PHOTOREDUCTIVE SEQUESTRATION OF CO2 TO FORM C1 PRODUCTS AND FUEL

Mill, Theodore ; Tungudomwongsa, Haruthai

SRI International (United States)

关键词: Acetates;    Gas Chromatography;    10 Synthetic Fuels;    Chromatography;    Formates;   

DOI  :  10.2172/837761
RP-ID  :  NONE
RP-ID  :  FC26-02NT41224
RP-ID  :  837761

美国|英语

来源: UNT Digital Library

【 摘 要 】

Analytical methods for determining formic, acetic and oxalic acids, formaldehyde, and methanol have been evaluated and/or optimized for measuring products from photoreduction of CO{sub 2} in illuminated, aqueous suspensions of photocatalysts. An electrophoresis anion separation method (CIA) can detect aqueous formate and oxalate ions at 22 and 17 {micro}M (1 ppm), respectively. Recalibration of the Nash formaldehyde determination shows that as little as 10 {micro}M (0.3 ppm) can be detected spectrally. Several experiments using suspensions of Pt/TiO{sub 2}, SrTiO{sub 3}, and SrTiO{sub 3} with Cr and Sb were illuminated in CO{sub 2} saturated solutions. No acids were detected in most experiments using CIA; however, ion chromatography (IC) was able to detect formate and acetate at low {micro}M (sub ppm) concentrations in several experiments using Pt/TiO{sub 2} and SrTiO{sub 3} in sunlight and with xenon uv light. Analysis for methanol by gas chromatography showed that not more than 2 ppm methanol could have formed and probably less. Adding 0.6 mM 2-propanol to an irradiated CO{sub 2}/TiO{sub 2} suspension led to formation of 550 {micro}M formate, but no formaldehyde, probably because re-oxidation of formate by semiconductor holes was competitively blocked. Loss of C{sub 1} products at higher concentrations by re-oxidation may be an important process, limiting the accumulation of products. Preliminary estimates were made of the physical size of a solar CO{sub 2} photoreduction unit large enough to reduce the CO{sub 2} produced from a 1000 MW coal-fired electricity plant. A perfectly efficient system could be as small as 2 to 3 km{sup 2}.