Solubility of Multicomponent Systems in the Biodiesel Production by Transesterification of <i>Jatropha </i><i>c</i><i>urcas</i> L. Oil with Methanol

Biodiesel is manufactured by transesterification of animal fat or vegetable oil. The reactants (oil and methanol) and the products (fatty acid methyl ester and glycerol) are partially mutual soluble in the reaction process. Inter-solubility of the reaction components is essential data for the production design and process operation. In this work, the Jatropha curcas L. oil (oil) has been transesterified to give Jatropha curcas L. oil methyl ester (FAME). The inter-solubility of FAME + methanol + glycerol, oil + FAME + methanol, oil + glycerol + methanol, and oil + FAME + glycerol in the range from 298.15 K to 333.15 K has been conducted. Methanol is completely soluble in both FAME and glycerol but is not soluble in oil. With an increase in the mass fraction of FAME, the solubility of methanol in the oil + FAME phase increases. The transesterification reaction is carried out in the methanol phase, and as a result, the reaction shows an induction period. When FAME content increases to 70 %, the oil + methanol + FAME mixture becomes a homogeneous phase. Glycerol has a low solubility in both oil and FAME and, hence, is easily separated from the final product of biodiesel. The solubility is temperature insensible

Solubility Measurement for the Reaction Systems in Pre-Esterification of High Acid Value <i>Jatropha curcas</i> L. Oil

Crude Jatropha curcas L. oil (Oil) normally contains some free fatty acids (FFAs), and it must be pre-esterified with methanol before it is used as the feedstock of the transesterification operation in biodiesel production. The mutual solubility of the pre-esterification reaction mixture was measured over the reaction temperature range from (303.1 to 333.1) K. The phase diagrams included the ternary diagrams of FFA + oil + methanol, FFA + methanol + water, Jatropha curcas L. oil methyl ester (FAME) + methanol + water, and FAME + methanol + oil. The data show that the mutual solubility increases with temperature. High FFA content can increase the mutual solubility of methanol and oil. The products, namely, water and FAME, change the distribution of oil and methanol

Continuous Biodiesel Production Catalyzed by Trace-Amount Alkali under Methanol Subcritical Conditions

Biodiesel is a promising alternative biofuel, but the treatment of wastewater containing alkali catalyst and glycerol discharged from the washing unit operation increases the cost significantly. Here a novel continuous biodiesel production process with trace-amount alkali as the catalyst under the methanol subcritical condition was proposed and investigated. The optimal operation conditions of preliminary batch reaction experiment are temperature of 200 °C, catalyst concentration of 513 mg/kg, reaction time of 38 min, molar ratio of methanol to oil of 11.9:1, and system pressure of 1.5 MPa. The one-step conversion of raw oil in a batch reactor can reach up to 85.5%. The alkali residue in the biodiesel product can be further reduced by removing the methanol and washing by glycerol instead of by acid or water. The optimal weight ratio of glycerol to biodiesel is 1.5:1, and the residual alkali in the final ester product is about 4.6 mg/kg. The simulation and bench scale continuous experiment based on the optimal batch operation parameters confirmed that the biodiesel produced by the process is qualified well up to the Chinese standard of biodiesel, and the K⁺ concentration in biodiesel was less than 3.0 mg/kg. The economic evaluation showed that this new process is more economically feasible than the traditional processes

Electrochemical Acid-Catalyzed Desorption and Regeneration of MDEA CO₂‑Rich Liquid by Hydroquinone Derivatives (Tiron)

The acid-catalyzed desorption of the MDEA CO2-rich liquid under the electrochemical reaction can lower the desorption temperature, thereby reducing the energy consumption for regeneration. In this work, disodium 4,5-dihydroxy-1,3-benzenedisulfonate (tiron) was used as an acidic medium for the electrocatalytic regeneration of the MDEA CO2-rich solution. The results show that the CO2 desorption efficiency reaches more than 90% at 25 °C for the 0.3 M MDEA (0.1 M tiron) system. At 50 °C, compared with 3 M MDEA (without tiron), the maximum CO2 desorption rate and desorption efficiency of the 3 M MDEA (with 0.1 M tiron) CO2-rich solution increased by 27.4 and 18.3%, respectively. Elevating the temperature can increase the quantity of CO2 desorption and the degree of MDEAH+ deprotonation as well as the reactivity of tiron on the electrode, so the desorption rate of CO2 can be further improved by the oxidation of tiron releasing H+ in coordination with thermal desorption

Preparation and Antiscaling Application of Superhydrophobic Anodized CuO Nanowire Surfaces

Antiscaling technology is necessary in order to prevent the performance loss and blockage of heat exchangers. In this research, a superhydrophobic CuO nanowire layer was prepared and utilized for antiscaling process of CaCO₃ on the surface of copper. Modified with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS-17), the water contact angle on the CuO surface increased sharply from 4.5° ± 1° after anodization to 154° ± 2°, since the surface free energy decreased from 74.8 mJ/m² for the hydrophilic surface to 0.2 mJ/m² for the superhydrophobic surface. The scale inhibition performance of the surface of superhydrophobic CuO nanowires was confirmed since the corresponding scaling weight of deposited CaCO₃ decreased significantly from 0.6322 mg/cm² to 0.1607 mg/cm². This attractive antiscaling effect of the modified superhydrophobic CuO nanowire surface should ascribe to the slow CaCO₃ crystal nucleation rate, because of the low surface energy, low adhesion strength of CaCO₃ crystal, and air film retained on the superhydrophobic surface

Highly Efficient Nonaqueous Phase Change Absorbent for H₂S Absorption with Low Energy Consumption

