Catalysis 2022 issue

Co-processing renewable and recyclable feedstocks in the FCC unit As new regulations drive refiners to developmore sustainable processes to produce fuels and chemicals, they are exploring co-feeding renewable and recyclable feedstocks

LUCAS DORAZIO, JIAN SHI and JAMES FU BASF Corporation SNEHESH S AIL, MARCO J CASTALDI and GOLAM S CHOWDHURY The City College of New York

W hile the refining industry currently plays a vital role supplying much of the world’s transportation fuels and commodity chemicals, new regula - tions are forcing them to produce fuels and chemicals more sustaina - bly. As a result, refiners have begun exploring co-processing renewable and recyclable crude oils (RCOs) to replace conventional fossil based feedstocks. The new feeds pres - ent challenges such as additional metal contaminants and differences in feedstock chemistry. The ability of the FCC unit to manage metal contaminants and tolerate a wide variety of feedstock makes this pro - cess well suited to co-process these RCOs. At BASF, we are exploring alter - native feedstocks, their implica - tions on the operation of the FCC unit, and how the catalyst can be designed to address the new chal - lenges that will be created. Through collaborations and partnerships, we have access to a diverse collection

of RCOs, as well as the resources needed to prepare custom RCOs. We have also adapted our exist - ing catalyst testing laboratories to explore how these new feedstocks will behave in FCC units. Challenge of RCOs RCOs originate from three possi - ble sources: pyrolysis of recyclable waste streams such as plastics and tyres, plant based oils such as soy - bean oil and corn oil, and pyrolysis of biomass such as wood residues and corn stover. Depending on the source and the conditions used to prepare the RCO, the proper - ties will vary considerably. On one end of the spectrum, pyrolysis oils derived from polyethylene and polypropylene wastes contain high hydrogen to carbon and minimal oxygen content. This makes oil pro - duced from these materials easily upgradable. In contrast, pyrolysis oil derived from biomass will pres - ent challenges due to its inherently lower hydrogen to carbon content,

significantly higher oxygen content, and relatively high content of alkali metals. Between these two extremes will be plant based oils containing moderate content of oxygen and alkali metal contaminants. One way to illustrate the diver - sity of the different feedstock options is to examine their differ - ing carbon, hydrogen, and oxygen content, which is illustrated in a Van Krevelen diagram in Figure 1 . The lower the hydrogen to car - bon (H/C) content of the feedstock, the more challenging it will be to upgrade into transportation fuels and chemicals. For reference, H/C content of petroleum based crude oil is roughly 1.7. The relatively high H/C content of polyethylene and polypropylene (~2.0) makes these ideal starting points for deriv - ing RCOs. While biomass appears to have a H/C content similar to petroleum based oil, the other fac - tor that must be considered is the oxygen to carbon content (O/C). A lower O/C results in a feed that is easier for refiners to process. Figure 1 shows that biomass based and plant-derived oils have a higher O/C than crude oil. In plant-derived oils, oxygen is contained within the structure of the triglycerides comprising the oil. While sources of biomass wastes will vary, all are comprised of lignin, cellulose, and hemicellulose that are rich in oxy - gen. In an FCC process, the oxy - gen contained in biomass pyrolysis oils and plant oils will be removed through various deoxygenation pathways producing H 2 O (hydro - deoxygenation), CO (decarboxyl - ation), or CO 2 (decarbonylation), all low-value products for refiners.

2.5

Polypropylene Polyethylene

2.0

Plant -oils (Soybean)

Biomass sources

1.5

Crude oil

1.0

0.5

Deox ygenat i on requ i red

0.0

0.2

0.4

0.6

0.8

O/C

Figure 1 Van Krevelen diagram illustrating the diversity of the different RCO feedstocks in terms of their carbon, hydrogen, and oxygen content relative to conventional crude oil

50 Catalysis 2022