Nickel Catalyst Preparation for Aromatic Hydrogenation
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Solution Overview
Problem
Current catalysts for hydrogenation of aromatic compounds, particularly those based on nickel, face limitations in activity and selectivity due to factors like particle size distribution and the presence of additives, which affect diffusion and intrinsic properties, leading to suboptimal performance in converting aromatic rings to naphthenic rings.
Innovation Solution
A nickel-based catalyst supported on alumina, prepared using organic additives with carboxylic acid, alcohol, ester, or amide functions, is used in a process that involves separate or simultaneous steps of impregnation with a nickel precursor and the organic compound, followed by drying and calcination, to enhance catalytic activity and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the size of metal particles is decreased to increase catalytic activity, then the catalyst becomes more active, but the particle size distribution becomes harder to control and may lead to aggregation
Solution Approach 1:
An organic additive is introduced as an intermediary substance during catalyst preparation. This additive adsorbs onto the metal particle surfaces and acts as a spacing agent, preventing particle aggregation while enabling the formation of uniformly small particles. The additive mediates between the tendency of metal particles to aggregate and the requirement for small particle size, achieving both high activity and narrow size distribution.
Solution Approach 2:
The invention changes the chemical environment during catalyst preparation by introducing organic additives with specific functional groups. This parameter change in the preparation chemistry enables controlled formation of metal particles with optimized size and distribution, transforming the uncontrolled aggregation process into a controlled nucleation and growth process that yields uniform small particles.
2Reliability
If organic additives are used to improve catalytic performance, then selectivity and activity are enhanced, but the catalyst preparation process becomes more complex
Solution Approach 1:
The invention merges the impregnation of metal precursor and organic additive into a single combined solution, rather than separate sequential steps. This merging of steps simplifies the overall preparation process while maintaining the beneficial effects of the organic additive on catalytic performance, reducing process complexity without sacrificing activity or selectivity.
Solution Approach 2:
The organic additive performs multiple functions simultaneously: it acts as a structure-directing agent for particle formation, a dispersing agent to prevent aggregation, and a potential promoter of catalytic activity. This multi-functionality reduces the need for multiple separate additives or processing steps, thereby simplifying the overall preparation process while achieving superior catalytic performance.
3Productivity
If metal content is increased to improve conversion rate, then catalytic activity increases, but the cost and potential deactivation issues increase
Solution Approach 1:
The invention creates local high-concentration zones of active metal sites through uniform particle distribution enabled by the organic additive. Instead of requiring high overall metal content, the additive ensures that metal is evenly dispersed at optimal concentrations throughout the support, creating locally optimized active sites that maximize conversion efficiency without increasing total metal loading.
Solution Approach 2:
The organic additive acts as a temporary sacrificial component during catalyst preparation that can be used at low concentrations. It performs its function of controlling particle formation and distribution, then can be removed or decomposed during calcination, leaving behind a highly active catalyst with low metal content. This allows achieving high productivity without the costs and deactivation issues associated with high metal loading.
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 achieves improved catalytic performance by reducing nickel particle size and increasing dispersion, resulting in higher conversion rates of aromatic compounds to naphthenic compounds under identical operating conditions, exceeding the performance of prior art catalysts.
Implementation Method 1
a step of bringing said support into contact with at least one solution containing at least one organic compound
Implementation Method 2
a step of drying said impregnated support
Implementation Method 3
a step of calcining the dried support in order to obtain the catalyst
Implementation Method 4
The rate of the hydrogenation reaction is governed by several criteria, such as the diffusion of the reactants toward the surface of the catalyst
Implementation Method 5
the diffusion of the reactants toward the surface of the catalyst (external diffusional limitations), the diffusion of the reactants in the porosity of the support toward the active sites
Data Source
AI summary
Hydrogenation of at least one aromatic or polyaromatic compound contained in a hydrocarbon feedstock having a final boiling point below or equal to 650° C., at a temperature of between 30 and 350° C., at a pressure of between 0.1 and 20 MPa, at a hydrogen/(aromatic compounds to be hydrogenated) molar ratio between 0.1 and 10 and at an hourly space velocity HSV of between 0.05 and 50 h−1, in the presence of a catalyst comprising an alumina support and an active phase comprising nickel, prepared byi) contacting the support with a solution containing a nickel precursor;ii) bringing the support into contact with a solution containing an organic compound comprising a carboxylic acid, or alcohol, or ester, or amide function;iii) drying the impregnated support at a temperature below 250° C.;i) and ii) being carried out separately, in any order, or at the same time.