Effects Of Feed Composition Research Articles

HDS and HDN on SBA-supported RuS2 catalysts promoted by Pt and Ir

Simultaneous hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) reactions over RuS2/SBA and the effect of feed composition and the presence of Pt or Ir in the catalyst formulation have been studied. Activity tests were carried out in a flow reactor under a hydrogen pressure of 3.0MPa and WHSV 32h−1. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption desorption isotherms at −196°C, CO chemisorption, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy of adsorbed CO at low temperature. Characterization results reveal that under the presence of noble metals the dispersion of the RuS2 phase is not affected, the RuS2 coordinatively unsaturated sites (CUS) are in a very sulfided ambient and their population increases; while the noble metals are poorly sulfided and undergo reduction upon reaction. The evaluation of HDN and HDS activity for RuS2/SBA when both (dibenzothiophene) DBT and (quinoline) Q were present in the feed has highlighted the high activity of the RuS2 phase in hydrotreating. The HDS reaction is hardly affected by the presence of Q molecules, with only the hydrogenation (HYD) sites responsible for cyclohexylbenzene (CHB) formation being anyhow altered. HDN results improve in the presence of DBT, even showing high HDN conversion when Q is present in great quantities. These catalytic results strongly suggest that the HDN and HDS reactions must take place on different sites. CO-FTIR spectroscopy results have evidenced that N-containing molecules block the CUS sites responsible for CO adsorption although when S-containing molecules are present, N-containing molecules should be easily transformed since CO-adsorption sites are again available. The addition of small quantities of iridium and platinum to ruthenium sulfide improves the catalytic behavior of the RuS2 catalyst. This is probably due to the greater number of CUS sites and Ir and Pt acting as active hydrogen suppliers. Moreover, these noble metals can act as real active sites where the DBT HDS reaction takes place.

Effect of Natural Gas Composition on the Design of Natural Gas Liquid Demethanizers

The hydrocarbon composition of natural gas varies fairly significantly from location to location. The relative amounts of methane (C1) and ethane (C2) have a profound effect on the cryogenic high-pressure distillation column used to recover the C2 and heavier components as a bottoms product called “natural gas liquid” (NGL). This “demethanizer” column is a complex system that uses compression and expansion to achieve the required low temperatures (190 K) for achieving liquids at the operating pressure of 25 atm. Side-reboilers are used to cool the ambient-temperature natural-gas feed stream and to partially reboil the column. A multiunit heat exchanger network, multiple flash drums, and an expander are used to produce four different liquid and vapor feed streams to the column. This paper studies the effect of feed composition on the design of the demethanizer column. Natural gas feeds with C2 compositions ranging from 5 to 15 mol % are considered. Significant modifications in the design are required as th...

Effect of Feed Composition on the Gas Separation Performance of Binary and Ternary Mixed Matrix Membranes

Binary and ternary component mixed matrix membranes comprised of zeolite 4A and p-nitroaniline (pNA) in the polycarbonate (PC) matrix were prepared and appraised in gas separation. For comparison, homogenous membranes of PC and PC/pNA membranes were also investigated. The membranes were utilized to separate binary mixtures of CO2/CH4, H2/CH4, and CO2/N2. The effect of feed composition on the separation performance of membranes was investigated. Separation factors and ideal selectivities were similar for the PC membrane. A similar trend was also observed with the PC/pNA membrane. The separation factors of the PC/pNA membrane for CO2/CH4 were almost twice as high as those of the PC membrane regardless of the feed composition. The ideal selectivities were, however, higher than separation factors for PC/zeolite 4A and PC/pNA/zeolite 4A membranes. The PC/ pNA/zeolite 4A membrane has separation factors of 18 for 77% CO2/ 23% CH4 mixture, and 40 for 20% CO2/ 80% CH4 mixture, respectively. The separation factors of the mixed matrix membranes depended on the feed composition strongly. The PC/ pNA/zeolite 4A membrane had higher separation factors and lower permeabilities than the PC/zeolite 4A membrane. pNA assisted to eradicate partly the detrimental effects of interfacial voids and improved the molecular sieving effect of zeolite 4A dispersed in the PC.

