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Intercalation study and catalysis by lanthanum niobium oxides
CatalysisToday, (1993)455-462
455
Elsevier Science Publishers B.V., Amsterdam
Intercalation Niobium
Study
and Catalysis
by Lanthanum
Oxides
Tsuneo Matsuda, Tetsuya Fujita and Naosuke Miyamae Saitama University, Faculty of Engineering, Department of Applied Chemistry, Urawa, Saitama, 338, Japan Abstract For the study of the acidic character of layered perovskite oxide, HLaNba07 ( HLa 1, the intercalation of water and alcohols was performed and further the HLa was used of dehydration of l- and 2-butanol as a test reaction. The acidic properties of the HLa was greatly affected by the irreversible water in the interlayer removed in the temperature range of 35O"c-4OOO. In the presence of water, the intercalation of hydrophilic nalcohols having carbon number below 5 occurred. Dehydration activity of 2-butanol was higher than l-butanol and produced only n-butenes. On the other hand, butenes and n-butylaldehyde were produced in the reaction of l-butanol, especially the formation of the latter was predominant at the lower temperature temperature of as ZOO"c-250°C. With raising the heat-treatment the catalyst its acidity decreased and was almost lost at 500°C. n-butylaldehyde However, the selectivity to increased, indicating that the acidity did not concern to the nbutylaldehyde formation. The reaction behaviors of l-and 2butanol on the HLa catalyst were discussed. l.INTRODUCTION In recent years, considerable attentions have been given to the layered compounds in the natural clays and the synthesized compounds. It is known that they intercalate various kinds of amines, alcohols, and aldehyde and so on [1,2,31. When layered compounds, for instance, fluor-tetrasilicic mica [43 were used as catalyst, it was reported that a remarkable selectivity was obtained.
0920-5661/93/$6.00 0 1993Elsevier Science Publishers B.V. All rights reserved.
456 Therefore, in this study the layered and synthesized compounds These which have been recently developed were employed. compounds are written by the general formula, ALaNbzO7, and their The catalytic properties have been hardly investigated. compounds are built up of the layer compound, LaNbz07, having double perovskite structure which are interleaved by A atoms. In the case A = H it is known that the compound has water in the interlayer and exhibits the acidic property [53. Since the water higher montmorillonite dissociates 10" in the interlayer of than liquid water [61, it is also considered that the water in the interlayer will be concerned with the acidic properties of the connection with the HLaNbzO7 ( abbreviated as HLa ). In acidic properties, the reactions of butanols using the HLa as catalyst were attempted. 2.EXPERIMENTAL The catalyst, HLa, used in this study was prepared according of water and to the literatures [5,61. The intercalation alcohols in the interlayer of the HLa was carried out according to the previous papers The characterization of the [8,91. intercalated compounds was made by XRD,IR,TG-DTA and elementary analysis. The acidic properties of the HLa catalyst was measured by the two kinds of method. One is the isoelectric point method written in the previous paper 181 and the other is the NH3 adsorption method. The former method was carried out in order to examine the effect of water. About lg of the HLa treated at various temperatures in the stream of He was dipped in water at room temperature. Since the suspended solution containing the HLa showed pH values of the acidic range, the solution was titrated with O.lM aqueous ammonia in the nitrogen atmosphere until pH was attained to the original value prior to introduction of aqueous ammonia. From the titrated amount of aqueous ammonia the acidity was estimated as shown in Fig. 1. The latter was performed by use of the spring balance with the sensitivity of 0.5 mg per scale at the same temperature as the heat-treatment under evacuation. Basicity was measured with the same spring balance by adsorption of COz at the same temperature as the heat-treatment. The reactions of l- and 2-butanol were carried out by a pulse reactor in the temperature range of 18O'c and 350°C. The weight of the catalyst used was 100 mg for lbutanol and 50 mg for 2-butanol and the feed amount per a pulse was 1.93x1O-5 mol for 1-butanol and 1.2OX1O-5 mol for 2-butanol, respectively. The catalyst was treated with helium stream of 30 ml/min at various temperatures for an hour before the reaction
