Microstructural analysis of carbon nanomaterials produced from pyrolysis/combustion of Styrene-Butadiene-Rubber (SBR)

Styrene-Butadiene-Rubber (SBR) is a synthetic rubber copolymer used to fabricate several products. This study aims to demonstrate the use of SBR as feedstock for carbon nanomaterials (nanofibers and nanotubes) growth, and therefore to establish a novel process for destination of waste products containing SBR. A three stage electrically heated flow reactor was used. Small pellets of rubber were pyrolyzed at a temperature of 1000 ºC. The pyrolyzates were mixed with oxygen-containing gases and were burned. The products of combustion were used to synthesize the carbon nanomaterials (CNMs) at the presence of a catalyst. CNMs have a wide range of potential applications due to their extraordinary mechanical, thermal and electrical properties. Produced materials were characterized by SEM and TEM, whereas combustion products were assessed using GC. Results showed that CNMs with outer diameters of 30-100 nm and lengths of about 30 µm were formed. Therefore, it was demonstrated that waste products containing SBR can be used to generate CNMs which are value-added products of intense technological interest.CNPQCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES

Synthesis of carbon nanotubes from sugarcane bagasse

A tradicional produção de açúcar, associada à crescente produção de etanol, faz da indústria sucroalcooleira um dos principais segmentos da economia brasileira. As indústrias brasileiras de açúcar e álcool processaram cerca de 630 milhões de toneladas de cana em 2009, gerando, aproximadamente, 142 milhões de toneladas de bagaço. Este trabalho apresenta uma possibilidade de destinação para o bagaço da cana através da queima controlada associada à síntese de nanotubos de carbono (CNTs), materiais que possuem inúmeras possibilidades de aplicações tecnológicas devido as suas excepcionais propriedades. Foi utilizado o processo de pirólise a 1000ºC associado a um sistema catalisador, visando à recuperação dos gases gerados como matéria-prima para a síntese dos CNTs. As emissões gasosas foram analisadas por cromatografia e os materiais produzidos foram caracterizados com o emprego de MEV, MET, TGA e espectroscopia Raman. Os resultados mostraram que o uso do catalisador resultou na diminuição das emissões gasosas. Nanotubos de carbono com comprimentos de 10 a 40 µm e diâmetros entre 20 e 50 nm foram produzidos

Synthesis of carbon nanotubes from waste polyethylene plastics

Generation of non-biodegradable wastes, such as plastics, and resulting land as well as water pollution therefrom discarded plastics have been continuously increasing, while landfill space decreases and recycling markets dwindle. Exploration of novel uses of such materials becomes therefore imperative. Here I present an innovative and unique partial conversion of plastic waste to valuable carbon nanomaterials. It is an overall exothermic and scalable process based on feeding waste plastics to a multi-stage, pyrolysis/combustion-synthesis reactor. Plain stainless steel screens are used as substrates as well as low-cost catalyst for both carbon nanomaterials synthesis and pyrolyzates generation. Nano carbon yields of as high as 13.6% of the weight of the polymer precursor were recorded. This demonstration provides a sustainable solution to both plastic waste utilization, and carbon nanomaterials mass production

ANALYSIS AND CONTROL OF HYDROCARBONS GENERATED IN THE COMBUSTION OF PET WASTES

Brazilian production of PET (polyethylene terephthalate) in 2010 was of 505,000 tones. The PET waste may be used to generate energy by controlled burning. In this study, emissions of light hydrocarbons generated during combustion of these wastes are characterized. Samples of post-consumer PET bottles were inserted in an electric furnace at temperatures of 600, 800 and 1000°C under an atmosphere of 15% O2 and 85% N2. The effluents were subjected to a SiC filter and channeled into the second furnace at 1000°C. Stainless steel meshes were placed in the second furnace in order to work as catalyst. Gas chromatography is used to evaluate the effluent with and without the catalyst use, wherein is showed a significant reduction in the emissions using the meshes. Results allow a characterization of the hydrocarbons generated during the controlled burning of PET waste providing information for control and recovery of these gases emission

Síntese de nanomateriais de carbono a partir do resíduo de milho (DDGS)

The world's largest ethanol producer (USA) uses corn as feedstock. DDGS (distillers dried grains with solubles) is the main waste generated from this process (around 32 million t/year). DDGS samples were pyrolyzed at 1000 ºC in a furnace with controlled atmosphere. The effluent was channeled to a second furnace, in which catalyst substrates were placed. Chromatographic analysis was used to evaluate the gaseous effluents, showing that the catalyst reduced hydrocarbon emissions. The solid products formed were analyzed by SEM and TEM. Graphitic structures and carbon nanofibers, 50 µm in length and with diameters of 80-200 nm, were formed

Use of Stainless Steel AISI 304 for Catalytic Synthesis of Carbon Nanomaterials from Solid Wastes

Nanomaterials (CNMs) have extraordinary mechanical, thermal, and electrical properties, which provide a wide range of potential applications. However, the high cost to produce CNMs limits their usage. This work aims to decrease the cost of these materials by reducing the expenses associated with raw materials (using low-cost wastes) and with catalyst (using stainless steel meshes). Samples of sugarcane bagasse, corn residue (DDGS), scrap tires, and post-consumer PET bottles were burned in a controlled atmosphere. The effluent gases were subjected to AISI 304 stainless steel meshes, which worked as catalysts. The stainless steel decomposed the gaseous hydrocarbons into Csolid and H2, resulting in a precipitation of carbon on the metal surface and leading to the formation of CNMs. The catalyst system decreases the gaseous emissions from the solid wastes burned, as showed by the gas chromatography. Scanning Electronic Microscopy (SEM) and Transmission Electron Microscopy (TEM) analysis were used to check structures of the formed materials. Results showed the formation of carbon nanomaterials with lengths of 20μm to 50μm and diameters in the range of 20nm to 200nm. Value-added products, including carbon nanotubes, were successfully synthesized using solid wastes as carbon donors and AISI 304 stainless steel meshes as catalysts

Catalytic conversion of wastes from the bioethanol production into carbon nanomaterials

This work addressed the production of carbon nanomaterials (CNMs) by catalytic conversion of wastes from the bioethanol industry, in the form of either sugarcane bagasse or corn-derived distillers dried grains with solubles (DDGS). Both bagasse and DDGS were pyrolysed at temperatures in the range of 600-1000 degrees C. The pyrolyzate gases were then used as CNM growth agents by chemical vapor deposition on stainless steel meshes, serving as both catalysts and substrates. CNM synthesis temperatures of 750-1000 degrees C were explored, and it was determined that their growth was most pronounced at 1000 degrees C. The nanomaterials produced from pyrolysis of bagasse were in the form of long, straight, multi-wall nanotubes with smooth walls and axially uniform diameters. Typical lengths were circa 50 mu m and diameters were in the range of 20-80 nm. The nanomaterials produced from pyrolysis of DDGS were in the form of long, entangled, rope-like structures with rugged walls, and axially non-uniform diameters. Typical diameters were in the range of 100-300 nm and their lengths were in the tens of microns. This process also produces a bio-syngas byproduct that is enriched in hydrogen. (C) 2011 Elsevier B.V. All rights reserved.CNPQ-BrazilCAPES[04/CII-2008 - Rede Nanobiotec-Brasil