Recycling of Wastes from the Production of Alumina-Based Catalyst Carriers

Abstract

Preparation of microspherical chromia−alumina KDM-type catalysts for alkane dehydrogenation is based on utilization of an amorphous nanostructured hydroxide−oxide Al 2 O 3 −x(OH) 2 •nH 2 O (where x = 0−0.28, n = 0.03−1.8) prepared via the centrifugal thermal activation (CTA) of gibbsite. The fine fraction of this carrier is considered as industrial waste, requiring efficient recycling options, which are explored in this work. A range of physicochemical methods was applied to analyze the main properties (phase composition, morphology, reactivity, etc.) of pilot and industrial batches of gibbsite CTA products. It has been clearly shown that the properties of CTA products are dependent on the nature of gibbsite used. The largest amount of the active amorphous phase of alumina is formed using gibbsite made from concentrated nepheline. Regularities of rehydration of the CTA-products fine fraction in acidic/ alkaline media and dissolution in sulfuric acid of the fine fraction of gibbsite and the industrial CTA product were explored to prepare aluminum sulfate, which is a water purification coagulant.

Fluidized-Bed Isobutane Dehydrogenation over Alumina-Supported Ga2O3 and Ga2O3–Cr2O3 Catalysts

“…In addition, a sharp drop of the baseline after 40°2θ indicated the presence of a certain amorphous phase. 35 Figure 3 depicts the diffractograms of the CTA samples after heat-treatment at 650, 750, and 850 °C. According to the phase analysis, a metastable form of crystalline alumina with the cubic structure known as γ-phase prevailed in the CTA-product treated at 650 °C.…”

“…The broad diffraction peak at 67.1° 2θ suggested that the sample contained also a well-dispersed phase of Al 2 O 3 . In addition, a sharp drop of the baseline after 40° 2θ indicated the presence of a certain amorphous phase …”

“…This product obtained using CEFLAR technology is an amorphous nanostructured aluminum hydroxide–oxide . Details of this technology and the properties of the resulting support are described in detail in refs – .…”

Study on Controlled Synthesis of Mesoporous Pseudoboehmite via Carbonation Reaction

“…The sodium aluminate solution is mainly derived from the Bayer process or the alkaline process of smelting bauxite. Additionally, with the increasing demands for environmental protection and the development of resource recycling, businesses not only smelt bauxite but also are now utilizing aluminum-rich fly ash, ,− coal gangue, red mud, , waste alumina, ,, and nuclear-contaminated sludge ,, to extract aluminum to produce sodium aluminate solution. Due to variations in raw materials and processing techniques, the concentration and component ratios of sodium aluminate solution differ, thereby influencing the process and reaction conditions of carbonate reaction to produce pseudoboehmite, consequently affecting process control and the properties of the products.…”

Pt- and K-promoted supported gallia as a highly stable alternative catalyst for isobutane dehydrogenation

“…Another feature of this study is that the catalyst support is produced using a waste-free and reagentless technology by thermal activation of gibbsite. 15 This technology results in the particle size of alumina in the range of 40-100 μm allowing thus the dehydrogenation to be carried out using a fluidized-bed reactor. The thermal activation method is based on the transformation of nonporous crystalline gibbsite (Al(OH) 3 ) into an amorphous product via pulsed heating of gibbsite on a metallic preheated surface (or in a gas flow) to the temperature of dehydration, which is followed by a rapid cooling step.…”