Transhydrogenation of propyne with butane over a vanadia/θ-alumina catalyst

Abstract

The transhydrogenation of propyne and butane was studied over a 1 % VO x /alumina catalyst at 873 K. In the absence of the vanadia, the alumina support was active for cracking and alkylation. However, the addition of the vanadia reduced the propensity for both cracking and alkylation and added dehydrogenation activity. When propyne and butane were co-fed over the catalyst there was a synergistic effect resulting in an increased conversion of propyne (81 cf. 26 % when fed alone); however, much of this increased conversion was converted to carbon deposited on the catalyst. Transhydrogenation of propyne to propene was detected with an enhanced yield of propene when the propane/butane mix was passed over the catalyst. Taking a yield based on propyne fed then the yield of propene increased from 1.2 to 5.0 %. The conversion of butane to value-added products was also enhanced with all the butane converted accounted for in the production of 1-butene, trans-2-butene, iso-butane and iso-butene.

Transhydrogenation of pentane and 1-hexyne over CrOx/Al2O3 and potassium-doped CrOx/Al2O3 catalysts

“…The primary purpose of the transhydrogenation process historically has been to convert low-value cracked hydrocarbons into valued distillate products. Although transhydrogenation is not a new technology for production of olefins [6][7][8][9][10][11], there is scant scientific attention towards the invention, even though the invention has the potential to lift the equilibrium limitation of direct alkane dehydrogenation for the production of olefins by constantly removing the hydrogen produced through hydrogenation of an alkyne or alkadiene [12][13][14]. Hence, transhydrogenation combines the two processes (alkane dehydrogenation and alkyne hydrogenation) over a catalyst to form two alkenes.…”

“…The recent literature has revealed transhydrogenation reactions on various catalysts such as supported vanadia, chromia and doped chromia, most of which involved the use of LPG hydrocarbons. Jackson et al [12][13][14] studied transhydrogenation of propane and propyne over chromia/ alumina in a 1:1 ratio. The transhydrogenation reaction was shown to produce propene above the equilibrium value expected from propane dehydrogenation at 823 K. By 873 K, the conversion of propane was ~ 80%, but the yield of propene was low, which was suggested to be due to secondary reaction of the propene forming methane and carbon deposits.…”

Catalytic upgrading of refinery cracked products by trans-hydrogenation: a review

“…The role of both these modifiers is to reduce carbon deposition and more general by-product formation from the dehydrogenation process. Vanadia has also been used in the academic literature [27].…”

“…In a recent study by Wigzell et al [27] a trans-hydrogenation reaction was performed between propyne and butane over a 1% vanadia/h-alumina catalyst at 600°C. Propyne and butane were co-fed, which resulted in an increase conversion of propyne to propene compared to when it was fed singly over the catalyst.…”

“…However, it has only recently been studied in the academic literature [25][26][27]. The trans-hydrogenation process has significance as a safe environmentally acceptable technique for upgrading feedstock containing C2-C5 alkanes and alkynes/alkadienes.…”