Phenol Recovery Process Using Cascading Liquid-Liquid Extraction
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Solution Overview
Problem
Current methods for recovering phenol and tar acids from oil feedstocks are inefficient due to high energy consumption, substantial waste generation, and contamination issues, particularly when dealing with low phenol and tar acid content or small oil streams, as they require multiple solvents and complex recovery loops.
Innovation Solution
A process involving two cascading liquid-liquid extraction units using water and a mono- or polycyclic aromatic hydrocarbon as solvents, followed by distillation and crystallization to produce pure phenol and tar acids, eliminating the need for caustic agents and reducing waste, with selective solvent recovery and no residual solid wastes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If caustic soda is used to extract phenol and tar acids from feedstock oils, then high extraction efficiency is achieved, but substantial volumes of aqueous waste are generated
Solution Approach 1:
The patent extracts phenol and tar acids from feedstock oils using water as the extracting solvent instead of caustic soda. The water-soluble phenolic compounds are selectively transferred to the aqueous phase, achieving high extraction efficiency while avoiding the generation of saline aqueous waste that would require disposal.
Solution Approach 2:
The patent changes the chemical parameter of the extracting agent from a strong base (caustic soda) to a neutral solvent (water). This parameter change fundamentally alters the extraction mechanism from chemical reaction-based to physical solubility-based, eliminating salt formation and waste generation while maintaining extraction effectiveness.
2Productivity
If exhaustive liquid-liquid extraction with water is used to recover phenol and tar acids, then high recovery is achieved, but the volume of extract to be processed increases significantly
Solution Approach 1:
The patent introduces a hydrocarbon solvent as an intermediary extracting agent between the feedstock oil and the final water-based extract. This intermediary selectively transfers phenolic compounds to the hydrocarbon phase, which can then be easily separated and concentrated, reducing the overall volume of water-based extract requiring further processing.
Solution Approach 2:
The patent segments the extraction process into two distinct stages: first using water to extract phenolic compounds, then using a hydrocarbon solvent to further extract and concentrate them. This segmentation allows for more efficient processing by handling smaller volumes at each stage rather than processing one large volume of diluted extract.
3Productivity
If multiple solvents and complex recovery loops are used to treat low phenol and tar acid content streams, then complete recovery is achieved, but device complexity and energy consumption increase
Solution Approach 1:
The patent employs water as a universal extracting solvent that effectively recovers phenolic compounds from feedstocks with varying phenol and tar acid content ranges. This single solvent system replaces multiple specialized solvents and complex recovery loops, simplifying the process while maintaining complete recovery efficiency across different feedstock compositions.
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 process enhances the efficiency of phenol and tar acid recovery by minimizing waste, reducing energy consumption, and maintaining the commercial value of the treated oil, making it suitable for low phenol and tar acid content streams without the need for additional distillation or solvent replacement.
Implementation Method 1
The extraction of phenol and tar acids was conducted under high temperature (circa 160°C) and pressure (circa 20 barg)
Implementation Method 2
liquid-liquid extraction using water as a solvent... followed by an important dilution of the aqueous extract with 2 to 6 volumes of diluent for one volume of extract
Implementation Method 3
Direct normal distillation processes are therefore not considered as being suitable for recovering the phenol and tar acids
Implementation Method 4
a purification section where pure phenol and pure isolated tar acids might be obtained by combined crystallizations from the melt and distillation
Data Source
Figure 1
AI summary
The following invention relates to a process for recovering phenol and tar acids (cresols, xylenols) from different material feedstocks containing the said phenol and tar acids. The process comprises three to four main units including two cascading liquid-liquid extraction equipment, a solvent recovery unit where a pure blend of phenols (phenol and tar acids) might be obtained, and a purification section where pure phenol and pure isolated tar acids might be obtained by combined crystallizations from the melt and distillation. The primary solvent of the first liquid-liquid extraction unit is water. The secondary solvent in the second liquid-liquid extraction unit is a single water immiscible mono- or polycyclic aromatic hydrocarbon, substituted or not, or a mixture thereof.