Influence of Montmorillonite K10 Modification with Tungstophosphoric Acid on Hybrid Catalyst Activity in Direct Dimethyl Ether Synthesis from Syngas

Abstract

Dimethyl ether synthesis was performed from syngas over hybrid catalysts comprising a Cu/Zn/Al as metallic function and K10-montorillonite (K10) as acidic function. The acidic properties of K10 were tuned by deposition of one monolayer of tungstophosphoric acid (H 3 PW 12 O 40 Á23.5 H 2 O, TPA). The changes in acidity were determined based on pyridine adsorption with FTIR detection. Due to the fact that TPA does not possess Lewis acid sites, deposition of TPA on the K10 surface (TPA-K10) resulted only in increase in Brønsted acid site concentrations and in increase in their strength in comparison with unmodified K10. Since both modified and unmodified K10 exhibited the same Lewis acid site concentrations and their strength, it was possible to investigate solely the impact of Brønsted acidity differences of acidic functions on the hybrid catalysts activity in syngas-to-DME process (STD). Additionally, the effect of TPA supported on K10 was investigated in methanol dehydration to DME under atmospheric pressure. In order to prepare metallic functions which differed in activity in CO hydrogenation to methanol (first step of STD), two synthesis methods were used: co-precipitation method (metallic function CZA) and decomposition of citrate complexes of metals (metallic function CZA citric). The hybrid catalysts (CZA/K10, CZA/ TPA-K10, CZA citric /K10, CZA citric /TPA-K10) for STD were prepared by physical mixing of metallic and acidic function in volume ratio equal to 2:1. The impact of K10 substitution with TPA-10 in hybrid catalysts depended on whether STD process was controlled by methanol synthesis step or dehydration methanol step. When K10 possessed adequate acidity to dehydrate methanol formed on metallic function (i.e. CZA citric), it substitution with TPA-K10 in hybrid catalyst did not improve DME yield. On the other hand, when metallic function (i.e. CZA) exhibited higher methanol activity and methanol dehydration rate was limited by insufficient acidity of K10 then usage of TPA-K10 of higher acidity in hybrid catalyst was found to increase significantly DME yield without light parrafins formation.

Physiochemical characterization and support interaction of alumina‐supported heteropolyacid catalyst for biodiesel production

“…It was found that the Lewis acid site always prevail despise the TPA content and might be due to the free electrons in the tungsten . In montmorillonite K10 modification with tungstophosphoric acid, Sliwa et al reported the presence of the predominance of the Bronsted acidity, whereas, the dominance of Lewis acid was observed. This could be due to TPA and γ‐Al 2 O 3 interacting differently, depending on the degree of hydroxylation.…”

Design of a selective solid acid catalyst for the optimization of glucose production from Oryza sativa straw

“…S1 †). 27 The amount of the HPW in the ltrate obtained in the impregnation process is subtracted from the initial amount of HPW taken, which resulted in the actual amount of HPW loaded on the support to be 39 AE 1 wt%.…”

Alternative fuel additives from glycerol by etherification with isobutene: Structure–performance relationships in solid catalysts

“…In addition, oligomerization of IB was not observed over these heterogeneous catalysts except for Amberlyst 15. The reasons for low catalytic activities could be the relatively small pore size (average of 3.8 nm for Montmorillonite K-10 and N 1 nm for AMM) and the weak Brønsted acidity [136,137]. In addition, deposition of PTA on Montmorillonite K-10 has been proved to result in enhancement in density and strength of Brønsted acid sites [136].…”