Chemical Engineering

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Micro. -reaction/reactor technology has been used to intensify several chemical processes involving gas-liquid and liquid-liquid reactions. However, potential of intensifying gas-liquid-liquid reactions still remains unexplored. In the present work, we report experimental investigations of gas-liquid-liquid three-phase flows in microchannels. High-speed imaging experiments were performed to identify and to map flow regimes; to understand the effect of flow rates of continuous (kerosene) and dispersed phases (air and water) on the flow regimes, formation mechanisms of air bubbles/slugs and water drops/slugs and also to measure the slug lengths. In particular, the effects of different gas and liquid distributors and addition of surfactant were investigated to understand controlled generation of bubbles and drops and formation of different flow regimes in microchannels. The results presented in this manuscript will be important to device microreactor systems for catalytic reactions involving gas-liquid-liquid flows. © 2012 Elsevier B.V.

(SoE) School of Engineering

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Chemical Engineering Journal

Experimental characterization of gas-liquid-liquid flows in T-junction microchannels

The impact of micromixers on copolymers ' characteristics in a continuous-flow microprocess was studied. A stainless steel coiled tube was used as the microreactor. Several micromixers with different working principles, like bilamination, multilamination and impact jet, were used to mix the reactants ' streams before entering the reactor. (Co)polymers of 2-dimethyl amino ethyl methacrylate (DMAEMA) and benzyl methacrylate (BzMA) were synthesized by the atom transfer radical polymerization (ATRP) technique, with two different compositions of BzMA (20% and 40%). A faster polymerization rate was observed in case of microprocess, as compared to batch process, highlighting the inherent intensification nature of microfluidic-assisted processes. Despite equal conversion for the three micromixers, a remarkable difference in molecular weight was observed. The highest molecular weights with lowest polydispersity indices (PDIs) were obtained when the multilamination micromixer was used, while the bilamination gave polymers with high PDIs and low molecular weights. Diffusion constraints arising from the increase in viscosity was clearly visible for highest residence times in the microreactor, resulting in a deviation of molecular weight from the theoretical value.

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Green Processing and Synthesis

Intensifying the ATRP synthesis of statistical copolymers by continuous micromixing flow techniques

Hydrazones of different arylaldehydes were synthesized and their effect on endogenous proteolysis in liver was studied. It was observed that different functional groups on the benzene moiety altered the enzymatic activity and para-nitrobenzaldehyde hydrazone exhibited maximum inhibitory effect.

Asian Journal of Chemistry

Proteolytic studies in liver homogenate in presence of substituted aryl hydrazones

Jatropha curcas L. (JCL) is gaining global popularity as a potential feed stock of biodiesel and a candidate species for waste land reclamation. Although the oil yield of this species is better than any other non-edible oil yielding plants, the lack of agronomic practices defame this species for further exploitation. Furthermore, there is paucity of data on the growth performances and yield of JCL plantations. In this context, a systematic study on passport data and yield performance of JCL germplasms (including their indigenous collection number (IC No.), morphological characterization of seeds and seed oil content) growing in a large scale plantation site at Solar Energy Center, Gurgaon, India were carried out during 2007-2008. Ten elite accessions of JCL were screened from this site based on their growth performance and biomass characterization and were deposited at National Bureau of Plant Genetic Resources, New Delhi for registration. The oil content of the 10 registered accessions was ranged from 17% to 34%. Cluster analysis was performed to find out promising germplasms. Cluster analysis formed two prominent groups, each one with two sub-clusters. The promising accessions can be further explored for crop improvement programs. Furthermore, multi-locational trials are essential for optimizing the agropractices for maximum yield for a sustainable biodiesel production. © 2011 Elsevier Ltd.

