Catalytic aromatization of ethane on zinc-modified zeolites of various framework types

Abstract

420Present day development of promising novel pro cesses for the petrochemical and petroleum refining industry is largely associated with progress in zeolite catalysis. Research in the field of designing next gen eration zeolite systems having a high activity in the cracking, dehydrogenation, isomerization, and arom atization reactions opens a sound possibility of involv ing in catalytic processing of light hydrocarbons to produce valuable chemicals. Aromatization of gaseous hydrocarbons occurs in the presence of various cata lytic systems, of which high silica zeolites of the pen tasil family are considered the most effective [1][2][3][4][5]. These are ZSM 5, ZSM 8, and ZSM 11 zeolites and their domestic analogs, such as zeolites of the TsVK, TsVM, TsVN, and other brands [6,7]. Among poten tial catalysts for aromatization of light hydrocarbons, metal-zeolite systems command the major attention as they exhibit higher activity and selectivity compared with the unmodified zeolite supports. In this case, the initial zeolite structure affects the activity of a catalytic system. Therefore, studying the structural features of various zeolites and revealing their influence on the catalytic properties of modified zeolite forms are of considerable scientific interest and practical impor tance.The objective of this work is to examine the influ ence of zeolite framework type on the catalytic activity of zinc containing catalysts prepared from these zeo lites in the aromatization reaction of ethane, which is a component of both natural has and associated petro leum gas. EXPERIMENTALFor investigation, zeolites of the ZSM 5, ZSM 8, and ZSM 11 framework types having SiO 2 /Al 2 O 3 molar ratios of 70, 80, and 90, respectively, were pre pared from alkaline alumina-silica gels by hydrother mal synthesis under laboratory conditions. The ZSM 12 type zeolite was the commercial product manufac tured by the Angarsk Catalyst and Organic Synthesis Plant (molar ratio of SiO 2 /Al 2 O 3 = 83). Zinc contain ing zeolite systems were prepared by impregnating the zeolites with a zinc nitrate (Zn(NO 3 ) 2 · 6H 2 O) solution. The zinc concentration in the system were 3.0 wt % (on metal basis). The parameters of the zeo lites synthesized were monitored by means of IR spec troscopy and X ray diffraction analysis. The IR spec tra of the test samples were recorded on a Nicolet 5700 Fourier transform IR spectrometer within the range of 2000-400 cm -1 in KBr disks (1.2 mg of zeolite per 300 mg of KBr) in air. The phase composition of zeo lites was determined by X ray diffractometry on a DRON 3M diffractometer using Сu α radiation and a Ni filter.The acid properties of the zeolite catalysts were tested using the ammonia temperature programmed desorption (TPD) technique. The choice of ammonia as an adsorbate is due to a small size of its molecule, simplicity of dosage, and high basicity, allowing deter mination not only strong, but also weak acid sites. The concentration of acid sites in the test specimens was determined from the amount of ammonia deso...

Enhanced Catalytic Performance of Zn‐containing HZSM‐5 upon Selective Desilication in Ethane Dehydroaromatization Process

“…[7,15,18,[24][25][26][27] However, only a few studies have been dedicated to the performance and catalytic life-time enhancement of Zn-containing zeolite catalyst for ethane direct conversion to aromatics. Vosmerikova et al [28] studied the influence of zeolite framework structure for ethane dehydroaromatization on ZSM-5, ZSM-8, ZSM-11, and ZSM12 at 650°C. They demonstrated that the most effective catalyst is zinc containing ZSM-5.…”

Direct conversion of methane to C2 hydrocarbons using W supported on sulfated zirconia solid acid catalyst

“…Although silica and alumina have been reported as strong non-reducible catalyst supports [30,31], recent studies have revealed zirconium oxides to demonstrate higher strength in working conditions [32]. It has been reported that the sulfurized form of ZrO 2 known as sulfated zirconia (SZ), actively helps the active metal sites to stabilize on the oxide support at a greater degree [29,33].…”

Effect of Al Distribution in MFI Framework Channels on the Catalytic Performance of Ethane and Ethylene Aromatization

“…Though there is still some distance to go for ethane-to-aromatic industrialization, some important knowledge about the catalyst formulations for the ethane-to-aromatic process had been acquired by both academic groups and industrial entities since the 1970s. − It is believed that ethane aromatization consists of the transformation of ethane into ethylene and the transformation of as-formed ethylene into aromatic hydrocarbons, and bifunctional catalyst components with metal sites for ethane dehydrogenation and acid sites for the oligomerization and aromatization were employed. , For metal sites, Cu, Zn, Ga, Mo, and Pt are proved to be effective for dehydrogenation of ethane. ,, Among these metals, Pt possesses powerful dehydrogenation ability but with unfortunate high hydrogenolysis side reaction that usually leads to a large amount of unwanted methane. Secondary metal (Sn, Ge, Ga, and Fe)-modified Pt had been extensively investigated to overcome the weakness of Pt metal sites.…”