Ammoxidation methane

Because of the large price differential between propane and propylene, which has ranged from 155/t to 355 /1 between 1987 and 1989, a propane-based process may have the economic potential to displace propylene ammoxidation technology eventually. Methane, ethane, and butane, which are also less expensive than propylene, and acetonitrile have been disclosed as starting materials for acrylonitrile synthesis in several catalytic process schemes (66,67). 

Two synthesis processes account for most of the hydrogen cyanide produced. The dominant commercial process for direct production of hydrogen cyanide is based on classic technology (23—32) involving the reaction of ammonia, methane (natural gas), and air over a platinum catalyst it is called the Andmssow process. The second process involves the reaction of ammonia and methane and is called the BlausAure-Methan-Ammoniak (BMA) process (30,33—35) it was developed by Degussa in Germany. Hydrogen cyanide is also obtained as a by-product in the manufacture of acrylonitrile (qv) by the ammoxidation of propjiene (Sohio process). 

The full cost of acrylonitrile manufacture based on methane was about 22)4/lb in 1960 (allowing 15% return). But the marginal cost—with no capital charges or overheads—was only 7 /lb. The full cost of propylene ammoxidation (with 15% return) was about 13-16ff/lb according to location. Thus, as soon as it was clear that ammoxidation was likely to... 

In the direct ammoxidation of propane over Fe-zeolite catalysts the product mixture consisted of propene, acrylonitrile (AN), acetonitrile (AcN), and carbon oxides. Traces of methane, ethane, ethene and HCN were also detected with selectivity not exceeding 3%. The catalytic performances of the investigated catalysts are summarized in the Table 1. It must be noted that catalytic activity of MTW and silicalite matrix without iron (Fe concentration is lower than 50 ppm) was negligible. The propane conversion was below 1.5 % and no nitriles were detected. It is clearly seen from the Table 1 that the activity and selectivity of catalysts are influenced not only by the content of iron, but also by the zeolite framework structure. Typically, the Fe-MTW zeolites exhibit higher selectivity to propene (even at higher propane conversion than in the case of Fe-silicalite) and substantially lower selectivity to nitriles (both acrylonitrile and acetonitrile). The Fe-silicalite catalyst exhibits acrylonitrile selectivity 31.5 %, whereas the Fe-MTW catalysts with Fe concentration 1400 and 18900 ppm exhibit, at similar propane conversion, the AN selectivity 19.2 and 15.2 %, respectively. On the other hand, Fe-MTW zeolites exhibit higher AN/AcN ratio in comparison with Fe-silicalite catalyst (see Table 1). Fe-MTW-11500 catalyst reveals rather rare behavior. The concentration of Fe ions in the sample is comparable to Fe-sil-12900 catalyst, as well as... 

Hydrogen cyanide is an important building block chemical for the synthesis of a variety of industrially important chemicals, such as 2 hydroxy-4 methylthiobutyric acid, adiponitrile, nitrilotriacetic acid, lactic acid, and methyl methacrylate. The primary commercial routes to hydrogen cyanide are the reaction of methane and ammonia under aerobic (Andrussow Process) or anaerobic conditions (Degussa Process), or the separation of hydrogen cyanide as a by-product of the ammoxidation of propylene < ) The ammoxidation of methanol could represent an attractive alternate route to HCN for a number of reasons. First, on a molar basis, the price of methanol has become close to that of methane as world methanol capacity has increased. However, an accurate long term pricing picture for these two raw... 

One of the most important challenges in the modern chemical industry is represented by the development of new processes aimed at the exploitation of alternative raw materials, in replacement of technologies that make use of building blocks derived from oil (olefins and aromatics). This has led to a scientific activity devoted to the valorization of natural gas components, through catalytic, environmentally benign processes of transformation (1). Examples include the direct exoenthalpic transformation of methane to methanol, DME or formaldehyde, the oxidation of ethane to acetic acid or its oxychlorination to vinyl chloride, the oxidation of propane to acrylic acid or its ammoxidation to acrylonitrile, the oxidation of isobutane to... 

Ammoxidation, a vapor-phase reaction of hydrocarbon with ammonia and oxygen (air) (eq. 2). can be used to produce hydrogen cyanide (HCN), acrylonitrile, acetonitrile (as a by-product of acrylonitrile manufacture), methacrylonitrile, benzonitrile, and toluinitriles from methane, propylene, butylene, toluene, and xylenes, respectively. See also Acrylonitrile and Methacrylic Acid and Derivatives,... 

