Effects Of Feed Composition Research Articles

A Kinetic Investigation of the Copolymerization of Acrylonitrile and Vinyl Acetate in Bulk

AbstractThe free radical copolymerization, initiated by 2, 2′ azo‐bis‐isobutyronitrile (AIBN), of acrylonitrile (AN) and vinyl acetate (VAc) in bulk has been examined. Reactivity ratios were evaluated using the error in variables model (EVM). In addition, full conversion range experiments were undertaken, which examined polymerization rate, molecular weight development and copolymer composition with respect to the effects of feed composition, initiator concentration and temperature.

Selective separation of water from aqueous alcohol solution through fluorine-containing aromatic polyamide membranes by pervaporation

For dehydrating aqueous alcohol solution by pervaporation, a fluorine-containing aromatic polyamide membrane was synthesized. The fluorine-containing polyamides were prepared by direct polycondensation of 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, BAPPH, with various aromatic diacids by triphenyl phosphite and pyridine in N-methyl-2-pyrrolidinone. The novel aromatic polyamides were examined by elemental analysis, FTIR, and X-ray diffraction. The aromatic polyamides were crystalline except (A-B 2). The effects of feed composition, degree of swelling, and the molecular size of alcohols on pervaporation performances were investigated. Water molecules preferentially permeate through the aromatic polyamide membranes. A separation for water of 36 and a 383 g/m 2h permeation rate with a 90 wt% feed ethanol concentration was obtained.

Separation of n-hexane/acetone mixtures by pervaporation using natural rubber membranes

Natural rubber (NR) membranes crosslinked by four different systems viz., conventional (CV), efficient (EV), dicumyl peroxide (DCP), and a mixture consisting of sulfur and peroxide (mixed), were employed for the separation of n-hexane/acetone mixtures of different compositions. The membranes exhibited preferential permeation toward n-hexane because of the closer solubility parameter values. The selectivity of the membranes depended on the nature and distribution of crosslinks between the macromolecular chains of the membrane but was independent on the thickness of the membrane. The effects of feed composition, cure time of the membranes, and the molecular size of the permeate on the permeation flux and selectivity were investigated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2597–2603, 1997

Functionalization of polyolefins in the melt through reaction with molecules and macromolecules

AbstractFunctionalization of polyolefins with diethyl maleate (DEM) is investigated to improve compatibility with other polar polymers through reactive blending. Functionalization experiments were carried out in the melt with peroxide initiator and mechanical mixers as reactors. The effect of feed composition, reactor type and duration on the functionalization degree, degradation and crosslinking reactions were examined starting with different ethylene polymers. In this way conditions were identified allowing modulation of functionalization with 2‐(diethyl succinate) groups from 0.2 to 2.5% mole, and keep to negligible level undesired by‐reactions such as crosslinking and degradation. The chemical reactivity of these functional groups to form interchain covalent bonds was investigated in case of the reaction of the ester groups on the polyolefin backbone with the amino end group of linear polyamides (in particular PA 6). Evidences of the formation of grafted polymer on the basis of fractionation of the resulting mixture, instrumental analysis and morphological characterization are presented.

Effect of feed composition and upflow velocity on aggregate characteristics in anaerobic upflow reactors

Two upflow anaerobic hybrid reactors treated lactose and a mixture of ethanol, propionate and butyrate, respectively, at a volumetric loading rate of 3.7 kg chemical oxygen demand (COD) m−3day−1, a hydraulic retention time of 5 days and a liquid upflow velocity of 0.01 m/h. Under steady-state conditions, the lactose-fed sludge had much higher (20%–100%) specific methanogenic conversion rates than the volatile-fatty acid␣(VFA)/ethanol-fed sludge for all substrates tested, including VFA. In both reactors, a flocculant sludge developed, although a much higher content of extracellular polysaccharide was measured in the lactose-fed sludge [1900 μg compared to 305 μg uronic acid/g volatile suspended solids (VSS)]. When the liquid upflow velocity of a third, VFA/ethanol-fed reactor was increased to 0.5 m/h, granulation of the sludge occurred, accompanied by a large increase (200%–500%) in the specific methanogenic conversion rates for the syntrophic and methanogenic substrates studied. Granulation reduced the susceptibility of the sludge to flotation. Glucose was degraded at a high rate (100 mg glucose gVSS−1h−1) by the sludge from the third reactor, despite not having been exposed to a sugar-containing influent for 563␣days.

