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The catalytic performance of Fe/Si‐2 and Fe–Mn/Si‐2 catalysts for conversion of C2H6with CO2to C2H4was examined in a continuous‐flow and fixed‐bed reactor. The results show that the Fe–Mn/Si‐2 catalyst exhibits much better reaction activity and selectivity to C2H4than those of the Fe/Si‐2 catalyst. Furthermore, the coking–decoking behaviors of these catalysts were studied through TG. The catalytic performances of the catalysts after regeneration for conversion of C2H6or dilute C2H6in FCC off‐gas with CO2to C2H4were also examined. The results show that both activity and selectivity of the Fe–Mn/Si‐2 catalyst after regeneration reached the same level as those of the fresh catalyst, whereas it is difficult for the Fe/Si‐2 catalyst to refresh its reaction behavior after regeneration.

In the oxidative coupling of methane by carbon dioxide, La2O3/ZnO catalysts were found to have high C2 selectivity and good stability. The coupling selectivity on La2O3/ZnO is about 90%, which is much higher than that on pure La2O3 or ZnO. The consumption ratio of carbon dioxide to methane is approximately one. X-ray diffraction analysis reveals that the structural forms of the oxides are unchanged during the reaction. The reaction mechanism for C2 formation is discussed.

Mo/HZSM-5 catalysts show good catalytic reactivity in the absence of oxygen for the dehydrogenation and aromatization of methane at 973 K. The active Mo species were investigated by combining catalytic studies on Mo/HZSM-5 catalysts before and after NH4OH extraction with XRD, BET, NH3-TPD and TPR analysis. The XRD patterns show that Mo species are well dispersed on the zeolite surface. The specific surface areas decrease with increasing Mo loading but they can be restored to a large extent by NH4OH extraction. NH3-TPD results suggest that the Mo species prefer to deposit on the strong acid sites of HZSM-5 zeolite. TPR profiles show that there is a kind of Mo species which is easily reduced. No TPR peaks could be obviously observed if the Mo/ HZSM-5 catalysts were extracted by NH4OH solution. The results of NH4OH extraction experiment and other relevant characterization studies suggest that there are several kinds of Mo species deposited on the surface. By referring to the Mo species on Al2O3 supported MoO3 samples, we propose that the dissolvable Mo species in NH4OH solution are MoO3 crystallites and their aggregates in octahedral coordination, while the unsoluble Mo species mainly are Al2(MoO4)3 and MoO42- in tetrahedrally coordinated form. The catalytic performance of Mo/HZSM-5 catalysts before and after NH4OH extraction illustrates that Mo species in small MoO3 crystallites with octahedral coordination form are active for methane activation in the absence of oxygen on Mo/HZSM-5 catalysts, while Mo species in tetrahedrally coordinated form is less active for the reaction.

RhCo3(CO)12/SiO2, after decarbonylation under atmospheric O2 at 623 K, exhibits excellent catalytic performances in atmospheric ethylene hydroformylation at 423 K, which is consistent with the corresponding catalysis by the bimetallic cluster catalyst RhCo3/SiO2.

The TPSR technique was used to investigate the effect of the support on the secondary reactions of ethylene formed during CO hydrogenation. Based on the results of CO hydrogenation and CO/H2-TPSR characterization, it was found that different supports induced different secondary reactions, and thus affected the selectivity to light olefins directly. The Fe-MnO/MgO catalyst (based on basic support) causes disproportionation of C2H4, and thus, leads to the formation of C3H6. The Fe-MnO/Al2O3 catalyst (based on acidic support) showed obvious hydrogenation of C3H6. The disproportionation of C2H4 was also promoted by the Fe-MnO/Al2O3 catalyst, but because of its activity for C3H6 hydrogenation, a large amount of C3H8 was produced. The different C2H4 secondary reactions are relevant to different CO/H2 reaction pathways over the catalyst surface, so the Fe-MnO/MgO catalyst is a desirable catalyst for the production of light olefins from CO/H2 while the Fe-MnO / Al2O3 catalyst was not so.

Designed Pt/KL catalysts were prepared and characterized by CO chemisorption and XRD. Pulse catalytic tests usingn-hexane as the probe were performed. The results showed that Pt particles located in the L-zeolite channels were fundamental for aromatization, and the spatial effect of the channels was essential for dehydrocyclization. Obstruction of the channels, while having no influence on the high Pt dispersion, affects the product distribution ofnC6 in addition to a sharp reduction in reactivity.

