Hydrocarbon Processing - June 2022 - 35

Catalysts
N. PONGBOOT, Global R&D, Samut Prakan, Thailand;
and T. UPIENPONG and W. KARUNKEYOON,
PTT Global Chemical, Rayong, Thailand
Hydroprocessing catalyst selection-Part 2:
Considerations and best practices for catalyst testing
Hydroprocessing catalysts are an essential part of the refinery
involved in the treatment/conversion of most petroleum
fractions, ranging from naphtha to residue. Hydrotreating catalysts
help refiners meet fuel regulations and enhance the performance
of downstream catalysts and processes, [e.g., naphtha
reforming or fluid catalytic cracking (FCC)] by removing
sulfur (S), nitrogen (N) and metals from their feedstocks, as
well as improving product properties by hydrogen (H) addition.
Moreover, hydrocracking catalysts further improve refiners'
profits by converting low-value streams [e.g., vacuum
gasoil (VGO)] into high-value fuels and chemical feedstocks.
Therefore, the selection of hydroprocessing catalysts requires
great care from refiners to ensure maximum asset utilization
and profitability.
Part 1 of this article, which appeared in the May issue of
Hydrocarbon Processing, discussed pitfalls in planning and
selecting the catalyst evaluation method, and provided best
practices to guide refiners towards an optimal hydroprocessing
catalyst selection.
Part 2 discusses critical aspects of a hydroprocessing catalyst
testing program and presents readers with best practices/
suggestions to ensure a successful benchmarking campaign.
Industrial vs. laboratory-scale fixed-bed reactor. While
refiners conduct a catalyst testing campaign to assist their
catalyst selection process, experimental aspects remain that
require great care and consideration to ensure meaningful reParameter
Diameter
Length
sults
and minimum biases between catalyst vendors.
First, the laboratory-scale fixed-bed reactor should effectively
simulate phenomena in the commercial-scale reactor.
In most hydroprocessing applications, the trickle flow regime
is predominant. Scientists/engineers have proposed experimental
techniques to minimize the effects of non-ideal flow
behaviors on the performance of a laboratory-scale reactor.4
For example, a minimum value of reactor-to-particle diameter
ratio must be ensured to reduce wall effects. Typically, laboratory-scale
fixed-bed reactors have a higher than usual lengthto-diameter
ratio than commercial reactors for good similarities
between two different scales.
The differences between these two different scales are summarized
in TABLE 2. Even with perfect hydrodynamics, other
experimental factors can still cause discrepancies between the
laboratory-scale experiment and the commercial process. In
the authors' hydroprocessing experience, the laboratory-scale
unit's overall performance was often poorer than the commercial
one. Other critical experimental aspects are discussed here
to better explain how discrepancies can occur, as well as the
practical solutions to address them.
LHSV vs. WHSV. Linear hourly space velocity (LHSV) is a
widely accepted parameter to connect a laboratory-scale reactor
with a commercial one. LHSV is a ratio between volumetric
feed flowrate (m3
/hr) and reactor volume (m3
typical unit of LHSV is 1/hr.
TABLE 2. Differences between industrial and laboratory-scale fixed-bed reactor
Industrial-scale reactor
1 m-6 m
10 m-50 m
Flow distribution
Mode of operation
Axial dispersion
Catalyst wetting
Mass and heat transfer
Channeling and wall effects
Requires flow distribution devices to wet
the catalyst beds evenly
Non-isothermal: requires interbed cooling
or quenching in many cases
Negligible
Very good
Very good
Negligible
Laboratory-scale reactor
0.2 cm-4 cm
0.5 m-2 m
Using inert material is enough to promote
good flow distribution and catalyst wetting
Isothermal: no need of interbed cooling,
ideal for kinetic study
Significant in some cases
Generally poorer
Generally poorer
More significant in most cases
Hydrocarbon Processing | JUNE 2022 35
)-as such, the
Hydrocarbon Processing - June 2022

Table of Contents for the Digital Edition of Hydrocarbon Processing - June 2022
