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A systematic DoE approach is developed to optimize Mo-based ZSM-5 catalyst recipe for methane dehydro-aromatization process. Aim is to achieve maximum benzene productivity with improve catalyst stability. Three major factors - Si/Al ratio of ZSM-5, pH of Mo incorporation and catalyst activation along with two different responses - benzene yield and final/peak methane conversion (or in other words the extent of catalyst stability) were considered for constructing the DoE. The benzene yield and final/peak methane conversion vary significantly depending on the catalyst recipe including the catalyst activation protocol/conditions. The combination of Si/Al ratio of 15, pH of Mo incorporation 10 and control catalyst activation by pre-carburization identified through DoE helped to achieve maximum/optimum benzene yield and the catalyst stability. Moderate acidity of zeolite, high Mo dispersion and presence of higher quantity of catalytically active Mo-carbide/oxycarbide species seems to be the reason for high benzene productivity and catalyst stability.

With an aim to probe some of the safe and commercially available nonsulfur chemicals as simulants of sulfur mustard for testing of protective materials, the sorption of bis(2-chloroethyl) ether (2-CEE), 1,6-dichlorohexane, bis(4-chlorobutyl) ether, n-octane (OCT), dimethyl methylphosphonate, and ethylene glycol through butyl rubber (IIR) and polyisoprene (PI) rubber was studied at 30 ± 2°C using gravimetric method. Among these compounds, sorption of OCT was maximum while bis(4-chlorobutyl) ether was sorbed least. The sorption of dimethyl methylphosphonate was intermediate between 2-CEE and 1,6-dichlorohexane. With the exception of OCT/IIR, OCT/PI, and 2-CEE/PI, all other simulant/elastomer systems showed non-Fickian behavior, implying the potential of OCT as a model compound. The diffusivity of OCT was investigated in IIR and PI; the diffusion coefficient values for OCT/IIR and OCT/PI systems differed by one order of magnitude, being 6.95 × 10−15 m2/s and 3.74 × 10−14 m2/s, respectively, indicating the relative impermeability of IIR. The magnitude and dynamics of sorption in OCT/IIR as a function of its concentration and the amount of filler were further studied using the automated gravimetric analyzer. Incorporation of carbon black in IIR further reduced the extent of sorption, thereby implying an improvement in barrier performance. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1801–1806, 2007

Active carbon, grade 80 CTC, of surface area 1199m(2)/g, 12x30 BSS particle size and coconut shell origin was impregnated (5%, W/W) with various impregnants such as Cu(II) 1,1,1,5,5,5-hexafluoroacetylacetonate, Cu(II) 1,1,1-trifluoroacetylacetonate, 1-phenylbute-1,3-dione-2-oxime plus Cu(II) using incipient wetness technique. These impregnated carbons along with active carbon (Grade 80 CTC) and whetlerite were studied for the adsorption of dimethyl methylphosphonate (DMMP) at 33+/-1 degrees C under static conditions. Cu(II) 1,1,1,5,5,5-hexafluoroacetylacetonate impregnated carbon system showed highest uptake (68.5%, W/W) of DMMP amongst all the carbon systems, however, active carbon with higher surface area could adsorb 61.5% (W/W) of DMMP under same conditions. It indicated that the adsorption by Cu(II) 1,1,1,5,5,5-hexafluoroacetylacetonate impregnated carbon was not only due to physisorption but chemisorption as well. Kinetics of adsorption was also studied and various parameters such as equilibration time, equilibration capacity, rate constant (k), diffusional exponent (n) and constant (K) were determined. Carbons with and without DMMP exposure were also studied using IR and TGA techniques. Reaction products were analyzed using gas chromatography coupled with mass spectrometry (GC/MS) and found to be methyl methylphosphonic acid (MMPA) and methylphosphonic acid (MPA) for Cu(II) 1,1,1,5,5,5-hexafluoroacetylacetonate impregnated carbon.

Poly(vinyl acetal) PVAc was synthesized by the acid-catalyzed acetalisation of poly(vinyl alcohol). Three different morphologically modified variants of the polymer were prepared by the addition of supramolecules; namely α and β cyclodextrins (CD) and butyl calixerene (calix) to the PVAc sol. 20% (w/v) of the solution of the polymers in tetrahydrofuran (THF) was used to cast the membranes. These membranes were characterized using spectroscopic and thermoanalytical techniques, and also tested for their chemical resistance and mechanical strength. The pervaporative behaviour of modified membranes vis-a-vis PVAc for the separation of a wide composition of benzene (Bz)/cyclohexane (Chx) mixtures was evaluated. Addition of αCD or calix to PVAc reduced the overall flux while dispersion of βCD favoured an enhanced flux especially in the Bz-lean and azeotropic region.

