Ethanol Mole Research Articles

Co-production of acetone and ethanol with molar ratio control enables production of improved gasoline or jet fuel blends.

The fermentation of simple sugars to ethanol has been the most successful biofuel process to displace fossil fuel consumption worldwide thus far. However, the physical properties of ethanol and automotive components limit its application in most cases to 10-15 vol% blends with conventional gasoline. Fermentative co-production of ethanol and acetone coupled with a catalytic alkylation reaction could enable the production of gasoline blendstocks enriched in higher-chain oxygenates. Here we demonstrate a synthetic pathway for the production of acetone through the mevalonate precursor hydroxymethylglutaryl-CoA. Expression of this pathway in various strains of Escherichia coli resulted in the co-production of acetone and ethanol. Metabolic engineering and control of the environmental conditions for microbial growth resulted in controllable acetone and ethanol production with ethanol:acetone molar ratios ranging from 0.7:1 to 10.0:1. Specifically, use of gluconic acid as a substrate increased production of acetone and balanced the redox state of the system, predictively reducing the molar ethanol:acetone ratio. Increases in ethanol production and the molar ethanol:acetone ratio were achieved by co-expression of the aldehyde/alcohol dehydrogenase (AdhE) from E. coli MG1655 and by co-expression of pyruvate decarboxylase (Pdc) and alcohol dehydrogenase (AdhB) from Z. mobilis. Controlling the fermentation aeration rate and pH in a bioreactor raised the acetone titer to 5.1 g L(-1) , similar to that obtained with wild-type Clostridium acetobutylicum. Optimizing the metabolic pathway, the selection of host strain, and the physiological conditions employed for host growth together improved acetone titers over 35-fold (0.14-5.1 g/L). Finally, chemical catalysis was used to upgrade the co-produced ethanol and acetone at both low and high molar ratios to higher-chain oxygenates for gasoline and jet fuel applications. Biotechnol. Bioeng. 2016;113: 2079-2087. © 2016 Wiley Periodicals, Inc.

Coupling exothermic and endothermic reactions in an ethanol microreformer for H2 production

The steam reforming of ethanol is carried out in a microreactor for hydrogen production. The heat for the endothermic reactions is supplied by means of ethanol combustion in air, which is carried out in contiguous microchannels. The same Pd-based catalyst is assumed to be coated on both reforming and combustion channels. By means of a 1D heterogeneous mathematical model, the influence of the feed temperatures of both streams on the reactor performance is analyzed. The results show that the degree of preheating of both streams has a strong influence on the hydrogen yields and maximum temperatures. The effect of the flowrate and composition of the fuel stream on the hydrogen yields is also studied.Fairly high hydrogen yields were obtained (2.6<ηH2<3.4) with low methane slips, within a feasible range of temperatures for the Pd catalyst (700<TMAX<770°C) to avoid catalyst deactivation. These maximum temperatures could still be further reduced by means of an optimal selection of the air flowrate and ethanol molar fraction on the fuel side, or using distributed feed of fuel along the reactor length.

Experimental and exergy evaluation of ethanol catalytic steam reforming in a membrane reactor

The application of exergy analysis in the evaluation of the ethanol steam reforming (ESR) process in a catalytic membrane reactor (CMR) was presented. ESR experiments were performed at T=873–923K and P=4–12bar in a CMR containing Pd–Ag membranes sandwiched by Pd–Rh/CeO2 catalyst, aiming to produce fuel cell grade pure hydrogen. The effect of the operating conditions on the pure hydrogen production rate, hydrogen yield and recovery, exergy efficiency, and thermodynamic losses was investigated. Total hydrogen yield of 3.5mol H2 permeated per mol ethanol in feed with maximum hydrogen recuperation of 90% was measured at 923K and 12bar. The highest amount of exergy was destructed via heat losses and the retentate gas stream. Exergy efficiency up to around 50% was reached in the case of the insulated reactor at 12bar and 923K. Exergy efficiency placed between 70–90% in the case of recovery of the retentate gas in an insulated reactor. It was concluded that operating at the highest pressure, the lowest S/C ratio, and 923K gives the best exergy efficiency.

Co-production of hydrogen and ethanol from glucose by modification of glycolytic pathways in Escherichia coli - from Embden-Meyerhof-Parnas pathway to pentose phosphate pathway.

