Ratio Of Sulfuric Acid Research Articles

Enhancing acidity of Ru/Ce/ZrO2 bifunctional catalysts for promoting N2 selectivity in selective catalytic oxidation of NH3

To solve the problem of low N2 selectivity of Ru/Ce/ZrO2 (R/C/Z) catalysts in NH3 selective catalytic oxidation (NH3-SCO) reaction, herein ZrO2 supports were treated with sulfuric acid and its effects on NH3-SCO performance were investigated systematically. The results showed that Ru/Ce/ZrO2-10S (R/C/Z-10S) catalyst, in which the mass ratio of sulfuric acid to ZrO2 was 10 %, exhibited N2 selectivity of 95.7 % at 350 °C, that was significantly higher than R/C/Z catalyst (57.8 %). NH3-TPD tests indicated that sulfate treatment of ZrO2 supports in R/C/Z catalysts led to more abundant acidic sites on catalyst surface, which was in favor of enhancing NH3 adsorption capacity remarkably. But when mass ratio of sulfuric acid to ZrO2 increased up to 20 %, an aggregation of metal oxides on the surface of R/C/Z-20S catalyst could be observed clearly, which might impose an adverse impact on NH3-SCO performance. In-situ DRIFTS results revealed that, compared to R/C/Z catalyst, there were much more Brönsted acid sites on the surface of R/C/Z-10S catalyst, and the corresponding NH3 species on acidic sites could be consumed quickly in intermediate reactions. More importantly, amide (-NH2) species rather than imide (-NH) and nitrosyl (-HNO) species, were the majority on the surface of R/C/Z-10S catalyst, implying that there might be a suppressing effect on further dehydrogenation of -NH2 species into -NH species owning to sulfate treatment of ZrO2 supports in R/C/Z catalysts. Therefore, internal selective catalytic reduction (i-SCR) mechanism rather than -NH mechanism played a vital role in NH3-SCO reaction over R/C/Z-10S catalyst.

Fabrication of carbon black nanoparticles from green algae and sugarcane bagasse

There are several industrial uses for carbon black (CB), an extremely fine powdered form of elemental carbon that is made up of coalesced particle aggregates and almost spherical colloidal particles. Most carbon black is produced from petroleum-derived feedstock, so there is a need to find an alternative method to produce CB, which relies on renewable resources such as algae and agricultural waste. A process involving hydrolysis, carbonization, and pyrolysis of green algae and sugarcane bagasse was developed, as the optimal hydrolysis conditions (16N sulfuric acid, 70 °C, 1 h, 1:30 g/ml GA or SC to sulfuric acid ratio), a hydrolysis ratio of 62% for SC and 85% for GA were achieved. The acidic solution was carbonized using a water bath, and the solid carbon was then further pyrolyzed at 900 °C. The obtained carbon black has a high carbon content of about 90% which is confirmed by EDX, XRD, and XPS analysis. By comparison carbon black from sugar cane bagasse (CBB) and carbon black from green algae Ulva lactuca (CBG) with commercial carbon black (CCB) it showed the same morphology which was confirmed by SEM analysis. The BET data, showed the high specific surface area of prepared CB, which was 605 (m2/g) for CBB and 424 (m2/g) for CBG compared with commercial carbon black (CBB) was 50 (m2/g), also the mean pore diameter of CBB, CBG and CCB indicated that CBB and CBG were rich in micropores, but CCB was rich in mesoporous according to IUPAC classification. This study might have created a technique that can be used to make carbon black from different kinds of biomass.

