Heterogeneous Rhenium Catalyst for Bio-based Adipic Acid
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Solution Overview
Problem
Current methods for producing adipic acid and its esters from fossil resources are costly, environmentally harmful, and inefficient, as they require corrosive chemicals and gaseous reductive agents, with homogeneous catalysts being difficult to separate and recycle.
Innovation Solution
A heterogeneous Re catalyst system using metallic rhenium supported on solid carriers like carbon, alumina, or silica, which operates in an inert atmosphere, allowing for easy separation and reuse, and eliminates the need for corrosive reactants and gaseous reductive agents, facilitating the conversion of biobased aldaric acids to muconic and adipic acids and their esters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If homogeneous Re-based catalysts are used for dehydroxylation of aldaric acids, then catalytic activity is achieved, but catalyst separation and recycling becomes difficult
Solution Approach 1:
The patent employs porous solid supports (alumina, silica, carbon) with high surface area to load the Re catalyst, enabling heterogeneous catalysis. The porous structure provides abundant active sites while maintaining catalyst integrity for easy separation, directly resolving the contradiction between catalytic activity and separation difficulty.
Solution Approach 2:
The invention creates composite catalyst systems where Re is supported on solid matrices (Al2O3, SiO2, C). This composite structure combines the high catalytic activity of Re with the ease of separation and structural stability of solid supports, eliminating the need for complex separation procedures while maintaining reaction efficiency.
2Productivity
If corrosive reactants (HBr) and gaseous reductive agents (H2) are used in the process, then aldaric acid conversion is achieved, but environmental harm and operational complexity increase
Solution Approach 1:
The patent replaces corrosive HBr and gaseous H2 with an inert atmosphere (N2 or CO2). The inert gas environment eliminates harmful side reactions, corrosion issues, and safety concerns associated with reactive gases, while still enabling the dehydroxylation reaction to proceed through the solid Re catalyst, thus reducing environmental harm without sacrificing productivity.
Solution Approach 2:
The invention uses inexpensive, non-harmful inert gases (N2, CO2) that can be easily vented after reaction, replacing expensive and hazardous reagents. These simple gases serve their purpose and can be discarded without special treatment, reducing both operational complexity and environmental impact.
3Productivity
If fossil resources (crude-oil based cyclohexane) are used for adipic acid production, then current production demand is met, but climate change and environmental degradation are accelerated
Solution Approach 1:
The patent fundamentally changes the feedstock parameter from fossil-based cyclohexane to bio-based aldaric acids. This parameter change transforms the carbon source from non-renewable to renewable, enabling sustainable adipic acid production that meets current demand while reducing greenhouse gas emissions and environmental degradation associated with fossil resource extraction and processing.
Solution Approach 2:
The invention enables the catalyst system to function autonomously with bio-based feedstocks, eliminating the need for harmful intermediate steps and corrosive chemicals. The solid Re catalyst on solid support self-sustains the dehydroxylation reaction under inert atmosphere, creating a clean, self-contained process that produces adipic acid from renewable resources without external harmful inputs.
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
This process achieves high yields of adipic acid esters and muconic acid derivatives with reduced greenhouse gas emissions and operational costs, enabling sustainable production of nylon precursors by using a recyclable and easily separable solid catalyst.
Implementation Method 1
converting a bio-based starting material, selected from aldaric acids... over a heterogeneous catalyst consisting of rhenium (Re) in its metallic form and a solid support
Data Source
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AI summary
The present invention relates to the use of a heterogeneous Re catalyst for the conversion of biobased aldaric acids to muconic, hexenedioic acid, adipic acid and their esters in a batch stirred slurry reactor or continuous fixed-bed reactor. The process comprises conversion of aldaric acid (preferably mucic or glucaric acid) into muconic, hexenedioic or adipic acid and their esters. Aldaric acid in the concentration range of 0.01 - 50 wt% (with regards to the total mass of the liquid phase) is dissolved in the short chain primary or secondary alcohol (e.g. methanol) and a Re-based solid catalyst (0.1 - 400 wt% based on the mass of aldaric acid) is added to the reaction mixture, which is proceeded at the temperature within 80 - 250 °C under inert (N2) or hydrogen atmosphere for 1 - 340 h to yield esters of muconic, hexenedioic acid, adipic acid. Further hydrolysis of ester converts products into their free carboxylic acid form.