Modified Y Molecular Sieve Surface Gradient for Hydrocracking
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Solution Overview
Problem
Hydrocracking catalysts face a challenge in balancing nitrogen tolerance and catalytic activity, as conventional modification methods either reduce catalytic activity or fail to improve nitrogen tolerance effectively.
Innovation Solution
A modified Y molecular sieve is developed with a higher silica-alumina mole ratio in the surface layer compared to the body phase, achieved through ammonium exchange, primary and secondary dealumination, carbon deposition, and carbon burning, which enhances nitrogen tolerance while maintaining high catalytic activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional dealumination or dealumination with silicon reinsertion is used to reduce acid sites, then nitrogen tolerance is improved, but hydrocracking activity is severely decreased
Solution Approach 1:
The patent applies local quality by creating a surface layer with high silica-alumina ratio (20-100:1) on the molecular sieve particles, while maintaining the bulk phase with lower ratio (8-30:1). The surface layer provides nitrogen tolerance, while the bulk phase preserves hydrocracking activity. This is achieved through controlled dealumination that preferentially affects the surface region, creating a gradient structure where different zones have different compositions optimized for different functions.
2Productivity
If acid density in the molecular sieve is increased to maintain hydrocracking activity, then catalytic performance is improved, but nitrogen tolerance is severely degraded
Solution Approach 1:
The patent segments the molecular sieve structure into two distinct regions: a surface layer and a bulk phase. The surface layer contains the high acid density required for hydrocracking activity, while the bulk phase provides the nitrogen tolerance. This segmentation allows each region to be optimized independently - the surface layer can have high silica-alumina ratio for activity, while the bulk maintains lower ratio for stability against nitrogen poisoning.
3Reliability
If conventional modification methods are used to improve nitrogen tolerance, then catalyst stability is improved, but catalytic activity is reduced
Solution Approach 1:
The patent creates a composite structure within the molecular sieve, combining two different silica-alumina ratio regions. The surface layer acts as a protective composite shell with high silica content for stability and nitrogen resistance, while the bulk phase maintains the aluminum content needed for catalytic activity. This composite architecture allows the catalyst to simultaneously achieve both high stability and high activity.
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 modified Y molecular sieve improves nitrogen tolerance and catalytic activity, enabling higher reactivity and yield in hydrocracking processes, particularly for diesel oil and chemical materials, with more uniform properties and stable product quality.
Implementation Method 1
treating Na—Y zeolite by ammonium exchange, so that the Na content calculated in Na2O in the Y molecular sieve obtained after ammonium exchange is not higher than 3 wt %
Implementation Method 2
treating the Y molecular sieve after ammonium exchange in the step (1) by primary dealumination
Implementation Method 3
treating the product obtained in the step (3) by secondary dealumination, to form a surface layer of the modified Y molecular sieve
Implementation Method 4
treating the Y molecular sieve treated by secondary dealumination in the step (4) by carbon burning
Implementation Method 5
the hydrogenation function is usually provided by active metal elements in vulcanized state, such as W, Mo, and Ni, etc.
Implementation Method 6
the cracking function is provided by a molecular sieve
Data Source
AI summary
The present invention discloses a modified Y molecular sieve, a preparation method and a use of the modified Y molecular sieve, a supported catalyst, and a hydrocracking method. The silica-alumina mole ratio in the surface layer of the modified Y molecular sieve is 20-100:1, and the silica-alumina mole ratio in the body phase of the modified Y molecular sieve is 8-30:1. When a hydrocracking catalyst prepared from the modified Y molecular sieve is used for hydrocracking, the hydrocracking catalyst has higher reactivity and higher nitrogen tolerance. The hydrocracking catalyst prepared from the modified Y molecular sieve is suitable for use for increasing the yield of diesel oil, increasing the yield of chemical materials, and catalyzed hydrogenation conversion of diesel oil, etc.