Spent Nickel Catalyst Regeneration by Nitric Acid Redispersion
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Solution Overview
Problem
Existing methods fail to effectively re-disperse nickel crystallites and restore catalytic activity in spent steam reforming catalysts, leading to a loss in sulfur adsorption capacity and activity due to nickel sintering, necessitating the use of new catalysts.
Innovation Solution
A method involving treatment with concentrated nitric acid and optional organic acids to re-disperse nickel in spent steam reforming catalysts, followed by heat-treatment, drying, and calcination, preserving the catalyst's shape and regaining up to 100% of its original activity and sulfur capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If spent catalyst is used for steam reforming, then catalyst structure is preserved, but nickel crystallite sintering causes loss of catalytic activity and sulfur adsorption capacity
Solution Approach 1:
The patent applies parameter changes by treating the spent catalyst with concentrated nitric acid (changing chemical concentration parameters) and performing heat treatment at specific temperatures (changing thermal parameters). This combination transforms the sintered nickel crystallites back into a dispersed, active state while preserving the overall catalyst structure, thereby restoring catalytic activity and sulfur adsorption capacity.
2Reliability
If spent catalyst is pulverized for recycling, then nickel can be extracted or re-dispersed, but catalyst shape and structure are destroyed
Solution Approach 1:
The patent extracts nickel from its sintered state through chemical treatment with concentrated nitric acid, which dissolves the sintered nickel crystallites. The nickel is then re-dispersed on the support material through subsequent heat treatment, restoring catalytic activity without pulverizing the catalyst pellets and destroying their shape.
Solution Approach 2:
Concentrated nitric acid acts as an intermediary chemical agent that facilitates the transformation of sintered nickel back to a dispersed state. The acid temporarily complexes with nickel, enabling its re-dispersion without mechanical destruction of the catalyst structure, and the support material serves as an intermediary substrate for re-dispersing the nickel.
3Reliability
If conventional regeneration methods are used, then some activity is restored, but nickel crystallite size increases and sulfur adsorption capacity is not fully recovered
Solution Approach 1:
The patent achieves superior regeneration by changing multiple parameters simultaneously: using concentrated (而非 dilute) nitric acid, applying specific heat treatment temperatures and durations, and controlling the atmosphere during heat treatment. These parameter changes enable complete re-dispersion of nickel crystallites, restoring both catalytic activity and sulfur adsorption capacity to levels equal to or exceeding the original catalyst.
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 method effectively reactivates spent catalysts by re-dispersing nickel, maintaining or exceeding original activity and sulfur adsorption capacity, allowing for their reuse without the need for new catalysts.
Implementation Method 1
contacting the spent catalyst with a nitric acid solution... reacting nickel with nitric acid
Implementation Method 2
drying the catalyst at 100-125°C
Implementation Method 3
calcining and reducing the catalyst, in which the calcining step is conducted in air at 500-1300°C
Implementation Method 4
the reducing step is conducted in the presence of hydrogen at 400-600°C
Implementation Method 5
adding one or more organic acids... organic acids as promoters
Data Source
AI summary
The invention relates to a method of regenerating the catalytic activity of a spent catalyst comprising nickel on a refractory oxide support, said method comprising the steps of contacting the spent catalyst with a nitric acid solution, heat-treating the spent catalyst, calcining and reducing the catalyst.