NOPR Collection:

The nature of heat

2016-07-20T05:25:01Z

Title: The nature of heat Authors: Wisniak, Jaime Abstract: The nature and effects of heat have intrigued philosophers and scientists since ancient times. Different theories were developed to explain the phenomena, and of these, the wave theory and the caloric theory were the ones that remained in force until the second half of the nineteenth century when overwhelming evidence led to the conclusion that heat was not a material substance, that the molecules of a gas were not stationary but could move in space, and that radiation and light were basically the same phenomena. Page(s): 582-592

Crystallization of HMX in acetone-water system

2016-07-20T05:56:11Z

Title: Crystallization of HMX in acetone-water system Authors: Basu, Souraseni; Gawande, N M; Apte, ME; Narasimhan, V L Abstract: Cyclotetraillethylene-tetranitramine (HMX) is prepared by continuous nitrolysis of hexamine using nitric acid and ammonium nitrate in the presence of acetic anhydride and acetic acid. HMX obtained alter nitrolysis contains RDX and some nitro compounds as impurities. It is purified by evaporative crystallization technique using acetone as the solvent. In this work a ternary system consisting of HMX as the solute, acetone as solvent and water as anti -solvent was studied in order to obtain solubility data and influence of different parameters viz. percentage recovery of solvent , stirrer speed, cooling rate, and rate of recovery of solvent on the crystal size distribution (CSD) of HMX. The crystal morphology was also studied by using scanning electron microscope (SEM). The CSD of HMX obtained by using acetone-water mixture is compared with the CSD obtained by using acetone as solvent. It has been observed that under similar conditions of crystallization, crystals obtained from acetone-water mixture are smaller than those obtained from acetone. Also, the crystals obtained from acetone-water system arc more regular in shape and have smooth surfaces. Page(s): 575-581

Oxidative coupling of methane over La-promoted MgO catalysts: Influence of precursors and method of catalyst preparation

2016-07-20T05:54:58Z

Title: Oxidative coupling of methane over La-promoted MgO catalysts: Influence of precursors and method of catalyst preparation Authors: Choudhary, V R; Rane, V H; Chaudhari, S T Abstract: The influence of precursors for La₂O₃ (viz. lanthanum acetate and lanthanum nitrate) and MgO (viz. magnesium acetate, magnesium carbonate and magnesium hydroxide) and catalyst preparation methods (viz. physical mixing of the catalyst precursors and coprecipitation using different precipitating agents such as ammonium hydroxide, ammonium carbonate and sodium carbonate) of La-promoted MgO (La/Mg = 0.1) catalyst on its surface area, total and strong basicity (measured in terms of CO₂ chemisorbed at 50 and 500^oC, respectively) and catalytic performance in oxidative coupling of methane (OCM) to C₂-hydrocarbons at different temperatures (750-850^oC), CH₄/O₂ ratios (4.0 and 8.0) for a high space velocity (51,360 cm³.g^-1.h^-1) has been investigated. The catalyst prepared using the coprecipitation method have higher surface area and basicity (total and strong basic sites measured in terms of CO₂ chemisorbed at 50 and 500^oC, respectively) but lower activity/selectivity, whereas, the catalyst prepared using the physical mixing method have lower surface area and basicity (both total and strong basic sites) but show higher activity and selectivity in the OCM process, depending upon the La- and Mg- salts used as the catalyst precursors. The catalyst, prepared by physical mixing using lanthanum nitrate and magnesium carbonate (prepared by precipitation from magnesium nitrate and sodium carbonate) as the catalyst precursors showed best catalytic performance in the OCM at different process conditions. Page(s): 569-574

A facile synthesis of fatty acid esters of p-cresol catalysed by acid activated Indian bentonite

2016-07-20T05:50:43Z

Title: A facile synthesis of fatty acid esters of p-cresol catalysed by acid activated Indian bentonite Authors: Vijayakumar, B; Iyengar, Pushpa; Nagendrappa, Gopalpur; Prakash, B S Jai Abstract: p-Tolyl esters of some long chain fatty acids having commercial applications are synthesized using acid activated Indian bentonite as catalyst. Experimental conditions have been optimised to get the best yields. The effects of the molar ratio and reaction time have been investigated. The rate constant (κ), the equilibrium constant (K) and the standard Gibbs free energy (ΔG^o) are calculated. The spent catalyst on regeneration [by washing and heating to 110^oC ] shows the same activity, and is found to be reusable several times. Page(s): 565-568