ERTC 2024 Conference Newspaper

ERTC 2024

Biofeed FCC co-processing and maximising low-carbon propylene yield

R. González and S. Brandt W. R. Grace

With the refining industry striving towards decarbonisation of operations and pivot- ing towards the production of lower car- bon-intensity products, new challenges and opportunities are arising. Close col- laborations between partners are vital for adapting the existing assets of the refin- ing industry to assure a rapid progression in the world’s journey towards lower CO₂ emissions.¹ Propylene is one of the main petrochemi- cal products from crude oil refinery oper- ations. While current market conditions for propylene are somewhat suppressed globally, there is a projected increase of 45 MM tpy in global demand for C₃= by 2030, which will drive the demand for fluid catalytic cracking (FCC) propylene accord- ingly.² Propylene produced by the FCC already has a favourable carbon intensity compared to other on-purpose processes.³ The application of ZSM-5-containing tech- nology to improve FCC propylene yields is favoured due its neutral impact on the heat balance of FCC units and, therefore, Scope 1 emissions. In addition to its favourable carbon inten- sity, the carbon impact of FCC C₃= can be further reduced by using ZSM-5-based technology and/or co-processing biogenic feedstocks to the FCC unit. Grace has been partnering with a number of refiner- ies globally to contribute to assessing the opportunities and risks of co-processing bio-derived feeds, as well as closely moni- toring commercial trials and servicing con- tinuous operation. 1, 2, 4, 5 FCC proceeds via a b -scission mech- anism on the active sites of the catalyst ( Figure 1 ).⁶ The end product of b -scission is C₃=. To further reduce the carbon inten- sity of the FCC C₃= co-processing, some bio-derived feed streams to the FCC unit can be considered.³ The higher the co-processing rate, the greater the impact on the carbon inten- sity of the related FCC products. Assuming an equal distribution of the renewable car- bon among the FCC products, the co- processing rate (mass-based) can be directly related to a reduction in carbon intensity. Consideration of the oxygen content of the renewable feed source is required, as this oxygen content is mostly converted to water, carbon monoxide (CO), and CO₂ yields. It can be estimated that considering a co-processing rate of 10 wt% renewable feed with an oxygen content of about 10 wt% (in the range of many seed oils), the carbon intensity of the resulting C₃= would reduce by 9%. The ultimate impact of co-processing renewable feed components on the yield structure is likely to be different to this the- oretical mass balance approach. However, this must be determined in FCC unit pilot plant testing and commercial applications, as they depend on the fossil feed type,

the FCC process is propylene. The demand for low carbon intensity and bio-derived polyolefins is increasing, and the adaptabil- ity and sophistication of the FCC process are ideal conditions to contribute to meet- ing the demand for bio-derived polymers. Grace is supporting several refining cus- tomers on their paths to decarbonise the FCC unit’s operation and products. In addi- tion, Grace’s expertise in product purifica- tion by adsorbents or hydrogenation and downstream processing to polyolefins is providing solutions for the new challenges that can arise with the co-processing of bio-derived feed streams. References 1 Lee, G., Brandt, S. and Holder, D., Maximizing renewable feed coprocessing at an FCC, PTQ , July 2023. 2 Peréz, E, et al. , Decarbonize the FCCU through maximizing low-carbon propylene, Hydrocarbon Processing , March 2024. 3 Cipriano, B., Cooper, C. and Brandt, S., Paving the way to low-carbon propylene from the FCC unit, Decarbonisation Technology , November 2023. 4 Gonzalez, R., Bescansa, M., Fernandez, A., Mena, A. and Rivas, C., Defossilizing the FCCU via coprocessing of biogenic feedstocks: From laboratory to commercial scale, Hydrocarbon Processing, July 2023. 5 Riley, B., Brandt, S. and Bryden, K., Co-processing of bio-based feedstocks in the FCC unit, Decarbonisation Technology , August 2022. 6 den Hollander, M., Wissink, M., Makkee, M. and Moulijn, J. A., Gasoline conversion: reactiv- ity towards cracking with equilibrated FCC and ZSM-5 catalysts, Appl. Catal. A: General, 223 (2002), 85. 7 Seiser, R., Olstad, J. L., Magrini, K. A., Jackson, R. D., Peterson, B. H., Christensen, E. D. and Talmadge, M. S., Coprocessing catalytic fast pyrolysis oil in an FCC reactor, Biomass and Bioenergy, 2022. 8 Harding, R. H., Zhao, X., Qian, K., Rajagopalan, K. and Cheng, W.-C., Fluid catalytic cracking selectivities of gasoil boiling point and hydro- carbon fractions, Industrial and Chemical Engineering Research , 35 (1996), 2561. Contact: Stefan.brandt@grace.com did you know? the adaptability and sophistication of the FCC process are ideal conditions to contribute to meeting the demand for bio-derived polymers