Pervaporation performance of composite poly(dimethyl siloxane) membrane for butanol recovery from model solutions

Butanol has potential to become an important renewable transportation fuel and feedstock chemical in the future. However, low yield and high separation costs are the main obstacles in feasible industrial scale biobutanol production by the acetone–butanol–ethanol (ABE) fermentation process. Both problems can be overcome by using pervaporation as the product removal technique. The performance of a polydimethylsiloxane (PDMS) membrane with a support layer of polyacrylonitrile (PAN) was studied for the removal of acetone, butanol and ethanol from dilute aqueous model solutions. The effect of feed composition on permeation fluxes, permeances, separation factors and pervaporation separation indices was investigated by using binary aqueous solutions of acetone, butanol and ethanol followed by experiments with different aqueous ternary mixtures and quaternary ABE–water mixture. At feed temperature of 42°C, partial fluxes and permeate concentrations were found to be in the order of acetone≈butanol>ethanol, while the permeance order was butanol>ethanol≈acetone. Separation factors were in the range of 21–26, 22–29 and 5–7 for acetone, butanol and ethanol, respectively. Results indicate that the tested membrane has potential to be used in the ABE fermentation process.

Dry Reforming of Methane by DC Spark Discharge with a Rotating Electrode

A novel type of plasma reactor having a rotating electrode is proposed for CO2 reforming of methane without catalyst at room temperature and atmospheric pressure. Results indicated that employing rotating ground electrode leads to a stable discharge for any period of time. Effects of feed composition, feed flow rate, applied power and electrodes separation on the carbon dioxide and methane conversions as well as the products selectivity were investigated. Increasing CO2/CH4 molar ratio in the feed favors the reagents conversion and consequently promotes the formation of hydrogen and carbon monoxide. If the target product is hydrogen, it is proposed to operate the reactor at CO2/CH4 = 1 molar ratio and if the target product is carbon monoxide then CO2/CH4 = 3 molar ratio is the preferred option for feed composition. This reactor system has advantages of stable operation and high conversion ability. Also, the obtained syngas with flexible molar ratio of H2 to CO is suitable for vast industrial applications.

Effects of CNTs Content on Physicochemical and Pervaporation Separation Properties of PVA Membranes

In this study, the morphological and separation characteristics of PVA membranes incorporated with functionalized CNTs are reported. CNTs was extensively characterized using TGA, FESEM, and TEM. The physicochemical properties of PVA-CNTs membranes were characterized using FESEM, tensile test, DSC, and XRD. DSC measurements showed an increase in melting and glass transition temperature, implying enhancement of polymer chains compacting. XRD analysis confirmed the results of DSC and showed that CNTs can promote crystallinity of the PVA membranes. In addition, tensile measurements revealed that incorporating CNTs into the PVA membranes improves their mechanical properties. The synthesized nanocomposite membranes were then evaluated in pervaporation (PV) dehydration of isopropanol (IPA). The separation results showed that incorporating CNTs into the PVA membranes significantly increases water selectivity of the PVA membranes. This can be attributed to the fact that incorporating CNTs compacts and rigidifies PVA matrix and decreases its free volume. Furthermore, permeation of water molecules through the nanocomposite membranes decrease as a result of the polymer chains rigidification. Effects of feed composition and temperature on PVA-CNTs nanocomposite membranes were investigated. Besides, effects of CNTs content on permeation properties and activation energies of PVA membranes were evaluated.

