Bimetallic Nickel Copper Catalyst Sulfur Poisoning
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Solution Overview
Problem
Current catalysts for selective hydrogenation of polyunsaturated hydrocarbons face challenges in achieving high activity and selectivity, particularly when exposed to sulfur-containing hydrocarbon feeds, and require severe reduction conditions that are not always feasible.
Innovation Solution
A bimetallic catalyst comprising nickel and copper, with a specific Cu:Ni ratio, is prepared by sequential impregnation of metal precursors on a refractory oxide support, followed by a reduction step in the presence of a reducing gas at lower temperatures and shorter times, which enhances reducibility and resistance to sulfur poisoning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional reduction conditions (high temperature and long duration) are used to prepare nickel-based catalysts, then the catalyst achieves sufficient metallic form conversion, but the process requires severe operating conditions that are not always feasible and increases energy consumption
Solution Approach 1:
Copper acts as an intermediary substance that facilitates the reduction of nickel oxide to metallic nickel at lower temperatures. The copper precursor is first reduced to metallic copper, which then serves as a reducing agent to convert nickel oxide to metallic nickel through a solid-state redox reaction, enabling catalyst activation under milder conditions
Solution Approach 2:
The copper precursor is introduced and reduced first before the nickel reduction step. This preliminary action of copper reduction creates the reducing environment needed for subsequent nickel reduction at lower temperatures, avoiding the need for severe reduction conditions
2Productivity
If nickel-based catalysts are used for selective hydrogenation, then hydrogenation activity is achieved, but the catalyst is susceptible to sulfur poisoning which reduces its lifespan and performance
Solution Approach 1:
The catalyst combines nickel and copper in a bimetallic system where nickel provides the primary hydrogenation activity while copper provides sulfur tolerance. The composite structure allows nickel to function as the active hydrogenation site while copper acts as a sulfur trap, protecting nickel from poisoning and maintaining long-term catalyst performance
3Reliability
If copper is added to nickel-based catalysts to improve sulfur resistance, then resistance to sulfur poisoning increases, but the reduction process becomes more complex requiring sequential impregnation steps
Solution Approach 1:
The catalyst preparation is divided into distinct sequential steps: first impregnation with copper precursor, drying, reduction of copper, then impregnation with nickel precursor, drying, and reduction of nickel. This segmentation allows precise control over metal distribution and reduction conditions, achieving the desired bimetallic structure despite the increased procedural steps
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 results in a catalyst with improved activity, selectivity, and longer lifespan, capable of effectively hydrogenating polyunsaturated hydrocarbons while maintaining performance in sulfur-containing environments, and allows for reduced operating conditions compared to traditional methods.
Implementation Method 1
a reduction step is carried out by bringing said precursor into contact with a reducing gas at a temperature below 200°C
Implementation Method 2
the presence of copper greatly improves the reducibility of the nickel on the support
Implementation Method 3
selective hydrogenation of polyunsaturated hydrocarbon fractions
Implementation Method 4
the copper present in the catalyst captures more easily the sulfur compounds included in the feedstock
Data Source
AI summary
The invention relates to a method for preparing a catalyst comprising a bimetallic active phase made of nickel and copper, and a support comprising a refractory oxide, comprising the following steps: a) a step of placing the support in contact with a solution containing a nickel precursor; b) a step of placing the support in contact with a solution containing a copper precursor; the steps a) and b) being carried out separately in any order; c) a step of drying the catalyst precursor at the end of step a) and b), or b) and a), at a temperature less than 250°C; d) supplying the catalyst precursor obtained at the end of step c), into a hydrogenation reactor, and carrying out a reduction step by placing said precursor in contact with a reducing gas at a temperature less than 200°C for a period greater than or equal to 5 minutes and less than 2 hours.