Debarati Mitra

Desulfurization of Gasoline by Pervaporation

Worldwide concerns over the environment have stimulated increasing interest both in academic and industry for the deep desulfurization of gasoline. Due to some inherent disadvantages associated with the conventional hydrodesulfurization, several non-conventional techniques are being tried by researchers. Pervaporation is such a recently developed technology for gasoline desulfurization. Its efficiency has attracted worldwide attention. Compared with conventional sulfur removal technology for gasoline, pervaporation exhibits advantages of little reduction of octane number, low energy consumption, environmental benefits, simple operation, and easy scale-up. The advances of pervaporative operation for gasoline desulfurization are reviewed in this paper. The membrane materials used for desulfurization include polysiloxane, poly(ethylene glycol), polyimide, polyurethane and organic-inorganic hybrid membranes. Analysis of the selectivity–permeability with varying feed composition and operating parameters are investigated. Because of the attractive economic figures and high efficacy, the refiners expect that pervaporative desulfurization of gasoline shall soon become very important, either alone or coupled with presently available technologies.

A kinetic study on the Novozyme 435-catalyzed esterification of free fatty acids with octanol to produce octyl esters.

Octyl esters can serve as an important class of biolubricant components replacing their mineral oil counterparts. The purpose of the current work was to investigate the enzymatic esterification reaction of free fatty acids (FFA, from waste cooking oil) with octanol in a solvent‐free system using a commercial lipase Novozyme 435. It was found that the esterificaton reaction followed the Ping‐pong bi‐bi kinetics with no inhibition by substrates or products within the studied concentration range. The maximum reaction rate was estimated to be 0.041 mol L−1 g−1 h−1. Additionally, the stability of Novozyme 435 in the current reaction system was studied by determining its activity and final conversion of FFA to esters after 12 successive utilizations. Novozyme 435 exhibited almost 100% enzyme activity up to 7 cycles of reaction and gradually decreased (by 5%) thereafter. The kinetic parameters evaluated from the study shall assist in the design of reactors for large‐scale production of octyl esters from a cheap biomass source. The enzyme reusability data can further facilitate mass production by curtailing the cost of expensive enzyme consumption.

Fabrication of Aromatic Polyimide Membrane to Study the Pervaporative Separation of Phenanthrene/n-tetradecane Mixtures (Model Diesel) and Process Optimization Using Response Surface Methodology

To meet stringent fuel specifications, separation of aromatics from aliphatics is an everyday challenge for a refiner. In the present investigation, an aromatic polyimide membrane is fabricated and explored for the separation of a polyaromatic hydrocarbon (phenanthrene) from a model diesel composition (n-tetradecane) via pervaporation. The pervaporative membrane is prepared by casting a solution of polyamic acid, N,N-dimethylacetamide (DMAc), and phenanthrene using a simple and low-cost procedure. Scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FTIR), and swelling in feed solution of the synthesized membrane have been conducted for its characterization. The membrane allows preferential permeation of phenanthrene. The influence of different physico-chemical parameters, on permeation flux and enrichment factor for n-tetradecane/phenanthrene mixtures, has been studied. Statistical software Design Expert 7.1.4 is used to derive the regression equation, which describes the effect of time, downstream pressure, feed solute concentration, and operating temperature on the Pervaporation Separation Index (PSI). These factors are optimized using response surface methodology (RSM). The highest value of the PSI obtained is 0.623 kg m−2 h−1 and the corresponding optimized condition is: operating time is 11.58 h, the feed solute concentration is 162.96 ppm with a downstream pressure of 0.58 mm of Hg and an operating temperature of 449.03 K.

Green Techniques in Gas Chromatography

Gas chromatography (GC) is one of the most important analytical techniques among the various chromatographic processes currently in use. To widen it’s applicability and acceptability analysts are now concentrating to develop green GC, replacing conventional GC. The appreciating feature of green GC is it’s environment-friendliness by the way of reducing/eliminating the amount of solvents required for sample preparation and amount of waste generation or emission of volatile products. Reduction in chromatographic runtime and the possibilities of integrating GC with other efficient analytical tools are the other advantages of green GC which make it a highly efficient, sensitive and fast method of analysis in chemical science. This chapter highlights the different aspects of gas chromatography in the light of green techniques starting from sample preparation to the selection of mobile phase as well as chromatographic columns to be adopted. Coupling other analytical tools with GC to focus the versatility and high accuracy of analysis with dual system of separation and detection is also discussed.