Comprehensive evolved gas analysis of amorphous precursors for S-doped titania by in situ TG-FTIR and TG/DTA-MS Part 1. Precursor from thiourea and titanium(IV)-isopropoxide

J. Madarász, Ana Brǎileanu, G. Pokol

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Abstract

Decomposition of an amorphous precursor for S-doped titania (TiO 2) nanopowders, prepared by controlled sol-gel hydrolysis- condensation of titanium(IV) tetraisopropoxide and thiourea in aqueous isopropanol, has been studied up to 800 °C in flowing air by simultaneous thermogravimetric and differential thermal analysis coupled online with quadrupole mass spectrometer (TG/DTA-MS) and FTIR spectrometric gas cell (TG-FTIR) for analysis of gases and their evolution dynamics (by evolved gas analysis, EGA) in order to explore and model thermal annealing processes of fabrication techniques leading to S:TiO2 photocatalysts with photocatalytic activities under visible light. Precursor sample prepared with thiourea, releases first water endothermically from room temperature to 190 °C, carbonyl sulfide (COS) from 120 to 280 °C in two stages, and ammonia (NH3) from 170 to 450 °C in three steps. Evolution of CO 2, sulfur dioxide (SO2), and dinitrogen oxide, as of oxidation products, (N2O), as of oxidation products, occurs between 150 and 220, 180 and 330, 280 and 450°C, respectively. Exothermic DTA peaks at 170, 220, and 310 °C correspond to the maximum rate of CO2, SO2, and N2O evolution, respectively. The fourth exothermic heat effect at 430 °C is probably due to the simultaneous burning out of residual carbonaceous-species, solid-state oxidation of residual sulfureous and/or sulfurous species, and transformation of amorphous titania into anatase. Titaniumoxo-sulfate formation at 500 °C has been confirmed by FTIR. Furthermore, evolution of sulfur dioxide reoccurs again in a definite step between 550 and 800 °C, indicating the significant extent of previous sulfate formation processes. Anatase, which formed also in the exothermic peak at 430 °C, keeps its structure, no rutile formation is detected below or at 800 °C by XRD.

Original languageEnglish
Pages (from-to)292-297
Number of pages6
JournalJournal of Analytical and Applied Pyrolysis
Volume82
Issue number2
DOIs
Publication statusPublished - Jul 2008

Fingerprint

Thiourea
Gas fuel analysis
Thioureas
Differential thermal analysis
Titanium
Sulfur dioxide
Oxidation
Titanium dioxide
Sulfur Dioxide
Sulfates
Mass spectrometers
Photocatalysts
Gases
Thermal effects
Sol-gels
Condensation
Ammonia
Hydrolysis
Annealing
2-Propanol

Keywords

  • Anatase
  • Evolved gas analysis (EGA)
  • FTIR spectroscopic gas cell
  • Mass spectrometry (MS)
  • Simultaneous thermogravimetry (TG) and differential thermal analysis (DTA)
  • Thiourea
  • Titania precursor
  • Titanium(IV)-isopropoxide

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Chemistry(all)

Cite this

@article{0301ccf05aaf485cb41aa0275b3550c1,
title = "Comprehensive evolved gas analysis of amorphous precursors for S-doped titania by in situ TG-FTIR and TG/DTA-MS Part 1. Precursor from thiourea and titanium(IV)-isopropoxide",
abstract = "Decomposition of an amorphous precursor for S-doped titania (TiO 2) nanopowders, prepared by controlled sol-gel hydrolysis- condensation of titanium(IV) tetraisopropoxide and thiourea in aqueous isopropanol, has been studied up to 800 °C in flowing air by simultaneous thermogravimetric and differential thermal analysis coupled online with quadrupole mass spectrometer (TG/DTA-MS) and FTIR spectrometric gas cell (TG-FTIR) for analysis of gases and their evolution dynamics (by evolved gas analysis, EGA) in order to explore and model thermal annealing processes of fabrication techniques leading to S:TiO2 photocatalysts with photocatalytic activities under visible light. Precursor sample prepared with thiourea, releases first water endothermically from room temperature to 190 °C, carbonyl sulfide (COS) from 120 to 280 °C in two stages, and ammonia (NH3) from 170 to 450 °C in three steps. Evolution of CO 2, sulfur dioxide (SO2), and dinitrogen oxide, as of oxidation products, (N2O), as of oxidation products, occurs between 150 and 220, 180 and 330, 280 and 450°C, respectively. Exothermic DTA peaks at 170, 220, and 310 °C correspond to the maximum rate of CO2, SO2, and N2O evolution, respectively. The fourth exothermic heat effect at 430 °C is probably due to the simultaneous burning out of residual carbonaceous-species, solid-state oxidation of residual sulfureous and/or sulfurous species, and transformation of amorphous titania into anatase. Titaniumoxo-sulfate formation at 500 °C has been confirmed by FTIR. Furthermore, evolution of sulfur dioxide reoccurs again in a definite step between 550 and 800 °C, indicating the significant extent of previous sulfate formation processes. Anatase, which formed also in the exothermic peak at 430 °C, keeps its structure, no rutile formation is detected below or at 800 °C by XRD.",
keywords = "Anatase, Evolved gas analysis (EGA), FTIR spectroscopic gas cell, Mass spectrometry (MS), Simultaneous thermogravimetry (TG) and differential thermal analysis (DTA), Thiourea, Titania precursor, Titanium(IV)-isopropoxide",
author = "J. Madar{\'a}sz and Ana Brǎileanu and G. Pokol",
year = "2008",
month = "7",
doi = "10.1016/j.jaap.2008.05.003",
language = "English",
volume = "82",
pages = "292--297",
journal = "Journal of Analytical and Applied Pyrolysis",
issn = "0165-2370",
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T1 - Comprehensive evolved gas analysis of amorphous precursors for S-doped titania by in situ TG-FTIR and TG/DTA-MS Part 1. Precursor from thiourea and titanium(IV)-isopropoxide

AU - Madarász, J.

