Hydrolysis and Catalytic Oxidation of Cellulosic Materials J
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STRUCTURAL COMPONENTS OF VARIOUS CELLULOSIC MATERIALS R. F. NICKERSON2 AND J. A. HABRLEa Mellon Institute, Pittsburgh 13, Pa, The methods of a previous investigation are employed in a study of unmercerized and mercerized cottons, purified wood pulp, and high-tenacity viscose rayon. Estimates of so-called amorphous, meso-morphous, and crystalline components in these materials are derived. The amorphous (most disordered) component appears to hydrolyze readily and to have relatively high moisture affinity in comparison with the rest of the structure. It is found to be present in the following approximate amounts: unmercerized cotton, 3%; mercerized cotton, 7%; purified wood pulp, 3%; and high-tenacity viscose rayon, 8%. The distinctive hygroscopic and hydrolytic behavior of amorphous cellulose, as contrasted with the remaining accessible cellulose, may have significance in fiber structure and properties relations.
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HE structure of unsubstituted fibrous cellulosic materials may be regarded as a continuous network of submicroscopic crystalline and intercrystalline regions. The crystallites are believed to be shorter than cellulose mole,cules and, therefore, to represent highly ordered sections of a number of adjacent volecules while the intercrystalline matrix may consist of less wellordered sections. Few data are available on the proportions of ordered and disordered matter in various cellulosic materials, and even these data may depend upon the methods used to obtain them ( I ) . e A study recently reported from this laboratory indicated that the cellulose in purified cotton linters appears to exist in t h e e distinguishable states of organization. These states were designated as amorphous, mesomorphous, and crystalline, and were estimated to be present in amounts of 3,3, and 94%, respectively, by the use of a differential hydrolytic method (4). Comparable data on the proportions of these components in mercerized and unmercerized cottons, high-tenacity viscose rayon, and purified wood pulp ar*resented in this report. Amorphous cellulose in the linters was characterized by its highly hygroscopic nature and by a minimum of resistance to hydrolysis. It appeared to be completely hydrolysed by boiling in 2.5 molar hydrochloric acid for 4 minutes. Mesomorphous or transitional cellulose appeared to hydrolyze less readily and to be more heterogeneous, since it required an hour or more under the same conditions to be.comp1etely broken down; crystalline material exhibited high and uniform resistance to hydrolysis. I n the present work the assumption is made that the same time, temperature, and concentration conditions hold for the breakdown of corresponding parts of other materials. The behavior of intact linters in the hydrolysis-oxidation test employed was shown to be simulated almost perfectly by a glu-
cose-hydrocellulose mixture. The latter represented linters from which the amorphous cellulose had been removed by hydrolysis.and replaced by a calculated equivalent of reagent dextrose. I n other words, amorphous cellulose apparently hydrolyzes so readily that its test behavior is indistinguishable from that of glucose. Hydrolysis-oxidation data for analogous mixtures that simulate the cellulosic materials mentioned above are also presented. MATERIALS AND METHODS
Unmercerized cotton was in the form of bleached commercial sheeting which had been carefully washed to eliminate sizing. Mercerized cotton was prepared by immersing some of the above sheeting in cool, aqueous 25% sodium hydroxide for 30 minutes without tension, rinsing the swollen fabric thoroughly in cool water, transferring it to cool, 1% acetic acid for 30 minutes, and finally rinsing it in several changes of water. High-tenacity viscose rayon as tire cord, made from cotton linters, was washed in warm soapy water and rinsed. Purified wood pulp of acetate grade was used as received. The methods of investigation are described in detail elsewhere (4). Briefly, samples of each material were treated as follows: (a) Boiled in distilled water for 4 minutes, washed successively with dilute ammonia, hot water, acetone, and benzene, and finally air dried; the product is called “intact starting material”. ( b ) Boiled in 2 5 M hydrochloric acid for 4 minutes, then washed successively with water, dilute ammonia and organic solvents as above; the product is called ‘(0.07-hour hydrocellulose”. ( c ) Boiled in 2.5 M hydrochloric acid-0.6 M ferric chloride for 1 hour and 50 minutes, then for 10 minutes in 2.5 M hydrochloric acid, and finally washed and finished as above; the product is called “2-hour hydrocellulose”. Small (2-gram) samples of each preparation were oven-dried, accurately weighed, and subjected to hydrolysis-oxidation, carbon dioxide evolution being determined a t regular intervals over a 7-hour period. The undissolved residues remaining a t the end of the runs were recovered and determined by difference on ignition. The apparent glucose equivalents of cellulose removed by the two hydrolytic pretreatments were calculated from the carbon dioxide evolution data. For this purpose the equation was employed: #
where X = apparent mole fraction of glucose A , B , G = carbon dioxide values at time t for intact starting material, hydrocellulose, and glucose, respectively
1 Previous articles in this series appeared in 1941 (page 1022), 1042 (pages of INDUS85 and 1480). 1945 (page 11151, end in the ANALYTICAL EDITION TRIAL AND ENGINEERING CHEMISTRY, 1941, page 423. * Present address, 191 Western Ave., Westfield, Msnrs. 8 Present address, Crescent Heights, New Brighton, Pa.
