Pyrolysis Oil Purification via Dynamic Catalyst Circulation
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Solution Overview
Problem
Pyrolysis oils from plastics and solid recovered fuels contain high levels of impurities such as diolefins, metals, and halogenated compounds, leading to operability issues like corrosion, coking, and catalytic deactivation in steam cracking units, which reduces the yield of light olefins and requires frequent catalyst replacement in fixed bed hydrotreatment units.
Innovation Solution
A process involving selective hydrogenation, hydroconversion in bubbling, entrained, or moving bed reactors, followed by fixed bed hydrotreatment, to purify and transform the pyrolysis oils, allowing continuous catalyst addition and removal without unit shutdown, thereby extending cycle duration and improving the quality of the hydrocarbon effluent for steam cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed bed hydrotreatment is used to treat pyrolysis oils, then impurities are removed, but catalyst deactivation occurs frequently requiring unit shutdown for catalyst replacement
Solution Approach 1:
The patent transitions from static fixed bed reactors to dynamic fluidized bed or circulating fluidized bed reactors, where catalyst particles are continuously suspended and circulated. This dynamic system allows continuous catalyst regeneration and replacement without shutting down the treatment unit, resolving the contradiction between catalyst life and unit availability.
Solution Approach 2:
The invention implements continuous catalyst circulation and regeneration systems where spent catalyst is continuously regenerated in separate reactors while fresh catalyst continuously treats the pyrolysis oil. This continuous operation eliminates shutdowns for catalyst replacement, maintaining both high reliability and productivity simultaneously.
2Ease of manufacture
If pyrolysis oils with high impurity content are directly sent to steam cracking units, then processing simplicity is maintained, but operability problems occur including corrosion, coking, and catalytic deactivation
Solution Approach 1:
The patent divides the treatment process into multiple sequential stages: fluidized bed hydrotreatment for bulk impurity removal, followed by fixed bed hydrotreatment for polishing, and fractionation. This segmented approach effectively removes impurities while maintaining overall process manageability, resolving the contradiction between simplicity and reliability.
Solution Approach 2:
The invention introduces intermediate treatment stages with different catalyst types and reaction conditions between the pyrolysis oil feed and the steam cracking unit. These intermediate treatments act as mediators that progressively remove impurities, protecting the steam cracking unit while maintaining a structured but manageable process flow.
3Stability of the object's composition
If selective hydrogenation is performed at high temperature to remove diolefins, then gum formation is reduced, but energy consumption increases
Solution Approach 1:
The patent employs parameter optimization in the selective hydrogenation stage, using moderate temperatures (30-150°C) with high hydrogen pressure (30-200 bar) and specific catalysts (Ni, Pd, Pt on alumina or silica). This parameter combination achieves effective diolefin removal and gum prevention while minimizing energy consumption compared to high-temperature approaches.
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
The process effectively purifies pyrolysis oils, reduces impurity-related issues, extends catalyst cycle life, and enhances the yield of light olefins by transforming heavy compounds into lighter ones, making the oils compatible with steam cracking units and reducing corrosion and coking risks.
Implementation Method 1
a selective hydrogenation step is carried out in a reaction section supplied at least by said feedstock and a gas stream comprising hydrogen, in the presence of at least one selective hydrogenation catalyst
Implementation Method 2
a hydroconversion step is implemented in a hydroconversion reaction section using at least one ebullated bed, entrained bed and/or moving bed reactor
Implementation Method 3
a fixed bed hydrotreatment step is implemented in a hydrotreatment reaction section having at least one catalytic bed comprising at least one hydrotreatment catalyst
Implementation Method 4
a separation step is carried out supplied with the hydroconverted effluent from said hydroconversion step, to obtain at least one gaseous effluent, one aqueous effluent and one hydrocarbon liquid effluent
Data Source
Figure 1
AI summary
The present invention relates to a method for processing a pyrolysis oil from plastics and/or solid recovered fuels (SRF), comprising: a) optionally, selective hydrogenation of the feedstock; b) bubbling bed, entrained bed and/or moving bed hydroconversion in order to obtain a hydroconverted effluent; c) separation of the hydroconverted effluent in the presence of an aqueous flow in order to obtain a gaseous effluent, an aqueous liquid effluent and a hydrocarbon liquid effluent; d) fractionation of the hydrocarbon liquid effluent in order to obtain at least one gaseous flow and a fraction having a boiling point less than or equal to 385°C and a fraction having a boiling point greater than 385°C; e) hydroprocessing of the fraction comprising compounds having a boiling point less than or equal to 385°C in order to obtain a hydroprocessed effluent; f) separation in order to obtain at least one gaseous effluent and a hydroprocessed hydrocarbon liquid effluent.