Carbon dioxide reforming of methane on Ni/CaO-AI2O3 catalysts

NiO/AI2O3 and NiO/CaO-AI2O3 samples were prepared and calcined at 700-900°C. Characterization of these samples was made using X-ray diffraction, low temperature nitrogen adsorption, thermal programmed reduction [TPR] and chemisorption of hydrogen at 700°C. The samples were reduced and the initial catalytic methane reforming activities were determined at 700°C. The crystalline phases in each catalyst and their domination as well as textural properties of the catalysts depend on the chemical composition and calcination temperatures. The thermal programmed desorption profiles and the chemisorption of hydrogen depend on the chemical composition of the catalysts and their calcinations temperature. Hydrogen chemisorption allowed the determination of important catalytic parameters which play dominant roles in determining the initial activity of these catalysts toward methane reforming to synthesis gas by carbon dioxide at 700°C

Base catalyzed formation and ring cleavage of 2- acyl-4- alkoxycarbonyI- 4-cyano substituted cyclobexanoles

The reaction of 1, 3-diaryI-2-propen- 1 -ones [1 a, b] with ethyl cyanoacetate in absolute ethanol in the presence of a catalytic amount of KOH at 50-55°C afforded 3-aroyl-l-cyano-4-hydroxy-2,4, 6-triarylcyclohexanecarboxylates [2a,b]. Base-catalyzed ring cleavage of 2a,b in refluxing ethanolic KOH solution afforded the corresponding 3-aryl- 2-cyano-2-propenoic acid 4 along with 1 a, b. The structure of 2 was established through different spectroscopic techniques and confirmed via dehydration using thionyl chloride in refluxing pyridine afforded 3. However, reaction of la with ethyl cyanoacetate in refluxing ethanol in the presence of secondary amine [piperidine or morpholine] as a basic catalyst gave the open-chain Michael adduct 6. Treatment of the latter with ethanolic KOH solution yielded 1,5-pentanedione derivative 7. The relative configurations of 3b and 6 were determined through single crystal X-ray diffraction analysis

use of nano supported nickel catalyst in reduction of p-nitrophenol using hydrazine hydrate as hydrogen donor

P-aminophenol was prepared by reduction of p-nitro-pheilol over nano sized nickel catalysts supported on two different supports, SiO2 and AI2O3 using hydrazine hydrate as hydrogen source. Several loadings of nano-sized Ni were used thus, 20, 5, and 2.5 wt% were prepared. XRD and ESR were employed to investigate the prepared catalysts. The Ni/AI2O3 support was found to be more effective and gives high durability. The catalytic activity of the reaction was found to be influenced by the crystallinity of the nickel in addition to the strain between nano sized nickel particles. The catalytic activity of the prepared catalysts was compared with commercial Raney nickel and showed higher activity especially at lower loading. During the reaction a detectable change of the color was observed from yellow to green to colorless, which enables us to propose a mechanism of this reaction

Chemical modification studies of Rhizomucor miehei protease: evidence for the role of basic amino acids in enzyme catalysis.

The effect of chemical modification on milk clotting and proteolytic activities of aspartyl protease obtained from Rhizomucor miehei NRRL 3500 was examined in the absence and the presence of its specific inhibitor pepstatin A. The effect on the ratio of milk clotting activity (MC) to proteolytic activity (PA), an index of the quality of milk clotting proteases was also determined. Modification of the enzyme with trinitrobenzenesulfonic acid, diethylpyrocarbonate and phenylglyoxal produced an increase in the ratio of MC/PA, while modification with 2- hydroxy-5-nitrobenzyl bromide did not affect the ratio. Modification with N-acetylimidazole resulted in a marginal increase in MC/PA ratio. Protection using pepstatin A during modification with phenylglyoxal, N-acetylimidazole and 2-hydroxy-5-nitrobenzyl bromide, protected both MC and PA. In the case of modification by diethylpyrocarbonate, pepstatin A protected only MC. Pepstatin A did not protect both the activities on the modification of the enzyme by trinitrobenzene sulfonic acid. These observations indicate the presence of arginine, tyrosine and tryptophan at the catalytic site of the enzyme, for eliciting MC and PA of the enzyme. In general, modification of the positively charged residues increases the MC/PA ratio of the enzyme. In addition the modified lysine residues responsible for the inactivation of the enzyme were not involved in the active site of the enzyme. Thus the lysine residues might have a secondary role in enzyme catalysis. Further, histidine at the catalytic site was found to be exclusively involved in milk clotting activity. The enzyme with modified histidine residues were more susceptible to autocatalysis, indicating that histidine residues protect the enzyme against autolysis.