Catalytic wet-air oxidation of carboxylic acids on carbon-supported platinum catalysts

Catalytic wet-air oxidation (CWAO) of aqueous solutions (5 g · l⁻¹) of car☐ylic acids (formic, oxalic, and maleic) was carried out with air at 293–463 K on carbon-supported platinum catalysts. Platinum was loaded on active charcoal by cationic exchange, then reduced under H₂. Homogeneous dispersions of 1–2 nm metal particles were obtained. CWAO reactions were performed at 1 or 15 bar air pressure in stirred, batch reactors. Total conversion of formic and oxalic acids into carbon dioxide was obtained under very mild conditions (air at atmospheric pressure, 326 K). The Pt/C catalyst was almost inactive for the oxidation of acetic acid but maleic acid was oxidized under moderate conditions (15 bar of air pressure, 405 K) which indicates that the degradation of this acid does not occur via acetic acid.     

Catalytic wet air oxidation of carboxylic acids at atmospheric pressure

Catalytic wet air oxidation of carboxylic acids (maleic acid, oxalic acid and formic acid) was carried out in a batch reactor operated at 160 psi or atmospheric pressure. Pt/Al₂O₃ and the sulfonated poly(styrene-co-divinylbenzene) resin were used as catalysts. Maleic acid was proved to be a refractory substance which could not be oxidized on the Pt/Al₂O₃ catalyst at all atmoshperic pressure, and needed high pressure and high temperature operation for its oxidation. On the contrary, oxalic acid and formic acid were readily oxidized into carbon dioxide and water at 353 K and atmospheric pressure. The pathways of maleic acid oxidation were proposed, and the conversion of maleic acid into oxalic acid was the rate-determining step. When the sulfonated resin catalyst was present together with the Pt/Al₂O₃ catalyst, maleic acid could be oxidized at 353 K and atmospheric pressure. The sulfonated resin catalyst was suggested to hydrolyze maleic acid into readily oxidizable compounds.     

Carbon supported platinum catalysts for catalytic wet air oxidation of refractory carboxylic acids

Carbon supported platinum (1% wt) catalysts were prepared by the incipient wetness impregnation method and by organometallic chemical vapor deposition. Catalyst characterization was carried out by means of adsorption and thermogravimetric techniques, and by electron microscopy. The catalyst with higher metal dispersion was produced by incipient wetness impregnation. The catalysts were tested in the catalytic wet air oxidation (200°C and 6.9 bar of oxygen partial pressure) of aqueous solutions containing low molecular weight (C₂ to C₄) carboxylic acids. Significant conversions (greater than 60% over 2 h) and 100% selectivity towards water and non-carboxylic acid products were observed for both systems. The initial reaction rate was used to compare the performance of the two catalytic materials and direct correspondence to the metal dispersion was found. No metal leaching was observed during reaction and no significant deactivation occurred in three successive catalytic oxidation runs. A kinetic model based on the Langmuir–Hinshelwood formulation was applied and the results were analyzed in terms of a heterogeneously catalyzed free radical mechanism.     

Catalytic activity of supported solid catalysts for phenol hydroxylation

Cobalt(II), copper(II) and zinc(II) complexes of 2-phenylbenzimidazole (PhBzlH) encapsulated in the supercages of zeolite-Y and ZSM-5 have been synthesized and characterized by spectroscopic studies (IR, UV/visible, EPR), elemental analyses, thermal studies and X-ray diffraction patterns. The catalytic activity of encapsulated complexes was investigated for the hydroxylation of phenol using 30 % H₂O₂ as an oxidant. Under optimized reaction conditions, the hydroxylation of phenol yielded catechol and hydroquinone as the major products. All catalysts show good selectivity for diphenol products. A maximum conversion of phenol was obtained with [Cu(PhBzlH)]-Y as the catalyst. The results showed that conversion of phenol varies in the order [Cu(PhBzlH)]-Y (53 %) > [Cu(PhBzlH)]-ZSM-5 > (49 %) > [Co(PhBzlH)]-ZSM-5 (47 %) > [Co(PhBzlH)]-Y (46 %) > [Zn(PhBzlH)]-Y (45 %) > [Zn(PhBzlH)]-ZSM-5 (41 %) after 6 h of reaction time. Test for the recyclability of the reaction was also carried out and the results indicate their recyclability.     