Biomass and Bioenergy

Growth performance, variability in yield traits and oil content of selected accessions of Jatropha curcas L. growing in a large scale plantation site

Henry's constant H of carbon dioxide in a number of ionic liquids (ILs) has been studied using the predictive method COnductor-like Screening MOdel for Realistic Solvation (COSMO-RS). Experimental H values for 14 CO2-IL systems spread over a temperature range of (283 to 333) K have been used to estimate the parameters λ1 and λ2 of the combinatorial term to calculate the chemical potential. The H values of CO 2 in 18 other ILs have been validated and found to be in good agreement with the experimental data with a relative deviation of less than 10 %. Cation groups like imidazolium, pyridinium, ammonium, uronium, thiouronium, and phosphonium have been studied. A total of 12 anions such as L-, BF4-, EtSO4-, TFA-, OctSO4-, Tf2N-, mFAB-, eFAB-, mFAP-, eFAP-, pFAP-, and bFAP- were studied to find the most favorable cation and anion combination for high CO2 solubility. It was observed that increasing the fluorination of organic anions containing fluoro alkyl groups gave lower Henry's constant values (following the trend TFA- &gt; Tf 2N- &gt; mFAB- &gt; eFAB- &gt; mFAP- &gt; eFAP- &gt; pFAP- &gt; bFAP -), thus showing higher CO2 solubility. Among the cations studied, phosphonium-based cations are found to be most promising for higher solubility. It was observed that the entropic effects (combinatorial) arising due to the size and shape of ILs play a major role in the estimation of H values, whereas the enthalpic effects (residual) arising due to molecular interactions have a minor but significant role. A correlation has been developed to predict the H of the [Rnmim]+ cation-based IL by considering a reference value H2 of [R2mim]+. A common predictive equation has been developed to determine the temperature-dependent H values of CO2 in any cation/anion combination of ILs. © 2011 American Chemical Society.

Journal of Chemical and Engineering Data

Validation and prediction of the temperature-dependent Henry's constant for CO2-ionic liquid systems using the Conductor-like Screening Model for Realistic Solvation (COSMO-RS)

An ascorbate oxidase (EC 1.10.3.3) purified from Lagenaria siceraria fruit was immobilized onto egg shell membrane through glutaraldehyde coupling with 73.3% retention of its initial activity and a conjugation yield of 0.097 mg/cm2. The membrane consisting of ascorbate oxidase was mounted over an Au electrode to construct a working electrode for ascorbate biosensor. The biosensor showed optimum response i.e. current in mA within 10 s at pH 6.0, 40 °C and 0.6 V using Ag/AgCl reference and Cu wire as auxiliary electrode. There was a linear relationship between l-ascorbic acid concentration in the range 1 × 10-5 M and 4 × 10-4 M and current. The biosensor was employed for determination of l- ascorbic acid in serum, fruit juices and vitamin C tablets. The analytical recovery of added ascorbate in sera was 98.2% and 96.7%. Within batch and between batch coefficients of variations (CV) in ascorbate of sera were &lt;3.6% and &lt;4.49% respectively. l-Ascorbate values obtained for fruit juices and vitamin C tablets by present method and by DCPIP (2,6-dichlorophenolindophenol) method, showed a good correlation (r = 0.993). The biosensor has advantages such as fast response time (10 s), good repeatability (200 assays) and long-term stability (50% of its initial sensitivity after 4 months of storage). © 2010 Elsevier B.V. All rights reserved.

Journal of Molecular Catalysis B: Enzymatic

Fabrication of an amperometric ascorbate biosensor using egg shell membrane bound Lagenaria siceraria fruit ascorbate oxidase

A series of 16-membered macrocyclic complexes of cobalt(II) and nickel(II) of the type [M(H2Cy1-4)] have been synthesized and characterized on the basis of spectral, magnetic and conductivity studies. The macrocyclic ligands H4Cy1-4 are tetrabasic having four imido hydrogen but behave in a dibasic manner. Out of eight nitrogens, four imido and four imino, ligands utilize four imido nitrogens for square planar coordination forming four 7:5:7:5 chelate rings giving rise to a 16 membered macrocyclic framework. The red coloured nickel(II) complexes are diamagnetic in nature, whereas cobalt(II) complexes with chocolate brown colour are of low spin type. Low molar conductivity values in the range 3-7 ohm-1 cm2 mol-1 suggest complexes to be non-electrolytic in nature. High dilute conditions generally employed in the synthesis of macrocyclic complexes in order to dispense with polymerization reaction have been avoided in the present study and advantage of orientation effect has been taken to have high yield.