The synthesis of intermediates and monomers from alkanes by means of oxidative processes, in part replacing alkenes and aromatics as the traditional building blocks for the chemical industry [2]. Besides the well-known oxidation of n-butane to maleic anhydride, examples of processes implemented at the industrial level are (i) the direct oxidation of ethane to acetic acid, developed by Sabic (ii) the ammoxidation of propane to acrylonitrile, developed by INEOS (former BP) and by Mitsubishi, and recently announced by Asahi to soon become commercial (iii) the partial oxidation of methane to syngas (a demonstration unit is being built by ENI). Many other reactions are currently being investigated, for example, (i) the... 

Other catalytic reactions carried out in fluidized-bed reactors are the oxidation of naphthalene to phthalic anhydride [2, 6, 80] the ammoxidation of isobutane to mcthacrylonitrilc [2] the synthesis of maleic anhydride from the naphtha cracker C4 fraction (Mitsubishi process [81, 82]) or from n-butane (ALMA process [83], [84]) the reaction of acetylene with acetic acid to vinyl acetate [2] the oxychlorination of ethylene to 1,2-di-chloroethane [2, 6, 85, 86] the chlorination of methane [2], the reaction of phenol with methanol to cresol and 2,6-xylenol [2, 87] the reaction of methanol to gasoline... 

The industrially important direct methane conversion processes comprise oxidative coupling, reductive coupling including pyrolysis reactions, partial oxidation, halogenation and oxyhalogenation,26 and ammoxidation. Other direct conversions include alkylation, electrophilic substitution, and C-H bond activation over various complex and super acid catalysts. Several of these direct conversion technologies remain to be exploited to achieve their full commercial potentials. 

As can be seen from the above equation, formation of HCN is in reality a hetero-bimolecular oxidative coupling reaction of methane with ammonia. The ammoxidation reactor construction is a simple fixed-bed multi-tube and the catalyst is usually a platinum or sometimes a Group V or VI metal oxide on a silica or alumina support. The HCN product is recovered by condensation and fractionation. With the reaction simplicity and yield, and widespread availability of starting materials, in-situ HCN generation is an ideal industry solution to HCN supply. (See Chapter 29 for more details.)... 

Of coincidental interest, ammoxidation of propylene,33 itself an oxidative coupling product of methane as noted above, is the commercially practiced route to acrylonitrile, which is produced in high conversions and yields ... 

The activation of light saturated hydrocarbons becomes increasingly more difficult as the molecules become smaller, with methane reactions being the most difficult to control. On the other hand, the occurrence of non-catalysed gas phase oxidation makes selectivity control very complicted. This is a problem common to almost all oxidations, unless one of the products is extremely stable examples are unsaturated nitriles (e.g. acrylonitrile in the ammoxidation of propane) or maleic anhydride (in the oxidation of butane). There is a parallel trend in the changes of reactivity with molecular weight in catalytic and non catalytic (gas phase) oxidation. The challenge to catalysis to achieve selective reactions at lower temperature is thus equally important for all light hydrocarbons. 

Although substantial amounts of hydrogen cyanide are produced and recovered as a byproduct from the manufacture of acrylonitrile by the ammoxidation of propylene, some hydrogen cyanide is also made on purpose from methane. Basically, two main approaches are available. ... 

The reaction is highly exothermic and uses volumetric flow ratios, air/CH4/NH3, of about 5/1/1. Whereas propylene ammoxidation proceeds at about 440° C, the ammoxidation of methane requires temperatures... 

Supported metal oxides are currently being used in a large number of industrial applications. The oxidation of alkanes is a very interesting field, however, only until recently very little attention has been paid to the oxidation of ethane, the second most abundant paraffin (1). The production of ethylene or acetaldehyde from this feed stock is a challenging option. Vanadium oxide is an important element in the formulation of catalysts for selective cataljdic reactions (e. g. oxidation of o-xylene, 1-3, butadiene, methanol, CO, ammoxidation of hydrocarbons, selective catalytic reduction of NO and the partial oxidation of methane) (2-4). Many of the reactions involving vanadium oxide focus on the selective oxidation of hydrocarbons, and some studies have also examined the oxidation of ethane over vanadium oxide based catalysts (5-7) or reviewed the activity of vanadium oxide for the oxidation of lower alkanes (1). Our work focuses on determining the relevance of the specific oxide support and of the surface vanadia coverage on the nature and activity of the supported vanadia species for the oxidation of ethane. 

