Low Acidity Hydrotreating Catalyst for Lubricant Yield Stability
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Solution Overview
Problem
Conventional dewaxing processes for hydrocarbon feedstocks often result in yield loss of lubricant base oils at elevated temperatures due to catalyst aging and unwanted hydrocracking reactions, particularly when using conventional guard bed catalyst systems above 600°F.
Innovation Solution
A layered catalyst system comprising a hydrotreating catalyst with low acidity, supported on an inorganic oxide, is used upstream of a dewaxing catalyst to reduce catalyst aging and maintain lubricant oil yield, where the hydrotreating catalyst has a decalin conversion of less than 10% at 700°F, thereby minimizing hydrocracking and preserving yield over a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional guard bed catalyst systems are used above 600°F, then catalyst aging is accelerated, but lubricant oil yield is lost due to unwanted hydrocracking reactions
Solution Approach 1:
The patent applies local quality by creating distinct zones within the catalyst system: a hydrotreating catalyst zone with specific properties for removing impurities, and a dewaxing catalyst zone with different properties for wax removal. Each zone is optimized for its specific function, allowing the system to maintain catalyst stability while preventing unwanted hydrocracking that would reduce lubricant oil yield.
Solution Approach 2:
The catalyst system is segmented into multiple functional layers: a hydrotreating catalyst layer (comprising Group VIII metal on inorganic oxide support) and a dewaxing catalyst layer (comprising acidic zeolite or molecular sieve). This segmentation allows each catalyst type to perform its specialized function independently, preventing the catalyst aging and yield loss that occurs in conventional single-system approaches.
2Quantity of substance
If hydrocracking reactions are promoted to remove wax, then wax content is reduced, but yield is lost through production of lower molecular weight hydrocarbons
Solution Approach 1:
The patent segments the dewaxing function into two parts: hydroisomerization (performed by the hydrotreating catalyst) and physical dewaxing (performed by the dewaxing catalyst). This segmentation allows wax removal through isomerization and selective adsorption rather than extensive hydrocracking, thereby maintaining lubricant base oil yield while reducing wax content.
Solution Approach 2:
The hydrotreating catalyst acts as an intermediary that performs hydroisomerization of n-paraffins to iso-paraffins before the feed reaches the dewaxing catalyst. This intermediate transformation reduces the wax-forming potential of the feedstock, allowing the dewaxing catalyst to work more efficiently and with less yield loss.
3Manufacturing precision
If operating temperature is increased to maintain pour point, then dewaxing efficiency is improved, but catalyst aging accelerates and yield decreases
Solution Approach 1:
The patent segments the temperature requirements for different functions: the hydrotreating catalyst operates at lower temperatures (450-600°F) for impurity removal and hydroisomerization, while the dewaxing catalyst operates at higher temperatures (600-725°F) for effective wax removal. This segmentation allows the system to achieve pour point control without subjecting a single catalyst to excessive temperatures that would accelerate aging.
Solution Approach 2:
The hydrotreating catalyst performs preliminary hydroisomerization of n-paraffins to iso-paraffins at lower temperatures before the feed enters the dewaxing catalyst zone. This preliminary action reduces the wax content and improves the feedstock quality, allowing the dewaxing catalyst to operate more efficiently at lower temperatures and extend its cycle length.
4Productivity
If high acidity catalyst is used to enhance dewaxing activity, then dewaxing rate is improved, but unwanted hydrocracking increases causing yield loss
Solution Approach 1:
The patent segments the catalytic functions by acidity level: the hydrotreating catalyst has low acidity (designed for hydroisomerization with minimal cracking), while the dewaxing catalyst has high acidity (designed for effective wax removal). This segmentation allows each catalyst to operate at its optimal acidity level for its specific function, achieving high dewaxing rates without excessive hydrocracking and yield loss.
Solution Approach 2:
The patent applies local quality by assigning different acidity characteristics to different catalyst zones: the hydrotreating catalyst zone maintains low acidity to prevent unwanted hydrocracking, while the dewaxing catalyst zone has high acidity to maximize dewaxing activity. This localized optimization of acidity allows the system to achieve high productivity without sacrificing yield.
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 effectively maintains lubricant oil yield within 2% of the target pour point over a temperature range of 450°F to 725°F, reducing catalyst aging and minimizing yield loss, while achieving a lower pour point for the lubricant oil products.
Implementation Method 1
contacting a waxy hydrocarbon feedstock in a first reaction zone, under hydrotreating conditions in which the aromatics content of the feedstock is reduced, with a hydrotreating catalyst
Implementation Method 2
Hydroisomerization converts aliphatic, unbranched paraffinic hydrocarbons to iso-paraffins and cyclic species which do not easily form waxes
Implementation Method 3
contacting at least a portion of the first effluent in a second reaction zone with a dewaxing catalyst under dewaxing conditions to yield a lubricant oil, wherein the lubricant oil has a pour point lower than the pour point of the first effluent
Data Source
AI summary
The invention provides for a process for dewaxing a waxy hydrocarbon feedstock to form a lubricant oil. The invention is also directed to a catalyst system comprising a hydrotreating catalyst upstream of a dewaxing catalyst, used in the dewaxing of a waxy hydrocarbon feedstock to form a lubricant oil. In particular, the invention is directed to a process and catalyst system designed to maintain yield of lubricant oil product. Specifically, the yield of lubricant oil does not decrease more than 2%, at a target pour point, over a dewaxing temperature range. The hydrotreating catalyst helps prevent aging of the dewaxing catalyst and maintains lubricant oil product yield at a target pour point over a wide temperature range. The hydrotreating catalyst comprises platinum, palladium, or combinations thereof on a low acidity inorganic oxide support where acidity is measured by a decalin conversion of less than 10% at 700° F.