Hydrogen (H2) production from glucose by dark fermentation suffers from the low yield. As a solution to this problem, co-production of H2 and ethanol, both of which are good biofuels, has been suggested. To this end, using Escherichia coli, activation of pentose phosphate (PP) pathway, which can generate more NADPH than the Embden-Meyhof-Parnas (EMP) pathway, was attempted. Overexpression of two key enzymes in the branch nodes of the glycolytic pathway, Zwf and Gnd, significantly improved the co-production of H2 and ethanol with concomitant reduction of pyruvate secretion. Gene expression analysis and metabolic flux analysis (MFA) showed that, upon overexpression of Zwf and Gnd, glucose assimilation through the PP pathway, compared with that of the EMP or Entner-Doudoroff (ED) pathway, was greatly enhanced. The maximum co-production yields were 1.32 mol H2 mol(-1) glucose and 1.38 mol ethanol mol(-1) glucose, respectively. It is noteworthy that the glycolysis and the amount of NAD(P)H formed under anaerobic conditions could be altered by modifying (the activity of) several key enzymes. Our strategy could be applied for the development of industrial strains for biological production of reduced chemicals and biofuels which suffers from lack of reduced co-factors.

Measurement and Correlation of Solubility of Cefathiamidine in Water + (Acetone, Ethanol, or 2-Propanol) from (278.15 to 308.15) K

In this study, the solubility of cefathiamidine was measured in water + (acetone, ethanol, or 2-propanol) at temperature from (278.15 to 313.15) K by using a gravimeteic method. The solubility of cefathiamidine increased with increasing temperature. Besides, at a given temperature, solubility in different mixtures follows different rules. In water + (acetone or 2-propanol), it decreases with the increase of the initial molar fraction of acetone or 2-propanol; whereas synergistic effect of mixed solvents was observed in water + ethanol mixtures, and solubility reached maximum at the ethanol molar fraction of 0.4. The experimental data were well correlated by the modified Apelblat equation, the CNIBS/R-K model, the combined version of the Jouyban–Acree and van’t Hoff model, and the combined version of the Jouyban–Acree and the modified Apelblat model. Furthermore, the thermodynamic functions of dissolution of cefathiamidine in different mixtures were obtained based on the van’t Hoff equation and the modified Apelblat equation. The results indicate that the dissolution process of cefathiamidine is endothermic.

The Effect of Fatty Acid Ethyl Esters Concentration on the Kinematic Viscosity of Biodiesel Fuel

Several biodiesel fuel samples produced from rapeseed oil by the noncatalyzed transesterification reaction with supercritical ethanol at various temperatures from (593 to 653) K and molar ethanol to rapeseed oil ratios from (6:1 to 20:1) were used to measure kinematic viscosity. Measurements were made using the capillary viscometer (VPZ-2, Labtex Com., Moscow). The combined expanded uncertainty of the kinematic viscosity measurements at the 95 % confidence level with a coverage factor of k = 2 is estimated to be 0.35 %. All measurements were made at temperature of 313.5 K (ASTM D445) and at atmospheric pressure. The effect of fatty acid ethyl esters (FAEEs) content on the kinematic viscosity of biodiesel fuel samples at 313.15 K was studied. The correlation between the FAEEs concentration in biodiesel fuel samples and their measured kinematic viscosity at 313.15 K was found. The derived correlation between the kinematic viscosity and the FAEEs contents allows controlling the progress of the rapeseed oil t...

Enthalpies of dissolution of flavonoids in 96% ethanol at 25°C

The enthalpies of dissolution of pinostrobin hydrazone C16H16N2O3, (N-ethyl-2-(5-hydroxy-7-methoxy-2-phenylchroman-4-ylidene)hydrazino-1-carbothiamide) thiosemicarbazone C19H21N3O3S, salvigenine C18H16O6, and pinostrobin-2-(5-hydroxy-7-methoxy-2-phenylchroman-4-ylidene)-N-phenylhydrazino- 1-carbothiamide thiosemicarbazide C23H21N3O3S are measured on a DAK-I-IA calorimeter at flavonoid: ethanol molar ratios of 1 : 9000, 1 : 18000, and 1 : 36000. Their standard enthalpies of dissolution in 96% ethanol are calculated from the obtained data. Their standard enthalpies of combustion, melting, and formation are estimated by approximate methods.

