Main reaction.

As an example of the application of a fixed-bed tubular reactor, consider the production of methanol. Synthesis gas (a mixture of hydrogen, carbon monoxide, and carbon dioxide) is reacted over a copper-based cat dyst. The main reactions are... 

Dealing with NO emissions. There are two main reaction paths for NO,r formation ... 

The main reactions involved are the exothermic producer gas reactions, which are basically... 

When a mixture of aniline, hydrochloric acid and acetaldehyde is heated (in the absence of an oxidising agent), a vigorous reaction occurs with the pro duction of quinaldine. In these circumstances, the main reactions are undoubtedly, (i) the acetaldehyde undergoes the aldol condensation, and the... 

It is convenient to include under Aromatic Amines the preparation of m-nitroaniline as an example of the selective reduction of one group in a polynitro compound. When wt-dinitrobenzene is allowed to react with sodium polysulphide (or ammonium sulphide) solution, only one of the nitro groups is reduced and m-nitroanUine results. Some sulphur separates, but the main reaction is represented by ... 

In a 2 litre bolt-head flask, equipped with an efficient mechanical stirrer, place 60-5 g. (50 ml.) of pure nitrobenzene and a solution of 30 g. of ammonium chloride in 1 litre of water. Stir vigorously and add 75 g. of a good quality zinc powder (about 90 per cent, purity) in small portions over a period of 5 minutes. The main reaction occurs about 5 minutes after the addition and the temperature rises. When the temperature reaches about 65°, add enough ice to the weU-stirred mixture to reduce the temperature to 50-55°. Filter the solution through a Buchner funnel twenty minutes after the first portion of zinc powder was introduced wash the zinc oxide residues with 600-700 ml. of boiling water. 

This catalyst is prepared by the decomposition of basic copper ammonium chromate the main reactions may be written as ... 

The reason for this is that reaction (i) is usually much slower than (ii) and (iii) so that the main reaction appears to be (Iv) (compare the preparation of tertiary butyl chloride from tertiary butyl alcohol and concentrated hydrochloric acid, Section 111,33). If the reaction is carried out in the presence of P3rridine, the latter combines with the hydrogen chloride as it is formed, thus preventing reactions (ii) and (iii), and a good yield of the ester is generally obtained. The differentiation between primary, secondary and tertiary alcohols with the aid of the Lucas reagent is described in Section III,27,(vii). 

With the exception of the nuclear amination of 4-methylthiazole by sodium amide (341, 346) the main reactions of nucleophiles with thiazole and its simple alkyl or aryl derivatives involve the abstraction of a ring or substituent proton by a strongly basic nucleophile followed by the addition of an electrophile to the intermediate. Nucleophilic substitution of halogens is discussed in Chapter V. 

Hydroxyalkylthiazoles are also obtained by cyclization or from alkoxyalkyl-thiazoles by hydrolysis (36, 44, 45, 52, 55-57) and by lithium aluminium hydride reduction of the esters of thiazolecarboxylic acids (58-60) or of the thiazoleacetic adds. The Cannizzaro reaction of 4-thiazolealdehyde gives 4-(hydroxymethyl)-thiazole (53). The main reactions of hydroxyalkyl thiazoles are the synthesis of halogenated derivatives by the action of hydrobroraic acid (55, 61-63), thionyl chloride (44, 45, 63-66), phosphoryl chloride (52, 62, 67), phosphorus penta-chloride (58), tribromide (38, 68), esterification (58, 68-71), and elimination that leads to the alkenylthiazoles (49, 72). 

Indirect Hquefaction of coal and conversion of natural gas to synthetic Hquid fuels is defined by technology that involves an intermediate step to generate synthesis gas, CO +. The main reactions involved in the generation of synthesis gas are the coal gasification m2LC ions Combustion... 

Butane-Based Fixed-Bed Process Technology. Maleic anhydride is produced by reaction of butane with oxygen using the vanadium phosphoms oxide heterogeneous catalyst discussed earlier. The butane oxidation reaction to produce maleic anhydride is very exothermic. The main reaction by-products are carbon monoxide and carbon dioxide. Stoichiometries and heats of reaction for the three principal reactions are as follows ... 

Otherwise, the main reactions at the methylene group are the dialkylation with alkyl haUdes (77), the acetylation with acetyl chloride which yields acetylma1 ononitrile [1187-11-7] (78), the Knoevenagel condensation, as well as the condensation with triethyl orthoformate, gives... 

Most ionic nitrations are performed at 0—120°C. For nitrations of most aromatics, there are two Hquid phases an organic and an acid phase. Sufficient pressure, usually slightly above atmospheric, is provided to maintain the Hquid phases. A large interfacial area between the two phases is needed to expedite transfer of the reactants to the interface and of the products from the interface. The site of the main reactions is often at or close to the interface (2). To provide large interfacial areas, a mechanical agitator is frequently used. 

When nitrogen dioxide is used, the main reaction steps are as in equations 8 and 9. 

Transition-metal-catalyzed oxidations may or may not proceed via peroxocomplexes. Twelve important industrial organic oxidation processes catalyzed by transition metals, many of which probably involve peroxo intermediates, have been tabulated (88). Even when peroxo intermediates can be isolated from such systems, it does not necessarily foUow that these are tme intermediates in the main reaction. 

