05 · Why Genosorb
Vent-gas recovery, not solvent distillation
This page is about recovering solvent that has evaporated into air or nitrogen — from vents, dryers and hoods — and turning it back into liquid. A solvent distillation unit (“solvent recycler”) purifies used liquid solvent; the two do different jobs and can work together. See how Genosorb VOC recovery works.
Most of the physical absorbents are specific for a few VOC or for gases like CO₂, H₂S etc. Apart from single solvents recent work is reported on use of deep eutectic solvents (DES) and ionic liquids; they are still to reach commercial scale.
The desired properties would be high affinity for the VOC to be recovered, high boiling point so that separation can be done easily and the product will not be contaminated, low viscosity so that heat and mass transfer is not hindered, and low heat capacity to lower the energy needs. A low surface tension is desirable as it makes for easy spreading — a larger surface area is obtained in the mass transfer equipment. High selectivities can be an advantage as separation of VOC is possible.
VOCs to be recovered have wide-ranging chemical and physical properties such as boiling point and polarity — there may not be a single "one size fits all" solvent. Among glycol ethers, Clariant A.G. has developed a range of polyethylene glycol ethers under the brand Genosorb® — mixtures of varying chain lengths tuned for polar and non-polar VOC as well as gases like CO₂, H₂S and SO₂. Various inhibitors prevent oxidation and give a long life. All Genosorbs have good affinity for water, so the treated gas gets dehydrated.
Genosorb Grades
| Grade | Target | Examples |
|---|---|---|
| Genosorb 300 | Polar solvents | Alcohols, ketones, esters, ethers |
| Genosorb 1843 | Non-polar solvents | Aliphatics, aromatics, chlorinated |
| Genosorb 1753 | H₂S / CO₂ | Biogas upgrading, sour gas |
| Genosorb 1900 | SO₂ | Sulphur dioxide capture |
Key benefit
Simultaneous dehydration
Genosorb's strong affinity for water means the treated gas stream comes out dehydrated as a side benefit of VOC removal — no extra process step.
Key Physical Properties — Genosorb®
| Property | Value | Significance | Property | Value | Significance | |
|---|---|---|---|---|---|---|
| Boiling point | >250 °C | Absorbent stays liquid through stripping — no loss alongside the VOC | Specific heat | 2.13–2.26 J/g·K | Well-understood thermal behaviour for heat-integration design | |
| Vapour pressure | <0.002 mbar | Minimal absorbent carryover into the treated gas stream | Thermal conductivity | 0.149–0.169 W/m·K | Supports efficient inter-stream heat exchange | |
| Density at 20 °C | 0.93–1.03 g/cm³ | Stable across operating temperature range | Annual make-up loss | ~2% of inventory | Inhibitors prevent oxidation; long service life | |
| Viscosity at 20 °C | 4–7 mm²/s | Moderate — keeps heat and mass transfer efficient |