Polyquaterniums are a group of cationic polymers used in hair and

skincare products to provide conditioning, smoothing, and

static-reducing benefits by neutralizing negative charges on hair and

skin. They can be derived from natural polymers like cellulose or

synthesized from organic monomers. The specific benefits and chemical

properties of each polyquaternium are distinguished by a unique number

(e.g., Polyquaternium-7, Polyquaternium-10), assigned in the order they

are registered with the International Nomenclature of Cosmetic

Ingredients (INCI) --- [(refs)](https://www.google.com/search?q=Polyquaterniums).

Hexamethylenediamine (HMD) is produced by the catalytic hydrogenation of

adiponitrile (ADN), a process where hydrogen gas is added to

adiponitrile molecules in the presence of a catalyst like Raney nickel

or cobalt, often in a solvent like molten adiponitrile or ammonia.

Adiponitrile itself is typically made from butadiene through a process

involving hydrogen cyanide. Emerging bio-based routes, like those via

fermentation of amino acids or other precursors, are also under

development to provide more sustainable alternatives ---

[(refs)](https://www.google.com/search?&q=Hexamethylenediamine+production).

Ethyl acrylate is produced through the acid-catalyzed esterification of

acrylic acid with ethanol. This process typically occurs in the liquid

phase and utilizes an acid catalyst like sulfuric acid or a solid acid.

After the reaction, the crude product undergoes distillation to separate

and purify the ethyl acrylate, which is then stabilized with

a polymerization inhibitor like hydroquinone. References:

- [BASF’s Rheovis range transitions to bio-based Ethyl Acrylate (EA)](https://www.greencarcongress.com/2025/06/20250611-basf.html).

- [Reactive distillation configuration for the production of ethyl acrylate](https://www.sciencedirect.com/science/article/abs/pii/S0255270124002022).

Dihydrolevoglucosenone (cyrene) is a bicyclic, chiral, seven-membered

heterocyclic cycloalkanone which is a waste derived and fully

biodegradable aprotic dipolar solvent. It is an environmentally friendly

alternative to dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP)

--- [(refs)](https://en.wikipedia.org/wiki/Dihydrolevoglucosenone).

Thermochemical recycling breaks down polyethylene (PE) into basic

chemical building blocks using high temperatures. Key processes include

pyrolysis, which converts PE into oil, char, and gas, and gasification

or steam cracking, which can also produce syngas or fuels. These methods

offer an alternative to mechanical recycling for challenging PE waste,

yielding valuable raw materials like hydrocarbons and chemicals for

reintroduction into the production cycle. References:

- [Thermochemical recycling](https://www.google.com/search?q=Thermochemical+recycling+of+polyethylene+plastic+fractions).

- [Polyolefin waste to light olefins](https://www.science.org/doi/10.1126/science.adq7316)

- [ENEOS Mistubishi plant](https://chemanager-online.com/en/news/mitsubishi-chemical-group-launches-chemical-recycling-plant-for-plastic-to-oil-conversion).

[](/PIEQ/Themes%202024-25/Plasticos-h3t96ur42spd1.jpg "Plásticos nos oceanos.")

2-methyltetrahydrofuran (2-MeTHF) has been promoted as an

ecologically-friendly alternative to THF. 2-MeTHF is produced from

renewable biomass via two primary catalytic hydrogenation pathways: from

furfural, which is first hydrogenated to 2-methylfuran (2-MF) and then

to 2-MeTHF, and from levulinic acid (LA), where LA is converted to

γ-valerolactone (GVL), then 1,4-pentanediol, which is finally dehydrated

to 2-MeTHF. The raw materials are lignocellulosic biomass, such as

corncobs or bagasse, with hydrogenation catalysts including Nickel,

Palladium, Copper, or Ruthenium on supports like alumina or carbon ---

[(refs)](https://www.google.com/search?q=2-Methyltetrahydrofuran+production).

Syngas cleaning removes contaminants like dust, sulfur, ammonia, and

heavy metals to meet product quality, downstream process requirements,

and environmental regulations. Cleaning methods are categorized as cold

gas (low temperature, often using water scrubbing) or hot gas (high

temperature, using filters, sorbents, or catalysts). Key technologies

include cyclones, filters, wet scrubbers, solid adsorbents, catalytic

converters, and acid gas removal (AGR) systems, with choices depending

on the application and required purity ---

[(refs)](https://www.google.com/search?q=syngas+cleaning).

Renewable methanol is produced from urban waste by first processing the

waste into a synthesis gas (syngas) through methods like gasification or

partial oxidation, which is then purified and converted into methanol.

This process offers a way to recycle non-recyclable waste and create

a versatile fuel for transportation and chemicals, contributing to

carbon neutrality and the circular economy. References:

- [Renewable methanol from urban

waste](https://www.google.com/search?q=Production+of+renewable+methanol+from+urban+waste).

- [New Repsol / Enerkem Ecoplanta in

Tarragone](https://www.repsol.com/en/sustainability/sustainability-pillars/environment/circular-economy/our-projects/transforming-waste-into-chemicals/index.cshtml).

Caprolactone (ε-CL) is a monomer used in the production of highly

specialised polymers. Ring-opening polymerization, for example, gives

polycaprolactone. Another polymer is polyglecaprone, used as suture

material in surgery. ε-caprolactone is produced industrially through

several methods, primarily via the Baeyer-Villiger oxidation of

cyclohexanone using peracetic acid or catalytic systems with oxygen.

Alternative methods include the biocatalytic conversion of cyclohexanol

using enzymes like Baeyer-Villiger monooxygenases and the direct

condensation of 6-hydroxyhexanoic acid ---

[(refs)](https://www.google.com/search?q=%CE%B5-caprolactone+sources).