Regional  Research  Grant  Quarterly  Reports    

 

 

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Microemulsions  for  Enhanced  Biomass  Pretreatment    Recipient Organization: North Carolina State University Principal Investigator: Orlando Rojas Project Location: Raleigh, North Carolina Reporting Period: February 1, 2010 to December 31, 2010 Date of Report: April 16, 2011 Written by: Orlando J. Rojas 1. Planned Activities:

1.1. Development of SOW(Surfactant-Oil-Water) systems Resources: Oils, water, surfactants, standard bench and pilot-scale equipment, viscometry, rheometry, turbidimetry and tensiometry. Surface and interfacial tension. Phase behavior scans Performance metrics: The formulations are created. Emulsion stability, viscosity and drop size will be evaluated and best conditions of use analyzed.

1.2. Application against biomass samples and measurements Resources: Same as work task 1 above plus mass balances Performance metrics: How well does it penetrate the lignocelluloses matrix? Does it work better on one type of matrix than another? 1.3. Evaluate effects of microemulsion treatments on the capillary nature and swelling of cellulosic substrates Resources: Weight gain (water retention tests); solute exclusion (with very-high-mass dextrans); fluid uptake (streaming current titrations of supernatant solution, diffusion tritiated water) Performance metrics:  Are important changes in lignocellulose capillary structure produced? To what extent the swelling of the lignocellulose matrix is affected by different SOW formulations?

2. Actual Accomplishments:

Mr. Carlos Carrillo was hired as a graduate student to carry out the experimental work in this project. He is a chemical engineer with excellent experience in emulsion formulation and therefore in his first semester he started to work on the project very actively. All supplies and materials required in this phase of the project were acquired. Weekly meetings were held to discuss the experimental work. Different microemulsion formulations were prepared. For these preliminary experiments we are studying one-phase systems with excess of water as well as systems with equal amounts of water and oil. In order to illustrate the different formulations that are being tested we employ the Winsor phase diagrams (Figure1)

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Figure 1: Winsor phase diagram for Surfactant-Oil-Water Systems (SOW) The main differences in the Winsor type can be illustrated by the actual phases observed in test tubes (see Figure 2)

Figure 2: Test tubes indicating the location of the surfactant (blue color) in the SOW system. IN our case the formulation variable used was salinity (increases from left to right). In Winsor Type I (WI) the surfactant has more affinity with the water phase; in Winsor Type II (WII) the surfactant has more affinity with the oil phase. Finally, in Winsor Type III (WIII) system the surfactant has equal affinity with both the water and oil phases. The formulations scans that we designed can be illustrated in Figure 3 which indicate the change in the ternary diagrams for SOW systems (see changes in the partition (tie) lines) as the salt concentration is increased (left to right).

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Figure 3: Illustrative summary of ternary diagram and component distribution with changes in the formulation variable (salinity). The equivalent alkane carbon number (EACN) of the chosen oil (limonene) was determined. This was done by locating the optimum formulation which occurs for the NaCl concentration where the amounts of water and oil in the microemulsion are the same (WIII system). We used the SAD (Surfactant Affinity Difference) approximation to calculate the EACN by using reference oil, of known ACN values:

Where the sub index “2” indicated limonene and sub-index “1” indicate reference oil (heptane in the present case). The EACN for limonene resulted to be 8.7. This quantification will be important as we will try to study wood impregnation by using phenomenological approaches based on the SAD theory. Several different formulations have been tested. A typical example is as follow: Oil : Limonene Surfactant 1: Sodium Dodecyl Sulfate (Anionic) Surfactant 2: Tween 80 (No ionic) Co – surfactant: 1 - Pentanol Electrolyte: Sodium Chloride

As far as the composition variable we used a WOR (water to oil ratio) of 1 and various concentrations of the components were used. The experimental results fitted quite well the predictions of Winsor, according to the scans shown in Figure 4.

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Figure 4: Experimental results for salinity scans in the case of two different SOW systems. Many others have been developed and the two presented here are used just as illustration of transitions WI-WIII-WII (see Figure 2). Emulsion stability, viscosity and drop size are being evaluated and best conditions of use analyzed. Concurrent with the formulation work we developed a new method to determine wood impregnation by using the Cahn balance. This method has allowed us to determine on-line and real time emulsion pick up by samples of wood. The method consists in the measurement of surface tension and buoyancy forces which are analyzed and a chart with the mass gain can be produced. We prepared microemulsion according to the concentration of microemulsion phases for systems Winsor I, II and III, characterized the microemulsions, impregnated wood samples and determined the rate of flooding. A detailed report will be provided in the next reporting period in the form of a manuscript which is being drafted.

3. Explanation of Variance:

No variance in plans and accomplished are to be noted. The project is following its course as initially planned.  Efforts noted in the area of solute exclusion (with very-high-mass dextrans) and fluid uptake (streaming current titrations of supernatant solution, diffusion tritiated water) are to be performed after we optimize the emulsion systems.

4. Plans for Next Quarter:

• Study of effect of variables (pH, osmolality, temperature) on the penetration profile • Continue generating flooding curves and select best performance conditions. • Analysis of biomass crystallinity and pore volume before and after the impregnation. • X-ray diffractometer, Solid-state 13C NMR, DSC (differential scanning calorimeter). • Analysis of change in lignin content and structure: NMR spectrometer, lignin assay.

5. Budget:

According to the MyPortal reporting system in NC State the following expenses and r emaining funds can be listed (rounded off):

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a. Funds Expended to Date (End of Reporting Period): 16,000 (salary), 2500 (fringes), 1,500 (travel), 2,600 (fixed charges and supplies), student tuitions (10,700).

b. Remaining Balance of Funds: 83,000 (salaries), 13,100 (fringes), 29,000 (supplies and materials), travel (10,000), 23,000 (services), 19,000 (student aid and tuition).

6. Patents: No patent has been filed

7. Publications / Presentations:

Weekly internal project presentations..

Seminar within the department delivered by Carlos Carrillo.

“Complex Fluids in Wood Impregnation and Deconstruction”, Dept. of Forest Products Technology, Aalto University, June 9, 2010 (Rojas).

Attended invited talk on “Surface chemistry in profiling biomass conversion “ in the meeting “Frontiers in Biorefining – Biobased Products from Renewable Carbon” , St. Simons Island, GA, October 19-22, 2010 (Organized by UT Sun Grant program)