1. Catalytic zeolite membrane reactors for the selective CO oxidation
Paola Bernardo, Catia Algieri, Giuseppe Barbieri, Enrico Drioli
Istituto per la Tecnologia delle Membrane (ITM-CNR), Rende CS, Italy CO H2
Clean H2 Pt
Zeolites
Regular structure (micropores of molecular size)
Thermal and chemical stability (up to °C)
Properties can be adjusted (varying the Si/Al ratio
or by cation-exchange)
Catalytic activity
This work
Na-Y zeolite membranes prepared by Secondary growth
Continuous Seeding (tubular supports)
Pt-loaded Zeolitic Catalytic Membranes for CO Selox
CO selective oxidation (Selox)
2 CO + O2 → 2 CO2
Interesting and economic approach for CO removal from H2–rich gas streams (less than 50 ppm for PEMFCs applications).
Pt–supported catalysts
Compromise between costs and good functionality.
Membrane preparation
Seeding A: no DP
Seeding B: Cross-flow filtration, DP>0
Key-factor : pH
Supported Zeolite Membrane
Zeolite film
a-Al2O3 support
a-Al2O3 pzc = 9
Na-X pzc = 10 pH
Electrostatic interaction
Permeation tests (room temperature, DP up to 1 bar)
Seeding A, no DP
Seeding B, DP>0
MRs with a catalytic membrane
Zeolitic layer (few microns thick), low pressure drops
Selective permeation + Pt catalytic activity
Reduced by-pass with respect to fixed bed
Flow – through MR
N2 - support (dpore = 100 nm)
H2 - support (dpore = 100 nm) H2 N2
N2 support (dpore = 60 nm)
H2 support (dpore = 60 nm)
Selox MR Reaction tests (T = 200°C, Feed = ca. 600 cc (STP)/min)
Pt-Y membranes (b and c) prepared by Seeding A
2.0
1.5
1.0
0.5
2 bar
2.6 bar
○ O2:CO:H = 1 : 1 : [b]
∗ O2:CO:H2:N = 1: 1 : 87 : [b]
□ O2:CO:H2:N = 1 : 1 : 61 : [b]
△O2:CO:H2:N = 1 : 0.9 : 59.5 : [c]
● O2:CO:H2 N2:CO2 = 1 : 0.9 : 60.2 : 22.7 : [c]
l= 2.2
l = 2
4 bar
3 bar
, - -
N2 = 11% [c]
N2 = 23% CO2= 15% [c]
N2 = 37% [c]
N2 = 37% [d]
N2 = 48% [d]
Seeding A
The Pt–Y catalytic MRs expand the CO conversion-selectivity region, even with lower space-time values [ca. 1 mgPt min/cm3(STP)] than Pt–based TRs (at 200°C), as reported in the open literature [1].
Seeding B
PFeed, bar
C O N C L U S I O N S
Tubular zeolite (FAU) membranes were prepared by a continuous seeding.
The cross-flow filtration seeding (Seeding B) resulted in an improved membrane quality.
Pt-loaded (by ion-exchange) membranes were used in MRs for the H2 purification by means of CO Selox.
Membranes prepared by Seeding A: Improved MR performance by increasing the operating pressure and the N2% in the feed (realistic stream; H2 ca. 60%).
The improved membrane quality (Seeding B) resulted in reduced CO amount operating at the same conditions as the membranes prepared by Seeding A.
References: [1] P. Bernardo, C. Algieri, G. Barbieri, E. Drioli, Catalytic (Pt–Y) membranes for the purification of H2–rich streams, Catalysis Today (2006), in press.
Acknowledgments: Progetto di ricerca “CAMERE RBNE03JCR5 – Nuove membrane catalitiche e reattori catalitici a membrana per reazioni selettive come sistemi avanzati per uno sviluppo sostenibile” funded by the Italian Ministry of Education, University and Research (MIUR).