Fluid Distributing Device for Hydroalkylation Reactor
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Solution Overview
Problem
The existing hydroalkylation process for producing cyclohexylbenzene and phenol faces challenges in maintaining uniform liquid distribution across the catalyst bed, leading to hot spots, unwanted by-products, and inefficient gas-to-liquid molar ratios, which affect the yield and purity of the products.
Innovation Solution
A fluid distributing device is used to ensure a uniform distribution of the liquid benzene across the upper surface and throughout the catalyst bed, maintaining a consistent gas-to-liquid molar ratio, thereby preventing hot spots and reducing the formation of undesired by-products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid benzene is supplied to the catalyst bed in the hydroalkylation reactor, then the exothermic reaction can be cooled, but uneven liquid distribution leads to hot spots and unwanted by-products
Solution Approach 1:
The liquid distribution system is segmented into multiple injection points arranged in a grid pattern across the catalyst bed cross-section. This segmentation divides the single liquid supply stream into multiple smaller streams, ensuring more uniform spatial distribution of liquid benzene throughout the catalyst bed, thereby preventing hot spots and improving temperature uniformity.
Solution Approach 2:
The injection points are strategically positioned at different locations (corners, edges, and center) of the catalyst bed cross-section to provide localized liquid supply where needed. This local quality approach ensures that liquid distribution matches the spatial requirements of the catalyst bed, preventing both hot spots and hydrogen depletion zones.
2Productivity
If hydrogen is oversupplied relative to benzene, then the alkylation reaction can proceed, but hot spots are created leading to undesirable side reactions
Solution Approach 1:
The system uses feedback control by monitoring the liquid distribution pattern and adjusting the injection rates at different points accordingly. This feedback mechanism ensures that hydrogen and benzene are supplied in appropriate proportions throughout the catalyst bed, maintaining high productivity while preventing hot spots that cause side reactions.
3Temperature
If liquid benzene is oversupplied forming continuous liquid area, then cooling is improved, but hydrogen depletion occurs generating by-products
Solution Approach 1:
The liquid supply is segmented into multiple discrete injection points rather than forming a continuous liquid area. This segmentation maintains adequate cooling through distributed liquid presence while preventing large continuous liquid zones that would cause hydrogen depletion and by-product formation.
4Ease of operation
If liquid distribution is non-uniform, then the reactor operation is simpler, but catalyst life is reduced due to coking
Solution Approach 1:
The segmented injection system distributes liquid uniformly across the catalyst bed through multiple simple injection points, maintaining ease of operation while preventing localized coking that would reduce catalyst life. The segmentation approach achieves uniform distribution without complex liquid delivery mechanisms.
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 achieves a uniform distribution of reactants, minimizing the production of by-products like biphenyl and bicyclohexane, resulting in higher purity and yield of cyclohexylbenzene and phenol, and extends catalyst life by preventing coking.
Implementation Method 1
The flow of the liquid in the catalyst bed functions in part to cool the catalyst and the reactor
Implementation Method 2
The highly exothermic hydroalkylation reaction of benzene over an acid catalyst
Data Source
AI summary
An alkylating process such as hydroalkylating process comprising feeding a gas material and a liquid material into the reactor, distributing the liquid material to the upper surface of a bed of a catalyst substantially uniformly. The substantial uniform distribution of the liquid material to the upper surface allows for substantially uniform distribution of liquid reaction medium in the bed, thereby preventing hot spot and undesirable continuous liquid zone, both of which can cause the production of undesired by-products. The invention is particularly useful for the hydroalkylation reaction of benzene in making cyclohexylbenzene, which can be used for making cyclohexanone and phenol.