Structure, activity and selectivity relationships in propane ammoxidation to acrylonitrile on V–Sb oxides Part 3Modifications during the catalytic reaction and effect of feed composition

The change in surface reactivity up until steady-state behavior is reached in propane ammoxidation of a series of V–Sb-oxide catalysts with Sb:V ratios in the range 1–10 and prepared either by calcination or heat treatment in vacuum at 600°C is reported and analyzed in terms of the change in the structural features of the catalyst determined as a function of the time on stream by IR spectroscopy, X-ray diffraction and chemical analysis data. The results indicate that during the catalytic reaction, V 5+ oxide when present, quickly reduces forming a V 4+ O 2 /VSbO 4 solid solution with an increase in the selectivity to propene, but not to acrylonitrile. An increase in the selectivity and productivity to acrylonitrile occurs when an Sb-rich approximate VSbO 4 phase forms (‘VSbO 4 ’). This phase, however, is partially metastable, decomposing to ‘VSbO 4 ’+Sb 2 O 4 when Sb 5+ ions are reduced and not rapidly reoxidized. V 5+ ions on the surface of the rutile phase stabilize the Sb-rich ‘VSbO 4 ’ phase, and catalyze the reoxidation of Sb 3+ . This side oxidation of ammonia to nitrogen competes for the reduction of these V 5+ ions and influences the above redox and solid-state reactions. Therefore, a considerable dependence of the surface reactivity on the feed was observed. The optimal catalytic behavior determined for the series of catalysts studied was found to depend on the feed composition indicating that in the analysis of the structure, activity and selectivity relationships in propane ammoxidation the concentration of reactants in the feed plays a specific important role.

Reverse Screw Element(s) and Feed Composition Effects during Twin‐Screw Extrusion of Rice Flour and Fish Muscle Blends

ABSTRACTThe influence of location and spacing of reverse screw element(s) on specific mechanical energy input and product attributes during twin‐screw extrusion of rice flour and pink salmon blends was investigated. Incorporation of reverse screw element(s) increased specific mechanical energy, expansion ratio and water solubility index; but decreased bulk density and Warner‐Bratzler shear stress. Opposite trend was observed with increasing fish content except for shear stress, which was little affected either for rice flour or its blends with 30% fish solids in the expansion ratio range 5 to 10. Linear relationships were found between shear stress and bulk density and between solubility index and specific mechanical energy.

Pervaporation of aqueous alcohol mixtures through a chemically grafted glycidyl methacrylate on to poly(4-methyl-1-pentene) membrane

To improve the pervaporation performances of a poly(4-methyl-1-pentene) (TPX) membrane, this study attempts to utilize chemical initiation which includes a hydrophilic monomer of glycidyl methacrylate (GMA) homografted on to poly(4-methyl-1-pentene) (TPX-g-PGMA). The sulfonating process was also applied to improve the hydrophilicity of the TPX-g-PMGA membrane. The effects of feed composition, feed temperature and molar volume of alcohol on the pervaporation performances of the modified TPX membrane were investigated. The water permselectivity and permeation rate for both modified TPX membranes were higher than those of the unmodified TPX membrane. The separation factor towards water and the permeation rate through the sulfonated TPX-g-PGMA membrane (TPX-g-PGMAS) with a degree of grafting 5.8% were 49 and 100 g/m 2hr, respectively.

Pervaporation of aqueous alcohol mixtures through a membrane prepared by grafting of polar monomer onto nylon 4

AbstractA hydrophilic pervaporation membrane was prepared via a homografting polymerization of N,N′‐(dimethylamino)ethyl methacrylate (DMAEM) onto nylon 4 backbone, DMAEM‐g‐N4. The water permselectivity was improved by the ammonium quaterization of the pendant N,N′‐dimethylamino group on the DMAEM‐g‐N4 membrane using demethyl sulfate, DMAEMQ‐g‐N4. The separation factor and permeation rate for both chemically modified nylon 4 membranes were higher than those of the unmodified nylon 4 membrane. The effects of feed composition, feed temperature, and molar volume of the alcohols on pervaporation performance were investigated. Optimum pervaporation was obtained by a DMAEMQ‐g‐N4 membrane with a degree of grafting of 12.7% for a 90 wt % ethanol feed concentration, giving a separation factor of 36 and a permeation rate of 564 g/m2h. © 1995 John Wiley & Sons, Inc.

