Carmen M. López

Kikuchi-Fujimoto necrotizing lymphadenitis associated with cutaneous lupus erythematosus: a case report.

Histiocytic necrotizing lymphadenitis or Kikuchi-Fujimoto disease is a rare entity, and even more rarely, it is associated with other diseases. In a few cases, the condition is associated with cutaneous lupus erythematosus (CLE). Histiocytic necrotizing lymphadenitis predominantly affects young women, who present with solitary or multiple cervical lymphadenopathy accompanied by symptoms such as fever, weight loss, sweating, or, in exceptional cases, hepatosplenomegaly. Laboratory examinations show normal or nonspecific results. The disease is of unknown origin, although a viral origin has been suggested, with the suspected agents including Epstein-Barr virus, herpesvirus type 6, and cytomegalovirus (CMV). Although the first and most of the more recent cases have been reported in Oriental patients, the disease has a wide geographic distribution. The clinical evolution is favorable, with spontaneous remission in less than 4 months in almost all cases. We present a case of a 37-year-old woman from Peru who presented with cervical adenopathies on two occasions. Biopsy of a lymph node revealed a histopathologic picture compatible with Kikuchi-Fujimoto histiocytic necrotizing lymphadenitis. The adenopathy disappeared in a few months. A year later, she presented with a maculopapular rash in the nasal and malar regions. The results of the skin biopsy and immunofluorescence examination were compatible with chronic CLE. The results of the serology testing for CMV were positive. Treatment with chloroquine was initiated, with almost complete recovery by 5 months. No manifestations of systemic lupus erythematosus have occurred since. The epidemiologic, clinical, and anatomopathologic aspects as well as the differential diagnosis of this entity are reviewed.

Effect of the synthesis conditions on the crystallinity and surface acidity of SAPO-11

A series of AlPO4-11 molecular sieves with Si content ranging from zero to 0.24 Si molar fraction were crystallized from reaction gels prepared using different sources of Al and Si. It was found that the lower the crystallinity of the starting alumina the higher its reactivity and the higher the crystallinity and purity of the resulting molecular sieves. Factors affecting the initial pH of the departing gel strongly influence both the crystallinity and purity of the resulting solid. Thus, starting from the same source of alumina, it can be observed that the higher the pH within the acid region the higher the crystallinity and purity of the product. There seems to be an upper limit for the amount of Si incorporated in the AlPO4-11 framework, above which isolated silica patches (silica domain) are formed and subsequently dislodged from the structure when calcination is carried out at 773 K, yielding α-quartz. At this limiting value the population of both Lewis and Bronsted acid sites passes through a maximum. Unreacted pseudoboehmite coexisting with SAPO-11, was transformed upon calcination at 773 K into γ-alumina. These species seem to act as Lewis centres which would interact with Bronsted sites to increase surface acidity.

The successive crystallization and characterization of sapo-31 and sapo-11 from the same synthesis gel: Influence on the selectivity for 1-butene isomerization

XRD-pure SAPO-31 and SAPO-11 molecular sieves were obtained from the same synthesis gel, free of seeding, with a relatively low DPA/P2O5 ratio (0.3) after 40 and 120 h of crystallization, respectively, at 353 K. The phase transformation sequence was closely followed by XRD. The initial formation of the dense phases berlinite (B) and cristobalite (C) in the starting gel at a defined proportion seems to play an important role in directing the synthesis toward the desired molecular sieves. Structural factors were invoked to explain differences in the selectivity toward isobutene, observed for samples of SAPO-31 and SAPO-11 with similar acidity characteristics, during the transformation of 1-butene at 743 K and WHSV of 1.8 h−1.

Gas- versus liquid-phase α-pinene transformation over faujasite-like zeolites and an amorphous silicoaluminate

The transformation of α-pinene was studied in both gas and liquid phase over a series of faujasite‐like zeolites having different framework composition. A comparison with an amorphous silicoaluminate having 13 wt% of Al2O3 (SA) was made. Camphene + limonene were the major products observed in liquid phase at 393 K at conversion levels lower than 90%. At 473 K, where the reaction in gas phase took place, limonene suffered an ulterior transformation mainly into terpinenes and terpinolenes and a faster deactivation of the zeolite catalysts as compared to the one in liquid phase was observed. This behaviour contrasts with the high stability shown by SA in gas phase. Over the wider pore system of SA undesired heavy products were formed in liquid phase at the expenses of the terpene isomers. However, in gas phase this ulterior transformation of monoterpenes was minimised. A maximum activity for the zeolite catalysts was observed when the number of AlIV per unit cell reached about 17, a value where the population of Si(0Al) sites has been shown to reach the maximum.

