temperature programmed surface reaction
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2022 ◽  
Vol 964 (1) ◽  
pp. 012026
Author(s):  
Nguyen Tan Luon ◽  
Le Nguyen Quang Tu ◽  
Nguyen Quang Long

Abstract Silver nanoparticles (AgNPs) are increasingly drawing a great deal of attention because of their exclusive properties and a huge variety of applications. In recent years, using AgNPs supported on various carriers as heterogeneous catalysts has become promising for treating some toxic gases in the environment, such as HCHO. This study has successfully synthesized AgNPs onto ZSM-5 microporous zeolite and ZSM-5 mesopore-modified zeolite (Meso-ZSM-5) by ion-exchange method using sodium borohydride as a reducing agent. The resulting catalysts were then characterized by N2 adsorption-desorption method. In order to evaluate HCHO adsorption, desorption, and the surface reaction of these catalysts, temperature-programmed desorption (TPD) and temperature-programmed surface reaction (TPSR) were employed. The TPD and TPSR experiments were conducted with different relative humidity. The results showed that Ag/Meso-ZSM-5 exhibited higher catalyst activity in HCHO complete oxidation than Ag/ZSM-5 at high temperatures because of a new larger pore system within the zeolite. Furthermore, TPD and TPSR experiments provided an explanation for the poor performance of the catalysts at low temperatures, which was associated with the high adsorption capacity of the zeolite.


2021 ◽  
Author(s):  
Toyin Omojola ◽  
Andre van Veen

Rates of adsorption, desorption, and surface reaction of dimethyl ether (DME) to olefins over fresh and working ZSM-5 catalysts of different Si/Al ratios (36 and 135) have been decoupled using a combination of temperature programmed surface reaction experiments and microkinetic modelling. Transient reactor performance was simulated by solving coupled 1D non-linear partial differential equations accounting for elementary steps occurring during the induction period based on the methoxymethyl mechanism on the zeolite catalyst, and axial dispersion and convection in the reactor. Propylene is the major olefin formed and scaling relations between activation energies of DME desorption and barriers of formation of methoxymethyl and methyl propenyl ether are observed. Six ensembles of sites are observed with a maximum of three adsorption/desorption sites and three adsorption/desorption/reaction sites. Barriers are generally higher over working catalysts than fresh catalysts. Activation energies of propylene formation of ca. 200 kJ mol<sup>-1</sup> are obtained corroborating direct mechanistic proposals.


2021 ◽  
Author(s):  
Toyin Omojola ◽  
Andre van Veen

Rates of adsorption, desorption, and surface reaction of dimethyl ether (DME) to olefins over fresh and working ZSM-5 catalysts of different Si/Al ratios (36 and 135) have been decoupled using a combination of temperature programmed surface reaction experiments and microkinetic modelling. Transient reactor performance was simulated by solving coupled 1D non-linear partial differential equations accounting for elementary steps occurring during the induction period based on the methoxymethyl mechanism on the zeolite catalyst, and axial dispersion and convection in the reactor. Propylene is the major olefin formed and scaling relations between activation energies of DME desorption and barriers of formation of methoxymethyl and methyl propenyl ether are observed. Six ensembles of sites are observed with a maximum of three adsorption/desorption sites and three adsorption/desorption/reaction sites. Barriers are generally higher over working catalysts than fresh catalysts. Activation energies of propylene formation of ca. 200 kJ mol<sup>-1</sup> are obtained corroborating direct mechanistic proposals.


2021 ◽  
pp. 174751982098472
Author(s):  
Jun Yu ◽  
Ying Han ◽  
Guoqing Chen ◽  
Xiuzhen Xiao ◽  
Haifang Mao ◽  
...  

The effect of carbon nanotubes on the catalytic properties of Rh-Mn-Li/SiO2 catalysts was investigated for CO hydrogenation. The catalysts were comprehensively characterized by means of X-ray power diffraction, N2 sorption, transmission electron microscope, H2–temperature-programmed reduction, CO–temperature-programmed desorption, temperature-programmed surface reaction, and X-ray photoelectron spectroscopy. The results showed that an appropriate amount of carbon nanotubes can be attached to the surface of the SiO2 sphere and can improve the Rh dispersion. Moderate Rh-Mn interaction can be obtained by doping with the appropriate amount of carbon nanotubes, which promotes the formation of strongly adsorbed CO and facilitates the progress of CO insertion, resulting in the increase in the selectivity of C2+ oxygenate synthesis.


Catalysts ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 43
Author(s):  
Xincheng Wang ◽  
Fenghe Zhao ◽  
Long Huang

Temperature programmed surface reaction (TPSR) was developed as a method for rapid screening of catalysts. In this study, a series of acid catalysts was screened for the low-temperature dehydration of glycerol to acrolein via TPSR. Results suggested that most catalysts show activity of glycerol conversion to acrolein at a greatly different temperature range. HY, SiO2 supported H4SiW12O40 (STA/SiO2), SO42−/ZrO2, and SO42−/TiO2 were observed to be efficient for the conversion of glycerol into acrolein at 210 °C, which was significantly lower than that generally reported (250–340 °C). Moreover, high selectivity of acrolein was gained at 85% and 86% over SiW/SiO2 and SO42−/TiO2, respectively. A new style catalyst, ZnCl2/SiO2, was also found to be highly selective to acrolein and evaluated in a conventional fixed-bed reactor. Especially, stability tests showed that the catalyst life was up to 300 h with no clear deactivation on ZnCl2/SiO2 with hydrogen as dilution.


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