Hydrogenolysis of saturated hydrocarbons on a nickel catalyst I. Kinetics of hydrogenolysis of ethylcyclohexane and reactivity of alkylcyclohexanes

Efficient Hydrogenolysis of Alkanes at Low Temperature and Pressure Using Tantalum Hydride on MCM‐41, and a Quantum Chemical Study

“…We calculated the energies for the first step in this reaction, that is, the CÀH bond activation of ethane through s-bond metathesis with use of both forms of tantalum hydrides ( Figure 5). Our DFT calculations ( Figure 5) 3 , then this catalyst system should be deactivated over time. This is not the case, however, and the catalyst stays active for at least 50 h. This ob-servation confirms that [Ta](H) 3 is an important catalytically active species, and we therefore consider it as an active site model for further DFT calculations.…”

“…However, during our previous study of this catalyst system, which was characterized by means of several techniques, such as IR and EXAFS spectroscopies, solid-state NMR analysis, and mass balance analysis, [24] we observed that both the forms of tantalum hydrides, [Ta](H) and [Ta](H) 3 , exist in substantial 3 during the hydrogenolysis of ethane. We calculated the energies for the first step in this reaction, that is, the CÀH bond activation of ethane through s-bond metathesis with use of both forms of tantalum hydrides ( Figure 5).…”

“…The reaction mechanism was modeled with use of a 2T cluster (in which T is four tetrahedral units of SiO 4 ) of (Si 2 O 7 H 4 )Ta (which, for simplicity, is hereafter written as [Ta]). In both [Ta](H) and [Ta](H) 3 , the tantalum atom is covalently bonded to two vicinal oxygen surface atoms, which leads to a nonconstrained six-membered ring. We first calculated the energy of [Ta](H) and [Ta](H) 3 (Figure 4), and [Ta](H) 3 appeared to be more stable than the monohydride [Ta](H) by 27 kcal mol À1 .…”

“…[1,2] Commonly used catalysts for hydrogenolysis reactions are supported metal particles, particularly Ni, Pt, Rh, and Re, which are active but require rather high temperatures. [3][4][5][6][7][8][9][10] The high temperature was a central issue leading to the recent development of surface organometallic chemistry, which has yielded highly reactive single-site catalysts. [11][12][13][14][15][16][17][18] During the last two decades, various organometallic complexes of Ti, Zr, Hf, Cr, Mo, W, and Re were successfully supported on various oxides and, in several cases, their hydrides have shown unprecedented and striking activity.…”

Selective Catalytic Hydrogenolysis of Carbon–Carbon σ Bonds in Primary Aliphatic Alcohols over Supported Metals

“…In fact, early studies indicated that the heterogeneous Ni/Al 2 O 3 system could catalyze the hydrogenolysis of carbon–carbon bonds for the dealkylation of cage hydrocarbons, i.e. polyalkyladamantanes, at high temperatures. , The successive hydrogenolysis of various saturated hydrocarbons has been extensively investigated with Ni/Al 2 O 3 , , Pt/Al 2 O 3 , and silica-supported metal hydrides − as heterogeneous catalysts. For the cleavage of carbon–carbon bonds via hydrogenolysis, a very interesting old study demonstrated that the hydrogenolysis of primary alcohols to hydrocarbons with one less carbon could be achieved over a nickel catalyst under harsh conditions: i.e., at 10–20 MPa of H 2 and 523 K …”