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High Efficiency Desulfurization of Synthesis Gas, September 2002 - March 2004 Final Report

Yi, Kwang-Bok
Mukherjee, Anirban
Podlaha, Elizabeth J.
Harrison, Douglas P.

Louisiana State University

In the pdf format this document has 69 pages and is 2.05mb

Table of Contents

Disclaimer

ii
Abstract

iii
Table of Contents

v
List of Figures vii
List of Tables ix
Executive Summary x

1

 INTRODUCTION 1
 

1.1

 High Temperature Gas Desulfurization 1

1.2

 Ceria-Zirconia Catalyst Research 3

1.3

 Objectives of the Research 3

2

 ELECTROCHEMICAL SYNTHESIS AND CHARACTERIZATION OF CeO2-ZrO2 4
 

2.1

 Electrochemical Experimental 4

2.2

 Solid State Analyses 5

2.3

 Electrosynthesis Results and Discussion 6

 

2.3.1

 Composition 6

2.3.2

 XRD and TEM Characterization 6

2.3.3

 Electrochemical Process Characterization 12

3

 REACTION AND SORBENT CHARACTERIZATION EQUIPMENT 16
 

3.1

 Fixed-Bed Reactor 16

3.2

 Gas Analysis 18

3.3

 Electrobalance Reactor 21

3.4

 BET Surface Area 24

3.5

 X-Ray Diffraction 24

4

 SORBENT MATERIALS 24
 

4.1

 Commercial Sorbents 25

4.2

 Sorbents Synthesized at LSU 25

4.3

 Sorbent Nomenclature 26

5

 SORBENT CHARACTERIZATION RESULTS 26
 

5.1

 X-Ray Diffraction Spectra 26

5.2

 BET Surface Area and Crystallite Size 28

5.3

 Sorbent Reduction 29

6

 FIXED-BED DESULFURIZATION RESULTS 33
 

6.1

 Reaction Conditions and Dimensionless Time 33

6.2

 Typical Reactor Response Curves 36

6.3

 Commercial Ceria Sorbents 38
 

6.3.1

 Ce(RP) vs Ce(Alfa) 38

6.3.2

 The Effect of Temperature on Ce(RP) 40

6.3.3

 Pre-reduction of Ce(RP) 40

6.3.4

 The Effect of CO2 on Sulfidation of Ce(RP) 42

6.4

 Commercial Ceria-Zirconia Sorbents 43

 