Polyethylene maleate (PEM) was synthesised by direct polycondensation of maleic anhydride and ethylene glycol in toluene under reflux usingp-toluene sulphonic acid as a catalyst. Structure of PEM was further modified by varying nature of diols and acid components, chain length of glycols, incorporation of aromatic and fluorine groups in the chain. Formation of PEM was monitored by gas chromatography. The parameters like degree of polymerisation, number average molecular weight (Mn), and weight average molecular weight (Mw) were calculated from the extent of reaction and stoichiometric ratio of the reactants. The number average molecular weight was also determined using Knauer vapour pressure osmometer. Cohesive energy, volume, and solubility parameters of PEM-based copolyesters were calculated by group contribution method. These PEM-based copolyesters’ have been evaluated as sorbent-coating materials for the detection of organ0 phosphorus(OP)compo using dimethylmethylphosphonate (DMMP) as model compound and piezoelectric crystal detector. PEMbisphenol A is found to be the most sensitive and potential coating material for the detection of OP compounds using piezoelectric crystal detector. Potential PEM-based copolyesters have been characterised by viscosity, infrared spectroscopy, NMR spectroscopy, Mn and thermal stability.

A simpler technique for the synthesis of 2,2-bis(4-allyoxyphenyl)hexafluoropropane has been achieved from 4,4′-(hexafluoroisopropylidene)diphenol for obtaining 2,2-bis(3-allyl-4-hydroxyphenyl)hexafluoropropane. This monomer and its corresponding hybrid organic/inorganic siloxane polymer are successfully used as a coating material for the detection of toxic chemical warfare agents.

Cellulose membrane produced by bacterial Acetobacter xylinum was deproteinated and investigated for pervaporative separation of aqueous organic mixtures. The permeate flux, selectivity, pervaporation separation index (PSI), solubility and degree of sorption were studied as a function of increasing concentration of organics in the feed. The membrane was found highly selective to water; highest selectivity [αp = 186] was obtained for a mixture of trihydric alcohol viz. glycerol (Gly) with 40% (v/v) water. The binary system of monohydric alcohol viz. ethanol (EtOH) and water (40% (v/v)) showed the lowest selectivity [αp = 12] but the highest pervaporative flux of 614 gm−2 h−1 at 35 °C which further increased to 1429 gm−2 h−1 at 75 °C. However, selectivity decreased to 1.3 with the increase in temperature. The pervaporation behaviour was interpreted in terms of sorption and diffusivity of the organics, which in turn, was influenced by the extent of their hydrogen bonding with the cellulose units in the membrane and the plasticization induced by the permeating water present in the binary mixture. Substantially high pervaporative separation index (PSI) of the order of 103–104 gm−2 h−1 and comparatively lower energy of activation (Ej) of 10 kJ/mol is indicative of the pervaporative potential of the bacterial cellulose membrane (BCM) in the separation of aqueous binary mixtures.

The pervaporative (PV) performance with respect to the separation of ethanol/water (EtOH/H2O) azeotrope was assessed for a bacterial cellulose membrane (BCM) impregnated with chitosan (CTSN), designated as CTSN–BCM. The PV potential of CTSN–BCM was compared with that of parent polymers and also with the blends of CTSN with poly(vinyl alcohol) (PVA). The blends and CTSN–BCM were characterized using spectroscopic and thermoanalytical techniques, and also tested for their mechanical strength and sorption of EtOH/H2O mixtures. While PVA and the blends tend to dissolve at higher concentration of water, CTSN–BCM was found to be intact over the entire composition range. When evaluated against pervaporation of 95:5 w/w EtOH/H2O azeotrope at 24 ± 1 °C; CTSN–PVA (1:1) blend showed comparatively higher selectivity (22.0) but a poorer flux (1.7 kg μm m−2 h−1). The flux was significantly higher (42.8 kg μm m−2 h−1) in CTSN–BCM and selectivity (∼10) was at par with PVA. The temperature dependence of selectivity and flux through CTSN–BCM was also investigated. Substantially high pervaporative separation index (PSI) of the order of 350 kg μm m−2 h−1 and low energy of activation of 10 kJ/mol is indicative of the potential of CTSN–BCM in the pervaporative separation of EtOH/H2O azeotrope.

