Hydrocarbon Separation via
Metal–Organic Frameworks
Article: Hydrocarbon Separations in a Metal-Organic Framework
with Open Iron(II) Coordination Sites. Eric D. Bloch. Science: 335
(6076), 1606-1610. [DOI:10.1126/science.1217544]
Group 14
Marcela HERNANDEZ
Matt TRAHAN
Clemence CHAPEAUX
Christian MORENO
Source: <http://www.sulzer.com/en/Industries/Hydrocarbon-Processing/GasProcessing>
Summary
•
Introduction
•
Olefin-Paraffin Mixture
•
Cryogenic Distillation
•
Fe2(dobdc)
•
Tests for Analysis of Fe2(dobdc)
•
Hydrocarbon Adsorption
•
Neutron Powder Diffraction
•
Variable Temperature Magnetic Susceptibility
•
Binding strength of Hyrdocarbons
•
Absorption Selectivities
•
Fe2(dobdc) Performance
•
Overall Separation Process
•
Conclusion
•
Assessment
•
Comparing to other research
•
Further research suggestions
Fe2(dobdc) molecule
Source: http://www.sciencemag.org/content/335/6076/1606.full
Introduction
•
•
•
Separation of Olefin-Paraffin mixtures is performed via cryogenic distillation
New material to perform the separation would save time, money, and energy
Fe2(dobdc) provides an active metal-organic framework for separation of
hydrocarbons
Metal Framework isolating different
hydrocarbon molecules
Source: http://www.nature.com/srep/2013/130128/srep01149/full/srep01149.html?WT.ec_id=SREP-639-20130201
What is an Olefin-Paraffin Mixture?
•
Olefin: Unsaturated carbon molecule
•
Paraffin: Saturated carbon molecule
•
Definition of Saturation: A saturated compound has no double or triple bonds
•
Example of Mixture includes: ethylene/ethane and propylene/propane
Ethylene
Ethane
Propylene
Propane
Source: <http://en.wikipedia.org/wiki/Propylene>, <http://en.wikipedia.org/wiki/Propane>, <http://en.wikipedia.org/wiki/Ethylene>,
<http://en.wikipedia.org/wiki/Ethane>
Olefin-Paraffin Mixture
•
Due to similar size and volatilities, separation requires cryogenic distillation
•
Molecular Weight of Ethane:
30.07 g/mol
•
Molecular Weight of Ethylene:
28.05 g/mol
•
Molecular Weight of Propane:
44.10 g/mol
•
Molecular Weight of Propylene:
42.08 g/mol
Various Hydrocarbon Boiling Points
Source: <http://www.google.com/patents/EP1515790A2?cl=en>
Cryogenic Distillation
•
Olefin-Paraffin mixture
stream is compressed to cold
temperatures and high
pressures
•
These cold temperatures and
high pressures allow for the
distillation of the olefinparaffin mixture
•
The process is very energyintensive
Cryogenic Distillation Tower
Source: <http://www.polarisengineering.com/polaris/technologies/cryogenic-distillation/>
The Problem with Distillation
•
Olefin-Paraffin mixtures are created by "cracking" long chain hydrocarbons at high
temperatures
•
Cracking: cracking is the process where heavy, large hydrocarbons are broken
down into simpler molecules such as light hydrocarbons by the breaking of
carbon-carbon bonds
Long Chain Hydrocarbon
Cracking
Olefin-Paraffin Mixture
Source: <http://www.educationquizzes.com/gcse/chemistry/crude-oil-2/>
Problem with Distillation
•
Substantial energy cost arises from cooling these hot gases to the low
temperatures required for cryogenic distillation
Source: <www.prometheusenergy.com>
Solution
•
•
•
•
Use new material to enable efficient separation at higher temperatures and
atmospheric pressure
Process would include a Packed Bed Reactor using Swing Adsorption
Distillation not required
Result would be huge energy savings
Packed Bed Adsorption Pellets
Source:<http://encyclopedia.che.engin.umich.edu/Pages/Reactors/PBR/PBR.html>
Material: Fe2(dobdc)
•
•
•
Metal organic Framework
Exposed iron (II) coordination sites
May be capable of fractionating a methane/ethane/ethylene/acetylene mixture
into its pure components
Fe2(dobdc) Molecule
Source: <http://www.sciencemag.org/content/335/6076/1606.full>
Test 1: Hydrocarbon Adsorption
•
Purpose: Determine the ability of
Fe2(dobdc) to adsorb light hydrocarbons
•
Use pure component equilibrium
isotherms for methane, ethane,
ethylene, acetylene, propane and
propylene
•
These isotherms were measured at 318,
333 and 353K
Diagram demonstrating adsorption
Source: commons.wikimedia.org
Hydrocarbon Absorption Results
Results:
Graph that determines Fe2(dobdc)'s affinity from
different hydrocarbons at 318K
Source: http://www.sciencemag.org/content/335/6076/1606.full
Conclusion: Fe2(dobdc) has a strong affinity for unsaturated hydrocarbons (acetylene,
ethylene, propylene) at 1 bar
Test 2: Neutron Powder Diffraction
•
Purpose: Determine nature of the
interactions of the hydrocarbons with
Fe2(dobdc)
•
Fe2(dobdc) is dosed with deuterated
gas at 300K and cooled
at 4K to collect data
•
Rietveld refinements (computational
model to obtain the characterization of
crystalline materials) were performed
against this data to acquire structural
models
Diagram of the Neutron Powder
Diffraction process
Source: neutrons.ornl.gov
Neutron Powder Diffraction Results
Results:
• Provided structural models for
Fe2(dobdc)
• All these hydrocarbons have an
orientational disorder
Conclusion
• Fe2(dobdc) has one adsorption site
where unsaturated hydrocarbons
have a predisposition to bind to
•
Fe2(dobdc) maintains a high spin
electron configuration when bond
to these unsaturated gases
Molecules obtained during neutron powder
diffraction
Source: http://www.sciencemag.org/content/335/6076/1606.full
-----
Test 3: Variable-Temperature Magnetic
Susceptibility
•
Purpose: To probe the electronic state of the iron centers upon gas binding
•
On its own, Iron(II) exhibits weak ferromagnetic coupling along the oxo-bridged
chains, and weaker antiferromagnetic coupling between chains.
