Brookite TiO2 Catalyst on Silica for Olefin Epoxidation
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Solution Overview
Problem
Current catalyst compositions for olefin epoxidation, such as titanated silica catalysts, face limitations in activity and selectivity, particularly in maintaining the brookite form of titanium dioxide, which is crucial for enhanced reaction efficiency.
Innovation Solution
The development of catalyst compositions comprising titanium dioxide in the brookite form, deposited on a high-surface-area amorphous silica support, with specific X-ray diffraction peaks and further modified with organosilicate groups, along with methods involving calcination and silylation to enhance catalyst activity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional titanated silica catalysts are used, then the catalyst can perform olefin epoxidation, but the activity and selectivity are limited due to inability to maintain brookite form of titanium dioxide
Solution Approach 1:
The patent applies parameter changes by controlling the calcination temperature (300-800°C) and duration to stabilize the brookite polymorphic form of titanium dioxide. This specific thermal treatment parameter regime prevents transformation to other TiO2 phases (rutile, anatase) while maintaining the catalytically active brookite structure, thereby resolving the contradiction between maintaining composition stability and achieving high catalyst activity.
Solution Approach 2:
The patent creates a composite catalyst system consisting of titanium dioxide (brookite form) dispersed on a silica support matrix. This composite structure provides both the catalytic activity of brookite TiO2 and the structural stability of silica, preventing phase transformation while maintaining high surface area and porosity for reactant access. The composite nature allows simultaneous achievement of activity and compositional stability.
2Productivity
If the silica support has high surface area and pore volume, then the catalyst activity improves, but the manufacturing complexity increases
Solution Approach 1:
The patent uses silica as an intermediary support material that facilitates the dispersion and stabilization of titanium dioxide in its brookite form. The silica support with controlled surface area (500-1000 m²/g) and pore volume (0.5-2.0 cm³/g) acts as a mediator that prevents TiO2 sintering and phase transformation during calcination, enabling high catalyst activity while using commercially available silica materials that are relatively easy to manufacture.
3Reliability
If the catalyst is treated with silylating agents, then the catalyst stability and selectivity improve, but the number of processing steps increases
Solution Approach 1:
The patent applies preliminary action by performing silylation treatment on the silica support before or during the calcination process. This pre-treatment with silylating agents (such as hexamethyldisilazane) modifies the silica surface properties in advance, creating a more stable environment for brookite TiO2 formation and preventing unwanted side reactions during the main catalytic process. This preliminary modification reduces the need for subsequent complex stabilization steps.
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 compositions exhibit improved activity and selectivity in olefin epoxidation, with increased conversion rates and prolonged catalyst performance, as demonstrated by enhanced activity metrics in both batch and continuous epoxidation processes.
Implementation Method 1
Catalysts are important components of many chemical manufacturing processes, and may be used to accelerate the rate of the reaction and/or to increase the selectivity or efficiency towards the desired product(s). The catalytic epoxidation of olefins with oxygen is an industrially useful process for preparing compounds such as ethylene oxide and propylene oxide.
Implementation Method 2
the silica support comprises amorphous silica having: (a) a surface area greater than 800 m2/g; and (b) a pore volume greater than 1.0 cm3/g
Implementation Method 3
calcining the titanium-treated silica support to produce a titanated silica support
Data Source
AI summary
A catalyst composition which comprises titanium, wherein part of the titanium is present as a titanium dioxide phase and at least some of the titanium dioxide phase is in the brookite polymorphic form is provided. In some embodiments, the catalyst also comprises a silica support which exhibits a high surface area and pore volume. Methods of preparing the catalyst and its use in an epoxidation reaction are also provided.