N-Methylmorpholine N-oxide

About: N-Methylmorpholine N-oxide is a research topic. Over the lifetime, 187 publications have been published within this topic receiving 5251 citations. The topic is also known as: N-Methylmorpholine oxide & N-Methylmorpholine 4-oxide.

Formation and characterization of cellulose membranes from N-methylmorpholine-N-oxide solution

Abstract: Regenerated cellulose membranes have been raditionally manufactured using the viscose or the copper-ammonia process. Today, membranes made by this process are still used in many fields such as dialysis. However, there are some serious environmental problems inherent in the existing processing routes. The new N methylmorpholine-N-oxide (NMMO) process can over-come these disadvantages and provides membranes with improved mechanical properties. In the present work, cellulose membranes were successfully prepared from NMMO solution under various conditions. It was found that the cellulose concentration is a decisive factor in controlling the membrane permeation properties. For a given coagulation system, higher cellulose concentration leads to membranes with greater rejection of bovine serum albumin (BSA) and lower pure water flux. It was also found that both the degree of polymerization (DP) and the type of cellulose pulp have great effect on the morphology and permeation properties of the membrane support layer. With increasing NMMO concentration and temperature of the coagulation bath, the pure water flux increases while the rejection of BSA decreases; a result of the larger mean pore size formed during coagulation.

An Analysis of Lyocell Fiber Formation as a Melt–spinning Process

Abstract: In order to gain an understanding of the process of Lyocell fiber formation, the melting and solidification behaviors, heat capacity and density of cellulose N-methylmorpholine-N-oxide monohydrate (NMMO-MH) solutions were studied by differential scanning calorimetry (DSC) and dilatometry, and the diameter development of Lyocell fibers in the air gap was measured online. It was found that the Lyocell process can be considered as both a melt–spinning process in the air gap and a wet-spinning process in the coagulation bath. Cellulose chains in the solutions hindered the crystallization of NMMO-MH, and the melting point of the solutions decreased with increasing cellulose concentration. The density of cellulose NMMO-MH solutions decreased linearly with increasing temperature in the solid or the liquid state, and it increased with increasing cellulose concentration. The heat capacity of the solutions increased slightly with increasing temperature and concentration. The development of fiber diameter, the velocity gradient, and the gradient of the filaments in the air gap were limited to a short distance from the spinneret orifice. The position at which the velocity and the tensile stress gradient reached their maximum values moved closer to the spinneret orifice with increasing take-up speed.

Kinetic modeling of rapid enzymatic hydrolysis of crystalline cellulose after pretreatment by NMMO

Abstract: Pretreatment of cellulose with an industrial cellulosic solvent, N-methylmorpholine-N-oxide, showed promising results in increasing the rate of subsequent enzymatic hydrolysis. Cotton linter was used as high crystalline cellulose. After the pretreatment, the cellulose was almost completely hydrolyzed in less than 12 h, using low enzyme loading (15 FPU/g cellulose). The pretreatment significantly decreased the total crystallinity of cellulose from 7.1 to 3.3, and drastically increased the enzyme adsorption capacity of cellulose by approximately 42 times. A semi-mechanistic model was used to describe the relationship between the cellulose concentration and the enzyme loading. In this model, two reactions for heterogeneous reaction of cellulose to glucose and cellobiose, and a homogenous reaction for cellobiose conversion to glucose was incorporated. The Langmuir model was applied to model the adsorption of cellulase onto the treated cellulose. The competitive inhibition was also considered for the effects of sugar inhibition on the rate of enzymatic hydrolysis. The kinetic parameters of the model were estimated by experimental results and evaluated.