Image of Oxo-Bridge Chain of Lead
Source: http://origin-ars.els-cdn.com/content/image/1-s2.0-S1387700308003341-gr3.jpg
Test 3: Variable-Temperature Magnetic
Susceptibility (cont.d)
• Figure 3. Weak interacting adsorbates
(alkanes) only slightly diminished the
strength of ferromagnetic exchange.
Strong interacting (alkenes) had a
stronger effect on the iron centers,
enough to make intrachain coupling
from ferro to antiferromagnetic.
• Conclusions: Strength of ironhydrocarbon interactions increase as
such: methane < ethane < propane <
propylene < acetylene < ethylene
Figure 3. Variable –temperature magnetic
susceptibility Data
Source: http://www.sciencemag.org/content/335/6076/1606.full
Test 4: Binding Strength of Hydrocarbons
with Fe2(dobdc)
•
Determine the
strength of hydrocarbon
•
binding within Fe2(dobdc)
through the analysis of
adsorption data
Calculate
isosteric heats of
adsorption to compare
the binding enthalpies
of the gases
Hydrocarbons tested for bonding strength with
Fe2(dobdc)
Source: http://sijieluo.files.wordpress.com/2012/09/mof.png
Binding Strength cont'
Results:
•
Heats of adsorption for the gasses show
a significant reduction as the loading
approaches the value corresponding to
one gas molecule per iron(II) center
presenting the strongest adsorption
sites in the material
Conclusion:
•
Fe2(dobdc) binds strongly to the light
hydrocarbons tested
Hydrocarbon bonding with Fe2(dodbc)
Source:http://patentimages.storage.googleapis.com/US20130053585A1/US201
30053585A1-20130228-D00031.png
Test 5: Adsorption Selectivities
•
After determining that hydrocarbons bond strongly with Fe2(dobdc), the next
test was to compare the adsorption of hydrocarbons to Fe2(dobdc) with other
metal organic frameworks to determine which would be the most effective at
separation
•
•
Calculate adsorption selectivities using ideal adsorbed solution theory
Compare adsorption select of Fe2(dobdc) and a number of other porous
materials with analogous gas uptake properties
Source: http://chemistry.st-andrews.ac.uk/staff/rem/group/?page_id=4
Adsorption Selectivities cont'
Results: The adsorption selectivities
obtained for Fe2(dobdc) are significantly
greater than those calculated for either
zeolite NaX or the isostructural metalorganic framework Mg2(dobdc)
Conclusion: Fe2(dobdc) is a better choice
for adsorbing hydrocarbons than
Mg2(dobdc) or zeolite NaX
Associating Binding Sites with
Increased Enthalpy of Adsorption
Source: http://www.ncnr.nist.gov/staff/craig/
Test 6: Fe2(dobdc) Performance
• Material performance was evaluated in an
experimental packed bed reactor with an
adsorption based process
• Packed Bed: a packed bed is vessel that is
filled with a packing material that could
contain catalyst particles or adsorbents
• Adsorption: the adhesion of molecules
from a gas or liquid to an adsorbent
surface such as Fe2(dobdc)
• Breakthrough experiments were
performed over a packed bed with
equimolar mixtures of ethylene/ethane
and propylene/propane
Small Scale Packed Bed Reactor
Source: <http://seat.massey.ac.nz/projects/yearbook/yearbook12/project.asp?id=09084363363>
•
•
Fe2(dobdc) Performance cont'd
Outlet gas was monitored by gas chromatograph equipped with flame ionization
detector to detect purity of each component of the gas mixture
As expected, alkane was first to elute from the packed bed while the solid
adsorbent (Fe2(dobdc)) retained the olefin
Flame Ionization Detector
Source:
<http://www.cambustion.com/products/hfr500/fastfid-principles>
Fe2(dobdc) Performance Results
•
Outlet Propane was 100% pure
•
Outlet Propylene during desorption was 99% pure
•
Outlet ethane was 99.5% pure
•
Outlet ethylene during desorption was 99% pure
•
Desorption: process where a substance is released from the adsorbent. The
process is the opposite of adsorption
Packed Beds of
Fe2(dobdc)
Adsorbent
Feed
Source:
<http://www.sciencedirect.com/science/article/pii/S1383586602002083>
Purified Outlet Propane or Ethane
Outlet Propylene or Ethylene During Desorption
Fe2(dobdc) Performance Results
•
Breakthrough simulations indicated Fe2(dobdc) with greater production
capacities than Mg2(dobdc) and zeolite NaX
•
Fe2(dobdc) proved to be effective with purifications of at least 99% for both
ethane/ethylene and propane/propylene mixtures
Fe2(dobdc)
Source:
<http://www.sciencemag.org/content/335/6076/
1606.full>
Mg2(dobdc)
Source:
<http://www.cchem.berkeley.edu/co2efrc/publica
tions/2011/selective-binding-of-o2.html>
Zeolite NaX
Source:
Overall Separation Process
How would this process potentially work in place of cryogenic distillation?
