Juan P. Gómez

New catalytic routes for syngas and hydrogen production

This review summarizes different catalytic options for the production of syngas and hydrogen starting from simple hydrogen-containing molecules. Particular attention is given to new direct catalytic alternatives in natural gas conversion. Improvements in syngas technology are discussed, including partial oxidation, autothermal reforming, combined reforming and carbon dioxide reforming, and the energy efficiencies of direct and indirect methane conversion are compared. Processes, issues and practical difficulties are discussed with academic and applied efforts presented in parallel. It is emphasized that most of the ongoing research related to the direct processes is at the exploratory stage while technology utilizing indirect approach has advanced to semi-works and initial commercialization plants. The new emerging processes based on partial oxidation features are unique for syngas generation. Further enhancement of such processes plus improvements in other second generation technologies and advances in direct processes are anticipated to provide additional, new attractive paths to the chemical conversion of natural gas. Similarly, on board generation of hydrogen-rich gaseous fuels either for spark ignition engines or for coupled-fuel-cells electric engines is discussed within the scope of both partial oxidation and catalytic decomposition of methanol. A concept based in the thermochemical water splitting, which provides a renewable portable fuel from water in the form of H2, is also presented. Above all, as the chemistry involved in most of these catalytic alternatives takes place under extreme conditions, highly stable catalysts and engineering concepts are being developed.

Hydroisomerization of a hydrocarbon feed containing n-hexane, n-heptane and cyclohexane on zeolite-supported platinum catalysts

Bifunctional catalysts consisting of platinum supported on various types of zeolites (viz. beta, mordenite, USY, ZSM-5 and ferrierite) were prepared by using an incipient wetness impregnation method to obtain a 0.5 wt.% metal load. A beta zeolite sample was dealuminated with nitric or oxalic acid to obtain solids that were used as catalytic supports. The catalysts thus obtained were characterized by using various techniques. Analyses included specific surface area and acid properties; the latter were determined either by adsorption of pyridine or by temperature-programmed desorption of the same chemical. The metal phase was characterized by temperature-programmed desorption of hydrogen and by hydrogen chemisorption, which allowed the dispersion of the metal on the support surface to be determined. The catalysts obtained were assessed for activity and selectivity in the isomerization of a mixture consisting of n-hexane (65 wt.%), n-heptane (15 wt.%) and cyclohexane (20 wt.%). Both parameters were correlated with the acid and metal properties of the catalysts, as well as with the topology and pore geometry of the zeolites. The effect of each feed component on catalytic activity was also studied, using binary mixtures of the three hydrocarbons.

Characterization of Ni-honeycomb catalysts for high pressure methane partial oxidation

Nickel-honeycomb catalysts prepared by different procedures have been characterized by temperature-programmed reduction and X-ray photoelectron spectroscopy. Prereduced catalysts were tested in the partial oxidation of methane under high pressure (20 bar). The influence of the method of incorporation of the catalytic component, the metal loading and the activation temperature on the catalytic performance were investigated. It appeared that the formation of a NiAl 2 O 4 phase between the Ni precursor and the Al 2 O 3 phase of the carrier, while maintaining high dispersion is a key parameter to maintain high activity and good stability during on-stream operation.

Hydrogen production on nickel-monolith structures by partial oxidation of methane at high pressure

Abstract We report here our preliminary studies disclosing the use of nickel honeycomb catalysts in the partial oxidation of methane (POM) to syngas at 12 bar, at temperatures above 973 K and CH 4 /O 2 molar ratios of 2 in the feed. It has been observed that both CH 4 conversion and CO and H 2 selectivities approach that predicted by thermodynamic equilibrium. Moreover, activity and stability during on-stream processing depend markedly on the method of nickel incorporation and on the nature of the phases present at catalyst surfaces, which in turn control the formation of metallic Ni, the active species in POM reaction.

Partial oxidation of methane to syngas over Ni-loaded ultrastable HY zeolite catalysts

Abstract Ni-containing HY zeolites are active in the partial oxidation of methane to synthesis gas. The activity of these zeolites was found to depend strongly on the Ni-loading. Thus, at low Nicontent content where Ni was essentially ion-exchanged, catalysts were almost inactive, whereas the zeolites with high Ni contents were very active. Results from TPR, CO chemisorption and XPS studies revealed that small clusters of Ni species formed on the zeolite act as catalytic centers for the reaction.

Mg-Ni-O based OCM catalyst obtained by carbonate precursor method

Abstract The magnesium-nickel mixed oxide OCM (oxidative coupling of methane) catalyst Ni 0.1 Mg 0.9 O has been prepared following the carbonate precursor method. The thermal decomposition of the precursor has been monitored by the thermogravimetric technique, and the stages of the decomposition have been followed by different techniques.