Thermal Transformations of Porous Anodic Aluminum Oxide Formed in Sulfuric Acid/Oxalic Acid Mixed Electrolytes

Aluminum anodizing in electrolytes comprising mixtures of several acids opens way to manufacture porous films of anodic aluminum oxide (AAO) with a widely tunable structure period. Study of thermal transformations in AAO films produced in mixed electrolytes is a separate task, as a complex chemical composition of the material can give rise to some specifics in subsequent annealing. Impurity oxalate and sulfate ions were detected in the AAO produced by aluminum anodizing in sulfuric acid/oxalic acid mixed electrolytes. The sulfate weight fraction appears about one order of magnitude higher than the oxalate weight fraction, and it increases as the concentration ratio of sulfuric acid to oxalic acid in the electrolyte increases. In the same way, the crystallization temperature of amorphous AAO to a mixture of low-temperature Al2O3 polymorphs increases in response to increasing concentration ratio of sulfuric acid and oxalic acid. Thus, the component ratio in the mixed electrolyte used influences the composition and thermal transformations of AAO.

Enhanced removal of organic matter from oxygen-pressure leaching solution by modified anode slime

Organic matter has become a typical harmful impurity, posing a serious problem and catastrophic effects in the hydrometallurgical extraction of zinc. The highly efficient and inexpensive method for the removal of organics from the leaching solution is of great practical significance for the efficient operation of zinc hydrometallurgy. For this reason, the removal of organic matter from oxygen-pressure leaching solution using modified anode slime was investigated by TOC analysis, FTIR spectroscopy, XRD, GCMS, and other characterization methods, and its mechanism was also discussed. The results show that the removal of organic matter using anode slime modified with sulfuric acid was significantly improved, and the removal of TOC reached 57.83% for anode slime modified at a temperature of 80 °C with a ratio of sulfuric acid to anode slime of 14 mL/100 g, which was more than 2.7 times that of untreated anode slime. The good removal effect of organic matter using the modified anode slime could be attributed to the transformation of inert α-MnO2 to active MnOOH by concentrated sulfuric acid-mediated modification. It was also found that the acid–solid ratio and temperature exhibited a significant effect on the modification of anode slime. The XPS analysis results of Mn 2p, Mn 3s, and O 1s, combined with the XRD patterns of the modified products indicated that the modification of anode slime led to the conversion of MnO2 in anode slime to MnOOH in the presence of H2SO4. However, MnO2 was further converted into high crystallinity MnOOH, even MnSO4 when the temperature exceeded 80 °C or the acid–solid ratio exceeded 18 mL/100 g, resulting in the decreased degradation performance for organic matter. The characterization results of FTIR spectroscopy and GCMS show that modified anode slime does not exhibit a degradation effect on all types of organic substances in leaching solution; however, it is very effective for some alcohols, olefins, and esters.

Rapid preparation of starch nanocrystals by the mixed acid of sulfuric acid and hydrochloric acid

In this work, waxy maize starch nanocrystals were prepared by mixed acid of sulfuric acid and hydrochloric acid for the first time. Physicochemical properties, crystalline structure, and particle size of starch nanocrystals prepared by mixed acid (HSNC) were measured. The results showed that there was no difference in particle morphology, group structure, and surface elements of HSNC and starch nanocrystals prepared by sulfuric acid (SNC), which was a conventional preparation method. The yield of HSNC was lower than that of SNC. However, the preparation time of HSNC was greatly shortened to 1 h which is only 0.83 % of the time (5 d) to prepare SNC by the sulfuric acid, and HSNC showed higher relative crystallinity and smaller size than those of SNC. In addition, when the ratio of sulfuric acid and hydrochloric acid to provide H ion concentration was 1:1 to hydrolyze starch for >1 h, the crystal pattern of HSNC would be changed to V-typed, while the crystal pattern of SNC was still A-typed. Thus, this work provided efficient method for preparing starch nanocrystals is provided, which can replace sulfuric acid hydrolysis to prepare SNC.

