Catalysis 2023 Issue

As a first preparation step, pilot plant tests were conducted in the refinery’s research facility using Topsoe catalysts installed in the industrial unit. Pilot plant results were anal - ysed and interpreted in comparison with estimates made by Topsoe. The refinery then decided to conduct a test run in the hydrocracking unit using 5 vol% refined palm oil feed - stock co-processed during normal operation (see Figure 2 ). At operating conditions of the hydrocracking unit, the hydrotreating of triglycerides in vegetable oil are relatively easy reactions and are expected to occur over the first NiMo pretreat catalyst bed (see Figure 3 ). The weighted average bed temperatures (WABT) for pretreat and cracking beds show that catalytic severity was lower during the co-processing run. This is in line with expectations due to the following factors:  Effect over pretreat catalysts : Vegetable oil replaces VGO feed. Pretreat reactions on triglyceride are easier com - pared to HDS, HDN, and HDA reactions on VGO molecules that are more complex.  Effect over hydrocracking catalysts : Pretreat effluent during co-processing has a higher number of C16-C18 mol - ecules from triglyceride side chains. These boil in the distil - late fraction. Hence, the true conversion over hydrocracking catalysts is lower during co-processing compared to the fossil run to achieve a similar UCO yield/gross conversion (see Figure 4 ).

HC Bed 2

HC Bed 1

PTR Bed 2 PTR Bed 3

PTR Bed 1

HC Bed 2

HC Bed 1

PTR Bed 3

PTR Bed 2

Fossil run

Co-processing run

PTR Bed 1

5˚C

composition of diesel stream in the following product prop - erties discussion.  Unconverted oil (UCO) yield/gross conversion: Vegetable oil replaces VGO in feed during the co-pro - cessing run. Molecules in vegetable oil are relatively easy to treat at hydrocracking unit conditions. Hence, the feed during the co-processing run is relatively easy to process compared to 100% VGO feed. Even at directionally lower catalytic severity, UCO yield is lower, i.e., gross conversion is higher during the co-processing run  Off-gas make : Higher off-gas flows are recorded dur - ing the co-processing run. As explained in the feedstocks and chemistry section, C3 is expected from the triglycer - ide backbone, and C1 is expected from the methanation reaction. These are also consistent with higher C1 and C3 recorded in the treat gas composition during the co-pro - cessing run. Product properties Vegetable oil feed has predominantly C16 and C18 chain length side chains. These are expected to fully saturate to n-paraffins and boil in the middle distillate product fraction. The following plots compare chromatograms of distillate samples recorded during the test run. The peaks in the chromatograms are representative of the concentration of molecules boiling at the specified temperature. Following are the theoretical boiling points of isomers of varying chain lengths: Figure 3 The recorded temperatures show that almost all reactions related to triglycerides in the vegetable oil occur in the first pretreat bed during the co-processing run. Thereafter, the temperature profile in the catalyst beds is almost identical for fossil and co-processing runs

PTR WABT

HC WABT

Fossil run

Base

Co-processing run

Base – 1°C

↓

Yield structure Mass balance during both fossil and co-processing runs closed well within the accepted tolerance for commercial hydrocracking units (see Figure 5 ). Hence, the yield struc - ture could be evaluated in more detail with a good degree of confidence. The following are salient points from the fossil and co- processing runs:  Hydrogen consumption : Co-processing vegetable oil consumes additional hydrogen as expected and explained in the previously discussed feedstocks and chemistry section.  Diesel yield: Diesel yield is higher during the co-pro - cessing run. This is an indication that C16 and C18 molecules expected from the triglyceride side chain in the feed are retained in the diesel fraction. See further discussion on the

Fossil run Co-processing run

2 wt%

Co-processing run

5 wt%FF

Fossil run

True conversion

Gross conversion

Figure 4 Even at lower catalytic severity during co-processing test run, higher gross conversion was recorded, further validating the two factors mentioned in WABT discussion above

Naphtha

Kero

Diesel

UCO

Figure 5 Mass flows recorded during the test run as a percentage of fresh feed processed

Catalysis 2023