−1 | 116.07 g mol−1 | 192.12 g mol−1 |
| Melting range | 185–187 °C | 151–154 °C | 287 °C, decomposes | 153–159 °C |
| pKa1 | 4.21 | 4.42 | 3.03 | 3.13 |
| Aqueous solubility at 20–25 °C | 58 g L−1 | 14–23 g L−1 | 6–7 g L−1 | 592 g L−1 |
| Main industrial derivative | 1,4-butanediol and PBS | nylon 66 and polyester polyols | L-aspartic acid and unsaturated polyester resins | Citrate esters and food acidulant |
Unsaturated polyester resins formulated for styrene crosslinking require an α,β-unsaturated diacid such as maleic or fumaric acid. Succinic acid is saturated and therefore introduces no reactive double bond for free-radical cure. The distinction is measurable by iodine value according to ASTM D5559-24; maleic and fumaric acids show high iodine values, while succinic acid shows essentially zero. In stereochemistry, maleic acid is the cis isomer of butenedioic acid and fumaric acid is the trans isomer; both have lower steric bulk than the tetramethylene backbone of succinic acid. Succinic acid also has a lower pKa1 than adipic acid but higher than maleic acid, so acid strength does not track chain length alone. The electron-withdrawing double bond of maleic acid lowers pKa1 to 1.92, whereas succinic acid is 4.21. This makes maleic acid more aggressive in aqueous cleaning formulations at equal mass loading, but also more corrosive to carbon steel.
In food and pharmaceutical systems, succinic acid functions as a pH adjuster, acidulant, and chelating agent under the food additive code E 363. The pH of a saturated aqueous solution at 20 °C is approximately 2.7, and the buffer capacity around pH 4.2–5.6 is higher than that of acetic acid but lower than citric acid at equal molarity. Succinic acid is less hygroscopic than citric acid, which makes it preferable in effervescent tablets and dry electrolyte blends where premature acid–base reaction with bicarbonate must be prevented. Pharmaceutical grades are tested against the succinic acid monograph in the current USP/NF and the FCC food chemicals codex for identity, assay, melting range, heavy metals, and residue on ignition. The acid is incompatible with strong oxidizing agents, ammonia, and primary amines at elevated temperature because amidation and decarboxylation can occur. Mixtures with sodium nitrite or chlorates should be segregated according to storage hazard classification.
Succinic acid is thermally stable up to its melting point but undergoes intramolecular dehydration to succinic anhydride at temperatures above 190 °C and decarboxylation above 235 °C. Bulk handling should use nitrogen-blanketed silos when ambient relative humidity exceeds 60%, because surface moisture accelerates caking and dust adhesion to screw conveyors. Pneumatic conveying of crystalline SA-99.5 should be designed for bulk densities of 0.70–0.90 g cm−3 and particle attrition below 15% fines generation per transfer step; excessive fines increase dust explosion hazard and downstream bridging. Dust from succinic acid is combustible as an organic acid dust. The minimum ignition energy and dust deflagration index should be measured per ASTM E2019 and ASTM E1226 before designing collection systems. The material is not classified as dangerous for transport under REACH and CLP as an acute toxicant, but it is a skin and eye irritant as a weak organic acid. Bulk workers should use particulate respirators and nitrile gloves when handling micronized grades. Storage tanks and piping in aqueous service should be lined or constructed from 316L stainless steel because the saturated solution has a pH below 3.0 and promotes chloride-induced pitting when chloride is present. In polymer plants, succinic acid should not be blended with amine-based nucleating agents or basic fillers prior to esterification; premature salt formation with calcium carbonate or hydrotalcite reduces the free acid available for condensation and produces water that must be stripped from the reactor.
