The deactivation of a ZnO doped ZrO₂–SiO₂catalyst in the conversion of ethanol/acetaldehyde to 1,3-butadiene

Abstract

Deactivation study on the ethanol/acetaldehyde conversion to 1,3-butadiene over a ZnO–ZrO2–SiO2catalyst.

Properties and activity of Zn–Ta-TUD-1 in the Lebedev process

“…5,101,102 Understanding the deactivation mechanism would assist the design of more resistant catalysts. While recent work has provided precious insights, 15,35,36 catalyst deactivation has not been fully understood, in part due to the multiplicity of materials and reaction conditions used.…”

“…Coking has been identify major as source of deactivation during the conversion of ethanol to BD over many different catalysts. 19,24,[34][35][36] Moreover, our team previously reported that calcination under air regenerated the catalytic activity of Zn-Ta-TUD-1-a possible sign of deactivation by coking. 37,102 Coke deposits occurring in the Lebedev process on ZTT-1 were quantified by the TGA of spent catalysts after 1.5-72 hours on stream at 400°C.…”

“…Many authors argue that coke deposition on the catalyst surface results in loss of activity. 24,34,35 Accordingly, highly active acidic or basic sites are responsible for the formation polyaromatic carbonaceous species that, once deposited at the surface of the catalyst, block the access to active sites. Alternatively, Li et al suggested that relatively lighter oxygenated cyclic species formed by the condensation of aldehydes poison the sites responsible for butadiene formation.…”

Ethanol conversion into 1,3-butadiene over a mixed Hf-Zn catalyst: Effect of reaction conditions and water content in ethanol

“…This Lewis-to-Brønsted acid sites transformation was postulated to be responsible for the detrimental effect on activity and selectivity of water generated in situ during the ethanol-to-1,3-butadiene reaction. Other works have reported the effect of water content on one-step catalysts but using a mixture of ethanol/acetaldehyde as feed, namely, Zhu et al [43] over a Mg/SiO2 catalyst and Zhang et al over a ZnO/ZrO2/SiO2 catalyst [44]. Surprisingly, in these works the selectivity to ethanol dehydration products (ethene and diethyl ether) decreased with water content, just the opposite trend reported by Ochoa et al [7].…”

“…The likely reason for this behaviour is that, at this temperature, acetaldehyde is so reactive (steep slope of acetaldehyde curve, Figure 2b) that it is rapidly converted into heavy compounds (C6+) through aldol condensation with itself and heavier aldehydes (Figure 2e). The excessive formation of heavy products results in operational problems, such as faster catalyst deactivation [33,44], and in lower 1,3-butadiene selectivity (Table S1). Furthermore, the formation of ethene and diethyl ether, ethanol dehydration products, and of butenes (1-butene, isobutene, cis-2-butene and trans-2-butene), 380 ºC 360 ºC 340 ºC products of butanol dehydration, is also undesired in one-step catalysts in order to avoid low selectivity to 1,3-butadiene.…”