Mixed Metal Oxide Catalyst Preparation for Ammoxidation
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Solution Overview
Problem
Existing catalysts for the ammoxidation of propylene and isobutylene to acrylonitrile and methacrylonitrile face challenges in maintaining high acrylonitrile yields while minimizing hydrogen cyanide production, as historical trends show a decrease in hydrogen cyanide yield concurrent with increased acrylonitrile yield.
Innovation Solution
A multi-component mixed metal oxide catalyst with specific elemental ratios and preparation methods, including combining source compounds of bismuth, cerium, and molybdenum in an aqueous solution, followed by calcination, is used to enhance the conversion of propylene and isobutylene to nitriles, maintaining high acrylonitrile yields without significant hydrogen cyanide loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional catalyst preparation methods are used, then manufacturing simplicity is maintained, but catalyst performance and stability are insufficient
Solution Approach 1:
The patent applies preliminary action by pre-forming a bismuth molybdate core structure before adding other metal components. This sequential preparation approach (first combining Bi and Mo sources, then adding Fe, Ce, and other elements) ensures proper phase formation and enhances catalyst stability while maintaining a manageable preparation process through staged synthesis
2Productivity
If acrylonitrile yield is increased, then productivity is improved, but hydrogen cyanide loss increases
Solution Approach 1:
The patent applies parameter changes by optimizing the atomic ratios of metal components (Bi: 0.05-7, Fe: 0.1-7, Ce: 0.01-5 relative to Mo12) and controlling calcination parameters to achieve a catalyst composition that selectively promotes acrylonitrile formation while minimizing hydrogen cyanide byproduct, thus improving productivity without proportional substance loss
3Reliability
If catalyst attrition resistance is improved, then reliability is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent applies composite materials by creating a multi-metal oxide system (Bi-Mo-Fe-Ce with optional Na, K, Rb, Cs, Ca, rare earth elements, Pb, W) where the synergistic interaction between components enhances attrition resistance. The specific composite structure formed through controlled precipitation and calcination provides mechanical strength while maintaining catalytic 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 catalyst achieves higher overall conversion of propylene and isobutylene to nitriles, including acrylonitrile, methacrylonitrile, and hydrogen cyanide, with improved attrition resistance and stability, as demonstrated by XRD patterns and submerged jet attrition tests.
Implementation Method 1
the aqueous precursor slurry so obtained is dried to form a catalyst precursor
Implementation Method 2
the catalyst precursor is calcined to form said catalyst
Implementation Method 3
Catalysts containing oxides of iron, bismuth and molybdenum, promoted with suitable elements, have long been used for the conversion of propylene and/or isobutylene at elevated temperatures in the presence of ammonia and oxygen
Data Source
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AI summary
A process for the preparation of a catalyst wherein the relative ratios of the elements in said catalyst are represented by the following formula: Moi2 Bia Feb Ac Dd Ee Ff Gg Cej, Ox wherein: A is at least one element selected from the group consisting of sodium, potassium, rubidium and cesium; and D is at least one element selected from the group consisting of nickel, cobalt, manganese, zinc, magnesium, calcium, strontium, cadmium and barium; E is at least one element selected from the group consisting of chromium, tungsten, boron, aluminum, gallium, indium, phosphorus, arsenic, antimony, vanadium and tellurium; F is at least one element selected from the group consisting of a rare earth element, titanium, zirconium, hafnium, niobium, tantalum, aluminum, gallium, indium, thallium, silicon, germanium, and lead; G is at least one element selected from the group consisting of silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum and mercury; and a, b, c, d, e, f, g, h and n are, respectively, the atomic ratios of bismuth (Bi), iron (Fe), A, D, E, F, cerium (Ce) and oxygen (O), relative to 12 atoms of molybdenum (Mo), wherein a is from 0.05 to 7, b is from 0.1 to 7, c is from 0.01 to 5, d is from 0.1 to 12, e is from 0 to 5, f is from 0 to 5, g is from 0 to 0.2, h is from 0.01 to 5, and n is the number of oxygen atoms required to satisfy the valence requirements of the other component elements present; and wherein the elements in said catalyst are combined together in an aqueous catalyst precursor slurry, the aqueous precursor slurry so obtained is dried to form a catalyst precursor, and the catalyst precursor is calcined to form said catalyst, the process comprising: (i) combining, in an aqueous solution, source compounds of Bi and Ce, and optionally one or more of Na, K, Rb, Cs, Ca, a rare earth element, Pb, W and Y, to form a mixture, (ii) adding a source compound of molybdenum to the mixture to react with the mixture and form a precipitate slurry, and (iii) combining the precipitate slurry with source compounds of the remaining elements and of the remaining molybdenum in the catalyst to form the aqueous catalyst precursor slurry.