Conversion to butadienes

Maximum % diene maximum conversion to butadiene (usually at temperature T50). 

The second experiment is to perform adsorption-desorption of butene on a catalyst that is depleted of selective oxidation sites. When 10 pulses of cis-2-butene are passed over a catalyst at 210°C (5), which is a temperature too low for the production of C02, the catalyst is reduced. The number of selective oxidation sites is substantially reduced as is evident by the much lower conversion to butadiene in the last pulse. Then the oxide is cooled to 22°C, and cis-2-butene is adsorbed. The resulting desorption profile is shown in Fig. 1, curve d. Clearly, there is no more butadiene production, while the combustion products are produced in a somewhat larger quantity. These results again support the conclusion that the selective oxidation and the combustion sites are independent. 

Is there any simple relationship between (a) the equilibrium constants for these reactions and the reactions in Prob. 1-4 and (b) the conversion to butadiene for these reactions and the reactions in Prob. 1-4. 

Dehydrogenation over Chromia—Alumina. Chromia—alumina catalyst CR-0205 was studied relative to butane dehydrogenation and gave low conversion to butadiene under conditions of appreciable conversion to butenes. In addition, there was an exceptionally small amount of cracked products and essentially no skeletal isomerization. Accordingly, this well-known catalyst was evaluated for n-dodecane dehydrogenation. Conditions of evaluation were temperature of 440°C, atmospheric pressure, hydrogen diluent with a hydrogen to n-dodecane mole ratio of 8 to 1. The results obtained were as follows ... 

A typical example is total monomers. 100 sodium stearate, 5 potassium persulfate, 0.3 lauryl mercaptan, 0.4 to 0.7 and water, 200 parts. In this formula, 75 parts of 1,3-butadiene and 25 parts of 4-methyl-2-vinylthiazole give 86% conversion to a tacky rubber-like copolymer in 15 hr at 45°C. The polymer contains 62% benzene-insoluble gel. Sulfur analysis indicates that the polymer contains 21 parts of combined 4-methyl-2-vinylthiazole (312). Butadiene alone in the above reaction normally requires 25 hr to achieve the same conversion, thus illustrating the acceleration due to the presence of 4-methyl-2-vinylthiazole. 

Nylon-12. Laurolactam [947-04-6] is the usual commercial monomer for nylon-12 [24937-16-4] manufacture. Its production begins with the mixture of cyclododecanol and cyclododecanone which is formed in the production of dodecanedioic acid starting from butadiene. The mixture is then converted quantitatively to cyclododecanone via dehydrogenation of the alcohol at 230—245°C and atmospheric pressure. The conversion to the lactam by the rearrangement of the oxime is similar to that for caprolactam manufacture. There are several other, less widely used commercial routes to laurolactam (171). 

Oxydehydrogenation of /i-Butenes. Normal butenes can be oxidatively dehydrogenated to butadiene in the presence of high concentration of steam with fairly high selectivity (234). The conversion is no longer limited by thermodynamics because of the oxidation of hydrogen to water. Reaction temperature is below about 600°C to minimise over oxidation. Pressure is about 34—103 kPa (5—15 psi). 

G-20 Dicarboxylic Acids. These acids have been prepared from cyclohexanone via conversion to cyclohexanone peroxide foUowed by decomposition by ferrous ions in the presence of butadiene (84—87). Okamura Oil Mill (Japan) produces a series of commercial acids based on a modification of this reaction. For example, Okamura s modifications of the reaction results in the foUowing composition of the reaction product C-16 (Linear) 4—9%, C-16 (branched) 2—4%, C-20 (linear) 35—52%, and C-20 (branched) 30—40%. Unsaturated methyl esters are first formed that are hydrogenated and then hydrolyzed to obtain the mixed acids. Relatively pure fractions of C-16 and C-20, both linear and branched, are obtained after... 

Separation of individual saturated hydrocarbons from the petroleum fractions and subsequent conversion to more useful products. Important examples are n-butane to butadiene and cyclohexane to nylon intermediates. 

An interesting probe of reactivity was presented by Burton in his study of cycloadditions of l,2-disubstituted-3,3,4,4-tetrafluorocyclobutenes and 1,2-disub-stituted-3,3,4,4,5,5-hexaf1uorocyclopentenes with butadiene, 2-methylbutadiene, and 2,3-dimethylbutadiene [86], On the basis of the extent of their conversions to adducts, the relative reactivities of the cyclobutenes and of the cyclopentenes are as shown in equation 74. A typical reaction is shown in equation 75. 

It was found that the introduction of a sulfonyl substituent considerably enhances the furanone reactivity in Diels-Alder reaction. Thus, (55)-5-(reacted with cyclopentadi-ene at room temperature in benzene with complete conversion to the adduct 212. Also, the reaction of 211 with 2,3-dimethyl-1,3-butadiene was readily performed in refluxing benzene to give the adduct213 in 98% yield (Scheme 57) (91TL7751). 

