Increasing Catalyst Concentration Research Articles

CFD simulation of a pilot scale slurry photocatalytic reactor and design of multiple-lamp reactors

The hydrodynamics behaviour and radiation transport occurring inside a pilot-scale slurry photocatalytic reactor (treating real shower water) with large diameter was investigated using computational fluid dynamics (CFD). The multiphase flow system was solved using a granular Eulerian model while the solution of the radiative transport equation (RTE) was solved using the finite volume based discrete ordinate model (DOM). Multiphase simulation showed recirculation zones caused by the high slurry inlet velocity. Due to the rapid attenuation of light occurring radially within the reactor, regions of varying reaction orders exist, i.e., half order reaction close to the lamp and first order reaction further from the lamp, as the incident radiation goes below a certain value. A rate equation relating pollutant degradation to the rate occurring in the half and first order reaction regions (in terms of local volumetric rate of energy absorption – LVREA) was proposed. Using a value of 225Wm−2 as the minimum incident light intensity at which half order reactions take place, a Pearson correlation of 0.88 between simulated and experimental data indicated that the proposed model satisfactorily described the experimental observations. Next, simulations performed with a system of multiple lamps (2 and 4 lamps) at different geometrical arrangements (i.e. with the lamps separated by the distance Xlamp) showed that within the range of catalyst concentration investigated, the maximum potential increases in reaction rate was 56% and 123% when using 2 and 4 lamps (at optimum lamp arrangement) respectively, as compared to using one lamp. The increase in reaction rate occurred due to the maximisation of incident radiation contours at which first order reactions take place. The optimum lamp separation was dependent on the catalyst concentration in the wastewater and decreased with increasing catalyst concentration.

Gelation and Cross-Linking in Multifunctional Thiol and Multifunctional Acrylate Systems Involving an in Situ Comonomer Catalyst

Dynamic rheology in combination with Fourier transform infrared spectroscopy (FTIR) is used to examine the gelation kinetics, mechanism, and gel point of novel thiol–acrylate systems containing varying concentrations of an in situ catalyst. Gelation, as evidenced from the gel time determined using the Winter–Chambon criterion, is found to occur more quickly with increasing catalyst concentration up until a critical catalyst concentration of 22 mol %, whereupon the gel time lengthens. Such a minimum in gel time may be attributed to changes in the number of available reaction sites and percentage conversion required for gelation. Chemical conversions at the gel point measured for representative samples are consistent with theoretical values calculated using Flory–Stockmayer’s statistical approach, confirming our hypothesis. Relaxation exponents of 0.97 and fractal dimensions of 1.3 are calculated for all samples, consistent with coarse-grained discontinuous molecular dynamics (DMD) simulations. The elevated...

Effective Parameters on Biodiesel Production from Feather fat oil as a Cost-Effective Feedstock

Using low-cost feedstocks such as rendered animal fats in biodiesel production willreducebiodieselexpenditures. One of the low-cost feedstocksfor biodiesel production could be the fatextracted from poultry feathers producedin slaughterhouses abundantly. This paper describes a new andenvironmentally friendly process for developing biodiesel production technology from feather waste producedin poultry industry. In this research the crude oil of poultry feather fat was extracted by soxhlet method using hexane as a solvent. The data resulted from gas chromatography (GC) revealed these percentages for fatty acid compositions: myristic acid (3%), palmitic acid (30%), stearic acid (22%), oleic acid (8.1%), linoleic acid (3%) and arachidonic acid (7%).In this experimental research, the effects of some parameters such as alcohol to oil molar ratio (4:1,6:1, 8:1), catalyst concentration (0.75,1 and 1.25% w/w) and the transesterification reaction time(40,60 and80min) on the percentage offatty acids conversioninto methyl ester(biodiesel) are studied. The results show increasing catalyst concentration up to 1% causes the oil to biodiesel conversion percentage having an upward trend and then adownward trend byincreasing catalyst concentration up to 1.25%. With increasing molar ratio from 4:1 to 6:1 and then 8:1, oil to biodiesel conversion percentage increased16% and2%, respectively. Ultimatelythe optimum point defined by response surface method (RSM) forproducing biodiesel from feather fat is calculated catalyst concentration of 1 wt%, 7.24:1 molar ratio and in 75 minutes resulting in conversion percentage of97.62%.

Solar photocatalysis: A green technology for E. coli contaminated water disinfection. Effect of concentration and different types of suspended catalyst

Photocatalytic and photolytic disinfection of Escherichia coli in water was studied under natural sunlight using different types of photocatalyst (TiO2 P-25, PC500, Ruana and Bi2WO6) at different concentrations. The solar photo-inactivation yielded complete inactivation results, which varied with the solar light intensity. Meanwhile, dark control samples in the lab (temperature constant at 25 °C) remained at constant concentration and dark samples outside laboratory showed a decrease due to the mild solar heating occurred during the experiments. The adding of any kind of photo-catalyst to the water accelerated the bactericidal action of solar irradiation and led to complete disinfection (until detection limit). The photocatalytic disinfection efficiency was not enhanced by the increase of catalyst concentration above 0.5 g/L for P-25, PC500 and Bi2WO6, where about 106 CFU/mL were completely inactivated within 5 min, 30 min and more than 150 min of solar exposure under clear sky, respectively. An increase of the concentration to 1 g/L slightly decreased the total inactivation time. Rutile (Ruana) catalyst behaves differently, optimal concentration was lower than for the other titania materials; agglomeration of particles occurred as the concentration of catalyst increases. Durability of photocatalytic treatment and chemicals analyses of inorganic anions and cations have also been investigated.

Degradation of Humic Acid by Photocatalytic Reaction Using Nano-sized ZnO/Laponite Composite (NZLC)

Humic acids (HA) are known as the precursors of carcinogenic compounds formed by the disinfection of drinking water. While conventional treatments were found to be inefficient HA removal processes in drinking water, advanced oxidation processes have been proven to have a significant effect in the treatment of HA. The degradation of HA was investigated using nano-sized zinc oxide (ZnO)/laponite composite (NZLC). The reactions occurred in a UVC reactor by considering following variables: pH, initial HA concentration, catalyst loading, addition of hydrogen peroxide (H2O2), and catalyst reuse. Water samples containing HA were analysed by ultraviolet/visible spectrophotometer and high-performance size-exclusion chromatography. Initial HA concentrations were tested by the Langmuir–Hinshelwood model with k and K ads values, determined to be 0.126 mg/L.min and 0.0257 L/mg, respectively. The change in pH affected the HA degradation efficiency by the photocatalytic activity where it was higher under acidic conditions rather than alkaline ones. Optimal catalyst loading was proved to be a constrained factor in influencing the photocatalytic efficiency: the increase of catalyst concentration enhanced the HA decomposition efficiency up to an optimum value of 20 g/L, where there was no further degradation with excess loading. The addition of H2O2 was investigated through homogenous and heterogeneous photocatalysis, and, heterogeneous photocatalysis showed higher removal efficiency due to the combined effect of both catalysts and H2O2. Finally, NZLC was effective for reuse and exhibited an excellent stability after six times of usage.

Hydrocracking of Maya crude oil in a slurry-phase reactor. I. Effect of reaction temperature

The effect of reaction temperature in the hydrocracking of Maya crude oil using a slurry-phase reactor was studied. The results indicate that the product distribution is clearly affected by the reaction temperature. In general, the transformation of heavy Maya crude oil into lower fractions follows a parallel-consecutive reaction scheme where vacuum residue converts to smaller fractions, and these fractions in turn, in a consecutive reaction path, are transformed to even lower liquid fractions and gases. Naphtha is the main product and does not seem to contribute significantly to the formation of gases. Solids appear to be formed by two main contributions: coke formation induced by thermal cracking, and precipitation of asphaltenes and other polycondensed aromatics. The precipitation of solids also seems to induce the elimination of sulfur and nitrogen compounds presents in the liquid phase. Increasing catalyst concentration from 300ppm Mo to 1000ppm Mo decreases the amounts of solid and gases, and increases liquid yield.

