A Synthetic Methodology for Preparing Impregnated and Grafted Amine-Based Silica Composites for Carbon Capture

Summary

This work aims to facilitate the development of standardized techniques for impregnating or grafting aminated compounds onto silica substrates, which are often broadly described in the literature. Specific amounts of solvent, substrate, amines, and the values of other important experimental parameters will be discussed in detail.

Abstract

Recently, there has been a significant effort towards reducing or mitigating CO₂ emissions through the use of carbon capture materials for point source or direct air capture (DAC) methods. This work focuses on amine-functionalized CO₂ adsorbents for DAC. These materials show promise for CO₂ removal because they have low regeneration energy consumption and high adsorption capacity. The incorporation of amine species into a porous substrate combines the advantages of the amine species' affinity to CO₂ with the large pore volumes and surface areas of the porous substrate. There are three methods commonly used to prepare amine-based CO₂ sorbents, depending on the selection of the amine species, material support, and preparation method. These methods are impregnation, grafting, or chemical synthesis. Silica is a prevalent choice of substrate material because of its adjustable pore size, moisture tolerance, temperature stability, and ability to adsorb CO₂ in low concentrations for DAC applications. Typical synthetic procedures and primary attributes of both impregnated and grafted amine-silica composites are described herein.

Introduction

The anthropogenic CO₂ emissions over the past several decades have been widely implicated as the main factor driving the greenhouse gas effect and consequently, related climate change^1,2,3,4. There are two general methods for CO₂ capture, point source and direct air capture. For more than 50 years, wet-scrubbing CO₂ capture technologies have been utilized for point source capture within the industry to mitigate CO₂ emissions^5,6. These techn....

Protocol

NOTE: Details related to the equipment, instrumentation, and chemicals used in this section can be found in the Table of Materials.

1. Impregnation of silica with polyethyleneimine of 800 g/mol molar mass (PEI 800)

1. Preparation of reaction
   1. Use anhydrous methanol as the solvent in this reaction. It has a low boiling point; thus, its volatility facilitates its later removal at lower temperatures.
      NOTE: Anhydrous solvent is importan.......

Discussion

The methods described herein are intended to provide a protocol for preparing impregnated and grafted amine silica-composite adsorbents. The procedures we have documented are based on review of techniques reported in the literature and those refined in our laboratory.^1,2,3. Preparation of these materials is useful within the field of carbon dioxide removal research to develop or benchmark other materials that may be used to lowe.......

Materials

Name	Company	Catalog Number	Comments
Anhydrous methanol	Sigma-Aldrich	322415	Does not come with sure-seal
Anhydrous toluene	Sigma-Aldrich	244511	Comes with sure-seal
Ceramic Stirring Hot Plate	NA	NA	The size, watage, and thermal capabilities of the stirr plate will differ depending on individual lab facilities.
Fourier Transform Infrared Spectroscopy (FTIR)	Nicolet i550 series spectrometer	NA	Run on OMNIC standard software
Gastight syringe	NA	NA	As long as the gas tight syringe has a PTFE plunger and luer tip, is suited for air sensitive technique and can be used in this protocol.
Glass vial	NA	NA	As long as the vial is made if borosilicate glass and has a screw based cap the brand name, size, or general shape does not matter for the protocol.
MCM-41 silica	ACS Material	MSM41A01	Cas no. 7631-86-9
Metal needle	NA	NA	Syringe needles need to be stainless steel. It is recommended to determine length and outerdiameter of needle by what will be transferred using the gas tight syringe. For large quantities of liquid a larger outer diameter will improve transfer rates.
N’-(3-trimethylsilyl propyl) diethyleneamine (DAS)	Sigma-Aldrich	104884	Comes with sure-seal
Polyethyleneimine (PEI)	Sigma-Aldrich	408719	Does not come with sure-seal
Schlenk round bottom flask	ChemGlass AirFree	NA	As long as the flask is suited for high pressure and temperture but the brand name, size, or general shape does not matter for the protocol
Thermogravemetric Anlysis (TGA)	TA Advantage	NA	550 series from Waters and TA Instruments