Hydrodechlorination Process with Nitrogen Stripping for DCA Removal
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Solution Overview
Problem
The existing processes for producing monochloroacetic acid are inefficient due to the high energy consumption and catalyst separation challenges in hydrodechlorination, and there is a risk of hydrogen accumulation leading to explosions in liquid phase reactions.
Innovation Solution
A catalytic hydrodechlorination process in a vertical tubular reactor using a fixed bed of heterogeneous catalysts, where hydrogen gas is contacted with a liquid feed of dichloroacetic and monochloroacetic acids, followed by nitrogen stripping to remove dissolved hydrogen, and optimized operating conditions to prevent flooding and ensure safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If liquid phase hydrodechlorination is used to reduce DCA levels, then DCA removal efficiency is improved, but hydrogen accumulation in the vacuum system creates explosion risk
Solution Approach 1:
The patent extracts and removes dissolved hydrogen gas from the liquid product stream using a degasifier or vacuum stripping unit. This separation step removes the harmful hydrogen accumulation before the stream enters the vacuum system, eliminating the explosion risk while maintaining the benefits of liquid phase hydrodechlorination for DCA removal.
Solution Approach 2:
The patent introduces an intermediary device (degasifier/vacuum stripping unit) between the hydrodechlorination reactor and the vacuum system. This intermediary component facilitates the removal of dissolved hydrogen through controlled vacuum stripping, acting as a buffer that prevents hydrogen from reaching the vacuum system where it could accumulate and create explosion hazards.
2Manufacturing precision
If vapour phase hydrodechlorination is used to reduce DCA levels, then DCA removal efficiency is improved, but energy consumption and investment costs increase
Solution Approach 1:
The patent changes the physical state parameter of the reaction medium from vapour phase to liquid phase. By conducting hydrodechlorination in the liquid phase, the process avoids the high energy requirements for vaporization and condensation equipment, significantly reducing both energy consumption and investment costs while maintaining effective DCA removal through catalytic hydrogenation.
3Manufacturing precision
If multiple crystallization stages are used to reduce DCA concentration, then DCA removal is improved, but space and time requirements increase
Solution Approach 1:
The patent replaces the mechanical crystallization process with a chemical reaction process (catalytic hydrodechlorination). Instead of relying on repeated crystallization cycles that require extensive time and space, the process uses hydrogenation reaction over a catalyst to chemically convert DCA to MCA, achieving rapid and efficient DCA removal in a single continuous operation.
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 effectively reduces dichloroacetic acid levels to less than 1% in the product stream, minimizing energy use and avoiding hydrogen accumulation risks, while allowing for a broader operating window and safer operation.
Implementation Method 1
the MCA/DCA feed is in the liquid phase. Said liquid feed is contacted with hydrogen gas in the presence of a catalyst to form monochloroacetic acid and hydrogen chloride
Implementation Method 2
a catalytic hydrodechlorination (for example in accordance with U.S. Pat. Nos. 5,191,118 and 5,356,850). This reaction can be carried out in the vapour phase
Implementation Method 3
the product stream is contacted with nitrogen gas so as to remove hydrogen gas present in the product stream. When contacting the liquid product stream with nitrogen gas, any hydrogen gas dissolved in the product stream will be taken up into the nitrogen gas
Data Source
AI summary
The present invention is directed to a process for catalytic hydrodechlorination of dichloroacetic acid, wherein hydrogen gas is contacted with a liquid feed comprising dichloroacetic acid and monochloroacetic acid to form a product stream comprising monochloroacetic acid and an off gas stream comprising hydrogen chloride and hydrogen, and wherein the product stream is contacted with nitrogen gas so as to remove hydrogen gas present in the product stream.