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Suitable carbon dioxide values for glucose are available (4). By this equation the proportions of glucose and 0.07-hour hydrocelluloses required to simulate each intact starting material were calculated from the appropriate carbon dioxide data. These mixtures were then prepared and subjected to hydrolysis-oxidation in the usual way.
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CUMULATIVE carbon dioxide-time data obtained with the different intact starting materials are shown in Table I, together with the comparable experimental values for the various glucose0.07-hour hydrocellulose mixtures. It is evident that there is good agreement and, consequently, that the intact starting materials behave as if they were constituted of glucose and 0.07-hour hydrocellulose fractions.
TABLEI. CUMULATIVECARBON DIOXIDE-TIMEDATA FOR
INTACTMATERIALS . ~ N DSINTI~ATIXG MIXTCRESIS HCl--FeC13 RKAGENT
------Mole of Carbon Dioxide per hlole pf Anhydrog!ucose-Unmercerized Mercerized Purified High-Tenacity Wood Pulp Viscose Rayon Cotton Cotton _____ Time. SimuSimG Simu-’ &muHr. Intact ulated Intact lated Intact lated Intact l a t e d 0.004 0.005 0.010 0.011 0.005 0.005 0 . 8 0.003 0.002 0.031 0.030 0.012 0.012 0.016 0.016 1 . 3 0.008 0.008 0.064 0.064 0.026 0.027 0.033 0.035 1 . 9 0.016 0.017 0.103 0 . 1 0 5 0.054 0.056 0 . 0 4 1 0.044 2.5 0.027 0.028 0.150 0. 150 0.037 0.062 0.077 0 079 3 . 1 0.040 0.041 0.227 0 226 0.089 0.093 0.116 0 , 1 2 0 4 . 0 0.061 0.061 0.127 0.129 0 319 0.316 0.162 0.169 5 . 0 0.087 0.086 0.419 0,409 0.214 0.219 0.169 0.170 6 . 0 0.115 0.110 0.213 0 . 2 1 3 0.519 0.603 0.268 0 . 2 7 0 7 . 0 0.144 0.137
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Table I1 indicates the proportions of glucose and 0.07-hour hydrocellulose contained in the mixtures. Each of the mole fractions of glucose is an average of the nine separate estimates that can be calculated by Equation 1 from sets of carbon dioxide data for intact starting material and its 0.07-hour hydrocellulose. The other fraction in each case is found by difference.
TABLE11.
PROPORTIONS O F GLVCOSE A N D O.07-HOUR HYDROCELLULOSE CALCUL.4TED TO SIMULATE I N T A C T %lATERI.ILY
Material Unmercerized cotton Mercerized cotton Purified wood pulp High-tenacity viscose rayon
Mole Fraction of Glucose 0.033 0.070 0.032 0.080
Mole Fraction of 0.07-Hr. Hydrocellulose 0.967 0.930 0.968 0.920
Table I11 shows hydrolysis-oxidation results as cumulative carbon dioxide values for the sevrwl 2-hour hydrocelluloses. These data illustrate the similarity in behavior of the 2-hour hydrocelluloses from mercerized cotton and purified wood pulp.
TABLW 111. CUMULATIVE C A l t B o N DIOXIDE-TIME DAT~A FOR
%HOUR HYDROCELLULOSES DERIVEDF R O M VARIOUS SOURCES Time,
Hr.
0.8 1.3 1.9 2.6 3.1 4.0 5.0
6.0 7.0
Mole Con per Mole Anhydroglucose Unmercerized hlercerized Purified High-tenacity cotton cotton wood pulp viscose rayon 0.001 Trace 0.001 0.005 0.002 0.005 0.005 0.016 0.004 0.014 0.012 0.037 0.009 0.026 0.022 0.063 0.016 0.042 0.035 0.096 0.067 0.029 0. 056 0.154 0.046 0.100 0.086 0.228 0.062 0.136 0.118 0.304 0.082 0.172 0.155 0.390
Table IV presents the successions of apparent glucose equivalents, calculated as described above from the differential response of each intact starting material and its 2-hour hydrocellulose. These values, like similar ones for linters ( 4 ) ,exhibit considelable experimental error but in general appear to increase steadily 1%ith time from origins a t aero time in the vicinity of values shown in Table 11. Table V gives the recovery of combustible, insoluble matter at the end of the runs. The quantities of the three structural compo,nents estimated to be present in the intact starting materials are assembled in Table VI. The values for amorphous cellulose are taken from Table 11; those for mesomorphous are differences between the ultimate figures in Table I V and the amorphous.
