Molecular Modeling of Naphtha Catalytic Reforming

Molecular Modelling of Naphtha Catalytic Reforming

Catalytic reforming is one of the most important refinery processes providing high octane number gasoline components, and aromatic compounds for the petrochemical industry as well as the valuable by-product of hydrogen.

Several issues are widely concerned in reformer performances. Some of them, such as catalyst formulation and reactor design, are investigated by experimental work, others fundamental aspects such as characterisation of feedstock and product, operation conditions can be studied by modelling and simulation. Different types of catalytic reforming models were developed for different application purposes during the past several decades from very simple 3 lumps PNA model to complicated mechanism-level kinetic models. But these models were only focused on the particular catalytic reforming process and neglect the compatibility with other refining processes such as separation and blending.

Recent product specifications and environmental legislations make strong restriction to the benzene and aromatics content in gasoline products, which motivate refiners to understand, characterize and simulate reforming feedstocks and products on molecular-level. The objective of this work is to build up an adaptive catalytic reforming model which not only provides molecular level reaction details but also have capability of connecting to other refining processes.

In this work, kinetic and reactor model of naphtha catalytic reforming is developed based on the characterisation method in terms of pseudo-component based molecular type homologous series matrix. The naphtha feedstock composition is represented by the MTHS matrix, and the kinetic network is constructed according to conversions among the matrix elements. By adopting the kinetic model, the product composition and its corresponding bulk properties are predicted. The proposed kinetic model is built on molecular-level and then applied to a bench-scale semi-regenerative catalytic reforming unit which contains 3 fixed-bed reactors. The influences of essential operating conditions, such as reactor inlet temperature, pressure and weight hourly space velocity (WHSV), on the product distribution and quality are explored.