HI Concentration Control in Acetic Acid Distillation
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Solution Overview
Problem
In acetic acid production via methanol carbonylation, the presence of hydrogen iodide (HI) outside the reactor poses corrosion challenges and existing methods to minimize its concentration outside the reactor have not effectively realized benefits associated with specific HI concentrations.
Innovation Solution
Control the densities of streams during distillation to separate phases, allowing for the production and control of HI within specific concentration ranges outside the reactor, facilitating the formation of dimethyl ether and reducing methyl iodide waste, by using a process that includes carbonylating a reaction medium with methanol, methyl acetate, and a rhodium catalyst, followed by biphasic separation and distillation in multiple columns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If HI concentration is minimized outside the reactor to reduce corrosion, then corrosion resistance is improved, but the ability to form dimethyl ether and reduce methyl iodide waste is compromised
Solution Approach 1:
The patent applies parameter changes by controlling HI concentration within a specific range (0.1-5.0 wt%, preferably 0.2-2.0 wt%) rather than simply minimizing it. This optimized parameter range enables both corrosion management and beneficial chemical reactions (dimethyl ether formation) that reduce methyl iodide waste, resolving the contradiction between corrosion protection and substance loss prevention.
Solution Approach 2:
The patent converts the harmful aspect of HI (corrosiveness) into a beneficial function by utilizing controlled HI concentration to promote dimethyl ether formation. The HI that would normally be considered a harmful corrosive agent is instead used as a catalyst/promoter for beneficial reactions that reduce methyl iodide waste, transforming the harmful factor into a useful one.
2Manufacturing precision
If density control is implemented to separate phases in distillation, then separation efficiency is improved, but process complexity increases
Solution Approach 1:
The patent utilizes parameter changes by controlling density differences through temperature and composition adjustments during distillation. By manipulating these parameters, the process achieves effective phase separation without requiring complex additional equipment, as the density-based separation is accomplished through controlled distillation conditions rather than additional mechanical separation devices.
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 enables the effective separation and control of HI concentrations, leading to reduced methyl iodide loss and improved phase separation, thereby enhancing the acetic acid production process by utilizing HI within the distillation column to form dimethyl ether, which lowers methyl iodide concentrations in waste streams.
Implementation Method 1
the densities of the streams are controlled to ensure separation of phases
Implementation Method 2
distilling the feed stream at a pressure and a temperature sufficient to produce an overhead stream
Implementation Method 3
HI allows for formation of dimethyl ether within the purification processes disclosed, which facilitates phase separation and reduces the amount of methyl iodide lost as waste
Data Source
AI summary
A process directed to acetic acid production comprising providing a feed stream having a first density comprising water, acetic acid, methyl acetate, at least one PRC, and greater than about 30 wt % methyl iodide to a distillation column comprising a distillation zone and a bottom sump zone; and distilling the feed stream at a pressure and a temperature sufficient to produce an overhead stream having a second density and comprising greater than about 40 wt % methyl iodide and at least one PRC; wherein a percent decrease between the first density and the second density is from 20% to 35%.