Catalyst (Acid site)

H +

H H H H

Protonation

H H H H

Carbenium ion

H H

β-scission

H H H H

Olen product

Figure 1 Catalytic cracking reaction mechanisms²

SR-SCT MAT pilot plant test results

91% VGO + 9% Palm oil

100% VGO

2.6 3.0 3.8 3.4 4.2 4.6 5.0

3.8

3.6

9% Palm oil

3.4

100% VGO

3.2

2.2

1.5

2.5

3.5

4.5

Cat to oil

3.0

Figure 2 SR-SCT MAT results of C₃= yield for 100% fossil-based VGO and a blend with 9 wt% palm oil²

ing of renewable feed co-processing, the effects of trace oxygenates are often not considered. Nevertheless, these are likely to occur with oxygen-containing feed streams. Trace amounts of oxygen- ates are commonly found in fossil feed- based FCC product streams like liquefied petroleum gas (LPG) or cracked naphtha. Increasing the combined FCC feed oxygen content by the co-processing of renew- able feed streams like vegetable oils will increase the amount of these oxygenate species. This might negatively influence the downstream processing of the FCC unit products while also causing products to exceed specification limits. Pilot plant testing will help understand the magnitude of changes in oxygenates and water, CO, and CO₂ yields. In addition, close cooper- ation with the catalyst supplier will help discover areas of concern and monitoring requirements. Conclusions The drive towards decarbonisation and the energy transition inspire the refining industry to a new way of thinking, recon- sidering value chains and associated pro- cess schemes. The importance of the FCC process in refining and its high flexibility makes it one of the main processes to be considered for adaptation to new opportu- nities arising. Besides lower carbon intensity transpor- tation fuels, one of the target products of

unit conditions, and FCC catalyst proper- ties. To assess the amount of C₃= stem- ming from the renewable feed component, highly sophisticated analytical methods for modern carbon determination might be required.⁷ Data testing for some renewable feed types and test conditions within Grace showed that the renewable carbon- containing feed might be preferentially con- verted to C₃= compared to fossil feed com- ponents. Figure 2 shows bench-scale pilot plant testing results, which indicate that the C₃= yield in this case increased by about 0.3 wt% FF by blending 9 wt% palm oil with the vacuum gasoil (VGO). Considering the incremental yield concept,⁸ it is esti- mated that palm oil yields 6-7 wt% FF C₃=, nearly double the yield of the fossil-based VGO in this particular case. While Figure 2 illustrates the potential C₃= increase by renewable co-processing, challenges with co-processing should be considered. These potential challenges are often associated with the significantly higher oxygen content of the renewa- ble feed component relative to traditional feedstocks. Despite the absence of added hydrogen (H₂), the FCC process offers a high degree of deoxygenation of renew- able feed streams. Most oxygen species are converted to hydrocarbons and water, CO₂ and CO, which will leave the FCC unit on the reactor side and could pose chal- lenges downstream. In pilot plant test-