Vol. 38, No. 3
TABLEIV. APPAREXTGLUCOSEEQUIVALENTS CALCULATED F R O k DIFFERENTIAL BEHAVIOR O F I N T A C T MATERIALSA K D THEIR2-Houn HYDROCELLCLOSES Apparent h i o h Fraction of GlucosUnmercerized Mercerized Purified cotton cotton wood pulp 0.051 0.087 0.051 0.093 0.058 0.096 0.060 0.099 0.094 0.060 0.099 0.060 0,102 0.062 0.109 0.067 0.119 0.069
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Time,
Hr.
0.8 1.3 1.9 2.5 3.1 4.0 5.0 6.0 7.0
High-tenacity vmco8e rayon
The estimatcs of crystalline ccllulose emanate from Table V and are obtained as the rat,io of recovcry from intact material to that from corresponding 2-hour hydroccllulose.
THAT there are considerable errors in the final cslimatcs of the, various component,s is apparent, but, the orders of magnitude arc: believed t o be correct. In vicw of the assumpt,ions involved, the estimates of crystallinc matter should be regarded as lcnst accurate. However, in one case, that of high-t,enacity rayon, unpuhlished experiments indicate that the amount of amorphous ccllulose may be somewhat higher than the value in Table VI. Invest’igations by more precise methods are obviously desirable. I t should be borne in mind that accessible cellulose is probably the total noncrystalline material and mould be equal to the sum of amorphous and mesomorphous components. Sums so obtained from the present data agree well with previous estimates of noncrystalline material (3)and with the amounts of accessible cellulose given for comparable materials by Conrad and Scroggie (2)* Data obtained at 65% relative humidity on hydrocelluloses recovered after varying times of hydrolysis show that moisture regain capacity undergoes an initial sharp fall which is followed in most cases by a long, slow rise (5). I t is assumed that minimurn regain represents removal of the expanded, hygroscopic, amorphous regions. I n the case of cotton linters calculations based on the amount of amorphous cellulose removed and the accompanying loss in regain capacity indicated that, 4.5 moles of water are associated with each mole of anhydroglucose in the amorphous regions (4). Similar calculations made with the data in Table I1 and moisture data already available for these materials (3) yield the following values for moles of water per mole of anhydroglucose in the amorphous regions: Unmercerized cotton Mercerized cotton
3.7 3.5
Purified wood pulp High-tenacity rayon
3.1 5.1
These figures, like that for linters, also suggest that the anhydroglucosc units in the amorphous parts of the fiber structures may
TABLEV.
INSOLUBLE MATTERRECOVERED AFTER 7-HOCIi MATERIALS AXI) HI-DROLYSIS-~XIDATIOS R u m ON INTACT DERIVED HYDROCELLULOSE
Material Unmercerized cotton Mercerized cotton Purified wood pulp High-tenacity rayon
2-Rr. Hydrocellulose,
Intact,
0.07-Hr. Hydrocellulose,
%
%
%
77.2 59.9 68.0 29.2
79.5 04.2 70.7 31.6
84.9 71.2 74.1 39.8
TARLCT’I. ERTIJIATED COnrPOSITION R~ATERIALS Material Unmercerized cotton Mercerized cotton Purified wood pulp High-tenacity viscose rayon
OF
INTACT CELIXLOSIC
Nonci>stalline Cellulose, % Amorphoiis Nesomorphous 3 4 7 5 3 4 8 14
% 91 84 92 73
March, 1946
INDUSTRIAL AND ENGINEERING CHEMISTRY
possess three free hydroxyls, each of which can bind one molecule of water. I n this calculation such factors as condensation in capillaries are assumed to be little changed by removal of the amorphous component. A possible cause of the high figure for viscose rayon may be an error in the amorphous estimate already discussed. The fact that noncrystalline or accessible cellulose appears to be divisible into two roughly equal parts on the basis of hygroscopicity and hydrolytic susceptibility may be important, especially where consideration is being given to possible fiber structure and properties relations. Clearly, in hygroscopic and hydrolytic behavior the mesomorphous component bears a closer resemblance to the crystalline than to the amorphous component. For this reason, in the determination of properties-structure relations it may prove advantageous to consider mesomorphous
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and crystalline components together as a single component. This would tend to emphasize the importance of the amorphous component, but such emphasis appears to be justified by the present evidence. I n any case the amorphous component should be distinguished from the remaining accessible cellulose to which i t apparently is not closely akin in chemical behavior. LITERATURE CITED
(1) Badgley, W.,Frilette, V. J., and Mark, H., IND.ENO.CBEM.,37, 226 (1945).