1,3-二氧环辛烷-2-羧酸类三环化合物的合成及其除草活性

二苯并1,3-二氧环辛烷-2-羧酸类三环化合物(见通式Ⅰ)(dibenzodioxocincarboxylic acid简称DBZ)的应用研究早期主要在医药方面(1977).Dow化学公司首先报道了此类化合物作为除草剂在农业上的应用(US 4976770 A,1990).1994年罗门哈斯公司的Lori Spangler博士注意到这类化合物结构新颖、公开专利较少(不超过10篇),开始了先导优化工作.沈阳院首先合成出专利中化合物(Ⅱ),经生测表明,化合物(Ⅱ)作用方式较慢、苗后活性高于苗前、杀草谱广、活性高(150g／ha),符合当前除草剂的发展方向.因此,双方成立了DBZ项目小组,其中包括合成人员、生测人…     

Electrochemical reactions of halohydrins. II. Olefins formation

2-Bromoethanol was reduced to ethylene, 1-bromo-2-propanol to propylene, and 2-bromo-l-indanol to indene on Pb or Cu electrodes with R₄N⁺ electrolytes, in DMF with and without addition of water. Material and current efficiencies were high. Hydrogen was the only by-product in all cases. It is suggested that this represents a general method for the conversion of bromohydrins to olefins.     

一水合硫酸氢钠的催化酯化作用

研究了以一水合硫酸氢钠催化合成乙酸正丁酯的最佳反应条件,在相同反应条件下,利用一水合硫酸氢钠催化合成了乙酸和丙酸的８种酯,其收率在８５．９％～９６．２％之间。     

Highly unsaturated fatty acids. II. Fractionation by urea inclusion compounds

Summary 1. Urea segregation has been found to be a useful tool in concentration of highly unsaturated acids and esters. Fatty acids and esters derived from fish oils and methyl esters of hog adrenal fatty acids have been fractionated, and the polyunsaturated acids have been enriched. 2. The tendency for fatty acids and esters to combine with urea decreases with increasing unsaturation. Combination is favored by lowered temperature. Polyunsaturated acids are concentrated in the final filtrate whereas esters of these acids appear in the final inclusion compound fractions. Fatty acid concentrates have been obtained with iodine values ranging from 294 to 356. Bound esters exhibited iodine values as high as 338. 3. The increased chain length brought about by esterification has a minor role in increasing the yield of inclusion compounds. Likewise, shifting of the terminal polar group in an acid toward the center of the molecule by esterification does not explain the higher yield of inclusion compound from esters. 4. The improved tendency of esterified acids to form urea inclusion compounds is probably due to blocking of association of acid groups. This effect is found in unsaturated acids and in short chain saturated acids. In long chain saturated acids and esters this effect is not noticed. Both give high yields of inclusion compounds because the effect of the carboxyl group is overshadowed by the high energy of formation contributed by the long carbon chain. Taken from a dissertation presented by A. M. Abu-Nasr to the Graduate School of Texas Agricultural and Mechanical College in partial fulfillment for the requirements of the Ph.D. degree, May, 1953. Supported in part by contract N8onr-66218 of the Office of Naval Research. Hormel Institute publication No. 93.     

Ketones from carboxylic acids over supported magnesium oxide and related catalysts

Silica-supported alkaline earth oxides revealed excellent activity to convert acetic acid selectively into acetone in a vapor-phase fixed-bed flow system. Acetone was obtained through the cyclic formation of alkaline earth acetate followed by decomposition. Magnesium oxide should be supported on the silica surface without formation of magnesium silicate, which was inactive for the present reaction. Attempted syntheses of benzophenone and acetophenone are also described.     

Novel mesoporous aluminosilicate supported palladium-rhodium catalysts for diesel upgrading: II. Catalytic activity and improvement of industrial diesel feedstocks

Bimetallic PdRh catalysts (molar ratio Pd/Rh = 1 and 2) were prepared by impregnation of a mesoporous aluminosilicate (molar ratio Si/Al = 10 and 20). These materials are destined to be used in industrial processes aiming to improve diesel quality by hydrogenation and ring-opening of aromatic components. The four catalysts were examined for their activity in hydrogenation of naphthalene and tetralin model feedstocks, at 6 MPa, including in the presence of sulfur containing compounds. The capacity of one of these catalysts to improve the quality of hydrogenated industrial light cycle oil containing ≤50 wt ppm of sulfur was evaluated in a pilot plant. In these industrial conditions, the catalyst has a higher catalytic activity at lower temperature than a reference state of-the-art catalyst, giving a seven-point improvement of the cetane number at 280–300 °C and with formation of less than 10% of non-selective cracking products.     

