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Title: Selective methane oxidation over promoted oxide catalysts. Quarterly report, March--May 1995

Abstract

The objective of this research is the selective oxidative coupling of methane to C{sub 2}H{sub 4} hydrocarbons and oxygenates, in particular formaldehyde and methanol. Air, oxygen or carbon dioxide, rather than nitrous oxide will be utilized as the oxidizing gas at high gas hourly space velocity, but mild reaction conditions (500-700 {degrees}C, 1 atm total pressure). All the investigated processes are catalytic, aiming at minimizing gas phase reactions that are difficult to control. The research is divided into the following three tasks: (1) maximizing selective methane oxidation to C{sub 2}H{sub 4} products over promoted Sr/La{sub 2}O{sub 3}; (2) selective methane oxidation to oxygenates; and (3) catalyst characterization and optimization. Task 1 dealt with the preparation, testing, and optimization of acidic promoted lanthana-based catalysts for the synthesis of C{sub 2}H{sub 4} hydrocarbons and is essentially completed. Task 2 aims at the formation and optimization of promoted catalysts for the synthesis of oxygenates, in particular formaldehyde and methanol. Task 3 involves characterization of the most promising catalysts so that optimization can be achieved under Task 2. Accomplishments for this period are presented.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Lehigh Univ., Bethlehem, PA (United States). Zettlemoyer Center for Surface Studies
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
208299
Report Number(s):
DOE/MC/29228-5095
ON: DE96000627
DOE Contract Number:
FG21-92MC29228
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Aug 1995
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; 10 SYNTHETIC FUELS; 40 CHEMISTRY; METHANE; OXIDATION; CONVERSION; CATALYSTS; COMPARATIVE EVALUATIONS; CHEMICAL PREPARATION; PROGRESS REPORT; EXPERIMENTAL DATA; STRONTIUM; LANTHANUM OXIDES; PALLADIUM; PLATINUM; SILICA; ALUMINIUM OXIDES; IRON; ZIRCONIUM OXIDES

Citation Formats

Klier, K., Herman, R.G., Wang, Chaun-Bao, Shi, Chunlei, and Sun, Qun. Selective methane oxidation over promoted oxide catalysts. Quarterly report, March--May 1995. United States: N. p., 1995. Web. doi:10.2172/208299.
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Klier, K., Herman, R.G., Wang, Chaun-Bao, Shi, Chunlei, & Sun, Qun. Selective methane oxidation over promoted oxide catalysts. Quarterly report, March--May 1995. United States. doi:10.2172/208299.
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Klier, K., Herman, R.G., Wang, Chaun-Bao, Shi, Chunlei, and Sun, Qun. Tue . "Selective methane oxidation over promoted oxide catalysts. Quarterly report, March--May 1995". United States. doi:10.2172/208299. https://www.osti.gov/servlets/purl/208299.
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@article{osti_208299,
title = {Selective methane oxidation over promoted oxide catalysts. Quarterly report, March--May 1995},
author = {Klier, K. and Herman, R.G. and Wang, Chaun-Bao and Shi, Chunlei and Sun, Qun},
abstractNote = {The objective of this research is the selective oxidative coupling of methane to C{sub 2}H{sub 4} hydrocarbons and oxygenates, in particular formaldehyde and methanol. Air, oxygen or carbon dioxide, rather than nitrous oxide will be utilized as the oxidizing gas at high gas hourly space velocity, but mild reaction conditions (500-700 {degrees}C, 1 atm total pressure). All the investigated processes are catalytic, aiming at minimizing gas phase reactions that are difficult to control. The research is divided into the following three tasks: (1) maximizing selective methane oxidation to C{sub 2}H{sub 4} products over promoted Sr/La{sub 2}O{sub 3}; (2) selective methane oxidation to oxygenates; and (3) catalyst characterization and optimization. Task 1 dealt with the preparation, testing, and optimization of acidic promoted lanthana-based catalysts for the synthesis of C{sub 2}H{sub 4} hydrocarbons and is essentially completed. Task 2 aims at the formation and optimization of promoted catalysts for the synthesis of oxygenates, in particular formaldehyde and methanol. Task 3 involves characterization of the most promising catalysts so that optimization can be achieved under Task 2. Accomplishments for this period are presented.},
doi = {10.2172/208299},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Aug 01 00:00:00 EDT 1995},
month = {Tue Aug 01 00:00:00 EDT 1995}
}
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Technical Report:
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DOI:  10.2172/208299
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    Series of catalysts consisting of MoO{sub 3}, V{sub 2}O{sub 5}, TiO{sub 2}, and SnO{sub 2} impregnated onto oxide supports consisting of SiO{sub 2} (Cab-O-Sil), TiO{sub 2} or SnO{sub 2} were previously prepared and tested for the selective oxidation of methane to oxygenates, and it was found that the V{sub 2}O{sub 5}/SiO{sub 2} catalyst was the most active and most selective toward the formation of formaldehyde. These catalysts have been characterized by laser Raman spectroscopy after dehydration and during the methane oxidation reaction with a CH{sub 4}/02 = 10/1 reaction mixture at 500{degrees}C in a continuous flow in situ reaction cell.more » With the V{sub 2}O{sub 5}/SiO{sub 2} catalyst (the most active catalyst among those studied), no significant structural changes were revealed by in situ Raman analyses, indicating that the fully oxidized surface sites were related to the high formaldehyde selectivivity. Over the V{sub 2}O{sub 5}/TiO{sub 2} and V{sub 2}O{sub 5}/SnO{sub 2} catalysts, CO and CO{sub 2} were the principal products produced by oxidation of methane. For the first time, in situ Raman analysis clearly showed that for these latter catalysts, the surface vanadium(V) oxide species were partially reduced under the steady-state reaction conditions. The performance of the V{sub 2}O{sub 5}/TiO{sub 2}/SiO{sub 2} catalyst was similar to that of the V{sub 2}O{sub 5}TiO{sub 2} catalyst, consistent with the earlier observation that vanadia was largely bound to the titania overlayer. It appears that formaldehyde selectivity decreased with increasing catalyst reducibility, but no direct correlation of catalyst activity with reductibility was observed.« less