Energy Conservation Associated with Ethanol Formation from H2 and CO2 in Clostridium autoethanogenum Involving Electron Bifurcation.

Most acetogens can reduce CO2 with H2 to acetic acid via the Wood-Ljungdahl pathway, in which the ATP required for formate activation is regenerated in the acetate kinase reaction. However, a few acetogens, such as Clostridium autoethanogenum, Clostridium ljungdahlii, and Clostridium ragsdalei, also form large amounts of ethanol from CO2 and H2. How these anaerobes with a growth pH optimum near 5 conserve energy has remained elusive. We investigated this question by determining the specific activities and cofactor specificities of all relevant oxidoreductases in cell extracts of H2/CO2-grown C. autoethanogenum. The activity studies were backed up by transcriptional and mutational analyses. Most notably, despite the presence of six hydrogenase systems of various types encoded in the genome, the cells appear to contain only one active hydrogenase. The active [FeFe]-hydrogenase is electron bifurcating, with ferredoxin and NADP as the two electron acceptors. Consistently, most of the other active oxidoreductases rely on either reduced ferredoxin and/or NADPH as the electron donor. An exception is ethanol dehydrogenase, which was found to be NAD specific. Methylenetetrahydrofolate reductase activity could only be demonstrated with artificial electron donors. Key to the understanding of this energy metabolism is the presence of membrane-associated reduced ferredoxin:NAD(+) oxidoreductase (Rnf), of electron-bifurcating and ferredoxin-dependent transhydrogenase (Nfn), and of acetaldehyde:ferredoxin oxidoreductase, which is present with very high specific activities in H2/CO2-grown cells. Based on these findings and on thermodynamic considerations, we propose metabolic schemes that allow, depending on the H2 partial pressure, the chemiosmotic synthesis of 0.14 to 1.5 mol ATP per mol ethanol synthesized from CO2 and H2. Ethanol formation from syngas (H2, CO, and CO2) and from H2 and CO2 that is catalyzed by bacteria is presently a much-discussed process for sustainable production of biofuels. Although the process is already in use, its biochemistry is only incompletely understood. The most pertinent question is how the bacteria conserve energy for growth during ethanol formation from H2 and CO2, considering that acetyl coenzyme A (acetyl-CoA), is an intermediate. Can reduction of the activated acetic acid to ethanol with H2 be coupled with the phosphorylation of ADP? Evidence is presented that this is indeed possible, via both substrate-level phosphorylation and electron transport phosphorylation. In the case of substrate-level phosphorylation, acetyl-CoA reduction to ethanol proceeds via free acetic acid involving acetaldehyde:ferredoxin oxidoreductase (carboxylate reductase).

Ethanol production by a Paenibacillus species isolated from an Icelandic hot spring – Production yields from complex biomass

Ethanol production using Paenibacillus strain J2 was studied on carbohydrates and lignocellulosic biomass hydrolysates including grass (Phleum pratense) and barley straw (Hordeum vulgare). The strain has a broad substrate spectrum; fermentation of glucose yielded ethanol (major product), acetate, butyrate (minor), hydrogen, and carbon dioxide. At glucose concentrations below 30 mM fermentation was not inhibited. Higher substrate loadings resulted in decreased glucose utilization and a shift of end products towards butyrate. The maximum yields of ethanol were 1.45 mol ethanol mol glucose -1 . The end products from lignocellulosic (4.5 g L -1 dw) biomass hydrolysates pretreated with 0.5% HCl or NaOH (control was unpretreated) prior to cellulase treatment were investigated. Ethanol production from cellulose hydrolysates without chemical pre-treatment yielded 5.5 mM ethanol g -1 with lower yields from paper and lignocellulosic biomasses (1.2-1.7 mM g -1 ). Ethanol production was enhanced by dilute acid or base pre-treatment combined with enzymatic treatment with the highest yields from grass (3.2 mM ethanol g -1

Degradation of Acetaldehyde and Its Precursors by Pelobacter carbinolicus and P. acetylenicus

