Rare Earth Catalyst Recovery in Dialkyl Carbonate Synthesis
Solution Overview
Problem
There is a need for a process to recover and regenerate rare earth metal salts used as catalysts in the synthesis of dialkyl carbonates, as they often precipitate during the reaction, leading to reduced activity and selectivity, and existing methods do not address the reactivation and regeneration of homogeneous catalysts based on rare earth metal salts.
Innovation Solution
A process involving the addition of alkyl carbamate, alcohol, and rare earth metal salts in a reactor to form dialkyl carbonates, followed by separating the deactivated catalyst residue and dissolving it in an acid corresponding to the rare earth metal salt, with optional ammonia addition to precipitate and re-dissolve the catalyst, maintaining catalytic activity similar to fresh catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rare earth metal salts are used as homogeneous catalysts for dialkyl carbonate synthesis, then catalytic activity and selectivity are improved, but catalyst precipitation occurs leading to reduced activity over time
Solution Approach 1:
The patent implements a catalyst recovery system where precipitated rare earth metal catalyst is continuously removed from the reaction mixture and regenerated externally. The spent catalyst is dissolved in acid to reform the active rare earth metal salt, which is then returned to the reactor. This closed-loop recovery process maintains high catalytic activity over extended reaction periods by preventing permanent catalyst loss.
Solution Approach 2:
The patent utilizes parameter changes in the catalyst's physical state and chemical environment. By controlling pH, temperature, and solvent composition, the catalyst can be maintained in solution during reaction, then induced to precipitate for easy separation, and subsequently redissolved in acid for regeneration. These parameter transitions enable continuous catalyst recovery and reuse.
2Ease of manufacture
If catalyst recovery processes are implemented, then economic viability is improved, but process complexity increases
Solution Approach 1:
The catalyst recovery system is designed to be self-sufficient, using readily available reagents like dilute acids for dissolution and standard filtration equipment for separation. The process regenerates catalyst in-situ without requiring external specialized facilities, making the system economically viable while keeping operational complexity manageable through use of conventional unit operations.
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 effectively recovers and regenerates rare earth metal salts, maintaining catalytic activity and selectivity over multiple cycles, ensuring consistent production of dialkyl carbonates with performance comparable to fresh catalysts, thus enhancing the economic viability of the process.
Implementation Method 1
adding alkyl carbamate, alcohol and rare earth metal salt as catalyst selected from lanthanide series in a reactor to afford corresponding dialkyl carbonate
Implementation Method 2
Separating deactivated catalyst residue from the reaction mixture of step (b) and dissolving in acid corresponding to the rare earth metal salt
Implementation Method 3
dissolving in acid corresponding to the rare earth metal salt to afford regenerated catalyst
Data Source
AI summary
The present invention discloses a process for recovery and regeneration of rare earth metals or salts thereof used as catalyst and which is conveniently integrated within the overall flow sheets of manufacturing dialkyl carbonates. Alkyl carbamate, alcohol and a rare earth metal salt as catalyst selected from the lanthanide series are added in a reactor to afford dialkyl carbonate. The rare earth metal catalyst is selected from samarium, cerium, lanthanum, neodymium, ytterbium, europium and gadolinium. Ammonia is added to a portion of the reaction mixture to precipitate the catalyst and the separated deactivated catalyst is dissolved in acid to afford regenerated catalyst, e.g., in triflic acid in the case of samarium triflate catalyst.