Is the Liquid-Phase H2O2-Based Ethylene Oxide Process More Economical and Greener Than the Gas-Phase O2-Based Silver-Catalyzed Process?

Molecular Structure Effect on the Epoxidation of 1-Butene and Isobutene on the Titanium Silicate Catalyst under Transient Conditions in a Trickle Bed Reactor

Epoxidation of two butane isomers (1-butene and isobutene) on the commercial titanium silicate (TS-1) catalyst was studied in a laboratory-scale trickle bed reactor. The transient step response technique was used as the main tool in the investigation. The transient responses revealed different dynamics of product formation in continuous operation. The study of isomers showed the impact of the molecular structure on the transient and stationary states of the system. The four-carbon chain present in 1-butene displayed a dynamic behavior with a prominent maximum of the conversion as a function of time-on-stream. On the contrary, the behavior of isobutene was displayed to be closer to ethene and propene under similar conditions reaching a steady state after ca. 2 h. The structure of the epoxide was an important factor in order to achieve a high epoxide selectivity. In isobutene epoxidation, the primary product 1,2-epoxy-2-methylpropane was highly reactive, giving a spectrum of parallelly formed byproducts. Therefore, the selectivity of the epoxide from isobutene was limited to ca. 70%. In the epoxidation of 1-butene, 1,2-epoxybutane was displayed to be a highly stable product with a selectivity close to 99%. Based on the transient and stationary data, a reaction mechanism was proposed for the epoxidation and ring-opening reactions present in the system.

Electrochemical Manufacturing Routes for Organic Chemical Commodities

Electrochemical synthesis of organic chemical commodities provides an alternative to conventional thermochemical manufacturing and enables the direct use of renewable electricity to reduce greenhouse gas emissions from the chemical industry. We discuss electrochemical synthesis approaches that use abundant carbon feedstocks for the production of the largest petrochemical precursors and basic organic chemical products: light olefins, olefin oxidation derivatives, aromatics, and methanol. First, we identify feasible routes for the electrochemical production of each commodity while considering the reaction thermodynamics, available feedstocks, and competing thermochemical processes. Next, we summarize successful catalysis and reaction engineering approaches to overcome technological challenges that prevent electrochemical routes from operating at high production rates, selectivity, stability, and energy conversion efficiency. Finally, we provide an outlook on the strategies that must be implemented to achieve large-scale electrochemical manufacturing of major organic chemical commodities.

CO2 free production of ethylene oxide via liquid phase epoxidation of ethylene using niobium oxide incorporated mesoporous silica material as the catalyst

Ethylene Oxide (EO) is an essential raw material used in various consumer products like different glycol derivatives, ethoxylates, and polymers. We hydrothermally synthesize niobium oxide incorporated with mesoporous silica material (Nb/MSM), an efficient catalyst for CO₂ free-ethylene oxide (EO) production via partial oxidation of ethylene. The structural properties of Nb/MSM catalysts were characterized using XRD, TEM, and N₂ adsorption-desorption. The catalytic activity of synthesized materials in liquid phase epoxidation (LPE) of ethylene was evaluated in the presence of peracetic acid (PAA) as an oxidant to avoid the production of CO₂ and also minimize metal leaching. GC chromatography was used to investigate the successful production of EO, and a peak with a retention time (RT) of 9.01 min served as confirmation. Various reaction parameters viz. temperature, catalyst concentration, ethylene to PAA molar ratio, and solvent effect were investigated in order to optimize the reaction conditions for enhancing the ethylene conversion and selectivity for EO production. By this approach, the challenges of greenhouse gas production and metal leaching were addressed which were associated with previously reported catalysts.

Plant-Wide Modeling and Economic Analysis of Monoethylene Glycol Production

Monoethylene glycol (MEG) is used to produce polyester fibers and polyethylene terephthalate resins. It is also utilized in antifreeze, pharmaceuticals, and cosmetics applications. In this research, we consider the development of a novel process plant that produces MEG from ethylene. The proposed ethylene-to-ethylene oxide (EO) plant is integrated with an EO-to-MEG plant to reduce utility costs and recover high-value products. Energy-saving opportunities are analyzed via heat integration tools. Furthermore, a multitube glycol reactor is used in conjunction with a novel MTO catalyst in the ethylene-to-EO reactor. Our results demonstrate that the integrated EO/EG plant produces ethylene glycols with that same purity and product recovery as conventional designs. A comparative economic assessment based on a 200,000 t/y plant indicates that process integration techniques can reduce costs significantly.

Toward Replacing Ethylene Oxide in a Sustainable World: Glycolaldehyde as a Bio-Based C2 Platform Molecule

Fossil-based platform molecules such as ethylene and ethylene oxide currently serve as the primary feedstock for the C₂ -based chemical industry. However, in the search for a more sustainable chemical industry, fossil-based resources may preferentially be replaced by renewable alternatives, provided there is realistic economic feasibility. This Review compares and critically discusses several production routes toward bio-based structural analogues of ethylene oxide and the required adaptations for their implementation in state-of-the-art C₂ -based chemical processes. For example, glycolaldehyde, a structural analogue obtainable from carbohydrates by atom-economic retro-aldol reactions, may replace ethylene oxide's leading role. This alternative chemical route may not only allow the carbon footprint of conventional chemicals production to be lowered, but the introduction of a bio-based pathway may also contribute to safer production processes. Where possible, challenges, drawbacks, and prospects are highlighted.

Recent Advances in Facile Liquid Phase Epoxidation of Light Olefins over Heterogeneous Molybdenum Catalysts

Molybdenum complexes are versatile and efficient for liquid phase olefin epoxidation reactions. Rational design of catalysts is critical to achieve high atom efficiency during epoxidation processes. Although liquid phase epoxidation has been a popular topic for decades, three key issues, (a) rational control of morphology of molybdenum nanoparticles, (b) manipulating metal-support interaction and (c) altering electronic configuration at molybdenum center remains unsolved in this area. Therefore, in this paper, we have critically revised recent research progress on heterogeneous molybdenum catalysts for facile liquid phase olefin epoxidation in terms of catalyst synthesis, surface characterization, catalytic performance and structure-function relationship. Furthermore, plausible reaction mechanisms will be systematically discussed with the aim to provide insights into fundamental understanding on novel epoxidation chemistry.

Lignocellulosic biomass: a sustainable platform for the production of bio-based chemicals and polymers

The ongoing research activities in the field of lignocellulosic biomass for production of value-added chemicals and polymers that can be utilized to replace petroleum-based materials are reviewed.

Towards highly selective ethylene epoxidation catalysts using hydrogen peroxide and tungsten- or niobium-incorporated mesoporous silicate (KIT-6)

Nb- and W-KIT-6 materials display significant ethylene epoxidation activity with H₂O₂ as the oxidant at mild temperatures that eliminate substrate burning.