Synthesis of a Green Fuel Additive Over Cation Resins

Mechanistic exploration of CO2 conversion to dimethoxymethane (DMM) using transition metal (Co, Ru) catalysts: an energy span model

The conversion of CO₂ to DMM is an important transformation for various reasons. Co and Ru-based triphos catalysts have been investigated using density functional theory (DFT) calculations to understand the mechanistic pathways of the CO₂ to DMM conversion and the role of noble/non-noble metal-based catalysts. The reaction has been investigated sequentially through methylformate (MF) and methoxymethane (MM) intermediates as they are found to be important intermediates. For the hydrogenation of CO₂ and MF, the hydrogen sources such as H₂ and methanol have been investigated. The calculated reaction free energy barriers for all the possible pathways suggest that both hydrogen sources are important for the Co-triphos catalyst. However, in the case of the Ru-triphos catalyst, molecular H₂ is calculated to be the only hydrogen source. Various esterification and acetalization possibilities have also been explored to find the most favorable pathway for the conversion of CO₂ to DMM. We find that the hydride transfer to the CO₂ is the rate determining step (RDS) for the overall reaction. Our mechanistic investigation reveals that the metal center is the active part for the catalysis rather than the Brønsted acid and the redox triphos ligand plays an important role through the push-pull mechanism. The implemented microkinetic study shows that the reaction is also quite dependent on the concentration of the gaseous reactants and the rate constant increases exponentially above 363 K.

Combination of Theoretical and Experimental Insights into the Oxygenated Fuel Poly(oxymethylene) Dibutyl Ether from n-Butanol and Paraformaldehyde

Oxygenated fuel has the function of self-supplying oxygen during the combustion process, which can greatly improve emission performance and reduce diesel fuel soot production. In this paper, a novel oxygenated fuel poly(oxymethylene) dibutyl ether (PODBE _n ) is designed and synthesized through experiments in combination with density functional theory (DFT) calculation. The experimental results show that PODBE _n has the advantages of high cetane number (73.6), moderate density (868 kg/m³), and low condensation point (-72 °C). According to the DFT calculation results, the molecular (PODBE _n ) polarity index of different polymerization degrees is similar to the value of diesel and has good mutual solubility with diesel. Moreover, the mechanism of the entire path of synthesis is calculated at the M06-2X/6-311G(d,p) level of theory. The energetic profile reveals that the rate-determining step is the nucleophilic addition step with the highest barrier energy (TS1 = 21.59 kcal/mol). This work provides a feasible method to synthesize high-performance oxygenated fuel PODBE _n using NKC-9 ion-exchange resins.

Carbon Supported Phosphoric Acid Catalysts for Gas-Phase Synthesis of Diesel Additives

Abstract

Carbon supported phosphoric acid (H3PO4/C) was found to be a more productive catalyst for the gas-phase synthesis of the diesel fuel additive/substitute oxymethylene ethers (OME) as compared to benchmark zeolite catalysts. In this contribution, the performance of catalysts H3PO4/C and related H2PO4−/C and HPO42−/C materials in OME synthesis from methanol and formaldehyde is described.

Graphic Abstract

Synthesis of polyoxymethylene dimethyl ethers over different microporous and mesoporous zeolites: the effects of acidity and pore size

Polymethoxydimethyl ether (PODE_n) is an ideal blending component of diesel oil.

Novel polymeric acidic ionic liquids as green catalysts for the preparation of polyoxymethylene dimethyl ethers from the acetalation of methylal with trioxane