457 in the case of 1-butanol. In the case of 2-butanol, the catalyst was treated at 200°C for an hour. The reaction products were analyzed by two sets of gas-chromatograph equipped with the porapack Q column ( 2m ) at 160°C to separate butenes, nbutylaldehyde and l- or 2-butanol and.VZ-7 column ( 5m ) at 0°C to separate butene isomers. The surface areas of the HLa treated at various temperatures were measured by the BET method with nitrogen adsorpton. 3.RESULTS AND DISCUSSION Aciditic properties of the catalyst treated at various temperatures are shown in Fig.1. Acidities measured by both the isoelectric point and the NH3 adsorption method decreased with an increase of temperature of the heat-treatment and rapidly decreased or were almost lost between 400°C and 500°C. When the HLa was dipped in water, the suspended solution exhibited the acidic pH values by the dissociation of proton in the HLa ( see Fig.1 ). The dissociation may be due to the action of the water intercalated into the interlayer. With raising the treatmenttemperature the pH value turned to the higher values, which would be ascribed to the decrease of the amount of the water in the inter-layer. The acidity measured by the titration of aqueous ammonia did not agree with that obtained adsorption by NH3 except the case at 200°C. This cause may be due to the differece in the temperature of the measurement and the following supposition. Below 200°C the adsorbed amount of NH3 was larger than the titrated amount of aqueous ammonia. This cause may be ascribed to dissolution of NH3 into water which still remains in the interlayer. Above 200°C. it is considered that aqueous ammonia intercalates some extent into the interlayer to form NH4LaNb207 [53. This will cause the higher value of the acidity by the isoelectric point method than the NH3 adsorption. At 2OOc, both acidities obtained by the two methods happened to exhibit the nearly same value. It has been already detected by DTA-TG that in the range of lOO"c--3OO'c the water in the interlayer was gradually lost and between 350°C and 4OOC a slightly large weight loss was detected [81. The water removed at 35O"c-400°C is irreversible, because intercalate again [8]. By the loss of the it can not irreversible water, the acidity of the HLa greatly decreased and was almost lost. Thus, the irreversible water is greatly participated to the appearance of the aciditic property of the HLa. The HLa treated at 400°C is in the transition state that the water has not been completely removed yet. Consequently, some
458 extent of acidity could be detected. On the HLa treated at 200°C and 5OO"c, NH3 was adsorbed at room temperature and then IR measurement was performed after a slight evacuation. As shown in Fig.2, the bands at 1430-1450 cm-l assigned to Briinsted acid sites could be detected, but at 500°C no acidic sites could be already detected, which might be due to the almost complete removal of the water in the inter-layer. The band assigned to Lewis acid sites which will be seen in 1630-1650 cm-i could slightly be found with nearly the same magnitude on the samples
100
200
temperature
300
400
500
(C)
Fig.1 Acidity of the HLa treated at various temperature
459
treated at 200°C and 500°C. The presence of the basicity was examined by CO2 adsorption, but the badicity was so small as to be impossible to measure. The surface areas of the HLa treated at 100°C and 400"Cwere 18.4 and 20.3 m2/g,respectivity. The surface area slightly increased with an increase of the temperature of the treatment, but it would be regarded to be almost constant. The intercalation of n-alcohols having carbon number from one to five in the presence of water could be detected, but the alcohols of carbon number above 6 did not enter in the interlayer. In the absence of water, the intercalation could not entirely occur, even though alcohols have the hydrophilic
wave number Fig.2
(
cm -1)
IR spectra of NH3 adsorbed
on the HLa
HLa was treated under evacuation before adsorption (a) at 200X,
of NH3
(b) at 5OO’C