At pH 4—6, the cure is slower than it is at pH 8 and higher, and much slower than at pH 1—3. Reactions at pH 4—6 resemble those on the more alkaline side, but with a substantial increase in side-products. This is partly the result of the low rates of the main reactions and partly the result of stable intermediates at this pH range. 

In addition, however, several minor but important side reactions concurrently proceed with the main reaction. These side reactions may become significant under certain conditions, particularly when the main reaction is slow because of low monomer reactivities or low concentrations. The principal pathways involved in the formation of poly(amic acid) are as shown in Eigure 1. 

The main reactions involved in alkyd lesin synthesis are polycondensation by estetitication and ester interchange. Figure 1 uses the following symbols to... 

The following HF alkylation reactions are based on straight-chain olefins. A similar chemistry can be written for the branched-chain process. The main reaction is the alkylation of benzene with the straight-chain olefins to yield a linear alkylbenzene ... 

The Tatoray process, which was developed by Toray Industries, Inc., and is available for Hcense through UOP, can be appHed to the production of xylenes and benzene from feedstock that consists typically of toluene [108-88-3] either alone or blended with aromatics (particularly trimethylbenzenes and ethyl-toluenes). The main reactions are transalkylation (or disproportionation) of toluene to xylene and benzene or of toluene and trimethylbenzenes to xylenes in the vapor phase over a highly selective fixed-bed catalyst in a hydrogen atmosphere at 350—500°C and 1—5 MPa (10—50 atm). Ethyl groups are... 

In addition to the two main reactions, ie, methylolation and condensation, there are a number of other reactions important for the manufacture and uses of amino resins. For example, two methylo1 groups may combine to produce a dimethylene ether linkage and Hberate a molecule of water ... 

Of the main reactions, aromatization takes place most readily and proceeds ca 7 times as fast as the dehydroisomerization reaction and ca 20 times as fast as the dehydrocyclization. Hence, feeds richest in cycloparaftins are most easily reformed. Hydrocracking to yield paraffins having a lower boiling point than feedstock proceeds at about the same rate as dehydrocyclization. 

Chain transfer to monomer is the main reaction controlling molecular weight and molecular weight distribution. The chain-transfer constant to monomer, C, is the ratio of the rate coefficient for transfer to monomer to that of chain propagation. This constant has a value of 6.25 x lO " at 30°C and 2.38 x 10 at 70°C and a general expression of 5.78 30°C, chain transfer to monomer happens once in every 1600 monomer... 

Reforming Chemistry. The main reactions occurring ia a reformer are shown ia Figure 5 (6,13—15) most are reversible iadicating the potential importance of reaction equilibrium. 

Fig. 5. Main reactions of catalytic reforming. Pt and acid refer to predominant active catalytic sites.

A catalyst manufactured using a shaped support assumes the same general size and shape of the support, and this is an important consideration in the process design, since these properties determine packing density and the pressure drop across the reactor. Depending on the nature of the main reaction and any side reactions, the contact time of the reactants and products with the catalyst must be optimized for maximum overall efficiency. Since this is frequendy accompHshed by altering dow rates, described in terms of space velocity, the size and shape of the catalyst must be selected carehiUy to allow operation within the capabiUties of the hardware. 

Only recently has a mechanism been proposed for the copper-cataly2ed reaction that is completely satisfactory (58). It had been known for many years that a small amount of carbon dioxide in the feed to the reactor is necessary for optimum yield, but most workers in the field beHeved that the main reaction in the formation of methanol was the hydrogenation of carbon monoxide. Now, convincing evidence has been assembled to indicate that methanol is actually formed with >99% selectivity by the reaction of dissociated, adsorbed hydrogen and carbon dioxide on the metallic copper surface in two steps ... 

The adsorbed oxygen atom on the copper surface is removed by reaction with carbon monoxide and provides a pathway for the formation of the carbon dioxide needed in the main reaction. 

These ate the main reactions ia Pordand cements because the two calcium siHcates constitute about 75% of the cement. The average lime—silica ratio (C S) may vary from about 1.5 to about 2.0 or even higher, the average value is about 1.7. The water content varies with the ambient humidity, the three moles of water being estimated from measurements ia the dry state and stmctural considerations. As the lime—silica ratio of the C—S—H iacreases, the amount of water iacreases on an equimolar basis, ie, the lime goes iato the stmcture as calcium hydroxide, resulting ialess free calcium hydroxide. 

Many techniques have been developed to accomplish this, for example, the use of a cooled recirculating system in which the chlorine is dissolved in one part and the allyl chloride is dissolved and suspended in another (61). The streams are brought together in the main reaction zone and thence to a separator to remove water-insoluble products. Another method involves maintaining any organic phase present in the reaction zone in a highly dispersed condition (62). A continuous reactor consists of a recycle system in which make-up water and allyl chloride in a volume ratio of 10—50 1 are added... 

AH ethylene oxide direct-oxidation plants are based on the original process chemistry discovered by Lefort in 1931 (7,8). The main reaction is as follows ... 

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