What is HPPO/HPPG?
These so-called HP Plus technologies are innovative processes for directly synthesizing materials in global demand in manufacturing industry, namely propylene oxide and propylene glycol. Evonik Active Oxygens developed these processes together with partners and made them marketable. You can read about how HPPO and HPPG work and why these processes are particularly sustainable here.
What is HPPO?
Demand for foam and insulating materials, for example, for vehicles and living spaces, is increasing worldwide — for sustainability reasons too. This requires polyurethane. This is a product made from propylene oxide. As previous propylene oxide manufacturing processes produced large quantities of byproducts, some of which were harmful to the environment, Evonik Active Oxygens developed an innovative manufacturing process together with thyssenkrupp Industrial Solutions well over 20 years ago.
The “Hydrogen Peroxide to Propylene Oxide (HPPO)” process is ‒ as the name suggests ‒ a process in which in-demand propylene oxide is produced based on hydrogen peroxide (H2O2).
In simplified terms, it works like this: you take 70 percent hydrogen peroxide (H₂O₂), propene and other additives. Then you add small quantities of steam and electricity. The hydrogen peroxide then reacts with the propene — producing propylene oxide and, as a byproduct, just water, which does no harm to the natural environment and can be biologically purified.
The key element here is a catalyst developed by Evonik specifically for the HPPO process. This catalyst ensures that the yield from the reaction is very high. Moreover, all the thermal energy required here is utilized several times over. It is therefore a very resource-efficient process that is constantly being enhanced. Four industrial-scale HPPO plants have already been licensed worldwide by Evonik/tkIS: the first has been operating in South Korea since 2008. Two more have been added in China, and one in Hungary.
What is HPPG?
An in-demand product similar to polyurethane is propylene glycol, which can replace harmful additives in skin creams, toothpaste and ointments, for example. But it is also required for antifreeze, plastics – or to give chewing gum a good texture. To date, propylene glycol was produced in a series of steps: first, the precursor, propylene oxide, was produced, followed by propylene glycol as the next step in the process.
The Hydrogen Peroxide to Propylene Glycol (HPPG) process means this indirect route is no longer necessary. Under the brand name HYPROSYN®, Evonik Active Oxygens has developed a process that allows propylene glycol to be produced directly from propene and hydrogen peroxide. Here too, a catalyst ensures that the two basic substances are converted efficiently and in an energy-saving way. In cooperation with US company Dow, Evonik Active Oxygens is now bringing HYPROSYN® to market.
Why are these processes sustainable?
An efficient process for producing hydrogen peroxide and the HPPO process are required to produce propylene oxide sustainably. Both production facilities should ideally be located close to each other to reduce transportation distances.
The HPPO process is efficient and sustainable because …
- …no (environmentally harmful) byproducts are produced that have to be disposed of.
- … the investment costs are lower than for conventional propylene oxide production processes.
- … raw materials are used efficiently and the reaction yield is high.
The same applies to the HPPG process for the production of propylene glycol. Here too, it makes sense for the production facilities for hydrogen peroxide and propylene glycol to be located in close proximity.
The HPPG process is sustainable and environmentally compatible because …
- … fewer process steps than in alternative processes are more cost- and resource-efficient.
- … the energy requirement is low and the yield is high.
- … conventional propylene glycol plants can be converted cost-effectively.
- … the propylene oxide previously produced as a precursor for propylene glycol can be used for alternative applications, for example for further processing into polyurethane.
To make both processes even more sustainable, Evonik Active Oxygens is not only working on continuously improving them. Increasing attention is also being paid to the origin of the raw materials.
There is potential, for example, in using …
- … green hydrogen.
- …electricity from renewable sources.
- …bio-based propylene.