Renewable Aromatics from Tree-Borne Oils over Zeolite Catalysts Promoted by Transition Metals

Abstract

Despite the ever-growing demand for benzene–toluene–xylene (BTX), the alternative route of production from tree-borne oils is rarely investigated and poorly understood. Here, we have synthesized a Zn-loaded Y-zeolite catalyst for the continuous production of bio-BTX from tree-borne oils (nonedible seed oil), e.g., neem oil. Our approach involves low-temperature selective cracking–dehydrogenation–aromatization of neem oil over metal-supported catalysts to xylene-rich aromatics. The physicochemical properties of the prepared catalyst were characterized using powder XRD, N2 physisorption, TEM, NH3-TPD, XPS, Py-FTIR, solid-NMR, and TG analyses. Mesoporous Y-zeolites with a pore diameter of 7.4 Å showed better selectivity toward aromatics and were found to be the most effective catalyst for the aromatization process, especially for BTX. The aromatic yield was found to increase with the addition of Zn, and the highest conversion of 90–94% with an ∼75% BTX yield was achieved with the ZnY catalyst. During aromatization, a sizable number of short alkanes and olefins were also obtained on acidic Y-zeolites. The off-gas composition shows the presence of ∼45% C2–C4 olefins with 8.9% H2. The incorporation of Zn species can promote the dehydrogenation activity, and the subsequent aromatization required a suitable pore network. The optimized ZnY catalyst inspires the formation of toluene and xylenes, inhibiting the formation of benzene and gaseous alkanes.

A comprehensive review on the synthesis techniques of porous materials for gas separation and catalysis

“…This process involves the removal of ammonia by adsorption directly from the synthesis loop, which allows the unreacted nitrogen and hydrogen to be recycled (Figure 20). This reduces the need for high pressures and decreases operating and capital costs, Van Rhijn et al [113] Mesoporous silica nanoparticles Brønsted acid Nitroaldol condensation Huang et al [114] HZSM-5 zeolite Gd and Si nanoparticles Methanol to aromatics Li et al [115] SBA-15 Pluronic P123, HCl Polycondensation of furfuryl alcohol Janus et al [116] Mesoporous SBA-15 Mesoporous graphitic carbon CO 2 adsorption Wang et al [117] Nanostructured carbon employing Ti-SBA-15 Titania Hydrogen uptake and storage Ju arezet al [118] Zn/Y-zeolite Zn(NO 3 ) 2 Aromatization Singh et al [119] Potassium-modified ordered mesoporous carbon materials…”

Recent Advances in Catalysis Based on Transition Metals Supported on Zeolites

“…The catalytic pyrolysis of the lipid-extracted residue of Tribonema with a maximum yield of alkylbenzene was reported over 6% NiO-2% MgO/ZSM-5 ( Ji et al, 2017 ). The low-temperature selective cracking-dehydrogenation-aromatization of tree-borne oils to xylene-rich aromatics was performed by Zn/Y ( Singh et al, 2020 ). Also Zn or Cr ion-exchanged with MFI was applied as a catalyst of rapeseed oil hydroconversion to aromatic hydrocarbons ( Dedov et al, 2016 ).…”

Production of aromatics from butanol over Ga-promoted HZSM5 catalysts: tuning of benzene–toluene–xylene and ethylbenzene (BTEX) selectivity

“…For example, BTX aromatics derived commodity chemicals are used to manufacture various products like automotive parts, detergents, pesticides, resins, polymers, synthetic fibers, and other value added products. [2][3][4] BTX is also used as octane enhancers by blending with gasoline. In 2015, the consumption of benzene, toluene and xylene reached 50, 45, and 56 MT, respectively, globally and the rise in annual consumption rate is projected to be 1.5-3%.…”