Pelobacter carbinolicus and P. acetylenicus oxidize ethanol in syntrophic cooperation with methanogens. Cocultures with Methanospirillum hungatei served as model systems for the elucidation of syntrophic ethanol oxidation previously done with the lost “Methanobacillus omelianskii” coculture. During growth on ethanol, both Pelobacter species exhibited NAD+-dependent alcohol dehydrogenase activity. Two different acetaldehyde-oxidizing activities were found: a benzyl viologen-reducing enzyme forming acetate, and a NAD+-reducing enzyme forming acetyl-CoA. Both species synthesized ATP from acetyl-CoA via acetyl phosphate. Comparative 2D-PAGE of ethanol-grown P. carbinolicus revealed enhanced expression of tungsten-dependent acetaldehyde: ferredoxin oxidoreductases and formate dehydrogenase. Tungsten limitation resulted in slower growth and the expression of a molybdenum-dependent isoenzyme. Putative comproportionating hydrogenases and formate dehydrogenase were expressed constitutively and are probably involved in interspecies electron transfer. In ethanol-grown cocultures, the maximum hydrogen partial pressure was about 1,000 Pa (1 mM) while 2 mM formate was produced. The redox potentials of hydrogen and formate released during ethanol oxidation were calculated to be EH2 = -358±12 mV and EHCOOH = -366±19 mV, respectively. Hydrogen and formate formation and degradation further proved that both carriers contributed to interspecies electron transfer. The maximum Gibbs free energy that the Pelobacter species could exploit during growth on ethanol was −35 to −28 kJ per mol ethanol. Both species could be cultivated axenically on acetaldehyde, yielding energy from its disproportionation to ethanol and acetate. Syntrophic cocultures grown on acetoin revealed a two-phase degradation: first acetoin degradation to acetate and ethanol without involvement of the methanogenic partner, and subsequent syntrophic ethanol oxidation. Protein expression and activity patterns of both Pelobacter spp. grown with the named substrates were highly similar suggesting that both share the same steps in ethanol and acetalydehyde metabolism. The early assumption that acetaldehyde is a central intermediate in Pelobacter metabolism was now proven biochemically.

A new sustainable route in supercritical CO2 to functionalize silica SBA-15 with 3-aminopropyltrimethoxysilane as material for carbon capture

A new sustainable route to functionalize silica SBA-15 with 3-aminopropyltrimethoxysilane (3APTS) in supercritical CO2 (scCO2) is proposed. The aminosilane/carbamate salt formed (organic salt) by reaction between CO2 and the primary amine group of 3APTS was solubilized in scCO2 by adding 10%mol ethanol as cosolvent. For the first time such a mixture was used to perform the surface functionalization whilst keeping the advantages of performing the reaction in a supercritical fluid at a moderate temperature. Firstly, the phase behaviour of the 3APTS/carbamate+CO2+ethanol was studied to select the process experimental conditions. Then, the functionalization experiments were performed at temperatures of 313 and 333K, pressures ranging from 12.5 to 20.0MPa and concentration values of 3APTS in the modified scCO2 ranging from 0.5 to 3.5×10−3 in molar fraction. The amine functionalized materials were characterized by IR, thermogravimetric analysis, elemental analysis and N2 adsorption isotherms. The effect of pressure and temperature on the amount of 3APTS grafted on silica SBA-15 was not significant. However, as the 3APTS concentration in scCO2 modified with ethanol increased, the grafting density of 3APTS increased gradually and the surface area, pore volume and size of silica SBA-15 were also progressively reduced. The functionalization process in scCO2 was compared to that of the conventional method using toluene. Finally, the performance of the materials for CO2 sorption at low and high-pressure was evaluated. The amine functionalized silica SBA-15 exhibited good CO2 adsorption capacity: 0.7–1.5mmolg−1 at ambient pressure and 8–12mmolg−1 at 4.0MPa. These values indicate the great potential of the amine functionalized silica obtained in scCO2 for carbon capture technology.

Biological reformation of ethanol to hydrogen by Rhodopseudomonas palustris CGA009

A future hydrogen economy requires the sustainable production of renewable hydrogen. One method to produce hydrogen from stored renewable energy could be through reformation of bioethanol. However, chemically catalyzed reformation processes, although well studied, still present a number of significant technical challenges. Here, bioreformation of ethanol to hydrogen by photofermentation with the photosynthetic bacterium Rhodopseudomonas palustris is described. Cultures were shown to tolerate up to 2% ethanol. An RSM (response surface methodology) was carried out in which three key factors, light intensity, and ethanol and glutamate concentrations were varied. The results showed that nearly 2mol of H2 could be obtained from one mole of ethanol, 33% of that theoretically possible.

