Photocatalytic synthesis of organic compounds from CO and water: Involvement of surfaces in the formation and stabilization of products

Hubbard, J. S.; Hardy, James P.; Voecks, Gerald E.; Golub, Ellis E.

doi:10.1007/bf01653995

Cited by 55 publications

(26 citation statements)

References 15 publications

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“…The v a c u u m s y s t e m for the a d d i t i o n of gases to s u b s t r a t a was e s s e n t i a l l y i d e n t i c a l to that p r e v i o u s l y d e s c r i b e d (Hubbard et al, 1973). B r i e f l y , the s y s t e m c o n s i s t e d of a 600 cc Pyrex r e s e r v o i r in w h i c h 14CO w a s d i l u t e d w i t h e i t h e r N 2 or 12CO 2, a v a c u u m m a n i f o l d for a t t a c h m e n t of 5 q u a r t z s a m p l e tubes (volume = 5.5 cc), a port for i n t r o d u c t i o n of NH3 or o t h e r d i l u e n t gases, a W a l l a c e and T i e r n a n v a c u u m gauge (0-1OO torr range) and a t h e r m o c o u p l e v a c u u m g a u g e (Consolid a t e d V a c u u m Corp., 10-3 to I torr range).…”

Section: Gas M I X T U R E S For S a M P L E S U S E D In S U R F A Cmentioning

confidence: 98%

“…An a d d i t i o n a l objective was to explore the p o s s i b i l i t y of p h o t o c a t a l y t i c syntheses from CO and NH 3. This i n v e s t i g a t i o n was p r o m p t e d by our p r e v i o u s demonstration of s u r f a c e -d e p e n d e n t reactions of CO and w a t e r using u l t r a v i o l e t r a d i a t i o n (UV) of w a v e l e n g t h s longer than those a b s o r b e d by the gaseous reactants (Hubbard et al 1971;Hubbard et al, 1973). The p o s s i b i l i t y of u t i l i z i n g long w a v e l e n g t h UV in the catalysis of CO-NH 3 reactions w o u l d be a d v a n t a g e o u s due to the abundant energy in the solar s p e c t r u m at these w a v e l e n g t h s and because the shorter UV may be filtered from the solar s p e c t r u m by a b s o r b i n g gases in p l a n e t a r y atmospheres.…”

Section: O D O N O V a (1963) R E P O R T E D That Urea H E X A M mentioning

confidence: 98%

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Ultraviolet-gas phase and -photocatalytic synthesis from CO and NH3

et al. 1975

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The major photoproduct obtained on irradiation of gaseous NH3 and CO mixtures is ammonium cyanate; lesser amounts of urea, biurea, biuret semi-carbazide, formamide and cyanide were observed. The formation of the major gas phase photolysis product may be rationalized by the following reaction sequence: (see article). Urea is probably formed from NH4NCO in a thermal reaction while formamide may result from the disproportionation of NH2CO. Photocatalytic syntheses of 14C-urea, -formamide, and -formadehyde are effected by irradiation of 14CO and NH3 in the presence of Vycor, silica gel, or volcanic ash shale surfaces. These syntheses are catalyzed by ultraviolet wavelengths longer than those absorbed by the gaseous reactants. The syntheses are also effected when the surface material is first irradiated in the presence of CO followed by a dark incubation with NH3. Apparently, the initiating step is a light dependent formation of a reactive form of CO on the surface. A discussion is given on the possible contribution of these reactions to the abiotic synthesis of organic nitrogen compounds on Mars, on the primitive Earth and in interstellar space.

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Section: Gas M I X T U R E S For S a M P L E S U S E D In S U R F A Cmentioning

confidence: 98%

Section: O D O N O V a (1963) R E P O R T E D That Urea H E X A M mentioning

confidence: 98%

Ultraviolet-gas phase and -photocatalytic synthesis from CO and NH3

et al. 1975

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“…The examination suggests that organic compounds that arrive on Mars via meteorite are most likely to be converted to carboxylic acid derivatives that would not be easily detected by GC-MS. Organic molecules generated on Mars itself by nonbiological (11)(12)(13)(14) or (entirely hypothetical) biological synthesis (15) should suffer similar fates at or near the surface.…”

Section: Gc-ms On the Viking 1976mentioning

confidence: 99%

The missing organic molecules on Mars

Benner

Devine

Matveeva

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

377

350

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GC-MS on the Viking 1976Mars missions did not detect organic molecules on the Martian surface, even those expected from meteorite bombardment. This result suggested that the Martian regolith might hold a potent oxidant that converts all organic molecules to carbon dioxide rapidly relative to the rate at which they arrive. This conclusion is influencing the design of Mars missions. We reexamine this conclusion in light of what is known about the oxidation of organic compounds generally and the nature of organics likely to come to Mars via meteorite. We conclude that nonvolatile salts of benzenecarboxylic acids, and perhaps oxalic and acetic acid, should be metastable intermediates of meteoritic organics under oxidizing conditions. Salts of these organic acids would have been largely invisible to GC-MS. Experiments show that one of these, benzenehexacarboxylic acid (mellitic acid), is generated by oxidation of organic matter known to come to Mars, is rather stable to further oxidation, and would not have been easily detected by the Viking experiments. Approximately 2 kg of meteorite-derived mellitic acid may have been generated per m 2 of Martian surface over 3 billion years. How much remains depends on decomposition rates under Martian conditions. As available data do not require that the surface of Mars be very strongly oxidizing, some organic molecules might be found near the surface of Mars, perhaps in amounts sufficient to be a resource. Missions should seek these and recognize that these complicate the search for organics from entirely hypothetical Martian life.Viking ͉ organic compounds ͉ exobiology ͉ astrobiology

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“…Although solar wavelengths as short as 200 nm reach the surface c:if Mars we have excluded wavelengths shorter than 320 nm from the 'test chamber in order to prevent a nonbiological, photocatalyzed synthesis of organic compounds from CO and adsorbed water vapor that we find to occur on. silicate and other mineral surfaces irradiated with ultraviolet shorter than 300 nm [Hubbard et al, 1971[Hubbard et al, , 1973[Hubbard et al, , 1975. Since these short wavelengths are generally destructive to organic matter except under the special conditions of the synthesis, we assume that Martian life, if it exists, must also avoid this spectral region; its deletion from the radiation entering the test chamber therefore does not constitute a significant change in the biological environment.…”

Section: Experiments Descriptionmentioning

confidence: 99%

Viking on Mars: The carbon assimilation experiments

1977

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A fixation of atmospheric carbon, presumably into organic form, occurs in Martian surface material under conditions approximating the actual Martian ones. The reaction showed the following characteristics: The amount of carbon fixed is small by terrestrial standards; highest yields were observed in the light, but some dark activity was also detected; and heating the surface material to 90°C for nearly 2 hours had no effect on the reaction, but heating to 175°C for 3 hours reduced it by nearly 90%. New data from Mars do not support an earlier suggestion that the reaction is inhibited by traces of water. There is evidence of considerable heterogeneity among different samples, but different aliquots from the same sample are remarkably uniform in their carbon‐fixing capacity. In view of its thermostability it is unlikely that the reaction is biological.

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Photocatalytic synthesis of organic compounds from CO and water: Involvement of surfaces in the formation and stabilization of products

Cited by 55 publications

References 15 publications

Ultraviolet-gas phase and -photocatalytic synthesis from CO and NH3

Ultraviolet-gas phase and -photocatalytic synthesis from CO and NH3

The missing organic molecules on Mars

Viking on Mars: The carbon assimilation experiments

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