Metal dihydrazide precursors as building blocks for new macrocyclic architectures with tetradentate octaaza dibasic ligands

This study investigated the thermal degradation energy (activation energy, Ea) for nitrocellulose (NC) with low nitrogen content of 11.71 mass%, so-called NC3, by using two different kinds of thermal analysis instruments: thermogravimetric analyzer (TGA) and differential scanning calorimetry (DSC). A comparison of Ea for various nitrogen content NC samples at two scanning rates (5 and 10 °C min-1) tested by TGA and DSC is also discussed in this paper. Meanwhile, our aim was to analyze the anti-degradation of Ea for NC with high nitrogen content, as so-called NC1. Thermal stability for NC1 with diphenylamine (DPA) was tested via DSC with 10 DPA concentrations in weights of 0, 0.25, 0.50, 0.75, 1.0, 1.25, 1.50, 1.75, 2.0, and 3.0 mass%. Experimental results indicated that Ea of NC3s was 319.91 kJ mol-1. Moreover, that while dosing DPA into NC1 the best recipe could be employed to avoid any violent NC1 runaway and also can be used to distinguish the differences of thermal decomposition Ea between NC with different nitrogen contents. This study established a fast and efficient procedure for thermal decomposition properties of NC, and could be applied as an intrinsically safer design during relevant operations. © 2010 The Institution of Chemical Engineers.

Process Safety and Environmental Protection

Comparisons of TGA and DSC approaches to evaluate nitrocellulose thermal degradation energy and stabilizer efficiencies

Correlations for bubble point pressure, solution gas-oil ratio (GOR), oil formation volume factor (OFVF) (for both saturated and undersaturated crude) and viscosity (for both saturated and undersaturated crude) have been developed for Indian (west coast) crude using Artificial Neural Networks (ANN). Detailed comparison has also been made with various important correlations currently available in the literature. Sensitivity analysis of the developed models was also performed to determine the relative importance of various input parameters. The training scheme used here is different from those used previously for developing ANN models. Bayesian regularization technique was used to ensure generalization and prevent over fitting. Also genetic algorithm (real coded with parent-centric crossover) was used coupled with a local optimizer (Marquardt-Levenberg) to obtain the global optimum network weights. It was found that the developed models outperformed most other existing correlations by giving significantly lower values of average absolute relative error for the parameters studied. This study shows highly favorable results which can be integrated in most reservoir modeling software. © 2010 Elsevier B.V.

Journal of Petroleum Science and Engineering

PVT correlations for Indian crude using artificial neural networks

Chemical process industries (CPI) handling hazardous chemicals in bulk can be attractive targets for deliberate adversarial actions by terrorists, criminals and disgruntled employees. It is therefore imperative to have comprehensive security risk management programme including effective security risk assessment techniques. In an earlier work, it has been shown that security risk assessment can be done by conducting threat and vulnerability analysis or by developing Security Risk Factor Table (SRFT). HAZOP type vulnerability assessment sheets can be developed that are scenario based. In SRFT model, important security risk bearing factors such as location, ownership, visibility, inventory, etc., have been used. In this paper, the earlier developed SRFT model has been modified using the concepts of fuzzy logic. In the modified SRFT model, two linguistic fuzzy scales (three-point and four-point) are devised based on trapezoidal fuzzy numbers. Human subjectivity of different experts associated with previous SRFT model is tackled by mapping their scores to the newly devised fuzzy scale. Finally, the fuzzy score thus obtained is defuzzyfied to get the results. A test case of a refinery is used to explain the method and compared with the earlier work. © 2009 Elsevier B.V. All rights reserved.