An efficient method for Synthesis of flavanone

The main aim of present work is to develop efficient method for synthesis of flavanone. For the synthesis of flavanone acid and based catalyzed methods were tried in which base catalyzed methods proved ineffective. No reaction was take place upon using HCl, H2SO4, glacial acetic acid and p-TSA as catalyst. In presence of methane sulphonic acid as catalyst, flavanone was formed in lower yield. Mixture of sulfuric acid and glacial acetic acid proved better catalyst than previous ones and leads to 65% yield. The reaction condition parameters effects on product yield were carried out. Ratio of sulfuric acid and glacial acetic acid in (4:1) proved highly beneficial. In methanol product yield was higher compare to other selected solvents. Solvent quantity effect on yield was also screened which proved that 50ml solvent necessary for 0.004mol of reactant. From which 90˚C temperature was highly favorable to reaction that takes minimum 6hr to complete the reaction. So, in this study we developed new efficient method for synthesis of flavanone.

Efficient Selective Extraction of Scandium from Red Mud

ABSTRACT The huge reserves of red mud have a significant potential source of scandium. The scandium can be recovered from red mud by direct acid leaching but the extraction yields are generally low, and the leaching efficiency of iron and silicon is higher. Therefore, the highly selective process steps (a combined sulfation-roasting-water leaching process) were studied to extract scandium from red mud, and in order to minimize costs and waste generated. This study focuses on the phase transformation mechanism and leaching behavior of Sc, Na, Al, Fe, Ti, Ca, and Si in the red mud sulfation-roasting-water leaching process. The results show that the maximum Sc leaching efficiency of 91.98% was obtained at optimum conditions: the roasted at 1023 K for 60 min, the ratio of sulfuric acid to red mud of 0.9 mL/g, the leaching temperature is 323 K, the liquid-to-solid ratio of 5 mL/g, and stirred constantly at 200 rpm leach for 2 h. While the leaching efficiencies of Ca, Na, Fe, Al, Si, and Ti are 21.05%, 93.26%, 1.21%, 9.51%, 1.42%, and 0, respectively. The sulfation-roasting-water leaching process proves to be a promising technique and commercially viable process that allows selective extraction of scandium from red mud, which may contribute to provide options for the treatment of red mud produced continuously by the aluminum industry.

Assessment of the Influence of Sulfuric Acid/Hydrogen Peroxide Mixture on Organic Sulfur Reduction of High Sulfur Coals and Their Chemical Composition

One of the contaminants in coal is sulphur. The adverse impact of sulfur on coal, such as environmental pollution, degradation of steel quality, and reduction of coal’s thermal value, has led to the attention of sulfur separation methods in recent decades. Leaching (chemical dissolution) is one of the best methods for desulfurising coal, reducing sulfur in coal. In this study, hydrogen peroxide as an oxidising agent on sulfuric acid yield in reducing sulfur types of coal and chemical structure and the organic texture of high sulfur coal was investigated. The experiments were designed using a three-level response surface methodology with four duplicate points and 27 experiments. The independent variables studied were temperature, time, stirring speed and ratio of sulfuric acid to hydrogen peroxide. Dependent variables included reduction percentage of total, pyritic and organic sulfur. This study showed that 99.99% of total sulfur, 30.11% of pyritic sulfur and 69.08% of organic sulfur were reduced. These values were obtained at a temperature of 60°C, time 120 min, stirring speed 200 rpm and 3:1 ratio of sulfuric acid to hydrogen peroxide. Significant changes were observed by infrared spectroscopy (FTIR) of the coal structure before and after desulphurisation. On the other hand, the studies showed no specific changes in the bonds related to the organic coal matrix. The results showed that this method could be used as a secure process for removing inorganic and organic sulfur without destroying the organic coal matrix.