Effects of feed intake on enteric methane emissions from sheep fed fresh white clover (Trifolium repens) and perennial ryegrass (Lolium perenne) forages

Published analyses of enteric methane (CH4) emissions from sheep and cattle show an inverse relationship between feed intake and CH4 yield (gCH4/kg dry matter (DM) intake), which suggests opportunities for reducing CH4 emissions from feed eaten and per unit of animal production. Most relationships between feed intake and CH4 yield have been based on animals fed conserved feeds, especially silages and grains. Our research is a series of experiments with fresh white clover (Trifolium repens) and perennial ryegrass (Lolium perenne; ryegrass) forages fed to sheep at a range of feed intake levels. This study was comprised of four experiments where good quality freshly harvested white clover or ryegrass were fed to sheep over a three-fold range in DM intake, and CH4 emissions were measured in respiration chambers for two consecutive days in each experiment. Measurements were made from 16 sheep in Experiment 1 (fed at 1.6×metabolizable energy requirements for maintenance; MEm), 28 sheep in Experiment 2 (at 0.8 and 2.0×MEm), eight sheep and two measurement periods in Experiment 3 (at 1.6×MEm), and 30 sheep in Experiment 4 (fed at 0.8, 1.2, 1.6, 2.0 and 2.5×MEm). Prior to each experiment, sheep had a 10d acclimatization period to diets. Apparent digestibility was measured over 7d from sheep in Experiments 1, 3 and 4, along with collection of rumen digesta for volatile fatty acid (VFA) determination. Although CH4 yields differed when sheep were fed white clover or ryegrass at similar intakes, the differences were inconsistent and mean values similar across all experiments. This, and a similar structure of all experiments, enabled combined analysis of data from all four experiments using the restricted maximum likelihood (REML) procedure to estimate effects of feed intake level on digestibility, digestible nutrient intake, gas emissions, and VFA concentrations in the rumen. The REML analysis showed that when DM intake increased from 0.40 to 1.60kg/d, the predicted responses were an increase in CH4 production (g/d) of 187% (12.4–35.6g/d; P<0.001), and a decline in CH4 yield of 21% (25.6–20.2g/kg DM intake; P<0.001). High feed intake levels were associated with increased molar proportions (mM of total VFA) of propionate from 0.17 to 0.21 (P=0.038). Single and multiple regressions were completed on the data from all experiments, with organic matter (OM) intake predicting 0.87 of the variation in CH4 production, and molar proportion of propionate predicting 0.60 of the variation in CH4 yield. Increasing feed intakes by 1kg/d of DM reduced CH4 yield by 4.5g/kg DM intake. Plant chemical composition was weakly related to CH4 yield. High intakes of fresh forages will lower CH4 yield from fermentation, but effects of feed composition on CH4 emissions were minor. The interaction between effects of feed intake and rumen function requires further investigation to understand relationships with CH4 emissions.

Multidisciplinary analytical investigation of phospholipids and triglycerides in offshore farmed gilthead sea bream (Sparus aurata) fed commercial diets

In this work, a quantitative characterisation of lipid (both triglycerides and phospholipids) rearrangements in the muscle of offshore-raised gilthead sea bream was carried out as a function of fish growth between April and September. Relative percentages of lipid classes and fatty acids/acyls composition of the commercial feeds and fish dorsal muscles were assessed by means of an interdisciplinary analytical approach. A combination of preparative chemistry and experimental results from NMR spectroscopy, GC, 3D-TLC as well as proximate analysis permitted the observed growth parameters in key metabolic events to be linked with fish fattening and lipid turnover. While defined effects of feed composition on fatty acid profiles of fillets were ascertained, the relative increase of fatty acyls in triglycerides and phospholipids were also estimated enabling detailed evaluation of TAG:PL ratio in adult offshore-farmed gilthead sea bream. NMR was also used to quantify PUFA regiospecific distribution in TAG and PL.

Effect of Operating Conditions on PV Performance of PVA Membranes: Experimental and Neural Network Modeling

Poly (vinyl alcohol) membranes were prepared by in-situ crosslinking of poly(vinyl alcohol) with glutaraldehyde as crosslinking agent and hydrochloric acid as catalyst and used for dehydration of IPA mixtures. Effects of feed composition, operating temperature, vacuum pressure, and Reynolds number on the permeation performance of the membranes were evaluated. Eighty-nine experimental data was applied to investigate ANN modeling. A multi layered feedforward neural network was applied to model the PV membranes. Two major training algorithms and optimum number of neurons and layers were investigated. As a result, Bayesian regularization successfully predicted experimental data. Different network structures were optimized, using multi object genetic optimization algorithm. The results concluded that the network with structure composing two hidden layers performs better than the other with one hidden layer, and also there is an excellent compatibility between the experimental data and the predicted values of optimum network structure (4:3:2:2). Furthermore, the optimum network was applied to predict extrapolation data and the results showed that this network can extrapolate data as well as interpolating.

