Catalyst Systems for Cyclic Flow Reactors
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Solution Overview
Problem
High-temperature hydrocarbon reforming processes face challenges in maintaining catalytic activity and structural stability due to cyclic oxidizing and reducing conditions, leading to catalyst degradation and reduced operating lifetime in reverse flow reactors.
Innovation Solution
A catalyst system comprising Ni, Rh, Ru, Pd, Pt, Cu, or Ir with a thermally stable metal oxide support layer like stabilized zirconia, perovskite, or spinel, annealed at high temperatures and exposed to cyclic reforming conditions, which forms a stable NiAl2O4 phase, maintaining activity and adhesion to the support structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If conventional catalysts are used in high-temperature cyclic reforming conditions, then initial catalytic activity can be achieved, but catalyst degradation occurs rapidly leading to reduced operating lifetime
Solution Approach 1:
The invention uses composite materials consisting of nickel oxide particles dispersed on a mixed metal oxide support containing at least two metal oxides (such as alumina and magnesia, or alumina and silica). This composite structure provides both high initial catalytic activity and enhanced stability under cyclic oxidizing and reducing conditions, resolving the contradiction between catalyst lifetime and stability.
Solution Approach 2:
The invention changes the chemical and physical parameters of the catalyst system by using nickel oxide rather than metallic nickel, and employing a mixed metal oxide support with specific surface area and pore structure characteristics. These parameter changes enable the catalyst to maintain stability through cyclic conditions while preserving activity.
2Quantity of substance
If high surface area support structures are used to increase catalytic activity, then more active sites are available, but structural stability at high temperatures deteriorates
Solution Approach 1:
The support structure is designed as a composite of at least two metal oxides (e.g., alumina-magnesia or alumina-silica) where the combination provides both high surface area and thermal stability. The synergistic interaction between the different metal oxides maintains structural integrity at high temperatures while providing sufficient surface area for catalytic activity.
Solution Approach 2:
The invention applies local quality by creating a hierarchical structure where nickel oxide particles are dispersed on the metal oxide support surface. The support provides thermal stability in the bulk while maintaining high surface area regions for catalytic activity, and the nickel oxide particles are strategically positioned to maximize active sites without compromising overall structural stability.
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 catalyst system exhibits extended catalytic activity and structural stability under high-temperature cyclic conditions, reducing degradation and maintaining performance over time.
Implementation Method 1
annealing the supported catalyst system and the support structure at an annealing temperature of 1000° C. or more to form an annealed catalyst system and support structure
Implementation Method 2
forming a stable NiAl2O4 phase
Implementation Method 3
reacting a mixture comprising fuel and 0.1 vol % or more of O2 under combustion conditions in a combustion zone
Implementation Method 4
exposing the reactant stream to the catalyst system in the reaction zone at a temperature of 1000° C. or more to form a product stream containing H2
Implementation Method 5
cyclic oxidizing and reducing conditions
Implementation Method 6
cyclic oxidizing and reducing conditions
Data Source
AI summary
Catalyst systems are provided for reforming of hydrocarbons, along with methods for using such catalyst systems. The catalyst systems can be deposited or otherwise coated on a surface or structure, such as a monolith, to achieve improved activity and/or structural stability. The metal oxide support layer can correspond to a thermally stable metal oxide support layer, such as a metal oxide support layer that is thermally phase stable at temperatures of 800° C. to 1600° C. The catalyst systems can be beneficial for use in cyclical reaction environments, such as reverse flow reactors or other types of reactors that are operated using flows in opposing directions and different times within a reaction cycle.