Stacked-bed hydrotreating catalysts for low-pressure gas oil
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Solution Overview
Problem
Current processes for hydrotreating gas oils to produce low-sulfur diesel face challenges in achieving low sulfur and nitrogen concentrations at reduced reactor pressure without significant increases in hydrogen consumption.
Innovation Solution
A low-pressure process using a stacked-bed reactor system with multiple catalyst beds, comprising cobalt and molybdenum on alumina, nickel and molybdenum on alumina, and cobalt and molybdenum on alumina catalysts, arranged in a specific configuration to enhance hydrodenitrogenation and hydrodesulfurization efficiency with minimal hydrogen consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional single-bed hydrotreating catalysts are used, then the process is simple to operate, but the ability to achieve low sulfur and nitrogen concentrations at reduced pressure is insufficient
Solution Approach 1:
The reactor system is segmented into multiple catalyst beds, each containing different catalyst compositions optimized for specific functions (hydrodesulfurization, hydrodenitrogenation, and hydrogenation). This segmentation allows each bed to specialize in removing particular contaminants under low-pressure conditions, achieving high purification precision without requiring excessively high pressure
Solution Approach 2:
Different catalyst compositions are placed in different local positions within the reactor. The first bed uses a catalyst optimized for hydrodesulfurization, the second for hydrodenitrogenation, and the third for hydrogenation. This local quality differentiation enables each section to perform its specific function efficiently at reduced pressure
2Use of energy by moving object
If reduced reactor pressure is used, then energy consumption is reduced, but the catalytic activity and effectiveness of hydrodenitrogenation and hydrodesulfurization decrease
Solution Approach 1:
The catalyst composition parameters are changed to include specific metal combinations (Co-Mo, Ni-Mo, Co-W) with optimized ratios and support materials (alumina, silica-alumina). These parameter changes enable the catalysts to maintain high activity at lower pressures by reducing the activation energy required for hydrodenitrogenation and hydrodesulfurization reactions
Solution Approach 2:
Composite catalyst materials are used, combining different metal sulfides (CoMoS, NiMoS, CoWS) on various support structures. These composite materials provide synergistic effects that enhance catalytic activity for both hydrodesulfurization and hydrodenitrogenation at low pressure, maintaining reliability without requiring high energy input
3Productivity
If multiple catalyst beds are stacked, then hydrodenitrogenation and hydrodesulfurization efficiency is enhanced, but the device complexity and reactor volume increase
Solution Approach 1:
Multiple catalyst beds are nested vertically within a single reactor vessel in a stacked configuration. Each catalyst bed is contained within the same reactor space, with beds arranged one above the other. This nesting approach allows high productivity through multiple catalytic functions while minimizing the overall reactor volume footprint
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 reduces organic nitrogen and sulfur concentrations in gas oils to produce low-sulfur diesel with improved catalytic activity and reduced hydrogen consumption, achieving ultra-low sulfur and nitrogen levels under low-pressure conditions.
Implementation Method 1
a first catalyst bed of a first bed volume that includes a first catalyst comprising cobalt and molybdenum supported on alumina
Implementation Method 2
a second catalyst bed of a second bed volume that includes a second catalyst comprising a support material containing nickel, molybdenum, a hydrocarbon oil and a polar additive
Implementation Method 3
a third catalyst bed of a third bed volume that includes a third catalyst comprising cobalt and molybdenum on an alumina support
Implementation Method 4
A gas oil feedstock, having an organic nitrogen concentration and an organic sulfur concentration, is introduced into the reaction zone
Data Source
AI summary
A low-pressure process for hydrodenitrogenation and hydrodesulfurization of a gas oil feedstock. The process uses a multi-bed, stacked-bed reactor system. The first and third beds of the multi-bed, stacked-bed reactor system include catalysts that comprise cobalt and molybdenum supported on alumina. The middle, second bed, includes a catalyst comprising nickel and molybdenum supported on alumina that preferably includes an additive. The stacked bed arrangement with the use of the specific catalysts provides for the low-pressure operation and significantly improved HDN and HDS activity with relatively insignificant differences in hydrogen consumption.