The catalyst activity is so high that uranium concentration lower than 0.1 millimoles per liter allows a complete conversion of butadiene to be obtained in a few hours, at 20°C, The transfer reaction of uranium based catalyst is similar to that of conventional 3d-block elements (titanium, cobalt, nickel) so that the molecular weight of the polymer is affected by polymerization temperature, polymerization time and monomer concentration in the customary way. This is in contrast, as we shall see later on, to some catalysts based on 4 f-block elements. Uranium based catalysts are able to polymerize isoprene and other dienes to high cis polymers the cis content of polyisoprene is 94%, somewhat inferior to titanium based catalysts. In contrast, with 3d-block elements an "all cis", random butadiene-isoprene... 

A wide variety of new approaches to the problem of product separation in homogeneous catalysis has been discussed in the preceding chapters. Few of the new approaches has so far been commercialised, with the exceptions of a the use of aqueous biphasic systems for propene hydroformylation (Chapter 5) and the use of a phosphonium based ionic liquid for the Lewis acid catalysed isomerisation of butadiene monoxide to dihydrofuran (see Equation 9.1). This process has been operated by Eastman for the last 8 years without any loss or replenishment of ionic liquid [1], It has the advantage that the product is sufficiently volatile to be distilled from the reactor at the reaction temperature so the process can be run continuously with built in product catalyst separation. Production of lower volatility products by such a process would be more problematic. A side reaction leads to the conversion of butadiene oxide to high molecular weight oligomers. The ionic liquid has been designed to facilitate their separation from the catalyst (see Section 9.7)... 

The effect of ligands has been studied (49). Phosphites, instead of phosphine, affect the ratio of isomers 47 and 48. Using triphenyl phosphite in the reaction of acetic acid at 50°C in 0.5 hour, 75% conversion of butadiene was attained. The selectivity to the acetoxyoctadienes was 93%, and the ratio of 47 to 48 was 92 8. Trimethylolpropanephosphite... 

Hexadiene is the immediate product found in the codimerization reaction described above in a mixture of ethylene and butadiene. However, the reaction will not stop at this stage unless there is an overwhelming excess of butadiene and an adequate amount of ethylene present. As the conversion of butadiene increases, some catalyst begins to isomerize... 

Initial butadiene 180 g. Butadiene conversion = wt. butadiene used/wt. initial butadiene. The yield of C diene with respect to butadiene converted decreased with increasing conversion. c No activator added. d Addition of 200 mmoles PhCCla-... 

Relative rates were measured by the time required to achieve 43% conversion of butadiene under the same reaction conditions. Yield of 1,4-hexadiene at 43% conversion of butadiene. 

Dienes can be obtained from silylallenes by protodesilylation using boron trifluo-ride-acetic acid complex (equation 29)62. Since silylallenes can be obtained by the reaction of propargyl acetate with cuprous reagent derived from chloromethyltrimethylsilane, this reaction sequence constitutes conversion of propargylic acetate to butadiene through one carbon homologation. 

A gas-phase reaction between butadiene (A) and ethene (B) is conducted in a PFR, producing cyclohexene (C). The feed contains equimolar amounts of each reactant at 525°C (T,) and a total pressure of 101 kPa. The enthalpy of reaction is — 115 kj (mol A)- , and the reaction is first-order with respect to each reactant, with kA = 32,000 13,850/7 m3 moi-l S 1. Assuming the process is adiabatic and isobaric, determine the space time required for 25% conversion of butadiene. 

The patent literature contains several references to the use of sulfoxide complexes, usually generated in situ, as catalyst precursors in oligomerization and polymerization reactions. Thus, a system based upon bis(acrylonitrile)nickel(0> with added Me2SO or EtgSO is an effective cyclotrimerization catalyst for the conversion of butadiene to cyclo-1,5,-9-dodecatriene (44). A similar system based on titanium has also been reported (407). Nickel(II) sulfoxide complexes, again generated in situ, have been patented as catalyst precursors for the dimerization of pro-pene (151) and the higher olefins (152) in the presence of added alkyl aluminum compounds. 

Feed enters the reactor at tube side, oxygen at shell side. Oxidative dehydrogenation of 1-butene to butadiene. W3Sb203 catalyst placed in the pores of the tube. T 462 C. Conversion 30%, Selectivity 92%. T = 505°C. Conversion 57%, Selectivity 88%. ... 

Alternatively, dimethylisosorbide was used as green solvent instead of isopropanol. Dimethylisosorbide (DMI) is a bio-sourced non-protic solvent, with a very low vapor pressure and environmentally friendly [53]. When the telomerization was carried out in the presence of 5 mL DMI or /-PrOH, the same conversion of butadiene was achieved after 24 h corresponding to a DS = 0.05. 

The cyclodimer cis-l,2-divinyFcyck)butane, which is also formed, rearranges to 5 and 6 during the catalysis and can no longer be detected after the long reaction time chosen (complete conversion of butadiene)... 

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