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Catalytic Processes for the Transformation of Ethanol Into Acetonitrile

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Catalytic Processes for the Transformation of Ethanol Into Acetonitrile Allma Mater Studiiorum – Uniiversiità dii Bollogna DOTTORATO DI RICERCA IN Chimica Industriale Ciclo XXV Settore Concorsuale di afferenza: 03/C2 Settore Scientifico disciplinare: CHIM 04 Catalytic processes for the transformation of ethanol into acetonitrile Presentata da: Federico Folco Coordinatore Dottorato Relatore Prof. Fabrizio Cavani Prof. Fabrizio Cavani Esame finale anno 2013 Allma Mater Studiiorum – Uniiversiità dii Bollogna DOTTORATO DI RICERCA IN Chimica Industriale Ciclo XXV Settore Concorsuale di afferenza: 03/C2 Settore Scientifico disciplinare: CHIM 04 Catalytic processes for the transformation of ethanol into acetonitrile Presentata da: Federico Folco Coordinatore Dottorato Relatore Prof. Fabrizio Cavani Prof. Fabrizio Cavani Esame finale anno 2013 ABSTRACT This thesis deals with the transformation of ethanol into acetonitrile. Two approaches are investigated: (a) the ammoxidation of ethanol to acetonitrile and (b) the amination of ethanol to acetonitrile. The reaction of ethanol ammoxidation to acetonitrile has been studied using several catalytic systems, such as vanadyl pyrophosphate, supported vanadium oxide, multimetal molibdates and antimonates. The main conclusions are: (I) The surface acidity must be very low, because acidity catalyzes several undesired reactions, such as the formation of ethylene, and of heavy compounds as well. (II) Supported vanadium oxide is the catalyst showing the best catalytic behaviour, but the role of the support is of crucial importance. (III) Both metal molybdates and antimonates show interesting catalytic behaviour, but are poorly active, and probably require harder conditions than those used with the V oxide-based catalysts. (IV) One key point in the reaction network is the rate of reaction between acetaldehyde (the first intermediate) and ammonia, compared to the parallel rates of acetaldehyde transformation into by-products (CO, CO2, HCN, heavy compounds). Concerning the non-oxidative process, two possible strategies are investigated: (a) the ethanol ammonolysis to ethylamine coupled with ethylamine dehydrogenation, and (b) the direct non- reductive amination of ethanol to acetonitrile. Despite the good results obtained in each single step, the former reaction does not lead to good results in terms of yield to acetonitrile. The direct amination can be catalyzed with good acetonitrile yield over catalyst based on supported metal oxides. Strategies aimed at limiting catalyst deactivation have also been investigated. SUMMARY INTRODUCTION ...................................................................................................................................................... 1 Nitriles: features, synthesis and uses of most common nitriles ......................................................................... 1 Acetonitrile: The 2008 – 2009 shortage ............................................................................................................. 7 Acetonitrile: Dedicated processes .................................................................................................................... 11 1. Reaction between CO, H2 and NH3 ....................................................................................................... 11 2. Hydrocyanation of C1-C2 compounds ................................................................................................... 13 3. Ethane or ethylene amination or ammoxidation ................................................................................. 15 References ........................................................................................................................................................ 19 EXPERIMENTAL ..................................................................................................................................................... 21 Setting up the reaction apparatus .................................................................................................................... 21 Catalyst characterization .................................................................................................................................. 24 A. THE AMMOXIDATION OF ETHANOL TO ACETONITRILE.................................................................................. 26 Introduction ...................................................................................................................................................... 26 Results and Discussion ...................................................................................................................................... 29 1. Ethanol ammoxidation with the vanadyl pyrophosphate (VPP) catalyst ................................................. 29 2. Ethanol ammoxidation with supported vanadium oxide catalyst ............................................................ 59 3. Ethanol ammoxidation with metal antimonates and metal molybdates catalysts .................................. 84 Conclusions ....................................................................................................................................................... 87 References ........................................................................................................................................................ 89 B. THE AMINATION OF ETHANOL TO ACETONITRILE .......................................................................................... 91 Introduction ...................................................................................................................................................... 91 The (oxi)dehydrogenation of primary amines into nitriles ........................................................................... 93 The hydroamination of ethanol .................................................................................................................... 94 The non-reductive amination of ethanol ...................................................................................................... 97 Results and Discussion .................................................................................................................................... 100 1. The synthesis of acetonitrile by a two-step process: (a) Ethanol amination to ethylamine, and (b) Ethylamine dehydrogenation to acetonitrile.............................................................................................. 100 2. The non-reductive amination of ethanol over dehydrogenating catalysts ............................................ 116 Conclusions ..................................................................................................................................................... 139 References ...................................................................................................................................................... 140 INTRODUCTION Introduction Nitriles: features, synthesis and uses of most common nitriles Nitriles are important starting materials for solvents and polymers as well as for the synthesis of many pharmaceuticals and pesticides. The –CN moiety is extremely polar, which results in nitriles having a high dipole moment. This large dipole moment leads to intermolecular association; hence, nitriles have higher boiling points than would be expected from their molecular mass. Most of the lower molecular mass aliphatic nitriles are liquids at room temperature. Simple nitriles such as acetonitrile, propionitrile, glycolonitrile, and malononitrile are miscible with water; the latter two having a higher solubility because of the presence of two polar groups. Nitriles with higher molecular mass are sparingly water- soluble. Nitriles are good solvents for both polar and nonpolar solutes. Aromatic and arali- phatic nitriles are liquids or crystalline solids, mostly sparingly soluble in water (some heteroaromatic cyano-compounds have a higher water solubility) with sometimes considerable thermal stability. Benzonitrile and a range of substituted benzonitriles have a characteristic odor resembling bitter almonds. Some substituted benzonitriles sublime readily [1] Some physical characteristics are shown in table 1. 20 Nitrile Mr mp, °C Bp, °C d20 n D Acetonitrile 41.05 -45 81.6 1.3441 0.7138 Propionitrile 55.08 -93 97.2 1.3670 0.782 Butyronitrile 69.10 -111.9 116 – 117 1.3838 0.7936 Valeronitrile 83.13 -96 141.3 1.3971 0.8008 Tetradecanonitrile 209.38 19.25 226 (10 kPa) 1.4392 0.8281 Malononitrile 66.06 30 – 31 218 – 219 1.4146 1.0494 Succinonitrile 80.09 57 265 – 267 1.4173 0.9867 Glutaronitrile 94.12 -29 286 1.4295 0.9911f Allyl cyanide 67.09 -84 119 1.4060 0.8329 Methyleneglutaronitrile 106.12 -9.0 113 (0.66 kPa) 1.4558 0.9831 Table 1. Properties of nitriles. 1 INTRODUCTION The major part of both aliphatic and aromatic nitriles are mainly produced through the following four processes: 1. Reaction of nitrogen-free precursors (alkanes, olefins, alcohols, aldehydes, or acids) with ammonia. Gas phase reaction of olefins with ammonia in the presence of oxygen (ammoxidation) and oxidation catalysts (vanadium or molybdenum based catalysts) has attained the greatest industrial importance for the production of acrylonitrile from propene. Acetonitrile and hydrogen cyanide are formed as byproducts in typical quantities of 30 – 40 kg and 140 – 180 kg, respectively per 1000 kilograms of acrylonitrile [2]. Propane can also be used as feedstock (the first step being the dehydrogenation to propene) as well as acrolein [3]; recently, direct
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