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Synthesis of Ethanol from Syngas over Rh/MCM-41 Catalyst: Effect of Water on Product Selectivity
KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi. UMSA Universidad Mayor de San Andrés, Bolivia.ORCID-id: 0000-0001-8488-4429
KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi. UMSA Universidad Mayor de San Andrés, Bolivia.ORCID-id: 0000-0002-3793-1197
Visa övriga samt affilieringar
2015 (Engelska)Ingår i: CATALYSTS, ISSN 2073-4344, Vol. 5, s. 1737-1755Artikel i tidskrift (Refereegranskat) Published
Resurstyp
Text
Abstract [en]

The thermochemical processing of biomass is an alternative route for the manufacture of fuel-grade ethanol, in which the catalytic conversion of syngas to ethanol is a key step. The search for novel catalyst formulations, active sites and types of support is of current interest. In this work, the catalytic performance of an Rh/MCM-41 catalyst has been evaluated and compared with a typical Rh/SiO2 catalyst. They have been compared at identical reaction conditions (280 degrees C and 20 bar), at low syngas conversion (2.8%) and at same metal dispersion (H/Rh = 22%). Under these conditions, the catalysts showed different product selectivities. The differences have been attributed to the concentration of water vapor in the pores of Rh/MCM-41. The concentration of water vapor could promote the water-gas-shift-reaction generating some extra carbon dioxide and hydrogen, which in turn can induce side reactions and change the product selectivity. The extra hydrogen generated could facilitate the hydrogenation of a C-2-oxygenated intermediate to ethanol, thus resulting in a higher ethanol selectivity over the Rh/MCM-41 catalyst as compared to the typical Rh/SiO2 catalyst; 24% and 8%, respectively. The catalysts have been characterized, before and after reaction, by N-2-physisorption, X-ray photoelectron spectroscopy, X-ray diffraction, H-2-chemisorption, transmission electron microscopy and temperature programmed reduction.

Ort, förlag, år, upplaga, sidor
MDPI AG , 2015. Vol. 5, s. 1737-1755
Nyckelord [en]
ethanol, syngas, Rh/MCM-41 catalyst, water vapor
Nationell ämneskategori
Kemi
Identifikatorer
URN: urn:nbn:se:kth:diva-180993DOI: 10.3390/catal5041737ISI: 000367535300008Scopus ID: 2-s2.0-84944885472OAI: oai:DiVA.org:kth-180993DiVA, id: diva2:898193
Forskningsfinansiär
Sida - Styrelsen för internationellt utvecklingssamarbete
Anmärkning

QC 20160127

Tillgänglig från: 2016-01-27 Skapad: 2016-01-26 Senast uppdaterad: 2016-11-24Bibliografiskt granskad
Ingår i avhandling
1. Catalytic conversion of syngas to ethanol and higher alcohols over Rh and Cu based catalysts
Öppna denna publikation i ny flik eller fönster >>Catalytic conversion of syngas to ethanol and higher alcohols over Rh and Cu based catalysts
2017 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

The thermochemical process converts almost any kind of biomass to a desired final product, i.e. gaseous or liquid transportation fuels and chemicals. The transportation fuels obtained in this way are renewable biofuels, which are alternatives to fossil fuels. During the last few years, thermochemical plants for the production of bioethanol have been launched and another is under construction. A total of about 290 million liters of ethanol are expected to be processed per year, mostly using municipal solid waste. Considerable efforts have been made in order to find a more selective catalyst for the conversion of biomass-derived syngas to ethanol.

The thesis is the summary of five publications. The first two publications (Papers I and II) review the state of the art of ethanol and higher alcohols production from biomass, as well as the current status of synthetic fuels production by other processes such as the Fischer-Tropsch synthesis. Paper III analyses the catalytic performance of a mesoporous Rh/MCM-41 (MCM-41 is a hexagonal mesoporous silica) in the synthesis of ethanol which is compared to a typical Rh/SiO2 catalyst. Exhaustive catalytic testing including the addition of water vapor and modifying the hydrogen partial pressure in the syngas feed-stream which, in addition to the catalyst characterization (XRD, BET, XPS, chemisorption, TEM and TPR) before and after the catalytic testing, have allowed concluding that some water vapor can be concentrated in the pores of the Rh/MCM-41 catalyst. The concentration of water-vapor promotes the occurrence of the water gas shift reaction, which in turn induces some secondary reactions that change the product distribution, as compared to results obtained from the typical Rh/SiO2 catalyst. These results have been verified in a wide range of syngas conversion levels (1-68 %) and for different catalyst activation procedures (catalyst reduction at 200 °C, 500 °C and no-reduction) as shown in Paper IV. Finally, similar insights about the use of mesoporous catalyst have been found over a Cu/MCM-41 catalyst, shown in Paper V. Also in Paper V, the effect of metal promoters (Fe and K) has been studied; a noticeable increase of ethanol reaction rate was found over Cu-Fe-K/MCM-41 catalyst as compared to Cu/MCM-41. 

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2017. s. 98
Serie
TRITA-CHE-Report, ISSN 1654-1081 ; 2017:2
Nyckelord
thermochemical process, ethanol, higher alcohols, mesoporous catalysts, rhodium, copper, metal promoters
Nationell ämneskategori
Kemiteknik
Forskningsämne
Kemiteknik
Identifikatorer
urn:nbn:se:kth:diva-196808 (URN)978-91-7729-206-7 (ISBN)
Disputation
2017-01-27, Q2, Osquldas väg 10, Våning 2, Stockholm, 10:00 (Engelska)
Opponent
Handledare
Forskningsfinansiär
Sida - Styrelsen för internationellt utvecklingssamarbete
Anmärkning

QC 20161125

Tillgänglig från: 2016-11-25 Skapad: 2016-11-22 Senast uppdaterad: 2017-02-03Bibliografiskt granskad

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Velasco, Jorge

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