A Mini-Review on the Advances in the Kinetic Understanding of the Combustion of Linear and Cyclic Oxymethylene Ethers

In the field of alternative diesel fuels, so-called oxymethylene ethers (OMEs) are currently intensely investigated. Particularly OMEs of the type CH3O(CH2O)nCH3 with n = 3–5 exhibit promising fuel properties and combustion characteristics with strongly reduced particle and NOx emissions. According to their molecular structure, OMEs can be produced from methanol thus enabling sustainable production strategies from CO2 and renewable resources. Compared to the methyl derivatives, analogous compounds with higher alkyl groups (oxymethylene dialkyl ethers, OMDAEs) have been investigated to a much lesser extent. Thus, commercially available OMDAEs, i.e. compounds of the type ROCH2OR bearing ethyl, propyl, butyl and 2-ethylhexyl groups, have been studied. Furthermore, asymmetric compounds of the type R1OCH2OR2 have been synthesized from the symmetric compounds employing transacetalization reactions catalyzed by zeolite BEA-25. The OMDAEs have been characterized by spectroscopic and spectrometric methods and several physico-chemical, thermodynamic and fuel-related data have been determined and compared. Despite their structural peculiarities, such as the oxygen-containing acetal moiety in the molecular backbone, all OMDAEs exhibit properties similar to conventional diesel fuels. Based on experimental and analytical data, the development of tools for the prediction of properties by a simple regression method is described. Furthermore, the suitability of group contribution modelling is investigated for OMDAE compounds.

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Synthesis of tailored oxymethylene ether (OME) fuels via transacetalization reactions

The need to arrest the continued environmental contamination and degradation associated with the consumption of fossil-based fuels has continued to serve as an impetus for the increased utilization of renewable fuels. The demand for biodiesel has continued to escalate in the past few decades due to urbanization, industrialization, and stringent government policies in favor of renewable fuels for diverse applications. One of the strategies for ensuring the intensification, commercialization, and increased utilization of biodiesel is the adaptation of reactor technologies, especially tubular reactors. The current study reviewed the deployment of different types and configurations of tubular reactors for the acceleration of biodiesel production. The feedstocks, catalysts, conversion techniques, and modes of biodiesel conversion by reactor technologies are highlighted. The peculiarities, applications, merits, drawbacks, and instances of biodiesel synthesis through a packed bed, fluidized bed, trickle bed, oscillatory flow, and micro-channel tubular reactor technologies are discussed to facilitate a better comprehension of the mechanisms behind the technology. Indeed, the deployment of the transesterification technique in tubular reactor technologies will ensure the ecofriendly, low-cost, and large-scale production of biodiesel, a high product yield, and will generate high-quality biodiesel. The outcome of this study will enrich scholarship and stimulate a renewed interest in the application of tubular reactors for large-scale biodiesel production among biodiesel refiners and other stakeholders. Going forward, the use of innovative technologies such as robotics, machine learning, smart metering, artificial intelligent, and other modeling tools should be deployed to monitor reactor technologies for biodiesel production.

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Application of Tubular Reactor Technologies for the Acceleration of Biodiesel Production

In this work the oxidative degradation of the synthetic fuel oxymethylene dimethyl ether was investigated. The main focus of this work are the degradation kinetics of oxymethylene dimethyl ether (OME) under atmospheric conditions with a focus on storage stability. It was found that hydroperoxides have a detrimental effect on the oxidation stability of the fuel. The antioxidant butylated hydroxytoluene (BHT) inhibited the degradation and lead to a higher oxidation stability. The activation energy of the degradation was measured and was found to be similar to that of the degradation of polyoxymethylene (POM). The degradation products of OME were mainly formaldehyde, methanol and formates. Side products were found to be carbonates and formic acid. These findings indicate that the oxidative degradation mechanisms of OME are closely related to those of the polymer POM.

Investigation of the Oxidative Degradation of the Synthetic Fuel Oxymethylene Dimethyl Ether

Determination of formaldehyde using a novel Pt-doped nano-sized sensitive material: Operating conditions optimization by response surface method.

Characterization of Residence Time Distribution in a Plug Flow Reactor

In this study, the formaldehyde content in the synthetic fuel oxymethylene dimethyl ether (OME) was measured with three different methods. The formaldehyde concentration was below 1000 mg/L. Only t...

Voltammetric Determination of Formaldehyde at Low Concentrations in the Synthetic Fuel Oxymethylene Dimethyl Ether

In Dynamic Process Intensification (DPI) a more economic operation compared to a steady state is achieved by blending the product of multiple operating states. In our study we present a systematic approach for the determination of these operating states for reactive distillation processes. Furthermore a closed loop control scheme is presented and validated with a dynamic simulation. As DPI has already been shown to be feasible for the reactive distillation of dimethyl ether from methanol, it was used as the first case study. The combined reboiler and condenser duty is reduced by 4.2% compared to the optimal operating point without DPI. The time average methanol conversion and the product purity remain unchanged compared to the optimal steady state. It is demonstrated that the proposed closed loop control scheme ensures stable operation in the event of disturbances up to 10% to the column feed flow, while maintaining the characteristics of DPI. The reactive distillation of methyl acetate from methanol and acetic acid is used as a second case study, since extensive literature data are available for such an analysis. It is demonstrated that DPI is infeasible for this process and the column should be operated in the optimal steady state. 

Insights into Dynamic Process Intensification for reactive distillation columns

Oxymethylenether (OME) ist ein synthetischer Dieselkraftstoff. Der Kraftstoff verbrennt rusfrei und hat eine hohe Cetanzahl. OME verfugt somit uber vorteilhafte Verbrennungseigenschaften. In dieser Arbeit wird der Aufbau und der aktuelle Stand der OME-Spezifikation vorgestellt. Die Bedeutung der Parameter ‘Cetanzahl’, ‘Flammpunkt’, ‘Gefrierpunkt’ und ‘Oxidationsstabilitat’ fur OME als Kraftstoff werden erlautert. Diese Parameter lassen sich in der Produktion durch destillative Abtrennung und Recycling der kurzkettigen OME1-2 und der langkettigen OME-Komponenten OME5-6 auf einfache Weise einhalten.

Innokentij Bogatykh

Papers

Characterization of Residence Time Distribution in a Plug Flow Reactor

Investigation of the Oxidative Degradation of the Synthetic Fuel Oxymethylene Dimethyl Ether

Voltammetric Determination of Formaldehyde at Low Concentrations in the Synthetic Fuel Oxymethylene Dimethyl Ether

Insights into Dynamic Process Intensification for reactive distillation columns

Fahrplan zu einer OME-Spezifikation (Roadmap to an OME specification)