Formation and reactions of cluster ions from aromatic carboxylic acids together with amino acids

The cluster formation of several aromatic carboxylic acids, ferulic acid, vanillic acid, sinapinic acid, and 3,4-dihydroxybenzoic acid was investigated by means of laser desorption into a supersonic beam followed by multiphoton ionization-time-of-flight mass spectrometry. The formation of not only homogeneous clusters, but also of heterogeneous clusters with some small amino acids was studied. The different neutral clusters formed in the supersonic expansion were ionized by a multiphoton process employing either nano- or femtosecond laser pulses. Strong differences in the detection of cluster ions due to the laser pulse length employed for multiphoton ionization were observed. Only femtosecond activation led to mass spectra with intense signals of the cluster ions. In addition, in the case of femtosecond ionization, protonated amino acids were detected in the mass spectra. As direct ionization of the free amino acids is not possible under the chosen ionization conditions because they lack an adequate chromophore, these protonated amino acids are assumed to be formed via an intracluster proton transfer in the heterogeneous dimer and subsequent decay of the ionized cluster (dissociative proton transfer). Such well-known processes for heterogeneous clusters consisting of a substituted aromatic molecule and small polar solvent molecules may be involved in the matrixassisted laser desorption ionization (MALDI) process.     

New catalysts for urea formation reaction. I. Effect of catalyst on molecular weight of polyureaurethane and determination of the minimum demolding time

2-Methyl benzoic acid as a new catalyst for urea formation reaction has a significant effect on the molecular structure of polyureaurethane. For instance, it increased molecular weight of polyureaurethane, but decreased chemical crosslink density. The minimum demolding time (DT) of polyureaurethane as an index of catalytic activity was also discussed based on the mechanical properties. DT is defined as the torque time for a mixture of curative and prepolymer to reach 90% of its nearly final value. A marked increase in extension ratio at break (E_B) before DT was partially attributed to intermolecular entanglements which arose at molecular weights higher than 4500 [rheological critical molecular weight of poly(oxytetramethylene)glycol]. Primary aliphatic amines in amide solvents selectively cleaved biuret or allophanate bonds of polyureaurethane. This helped to determine molecular weight of crosslinked polyureaurethane.     

Ni-Mo双金属催化剂的甲烷化性能与耐硫稳定性

采用沉淀-浸渍法合成一系列Ni-Mo基双金属催化剂,在固定床反应器中对其催化活性和耐硫性能进行评价,并辅以不同的表征手段阐释其作用机理。实验结果表明,以MCM-41分子筛为载体的催化剂活性和稳定性优于以NaY、γ-Al₂O₃和拟薄水铝石（PB）为载体的催化剂;反应前后催化剂的表征结果则说明Ni-Mo分子间适宜的相互作用是决定催化剂性能的关键。MCM-41载体催化剂中适宜的Ni-Mo分子间相互作用使得此催化剂中活性组分与载体间的相互作用适中,还原后的活性金属Ni能够均匀分散在载体表面,从而提高了催化剂的耐硫稳定性和抗积炭能力。不同Ni-Mo比同样会影响Ni-Mo分子间的相互作用,通过考察确定20Ni-10Mo/MCM-41的活性和稳定性最优。     

Enantioselective hydrogenation of fluorinated unsaturated carboxylic acids over cinchona alkaloid modified palladium catalysts

The hydrogenation of trifluoromethyl substituted prochiral α,β-unsaturated carboxylic acids has been studied over cinchona alkaloid modified palladium heterogeneous catalysts. Low enantioselectivities were obtained in the hydrogenation of all three test compounds, 2-trifluoromethylacrylic acid, 4,4,4-trifluoro-3-methyl-2-butenoic acid and (E)-4,4,4-trifluoro-3-phenyl-2-butenoic acid, respectively. Significant increase in the enantioselectivity, up to 43%, was obtained in the hydrogenation of 4,4,4-trifluoro-3-methyl-2-butenoic acid by using benzylamine as additive. The presented results showed for the first time the possibility of enantioselective hydrogenation of α-unsubstituted β-disubstituted α,β-unsaturated carboxylic acids in the cinchonidine modified palladium catalytic system, that resulted in optically enriched saturated acids having the chiral center in β position.     

Reactions of peroxides: II. Reaction of carboxylic acids with iodine and peroxides

Aroyl peroxides andt-butylperoxy isopropyl carbonate decarboxylate aliphatic carboxylic acids in the presence of iodine to form iodides in high yields. The aroyl peroxides also abstract carboxylic acid hydrogen from aromatic and perfluorocarbon acids. A proposed scheme is presented for the reaction of aroyl peroxides with carboxylic acids illustrating homolytic decarboxylation as taking place in an equilibrium between a pair of acyloxy radicals. These radicals are derived from the peroxide and acid and maintained in association by hydrogen bonding and iodine complexation. Presented at the AOCS Meeting, Washington, D.C., March 1968. ARS, USDA.     

