The transhydrogenation of pentane (P) and 1-hexyne (1HY) was investigated over 4% CrO_x/Al₂O₃ and potassium-doped 4% CrO_x/Al₂O₃ catalysts over a range of temperatures (523–773 K) with a 5:1 P:1HY ratio. Over the CrO_x/Al₂O₃ catalyst, transhydrogenation clearly occurred at temperatures below 625 K where the yield of alkenes was higher for the co-fed system than for a combination of the individual yields. Due to the acidic nature of the alumina, many of the products were alkylated olefins and alkylated hydrocarbons formed by coincident alkylation and isomerisation. When pentane was added to a feed containing 1-hexyne, the extent of carbon deposition was reduced. By comparing transhydrogenation to limited hydrogen 1-hexyne hydrogenation at 623 K, it was shown that the processes of hydrogenation and transhydrogenation were different, with hydrogenation favouring alkanes, while transhydrogenation favoured alkenes. This may be because pentane dehydrogenation only releases two hydrogen atoms, which only allows 1-hexyne to hydrogenate to 1-hexene. Therefore, if the rate of alkene isomerisation and desorption is faster than that of pentane dehydrogenation, only alkenes will be observed. The latter proposal would suggest that the dehydrogenation/hydrogenation process is closely coupled and would be consistent with pentane influencing 1-hexyne surface chemistry. The effect of the potassium doping was to increase the yield of alkenes. The reason for this may be related to changes in the nature of the surface chromia species. The potassium also neutralised the acid sites on the alumina, reducing the extent of alkylation and hydrogenolysis, which suppressed the formation of other alkynes in the product mix.

中文翻译：

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CrO x / Al 2 O 3和钾掺杂CrO x / Al 2 O 3催化剂上戊烷和1-己炔的加氢反应

研究了戊烷（P）和1-己炔（1HY）在4％CrO _x / Al ₂ O ₃和掺杂钾的4％CrO _x / Al ₂ O ₃催化剂在一定温度范围内的氢化作用（523-773 K ），P：1HY比例为5：1。在CrO _x / Al ₂ O _3上对于催化剂，显然在低于625 K的温度下发生了加氢反应，在该温度下，共进料系统的烯烃收率高于各个收率的总和。由于氧化铝的酸性，许多产物是烷基化的烯烃和通过同时烷基化和异构化形成的烷基化的烃。当将戊烷添加到含有1-己炔的进料中时，碳沉积的程度降低。通过比较在623 K下的氢化反应与有限的氢1-己炔氢化反应，可以看出氢化反应和氢化反应的过程不同，氢化反应有利于烷烃，而氢化反应有利于烯烃。这可能是因为戊烷脱氢仅释放两个氢原子，这仅允许1-己炔氢化为1-己烯。因此，如果烯烃的异构化和解吸速率比戊烷脱氢的速率快，则只能观察到烯烃。后面的提议表明脱氢/氢化过程是紧密耦合的，并且与影响1-己炔表面化学的戊烷是一致的。钾掺杂的作用是增加烯烃的产率。其原因可能与表面氧化铬种类的性质变化有关。钾还中和了氧化铝上的酸位，减少了烷基化和氢解的程度，从而抑制了产物混合物中其他炔烃的形成。后面的提议表明脱氢/氢化过程是紧密耦合的，并且与影响1-己炔表面化学的戊烷是一致的。钾掺杂的作用是增加烯烃的产率。其原因可能与表面氧化铬种类的性质变化有关。钾还中和了氧化铝上的酸位，减少了烷基化和氢解的程度，从而抑制了产物混合物中其他炔烃的形成。后面的提议表明脱氢/氢化过程是紧密耦合的，并且与影响1-己炔表面化学的戊烷是一致的。钾掺杂的作用是增加烯烃的产率。其原因可能与表面氧化铬种类的性质变化有关。钾还中和了氧化铝上的酸位，减少了烷基化和氢解的程度，从而抑制了产物混合物中其他炔烃的形成。