460 property. Thus, water greatly concerns to the intercalation of n-alcohols. Secondary alcohols did not intercalate owing to the steric hindrance 191. The mechanism of the intercalation of the hydrophilic n-alcohols is proposed as follows. Alcohol will be polarized by the action of the proton produced by the dissociation of water inserted into the interlayer, and then will intercalate in the space between the layers. In such case, the hydrophobic alcohols will be difficult to receive the action of the proton. On the basis of the results of the intercalation of both water and n-alcohol, mentioned above, dehydration of l- and 2butanols on the WLa catalyst was attempted, because the reaction would proceed on the acidic sites The stationary [lOI. conversion and selectivity were attained after the second or third pulse. The results of the reaction of l-butanol at the temperature range between 200°C and 350°C with 50°C interval are summarized in Table 1. The material balance indicated in Table 1 was that at the first pulse and was improved with an increase of the pulse number and by raising the reaction temperature. At the temperatures below 19O'c no reaction of I-butanol was entirely detected. However, the formation of I.-butene was predominant at
Table 1 Results of the reaction of l-butanol Selectivity (%)
Reaction @mp.(U
Conversion (%I
200
4.2
trace
trace
250
33.4
50.9
300
59.8
350
90.6
n-BuCHO
m.b. (%)
trace
100
30.2
18.9
18.0
12.2
52.8
54.6
17.6
15.6
12.0
92.0
46.4
26.6
26.9
trace
100
l-C4
t-z-C4
C-IX4
Table 2. Results of the reaction of 2-butanol Reaction temp. Conversion (%I (Q
Selectivity (%) l-C4
t-z-c4
m.b. c-Z-C4
180
9.0
14.0
29.0
56.9
190
15.3
14.2
29.4
56.4
30.2 36.4 13.7 200 I-C4 ; I-butene, t-Z-C4 ; tram-2-butene, c-Z-C4 ; cis-Zbutene m.b. ; material balance
56.1
(%)
100
461 200°C , although the equilibrium composition of dehydration products of 1-butanol was calculated as follows; 1-butene : trans-2-butene : cis-2-butene = 26.4 : 53.1 : 20.5, respectively. Furthermore, from the thermodynamic calculation, the ratio of 1-butene and n-butylaldehyde at equilibrium of 200°C can be estimated as 158 : 1. However the experimental results were entirely contrary to the calculation, although the selectivity to butenes increased with raising the reaction temperature. By the heat-treatment of the HLa at 4OO"c~5OO"c, the activity for the reaction at 200°C remarkably decreased, but the selectivity to n-butylaldehyde was attained to ca.lOO%. This result suggests that the formation of n-butylaldehyde is not concerned with the acidic property of the catalyst. The reaction behavior of 1-butanol may be considered as to form butenes will proceed on the follows. The dehydration acidic sites in the interlayer. When 1-butanol is once inserted it will stay there and take much time to in the interlayer, diffuse into bulk. This will cause the low material balance as shown in Table 1. With raising temperature, the diffusion rate in the interlayer is improved to exhibit the better material balance (see Table l),On the other hand, n-butylaldehyde will be formed on the active sites situated on the outer surface or the edge standing near the outlet of the inter-layer. If it is considered that the formation of n-butylaldehyde does not proceed in the interlayer, the reaction rate will be fast. The for the formation of n-butylaldehyde by active sites dehydrogenation of 1-butanol seems to be basic. However, it may be difficult to consider that the number of basic sites is so small to be neglected. Dehydration of 2-butanol occurred at 18O'c despite no intercalation of the alcohol [9] and the reactivity of the alcohol was rather higher than that of 1-butanol as shown in Table 2. The formation of n-butylaldehyde could not be detected and only butenes were produced. The material balance of 100% was attained from the first pulse. Dehydration will proceed through the two kinds of the intermediate, CH3-C+H-CH2-CH2 in the case of.2-butanol and C+H2It is generally known that the CH2-CH2-CH3 for 1-butanol. the secondary ion is more stable than the latter. Therefore, reactivity of 2-butanol will be higher than that of 1-butanol. was The formation of cis-2-butene in the 2-butanol reaction predominant as shown in Table 2, which agreed with the results obtained at 150°C by Jewur and Moffat [ill, although trans -2butene would be much produced in thermodynamic calculation.
462 The hydration of 2-butanol will probably proceed on the outer surface or the edge as already mentioned in the formation of nbutylaldehyde. The fact that no dehydration of l-butanol was observed at the reaction temperature below 190°C will be ascribed to very slow formation rate of n-butylaldehyde as neglected in comparison with the butenes formation rate from 2-butanol. Why nbutylaldehyde is produced from 1-butanol and n-butenes are produced from 2-butanol on the outer surface or the edge is still obscure. These interesting reaction behaviors of l- and 2butanol on the HLa catalyst necessitate further study on the reaction mechanism. The authors acknowledge to CBMM Ltd. for the supply the niobium oxide.
REFERENCES 1
B. K. G. Theng, The Chemistry of Clay Organic Reactions, Adam Plenum press, 1986 2 M.S.Dresselhous (ed.),Intercalation in Layered Materials, Plenum Press, 1986 3 A. P. Legrand and S. Flandreis ( ed.) , Chemical Physics of Intercalation, Plenum Press, 1987 4 Y. Morikawa, K. Takagi, Y. Moro-oka and T. Ikawa, J. Chem. Commun.,(1983), 845 5 J. Gopalakrishinan, V. Bhat and B. Ravau, Mater. Res. Bull., 22, (19871, 413 6 A. J. Jacobson, J. W. Johnson and J. T. Lewandwski, Mater. Res. Bull., 22, (19871, 45 7 T. Matsuda, T. Fujita and M. Kojima, J. Mater. Chem., 1, (19911, 559 8 T. Matsuda, T. Fujita, N. Miyamae, M. Takeuchi and K. Kanda, Bull. Chem.Soc. Jpn., in press 9 T. Matsuda, N.Miyamae and M. Takeuchi, Bull. Chem. Sot. Jpn., in press 10 K. Tanabe, M. Misono, Y. Ono and H. Hattori, New Solid Acids and Bases, P 260, Kodansha, Elsevier Pub. Co., Tokyo,1979 11 S. S. Jewur and J. B. Moffat., J. cat., 57, (19791, 167
455
Elsevier Science Publishers B.V., Amsterdam
Intercalation Niobium
Study
and Catalysis
by Lanthanum
Oxides
Tsuneo Matsuda, Tetsuya Fujita and Naosuke Miyamae Saitama University, Faculty of Engineering, Department of Applied Chemistry, Urawa, Saitama, 338, Japan Abstract For the study of the acidic character of layered perovskite oxide, HLaNba07 ( HLa 1, the intercalation of water and alcohols was performed and further the HLa was used of dehydration of l- and 2-butanol as a test reaction. The acidic properties of the HLa was greatly affected by the irreversible water in the interlayer removed in the temperature range of 35O"c-4OOO. In the presence of water, the intercalation of hydrophilic nalcohols having carbon number below 5 occurred. Dehydration activity of 2-butanol was higher than l-butanol and produced only n-butenes. On the other hand, butenes and n-butylaldehyde were produced in the reaction of l-butanol, especially the formation of the latter was predominant at the lower temperature temperature of as ZOO"c-250°C. With raising the heat-treatment the catalyst its acidity decreased and was almost lost at 500°C. n-butylaldehyde However, the selectivity to increased, indicating that the acidity did not concern to the nbutylaldehyde formation. The reaction behaviors of l-and 2butanol on the HLa catalyst were discussed. l.INTRODUCTION In recent years, considerable attentions have been given to the layered compounds in the natural clays and the synthesized compounds. It is known that they intercalate various kinds of amines, alcohols, and aldehyde and so on [1,2,31. When layered compounds, for instance, fluor-tetrasilicic mica [43 were used as catalyst, it was reported that a remarkable selectivity was obtained.
0920-5661/93/$6.00 0 1993Elsevier Science Publishers B.V. All rights reserved.
