Hydrogen Acetic Acid Research Articles

Aqueous Phase Hydrogenation of Acetic Acid and Its Promotional Effect on p-Cresol Hydrodeoxygenation

A systematic study of the comparative performances of various supported noble metal catalysts for the aqueous phase hydrogenation of acetic acid (as a model carboxylic acid in bio-oils) by itself and in combination with p-cresol (as a model phenolic compound in bio-oils) is presented. It was found that Ru/C catalyst shows the highest activity for acetic acid hydrogenation among the tested catalysts, followed by Ru/Al2O3, Pt/C, Pt/Al2O3, Pd/Al2O3, and Pd/C. CH4 and CO2 were observed to be the major products on all of these catalysts at typical hydroprocessing temperatures (∼300 °C). A systematic study on parametric effects with the Ru/C catalyst shows that the product distribution is dependent upon the temperature and presence of water. At low temperatures (∼150 °C), acetic acid hydrogenation is favored with higher selectivity to ethanol, while at high temperatures (∼300 °C), acetic acid decomposition and ethanol reforming/hydrogenolysis dominate with CO2 and CH4 as the major products. When water is replac...

A green one-step process of obtaining microcrystalline cellulose by catalytic oxidation of wood

A green one-step catalytic process of obtaining microcrystalline cellulose (MCC) from wood in the medium “acetic acid–hydrogen peroxide–water” in the presence 2% wt. sulfuric acid catalyst is described. The influence of wood nature and conditions of the process on the yield, composition and structure of obtained samples of MCC was investigated. For hardwood (aspen wood and birch wood) the minimal content of residual lignin (<1% wt.) was achieved under the following conditions: temperature 130 °C, the concentration of H2O2 4% wt., the concentration of CH3COOH ~ 26% wt., liquor ratio of 10 and the process time of 3 h. At these conditions, the degree of delignification of softwood (spruce wood and larch wood) is lower than for hardwood. According to X-ray and FTIR data, the structure of MCC samples obtained from wood is close to that of MCC Avicel and MCC from cotton linter.

Catalytic asymmetric hydrogenation to access spiroindane dimethyl acetic acid

Asymmetric hydrogenation of achiral spiroindene dimethyl acetic acid 2 with 4% of Ru(II)-Mandyphos in acetone produced (S)-spiroindane dimethyl acetic acid 1 in 86% isolated yield and 96.8:3.2 enantiomeric ratio.

Dicationic phenyl-2,2′-bichalcophenes and analogues as antiprotozoal agents

A series of phenyl-2,2'-bichalcophene diamidines 1a-h were synthesized from the corresponding dinitriles either via a direct reaction with LiN(TMS)₂, followed by deprotection with ethanolic HCl or through the bis-O-acetoxyamidoxime followed by hydrogenation in acetic acid and EtOH over Pd-C. These diamidines show a wide range of DNA affinities as judged from their ΔT(m) values which are remarkably sensitive to replacement of a furan unit with a thiophene one. These differences are explained in terms of the effect of subtle changes in geometry of the diamidines on binding efficacy. Five of the eight compounds were highly active (below 6 nM IC₅₀) in vitro against Trypanosoma brucei rhodesiense (T. b. r.) and four gave IC₅₀values less than 7 nM against Plasmodium falciparum (P. f.). Only one of the compounds was as effective as reference compounds in the T. b. r. mouse model for the acute phase of African trypanosomiasis.

Aqueous‐Phase Hydrogenation of Acetic Acid over Transition Metal Catalysts

Catalytic hydrogenation of acetic acid to ethanol has been carried out in aqueous phase on several metals, with ruthenium being the most active and selective. DFT calculations suggest that the initial CO bond scission yielding acetyl is the key step and that the intrinsic reactivity of the metals accounts for the observed activity.

Cover Picture: Aqueous‐Phase Hydrogenation of Acetic Acid over Transition Metal Catalysts (ChemCatChem 11/2010)

The cover picture shows the conversion of acetic acid to ethanol through the formation of acetyl over metal particles. In the combined experimental and theoretical study reported by Xu, Huber et al. on p. 1420 ff., high activity and selectivity are obtained over supported metal catalysts, especially Ru, at mild temperature in aqueous phase. DFT calculations suggest that C–O bond scission to form acetyl is a key step in the reaction. A simple kinetic model captures the activity trend across the different metals, allowing the catalytic activity for acetic acid hydrogenation to be estimated based on acetyl binding energies.