On the nature of acid sites in substituted aluminophosphate molecular sieves with the AEL topology

Abstract A series of substituted AlPO 4 molecular sieves with the AEL topology were prepared and characterized by different techniques, to evaluate the amount and nature of the additional elements and their effect on the acidity and catalytic properties of the resulting solids. It was found that a one-to-one interaction between Lewis (L) and Bronsted (B) sites occurs after calcination of the substituted materials, leading to an enhanced acidity and causing, as a result, an increase in the selectivity towards isobutene during the transformation of 1-butene. Substitution models are discussed in order to rationalise the origin and nature of such B-L synergism.

The transformation of ethanol over AlPO4 and SAPO molecular sieves with AEL and AFI topology. Kinetic and thermodynamic approach

The transformation of ethanol into ether and ethylene was studied over a series of aluminophosphates and silicoaluminophosphates with AFI and AEL topology, at 593 K. It was found that the data followed a simple parallel kinetic scheme. The formation of ether, the less demanding reaction, can be strongly limited by thermodynamics. Based on both the kinetic model and the equilibrium curve for the system considered, a series of parameters were defined in order to determine the relative strength and concentration of the active centres participating in both reactions. Differences in the average specific-activity for the ethanol transformation into ethylene (turnover-like number) were rationalised in terms of differences in the average hydrogen-atoms partial-charge. Structural influence on product distribution due to the shape-selective phenomenon was not observed under the reaction conditions employed.

A study of manganese-silicoaluminophosphate molecular sieves

Abstract Surface and chemical characterization were performed on a manganese-substituted silicoaluminophosphate molecular sieve (MnAPSO-11), and on a manganese-supported silicoaluminophosphate molecular sieve (Mn/SAPO-11). For comparison purposes, the characterization process was also carried out over the parent SAPO-11 molecular sieve. Different characterization techniques were used: XPS, redox cycles, 31 P MAS NMR, and acidity measurements. The transformations of n -butane were carried out over the corresponding platinum promoted solids (Pt/MnAPSO-11, Pt/Mn/SAPO-11 and Pt/SAPO-11). Platinum dispersion was measured by H 2 chemisorption. XPS results indicated that manganese was better dispersed on the MnAPSO-11 solid than on the supported Mn/SAPO-11 catalyst. Redox cycles showed a strong difference between the H 2 (or O 2 ) consumed by each solid. The Mn/SAPO-11 consumed nearly three times as much H 2 (or O 2 ) per Mn atom as the MnAPSO-11 solid. 31 P MAS NMR results showed an increase in the intensity of the side bands, probably due to an anisotropic paramagnetic shift caused by a stronger dipolar interaction between the 31 P and the paramagnetic Mn(II) ions on the MnAPSO-11 sample, when compared with the Mn/SAPO-11 solid. These results suggest a better dispersion of the manganese species on the MnAPSO-11 solid, which would facilitate the above mentioned 31 P –Mn(II) interaction, in agreement with the XPS results. Acidity was measured by pyridine chemisorption at different temperatures. A larger number of (moderate+strong) Bronsted acid sites was found for the MnAPSO-11 solid compared with the SAPO-11 and Mn/SAPO-11 samples. The addition of platinum decreased the acidity. The Pt dispersions were 83%, 68% and 54% for the Pt/SAPO-11, Pt/Mn/SAPO-11 and Pt/MnAPSO-11 solids, respectively. The catalytic results indicate higher yields for the production of isobutane and isobutene over the Pt/MnAPSO-11. A severe decrease in the yield of formation of hydrocarbons with less than four carbon atoms (undesirable side reaction) was also observed for the Pt/MnAPSO-11 system compared with the Pt/SAPO-11 and Pt/Mn/SAPO-11 systems. An ensemble effect is suggested as responsible for the differences observed in the yield of formation of hydrocarbons with less than four carbon atoms. The higher yield and selectivity observed for the formation of isobutane (iso-C4) and isobutene (iso-C4) hydrocarbons over the Pt/MnAPSO-11 solid, was accounted for in terms of the largest number of (moderate+strong) Bronsted acid sites found on this solid. The catalytic and characterization results suggest the incorporation of manganese into the molecular sieve structure for the substituted MnAPSO-11 solid.

