Manganese Oxide Coating for Coke Resistance in Steam Pyrolysis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current technologies in hydrocarbon steam pyrolysis for olefin production face challenges with carbon-based fouling and catalytic reactions, leading to reduced furnace efficiencies and increased maintenance costs due to the limitations of chromia-forming austenitic stainless steels under high-temperature, carburizing conditions.
Innovation Solution
A functionally-graded coating system comprising Mn x O y and MnCr 2 O 4, combined with a W-based matrix, is applied to the substrate, providing a catalytically active surface that resists filamentous coke formation and enhances corrosion protection, while maintaining chemical and thermo-mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chromia-forming austenitic stainless steels are used as substrate, then corrosion protection is provided, but under high-temperature carburizing conditions the chromia converts to chromium carbides leading to volume expansion, embrittlement, and loss of protection
Solution Approach 1:
The coating system is divided into two distinct regions: an outer catalytic region containing MnO, Mn2O3, Mn3O4, or MnCr2O4 that provides coke-resistant properties, and an inner buffer region containing Ni-W-Si-C alloy that provides mechanical stability and adhesion to the substrate. This segmentation allows each region to perform its specific function independently, resolving the contradiction between corrosion protection and compositional stability under high-temperature carburizing conditions.
Solution Approach 2:
The invention uses a composite coating structure with two different material regions: an oxide-based outer layer for catalytic activity and coke resistance, and a metal alloy inner layer for mechanical stability and adhesion. This composite approach combines the advantages of different material systems to simultaneously achieve corrosion protection, compositional stability, and catalytic functionality.
2Productivity
If higher operating temperatures and greater cracking severity are used, then olefin production efficiency is improved, but unwanted catalytic reactions increase leading to carbon or coke build-up on coil surfaces
Solution Approach 1:
The invention converts the harmful catalytic activity of the coil surface that causes coke build-up into a beneficial catalytic function. The outer region containing MnO, Mn2O3, Mn3O4, or MnCr2O4 provides controlled catalytic activity that promotes desired cracking reactions while resisting unwanted coke formation, allowing higher operating temperatures and cracking severity to be used for improved productivity without the harmful side effects.
Solution Approach 2:
The invention changes the chemical and physical parameters of the coil surface by applying a specialized coating with specific oxide compositions (MnO, Mn2O3, Mn3O4, or MnCr2O4) in the outer region. This parameter change modifies the surface properties to provide coke-resistant catalytic activity, enabling the process to operate at higher temperatures and cracking severity for improved olefin production efficiency without excessive coke build-up.
3Object-generated harmful factors
If inert coatings are applied to shut down catalytic reactions, then filamentous coke formation is reduced, but the coatings rarely extend run lengths beyond 100 days and require frequent maintenance
Solution Approach 1:
The invention applies local quality by creating an outer region with specific catalytic properties (MnO, Mn2O3, Mn3O4, or MnCr2O4) that is tailored to resist filamentous coke formation while maintaining catalytic activity for desired reactions. This localized functional differentiation allows the coating to selectively inhibit harmful coke formation while permitting beneficial cracking reactions, extending furnace run length beyond the 100-day limitation of conventional inert coatings.
Solution Approach 2:
The invention changes the functional parameters of the coating surface from completely inert to selectively catalytic. The outer region containing manganese oxides or spinel provides controlled catalytic activity that promotes desired cracking reactions while resisting unwanted filamentous coke formation. This parameter change from inertness to selective catalysis extends the coating's operational life and furnace run length while maintaining protection against coke buildup.
4Ease of operation
If conventional austenitic stainless steels are used, then adequate chemical and mechanical properties are provided, but the surfaces are prone to filamentous coke formation catalyzed by transition metal species
Solution Approach 1:
The invention extracts the harmful catalytic function from the substrate surface by applying a specialized coating. The outer region containing MnO, Mn2O3, Mn3O4, or MnCr2O4 replaces the unwanted catalytic activity of transition metal species in conventional austenitic stainless steels, eliminating filamentous coke formation while preserving the underlying substrate's adequate mechanical and physical properties.
Solution Approach 2:
The invention creates a composite structure where the conventional austenitic stainless steel substrate provides adequate mechanical and physical properties, while the applied coating with MnO, Mn2O3, Mn3O4, or MnCr2O4 in the outer region provides coke-resistant surface properties. This composite approach allows the substrate to maintain its structural integrity while the coating surface prevents catalytic coke formation.
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 coated substrates significantly extend the operational run length, reduce energy requirements, and minimize greenhouse gas emissions by promoting carbon gasification and inhibiting unwanted catalytic reactions, thereby improving plant efficiencies and profitability.
Implementation Method 1
the first region is outermost and comprises Mn x O y, MnCr 2 O 4, or combinations thereof
Implementation Method 2
providing a catalytically active surface that resists filamentous coke formation and enhances corrosion protection
Implementation Method 3
promoting carbon gasification and inhibiting unwanted catalytic reactions
Data Source
Figure 1a~1b
Figure 2
Figure 3
AI summary
This disclosure describes a coating composition comprising: MnxOy, MnCr2O4, or combinations thereof in a first region of a coating having a first thickness, wherein x and y are integers between 1 and 7; and X6W6(SiZ, C1-Z) in a second region of the coating having a second thickness, wherein X is Ni or a mixture of Ni and one or more transition metals and z ranges from 0 to 1.