Effect of Feed Composition on the Performance of Polymer-Zeolite Mixed Matrix Gas Separation Membranes

Abstract An emerging membrane morphology with future potential is mixed matrix membranes composed of two interpenetrating matrices of different materials. In this study, mixed matrix membranes of an amorphous glassy polymer (polyethersulfone) and hydrophilic zeolite (4A) were prepared. An elaborate membrane preparation technique that enables incorporation of high zeolite loading into the membrane was developed. Performance of membranes was tested by using a laboratory-scale gas separation apparatus. The permeation rates of N2, CH4, Ar, O2, CO2, and H2 were evaluated through a dense homogeneous PES membrane and a PES-4A mixed matrix membrane. For the mixed matrix membrane, gas permeabilities were either not changed or significantly improved. The ideal separation factors of economically important gas pairs were substantially increased due to the faster permeation of H2 and CO2 through the mixed matrix membrane. In order to understand their interaction with each other and with membrane matrices, permeabilities and selectivities of CO2/CH4, CO2/Ar, and H2/CH4 binaries as a function of gas composition were measured through a dense homogeneous PES membrane and a PES-4A mixed matrix membrane. Observed selectivity independence with respect to gas composition for a dense homogeneous PES membrane indicates that ternary interactions and factors like plasticization and gas fugacity do not affect the gas permeation mechanism appreciably for this type of membrane. However, selectivities demonstrated a strong concentration dependency through a PES-4A mixed matrix membrane. For CO2/CH4 and CO2/Ar systems, when the CO2 concentration in the feed increased, selectivity decreased linearly. In the case of H2/CH4 binaries, unlike the cases with CO2 binaries, a higher H2 concentration in the feed caused higher selectivity values. The trend was also linear with H2 concentration in the feed. This indicates that, for mixed matrix membranes, the existence of a third component causes the gas molecules to interact with the heterogeneous membrane matrix, affecting selectivities. Selectivity dependency indicates the importance of gas-membrane matrix and gas-gas-membrane matrix interactions.

Chemical grafted 4‐vinylpyridine onto polycarbonate membranes for pervaporation

Abstract4‐Vinylpyridine‐homografted‐polycarbonate (PC‐g‐4VP) membrane was prepared for water perselective pervaporation. The conditions of the chemical grafting reaction for synthesis PC‐g‐4VP were studied in terms of the reaction time, reaction temperature, monomer concentration, and the concentration of initiator in the reaction. The effect of feed composition, degree of swelling, and operation on temperature on the pervaporation performances were investigated. It was found that water permeated through the PC‐g‐4VP membrane perferential in all range of feed compositions. The permeation rate and separation factor increased with increasing 4‐vinylpyridine content in the membrane. PC‐g‐4VP membrane effectively improved both the water permeation rate and water–ethanol separation factor of the unmodified polycarbonate membrane. The total permeation rate of PC‐4‐VP membrane with 26.7% degree of grafting was 153 g/m2 h, and the separation factor was above 6300 for a 90 wt % aqueous ethanol feed solution. © 1995 John Wiley & Sons, Inc.

Theoretical effects of feed composition, feed conversion and feed spillage on waste discharge in fish culture

Based on feed composition, fish composition and feed conversion, some theoretical effects of feeding on waste discharge are calculated to illustrate the appropriateness of farm effluent monitoring. The effects of feed conversion and feed spillage and feed composition on waste discharge (suspended and dissolved N, P & COD) are demonstrated. Slight variations in feed conversion at the moment of sampling, especially those evoked by feed spillage, have tremendous consequences for discharge values. It appears crucial to determine whether observed conversions are explained by inherent efficiencies of fish growth, or whether higher growth efficiencies are combined with feed spillage. Therefore, thorough knowledge of relationships between nutrient intake and growth should be applied to effluent assessment. A calculation is presented to serve as a preliminary assessment of the impacts of these variables on water quality monitoring. The concept is illustrated using measurements from a recirculation pilot eel culture system.

