Unsaturated Symmetrical Anhydride Process With Two-Stage Conversion
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Solution Overview
Problem
Existing processes for producing unsaturated symmetrical carboxylic acid anhydrides suffer from low space-time yield, formation of byproducts like acetic acid, and incomplete conversion, with inefficiencies in catalyst removal and polymerization issues.
Innovation Solution
A process involving the reaction of unsaturated carboxylic acid with ketene in two stages, followed by rectification to isolate symmetrical anhydrides, with recycling of unreacted mixed anhydride and use of catalysts to enhance conversion and purity, while avoiding polymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If acetic anhydride is used in excess to achieve complete conversion, then conversion of carboxylic acid is improved, but mixture of acetic acid and acetic anhydride is formed at column head requiring subsequent removal
Solution Approach 1:
The process divides the reaction into two distinct stages: first reaction area where unsaturated carboxylic acid reacts with ketene to form crude anhydride mixture, and second reaction area where further reaction occurs to achieve complete conversion. This segmentation allows each stage to be optimized independently, preventing contamination while ensuring complete conversion.
Solution Approach 2:
The invention extracts and removes the problematic byproduct formation by using a two-stage process with intermediate separation. The first reaction area produces crude anhydride which is then subjected to further reaction in the second area, effectively separating the conversion process from the purification challenge and eliminating acetic acid contamination at the column head.
2Manufacturing precision
If batch process is used with excess starting material to achieve complete conversion, then conversion is improved, but excess starting material is wasted and polymerization occurs
Solution Approach 1:
The invention transitions from batch process to continuous process, maintaining continuous reaction and separation operations. This continuity ensures complete conversion without accumulation of excess starting material, eliminating waste while preventing polymerization through constant flow and controlled residence times in each reaction area.
Solution Approach 2:
The continuous process is divided into two reaction areas with distinct functions. The first area handles the initial reaction between unsaturated carboxylic acid and ketene, while the second area completes the conversion. This segmentation allows optimal control of reaction conditions in each zone, achieving complete conversion without excess starting material waste.
3Manufacturing precision
If rectification column is used to isolate symmetrical anhydrides, then product purity is improved, but unreacted mixed anhydride accumulates requiring removal
Solution Approach 1:
The invention implements a feedback loop where unreacted mixed anhydride separated in the rectification column is recycled back to the first reaction area. This feedback mechanism ensures that unreacted material is reprocessed rather than discarded, maintaining high product purity while eliminating waste of unreacted mixed anhydride through continuous recirculation and rereaction.
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
Achieves high purity and complete conversion of reactants, increasing the space-time yield and minimizing byproduct formation, particularly acetic acid, through a continuous and efficient production method.
Implementation Method 1
the symmetrical anhydrides (I) and (II) are isolated from the mixture obtained in step (b) by rectification
Data Source
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AI summary
The invention relates to a process for the simultaneous production of symmetrical carboxylic anhydrides of the general formulas RC(O)-OC(O)-R (I) and R'R"HC-C(O)-OC(O)-CHR'R" (II) by reacting an unsaturated carboxylic acid with a ketene, wherein (a) the unsaturated carboxylic acid (III) is reacted with the ketene in a first reaction area to form a crude anhydride mixture, (b) the crude anhydride mixture obtained in step (a) is further reacted in a second reaction area, preferably in the presence of a catalyst, (c) the symmetrical anhydrides (I) and (II) are isolated from the mixture obtained in step (b) by rectification, and (d) unreacted mixed anhydride obtained during the rectification in step (c) is recycled to the first reaction area and/or to the second reaction area.