Enhancement of Esterification Reaction between Ethanol and Sulphuric Acid Using Ionic Liquids

Experiments were conducted in a batch reactor under isothermal conditions to study the enhancement of the esterification reaction between ethanol and sulphuric acid with ionic liquid as catalyst. The three catalysts used for the study were 1-butyl 3-methylimidazolium octyl sulphate, 1-ethyl 3-methylimidazolium octyl sulphate and 1-butyl 3-methylimidazolium methyl sulphate. The effect of reaction temperature, catalyst concentration and type of catalyst on conversion of the reactant was studied to obtain the kinetics of the reaction. The conversion levels increased with increasing catalyst concentration and decreased with increasing reaction temperature in the temperature range investigated. The rate data fitted first-order kinetics at high concentrations of the reactant and zero-order kinetics at low concentrations of the reactant, thus exhibiting shifting order-type kinetics. The proposed reaction mechanism suggested the possibility of splitting of the ionic liquid before participating in the reaction.

Pesticide removal from water suspension by UV/TiO2 process: a parametric study

Linuron is a phenylurea herbicide which is generally used for eliminating various herbs. The advanced oxidation processes represent a promising alternative technology for the destruction of pesticides contained in wastewater. In this present work, the degradation of linuron is performed using a helical photochemical reactor. The UV lamp (HPA 18 W/S with a monochromatic radiation at 365nm and a nominal power of 18 W) is set in axial position in the open space of the sheath. The experimental results showed that the photodegradation of linuron increased significantly compared with adsorption and photolysis. The parametric study of the pollutant oxidation showed that an increase in the initial concentration of catalyst (0.1–0.8 g/L) revealed the existence of an optimum for 0.3 g/L where the oxidation was complete after 4 h of radiation exposure. The best degradation of linuron was obtained at an optimum flowrate of 396 mL/min, where 98% of herbicide was oxidized after 4 h of UV illumination. Results showed also that the presence of hydrogen peroxide (an electron acceptor), acids or bases disadvantaged the photocatalytic process. Removal of linuron increased at low pH (3 and 5 adjusted along the photodegradation), where 93% was oxidized. Photodegradation of linuron process accords well with Langmuir–Hinshelwood pseudo-first-order kinetics.

Degradation of flumequine by photocatalysis and evaluation of antimicrobial activity

This study evaluated the efficiencies of advanced oxidation processes (UV/TiO2 and UV/TiO2/H2O2) for the flumequine degradation, an antimicrobial and emergent pollutant. The photocatalytic process was capable of degrading approximately 55% of the drug after 15min of reaction using 0.31mmolL−1 TiO2 in suspension; the addition of H2O2 (0.5mmolL−1) increased flumequine degradation to 81.6%. For UV/TiO2, increasing catalyst concentration (0.08–0.62mmolL−1) corresponded to an increase in the degradation efficiency. Using mass spectrometry, it was possible to identify five putative byproducts formed during the advanced oxidation processes. Due to the risks of bacterial resistance, the antimicrobial activity of the treated solutions was evaluated and compared to an untreated solution. Residual antimicrobial activity was detected after 15min of reaction in all of the evaluated conditions. The antimicrobial activity was considerably reduced by the photocatalytic processes (UV/TiO2 and UV/TiO2/H2O2) throughout the reaction.

