Problem 109 - A Complete Resource Book in Chemistry for JEE Main

Question

The catalyst used in Zeigler process for polyethylene manufacture (a) consists of aluminium triethyl and titanium 1 tetrachloride (b) is vanadium pentoxide (c) consists of aluminium chloride and titanium dioxide (d) is finely divided nickel

Step-by-Step Solution

Answer

The correct answer is (a) consists of aluminium triethyl and titanium 1 tetrachloride.

Step 1: Understanding the Options

Read each option carefully to understand the catalysts mentioned. Each option describes a different combination of chemicals that could potentially be used in the Zeigler process.

Step 2: Identifying the Zeigler Process

The Zeigler process is a polymerization technique used to produce polyethylene. It requires a specific type of catalyst known as the Ziegler-Natta catalyst. This catalyst typically involves a combination of aluminum compounds and titanium compounds.

Step 3: Matching the Catalyst

From the description of the Zeigler process, identify which option aligns with the known catalyst composition. Ziegler-Natta catalysts are typically composed of aluminum alkyls, such as aluminum triethyl, and titanium chlorides, such as titanium tetrachloride.

Step 4: Evaluating the Options

Examine each option: - Option (a) mentions aluminum triethyl and titanium tetrachloride, which matches the known components of the Ziegler-Natta catalyst. - Option (b) mentions vanadium pentoxide, which is not used in the Ziegler process. - Option (c) mentions aluminum chloride and titanium dioxide, which do not match the Ziegler-Natta catalyst. - Option (d) mentions finely divided nickel, which is not used in this context.

Step 5: Choosing the Correct Option

Since option (a) matches the description of the Ziegler-Natta catalyst using aluminum triethyl and titanium tetrachloride, it is the correct answer.

Key Concepts

Polyethylene Manufacture

Polyethylene is one of the most versatile and widely used plastics in the world. It is made through a process called polymerization, which joins many small molecules, called monomers, into a long chain called a polymer. Polyethylene is known for its durability, flexibility, and resistance to moisture, making it ideal for a variety of products like plastic bags, bottles, and even toys.

In the manufacture of polyethylene, the choice of catalysts is crucial. Catalysts are substances that speed up chemical reactions without being consumed in the process. In the case of creating polyethylene, the Ziegler-Natta catalyst is a game-changer. This catalyst allows for the polymerization to occur under mild conditions, contributing to the efficient and economical production of polyethylene. It's widely used because it produces plastic that is of a higher quality and has a more controlled structure than polyethylene made by other methods. The Ziegler-Natta catalyst allows manufacturers to produce different forms of polyethylene, each with unique properties, expanding the range of possible applications.

Catalyst Composition

Understanding the composition of catalysts used in polyethylene manufacture is essential. The Ziegler-Natta catalyst, a special type of catalyst, is pivotal for producing polyethylene efficiently. The most common composition includes aluminum-based compounds, such as aluminum triethyl, and titanium-based compounds, especially titanium tetrachloride.

These components are responsible for creating the optimal conditions under which ethylene, the monomer for polyethylene, can be polymerized to form long chains. The presence of aluminum triethyl helps activate the titanium component, which then facilitates the transformation of ethylene into polyethylene efficiently.

This specific composition allows for a controlled and orderly transformation, resulting in high-quality polyethylene. Other combinations, like those involving vanadium pentoxide, aluminum chloride, or finely divided nickel, do not facilitate the Ziegler process, and thus are not used in this context due to their ineffectiveness in producing polyethylene through this method.

Polymerization Technique

The polymerization technique used in the manufacture of polyethylene is a well-refined process that benefits significantly from the use of the Ziegler-Natta catalyst. This technique typically involves the polymerization of ethylene gas to form polyethylene.

The Ziegler-Natta catalyst allows the reaction to occur at relatively low pressures and temperatures, a distinct advantage over older methods that required high-energy conditions. This not only makes the process more energy efficient but also more economically viable. It provides more control over the polymerization process, which influences the molecular weight and branching of the polymer, key factors that determine the physical properties of the finished product.

• Low pressure and temperature lead to energy savings.
• Control over molecular weight and polymer branching results in tailor-made polyethylene properties.
• Enhanced product quality and reduced production costs.

The technique's ability to precisely control these variables makes it invaluable in producing a wide range of polyethylene grades suitable for diverse applications, from rigid, impact-resistant products to flexible items.