Molecular Sieve Rejuvenation via Rapid Thermal Cycling
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Solution Overview
Problem
Molecular sieve catalysts, such as SAPO, experience decreased catalytic activity due to moisture exposure, leading to structural changes and reduced effectiveness in catalytic processes, particularly in large-scale industrial applications where storage and transport times can exceed several months.
Innovation Solution
Rejuvenating the molecular sieve by heating it at a rate greater than 40°C/min over a temperature range of 25°C to 475°C to increase the CMCPS index by at least 5%, thereby restoring its catalytic activity, using a calciner or other heating units for efficient rejuvenation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If molecular sieve is stored and transported for extended periods, then it can be readily available for use, but its catalytic activity decreases due to moisture exposure
Solution Approach 1:
The patent applies preliminary action by rapidly heating the molecular sieve to high temperature (greater than 40°C/min) before catalytic use to remove adsorbed moisture and restore catalytic activity. This pre-treatment ensures the sieve is reactivated in advance of its actual catalytic application, resolving the contradiction between extended storage and maintained activity.
2Reliability
If molecular sieve is protected from moisture by shielding catalytic sites, then catalytic activity is maintained, but the complexity of the catalyst structure increases
Solution Approach 1:
The patent applies parameter changes by modifying the thermal history and heating rate parameters of the molecular sieve to control moisture removal and catalytic activity restoration. By changing temperature and heating rate parameters, the sieve can be reactivated without requiring structural modifications or shielding mechanisms.
3Productivity
If molecular sieve is rapidly heated to restore catalytic activity, then activity is quickly restored, but energy consumption increases
Solution Approach 1:
The patent applies universality by using a calciner or other heating units that can serve multiple functions - not only rejuvenating the molecular sieve but also potentially drying other materials, heating reaction mixtures, or performing other thermal processing tasks. This multi-functionality helps justify the energy investment in the rejuvenation process.
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 rejuvenation process effectively reverses the decline in catalytic activity, enhancing the molecular sieve's performance by increasing the CMCPS index, allowing for improved conversion of methanol to olefin products like ethylene and propylene, which are crucial for producing polyethylene and polypropylene.
Implementation Method 1
heating the molecular sieve at a heat rate of greater than 40°C/min until the molecular sieve has a CMCPS that is increased by at least 5% relative to that at a heat rate basis of 40°C/min over a temperature range of from 25°C to 475°C
Implementation Method 2
the greater the amount of water adsorbed, the greater the rate of deactivation of the catalyst
Data Source
AI summary
This invention is directed to a method of rejuvenating a molecular sieve that has decreased catalytic activity as a result of contact with moisture, and a method of using the rejuvenated catalyst to make an olefin product from methanol feed. The molecular sieve can be rejuvenated by heating at a rate sufficient to increase the catalytic activity of the molecular sieve. The molecular sieve is considered to be rejuvenated when the molecular sieve has a CMCPS that is increased by at least 5% relative to that at a heat rate basis of 40° C./min over a temperature range of from 25° C. to 475° C.