Physicochemical properties, strength and phytotoxicity of building blocks with waste cooking oil as binder

From year to year, the number of catering outlets, in particular fast-food restaurants, using oils increases, which causes a significant increase in the amount of oil waste generated.One potential use for waste cooking oil (WCO) is in the production of new forms of building materials. These new materials, where the cement binder is replaced with WCO, show high strength parameters compared to traditional building blocks. For the sake of the environment, it is necessary to test oil blocks in terms of the release of substances that are hazardous to the environment.In this study the process of producing oil blocks was optimized and construction materials based on WCO were produced. The physicochemical properties, strength and phytotoxicity of oil blocks were determined.Oil blocks were obtained with used cooking oil from thermal food treatment as a binder. The process parameters to obtain solid materials based on WCO were: annealing temperature 180–220 °C, annealing time 12–20 h, mass ratio of sulfuric acid (VI) to catalyzed oil in the range of 0.03–0.27. The oil blocks contained a fixed amount of catalyzed WCO relative to the weight of the whole mixture equal to 15%. Leaching tests of harmful substances from the blocks confirmed the presence of small amounts of dibenzo[a,h]anthracene; no heavy metals were detected. More than three times the growth of shoots of Sorghum saccharatum grown in soil soaked in rainwater in which the oil blocks were immersed was observed compared to the control.

Porous PEDOT:PSS Particles and their Application as Tunable Cell Culture Substrate

AbstractDue to its biocompatibility, electrical conductivity, and tissue‐like elasticity, poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) constitutes a highly promising material regarding the fabrication of smart cell culture substrates. However, until now, high‐throughput synthesis of pure PEDOT:PSS geometries was restricted to flat sheets and fibers. In this publication, the first microfluidic process for the synthesis of spherical, highly porous, pure PEDOT:PSS particles of adjustable material properties is presented. The particles are synthesized by the generation of PEDOT:PSS emulsion droplets within a 1‐octanol continuous phase and their subsequent coagulation and partial crystallization in an isopropanol (IPA)/sulfuric acid (SA) bath. The process allows to tailor central particle characteristics such as crystallinity, particle diameter, pore size as well as electrochemical and mechanical properties by simply adjusting the IPA:SA ratio during droplet coagulation. To demonstrate the applicability of PEDOT:PSS particles as potential cell culture substrate, cultivations of L929 mouse fibroblast cells and MRC‐5 human fibroblast cells are conducted. Both cell lines present exponential growth on PEDOT:PSS particles and reach confluency with cell viabilities above 95 vol.% on culture day 9. Single cell analysis could moreover reveal that mechanotransduction and cell infiltration can be controlled by the adjustment of particle crystallinity.

Atmospheric drying preparation and microstructure characterization of fly ash aerogel thermal insulation material with superhydrophobic

In this paper, silica aerogel is prepared cheaply by atmospheric drying method using coal fired fly ash, a solid waste produced by power generation. By means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), pore size and surface area analysis, X-ray diffraction (XRD), Fourier transform infrared spectrum(FT-IR), laser confocal Raman spectrum(LRS), differential scanning calorimeter(DSC), thermogravimetric analyser(TG) and coefficient of thermal conductivity meter and other modern characterization methods, to explore the surface morphology, microstructure, chemical bond state, thermal stability, chemical stability and thermal conductivity of silica aerogels, and the effect of acid amount on its performance are analyzed. The results show that fly ash can prepare silica aerogel with high purity, high specific surface area, low thermal conductivity, and good chemical stability. When the volume ratio of sulfuric acid to calcining mixture is 10, the silica aerogel prepared has the best performance, the thermal conductivity is as low as 0.0234 W/m·K, the surface is super hydrophobic, the hydrophobic angle can reach 146°, the limit service temperature is 400°C, and the specific surface area is 809.923 m2/g.

Synthesis and characterization of two new molten acid salts: Safe and greener alternatives to sulfuric acid for the hydrolytic conversion of 1,1,1,3-tetrachloro-3-phenylpropane to cinnamic acid

