Mo-Bi-Nb-Te Catalyst for Acrylic Acid Selectivity
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Solution Overview
Problem
Conventional catalysts used in the production of (meth)acrylic acid from propylene result in low yields of (meth)acrylic acid, with the first-step catalyst producing up to 10% (meth)acrylic acid and the second-step catalyst facing increased load and degradation due to high (meth)acrolein selectivity, leading to inefficient processes and catalyst lifetime reduction.
Innovation Solution
A Mo—Bi—Nb—Te based composite metal oxide is used as the first-step catalyst, which increases the yield and selectivity of (meth)acrylic acid, reducing (meth)acrolein load and concentration, allowing for complete conversion in the second-step reaction and extending catalyst lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional Mo-Bi-based catalyst is used in the first step, then (meth)acrolein selectivity is high (89.6 mole%), but (meth)acrylic acid yield is low (6.2 mole%)
Solution Approach 1:
The catalyst composition parameters are changed by adding Nb and Te elements to the conventional Mo-Bi system, creating a Mo-Bi-Nb-Te quaternary catalyst. This compositional parameter change enables simultaneous improvement of acrylic acid yield (20-30 mole%) while maintaining acceptable acrolein selectivity, resolving the trade-off between these two parameters.
Solution Approach 2:
The invention uses a composite metal oxide catalyst combining Mo, Bi, Nb, and Te elements in specific ratios. This composite material approach creates synergistic effects among the different metal oxides, where Nb and Te modify the electronic and structural properties of the Mo-Bi base, enabling enhanced acrylic acid production without completely sacrificing acrolein selectivity.
2Quantity of substance
If conventional first-step catalyst produces high (meth)acrolein selectivity, then second-step catalyst load increases, but catalyst lifetime is reduced
Solution Approach 1:
The first-step catalyst performs preliminary oxidation of (meth)acrolein to (meth)acrylic acid concurrently with the main propylene oxidation reaction. By producing 20-30 mole% acrylic acid in the first step, the load on the second-step catalyst is reduced, preventing overload and extending the overall process efficiency and catalyst system lifetime.
3Quantity of substance
If two-step process is used with separate catalysts, then (meth)acrylic acid production is achieved, but process complexity increases
Solution Approach 1:
The invention merges the functions of producing both (meth)acrolein and (meth)acrylic acid into a single first-step catalytic oxidation process. The Mo-Bi-Nb-Te catalyst performs dual functions: selective propylene oxidation to acrolein and concurrent oxidation of acrolein to acrylic acid, reducing process complexity compared to traditional two-step systems requiring separate catalysts and reactors.
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 Mo—Bi—Nb—Te composite metal oxide catalyst achieves a (meth)acrylic acid yield of 20 mole % or higher in the first-step reaction, enabling a (meth)acrolein conversion ratio of 98–100% in the second-step, thereby improving overall process efficiency and catalyst longevity.
Implementation Method 1
A Mo-Bi-Nb-Te based composite metal oxide is used as the first-step catalyst, which increases the yield and selectivity of (meth)acrylic acid
Implementation Method 2
propylene or the like is oxidized by oxygen, inert gas for dilution, water steam and a certain amount of a catalyst, so as to produce (meth)acrolein as a main product
Data Source
AI summary
Disclosed are a Mo—Bi—Nb—Te based composite metal oxide; and a process for producing (meth)acrylic acid from at least one reaction material selected from the group consisting of propylene, propane, isobutylene, t-butyl alcohol and methyl-t-butyl ether, wherein the Mo—Bi—Nb—Te based composite metal oxide is used as a catalyst. Also, disclosed is a process for producing (meth)acrylic acid comprising a first step of producing (meth)acrolein as a main product from at least one reaction material selected from the group consisting of propylene, propane, isobutylene, t-butyl alcohol and methyl-t-butyl ether, and a second step of producing (meth)acrylic acid from the (meth)acrolein, wherein yield of (meth)acrylic acid in the product of the first step is 20 mole % or higher.