456 Therefore, in this study the layered and synthesized compounds These which have been recently developed were employed. compounds are written by the general formula, ALaNbzO7, and their The catalytic properties have been hardly investigated. compounds are built up of the layer compound, LaNbz07, having double perovskite structure which are interleaved by A atoms. In the case A = H it is known that the compound has water in the interlayer and exhibits the acidic property [53. Since the water higher montmorillonite dissociates 10" in the interlayer of than liquid water [61, it is also considered that the water in the interlayer will be concerned with the acidic properties of the connection with the HLaNbzO7 ( abbreviated as HLa ). In acidic properties, the reactions of butanols using the HLa as catalyst were attempted. 2.EXPERIMENTAL The catalyst, HLa, used in this study was prepared according of water and to the literatures [5,61. The intercalation alcohols in the interlayer of the HLa was carried out according to the previous papers The characterization of the [8,91. intercalated compounds was made by XRD,IR,TG-DTA and elementary analysis. The acidic properties of the HLa catalyst was measured by the two kinds of method. One is the isoelectric point method written in the previous paper 181 and the other is the NH3 adsorption method. The former method was carried out in order to examine the effect of water. About lg of the HLa treated at various temperatures in the stream of He was dipped in water at room temperature. Since the suspended solution containing the HLa showed pH values of the acidic range, the solution was titrated with O.lM aqueous ammonia in the nitrogen atmosphere until pH was attained to the original value prior to introduction of aqueous ammonia. From the titrated amount of aqueous ammonia the acidity was estimated as shown in Fig. 1. The latter was performed by use of the spring balance with the sensitivity of 0.5 mg per scale at the same temperature as the heat-treatment under evacuation. Basicity was measured with the same spring balance by adsorption of COz at the same temperature as the heat-treatment. The reactions of l- and 2-butanol were carried out by a pulse reactor in the temperature range of 18O'c and 350°C. The weight of the catalyst used was 100 mg for lbutanol and 50 mg for 2-butanol and the feed amount per a pulse was 1.93x1O-5 mol for 1-butanol and 1.2OX1O-5 mol for 2-butanol, respectively. The catalyst was treated with helium stream of 30 ml/min at various temperatures for an hour before the reaction
457 in the case of 1-butanol. In the case of 2-butanol, the catalyst was treated at 200°C for an hour. The reaction products were analyzed by two sets of gas-chromatograph equipped with the porapack Q column ( 2m ) at 160°C to separate butenes, nbutylaldehyde and l- or 2-butanol and.VZ-7 column ( 5m ) at 0°C to separate butene isomers. The surface areas of the HLa treated at various temperatures were measured by the BET method with nitrogen adsorpton. 3.RESULTS AND DISCUSSION Aciditic properties of the catalyst treated at various temperatures are shown in Fig.1. Acidities measured by both the isoelectric point and the NH3 adsorption method decreased with an increase of temperature of the heat-treatment and rapidly decreased or were almost lost between 400°C and 500°C. When the HLa was dipped in water, the suspended solution exhibited the acidic pH values by the dissociation of proton in the HLa ( see Fig.1 ). The dissociation may be due to the action of the water intercalated into the interlayer. With raising the treatmenttemperature the pH value turned to the higher values, which would be ascribed to the decrease of the amount of the water in the inter-layer. The acidity measured by the titration of aqueous ammonia did not agree with that obtained adsorption by NH3 except the case at 200°C. This cause may be due to the differece in the temperature of the measurement and the following supposition. Below 200°C the adsorbed amount of NH3 was larger than the titrated amount of aqueous ammonia. This cause may be ascribed to dissolution of NH3 into water which still remains in the interlayer. Above 200°C. it is considered that