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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]
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 ...
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.
An example of heterogeneous catalysis is the reaction of oxygen and hydrogen on the surface of titanium dioxide (TiO 2, or titania) to produce water. Scanning tunneling microscopy showed that the molecules undergo adsorption and dissociation. The dissociated, surface-bound O and H atoms diffuse together.
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.
The reaction is driven by relieving ring strain in cyclic olefins. [2] A variety of heterogeneous and homogeneous catalysts have been developed for different polymers and mechanisms. [3] Heterogeneous catalysts are typical in large-scale commercial processes, while homogeneous catalysts are used in finer laboratory chemical syntheses. [4]
Catalytic converter; Catalytic cycle; Catalytic oxidation; Catalytic resonance theory; Catalytic triad; Cativa process; Ceria based thermochemical cycles; Karen Chan; Chemisorption; Circe effect; Cobalt(II)–porphyrin catalysis; Coking; Committed step; Concurrent tandem catalysis; Contact process; Contact-electro-catalysis; Coupling reaction ...