Solubility of polyethylene in mixed xylene was determined experimentally under atmospheric pressure by an indigenously developed laser based technique. In this work, a PC-SAFT equation of state was used to model solid–liquid equilibrium (SLE). With the experimental SLE data available in the literature for low molecular weight n-alkanes and aromatic compounds under atmospheric pressure, the suitability of the developed SLE model based on the PC-SAFT equation of state was tested. Subsequently a sensitivity study was performed to understand the effects of different parameters that affect the solubility of polyethylene. The validated model was then used to correlate the experimentally determined solubility data for the polyethylene system.
It has been recognized that flow and mixing in industrial crystallizers have complex influences on the kinetics of crystal particle growth, dissolution, nucleation and agglomeration and, consequently, on the particle size distribution. In the present study, we performed a numerical analysis of the crystal particle motion in a stirred vessel by means of Lagrangian particle tracking in order to investigate the detailed particle motion, which affects the mass transfer rate from a particle. Further, the effects of instantaneous slip velocity and local solute concentration on the dissolution process of crystal particles were clarified. The results show that a detailed estimation of the instantaneous slip velocity and local solute concentration is necessary in order to accurately estimate the particle size distribution. It is also shown that the complete dissolution time calculated by this study based on the instantaneous slip velocity is shorter than that based on terminal velocity by a maximum of about 30%, mainly because of the centrifugal force. The numerical results were verified through dissolution experiments conducted under the same conditions as in the numerical analysis.
Oxidative coupling of methane was studied in a solid oxide fuel cell (SOFC) tube type reactor. La0.85Sr0.15MnO3/8 mol% Y2O3-ZrO2/La1.8Al0.2O3 (abbreviated as LSM/YSZ/LaAlO) were used as a cathode, electrolyte and anode. The C2 selectivity and the methane conversion were 91.7% and 23.7% at 1273 K, respectively. The kinetic rate expression was proposed with two different oxygen species. The internal resistance of cell could be lumped and estimated by maximum power transfer theorem. The effect of external load was investigated both in experiments and calculations. The proposed modeling agreed well with the experimental results.
A new mechanical foam-breaker was developed. It uses the shear force between a fixed orifice plate and a rotating disk (MFUS). Foam-breaking performance of the MFUS fitted to a stirred-tank reactor (STR) was evaluated from changes in foam density and shearing power. The maximum value of the ratio of foam density (after foam breaking) to liquid density was 0.90. Change in foam densities before and after foam breaking in the MFUS was considerably larger than that in existing mechanical foam-breakers with rotating parts at the same level of power for foam breaking. The volumetric liquid-phase oxygen transfer coefficient was measured in the bubble-dispersing and foam-ascending sections of the STR with the MFUS. Comparison of the volumetric liquid-phase oxygen transfer coefficient between the STR with the MFUS and the STR or the foam column in terms of the specific power input demonstrated higher oxygen transfer performance and saving power requirements for the STR with the MFUS.
Catalytic combustion of volatile organic compounds (VOCs) has a low oxidation temperature, which leads to low energy consumption. It is widely used in industry. A novel technology for preparing Pt/Al2O3/Al catalysts for catalytic combustion of VOCs is presented here. An Al2O3 film was formed on an aluminum plate by anodic oxidation in an oxalic acid solution at a current density of 50 A·m–2. After the anodic oxidation, platinum was supported on the oxidized plate by the electrolysis supporting method with alternating current, in several minutes. The platinum loading of developed catalysts was about 0.3 wt% and the dispersion was about 50%. This indicated that platinum can be deposited on the anodized aluminum film. The activity of the catalyst was evaluated through the combustion of benzene and toluene. Above 90% conversion was obtained at 523 K in a combustion system with a space velocity of 40000 l·h–1·m–2 and a VOC concentration of 1000 ppm. Comparison with the traditional impregnation method was also carried out. Research shows that catalysts prepared using the electrolysis supporting method have lower platinum loadings and higher metal dispersion than those prepared by the traditional impregnation method. In this paper, the supporting method effect was concluded to be an ‘embedding effect’, by TPD and TPR analyses. Based on this study, it can be concluded that the electrolysis supporting method has the advantages of a short time requirement, high activity and no use of ammonia, compared with the impregnation method. It can be regarded as a novel technology for preparing catalysts.
Coffee residues from instant coffee plants were used to produce mesoporous activated carbon. A series of carbonization and activation conditions were examined to elucidate the effect of each condition. The specific surface area, mesopore and total pore volumes were evaluated by nitrogen adsorption at 77 K, and the surface chemistry was characterized by FTIR. The activated carbon derived in the conditions of a ZnCl2/coffee weight ratio of 3, an activation temperature of 600°C and a CO2 activation time of 4 h (R30T600H4) yielded a surface area of 900 m2/g, a total pore volume of 1.01 cm3/g with a mesopore content of 92%. The FTIR results demonstrated that the C–H group was the main functional group on the surface of coffee-derived activated carbon. The adsorptive capacities of R30T600H4 compared with a commercial activated carbon CAL for phenol, methylene blue and erythrosine red. We found that for small molecules such as phenol and methylene blue the adsorption capacity of R30T600H4 was lower than that of CAL, whereas, for larger molecules such as erythrosine red R30T600H4 was higher. The mesoporous structure and the surface chemistry of coffee-derived activated carbon associated in the adsorption were discussed.
