{"id":1288,"date":"2026-07-26T14:22:37","date_gmt":"2026-07-26T06:22:37","guid":{"rendered":"https:\/\/bastone-petrochem.com\/?p=1288"},"modified":"2026-07-23T16:01:59","modified_gmt":"2026-07-23T08:01:59","slug":"triethylene-glycol-di-2-ethylhexanoate-production","status":"publish","type":"post","link":"https:\/\/bastone-petrochem.com\/ru\/triethylene-glycol-di-2-ethylhexanoate-production\/","title":{"rendered":"How Is Triethylene Glycol Di-2-Ethylhexanoate (TEG-2EH) Produced From 2-Ethylhexanoic Acid?"},"content":{"rendered":"\n

Every metric ton of polyvinyl butyral (PVB) interlayer film carries roughly 260 kg of a single plasticizer: triethylene glycol di-2-ethylhexanoate, or TEG-2EH.<\/p>\n\n\n\n

TEG-2EH (CAS 94-28-0, also sold as 3G8) is produced from 2-ethylhexanoic acid in three stages: esterification with triethylene glycol, vacuum recovery of the excess acid, and refining to spec.<\/p>\n\n\n\n

The consumption figure and the stage parameters that follow come from a 2020 disclosure by Ouyang Kongbo of Anhui Wanwei, a Chinese PVB-chain producer; they document one plant’s practice, not a universal standard.<\/p>\n\n\n\n

Step 1: Esterification of 2-EHA and Triethylene Glycol<\/h2>\n\n\n\n

Esterification runs in a stirred, steam-heated kettle held at 180 to 220 \u00b0C, where triethylene glycol (TEG) reacts with an excess of 2-ethylhexanoic acid under a nitrogen blanket.<\/p>\n\n\n\n

The acid arrives as a finished upstream product of 2-ethylhexanal oxidation<\/a>, so the ester plant inherits its purity and color as fixed inputs. The nitrogen gauge pressure is barely positive, 0.01 to 0.02 kPa, enough to keep air out of a vessel running hot enough to darken any ester.<\/p>\n\n\n\n

How the Two-Step Reaction Reaches Completion<\/h3>\n\n\n\n

TEG carries two terminal hydroxyls, and they esterify in sequence: acid plus glycol forms the monoester and one water, then a second acid molecule converts the monoester to the diester.<\/p>\n\n\n\n

Both steps are reversible. Unless water leaves the system continuously, conversion stalls short of the diester, which is why the kettle’s vapor line matters as much as its heating coil.<\/p>\n\n\n\n

Overhead vapor passes through a condenser into a phase separator. The condensed 2-EHA layer drains back to the kettle while the water layer is rejected, and that steady water removal pulls the equilibrium toward the diester.<\/p>\n\n\n\n

\"Esterification<\/figure>\n\n\n\n

Ouyang’s endpoint is analytical, not scheduled: the batch closes when sampled monoester content falls to 0.5 to 1.5 percent.<\/p>\n\n\n\n

Why the Catalyst Is Tin Chloride, Not Sulfuric Acid<\/h3>\n\n\n\n

The disclosed system pairs stannous chloride (SnCl2) as the main catalyst with titanium dioxide and activated carbon as co-catalysts, a combination developed over years by Jinquan Co. and Anhui Wanwei.<\/p>\n\n\n\n

Sulfuric or phosphoric acid would drive the same reaction at lower catalyst cost, but the plant pays elsewhere: corroded equipment, a neutralization step, salt-laden wash water, and a darker ester.<\/p>\n\n\n\n

A 2020 Eastman patent puts a number on the color penalty. Its p-toluenesulfonic acid run reached 96.3 percent diester but produced a dark-brown product that required bleaching.<\/p>\n\n\n\n

Tin chemistry avoids that trade. Silva and Cardoso’s 2016 esterification study, run on oleic acid rather than 2-EHA, ranked SnCl2 the most active of six tin catalysts and noted it needs no end-of-batch neutralization.<\/p>\n\n\n\n

In the kettle, the tin system works at atmospheric pressure and leaves with the activated carbon in the first filtration pass. SnCl2 itself is not static: it sheds hydration water above 80 \u00b0C, so the species catalyzing at 200 \u00b0C is not the dihydrate you charged.<\/p>\n\n\n\n

Direct esterification is not the only industrial route. The same patent claims transesterification of methyl 2-ethylhexanoate with TEG over potassium carbonate at 135 to 165 \u00b0C, reaching over 99 percent diester in 3.5 hours.<\/p>\n\n\n\n

Both paths draw on the same upstream chain; the methyl ester comes from 2-ethylhexanal, the aldehyde that otherwise oxidizes to 2-EHA.<\/p>\n\n\n\n

Don’t substitute one catalyst family for the other without re-qualifying the endpoint spec; the residues, monoester tails, and color loads differ, and the refining train downstream was sized for one of them.<\/p>\n\n\n\n

Step 2: Recovering and Recycling Excess 2-EHA<\/h2>\n\n\n\n

Excess acid comes off the crude ester by vacuum stripping at 15 to 40 kPa absolute and 200 to 240 \u00b0C for 3 to 5 hours, with nitrogen sparged through the kettle bottom.<\/p>\n\n\n\n

The stripped acid condenses into a collection tank and charges the next batch. Stripping ends on a number, not a clock: the batch is done when kettle acid value falls to 1 to 6 mg\/g.<\/p>\n\n\n\n

\"Closed<\/figure>\n\n\n\n

Each cycle tops the loop up with fresh technical-grade 2-EHA<\/a> to cover losses. Hold that makeup acid to the same purity bar as the virgin charge; whatever rides in with it concentrates over successive recycles.<\/p>\n\n\n\n

If I audit one thing on a line like this, it is the acid-value trend across recycle batches. A creeping endpoint is the earliest sign the loop is accumulating heavies the strip step cannot remove.<\/p>\n\n\n\n

Step 3: Refining Crude TEG-2EH to Finished Spec<\/h2>\n\n\n\n

Refining takes the crude ester from an acid value of 1 to 6 mg\/g down to 0.1 mg\/g or less, while bringing purity to at least 98 percent.<\/p>\n\n\n\n

The Five-Operation Refining Train<\/h3>\n\n\n\n

Ouyang’s disclosure runs five unit operations in fixed order:<\/p>\n\n\n\n