aqueous ammonia intercalates some extent into the interlayer to form NH4LaNb207 [53. This will cause the higher value of the acidity by the isoelectric point method than the NH3 adsorption. At 2OOc, both acidities obtained by the two methods happened to exhibit the nearly same value. It has been already detected by DTA-TG that in the range of lOO"c--3OO'c the water in the interlayer was gradually lost and between 350°C and 4OOC a slightly large weight loss was detected [81. The water removed at 35O"c-400°C is irreversible, because intercalate again [8]. By the loss of the it can not irreversible water, the acidity of the HLa greatly decreased and was almost lost. Thus, the irreversible water is greatly participated to the appearance of the aciditic property of the HLa. The HLa treated at 400°C is in the transition state that the water has not been completely removed yet. Consequently, some
458 extent of acidity could be detected. On the HLa treated at 200°C and 5OO"c, NH3 was adsorbed at room temperature and then IR measurement was performed after a slight evacuation. As shown in Fig.2, the bands at 1430-1450 cm-l assigned to Briinsted acid sites could be detected, but at 500°C no acidic sites could be already detected, which might be due to the almost complete removal of the water in the inter-layer. The band assigned to Lewis acid sites which will be seen in 1630-1650 cm-i could slightly be found with nearly the same magnitude on the samples
100
200
temperature
300
400
500
(C)
Fig.1 Acidity of the HLa treated at various temperature
459
treated at 200°C and 500°C. The presence of the basicity was examined by CO2 adsorption, but the badicity was so small as to be impossible to measure. The surface areas of the HLa treated at 100°C and 400"Cwere 18.4 and 20.3 m2/g,respectivity. The surface area slightly increased with an increase of the temperature of the treatment, but it would be regarded to be almost constant. The intercalation of n-alcohols having carbon number from one to five in the presence of water could be detected, but the alcohols of carbon number above 6 did not enter in the interlayer. In the absence of water, the intercalation could not entirely occur, even though alcohols have the hydrophilic
wave number Fig.2
(
cm -1)
IR spectra of NH3 adsorbed
on the HLa
HLa was treated under evacuation before adsorption (a) at 200X,
of NH3
(b) at 5OO’C
460 property. Thus, water greatly concerns to the intercalation of n-alcohols. Secondary alcohols did not intercalate owing to the steric hindrance 191. The mechanism of the intercalation of the hydrophilic n-alcohols is proposed as follows. Alcohol will be polarized by the action of the proton produced by the dissociation of water inserted into the interlayer, and then will intercalate in the space between the layers. In such case, the hydrophobic alcohols will be difficult to receive the action of the proton. On the basis of the results of the intercalation of both water and n-alcohol, mentioned above, dehydration of l- and 2butanols on the WLa catalyst was attempted, because the reaction would proceed on the acidic sites The stationary [lOI. conversion and selectivity were attained after the second or third pulse. The results of the reaction of l-butanol at the temperature range between 200°C and 350°C with 50°C interval are summarized in Table 1. The material balance indicated in Table 1 was that at the first pulse and was improved with an increase of the pulse number and by raising the reaction temperature. At the temperatures below 19O'c no reaction of I-butanol was entirely detected. However, the formation of I.-butene was predominant at
Table 1 Results of the reaction of l-butanol Selectivity (%)
Reaction @mp.(U
Conversion (%I
200
4.2
trace
trace
250
33.4
50.9
300
59.8
350
90.6
n-BuCHO
m.b. (%)
trace
100
30.2
18.9
18.0
12.2
52.8
54.6
17.6
15.6
12.0
92.0
46.4
26.6
26.9
trace
100
l-C4
t-z-C4
C-IX4
Table 2. Results of the reaction of 2-butanol Reaction temp. Conversion (%I (Q
Selectivity (%) l-C4
t-z-c4
m.b. c-Z-C4
180
9.0
14.0
29.0
56.9
190
15.3
14.2
29.4
56.4
30.2 36.4 13.7 200 I-C4 ; I-butene, t-Z-C4 ; tram-2-butene, c-Z-C4 ; cis-Zbutene m.b. ; material balance
56.1
(%)
100