What is the state of aggregation of ethanol molecules in ethanol–supercritical carbon dioxide mixtures? An FTIR investigation in the full molar fraction range

The evolution of the degree of hydrogen bonding of ethanol molecules in scCO2–ethanol mixtures for different molar fraction (from 0.5 to 100% in ethanol) in the temperature range 40–200°C and at two different constant pressures P=15 and 20MPa is reported in this paper. For a given pressure, we observe a strong dependence of the degree of hydrogen bonding as a function of temperature and ethanol molar fraction. We emphasize that a detailed knowledge of the degree of hydrogen bonding of ethanol molecules in these binary systems is important for the understanding and the further development of the supercritical fluid technology.

Hydrogen production by ethanol steam reforming over Rh nanoparticles supported on lanthana/silica systems

The aim of the present work was to investigate Rh nanoparticle catalysts supported on La2O3–SiO2, with different contents of La2O3, in the ethanol steam reforming reaction. The size of Rh particles was determined by both XPS, applying the Davis model, and CO chemisorption measurements. Particle sizes between 1.2 and 3nm were estimated with these techniques. The catalyst with 15wt.% of La2O3 was the most stable one under the different reaction conditions under study, i.e. 773K and water to ethanol molar ratios of 3 and 5. In order to explain the deactivation observed in the other catalysts, the samples used in the reaction were characterized by XPS, TEM and in situ Raman spectroscopy. The TEM results allowed a direct visualization of the carbon deposits that presented different degrees of catalyst coverage. The surface of the most stable catalyst was not fully covered by carbon while the Rh/La2O3(40)–SiO2 sample, which deactivated partially, exhibited a carbon layer uniformly distributed over the surface. The oxidation of the carbon deposits was analyzed using in situ Raman spectroscopy. Results were in agreement with those obtained by TEM microscopy. DRIFTS experiments under reaction conditions suggested that the direct decomposition of ethoxy species would produce hydrogen, CO, and CHx species, which could result in carbon formation.

Bioethanol Production from Glycerol by Mixed Culture System

Glycerol, a by-product from biodiesel industry, is a promising feedstock for subsequent bioconversion to higher-value products. Potential application of a mixed microbial consortium on the fermentative conversion of glycerol to ethanol was demonstrated in this study. Maximum ethanol concentration of 11.1 g l-1 was produced after 72 h fermentation from the initial pure glycerol concentration of 45 g l-1, at 30 ̊C, and pH 7 under anaerobic conditions, corresponding to the ethanol production rate and yield of 0.34 g l-1 h-1, and 0.81 mol ethanolmol-1 glycerol, respectively. The microbial consortium yielded lower ethanol concentration (6.5 g l-1) but similar ethanol yield (0.85 mol ethanol mol-1 glycerol) when crude glycerol of 45 g l-1 was fermented at the same condition. At the optimum fermentative condition of the pure glycerol, phylogenetic analysis of microbial consortium based on 16S rRNA gene sequences indicated that Gammaproteobacteria represented 95% of the microbial diversity in the consortium while the rest belonged to Betaproteobacteria. The consortium was dominated by bacteria closely related to genera Enterobacter and Klebsiella, which could play the role on conversion of glycerol to ethanol in this system.

Continuous Catalyst-Free Esterification of Oleic Acid in Compressed Ethanol

The esterification of oleic acid in a continuous catalyst-free process using compressed ethanol was investigated in the present study. Experiments were performed in a tubular reactor and variables investigated were temperature, pressure, and oleic acid to ethanol molar ratio for different residence time. Results demonstrated that temperature, in the range of 473 K to 573 K, and pressure had a positive effect on fatty acid ethyl esters (FAEE) production. In the experimental range investigated, high conversions can be obtained at low ethanol concentrations in the reaction medium and it was observed that oleic acid to ethanol molar ratios greater than 1 : 6 show no significant increase in conversion. Nonnegligible reaction conversions (&gt;90%) were achieved at 573 K, 20 MPa, oleic acid to ethanol molar ratio of 1 : 6, and 20 minutes of residence time.

