In this paper six new or innovated procedures of fatty acids methyl esters (FAME) preparation from natural triacylglycerols (TAG) with higher acidity are described. The extraction of soaps of free fatty acids (FFA) by a polar solvent such as glycerol (G), but primarily by the G-phase originating from own FAME production, is a simple procedure applicable mainly in small-scale production plants. The effective TAG deacidification is obtained also using FFA vacuum distillation in wiped film evaporators. Preliminary acidcatalyzed FFA esterification with methanol (MeOH) performed before alkali-catalyzed TAG transesterification to FAME allows a simple separation of reaction water, excess of MeOH, and acidic catalyst at appropriate reactant ratios. During FFA esterification at temperatures over 110 °C, ambient pressure and at continuous MeOH feeding to the reaction mixture, advantageous nonequilibrium conditions for effective mass and heat transfer are created. Ethanolamines, used in TAG degumming for technical application, form separable adducts with water and FFA. At high-temperature FFA esterification with G in acid oils, acidic functional groups are blocked. The mentioned procedures are technically feasible and allow decreasing TAG acidity down to 1.0 mg KOH/g or less. Conversion of acyl glycerols to FAME complies with the standard EN 14 214.

During the catalytic cracking of agricultural lignocellulosic bio-waste it is possible to obtain a liquid condensate with the yield of the bio-oil is up to 19wt. % in experiments with vegetable oil in input material. Bio-oils originating only from agricultural biomass give the yield of max. 2wt. % with the respect to the input. In the batch process, better results in the yield of bio-oil were found. Cracking of agricultural waste, running in continuous pilot scale reactor with screw mixers at temperatures from 390 to 450°C, results in the significant yield of bio-gasses. The portion of gaseous products varies from 25wt. % (corn combs with vegetable oil, reed) to 62wt. % (dry leaves), depending on cracking conditions, type of biomass, presence of zeolite catalyst or vegetable oil. These gases are flammable and can be used as motor fuel and/or energetic purposes.

Fatty acid methyl esters (FAME) are used as alternative diesel fuel originating from renewable sources. The attention is focused on the materials that do not compete with food and feed production. Algae have a significant potential as an alternative biodiesel feedstock. In comparison to other crops, they have the advantage in very fast reproduction cycles, enhanced resistance to high UV radiation doses and higher effectiveness of energy conversion to biomass due to low demands on other metabolic functions. Moreover, they fix waste CO2 very efficiently. The key problem is to destroy the algae cell in order to obtain the oil. In this work, the results of FAME preparation from received algae oils are presented. This study confirms that Nannochloropsis and Chlorella microalgae provide valuable triacyglycerols for the biofuel production. Characteristics of prepared FAME meet the EN 14 214 standard requirements. However, FAME from algae oil may exhibit impaired oxidative stability due to higher level of unsaturation.

The effect of catalyst acidity on the activity of unmodified and modified zeolites in the gasphase condensation reaction of ethanol, formaldehyde and ammonia was studied. Condensation of ethanol, aqueous formaldehyde and ammonia (molar ratio 1: 0.2 1: 1.24) was investigated at a temperature of 400 degrees C in nitrogen atmosphere and a space velocity 0.5 h(-1). The main products of the reaction are pyridine, methyl- and dimethylpyridines. The yield of pyridine and the total yield of pyridine bases depend oil the Si/Al ratio of zeolites. Acidity, activity and lifetime of the catalyst are profoundly influenced by the temperature and duration of calcination. The initial activity of the modified catalysts, but also the rate of their deactivation, increases with increasing concentration of the Zn modifier. Higher yields of pyridine and its bases were achieved with the catalysts having an initial acidity under 0.52 mmol.g(-1).

From the point of view price and available capacity used frying oils or fats (UFO) represent an attractive raw material for the production of methyl esters (ME) of higher fatty acids as alternative fuels for diesel engines. If they are treated such that the required quality, with an acidity number up to 3.0mgKOH/g and a water content up to 0.1wt%, is achieved they can be processed to ME using standard techniques of alkali-catalysed transesterification with methanol which are utilized for production of the ME from new oils/fats. The problematic waste can thus be converted to an ecologically friendly fuel. Vacuum distillation of free fatty acids in a film evaporator is an effective method for simultaneously decreasing the content of FFA and water in UFO. Final distillation of raw ME in a film vacuum evaporator results in practically all parameters required by the standard, in the final ME being achieved. Undesirable low-temperature properties of ME derived from UFO, due to higher fraction of saturated acyls, can be adjusted by the addition of depressants—flow improvers for winterization. Some simplified methods for the quality control of UFO and ME are discussed. The conversion of acylglycerols to ME is monitored by GLC with a packed column, where the peak areas of ME in the sample before and after the reaction with an effective methylation agent are compared. The method for the determination of the water content in esters utilizes the reaction of calcium carbide with water, the volume of acetylene being measured.

