8/4/2019 ACS Present a Ion in Dever
1/20
Molecular Sieves SAPO-34 with Chabazite (CHA)
Structure:Theoretical Study of Silicon Incorporation and
Structural Properties
Hong Wang1, Yingxu Wei2, Cecil ODell1, Zhongmin Liu2 and James P. Lewis11Department of Physics, West Virginia University, Morgantown, WV2Dalian Institute of Chemical Physics, Dalian, P. R. China
8/4/2019 ACS Present a Ion in Dever
2/20
Introduction
Zeolite is a broad term used to describe a family ofmicroporous aluminosilicate minerals.
Contain small pores and large surface area Constructed of AlO4-5 and SiO4-4 groups bound by oxygen Zeolites are synthesized by manipulating:
Structure Silica-Aluminum Ratio Pore Size Density
"Green Chemistry with Zeolite Catalysts." Chemical Engineering, The Chemical Engineers'ResourcePage, Distillation, HeatTranser, Design, Spreadsheet Solutions, Departments, Chemistry. Web. 22 Apr. 2010..
8/4/2019 ACS Present a Ion in Dever
3/20
Application of Zeolite Materials Adsorption
Drying, purification, and separation Carbon dioxide separation
Catalysis Shape-selective catalyst- on the basis
of molecular diameter Acid catalysts used in thepetrochemical industry
Ion Exchange Detergent formulas- replace
phosphates as water softening agents
Exchange Na in zeolite for Ca or Mgin water
http://s3.amazonaws.com/memebox/uploads/3562/kanatzidis-gasNorthwester.jpg
8/4/2019 ACS Present a Ion in Dever
4/20
Zeolite Catalysis in Methanol to Olefins Conversion (MTO)
CoalNatural
Gas
Synthesis Gas
Methanol
Olefins
MTO
https://mailhost-2.tamu.edu/service/home/~/Zeolite_seminar.pdf?auth=co&loc=en_US&id=46940&part=5
Z-H +n(CH3OH) Z +H2O+olefin(C2, C3, C4)
Z-H: ZSM-5 catalytic zeolite1977, Chang, Lang and Silvestri, US patent 4062905
8/4/2019 ACS Present a Ion in Dever
5/20
SAPO-34:Microporous Silico-Aluminophosphate Molecular Sieve
ZSM-5 SAPO-34
Al P
Al Si P
Al
Al
P
Al
Al
Al (Al-O)3-Si
HO
Al-(O-P)3
Pore size around Strong acid sites Low selectivity in
light olefins High selectivity
ZSM-5
8/4/2019 ACS Present a Ion in Dever
6/20
SAPO-34
SAPO-34:Microporous Silicon Aluminumphospate Molecule Sieve
Al P
Al Si P
Al
Al
P
Al
Al
Al (Al-O)3-Si
HO
Al-(O-P)3
Small size pores Suitable acid sites Strong stability High selectivity
0.43n
m
C2H4 0.39nm
C3H6 0.43nm
C6H6 0.58nm
8/4/2019 ACS Present a Ion in Dever
7/20
SAPO-34: Crystallization Mechanism
J. Tan, Z. M. Liu, X. H. Bao, X. C. Liu, X.W. Han, C. Q. He, R. Z. Zhai,Microporous andMesoporousMateirals 53 (2002), 97 (108)
SM1: Al Si (not yield)
SM2: P Si, H SM3: Al,P Si,SiAcidity: Si(4Al)
8/4/2019 ACS Present a Ion in Dever
8/20
Current Challenge of Silicon Incorporationin SAPO-34 Framework
Substantial computational timeinvolved
Extensive possibilities of silicon
incorporation into a largerframework Identify optimal acid sites with a
variety of silicon-incorporatingenvironments
Unravel the puzzle of silicon
incorporation trends during theSAPO-34 crystallization processand accompany the experimentaldesign with a full-knowledgeframework.
