Heiji Enomoto

Rapid and highly selective conversion of biomass into value-added products in hydrothermal conditions: chemistry of acid/base-catalysed and oxidation reactions

An overview of recent advances in research on selective conversion of carbohydrates into products with hydrothermal chemistry is given. Conversion methods tend to use acid- or base-catalysed reactions and oxidation reactions. Conversion products that can be selectively produced include acetic acid, formic acid, lactic acid, levulinic acid, 5-hydroxymethyl-2-furaldehyde (HMF) and 2-furaldehyde (2-FA). Future conversion paths and possible new products that can be formed with hydrothermal chemistry include aldol/reverse condensation, dehydration, benzilic acid rearrangement, keto-enol tautomerization, Lobry de Bruyn–Alberda van Ekenstein transformation and oxidation reactions.

Hydrothermal conversion of carbohydrate biomass into formic acid at mild temperatures

The production of formic acid or formate salts by hydrothermal oxidation of glucose, a model compound of carbohydrate biomass, was investigated in the presence and absence of alkali using a batch reactor with H2O2 oxidant. Results showed that glucose was converted into formate salts with an excellent yield of 75% at a mild temperature of 250 °C in the presence of alkali. The results should be helpful to facilitate studies for developing a new green process for the conversion of carbohydrate biomass into formic acid, which can be a potential intermediate for fuels, as well as other value-added products.

Kinetics of oxidation of food wastes with H2O2 in supercritical water

Abstract In this study, supercritical water oxidation (SCWO) of carrots and beef suet was carried out in a batch reactor system with an H 2 O 2 oxidant, at a temperature between 400 and 450°C and reaction times from 10 s to 10 min. The results showed that the oxidative decomposition of carrots and beef suet proceeded rapidly and a high total organic carbon (TOC) decomposition of up to 97.5% was obtained within 3 min at 420°C for carrots and within 5 min at 450°C for beef suet when there was a sufficient supply of oxygen. It was also found that the oxidation reaction for both carrots and beef suet might be separated into a fast reaction at the early stage and a slow reaction at the later stage. In the later stage following the early stage reaction, acetic acid, which is a fairly stable product of the early stage reaction, is the reactant and the rate of overall oxidation reaction for complete decomposition is dominated by the later stage reaction. Global kinetic analysis based on the model described above showed that the early stage oxidative reaction of beef suet could be considered as a first-order reaction with respect to the concentration of organic carbon. The activation energy was 37.3 kJ mol −1 . Oxidation of acetic acid could also be expressed as a first-order reaction, and the activation energy was 106.5 kJ mol −1 . The early stage oxidation reaction of carrots was too fast to be analyzed. On the basis of intermediate products identified, reaction pathways were discussed. For carrots, polysaccharides may first be hydrolyzed to glucose and then oxidation of the glucose may take place. For beef suet, glyceride is first hydrolyzed to glycerin and carboxylic acids corresponding to the components of glyceride, followed by consecutive reactions for oxidative decomposition.

Characteristics of polyethylene cracking in supercritical water compared to thermal cracking

Polyethylene (PE) cracking obtained from hydrothermal experiment with supercritical water was compared to the water-free thermal cracking. Degradation of polymers was slow in supercritical water cracking and the yield of oil, because coke production was suppressed, was higher. In a comparison of the intermediate products during degradation between supercritical water and thermal crackings, the results of the experiments using n-dodecane (model intermediate of n-alkanes) and 1-dodecene (model intermediate of l-alkenes) showed significant differences in product species and cracking rate for l-dodecene but the results were not significant for n-dodecane. In supercritical water cracking, the conversion of l-dodecene was slow and the intramolecular transfer of double bonds occurred easily compared to thermal cracking. A difference in the reaction mechanism is supposed to explain the different cracking rates and products. The main products in the aqueous phase after supercritical water cracking were 2-propanol and 2-butanol (secondary alcohols) and 2-propanone and 2-butanone (ketones). It was confirmed that, in supercritical water, lower l-alkenes are hydrated into secondary alcohols, as shown by the hydration of propylene into 2-propanol. This 2-propanol is further oxidized into 2-propanone. It is plausible that the hydrogen, which is liberated into supercritical water, participates in PE cracking.

Some aspects in testing and assessment of metal dust explosions

Abstract The dust explosion committee of the Association of Powder Process Industry and Engineering, Japan recently established two testing standards for dust explosions. In the investigations for the standardization, many experimental data have been obtained for the dusts currently used in Japanese industries. Data for zirconium, tantalum and silicone dusts are presented to discuss the use of test methods, which have been accepted internationally. The test methods for dust explosions have to consider a variety of kinds and forms of dusts to be tested.

