Nitrate Ester Synthesis via In Situ Nitric Acid Generation
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Solution Overview
Problem
Conventional nitrate ester production methods, such as mixed acid nitration reactions, face challenges including thermal runaway risks, poor separation of nitrate esters, oxidative side reactions, and hazardous waste management, making large-scale production economically unattractive and sporadically available.
Innovation Solution
A method involving the combination of a nitrate salt and sulfuric acid to form a nitrating solution, where nitric acid is formed in situ, allowing for the direct nitration of aliphatic polyols under milder conditions, reducing safety concerns and waste disposal issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mixed acid nitration reaction is used to produce nitrate esters, then nitrate esters can be synthesized, but thermal runaway and explosions may occur due to exothermic nature of the reaction
Solution Approach 1:
The patent changes the chemical parameters of the nitrating system by replacing conventional mixed acid (HNO3-H2SO4) with ammonium nitrate-sulfuric acid system. This parameter change moderates the reaction exothermicity and allows better temperature control, resolving the safety issue while maintaining productivity
Solution Approach 2:
The patent introduces ammonium nitrate as an intermediary substance that reacts with sulfuric acid to generate nitric acid in situ. This intermediary approach allows controlled nitration while avoiding direct handling of concentrated nitric acid, thereby improving safety
2Productivity
If mixed acid nitration reaction is used, then nitrate esters can be synthesized, but poor separation of nitrate ester occurs due to high solubility in mixed acid
Solution Approach 1:
The patent extracts the nitrate ester product from the reaction mixture by adding water, which causes the nitrate ester to separate out due to its low water solubility. This simple extraction method resolves the separation difficulty without requiring complex equipment
Solution Approach 2:
The patent changes the solvent composition parameter by using ammonium nitrate-sulfuric acid system instead of conventional mixed acid. This parameter change results in nitrate ester having lower solubility in the reaction medium, facilitating easier separation
3Productivity
If mixed acid nitration reaction is used, then nitrate esters can be synthesized, but oxidative side reactions and fume-off of nitric acid reduce the concentration of active nitrating agent
Solution Approach 1:
The patent uses ammonium nitrate as an intermediary that provides controlled generation of nitric acid in situ. This prevents excessive nitric acid concentration and associated oxidative side reactions and fume-off, maintaining stable active nitrating agent concentration throughout the reaction
Solution Approach 2:
The patent converts the potential harm of nitric acid volatility and oxidation into a benefit by using ammonium nitrate-sulfuric acid system. The controlled in situ generation of nitric acid prevents oxidative degradation and fume-off, while still providing sufficient nitrating power
4Ease of manufacture
If extended washing train system is used to extract nitrate ester, then separation is improved, but additional processing equipment and hazardous waste management are required
Solution Approach 1:
The patent simplifies the extraction process by adding water to the reaction mixture, which causes nitrate ester to separate out as a distinct layer or precipitate. This single-step extraction eliminates the need for extended washing trains and complex processing equipment
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 safer, more cost-effective production of nitrate esters with higher yields and purity, minimizing oxidative side reactions and hazardous waste, and simplifying the production process by reducing the need for complex equipment and handling of corrosive nitric acid.
Implementation Method 1
combining at least one nitrate salt and sulfuric acid to form a nitrating solution wherein nitric acid is formed in situ
Implementation Method 2
The mixed acid contains nitrating species, such as nitronium ions (—NO2+) which react with hydroxyl groups on a polyol starting material, substituting a nitro group for the hydrogen in an O-nitration reaction
Implementation Method 3
Because the nitration reactions are exothermic, special care must be, and is, taken to avoid thermal runaway and explosions
Data Source
AI summary
Methods of forming a nitrate ester include combining at least one nitrate salt and sulfuric acid to form a nitrating solution and adding an aliphatic polyol to the nitrating solution. Nitrate esters formed by this method may be, for example, triethylene glycol dinitrate (TEGDN), pentaerythritol tetranitrate (PETN), diglycerol tetranitrate (DGTN), 1,1,1-tris(methylol)ethane trinitrate (TMETN), 1,2,4-butanetriol trinitrate (BTTN), nitroglycerin (NG), diethylene glycol dinitrate (DEGDN), ethylene glycol dinitrate (EGDN), metriol trinitrate (MTN), nitrocellulose (NC), or 1,2-propanediol dinitrate (PDDN).