Catalysis 2023 Issue

1.2

Biogenic carbon

Fossil carbon

0.8

Co-processing run, UCO product

Fossil run, UCO product

0.6

0.4

being one of the most versatile units in the refinery, are ideally suited to co-process renewable feedstocks. They can better overcome the operational challenges related to H 2 consumption, temperature rises, and contaminants, as well as separate the renewable products into different product streams. Hydrocracking catalyst options also provide the func- tionality needed to make products with desired properties, such as good cold flow properties or high degree of satu - ration, as demonstrated with the recent industrial test run co-processing 5 vol% vegetable oil in a hydrocracking unit using Topsoe catalysts. The bulk catalysts already loaded in the reactors were found adequate for co-processing mod- erate quantities of renewable feedstock. Most exothermic hydrotreating and hydrodeoxygen- ation reactions occur in the first/grading bed. There was a slight increase in exotherm in this bed, but this could eas- ily be handled by reducing the reactor inlet temperature. Thorough product analyses showed that the kero/jet prod- uct stream had 2% biogenic carbon, and the diesel stream had 9% biogenic carbon during the co-processing test run. Most of these carbon molecules are n-paraffins, as noted by chromatogram peaks. Activity requirement during co-processing was lower compared to normal operation, as noted by lower pretreat WABT, as well as higher gross conversion during co-pro- cessing, indicating feed during co-processing is easier to treat compared to typical fossil-based VGO feed in this unit. This test run has helped establish base-line performance for processing biogenic feedstocks in commercial applica- tions and validated estimates made by Topsoe based on fundamental research. The hydrocracking unit will remain a critical component of the renewable transition. Peter Nymann is Senior Solution Specialist at Topsoe, involved in technical service for hydrocrackers, hydrotreaters, and renewable units worldwide. He graduated as a chemical engineer from Technical Uni- versity of Denmark. Email: pan@topsoe.com Pronit Lahiri is Principal Technical Service Engineer, Clean Fuels, at Topsoe in Denmark, involved in technical sales and service, as well as R&D for making estimates of catalyst performance and planning pilot plant tests. He holds a BTech in chemical engineering from National Institute of Technology in Jaipur, India. Email: prla@topsoe.com Figure 11 Result from ASTM D6866 for distinguishing carbon isotopes in unconverted oil sample drawn during the test run

0.2

250

300

350

400

450

500

550

600

Temp, ˚C

UCO product - 100% fossil run

UCO product - 5% co-processing run

peaks correspond to nC15 (BP 271°C) and nC17 / iC18 (BP 303°C). Biogenic carbon analyses of diesel from fossil and co- processing runs validated significant retention of vegetable oil feed in diesel product fraction, as shown in Figure 9 . Unconverted oil Unconverted oil product during both fossil and co-process- ing runs appears to have similar boiling range distribution. This is also validated by biogenic carbon analyses that show no presence of carbon-14 isotope during co-processing (see Figure 10 ). The most significant UCO properties recorded during the test run bear testimony to the lower true conversion over the hydrocracking catalyst during co-processing. Typically, it is seen that the UCO density and viscosity reduce with increasing conversion severity (see Figure 11 ). The higher density and higher viscosity of UCO during the co-process - ing run are an indicator of lower conversion severity on the VGO part during this operation. Figure 10 Chromatogram of unconverted oil sample drawn during the test run

Test

Method D4052

Fossil run

Co-processing run

SG 60/60°F Viscosity at 100°C, cSt

0.870

0.872

D7042

5.903

6.247

Conclusions Processing renewable feedstocks in existing refinery assets is a strategy being used by many refiners globally to reduce CO2 emissions originating from fossil-based feedstocks. In addition to the local availability of renewable feedstocks, another critical consideration has been to evaluate which unit in an existing refinery is best suited for co-processing biogenic feeds together with fossil-based feedstock. Hydrotreaters are widely used, but hydrocracking units,

Catalysis 2023