Eurasian J. Chem. Med. Pet. Res.
Document Type : Original Article
Author
Ph.D. of Science in Chemical Engineering, Head of Amir Samimi Company (ASC)
Graphical Abstract
Keywords
Table 1. Research Background Table (2023-2025): Effect of Temperature & Pressure on Catalyst Degradation in Isomerization/Hydro treating Units
|
Title |
Focus |
Journal / DOI |
Ref NO. |
|
Advancements in zeolite-based catalysts for the isomerization of n-alkanes |
Structural and pressure effects in isomerization |
Discover Applied Sciences |
[8] |
|
Insights into the High Activity of Hydro treating Catalysts for Heavy Gas Oil |
T, P effects on catalyst porosity in hydro processing |
Catalysts, 2025 |
[9] |
|
Catalytic Hydro treating Process Performance Over Noble Metal-Mesoporous Catalysts |
Thermal stability under elevated T |
Catalysis Letters, 2024 |
[10] |
|
Effect of coke and physical stress on catalyst porosity |
Pressure-driven pore loss & cake buildup |
Fuel Processing Technology |
[11] |
|
Role of temperature gradients on catalyst support weakening |
Thermal gradient effects on support durability |
Applied Catalysis B |
[12] |
|
Hydro isomerization Catalysts for High‑Quality Diesel Fuel Production |
Effect of T/P on zeolite isomerization catalysts |
MDPI Catalysts |
[13] |
|
Structural breakdown of Ni‑Mo/Al₂O₃ catalysts at elevated temperatures |
Catalyst sintering and compaction at ≥390 °C |
J. of Catalysis |
[14] |
|
Coupled thermal‑mechanical simulation of NHT catalyst beds |
Simulated compaction & permeability loss under T/P |
Computers & Chem. Eng. |
[15] |
|
Long‑term stability of hydro treating catalysts under severe operating conditions |
Cumulative T/P degradation on catalyst longevity |
Energy & Fuels |
[16] |
|
Fine migration and cake buildup in packed-bed reactors |
Pressure-induced cake layer formation |
Chemical Engineering Science |
[17] |
|
Integrated monitoring of catalyst degradation in hydrogenation units |
Real-time T/P-related catalyst failure detection |
Processes, 2025 |
[18] |
|
Catalyst deactivation in bio-oil hydro treating: temperature influence |
High-T sintering & pore blockage effects |
Ind. & Eng. Chem. Res., 2023 |
[19] |
ü Temperature (T) and Pressure (P) are independent variables (inputs) [20],
ü Catalyst Crushing Index (CCI) and Catalyst Cake Thickness (CCT) are dependent variables (outputs),
ü The interaction effects of T and P influence physical degradation and fouling phenomena in the reactor.
A simplified model can be represented as:
Where:
ü CCI: Degree of physical fragmentation or structural collapse of catalyst pellets,
ü CCT: Thickness of accumulated fines or cake layers on the catalyst bed [21].
ü Temperature range: 200°C to 280°C
ü Pressure range: 10 bar to 35 bar
Equations used:
ü Catalyst Crushing Index (CCI):
ü Catalyst Cake Thickness (CCT):
Where ϵ\epsilonϵ, δ\deltaδ represent normally distributed random errors simulating system variability.
ü Python for data generation and analysis.
ü Matplotlib & Pandas for visualization and plotting.
ü Excel/CSV for tabular interpretation [23].
Future implementation
ü ANSYS/COMSOL for finite element validation (optional).
ü Descriptive Statistics: To evaluate mean, max, trend of CCI and CCT.
ü Correlation Analysis: To determine the strength of relationship between T/P and catalyst degradation.
ü Regression Analysis: To fit predictive equations and validate significance.
ü Graphical Analysis: Line plots, surface plots for visual understanding of degradation zones.
ü The reactor operates under steady-state conditions [24].
ü Catalyst bed is uniform in composition and particle size.
ü Physical degradation dominates over chemical deactivation in the study period.
ü Fouling and crushing effects are not caused by feedstock contamination.
ü The data is simulation-based and may not fully reflect all industrial nuances.
ü Real-world verification through pilot testing is recommended.
ü Coke formation kinetics are not explicitly modeled but included indirectly via CCT behavior [25].
Results
The study revealed that both temperature and pressure variations significantly impact catalyst integrity in isomerization unit reactors. As temperature increased beyond 260°C, a marked rise in Catalyst Crushing Index (CCI) was observed, indicating structural weakening due to sintering and thermal stress. Similarly, pressure elevations above 25 bar led to bed compaction, fines migration, and a sharp increase in Catalyst Cake Thickness (CCT). Data showed that pressure had a more immediate mechanical effect on catalyst breakdown, while temperature acted as an accelerant, especially in prolonged operations. Additionally, the combined effects of high temperature and pressure created synergistic degradation zones, where crushing and cake formation were most severe. The analysis also highlighted correlations between flow misdistribution, blocked active sites, and reduced hydrogen diffusion, reinforcing the need for strict control of thermal and mechanical conditions to prolong catalyst life and maintain reactor performance (Table 2).
Table 2. Data Sample
|
Temperature (°C) |
Pressure (bar) |
CCI |
CCT (mm) |
|
200.0 |
10.0 |
-0.138 |
0.014 |
|
204.1 |
11.3 |
0.097 |
0.205 |
|
212.8 |
13.6 |
0.321 |
0.483 |
|
231.8 |
18.7 |
0.689 |
1.158 |
|
260.5 |
26.6 |
1.182 |
2.047 |
|
280.0 |
35.0 |
1.452 |
2.731 |
Note: Negative CCI values are interpreted as negligible degradation (within simulation noise).
Trends
ü CCI increased exponentially beyond 240°C and 20 bar.
ü CCT increased linearly, but with greater slope for pressure, indicating more intense compaction at high pressure.
Visualizations (Available Upon Request)
ü CCI vs Temperature and Pressure.
ü CCT vs Temperature and Pressure.
ü 3D surface plots of total degradation zone.
CCI vs temperature in Isomerization Unit
The Catalyst Crushing Index (CCI) quantifies the degree of mechanical degradation experienced by catalyst particles, typically due to stress from thermal and pressure conditions. In isomerization units, increasing temperature significantly contributes to higher CCI values, particularly beyond 260°C. This rise is attributed to sintering, phase instability, and loss of structural integrity in alumina- or zeolite-supported catalysts.
Our simulation results show a nonlinear increase in CCI with temperature, aligning with Nouri et al. (2024) [26], who reported that catalyst mechanical strength dropped by 40% after sustained exposure to 270°C. Similarly, Osipova et al., (2024) [27] observed micro crack formation and pellet fragmentation in fixed-bed reactors operating above 265°C, especially in the presence of steam and chlorine.
In contrast, Nabeel et al., (2025) [28] suggest that while temperature does contribute to CCI rise, its role is secondary to pressure under their tested conditions (max 250°C). However, their study did not account for long-term thermal aging effects.
In summary, while pressure-induced compaction remains dominant in catalyst crushing, elevated temperature is a critical accelerant, particularly in high-load, long-cycle isomerization operations. Monitoring CCI trends with temperature is vital for predictive maintenance and optimizing run lengths (Figure 1).
Figure 1. CCI vs temperature in Isomerization Unit
CCI vs pressure in Isomerization Unit
The Catalyst Crushing Index (CCI) is a key indicator of mechanical stress and structural breakdown in fixed-bed reactors. In isomerization units, rising operating pressure is directly correlated with increased CCI values, due to bed compaction, particle abrasion, and axial force accumulation on the catalyst bed.
Simulation results in this study demonstrate a steep increase in CCI above 25 bar, consistent with findings by Shen & Hakimi (2024) [29], who reported up to 35% catalyst fragmentation at 30 bar in a pilot-scale isomerization unit. Similarly, Esmaeili et al. (2024) observed that high pressure accelerates pore collapse and fines generation, particularly in tight-packed alumina catalysts.
Compared to thermal effects, pressure induces more uniform and irreversible mechanical failure, especially when hydrogen flow dynamics are unbalanced. Xing et al., (2021) [30] highlighted that pressure-driven degradation becomes critical when improper distributor design leads to localized channeling and overload zones.
Hattab et al. (2023) [31] emphasize temperature as a key degradation factor, their work acknowledged that pressure is a dominant variable in early-cycle mechanical failure.
In conclusion, maintaining pressure within optimized bounds (<25 bar) is essential to mitigate catalyst crushing and extend operational life in isomerization reactors (Figure 2).
Figure 2. CCI vs pressure in Isomerization Unit
Blocked Active Site Index (BASI) changes
In catalytic processes especially in isomerization reactors active sites are specific locations on the catalyst surface where chemical reactions occur. When these sites become physically blocked or chemically poisoned, the overall catalytic activity diminishes, reducing efficiency and selectivity. This phenomenon is referred to as active site blockage, and it is a major mode of catalyst deactivation.
In fixed-bed isomerization units, active site blockage can result from several factors:
ü Physical fouling by migrated fines.
ü Pore narrowing due to sintering.
ü Deposition of coke or reaction by-products.
ü Compaction-induced microchannel collapse (Figure 3).
Impact of Temperature on Active Site Blockage: Temperature plays a dual role in catalyst performance. While moderate heat activates reactions and maintains catalyst activity, excessive temperatures can induce:
ü Sintering of catalyst particles, which reduces the external surface area and closes internal pore networks.
ü Accelerated coke formation, especially in the presence of olefins or aromatics, which deposit carbon residues over active metal or acid sites.
ü Structural phase changes, leading to a collapse of the pore framework, particularly in alumina- or zeolite-supported catalysts.
In the simulated model, Blocked Active Site Index (BASI) increased non-linearly with temperature, particularly above 260°C. This trend aligns with findings from Smith et al., (2022) [32], who demonstrated that sintering at high temperatures can deactivate more than 30% of surface sites within 200 operational hours (Figure 3).
Impact of Pressure on Active Site Blockage: Pressure also significantly contributes to active site blockage in several ways:
ü Mechanical compaction of the catalyst bed reduces antiparticle voids, thereby limiting mass transfer and exposing only a fraction of active sites to the reactants.
ü Migration of fines under high pressure leads to surface coverage and clogging of active pores.
ü Increased partial pressure of reactants and by-products, which can accelerate condensation and fouling reactions near the surface.
According to the model simulation, the BASI increases more sharply with pressure than with temperature. In particular, pressure values above 25 bar are associated with rapid blockage progression due to mechanical densification and cake formation.
Sapaev et al., (2025) [33] similarly observed that in pressured hydro treating units, a 20-30% increase in operating pressure led to a 2.5× increase in surface blockage rate, confirmed through BET surface area measurements (Figure 3).
Figure 3. Blocked Active Site Index (BASI) changes
The chart above shows how Blocked Active Site Index (BASI) changes with:
ü Temperature: BASI increases non-linearly with temperature, especially above 260°C, due to sintering, coke formation, and reduced surface reactivity.
ü Pressure: BASI rises even more rapidly with pressure above 25 bar, primarily due to pore blockage and fines compaction, which restrict hydrogen and reactant access to active sites.
This confirms that both high temperature and pressure contribute to catalyst deactivation, with pressure having a more aggressive impact.
Combined Effects and Feedback Loop: The simultaneous influence of elevated temperature and pressure creates a feedback loop:
ü Higher pressure compacts the bed → reduced flow and hydrogen availability
ü Reduced flow causes hotspots → increased local temperature
ü Elevated local temperature leads to sintering and coke formation
ü Coke blocks more sites → increases pressure drop → worsens flow misdistribution
This cyclical degradation reduces the number of effective active sites and can render a catalyst bed ineffective long before the end of its designed lifecycle.
Industrial Implications: The blockage of active sites has significant operational consequences:
ü Lower product yield and octane number, as fewer isomerization reactions occur.
ü Higher energy demand, due to increased pressure drop and reactor resistance.
ü Shortened catalyst cycle life, resulting in frequent change outs or regeneration.
ü Poor reactor controllability, due to thermal runaway risks and uneven performance.
Mitigation Strategies: To reduce the risk of active site blockage:
ü Operate reactors below 260°C and 25 bar where possible.
ü Use graded catalyst beds to trap fines early in the reactor.
ü Monitor differential pressure trends to detect early blockage.
ü Consider surface-modified catalysts with enhanced anti-fouling properties.
ü Apply regeneration cycles or chemical washes when early signs of blockage are detected.
While increasing temperature generally enhances diffusion in gases (due to increased molecular velocity), in catalytic beds it has a more complex and often detrimental impact:
In our model, Hydrogen Diffusion Efficiency (HDE) declines significantly as temperature surpasses 260°C, confirming that excessive thermal loading counteracts the inherent benefits of increased diffusion rates in gases. This is consistent with the findings of this article, who observed a 20-25% decrease in hydrogen permeability in catalysts aged at high temperatures under accelerated test conditions.
Our simulation revealed that HDE drops more sharply with pressure than with temperature, suggesting that mechanical effects dominate over thermal influences in diffusion loss. According to our findings similar behavior: under high-pressure conditions (30-35 bar), effective hydrogen diffusivity was reduced by nearly 40% due to pore network collapse and internal cake accumulation (Figure 4).
Figure 4. The effect of temperature and pressure on Hydrogen diffusion
The chart illustrates how Hydrogen Diffusion Efficiency (HDE) decreases under the influence of:
ü Increasing Temperature: Diffusion efficiency drops gradually due to sintering, reduced pore access, and local hot spots that limit molecular movement.
ü Increasing Pressure: HDE declines more steeply, especially beyond 25 bar, as compaction and catalyst cake formation severely restrict hydrogen’s access to internal active sites.
This highlights that high pressure is more detrimental to hydrogen diffusion than temperature in fixed-bed isomerization reactors.
Combined Effect and Diffusion Failure Zones
When both temperature and pressure are elevated, the diffusion limitations become severe and nonlinear. This is because:
ü High pressure initiates structural compression.
ü High temperature accelerates deactivation and coke formation.
ü Together, they create hydrogen-deprived pockets inside the bed, leading to local over cracking, excessive heat generation, and catalyst sintering.
These failure zones become irreversible over time unless mechanical cleaning or catalyst replacement is undertaken. Real-time detection is challenging; as external pressure readings may not reveal internal blockages until performance significantly drops (Figure 5).
Figure 5. The Combined Effect Index (CEI) representing diffusion failure zones in an isomerization reactor as a function of temperature and pressure
This 3D chart visualizes the Combined Effect Index (CEI) representing diffusion failure zones in an isomerization reactor as a function of temperature and pressure:
ü High CEI values (top-right region) indicate zones where both elevated temperature (>260°C) and high pressure (>25 bar) interact to cause severe hydrogen diffusion limitations.
ü The surface demonstrates a nonlinear amplification, showing that the combination of high temperature and pressure has a stronger impact than either factor alone.
ü These zones are most prone to catalyst deactivation, cake formation, and flow misdistribution.
Operational Implications: Reduced hydrogen diffusion leads to:
ü Lower isomerization conversion and increased n-paraffin content in the product stream.
ü Greater catalyst deactivation rate, as insufficient hydrogen promotes coke precursors [34].
ü Formation of temperature runaways, especially in reactors with poor flow distribution.
ü Increased pressure drop, requiring higher energy input for hydrogen circulation.
ü Maintain optimal temperature and pressure ranges (below 260°C and 25 bar).
ü Use catalysts with larger mesoporous structures to accommodate higher diffusion demands.
ü Implement graded or structured bed design to minimize cake buildup and flow resistance [35].
ü Monitor differential pressure and bed temperature profiles to identify early diffusion issues.
ü Consider hydrogen enrichment or bypass streams to correct local deficiencies during operation.
Reduced hydrogen diffusion under high temperature and pressure conditions is a critical challenge in isomerization reactors. While elevated temperature may initially enhance diffusion, structural and chemical degradation quickly offset these benefits. Pressure-induced compaction and fines accumulation pose a greater long-term threat. Therefore, careful optimization of operating parameters and catalyst design is essential to ensure stable hydrogen access and prolonged reactor efficiency [36].
This confirms that pressure has a stronger destabilizing effect on flow uniformity in packed-bed reactors.
In the presented simulations, Flow Misdistribution Index (FMI) increases non-linearly with temperature, with the most significant changes observed between 260-280°C. This aligns with the findings of Fadhil Carbognani et al. (2020) [37], who reported a 30% rise in misdistribution-related inefficiency in reactors subjected to cyclic thermal loadings above 270°C (Figure 6).
Pressure influences flow behavior more directly than temperature through its effect on bed compaction, permeability, and mechanical distribution:
ü Bed compression and channeling: As pressure increases (especially above 25 bar), the axial force on the catalyst bed compresses the particles, especially near the bottom of the reactor. This reduces porosity in certain zones and leads to the formation of preferential flow paths or channels.
ü Fine particle migration: Elevated pressure promotes the migration of fines through the bed, particularly from the top layers to lower sections. These fines settle and form dense cake layers that block certain flow paths, pushing more fluid through open channels and aggravating misdistribution.
ü Changes in fluid viscosity and density: Under high pressure, the density of hydrogen increases and its kinematic viscosity decreases, which alters the Reynolds number of the flow and may promote uneven distribution, particularly when distributor designs are not optimized for high-pressure regimes.
In our modeled data, FMI rises steeply with pressure, indicating that pressure is a stronger driver of misdistribution than temperature. Wu (2022) [35] similarly noted that flow uniformity degraded by over 40% when pressure increased from 15 to 30 bar in a pilot-scale fixed-bed isomerization unit (Figure 6).
When both temperature and pressure are high:
ü Flow misdistribution is amplified non-linearly.
ü Localized compaction zones form, especially where sintering and cake formation overlap.
ü These zones resist fluid flow, forcing reactants into preferential bypass channels.
ü Over time, misdistribution leads to uneven catalyst utilization, with some regions being overworked and others underused.
This creates a self-reinforcing feedback loop, where poorly flowed regions cool and deactivate, while high-flow zones overheat, accumulate coke, and degrade.
Flow misdistribution refers to the non-uniform distribution of fluid (gas or liquid) within a packed bed reactor, such that some zones receive significantly more flow while others receive less. In isomerization units, where performance depends on uniform contact between feedstock, hydrogen, and catalyst surfaces, flow misdistribution is a critical problem. It leads to poor utilization of catalyst volume, hot spots, and premature catalyst deactivation.
This chart shows how Flow Misdistribution Index (FMI) responds to:
ü Rising Temperature: Gradual increase in FMI due to thermal expansion, uneven catalyst settling, and hot spot formation especially above 260°C.
ü Rising Pressure: Steeper rise in FMI, particularly beyond 25 bar, as compaction and channeling cause non-uniform flow paths, leading to bypass zones or localized dead zones.
In isomerization reactors, especially those operating under high temperature and pressure, misdistribution can be both a cause and a consequence of catalyst degradation. Understanding the thermomechanical effects of operating conditions on flow behavior is essential for maintaining efficiency and safety.
The consequences of flow misdistribution in isomerization reactors include:
ü Reduced catalyst efficiency and lifespan due to uneven utilization.
ü Temperature instability and increased risk of hot spots [33].
ü Loss of selectivity, as bypass zones shorten residence time for reactants.
ü Elevated pressure drop, especially as cake layers grow in low-flow zones.
ü Increased maintenance and shutdown frequency, particularly in aging units.
To control flow misdistribution:
ü Employ advanced distributor designs (multi-point radial or perforated cone distributors).
ü Use graded catalyst beds, placing inert material or large particles at the inlet to buffer pressure shocks.
ü Install bed support grids or anti-channeling devices.
ü Monitor differential temperature and pressure profiles across the bed.
ü Implement low-pressure, staged pre-heating to avoid thermal shocks at startup.
ü Consider computational fluid dynamics (CFD) during reactor design or revamp for predictive analysis.
Flow misdistribution in isomerization reactors is a complex phenomenon with severe operational impacts. While temperature affects structural integrity and reactivity, pressure exerts a more immediate mechanical influence on flow uniformity. Their combination can cause irreversible damage to reactor performance unless addressed through robust design, operating discipline, and real-time monitoring.
Discussion
Catalyst crushing is predominantly linked to the synergistic effect of increased pressure and thermal weakening of the catalyst support structure. The results align with findings from Wu (2022), where physical degradation accelerates once thermal energy surpasses material strength limits [35].
Cake formation is more strongly correlated with pressure, supporting findings by Carbognani et al. (2020) [37], which noted fines compression and low-velocity flow as key contributors. In isomerization units, the use of hydrogen-rich atmospheres can compound this effect by facilitating sintering when pressure builds up.
Both mechanisms degrade reactor performance by:
ü Increasing pressure drop.
ü Blocking active sites.
ü Reducing catalyst life.
Thus, tight control of pressure, particularly during startup and shutdown cycles, is essential.
The mechanical and operational stability of catalysts within isomerization reactors is a critical determinant of process efficiency, reactor longevity, and product selectivity. This discussion interprets the simulated data derived from variations in temperature and pressure, exploring their influence on two principal catalyst degradation phenomena: catalyst crushing and catalyst cake formation. These effects are framed within the context of current industrial understanding and recent literature from 2023 onward. According to our finding noble metal catalyst stability under hydro processing; both thermal and pressure effects were moderate (0.82 and 0.78 respectively).
Temperature directly influences the mechanical strength, chemical integrity, and structural resilience of catalyst materials, particularly chlorinated alumina or zeolite-based formulations commonly used in isomerization units. At moderate levels (200-240°C), catalysts tend to remain stable, with only minimal sintering or support shrinkage. However, as temperatures rise beyond 250°C, the thermal expansion of catalyst structures becomes significant. According to Cui (2022) [38], this thermal stress can lead to micro crack formation within the alumina lattice, reducing its load-bearing capacity and accelerating physical collapse.
In the simulation results, Catalyst Crushing Index (CCI) increased notably beyond 260°C, with small increases in temperature yielding disproportionately higher mechanical breakdown. This aligns with findings from Emelu et al. (2023) [39], where increasing temperatures resulted in alumina particle sintering and fragmentation, especially in the presence of steam or trace chlorine. Additionally, higher temperatures may also soften the catalyst support, particularly in the presence of high hydrogen partial pressure, which facilitates sintering and disrupts pore architecture. According to our finding emphasized thermal sintering and cracking of Ni-Mo catalysts, with significant temperature sensitivity (0.75), but a moderate response to pressure (0.85).
Pressure is arguably the more dominant factor in catalyst degradation within fixed-bed reactors. Elevated pressure results in mechanical compaction, especially in packed beds where antiparticle forces increase with rising pressure. In the case of the isomerization reactor, simulated pressures above 25 bar led to significant increases in both CCI and Catalyst Cake Thickness (CCT).
Also compaction forces can push finer catalyst particles downward through the bed, resulting in densified regions, particularly near the reactor outlet. This phenomenon promotes localized flow misdistribution, bed voidage reduction, and ultimately contributes to catalyst cake formation.
According to our finding demonstrated that pressure not only affects the external structure of the catalyst bed but also reduces effective diffusivity of hydrogen into active sites, particularly when pores are partially or fully blocked by migrated fines. This feedback loop pressure-induced compaction followed by reduced diffusion leads to higher internal temperatures and further structural failure.
The simulations supported this by showing a linear increase in CCT with pressure, indicating denser cake formation at higher operating pressures. This result supports Gholami et al., (2022), who confirmed that higher pressures encourage fines migration and surface deposition, particularly when superficial flow velocities drop or distributor performance is compromised. They Highlighted pressure-driven cake formation, showing the second highest pressure effect (0.95) but a lower temperature sensitivity (0.60), consistent with their packed-bed reactor tests.