Some functional properties of extruded acha/soybean blends using response surface analysis

The feed, comprising of acha flour and raw full fat soybean flour were mixed in ratios of 0:100, 12.5:87.5, 25:75, 37.5:62.5 and 50:50 of soybean flour to acha flour. The feed moisture content was adjusted to 15, 20, 25, 30 and 35% levels. Extrusion was carried out in a laboratory single screw extruder with variable screws and heaters following a 4K central composite (CCD) rotatable and nearly orthogonal design that required 36 extrusion runs. The extruder screw speed was varied at 90, 120, 150, 180 and 210 rpm while the extruder barrel temperature was adjusted to 100, 125, 150, 175 and 200°C. Effects of feed composition (FC), feed moisture content (FMC), extruder screw speed (SS) and extruder barrel temperature (TP) on extrudate bulk density (BD), browning index (BI) and expansion ratio (ER), were evaluated. Results showed that the BD ranged from 1.39 to 9.48 g/m3 while the BI ranged from 0.60 to 5.72. Extrudate expansion ratio ranged from 2.75 to 6.80. The 2nd order polynomial was adequate in modeling the dependence of BD, ER and BI on the extrusion variables. The cross product effects of the process variables had significant (P ≤ 0.05) effects on BD and BI, while the quadratic effect of feed composition had the greatest (P ≤ 0.00) effect on the expansion ratio. Predicted values were very close to the experimental values, making the model ideal for prediction of the dependence of the extrudate functional properties on the extrusion variables. Key words: Blends, acha, soybeans, response surface, extrusion.

Semicontinuous heterophase copolymerization of styrene and acrylonitrile

The synthesis of styrene-acrylonitrile copolymers by semicontinuous heterophase polymerization is reported here. The effect of feed composition at a fixed addition rate of monomer mixture on kinetics, particle size, polymer content, and molar masses, was studied. This process permits the synthesis of nanolatexes containing narrow size-distribution particles with number-average diameter (Dn) of about 18 nm, polymer content as high as 23 wt %, and copolymer-to-surfactant weight ratios between 23 and 25, depending on monomer feeding rate, which are larger than those reported for microemulsion copolymerization of several comonomers. Copolymers with homogeneous composition similar to the feeding monomers composition were obtained thorough the reaction, which is difficult to achieve by batch polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Cross-flow ultrafiltration of protein solutions through unmodified and surface functionalized polyethersulfone membranes – Effect of process conditions on separation performance

In the present work, polyethersulfone ultrafiltration membranes were UV-initiated grafted with poly(ethylene glycol) methacrylate by varying the UV irradiation dose. The flux and selectivity performance of the prepared low-fouling thin-layer hydrogel composite membranes were tested in cross-flow filtration experiments and compared to unmodified commercial membranes with similar properties (water permeability and molecular weight cut-off). Here, the effects of feed composition (single proteins and protein mixtures), pH and cross-flow velocity were evaluated. Furthermore, the stability of these membranes was tested during three cycles of ultrafiltration and cleaning. The results showed that the performed surface hydrophilization increased the permeate flux and stabilized the membrane selectivity (relevant for separation of protein mixtures). The proteins charge was still important for flux and rejection during ultrafiltration with functionalized membranes. Increasing cross-flow velocity was more efficient for these membranes, since fouling effects were minimized by the grafted hydrogel layer. Furthermore, the membrane stability after three cycles of ultrafiltration and chemical cleaning at pH=13 was proven and the cleanability of the hydrogel composite ultrafiltration membranes was much better compared to that of comparable unmodified polyethersulfone ultrafiltration membranes.

