NHPI Production via Segmented Temperature Control
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Solution Overview
Problem
There is a lack of effective processes and systems for producing N-hydroxyphthalimide (NHPI) on an industrial scale, which is necessary for catalyzing oxidation reactions such as the conversion of cyclohexylbenzene to cyclohexylbenzene hydroperoxide, a crucial step in producing cyclohexanone and phenol from benzene.
Innovation Solution
A process involving the reaction of hydroxylamine with phthalic anhydride, where the reaction medium is heated through specific temperature ranges to convert intermediate hydroxamic acid to solid NHPI, utilizing continuous or semi-batch reactors with steam and water addition for efficient conversion, and subsequent solid/liquid separation to recover NHPI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydroxylamine reacts with phthalic anhydride at high temperature to form NHPI, then conversion efficiency improves, but intermediate hydroxamic acid decomposes uncontrollably
Solution Approach 1:
The reaction process is divided into two distinct stages: first forming the intermediate hydroxamic acid at lower temperature (60-70°C), then converting it to NHPI at higher temperature (150-200°C). This segmentation prevents the intermediate from decomposing by controlling temperature zones, ensuring both high conversion efficiency and stable reaction control.
Solution Approach 2:
The intermediate hydroxamic acid is formed and stabilized at lower temperature before the high-temperature conversion to NHPI. This preliminary formation step ensures the intermediate is properly established and controlled before subjecting it to conditions that would cause uncontrolled decomposition.
2Productivity
If continuous reaction mode is used, then production efficiency improves, but heat management and reaction control become more difficult
Solution Approach 1:
The patent employs a continuous reaction mode where reactants are continuously fed and products continuously removed, maintaining steady-state operation. This continuous action maximizes production efficiency while the two-stage temperature control manages heat generation systematically throughout the process.
Solution Approach 2:
The reaction parameters (temperature, flow rate, reactant ratios) are precisely controlled and adjusted across the two stages. Temperature increases from 60-70°C in stage one to 150-200°C in stage two, while continuous monitoring and adjustment of other parameters manage the complexity of heat management in continuous operation.
3Manufacturing precision
If two-stage temperature process is implemented, then NHPI purity improves, but process complexity increases
Solution Approach 1:
The manufacturing process is segmented into two temperature stages: first stage (60-70°C) for controlled intermediate formation with high purity, second stage (150-200°C) for NHPI conversion. This segmentation achieves high NHPI purity through selective temperature control while using a single reactor system minimizes overall process complexity.
Solution Approach 2:
Temperature is changed as the key parameter between stages, from 60-70°C to 150-200°C. This parameter change drives the chemical transformations while maintaining purity. The controlled change in this single parameter simplifies the overall process complexity compared to manipulating multiple parameters simultaneously.
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 method allows for the production of high-purity NHPI suitable for industrial-scale oxidation reactions, enabling efficient conversion of cyclohexylbenzene to cyclohexylbenzene hydroperoxide, thereby facilitating the production of cyclohexanone and phenol.
Implementation Method 1
raising the reaction medium temperature to a transition temperature Tt within the range from 65° C. to less than 75° C.
Implementation Method 2
further heating the reaction medium to a final temperature Tf within the range from 75° C. to 200° C., thereby converting at least a portion of the solid intermediate hydroxamic acid to solid cyclic imide
Implementation Method 3
utilizing continuous or semi-batch reactors with steam and water addition for efficient conversion
Implementation Method 4
subsequent solid/liquid separation to recover NHPI
Data Source
AI summary
Disclosed are novel processes for the production of cyclic imide compounds such as N-hydroxyphthalimide (NHPI). The processes may be particularly well-suited for commercial-scale production of cyclic imides such as NHPI. Such cyclic imide compounds are suitable for use as oxidation catalysts, and specifically may be used to oxidize cyclohexylbenzene to cyclohexyl-1-phenyl-1-hydroperoxide. Such an oxidation may be particularly useful in a process for the production of phenol and/or cyclohexanone from benzene via a process comprising hydroalkylation of benzene to cyclohexylbenzene, oxidation of the cyclohexylbenzene to cyclohexyl-1-phenyl-1-hydroperoxide, and cleavage of the cyclohexyl-1-phenyl-1-hydroperoxide to phenol and cyclohexanone. The cyclic imide production process may advantageously include water washing and reactant recovery steps to maximize purity and yield.