Butyraldehyde, from crotonaldehyde

Organic constituents in the first wastestream totaled about 14,000 mg/L (acetaldehyde, acetal-dol, acetic acid, butanol-1, butyraldehyde, chloroacetaldehyde, crotonaldehyde, phenol, and propionic acid) and about 5200 mg/L inorganic constituents. The pH ranged from 4 to 6, and TDS ranged from 3000 to 10,000 mg/L. 

From the results of this kinetic study and from the values of the adsorption coefficients listed in Table IX, it can be judged that both reactions of crotonaldehyde as well as the reaction of butyraldehyde proceed on identical sites of the catalytic surface. The hydrogenation of crotyl alcohol and its isomerization, which follow different kinetics, most likely proceed on other sites of the surface. From the form of the integral experimental dependences in Fig. 9 it may be assumed, for similar reasons as in the hy-drodemethylation of xylenes (p. 31) or in the hydrogenation of phenol, that the adsorption or desorption of the reaction components are most likely faster processes than surface reactions. 

It is noteworthy that even a separate treatment of the initial data on branched reactions (1) and (2) (hydrogenation of crotonaldehyde to butyr-aldehyde and to crotyl alcohol) results in practically the same values of the adsorption coefficient of crotonaldehyde (17 and 19 atm-1)- This indicates that the adsorbed form of crotonaldehyde is the same in both reactions. From the kinetic viewpoint it means that the ratio of the initial rates of both branched reactions of crotonaldehyde is constant, as follows from Eq. (31) simplified for the initial rate, and that the selectivity of the formation of butyraldehyde and crotyl alcohol is therefore independent of the initial partial pressure of crotonaldehyde. This may be the consequence of a very similar chemical nature of both reaction branches. 

According to Scheme 6.2, the hydrogenation products for crotonaldehyde were butyraldehyde (SAL), crotyl alcohol (UOL), butanol (SOL) and cracking products only at trace levels. Selectivities to UOL, SAL and SOL were maintained from one cycle to the next [20]. 

Figure 3. LC chromatogram of carbonyls collected on a DNPH-impregnated silica gel cartridge. Peak identities 1, DNPH 2, formaldehyde 3, acetaldehyde 4, acrolein 5, acetone 6, propionaldehyde 7, x-acrolein 8y crotonaldehyde 9, butyraldehyde and 10, benzaldehyde. (Reproduced with permission from reference8. Copyright 1992.)...

As many as 70 products were at one time produced commercially from ethanol. Some of these downstream products are butanol, 2-ethyl hexanol, crotonaldehyde, butyraldehyde, acetaldehyde, acetic acid, butadiene, sorbic acid, 2-ethylbutanol, ethyl ether, many esters, ethanol-glycol ethers, acetic anhydride, vinyl acetate, ethyl vinyl ether, even ethylene gas. Many of these products are now more economically made from other feedstocks such as ethylene for acetaldehyde and methanol-carbon monoxide for acetic acid. Time will tell when a revival of biologically-oriented processes will offer lower-cost routes to at least the simpler products. 

Pure compound studies demonstrated (Adkins and Kresk, 7) that certain olefinic compounds reacted exclusively by hydrogenation rather than by hydroformylation, Treatment of crotonaldehyde with synthesis gas and dicobalt octacarbonyl at 125° gave butyraldehyde in about 50% yield. The addition of small amounts of diphenylsulfide to the dicobalt octacarbonyl did not interfere with the hydrogenation. Later it was shown (Wender, Levine, and Orchin, 9) that if the temperature was raised from 125° to 170-185°, crotonaldehyde was reduced to butanol ... 

Fig. 5.3. Gas chromatogram of 2,4-dinitrophenylhydrazones of ten aliphatic aldehydes. Peaks 1 = formaldehyde 2 = acetaldehyde 3 = propionaldehyde 4 = acrolein 5 = isobutyraldehyde 6 = n-butyraldehyde 7 = isovaleraldehyde 8 = n-valeraldehyde 9 = crotonaldehyde 10 = n-capronaldehyde. For conditions see text. (Reproduced from / Chromatogr., 120 (1976) 379, by courtesy of Y. Hoshika.)...

Type II selectivity involves the differentiation between two parallel reactions in which different products are formed by separate paths from the same starting material.33 This type of selectivity is encountered in the hydrogenation of crotonaldehyde to either butyraldehyde or 2 buten-l-ol (Eqn. 5.8). When both reactions are of the same kinetic order changes in mass transport will influence them both to the same extent and there will be no effect on reaction selectivity. When the reactions are of different kinetic orders, that one with the higher order will be more affected by mass transport limitation. 

The selective hydrogenation of crotonaldehyde to n-butyraldehyde was studied using Pd/C catalyst. The initial rate of hydrogenation was analysed mainly to assess the importance of various mass transfer effects from which it was found that all the rate data under the conditions of the present work were in the kinetic regime. A Langmuir - Hinshelwood type rate model has been derived and the rate parameters were evaluated by using concentration-time data. The agreement of the predicted results with the experimental data was found to be excellent. 

Butyraldehyde can be synthesized from propylene, butanol, or crotonaldehyde as shown in Figure 7.31. 

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