Acetic Acid Molar Research Articles

Kinetics and mechanism of the photocatalytic degradation of acetic acid in absence or presence of O 2

Abstract Transforming pollution into valuable compounds and more especially into energy is an important challenge for a sustainable future. The objective of our work was to better understand the mechanism of the photocatalytic degradation of acetic acid (AA) in the gas phase under an air or oxygen-free atmosphere, by comparing the disappearance, mineralization and selectivity of the intermediate products formed in the presence of non-doped TiO 2 . It was found that in both environments decarboxylation is the first step of AA degradation. However, the fate of the methyl group depends on the carrier gas and gas phase concentration. In air, at low AA molar flow the methyl group is oxidized into methanol, formaldehyde, and CO 2 with no formic acid detected. At molar flows larger than 0.55 μmol/min, corresponding to the saturation of the TiO 2 surface, ethane is formed due to the combination of two methyl groups. In an O 2 -free atmosphere, three new products were detected: methane (CH 4 ), acetone (CH 3 COCH 3 ) and acetaldehyde (CH 3 COH). However, the use of CH 3 13 COOH shows that acetone and acetaldehyde do not arise from the reduction of the carboxylic group. Under air, a mechanism explaining the formation of methanol, formaldehyde and ethane occurring on the surface of TiO 2 , involving either a direct oxidation of AA with the holes or an oxidation with the hydroxyl radicals was proposed, together with the regeneration of the TiO 2 surface and the formation of H 2 O 2 .

Syngas production from steam reforming of acetic acid over Ni- and Co-based catalysts supported on La2O3 and AlLaOx

Ni and Co promoted catalysts supported on single La2O3 and mixed AlLaOx were tested in a fixed bed reactor for the steam reforming of acetic acid. Their performance in AcOH conversion and syngas production was evaluated for its application in solid oxide fuel cells for electricity generation. The samples were prepared with an active metal loading of 10% by wetness impregnation method. The catalytic tests were performed at atmospheric pressure, starting from a steam to acetic acid molar ratio of 2/1, and in the temperature range of 600–800°C. The catalyst composition was analyzed by in-situ XRD analysis in order to see the phase transformations inside the catalyst from room until reactor temperature. Perovskite structures were observed on both single and mixed oxide supported catalysts. All catalysts were active and showed high selectivity to syngas during the screening tests. The obtained selectivities were close to the thermodynamic equilibrium values. Ni/La2O3 catalyst showed a stable performance up to 33h.

Optimization studies on a continuous catalytic reactive distillation column for methyl acetate production with response surface methodology

Esterification of acetic acid with methanol to produce methyl acetate has been studied in a continuous packed bed catalytic reactive distillation column. A novel solid catalyst Indion 180 ion exchange resin was used. The response surface methodology (RSM) technique based on central composite design (CCD) optimization method was used to design the experiments. Experiments were performed under different operating conditions of reboiler temperature, reflux ratio, total feed flow rate, methanol to acetic acid mole ratio, feed locations of acetic acid and methanol with respect to reactive zone and their effect on the conversion of acetic acid as well as on compositions of distillate and bottom products. Based on experimental data and central composite design, a regression model has been developed. The model correlates the purity of methyl acetate in the distillate and six most significant independent variables. From the statistical tests it has been established that the model truly represents the experimental data. There is a good agreement between optimum conditions for methyl acetate concentration in the distillate, predicted by model and experimental data. The comparison of the experimental results with the simulation results from equilibrium stage-wise model compared and found that there is good agreement between them.

Synthesis of cross-linked PVA membranes embedded with multi-wall carbon nanotubes and their application to esterification of acetic acid with methanol

The present study focused on the performance enhancement of cross-linked PVA membrane using citric acid as the cross-linking agent, and by incorporation of treated multi-wall carbon nanotubes (TCN). Hybrid membranes were synthesized and applied as a separation element in a membrane reactor to improve the esterification of acetic acid with methanol in which Amberlyst 15 was used as the catalyst. The properties of the membranes were investigated by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electronic microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), derivative thermal gravimetry (DTG), differential scanning calorimetry (DSC), and tensile test. Moreover, swelling of prepared membranes at 25°C was found for a quaternary feed solution. Results showed that the acid conversion rate was improved with the increasing TCN content of the membranes. It was also indicated that the hybrid membranes had good separating properties for removing water from the reaction mixture. The final conversion of acid was increased from 52.30% to 99.25% using the membrane with 2wt.% TCN instead of the pure membrane at optimized condition and 4h of operation. The operating conditions were optimized as the initial methanol to acetic acid molar ratio of 4:1, reaction temperature of 70°C and catalyst loading of 15wt.% relative to acetic acid.

