Papers by Keyword: Lactic Acid

Abstract: Supported 3wt%Pd/α-Al₂O₃ catalyst was tested in selective oxidation of 1,2-propanediol by molecular oxygen. It was found that the catalyst is active in an alkaline water solution. Lactic acid was obtained as the main product of the reaction. Influence of different reaction conditions on 1,2-PDO conversion and oxidation process selectivity was studied. Partial kinetic orders of the reaction with respect to 1,2-propanediol, c₀(NaOH), p(O₂), n(1,2-PDO)/n(Pd)) were determined and an experimental kinetic model of the catalytic oxidation reaction was obtained. Activation energy of the process was calculated and was found to be about 53 ± 5 kJ/mol.

Abstract: In this study, facile preparation using a new solvent – lactic acid and physical properties of PAni-Cs films are observed. The main goal of the study is to easily synthesize PAni-Cs films using lactic acid as solvent through the solvent casting method and investigate if producing PAni-Cs with lactic acid will enhance its properties. The presence of PAni-Cs was confirmed by observing its structure using Fourier transform infrared (FTIR) spectroscopy. The wettability of the films showed that films produced with lactic acid are less hydrophobic than those produced with acetic acid. Consequently, the computed surface energies revealed PAni-Cs films produced using lactic acid were higher. Water uptake of the films showed deviations when PAni and the solvents (lactic acid and acetic acid) were introduced. Furthermore, films produced with lactic acid were observed to be more flexible. These characterizations revealed that PAni-Cs produced with lactic acid are comparable to the properties of those produced with acetic acid showing that lactic acid helps in the improvement of PAni-Cs surface properties.

Abstract: Esterification reaction of lactic acid with butanol to produce butyl lactate and its optimal conditions were investigated. Cyclohexane was used as entrainer to remove water to promote reaction yield. Catalyst of NaHSO₄ was also used to increase reaction rate. Reaction parameters of butanol/lactic acid ratio, cyclohexane/lactic acid ratio, catalyst amount, and reaction time were optimized using Response Surface Methodology (RSM). Results showed that the butanol/lactic acid ratio was the most significant factor for esterification yield while interactions between butanol/lactic acid ratio and cyclohexane/lactic acid ratio, butanol/lactic acid ratio, and reaction time were less significant. The correlation coefficient between predicted values and experiment values was 0.985. The optimal conditions for the experiment are: ethanol/lactic acid ratio 5:1, cyclohexane/lactic acid ratio 1:1, catalyst loading 1.5%, and incubation period 3 hours. The esterification yield reaches 99.8% under these conditions.

Abstract: 1.25 – 5wt%Pt/Al₂O₃, 1.25 – 5wt%Pd/Al₂O₃, 1wt%Pd/TiO₂, 1 – 5wt%Pd/TiO₂-NF, 1.25wt%Pt+1.25wt%Pd/Al₂O₃, 5wt%Pt/SiO₂, 5wt%Pt/C catalysts were synthesised and tested in the selective oxidation of 1,2-propanediol by molecular oxygen. It was found that all catalysts were active in alkaline water solutions; lactic acid was obtained as the main product of the reaction. The conversion of 1,2-propandiol and the yield of lactic acid depended on the content of active metal in the catalysts. The most active for the oxidation of 1,2-propandiol were palladium-containing catalysts supported on TiO₂ nanofibers (Pd/TiO₂-NF). The highest 1,2-propanediol conversion (100 %) and lactic acid yield (96 %) were obtained using the 5wt%Pd/TiO₂-NF catalyst at the following oxidation parameters: c₀(1,2-propanediol) = 0.3 mol/L, P(O₂) = 1 atm, n (1,2-propanediol)/n (Pd) = 500 mol/mol, t = 60 °C, c₀(NaOH) = 1.5 mol/L.

Abstract: This work demonstrates that 5wt% gold catalysts supported on Al₂O₃ and TiO₂ nanopowders as well as on TiO₂ nanofibers are active in the 1,2-propanediol (1,2-PDO) oxidation to lactic acid. The influence of catalysts different parameters and reaction conditions on 1,2-PDO conversion and oxidation process selectivity was studied. The best result was achieved using 5wt%Au/TiO₂ catalyst over the following oxidation parameters: c₀(1,2-PDO) = 0.3 mol/L, n (1,2-PDO)/n (Au) = 4000 mol/mol, p (O₂) = 6 bar, c₀(NaOH) = 2 mol/L, t = 60 °C: 1,2-propanediol conversion was 98 % and lactic acid selectivity 89 %.