Pervaporation Separation of Aqueous Alcohol Solution through Asymmetric Polycarbonate Membrane

Abstract In the present work the separation of aqueous alcohol mixtures through wetphase inversion prepared polycarbonate membranes was studied by using the pervaporation process. The formation of asymmetric pervaporation membranes was discussed in terms of the presence of a nonsolvent in the casting solution, the polycarbonate concentration, and the kinds of coagulation media. The effects of feed composition, swelling degree, and the size of the alcohols on the pervaporation performances were investigated. The rate of liquid-liquid demixing increases with a decreasing number of carbon atoms of the alcohol coagulation medium. The permeation rate of the pervaporation process for the nonsolvent-added membrane was much higher than that of the membrane without nonsolvent additive. In binary alcohol mixtures, the permselectivities of small-sized alcohols through the asymmetric membrane are decided by two factors: preferential solubility of larger-sized alcohol and predominant diffusivity of small-sized alcohol.

Selective reduction of nitrogen oxides (NOx) by ammonia over honeycomb selective catalytic reduction catalysts

Data are presented for the effects of feed composition (O[sub 2], NO [sub x], NH[sub 3], H[sub 2]0, SO[sub 2] concentrations) and of the operating conditions (area velocity, reaction temperature, and Re number) on the NO[sub x] removal efficiency over commercial-type honeycomb DeNOxing catalysts with different compositions and geometric characteristics. All of these data are explained by a Rideal type kinetic expression, derived assuming reaction between strongly adsorbed ammonia and gaseous or weakly bonded NO. The significance of interphase and intraparticle diffusion limitations is discussed, and a comprehensive model of the SCR monolith reactor is illustrated which fully accounts for both external and internal transport of the reactants as well as for the effects of the operating variables and of the feed composition under representative SCR conditions.

Pyrolysis and oxidative pyrolysis of chloromethane in steam

The chlorine-catalyzed oxidative pyrolysis (CCOP) process was recently developed as a method to convert methane, the major component in natural gas, into more valuable products such as ethylene, acetylene, and vinyl chloride. The CCOP process involves the initial chlorination of methane into CH[sub 3]Cl, followed by the oxidative pyrolysis of CH[sub 3]Cl into higher molecular products. Pyrolysis and oxidative pyrolysis of CH[sub 3]Cl into high molecular weight products such as C[sub 2]H[sub 2] and C[sub 2]H[sub 4] has been studied in a flow reactor in the presence of steam as diluent. The effects of feed composition, in particular the CH[sub 4] and O[sub 2] levels, residence time, and temperature on CH[sub 3]Cl conversion and C[sub 2] selectivities have been investigated. The presence of small amounts of oxygen in the feed inhibited the formation of carbonaceous deposit such as soot, tar, and coke without decreasing C[sub 2] selectivities. It was possible to generate product streams with C[sub 2] concentrations in excess of 45 mol % (C[sub 2]H[sub 2] + C[sub 2]H[sub 4] + C[sub 2]H[sub 3]Cl) following the removal of steam, HCl, and unreacted CH[sub 3]Cl, at C[sub 2] product yields in the range 25-30%.

Analysis of Heterogeneous Azeotropic Distillation Using Infinite Reflex Ratio Algorithms.

Algorithms for solving heterogeneous azeotropic distillations at total reflux (D=0) and at infinite reflux (L0→∞) are proposed. Using the total reflux algorithm, the characteristics of distillation profiles of ethanol dehydration with benzene are analyzed. Furthermore, a procedure for determining the amount of entrainer required for start-up of the azeotropic column is proposed. The effects of feed compositions and holdup distribution on the entrainer amount required at start-up are discussed. Using the infinite reflux algorithm, a two-column distillation system of ethanol dehydration with benzene is investigated, and an effective operation region for the entrainer makeup is found. The minimum theoretical stage number of the azeotropic column is also determined from the calculated results at infinite reflux.

