HOUSTON (ICIS)--The US-based company Agilyx, which is already making styrene oil from waste plastic, has now adapted its pyrolysis technology to produce a naphtha base-stock, opening up the possibility of producing olefins from recycled materials.
If successful, the technology would satisfy several demands coming from the petrochemical industry and from policy makers.
The world's crackers are relying increasingly on lighter feedstocks, which produce much less propylene and aromatics. For propylene in particular, petrochemical companies have said the world will have a chronic shortage. This new technology could help address that shortage.
Concern is rising about plastic waste entering the oceans. Governments are placing more emphasis on developing the circular economy, and companies are making pledges to ban plastic straws and other items
The chemical industry is developing its own programme to reduce and ultimately eliminate plastic waste.
A process technology that converts waste plastic into feedstock would thus meet these environmental goals and address the shortages in monomers that are emerging from crackers switching to lighter feedstock.
Pyrolysis itself is an ancient technology and is fundamental to the modern chemical industry. It lies at the heart of steam crackers.
When Agilyx started 14 years ago, it intended to use pyrolysis to convert the most contaminated waste plastics into synthetic oil, said Joseph Vaillancourt, CEO. Ultimately, the company was able to develop a product similar to vacuum gas oil (VGO) that was later refined to produce jet fuel for the US Department of Defense.
All was well until 2014, when oil prices collapsed, Vaillancourt said. Agilyx started poring through its research to find another pathway that could earn the company better returns.
It was this research – and not the company's process technology – that would ultimately prove to be Agilyx's most valuable asset, Vaillancourt said.
For more than a decade, the company had been processing various streams of plastic waste. In all, the company had characterised about 1,500 commercial runs and made about 750 different products.
With that data, Agilyx was able to develop predictive modelling of what products its technology could make from a particular batch of waste plastics. Agilyx could develop recipes of these batches of waste plastics to produce a specific grade of an end product.
If a refiner gave Agilyx specifications for a particular grade of oil, the company could reverse engineer what waste plastics it had to use to make a product that met those specs, Vaillancourt said.
"We'd come up with liquids samples, and in every case, we met the specs," he added.
In a sense, Agilyx was doing to waste plastics what refiners had done with the various grades of crude oil. The company learned to adjust its feedstock slate and operating conditions to make a product that met a tight range of specifications.
With its data in hand, Agilyx decided to branch out from synthetic oil. It developed a recipe that would convert waste polystyrene (PS) to styrene oil. That oil would later be refined into styrene monomer and re-polymerised into plastic.
The company began developing a commercial-scale plant employing this technology in Tigard, Oregon, that started operations earlier this year. It can handle up to 10 tonnes/day of PS waste. AmSty and INEOS Styrolution are processing the styrene oil and using the material to make polystyrene.
Late in August, the company announced another milestone. It adapted its technology to produce a naphtha base-stock that, with further refining, can be used in crackers.
For Agilyx, the characteristics of the waste plastic are critical, just as it is for any other feedstock used in a chemical process, Vaillancourt said. Variations in the polymer composition and contamination in the waste plastic will affect the end product.
When Agilyx finds a new supply of waste plastic, it does not accept it until it is chemically characterised. "We will take many samples of the feedstock to make sure we have statistically relevant data," he added.
From there, the company will model what the yields and chemical quality will be for the particular batch of waste plastic. The company will then determine what other waste streams it has to add to make a stable product.
The quality of the end product also depends on scale. Right now, most of Agilyx's products require further refining. Vaillancourt expects that if the company can build larger plants, it can justify adding the downstream units that can refine the output, allowing Agilyx to produce a truly drop-in material that could go directly into refineries or crackers.
Agilyx is still developing other products from its output. The off gas contains a high concentration of propylene. Other adaptions could produce aromatics.
This could help the petrochemical industry ensure supplies of these monomers when the switch to lighter feedstock has limited their production from crackers.
Propylene and aromatic supplies could tighten further if predictions about flattening gasoline demand become true. This prediction rests on the assumption that electric vehicles (EV) will displace those powered by internal combustion engines. Also, automobiles running on gasoline could continue becoming more efficient, putting further limits on fuel demand.
Refineries also produce aromatics and propylene as by-products, so any changes in fuel demand would affect refining rates and, hence, supplies of these chemical intermediaries.
This scenario is far from universal. Earlier this year, the CEO of Saudi Aramco explained why the world will continue to need oil products.
While there is debate about the future of oil, there is no question that the world will need more petrochemicals. As more consumers adopt middle class buying habits, demand for plastics and other chemicals will increase, and companies will need more feedstock, regardless of whether they come from oil or waste plastic.
Vaillancourt said if all goes according to plan, Agilyx should be cost competitive with oil-based production while having a better environmental profile.
Studies that Agilyx commissioned with independent third parties show that the company's product has a carbon profile that is 50-70% lower than petroleum-based material.
That carbon profile is becoming more critical as policy makers and the public become more concerned about plastic waste.
Governments are making pledges to reduce plastic waste.
Chemical companies are also setting similar goals. The American Chemistry Council (ACC) has set goals to recover and recycle all plastic packaging by 2040.
A group of five chemical companies has formed an alliance that aims to engage with the entire plastics value chain on how it can tackle the circular economy, said Bob Patel, CEO of LyondellBasell, one of the participating companies.
Technology that converts waste plastic into useful products will not only reduce pollution, it will make it more economical to do so.
By Al Greenwood