A new process for producing calcium acetate from vegetable wastes for use as an environmentally friendly deicer

A new process for producing calcium acetate, a non-corrosive deicer, is proposed. The process consists of a two-step continuous-flow hydrothermal conversion of vegetable wastes into acetic acid and the production of calcium acetate, followed by the separation and condensation of the product. The experiments for acetic acid production showed that there were almost no significant differences in acetic acid yields for the five different kinds of vegetables selected for the batch experiments or for their mixture in batch and continuous-flow experiments. Electrodialysis was chosen as a satisfactory method for separating and condensing the calcium acetate produced from the acetic acid solution obtained from the vegetable wastes. After purification by reverse-osmosis, the residual, depleted acid solution could be safely discharged. The calculation of the carbon balance for the proposed process showed that 21.3% of the TOC from vegetable wastes could be used as calcium/magnesium acetate (CMA) and over 22% as an environmentally friendly deicer.

Formic acid production from carbohydrates biomass by hydrothermal reaction

The formation of formic acid or formate salts by hydrothermal oxidation of model biomass materials (glucose, starch and cellulose) was investigated. All experiments were conducted in a batch reactor, made of SUS 316 tubing, providing an internal volume of 5.7 cm3. A 30 wt% hydrogen peroxide aqueous solution was used as an oxidant. The experiments were carried out with temperature of 250°C, reaction time varying from 0.5 min to 5 min, H2O2 supply of 240%, and alkaline concentration varying from 0 to 1.25 M. Similar to glucose, in the cases of the oxidation of hydrothermal starch and cellulose, the addition of alkaline can also improve the yield of formic acid. And the yield were glucose>starch> cellulose in cases of with or without of alkaline addition.

Chapter 15 Biotechnological approach for development of microbial enhanced oil recovery technique

Publisher Summary This chapter discusses microbial enhanced oil recovery (MEOR) as MEOR is one of the techniques expected to be both economically feasible and environmental friendly, while also considerably increasing oil production. The chapter also discusses the types of MEOR processes and the present stage of MEOR. Biotechnological tools for estimating the behavior of indigenous microbes in the reservoir, as well as injected microbes, were successfully developed. In the chapter, valuable data to demonstrate the MEOR effect were successfully collected, and the results obtained from this research support the theory that MEOR can effectively increase oil recovery. Though the results are seen in only a few cases yet at most, it is believed that this is an example of a successful application of MEOR to a broad range of reservoirs.

Oxidation of garbage in supercritical water

Abstract In the present study, 17 kinds of organic materials selected from groups of vegetable, meat, fat and fish as main components of garbage were oxidized with H2O2, using a batch reactor system under the condition of supercritical water, in order to treat organic wastes of high water content and low calorific value. It was found that they were easily oxidized, and remarkable influence of the kind of material in each group on the TOC decomposition was not recognized, but meats, fats and fishes, especially beef suet, were more difficult to be oxidized than vegetables. The residual intermediate product was acetic acid in reactions of one minute at 400°C for all materials. Based on this result, the rate expression for supercritical water oxidation of acetic acid was determined.

Recent development of standardization of testing methods for dust explosion in Japan

Abstract The Dust Explosion Committee of the Association of Powder Process Industry and Engineering (APPIE) of Japan has acted to establish the standard for the member of the Association. Two testing methods have been authorized by the Association. The methods are established to evaluate sensitivity and severity for dust explosion. The ignition sensitivity is evaluated by the minimum explosive dust cloud concentration. Tapping sieve equipment and a strictly-specified Hartmann-type explosion tube have been selected as the testing apparatus. The tapping sieve equipment is applied to measure the minimum explosive concentration by forming a dust cloud supplied from a sieve on the top of the explosion chamber. The Hartmann-type tube is used to investigate roughly whether the test powder is explosive or not. A lot of explosion tests had been carried out to standardize the equipment and evaluate the sensitivity. This APPIE standard is being revised. Along with the ISO standard for explosion severity, Research Institute of Industrial Safety, the Ministry of Labour published a Guide to Test Method for Explosion Pressure and Rate of Pressure Rise for Combustible Dusts in 1994. Based on this Guide, The APPIE Committee has made the draft for the member. These standards and drafts are aimed to be the Japanese Industrial Standard (JIS). No other similar standard exists in Japan. In the present paper, technical data and explosion statistics which are the background of the APPIE standard for the ignition sensitivity are to be described.