Efficient synthesis of ethanol and acetic acid from methane and carbon dioxide with a continuous, stepwise reactor

AbstractThe synthesis of C2‐oxygenates such as ethanol and acetic acid accomplished by CH4 dissociation and subsequent CO2 insertion onto methyl radicals, named the stepwise reaction technology, has been demonstrated to be both feasible and efficient through initial experiments conducted in microreactor units. This article describes the development of this technology, highlighting the aforementioned stepwise technology using a dual‐reactor system, which can ensure that two raw gases enter the reactor uninterruptedly and are not mixed after reaction. The system productivity for acetic acid and ethanol displayed efficiencies greater than 5–10 times that of previous microreactor units. The investigation of mechanism indicates that acetic acid arises from insertion of CO2 into MCHx, while ethanol is formed either by hydrogenation of acetic acid or by hydration of C2H4, which results from homo‐coupling of CH4. The latter route is the preferred of the two. © 2009 American Institute of Chemical Engineers AIChE J, 2010

Influence of UV pretreatment on the abies wood catalytic delignification in the medium “acetic acid–hydrogen peroxide–TiO2”

Some regularities of abies-wood oxidative delignification by acetic acid–hydrogen peroxide mixture under the action of suspended TiO2 catalyst and UV pretreatment of wood pulp were studied. The combined action of TiO2 catalyst and of UV-pretreatment of abies-wood allow to produce at optimal conditions of the delignification process the chemically pure cellulose containing no residual lignin. The major characteristics of cellulose product obtained from abies-wood correspond to the characteristics of microcrystalline cellulose.

Acetic acid steam reforming in a Pd–Ag membrane reactor: The effect of the catalytic bed pattern

In this experimental work, the acetic acid steam reforming reaction for producing pure hydrogen was studied in a Pd–Ag dense membrane reactor (MR). Two kinds of catalytic bed patterns have been considered: in the first pattern a Ni-based commercial catalyst has been packed inside the membrane lumen while, in the second one both a Ru-based and a Ni-based commercial catalysts have been packed together in the membrane lumen. The experimental tests have been performed in the temperature range 400–450 °C and in the pressure range 1.5–2.5 bar. The results are reported in terms of acetic acid conversion, hydrogen recovery and products selectivities. It has been found that the MR is able to give a rather high acetic acid conversion with a 30–35% hydrogen recovery. Moreover, the second catalytic bed pattern is able to increase the hydrogen production and to decrease the methane production with respect to the first pattern.

Examination of catalytic behavior and origin of the initial transient period for Pt nanoclusters modified with cinchonidine

Nanoclusters prepared by a novel water-free method are compared directly with nanoclusters prepared by the known aqueous preparation as well as conventional Pt/Al2O3 for the enantioselective hydrogenation of ethyl pyruvate. The catalytic behavior of cinchonidine on colloidal Pt was investigated during ethyl pyruvate hydrogenation in acetic acid under 10 bar of hydrogen at 22 °C with (1 mmol L−1) and without addition of free cinchonidine. The effect of hydrogen pressure, cinchonidine concentration, ethyl pyruvate and catalyst loading on the enantiomeric excess (EE) with time were also studied. Through these studies, we propose that the nature of the observed initial transient period (ITP) for these “quasi-homogeneous” systems may be explained by desorption of the weakly adsorbed tilted “N lone pair bonded” cinchonidine species from the Pt surface due to interaction with hydrogen.

Synthesis of 7α-substituted derivatives of 17β-estradiol

Estrogen receptor (ER) pure antagonists such as ICI-182,780 (fulvestrant) are effective alternatives to tamoxifen (an ER antagonist/weak partial agonist) in the treatment of postmenopausal, receptor-positive human breast cancers. Structurally, these pure antagonists contain the basic core structure of 17β-estradiol (E 2) with a long side chain attached to its C-7α position. We explored and compared in this study various synthetic routes for preparing a number of C-7α-substituted derivatives of E 2, which are highly useful for the design and synthesis of high-affinity ER antagonists, ER-based imaging ligands, and other ER-based multi-functional agents. Using E 2 as the starting material and 1-iodo-6-benzyloxyhexane as a precursor for the C-7α side chain, a seven-step synthetic procedure afforded 3,17β-bis(acetoxy)-7α-(6-hydroxyhexanyl)-estra-1,3,5(10)-triene (one of the derivatives prepared) in an overall yield of ∼45% as compared to other known procedures that afforded substantially lower overall yield (8–27%). The synthetic steps for this representative compound include: (1) protection of the C-3 and C-17β hydroxyls of E 2 using methoxymethyl groups; (2) hydroxylation of the C-6 position of the bismethoxymethyl ether of E 2; (3) Swern oxidation of the C-6 hydroxy to the ketone group; (4) C-7α alkylation of the C-6 ketone derivative of E 2; (5) deprotection of the two methoxymethyl groups; (6) reprotection of the C-3 and C-6 free hydroxyls with acetyl groups; (7) removal of the C-6 ketone and the benzyl group on the side chain by catalytic hydrogenation in acetic acid. As predicted, two of the representative C-7α-substituted derivatives of E 2 synthesized in the present study retained strong binding affinities (close to those of E 2 and ICI-182,780) for the human ERα and ERβ subtypes as determined using the radioligand–receptor binding assays.

