New way of the nickel catalyst preparation for carbon nanotubes synthesis by pyrolysis of ethanol vapor

Abstract

The process of carbon nanotubes (CNTs) synthesis by the method of catalytic pyrolysis of ethanol vapor was studied. It was shown that the synthesis can be carried out in a simple flow reactor by feeding liquid ethanol into the reactor without using carrier gas and hydrogen. Nickel nitrate hexahydrate (Ni(NO3)2•6H2O) was used as a catalyst precursor. A new method of preliminary preparation of the catalyst by decomposition of the precursor in alcohol vapor has been proposed. The activity of catalysts obtained by thermal decomposition of the precursor in air (type I) and in alcohol vapor (type II) was compared. The influence of the synthesis temperature, the process duration, and the reagent consumption rate on the output of CNTs and the degree of alcohol conversion was studied. The obtained carbon nanomaterials were examined by scanning electron microscopy and Raman spectroscopy. It is shown that the type II catalyst in all parameters exceeds the type I catalyst. The yield of CNTs to the mass of the catalyst exceeds 10000%, the degree of ethanol conversion approaches 100%, which roughly corresponds to the synthesis of 100 g of product from 1 liter of alcohol. Proposed improvements make the described method one of the most simple and appropriate for the production of large quantities of inexpensive CNTs that are promising for use as sorbents, catalyst carriers, supercapacitor materials, etc.