Platinum Encapsulated in Microporous Silica for Sulfur-Tolerant Hydrocracking
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Solution Overview
Problem
Conventional zeolite-Y catalysts are ineffective for hydrocracking large molecules in crude oil due to their small pore size, and platinum catalysts are prone to sulfur poisoning, limiting the production of olefins, benzene, toluene, and xylene.
Innovation Solution
Development of a platinum-based hydrogen spillover catalyst encapsulated within a microporous silica shell, combined with zeolite, alumina, and hydrogenation metals, which allows hydrogen to spill over to adjacent sites, excluding sulfur compounds and enabling effective hydrocracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional zeolite-Y is used as hydrocracking catalyst, then the catalyst provides good cracking activity for accessible molecules, but the small pore size prevents large molecules (greater than 3 nm in diameter) from diffusing into active sites
Solution Approach 1:
The catalyst system is segmented into multiple functional components: zeolite-Y for cracking activity, alumina with surface sites for large molecule adsorption, and platinum for hydrogen spillover. Each component handles specific size ranges or functions, allowing the system to process both small and large molecules effectively.
Solution Approach 2:
Alumina acts as an intermediary between the zeolite-Y and large hydrocarbon molecules. The alumina surface sites adsorb large molecules that cannot enter zeolite pores, and through hydrogen spillover from platinum, these adsorbed molecules are converted and then transferred to zeolite for final cracking.
2Productivity
If platinum catalyst is used for hydrogenation, then the catalyst provides high hydrogenation efficiency, but the catalyst is rapidly poisoned by sulfur compounds
Solution Approach 1:
A silica shell is deposited on the platinum nanoparticles to create a protective barrier. This shell is designed with controlled porosity and thickness (1-10 nm) to allow hydrogen molecules to pass through via spillover while blocking larger sulfur compounds from reaching and poisoning the platinum active sites.
Solution Approach 2:
The silica shell is engineered with specific porosity characteristics that enable selective transport. The porous structure allows small hydrogen molecules to diffuse through to the platinum surface while preventing larger sulfur-containing molecules from accessing the platinum, thus maintaining catalyst activity in sulfur-containing feeds.
3Reliability
If the silica shell thickness is increased to protect platinum from sulfur, then sulfur tolerance improves, but hydrogen spillover efficiency may be reduced
Solution Approach 1:
The silica shell parameters (thickness and porosity) are optimized to achieve the desired balance. By controlling the shell thickness within 1-10 nm and adjusting porosity, the system maintains sufficient hydrogen permeability while providing adequate protection against sulfur poisoning.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The catalyst effectively converts heavy fractions into lighter products while withstanding significant sulfur levels, maintaining high aromatic compound conversion rates and resisting deactivation.
Implementation Method 1
a microporous silica shell, and further combining the encapsulated platinum with other cracking catalyst components
Implementation Method 2
H2 and H can pass through the sieve but sulfur compounds, such as H2S cannot
Implementation Method 3
Hydrogen spillover catalysts can produce free hydrogen atoms at one site on a catalyst and the hydrogen atoms can travel to other sites on the catalyst where they react with the large molecules
Implementation Method 4
cracking catalysts which incorporate a platinum catalyst encapsulated within a molecular sieve
Data Source
AI summary
According to the subject matter of the present disclosure, a cracking catalyst may comprise zeolite, alumina, nickel oxide, hydrogenation metal, and a core shell Pt/SiO2. The core shell Pt/SiO2 may comprise a platinum nanoparticle encapsulated by a microporous SiO2 layer.