Catalyst Design and Preparation Quiz

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Questions and Answers

Which of the following factors is NOT directly mentioned as contributing to the increased surface area of a supported catalyst?

The use of an inert support material with many pores

The presence of active sites on the catalyst surface (correct)

The design of the catalyst with specific functional groups

Careful selection of the catalyst's size and shape

Based on the provided information, what is the primary goal of the catalyst preparation step in the flow process?

To determine the catalyst's specific function

To ensure the catalyst is commercially viable

To activate the catalyst using a lab/reactor setting

To fully understand the catalyst's properties and functionality (correct)

What is the primary advantage of using a catalyst with a high surface area?

It ensures that the catalyst is suitable for commercial applications.

It simplifies the process of synthesizing the catalyst.

It allows for the creation of a larger number of active sites, increasing reaction efficiency (correct)

It makes the catalyst more stable and less prone to deactivation.

The text emphasises 'proper functional groups' for the design of a catalyst. What is the primary role of these functional groups?

To directly catalyze the chemical reaction, acting as the primary active sites. (B) Signup and view all the answers

Based on the provided information, what is the primary purpose of the 'pore' in the catalyst's design?

To control the selectivity of the catalyst by regulating the size of molecules that can interact with the active sites (C) Signup and view all the answers

Why is the synthesis of a catalyst followed by characterization?

To identify key properties like surface area, active sites, and pore structure for understanding its functionality. (A) Signup and view all the answers

Which of the following is a key step in catalyst design?

Selecting proper functional groups to ensure the desired reaction occurs (A) Signup and view all the answers

Which of the following best describes the 'catalytic activity' step in the flow process?

The stage where the catalyst's performance in a specific reaction is tested and evaluated (B) Signup and view all the answers

What is the primary difference between unsupported and supported catalysts?

Supported catalysts require a high surface area support to disperse the primary catalyst. (D) Signup and view all the answers

What are the three fundamental stages of catalyst synthesis?

Preparation, processing, and activation. (B) Signup and view all the answers

Which of the following is NOT a common parameter in the preparation of the primary solid?

The specific type of catalyst used. (D) Signup and view all the answers

What is a key characteristic of an ideal catalyst?

High thermal and mechanical strength. (A) Signup and view all the answers

Which of the following is an example of a supported catalyst?

A platinum catalyst on an alumina support. (C) Signup and view all the answers

What is the purpose of the 'functionalization or activation' stage in catalyst synthesis?

To form sulfides, de-ammoniation, or sulfonation. (A) Signup and view all the answers

Which of these is NOT a method to prepare the primary solid?

Crystallization. (B) Signup and view all the answers

What is the main purpose of the 'processing' stage in catalyst synthesis?

To treat the intermediate solid by drying, calcination, or thermal decomposition. (A) Signup and view all the answers

Which of the following factors influences the rate of impregnation processes? *

Selective adsorption of species by coulomb force, van der Waals forces, or H-bonds (A), Ion exchange between the charged surface and the electrolyte (B), Polymerisation/depolymerisation of the species (molecules, ions) attached to the surface (C) Signup and view all the answers

What is the main property of the catalyst that needs to be highlighted in impregnation processes?

All of the above (D) Signup and view all the answers

Which types of impregnation involve using an excess of solution?

Impregnation by soaking or with an excess of solution (D) Signup and view all the answers

Which of the following is NOT a type of impregnation?

Deposition by chemical vapor deposition (B) Signup and view all the answers

What is a characteristic of gas phase deposition?

It can ensure excellent dispersion and controlled distribution. (D) Signup and view all the answers

Which of the following best describes the method of preparing monolith catalysts?

By covering the channel surfaces with a slurry of small particles. (D) Signup and view all the answers

In precipitation processes, which step must occur before particles start to grow?

Nucleation must take place under high supersaturation. (A) Signup and view all the answers

What is the main challenge of using solid salts to impregnate the support in a laboratory setting?

It produces uncontrollable outcomes. (D) Signup and view all the answers

What factors need to be controlled during the precipitation process?

The pH and the mixing procedure. (A) Signup and view all the answers

Which of the following is not a factor influencing nucleation?

The existing equilibrium state of the solution. (B) Signup and view all the answers

What aspect differentiates precipitation from other deposition methods?

Precipitation involves the formation of solids in a solution. (A) Signup and view all the answers

Which of the following components is essential for gas phase deposition?

The presence of active species in a gaseous state. (D) Signup and view all the answers

What factor influences the abrasion resistance of catalysts during usage?

Size and shape of the catalyst (C) Signup and view all the answers

Which of the following methods is NOT mentioned as a method for activating a catalyst precursor?

Dehydration (C) Signup and view all the answers

What is the primary reason different reactivities are found within a catalyst?

Heterogeneity in crystallite sizes (D) Signup and view all the answers

Which condition is critical for ensuring complete reaction in the catalysis process?

Adequate supply of gas or liquid (D) Signup and view all the answers

What type of physical forms can catalysts take according to the forming methods described?

Larger size entities and defined shapes (B) Signup and view all the answers

What is a main characteristic of powder catalysts that can influence shaping operations?

The particles can have different shapes (D) Signup and view all the answers

Which of these is an example of a catalyst activation precursor?

Reduction to metal (D) Signup and view all the answers

What issue might arise during the catalysis reaction process?

Reaction proceeds without ever completing (C) Signup and view all the answers

What is the primary goal of the crushing and/or grinding operation?

To produce particles of a size suitable for forming operations (A) Signup and view all the answers

In spray drying, the main purpose of spraying a slurry into hot air is to achieve what?

To produce particles of almost identical shapes and sizes (B) Signup and view all the answers

What characterizes the granulation process?

