The effect of water on the kinetics of oxymethylene dimethyl ethers (OME) synthesis from dimethoxymethane (OME 1 ) and trioxane (TRI) has been investigated in a combined kinetic and in situ infrared spectroscopy study. The kinetic study revealed that a water content in OME 1 as low as 0.21 wt. % can significantly hamper the reaction rate. The apparent activation energy increased with the water concentration but the frequency factor was more severely affected and decreased by an order of magnitude when the water concentration was doubled. With increasing water content, the chain growth mechanism shifted from competition between the direct insertion of TRI and the dissociation of TRI with formaldehyde incorporation, to reaction of TRI with water to form methylene glycols units which were inserted in the OME chain. The competition between water and the reactants for binding to the active sites of the zeolite was studied by means of modulated excitation attenuated total reflection infrared (ME-ATR-IR) spectroscopy experiments. It demonstrated a competition for silanol sites and Brønsted acid sites (BAS) according to the binding affinity order: OME 1 > H 2 O > TRI. This trend was confirmed by a DFT study of the interaction of OME 1 , TRI and H 2 O with BAS. Combined together, these results indicated that the presence of water inhibited the adsorption of TRI on the binding sites, which prevented OME growth. Hence, even very low levels of water must be controlled for an efficient catalytic process.

Ni-H-Beta catalysts for ethylene oligomerization (EO) were prepared by ion exchange of NH4-Beta and H-Beta zeolites with aqueous Ni(NO3)2 and characterized by H2-temperature-programmed reduction (TPR), NH3-temperature-programmed desorption (TPD), and diffuse-reflectance infrared Fourier-transform spectroscopy (DRIFTS). Quadruple exchange of NH4-Beta at 70 °C resulted in 2.5 wt.% Ni loading corresponding to a Ni2+/framework aluminum (FAl) molar ratio of 0.52. [NiOH]+ and H+ are the primary charge-compensating cations in the uncalcined catalyst, as evidenced by TPR and DRIFTS. Subsequent calcination at 550 °C in air yielded a Ni-H-Beta catalyst containing primarily bare Ni2+ ions bonded to framework oxygens. Quadruple exchange of H-Beta at 70 °C gave 2.0 wt.% Ni loading (Ni2+/FAl = 0.41). After calcination at 550 °C, the resulting Ni-H-Beta catalyst comprises a mixture of bare Ni2+ ions: [NiOH]+ and NiO species. The relative abundance of [NiOH]+ increases with the number of exchanges. In situ pretreatment at 500 °C in flowing He converted the [NiOH]+ species to bare Ni2+ ions via dehydration. The bare Ni2+ ions interact strongly with the Beta framework as evidenced by a perturbed antisymmetric T-O-T vibration at 945 cm−1. DRIFT spectra of CO adsorbed at 20 °C indicate that the Ni2+ ions occupy two distinct exchange positions. The results of EO testing at 225 °C and 11 bar (ethylene) suggested that the specific Ni2+ species initially presented (e.g., bare Ni2+, [NiOH]+) did not significantly affect the catalytic performance.

The difficulties in the liquefaction and transportation of ethane in shale gas has led to significant rejection, via reinjection or flaring, of this valuable hydrocarbon resource. Upgrading this low-value, isolated ethane into easily transportable liquid fuels is a promising solution to this supply glut. In this study, we present a modular system that can potentially be operated economically at geographically isolated gas-processing facilities. The modular ethane-to-liquids (M-ETL) system uses a chemical looping-oxidative dehydrogenation (CL-ODH) technology to efficiently convert ethane and natural gas liquids into olefins (primarily ethylene) via cyclic redox reactions of highly effective redox catalyst particles. The resulting olefins are then converted to gasoline and mid-distillate products via oligomerization. CL-ODH eliminates air separation and equilibrium limitations for olefin generation. It also simplifies the process scheme and reduces energy consumption. Here, we present experimental proof-of-concept data on CL-ODH conversion of ethane to ethylene. Using the CL-ODH performance data at 750 C, we show that a simple, single-pass configuration can be economically viable at distributed sites. We identify that economic factors such as the capital cost, price of ethane feed, and value of electricity byproduct have strong effects on the required selling price of the liquids. It is also noted that the economic viability of the M-ETL system is relatively insensitive to the liquid yield under a low ethane price scenario. The demand and value of electricity at distributed locations, on the other hand, can play an important role in the optimal process configuration and economics. K E Y W O R D Sethane, fuel, gas-to-liquids, natural gas liquids, oxidative dehydrogenation, shale gas