Plasma deposition of a-C:H, F thin films from H2-C2F6 fed RF glow discharges

Thin films have been deposited from 0-20% C2F6-H2 fed radiofrequency (RF) glow discharges in a triode reactor. Deposits contain carbon, hydrogen and fluorine in a variable extent, and can be classified as a-C:H, F materials. The effects of feed composition, substrate temperature and substrate bias on the overall deposition process and on the chemical composition of the films have been studied. Actinometric optical emission spectroscopy has been utilized as a diagnostic tool of the plasma, while the film composition has been investigated by means of electron spectroscopy for chemical analysis. A deposition mechanism is proposed which involves carbon atoms and CH radicals as film precursors, and fluorine atoms as responsible for the material fluorination. The net deposition rate is the result of competition between deposition kinetics and ablation steps, all steps being assisted by ions.

Short-term Effects of Feed Composition on Sleeping and Crying in Newborns

To determine whether the composition of feedings would affect newborn behavior independently of the act of feeding itself, 53 two- to three-day-old normal newborns were randomly assigned to receive an extra feeding of water, carbohydrate (lactose), or balanced formula 3 hours after their usual early morning feeding. Previous studies in adult humans and animals, and a single study in human newborns, have indicated that more sleep might be expected following the carbohydrate feed compared with the water and balanced-formula feeds because of recruitment of centrally mediated serotonergic systems. Behavioral effects were assessed for 40 minutes postfeeding by direct observation of the newborn's states (quiet, active, and indeterminate sleep; drowsiness; non-cry wakefulness; and fret/cry). Feed composition did affect behavior, and the effects were fairly specific to particular newborn states. Non-cry wakefulness and drowsiness were unrelated to the presence or type of nutrients, but they tended to occur soon after the meal in all groups. Crying was increased in water-fed newborns relative to both carbohydrate- and formula-fed newborns. Sleeping showed specific patterns of change in all three groups. Sleep duration was increased in the balanced-formula group compared with the water group throughout the observation period. Contrary to the prediction, sleeping duration in carbohydrate-fed newborns never exceeded that of formula-fed newborns; rather, it resembled that of water-fed newborns early in the postprandial period, but formula-fed newborns later. These effects could not easily be explained by potential confounding factors such as handling, volume ingested, caloric intake, or plasma glucose concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Melt grafting of t-butylaminoethyl methacrylate onto polyethylene

The preparation of a polymer containing secondary amino groups by grafting of t-butylaminoethyl methacrylate (t-BAEMA) onto linear low-density polyethylene (LLDPE) in the melt has been investigated. Using a peroxide initiator, the effects of feed composition and reaction time were studied. Materials containing up to 3 wt% grafted t-BAEMA, 5 wt% t-BAEMA homopolymer and displaying minor crosslinking were obtained by the choice of appropriate feed composition and reaction conditions. Attempts were made to increase the degree of grafting and to minimize the homopolymerization by adding a variety of compounds. The homopolymerization was considerably reduced and relatively high grafting efficiency achieved by using p-benzoquinone as a chain terminator. Carbon tetrabromide, a chain transfer agent, suppressed polyethylene crosslinking but decreased grafting and increased homopolymerization. n-Hexane, known to be able to accelerate radiation-induced solution grafting of t-BAEMA onto a PE film, only accelerated t-BAEMA homopolymerization rather than grafting for this peroxide-initiated melt grafting case. Other compounds containing nitrogen, phosphorous or sulphur, known to be chain terminators for maleic anhydride and methyl methacrylate homopolymerization, acted only as inert additives. Preliminary studies on the potential interpolymer melt reaction between this graft polymer and acid polymers are also reported.

Pervaporation of aromatic C 8-isomers

A pervaporation process was applied to the separation of different mixtures of aromatic C 8-isomers using a dense homogeneous polyethylene membrane. The influence of feed temperature and downstream pressure on the flux of pure components was investigated. For mixtures, the effect of feed composition on permeation rates and separation characteristics was determined. Molar fluxes and separation factors depend on the feed composition. Coupled transport occurs and the extent of coupling depends on the difference in the permeabilities of the pure components. p]The mass transport of pure components through the membrane was modelled for varying downstream pressures with diffusivities linearly dependent on the concentration of all the permeants in the membrane. On the basis of this model, molar fluxes of each component in the mixture of ethylbenzene and p-xylene were calculated and compared with the experimental data. The model and experimental data show good agreement.