A Versatile Equilibrium Method for the Synthesis of High-Strength, Ladder-like Polyphenylsilsesquioxanes with Finely Tunable Molecular Parameters

A versatile equilibrium method for synthesizing ladder-like polyphenylsilsesquioxanes (L-PPSQs) with various molecular weights (from 4 to 500 kDa) in liquid ammonia was developed. The effect of diverse parameters, such as temperature, monomer concentration, reaction time, addition or removal of water from the reaction medium, on the polycondensation process was determined. The molecular weight characteristics and structure of the L-PPSQ elements obtained were determined by GPC, 1H, 29Si NMR, IR spectroscopy, viscometry, and PXRD methods. The physicochemical properties of L-PPSQs were determined by TGA and mechanical analyses.

Preparation, Characterization and Application of Amorphized Cellulose—A Review

This review describes the methods of cellulose amorphization, such as dry grinding, mercerization, treatment with liquid ammonia, swelling in solvents, regeneration from solutions, etc. In addition, the main characteristics and applications of amorphized celluloses are discussed. An optimal method for preparing completely amorphous cellulose (CAC) via the treatment of original cellulose material with a cold NaOH/Urea-solvent at the solvent to cellulose ratio R ≥ 5 is proposed. Structural studies show that amorphous cellulose contains mesomorphous clusters with a size of 1.85 nm and specific gravity of 1.49 g/cm3. Furthermore, each such cluster consists of about five glucopyranose layers with an average interlayer spacing of 0.45 nm. Amorphous cellulose is characterized by increased hydrophilicity, reactivity, and enzymatic digestibility. Due to its amorphous structure, the CAC can be used as a promising substrate for enzymatic hydrolysis to produce glucose, which can be applied in biotechnology for growing various microorganisms. In addition, the application of CAC in agriculture is described. A waste-free method for producing amorphous nanocellulose is considered, and the main applications of nanosized amorphous cellulose are discussed.

Fire and Explosion Hazard during Depressurization of Equipment with Ammonia

The statistics of fires and explosions of ammonia in the sphere of its circulation (production, storage, use) indicate the relevance of studies aimed at preventing emergency situations, localization, and elimination of accidents consequences. Equally important are studies on the development of assessments of accidents consequences associated with the release and spillage of ammonia from the equipment in various aggregate state. When ammonia is released, the resulting mixture of the product with air can vary in density from the formation of gas-air clouds with a density below the air density to buoyancy and excess air density, depending on the release conditions (pressure and temperature in the equipment; the sizes of the hole through which ammonia enters the surrounding space; the location of the hole in the equipment (gas or liquid phase). When the liquid ammonia leaks out, the spills are formed, from the surface of which the product evaporates especially rapidly in the first moments after the spill. Based on the computational and analytical studies, the design schemes and formulas were proposed for determining the parameters of the explosion: excess pressure and impulse of the undisturbed (incident) and reflected from the obstacles of the blast wave, as well as the nature of the destruction depending on the distance from the epicenter of the explosion, caused by the depressurization of equipment with ammonia. An accident scenario is considered, according to which the ammonia with a mass of 100 kg, when depressurizing, breaks out from the equipment of an industrial refrigerator. Ammonia vapors mix with the air to form a cloud that ignites and explodes. As an example, the overpressure and impulse during explosion of ammonia at a distance of 30 m from the epicenter of the explosion were determined. According to the empirical formula for estimating the distances from the epicenter of the explosion to a given place, the levels of the consequences of building destruction (complete, medium, small, moderate damage) can be established.

Pretreatment of Corn Stover Using an Extremely Low-Liquid Ammonia (ELLA) Method for the Effective Utilization of Sugars in Simultaneous Saccharification and Fermentation (SSF) of Ethanol

Extremely low-liquid ammonia (ELLA) pretreatment using aqueous ammonia was investigated in order to enhance the enzymatic saccharification of corn stover and subsequent ethanol production. In this study, corn stover was treated with an aqueous ammonia solution at different ammonia loading rates (0.1, 0.2, and 0.3 g NH3/g biomass) and various liquid-to-solid (L/S) ratios (0.55, 1.12, and 2.5). The ELLA pretreatment was conducted at elevated temperatures (90–150 °C) for an extended period (24–120 h). Thereafter, the pretreated material was saccharified by enzyme digestion and subjected to simultaneous saccharification and fermentation (SSF) tests. The effects of key parameters on both glucan digestibility and xylan digestibility were analyzed using analysis of variance (ANOVA). Under optimal pretreatment conditions (L/S = 2.5, 0.1 g-NH3/g-biomass, 150 °C), 81.2% glucan digestibility and 61.1% xylan digestibility were achieved. The highest ethanol yield achieved on the SSF tests was 85.4%. The ethanol concentration was 14.5 g/L at 96 h (pretreatment conditions: liquid-to-solid ratio (L/S) = 2.5, 0.1 g-NH3/g-biomass, 150 °C, 24 h. SSF conditions: microorganism Saccharomyces cerevisiae (D5A), 15 FPU/g-glucan, CTech2, 3% w/v glucan, 37 °C, 150 rpm).