As a highly toxic gas, H2S is conventionally removed via a chemical absorption process. However, the high regeneration energy is still a challenge. 1,5-Diazabicyclo[4.3.0]non-5-ene (DBN)/polyethylene glycol dimethyl ether (NHD) solution was developed as an efficient nonaqueous phase change absorbent for the removal of H2S with low energy consumption. A homogeneous DBN/NHD solution turns into two immiscible liquid phases upon the absorption of H2S, which results from the higher polarity of the product compared to that of the original solution. The loading capacity of H2S can reach 0.16 g·g–1 solvent even under a H2S partial pressure of 10 kPa at 30 °C. After absorption, more than 94% of the absorbed H2S is concentrated in the lower phase, which can be regenerated at 90 °C with an energy consumption estimated to be 1.69 GJ·t–1 H2S. The regeneration energy is 58% lower than that of 30 wt % aqueous solution of N-methyldiethanolamine. 81% of the initial H2S loading was maintained after 4 absorption–desorption cycles. In addition, the selectivity of DBN/NHD solution to absorb H2S from N2 containing H2S and CO2 or from N2 containing H2S and CH4 was investigated. It shows that the selectivity increases with the increase in the volume ratio of H2S to CO2, which can be as high as 27.8 when the ratio is 1:1. CH4 cannot be absorbed in the DBN/NHD solution in the presence of H2S and N2

CO₂ Capture from Flue Gas Using an Electrochemically Reversible Hydroquinone/Quinone Solution

Electrochemical methods are potentially an energy-saving way to capture CO2 from flue gas. Unlike the regeneration of amine through high-temperature thermal distillation in commercial CO2 absorption processes, the CO2 absorption solution is regenerated by electrolysis at a low temperature. In this work, tiron (disodium 4,5-dihydroxy-1,3-benzenedisulfonate, QH2) was employed as a pH mediator because its redox reactions can change the pH of the solution. Na2Q, which was prepared by QH2 and NaOH in a molar ratio of 1:2, was used to capture CO2 because of its alkalinity. Then, CO2 was desorbed by the oxidation of QH– and QH2 formed in the CO2-rich aqueous solution to quinone (Q) to release protons, and the alkalinity was recovered by the reduction of Q to the quinone dianion (Q2–). The redox performance of Na2Q in aqueous solution was investigated using cyclic voltammetry, and the CO2 capacity of Na2Q solutions at different concentrations (0.1–0.7 M) was measured. The results show that the redox behavior of Na2Q was reversible in the neutral or weakly alkaline solutions. However, the reduction of Q to Q2– by electrolysis was difficult in a high pH solution. During adsorption, the Na2Q solution absorbed CO2 at a molar ratio of about 1:1 (CO2/Q2– ≈ 1). The CO2-saturated Na2Q solution was electrolyzed in the anode zone under a constant current. The CO2 desorption rate reached 100%, and Q2–, QH–, and QH2 were oxidized to give Q. In the cathode zone, Q was reduced to Q2–, which could be used to adsorb CO2 from flue gas. On the basis of the potential difference between the cathode and anode, the regeneration energy consumption was estimated to be about 2.4 GJ/tonne of CO2

Silver Oxide as Superb and Stable Photocatalyst under Visible and Near-Infrared Light Irradiation and Its Photocatalytic Mechanism

Photocatalytic processes are an environmentally friendly technology for treatment of persistent organic pollutants. However, the majority of current photocatalysts cannot utilize sunlight sufficiently to realize fast decomposition of organic pollutants. In this research, a silver oxide nanoparticle aggregation with superb photocatalytic performance under artificial light source and sunlight was prepared and characterized. The results showed that methyl orange (MO) was decomposed completely in 120 s under irradiation of artificial visible light, artificial ultraviolet light, and sunlight, and in 40 min under near-infrared (NIR) light. The superb photocatalytic performance of as-prepared silver oxide remained almost constant after reuse or exposure under sunlight. It was confirmed that the co-working effect of photogenerated hole and ozone anion radicals did play an important role in the process of MO photodegradation with the existence of Ag₂O. The narrow band gap of Ag₂O, less than 1.3 eV, resulted in the photocatalytic performance of Ag₂O under NIR light. Furthermore, the high surface area and numerous crystal boundaries provided by the aggregation of Ag₂O nanoparticles efficiently increased the escape probability of photogenerated electrons and the contact probability of photogenerated holes with outside materials, assuring superb photocatalytic activity and excellent stability of as-prepared Ag₂O samples

Analysis of Wetting Behavior and Solidification Process of Molten Urea on a Superhydrophobic Surface and Its Application in Large Granular Urea Production

The wetting behavior of polar high-temperature melt on superhydrophobic surfaces is rarely studied, although water wetting process under normal temperature has been widely investigated. In this work, molten urea was considered as the typical polar melt substance, and its wetting behavior and solidifying process on a polytetrafluoroethylene (PTFE)-coated superhydrophobic stainless steel surface (PSSSS) were investigated. The results confirm the super-repellency of PSSSS on molten urea droplets with a static angle of over 155° and a rolling angle of 3.5 ± 1°, which is consistent with the Cassie–Baxter state. Such a superurea-melt-phobic state is ascribed to the high roughness of the PTFE-coated surface and high cohesive energy density difference between the urea and PTFE. The solidification process of the urea melt on PSSSS occurred from the outside to inside in 44 s at 18 °C to form a compact urea granule of large size and high mechanical strength. This occurrence provides a feasible and promising granulation strategy to produce qualified large urea granules using a green, simple, and cost-effective process