Towards these ends 14 selective oxidation reactions and two ammoxidation reactions have been evaluated through the use of selectivity-conversion plots, constructed fi om literature data [1]. Two examples of these plots are presented in figure 2 for ethylbenzene oxidation to styrene and methane oxidation to ethane. These selectivity-conversion plots were generated for a variety of catalysts for each reaction over a range of temperatures and space velocities. It should be stressed that the objective of this exercise was not to determine a reaction pathway or network, but simply to evaluate the best performance which has been achieved for any given reaction, hence the use of data fi om different catalysts and operating conditions. 

Desulfurization of petroleum feedstock (FBR), catalytic cracking (MBR or FI BR), hydrodewaxing (FBR), steam reforming of methane or naphtha (FBR), water-gas shift (CO conversion) reaction (FBR-A), ammonia synthesis (FBR-A), methanol from synthesis gas (FBR), oxidation of sulfur dioxide (FBR-A), isomerization of xylenes (FBR-A), catalytic reforming of naphtha (FBR-A), reduction of nitrobenzene to aniline (FBR), butadiene from n-butanes (FBR-A), ethylbenzene by alkylation of benzene (FBR), dehydrogenation of ethylbenzene to styrene (FBR), methyl ethyl ketone from sec-butyl alcohol (by dehydrogenation) (FBR), formaldehyde from methanol (FBR), disproportionation of toluene (FBR-A), dehydration of ethanol (FBR-A), dimethylaniline from aniline and methanol (FBR), vinyl chloride from acetone (FBR), vinyl acetate from acetylene and acetic acid (FBR), phosgene from carbon monoxide (FBR), dichloroethane by oxichlorination of ethylene (FBR), oxidation of ethylene to ethylene oxide (FBR), oxidation of benzene to maleic anhydride (FBR), oxidation of toluene to benzaldehyde (FBR), phthalic anhydride from o-xylene (FBR), furane from butadiene (FBR), acrylonitrile by ammoxidation of propylene (FI BR)... 

Other practical considerations are attrition of particles caking of catalyst from malfunctioning of the reactor due to formation of tarry products (resulting sometimes in cakes as large as the reactor diameter) and the need to avoid premixing of reactants (particularly when they can form explosive mixtures) and fix their relative locations within the bed (e.g., in the chlorination of methane and ammoxidation of propylene). Refer to Doraiswamy and Sharma (1984) for further details. 

The Andrussow process this involves the ammoxidation of methane ... 

Ammoxidation refers to the formation of nitriles by oxidation of hydrocarbons with oxygen in the presence of ammonia (Figure 1) [1]. Ammoxidation is best conducted with olefins, or with aromatic or heteroaromatic compounds, containing a readily abstractable H atom (allylic or benzylic intermediates are formed), although the ammoxidation of alkanes (e. g. propane to acrylonitrile [e. g. 2-4] or ethane to acetonitrile [e. g. 5]) is also possible. An exceptional example is the ammoxidation of methane to hydrogen cyanide by the Andrussov reaction [6]. 

In 1922 Wohl [13] published his observation that the oxidation of naphthalene in the presence of ammonia over vanadia gives phthalimide but this result went unnoticed both by the scientific community and by industry. Andrussov [6] found, in 1935, a route to produce hydrogen cyanide effectively by conversion of methane in the presence of air and ammonia over platinum catalysts at ca 1273 K. Thus, the first steps towards the development of ammoxidation had been taken. The conversion of aliphatic olefins was first claimed by Cosby in the late forties [e. g. 14] and the conversion of toluene to benzonitrile was first performed by Cosby and Erchak in 1950 [15]. The term ammoxidation was introduced by Hadley in 1961 [16]. Since the fifties the fundamentals of the reaction and the reaction technique, for different aromatic compounds, have been reviewed [e.g. 9,16,17]. 

This section includes the selective oxidation of hydrocarbons and oxygenated compounds, oxydehydrogenation and ammoxidation. Partial oxidation to syngas and oxidative coupling of methane will be treated in the following section. 

Except in the special case of methane ammoxidation to HCN, to undergo ammoxidation an organic substrate generally must... 

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