Olefin Oligomerization Catalyst Bed Segmentation
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Solution Overview
Problem
The oligomerization of high-olefin content feedstocks, particularly those containing sulfur, poses challenges due to catalyst agglomeration, pressure drop, and uncontrollable exotherms, leading to reduced catalyst lifetime and efficiency in commercial processes.
Innovation Solution
A process involving sequential contact of the feedstock with a crystalline molecular sieve catalyst having unidimensional channels followed by contact with a catalyst having multidimensional channels, specifically using ZSM-22 and ZSM-57, respectively, to manage sulfur impurities and exothermic reactions, thereby stabilizing the catalyst and maintaining isothermal reactor conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If solid phosphoric acid catalyst is used for oligomerization, then catalyst activity is sufficient, but catalyst agglomerates and forms single solid block requiring water jetting or drilling out of reactor
Solution Approach 1:
The catalyst bed is segmented into multiple layers with different functional properties: a lower layer containing solid phosphoric acid catalyst for high activity and an upper layer containing zeolite catalyst for structural stability and reduced agglomeration. This segmentation allows each catalyst type to perform its specialized function while preventing the problematic agglomeration of sPa catalyst throughout the entire bed.
Solution Approach 2:
The zeolite catalyst layer acts as an intermediary between the feedstock and the sPa catalyst layer. It provides a stable structural framework that prevents direct contact between feedstock and sPa catalyst, thereby reducing agglomeration while still allowing the sPa catalyst to maintain its high activity for oligomerization.
2Productivity
If sPa catalyst is used, then oligomerization activity is achieved, but pressure drop increases steadily due to catalyst agglomerization limiting useful lifetime
Solution Approach 1:
The catalyst system is segmented into two functional zones: the lower sPa catalyst layer maintains high oligomerization activity while the upper zeolite layer provides structural stability and prevents pressure drop increase. This segmentation allows the sPa catalyst to remain active without causing the steady pressure drop that limits its lifetime.
Solution Approach 2:
Different regions of the catalyst bed have different qualities: the lower region contains highly active sPa catalyst for oligomerization, while the upper region contains zeolite catalyst for structural stability and pressure drop control. This local differentiation allows each zone to optimize its specific function.
3Productivity
If olefin feedstock concentration is increased to maximize catalyst cycle length, then reaction rate improves, but catalyst fouling rate increases
Solution Approach 1:
The zeolite catalyst layer serves as an intermediary that protects the sPa catalyst from direct exposure to high concentrations of olefin feedstock. This mediator layer reduces catalyst fouling while still allowing the system to maintain high reaction rates through the active sPa catalyst below.
Solution Approach 2:
The zeolite catalyst, which has lower intrinsic activity than sPa, is positioned to handle the fouling-prone high olefin concentration conditions, converting the potential harm of fouling into a benefit by protecting the more active sPa catalyst from direct fouling exposure.
4Productivity
If sPa catalyst is used, then oligomerization is achieved, but large quantities of catalyst are required due to low productivity compared to other catalysts
Solution Approach 1:
The system merges two catalyst types with complementary strengths: sPa catalyst provides high oligomerization activity while zeolite catalyst provides structural stability and reduced fouling. This combination achieves high productivity with reduced total catalyst quantity by utilizing the complementary strengths of both catalysts.
Solution Approach 2:
The catalyst system is a composite structure combining sPa catalyst and zeolite catalyst in a layered configuration. This composite approach leverages the high activity of sPa and the structural stability of zeolite to achieve superior performance with reduced catalyst quantity compared to using sPa alone.
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 enhances catalyst stability and selectivity, allowing for the efficient oligomerization of high-olefin feedstocks without excessive exotherms, even with sulfur-containing molecules, thereby extending catalyst lifetime and optimizing reactor performance.
Implementation Method 1
contacting the feedstock with a catalyst comprising a crystalline molecular sieve having pores defined by unidimensional channels formed by 10-membered rings of tetrahedrally coordinated atoms
Implementation Method 2
contacting the feedstock under olefin oligomerization conditions with a catalyst comprising a crystalline molecular sieve having pores defined by multidimensional channels
Implementation Method 3
manage sulfur impurities and exothermic reactions, thereby stabilizing the catalyst and maintaining isothermal reactor conditions
Data Source
AI summary
In a process for oligomerizing an olefinic hydrocarbon feedstock comprising at least 65 wt % olefins and/or sulfur-containing molecules, the feedstock is contacted under oligomerization conditions with (a) a first unidimensional 10-ring molecular sieve catalyst and (b) a second multidimensional crystalline molecular sieve catalyst. The first and second catalysts may be contained in separate reactors or as separate beds in a single reactor.