Activated Sludge is a Potential Source for Production of Biodegradable Plastics from Wastewater

Increased utilization of synthetic plastics caused severe environmental pollution due to their non-biodegradable nature. In the search for environmentally friendly materials to substitute for conventional plastics, different biodegradable plastics have been developed by microbial fermentations. However, limitations of these materials still exist due to high cost. This study aims at minimization of cost for the production of biodegradable plastics P(3HB) and minimization of environmental pollution. The waste biological sludge generated at wastewater treatment plants is used for the production of P(3HB) and wastewater is used as carbon source. Activated sludge was induced by controlling the carbon : nitrogen ratio to accumulate storage polymer. Initially polymer accumulation was studied by using different carbon and nitrogen sources. Maximum accumulation of polymer was observed with carbon source acetic acid and diammonium hydrogen phosphate (DAHP) as nitrogen source. Further studies were carried out to optimize the carbon : nitrogen ratios using acetic acid and DAHP. A maximum of 65.84% (w/w) P(3HB) production was obtained at C/N ratio of 50 within 96 hours of incubation.

On the behaviour of Ru(I) and Ru(II) carbonyl acetates in the presence of H 2 and/or acetic acid and their role in the catalytic hydrogenation of acetic acid

The reactivity of phosphine substituted ruthenium carbonyl carboxylates Ru(CO) 2(MeCOO) 2(PBu 3) 2, Ru 2(CO) 4(μ-MeCOO) 2(PBu 3) 2, Ru 4(CO) 8(μ-MeCOO) 4(PBu 3) 2 with H 2 and/or acetic acid was investigated by IR and NMR spectroscopy to clarify their role in the catalytic hydrogenation of acetic acid. Evidences were collected to suggest hydride ruthenium complexes as the catalytically active species. Equilibria among ruthenium hydrides and carboxylato complexes take place in the presence of hydrogen and acetic acid, that is in the conditions of the catalytic reaction. Nevertheless the presence of acetic acid reduces the rate of the formation of hydrides. Working at a very high temperature (180°C) polynuclear phosphido hydrides such as [Ru 6(μ-H) 6(CO) 10(μ-PHBu)(μ-PBu 2) 2(PBu 3) 2(μ 6-P)] were formed. These phosphido clusters are suggested as the resting state of the catalytic system. Furthermore the bi- or tetranuclear Ru(I) carboxylato complexes react with acetic acid giving a mononuclear ruthenium complex Ru(CO) 2(MeCOO)(μ-MeCOO)(PBu 3), containing a monodentate and a chelato acetato ligands. This complex was spectroscopically characterised. Its identity and structure were confirmed by its reactivity with stoichiometric amount of PPh 3 to give Ru(CO) 2(MeCOO) 2(PBu 3)(PPh 3), a new mononuclear ruthenium carbonyl carboxylate containing two different phosphines, that was fully characterised.

Novel dicationic imidazo[1,2-a]pyridines and 5,6,7,8-tetrahydro-imidazo[1,2-a]pyridines as antiprotozoal agents.