Binary Oxides with Defined Hierarchy of Pores in the Esterification of Glycerol

Various porous binary oxides with elevated textural properties were obtained in this work. The as-synthesized solids were calcined or modified by reflux and extraction processes. Characterizations through SEM, nitrogen physisorption and TEM techniques demonstrated the formation of porous metal oxide networks over all solids. XRD, thermal analyses and FTIR measurements showed the existence of nanosized rutile TiO2, tetragonal ZrO2, SiO2 and γ-Al2O3 phases on the solids. The structure and texture of the as-synthesized SiAl sol-gel derived solid resulted in the formation of well-dispersed nanoparticles on the support. The removal of the organic compounds by ethanol extraction or reflux from SiAl resulted in the presence of structures with defined hierarchy of pores. Among the solids studied, the catalytic results in the esterification of glycerol with acetic acid indicated that best performances were obtained over SiAl sample when submitted to extraction and reflux treatments. This was due to the creation of accessible pores, which facilitated the reaction occurrence at glycerol to acetic acid molar ratio = 1:3 and T = 80 °C for 20 h using 75 mg of catalyst. The solids can be reused three times without complete loss of their catalytic performance.

Glucolytic fingerprinting reveals metabolic groups within the genus Bifidobacterium: an exploratory study.

Microorganisms of the genus Bifidobacterium are inhabitants of diverse niches including the digestive tract of humans and animals. The species Bifidobacterium adolescentis, Bifidobacterium animalis, Bifidobacterium bifidum, Bifidobacterium breve and Bifidobacterium longum have qualified presumption of safety status granted by EFSA and several strains are considered probiotic, and are being included in functional dairy fermented products. In the present work we carried out a preliminary exploration of general metabolic characteristics and organic acid production profiles of a reduced number of strains selected from these and other species of the genus Bifidobacterium. The use of resting cells allowed obtaining metabolic fingerprints without interference of metabolites accumulated during growth in culture media. Acetic acid was the most abundant organic acid formed per mol of glucose consumed (from 1.07 ± 0.03 to 1.71 ± 0.22 mol) followed by lactic acid (from 0.34 ± 0.06 to 0.90 ± 0.12 mol), with moderate differences in production among strains; pyruvic, succinic and formic acids were also produced at considerably lower proportions, with variability among strains. The acetic to lactic acid ratio showed lower values in stationary phase as regard to the exponential phase for most, but not all, the microorganisms; this was due to a decrease in acetic acid molar proportions together with increases of lactic acid proportions in stationary phase. A linear discriminant analysis allowed to cluster strains into species with 51-100% probability, evidencing different metabolic profiles, according to the relative production of organic acids from glucose by resting cells, of microorganisms collected at the exponential phase of growth. Looking for a single metabolic marker that could adequately discriminate metabolic groups, we found that groups established by the acetic to lactic acid ratio fit well with differences previously evidenced by the discriminant analysis. The proper establishment of metabolic groups within the genus Bifidobacterium could help to select the best suited probiotic strains for specific applications.

Investigation of purification process stresses on erythropoietin peptide mapping profile.

Background:Full compliance of recombinant protein peptide mapping chromatogram with the standard reference material, is one of the most basic quality control tests of biopharmaceuticals. Changing a single amino acid substitution or side chain diversity for a given peptide changes protein hydrophobicity and causes peak shape or retention time alteration in a peptide mapping assay. In this work, the effect of different stresses during the recombinant erythropoietin (EPO) purification process, including pH 4, pH 5, and room temperature were checked on product peptide mapping results.Materials and Methods:Cell culture harvest was purified under stress by different chromatographic techniques consisting of gel filtration, anionic ion exchange, concentration by ultrafiltration, and high resolution size exclusion chromatography. To induce more pH stresses, the purified EPO was exposed to pH stress 4 and 5 by exchanging buffer by a 10 KDa dialysis sac overnight. The effects of temperature and partial deglycosylation (acid hydrolysis) on purified EPO were also studied by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and peptide mapping analysis. Removal of sialic acid by mild hydrolysis was performed by exposure to two molar acetic acid at 80°C for 3 h.Results:No significant effect was observed between intact and stressed erythropoietin peptide mapping profiles and SDS-PAGE results. To validate the sensibility of the technique, erythropoietin was partially acid hydrolyzed and significant changes in the chromatographic peptide map of the intact form and a reduction on its molecular weight were detected, which indicates some partial deglycosylation.Conclusions:Purification process does not alter the peptide mapping profile and purification process stresses are not the cause of peptide mapping noncompliance.