Study of MoS2 Catalyst Recycle in Slurry-Phase Residue Hydroconversion

A study of MoS2 catalyst recycle during slurry-phase hydroconversion of residue oil, under high hydroconversion conditions, is reported. Different concentrations of MoS2 (100, 300, 600, and 1800 ppm Mo derived from Mo-micelle and Mo-octoate precursors) were investigated in a semibatch stirred reactor. Catalyst recycle was simulated by reusing the solid coke-catalyst recovered from the reactor in subsequent experiments. The process was repeated several times until the catalyst deactivated. The recycled catalyst had a very similar activity to the fresh catalyst in the early stages of recycling. Experimental results showed that with increased catalyst concentration, an increased number of catalyst recycles with acceptable coke yield ( 80 wt %) were possible before deactivation was observed. At an initial concentration of 600 ppm Mo (using both Mo-micelle and Mo-octoate precursors), the catalysts were recycled 3 times without any significant lo...

Catalytic pyrolysis of Phragmites (reed): Investigation of its potential as a biomass feedstock

In this paper, thermogravimetry, TG, and pyrolysis are used for the thermochemical evaluation of the common reed (Pragmites australis) as a candidate biomass feedstock. The TG analysis indicated that the material loses 4% of its weight below 150°C through dehydration. The main decomposition reaction occurs between 200 and 390°C. The rate of weight loss, represented by the derivative thermogravimetric, DTG, signal indicated a multi-step reaction. Kinetic analysis helped in the resolution of the temperature ranges of the overlapping steps. The first step corresponds to the degradation of the hemi-cellulosic fraction and the second to the cellulosic fraction degradation. The TG and DTG signals of reed samples treated with increasing concentration of potassium carbonate (0.6–10wt%) indicated a catalytic effect of the salt on reed decomposition. The temperature of maximum weight loss rate, DTGmax, exponentially decreased with increasing catalyst content, whilst the initial temperature of the decomposition decreased linearly. The pyrolysis studies were carried out in a Pyrex vertical reactor with sintered glass disc to hold the sample and to aid the fluidization with the nitrogen stream flowing upwards. The reactor was connected to a cyclone and condenser and a gas sampling device. Tar and char are collected and weighed. The gas chromatographic analysis of the evolved gases demonstrated the effect of pyrolysis temperature (400, 450, and 500°C) on their composition. The temperature increase favors the yields of hydrocarbons, carbon monoxide and hydrogen at the expense of methanol and carbon dioxide. Similarly, reed samples treated with K2CO3 at 10wt% were pyrolyzed and analyzed. Comparisons for the various parameters (yields, gas composition and carbon–hydrogen recovery) between the untreated and catalyzed reed conversion were also made.

Effect of ozonation combined with heterogeneous catalysts and ultraviolet radiation on recycling of gas-station wastewater

Ozonation is extensively applied in the treatment of drinking water and wastewater due to the powerful oxidation potential of ozone. Heterogeneous catalytic ozonation (HCO) of wastewater proceeds through hydroxyl radicals as the oxidation species. The effect of ozonation alone and combined with catalysts in the presence and absence of UV-radiation was investigated to reuse the biologically pretreated gas-station wastewater instead of fresh water. Two types of catalysts: titanium dioxide (TiO2) and activated carbon (AC) were studied. The concentration of catalyst, dark adsorption, reaction time and the improvement of biodegradability were studied. The combination of catalysts and ozonation reveals a significant improvement in the removal of contaminants present in wastewater by using the ozonation, adsorption or photocatalysis systems. Maximum dissolved organic carbon (DOC) removal of 91% was achieved by the combination of ozone, TiO2 and the UV-radiation system. But, an increase in biodegradability from 0.12 to 0.33 was realised with ozone and the TiO2 system. Furthermore, the biodegradability was increased with increasing catalyst concentration combined with ozone up to 1g/L with TiO2 and 0.5g/L with AC.

