Modified Y-Type Molecular Sieve for Selective Hydrocracking
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Solution Overview
Problem
Existing Y-type molecular sieves used in hydrocracking catalysts have excessive cracking reactions and poor reaction selectivity due to the distribution of acid centers primarily in micropores, leading to secondary cracking and reduced yield of liquid products.
Innovation Solution
The modified Y-type molecular sieve is designed with acid centers predominantly distributed in large pore channels by controlling the distribution of sodium ions in micropores, using sodium ion exchange and ammonium salt treatment to concentrate acid centers in secondary pores, reducing secondary cracking and enhancing reaction selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If acid centers are distributed in micropores of molecular sieve, then cracking activity is enhanced, but secondary cracking increases and reaction selectivity deteriorates
Solution Approach 1:
The patent applies local quality by creating different acid center distributions in different regions of the molecular sieve structure. Specifically, the outer shell region contains acid centers that provide cracking activity, while the inner core region has reduced acid centers to minimize secondary cracking. This spatial differentiation of acid center density allows the catalyst to simultaneously achieve high cracking activity and good reaction selectivity by optimizing the function of different structural zones.
2Reliability
If conventional modification methods are used to enhance hydrothermal stability, then chemical stability is improved, but acid centers become distributed in both micropores and secondary pores causing excessive secondary cracking
Solution Approach 1:
The patent uses local quality by implementing a core-shell structure where the outer shell undergoes conventional modification (desilication, dealumination) to enhance hydrothermal stability, while the inner core maintains a different composition that limits acid center formation. This localized modification approach allows the outer region to provide stability while the inner region controls selectivity, resolving the contradiction between stability enhancement and selectivity maintenance.
Solution Approach 2:
The molecular sieve is segmented into distinct structural zones (outer shell and inner core) with different chemical compositions and acid center distributions. The outer shell contains modified regions with enhanced stability, while the inner core has a different Si/Al ratio and acid center density. This segmentation allows independent optimization of stability and selectivity functions in different parts of the catalyst particle.
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
This approach improves the selectivity of catalytic reactions, reduces secondary cracking, enhances the quality of hydrocracking tail oil, and increases the yield of liquid products in hydrocracking processes.
Implementation Method 1
The modified Y-type molecular sieve contains 0.5-2 wt.% of Na2O based on the total amount of the modified Y-type molecular sieve
Implementation Method 2
the chemical dealuminization modification method such as an inorganic acid, an organic acid, a salt and a complexing agent
Implementation Method 3
The cracking function is provided by an acidic carrier material such as molecular sieve
Data Source
AI summary
The present disclosure relates to the technical field of hydrocracking, and discloses a modified Y-type molecular sieve and process for preparing same, a hydrocracking catalyst and preparation method thereof, and a method for hydrocracking a hydrocarbon oil. The modified Y-type molecular sieve contains 0.5-2 wt.% of Na2O based on the total amount of the modified Y-type molecular sieve; the ratio between the total acid amount measured by pyridine and infrared spectrometry of the modified Y-type molecular sieve and total acid amount measured by n-butyl pyridine and infrared spectrometry of the modified Y-type molecular sieve is 1-1.2; the total acid amount measured by pyridine and infrared spectrometry of the modified Y-type molecular sieve is 0.1-1.2 mmol/g. The acid center sites of the molecular sieve of the modified Y-type molecular sieve are intensively distributed in the large pore channels, the molecular sieve is used in the hydrocracking reaction process of a wax oil, which is beneficial to enhancing reaction selectivity of the macromolecular cyclic hydrocarbons in the wax oil, reducing the occurrence of secondary cracking reaction, improving quality of hydrocracking tail oil, and increasing yield of the reaction liquid products.