Dual-Function Catalyst for Arsenic Removal and Selective Hydrodesulfurization
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Solution Overview
Problem
Current hydrodesulfurization processes for gasoline cuts from fluidized bed catalytic cracking units face challenges in selectively removing arsenic and sulfur while preserving the high octane number, as existing adsorbents are not stable over time and lead to significant hydrogenation of mono-olefins, causing catalyst deactivation and octane number loss.
Innovation Solution
A catalytic adsorbent comprising at least one metal from group VIB and two metals from group VIII, specifically molybdenum, cobalt, and nickel, deposited on a porous support, which maintains arsenic adsorption and hydrodesulfurization activity over time with selective hydrogenation of mono-olefins, thereby reducing sulfur and arsenic content in hydrocarbon feedstocks without compromising octane number.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional adsorbents are used to capture arsenic, then arsenic removal is achieved, but the adsorbents are catalytically inactive for hydrodesulfurization and occupy significant reactor volume
Solution Approach 1:
The patent combines arsenic adsorption and hydrodesulfurization functions into a single catalyst by depositing group VIB metals (molybdenum, tungsten) and group VIII metals (nickel, cobalt) on a porous support. This dual-function catalyst eliminates the need for separate adsorbent and catalyst beds, optimizing reactor volume while maintaining both arsenic removal and sulfur hydrodesulfurization activities.
Solution Approach 2:
The catalyst is designed to perform multiple functions simultaneously: adsorbing arsenic through surface interactions, catalyzing hydrodesulfurization reactions, and providing structural stability. The group VIB and group VIII metal combination enables the single material to handle both heavy metal removal and sulfur compound conversion.
2Reliability
If non-selective hydrodesulfurization processes are used, then sulfur content is reduced, but a large proportion of mono-olefins is hydrogenated resulting in significant octane rating loss
Solution Approach 1:
The catalyst exhibits different active sites with distinct functions: group VIB metal sulfides (MoS2, WS2) primarily promote hydrodesulfurization reactions, while group VIII metals (Ni, Co) enhance activity but in controlled proportions. The specific metal ratio and distribution create localized active zones that favor sulfur removal over olefin hydrogenation, preserving octane rating.
Solution Approach 2:
The catalyst composition parameters are optimized to achieve selective hydrodesulfurization. The metal ratio (group VIB:group VIII), metal loading amounts, and support properties are adjusted to create a catalyst that operates at conditions where HDS activity dominates over hydrogenation activity, thereby removing sulfur while preserving mono-olefins and maintaining octane number.
3Reliability
If existing adsorbents are used in the presence of hydrogen, then arsenic is captured, but unsaturated compounds undergo hydrogenation leading to decreased octane rating
Solution Approach 1:
The invention merges arsenic capture and selective hydrodesulfurization into a single catalytic step that occurs simultaneously in the presence of hydrogen. The dual-function catalyst captures arsenic while selectively hydrodesulfurizing sulfur compounds without excessive mono-olefin hydrogenation, eliminating the need for separate treatment stages and avoiding octane loss associated with sequential processing.
4Productivity
If hydrodesulfurization catalysts are used without prior arsenic removal, then sulfur is removed, but heavy metals like arsenic cause rapid catalyst deactivation
Solution Approach 1:
The catalyst integrates arsenic capture capability with hydrodesulfurization activity in a single material. The group VIB and group VIII metals on porous support work together to adsorb arsenic species while maintaining active sites for sulfur hydrodesulfurization, preventing arsenic-induced deactivation and ensuring long-term catalyst stability and continuous operation.
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 catalytic adsorbent effectively captures arsenic and sulfur from hydrocarbon feedstocks, maintaining hydrodesulfurization activity and selectivity, ensuring a low sulfur and arsenic content with minimal loss of octane number, even after prolonged use, thus enhancing the stability and performance of hydrodesulfurization processes.
Implementation Method 1
a catalytic adsorbent having the properties of capturing arsenic
Implementation Method 2
selectively desulfurizing a hydrocarbon feedstock over time while maintaining a high octane rating
Implementation Method 3
limiting the hydrogenation of the mono-olefins present in said feedstock
Data Source
AI summary
Catalytic adsorbent, comprises a metal (M1) from group VIB, and metals (M3 and M2) from group VIII deposited on a porous carrier, where: a molar ratio of the metal (M2+M3)/M1 is 1-6; the amount of M1 is 3-14 wt.%; the amount of M2 is 1-20 wt.%; and the amount of M3 is 5-28 wt.%. An independent claim is included for process for hydrodesulfurization of a hydrocarbon feedstock, comprising contacting hydrogen with hydrocarbon feedstock in presence of the catalytic adsorbent.