Abstract: 1,2-Propanediol selective oxidation with molecular oxygen in presence of heterogeneous catalyst is one of the most nature friendly 1,2-propanediol conversion methods. This work demonstrates Au, Pt and Pd containing catalysts’ activity and selectivity in a 1,2-propanediol oxidation process. The main product of the 1,2-propanediol catalytic oxidation was lactic acid, by-products were acetic and formic acids. It was found that Au based catalysts are best for 1,2-propanediol oxidation in alkaline water solutions. The best result was achieved using the 4.8wt%Au/Al₂O₃ catalyst: selectivity by lactic acid was 94% with 1,2-propanediol conversion 100% (c₀(1,2-propanediol) = 0.3 mol/L, P(O₂) = 6 atm, n (1,2-propanediol)/n (Au) = 500, t = 60°C, c₀(NaOH) = 1.5 mol/L).

Abstract: The paper brings current results of a project that places emphasis on comparison of different fine-grained concrete resistance to influence of aggressive solutions of biogenic or biological origin. For laboratory testing, there were preferentially selected aggressive environments, to which concrete constructions of agricultural structures or sewage networks are exposed. Basic physical-mechanical parameters of concrete samples exposed to aggressive solutions for 1 year are stated in the paper.

Abstract: In this study, esterification of lactic acid and ethanol to produce ethyl lactate using different cation-exchange resin catalysts was performed at 100 °C. The catalysts used for the esterification process were amberlyst 16 and dowex 50W8x cation-exchange resins. Two simplified mechanisms based on Langmuir-Hinshelwood model were employed to describe the components that adsorbed most on the surface of the catalysts. Fourier Transform Infrared (Nicolet iS10 FTIR) was employed to verify the rationality of the mechanisms. FTIR of the esterification product reflected C=O, H=O and C=C bonds on the spectra confirming water and ethanol as the most adsorbed components. The kinetic study of the retention time and the peak areas of the esterification produced with the different catalysts were compared using an autosampler gas chromatography/mass spectrometry (autosampler GC-MS). The chromatogram of the esterification product catalysed by amberlyst 16 showed a faster elution at 1.503 mins with the peak area of 1229816403 m² in contrast to the dowex 50W8x. The BET surface area and BJH pore size distribution of the resin catalysts were determined using liquid nitrogen adsorption (Quantachrome, 2013) at 77 K. The BET surface area results of amberlyst 16 resin catalysts was found to be 1.659m²/g compared to 0.1m²/g for the dowex 50W8x. The BJH results of the catalysts exhibited a type IV isotherm with hysteresis confirming that the materials were mesoporous with pore size in the region of 2 – 50 nm.

Abstract: The removal of lead from aqueous solutions was studied using the liquid-solid extraction method. The solids used are the crude phosphocalcic hydroxapatite [Ca₁₀(PO₄)₆(OH)₂] (HAPc), and phosphocalcic hydroxapatite treated with 5 % lactic acid solution (HAPal). The extraction results showed the influence of the initial concentration of Pb (II) and temperature of the suspensions. The maximum adsorption capacities of each material (HAPc and HAPal) were obtained with the application of Langmuir adsorption model. The most important quantity was founded as 41,84mg/g for HAPal. Isotherms established at different temperatures showed that this parameter affects greatly the adsorption of Pb (II) on both adsorbents. The best results were obtained at room temperature (25°C) compared with those recorded at 50°C.Finally, the results of this study allow us to note that the hydroxiapatite material can be as good extractant solid, for heavy metals, especially when it is modified with lactic acid.

Abstract: Bedak sejuk, is a traditional cosmetic product that still being used and fond by many women in Malaysia. It is produced by the traditional methods that passed from generation to generation. Rice grains were soaked in water at least for three months or until it fully dissolved. The aim of the study is to determine the effects of soaking on rice granules for bedak sejuk production. Local rice grains (Indica) were soaked in water at ratio of 1:1 (w/v) in a container with lid for 42 days and the water were changed at 14 days interval. The soaking process was a series of batch process. A growth profile of microbial in the fermented supernatant showed that the lag phase started on day 3 of soaking process and the exponential phase started on day 8 of soaking process. The final pH value of fermented supernatant was 4.04 while the final titratable acidity which is expressed as lactic acid was 0.62 mg mL^-1. Reducing sugar increased while total starch decreased during the soaking process. For particle size distribution of rice granules, there is no clear differences in the size distribution but there is slight changes of weight fraction of the rice granules. The analysis of fermented supernatant suggests that natural fermentation occurred during the soaking process while the analysis of rice granules suggests that hydrolysis of rice starch occurred during the natural fermentation process.