The oxidation of cyclohexylamine was studied over tungsten, molybdenum and vanadium oxides containing catalysts supported on silica, γ-alumina or hydrotalcite in the temperature range 170°C–230°C. Depending on the catalyst and reaction conditions, the main products of the reaction are cyclohexanone oxime, cyclohexylidenecyclohexylamine or cyclohexanone. About 70% selectivity of cyclohexanone oxime formation at about 20% conversion of cyclohexylamine is obtained over tungsten catalysts. The activity of the tested catalysts usually passes through a maximum and, then, gradually decreases with time on stream. The deactivation of the catalyst is caused by the formation of tar products on the catalyst surface. The mechanism of oxidation involves formation of oxygen species on the catalyst surface which oxidizes cyclohexylamine.

The direct synthesis of phenol from benzene in the gas phase was studied over hydroxyapatite catalysts. The reaction was carried out in a fixed-bed reactor at atmospheric pressure and reaction temperature of 450°C in the presence of ammonia. A high selectivity (about 97%) of phenol formation at about 3.5% conversion of benzene was achieved over catalysts containing Ca and Cu ions in the cation part of hydroxyapatite. Besides phenol as the main reaction product, aniline is also formed. The reaction mechanism involves formation of N2O from NH3 in the first step of reaction. Benzene is oxidized by active oxygen species which are formed on the catalyst by decomposition of N2O.

Monoalkylbenzenes, polymethylbenzenes, para-substituted toluenes and monomethylnaphthalenes were oxidized in the vapor phase by oxygen-containing gas in the presence of water over a Sb2O3-promoted V2O5/TiO2 catalyst. This type of catalyst yields carboxylic acids with high selectivity. In the oxidation of substituted alkylbenzenes only alkyl groups were oxidized. No products of oxidative dimerization were detected. Only in the oxidation of methylnaphthalenes, also products of aromatic ring oxidation are formed. A correlation between experimental data and results of quantum-chemical calculations of bond dissociation energies is discussed.

Polymer-supported palladium catalysts based on microporouspolydimethylacrylamide-p-styryl-sulphonate-methylenebis(acrylamide) with 4 and 8% m/m crosslinking degree and various metal contents were prepared. The influence of the crosslinking degree on the metal distribution and on the final activity of the catalyst was studied by a combination of diverse physico-chemical techniques like X-ray microprobe analysis, inverse steric exclusion chromatography, powder X-ray diffraction, electron spin resonance, and catalytic tests.

Oxidation kinetics of formic acid with aqueous hydrogen peroxide (30-70%) has been studied at 45 °C with 0-0.1 M H 2 SO 4 as a catalyst. A kinetic model has been suggested which satisfactorily describes the oxidation process of formic acid to peroxyformic acid.

A study has been made of the liquid phase conversion of cyclohexene over metallic palladium and platinum catalysts under oxygen and nitrogen atmosphere. Special attention has been given to the effect of oxygen pressure, catalyst support, solvent and metal modifiers on the activity of metal catalysts and distribution of products. In every case the main reaction pathway is disproportionation of cyclohexene to benzene and cyclohexane. Formation of oxygenated products is low even at 2–6 atm of oxygen. Doping of Pd and Pt catalysts with metal modifiers strongly suppresses the conversion of cyclohexene and has no influence on the ratio of benzene/cyclohexane at experiments carried out in an inert atmosphere. An interpretation of these effects is presented.