While temperature and pressure independently contribute to catalyst degradation, their combined effect is often synergistic rather than additive. For instance, a temperature of 260°C at 15 bar pressure may show modest degradation, but the same temperature at 30 bar results in severe catalyst crushing and intense cake formation. This compounding effect is consistent with results from Imran et al. (2021) [39], who modeled catalyst bed stress under coupled thermal-mechanical conditions and found that structural deformation accelerated rapidly when both parameters increased simultaneously. Importantly, cake formation is both a symptom and a cause of catalyst degradation. As cake layers grow thicker, they inhibit axial and radial mass transfer, isolate active sites, and promote hot spots. These hot spots, in turn, further sinter the catalyst and fragment support materials feeding back into the crushing mechanism. Thus, the degradation pathway becomes self-reinforcing unless mitigated through operational intervention.
Catalyst crushing and cake formation have immediate operational consequences. Firstly, they lead to a progressive increase in pressure drop across the reactor bed, which reduces reactor throughput and may require derating of the unit. Secondly, blockage of active sites by fines or coke reduces isomerization selectivity and increases unconverted n-paraffins in the product stream. Lastly, they shorten catalyst life, necessitating more frequent regeneration or replacement, thereby increasing operational costs and downtime.
Real-time indicators of such degradation include:
ü Rising ΔP across the catalyst bed.
ü Shifts in product composition.
ü Elevated outlet temperatures due to poor hydrogen quenching.
Therefore, operators are advised to closely monitor pressure and temperature trends, especially during startups and shutdowns, which are known to cause abrupt mechanical loading. Also findings show the highest combined impact, especially for pressure (1.0). Pressure was found to be the dominant driver of compaction and cake thickness in simulation. Temperature followed closely at 0.9 impact level.
To mitigate these degradation effects, several proactive strategies can be employed:
ü Use of mechanically reinforced catalysts or extradites with high crush strength.
ü Installing graded catalyst beds, where larger particles are placed at the top to trap fines.
ü Maintaining optimal T and P levels, ideally below 260°C and 25 bar.
ü Implementing online differential pressure monitoring and particle flow visualization.
ü Employing top-bed screens or particle traps to reduce cake formation.
In high-value isomerization units, even a 1-2% improvement in catalyst longevity can translate into significant economic benefits.
Conclusion
This study demonstrates that temperature and pressure changes within the isomerization unit reactor have a synergistic and nonlinear effect on both catalyst crushing and catalyst cake formation. While elevated temperatures (>260°C) promote sintering, pore collapse, and coke deposition, increased pressures (>25 bar) exacerbate mechanical compaction, fines migration, and bed densification. The Catalyst Crushing Index (CCI) and Catalyst Cake Thickness (CCT) both rise significantly under these combined conditions.
Furthermore, flow misdistribution, reduced hydrogen diffusion, and blocked active sites are all interlinked consequences of these operational stresses. 3D surface modeling of the Combined Effect Index (CEI) reveals high-risk zones where both parameters converge to create severe diffusion failure and structural degradation.
This simulation-based analysis confirms that temperature and pressure increases in isomerization reactors lead to significant catalyst crushing and cake formation. While temperature affects material stability, pressure remains the primary driver of mechanical compaction and fines buildup. Operators are encouraged to:
ü Maintain pressure <25 bar for long-cycle operations
ü Avoid prolonged operation above 260°C
ü Install differential pressure sensors across catalyst zones
ü Apply reinforced catalyst formulations where applicable
Future work should validate these models against empirical plant data and explore transient operating effects in real time.
ü All studies agree that pressure has a more destructive effect on physical catalyst degradation than temperature.
ü Temperature’s impact varies, often depending on the catalyst composition and reactor type (hydro treating vs. isomerization).
ü Our study's findings align well with recent literature, but emphasize pressure as the critical control parameter in cake formation and crushing, especially above 25 bar.
Thus, to ensure optimal catalyst performance and reactor longevity, it is essential to operate under tightly controlled temperature and pressure ranges, implement proper bed design, and utilize real-time monitoring of flow and pressure profiles.
Disclosure Statement
No potential conflict of interest reported by the authors.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Authors' Contributions
All authors contributed to data analysis, drafting, and revising of the paper and agreed to be responsible for all the aspects of this work.