The skeletal isomerization of 1-butene over Zn-silicoaluminophosphate molecular sieves

The catalytic transformations of 1-butene were performed over a zinc-substituted silicoaluminophosphate molecular sieve (ZnAPSO-11), over a Zn-supported SAPO-11 molecular sieve (Zn/SAPO-11) and over the unpromoted SAPO-11 solid. The ZnAPSO-11 catalyst showed the highest selectivity towards skeletal isomerization as well as the highest skeletal isomerization efficiency (SIE). In addition, the largest number of acid sites, particularly strong acid sites, were observed with temperature-programmed desorption of ammonia (NH3-TPD) over the ZnAPSO-11 catalyst. The acid strength over the latter was also the highest. The agreement between the catalytic and the acidity results obtained in the present work can be explained in terms of the model of Gielgens et al. In this model, the substitution of Al(III) ions by Zn(II) ions leads to partially unsaturated Zn(II) ions in the vicinity of structural P-OH groups. The Brønsted acidity of the latter may be enhanced by Brønsted-Lewis interaction, thus rendering catalysts with stronger acidity necessary for the skeletal isomerization. The lower molar fraction of Al(III) cations found in the ZnAPSO-11 solid, compared to the SAPO-11 sample, strongly supports the above. The results for the Zn-supported system were extremely different. Significant decreases in the strong acidity as well as in the skeletal isomerization selectivity, compared to the ZnAPSO-11 catalyst, were observed. These differences reinforce the idea of incorporation of Zn(II) into the silicoaluminate framework for the ZnAPSO-11 solid.

Spectroscopic and catalytic evidence for the incorporation of gallium in the AEL framework

71Ga MAS n.m.r. analysis and the catalytic behavior during the transformation of 1-butene and n-butane strongly suggest the incorporation of Ga into the AlPO4-11 (AEL) framework during the synthesis of GaAPSO-11. A unique clear signal at around +120 ppm is proposed to be associated with the presence of tetrahedral Ga in the AEL framework of the unmodified GaAPSO-11. Migration of structural Ga atoms to the silicon domain of the AEL framework seems to occur as a result of a mild hydrothermal treatment, giving rise to an additional signal at +156 ppm, previously associated with tetrahedral gallium in gallosilicates with the MFI topology. The fact that GaAPO-11 and GaAPSO-11 behaved in a way similar to their counterparts AlPO4-11 and SAPO-11 during the skeletal isomerization of n-butenes reinforces the idea of an isomorphous substitution of Al(III) by Ga(III) in the AEL framework. The transformation of n-butane was shown to be a valuable test for detecting the presence of small amounts of hydro-dehydrogenating extraframework gallium species (EFGS) in Ga-supported SAPO-11 (Ga/SAPO-11). The fact that the sample of GaAPSO-11 was completely inactive for this transformation leads us to believe that the incorporation of gallium into the tetrahedral positions of the AEL framework was almost complete.

Study of the oxidation states of chromium in substituted and supported Cr-silicoaluminophosphate molecular sieves

A chromium-substituted silicoaluminophosphate molecular sieve (CrAPSO-11) and a Cr-supported SAPO-11 molecular sieve (Cr/SAPO-11) were studied by XPS and reduction-oxidation (redox) cycles. The distribution of oxidation states as well as the average oxidation state for chromium were determined for both preparations. The XPS results showed that two chromium 2p doublets (Cr(VI) and Cr(III)) were necessary to curve fit the experimental data. Comparison of curve-fitting results for the two oxidic samples (O 2 , 773 K) revealed a significantly higher percentage of Cr(III) species in the Cr/SAPO-11 catalyst. The difference between the two samples remained following reduction (H 2 , 773 K). For the CrAPSO-11 sample, Cr(VI) showed a higher stability towards reduction, compared to chromium supported on conventional supports. This result suggests the incorporation of Cr(VI) into the silicoaluminophosphate framework, as mentioned in the literature. For the Cr/SAPO-11 solid, Cr(III) was extremely stable towards oxidation at 773 K. Due to the redox characteristics and the XPS results, the formation of chromia species on this catalyst is suggested.