Nickel Shell Catalyst Preparation for Better Mass Transfer
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Solution Overview
Problem
Existing nickel-based catalysts for the selective hydrogenation of polyunsaturated compounds and aromatics require high nickel content and uniform distribution, leading to inefficiencies in activity and selectivity due to intragranular mass transfer issues.
Innovation Solution
A process for preparing a nickel-based catalyst with a specific distribution of nickel on the periphery and core of an alumina support, using a butanol impregnation and maturation step to create a 'ring of free pores' that limits nickel migration, resulting in a catalyst with improved accessibility and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If nickel is distributed homogeneously within the support, then the catalyst structure is simple, but intragranular mass transfer problems occur leading to activity defects and loss of selectivity
Solution Approach 1:
The patent applies local quality by creating an eggshell catalyst where nickel is concentrated in a peripheral crust (0.05-0.20 mm thickness) rather than uniformly distributed. This localized concentration of active phase in the support periphery optimizes mass transfer by placing catalytic sites where reactants first contact the catalyst, while avoiding intragranular diffusion limitations that would occur with homogeneous distribution throughout the entire support volume.
2Productivity
If nickel content is increased to 5-50 wt% to improve activity, then catalytic activity increases, but the quantity of nickel required is large
Solution Approach 1:
The patent concentrates nickel in a peripheral crust containing 10-50 wt% nickel, rather than distributing it uniformly throughout the entire support. This localized concentration means that while the overall nickel content in the catalyst may be moderate (5-50 wt% relative to total catalyst), the active peripheral region has high nickel density where it is most needed for catalysis, improving activity per unit nickel and avoiding the need for large quantities of nickel distributed throughout the bulk support.
3Productivity
If nickel is deposited in a concentrated form on the periphery, then activity and selectivity improve, but the preparation process becomes more complex
Solution Approach 1:
The patent employs preliminary action by first forming a peripheral crust structure on the support before depositing nickel. The support is pre-treated to create an eggshell geometry with a nickel-concentrated peripheral crust (0.05-0.20 mm thickness), and then nickel precursor is impregnated which preferentially deposits in this peripheral region. This preliminary structuring of the support simplifies the overall process compared to attempting to directly create the nickel distribution pattern in a single step.
4Quantity of substance
If a thin palladium crust is obtained with low palladium content, then cost is reduced, but the same approach with nickel requires high nickel content to achieve comparable activity
Solution Approach 1:
The patent applies local quality by concentrating nickel in a thin peripheral crust (0.05-0.20 mm) rather than distributing it uniformly. This creates a high local concentration of active phase at the catalyst periphery where mass transfer is most efficient, compensating for nickel's lower intrinsic activity compared to palladium. The result is that moderate overall nickel content (5-50 wt%) can achieve good activity because the nickel is strategically positioned in the high-flux peripheral region rather than diluted throughout the bulk support.
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 catalyst achieves enhanced activity and selectivity in selective hydrogenation reactions using a lower quantity of nickel, addressing the inefficiencies of traditional catalysts by optimizing nickel distribution.
Implementation Method 1
The process comprises the following steps: a) said support is impregnated with a volume V1 of a butanol solution between 0.2 and 0.8 times the total pore volume VPT of said support
Implementation Method 2
a volume V1 of a butanol solution between 0.2 and 0.8 times the total pore volume VPT of said support
Implementation Method 3
c) the matured impregnated support obtained at the end of step b) is impregnated with a solution comprising at least one precursor of the active nickel phase
Implementation Method 4
The present invention relates to a process for preparing a catalyst comprising a nickel-based active phase... particularly intended for the hydrogenation of unsaturated hydrocarbons, and more particularly, for the selective hydrogenation of polyunsaturated compounds or the hydrogenation of aromatics
Data Source
Figure 1
AI summary
Disclosed is a method for preparing a catalyst comprising a nickel-based active phase and an alumina carrier, which method includes the following steps: (a) impregnating said carrier with a volume V1 of a butanol solution representing between 0.2 and 0.8 times the total pore volume VPT of said carrier so as to obtain an impregnated carrier; (b) leaving the impregnated carrier obtained at the end of step (a) to mature for 0.5 to 40 hours; (c) impregnating the impregnated matured carrier obtained at the end of step (b) with a solution comprising at least one precursor of the active nickel phase so as to obtain a catalyst precursor; (d) drying the catalyst precursor obtained at the end of step (c) at a temperature of less than 250°C.