Molecular simulation study of polyurethane membranes

Structural, physical and separation properties of polyurethane membrane were investigated by configuration bias grand canonical Monte Carlo and molecular dynamic methods and the effects of degree of polymerization on these properties were studied. To understand the effect of degree of polymerization of polyurethane membrane on its separation property, the adsorption of furfural as pure and binary mixture with water was studied for polyurethane membrane with varied degrees of polymerization from 5 to 100. The temperature range for simulation calculation was 298 K–360 K and the pressure range was 0–10 bar. Also the effects of feed composition, density and free volume of polyurethane membrane on its separation property were studied. It was found that the adsorption of furfural and water in polyurethane membrane depends on free volume of polyurethane and this dependency is more significant for the adsorption of water molecule. The results indicate that the maximum adsorption of furfural and water occurs on polyurethane membrane with polymerization degree of 10.

System Parameters and Product Properties Responses During Extrusion of Fura from Millet-Soybean Mixtures

A three-factor, three-level central composite rotatable composite design (CCRD) was adopted to study the effect of feed composition (X1), feed moisture content (X2) and screw speed (X3) on the system parameters (torque, pressure, and specific mechanical energy) and fura extrudate properties (expansion ratio and bulk density) from blends of pearl millet and soybean flour mixtures. The torque was influenced negatively but significantly (p Feed Moisture (X2) > Screw Speed (X3). Response variables predicted with model equations under optimum conditions were in general agreement with experimental data. The data obtained from the study could be used for control of product characteristics and possible projection for the commercial production of fura.

Formaldehyde biodegradation using an immobilized bed aerobic bioreactor with pumice stone as a support

The objective of this study is the investigation of formaldehyde degradation in a bioreactor with pumice stone as a support. The reactor was tested at different synthetic wastewater concentrations with total COD of 500, 1000 and 1500 mg/L, respectively, at 24 h hydraulic retention time. The effect of feed composition was tested by changing the CODT/CODFA ratio in order to analyze the impact of formaldehyde concentration. The average formaldehyde and COD removal efficiencies obtained in the reactor were 97.1% and 88%, respectively. The maximum COD and formaldehyde removal efficiencies occurred at the CODT/CODF of 4/1 at CODT=1000mg/L. The effect of toxic shock on reactor performance was examined; the reactor has good resistance against a sudden increase in formaldehyde concentration. The formaldehyde concentration threshold at which toxic effects severely inhibited the biological process was 1370 ppm. So a fixed film bioreactor packed with pumice stone could be recommended for the treatment of formaldehyde-containing wastewater.

Effects of Sorption Enhancement and Isobutene Formation on Etherification of Glycerol with tert-Butyl Alcohol in a Flow Reactor

In the presented work, liquid phase etherification reaction of glycerol (G) with tert-butyl alcohol (TBA) was investigated in a continuous flow reactor using Amberlyst-15 (A-15) as the catalyst. Some experiments were also repeated in a batch reactor at autogenous pressure. Effects of feed composition, reaction temperature (70–110 °C), and reaction pressure (1–5 bar) on the product distribution were investigated. When flow reactor pressure was reduced from 5 to 1 bar, enhanced glycerol conversion and isobutene formation were observed. Conversion of glycerol reached 66% at 110 °C, at a space time of 18 s·g·cm–3. However, batch reactor results indicated glycerol conversion values over 90% with diether selectivity of about 36% at much longer reaction times, over 400 min. Results indicated significance of equilibrium limitations, which initiated the idea of performing sorption enhanced reaction experiments in the flow reactor using Zeolite 4A and 5A as water adsorbents. Results of these sorption enhanced react...