[AlPO4]+(n+m)Si4++(m-n)H+ [(n+m)Si,(m-n)H]nAl,mP+mP5++nAl3+
8/4/2019 ACS Present a Ion in Dever
9/20
SAPO-34 Computational Model and Goal
Rhombohedral unit cell
12 tetrahedral (T) sites- 6 Al & 6 PSpace Group:
2x2x2 supercell (288 atoms total)
96 tetrahedral (T) sites- 48 Al & 48 PSpace Group: P1 (after silicon substitution)
[AlPO4]+(n+m)Si4++(m-n)H+ [(n+m)Si,(m-n)H]nAl,mP+mP5++nAl3+
3R
8/4/2019 ACS Present a Ion in Dever
10/20
We investigate the properties of a non-uniformly distributed Si in a2x2x2 AlPO-34 supercell.
6 Sis in 288 atoms supercell - 1010 possible arrangements(C48/5*C48.)
Randomly distribute Si throughout the supercell and see what trends wecan learn.
Clustering Factor root mean square from perfect Si-Si distance (3.15 )in Si-O-Si configuration.
For each Si in the supercell, sum over all Si neighbors of Si (choosing
smallest Si cluster in supercell). Each 288 atom supercell optimization is approximately 10-12 hours. Generate high-throughput scenario from 100s of supercell calculations (a
few 1000s are also feasible).
High Throughput Calculations Clustering
8/4/2019 ACS Present a Ion in Dever
11/20
Pseudopotentials, density-functional theorymulti-center approximations
Local excited" orbitals (fireball orSankey-Niklewski orbitals)Atom in the box Fermi compressionfinite wavefunction
Linear-scaling, massively-parallelmolecular-dynamics capabilitiessimulate 1000s of atoms
J.P. Lewis et al., Phys. Rev. B. 64, 195103 (2001)S.D. Shellman et al.,J. Comp. Phys. 188, 1-15 (2003)P. Jelineket al.,Phys. Rev. B. 64, 235101 (2005)
J.P. Lewis et al., Phys. Stat. Sol. B. 248, 1989-2007 (2011)
Fast Computational Approach to Evaluation of MaterialProperties and Chemical Reactivity:Ab initio DFT (FIREBALL)
8/4/2019 ACS Present a Ion in Dever
12/20
167
49 213
361
364
108
Clustering/Energy Correlation of 720 individual Structures
8/4/2019 ACS Present a Ion in Dever
13/20
structure No. 49 structure No. 167
Low clustering factor, but different energies.
2 (Al,P Si,Si)pair substitution Al,5P Si(4P), 4Si(4Al)all isolated
8/4/2019 ACS Present a Ion in Dever
14/20
167
49 213
361
364
108
Clustering/Energy Correlation
8/4/2019 ACS Present a Ion in Dever
15/20
structure No. 49 structure No. 364structure No. 213
2 (Al,P Si,Si)two pairs close
2 (Al,P Si,Si)
two pairs far away
Lower energy structure compared to smallerclustering factor
(2Al, P) Si Si Si
triplet
8/4/2019 ACS Present a Ion in Dever
16/20
167
49 213
361
364
108
Clustering/Energy Correlation
8/4/2019 ACS Present a Ion in Dever
17/20
structure No. 108structure No. 364
4 (P Si) Si(4Al)(2Al, P) Si Si Sitriplet
Lower energy structure compared to larger
clustering factor
8/4/2019 ACS Present a Ion in Dever
18/20
What we see ..
Higher clustering factors mean thatthe silicon incorporation in theframework is spread throughoutthe entire supercell.
Silicon substitution of Al, P pair is acommon trend for our random
silicon incorporation calculationsand these pairs lower the bindingenergy.
In our low concentrationincorporation (6 out of 96 possiblesites), silicon prefers to form short
range clusters.
structure No. 364
8/4/2019 ACS Present a Ion in Dever
19/20
Future Steps and Outline
Calculate the electrostatic potentialsfor our random networks todetermine the affects introduced bysilicon incorporation into the SAPO-34 framework.
Design a computational route to alsonon-uniformly add hydrogen into theSAPO-34 framework based oncurrent data and determine trends.
Increase silicon substitutionconcentrations and double SAPO-34
supercell to detect siliconincorporation trends (i.e. increasingthe non-unformity)
Determine the acid site strengths forfurther CH3OH adsorption
8/4/2019 ACS Present a Ion in Dever
20/20
Acknowledgements
WVU HPC Supercomputering Facility Prof. Zhongmin Liu Dr. Yingxu Wei
Dalian Institute of Chemical Physics, P.R.C
Thank you!