Presence Of Solid Acid Research Articles

Porous Materials for Hydrolytic Dehydrogenation of Ammonia Borane.

Hydrogen storage is still one of the most significant issues hindering the development of a “hydrogen energy economy”. Ammonia borane is notable for its high hydrogen densities. For the material, one of the main challenges is to release efficiently the maximum amount of the stored hydrogen. Hydrolysis reaction is a promising process by which hydrogen can be easily generated from this compound. High purity hydrogen from this compound can be evolved in the presence of solid acid or metal based catalyst. The reaction performance depends on the morphology and/or structure of these materials. In this review, we survey the research on nanostructured materials, especially porous materials for hydrogen generation from hydrolysis of ammonia borane.

Biodiesel production using supercritical methanol/carbon dioxide mixtures in a continuous reactor

Fatty acid methyl esters (biodiesel) were produced by the transesterification of triglycerides with compressed methanol (critical point at 240°C and 81bar) in the presence of solid acids as heterogeneous catalyst (SAC-13). Addition of a co-solvent, supercritical carbon dioxide (critical point at 31°C and 73bar), increased the rate of the supercritical alcohols transesterification, making it possible to obtain high biodiesel yields at mild temperature conditions. Experiments were carried out in a fixed bed reactor, and reactions were studied at 150–205°C, mass flow rate 6–24ml/min at a pressure of 250bar. The molar ratio of methanol to oil, and catalyst amount were kept constant (9g). The reaction temperature and space time were investigated to determine the best way for producing biodiesel. The results obtained show that the observed reaction rate is 20 time faster than conventional biodiesel production processes. The temperature of 200°C with a reaction time of 2min were found to be optimal for the maximum (88%) conversion to methyl ester and the free glycerol content was found below the specification limits.

Enhancing effect of S and F moieties on the performance of Fenton system in the selective oxidation of propane

The selective oxidation of propane to oxygenated products (isopropanol, n-propanol, propionic aldehyde and acetone) mediated by the Fe(II)/H 2O 2 Fenton system at 80 °C in the presence of solid acid and superacid promoters containing S and F moieties has been studied. The occurrence of a radical reaction pathway accounting for the activation of the C H bonds of the propane molecule by OH radicals has been proved by assessing the inhibiting effect of both Cl − and NO 3 − radical scavengers and organic (CH 3COOH, CH 3CN, DMSO) reaction media on the reaction pattern. S and F functionalities of several solid agents promote the electron transfer processes controlling the H 2O 2 activation. Any effect of the Brönsted acid features of the solid promoters on the reaction kinetics and pathway has been disregarded.

Biodiesel production by the transesterification of cottonseed oil by solid acid catalysts

Methyl esters (biodiesel) were produced by the transesterification of cottonseed oil with methanol in the presence of solid acids as heterogeneous catalysts. The solid acids were prepared by mounting H2SO4 on TiO2 · nH2O and Zr(OH)4, respectively, followed by calcining at 823K. TiO2-SO4 2− and ZrO2-SO4 2− showed high activity for the transesterification. The yield of methyl esters was over 90% under the conditions of 230°C, methanol/oil mole ratio of 12:1, reaction time 8 h and catalyst amount (catalyst/oil) of 2% (w). The solid acid catalysts showed more better adaptability than solid base catalysts when the oil has high acidity. IR spectral analysis of absorbed pyridine on the samples showed that there were Lewis and Brønsted acid sites on the catalysts.

Modified procedure for improved synthesis of some octameric silsesquioxanes via hydrolytic polycondenzation in the presence of Amberlite ion-exchange resins

Practical alternative procedures are described for the syntheses of octavinylsilsesquioxane 1, octaphenylsilesquioxane and octabenzylsilsesquioxane. The hydrolytic polycondensation of RSiX3 (R = CH2=CH-, C6H5- or C6H5CH2-; X = Cl, OCH3, or OC2H5) in the presence of solid acid or base Amberlite ion-exchange resin gave improved yields of the corresponding octameric oligosilsesquioxanes. Repetitive usage of the Amberlite resin as the hydrolysis reagent was tested during synthesis of 1. The results indicate that it could be used many times in the same solvent making the procedure a more economically viable technique.

Microwave‐Assisted Synthesis of 10‐Substituted Isoalloxazines in the Presence of Solid Acids.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Microwave-Assisted Synthesis of 10-Substituted Isoalloxazines in the Presence of Solid Acids

The microwave-enhanced synthesis of 10-substituted isoalloxazines is achieved rapidly (˜4 min) and in good yield (>80–95%) via the cyclocondensation of 2-substituted aminoanilines with alloxan or N-methylalloxan monohydrate in the presence of acidic alumina or montmorillonite clays (KSF and K10).

CONDENSED THIADIAZINES: SYNTHESIS OF [1,2,4]TRIAZINO[3,4-B] [1,3,4]THIADIAZINES

A [1,2,4]triazino [3,4-b]thiadiazine was prepared by cyclization of 4-amino-3-phenacylmer-capto [1,2,4] triazin-5-one 2 in the presence of solid acid via an unusual pathway.

Activation of Ethane in the Presence of Solid Acids: Sulfated Zirconia, Iron- and Manganese-Promoted Sulfated Zirconia, and Zeolites

Ethane was activated in the presence of solid acids [sulfated zirconia (SZ), iron- and manganese-promoted sulfated zirconia (FMSZ), HZSM-5, and USY zeolite] at 1 atm, 200–450°C, and ethane partial pressures in the range 0.01–0.2 atm. The data were measured with a flow reactor at low conversions (<0.005) such that reaction of ethane took place in the near absence of alkenes. Catalysis was demonstrated for ethane conversion in the presence of FMSZ at 450°C and 0.2 atm ethane partial pressure, but the reactions were not shown to be catalytic for the other solid acids and other conditions. FMSZ was active for converting ethane into methane, ethene, and butane at an ethane partial pressure of 0.2 atm and at temperatures of 200–300°C; the other solid acids had no detectable activities under these conditions. At higher temperatures, each of the solid acids was active for conversion of ethane into ethene; butane and methane were also formed in the presence of FMSZ, HZSM-5, and USY zeolite, whereas methane was the only other hydrocarbon observed in the presence of SZ. The initial (5 min on stream) selectivities to ethene at approximately 0.1% conversion, ethane partial pressure of 0.2 atm, and 450°C were approximately 98, 94, 97, and 99%, for SZ, FMSZ, HZSM-5, and USY zeolite, respectively. Under the same reaction conditions, the initial rates of ethane conversion were 0.15×10−8, 3.5×10−8, 3.9×10−8, and 0.56×10−8mol/(s·g) for SZ, FMSZ, HZSM-5, and USY zeolite, respectively. The reactivities are consistent with chemistry analogous to that occurring in superacidic solutions and with the suggestion that FMSZ is a stronger acid than the others investigated here.