AU - Brǎileanu, Ana

AU - Pokol, G.

PY - 2008/7

Y1 - 2008/7

N2 - Decomposition of an amorphous precursor for S-doped titania (TiO 2) nanopowders, prepared by controlled sol-gel hydrolysis- condensation of titanium(IV) tetraisopropoxide and thiourea in aqueous isopropanol, has been studied up to 800 °C in flowing air by simultaneous thermogravimetric and differential thermal analysis coupled online with quadrupole mass spectrometer (TG/DTA-MS) and FTIR spectrometric gas cell (TG-FTIR) for analysis of gases and their evolution dynamics (by evolved gas analysis, EGA) in order to explore and model thermal annealing processes of fabrication techniques leading to S:TiO2 photocatalysts with photocatalytic activities under visible light. Precursor sample prepared with thiourea, releases first water endothermically from room temperature to 190 °C, carbonyl sulfide (COS) from 120 to 280 °C in two stages, and ammonia (NH3) from 170 to 450 °C in three steps. Evolution of CO 2, sulfur dioxide (SO2), and dinitrogen oxide, as of oxidation products, (N2O), as of oxidation products, occurs between 150 and 220, 180 and 330, 280 and 450°C, respectively. Exothermic DTA peaks at 170, 220, and 310 °C correspond to the maximum rate of CO2, SO2, and N2O evolution, respectively. The fourth exothermic heat effect at 430 °C is probably due to the simultaneous burning out of residual carbonaceous-species, solid-state oxidation of residual sulfureous and/or sulfurous species, and transformation of amorphous titania into anatase. Titaniumoxo-sulfate formation at 500 °C has been confirmed by FTIR. Furthermore, evolution of sulfur dioxide reoccurs again in a definite step between 550 and 800 °C, indicating the significant extent of previous sulfate formation processes. Anatase, which formed also in the exothermic peak at 430 °C, keeps its structure, no rutile formation is detected below or at 800 °C by XRD.

AB - Decomposition of an amorphous precursor for S-doped titania (TiO 2) nanopowders, prepared by controlled sol-gel hydrolysis- condensation of titanium(IV) tetraisopropoxide and thiourea in aqueous isopropanol, has been studied up to 800 °C in flowing air by simultaneous thermogravimetric and differential thermal analysis coupled online with quadrupole mass spectrometer (TG/DTA-MS) and FTIR spectrometric gas cell (TG-FTIR) for analysis of gases and their evolution dynamics (by evolved gas analysis, EGA) in order to explore and model thermal annealing processes of fabrication techniques leading to S:TiO2 photocatalysts with photocatalytic activities under visible light. Precursor sample prepared with thiourea, releases first water endothermically from room temperature to 190 °C, carbonyl sulfide (COS) from 120 to 280 °C in two stages, and ammonia (NH3) from 170 to 450 °C in three steps. Evolution of CO 2, sulfur dioxide (SO2), and dinitrogen oxide, as of oxidation products, (N2O), as of oxidation products, occurs between 150 and 220, 180 and 330, 280 and 450°C, respectively. Exothermic DTA peaks at 170, 220, and 310 °C correspond to the maximum rate of CO2, SO2, and N2O evolution, respectively. The fourth exothermic heat effect at 430 °C is probably due to the simultaneous burning out of residual carbonaceous-species, solid-state oxidation of residual sulfureous and/or sulfurous species, and transformation of amorphous titania into anatase. Titaniumoxo-sulfate formation at 500 °C has been confirmed by FTIR. Furthermore, evolution of sulfur dioxide reoccurs again in a definite step between 550 and 800 °C, indicating the significant extent of previous sulfate formation processes. Anatase, which formed also in the exothermic peak at 430 °C, keeps its structure, no rutile formation is detected below or at 800 °C by XRD.

KW - Anatase

KW - Evolved gas analysis (EGA)

KW - FTIR spectroscopic gas cell

KW - Mass spectrometry (MS)

KW - Simultaneous thermogravimetry (TG) and differential thermal analysis (DTA)

KW - Thiourea

KW - Titania precursor

KW - Titanium(IV)-isopropoxide

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U2 - 10.1016/j.jaap.2008.05.003

DO - 10.1016/j.jaap.2008.05.003

M3 - Article

VL - 82

SP - 292

EP - 297

JO - Journal of Analytical and Applied Pyrolysis

JF - Journal of Analytical and Applied Pyrolysis

SN - 0165-2370

IS - 2

ER -