Available online Two new acid salts were synthesized, and their chemical structures were characterized by various spectra data analyses. Although 1H NMR did not show acid proton of [HSO4]−, the FTIR spectra of molten acid salts act as key support to approve of their chemical structures. The structure elucidation of the molten acid salts demonstrated the existence of 4,4ʹ-trimethylene-N,Nʹ-dipiperidinium dication with sulfate and hydrogen sulfate anion(s). Thus, sulfuric acid can act as a diprotic or monoprotic Brönsted acid when it is treated by a secondary amine regarding the initial mole ratio of sulfuric acid and amine. Also, the catalytic activity of these molten acid salts was investigated for the hydrolytic conversion of (1,3,3,3-tetrachloropropyl)benzene to cinnamic acid. The desired product was obtained in 88 ± 2.0% yield under optimal conditions. The molten acid salts were high recyclable and their chemical structure and catalytic efficiency showed no significant change even after the 5th run. Furthermore, TMDP-SA (1:1) showed a much weaker corrosive property compared with TMDP-SA (1:2) and SA (98%), and the surface of stainless steel was intact even after 24 h. This fact and the acidity of two molten acid salts also confirm the proposed chemical structures.

Experimental and theoretical evaluation of zinc recovery from zinc oxide ore: process optimization and simulation using Aspen Plus software

AbstractIn the present study, the production process of zinc sulfate from the zinc oxide ore was experimentally investigated. The effect of main operating condition such as weight ratio of sulfuric acid to zinc content of ore (H2SO4/zinc), leaching temperature (°C), stirring speed (rpm), leaching time (min), particle size (mm), solid to liquid ratio (pulp density, wt. %), additives amount (kg/m3) and leaching pH on dissolution process of zinc oxide ore in H2SO4 solution were evaluated. Taguchi method and Aspen Plus software were used to determine the optimum condition and simulate the production process of zinc sulfate. Also, Aspen Plus software was used to determine the efficiency of zinc sulfate production. The experimental factors and their levels were as follows: 0.937–1.875 for the weight ratio of sulfuric acid to zinc content of ore, 50–80 °C for the leaching temperature, 100–400 rpm for stirring speed, 30–120 min for leaching time, 0.01–10 mm for particle size, 10–40 wt% for pulp density, 10–50 kg/m3 for additives amount and 1.4–2 for solution pH. The optimum condition was found to be H2SO4/Zinc ratio, 1.25; temperature, 70 °C; agitation rate, 200 rpm; leaching time, 30 min; particle size, 1 mm; pulp density, 10 wt%; additives amount, 30 kg/m3 and pH, 1.8. The most effective factors for maximizing the dissolution of ZnO in H2SO4 was the leaching pH. The predicted results by Aspen Plus simulation indicated that the total efficiency of zinc recovery at optimum condition is more than 97%.

Functionalized Graphitic Carbon Nitride Decorated with Palladium: an Efficient Heterogeneous Catalyst for Hydrogenation Reactions Using KHCO2 as a Mild and Noncorrosive Source of Hydrogen.

Functionalization of the widely known graphitic carbon nitride (GCN) material has been performed, and a novel heterogeneous catalyst is reported by incorporating palladium over the surface of functionalized GCN. GCN was functionalized using an optimized ratio of sulfuric acid, nitric acid, and hydrogen peroxide. The developed catalyst was characterized by powder X-ray diffraction, IR, scanning tunneling microscopy, tunneling electron microscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller, thermogravimetric analysis, and solid-state CP-NMR. The developed material containing ≤1% Pd exhibits superior catalytic activity in comparison to other carbon support materials (such as 5% Pd/C) for various hydrogenation reactions under mild conditions. Potassium formate has been chosen as the best hydrogen source among other alkali metal formates. The developed catalyst was also able to catalyze a one-pot three-step reaction for the synthesis of N-benzylaniline which is a precursor of various antihistamine and anticholargenic drugs. Moreover, the catalyst could be recycled multiple times and consistent activity was reported.

