Acidic and Catalytic Properties of Zeolites Modified by Zinc in the Conversion Process of Lower C3–C4 Alkanes

Abstract

The acid and catalytic properties of the modified MFI zeolite catalysts during the conversion of the propane–butane fraction of the associated petroleum gases into the aromatic hydrocarbons were studied. It was established that the high-silica zeolites synthesized with the new structure-forming additive of the alcohol fraction (ZKE-AF) belong to the high-silica MFI zeolites. The resulting zeolites were modified by 1–5 wt. % additives consisting of zinc oxide and sulfide. The influence of the modifying additive concentration containing zinc oxides and sulfides in an amount of 1–5% on the acid and catalytic properties of the catalysts in the conversion process of lower C3–C4 alkanes into liquid hydrocarbons was studied. The research of the acid properties of the modified zeolite catalysts by thermal desorption of ammonia showed that the total concentrations of the acidic centers of H-ZKE-AF modified by 3% and 5% ZnO increased. It was found that the highest yield of liquid hydrocarbons was on the zeolite catalysts modified by 3% and 5% ZnS, and is 60.6% and 60.5%, respectively, which is 9% more than in the initial H-ZKE-AF. The activity of the zeolite catalysts modified by zinc oxide and zinc sulfide was in correlation with their acid properties.

Conversion of the Propane–Butane Fraction into Arenes on MFI Zeolites Modified by Zinc Oxide and Activated by Low-Temperature Plasma

“…The high-temperature peak, in the region of 350-500 • C with the T m peak at 405 • C, related to the desorption of ammonia with the strongly Bronsted acid sites of the zeolite hydrogen ions of which are bridged hydroxyl groups (Figure 11, curve 1, Table 2). The concentration of weak acid sites for 1% ZnO/99% H-ZKE-XM determined by the amount of desorbed ammonia is 600, and for strong-acid sites, it is 421 μmol/g [12,23]. The modification of H-ZKE-XM 1-5% ZnO leads to a change in their acid characteristics.…”

“…The concentration of weak acid sites for 1% ZnO/99% H-ZKE-XM determined by the amount of desorbed ammonia is 600, and for strong-acid sites, it is 421 µmol/g [12,23]. The modification of H-ZKE-XM 1-5% ZnO leads to a change in their acid characteristics.…”

“…The dependence of the PBF conversion on temperature on the zeolite catalysts is shown below: With a growth of the reaction temperature of the gaseous products of PBF conversion, the yield of lower olefins (ethylene and propylene) rises, and the total content of C 2 -C 3 olefins increases from 6.6 to 12.7% due to the intensification of dehydrogenation and cracking reactions' lower alkanes C 3 -C 4 [12,16,17].…”

“…The acid properties of the zeolite catalysts modified by 1-5% ZnO and activated by plasma were studied at the thermal desorption installation by adsorption of ammonia in a helium carrier gas stream in the range of 50-650 • C, with a linear heating rate of 10 • C/min according to the procedure described in reference [12]. The concentration of acid sites (µmol/g catalyst) in the zeolite-containing catalysts was determined from the amount of ammonia in desorption peaks (forms), and the accuracy of determining the amount of the adsorbed ammonia by the gas chromatography method was 2.5%.…”

“…In references [11,12], the authors studied the conversion of bioethanol and PBF on the microporous high-silica MFI zeolites, synthesized using multicomponent structure-forming additives of the "alcohol fraction" and the "X-oil" fraction (by-products of caprolactam industrial production) and their high catalytic activity was established in the conversion of ethanol and lower C 3 -C 4 alkanes to liquid hydrocarbons and aromatic hydrocarbons, respectively.…”