Integrated Propylene Oxide Process Using Two-Phase Catalyst Recycling
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Solution Overview
Problem
Existing integrated processes for producing propylene oxide and propylene glycol require significant capacity increases and additional equipment, leading to increased energy consumption and operational complexity, particularly when using chlorine, organic hydroperoxides, or hydrogen peroxide as oxidants.
Innovation Solution
Introduce a new step in the process involving the reaction of propene and hydrogen peroxide in the presence of a catalyst mixture comprising a phase transfer catalyst and a heteropolytungstate, maintaining a maximum apparent pH of 6, to produce a solution containing propylene glycols, which is then separated to yield monopropylene glycol and dipropylene glycol, thereby reducing the propylene oxide fed to the water reaction step and increasing overall output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the capacity of the reaction unit for reacting propene with oxidant is increased to increase propylene oxide production, then propylene oxide output increases, but additional equipment and substantial investment are required
Solution Approach 1:
The patent merges the propylene oxide production reaction and propylene glycol production reaction into a single integrated reaction unit. Propene reacts with hydrogen peroxide to form propylene oxide, which immediately reacts with water present in the reaction mixture to form propylene glycol. This combined reaction approach eliminates the need for separate production units and increases propylene oxide output without requiring additional equipment for oxidant production or alcohol conversion.
Solution Approach 2:
The reaction unit performs multiple functions simultaneously: it produces propylene oxide, converts propylene oxide to propylene glycol, and handles oxidant conversion. The single reaction unit serves as both a propylene oxide synthesis reactor and a propylene glycol production reactor, maximizing the utility of existing equipment and avoiding the need for additional specialized equipment.
2Productivity
If chlorine or organic hydroperoxide is used as oxidant to produce propylene oxide, then propylene oxide can be produced, but additional equipment is needed for producing the oxidant and preventing its transport
Solution Approach 1:
The patent extracts and eliminates the problematic oxidant production and handling steps by using hydrogen peroxide as the oxidant. Hydrogen peroxide can be produced on-site through anthraquinone process or imported in aqueous solution, avoiding the need for complex chlorine handling equipment or organic hydroperoxide production units. This extraction of the problematic oxidant step resolves the contradiction between productivity and device complexity.
3Adaptability or versatility
If organic hydroperoxide is used as oxidant with conversion of resulting alcohol to marketable product, then propylene oxide production is integrated, but additional equipment is needed for further reacting the alcohol
Solution Approach 1:
The patent extracts and eliminates the alcohol conversion step by using hydrogen peroxide as oxidant instead of organic hydroperoxide. When hydrogen peroxide is used, water is formed as the byproduct rather than alcohol, eliminating the need for additional equipment to convert alcohol to marketable products like MTBE or styrene. This maintains process integration while reducing device complexity.
4Productivity
If hydrogen peroxide is used as oxidant with zeolite catalyst, then propylene oxide can be produced, but solvent separation equipment is needed leading to increased energy consumption
Solution Approach 1:
The patent extracts and eliminates the solvent separation step by using a phase transfer catalyst system that operates without requiring organic solvents. The reaction uses a two-phase system (aqueous phase with hydrogen peroxide and organic phase with propene) separated by a phase transfer catalyst, eliminating the need for solvent recovery and separation equipment, thereby significantly reducing energy consumption.
Solution Approach 2:
The patent changes the reaction parameters by using a phase transfer catalyst system that operates with immiscible aqueous and organic phases. This parameter change eliminates the need for soluble organic solvents that would require energy-intensive separation and recycling, while maintaining high reaction efficiency and propylene oxide production capacity.
5Productivity
If a new unit for reacting propene and hydrogen peroxide is added to increase propylene oxide output, then additional propylene oxide for sale is available, but process complexity increases
Solution Approach 1:
The patent merges the propylene oxide production and propylene glycol production into a single integrated reaction unit. By operating this unit at optimized conditions with phase transfer catalyst, the system produces both propylene oxide (for sale) and propylene glycol (for the existing glycol production line) simultaneously, increasing overall productivity without adding separate reaction units or equipment.
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 approach enhances propylene oxide production capacity without expanding existing units, reduces energy consumption, and simplifies the process by recycling the organic phase, thus optimizing the production of propylene glycols and propylene oxide.
Implementation Method 1
reacting propene and hydrogen peroxide in the presence of a catalyst mixture comprising a phase transfer catalyst and a heteropolytungstate
Implementation Method 2
catalyst mixture comprising a phase transfer catalyst and a heteropolytungstate
Implementation Method 3
dividing the two-phase mixture from step a) into an aqueous phase and an organic phase containing propylene oxide
Data Source
AI summary
An integrated process for making propylene oxide and propylene glycol involves reacting propene with an oxidant to provide propylene oxide, reacting a fraction of the propylene oxide with water to provide an aqueous glycol solution containing monopropylene glycol and dipropylene glycol, and separating monopropylene glycol and dipropylene glycol from the glycol solution by a multi-step distillation. The propylene oxide output can be increased without increasing capacity of the unit for reacting propene to propylene oxide, by reacting propene and hydrogen peroxide in the presence of a catalyst mixture, containing a phase transfer catalyst and a heteropolytungstate, in a liquid reaction mixture which contains an aqueous phase with a maximum apparent pH of 6 and an organic phase. The reaction mixture is separated into an organic phase, which is recycled to the reaction, and an aqueous phase containing monopropylene glycol and dipropylene glycol, which is passed to replace the glycol solution.