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Often, substances are intentionally added to the reaction feed or on the catalyst to influence catalytic activity, selectivity, and/or stability. These compounds are called promoters. For example, alumina (Al 2 O 3) is added during ammonia synthesis to providing greater stability by slowing sintering processes on the Fe-catalyst. [2]
A slurry reactor contains the catalyst in a powdered or granular form. [7] This reactor is typically used when one reactant is a gas and the other a liquid while the catalyst is a solid. The reactant gas is put through the liquid and dissolved. It then diffuses onto the catalyst surface.
Rather than enabling the productive catalytic cycle, the solid phase acts as a reservoir of Pd that is accessible to the productive catalytic cycle. For heterogeneous catalytic cross-coupling which involves unligated Pd (for example, when Pd/C is used as the catalyst), there exists a significant equilibrium that partitions Pd(0) between atomic ...
The reaction order is 1 with respect to B and −1 with respect to A. Reactant A inhibits the reaction at all concentrations. The following reactions follow a Langmuir–Hinshelwood mechanism: [4] 2 CO + O 2 → 2 CO 2 on a platinum catalyst. CO + 2H 2 → CH 3 OH on a ZnO catalyst. C 2 H 4 + H 2 → C 2 H 6 on a copper catalyst. N 2 O + H 2 ...
Often cross-coupling reactions require metal catalysts. One important reaction type is this: R−M + R'−X → R−R' + MX (R, R' = organic fragments, usually aryl; M = main group center such as Li or MgX; X = halide) These reactions are used to form carbon–carbon bonds but also carbon-heteroatom bonds.
In chemistry, the Sabatier principle is a qualitative concept in heterogeneous catalysis named after the French chemist Paul Sabatier. It states that the interactions between the catalyst and the reactants should be "just right"; that is, neither too strong nor too weak. If the interaction is too weak, the molecule will fail to bind to the ...
Heterogeneous supported catalysts based on titanium compounds are used in polymerization reactions in combination with cocatalysts, organoaluminum compounds such as triethylaluminium, Al(C 2 H 5) 3. This class of catalyst dominates the industry. [1] Homogeneous catalysts usually based on complexes of the group 4 metals titanium, zirconium or ...
In chemistry, a phase-transfer catalyst or PTC is a catalyst that facilitates the transition of a reactant from one phase into another phase where reaction occurs. Phase-transfer catalysis is a special form of catalysis and can act through homogeneous catalysis or heterogeneous catalysis methods depending on the catalyst used.