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    Experimental work aiming at developing active catalysts for selective oxidation of methane to methanol was started in this quarter. Some of the experiments used a double catalyst bed design and with H{sub 2}O as cofeed. The first catalyst bed, which serves as CH{sub 3} radical generator, was chosen to be 1 wt % SO{sub 4}{sup 2{minus}}/Sr/La{sub 2}O{sub 3}, as this catalyst exhibits remarkable activity and selectivity at lower temperature (500{degrees}C--550{degrees}C). A few transition metal oxides were used as the second catalyst bed to react with CH{sub 3} to form CH{sub 3}O{sup {minus}}M{sup +} species, which was then hydrolyzed to formmore » CH{sub 3}OH. It was found that unsupported metal oxides ZrO{sub 2}, Y{sub 2}O{sub 3}, SrO; Fe{sub 2}O{sub 3},MnO{sub 2}, Cr{sub 2}O{sub 3}, CaO, and MgO did not produce CH{sub 3}OH between 430{degrees}C and 600{degrees}C when used as the only catalysts, while MoO{sub 3} supported on silica produced CH{sub 3}0H in the temperature range of 430{degrees}C--480{degrees}C under the current single-bed reactor configuration. However, when the double-bed configuration was used with the 1 wt % SO{sub 4}{sup 2{minus}}/Sr/La{sub 2}O{sub 3} as the first methyl radical generating catalyst bed, CH{sub 3}0H was observed when ZrO{sub 2}and Y{sub 2}O{sub 3} were used as the second bed catalysts. Preliminary quantitative analysis showed that the ability of producing CH{sub 3}OH was in the order of unsupported Y{sub 2}O{sub 3} > unsupported ZrO{sub 2} > MoO{sub 3} on silica. For all of these cases, the CH{sub 3}OH space time yield was within a dozen grams per kilogram catalyst per hour.« less

  • ; ; ; ...
    A 1 wt% SO{sub 4}{sup 2{minus}}/1 wt% Sr/La{sub 2}O{sub 3} catalyst has been shown by us to be one of the most active catalyst for the oxidative coupling of CH{sub 4} to C{sub 2} hydrocarbons. One of the by-products is CO{sub 2} and this is a potential strong poison for the formation of C{sub 2}{sup +} products. Hence, various pretreatments of this catalyst were studied in terms of effect on the catalytic performance. Before the reaction was carried out at 500 or 550{degrees}C, the catalyst was pretreated in flowing air or He at 500, 700, or 800{degrees}C. Relative to themore » 500{degrees}C treatment, the pretreatment in air at 700{degrees}C only slightly decreased the C{sub 2}{sup +} selectivity while the CO{sub x} selectivity increased. This effect was larger when the pretreatment was carried out at 800{degrees}C. It was observed that the deactivation effect was slightly smaller when the pretreatments were carried out in He instead of air. For both air and He, the CH{sub 4}, conversion and the C{sub 2} %yield showed more or less parallel changes (small decreases) with increasing pretreatment temperature. After a standard pretreatment (air, 500{degrees}C, 1 hr), the reaction temperature was increased stepwise from 500 to 700{degrees}C and then lowered to 550 (or 500){degrees}C. It was observed that the catalytic performance showed deactivation towards the C{sub 2}{sup +} products. Decreasing stepwise the total flow rate (GHSV) of the reacting gas mixture (CH{sub 4}/air = 1/1) from 70,175 to 5,388 {ell}/kg catal/hr at a reaction temperature of 550{degrees}C caused large changes in both the activity and selectivity. After going back at 550{degrees}C to the original GHSV = 70,175 {ell}/kg catal/hr, the temperature was increased stepwise up to 600{degrees}C. Up to 580{degrees}C, the catalytic activity and selectivity did not change very much.« less

  • ; ; ; ...
    The objective of this research is the selective oxidative coupling of methane to C{sub 2} hydrocarbons and oxygenates, in particular formaldehyde and methanol. Air, oxygen, or carbon dioxide, rather than nitrous oxide will be utilized as the oxidizing gas at high gas hourly space velocity, but mild reaction conditions (500--700{degree}C, 1 atm total pressure). All the investigated processes are catalytic, aiming at minimizing gas phase reactions that are difficult to control. In order to optimize oxygenate space time yields over supported vanadium catalysts, testing of catalysts with various vanadium contents was carried out during this quarter. The highest oxygenate productivitymore » from CH{sub 4}/air/steam reactants that has been observed so far was achieved with the 2.0 wt % catalyst. The effects of steam on activity and selectivity were explored in more detail over a 2 wt % V{sub 2}O{sub 5}/SiO{sub 2} catalyst prepared by impregnation of a methanol solution of vanadium(V) triisopropoxide oxide and amorphous silica. An interesting observation was that the HCHO space time yields were not significantly affected by increasing steam in the feed while those of methanol were, which indicated that the two oxygenates may be formed by separate pathways on the surface. Experiments were carried out in which the 1 wt % SO{sub 4}{sup 2{minus}}/Sr/La{sub 2}O{sub 3} and 1 wt % V{sub 2}O{sub 5}/SiO{sub 2} catalysts were physically mixed (mixed bed) instead of one lying on top of the other (double bed). With the mixed bed, the total oxygenate space time yields decreased and the HCHO space time yields dropped to virtually zero. However, the space time yields of methanol were still significant.« less

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