Two-Stage Fixed-Bed Catalysis for High-Yield BTX From Pyrolysis Oil
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for upgrading pyrolysis oil to light aromatic compounds, such as benzene, toluene, and xylenes, face challenges in achieving sufficient yield under mild conditions while minimizing coke production and reactor plugging, often requiring complex and costly processes.
Innovation Solution
A two-stage fixed-bed catalytic process using a first reactor with a treating catalyst and a second reactor with a mesoporous supported metal catalyst, converting multi-ring aromatic compounds to light aromatics through sequential reactions in fixed-bed reactors, avoiding severe conditions and coke formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multiple reactions are accomplished in a single processing step, then the process complexity is reduced, but the yield is insufficient and severe conditions are required which increases capital and operating costs
Solution Approach 1:
The single processing step is segmented into two sequential fixed-bed reactor stages, each containing different catalyst beds optimized for specific reactions. The first reactor handles hydrogenation and ring-opening, while the second reactor performs disproportionation and transalkylation, allowing each stage to operate under optimized conditions for its specific function.
Solution Approach 2:
Different catalyst compositions are placed in different locations (reactor stages) to perform different functions. The first reactor uses catalysts suitable for hydrogenation and ring-opening, while the second reactor uses catalysts optimized for disproportionation and transalkylation, creating local optimization of reaction conditions.
2Productivity
If severe processing conditions are employed to increase yield, then the demand for BTEX can be met, but capital and operating costs increase
Solution Approach 1:
The two-stage process allows different temperature, pressure, and catalyst parameters to be optimized for each stage. The first reactor operates under conditions optimized for hydrogenation and ring-opening, while the second reactor operates under conditions optimized for disproportionation and transalkylation, achieving high yield without requiring uniformly severe conditions throughout the entire process.
3Device complexity
If conventional methods are used to accomplish the reactions, then the process can be simplified, but excessive coke production occurs which causes reactor plugging
Solution Approach 1:
The harmful coke formation problem is extracted and addressed by separating the reaction into two stages with different catalysts. The first reactor's catalysts are selected to minimize coke formation during hydrogenation and ring-opening, while the second reactor's catalysts are optimized to prevent coke deposition during disproportionation and transalkylation, removing the plugging issue from the simplified process.
4Device complexity
If a single reactor system is used, then the device complexity is reduced, but the ability to handle raw heavy pyrolysis oil feeds effectively is compromised
Solution Approach 1:
The reactor system is segmented into two fixed-bed reactors in series, allowing the first reactor to handle the challenging raw heavy pyrolysis oil feed with catalysts designed for hydrogenation and ring-opening, while the second reactor processes the intermediate stream with catalysts optimized for disproportionation and transalkylation, effectively handling the complex feedstock.
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 achieves higher yields of light aromatic compounds with reduced coke formation and reactor plugging, utilizing a fixed-bed system that does not require catalyst separation, and can handle raw heavy pyrolysis oil feeds effectively.
Implementation Method 1
Multi-ring aromatic compounds in the pyrolysis oil can be converted to light aromatic compounds, which can include benzene, toluene, ethylbenzene, xylenes (BTEX), other aromatic compounds, or combinations of these by various reactions, such as, but not limited to hydrogenation, ring opening, disproportionation, dealkylation, transalkylation, cracking, or aromatic cracking.
Implementation Method 2
The first fixed-bed reactor may be operable to contact a pyrolysis oil feed with hydrogen in the presence of the treating catalyst and the mixed metal oxide catalyst to produce an intermediate stream comprising light aromatic compounds
Implementation Method 3
The second fixed-bed reactor may include a mesoporous supported metal catalyst and may be operable to convert at least a portion of the intermediate aromatic compounds to BTEX
Data Source
AI summary
Systems for upgrading pyrolysis oil include a first fixed-bed reactor having a first catalyst bed and a second catalyst bed. The first catalyst bed includes: a first treating catalyst containing alumina, binder, Mo, Ni, and P; a second treating catalyst made of Al2O3, SiO2, ZrO2, NiO, and WO3; or both. The second catalyst bed includes mixed metal oxide catalyst. The first fixed-bed reactor contacts the pyrolysis oil with hydrogen in the presence of the treating catalyst and the mixed metal oxide catalyst to produce an intermediate stream comprising light aromatic compounds. The system includes a second fixed-bed reactor downstream that includes a mesoporous supported metal catalyst having nickel and tungsten on a mesoporous support. The second fixed-bed reactor contacts the intermediate stream with hydrogen in the presence of the mesoporous supported metal catalyst to produce a second reactor effluent comprising aromatic compounds having six to eight carbon atoms.