Recovery of alcohols from water using polydimethylsiloxane–silica nanocomposite membranes: Characterization and pervaporation performance

AbstractDifferent polydimethylsiloxane (PDMS) nanocomposite membranes were synthesized by incorporating various contents of nanosized silica particles to improve the PDMS pervaporation (PV) performance. A uniform dispersion of silica nanoparticles in the PDMS membranes was obtained. The nanocomposite membranes were characterized morphologically by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results showed that surface roughness increases by incorporating silica, and this decreases absorption of penetrants on the membrane. Swelling studies showed that the presence of silica nanoparticles into the PDMS membranes decreases degree of swelling, which can be attributed to rigidification of the PDMS matrix. Additionally, the results revealed that helium permeability decreases through the nanocomposite membranes, due to the more polymer chains packing. Effects of silica on recovery of isopropanol (IPA) from water mixtures were also investigated. Based on the results, incorporating silica nanoparticles promotes significantly the PDMS membrane selectivity because the polymer chains are rigidified and also the polymer free volume decreases. However, permeation flux decreases as diffusion of the penetrants reduces in the presence of silica nanoparticles within the PDMS membranes. As PV performance depends on operating conditions, effects of feed composition, and temperature were also studied. Moreover, recoveries of IPA, ethanol, and methanol from water mixtures were compared using the PDMS‐silica nanocomposite membranes. The results demonstrated that polarity and solubility of alcohols affect permeation flux and selectivity resulting in the higher permeation flux and selectivity for IPA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Hydrogen Storage in a Recyclable Organic Hydride: Kinetic Modeling of Methylcyclohexane Dehydrogenation Over 1.0 wt% Pt/θ-Al2O3

The methylcyclohexane-toluene-hydrogen system is a potential solution for the implementation of a successful hydrogen economy. The dehydrogenation reaction, the backbone of the methylcyclohexane-toluene-hydrogen system, is studied over 1.0 wt% Pt/θ-Al2O3. Experiments were performed in a 1.02-cm internal diameter fixed-bed reactor. The effects of feed composition, temperature, space velocity, and pressure on conversion of methylcyclohexane were studied. An enhancement in the rate is observed with the addition of hydrogen in the feed. Both the power law kinetics and Langmuir-Hinshelwood-Hougen-Watson kinetics were employed to best fit the experimental data. Langmuir-Hinshelwood-Hougen-Watson kinetics based on single-site surface reaction kinetics were found to be appropriate to the experimental data.

Catalytic NO x removal by single-wall carbon nanotube-supported Rh nanoparticles

Single-wall carbon nanotubes functionalized with polyethylene glycol and doped with Rh nanoparticles were prepared and tested as catalyst for NO x reduction. Gravimetric adsorption studies were employed to elucidate the mechanism of NO adsorption on the active surface sites and to determine the onset of the desorption of oxygen. These studies provided information about the reaction kinetics and the lifetime of the catalyst, as well as the NO scission onset temperature and abatement rate, thus making possible to predict the conversion and define the optimum reaction conditions for efficient NO removal. Catalytic experiments were performed under different operating conditions and feed compositions, such as under rich operation, in presence of oxygen, and in presence of reducing CO and hydrocarbons. The developed nanostructured catalyst exhibits enhanced activity at lower temperatures in comparison to that reported for other Rh-based catalytic systems, while data about feed composition effects and carbon support depletion provided operating conditions that suppress N 2O formation and extent the catalyst lifetime.

Effects of Feed Composition and Feed Impurities in the Catalytic Conversion of Syngas to Higher Alcohols over Alkali-Promoted Cobalt–Molybdenum Sulfide

Alkali-promoted cobalt–molybdenum sulfide is a potential catalyst for the conversion of syngas into higher alcohols. This work is an investigation of how the feed composition influences the behavior of the sulfide catalyst. In a sulfur-free syngas the production of higher alcohols is observed to be optimal with an equimolar mixture of CO and H2 in the feed, while the methanol production benefits from an increasing hydrogen content in the feed. The influence of NH3 and H2O in the syngas feed has also been investigated. Ammonia (741 ppmv) in the feed is observed to cause a general and largely reversible deactivation of the catalyst. Operation with elevated water levels in the syngas feed (4.7–13.4 mol %) is observed to cause a deactivation of the catalyst, and it is especially the chain growth that is affected.