The Amount Effect of Catalyst on the Urethane Reaction of 1,2-Propanediol in Xylene

The urethane reaction kinetics of 1,2-propanediol with phenyl isocyanate is monitored with in-situ FT-IR with xylene as solvent. Triethylamine is used as catalyst and its amount effect is investigated. Rate constants for the reaction with different concentrations of triethylamine are worked out. The urethane reaction has been found to be a second order reaction and the reaction is largely accelerated with the increase of catalyst concentration. Furthermore, when triethylamine is used as catalyst, the rate constants are different between initial stage and final stage, which belong to different hydroxyls in 1,2-propanediol. However, the rate constant is the same when there is no catalyst, which shows no reactivity difference for hydroxyls in 1,2-propanediol.

The Amount Effect of Catalyst on the Urethane Reaction of 1,2-Propanediol in Xylene

The urethane reaction kinetics of 1,2-propanediol with phenyl isocyanate is monitored with in-situ FT-IR with xylene as solvent. Triethylamine is used as catalyst and its amount effect is investigated. Rate constants for the reaction with different concentrations of triethylamine are worked out. The urethane reaction has been found to be a second order reaction and the reaction is largely accelerated with the increase of catalyst concentration. Furthermore, when triethylamine is used as catalyst, the rate constants are different between initial stage and final stage, which belong to different hydroxyls in 1,2-propanediol. However, the rate constant is the same when there is no catalyst, which shows no reactivity difference for hydroxyls in 1,2-propanediol.

Photoinitator surface segregation induced instabilities from polymerization of a liquid coating on a rigid substrate

Periodic wrinkled surfaces have generated significant interest over the past decade as these structures can be easily fabricated over large areas with minimal fabrication cost, but these structures have generally been limited to thin films on soft elastomeric substrates, which limits their general applicability and utility. Here we present a simple methodology to generate wrinkled surfaces on rigid substrates by surface segregation of a photocatalyst. Upon ultraviolet light (UV) induced photopolymerization, increased catalyst concentration yields a cross-linked layer at the free surface that is supported on top of a more liquid-like bulk film due to differences in polymerization rate. Further polymerization of the underlayer provides the requisite mechanical stress (contraction due to polymerization) to create a wrinkled pattern. A system based upon the renewable monomer, furfuryl alcohol, that is cross-linked with a photoacid generator, triphenyl sulfonium triflate, is utilized to illustrate this concept. Moreover, the polymerized furfuryl alcohol can be transformed into amorphous carbon by heating at elevated temperatures in an inert environment. The role of photoacid generator concentration and substrate temperature on the wrinkle formation and morphology is presented. Finally, exposure through a simple mask can generate hierarchical structures with the wrinkled structure conforming to the geometric constraints of the photopatterned area, including curvilinear structures. This photocatalyzed surface segregation-based methodology provides a promising route to the facile fabrication of microstructured surfaces based upon the wrinkling instability.

Metathesis hydrogenation of natural rubber latex

Metathesis hydrogenation of deproteinized natural rubber (NR) latex was studied using 2nd generation Grubbs catalyst. More than 97% hydrogenation was achieved under mild conditions and without organic solvent addition other than that used to dissolve the catalyst. The olefin conversion plot exhibited an S-curve characteristic which indicated the effect of competition between the metathesis reaction and the hydrogenation reaction. Molecular weight of NR dramatically changed along the reaction time in the first region due to the metathesis reaction and then slightly changed in the second region where the hydrogenation consumption plot obeyed a first-order kinetic model. The kinetic behavior of the hydrogenation region increased with an increase in catalyst concentration and hydrogen pressure. The results showed an inverse behavior with an increase in rubber concentration. The apparent activation energy over the temperature range of 80–96 °C for the hydrogenation of metathesized natural rubber was found to be approximately 169 kJ/mol.

