Coal Tar Hydrocracking Process for Xylene Yield
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Solution Overview
Problem
There is a need for additional processes to increase the yield of desirable aromatics, such as xylenes, from hydrocarbons derived from coal tar organic compounds, as the cost of petroleum-based chemicals has increased due to rising demand.
Innovation Solution
A process involving the transalkylation and hydrogenation of coal tar streams, where a coal tar stream is fractionated to produce hydrocarbon streams, hydrotreated, and then hydrocracked in the presence of a light aromatics stream to convert polycyclic aromatics into monocyclic aromatics and hydrogen donor molecules, enhancing the production of xylenes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional hydrocracking processes are used on coal tar streams, then the processing of polycyclic aromatics is limited, but the yield of desirable aromatics such as xylenes is insufficient
Solution Approach 1:
The patent changes the chemical parameters by introducing a light aromatics stream with specific methyl/aromatic available position ratio characteristics. This parameter change enables the hydrocracking zone to simultaneously achieve polycyclic aromatic conversion and xylene production, resolving the contradiction between productivity and ease of manufacture.
Solution Approach 2:
The light aromatics stream acts as an intermediary substance that facilitates the transalkylation reaction in the hydrocracking zone. It mediates between the polycyclic aromatics feedstock and the desired xylene product, enabling efficient conversion while maintaining high yield.
2Productivity
If polycyclic aromatics are directly hydrocracked without light aromatics addition, then the process is simpler, but the conversion to monocyclic aromatics and hydrogen donor molecules is inefficient
Solution Approach 1:
The patent merges two functions into a single hydrocracking zone: the conventional hydrocracking function and the new transalkylation function enabled by light aromatics. This combining allows efficient conversion to monocyclic aromatics and hydrogen donor molecules without adding separate process units, thus managing complexity while improving productivity.
Solution Approach 2:
The hydrocracking zone is made multi-functional by introducing the light aromatics stream. It simultaneously performs hydrocracking of polycyclic aromatics, transalkylation to produce xylenes, and generation of hydrogen donor molecules, achieving multiple objectives in one unit operation.
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 effectively increases the yield of xylenes by transalkylating and hydrogenating coal tar streams, improving the conversion of polycyclic aromatics to monocyclic aromatics and hydrogen donor molecules, thereby optimizing the production of valuable aromatic compounds.
Implementation Method 1
The coal tar stream is fractionated to provide at least one hydrocarbon stream having polycyclic aromatics
Implementation Method 2
The hydrocarbon stream is hydrotreated in a hydrotreating zone
Implementation Method 3
The hydrocarbon stream is hydrocracked in a hydrocracking zone to convert a first portion of the polycyclic aromatics to monocyclic aromatics
Implementation Method 4
The hydrocracked stream is transalkylated in the hydrocracking zone
Data Source
AI summary
A process for transalkylating a coal tar stream is described. A coal tar stream is provided, and is fractionated to provide at least one hydrocarbon stream having polycyclic aromatics. The hydrocarbon stream is hydrotreated in a hydrotreating zone, and then hydrocracked in a hydrocracking zone. A light aromatics stream is added to the hydrocracking zone. The light aromatics stream comprises one or more light aromatics having a ratio of methyl/aromatic available position that is lower than a ratio of methyl/aromatic available position for the hydrotreated stream. The hydrocracked stream is transalkylated in the hydrocracking zone.