Mo-V-W-Bi Oxide Catalyst for Alkane Dehydrogenation
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Solution Overview
Problem
Conventional oxidative dehydrogenation processes for converting alkanes to olefins require oxygen co-feed, leading to increased costs and safety concerns due to oxygen and hydrocarbon mixing, and result in undesired byproducts like carbon oxides and oxygenated hydrocarbons, with catalyst stability issues under reducing conditions.
Innovation Solution
Development of an oxidative dehydrogenation catalyst comprising oxides of molybdenum, vanadium, tungsten, or tantalum, and bismuth with a Pba2-32 space group crystal structure, synthesized through hydrothermal methods, which allows for stable redox cycling and selective conversion of alkanes to olefins without the need for oxygen co-feed, using air for catalyst reoxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional oxidative dehydrogenation processes use oxygen co-feed, then the conversion of alkanes to olefins can proceed at low temperature, but safety concerns increase due to oxygen and hydrocarbon mixing and undesired byproducts are formed
Solution Approach 1:
The patent extracts the oxygen requirement from the process feed and replaces it with a catalyst that contains lattice oxygen. The oxygen is taken out from the molecular oxygen feed and embedded in the catalyst structure (Mo-V-W-Bi oxide with Pba2-32 space group), allowing the reaction to proceed without direct oxygen-hydrocarbon mixing while maintaining oxidative dehydrogenation functionality.
Solution Approach 2:
The patent changes the oxygen delivery mechanism from molecular oxygen in the feed stream to lattice oxygen in the catalyst structure. This parameter change transforms the process from requiring oxygen co-feed to using a pre-oxygenated catalyst that releases oxygen during the reaction, thereby eliminating safety concerns while maintaining low-temperature operation.
2Reliability
If conventional catalysts use tellurium as promoter, then the catalytic activity is maintained, but catalyst stability deteriorates under reducing conditions due to volatilization
Solution Approach 1:
The patent replaces the unstable tellurium promoter with bismuth, which forms a more stable compound under reducing conditions. The Bi substitution creates a catalyst composition (Mo-V-W-Bi oxide) that maintains catalytic activity while resisting volatilization and degradation during cyclic redox operations, effectively replacing a short-lived unstable component with a stable alternative.
Solution Approach 2:
The patent creates a composite oxide catalyst system combining Mo, V, W, and Bi in specific ratios within the Pba2-32 space group structure. This composite material synergistically combines the catalytic activity of Mo-V-W oxides with the stability provided by Bi, resulting in a catalyst that maintains both high activity and stability under cyclic redox conditions.
3Productivity
If oxidative dehydrogenation process is used, then the conversion of paraffins to olefins is achieved, but undesired byproducts like carbon oxides and oxygenated hydrocarbons are formed
Solution Approach 1:
The patent converts the potential harm of oxygen over-oxidation into benefit by using lattice oxygen that is released in a controlled manner during the reaction. The lattice oxygen provides just enough oxidation for dehydrogenation without excess oxygen that would lead to complete oxidation to COx, thereby converting the potential harmful over-oxidation into selective dehydrogenation.
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 achieves high ethane conversion (>10%) and ethylene selectivity (>75%) in a circulating reactor, eliminating the need for oxygen and maintaining stability under cyclic redox conditions, while reducing byproduct formation and reactor contamination.
Implementation Method 1
converting at least a portion of the paraffins to olefins in the feed stream, thereby yielding a product stream comprising paraffins and olefins
Implementation Method 2
an oxidative dehydrogenation catalyst comprises: (i) a structure comprising oxides of molybdenum (Mo), vanadium (V), tungsten (W) or tantalum (Ta), and bismuth (Bi)
Implementation Method 3
stable redox cycling and selective conversion of alkanes to olefins without the need for oxygen co-feed, using air for catalyst reoxidation
Implementation Method 4
synthesizing Mo v V w A y Bi z O x by hydrothermal synthesis at a hydrothermal synthesis temperature for a period of time
Implementation Method 5
a crystalline structure with the Pba2-32 space group
Data Source
AI summary
An oxidative dehydrogenation catalyst having: a structure having a formula MovVwAyBizOx, where v is 1, w is from 0.2 to 0.5, A is W or Ta, y is from 0.001 to 0.3, z is from 0.01 to 0.3, and x is the oxygen content required to charge-balance the structure. The oxidative dehydrogenation catalyst comprises a crystalline structure (Pba2-32 space group) characterized by reflections determined with Cu-Kα X-ray diffraction (XRD) as follows: