PTQ Q3 2023 Issue

Prehydrogenation Pyoils often contain certain amounts of highly reactive compounds, mostly dienes and styrenes, although there is a wider spectrum of polyunsaturates. The exact level of these components is highly dependent on the composi- tion of mixed plastics waste and pyrolysis process design. Values typically range from about 1-10 wt%. Due to high reactivity, these species tend to oligomerise when subject to elevated temperatures, substantially impacting the prop- erties of pyoil and making it less stable. As a result, such pyoils are more challenging to process and transport. For these conditions, PuriCycle SH chem - istries are designed to selectively hydrogenate reactive compounds frequently seen in waste plastics pyrolysis streams, improving feed stability. Prehydrogenation pro- cess conditions are comparatively mild, with temperatures ranging from 80-150°C and hydrogen pressures from 15-25 barg, allowing for easy integration with available on-site plant infrastructure. Hydrotreating Hydrotreating is a well-established commercial process and well-suited technology to upgrade waste plastics pyoils. It enables the removal of nitrogen, oxygen, and sulphur com- pounds. It allows the saturation of olefins and aromatics to produce a feed with purity sufficient to be used in steam crackers without having to blend it with fresh conventional feedstocks. High nitrogen (250-2500 ppmw) and oxygen (0.1-1 wt%) levels in waste plastics-derived pyoils and the compositional complexity of the feed require a proper cat- alyst design. PuriCycle HP products are optimised for compositions normally seen in waste plastics pyoils. Proper catalyst for- mulation is essential to tackle nitrogen compounds originat- ing from nitrogen-containing plastics such as polyamides. Typical process conditions for PuriCycle HP catalysts are a temperature of 300-350°C and hydrogen pressure of 40-80 barg. Exact process condition recommendations are issued based on specifics of the pyoils composition and product stream purity requirements.

Reference 2 Reference 1

PuriCycle HPF5

PuriCycle HPF1

complex waste plastics pyrolysis feeds (pyoils). A wide range of the pyoil’s impurities are selectively converted or removed, enabling downstream processing of circular plas- tics streams. Purification of pyoils obtained from waste plastics is among the most demanding technical tasks in chemical plastics recycling. Impurities, such as halogen, nitrogen, and oxygen compounds, plus higher levels of reactive com- ponents, such as dienes, complicate the downstream use and impose strict limitations on further processing of such streams in new polymers production. PuriCycle is not a purification process, but a set of cat - alysts and adsorbents designed to purify plastic pyrolysis feeds. It covers products in four application segments: decontamination, prehydrogenation, dehalogenation, and hydrotreating. These process technologies are generally known to industry as, for example, prehydrogenation and hydrotreating (widely used in refining). However, the com - positional complexity of waste plastics pyoils imposes new requirements on adsorbents and catalysts formulations designed in accordance with the ‘finger - prints’ of impurities seen in pyoils. Decontamination Figure 1 Nitrogen in a product stream from hydrotreating commercial waste plastics pyoil with PuriCycle HP F1 and HP F5 and two competitive reference catalysts. Conditions: temp 300°C, 50 barg hydrogen, LHSV 1 h-1

The high efficiency of these catalysts is shown in Figure 1 . Commercial waste plas- tics pyoil feed with properties listed in Table 1 was used to compare the nitrogen removal performance of PuriCycle HP F1 and F5 with two competitive reference products. Reference samples sourced from undis- closed suppliers are commercially proven hydrotreating catalysts used to process refining distillates requiring denitrogenation. As seen from Figure 1 at 300°C and 50 barg, hydrogen BASF catalysts reached extremely low nitrogen levels, non-detectable and only 1.5 ppmw for HP F1 and F5, correspond - ingly. Under the same conditions, reference 1 and 2 hydrotreating catalysts could only achieve 15 ppmw and 30 ppmw, respec- tively, pointing to inferior efficiency in nitro - gen hydrogenation. While recognising that

Properties of commercial waste plastics

A wide range of pyrolysis process con- figurations and plant arrangements exist, with some plants producing lower-grade pyoils requiring some basic purification (removal of microns range-sized ash par- ticulates and heavy deposits). Activated alumina-based adsorbents are well posi- tioned to perform this duty. A wide range of high pore volume, high surface area alumina sphere and granule adsorbents can be provided as a drop-in solution. Depending on customer needs, they can be used at the production site to improve pyoil colour properties, making them suit- able for further purification.

Value

Sulphur, ppmw Chlorides, ppmw Nitrogen, ppmw Water, ppmw Density, kg/m 3 Naphtha, wt% Kerosene, wt%

242

296

0.812

35.5 61.1

GO, wt% VGO, wt%

2.2 1.2

Table 1 Properties of commercial waste plastics pyoil feed used in hydrotreating with PuriCycle HP catalysts

PTQ Q3 2023