Coupling of propane with CO2 to propylene over Zn-promoted In/HZSM-5 catalyst

The ZnIn/HZSM-5 catalyst was prepared by the wetness impregnation method, and the structure of catalyst was characterized by XRD, SEM, TEM, [H.sub.2]-TPR, N[H.sub.3]-TPD, XPS, TG, and [N.sub.2] adsorption-desorption and then investigated in the coupling of propane with C[O.sub.2] to propylene. It is found that the addition of Zn species is beneficial to the dispersion of [In.sub.2][O.sub.3] over HZSM-5, which plays an important role in propene formation, and adjusts the acidity distribution of In/HZSM-5 catalyst, aswell assignificantly improves the activity of In/HZSM-5 catalyst. The selectivity of propylene is 68.21% in the coupling of propane with C[O.sub.2] over ZnIn/HZSM-5 catalyst when the time on stream (TOS) is 2 h, reaction temperature is 580 [degrees]C, reaction pressure is 0.3 MPa, [C.sub.3][H.sub.6]:C[O.sub.2]:[N.sub.2] = 1:4:5, catalyst mass is 0.2 g, and space velocity is 6000 mL [g.sub.cat.sup.-1] [h.sup.-1]. However, the selectivity of propylene is only 63.33% and 0.25% in the propane dehydrogenation or C[O.sub.2] hydrogenation reaction, respectively. The ZnIn/HZSM-5 catalyst showed a higher stability with only 0.80% conversion drop after three cycles. Key words: ZnIn/HZSM-5, coupling reaction, propane, C[O.sub.2], propylene. Nous avons prepare le catalyseur ZnIn/HZSM5 par la methode d'impregnation a l'humidite naissante, et nous en avons caracterise la structure par diffraction des rayons X (DRX), microscopie electronique a balayage (MEB), microscopie electronique en transmission (MET), reduction en temperature programmee sous hydrogene ([H.sub.2]TPR), desorption thermo-programmee de l'ammoniac (N[H.sub.3]TPD), spectroscopie de photoelectrons X (XPS), thermogravimetrie (TG) et analyse d'adsorption-desorption d'azote. Nous avons ensuite etudie ce catalyseur dans la reaction de couplage du propane avec le C[O.sub.2] pour former le propylene. Nous avons observe que l'ajout d'especes de Zn favorise d'une part la dispersion de l'In2O3 dans la zeolithe HZSM5--un facteur important dans la formation du propene--et d'autre part la distribution de l'acidite dans le catalyseur In/HZSM5, ce qui ameliore de facon significative de l'activite catalytique de ce dernier. Le couplage du propane avec le C[O.sub.2] sur le catalyseur ZnIn/HZSM5 offre une selectivite pour le propylene de 68,21% lorsque le temps de reaction est de 2 h, la temperature de reaction de 580 [degrees]C, la pression de reaction de 0,3 MPa, le rapport des reactifs [C.sub.3][H.sub.6]:C[O.sub.2]:[N.sub.2] de 1:4:5, le poids du catalyseur de 0,2 g et la vitesse spatiale de 6000 mL [g.sub.cat-1] [h.sup.-1]. Toutefois, la selectivite pour le propylene n'est que de 63,33% pour la reaction de deshydrogenation du propane et de 0,25% pour la reaction d'hydrogenation du C[O.sub.2]. Le catalyseur ZnIn/HZSM5 a montre une stabilite superieure, la baisse de conversion etant de seulement 0,80% apres trois cycles. [Traduit par la Redaction] Mots-cles: ZnIn/HZSM-5, reaction de couplage, propane, C[O.sub.2], propylene.
1. Introduction Emissions of carbon dioxide have continuously increased over the past few decades, mainly from the combustion of natural gas, coal, and petroleum. (1) The increased concentration of C[O.sub.2] [...]