461 200°C , although the equilibrium composition of dehydration products of 1-butanol was calculated as follows; 1-butene : trans-2-butene : cis-2-butene = 26.4 : 53.1 : 20.5, respectively. Furthermore, from the thermodynamic calculation, the ratio of 1-butene and n-butylaldehyde at equilibrium of 200°C can be estimated as 158 : 1. However the experimental results were entirely contrary to the calculation, although the selectivity to butenes increased with raising the reaction temperature. By the heat-treatment of the HLa at 4OO"c~5OO"c, the activity for the reaction at 200°C remarkably decreased, but the selectivity to n-butylaldehyde was attained to ca.lOO%. This result suggests that the formation of n-butylaldehyde is not concerned with the acidic property of the catalyst. The reaction behavior of 1-butanol may be considered as to form butenes will proceed on the follows. The dehydration acidic sites in the interlayer. When 1-butanol is once inserted it will stay there and take much time to in the interlayer, diffuse into bulk. This will cause the low material balance as shown in Table 1. With raising temperature, the diffusion rate in the interlayer is improved to exhibit the better material balance (see Table l),On the other hand, n-butylaldehyde will be formed on the active sites situated on the outer surface or the edge standing near the outlet of the inter-layer. If it is considered that the formation of n-butylaldehyde does not proceed in the interlayer, the reaction rate will be fast. The for the formation of n-butylaldehyde by active sites dehydrogenation of 1-butanol seems to be basic. However, it may be difficult to consider that the number of basic sites is so small to be neglected. Dehydration of 2-butanol occurred at 18O'c despite no intercalation of the alcohol [9] and the reactivity of the alcohol was rather higher than that of 1-butanol as shown in Table 2. The formation of n-butylaldehyde could not be detected and only butenes were produced. The material balance of 100% was attained from the first pulse. Dehydration will proceed through the two kinds of the intermediate, CH3-C+H-CH2-CH2 in the case of.2-butanol and C+H2It is generally known that the CH2-CH2-CH3 for 1-butanol. the secondary ion is more stable than the latter. Therefore, reactivity of 2-butanol will be higher than that of 1-butanol. was The formation of cis-2-butene in the 2-butanol reaction predominant as shown in Table 2, which agreed with the results obtained at 150°C by Jewur and Moffat [ill, although trans -2butene would be much produced in thermodynamic calculation.
462 The hydration of 2-butanol will probably proceed on the outer surface or the edge as already mentioned in the formation of nbutylaldehyde. The fact that no dehydration of l-butanol was observed at the reaction temperature below 190°C will be ascribed to very slow formation rate of n-butylaldehyde as neglected in comparison with the butenes formation rate from 2-butanol. Why nbutylaldehyde is produced from 1-butanol and n-butenes are produced from 2-butanol on the outer surface or the edge is still obscure. These interesting reaction behaviors of l- and 2butanol on the HLa catalyst necessitate further study on the reaction mechanism. The authors acknowledge to CBMM Ltd. for the supply the niobium oxide.
REFERENCES 1
B. K. G. Theng, The Chemistry of Clay Organic Reactions, Adam Plenum press, 1986 2 M.S.Dresselhous (ed.),Intercalation in Layered Materials, Plenum Press, 1986 3 A. P. Legrand and S. Flandreis ( ed.) , Chemical Physics of Intercalation, Plenum Press, 1987 4 Y. Morikawa, K. Takagi, Y. Moro-oka and T. Ikawa, J. Chem. Commun.,(1983), 845 5 J. Gopalakrishinan, V. Bhat and B. Ravau, Mater. Res. Bull., 22, (19871, 413 6 A. J. Jacobson, J. W. Johnson and J. T. Lewandwski, Mater. Res. Bull., 22, (19871, 45 7 T. Matsuda, T. Fujita and M. Kojima, J. Mater. Chem., 1, (19911, 559 8 T. Matsuda, T. Fujita, N. Miyamae, M. Takeuchi and K. Kanda, Bull. Chem.Soc. Jpn., in press 9 T. Matsuda, N.Miyamae and M. Takeuchi, Bull. Chem. Sot. Jpn., in press 10 K. Tanabe, M. Misono, Y. Ono and H. Hattori, New Solid Acids and Bases, P 260, Kodansha, Elsevier Pub. Co., Tokyo,1979 11 S. S. Jewur and J. B. Moffat., J. cat., 57, (19791, 167