The agglomeration of particles through progressive humidification (B) Signup and view all the answers

What is the method by which a paste is formed into sections during extrusion?

By pushing it through a die to shape it (A) Signup and view all the answers

What is a significant risk when water contaminates a catalyst during handling and storage?

It could lead to hydrolysis and corrosion of active elements (D) Signup and view all the answers

What is the primary formation achieved through the oil drop method?

Spheroidal particles from gel drops (B) Signup and view all the answers

Which of the following described granulators can result in spheroidal particle formation?

Hemispheric granulator (C) Signup and view all the answers

How does carbon dioxide contamination affect the catalyst preparation process?

It results in unwanted carbonate formation altering the catalyst's texture (B) Signup and view all the answers

Study Notes

Catalyst Synthesis

Catalyst synthesis involves creating a catalyst, a substance that speeds up a chemical reaction without being consumed.
The process typically involves several steps:
- Preparation of the primary solid: Includes various methods (e.g., deposition/impregnation, co-precipitation, gel formation, etc.)
- Processing/Treatment of the primary solid: Involves techniques for treatment of the primary solid(s) (e.g., drying, thermal decomposition of salts, calcination)
- Activation of the precursor: This encompasses procedures of activating the catalyst (e.g., reduction, sulfonation, deammoniation, etc.)
Catalyst properties and characteristics are important:
- Texture and surface characteristics (number and strength of acidic/basic sites, isoelectric point)
- The presence of exchangeable ions
- Chemical properties (e.g., reactivity in acidic or basic solutions)
The types of products and properties of the catalyst depend on:
- The reactants themselves
- Reaction conditions (e.g., temperature, pressure, and time)
Key criteria for a good catalyst:
- High activity
- High selectivity
- High thermal and mechanical strength
- Low cost
Catalyst formation methods (e.g.: powder, spray drying, oil drop, granulation, tableting, extrusion)

Types of Catalyst Impregnation

Impregnation: involves contacting a solid with a liquid or gas containing the components to be deposited.
Factors affecting impregnation rates:
- Selective adsorption
- Coulombic forces
- Van der Waals forces
- Hydrogen bonding
- Ion exchange
- Polymerization/depolymerization
- Partial dissolution
Different impregnation types exists:
- Soaking method
- Dry or pore volume impregnation
- Incipient wetness impregnation
- Deposition by selective reaction
- Co-impregnation
- Successive impregnation
- Impregnation by percolation

Precipitation & Co-precipitation

Precipitation: One or more metals are precipitated together with the support to create the catalyst.
Factors that influence precipitation reactions:
- Order and rate of adding solutions
- Mixing techniques
- Control of pH during the process
Important processes in precipitation:
- Nucleation (high supersaturation)
- Growth (approaching equilibrium)
Co-precipitation: Process in which normally soluble compounds are carried out of solution by a precipitate.
Co-precipitation types: surface adsorption, mixed-crystal formation, occlusion, mechanical entrapment
Co-precipitation affects particle size and purity.

Other Deposition Methods

Gas-phase deposition is a method of catalyst deposition via adsorption or reaction from a gas phase. It improves dispersion and distribution control.
Solid-solid reactions are also suitable methods to create specific catalysts using solid salts. This process is beneficial for industrial production but poses challenges regarding reproducibility in laboratories.
Wash coat is an approach used to coat monoliths using slurry, a mixture of small particles. This process enables the particles to adhere, and evaporation of water results in adhesion to the monolith.

Catalyst Stability

Common contaminants to catalysts during handling and storage include water, CO2, hydrocarbons, and poisons/inhibitors.
Water, corrodes and causes hydrolysis.
CO2 causes carbonate formation and texture changes.
Hydrocarbons can have uncontrolled reactions during treatment/activation.
Poisons/inhibitors can alter reactions.

Catalyst Protection

Methods for protecting catalysts from alteration include Passivation, Inert gas protection, protection by a condensed phase.
Passivation: controlled exposure to air to reduce rapid exothermic reactions and surface layer inhibition
Inert gas protection: using an inert atmosphere to prevent reactions
Condensed phase protection: using a wax or other solid material to protect the catalyst

Catalyst Forming Methods

Methods for creating various shapes/sizes:
- Powder: preparation, crushing, grinding
- Spray drying
- Oil drop
- Granulation
- Tableting
- Extrusion

Gel Formation

Gels are solid-like substances that retain active elements and eliminate reaction byproducts through evaporation/sublimation.
Methods for gel formation include chemical reactions (like polymerization), complexation, freeze drying, and gum/gelling addition.

Selective Removal

Some catalysts use selective removal of a component in an alloy to create a highly dispersed form.
Raney Ni is an example of a catalyst resulting from selective removal of one element.

Pillared Layer Method

This method uses layered structures (like clays), and adjustments in charge balance (often using Na) to create slit-shaped pores.
Catalyst loading in the reactor is another part of the catalyst creation process, which involves methods to insert prepared catalysts into the reactor.

Zeolite Synthesis via Precipitation/Co-precipitation

Zeolites are prepared via crystallization under hydrothermal conditions.
High temperatures and pressure are generally used.
Both batch and continuous synthesis methods are applicable.

Other important information

A catalyst can be described as a material that increases the rate of a reaction, usually by creating a lower activation energy pathway, without being consumed in the overall reaction. A catalyst will increase the rate of the reaction.

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Description

Test your knowledge on the fundamental concepts of catalyst design and preparation. This quiz covers key factors that contribute to catalyst performance, the roles of functional groups, and the stages of catalyst synthesis. Assess your understanding of supported versus unsupported catalysts and their characteristics.