The heart of a chemical sensor based on bulk or surface acoustic wave devices is a polymer-coated piezoelectric substrate that selectively sorbs and concentrates the target analyte vapors. The development of such sensors often necessitates the screening and evaluation of suitable polymeric interface materials meeting the specified sensitivity and selectivity toward the analytes of interest. The magnitude and dynamics of sorption–desorption of the vapors in the polymer and the extent of polymer–vapor interactions largely determine the performance of a sensor. The standard protocol used for the purpose is rather tedious, involving the generation and calibration of individual analyte vapors, with stringent control on temperature, humidity, and test parameters. This article outlines four different alternative techniques based on mass uptake of the analyte vapors, on its partitioning in polymers, or both, which in combination can determine the characteristics of an interface material used for coating a piezoelectric substrate in acoustic wave-based chemical sensors. These methods were applied to poly(ethylene maleate), a representative interface material. The analytes ranged from volatile organic chemicals to sarin—a chemical warfare agent—and its simulant, dimethyl methylphosphonate. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3428–3432, 2004

Poly(vinyl alcohol) (PVA) was chemically modified by acid-catalysed acetalisation, resulting in the formation of poly(vinyl acetal) (PVAc). The addition of a molecular recognition compound, namely, O , O -bis(diethoxyphosphoryl)- tert -butyl calixarene (calix) to the PVA sol, yielded the morphologically modified membranes, designated as PVA–calix. These membranes were characterised using spectroscopic and thermoanalytical techniques, and also tested for their chemical resistance, mechanical strength and pervaporative behaviour towards benzene (Bz)/cyclohexane (Chx) mixtures. The polymers were found to be selective towards Bz. When evaluated against pure Bz and Chx at 27±1 °C; PVA–calix showed an ideal selectivity tending towards infinity but a poor flux (5.9 kg μm/(m 2 h)) for Bz. The flux of Bz was significantly higher in PVAc and increased from 20 kg μm/(m 2 h) for 20% (v/v) Bz/Chx mixture to 65.8 kg μm/(m 2 h) for pure Bz. The swelling index also increased with the increasing concentration of Bz in the feed. Pervaporation in PVAc was thus sorption-controlled. The sorption isotherms for the pure components in PVAc were also obtained using an automated sorption analyser based on the principle of mass relaxation of the polymer accompanying vapour sorption. The high interaction of PVAc with Bz was interpreted in terms of solubility parameters and free volume in the polymer.

Hydrophobic comonomers bisphenol-A and hexafluorobisphenol-A were incorporated as diol components in the sensor-coating material poly(ethylene maleate) (PEM), resulting in modified polymers, HCPEM and HFPEM, respectively. To assess the suitability of these polymers as sensor interfaces, the sorption/desorption isotherms and kinetics of water and a range of volatile organic vapors were obtained over the entire relative pressure range of 0.1 to 1.0, using an automated intelligent gravimetric sorption analyzer. The extent and rate of sorption of organic vapors were higher in the modified polymers compared to those of the parent polymer. Sorption hysteresis was observed at high relative pressures, especially with water and other hydrogen-bonded polar organic vapors. Polarizable vapors like toluene and benzene were sorbed more than nonpolarizable cyclohexane vapors. The sorption results were interpreted in terms of semiempirical models based on concepts of thermodynamic interaction parameter, partition coefficient, and linear solvation energy relationship. The study reveals the potential of sorption/desorption isotherms and kinetics in characterizing the sorption properties of coating materials that are used as an interface in acoustic wave sensors. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1760–1767, 2003

Cellulose membrane produced by the bacterium Acetobacter xylinum was deproteinated and investigated for pervaporation (PV) of binary water–ethanol mixtures. The membrane was characterised using elemental analysis, infra-red spectroscopy, scanning electron microscopy as well as for mechanical strength and sorption characteristics. A batch stirred cell was used to study the PV behaviour of water–ethanol mixtures through the membrane. The permeate flux, selectivity, PV separation index (PSI), solubility and degree of sorption were studied as a function of increasing ethanol concentration in the feed. The membrane was found highly selective to water. Even when the feed was rich in ethanol (>70% (w/w)) the permeate contained higher than 95% (w/w) of water. For feed compositions containing less than 30% water, the selectivity towards water was in the range of 125–287, the flux was greater than 100 g/m2 h and PSI was of the order of 104 g/m2 h.

The diffusion of sulfur mustard (SM), a chemical warfare agent, through butyl (IIR) and nitrile (NBR) rubber membranes was studied with a standard spot disc breakthrough time test at temperatures ranging from 298 to 333 K. The mechanism of diffusion was interpreted on the basis of an Arrhenius relation and dynamic adsorption theory. The permeant SM was pictured to reversibly dwell at each adsorption site for about 1.5 × 10−13 s and hop randomly through the polymer matrices in small steps, with jump lengths of the order of a picometer. A comparatively lower activation energy, a solubility parameter closer to that of SM, and a lower thermodynamic interaction parameter also contributed toward faster uptake of SM by NBR in comparison with IIR. The diffusion data were also used to derive the collision diameter of SM in these polymer matrices. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1821–1827, 2002

