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Registry No. Ni, 7440-02-0; Mo, 7439-98-7; C, 7440-44-0.
Conclusions The following conclusions can be drawn from the preceding discussion. 1. The physical properties of the catalyst (Le., specific surface area, specific pore volume, average pore diameter, and density) change quite rapidly initially and then either level off or change very gradually. The decrease is due mainly to coke and metal deposition with only a very small or negligible effect due to sintering or blockage of small pores. Differences in the average pore diameters obtained by mercury porosimetry and BET surface measurements suggest that pore mouth blockage is occurring. 2. The rapid deposition of coke during the early stages of catalyst life is responsible for the initial rapid decline in catalyst activity. Carbon concentration leveled off at about 8.5 to 9 wt 70after the first 100 lb of resid/lb of cat. 3. Metals deposition appears to increase continuously throughout the run but at a decreasing rate. The deposition of metals affects the activity of the catalyst at longer times and prevents the restoration of the catalyst to its initial state upon regeneration. 4. The activity of the catalyst cannot be restored to its base-line level via controlled oxidation if its age exceeds approximately 200 lb of resid/lb of cat. Regeneration via controlled oxidation is unable to restore the catalyst to its original state.
Literature Cited Baker, R. T. K. 73rd Annual Meeting of AIChE, Chicago, Nov 16-20, 1980. Beeckman, J. W.; Froment, G. F. Ind. Eng. Chem. Fundam. 1070, 78, 245. Beuther, H.; Larson, 0. A.; Perrotta, A. J. I n “Catalyst Deactlvatlon”, Delmon, E.; Froment, G. F., Ed.; Elsevier Scientlflc Publkhlng Co.: New York, 1980. Chang, H. J.; Seapan, M.; Crynes, 8. L. ACS Symp. Ser. 1082, No. 196. Corella, J.; Asua, J. M. “Proceedings, 2nd World Congress of Chemical Engineering”; Montreal, Oct 4-9, 1981. Kovach, S. M.; Castle, L. J.; Bennett, J. V. Ind. Eng. Chem. Prod. Res. Dev. 1078, 76, 62. Prasher, B. D.; Gabriel, G. A.; Ma, Y. H. Ind. Eng. Chem. Process D e s . Dev. 1978, 77, 266. Quarterly Technical Progress Report, Jan-March 1984, Pittsburgh Energy Technology Center, Report No. DOE/PETC/QTR-84/2, 1984. Sanders, J. V.; Splnk, J. A.; Pollack, S. S. Appl. Catal. 1983, 5 , 65. Schindler, H. D.; Chen, J.; Potts, J. D. “Integrated Two-Stage Liquefaction Final Technlcal Report”, C.E. Lummus Co., DOE Contract No. DE-AC2279ET14804. June 1983. Stephens, H. P.; Stohl, F. V. Prepr., Div. Fuel Chem., Am. Chem. SOC. 1084. 2916). 79. Stiegel, G. J.’; Krishnamurthy, S.; Shah, Y. T. Rev. Chem. Eng. 1983, 7(4), 357. Stohl, F. V.; Stephens, H. P. ”Proceedings, US. DOE’S Direct Liquefaction Contractors’ Project Review Conference”, Albuquerque, NM, Oct 17-18, 1984. Stohl, F. V.; Stephens, H. P.; Stlegel, G. J.; Tischer, R. E. “Proceedings, 1984 EPRI Contractors’ Conference on Coal Liquefaction”, Palo Alto, CA, May 8-10, 1984. Technical Progress Report, Run 242, Catalytic, Inc., Document No. DOE/ PC150041-19, July 1983. Technical Progress Report, Run 243, Catalytic, Inc., Document No. DOE/ PC/50041-31, Feb 1984a. Technlcal Progress Report, Run 244, catalytic, Inc., Document No. DOE/ PC150041-37, 19S4b. Trlmm, D. L. Appl. Catel. 1983, 5 , 263. Wolf, E. E.; Alfani, F. Catal. Rev. Sci. Eng. 1982, 24(3), 329.
Acknowledgment The authors would like to acknowledge R. F. Hickey (formerly with DOE), Dr. S. E. Rogers (PETC), and Dr. M. Moniz (Catalytic, Inc.) for their cooperation in obtaining the catalyst samples and operational data for the various runs. The assistance of PETC’s Analytical Branch and, in particular, of Mrs. M. J. Mima and Dr. S. S. Pollack in analyzing the catalyst samples on a timely basis is very much appreciated.
