Oxygen‐Functionalized Boron Nitride for the Oxidative Dehydrogenation of Propane – The Case for Supported Liquid Phase Catalysis

Abstract

Boron and boron containing materials have created a new class of catalysts for the highly selective conversion of light alkanes to building block olefins. Boron oxide species seem to play an essential role for the oxidative dehydrogenation of propane. For boron nitride they are created through an induction process under reaction conditions. It is still not obvious how different kinds of oxidative pre-activation influences the observed activity and selectivity. Here we compare two different oxygen activation strategies of boron nitride, a classical activation by calcination at different temperatures and ball-milling with varying rotation velocity. These treatments allow to control the amount of introduced boron oxide species from 0.2 to 17.5 wt.-%, as quantified by alkalimetric titration. The catalytic experimental data together with the pre, post as well as in situ characterization, give insights how the catalyst's surface changes under reaction conditions. On this backdrop it can be deduced that molten boron oxide predominantly acts as catalyst under reaction conditions, and boron nitride as catalyst support.

Mechanistic Insights into Radical-Induced Selective Oxidation of Methane over Nonmetallic Boron Nitride Catalysts

“…According to recent progresses, − boron-based nonmetallic materials, such as BN and B 2 O 3 , possess a unique anti-overoxidation property in catalyzing aerobic oxidation of C 1 –C 6 alkanes, which renders a very low selectivity of CO 2 even at high alkane conversions. In particular, Wang et al reported that methane oxidation over hexagonal BN ( h -BN) at 963 K and a CH 4 /O 2 ratio of 2.0 led to the formations of CO, C 2 H 4 , and C 2 H 6 with a total carbon selectivity of 95.7% at ∼20% methane conversion, whereas the corresponding selectivity of CO 2 was merely 4.3% .…”

Tracking Active Phase Behavior on Boron Nitride during the Oxidative Dehydrogenation of Propane Using Operando X-ray Raman Spectroscopy

“…hBN undergoes a sampledependent induction period of up to several hours during which the propane conversion steadily increases before reaching a steady state (Figure 1a). 9,10 The exact shape and duration of the induction period depend on the reaction conditions. Based on ex situ characterization, this induction period can be attributed to the formation of the boron oxyhydroxide phase (B 2 (OH) 2x O 3−x (x ≤ 3)) necessary for catalytic activity.…”

“…Based on ex situ characterization, this induction period can be attributed to the formation of the boron oxyhydroxide phase (B 2 (OH) 2x O 3−x (x ≤ 3)) necessary for catalytic activity. 8,10 While there has been much debate about the active site structure, there is a general agreement that amorphous boron oxyhydroxide is required to achieve the catalytic activity typical for boron-based catalysts. Therefore, understanding the formation and behavior of the oxyhydroxide phase is crucial to understanding this exciting class of catalysts.…”

Correlation between the Properties of Surface Lattice Oxygen on NiO and Its Reactivity and Selectivity towards the Oxidative Dehydrogenation of Propane

“…The exploration of shale gas over the past decade has provided alternative source of light alkanes, particularly propane, making propane dehydrogenation and/or oxidative dehydrogenation (ODH) a potentially cost‐effective route to produce propene. The advantage of strong exothermic and low carbon deposition due to the presence of oxidant makes the ODH process attractive [7–9] . However, the presence of oxidant in ODH may cause overoxidation, and often complete oxidation to CO 2 , resulting in a low propene yield.…”

“…The advantage of strong exothermic and low carbon deposition due to the presence of oxidant makes the ODH process attractive. [7][8][9] However, the presence of oxidant in ODH may cause overoxidation, and often complete oxidation to CO 2 , resulting in a low propene yield. Therefore, an ODH catalyst selectively catalyze propane to propene at relatively low temperature while suppressing overoxidation is essential for industrial deployment of the ODH technology.…”