In catalytic alkylation, higher iso-butane to olefin ratio gives

ANS:A - low final boiling point product

In catalytic alkylation, a higher iso-butane to olefin ratio typically results in both (a) and (b):

• Low final boiling point product: Increasing the iso-butane to olefin ratio tends to favor the production of alkylate with lower final boiling points. This is because iso-butane is a lighter hydrocarbon that contributes to the formation of smaller, more volatile alkylate molecules.
• Higher yield: A higher iso-butane to olefin ratio also generally leads to higher yields of alkylate. This is because iso-butane acts as a reactant and a diluent, promoting the alkylation reaction and reducing side reactions that can lead to the formation of undesired byproducts.

Therefore, the correct answer is that a higher iso-butane to olefin ratio in catalytic alkylation gives both a low final boiling point product and a higher yield. A "low final boiling point product" in the context of catalytic alkylation refers to the alkylate produced having a final boiling point that is lower than the starting materials or other potential products of the alkylation reaction. Here’s an explanation:

1. Alkylation Process: Catalytic alkylation involves the reaction of an olefin (typically a lower-molecular-weight alkene like propylene or butylene) with an alkylating agent such as iso-butane. This reaction is catalyzed by strong acids like sulfuric acid (H₂SO₄) or hydrofluoric acid (HF).
2. Product Characteristics: The product of catalytic alkylation, known as alkylate, is a mixture of branched-chain hydrocarbons (alkylates) with higher octane numbers than the original components. The final boiling point of the alkylate depends on the molecular weight and structure of the alkyl groups added during the reaction.
3. Effect of Iso-Butane Ratio: Increasing the iso-butane to olefin ratio in the alkylation process has several effects:
   • Lower Final Boiling Point: Iso-butane is a lighter hydrocarbon compared to the olefinic reactants. It tends to produce alkyl groups that are smaller and less complex, resulting in alkylate products with lower molecular weights and, consequently, lower boiling points.
   • Improved Vapor Pressure: Lower boiling point products have lower vapor pressures, which can improve their performance in fuel applications by reducing vapor lock and volatility issues.
4. Application in Fuel Production: In the petroleum refining industry, low final boiling point alkylates are desirable for blending into gasoline to improve octane ratings without significantly increasing the final boiling point of the fuel. This helps in meeting regulatory specifications and improving the performance characteristics of gasoline.

In summary, achieving a low final boiling point product in catalytic alkylation involves optimizing the iso-butane to olefin ratio to favor the production of lighter alkylates. This is beneficial for producing high-quality alkylates suitable for blending into gasoline and other fuels. In the context of catalytic alkylation, "higher yield" refers to the increased production of desired alkylate products relative to the amount of starting materials used in the process. Here’s an explanation of what higher yield means and how it is achieved:

1. Alkylation Process: Catalytic alkylation involves the reaction of an olefin (such as propylene or butylene) with an alkylating agent, typically iso-butane, in the presence of a catalyst (e.g., sulfuric acid or hydrofluoric acid). This reaction forms branched-chain alkylates, which have higher octane numbers than the original olefinic compounds.
2. Yield Definition: Yield in chemistry refers to the amount of product obtained in a chemical reaction compared to the theoretical maximum amount that could be obtained (based on stoichiometry). It is typically expressed as a percentage.
3. Factors Influencing Yield:
   • Reactor Conditions: Optimal reactor conditions such as temperature, pressure, and residence time are crucial in maximizing yield. These conditions affect the rate of the alkylation reaction and the selectivity towards the desired products.
   • Catalyst Efficiency: The choice and condition of the catalyst play a significant role in determining yield. A more active and selective catalyst promotes higher conversion of reactants into desired products.
   • Reactant Ratios: The ratio of iso-butane to olefin (alkene) is critical. Higher ratios of iso-butane relative to olefin can lead to higher yields by ensuring that more of the olefin is reacted and converted into alkylate rather than undergoing undesired side reactions.
   • Process Optimization: Process engineers optimize various parameters to achieve higher yields, including the recycling of unreacted iso-butane and olefins, improving separation and purification steps, and minimizing catalyst deactivation.
4. Importance: Higher yield is economically advantageous because it maximizes the efficiency of the alkylation process, reducing waste and maximizing the production of valuable alkylate products. It also helps in meeting production targets and ensuring consistent supply of alkylates for blending into gasoline or other fuel products.

In summary, achieving a higher yield in catalytic alkylation involves optimizing reactor conditions, catalyst performance, and reactant ratios to maximize the conversion of olefins and iso-butane into desired alkylate products, thereby enhancing process efficiency and economic viability.