(669e) Cellulose Acetate Butyrate Prepared From Sugarcane Bagasse in Ionic Liquid

Energy crisis is a huge challenge that mankind will face up to today, The statistic made by the International Energy Agency (IEA) on oil resources based on the production rate and oil reserves estimated that the main fossil fuels??petroleum, gas and coal for humanbeings can be exploited for only 40, 50 and 240 years respectively. Since petroleum resources in China are relatively poor, domestic petroleum production can not meet with the demands. Pertinent institution predicts that in 2020, 60% of China's petroleum demand will depend on import, and petroleum deficiency has become an unavoidable worldwide problem. So there is a need to increase the effciency of the plentiful and regenerated biomass utilization in order to promote the continuable development of China.

The agricultural residues represent an abundant, inexpensive, and readily available source of renewable lignocellulosic biomass for the production of environmentally friendly industrial products and have received increasing attention. It usually contains more than 30% cellulose, and is of limited commercial value at present. Currently China produces around 700 million tons of agricultural straw annually, however, most of it is simply burnt in the fields, creating a significant local air pollution problem. Therefore, effective utilization of these commonly available by-products as a source for cellulose will offer significant benefits to the economy and the environment. In addition，the cost of harvesting, handling, storing and transporting biomass resources is relatively low in most developing countries than developed countries. During the last few decades, much effort has been devoted to increasing the utilization of the agriculture waste for several end uses.

Among the various agricultural crop residues, sugarcane bagasse (SB) is the most abundant agricultural material in Southern China. SB is a fibrous residue of cane stalks left over after the crushing and extraction of the juice from the sugarcane. Nowadays, most of the SB is burnt to generate energy for the mills, but even then there is a considerable amount of it still wasted. For this reason, several papers have been produced setting alternatives for recycling it. Since SB consists of approximately 50% cellulose, which makes it possible to use this residue by producing cellulose derivatives.

As we know that cellulose is the most abundant of all naturally occurring substances and widely used as a raw material in numerous industrial applications. However due to its high crystallinity, cellulose is insoluble in most of the traditional organic solvents, which limitate significantly its applicability at its original form. An alternative path for increasing the cellulose applicability is chemically modifying it by incorporating many kinds of chemical groups on the hydroxyl groups of the glycosidic units. According to this procedure, up to now several cellulose derivatives have already been sucessfully produced from sugarcane bagasse cellulose (SBC), as for example, cellulose phthalates, cellulose succinates, cellulose sulphate and so on.

Among cellulose derivatives, cellulose acetate butyrate (CAB) is one of the most important due to their multiple applications in the field of modern coatings, membranes, plastic, osmotic drug delivery and so on. The properties and practical applications of CAB depend on the butyryl content, which determines their compatibility with other plastics and resins, as well as their solubility in many solvents. CAB with relatively high butytyl content exhibited good solubility in organic solvents, while being more hydrophobic than CA. Therefore, it is recognized that the appearance of the mixed-cellulose ester provides the feasibility for improving the properties of cellulose esters.

Normally, CAB with full degree of substitute (DS) are prepared in heterogeneous medium, using excess of acetic anhydride and butyric anhydride in the presence of sulfuric acid as catalysis. CAB with a specific DS value lower than three can be obtained by hydrolysis. However, this method always results in the serious degradation of cellulose, uncontrollable structure of CAB and environmental pollution.

A major stimulation for the investigation of homogeneous paths for cellulose functionalization was the discovery of a variety of new solvents for cellulose with its extended supra-molecular structure. The interest in the derivatization of cellulose under homogeneous conditions resides mainly in the fact that it allows a more efficient control of the DS of the cellulose derivative through adjustment of the molar ratio of the derivatizing agent and cellulose. Moreover, the substituting groups can be introduced more regularly along the polymer chain and materials with well-defined characteristics can be produced using methods with good reproducibility

Up to now, several direct solvents are found suitable for chemical functionalization reactions of the cellulose. These solvents include N, N-dimethylacetamide(DMAc)/LiCl, dimethyl sulfoxide(DMSO)/tetrabuthlammonium fluoride trihydrate (TBAF) and some molten salt hydrate, such as LiClO4?3H2O, and LiSCN?2H2O. However, the drawbacks in the case of above solvent systems are toxicity, high cost, difficulty in solvents recovery, severe side-reaction, and instability during cellulose derivatization. At the same time, the cellulose esters reported in the literature are mostly the single-cellulose esters, such as CA;CP;CB and so on. While the mix-ester was only mentioned in DMAc/LiCl solvent system with few detail synthesis nor characteristic data.

Recently, room-temperature ionic liquids (ILs), being considered as green solvents, have been successfully used to dissolve and process cellulose. As a novel non-derivatizing cellulose solvent, ILs have also been found to be the promising reaction media for cellulose derivatization. The IL, 1-allyl-3-methylimidazolium chloride (AmimCl) has been used as reaction media for acylation of cellulose from both the high quality pulp and agriculture residue.

In this paper we are carrying out an experiment on synthesize CAB from SBC in AmimCl homogeneously. Preliminary experimental results shows that by a sequence of first adding butyric anhydride and then acetic anhydride in the cellulose/AmimCl solutions, the butyryl contents of the CAB prepare from SBC can reach as high as 46 wt %, and all the CAB sample can dissolve in acetone. While 1H NMR and FTIR spectra have been used to confirm the structure of CAB. Further researches such as the thermal stability, distribution of the substitution and viscosity are underway.