Mo/HZSM-5 catalysts show high reactivity and selectivity in the activation of methane without using oxidants. Mo/HZSM-5 catalysts with Mo loading ranging from 0 to 10% were prepared by impregnation with an aqueous solution of ammonium heptamolybdate (AHM). The samples were dried at 393 K, and then calcined at different temperatures for 4 h. The interaction between Mo species and NH4ZSM-5 zeolite was characterized by FT-IR spectroscopy, differential thermal analysis (DTA) and temperature programmed decomposition (TPDE) and NH3-TPD at different stages of catalyst preparation. The results showed that if Mo/HZSM-5 catalysts were calcined at a proper temperature, the Mo species will interact with acid sites (mainly with BrØnsted acid sites) and part of the Mo species will move into the channel. The Mo species in the form of small MoO3 crystallites residing on the external surface and/or in the channel, and interacting with BrØnsted acid sites may be responsible for the methane activation. Strong interaction between Mo species and the skeleton of HZSM-5 will occur if the catalyst is calcined at 973 K. This may lead to the formation of MoO42- species, which is detrimental to methane activation.

20%SrO-20%La2O3/CaO catalyst (SLC-2), prepared by impregnation, has shown 18% CH4 conversion and 80% C2-selectivity for the oxidative coupling of methane (OCM) at 1073–1103 K with CH4:O2 molar ratio=9:1 and total flow rate of 100 ml/min. Addition of SrO onto La2O3/CaO (LC) catalyst strengthens the surface basicity and leads to an increase in CH4 conversion and C2-selectivity. Meanwhile, the reaction temperature required to obtain the highest C2-yield increases with increasing SrO content. The formation of carbonate on the catalyst surface is the main reason for the deactivation of LC and SLC catalysts. If the amount of CO2 added into the feed is appropriate and the reaction temperature is high enough, there is no deactivation at all. In such case, the added CO2 will suppress the formation of CO2 produced via the OCM reaction, therefore, improves the C2-selectivity. The FT-IR spectra of CO2 adspecies recorded at different temperatures show that CO2 interacts easily with the catalyst surface to form different carbonate adspecies. Unidentate carbonate is the main CO2 adspecies formed on the catalyst surface. On the LC catalyst surface, the unidentate carbonate was first formed on Ca2+ cations at room temperature. If the temperature is higher than 473 K, it will form on La3+ cations. On the SLC catalyst surface, if the temperature is lower than 573 K, only the unidentate carbonate formed on Ca2+ cations could be observed. When the temperature is higher than 673 K, it will then form on Sr2+ cations. This suggests that the unidentate carbonate can migrate on the LC and SLC catalyst surface on one hand, and on the other hand, that the surface composition of SLC catalysts is dynamic in nature. On the basis of both the decomposition temperatures of the carbonate species, and the temperature dependence of the d? value which is the difference of symmetric and asymmetric stretching frequencies of surface carbonates, the in situ FT-IR technique offered two approaches to measure the surface basicity of the SLC catalyst. The results thus obtained are in good agreement with that of CO2-TPD. The role of the surface basicity of the SLC catalyst is also discussed.

Atmospheric hydroformylation of ethylene was studied under differential conditions over Rh4(CO)12-derived Rh/SiO2 catalysts. The specific activities as functions of Rh dispersions show that ethylene hydroformylation is structure sensitive and ethylene hydrogenation structure insensitive. These structural dependences and in situ IR observations show that Rh0 is the unique active site for catalytic ethylene hydroformylation on Rh/SiO2. The reactions of Rh0-coordinated CO and Rh0-adsorbed CO with C2H4 + H2 at 293 K were monitored by IR spectroscopy. The linear CO adsorbed on Rh0/SiO2 is consumed with formation of propanal, whereas the coordinated CO in Rh6(CO)16/SiO2 and its derivative do not participate in CO insertion. IR study of the thermal decomposition of Rh6(CO)16/SiO2 indicates that the cluster can be stabilized on the surface up to 548 K by gaseous CO under hydroformylation conditions. Moreover, the Rh6(CO)16/SiO2 system exhibits increased catalytic hydroformylation activity with reducing coordinated CO. These results show that coordinative unsaturation on the Rh0 surface is necessary for heterogeneously rhodium-catalyzed hydroformylation and that totally decarbonylated Rh0/SiO2 is most effective. In addition, the oxidation of Rh0 by surface OH- is discussed.

The addition of K2O and MnO promoters enhances catalyst activity and selectivity to light alkenes during CO hydrogenation over silicate-2 (Si-2) supported Fe catalysts. The results of CO hydrogenation and CO-TPD, CO/H2-TPSR, C2H4/H2-TPSR and C2H4/H2 pulse reaction over Fe/Si-2 catalysts with and without promoters clearly show that the MnO promoter mainly prohibits the hydrogenation of C2H4 and C3H6. Therefore, it enhances the selectivity to C2H4 and C3H4 products. Meanwhile further incorporating the K2O additive into the FeMn/ Si-2 catalyst leads to a remarkable increase in both the capacity and strength of the strong CO adspecies. These produce much more [Cad] via their dissociation and disproportionation at higher temperatures. This results in an increase in the CO conversion and the selectivity to light olefins. Moreover, the K2O additive modifies the hydrogenating reactivity of [Cad] and suppresses the disproportionation of C2H4 that occurs as a side-reaction. Both K2O and MnO promoters play key roles for enhancing the selective production of light alkenes from CO hydrogenation over Fe/Si-2 catalyst.