(2) Conrad, C . C . , and Scroggie, A; G., Ibid., 37, 592 (1945). (3) Nickeraon, R.F.,Zbid., 34, 1480 (1942). (4) Ibid., 37, 1115 (1945)~. CONTRIBUTION from the Cotton Research Foundation Fellowship a t Menon Institute.
Volumetric Behavior of 1-Butene R. H. ObDS, B. H. SAGE, AND W. N. LACEY Calgornia Institute of Technology, Pasadena, Calif.
The volumetric and phase behavior of 1-butene was experimentally determined at temperatures from 100' to 340" F. and at pressures up to 10,000 pounds per square inch. The results of these measurements were found to correlate well with those of other investigators.
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HE industrial importance of 1-butene has recently increased because of its role in the production of synthetic fuels and rubberlike polymers. The development of new products and the improvement of existing processes involving this substance will depend t o some extent upon the availability of accurate data relating t o its physical properties. Published literature concerning the volumetric and phase, behavior of 1-butene is not abundant. Coffin and Maass (5) reported values of the vapor pressure of 1-butene throughout the interval from -108" to 25" F., and determined the volume of the bubble-point liquid for temperatures from -51" to 50" F. Lamb and Roper (6) studied the vapor pressure of 1-butene between -70" and 32" F., and Roper (6) reported several measurements of the volumetric behavior of the gas for temperatures from -22" to 140" F. a t pressures less than 16.5 pounds per square inch absolute. The present work extends the range of the experimentally observed volumetric behavior *of 1-butene to 10,000 pounds per square inch and 340" F. The 1-butene was prepared by dehydration of n-butanol with activated alumina as a catalyst. Distilled technical n-butanol was vaporized and superheated t o about 660" F. at a pressure of approximately 15 pounds per square inch absolute. The gas was then passed through a catalyst chamber at 680" F., consisting of 24 inches of Pyrex tubing 1.4 inches in inside diameter, packed with 4-8 mesh granular alumina. Flow was controlled by a throttle in the feed line carrying liquid n-butanol, and a flow rate of about 35 drops per minute gave satisfactory resuIts. Greater rates resulted in the presence of excessive amounts of material believed t o be unreacted n-butanol in the condensate from the gas leaving the catalyst chamber. Lower flow rates gave a yellow, oily, nonvolatile liquid in the reaction products, which was assumed to be polymerized butene. The capacity of the catalyst a t 680" F. was roughly 2 pounds of n-butanol per hour per cubic foot of catalyst. A water-jacketed condenser
removed most of the water and reaction products of low volatility from the gas leaving the catalyst chamber. The gas was further dried by passage through granular anhydrous calcium chloride. The crude 1-butene vapor was passed directly from the dryer into the kett,le of a 4 f O O t , vacuum-jacketed fractionation column packed with helical glass rings. The material was distilled at atmospheric pressure with overhead withdrawal a t the rate of approximately 2% of the reflux in the column as long as the temperature of condensation at the head of the column stayed within 0.5" F. of the normal boiling point of 1-butene. The overhead product from the fractionation column was condensed at liquid air temperatures with continuous removal of noncondensable gases by means of a mercury diffusion pump backed by a Hyvac mechanical pump. This material was then subjected to two more fractionations in the same column, the initial and final tenth portions of the charge in the kettle being discarded .each time. A variation of less than 0.3 pound per square inch was observed in the vapor pressure of the final product of this process when a sample of it was isothermally vaporized from bubble point to dew point at 100" F. At the temperature of liquid air boiling at atmospheric pressure, the behavior of 1butene previously noted by Coffin and Maass (3) was observed by the authors, This substance apparently exhibits no definite freezing point, becomes increasingly viscous, and approaches B gel-like consistency as its temperature is lowered. An earlier publication (7) gave a detailed description of the equipment and procedures used in determining the volumetric properties of materials of this kind. No changes were found to be necessary for the present work. Three separately prepared and purified samples of 1-bubene were used. The data from the three samples were graphically correlated, and the results reported here were read from CUX-V~S drawn through the experimental points and smoothed in respect both to temperature and pressure. Figure 1 shows a series Of isotherms relating compressibility factor and pressure, UP $0 1000 pounds per square inch absolute. The experimentally observed states of the system are represented by circles. Alwgescale plot of this type was used t o establish the behavior of the system as a gas from infinite attenuation to dew point. The volumetric behavior of liquid 1-butene from bubble point to 10,000 pounds per square inch was obtained from isothermal