Preparation of N-Butyl Acetate from Dilute Acetic Acid Wastewater by Phase Transfer Catalyst CTMAB

The experiment disposing waste water with dilute acetic acid aimed to recycle acetic acid and synthesize high value added n-butyl acetate with cetyl trimethyl ammonium bromide (CTMAB) as the phrase transfer catalyst. Over-dose n-butanol was added and n-butyl acetate was extracted with the mixed solution of trioctylamine (TOA) (20%,w) and tributylphosphate (TBP) (80%,w) as the extractant. After the still standing and liquid separation, the organic phase was depressurized and distilled under the pressure 25kPa.The n-butanol and a part of acetic acid were recycled, and n-butyl acetate was collected between temperature 70°C-75°C. The synthetic process parameters were optimized, that was: CTMAB 0.35g /0.127mol acetic acid, TOA/TBP 30ml, the ratio of alcohol and acid 1.3:1.0, reaction time 2.5h, reaction temperature 30°C.The extraction rate of acetic acid was 88.2%.The yield of n-butyl acetate was 81.3% and phrase transfer catalyst with extractant was recycled for 6 times whose effect was reduced a little but good enough. This experiment, which included esterification reaction with phase transfer catalyst and extractive distillation process, has received a satisfactory effect and can be used in similar system.

Glycerol Valorization as Biofuel Additives by Employing a Carbon-Based Solid Acid Catalyst Derived from Glycerol

A two-step process was developed for the preparation of triacetylglycerol (TAG), a biofuel additive employing a solid acid catalyst derived from glycerol. The first step involves esterification of glycerol with acetic acid (1:4 mol) at 115 °C for 1 h in the presence of catalyst (5 wt %) to obtain 100% conversion of glycerol with 22, 67, and 11% MAG, DAG, and TAG, respectively. In the second step, the esterified product mixture after removal of excess acetic acid and moisture was acetylated with acetic anhydride (1 mol with respect to glycerol) at 115 °C for 30 min to obtain 100% TAG. The recovered catalyst was reused for five cycles without any significant loss of its initial activity. The protocol is cost-effective due to the use of highly stable and recyclable SO3H-carbon catalyst for the production of TAG with minimum moles of acetic acid and acetic anhydride in shorter reaction time.

Selective Esterification of Ethylene Glycol Ethyl Ether over Silica-Cerous

With silica-cerous of high activity as catalyst, ethylene glycol ethyl ether acetate was synthesized from ethylene glycol ethyl ether and acetic acid. The proper conditions for the synthesis were obtained by a single factor experiment and orthogonal experiment. Based on 0.3 mol acetic acid, the optimum conditions were as follows: the mass ratio of silica-cerous (15% loaded sulfate cerous) / acetic acid being 0.056 : 1, the mol ratio of acetic acid / ethylene glycol ethyl ether being1 : 1.2, the amount of cyclohexane being 30 mL, reaction temperature being 90 °C, and reaction time being 2 h. Such optimal conditions give the highest yield of 99.53 % and selectivity of 100 % of ethylene glycol ethyl ether acetate. Its structure was confirmed by IR, and the catalyst still has high activity after being reused for five times.

Biological Production of Succinic Acid Using Cull Peach Medium: Effects of Corn Steep Liquor Supplement and Hydrogen Sparging

<abstract> <bold><sc>Abstract</sc>.</bold> The feasibility of using cull peach, which is an agricultural waste generated in large quantities in the U.S. (13,000 MT in 2012), as a medium for the biological production of succinic acid by Escherichia coli AFP184 was investigated. The effects of corn steep liquor (CSL) supplement and exogenous hydrogen supply were also studied. Sucrose, the predominant but unmetabolizable sugar in cull peach medium, was converted to fermentable sugars (glucose and fructose) during sterilization and subsequently with invertase. Without CSL supplement, fructose consumption was incomplete and the final succinic acid concentration of 38.8 g L^-1 was achieved with a yield of 0.75 g g^-1 sugars consumed and a succinic acid:acetic acid molar ratio of 5.1:1. When CSL was supplemented to the medium, the final succinic acid concentration increased to 47.0 g L^-1 and the yield increased to 0.85 g g^-1 sugars consumed, but the succinic acid:acetic acid molar ratio remained at 5.6:1. With hydrogen sparging into the unsupplemented medium, the final succinic acid concentration increased to 45.5 g L^-1, the yield increased to 0.84 g g^-1 sugars consumed, and the succinic acid:acetic acid molar ratio increased to 7.7:1.

