Synergistic co-processing of Red Mud waste from the Bayer process and a crude untreated waste stream from bio-diesel production

Abstract

The production of the aluminum metal from bauxite ore and bio-diesel from triglyceride oils both generate large waste streams, and their management and valuation is therefore of great interest in Brazil and any other country with established or developing bio-fuel and aluminum industries. The integration of these two waste streams into the development of alternative technologies that utilize wastes as low-cost materials could potentially contribute to economic development as well as chemical sustainability and minimize the environmental and ecological impact of these industries. In this study, a crude untreated bio-diesel plant waste stream consisting of glycerol, methanol, free fatty acid salts and water was coprocessed with Red Mud, the highly alkaline by-product of bauxite refining through the Bayer Process, at elevated temperature and pressure (350 to 400 °C; 0-500 psi hydrogen gas) in an attempt to synergistically produce value-added products from these two waste streams. Comparative analysis between untreated and upgraded materials was performed by CHN EA, TGA, TPR, SEM, MS, FT-IR, Karl-Fischer-Titration, and 1 H/ 13 C NMR. The products obtained showed an increase in carbon and hydrogen content in both the organic product phase and the Red Mud catalyst recovered. Also observed in the organic phases was an increase in the paraffin content relative to starting material as determined by NMR with a concomitant reduction of the alcohol content confirming glycerol and methanol conversion. The Red Mud recovered after every upgrading reaction showed a change of color to dark gray to black, magnetic and amphiphilic properties, as well as a substantial decrease in its alkalinity and an increase in its carbon content. Catalyst recycling reactions were performed highlighting the possibility that the Red Mud could be reused as a catalyst promoting an increase in the observed crude glycerol conversion to paraffins potentially usable as a low-grade heavy fuel oil.Brazilian aluminum industry. According to ABAL (Brazilian Association of Aluminum), Brazil is the sixth largest primary aluminum producer in the world, exceeded only by China, Russia, Canada, United States and Australia. By extension, Brazil possesses the fifth largest bauxite deposits on the planet, is the fourth largest alumina producer and ranks fifth in exports of primary aluminum and its alloys. 1 Both the biodiesel and the aluminum industry generate a large amount of waste giving rise to increasing concerns over environmental impacts. In the production of aluminum, Red Mud is generated from the caustic soda digestion of bauxite ore to create pure alumina via the Bayer process. 2 The alumina production process used today is essentially the same as invented by Karl Bayer in 1887. Exploiting the amphoteric nature of Al 2 O 3 , it uses sodium hydroxide to selectively dissolve this oxide component of the bauxite ore as Na[Al(OH) 4 ]. This solution is then filtered. Concentrating it and adding lime (CaO) leads to the

Property and performance of red mud-based catalysts for the complete oxidation of volatile organic compounds

“…Table 3 lists the temperatures of the TPR peak (TTP) for all of the samples. Ordonez et al [36] and Schlaf et al [37] reported that the typical TPR [37]. HRM (400) showed a shoulder peak at 500℃ in addition to two reduction peaks.…”

The potential for the use of waste products from a variety of sectors in water treatment processes

“…Work has been carried out on the use of Bayer residue as a construction additive or filling material (Deelwal et al, 2014). Limited work has been carried out on the use of Bayer residue as a coagulant or as an industrial catalyst, showing it may have potential in this area (Wang, et al, 2008b), for example to purify a bio-diesel waste stream (Resende et al, 2013). Work has also been carried out on iron recovery from Bayer residue (Liu and Naidu, 2014).…”

Red Mud waste from the Bayer process as a catalyst for the desulfurization of hydrocarbon fuels

“…1,10,18 Any alternative use of Red Mud as a catalyst could contribute to the reduction of environmental impact and at the same time add value to this material. 1,9,19 Desulfurization Sulfur, in both, its volatile SO x oxide or reduced H 2 S forms, constitutes a considerable environmental and technical problem. The sulfur compounds are highly undesirable in rening processes as they can lead to the deactivation of some catalysts used in crude oil processing and cause corrosion problems in pipelines, pumping and rening equipments, resulting in substantial nancial losses to the industry.…”