SSZ-91 Molecular Sieve Catalyst for Hydroisomerization Thermal Stability
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Solution Overview
Problem
Current hydroisomerization catalytic dewaxing processes face challenges in achieving product specifications for base oils, such as cloud point, pour point, and viscosity, while maintaining high yield and reducing undesired cracking and hydroisomerization reactions, which affect the quality and lifecycle of the catalyst.
Innovation Solution
A hydroisomerization catalyst composition comprising an SSZ-91 molecular sieve and rare earth modified alumina, combined with a Group 8-10 metal and optional modifiers, is used to improve thermal stability and metal dispersion, reducing cracking and enhancing isomerization activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hydroisomerization catalysts are used, then base oil production is achieved, but thermal stability and metal dispersion are insufficient leading to reduced catalyst lifecycle
Solution Approach 1:
The patent employs a composite catalyst structure combining SSZ-91 molecular sieve with rare earth modified alumina support. This composite material approach creates synergistic effects where the molecular sieve provides shape-selective isomerization activity while the rare earth modified alumina enhances thermal stability and metal dispersion, resolving the contradiction between maintaining catalytic activity and improving thermal stability for extended lifecycle
Solution Approach 2:
The patent modifies the alumina support by incorporating rare earth metals (such as lanthanum, cerium, or neodymium) to change the physical and chemical parameters of the support material. This parameter change increases the surface area, pore volume, and thermal stability of the alumina, which in turn improves noble metal dispersion and maintains catalyst structure at high temperatures, extending catalyst lifecycle
2Productivity
If hydroisomerization reactions are promoted, then base oil yield increases, but undesired cracking reactions also increase reducing product quality
Solution Approach 1:
The patent utilizes the shape-selective properties of SSZ-91 molecular sieve with its specific pore structure and channel dimensions. The local geometry of the pores creates steric constraints that allow linear paraffins to enter and isomerize while preventing excessive branching and cracking reactions. This local structural quality enables selective promotion of desired isomerization while suppressing harmful cracking, improving both yield and product quality
Solution Approach 2:
The rare earth modified alumina acts as an intermediary between the SSZ-91 molecular sieve and the noble metal particles. It provides a stable support structure that enhances metal dispersion and creates optimal conditions for isomerization while the modified alumina surface properties help control reaction pathways, reducing cracking by stabilizing the catalyst structure and preventing unwanted side reactions
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 catalyst composition improves noble metal dispersion and thermal stability, leading to increased catalyst lifecycle and improved base oil quality by reducing cracking and enhancing isomerization activity, resulting in higher yield and better product properties.
Implementation Method 1
A hydroisomerization catalyst composition comprising an SSZ-91 molecular sieve and rare earth modified alumina, combined with a Group 8-10 metal and optional modifiers, is used to improve thermal stability and metal dispersion, reducing cracking and enhancing isomerization activity
Implementation Method 2
Catalysts formed from the combination of SSZ-91 molecular sieve and a rare earth modified alumina have been found to advantageously possess improved metal dispersion and thermal stability characteristics
Data Source
AI summary
A method for making a hydroisomerization catalyst having improved thermal stability and metal dispersion characteristics, the catalyst prepared therefrom, and a process for making a base oil product using the catalyst are disclosed. The catalyst is prepared from a composition comprising an SSZ-91 molecular sieve and a rare earth modified alumina, with the composition being modified to contain a Group 8-10 metal, typically through impregnation of a Group 8-10 metal composition. The catalyst may be used to produce dewaxed base oil products by contacting the catalyst under hydroisomerization conditions with a hydrocarbon feedstock.