Felipe Bustamante

Direct Synthesis of Diethyl Carbonate from CO2 and CH3CH2OH Over Cu–Ni/AC Catalyst

Cu–Ni/AC (Active carbon) catalysts were synthesized and characterized by temperature programmed reduction, X-ray diffraction, Scanning electron microscopy, chemical analysis, and N2 adsorption. Their activities (in terms of TOF) in the direct synthesis of diethyl carbonate from CO2 and CH3CH2OH were also evaluated. The presence of a Cu–Ni alloy phase may explain the significant increase in activity of bimetallic catalysts compared with monometallic samples.

The role of zeolite type on the lean NOx reduction by methane over Pd loaded pentasil zeolites

Abstract The lean selective catalytic reduction of NO x by methane over protonic palladium loaded ZSM-5, FER and MOR, as well as, on bimetallic Pd–Pt-HMOR was examined. Special emphasis was paid on the combined effects of water and SO 2 in the feed stream. Under dry conditions and in the absence of SO 2 , the degree of NO x conversion at 450°C decreases as follows: Pd-HZSM-5>Pd-HMOR>Pd-HFER. Sulfur dioxide alone has no apparent effect on the activity for NO x reduction, but the coexistence of water and SO 2 inhibits both NO x and methane conversions. The extent of inhibition by water and SO 2 on NO x reduction is Pd-HFER>Pd-HZSM-5>Pd-HMOR. Acid mordenite doped with low levels of Pt and Pd leads to an active catalyst that is more tolerant to the presence of either water or SO 2 than the corresponding monometallic Pt- and Pd-HMOR. Nevertheless, NO x reduction is also inhibited at temperatures below 450°C when SO 2 and water are both present. TPD experiments of water over calcined samples of protonic Pd supported pentasil zeolites, Pd/γ-Al 2 O 3 and Pt–Pd-HMOR with and without pretreatment in SO 2 +O 2 indicate that sulfation of the surface increases water chemisorption by the support. Therefore, the observed decrease of NO x reduction on Pd-loaded zeolite catalysts when SO 2 and H 2 O coexist in the feed stream may be due to enhanced water inhibition and presumably active site poisoning.

30-P-22-Performance of bi-and tri-metallic mordenite catalysts for the lean SCR of NOx by methane

Publisher Summary This chapter discusses the performance of bi- and trimetallic mordenite catalysts for the lean selective catalytic reduction (SCR) of mono-nitrogen oxide (NOx) by methane (CH4). The lean NOx reduction by CH4 in the presence of 10–15% water vapor is studied on bi- and trimetallic powder catalysts containing two or three of the species—namely, cobalt (Co), cesium (Ce), and platinum (Pt) on HMOR. A cooperative effect in the palladium (Pd)–Co, Pd–Ce, Pd–Ce–Co, and Pd–Pt–Ce systems is found for CH4-SCR under wet conditions. Pd–Ce/HMOR and Pd–Ce/Co-HMOR catalysts are more tolerant to the coexistence of H2O and SO2 in the gas feed than Pd/Co-HMOR. Co, Pd, and Ce species are impregnated on ceramic monoliths washcoated with mordenite. The results of NOx reduction are different for the monolithic and powdered catalysts. However, a similar trend in the CH4-SCR activity of both catalyst types is observed.

Synthesis at several length scales of zeolite A membranes using a continuous flow method

ABSTRACT Zeolite A membranes were synthesized in the inner side of porous TiO2 and α-Al2O3 tubular supports by a continuous method. The methodology was then used at several scales for preparing membranes on TiO2 and α-Al2O3 supports with lengths of 6, 12 and 25 cm. Formation of an homogeneous zeolite film was confirmed by XRD and SEM in all supports. Single-gas permeation experiments (He, H2, N2 and n-C3H8) indicated that Knudsen diffusion was the predominant mechanism in both supports. All the synthesized membranes present high flux and moderate selectivity to water in water–ethanol mixtures.