C4 Stream Distillation for MTBE, 1-Butene, and Propylene
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Solution Overview
Problem
Existing methods for producing MTBE and 1-butene face issues such as limited catalyst life due to deactivating compounds, incomplete utilization of C4 hydrocarbons, and high energy consumption in 1-butene purification.
Innovation Solution
An integrated system that includes a distillation unit to separate catalyst deactivating compounds and 2-butene from the C4 mixture, followed by metathesis to produce propylene, thereby improving catalyst life and utilizing C4 hydrocarbons more efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the crude C4 stream is directly fed into the MTBE synthesis unit after butadiene removal, then the process is simple, but the catalyst life is limited due to catalyst deactivating compounds
Solution Approach 1:
The crude C4 stream processing is segmented into multiple stages: first butadiene removal, then distillation to separate deactivating compounds, and finally MTBE synthesis. This segmentation allows each unit to handle specific components, extending catalyst life by removing harmful substances before they reach the catalyst.
Solution Approach 2:
Catalyst deactivating compounds are extracted from the crude C4 stream through distillation before the stream enters the MTBE synthesis unit. This extraction removes harmful substances (DMF, ACN, NMP, MOPN) that would otherwise poison the catalyst, thereby extending catalyst life without significantly increasing overall process complexity.
2Productivity
If conventional MTBE production methods are used, then the process is straightforward, but C4 hydrocarbons are not fully utilized resulting in waste of 2-butene and other C4 hydrocarbons
Solution Approach 1:
The distillation unit serves multiple functions: it separates catalyst deactivating compounds to protect the catalyst, divides C4 hydrocarbons into different streams for different purposes, and enables both MTBE production and propylene production from the same feedstock. This multi-functionality increases C4 utilization without proportionally increasing complexity.
Solution Approach 2:
Instead of discarding 2-butene and other C4 hydrocarbons as waste, the process recovers and utilizes them through metathesis reactions to produce propylene. The distillation unit separates these hydrocarbons into a bottom stream that is fed to the metathesis unit, transforming potential waste into valuable products.
3Loss of energy
If the raffinate is processed through two rectifiers in series to produce purified 1-butene, then high purity 1-butene is obtained, but the process is energy intensive causing high production cost
Solution Approach 1:
The distillation unit performs preliminary separation of C4 hydrocarbons into distillate and bottom streams before the MTBE synthesis step. This preliminary action removes deactivating compounds and separates 2-butene, which simplifies subsequent purification steps and reduces the energy required for achieving high 1-butene purity.
Solution Approach 2:
The process changes operating parameters by conducting distillation at optimized conditions to separate components based on their different volatilities. The distillation unit operates at parameters that efficiently separate deactivating compounds and C4 hydrocarbons, reducing the burden on subsequent purification steps and lowering overall energy consumption.
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 system enhances catalyst life, increases the utilization rate of C4 hydrocarbons, and reduces production costs by removing deactivating compounds and optimizing the 1-butene purification process.
Implementation Method 1
distilling a crude C 4 hydrocarbon stream that comprises n-butane, 1-butene, 2-butene, isobutane, isobutene, and a catalyst deactivating compound
Implementation Method 2
reacting at least some of the 2-butene of the bottom stream with ethylene in the one or more metathesis reactors to form a reaction stream comprising propylene and liquefied petroleum gas
Implementation Method 3
reacting the isobutene (isobutylene) of the distillate stream with methanol in the presence of a catalyst for MTBE synthesis to produce methyl tertiary butyl ether
Data Source
Figure 1A~1B
Figure 1C
Figure 2
AI summary
Systems and methods for producing MTBE and 1-butene are disclosed. A crude C4 hydrocarbon stream is obtained by removing butadiene from a C4 hydrocarbon mixture of a hydrocarbon cracking unit. The crude C4 hydrocarbon stream is then distilled to form (a) a first distillate stream comprising isobutylene, isobutane, 1-butene, or combinations thereof and (b) a first bottom stream comprising 2-butene, n-butane, a deactivating compound for catalyst of MTBE synthesis. The first distillate stream is then flowed to a MTBE synthesis unit to produce MTBE via reaction with methanol. The raffinate from the MTBE synthesis unit comprising isobutane and 1-butene is further separated in a distillation column to produce 1-butene.