1) A gas mixture of
methane, ethane,
ethylene, and
acetylene are fed
into the first of 3,
Fe2(dobdc) beds.
2) The first fraction,
methane, breaks
through first
because it has the
lowest adsorptivity.
Thus pure methane
can be collected.
3) Pure methane
can be collected
until ethane breaks
through.
Overall Process of Gas Separation
Source: http://www.sciencemag.org/content/335/6076/1606.full
Overall Separation Process (cont.d)
4a) Gas flow is
diverted to a second
iron bed, from which
more pure methane
is collected.
4b) A mixture of
ethane and ethylene
are desorbed from this
second bed.
Overall Process of Gas Separation
5) The third Fe2(dobdc) bed is
used to separate the ethane and
ethylene components
Source: http://www.sciencemag.org/content/335/6076/1606.full
Conclusion
•
The advantage of switching from current process technologies to the metal-organic
framework of Fe2(dobdc) is to save money and energy
•
The prospects of using this material as a solid adsorbent through:
•
pressure/temperature swing adsorption
•
membrane-based applications
Fe2(dobdc) Molecule
Source:
<http://www.sciencemag.org/content/335/6076/1606.full>
Source: <http://www.gtresearchnews.gatech.edu/energy-efficientseparations/l>
Assessment
•
Fe2(dobdc) is a good material to use for the separation of light hydrocarbon
gases
•
Fe2(dobdc) effectively separates hydrocarbons at a reduced cost compared to the
current methods
The multistage separation is illustrated above where different Hydrocarbons
are represented by each shape. Shows how each one can be separated out
individually as it passes through the metal organic framework, Fe2(dodbc)
Source: http://www.cchem.berkeley.edu/co2efrc/publications/2012/co2ch4-ch4h2-and-co2ch4h2.html
Comparing To Other Research
• Other research includes using Fe2+ to store hydrogen and absorb carbon dioxide
• Iron has a metal organic framework useful in capturing most gases
• Gases could also include harmful greenhouse gases
Smog and Pollution from Greenhouse Gases
Carbon Dioxide Molecule
Source: (Top Left)<http://scholarsinida.blogspot.com/, (Bottom Left)<http://commons.wikimedia.org/wiki/File:CO2.png>,
(Right)<http://www.deathandtaxesmag.com/190932/scientists-convert-greenhouse-gases-to-energy/>
Further research suggestions
•
•
•
Removal of acetylene from ethylene produced in naphtha cracker using
Fe2(dobdc)
Investigate the use of Fe2(dobdc) in membrane based technology
Full scale testing of Fe2(dobdc) in swing absorber
Membrane made
of Fe2(dobdc)
Large Scale Swing Adsorber Unit
Source: <http://www.beilsteinjournals.org/bjoc/single/articleFullText.htm?publicId=1860-5397-6-86>
Source: <http://www.gongtongmachinery.com/2-4-adsorptionplant.html>
References
• Bloch, E.D.; Brown, C.M.; Krishna, R.; Long, J.R.;
Queen,W.L.; Zadrozny, J.M., Science 2012, Vol 335,
1606-1610.
http://www.sciencemag.org/content/335/6076/160
6.full
• Brown, C.M.; Dailly, A.; Grandjean, F.; Herm, Z.R.;
Horike, S.; Kaye, S.S.; Long, G.J.; Long, J.R.; Queen,
W.L.; Sumida, K., Chemical Science 2010, Vol 1, 184191.
http://alchemy.cchem.berkeley.edu/jeff/paper112.p
df