A Joule Heating Monolithic Reactor Composed Of Mesoporous Carbon Supported Ag/Co₃O₄ For Catalytic Removal Of Formaldehyde

Formaldehyde（HCHO）is a key component of indoor air contaminants and volatile organic compounds mainly emitted from building materials,binders,paints,furnishings,ornaments,etc.,which significantly influences human health due to the migration of HCHO into the environment.To achieve excellent catalytic performance of indoor HCHO removal with high efficiency and low energy consumption,a mesoporous carbon monolithic catalyst supported Ag/Co₃O₄（Ag-Co₃O₄/MCM）was proposed for the catalytic oxidation of HCHO utilizing the Joule heating characteristics.The mesoporous carbon monolith（MCM）is synthesized through a self-assembly using resorcinol and formaldehyde as carbon precursors followed by a carbonization process.Ag-Co active components are supported by an impregnation method.The Ag-Co₃O₄/MCM catalyst with excellent mechanical property is easy to be shaped on-demand and produced in large scale.The hierarchical porous structure in the monolithic skeleton allows improved particle dispersion and an easy access for reactants and catalytic active components.Compared with powder catalyst,Ag-Co₃O₄/MCM shows considerably lower pressure drop and higher electrical conductivity.According to the optimization of Ag-Co loading amount and reaction conditions,complete conversion of 100 ppm HCHO was achieved at temperature as low as 90^oC at GHSV of 30,000 ml h^-11 g^-11 over the 1Ag-1Co/MCM catalyst.Furthermore,the catalytic performance had no change in presence of steam.The stability test at steady state for 100 h and during repeated heating-cooling process for 100 cycles demonstrated high durability of the 1Ag-1Co/MCM for the practical application of HCHO catalytic removal.Compared to traditional fixed bed reactors,the Joule-heating monolithic reactor shows faster heating-cooling rate and higher energy efficiency.The result of energy balance calculation of the Joule-heating monolithic reactor applied with the 1Ag-1Co/MCM-l indicates that the majority of energy input is consumed by convective,radiative and conductive losses at the steady state.A considerable cut of energy consumption can be achieved due to the lower surface temperature and heat radiating area of the Joule-heating monolithic reactor.1Ag-1Co/MCMs with different sizes applied in the Joule-heating monolithic reactor show similarly high catalytic activity compared to that of traditional fixed bed reactor.1Ag-1Co/MCM-l（d=40 mm,h=20 mm）exhibits a larger dT/dq value of 281^oC cm³ W^-1,and shows a better Joule-heating efficiency.To further evaluate the practical application of indoor HCHO catalytic removal,the large scale catalytic equipment is prepared and employed in an airtight cuboid box（volume of 2.16 m³）.98%HCHO was removed during 10 h in the presence of 45 ppm HCHO,demonstrating the Joule-heating monolithic reactor equipped with the Ag-Co₃O₄/MCM catalysts is promising for developing an energy-efficient technique for indoor HCHO removal.