Dynamic photocatalytic hydrogen production from ethanol–water mixtures in an optical fiber honeycomb reactor loaded with Au/TiO2

Cordierite honeycombs loaded with different amounts of Au/TiO2 have been used in an optical fiber photoreactor illuminated with UV LEDs to produce hydrogen from ethanol and water–ethanol mixtures. The photoreactions have been carried out at 298–348K, volume hourly space velocities of 300–2100h−1, Au contents of 0.5–2wt.% with respect to TiO2, and ethanol molar contents of 1–100%. Excellent dispersion and homogeneous particle size of gold has been obtained by using pre-formed, dendrimer-encapsulated Au nanoparticles. The best photocatalytic performance has been obtained over monoliths loaded with ca. 0.5mgcm−2 of Au/TiO2 (1.0–1.5wt.% Au), which corresponds to a photocatalyst layer thickness of about 1μm. In gas phase, acetaldehyde adsorption onto the photocatalyst surface plays an important role in the dynamics of the photoprocess by affecting hydrogen evolution sites, which is improved with temperature and short contact times. Hydrogen photogeneration in liquid phase is significantly enhanced (fivefold increase) in the optical fiber honeycomb photoreactor with respect to a conventional slurry photoreactor.

Investigation of dielectric properties of the reaction mixture during the acid-catalyzed transesterification of Brazil nut oil for biodiesel production

The design of processes involving microwave technology is dependent on the dielectric properties of the materials being processed. The dielectric constant and loss factor of the pure liquids methanol, ethanol, glycerin and sulfuric acid, as well as vegetable oils (Brazil nut and soybean), were measured using a vector network analyzer in an open-ended coaxial probe method (frequency range 300MHz to 13GHz) at various temperatures. For measurement during acid-catalyzed transesterification two oil:ethanol molar ratios at three different acid concentrations were employed. Dielectric properties of the pure samples and reaction mixtures during the transesterification reaction were frequency and temperature-dependent. The catalyst significantly affects the dielectric properties mainly at high alcohol concentrations where the mobility of counterions and the loss factor are high. The results indicate that the influence of the catalyst is reduced at low alcohol concentrations as the mobility of the counterions becomes more restricted decreasing the ionic conductivity.

Hydrogen Production Via Ethanol Steam Reforming Over Ni/Al2O3 Catalysts: Effect of Ni Loading

Catalytic systems play an important role in hydrogen production via ethanol reforming. The effect of Ni loading on the characteristics and activities of Ni/Al2O3 catalysts used in pure ethanol steam reforming are not well-understood. Two series of catalysts with various Ni loadings (6, 8, 10, 12, and 20 wt. %) were prepared by impregnation (IMP) and precipitation (PT) methods and were tested in reforming reactions. The catalysts were characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), temperature-programmed reduction (TPR), and scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM–EDAX). Powder XRD patterns of all the catalysts exhibited only NiO. Lower Ni loading catalysts were more efficient in H2 production, as evidenced by the finding that a 6 wt. % Ni catalyst, synthesized via the PT method, yielded 3.68 mol H2 per mol ethanol fed. The high surface area and small crystallite size of the low Ni loading catalysts resulted in sufficient dispersion and strong metal-support interactions, which closely related to the high activity of the 6 PT catalyst.

A study of ZnxZryOz mixed oxides for direct conversion of ethanol to isobutene

ZnxZryOz mixed oxides were studied for direct conversion of ethanol to isobutene. Reaction conditions (temperature, residence time, ethanol molar fraction, steam to carbon ratio), catalyst composition, and pretreatment conditions were investigated, aiming at high-yield production of isobutene under industrially relevant conditions. An isobutene yield of 79% was achieved with an ethanol molar fraction of 8.3% at 475°C on fresh Zn1Zr8O17 catalysts. Further durability and regeneration tests revealed that the catalyst exhibited very slow deactivation via coking formation with isobutene yield maintained above 75% for more than 10h time-on-stream. More importantly, the catalysts activity in terms of isobutene yield can be readily recovered after in situ calcination in air at 550°C for 2.5h. XRD, TPO, IR analysis of adsorbed pyridine (IR-Py), and nitrogen sorption have been used to characterize the surface physical/chemical properties to correlate the structure and performance of the catalysts.