A series of micro–mesoporous polymeric acidic ionic liquids (PAILs) have been successfully synthesized and subsequently characterized using Fourier transform-infrared spectroscopy, N₂ adsorption–desorption isotherms, scanning electron microscopy and thermogravimetry. Furthermore, the catalytic performance of the synthesized PAILs was investigated for the acetalation of methylal (DMM₁) with 1,3,5-trioxane (TOX), micro–mesoporous PAILs copolymerized by divinylbenzene with cations and anions exhibited moderate to excellent catalytic activities for the acetalation. In particular, VIMBs–AMPs–DVB, with higher specific surface area (25.51 m² g⁻¹) and total pore volume (0.15 cm³ g⁻¹) displayed an elevated conversion of formaldehyde (82.2%) and selectivity for polyoxymethylene dimethyl ethers (CH₃O(CH₂O)_nCH₃; PODE_n or DMM_n) n = 3–8 (52.6%) at 130 °C, 3.0 MPa for 8 h. Moreover, the influence of various reaction parameters was investigated by employing VIMBs–AMPs–DVB as the catalyst and it demonstrated high thermal stability and easy recovery.

Polyoxymethylene dimethyl ethers were successfully synthesized from acetalation under the catalysis of novel polymeric acidic ionic liquids (PAILs). PAILs copolymerized by divinylbenzene with ILs displayed exceptional catalytic efficiencies.

Theoretical Studies of the Hydrogen Abstraction from Poly(oxymethylene) Dimethyl Ethers by O2 in Relation with Cetane Number Data

Poly(oxymethylene) dimethyl ethers (PODME _n , n = 2-6) are novel oxygenated compounds that can be used as promising candidates for new-generation fuels because of their excellent combustion performance. The oxidation of PODME _n (n = 2-6) is essential for the understanding of the combustion process. It is necessary to study the relationship between kinetic parameters and cetane number (CN) of PODME _n (n = 2-6). In order to predict initiation step rate constants for the oxidation of PODME _n (n = 2-6), quantum mechanical calculations are performed using M06-2X/6-311G(d,p) and B3LYP/6-311G(d,p) methods. Structural, energetic, thermodynamics, and kinetics of the automatic ignition process are assessed. The kinetic model based on the conventional transition state theory is used to calculate the initiation step reaction rate constants at 1000 K. In both M06-2X/6-311G(d,p) and B3LYP/6-311G(d,p) methods, the calculated rate constants of the hydrogen abstraction process have an excellent correlation with the experimental CN of PODME _n (n = 2-6). Our methodology presented here can be used to simulate chemical kinetics for other fuel additives.

Nature of Synergy between Brønsted and Lewis Acid Sites in Sn-Beta Zeolites for Polyoxymethylene Dimethyl Ethers Synthesis

The role of Lewis and Brønsted acid sites and their potential synergy remains ambiguous for the production of polyoxymethylene dimethyl ethers (OME), which are suitable as a Diesel substitute. Here, this synergistic effect was investigated by using a series of beta polymorph A (BEA) zeolites with various degrees of Brønsted and Lewis acidity. Lewis acidity was introduced in dealuminated zeolites by Sn grafting in dichloromethane. These sites were only active in paraformaldehyde decomposition, OME growth, and acetalization. The Brønsted acid sites arising from bridging hydroxyl groups were active for all reaction steps, and notably for trioxane ring-opening and dissociation to formaldehyde (FA), which did not occur on the Lewis acid sites. Presence of both Lewis and Brønsted acid sites led to a four-fold increase in turnover frequency and a significant decrease of byproduct formation compared with the parent zeolite during OME synthesis from dimethoxymethane and trioxane. The synergistic effect between both types of acid sites is explained by FA insertion on Lewis acid sites leading to OME growth. Interaction between tetrahedral Sn and the carbonyl group of FA resulted in an activated carbonyl bond, which was likely the initial step for insertion of FA into OME.

