Multimetallic Catalyst Site Isolation for Alkane Dehydrogenation
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Solution Overview
Problem
Existing catalysts for oxidative dehydrogenation of alkanes to olefins suffer from active site agglomeration and deactivation, leading to reduced selectivity and efficiency, particularly for manganese and chromium-based catalysts, which are prone to sintering and combustion product formation.
Innovation Solution
A multimetallic catalyst system comprising a substrate, a transition metal or main group element promoter, and an oxidation-active transition metal, such as manganese, nickel, or vanadium, supported on oxides like SiO2, Al2O3, or ZrO2, with a Lewis acidic and redox-active promoter, is synthesized using methods like atomic layer deposition to maintain site-isolation and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If manganese oxide catalysts are used for oxidative dehydrogenation, then high selectivity for olefin products is achieved, but catalyst deactivation occurs due to site agglomeration and sintering
Solution Approach 1:
The patent applies segmentation by creating site-isolated manganese oxide clusters (e.g., Mn2O3 dimers, trimers, or tetramers) rather than using continuous bulk manganese oxide surfaces. This segmentation into discrete molecular-sized clusters prevents agglomeration and sintering while maintaining high selectivity for olefin production, directly resolving the contradiction between selectivity and stability.
Solution Approach 2:
The patent employs the nesting principle by placing manganese oxide clusters within a zeolite framework structure, where the zeolite cages accommodate and stabilize the Mn clusters. This nested arrangement protects the active sites from agglomeration while maintaining their catalytic activity, thereby improving both selectivity and long-term stability.
2Use of energy by moving object
If transition metal catalysts are used for oxidative dehydrogenation, then thermodynamic favorability is improved, but active site sintering leads to combustion product formation
Solution Approach 1:
The patent applies local quality by creating highly dispersed manganese oxide sites with specific local electronic structures that favor selective oxidation. The site-isolated clusters have different electronic properties compared to bulk materials, enabling them to promote dehydrogenation while suppressing complete combustion, thus resolving the contradiction between thermodynamic favorability and harmful combustion products.
3Ease of manufacture
If catalyst synthesis strategies are used to create distributed sites, then manufacturing is simplified, but varying reactivities reduce overall reaction selectivity
Solution Approach 1:
The patent applies parameter changes by precisely controlling the size, composition, and distribution parameters of manganese oxide clusters during synthesis. By optimizing cluster size to molecular dimensions and controlling their dispersion within the zeolite framework, the patent achieves both ease of manufacture through straightforward synthesis procedures and high reaction selectivity through precise control of active site parameters.
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 catalysts exhibit high selectivity and stability, achieving propylene yields of up to 15% at 500°C with 90% selectivity, and maintain activity over extended periods without site agglomeration or coke deposition, significantly improving the efficiency of alkane oxidative dehydrogenation.
Implementation Method 1
oxidative dehydrogenation of alkanes to olefins (alkenes) or diolefins (dienes)
Implementation Method 2
a Lewis acidic and redox-active promoter
Implementation Method 3
stabilize site-isolated and/or highly dispersed manganese oxide oligomers on catalyst support surfaces
Implementation Method 4
highly dispersed or isolated manganese oxide sites
Implementation Method 5
suppress hydrocarbon deep oxidation (combustion) and maintain catalyst activity
Data Source
AI summary
A catalyst for oxidative dehydrogenation of alkanes includes a substrate including an oxide; at least one promoter including a transition metal or a main group element of the periodic table; and an oxidation-active transition metal. The catalyst is multimetallic.