Doped Hexagonal Lanthanum Oxycarbonate Catalysts for Higher C2 Yield
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Solution Overview
Problem
Existing methods for synthesizing lanthanum dioxide carbonate result in low yields of C2 hydrocarbons during methane oxidative coupling reactions, and there is a lack of reports on element doping during the preparation process.
Innovation Solution
A lanthanum dioxide carbonate catalyst comprising hexagonal crystalline lanthanum dioxide carbonate with a doping element R, prepared by adding an alkali solution to a lanthanum source, followed by aging, solid-liquid separation, and drying, then contacting with a doping element solution, and calcining in a carbon-containing atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If element doping is performed by impregnating pre-synthesized lanthanum dioxide carbonate with doping element solutions, then the doping process is simple, but the doping efficiency is low and the distribution is uneven
Solution Approach 1:
The doping element is introduced during the preparation process of lanthanum dioxide carbonate rather than as a post-treatment step. By adding the doping element solution during the formation of the carbonate structure, the doping occurs at the source, ensuring uniform distribution throughout the material matrix and improving doping efficiency.
Solution Approach 2:
The doping process is merged with the lanthanum dioxide carbonate synthesis process. The doping element solution is added to the reaction mixture during carbonate formation, combining two separate operations (synthesis and doping) into one integrated process, which improves both efficiency and uniformity.
2Ease of manufacture
If conventional preparation methods are used to synthesize lanthanum dioxide carbonate, then the synthesis process is straightforward, but the C2 hydrocarbons yield in methane oxidative coupling reactions is low
Solution Approach 1:
The crystal structure parameter of lanthanum dioxide carbonate is changed from the conventional cubic phase to the hexagonal phase. This structural transformation, achieved by controlling the preparation conditions, fundamentally alters the catalytic properties of the material, resulting in significantly enhanced C2 hydrocarbons yield while maintaining a relatively simple synthesis approach.
Solution Approach 2:
The invention creates a composite catalyst system by incorporating doping elements (such as Fe, Zn, or Mn) into the hexagonal lanthanum dioxide carbonate structure. This composite approach combines the unique catalytic properties of the hexagonal phase with the specific electronic and structural contributions of the doping elements, achieving high C2 hydrocarbons yield.
3Adaptability or versatility
If the molar ratio of lanthanum to doping element R is outside the range of 1:0.01 to 1:0.3, then the catalyst composition can be adjusted freely, but the catalytic activity for methane oxidative coupling decreases
Solution Approach 1:
The invention identifies and optimizes the critical parameter of doping element concentration, establishing the optimal molar ratio range of 1:0.01 to 1:0.3 between lanthanum and doping element R. This parameter optimization ensures maximum catalytic activity for methane oxidative coupling while still allowing flexibility within the defined range for different specific applications.
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 a higher yield of C2 hydrocarbons during methane oxidative coupling reactions, with a molar ratio of lanthanum to doping element R ranging from 1:0.01 to 1:0.3, ensuring a predominantly hexagonal crystalline phase and no metal salt peaks in the XRD spectrum.
Implementation Method 1
adding an alkali solution to a solution of lanthanum source, and then optionally performing an aging, performing a solid-liquid separation and a drying to obtain solid lanthanum hydroxide
Implementation Method 2
adding a solution of a compound containing the doping element R to the solid lanthanum hydroxide obtained in step (1) so that the solution in an amount less than or equal to the saturated water absorption amount of the lanthanum hydroxide is in contact with the lanthanum hydroxide
Implementation Method 3
calcining the dried product of step (2) in a carbon-containing (e.g. CO and/or CO2) atmosphere to obtain a lanthanum dioxide carbonate catalyst
Implementation Method 4
the total content of hexagonal crystalline lanthanum dioxide carbonate and hexagonal crystalline lanthanum dioxide carbonate containing a doping element R in the lanthanum dioxide carbonate catalyst is not less than 98wt%
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to the technical field of lanthanum dioxide carbonate, and discloses a lanthanum dioxide carbonate catalyst, a preparation method and a use thereof. The lanthanum dioxide carbonate catalyst comprises hexagonal crystalline lanthanum dioxide carbonate and hexagonal crystalline lanthanum dioxide carbonate containing a doping element R. The method comprises: (1) adding an alkali solution to a solution of lanthanum source, and then performing a solid-liquid separation and a drying to obtain lanthanum hydroxide; (2) contacting a solution of a compound containing the doping element R with lanthanum hydroxide, and then performing a drying; (3) calcining the dried product of step (2) under a carbon-containing atmosphere to obtain a lanthanum dioxide carbonate catalyst. When the catalyst prepared by the invention is used in a methane oxidative coupling reaction, it has a high yield of C2 hydrocarbons.