Effects of CuCl Source and Content on Direct Synthesis of Triethoxysilane from Silicon and Ethanol

Effect of CuCl source and content on formation of triethoxysilane in the direct process is described and discussed. The two sources of CuCl and the contact masses from the reduction reaction by silicon and CuCl have been investigated by X-ray diffraction, scanning electron microscope and N2 adsorption-desorption with a purpose of studying the reasons that different CuCl sources cause different reaction effect. We found Si-Cu intermetallics in proportion to the contact area between CuCl and Si. So CuCl with the characteristics of finer particles and high specific surface area is beneficial to form vast scale active Si-Cu intermetallics. The CuCl concentration on the performance of the catalytic reaction between silicon and ethanol was investigated by online gas chromatogram. The catalyst concentration greatly influences various aspects of the direct synthesis of triethoxysilane, including the induction time, the reaction rate, the selectivity and the silicon conversion. The reaction activity and yield of triethoxysilane increase as the catalyst concentration increases. However, the reaction selectivity decreases when the catalyst concentration is more than 5%, in this case the yield of triethoxysilane is slightly lower than 10% catalyst concentration.

Formation and development of micropores in carbon prepared via catalytic carbonization of phenolic resin containing Fe or Ni compounds

The formation and development of micropores in carbon prepared by catalytic carbonization (graphitization) was investigated. Phenolic resin mixed with ferrocene or nickelocene was carbonized at 1000 °C in Ar. A novel mechanical method that was used for mixing phenolic resin and metallic compound favored formation of micropores in the resulting carbon, compared with conventional homogeneous mixing. Decreasing the catalyst content led to increased micropore surface area. At low catalyst content, catalyst particles were finely dispersed. Small (<10 nm) catalyst particles inhibited the development of stacked structures of carbon aromatic layers in the amorphous component (A-component), which in turn produced accessible micropores. Increasing catalyst content facilitated conversion of A-component into turbostratic component (Ts-component) with a partially graphitized structure, which decreased the number of micropores. The formation of Ts-component is related to the formation of mesopores, which progressively replaced micropores as the amount of Ts-component increased.

Nylon 3 synthesized by ring opening polymerization with a metal-free catalyst

We have synthesized nylon 3 via ring opening polymerization of 2-azetidinone (β-lactam) with 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)- phosphoranylidenamino]-2Λ5,4Λ5-catenadi(phosphazene) (t-BuP4) as the catalyst in a mixture of dimethylacetamide (DMAc) and LiCl. The polymers have been characterized by nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), laser light scattering (LLS) and viscometry. The synthesized nylon 3 is a linear and crystalline polymer with a molecular weight as high as 105 g mol−1. The intrinsic viscosity ([η]) relates to the weight average molecular weight (Mw) as [η] = 1.02 × 10−4Mw0.91. The effects of solvent, temperature and catalyst concentration on the polymerization have been examined. The molecular weight and yield increases with the amount of LiCl in the polymerization mixture, but both of them decrease with temperature at a temperature above 50 °C. As the catalyst concentration increases, the yield and the molecular weight of nylon 3 decrease. The possible mechanism for the initiation of polymerization is discussed.

Batch reactor kinetic studies on the reductive dechlorination of chlorinated ethylenes by tetrakis-(4-sulfonatophenyl)porphyrin cobalt

Tetrakis-(4-sulfonatophenyl)porphyrin cobalt was identified as a highly-active reductive dechlorination catalyst for chlorinated ethylenes. Through batch reactor kinetic studies, degradation of chlorinated ethylenes proceeded in a step-wise fashion with the sequential replacement of Cl by H. For perchloroethylene (PCE) and trichloroethylene (TCE), the dechlorination products were quantified and the C 2 mass was accounted for. Degradation of the chlorinated ethylenes was found to be first-order in substrate. Dechlorination trials with increasing catalyst concentration showed a linearly increasing pseudo first-order rate constant which yielded rate laws for PCE and TCE degradation that are first-order in catalyst. The dechlorination activity of this catalyst was compared to that of another water-soluble cobalt porphyrin under the same reaction conditions and found to be comparable for PCE and TCE.