Cellulose reaction temperature

Zinc chloride is a Lewis acid catalyst that promotes cellulose esterification. However, because of the large quantities required, this type of catalyst would be uneconomical for commercial use. Other compounds such as titanium alkoxides, eg, tetrabutoxytitanium (80), sulfate salts containing cadmium, aluminum, and ammonium ions (81), sulfamic acid, and ammonium sulfate (82) have been reported as catalysts for cellulose acetate production. In general, they require reaction temperatures above 50°C for complete esterification. Relatively small amounts (<0.5%) of sulfuric acid combined with phosphoric acid (83), sulfonic acids, eg, methanesulfonic, or alkyl phosphites (84) have been reported as good acetylation catalysts, especially at reaction temperatures above 90°C. 

Manufacture. Ethyl chloride undergoes reaction with alkah cellulose in high pressure nickel-clad autoclaves. A large excess of sodium hydroxide and ethyl chloride and high reaction temperatures (up to 140°C) are needed to drive the reaction to the desked high DS values (>2.0). In the absence of a diluent, reaction efficiencies in ethyl chloride range between 20 and 30%, the majority of the rest being consumed to ethanol and diethyl ether by-products. 

At first glance, the HRC scheme appears simple the polymer is activated, dissolved, and then submitted to derivatization. hi a few cases, polymer activation and dissolution is achieved in a single step. This simplicity, however, is deceptive as can be deduced from the following experimental observations In many cases, provided that the ratio of derivatizing agent/AGU employed is stoichiometric, the targeted DS is not achieved the reaction conditions required (especially reaction temperature and time) depend on the structural characteristics of cellulose, especially its DP, purity (in terms of a-cellulose content), and Ic. Therefore, it is relevant to discuss the above-mentioned steps separately in order to understand their relative importance to ester formation, as well as the reasons for dependence of reaction conditions on cellulose structural features. 

The TGA system was a Perkin-Elmer TGS-2 thermobalance with System 4 controller. Sample mass was 2 to 4 mgs with a N2 flow of 30 cc/min. Samples were initially held at 110°C for 10 minutes to remove moisture and residual air, then heated at a rate of 150°C/min to the desired temperature set by the controller. TGA data from the initial four minutes once the target pyrolysis temperature was reached was not used to calculate rate constants in order to avoid temperature lag complications. Reaction temperature remained steady and was within 2°C of the desired temperature. The actual observed pyrolysis temperature was used to calculate activation parameters. The dimensionless "weight/mass" Me was calculated using Equation 1. Instead of calculating Mr by extrapolation of the isothermal plot to infinity, Mr was determined by heating each sample/additive to 550°C under N2. This method was used because cellulose TGA rates have been shown to follow Arrhenius plots (4,8,10-12,15,16,19,23,26,31). Thus, Mr at infinity should be the same regardless of the isothermal pyrolysis temperature. A few duplicate runs were made to insure that the results were reproducible and not affected by sample size and/or mass. The Me values were calculated at 4-minute intervals to give 14 data points per run. These values were then used to... 

A cooler-burning pyrotechnic composition based on cellulose nitrate and guanidine nitrate has been developed which produces reaction temperatures of less than 500 °C, thus causing less destruction of the dye. 

Pacsu and coworkers144 have reported the preparation of the sodium alcoholatc of cellulose by treating either cotton or viscose rayon with either sodium methoxide or sodium 1-butoxide in anhydrous alcoholic media, at temperatures ranging from 25 to 120°. No proof of formation of alcoholate was offered. However, there is little reason to doubt its occurrence at the higher reaction temperatures. The ratio of sodium to D-glucose... 

The first section covers the chemistry of cellulose solutions in an amine N-oxide solvent (NMMO), the so-called Lyocell chemistry, as encountered in the industrial production of cellulosic Lyocell material. The system is characterized by high reaction temperatures, the presence of a strong oxidant and high complexity by multiple (homolytic and heterolytic) parallel reactions. Trapping was used to address the questions that reactive intermediates are present in Lyocell solutions and are responsible for the observed side-reactions and degradation processes of both solvent and solute. 

Figure 8. Effect of reaction temperature on the yield of copolymer in the pMMA-grafted dicarboxylcellulose using a Pyrex tube. Conditions cellulose, 0.3 g HsO, 10 mL. Key [cellulose COOH content (mmol/100 g)] O, 6.8 A, 18.1 0, 55.0. Key (reaction time) open mark, 1 h half closed mark, 1.4 h.

Other studies have shown that in the thermal treatment of cellulose at temperatures below 300 °C, the rate of weight loss can be accelerated by oxidation reactions such as the degradation of cellulose by atmospheric oxygen. When cotton cellulose was heated at 190 °C for 50 h, carboxyl and carbonyl groups formed at a linear rate. When rates of glycosidic bond scission at 170 °C in nitrogen and in air were compared, the rate in nitrogen was close to one-half of the rate in air (30). 

If the reaction time of the amount of hypophosphorous add are increased, the phosphorus content of the cellulose hyfxiphosphites will be increased. When the reaction temperature is raised from C,... 

Gasification assisted with partial oxidation is effective for cellulose gasification and a carbon gasification efficiency of 68% was obtained for nickel catalyst at a reaction temperature as low as 400 C and reaction time as short as 5 minutes. 

Minowa T, Fang Z. (1998) Hydrogen production from cellulose in hot compressed water using reduced nickel catalyst product distribution at different reaction temperatures. J. Chem. Eng. Jpn., 31, 488-91. 

In this paper, cellulose was reacted in hot-compressed water at different reaction temperatures and time using a reduced nickel catalyst. The aim of the study is to elucidate the overall reaction mechanism on the low temperature catalytic gasification and to get an insight into the hydrogen production. 

Fig. I Product distribution at different reaction temperatures cellulose water-soluble products -> gases (6)...

In our previous work, hydrolysis is played an important role at the first step of cellulose decomposition in hot-con ressed water without catalyst. In this study, the sugar, which is the hydrolyzed products of cellulose, was detected at low reaction temperature of 260 and 280 °C, and its concentration was about 40% in the water-soluble products. This means that hydrolysis also plays an important role for gasification with the nickel catalyst, and the obtained sugar can decomposed quickly to non-sugar products. 

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