2-[5-(4-Amidinophenyl)-furan-2-yl]-5,6,7,8-tetrahydro-imidazo[1,2-a]pyridine-6-carboxamidine acetate salt (7) was synthesized from 2-[5-(4-cyanophenyl)-furan-2-yl]-imidazo[1,2-a]pyridine-6-carbonitrile (4a), through the bis-O-acetoxyamidoxime followed by hydrogenation in glacial acetic acid. Compound 4a was obtained in four steps starting with two successive brominations of 2-acetylfuran first with N-bromosuccinimide, and second with bromine to form alpha-bromo-2-acetyl-5-bromofuran (2) in a moderate yield. The product (3a), of the condensation reaction between 6-amino-nicotinonitrile and 2, undergoes Suzuki coupling with 4-cyanophenylboronic acid to furnish 4a in good yield. Acetate salt of 2-[5-(4-amidinophenyl)-furan-2-yl]-imidazo[1,2-a]pyridine-6-carboxamidine (8a) was obtained from 4a, through the bis-O-acetoxyamidoxime followed by hydrogenation in a mixture of ethanol/ethyl acetate. N-Methoxy-2-(5-[4-(N-methoxyamidino)-phenyl]-furan-2-yl)-imidazo[1,2-a]pyridine-6-carboxamidine (6) was prepared via methylation of the respective diamidoxime 5a with dimethyl sulfate. By these approaches eight new diamidines and four potential prodrugs were prepared. All of the diamidines showed strong DNA affinities as judged by high DeltaT(m) values. Six of the eight diamidines gave in vitro IC(50) values of 63 nM or less vs T. b. rhodesiense with two exhibiting values of 6 nM and 1 nM. Also, six of the eight diamidines gave in vitro IC(50) values of 88 nM or less vs P. falciparum with two exhibiting values of 14 nM. Excellent in vivo activity in the trypanosomal STIB900 mouse model was found for five of the diamidines on ip dosage; these compounds gave 4/4 cures in this model. The oral activity of the prodrugs was modest with only one showing 2/4 cures in the same mouse model.

An efficient enantioselective synthesis of an indane acetic acid derivative: methyl (2 S)-2-[(1 S)-5-hydroxy-2,3-dihydro-1 H-inden-1-yl]butanoate

We have developed a practical enantioselective synthesis of 1, a novel indane acetic acid derivative with two contiguous stereogenic centers. The key indene acetic acid framework was constructed via a robust, unprecedented Reformatsky process. One stereogenic center was set via a resolution, and the other via a highly diastereoselective hydrogenation of the indene acetic acid.

Acetic Acid Reduction by H2 on Bimetallic Pt–Fe Catalysts

Vapor-phase acetic acid hydrogenation was studied over a family of supported Pt–Fe catalysts. These catalysts were characterized by Mössbauer spectroscopy, successive H2–O2–H2–O2 titration cycles at 300 K, and DRIFTS (diffuse reflectance FTIR spectroscopy) to determine the Fe phases present during the titration reactions as well as prior to and under reaction conditions, to count surface metal atoms and estimate the average surface composition of the bimetallic particles, and to observe surface species formed after acetic acid adsorption, respectively. Although the metallic mole fraction of Pt in the bimetallic Pt–Fe/SiO2 catalysts varied from 0.04 to 0.64, the estimated surface composition in the bimetallic particles ranged from 0.39 to 0.70. The addition of small amounts of Pt to Fe/SiO2 catalysts (i) increased Fe reducibility during the reduction pretreatment, (ii) enhanced activity more than 10-fold and turnover frequencies 10- to 100-fold, (iii) eliminated the induction period, (iv) lowered the apparent activation energy by 8–10 kcal/mol, and (v) still maintained a high selectivity to acetaldehyde of over 70%. The addition of Pt to an Fe/C catalyst prevented the severe deactivation that has been associated with iron carbide formation. Under reaction conditions, the best bimetallic catalyst contained both Fe0 and Fe2+ phases, which is a combination that seems to be required for stable selective acetaldehyde formation. A model consistent with our previous studies of Pt and Fe catalysts, which invokes one type of active site on a reduced metal surface and another type on a metal oxide phase, successfully describes this reaction on a bimetallic catalyst. It is proposed that the reaction sequence involves a rate-determining step between a hydrogen atom from the metallic site and an acyl species on the FeO surface.

