Palladium Activated Carbon Catalyst Depth Gradient
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Solution Overview
Problem
Current methods for preparing hydrogenation catalysts with metallic palladium on activated carbon supports face challenges in achieving uniform distribution and maintaining palladium content, leading to reduced catalytic activity and service life, especially during the purification of crude terephthalic acid.
Innovation Solution
A fluidized bed process is used to deposit metallic palladium uniformly on granular or shaped activated carbon supports, achieving a penetration depth of 10-100 μm and crystallite size of 40-120 Å, with 5-40% palladium in the surface layer, to enhance catalytic activity and service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large amount of metallic palladium concentrates on the surface of support, then the catalytic activity increases, but the formation of palladium cluster is facilitated and the crystallite size increases, causing decrease of surface area and catalytic activity
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of palladium with different concentrations at different depths. The surface layer (0-1 μm) contains 5-30 wt% Pd, while the inner layer (1-100 μm) contains 30-50 wt% Pd. This gradient distribution optimizes both surface area for activity and prevents excessive clustering by controlling local palladium concentration.
Solution Approach 2:
The patent changes the concentration parameter of palladium distribution by depth. By controlling the palladium content to be 5-30 wt% in the surface layer and 30-50 wt% in the inner layer, the patent optimizes the balance between surface area availability and prevention of cluster formation, maintaining crystallite size below 35 Å.
2Manufacturing precision
If the palladium content on the surface of support is at a relatively low level, then the formation of palladium cluster is reduced, but the surface area of palladium and the catalytic activity will decrease
Solution Approach 1:
The patent uses a nested structure with two layers: an outer surface layer (0-1 μm) with 5-30 wt% Pd and an inner layer (1-100 μm) with 30-50 wt% Pd. The inner layer provides a reservoir of palladium that prevents cluster formation, while the outer layer maintains sufficient surface area for catalytic activity.
Solution Approach 2:
The patent changes the concentration parameter of palladium by creating a depth-dependent distribution. The surface layer has lower Pd content (5-30 wt%) to maintain surface area, while the inner layer has higher Pd content (30-50 wt%) to prevent clustering, optimizing both parameters simultaneously.
3Reliability
If the active component is distributed on the surface of support, then the catalytic activity is high, but the active component distributed in the support is out of function
Solution Approach 1:
The patent applies local quality by distributing palladium with different concentrations at different depths. The surface layer (0-1 μm) with 5-30 wt% Pd provides high surface area for catalytic activity, while the inner layer (1-100 μm) with 30-50 wt% Pd ensures full utilization of the active component throughout the support.
Solution Approach 2:
The patent transitions from two-dimensional surface distribution to three-dimensional depth-dependent distribution. By controlling Pd concentration as a function of depth (0-1 μm surface layer vs. 1-100 μm inner layer), the patent maximizes both surface area for activity and total active component utilization.
4Reliability
If the crystallite size of metallic palladium is reduced to increase surface area, then the catalytic activity increases, but the uniform distribution of metallic palladium on support becomes more difficult to achieve
Solution Approach 1:
The patent applies local quality by controlling Pd distribution with different concentrations at different depths. The surface layer (0-1 μm) with 5-30 wt% Pd achieves uniform distribution of small crystallites (<35 Å) for high surface area, while the inner layer (1-100 μm) with 30-50 wt% Pd maintains uniform distribution to prevent clustering.
Solution Approach 2:
The patent changes the concentration parameter of Pd distribution by depth to achieve uniform crystallite size control. By maintaining 5-30 wt% Pd in the surface layer and 30-50 wt% in the inner layer, the patent ensures uniform distribution of small crystallites throughout, achieving both high surface area and uniformity.
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 exhibits higher activity and selectivity for reducing 4-CBA to 4-methylbenzoic acid, with improved surface area and longer service life, while minimizing noble metal loss and sintering issues.
Implementation Method 1
A fluidized bed process is used to deposit metallic palladium uniformly on granular or shaped activated carbon supports
Implementation Method 2
hydrogenation is the easiest route for removal of 4-carboxylbenzaldehyde (4-CBA) impurity from the crude terephthalic acid
Data Source
AI summary
The present invention discloses a hydrogenation catalyst comprising metallic palladium supported on activated carbon support, wherein the penetration depth of metallic palladium in the support is at least about 10 μm and up to about 100 μm, the crystallite size of palladium is between about 40 Å and about 120 Å, and the palladium in the surface layer from the surface of support to a depth of 1 μm is from about 5% to about 40% based on the total atom number of palladium and other elements. The present invention further discloses a process for preparing the hydrogenation catalyst, and a use of said hydrogenation catalyst in the purification of crude terephthalic acid.