Oxidative Dehydrogenation with Hydrocarbon Moderator Gas
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Solution Overview
Problem
Conventional oxidative dehydrogenation processes for producing butadiene are energy-intensive and impurity-sensitive due to the use of air as the oxygen source, which leads to high nitrogen levels in the feed, increasing operating costs and equipment size, and are limited by the scarcity and cost of n-butene raw material.
Innovation Solution
A process that uses a hydrocarbon moderator gas, such as methane, in place of nitrogen to reduce equipment size and costs, and produces butadiene by dimerizing ethylene to n-butene followed by oxidative dehydrogenation with an enriched oxygen feed, thereby reducing nitrogen levels and increasing the heating value of the gas stream for improved heat recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If air is used as the oxygen source for oxidative dehydrogenation, then the reaction temperature can be controlled due to nitrogen acting as a diluent, but the equipment size and operating costs increase due to high nitrogen levels in the feed
Solution Approach 1:
The patent removes nitrogen from the feed stream by using pure oxygen instead of air, extracting the harmful diluent that causes equipment size increases. This is achieved through oxygen enrichment processes that separate nitrogen from the oxygen feed, allowing the oxidative dehydrogenation reaction to proceed without the bulk nitrogen present in air-fed systems.
Solution Approach 2:
The patent changes the composition parameter of the oxygen source from air (21% O2, 79% N2) to enriched oxygen (higher O2 concentration), fundamentally altering the feed composition. This parameter change eliminates nitrogen's diluting effect while maintaining temperature control through alternative means such as steam injection and reaction heat management.
2Temperature
If air is used as the oxygen source, then nitrogen acts as a diluent to moderate the exotherm, but the heating value of the gas stream decreases making heat recovery less efficient
Solution Approach 1:
The patent extracts nitrogen from the gas stream to eliminate its negative impact on heating value. By using oxygen-enriched feeds and removing nitrogen through separation processes, the patent recovers heat from a concentrated hydrocarbon stream rather than diluting it with nitrogen, significantly improving heat recovery efficiency.
Solution Approach 2:
The patent converts the previously harmful presence of nitrogen (which diluted the stream and reduced heating value) into a beneficial system where oxygen enrichment is used to concentrate the hydrocarbon stream. This allows the exotherm to be managed more effectively while the gas stream maintains high heating value for efficient heat recovery.
3Temperature
If high steam flow rates are used to control the exotherm, then the reaction temperature can be managed, but the energy consumption and operating costs increase
Solution Approach 1:
The patent changes the thermal management approach by modifying the feed composition to oxygen-enriched streams with controlled steam-to-hydrocarbon ratios. Instead of relying on high steam flow rates to cool the exotherm, the patent uses optimized reaction conditions, catalyst selection, and feed composition to manage temperature, thereby reducing steam consumption and associated energy costs.
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 reduces capital and utility costs, decreases equipment size, and enhances heat recovery by increasing the heating value of the gas stream, making it more efficient and cost-effective compared to traditional air-fed processes.
Implementation Method 1
a hydrocarbonaceous n-butene rich stream is oxidized to a butadiene enriched product stream in an oxidative dehydrogenation process in the presence of a hydrocarbon moderator gas which acts as a heat sink
Implementation Method 2
oxidized to a butadiene enriched product stream in an oxidative dehydrogenation process in the presence of a hydrocarbon moderator gas
Data Source
AI summary
Oxidative dehydrogenation includes: (a) providing a gaseous feed stream to a catalytic reactor, the feed stream comprising a dehydrogenation reactant, oxygen, superheated steam, hydrocarbon moderator gas and optionally nitrogen, wherein the molar ratio of moderator gas to oxygen in feed stream is typically from 4:1 to 1:1 and the molar ratio of oxygen to nitrogen in the feed stream is at least 2; (b) oxidatively dehydrogenating the reactant in the reactor to provide a dehydrogenated product enriched effluent product stream; and (c) recovering dehydrogenated product from the effluent product stream. One preferred embodiment is a process for making butadiene including dimerizing ethylene to n-butene in a homogeneous reaction medium to provide a hydrocarbonaceous n-butene rich feed stream and oxidatively dehydrogenating the n-butene so formed.