Two-Step Alumina Catalyst Composition for Low-Stickiness Oxychlorination
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Solution Overview
Problem
Existing oxychlorination catalysts for converting ethylene to dichloroethane suffer from catalyst stickiness, particularly at high copper loadings, which adversely affects ethylene and hydrogen chloride feedstock efficiencies in fluidized bed reactors.
Innovation Solution
A two-step impregnation process is employed to prepare a catalyst composition using copper, alkali metal, alkaline earth metal, and optionally rare earth metal on an alumina support, where the second impregnation solution is devoid of alkali metal to minimize stickiness, allowing for higher alkali metal content without deleterious effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high copper loading is used in the catalyst to improve activity, then catalytic performance is improved, but catalyst stickiness increases
Solution Approach 1:
The patent divides the impregnation process into two separate steps: first impregnating the support with copper and alkaline earth metal, then separately impregnating with alkali metal. This segmentation allows each metal to be deposited in controlled amounts, preventing the synergistic stickiness effect that would occur with simultaneous high concentrations of all metals, while still achieving high overall copper loading for catalytic activity.
Solution Approach 2:
The patent changes the parameters of the impregnation process by controlling the concentration and sequence of metal deposition. Specifically, it limits alkali metal to ≤1 wt% in the final catalyst and uses a two-step process where the first impregnation uses copper salt and alkaline earth metal salt solutions, and the second step adds alkali metal salt solution. This parameter control resolves the contradiction between high copper loading for activity and low stickiness.
2Productivity
If alkali metal content is increased to improve catalyst performance, then catalytic activity is enhanced, but susceptibility to stickiness increases
Solution Approach 1:
The patent segments the impregnation process so that alkali metal is added in a separate second step rather than being mixed with copper and alkaline earth metals in the first step. This allows precise control of alkali metal content at ≤1 wt% while maintaining high copper loading, thereby enhancing catalytic activity without triggering the stickiness problem associated with high alkali metal concentrations.
Solution Approach 2:
The patent explicitly controls the alkali metal parameter by limiting its concentration to ≤1 wt% in the final catalyst composition and by controlling the amount added in the second impregnation step to provide no more than 0.1 wt% additional alkali metal after drying. This parameter control resolves the contradiction between improving catalytic activity and preventing stickiness.
3Ease of manufacture
If single-step impregnation is used to simplify the process, then manufacturing complexity is reduced, but control over metal distribution and stickiness prevention is compromised
Solution Approach 1:
The patent applies segmentation by dividing the impregnation into two distinct steps with different metal compositions. The first step uses copper salt and alkaline earth metal salt solutions, while the second step uses alkali metal salt solution. This segmentation provides precise control over metal distribution and prevents stickiness by limiting alkali metal to ≤1 wt%, while still being manufacturable through straightforward sequential processing.
Solution Approach 2:
The patent uses preliminary action by first impregnating the support with copper and alkaline earth metals before adding alkali metal in the second step. This preliminary deposition establishes a foundation that allows subsequent alkali metal addition without reaching stickiness thresholds, while ensuring proper metal distribution for optimal catalytic performance.
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 composition exhibits reduced stickiness, enabling higher HCl conversion, lower chlorinated by-products, and operation at high temperatures without carbon oxide formation, suitable for use in baffled bed reactors.
Implementation Method 1
impregnating an alumina support with a first aqueous solution including copper, an alkaline earth metal, and an alkali metal to thereby form a first catalyst component
Data Source
AI summary
In an oxychlorination process of the type where ethylene is converted to 1,2-dichloroethane in the presence of a supported copper catalyst, the improvement comprising: the use of a supported catalyst prepared by (i) impregnating, within a first step, an alumina support with a first aqueous solution including copper, an alkaline earth metal, and an alkali metal to thereby form a first catalyst component; and (ii) impregnating, within a subsequent step, the first catalyst component with a second aqueous solution including copper and alkaline earth metal, where the second aqueous solution is substantially devoid of alkali metal, to thereby form the supported catalyst.