Acetic acid hydrogenation over supported platinum catalysts

Acetic acid was chosen to probe the kinetic behavior of carboxylic acid hydrogenation over platinum supported on TiO2, SiO2, η-Al2 O3, and Fe2O3. The reaction was studied in the vapor phase underconditions of 423–573 K, 100–700 Torr hydrogen, and 7–50 Torr acetic acid in a differential, fixed-bed reactor. Product selectivity was strongly dependent on the oxide supports. Carbon-containing products during hydrogenation at low conversions consisted of about: 50% CO and 50% CH4 over Pt/SiO2; 8% ethanol, 4% ethyl acetate, 10% ethane, 40% CH4, 33% CO, and 5% CO2 over Pt/η-Al2O3; 50% ethanol, 30% ethyl acetate, and 20% ethane over Pt/TiO2 reduced at either 473 or 773 K; and about 80% acetaldehyde and 20% ethanol over Pt/Fe2 O3. The TiO2-supported Pt catalysts were the most active, and both theiractivities and their turnover frequencies were up to two orders of magnitude larger than those for Pt dispersed on SiO2, η-Al2O 3, or Fe2O3. The activity dependence on the partial pressures of hydrogen, P h 2, and acetic acid, P a , was determined for Pt/TiO2 catalysts at three operating temperatures—422,445, and 465 K —after reduction at either 473 or 773 K. The apparent reaction order with respect to H2 was found to vary between 0.4 and 0.6, while that with respect to acetic acid was between 0.2 and 0.4. One reaction model that correlated these data well involves a Langmuir-Hinshelwood-type catalytic sequence that incorporates dissociative hydrogen and acetic acid adsorption on one type of site existing on the Pt surface, but only molecular acetic acid adsorption at another type of site on the oxide surface. Only the latter species on the titania surface was considered catalytically significant in the formation of desired products, i.e., acetaldehyde, ethanol, and ethane. The resulting rate expression in terms of acetic acid disappearance has the form r H O A c = k 1 P A P H 2 1 / 2 / [ ( K 2 P H 2 1 / 2 + K 3 P A / P H 2 1 / 2 ) ( 1 + K 4 P A ) ] . Values of enthalpy and entropy of adsorption obtained from the optimized rate for hydrogen on platinum and acetic acid on titania were reasonable and thermodynamically consistent.

The structure of the specific capsular polysaccharide of Rhodococcus equi serotype 4

The specific capsular polysaccharide produced by Rhodococcus equi serotype 4 was found to be a high-molecular-weight acidic polymer composed of d-glucose, d-mannose, pyruvic acid and a previously unidentified 5-amino-3,5-dideoxynonulosonic (rhodaminic) acid in the proportions 2:1:1:1. Structural analysis, employing a combination of microanalytical methods, nuclear magnetic resonance spectroscopy, and mass spectrometric techniques, established that the polysaccharide consisted of linear repeating tetrasaccharide units having the sequence of residues shown below. In the native polysaccharide, the rhodaminic acid residues were present as their acetamido derivatives (RhoANAc) and carried 1-carboxyethylidene groups that bridged the O-7 and O-9 positions. Treatment of the capsular polysaccharide with dilute acetic acid and/or anhydrous hydrogen fluoride under hydrolytic/solvolytic conditions, resulted in the formation of four different oligosaccharide species. The 1H and 13C NMR resonances of these oligosaccharide fragments and of the native serotype 4 capsular polysaccharides were fully assigned by homo- and heteronuclear chemical shift correlation methods.

The extracellular polysaccharide of Pichia (Hansenula) holstii NRRL Y-2448: the phosphorylated side chains

The exopolysaccharide produced by Pichia (Hansenula) holstii NRRL Y-2448 is composed of a phosphomannan core to which oligosaccharide diester phosphate side chains are appended. The oligosaccharides of the side chains were released as oligosaccharide phosphates and neutral oligosaccharides by mild hydrolysis with aqueous acetic acid and aqueous hydrogen fluoride, respectively. The liberated oligosaccharide phosphates were studied by NMR spectroscopy and by electrospray and fast atom bombardment mass spectrometry. The structures of the neutral oligosaccharides were determined by 1D and 2D NMR spectroscopic experiments. Further insight into the length of the side chains was obtained from a matrix assisted laser desorption ionisation–time of flight mass spectrometric study of high and low molecular weight fragments obtained from partial acid hydrolysis of the native polysaccharide.

Identification of the Active Sites in the Selective Hydrogenation of Acetic Acid to Acetaldehyde on Iron Oxide Catalysts

Iron-based catalysts appeared to be very active and selective in the hydrogenation of acetic acid to acetaldehyde. The active and selective catalyst consists of a metallic and an oxidic phase. Probably, the metal is needed to activate hydrogen, and the oxide is needed to provide the reaction site for the selective hydrogenation. Catalyst pretreatment and reaction conditions must be carefully controlled: the catalyst must be prereduced and the hydrogen/acid ratio must be higher than four. Only then are both iron-containing phases formed and kept stable during the reaction. The function of hydrogen is twofold: it must keep the catalyst in its active, partly reduced, form and it acts as reactant in the hydrogenation of acetic acid.