Silica-Supported Catalyst Pore Size Optimization
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Solution Overview
Problem
Conventional silica-supported catalysts for vapor-phase catalytic ammoxidation of propane or isobutane suffer from high ammonia combustion rates and insufficient product yield due to inadequate pore size distribution and crystallite size, making them unsuitable for fluidized-bed reactions.
Innovation Solution
A silica-supported catalyst comprising Mo, V, and Nb with specific metal oxide composition and physical properties, including an average pore size of 60-120 nm, total pore volume of 0.15 cm^3/g, and crystallite size of 40-250 nm, optimized to reduce ammonia combustion and enhance product yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If silica sol and silica powder are mixed to increase pore volume, then fluidity is improved, but average pore size does not increase and target product yield is not improved
Solution Approach 1:
The patent changes the pore size parameter from conventional small pores to large pores (average pore size of 60-120 nm). This is achieved by using silica gel beads with controlled pore structures instead of mixing silica sol and powder. The parameter change in pore size directly addresses both fluidity and target product yield simultaneously.
2Manufacturing precision
If small-sized pores are used in alkane ammoxidation catalyst, then pore distribution is controlled, but combustion of raw material ammonia and degradation reaction of target product proceed
Solution Approach 1:
The patent changes the pore size parameter from small pores to large pores (average pore size of 60-120 nm). This parameter change prevents ammonia combustion and target product degradation while maintaining controlled pore distribution. The larger pore size allows better mass transfer and reduces harmful side reactions.
3Adaptability or versatility
If crystallite size is not defined, then catalyst composition is flexible, but improvement in yield is not sufficient
Solution Approach 1:
The patent defines the crystallite size parameter within a specific range (40-250 nm) to optimize target product yield. This parameter definition works together with the pore size control and metal oxide composition to achieve high productivity while maintaining composition flexibility through the specified ranges.
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 achieves a low ammonia combustion rate and high target product yield, making it suitable for efficient production of unsaturated nitriles in vapor-phase catalytic ammoxidation reactions, particularly in fluidized-bed processes.
Implementation Method 1
a method in which propylene or isobutylene is subjected to a vapor-phase catalytic oxidation or vapor-phase catalytic ammoxidation reaction to produce a corresponding unsaturated carboxylic acid or unsaturated nitrile
Implementation Method 2
D represents the average pore size (m), V represents the total pore volume (m3/g)
Data Source
AI summary
A silica-supported catalyst used when producing a corresponding unsaturated nitrile in a vapor-phase catalytic ammoxidation reaction of propane or isobutane, the catalyst including a metal oxide represented by the following formula (1), MoVaNbbXcTdZeOn (1) (wherein X represents at least one or more elements selected from Sb and Te; T represents at least one or more elements selected from Ti, W, Mn, and Bi; Z represents at least one or more elements selected from La, Ce, Yb, and Y; and a, b, c, d, e, and n are in the range of 0.05 ≤ a ≤ 0.5, 0.01 ≤ b ≤ 0.5, 0.001 ≤ c ≤ 0.5, 0 ≤ d ≤ 1, and 0 ≤ e ≤ 1, respectively, and n denotes a value that satisfies an atomic valence) wherein the silica-supported catalyst has an average pore size of 60 to 120 nm, a total pore volume of 0.15 cm3/g or more, a specific surface area of 5 to 25 m2/g, and a crystallite size of 40 to 250 nm as determined from half width of a (001) peak by X-ray diffraction.