6.4.1

 Comparison of CZ(Nex) and Ce(RP) 43

6.4.2

 Pre-reduction of CZ(Nex) 85 44

6.3.5

 The Effect of CO2 on sulfidation of CZ(Nex) 70 45

6.5

 LSU Ceria and Ceria-Zirconia Sorbents 45
 

6.5.1

 Defining Reference Time for Ceria-Zirconia Sorbents 46

6.5.2

 The Effect of Sulfidation Temperature 47

6.5.3

 The Effect of Pre-reduction 49

6.5.4

 The Effect of CO2 Addition 51

7

 SUMMARY AND CONCLUSIONS 55

8

 REFERENCES 56
 
LIST OF FIGURES

Figure 1

 Electrochemical Cell Schematic 5
Figure 2 Electrolyte Concentration vs. Final Powder Composition 7
Figure 3 TEM Images of (a) Ceria, (b) Ceria-7 mol% Zirconia (c) Ceria-18 mol% Zirconia 8
Figure 4 Selected-Area Electron Diffraction (SAED) Pattern Taken Over a Large Area Shown in Figure 3 9
Figure 5 XRD Analysis of (a) Electrochemically Generated Nanocrystalline Ceo(0.82)Zr(0.18)O2. (b) Cubic CeO2 (JCPDS 34-394), and (c) Monoclinic (JCPDS 37-1484) and Tetragonal (JCPDS 42-1164) ZrO2 10
Figure 6 XRD Patterns for Three Different Cel-xZrxO2 Samples, where x Represents the Mol Fraction of Zirconia 11
Figure 7 A Comparison Between the LSU and Commercial NexTech XRD Powder Patterns 11
Figure 8 Heat Treated 700oC, 18.7 mol % Zr Ceria-Zirconia with Resulting Crystallite Size of (a) 9.5 nm, (b) 10 nm, (c) 11 nm, (d) 12 nm, (e) 12.5 nm, (f) 12.5 nm, and (g) 14.5 nm 12
Figure 9 TEM Micrograph of 18.7% mol ZrO2 After 106 hrs of Heat Treatment at 700oC 13
Figure 10 Heat Treated 700oC, 65.2% mol Zr, Ceria-Zirconia with Resulting Crystallite Size of (a) 4 nm, (b) 5 nm, (c) 6 nm, (d,e) 7 nm, and (g) 8nm. Heat Treated Times Shown at Right 13
Figure 11 TEM Micrograph of 65.2% at Zr After 106 hr of Heat Treatment at 700oC 14
Figure 12 Current Characteristics for the Ce and Ce-Zr Electrolyte at an Applied Potential of - 2.0 V and Stagnant Solution 15
Figure 13 Current Characteristics of Ceria-Zirconia in Quiescent Solution and With a Stirring speed of 900 rpm at an Applied Potential of -2.0 V 15
Figure 14 Polarization Curves Corrected for Ohmic Drop, Solution C for a Scan Rate of 5mV/s 16
Figure 15 Fixed-Bed Reactor System 17
Figure 16 Details of the Quartz Reactor 18
Figure 17 Chromatograph Sampling Arrangement 20
Figure 18 PFPD Calibration Curve 22
Figure 19 PFPD Chromatogram at 0.1 ppmv H2S 22
Figure 20 TCD Calibration Curve 23
Figure 21 Electrobalance Reactor System 23
Figure 22 XRD Spectra of (a) LSU CeO2 (b) cubic CeO2 (JCPDS 34-394) 27
Figure 23 XRD Spectra of (a) CZ(Nex) 85, (b) Tetragonal ZrO2 (JCPDS 88-1007) 27
Figure 24 XRD Spectra of (a) Ce(LSU), (b) CZ(LSU)90, and (c) CZ(LSU)80 28
Figure 25 Weight Loss Associated with Heating in an Inert Atmosphere 30
Figure 26 Reduction of Ce(RP) in Three Reducing Gas Compositions 31
Figure 27 Comparison of Reducibility of Ce(RP) and CZ(Nex) 80 in Gas 2 32
Figure 28 Reducibility of Ce(LSU), CZ(LSU) 90 and CZ(LSU) 80 in Gas 3 32
Figure 29 Typical Sulfidation Breakthrough Curves and Sorbent Conversions (Full Concentration Scale) 37
Figure 30 Typical Sulfidation Prebreakthrough Curves (Expanded Concentration Scale) 37
Figure 31 Sulfidation Breakthrough Curves of Pure CeO2 Sorbents (Full Concentration Scale) 39
Figure 32 Sulfidation Breakthrough Curves of Pure CeO2 Sorbents (Expanded Concentration Scale) 39
Figure 33 Temperature Effect on Sulfidation of Ce(RP) 41
Figure 34 The Effect of Pre-reduction on Sulfidation of Ce(RP) 41
Figure 35 The Effect of CO2 on Sulfidation of Ce(RP) 42
Figure 36 Comparison of the Sulfidation of Ce(RP) and CZ(Nex) 44
Figure 37 The Effect of Pre-reduction on Sulfidation of CZ(Nex) 85 45
Figure 38 The Effect of CO2 on Sulfidation of CZ(Nex) 70 46
Figure 39 Complete Sulfidation Breakthrough Curves Using LSU Sorbents 48
Figure 40 The Effect of Temperature on Sulfidation of Ce(LSU) 48
Figure 41 The Effect of Temperature on Sulfidation of CZ(LSU)80 49
Figure 42 Comparison of the Sulfidation Performance of Ce(LSU), CZ(LSU)90, and CZ(LSU)80 50
Figure 43 The Effect of Prereduction on Sulfidation of CZ(LSU)90 50
Figure 44 The Effect of CO2 Addition Using Ce(LSU) (Full Concentration Scale) 52
Figure 45 The Effect of CO2 Addition Using Ce(LSU) (Expanded Concentration Scale) 52
Figure 46 The Effect of CO2 Addition Using CZ(LSU)80 (Full Concentration Scale) 53
Figure 47 The Effect of CO2 Addition Using CZ(LSU)80 (Expanded Concentration Scale) 53
 
LIST OF TABLES
Table 1 Composition of the Various Electrolyte Solutions (M) 5
Table 2 Resistivity of Solution C at Various Times of Deposition 14
Table 3 Gas Chromatograph Operating Conditions 19
Table 4 Average Crystallite Sizes and BET Surface Areas of Test Sorbents 29
Table 5 Summary of Reduction Results for Eight Test Sorbents 34
Table 6 Calculation of the Reference Times for Sulfidation Reactions 36
Table 7 Reference Times for Two Sulfidation Stoichiometries 47
Table 8 Summary of Sulfidation Test Results at 700oC Using LSU Sorbents and Varying CO2 Feed Gas Concentrations 54