Executive Summary
The current approach to p-xylene production includes an isomerization step that gives a nearly equilibrium distribution of mixed xylenes, followed by a separate step to recover p-xylene, then recycling of p-xylene depleted product for further isomerization. This project aims to develop and validate para-xylene ultra-selective zeolite membranes and integrate them with an appropriately designed isomerization catalyst in a membrane reactor to accomplish selective para-xylene production. A successful membrane reactor will increase the yield of para-xylene beyond the limits of equilibrium by selectively removing para-xylene from the reactor as it is produced. Increased productivity and reduced separation energy, capital intensity, and greenhouse gas emissions are the key drivers for developing such an approach. Recent breakthroughs introduced by the University of Minnesota for the synthesis of zeolite membranes using ultrathin zeolite crystals (2-dimensional zeolites and zeolite nanosheets) enabled unprecedented mixture separation factors for para-xylene over its isomers (up to 10,000). This ultra-selective performance has been validated by measurements at ExxonMobil Research and Engineering Company and membranes are currently being tested at temperatures, compositions and pressures relevant to membrane reactor operation.
Technical Challenge
- Design and operation of a membrane reactor operating at conditions needed to achieve desired conversion and separation (approx. ~300°C and 10 bar)
- Achieving defects free zeolite membrane with thickness of ≤100 nm to realize high para-xylene selectivity
Potential Impact
market value of $35 billion in 2014 to $67 billion by 2022. The current state-of-the-art commercial separation technology is a Simulated Moving Bed (SMB) adsorption process, which produces 99.9 wt. % pure para-xylene and accounts for ~70% of the global share. Although significant improvements over the last 15 years in the SMB technology have brought down its energy requirements, it is still an energy-intensive process with an annual operating cost corresponding to $13/MT. As the global para-xylene demand grows and the world drives toward a low carbon economy, decreasing the energy demand associated with hydrocarbon separations will be increasingly important. This project not only provides significant economic benefits and energy savings for the specific process of para-xylene production (by reducing or eliminating separation costs) but it also serves as a test-bed for a novel membrane-reactor technology based on ultra-selective membranes that can be coupled with high-temperature and high-pressure catalytic reactors.
Resources
This project leverages the expertise in membrane synthesis, characterization and simulations of adsorption and diffusion at the University of Minnesota with the catalysis expertise and capability to test membranes and catalysts at industrial conditions at ExxonMobil.
Investigator
Date Approved
Project Number
-
Initial TRL Level
-
Current TRL level
3
Project Funding
1,300,000
