Characteristics of conventional gasoil compared to select pyrolysis oils
Pyrolysis feedstock
Typical conventional gasoil
Pure LDPE
Mixed plastic waste
Soybean oil
Olive waste
Conradson Carbon Residue
~0.4%
0.02%
3.9%
0.5%
19.4%
API @ 60ºF
~24 ~1.7
44 1.9 0%
34 1.6
22 1.6
-5.4
Effective hydrogen index
0.6
Oxygen content
0%
3.6%
9.5%
24.0%
Hydrocarbon species Aliphatic Oxygenated aliphatic Oxygenated aromatic Aromatic
~68% ~32%
100%
31% 55% 14%
---
0% 1% 9%
0%
100%
0% 0%
--- ---
0%
90%
Table 1
The composition of the oil resulting from the pyroly- sis of biomass will be the result of the pyrolysis of these three structural components, yielding a molecularly diverse oil comprised of hundreds of oxygenated hydrocarbons. Cellulose and hemicellulose are similar in that they are both polysaccharides comprised of repeating sugar units that, during pyrolysis, yield a broad mixture of small carbonyl and furan/pyran ring compounds. The structure of lignin is quite different, consisting of a complex organic polymer made by cross-linking phenolic precursors. During pyrolysis, lignin will decompose into a mixture of phenols and guaiacols. 4 Biomass pyrolysis oils will be rich in oxygen and deficient in hydrogen, which together results in the very low effective hydrogen index shown in Figure 2. This, combined with the nature of oxygenated hydrocarbons, results in a high ten- dency to condense to coke during thermochemical conver- sion processes, which is reflected in the very high concarbon in Figure 2. The high tendency for coke formation will exceed what a conventional FCC unit can manage, and co-process- ing with gasoil will be required. Co-processing with gasoil will both reduce the blended concarbon and provide much-needed in-situ hydrogen on the catalyst surface. The amount of bio-oil that can be pro- cessed with gasoil will be dictated by where each feedstock falls in Figure 2. The more hydrotreated and deoxygenated the bio-oil, the higher the concentration of bio-oil that can be co-processed. However, this comes at the disadvantage of higher bio-oil costs. Co-processing bio-oil with gasoil was demonstrated in an ACE reactor using a pyrolysis oil prepared by Neoliquid using waste from olive processing as the biomass source. 5 The properties of this oil relative to the other examples discussed prior are illustrated in Table 1 . The high oxygen content of the bio-oil was measured to be 24 wt%, which results in a very low effective hydrogen index of ~0.6. Analysis of the bio-oil using GC combined with mass spectroscopy revealed a significant fraction of the expected mono- and di-aromatics consistent with lignin pyrolysis, consistent with the relatively high concarbon of ~20 wt%. Given its properties, the bio-oil had to be diluted in gasoil at a ratio of 10% bio-oil to 90% gasoil. Even at this relatively low level, the addition of the bio-oil resulted in the coke yield increasing. Additionally, the gasoline yield increased at the
expense of LPG and HCO, likely due to aromatics from the bio-oil accumulating in the gasoline product fraction. Conclusion Today, we need to improve the sustainability of our existing refinery operations and create new approaches to recy - cling materials or using renewable feedstocks. Developing these approaches to reduce the amount of fossil carbon extracted from petroleum reserves for the new produc- tion of transportation fuels and chemical feedstocks will become an increasingly important topic. This will likely be achieved by both recycling fossil carbon through chemical recycling processes and inserting renewable carbon-based feedstocks into manufacturing processes. For more than 80 years, FFC has been used to convert low-value heavy frac- tions of crude oil into higher-value transportation fuels and chemical feedstock. For upgrading challenging, sustainable feedstocks, the flexibility and low cost of FCC may again offer advantages. References 1 Degnan N Y C T, Liquid Fuel from Carbohydrates, ChemTech , August 1986, 506-511. 2 Anuar Sharuddin S D, et al., A review on pyrolysis of plastic wastes. Energy Conversion and Management , 2016, 115: 308-326. 3 Naji S Z, Tye C T, Abd A A, State of the art of vegetable oil transfor- mation into biofuels using catalytic cracking technology: Recent trends and future perspectives, Process Biochemistry , 2021. 109: 148-168. 4 Bagnato G, et al., Recent catalytic advances in hydrotreatment pro- cesses of pyrolysis bio-oil, Catalysts , 2021, 11(2), 157. 5 Mastry M C, et al., Processing renewable and waste-based feedstocks with fluid catalytic cracking: Impact on catalytic performance and consid - erations for improved catalyst design, Frontiers in Chemistry , 2023, 11. Lucas Dorazio is Team Leader, Refinery Catalysts at BASF Corporation’s Catalysts division in Iselin, New Jersey, USA. He holds a doctorate from Columbia University, New York City where his research was in the field of heterogeneous catalysis. He is also an adjunct professor at New Jersey Institute of Technology and has authored many articles, including co-authoring a textbook on industrial catalysis. He has been granted several patents in the field of catalysis. James Fu is Research Manager at BASF Corporation’s Catalysts division in Iselin, New Jersey, USA, responsible for FCC catalyst evaluation and testing methods development. He holds a PhD in chemical engineering.
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PTQ Q4 2023
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