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An illustrative example is the effect of catalysts to speed the decomposition of hydrogen peroxide into water and oxygen: . 2 H 2 O 2 → 2 H 2 O + O 2. This reaction proceeds because the reaction products are more stable than the starting compound, but this decomposition is so slow that hydrogen peroxide solutions are commercially available.
The disadvantage with a copper catalysts is that it is very sensitive when it comes to sulfide poisoning, a future use of for example a cobalt- molybdenum catalyst could solve this problem. The catalyst mainly used in the industry today is a copper-zinc-alumina (Cu/ZnO/Al 2 O 3) based catalyst.
These catalysts initiate radical chain reactions, autoxidation that produce organic radicals that combine with oxygen to give hydroperoxide intermediates. Generally the selectivity of oxidation is determined by bond energies. For example, benzylic C-H bonds are replaced by oxygen faster than aromatic C-H bonds. [2]
In specific acid catalysis, protonated solvent is the catalyst. The reaction rate is proportional to the concentration of the protonated solvent molecules SH +. [6] The acid catalyst itself (AH) only contributes to the rate acceleration by shifting the chemical equilibrium between solvent S and AH in favor of the SH + species. This kind of ...
Precatalysts are not catalysts but are precursors to catalysts. Precatalysts are converted in the reactor to the actual catalytic species. The identification of catalysts vs precatalysts is an important theme in catalysis research. The conversion of a precatalyst to a catalyst is often called catalyst activation.
A prominent example of proline catalysis is the addition of acetone or hydroxyacetone to a diverse set of aldehydes catalyzed by 20-30% proline catalyst loading with high (>99%) enantioselectivity yielding diol products. [37] As refined by List and Notz, the aforementioned reaction produces diol products as follows: [38]
In this context, simple organic acids have been used as catalyst for the modification of cellulose in water on multi-ton scale. [9] When the organocatalyst is chiral an avenue is opened to asymmetric catalysis; for example, the use of proline in aldol reactions is an example of chirality and green chemistry. [10]
The chemical and energy industries rely heavily on heterogeneous catalysis. For example, the Haber–Bosch process uses metal-based catalysts in the synthesis of ammonia, an important component in fertilizer; 144 million tons of ammonia were produced in 2016. [5]