PTQ Q2 2023 Issue

at the injection nozzles if normal feed temperature and steam partial pressures are applied; however, such chal- lenges can be managed using specifically designed feed nozzles at a separate location in the riser. Pyrolysis oils can contain up to 40 wt% oxygen, which can form excessive amounts of water, CO 2, and CO in the riser. Oxygenates in the form of carboxylic acids are a well-known source of corrosion, which may require upgrading metallurgy in some sections of the FCC. Contaminants Biomass pyrolysis oil is also challenging due to the pres - ence of contaminant metals such as calcium, potassium, and sodium. The detrimental effects of sodium and potas- sium in the FCC are well known. Sodium and potassium are both basic; hence, they neutralise acid sites in the zeolite and, thereby, permanently deactivate the catalyst. Calcium can also neutralise acid sites, but these tend to be on the catalyst matrix at the outer surface of catalyst particles. Calcium also enhances the deleterious effects of iron by promoting the fluxing of iron and glassy nodule formation in the regenerator. Recognising the challenges in processing biomass pyrol - ysis oil led Johnson Matthey to partner with the National Renewable Energy Laboratory (NREL), a national labora - tory of the US Department of Energy focusing on renew - able energy technology development. NREL provided biogenic feedstock and operated FCC micro-reactor testing equipment. Collaborative testing Johnson Matthey provided catalyst design expertise. Micro- reactors were operated under FCC conditions to observe the extent of biogenic carbon incorporation. Catalysts used included a standard refinery FCC equilibrium catalyst (Ecat) and purpose-made catalysts provided by Johnson Matthey. The objective of the study was to explore the extent of biogenic carbon incorporation into key fuel molecules and evaluate if this could be optimised using appropriate cata- lyst design. Conventional VGO (with naturally occurring carbon iso - topes, predominantly C12) was utilised as the reference feedstock, while the biogenic feed used consisted mainly of C 13 carbon isotopes from green oak grown in a C13 CO 2-enriched atmosphere. Due to the significant cost of producing a C 13 labelled feedstock, the work could only be conducted in micro-reactors. Use of distinct carbon isotopes for the VGO (C12) and biogenic (C13) feeds provided the ability to track the origin of carbon in products from these feed sources. Gas chro- matography (GC) was used to isolate specific key product molecules produced, and then mass spectroscopy (MS) was used to determine from which parent feedstock (C12 VGO or C 13 green oak) the product carbon atoms origi - nated. Further details of these methodologies can be found in ACS Sustainable Chem. Eng . 2020, 8, 2652-2664. Analysis of laboratory data was conducted on a range of different product molecules, including toluene, propylene, 2-pentene, and methylcyclohexane. Similar results were

VGO feed

MW (C) toluene = 92

Standard C VGO

C CH

CH with 6 C & 1 C

91 92 93

94 95 96 97 98 99

m/z (mass/charge) or MW

Figure 1 Outcome of GS-MS analysis when VGO is cracked over Ecat

observed for these molecules, but as an example, the focus in this instance is specifically on toluene. Toluene derived exclusively from C12 has a molecular weight of 92. In the mass spectrometer, the toluene molecule is ionised, dur- ing which fragmentation occurs. The main fragmentation peaks for C12 toluene to occur at M/Z (mass/charge) 92 (C7 H 8 + ) and 91 (C7 H 7 + ), with the loss of a single hydrogen atom. Any peaks with M/Z of 93 or above must incorpo - rate at least one C 13 atom. By comparison, toluene derived purely from a C13 source has its main fragmentation peaks at M/Z of 99 (C 13 7 H 8 + ) and 98 (C1 ³ 7 H 7 + ). Using GC-MS, therefore, allows for determination of which carbon atoms in product molecules originate from the C 12 VGO or C 13 green oak feedstock. Test runs Establishing a clear baseline is fundamental to achiev- ing good data, so the first test run was made using 100% VGO (C12) over standard FCC Ecat, providing an excellent baseline. The micro-reactor was operated using the same Ecat, operating at the same conditions, but this time using 100% green oak (C13) feedstock. Results from these test

Oak feed

MW (C) toluene = 99

C Oak pyrolysis oil

C CH

Trace C

C CH

91 92 93

94 95 96 97 98 99

m/z (mass/charge) or MW

Figure 2 Outcome of GC-MS analysis when biomass green oak is cracked over Ecat

PTQ Q2 2023