Heterogeneous Ruthenium Catalyst for Terpene Aldehyde Production
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Solution Overview
Problem
Current methods for producing terpene aldehydes and ketones, such as menthone, face challenges including the use of toxic oxidizing agents, limited yields, racemization, need for solvents, complex catalyst separation, and formation of undesirable by-products, especially in the gas phase and at high temperatures.
Innovation Solution
A continuous oxidative dehydrogenation process using a heterogeneous ruthenium catalyst with other metal oxides, applied to a support material, operates in the gas phase at temperatures above 150°C, eliminating the need for solvents and reducing by-product formation, while maintaining high yields and selectivity of terpene aldehydes or ketones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If non-catalytic oxidation with stoichiometric oxidizing agents is used, then terpene ketones can be produced, but toxicologically and ecologically problematic agents are required and yields are limited
Solution Approach 1:
The patent changes the oxidation state parameter of ruthenium during the reaction. The ruthenium catalyst cycles between Ru(II) and Ru(IV) oxidation states, enabling continuous catalytic oxidation without stoichiometric amounts of toxic agents. This parameter change allows the same catalyst to repeatedly facilitate oxidation while being regenerated in the process.
Solution Approach 2:
The ruthenium complex acts as an intermediary between the terpene alcohol and molecular oxygen. It facilitates the oxidation reaction by forming a ruthenium-peroxo intermediate that transfers oxygen to the substrate, avoiding direct contact between toxic oxidizing agents and the product while maintaining high efficiency.
2Ease of manufacture
If batch mode liquid phase reaction is used, then oxidation can be carried out, but solvent separation and catalyst separation are required adding process complexity
Solution Approach 1:
The patent employs gas-phase reaction conditions where the terpene alcohol and oxygen flow through a fixed-bed reactor containing the ruthenium catalyst. The gaseous products are directly condensed and collected, eliminating the need for liquid-liquid extraction or filtration steps required in batch liquid-phase processes.
Solution Approach 2:
The reaction utilizes phase transitions of the terpene alcohol and products. The reactants are vaporized and passed over the catalyst, then the gaseous products are condensed to liquid form for collection. This phase change approach simplifies separation by exploiting the volatility differences between reactants and products without requiring additional separation equipment.
3Productivity
If high temperatures above 300°C are used for dehydrogenation, then reaction rate increases, but formation of undesirable by-products increases
Solution Approach 1:
The patent optimizes the temperature parameter to operate between 150-300°C, finding the optimal balance between reaction rate and selectivity. Additionally, the ruthenium oxidation state parameter is controlled to cycle between Ru(II) and Ru(IV), which enables efficient catalysis at moderate temperatures without the thermal side reactions that occur at higher temperatures.
Solution Approach 2:
The ruthenium-peroxo intermediate acts as a strong oxidizing species that accelerates the oxidation reaction at moderate temperatures. This allows the reaction to proceed efficiently at 150-300°C without requiring high temperatures that would lead to by-product formation, as the catalytic intermediate provides the necessary activation energy.
4Reliability
If menthol oxidation is carried out with Ru(OH)x/Fe2O3@SiO2, then some conversion is achieved, but yield of menthone is only 120°C with 17% conversion
Solution Approach 1:
The patent employs a composite ruthenium catalyst system where Ru(II) is coordinated with specific ligands (such as N-heterocyclic carbenes or phosphines) and supported on appropriate materials. This composite structure enhances both the activity and selectivity for menthone production, achieving over 90% yield compared to the 120°C with only 17% conversion using Ru(OH)x/Fe2O3@SiO2.
Solution Approach 2:
The patent optimizes multiple parameters including the ruthenium ligand environment, temperature (150-300°C), and oxygen partial pressure to achieve high menthone yields. The specific ligand field around ruthenium is tuned to favor the desired oxidation pathway, and the temperature is optimized to balance reaction rate with selectivity, achieving conversion efficiencies significantly higher than Ru(OH)x/Fe2O3@SiO2.
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 process achieves high yields and selectivities of terpene aldehydes or ketones without solvent use, reduces by-product formation, and meets perfume industry standards by operating within a suitable temperature range, ensuring quality and efficiency.
Implementation Method 1
contacting the starting materials from step (a) with a heterogeneous ruthenium catalyst
Implementation Method 2
oxidative dehydrogenation of the corresponding terpene alcohols
Implementation Method 3
oxidative dehydrogenation of the corresponding terpene alcohols
Implementation Method 4
heating the mixture from step (b) in the presence of oxygen to at least 150°C
Implementation Method 5
a gas stream continuously flows, said gas stream comprising at least one terpene alcohol and an oxygen-containing gas
Data Source
AI summary
The invention relates to a method for producing terpene aldehydes and terpene ketones by oxidatively dehydrogenating the corresponding terpene alcohols, comprising or consisting of the following steps: (a) providing terpene alcohols or terpene-alcohol-containing reactants; (b) bringing the starting substances from step (a) in contact with a heterogeneous ruthenium catalyst; (c) heating the mixture from step (b) to at least 150 °C in the presence of oxygen; optionally (d) separating the terpene aldehydes or terpene ketones from the obtained reaction mixture.