Francisco José Romero

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.

Epoxidation of limonene with layered-double hydroxides as catalysts

This paper reports and discusses the results obtained in the epoxidation of limonene to limonene oxide by using H 2 O 2 over different layered double hydroxides (LDHs). The solid obtained by calcining Mg/Al LDH at 773 K was found to be the most active among the Mg/ M (III) LDHs tested (M = Al, Ga, In). The results are compared with those obtained by using conventional MgO and Al 2 O 3 catalysts.

The Meerwein–Ponndorf–Verley–Oppenauer reaction between 2-hexanol and cyclohexanone on magnesium phosphates

Various magnesium phosphates were tested as catalysts for the vapour-phase Meerwein–Ponndorf–Verley–Oppenauer (MPVO) reaction between 2-hexanol and cyclohexanone. Some of the solids studied are as selective as MgO in this reaction. Others are also active in the dehydration of the alcohols. The activity and selectivity of the catalysts are related to their structure and surface chemical properties.

Immunoelectrophoretic approach to the metabolic regulation of glutamine synthetase in Rhodopseudomonas capsulata E1F1: role of glutamine

Anti-glutamine synthetase serum was raised in rabbits by injecting purified glutamine synthetase (GS) of the phototrophic bacterium Rhodopseudomonas capsulata E1F1. The antibodies were purified to monospecificity by immunoaffinity chromatography in GS-sepharose gel. These anti-GS antibodies were used to measure the antigen levels in crude extracts from bacteria, grown phototrophically with dinitrogen, nitrate, nitrite, ammonia, glutamate, glutamine or alanine as nitrogen sources. The amount of GS detected by rocket immunoelectrophoresis was proportional to Mn2+-dependent transferase activity measured in the crude extracts. Addition of GS inhibitor l-methionine-d,l-sulfoximine (MSX) to the actively growing cells promoted increased antigen levels, that were not found in the presence of glutamine or chloramphenicol. The ammonia-induced decrease in GS relative levels was reverted by MSX. GS levels remained constant when phototrophically growing cells were kept in the dark.

Catalytic use of zeolites in the Prins reaction of arylalkenes

The Prins reaction of various arylalkenes with paraformaldehyde on different zeolites as solid acid catalysts was studied. The main product of the reaction under the experimental conditions used was found to be the corresponding 1,3-dioxane. Of the catalysts tested, beta (75) zeolite proved the most active and selective in the Prins reaction of styrene, with a selectivity of 41.4% and a conversion of 95%. Other zeolites such as USY and, especially, ZSM-5, provided much lower yields. The reactions of other arylalkenes were found to be strongly influenced by the substituents on the double bond.

Influence of the structure and composition of magnesium phosphate catalysts on the transformation of 2-hexanol

Abstract Various synthetic solids were prepared by precipitation with sodium hydroxide from magnesium chloride or nitrate solutions. The materials thus obtained were characterized in structural terms by using X-ray diffraction, thermogravimetric analysis, EDAX analysis and diffuse reflectance infrared spectroscopy. Their surface properties were determined from N 2 adsorption–desorption isotherms and their chemical properties by using various titrants. Once calcined, the solids were found to consist mainly of sodium–magnesium mixed phosphates; on the other hand, those washed with water were found to contain primarily Mg 3 (PO 4 ) 2 . The former exhibited a high selectivity towards the formation of hexanone from 2-hexanol; by contrasts, the latter also yielded the corresponding dehydration products (hexenes). The catalytic activity and selectivity results for the reactions leading to the different possible products are related to the structure and composition of the solids.

Microemulsion-assisted synthesis of catalysts based on aluminium and magnesium phosphates

Abstract Various materials consisting of magnesium (mMgPO-1 and mMgPO-2) or aluminium phosphates (mAlPO-1 and mAlPO-2) were synthesized from microemulsions and characterized in structural terms using X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), thermal analysis, and solid-state 31 P and 27 Al NMR spectroscopies. The morphology of the solids was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and their surfaces properties were determined from N 2 adsorption–desorption isotherms. The new materials thus prepared are structurally and compositionally similar to solids obtained by precipitation from solutions; their specific surface areas, however, are substantially greater and their pore size distribution more narrow. The catalytic activity of the materials in the dehydration–dehydrogenation of isopropyl alcohol was found to be similar to or greater than that of catalysts obtained by precipitation from aqueous solutions. The magnesium orthophosphates yielded acetone (the major product) and propene from 2-propanol; the aluminium orthophosphates, which possess dehydrating activity only, yielded propene alone.

Immunocytochemical localization of glutamine synthetase in Rhodobacter capsulatus E1F1 and Rhodopseudomonas acidophila

Intracellular localization of glutamine synthetase has been studied by immunochemical techniques with cryosections and London Resin sections of Rhodobacter capsulatus E1F1 and Rhodopseudomonas acidophila. For immunostaining, sections were sequentially incubated with monospecific anti-glutamine synthetase antibodies (R. capsulatus) and gold labelled goat anti-rabbit antibodies. Gold label was present in the cytoplasm but not in the cell walls. The antigen is not associated with the cell membrane or with photosynthetic vesicle whether these are round and randomly distributed (R. capsulatus) or flattened and organized in well defined stacks (R. acidophila). Our results also indicate that glutamine synthetase is absent from the central, nucleoid part of the cell. The enzyme is present in dense cytoplasmic patches, which appear to be RNA-ribosome-containing areas.

Knoevenagel Condensation between Benzaldehyde and Malononitrile Over Magnesium Phosphates

The Knoevenagel condensation between benzaldehyde and malonitrile over different magnesium phosphates was studied. The structure and chemical surface properties of each solid, which determine their catalytic activity, were found to depend on the synthetic procedure used. The results obtained were compared with their basicity measured by phenol adsorption and their dehydrogenation selectivity in the conversion of 2-hexanol.

Effects of Na2CO3 impregnation on the catalytic activity of Mg3(PO4)2 in the gas-phase conversion of 2-hexanol and the alkylation of aniline with methanol

Abstract Various Na 2 CO 3 -impregnated magnesium orthophosphates have been synthesized and characterized by XRD, TGA, DRIFT and adsorption measurements. No decomposition or reaction of the carbonate at temperatures up to 773 K was observed. The textural and chemical properties of the catalysts were found to be modified by the carbonate loading. These catalysts are active in the gas-phase transformation of 2-hexanol and in the N -alkylation of aniline with methanol. The activity and selectivity of the catalysts in both reactions are related to their acid–base properties and carbonate content.