Extraction of tellurium and high purity bismuth from processing residue of zinc anode slime by sulfation roasting-leaching-electrodeposition process

Anode slime and its processing residue contains a variety of valuable elements, which are the main source of tellurium and bismuth. A systematic study on the extraction of tellurium and bismuth from processing residue of zinc anode slime and electrodeposition to obtain high purity bismuth was carried out. Sulfation roasting thermodynamics, leaching thermodynamics, and reduction potential involved in the extraction were calculated and used as theoretical guidance for the experiment. In the process of extracting tellurium and bismuth: the minimum amount of sulfuric acid and the appropriate low temperature of sulfation roasting conditions for processing residue of zinc anode slime are explained that the ratio of sulfuric acid to anode slime was 0.54:1, and the temperature was 435 °C. The leaching process of the roasting product was optimized. The optimal water leaching conditions were a liquid to solid ratio of 6:1 and a reaction time of 0.5 h at 25 °C. The optimal alkali leaching condition is 10% NaOH liquid to solid ratio of 6:1 and reaction time of 0.5 h at 25 °C. Tellurium and bismuth were separated, and tellurium was enriched from a low content of anode slime raw materials. The recovery rate of tellurium and bismuth were 84.9% and 97.1%, respectively. The reduced deposition process of bismuth ions on the cathode was characterized by cyclic voltammetry in the nitric acid. In the stable deposition state, electrodeposition overpotential of the bismuth ion on the titanium plate was 0.1068 V. Tributyl phosphate (TBP) was used as extraction solvent and nitric acid solution was used as stripping solution to purify the impurities in the basic bismuth sulfate. After extraction process, the removal rates of tellurium (Te), arsenic (As), copper (Cu), and antimony (Sb) were 96.5%, 93.3%, 99.1% and 100%, respectively. The content of other impurity elements also reduced greatly. The electrical separation process further reduced the content of impurities in the electrolyte, in which the concentration of tellurium was reduced to less than 1 ppm. A standard-compliant high purity elemental bismuth was obtained by electrodeposition from purified electrolyte.

Experimental and simulation study of copper recovery process from copper oxide ore using aspen plus software: Optimization and sensitivity analysis of effective parameters

Aspen Plus software was used to simulate and measure the recovery efficiency of copper in leaching process of copper oxide in H2SO4 solution. The Taguchi experimental design method was applied to determine the optimum operating conditions for dissolution of copper oxide ore in H2SO4 solution. The experimental variables and their levels were as follow: (1) the weight ratio of sulfuric acid to copper content of ore (H2SO4/Cu ratio), 0.937–1.875; (2) leaching temperature (°C), 50–80; (3) agitation rate (rpm), 100–400; (4) reaction time (min), 30–120; (5) particle size (mm), 0.01–10; (6) solid/liquid ratio (Pulp density), 10%–40 wt.%; (7) additives values (kg/ton), 10–50 and (8) leaching pH, 1.4-2. The optimum conditions were found to be sulfuric acid/copper ratio: 1.25, temperature: 80 °C, agitation rate: 400 rpm, leaching time: 30 min, particle size: 0.1 mm, pulp density: 10 %, additives value: 20 kg/ton and pH: 1.8. The simulation results of the Aspen Plus software indicated that at optimum operating conditions obtained by Taguchi method, the copper recovery from copper oxide ore in H2SO4 solutions was 95 %.

A new facile process to remove Br− from waste printed circuit boards smelting ash: Thermodynamic analysis and process parameter optimization

Waste printed circuit boards smelting ash (WPCBs-SA) is generated by the smelting process of waste printed circuit boards (WPCBs), which contains valuable metals, such as copper (Cu), zinc (Zn), and sliver (Ag), and a large amount of harmful bromide (Br−). In this work, a facile sulfation roasting (SR) proposed for the removal of Br− from WPCBs-SA with high efficiency. The thermodynamic analysis is systemically investigated, and the results demonstrate that Br− in WPCBs-SA is converted into HBr or Br2 comfortably below 564.8 K during the SR process. The influences of essential variables such as the ratio of sulfuric acid into smelting ash, roasting temperature and time are systematically investigated, and the variables are also optimized via response surface methodology (RSM). Under the optimized experimental conditions, the Br− removal efficiency reached up to 98.97%, and the values of the three variables were 0.8 g/g, 590.04 K and 123.25 min, respectively. The proposed RSM model equation shows a good correlation with the experimental data, with a correlation coefficient (R2) of 96.05%. This work will be a new method to enrich the harmful elements of WPCBs-SA and reduce the potential environmental pollution of related hazardous wastes.