Synthesis of Epoxidized Canola Oil Using a Sulfated-SnO2 Catalyst

In the present investigation, a heterogeneous sulfated-SnO2 catalyst was synthesized and used for the epoxidation of unsaturation present in the canola oil. The physicochemical properties were studied to measure the surface and bulk properties of prepared SnO2 and sulfated-SnO2 samples. Process optimization studies were performed for parameters such as catalyst loading, ethylenic unsaturation in canola oil to hydrogen peroxide molar ratio, ethylenic unsaturation in canola oil to acetic acid molar ratio, and temperature. Sulfated-SnO2 demonstrated promising catalytic activity with 100% conversion of unsaturation in canola oil to epoxy canola oil in 6 h at optimum process conditions. Based on the experimental results and kinetic data, a Langmuir–Hinshelwood-Hougen-Watson type mechanism was proposed, and the reaction followed pseudo first order. Calculated energy of activation was 17.75 kcal/mol. The tribological properties of epoxy canola oil such as lubricity property in terms of wear scar length, kinemati...

Synthesis and investigation of the physicochemical properties of 2-(5-((theophylline-7'-yl)methyl)-4-phenyl-4H-1,2,4-triazole-3-ylthio)-acetic acid salts

Synthesis and investigation of the physicochemical properties of 2-(5-((theophylline-7'-yl)methyl)-4-phenyl-4H-1,2,4-triazole-3-ylthio)-acetic acid salts

Catalytic Synthesis of Isoamyl Acetate Catalyzed by (NH&lt;sub&gt;4&lt;/sub&gt;)&lt;sub&gt;6&lt;/sub&gt;[MnMo&lt;sub&gt;9&lt;/sub&gt;O&lt;sub&gt;32&lt;/sub&gt;]•8H&lt;sub&gt;2&lt;/sub&gt;O Supported Activated Carbon with Waugh Structure

The synthesis of isoamyl acetate with ammonium 9-molybdate manganese heteropolyacid salt supported activated carbon as catalyst was studied. The optimum reaction conditions are obtained as follows: isoamyl alcohol to acetic acid molar ratio = 1.646, the weight of catalyst is 40% of total weigh, m (acidulate catalyst)=0.2g, m (water carrying reagent toluene) = 3ml, reaction time is about 63 minutes. Selectivity is 100% and conversion rate is 89.48%.

Hydrogen Production via Sorption Enhanced Steam Reforming of Acetic Acid: A Thermodynamic Study

The reaction thermodynamics of sorption enhanced steam reforming (SESR) of acetic acid as a model compound of bio-oil for hydrogen production were investigated and contrasted with acetic acid steam reforming (SR). The most favorable temperature for SR is approximately 650 °C. However, the optimum temperature for SESR is around 550 °C, which is about 100 °C lower than that for SR. The highest hydrogen concentration from SR is only 67%, which is below the basic requirement of hydrogen purity for fuel cells. In SESR, hydrogen purities are over 99% in 500-550 °C with a calcium oxide to acetic acid molar ratio (CAMR) of 4 and a water to acetic acid molar ratio (WAMR) greater than 6. The results show that hydrogen production from sorption enhanced steam reforming of acetic acid should be a promising direction.

Molecular weight distribution of soluble fiber fractions and short chain fatty acids in ileal digesta of growing pigs.

The effect of dietary fiber source on molecular weight (MW) distribution of soluble fiber fractions and short chain fatty acids (SCFA) in ileal digesta of 7 post valve T-cecum (PVTC) cannulated growing pigs was studied. Pigs were fed semisynthetic diets with sugar beet (Beta vulgaris) pulp (SBP) or chicory (Cichorium intybus) forage (CFO) as fiber sources of which the soluble nonstarch polysaccharide (NSP) fraction originated mainly from pectin. Three MW intervals were selected-large MW (MWL): 10,000,000 to 1,000,000 g/mol, medium MW (MWM): 1,000,000 to 200,000 g/mol, and small MW (MWS): 200,000 to 10,000 g/mol-and the relative distribution (% of total) of molecules in each interval was calculated. The MWM fraction was higher (P < 0.05) in ileal digesta of pigs fed diet SBP and the MWS fraction was higher (P < 0.05) in ileal digesta of pigs fed diet CFO. The mole/100 mole of propionic acid (HPr) was higher (P < 0.010) in pigs fed diet SBP whereas pigs fed diet CFO had higher (P < 0.010) mole/100 mole of acetic acid (HAc). The proportion of the MWL and MWM fractions in ileal digesta were negatively correlated to HAc (r = -0.52, P = 0.05, and r = -0.62, P = 0.02, respectively). The proportion of MWM in ileal digesta was positively correlated to HPr (r = 0.83; P = 0.001) whereas MWS and HPr were negatively correlated (r = -0.76; P = 0.002). In conclusion, the bacterial degradation of the soluble NSP fraction is selective and MW distribution may explain differences in SCFA production.