Bis(2-chloroethyl)ether, a nonvesicant and easy to handle chemical, was proposed as a model compound for the vesicant sulfur mustard (SM) in routine permeation testing of protective devices. The proposition was based on detailed studies on sorption of these chemicals in elastomers. From the sorption plots and permeation parameters, it was found that the model compound diffuses faster than SM, and the diffusion follows Fickian kinetics. Free volume models, such as those developed by Lee and Salame, together with solubility and thermodynamic interaction parameters, validated the observed sorption phenomenon and afforded a criterion for predicting the barrier properties of elastomers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2472–2479, 2000

Butyl rubber (IIR) membranes containing a 0–50% volume fraction of carbon black (GPF N660) or nonblack fillers (talc/precipitated CaCO3/fullers earth) were prepared by solution casting and evaluated for permeation resistance to the vesicant, bis(2-chloroethyl)sulfide, or sulfur mustard (SM) and its oxygen analog (OA), bis(2-chloroethyl)ether. The diffusivity of the chemicals was determined from the breakthrough time (BTT), obtained using the spot disc test and a gravimetric method. The permeation parameters, calculated from the sorption data, were used to determine an optimum filler content for maximum protection against SM. To investigate the effect of carbon loading on the permeation properties of IIR, the permeation of SM and OA in carbon-loaded black membranes was compared with nonblack membranes and interpreted in terms of the dispersion of carbon in the membranes. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 503–511, 1998

An investigation was made of the effect of the nature of elastomer, thickness of the membrane and its formulation, and the temperature and relative humidity of the surroundings, on the permeation of bis(2-chloroethyl)sulfide (SM), a well-known chemical warfare agent, through solution-cast elastomer membranes. The permeation was evaluated in terms of the breakthrough time of the agent through the membrane, using the spot disk test and the weight gain method. Butyl rubber exhibited the highest permeation resistance, which increased linearly with thickness and was increased by incorporation of an optimum of 20 phr carbon black in the membranes. Increase in temperature and relative humidity lowered the permeation resistance. The observed data were correlated with permeation parameters and it is postulated that permeation of SM through elastomers is non-Fickian in nature.

Coconut charcoals of different grades were studied for assessing the removal efficiency of chemical warfare (CW) agents from aqueous solutions. Oxygen analogue of sulphur mustard and phenol were used as model compounds for CW agents for adsorption studies. Freundlich and Langmuir adsorption isotherms were plotted. Equilibrium constant and maximum adsorption capacity for carbons were computed from the isotherm data. These studies enabled identification of an activated carbon suitable for use in reverse-osmosis water filtration systems.

The present review surveys, integrates and gives a bibliographic account of studies carried out on the degradation of butyl rubber over the last few decades. Our objective was to extract the useful information from such studies. As a large fraction of the related literature is in inaccessible journals, many of which are not readily available in English translation, this paper should help in presenting an overview and insight into the nature of the work being done in the field. The effects of thermal and thermo-oxidative conditions, mechanical stresses (during processing and ultrasound treatment), catalysts, chemicals, ozone and radiation on the structure, and physicomechanical properties of butyl rubber have been discussed. This rubber was chosen as a representative elastomer in order to illustrate some trends in the degradation studies of other rubbers.

Butyl rubber was pyrolysed under an inert atmosphere in a furnace-type pyrolyser at 400°C. The pyrolysate was trapped cryogenically and analysed by GC, GC/MS and GC/FT-IR. Based on these data, a mechanism for the thermal degradation of butyl rubber is proposed. The effect of temperature on the reative yields of the major decomposition products was also studied.

The protective potential of protective devices such as respirators, suits, gloves, and overboots is widely evaluated using the standard colorimetric test (spot disc breakthrough time test, also called SD BTT) involving sulfur mustard (SM) as the challenge chemical. The vesicant nature of SM makes the test inconvenient and poses stringent safety demands. Moreover, such tests are allowed only at a limited number of facilities, causing delay in product development and supply. This prompted the present study on the search for suitable SM simulant responsive to SD BTT test. The diffusivities at BTT (DBTT) of 10 commercially available thiocompounds through butyl rubber (IIR) were compared vis-a-vis DBTT of SM. For three representative thiocompounds, namely methyl (phenyl thio)acetate, 2-chloroethyl phenyl sulfide (2-CEPS) and phenyl-n-propyl sulfide (PNPS), the transport parameters through IIR were obtained. PNPS and 2-CEPS were further compared with respect to DBTT in elastomers such as IIR, ethylene–propylene–diene methylene rubber, polydimethylsiloxane, nitrile rubber, polybutadiene, and natural rubber. 2-CEPS showed generally same order of DBTT as SM implying its potential use as a simulant. The transport parameters for various 2-CEPS/elastomer systems were also determined. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009