The Synergistic Effect of Acidic Properties and Channel Systems of Zeolites on the Synthesis of Polyoxymethylene Dimethyl Ethers from Dimethoxymethane and Trioxymethylene

A series of zeolites with different topology structures, including SAPO-34, SUZ-4, ZSM-5, USY, MOR, and beta, were used to synthesize polyoxymethylene dimethyl ethers (PODE_n) from dimethoxymethane (DMM) and trioxymethylene (TOM). The influence of acidic properties and channel systems were studied by activity evaluation, characterization, and theoretical calculation. The results confirmed that pore mouth diameter larger than a TOM molecule was an essential prerequisite for the synthesis of PODE_n over zeolites, and the synergistic effect between medium-strong Brønsted acid sites (Brønsted MAS) and the maximal space of zeolites available determined the catalytic performance of all studied zeolites. DMM and TOM were firstly decomposed into methoxymethoxy groups (MMZ) and monomer CH₂O over Brønsted MAS. Subsequently, the steric constraint of the maximum included sphere, with an appropriate size in zeolite channels, can promote the combination of CH₂O and MMZ to form transition species ZO(CH₂O)_nCH₃, which reacted with the methyl-end group to form PODE_n over Brønsted MAS. Moreover, the reaction temperature showed different effects on the product selectivity and distribution, which also mainly depends on the size of the maximum space available in zeolite channels.

Green chemical engineering in China

In China, the rapid development greatly promotes the national economic power and living standard but also inevitably brings a series of environmental problems. In order to resolve these problems fundamentally, Chinese scientists have been undertaking research in the area of green chemical engineering (GCE) for many years and achieved great progresses. In this paper, we reviewed the research progresses related to GCE in China and screened four typical topics related to the Chinese resources characteristics and environmental requirements, i.e. ionic liquids and their applications, biomass utilization and bio-based materials/products, green solvent-mediated extraction technologies, and cold plasmas for coal conversion. Afterwards, the perspectives and development tendencies of GCE were proposed, and the challenges which will be faced while developing available industrial technologies in China were mentioned.

Towards a Sustainable Synthesis of Oxymethylene Dimethyl Ether by Homogeneous Catalysis and Uptake of Molecular Formaldehyde

Oxymethylene dimethyl ethers (OME_n ; CH₃ (-OCH₂ -)_n O-CH₃ , n=3-5) are a novel class of sustainable synthetic fuels, which are of increasing interest due to their soot-free combustion. Herein a novel anhydrous OME_n synthesis route is presented. Catalyzed by trimethyloxonium salts, dimethoxymethane takes up monomeric gaseous formaldehyde instantaneously and forms high purity OME_n at temperatures of 25-30 °C. This new anhydrous approach using molecular formaldehyde and catalytic amounts of highly active trimethyloxonium salts represents a promising new step towards a sustainable formation of OME_n emanating from CO₂ and H₂ .

Describing oxymethylene ether synthesis based on the application of non-stoichiomsetric Gibbs minimisation

A naturally inspired non-Stochastic Global Optimiser is used to describe the synthesis of oxymethylene ethers.

Synthesis of polyoxymethylene dimethyl ethers catalyzed by sulfonic acid-functionalized mesoporous SBA-15

Sulfonic acid-functionalized mesoporous SBA-15 with different sulfur loading was synthesized and used to investigate the catalytic performance for PODE_n synthesis.

Poly(oxymethylene) dimethyl ether synthesis – a combined chemical equilibrium investigation towards an increasingly efficient and potentially sustainable synthetic route

Poly(oxymethylene) dimethyl ethers (denoted as OME) are potential sustainable energy carriers and platform chemicals.

Molecular size reforming of undersized and oversized polyoxymethylene dimethyl ethers

The equilibrium molecular size distribution of PODE_ncompounds followed the Schulz–Flory distribution and determined byM_eq.only.

Graphene oxide: an effective acid catalyst for the synthesis of polyoxymethylene dimethyl ethers from methanol and trioxymethylene

Graphene oxide as an acid carbocatalyst performs excellently in the synthesis of polyoxymethylene dimethyl ethers from methanol and trioxymethylene.

Synthesis of polyoxymethylene dimethyl ethers from methylal and trioxane catalyzed by Brønsted acid ionic liquids with different alkyl groups

The carbon chain length of ILs has effect on its catalytic activity and [C₆ImBS][HSO₄]shows the best catalytic performance.