B
A
200˚ – 250˚C
Melt hydroconversion Pt/WO /ZrO = HY zeolite
300˚ – 450˚C
Hydrogenolysis Pt/SrTio
Plastic
400˚
Pyrolysis
Hydroreforming Ni/BEA
500˚ – 600˚C
High temperature pyrolysis Thermal, catalytic
Plastic waste
Waste to fuel
Fuel
Figure 6 Current and in development route of plastics waste recycling routes ( based on Liu et. al., 2021)
1200
2050 More plastics than sh in the ocean
1907 Bakelite invented
1950s First plastics in consumer products
1000
800
600
1970s Plastics found in the stomach of marine animals
1997 Discovery of the Great Paci c Garbage patch
400
1930s and 1940s PE, PS and EPS invented
200
1977 First plastic bags in grocery retail
0
1900
1925
1950
1975
2000
2025
2050
Figure 7 Evolution of plastics production over the years (courtesy of Deloitte Company, 2021)
hydrocracking of plastics waste. In this case, the chemical principle involves cracking the carbon-carbon bonds of the polymer under high hydrogen pressure, leading to the pro- duction of stable low boiling point hydrocarbons. The hydrocracking route presents some advantages com- pared with thermal or catalytic pyrolysis once the number of aromatics or unsaturated molecules is lower than what is achieved in pyrolysis processes, leading to a more stable feedstock to steam cracking or other downstream pro- cesses. It is also more selective, producing gasoline-range hydrocarbons and can be easily applied in highly integrated refining hardware. Figure 6 summarises the available and promising routes to plastics recycling. Among the recycling routes involving the decomposi- tion of plastics waste (monomer recycling), solvolysis and microwave processes are also being considered. The chemical recycling of plastics is a great opportunity for technology developers and scientists, especially with the development of effective catalysts to promote depo- lymerisation reactions, which can ensure the recovery of high-value-added molecules like BTX. More than that, the chemical recycling of plastics is urgently needed to close the sustainability cycle of an essential industry (see Figure 7 ). It is fundamental to understand that plastics recycling is necessary to achieve a real circular economy as required by society, especially considering the growing demand for petrochemical intermediates. Data from 2019 suggested about $320 billion in capital investment is needed to build crude-to-chemicals refining assets to produce petrochemi - cals from crude oil, with minimum transportation fuels. Close to 64% of this capital investment is localised in the
Asian market, leading to a potential imbalance in the global downstream market. This data reinforces the relevance of plastics waste recycling technologies towards the sustainability of the downstream industry at the same level as the energy man- agement efforts of the players of this industry. Conclusion Nowadays, it is still difficult to imagine a global energetic matrix free of fossil transportation fuels, especially for developing economies. Despite this fact, recent forecasts, growing petrochemicals demand, and pressure to minimise the environmental impact produced by fossil fuels create the driving force for closer integration between refining and petrochemical assets. In the extreme scenario, zero fuels refineries tend to grow in the middle term, especially in developed economies. The synergy between refining and petrochemical pro - cesses raises raw material availability to petrochemical plants. It makes the supply of energy to these processes more reliable and, at the same time, ensures better refin - ing margins due to the high added value of petrochemical intermediates compared to transportation fuels. The development of crude-to-chemicals technologies reinforces the necessity for closer integration of refining and petrochemical assets by brownfield refineries aiming to face the new market, which tends to be focused on pet- rochemicals against transportation fuels. It is important to note the competitive advantage of refiners from the Middle East, who have easy access to light crude oils, which can be easily applied in crude-to-chemicals refineries.
84
PTQ Q1 2023
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