Catalysis 2023 Issue

Increasing refinery profitability via propylene maximisation Case study at medium-sized US Midwest refinery on increasing FCC propylene via ZSM-5-based additive technology

Nate Hager, Abigail Devaney, Ally Payne, Stephen Amalraj and Bani H Cipriano W. R. Grace & Co.- Conn.

D emand growth for gasoline and propylene (C 3 =) is projected to undergo very different trajectories in North America. Figure 1 shows North American gasoline demand, which is expected to peak by the mid- 2020s and thereafter decrease: by 2030, gasoline demand is expected to decrease ~3% from its peak, and by 2040 the decrease will be about 30%. 1,2 Meanwhile, estimated propyl- ene growth in North America through 2030 is 2% annually, corresponding to a 17% total growth in that bespoke time period. 3 The decrease in fuels demand will certainly chal- lenge refinery profitability. One strategy for refineries to remain profitable is to pivot towards petrochemicals production using existing assets. An example of this can be seen with efforts to increase FCC pro- pylene production. The following example and discussion can better describe the advantages and challenges encountered when increasing FCC propylene production. Against this backdrop, is a case study of a medium-sized US. Midwest refinery that, through careful planning and investments, set itself up to use ZSM-5 technology from Grace to maximise value when propylene and octane economics are strong. Advantages and challenges Propylene is primarily generated via three processes: steam cracking (in this process, ethylene is typically the main prod- uct and propylene is a byproduct), propane dehydrogena- tion (PDH), and FCC operation. Propylene supply from steam crackers, FCC, and PDH stands at 45%, 29% and 16%, respectively, as shown in Figure 2 . In the last 10 years, PDH as a source of propylene grew in importance compared to 2010, when its share of the global supply was only 5%. Propylene yield from steam cracking decreased as the feed slate lightened from naphtha to lower- cost ethane, and growth in propylene supply from refineries slowed as investments in new refinery capacity grew at a slower pace. Significant PDH capacity was added world - wide to meet the growing gap between demand and sup- ply, 4 especially in China since this country was striving for propylene self-sufficiency. The main advantage of the FCC vs other technologies is that the FCC has the lowest cost position. This is a widely held view and is shown in Figure 3 . When the investment cost needed to build a new PDH is factored in, the attractive- ness of an existing FCC increases further.

An ample supply of inexpensive propane from North America provided a tailwind to PDH, but can an ample and inexpensive supply be assumed into the future? Demand growth for LPG (of which propane is an impor- tant component) is expected to be around 1% annualised through 2040. 2 Propane is used for heating and cooking in addition to being used as a petrochemical feedstock. Further, as nations seek to reduce their carbon emissions, natural gas and propane complement solar and wind and, therefore, will play an important role in the journey towards a lower carbon Figure 1 North America gasoline demand projections through 2040: by the end of this period, gasoline demand is expected to decrease by roughly 30% from its peak in 2024 2

Steam cracker Renery PDH Other

10%

16%

45%

29%

Figure 2 Current share of propylene supply by source Adapted from Wood Mackenzie ⁵

Catalysis 2023