WO3 Mesoporous Silica Catalyst Liquid Phase Nitration
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Solution Overview
Problem
Conventional nitration processes of aromatic compounds are environmentally hazardous due to the use of concentrated sulphuric acid, result in low selectivity, and require high temperatures, leading to inefficient and costly operations with catalyst deactivation and by-product contamination.
Innovation Solution
A liquid phase nitration process using tungsten oxide (WO3) supported on mesoporous silica as a solid acid catalyst, operating at low temperatures (80-110°C) with azeotropic removal of water, eliminating the need for sulphuric acid and enhancing catalyst stability and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional nitrating mixture (concentrated sulphuric acid and fuming nitric acid) is used, then nitration of aromatic compounds can be achieved, but large quantity of dilute sulphuric acid waste is generated requiring energy intensive concentration or disposal
Solution Approach 1:
The invention extracts and removes sulphuric acid from the conventional nitrating mixture system, replacing it with solid acid catalysts (zeolites, ion-exchange resins, or metal oxides) that can be easily separated from the reaction mixture. This eliminates the need for large quantities of sulphuric acid and the subsequent energy-intensive concentration or disposal processes, while maintaining effective nitration capability through alternative catalytic systems.
2Productivity
If conventional nitrating mixture is used, then nitration reaction proceeds, but selectivity of desired product is low
Solution Approach 1:
The invention applies local quality by using solid acid catalysts with specific active sites and pore structures that provide localized catalytic activity. The solid catalyst surfaces offer specific binding sites that selectively activate the nitrating agent and orient the aromatic substrate for preferential attack at desired positions, thereby improving product selectivity while maintaining reaction productivity through efficient catalytic cycles.
3Object-affected harmful factors
If vapor phase nitration is used to avoid liquid waste, then environmental issues are reduced, but reaction requires high temperature (275-310°C) leading to di-nitration explosion risk
Solution Approach 1:
The invention changes the physical state parameter of the reaction system from vapor phase to liquid phase, allowing the reaction to proceed at moderate temperatures (below 100°C) using solid acid catalysts in liquid media. This parameter change eliminates the high temperature requirement and associated explosion risks while still achieving environmental benefits through the use of solid catalysts that can be easily separated and reused, minimizing waste generation.
4Temperature
If vapor phase nitration is used, then process operates at high temperature, but conversions are low and space-time yield is low
Solution Approach 1:
The invention employs composite material systems combining solid acid catalysts (such as zeolites with specific pore structures, ion-exchange resins, or metal oxide supports) with liquid reaction media. This composite approach enhances the effectiveness of solid catalysts in liquid phase, providing high activity and selectivity at low temperatures, thereby achieving high conversions and space-time yields without requiring high temperature vapor phase conditions.
5Ease of manufacture
If conventional nitrating mixture is used, then nitration can be performed, but material of construction cost is high and safety aspects need implementation
Solution Approach 1:
The invention replaces expensive and hazardous concentrated sulphuric acid with solid acid catalysts that can be used in smaller quantities, are easier to handle, and can be disposed of or regenerated more simply. The solid catalysts eliminate the need for specialized corrosion-resistant equipment and complex safety systems required for handling concentrated acids, thereby reducing both material of construction costs and operational complexity while maintaining manufacturing ease.
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
The process achieves high conversion (85-90%) and selectivity (30-60%) for aromatic nitro compounds, is environmentally benign, cost-effective, and maintains catalyst stability for multiple cycles, avoiding the limitations of conventional methods.
Implementation Method 1
liquid phase nitration of aromatic compounds catalysed by WO3 supported on mesoporous silica support
Implementation Method 2
azeotropic removal of water
Data Source
AI summary
The present invention discloses an improved process for the liquid phase nitration of aromatic compounds catalyzed by WO3 supported on mesoporous silica support, at low temperature, with high conversion and selectivity.