02108nas a2200169   4500008004100000022001400041245011900055210006900174260000900243300001400252490000600266520148100272100001901753700001701772700001801789856013101807       2022                        eng d  a2058-988300aCharacterization of axial dispersion in a vertical helical coil for gas-liquid-liquid flow at low Reynolds numbers0 aCharacterization of axial dispersion in a vertical helical coil   cMAY   a1083-10950 v73 a<p>
	Gas-liquid-liquid (GLL) slug flow reactors offer several advantages like higher interfacial area, excellent mass transfer, and lower backmixing. Mesoscale (diameter similar to a few mm) helical coiled reactors operating in a slug flow regime can be used as GLL reactors even for reactions with long residence times. The long residence time invariably leads to low Reynolds number flows, which makes the backmixing or axial dispersion an important parameter influencing reactor performance. In this work, we have characterized the residence time distribution (RTD) and axial dispersion for single, gas-liquid, liquid-liquid, and gas-liquid-liquid flows through a vertical helical coil. Slow flows with low Reynolds numbers (&lt;100) were considered. RTD measurements were carried out with a step input and the outlet concentration was tracked by measuring light absorbance using a spectrophotometer. The applicability of the axial dispersion model was examined and verified for the studied systems. The axial dispersion was quantified in terms of dispersion coefficients. A significant reduction in the axial dispersion was observed by virtue of multiphase operation, in the order single &gt; gas-liquid &gt; liquid-liquid &gt; gas-liquid-liquid flow. This characterization of backmixing for multiphase flows in curved geometries will be helpful in the optimization of slow reactions in flow and also for processes like nanoparticle synthesis, crystallization, etc.</p>
1 aKhan, Muzammil1 aJoshi, Sunil1 aRanade, Vivek  uhttps://library.ncl.res.in/content/characterization-axial-dispersion-vertical-helical-coil-gas-liquid-liquid-flow-low-reynolds02458nas a2200229   4500008004100000022001400041245007800055210006900133260000800202300001200210490000700222520175400229653002301983653001702006653001302023653001702036653001102053100002302064700001702087700001702104856010702121       2023                        eng d  a0161-494000aComprehensive review on catalytic O-alkylation of phenol and hydroquinone0 aComprehensive review on catalytic Oalkylation of phenol and hydr  cAPR  a455-5000 v653 a<p>The alkylation process involves two competitive paths of O- and C-alkylation and achieving better selectivity for desired products is a very challenging problem. The development of new process for synthesis of O-methylated products of phenol and dihydric phenols is a subject of high industrial and academic interest. Alkyl phenyl ethers, especially anisole and 4-methoxyphenol, have captivated significant interest due to their increasing applications in pharmaceutical industries. The main emphasis of the present review is to explore the recent development in two catalytic O-alkylation processes. The first process is O-methylation of phenol into anisole and another is selective mono O-methylation of hydroquinone into 4-methoxyphenol. The present article covers O-alkylation methods with methanol and dimethyl carbonate as alkylating agent over various acidic and basic catalytic systems. The catalyst systems analyzed involves Bronsted and Lewis acidic and basic ionic liquids, conventional acids, metal oxides, solid acid and basic catalysts, hydrotalcites, various zeolites and heteropolyacids. The mechanistic behavior of alkylation reactions in presence of different catalytic system is reviewed critically which is important to design new and/or modified catalyst in order to maximize the yield of desired product. Additionally, an influence of reaction parameters, role of catalyst and their active sites on product distribution is described. The review paper gives useful insight for researchers in the field of catalysis and reaction engineering of alkylation reactions. Understandings of the reaction pathways will help in developing reliable kinetic models necessary for process scale-up to industrial scale reactor system.</p>
10aDimethyl carbonate10aHydroquinone10aMethanol10aO-alkylation10aphenol1 aBhongale, Priyanka1 aJoshi, Sunil1 aMali, Nilesh  uhttps://library.ncl.res.in/content/comprehensive-review-catalytic-o-alkylation-phenol-and-hydroquinone