This work examined the feasibility of applying the rotating packed bed (RPB) with the high-voidage packing to the removal of volatile organics compounds (VOCs) from gaseous streams. Isopropyl alcohol (IPA) and ethyl acetate (EA) were used as the model VOCs herein. The overall volumetric gas-side mass transfer coefficient (KGa) was observed as a function of rotor speed, gas flow rate and liquid flow rate. The obtained results demonstrated that the high-voidage RPB could achieve mass transfer efficiencies equivalent to the low-voidage RPB. Consequently, the high-voidage RPB has a great potential in the reduction of VOCs from the exhausted gases. An empirical correlation was also proposed, implying that the KGa value varied with the centrifugal force to the 0.326 power.
Interactions between cells, proteins, and salts in microfiltration of Corynebacterium glutamicum (C. glutamicum) slurry were investigated. First, dead-end microfiltration of mixed slurry of C. glutamicum cells and bovine serum albumin (BSA) was implemented at pH 4.5 and pH 7.0, where cells and BSA were oppositely and similarly charged, respectively. The rejection of BSA was observed during the course of microfiltration. According to the adsorption test, it was found that the rejection of BSA mainly resulted from the adsorption of BSA on cells, and that rejection caused by the capture within a cell cake layer or membrane accompanied with the filtrate flow was negligible. The effect of BSA addition on the average specific filtration resistance αav strongly depended on pH: αav decreased at pH 4.5 and hardly changed at pH 7.0. According to the measurements of particle size distribution and zeta potential, it was clarified that the electrostatic interaction between cells and BSA led to aggregation of cells at pH 4.5. Next, the effect of NaCl addition was investigated in microfiltration of the mixed slurry of cells and BSA. By addition of NaCl, αav was markedly influenced: αav increased at pH 4.5 and decreased at pH 7.0. It is a significant result for the improvement of the filtration performance in microfiltration of the cell slurry that αav decreased by addition of NaCl even at pH 7.0 where cells never aggregate due to an electrostatic repulsion force between cells and BSA.
The influence of operational parameters and the effect of viscosity on minimum fluidization velocity, Ulmf (minimum fluidization liquid velocity) and Ugmf (minimum fluidization gas velocity) were investigated in a three-phase inverse fluidized bed reactor using low-density polyethylene (LDPE) and polypropylene (PP) particles. The Ulmf showed an increasing trend with an increase in particle diameter. The effect of superficial gas velocity, Ug on Ulmf and the effect of superficial liquid velocity, Ul on Ugmf for water, glycerol and carboxy methyl cellulose (CMC) as the liquid phase were studied. With an increase in Ug, the Ulmf decreased and with an increase in Ul, the Ugmf also decreased. With an increase in the viscosity (concentration) of glycerol and CMC, Ulmf decreased. Correlations for the prediction of Ulmf in Newtonian and non-Newtonian systems are proposed.
Fungus and bacterium, which could grow under acidic conditions, were isolated, and their characteristics of growth and neutralization of acids were studied. They could grow in acidic media (pH 4.0) containing several kinds of acids at the same rate in the medium of pH 7.2 and neutralize acids. For bioremediation of pollutants in soil, we proposed a self-immobilization method of microorganisms forming aggregates in a shallow layer of soil. These isolated strains, which showed weak aggregation and were different in size, were successfully co-immobilized with Bacillus subtilis secreting viscous polymer in a shallow layer of model soil packed in a column and could neutralize acidic solutions flowing through packed soil.
The production of clean fuel oil from the municipal waste plastics without any simultaneous formation of heteroatom-containing organic compounds was investigated. When non-pretreated municipal waste plastics was thermally degraded at 450°C, the oil whose total chlorine and nitrogen contents were 3960 and 743 ppm, respectively, was produced at the per cent yield of 53.5 wt%. When the municipal waste plastics was pretreated with 0.2 N NaOH at 300°C for 60 min, however, 98% of the chlorines and 82% of the nitrogens originally present in the waste plastics were eluted. The total chlorine and nitrogen contents in the resultant oil decreased dramatically to 22 and 29 ppm, respectively, and at the same time the yield of oil increased to 63.9 wt%. The total chlorine content in oil further decreased to 11 ppm when 0.4 N Ca(OH)2 was used instead of 0.2 N NaOH. The oil produced from non-pretreated municipal waste plastics contained such heteroatom- containing organic compounds as benzoic acid, phthalic acids and ε-caprolactam, and their combined content was as high as 1.68 wt%. In contrast, only 24 ppm of ε-caprolactam was found in the oil produced via the hydrothermal pretreatment with 0.4 N Ca(OH)2 at 300°C. The correlations of the contents of chlorines, nitrogens and ammonium ions in oil with those of residual chlorines and nitrogens in the pretreated municipal waste plastics were obtained. The boiling point distribution, type of hydrocarbons, and physical and physicochemical properties such as kinetic viscosity were also analyzed for the oils obtained.
Using water in high temperature and pressure, we produced hydrogen gas from cross-linked polyethylene (XLPE) efficiently. Around two moles of hydrogen gas were produced from a mole of carbon in XLPE at the optimum conditions of 700°C, 30 min, 20 of molar ratio of water to carbon in XLPE and 20 wt% nickel catalyst. This fact showed that hydrogen gas exceeding hydrogen in XLPE was produced by the reaction of plastic and water at high temperature and pressure. The production was accelerated by increasing the temperature and molar ratio of water to carbon in XLPE, but suppressed by increasing the pressure. Nickel and alkali catalysts gave excellent performance on the gas productivity from XLPE. Both catalysts promoted the degradation of plastic and water–gas shift reaction but did not affect the methanation much. The order of the catalytic activity was nickel > potassium hydroxide > sodium hydroxide. The equilibrium gas-phase composition calculated by MALT2 agreed with the experimental results, when XLPE was gasified completely.