Thermodynamic Investigation of Acetic Acid Steam Reforming for Hydrogen Production

The thermodynamics of acetic acid steam reforming (AASR) for hydrogen production were simulated using a Gibbs free energy minimization method to study the influences of pressure, temperature and water to acetic acid molar feed ratios (WAFR) on the AASR. On the basis of the equilibrium calculations, the optimal operating conditions obtained were 700-800 oC, 1bar and WAFR = 6-10. At these conditions, the yield and selectivity of hydrogen were maximized and the formation of methane and coke was almost inhibited. Higher pressures had negative effects on the yields and selectivities of hydrogen and carbon monoxide. With increasing temperature from 300 to 1000 oC, the selectivity for hydrogen and carbon monoxide increased significantly along with a reduction in methane selectivity. Increase in the WAFR led to the increase in hydrogen selectivity and the decrease in carbon monoxide selectivity.

Glycerol acetylation catalysed by ion exchange resins

Five types of ion exchange resins (Amberlyst 15, Ambertlyst-36, Dowex 50Wx2, Dowex 50Wx4 and Dowex 50Wx8) have been compared in glycerol acetylation carried out at 378K and atmospheric pressure. The glycerol:acetic acid molar ratio was set to 8:1. In these conditions the best performances were exhibited by Amberlyst-36 and Dowex-2. The effects of catalyst loading and the pre-treatment were also studied for the latter catalysts, showing that the use of 6.25g of dry catalyst/l of glycerol resulted in the optimal conditions for our reaction. The catalytic performances of the resins were unaltered after washing with distilled water in a Soxhlet apparatus, showing that sulphonic species were not removed by leaching. Recyclability tests showed that these solids are directly reusable up to 4–5 esterification runs. No homogeneous catalysis was detected in the filtered liquid media obtained after contact with the solids. Resins are not deactivated by the presence of water in the reaction medium.

Synthesis of hybrid SBA-15 functionalized with molybdophosphoric acid as efficient catalyst for glycerol esterification to fuel additives

Fibrous mesoporous hybrid silica (SBAH-15) with mesopore diameter of 70Å was synthesized using pluronic P123 (EO20PO70EO20) as surfactant, with Brij S100 as nonionic co-surfactant. Series of catalysts with different molybdophosphoric acid (MPA) loading (5–25%) were synthesized by the thermal decomposition of MPA species in the lattice of SBAH-15. Catalysts calcined at 560°C undergone a thermal decomposition of MPA resulted in the formation of β-MoO3 active species. The effectiveness of the hybrid support was evaluated by comparison with analogous catalyst prepared by incorporating MPA into the framework of classical SBA-15. The catalytic performance of the prepared acid catalysts was examined during glycerol esterification with acetic acid. Mono-, di- and triacetyl glycerol (MAG, DAG and TAG, respectively) were the esterification reaction products. SBAH-15(15) catalyst, with 15wt.% MPA loading, exhibited an excellent activity during this reaction, indicated by the complete glycerol conversion (after 1h) with a corresponding combined selectivity of 86% toward both DAG and TAG. The best reaction conditions are: reaction temperature of 110°C, glycerol to acetic acid molar ratio of 1:6 and reaction time of 3h. The SBAH-15(15) catalyst demonstrated good stability in activity upon recycling for four times.

Biohydrogen production by Rhodobacter capsulatus Hup− mutant in pilot solar tubular photobioreactor

In this study, a pilot solar tubular photobioreactor was successfully implemented for fed batch operation in outdoor conditions for photofermentative hydrogen production with Rhodobacter capsulatus (Hup−) mutant. The bacteria had a rapid growth with a specific growth rate of 0.052 h−1 in the batch exponential phase and cell dry weight remained in the range of 1–1.5 g/L throughout the fed batch operation. The feeding strategy was to keep acetic acid concentration in the photobioreactor at the range of 20 mM by adjusting feed acetate concentration. The maximum molar productivity obtained was 0.40 mol H2/(m3 h) and the yield obtained was 0.35 mol H2 per mole of acetic acid fed. Evolved gas contained 95–99% hydrogen and the rest was carbon dioxide by volume.