Nitrobenzene Production via High-Pressure Adiabatic Nitration
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Solution Overview
Problem
Adiabatic nitration processes for producing nitrobenzene face challenges in achieving high space-time yields without compromising product quality, particularly due to high temperature differences leading to decreased selectivity and the need for compact, cost-effective reactor designs with minimal pressure losses.
Innovation Solution
The process involves introducing benzene and mixed acid into a reactor under separate or combined conditions, with intensive mixing using 1 to 30 dispersing elements, followed by phase separation under a pressure difference of 15 bar to 25 bar, allowing for efficient nitration in compact reactors with high selectivity and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If adiabatic nitration is carried out with high conversion to achieve high space-time yield, then productivity increases, but temperature difference increases leading to decreased selectivity and increased by-products
Solution Approach 1:
The patent applies parameter changes by operating at elevated pressures (15-25 bar) in the reactor to modify the reaction conditions. This pressure parameter change allows the system to achieve high conversion and space-time yield while maintaining better selectivity and reducing by-products, thereby resolving the contradiction between productivity and manufacturing precision.
2Manufacturing precision
If static mixing elements are used to achieve optimal mixing for high selectivity, then manufacturing precision improves, but pressure loss increases requiring higher pressure in front of the reactor
Solution Approach 1:
The patent compensates for the pressure loss caused by static mixing elements by operating at elevated pressures (15-25 bar) in the reactor. This parameter change allows the system to maintain the necessary pressure differential across the mixing elements while still achieving optimal mixing for high selectivity, thereby resolving the contradiction between manufacturing precision and stress/pressure.
3Reliability
If pressure in front of the reactor is increased to overcome pressure losses, then reliability improves, but device complexity increases due to higher pressure requirements
Solution Approach 1:
The patent establishes a specific pressure range (15-25 bar) as an operating parameter that simultaneously ensures reliable pressure stability and manages device complexity. By defining this optimal pressure window, the system achieves reliable operation without requiring excessively complex pressure control mechanisms, thereby resolving the contradiction between reliability and device complexity.
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 production of nitrobenzene in compact reactors with excellent yields and selectivities, achieving a space-time yield of over 7.0 t/nm³/h while maintaining low by-product contents, despite high adiabatic temperature differences.
Implementation Method 1
nitration of benzene with mixed acid... benzene and nitric acid are reacted in a large excess of sulfuric acid
Implementation Method 2
adiabatic nitration processes... no technical measures are taken to add or remove heat from the reaction mixture
Implementation Method 3
The sulfuric acid then absorbs the heat of reaction released and the water formed during the reaction
Implementation Method 4
intensive mixing using 1 to 30 dispersing elements... dispersed into one another in the reactor
Implementation Method 5
optimal mixing is achieved at the beginning of the reaction... intensive mixing
Implementation Method 6
phase separation in a phase separation apparatus... separating raw nitrobenzene and waste acid
Implementation Method 7
pressure difference of 15 bar to 25 bar... pressure in front of the nitration reactor is 15 bar to 25 bar above the pressure in the gas phase
Data Source
AI summary
The invention relates to a process for the continuous production of nitrobenzene by nitration of benzene with mixed acid, in which the pressure before the nitration reactor is 14 bar to 40 bar above the pressure in the gas phase of the phase separation apparatus for the separation of crude nitrobenzene and acetic acid.