PTQ Q4 2023 Issue

the concentration of H₂O in the feed by introducing a larger amount of water to the gas phase and creating a system upset that can eventually be exaggerated by increasing the temperature by 5-10°C. The degree of damage to the catalytic system can finally be evaluated by returning to the initial condition (for both temperature and H₂O concentration) to verify if any change in the value of the target parameter has occurred. If the target parameter is out of specification, we can increase the temperature by the amount necessary to go back to specification, and that D T is representative of the amount of damage experienced by the system. Additionally, to fully understand the behaviour of the HI catalyst in single-stage operation, it is also important to continuously monitor HDO catalyst performances. This can easily be achieved even when working with 1-10 mL of cat- alyst per reactor using a ‘twin’ reactor loaded with the same amount of HDO catalyst. The two twin reactors must share the same heater to ensure the same performance within the mass balance accuracy. Finally, if the single-stage con- figuration is chosen because the H₂ consumption in HDO can be high, it is important to work in a large excess of H₂ from the beginning. If a large H₂ excess is undesired, the missing hydrogen can be fed before the HI reactor. If the two-stage operation is desired, the set of reactors containing the HDO catalysts can be tested with fresh VO feed, but a hydrotreated vegetable oil (HVO) feed is required for the isomerisation catalysts. This can be provided from the start, allowing both reactions to be tested simultane- ously in one unit. Otherwise, HVO can also be produced in the test once the stable performance of the HDO catalysts is reached (no changes in density and propane yield). Once enough product has been accumulated from all reactors, working at the same operative conditions, the HI catalysts can start their run in the same unit with a delay of 1-2 weeks with respect to the HDO catalysts. In this case, the HI catalysts feed will be a mixture of feed produced by all the catalysts in the HDO stage. If the operative condi- tions of the catalysts are different or the performances of catalysts vary significantly, the two-stage approach can still be applied by receiving an additional HVO feed. Furthermore, the refineries very often work with a recycle that helps the processing of VO by diluting it with already processed products. To simulate the recycle, the recycled and the fresh feeds can be mixed according to the recy- cle ratio before the start of the test. If the recycle ratio is a parameter under investigation, it is possible to co-feed the VO and the recycle feed using two pumps. Finally, characterisation of the samples produced by the HDO reactors should be done using SIMDIST, offline and online gas chromatography (GC), density measurement, and S/N analysis (if the feed is rich in N). The online GC needs to be equipped with a thermal conductivity detec- tor (TCD) and a flame ionisation detector (FID) to quantify H₂O, CO, CO₂, and the light hydrocarbon products (mainly C1 and C3, but C1 to C18 can be detected). The SIMDIST or the offline GC can be used to quantify the paraffins in the liquid phase. In case the reactor temperature is insufficient to carry out

VO VO

VO HVO

HDO

Single stage

Two stage

Figure 3 hte high throughput technology. The 24-fold and 16-fold can be adapted to work in the configuration that is the most suitable to represent the units for which the catalysts are tested

HDO

Alkanes (C-C)

FFA, alcohols

Diglycerides/ monoglyceride

Triglycerides

300

400

500

600

Alkanes (C-C)

100

200

300

400

100

HC/HI

HDO

100

200

300

400

500

600

Temperature (˚C)

Figure 4 Example of possible SIMDIST results obtained by performing HDO followed by HI/HC of vegetable oil. Top: partial conversion of the VO (dark blue) when the catalyst works at low temperature. Middle: conversion of HVO (orange) to isomerised/cracked paraffines (red). Bottom : weight accumulation at each step of the reaction from right to left, 100% VO (dark blue), partially converted VO to HVO (cyan), 100% HVO (orange) and fuel mixture (red)

PTQ Q4 2023