Utilization of Hematite Particles for Economical Removal of o-xylene in a High-Temperature Gas-Solid Reactor.

Xiaolong Ma,Jinjin Qian,Dandan Zhao,Zichuan Ma,Jiansheng Cui

doi:10.3390/molecules27051509

Abstract

To establish a novel approach for VOCs resource utilization, coupled o-xylene oxidation and hematite reduction was investigated in this study in a high-temperature gas-solid reactor in the temperature range 300–700 °C. As the o-xylene-containing inert gas (N2) stream traveled through the hematite particle bed, its reaction behavior was determined in programmed heating and constant temperature modes. Consequently, the effect of bed temperature, flow rate and o-xylene inlet concentration on both o-xylene removal performance and degree of hematite reduction was studied. The raw hematite and solid products were analyzed by TGA, XRF, XRD and SEM-EDS. The results showed that a temperature above 300 °C was required to completely eliminate o-xylene by hematite, and both o-xylene removal capacity and degree of hematite reduction at 5% breakthrough points enhanced on increasing the temperature and decreasing the flow rate. The increment in temperature from 300 °C to 700 °C led to a gradual reduction of Fe2O3 to Fe3O4, FeO and metallic iron. Thus, this study provides a novel, economic and promising technology for treating the VOC pollutants.

Highlights

Volatile organic compounds (VOCs) are toxic pollutants, which are released in the environment through industrial emissions
As o-xylene passed through the heating hematite iron ore (HIO) bed, Fe2O3 was reduced to iron species with low valence states (Fe3O4, FeO and Fe), while it was oxidized to CO2/CO and H2O, achieving the dual goals of iron ore reduction and o-xylene removal
In the adsorption–desorption region, a high Xo-x value was observed for o-xylene removal followed by a decline, which could be attributed to the physisorption process at low temperatures and thermal desorption at high temperatures

Summary

Introduction

Volatile organic compounds (VOCs) are toxic pollutants, which are released in the environment through industrial emissions. The reduction of iron oxides by VOCs can offer advantages for achieving multiple targets such as the purification and resource utilization of VOCs, acquisition of DRI co-product and carbon emission reduction during the iron-making process. For these reasons, the iron oxide oxidation-based approach differs from those already published in the literature in both process principle and material used. A naturally hematite iron ore (HIO) was selected as the potential oxidizing agent to explore the feasibility of its reduction using o-xylene as a model VOC and investigate the effect of several process conditions on both o-xylene removal performance and hematite conversion. The results obtained in this study can provide a beneficial foundation for developing novel pathways for VOC resource utilization

Reactivity of HIO with o-xylene

Effect of Temperature on o-xylene Removal and HIO Conversion

Effect of Inlet Concentration of o-xylene on Its Removal and HIO Conversion

Materials and Methods

Characterization of Samples

Conclusions