Effect of Support and Promoter on Activity and Selectivity of Gold Nanoparticles in Propanol Synthesis from CO₂, C₂H₄, and H₂

Abstract

Direct propanol synthesis from CO2, H2, and C2H4 was investigated over TiO2- and SiO2-based catalysts doped with K and possessing Au nanoparticles (NPs). The catalysts were characterized by scanning transmission electron microscopy and temperature-programmed reduction of adsorbed CO2. Mechanistic aspects of CO2 and C2H4 interaction with the catalysts were elucidated by means of temporal analysis of products with microsecond time resolution. CO2, which is activated on the support, is reduced to CO by hydrogen surface species formed from gas-phase H2 on Au NPs. C2H4 adsorption also occurs on these sites. In comparison with TiO2-based catalysts, the promoter in the K–Au/SiO2 catalysts was found to increase CO2 conversion and propanol production, whereas Au-related turnover frequency of C2H4 hydrogenation to C2H6 decreased with rising K loading. The latter reason was linked to the effect of the support on the ability of Au NPs for activation of C2H4 and H2. The positive effect of K on CO2 conversion was explained by partial dissolution of potassium in silica with formation of surface potassium silicate layer thus inhibiting formation of potassium carbonate, which binds CO2 stronger and therefore hinders its reduction to CO.

Forty years of temporal analysis of products

“…For instance, TAP has been used to quantify the number of active sites present on catalysts, 36 and these were found to be in agreement with previously published steady-state isotopic transient kinetic analysis diffuse reflectance infrared Fourier transform spectroscopy (SSITKA DRIFTS) results. 43 Other examples of correlation/complementation of TAP experiments with other methods include electron paramagnetic resonance (EPR) spectroscopy, 44,45 X-ray photoelectron spectroscopy (XPS), 44,46,47 X-ray diffraction (XRD), 44,46,48 X-ray absorption spectroscopy (XAS), 44,47 Raman, 46 energy dispersive X-ray scanning transmission electron microscopy (EDX-STEM), 46 high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), 48,49 Fourier transfer Infrared (FTIR), 49 high resolution scanning transmission electron microscopy (HRTEM) 47,50,51 and prompt gamma-ray activation analysis (PGAA). 52 As such, while many reports have been dedicated solely to TAP, it should be noted that TAP is not a necessarily standalone characterization technique and can/should be used in a complimentary way with other methodologies.…”

“…Information regarding the mass transfer (diffusion, adsorption and desorption) and reaction of individual species (reactants, products and intermediates) over catalytic and inert materials is obtained by comparing the shape of their pulse response curves to a standard diffusion curve. [48][49][50][53][54][55][56][57][58][59][60][61] This latter curve corresponds to the pulse response that should be obtained if the species in question was chemically inert under the same conditions. 5,28 Qualitative analysis based on well-defined theoretical patterns can be used to compare the adsorption strength of different molecules, to determine if an adsorption process is reversible or irreversible, and to determine if molecules compete for the same adsorption sites.…”

Catalytic Conversion of CO2 to Value‐Added Products under Mild Conditions

“…3) and higher hydrocarbons from CO 2 and H 2 under low or even ambient temperature are realized for the first time over a prepared bimetallic catalyst composed of nanoparticles of Pt and Ru supported on Fe 3 O 4 (RuÀPt/Fe 3 O 4 ). [14][15][16] The conversion of CO 2 and H 2 to multi-carbon compounds (CCMC) should be an ideal CO 2 conversion route, and H 2 can be manufactured in a large scale from renewable energy sources, including solar energy, hydropower and biomass. As revealed by isotope tracer experiments using O 18 labeled water, in the hydrogenation of CO 2 over RuÀPt/Fe 3 O 4 , MCA could form by catalytic hydrolysis of alkyl, a novel reaction pathway enabling the formation of MCA at low temperature, which is different from the previously reported one based on CO insertion at high temperature.…”

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The catalytic synthesis of multi-carbon alcohols (MCA, C n H 2n + 1 OH, n ! [14][15][16] The conversion of CO 2 and H 2 to multi-carbon compounds (CCMC) should be an ideal CO 2 conversion route, and H 2 can be manufactured in a large scale from renewable energy sources, including solar energy, hydropower and biomass.Pioneering efforts have been made to create catalytic systems for the conversion of CO 2 to multi-carbon compounds. At 40 8C, the selectivity for alcohols, MCA, and higher hydrocarbons reached 77.1 %, 4.5 %, and 19.5 %, respectively, while that for methane was only 3.4 % (carbon based).

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Alcohol Synthesis from CO2, H2, and Olefins over Alkali‐Promoted Au Catalysts—A Catalytic and In situ FTIR Spectroscopic Study

“…[9][10][11][12][13] Higher alcohols are synthesized by catalytic homologation of methanol or directly from CO 2 and alkenes in homogeneously catalyzed reactions. [17][18][19][20][21][22] Finding multifunctional catalysts for this reaction is challenging because the RWGS reaction runs above 300 8Co wing to thermodynamic constraints, but hydroformylationr equires lower temperatures. [17][18][19][20][21][22] Finding multifunctional catalysts for this reaction is challenging because the RWGS reaction runs above 300 8Co wing to thermodynamic constraints, but hydroformylationr equires lower temperatures.…”