Catalytic activity of hydrodesulfurization catalysts prepared by two methods

Two sets of samples, ranging from molybdenum sulfide to cobalt sulfide, were prepared by two different methods: homogeneous sulfide precipitation (HSP), and a new preparation method of CoMo and NiMo bulk sulfides, called impregnated thiosalt decomposition (ITD). Hydrodesulfurization of thiophene was measured at temperatures between 533 K and 593 K in a conventional flow system. The products were analyzed by gas chromatography. Both sets of samples (HSP and ITD) present the typical volcano curve of specific activity with larger values for catalysts prepared by HSP than those by ITD. Samples prepared by ITD present comparable intrinsic activities than those prepared by HSP. Activation energies for both methods of preparation are larger for promoted catalysts with a value of 23 for HSP and 12.6 kcal/mol for ITD.     

Catalytic activity of copper-ceria catalysts supported on different zeolites for CO oxidation

Copper-ceria catalysts for CO oxidation supported on 4A, 5A, NaX and NaY zeolites were prepared by incipient wetness impregnation and excess-solution impregnation. Catalysts were characterized by SEM, EDX, XRD, N2 adsorption-desorption, H2-TPR and XPS. Results revealed that the catalysts were greatly affected by zeolites and preparation method. EDX results indicated the metal loading of 4A-ES (5.1 wt% Cu, 15.7 wt% Ce), 5A-ES (5.9 wt% Cu, 19.2% Ce), NaX-ES (11.7wt% Cu, 4.2 wt% Ce) and NaY-ES (11.0 wt% Cu, 7.9 wt% Ce) greatly varied. TPR results suggested that the peak at around 195 °C was presented in NaX-ES and 4A-IW, standing for dispersed copper species that is very active for CO oxidation. The catalytic activity of 4A-ES and NaX-ES was the best among catalysts made by excess-solution impregnation, demonstrated by the lowest T₅₀ at 127 and 129 °C, respectively. The catalytic activity of catalysts made by incipient wetness impregnation was worse than that of catalysts made by excess-solution impregnation, examined by the T₅₀ of 4A-IW and NaX-IW at 128 and 192 °C, respectively.     

pH effects on catalytic ozonation of carboxylic acids with metal on metal oxides catalysts

Summary The pH influence on the catalytic ozonation of small carboxylic acids (succinic (SA), chloroacetic (CAA) and pyruvic (PA) acids) was studied and compared to ozonation alone. In the acidic systems, the conversion of these carboxylic acids and total organic carbon (TOC) during the catalytic ozonation is mainly due to the catalytic effect. Experiments on SA indicate that in the pH range 3.6–5.0, in contrast to the ozone behavior, the efficiency of the catalytic ozonation system is decreased with increasing pH due to the change of charges on the catalyst surface. In the basic pH range (7.2–10.0), the effect of the ozonation alone becomes important and the reaction in the presence of the catalyst is a combined effect of ozonation alone and catalytic oxidation. Although the apparent SA conversion by the catalytic ozonation in the basic systems is higher than in the acidic systems, the Total Organic Carbon conversion is not so much higher than in the latter. During the ozonation with the same catalyst, more than 80 of the CAA converted are mineralized. The oxidation of CAA leads to almost equimolar release of chloride ions. This ion has no detrimental influence on the catalytic effects under our experimental conditions. However, in the very dilute systems with pH value lower than the pKa of CAA, when the CAA concentration is decreased to about 0.6mM, the catalytic oxidation is almost stopped. The low concentration of the dissociated CAA induces only weak adsorption and consequently small reaction rates. The total elimination of CAA with low concentration can be reached only if the pH is increased above the pKa. In addition to the distinct pH effect in the ozonation and catalytic ozonation system observed in this work, a further demonstration that separate mechanisms are involved in the two processes is provided by the analysis of oxidation by-products of pyruvic acid.     

Catalytic activity of copper and palladium based catalysts for toluene total oxidation

In this study, catalysts containing 0.5 wt.% of palladium or 5 wt.% of copper were compared towards toluene total oxidation using FAU Zeolite and ZrO₂ supports. A 0.5%Pd/NaFAU and 5%Cu/ZrO₂ were found to be promising catalysts for this reaction. Palladium presented then a better affinity for FAU zeolite and copper oxide had a better affinity for zirconia. The performances of Pd based catalysts were correlated to interaction between the active phase and the support whereas the activity of copper oxide was related to oxygen mobility property of the support leading to copper oxide particles easily reducible. Support modifications, yttrium addition for ZrO₂ and cation exchange for the zeolite FAU, still enhanced the catalytic activity. Therefore, 0.5%Pd/CsFAU and 5%Cu/Zr₉₅Y₅ samples were found to be interesting catalysts for total VOC oxidation.