The oxidation of cyclohexene with molecular oxygen catalyzed by solid Pd/C or Pd(II) acetate-hydroquinone-iron phthalocyanine gives cyclohexane, benzene and oxygenated products. Oxygen pressure and solvent used influence significantly the distribution of the products and at the pressure above 2 atm no cyclohexane is formed. Over Pd/C catalyst in the absence of oxygen, disproportionation to cyclohexane and benzene (the ratio is nearly 2:1) proceeds exclusively. Under comparable conditions 2-cyclohexenol is disproportionated to cyclohexanol and phenol and some of it rearranges to cyclohexanone. The explanation for the disproportionation of cyclohexene under the Wacker conditions is that Pd0 centres intermediately formed after stoichiometric oxidation of cyclohexene by Pd(II) are not completely reoxidized, but depending on the reaction conditions, they can partly aggregate and then, similarly to metallic surfaces, dehydrogenate cyclohexene to benzene. The hydrogen species formed migrate on the palladium surface and hydrogenate cyclohexene or at sufficient oxygen pressure they are oxidized to water.

A variety of aromatic and aliphatic alcohols and cyclohexanols were oxidized in the aqueous phase, both individually and competitively in pairs, over a carbon-supported palladium catalyst, or the same catalyst modified by Co and Cd as additives. Some of these alcohols were unreactive or less reactive individually, but more reactive in competition. These findings were explained in terms of the interaction of the substrate with oxygen-covered metal catalyst, which depends on the dissociation ability of the alcohols. The promoting effect of Co and Cd additives on the Pd catalyst was also based on the concept of metal-substrate interaction.

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The study of the vapor phase reaction of isomeric cresylbenzoates, phenyl-p-toluate and phenylsalicylate over copper based catalysts was used to elucidate the mechanism of the oxidation of aromatic acids to phenolic compounds. It is proposed that copper salts of toluic acids formed on the catalyst surface during the reaction are not transformed to cresol precursors, i.e. cresyltoluates, but are very rapidly decomposed to toluene and carbon dioxide. This explains why, unlike the liquid phase oxidation of toluic acids, a heterogeneous reaction does not produce cresols.

Activity and selectivity of supported Pd and Pt catalysts have been studied in the liquid-phase oxidation of hydrocarbons and alcohols to ketones and carboxylic acids. It was found that the rate of these reactions is mostly controlled by mass transfer effects. At higher partial pressure of oxygen the catalysts are reversibly deactivated by oxygen. Higher resistance against deactivation and higher catalytic activity of Pd and Pt catalysts is achieved by doping them with some metals.

A product study of p-xylene oxidation by the Co-Br-Py catalytic system has been investigated under anaerobic conditions at 120 °C. It was shown that in bromine-free systems the direct oxidation of p-xylene by Co(III) ions proceeds, while the distribution and yield of reaction products are only slightly influenced by the type of solvent. During the simultaneous oxidation of p-xylene and p-toluic acid in aqueous systems, the latter increases the selectivity of reaction: however, the methyl group of p-toluic acid is not attacked by Co(III) ions. In the presence of bromine compounds, p-xylene is attacked by bromine species formed by the preferred reaction of Co(III) with bromide ions. In contrast to reaction in acetic acid, in the aqueous system brominated products are formed to a lesser extent.

The oxidation of p-xylene in acetic acid a using cobalt(III)-bromide system or in conjunction with pyridine was studied under inert atmosphere. It was found that in the presence of p-xylene the preferential reaction of Co-(III) with Br− also produces molecular bromine or the complex PyBr2 which brominates the hydrocarbon. The formation of side-chain brominated products is suppressed in the presence of Co(II) and Co(III) ions or pyridine, probably as a result of the competitive reaction of intermediately formed ArCH2 radicals with Co(III) ions instead of bromine radicals. In the reaction mechanism, bromine anion radicals are assumed to initiate p-xylene oxidation and reoxidize Co(II) ions. The presence of pyridine in the reaction system facilitates the regeneration of Co(III) and bromide ions.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetics and mechanism of cobalt-catalyzed oxidation of p-xylene in the presence of waterMilan Hronec, Zuzana Cvengrosova, and Jan IlavskyCite this: Ind. Eng. Chem. Process Des. Dev. 1985, 24, 3, 787–794Publication Date (Print):July 1, 1985Publication History Published online1 May 2002Published inissue 1 July 1985https://pubs.acs.org/doi/10.1021/i200030a045https://doi.org/10.1021/i200030a045research-articleACS PublicationsRequest reuse permissionsArticle Views412Altmetric-Citations21LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts