Crude benzene hydrogenation pre-reactor

The crude benzene hydrogenation pre-reactor is a critical upstream equipment in the crude benzene refining process for producing benzene, toluene, and xylene (BTX). Its core function is to selectively catalyze the hydrogenation of the raw material under relatively mild conditions (typically 200-280°C and 2.5-4.0 MPa). It primarily removes easily polymerizable and coking-prone unsaturated hydrocarbons (such as styrene and indene) from the crude benzene, hydrogenating them into corresponding saturated hydrocarbons. Simultaneously, it partially removes impurities such as sulfur, nitrogen, and oxygen, preventing these impurities from causing coking and catalyst poisoning in the subsequent main reactor or separation system, thus ensuring the long-term stable operation of the entire plant. This reactor typically uses a fixed-bed configuration with palladium or nickel-based catalysts, and its efficient operation is a key prerequisite for achieving safe, stable, long-term, full-capacity, and optimal performance of the entire hydrogenation process.

1. Selective Hydrogenation of Polymerizable Impurities: Under relatively mild conditions (low temperature and pressure), it selectively hydrogenates highly reactive unsaturated hydrocarbons (like di-olefins, styrene, indene) into stable saturated compounds, preventing their polymerization.
2. Partial Removal of Heteroatoms: It partially removes sulfur (e.g., CS₂), nitrogen, and oxygen compounds, converting them to H₂S, NH₃, and H₂O.
3. Protection of Downstream Units: Acting as the "process guardian", its fundamental purpose is to purify the feedstock. This prevents polymerization and coking of unsaturates in the downstream main reactor (which operates at higher severity) or separation systems, thereby protecting the expensive main reactor catalyst and ensuring long-term (typically 2-3+ years), safe, stable, and efficient operation of the entire unit.