Protic Ionic Liquids Based on Oligomeric Anions [(HSO4)(H2SO4)x]− (x = 0, 1, or 2) for a Clean ϵ-Caprolactam Synthesis

Inexpensive Brønsted acidic ionic liquids, suitable for industrial-scale catalysis, are reported as reaction media and catalysts for the Beckmann rearrangement of cyclohexanone oxime to ϵ-caprolactam. A family of protic ionic liquids was synthesised from nitrogen bases (1-methylimidazole, N,N,N-triethylamine, N-methylpyrrolidine, 2-picoline) and sulfuric acid by proton transfer in a simple, inexpensive, solvent-free, one-step process. The density, viscosity, conductivity, and ionicity of the synthesised ionic liquids were determined. Variation in the molar ratio of sulfuric acid (χH2SO4=0.67 and 0.75) was used to tune the acidity of these protic ionic liquids, which showed extremely high catalytic activity in the Beckmann rearrangement of cyclohexanone oxime to ϵ-caprolactam. Both the structure of the cation and the sulfuric acid molar ratio strongly affect the rearrangement of cyclohexanone oxime. The most active ionic liquid, based on the 1-metyhylimidazolium cation, χH2SO4=0.75, afforded high conversion of oxime combined with very good selectivity under mild conditions (110°C, 15min). The product could be extracted from the reaction mixture, eliminating the need for the neutralisation step that exists in conventional processes. The combination of affordable catalyst and process advantages leads to a greener alternative, competitive against existent industrial applications.

High-Quality Biodiesel Production from Buriti (Mauritia flexuosa) Oil Soapstock.

The buriti palm (Mauritia flexuosa) is a palm tree widely distributed throughout tropical South America. The oil extracted from the fruits of this palm tree is rich in natural antioxidants. The by-products obtained from the buriti palm have social and economic importance as well, hence the interest in adding value to the residue left from refining this oil to obtain biofuel. The process of methyl esters production from the buriti oil soapstock was optimized considering acidulation and esterification. The effect of the molar ratio of sulfuric acid (H2SO4) to soapstock in the range from 0.6 to 1.0 and the reaction time (30–90 min) were analyzed. The best conditions for acidulation were molar ratio 0.8 and reaction time of 60 min. Next, the esterification of the fatty acids obtained was performed using methanol and H2SO4 as catalyst. The effects of the molar ratio (9:1–27:1), percentage of catalyst (2–6%) and reaction time (1–14 h) were investigated. The best reaction conditions were: 18:1 molar ratio, 4% catalyst and 14 h reaction time, which resulted in a yield of 92% and a conversion of 99.9%. All the key biodiesel physicochemical characterizations were within the parameters established by the Brazilian standard. The biodiesel obtained presented high ester content (96.6%) and oxidative stability (16.1 h).

Interactions among trioctylamine-sulfuric acid-water: experiments and molecular dynamics simulations

Trioctylamine (TOA) has been widely regarded as a cost effective extractant and received extensive applications in the metallurgical industry. However, TOA is prone to aggregate and form something like viscoelastic material when it meets the sulfuric acid. However, there is no unified understanding of the mechanism of aggregation. Based on the possible molecular interaction model proposed in our previous work, we are going to probe the interaction of TOA and the sulfuric acid as well as to obtain a chemical structure corresponding to various molar ratios through molecular dynamics calculations together with a specific distance distribution function. The results show that the hydrogen bonding of the whole system strengthens with the increase of the molar ratio of sulfuric acid and water to TOA. When the molar ratio of sulfuric acid and water to TOA is comparatively low, the hydrogen bonds interactions between TOA and water was predominated. When the ratio is high, TOA will react with sulfuric acid through protonation. The results of the simulation is consistent with our previous studies.