In-situ Synthesis Of Nitrogen-doped Porous Carbon Materials Using ZSM-39 Zeolite As Template For Selective CO₂ Capture

The 21st century is the era of low carbon economy, thus the nation or company, which owns low carbon technologies and develop low carbon economy, can have its future. Carbon dioxide (CO2) capture and sequestration is an important part of low carbon technologies, and the separation and recovery of CO2 have attracted great attention of scientists and researchers. Porous carbons are one of the leading sorbent contenders for CO2 capture. Their major advantages include low cost, easy regeneration, low energy requirement, high surface area and easy susceptiblility to surface and pore modifications. The CO2 adsorption performance can be improved by increasing the micropore volume and basic functional groups in these materials. Researchers synthesize nitrogen-doped carbon materials by post-treatment processing such as amine graft. However, the basic functional groups of carbon materials obtained from post-treatment processing are unstable and distribute on the surface. In-situ synthesis method introduces nitrogen into the interior of carbon materials, which can improve the dispersity of nitrogen atoms and enhance the stability of nitrogen-containing functional groups. In this thesis, microporous ZSM-39 zeolite was used as in-situ template to synthesize nitrogen-doped carbon materials. The conditions of synthesizing ZSM-39 zeolie and performance of as-made carbon materials were investigated. In combination with XRD, N2 sorption experiment, FT-IR, SEM and TG, textural property and morphology were studied. The main conclusions were as follows:1. For the viewpoint of purity, crystallinity and cost of ZSM-39 zeolite, the optium conditions were as follows:the initial sol composition was SiO2:0.00025Al2O3:0.8TMACl:2.0NH4F:50H2O, reaction temperature and reaction time were 473 K and 3 days, respectively;2. Using KOH as alkaline source, K-Mg-ZSM-39 and K-Ca-ZSM-39 zeolites shown high crystallinity. K-Mg-ZSM-39 zeolite had flower-like morphologies and had uniform diameter about 200 ?m, while the morphology of K-Ca-ZSM-39 single crystal was quasi-octahedral crystal with about 80 ?m in size. It implied heteroatoms imposed distinctly influences on growth behavior of ZSM-39 crystals, and it might be practicable to design ZSM-39 crystals for meeting the requirements of optical property by simply matching heteroatoms with alkali source;3. A series of nitrogen-doped carbon materials (Zeolite-templated Carbon, ZC) were prepared by calcinating ZSM-39 zeolite with high silica to alumina ratio in inert atmosphere. The obtained materials were amorphous porous carbon. FT-IR results showed that nitrogen could be kept in resultant carbon materials. ZC-450 exhibited highest CO2 capacity up to 1.32 mmol/g at 293 K and 0.93 bar. The CO2 adsorption capacity of ZC-450 was 14.7 times higher than N2 adsorption capacity under the same conditions, impling high CO2 selectivity;4. Another series of nitrogen-doped carbon materials (Pure silica Zeolite-templated Carbon, PZC) were prepared by calcining pure silica ZSM-39 zeolite in inert atmosphere. With increasing the temperature of carbonization, the graphitization trend of carbon materials increased and the materials transformed into carbon sphere with uniform diameter about 1.3 ?m from irregular particles. PZC-450 exhibited highest CO2 capacity up to 1.80 mmol/g at 253 K.