Zeolitic Catalyst Passivation for Hydrocracking Start-up Safety
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Solution Overview
Problem
The existing processes for starting up hydrocracking units are risky due to uncontrolled cracking reactions during the start-up phase, particularly in catalysts with high acidic zeolite content, which can lead to heat excursions and reactor damage, and require complex and costly safety precautions.
Innovation Solution
An ex-situ process that sulfurizes and activates the hydrogenating function while passivating the acid function of the catalyst by introducing nitrogen at a low temperature and sulfurizing with hydrogen sulfide, allowing the catalyst to be ready for use upon arrival, reducing the risk of premature cracking and simplifying the start-up procedure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the catalyst contains high acidic zeolite content to increase cracking activity and productivity, then the cracking capacity and productivity are improved, but the risk of uncontrolled cracking reactions and heat excursions during start-up increases
Solution Approach 1:
The patent applies preliminary action by introducing a nitrogen-containing compound to the catalyst before the start-up phase. This pre-treatment passivates the acid sites, reducing the cracking activity during start-up to prevent uncontrolled reactions and heat excursions. The nitrogen compound is introduced ex-situ before catalyst activation, allowing the catalyst to be safely commissioned without compromising its ultimate cracking capacity once steady-state operation is reached.
2Productivity
If the catalyst is activated by sulfurization to enhance hydrogenating function, then the hydrogenation activity is improved, but the catalyst becomes more reactive and requires longer start-up time with safety risks
Solution Approach 1:
The patent combines preliminary action with parameter changes by performing the nitrogen compound introduction ex-situ, before catalyst activation and sulfurization. This sequencing allows the catalyst to be pre-passivated, then activated and sulfurized in a controlled manner. The result is that the catalyst reaches its active state faster without the safety risks associated with introducing nitrogen after activation, thus reducing start-up time while maintaining safety.
Solution Approach 2:
The patent applies parameter changes by controlling the timing and conditions of nitrogen compound introduction. By introducing the nitrogen-containing compound before activation and sulfurization, the patent changes the chemical state parameters of the catalyst during the preparation phase. This allows optimization of both the hydrogenation activity (through proper sulfurization) and start-up safety (through pre-passivation), resolving the contradiction between activity enhancement and start-up time.
3Reliability
If nitrogen-containing compound is introduced after catalyst activation to passivate acid sites, then the start-up safety is improved, but the process becomes more complex and time-consuming
Solution Approach 1:
The patent resolves this contradiction by performing the nitrogen compound introduction as a preliminary action before catalyst activation and sulfurization. This ex-situ treatment simplifies the overall process by combining passivation with the catalyst preparation steps, rather than requiring a separate post-activation treatment. The process becomes more straightforward: prepare catalyst with nitrogen compound, activate and sulfurize, then commission directly, reducing both complexity and time.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach minimizes start-up time, reduces ammonia desorption, enhances safety, and ensures stable catalyst performance by effectively reducing initial cracking activity without compromising steady-state activity, thus enabling quicker production of specification-compliant petroleum products with improved productivity.
Implementation Method 1
The treatment comprises the sulfurization and the activation of the hydrogenating function and the passivation of the acid function of the catalyst... This passivation consists in reducing the hydrocracking activity of the acid sites
Implementation Method 2
The activation is implemented either in-situ (in the reactor) or ex-situ (outside of the reactor)... The ex-situ methods are of two types and produce catalysts that are either simply sulfurized, or sulfurized and activated
Data Source
AI summary
A process for ex-situ treatment of a catalyst that contains at least one hydrogenating phase, and at least one amorphous silica-alumina or a zeolite that contains acid. The process includes:a stage for introducing nitrogen by contact at a temperature that is less than 100° C., with at least one basic nitrogen-containing compound that is ammonia or a compound that can be decomposed into ammonia, the compound being introduced at a rate of 0.5-10% by weight (expressed in terms of N), anda sulfurization/activation stage with a gas that contains hydrogen and hydrogen sulfide at a temperature of at least 250° C., with this stage being carried out before or after the stage for introducing said nitrogen-containing compound,and optionally drying the catalyst that is obtained.This treatment allows a rapid, effective start-up on the hydrocracking unit.