In which of the following processes is a shape selective catalyst used?

Concept:

• A catalyst is a substance that can be added to a reaction to enhance the reaction rate without getting consumed in the process.
• Catalysts typically speed up a reaction by lowering the activation energy or changing the reaction mechanism.
• Enzymes are proteins that act as catalysts in biochemical reactions.
• A stoichiometric amount of one reactant can mean the amount that will react completely with a given amount of another reactant, leaving no excess of either one.
• Catalyst does not take part in balancing the chemical reaction hence catalysts are not required in Stoichiometric amounts.
• Most common catalysts are - Aluminosilicates, Iron, Vanadium, Nickel, Platinum + Alumina.

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​Shape selective catalysts:

• Some catalysis reactions depend upon the pore size of the reactant and the shape of catalyst used.
• The pore size and shape of catalysts is similar to the shape and size of the reactants then they can fit into each other and the reaction takes place.
• Zeolites are for example are shape-selective catalysts. They can catalyze only selective reactions.
• The pore size of Zeolites do not permit all transition state complex to pass through it, thus becomes selective in nature.
• Zeolites are large network of aluminosilicates having the network type Al-O-Si. Molecules like water and alkali metals are trapped inside the pores of the networks.

Explanation:

• Zeolites, a shape selective catalyst or HZSM-5 are the catalysts used in conversion of alcohols to gasoline.
• The temperature range is 300-400^oC.
• The alcohols first undergo dehydration to give unsaturated alkenes.
• The alkenes are then converted to higher alkenes via hydrogenation.
• The catalyst used in Haber's process synstesis of ammonia is Fe.
• It increases the rate of reaction between nitrogen and hydrogen.
• Finely divides solid Fe provides a surface for the reaction to occur.
• Gases nitrogen and hydrogen get adsorbed on the catalyst surface, a reaction occurs, and then the products diffuse out.
• catalysts used for synthesis of methanol from CO and H2 are copper and nickel.
• The catalyst used in polymerisation of ethelene is Zeigler-Natta catalyst.

Hence, a shape selective catalyst used in conversion of alcohol to gasoline.