Received for review October 15, 1984 Revised manuscript received January 22, 1985 Accepted February 7, 1985 Reference in this report to any specific commercial product, process, or service is to facilitate understanding and does not necessarily imply its endorsement or favoring by the United States Department of Energy.
Catalytic Decarboxylation of Benzoic Acid Yasuhlro Takemura, Aklra Nakamura, and Harehlko Taguchl College of Education, Akita University, Akita 0 70, Japan
KoJI Ouch1 Faculty of Engineering, HokkaMo University, Sapporo 060, Japan
Catalytic decarboxylation of benzoic acid was performed under nitrogen or hydrogen atmosphere in the temperature range of 370-440 O C in a batch autoclave. I n the absence of catalyst, the benzene yield is only 0.8% at 400 OC. Among the various catalysts examined, Y-type zeolites show the highest activities even under nitrogen. Of three rare-earth metal-exchanged Y zeolite catalysts, NdHY shows the highest activii, on which the benzene yield is 75.6% even under nitrogen at 390 OC. CeHY catalyst, doped with water, gives a benzene yield of 86.0% at 370 OC. Alumina-supported nickel and palladium catalysts facilitate decarboxylation of benzoic acid under both hydrogen and nitrogen atmospheres; however, their activities are lower than those of the zeolite catalysts. For comparison, decarboxylation reactions of anthranilic acid and p-hydroxybenzoic acid were performed on the CeHY catalyst.
of ”unactivated” carboxylic acids, these methods, e.g., quinoline-copper system, usually require rigorous reaction conditions and yet produce low yields (March et al., 1977). The development of new, efficient catalysts and simple methods for the direct decarboxylation of unactivated carboxylic acids is, therefore, a task for organic chemists.
Introduction Aromatic carboxylic acids are easily decarboxylated, if they are appropriately “activated” by the introduction of functional groups, e.g., NH4 and OH (March et al., 1977; Mosby, 1953; Orchin and Reggel, 1951). Although various methods have been proposed for the direct decarboxylation 0196-4321/85/ 1224-0213$01.50/0
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Table I. Preoaration of Grouos I and I1 Catalysts and Their Activities for Decarboxslation of Benzoic Acid" cat. redn reaction product yield calcn by H2 condition benzene, EtOH-insol, _ _ _ _ cat. "C h "C h atm temp, "C mol % wt 70 group
I1
Pd(8.8) Ni(16.4)
400 400 500 500
2 2
2 2
400 400 400 400
2 2 2 2
Hz N2 Hz Nz
390 390 390 390
35.0 42.9 28.7 40.7
12.4 4.1
tr 3.2
"Materials charged: - benzoic acid, 20 mmol; catalyst, 0.5 E; - N,,. 1.0 MPa; H2, 1.0 MPa. Nominal reaction time: 60 min. *Ketjenfine 124-1 5E HD. 'None.
Maier et al. (1982) have examined the gas-phase decarboxylation of benzoic acid under atmospheric pressure by use of a flow system with a fixed bed of catalyst. They have obtained benzene yields of 96 and 95% on aluminasupported nickel catalyst at 180 "C and silica gel-supported palladium catalyst a t 370 "C, respectively. In their experiment all the reactions were performed in the presence of excess amount of hydrogen. If decarboxylation of aromatic carboxylic acid can be performed effectively, the method would provide a fundamental process of "upgrading" substances derived from coal, such as nitric acid- or air-oxidized products which contain various aromatic carboxylic acids. Aiming primarily at the development of new efficient catalysts for the upgrading of coal-derived substances, we have examined the decarboxylation activities of various catalysts using benzoic acid as a model compound for the oxidation products of coal. For comparison purposes, decarboxylation reactions of anthranilic acid and p hydroxybenzoic acid were also performed. Experimental Section Batch-Autoclave Experiment. The aromatic carboxylic acids examined in this work were benzoic acid, anthranilic acid, and p-hydroxybenzoic acid. All the reactions were carried out in an 80-mL magnetically stirred stainless steel (SUS 316) autoclave. For most runs, 20 mmol of aryl carboxylic acid and 0.5 g of solid catalyst were charged to the autoclave; nitrogen as an inert gas or hydrogen was added at an initial pressure of 1.0 MPa at room temperature; the addition of nitrogen was done to depress vaporization of aryl carboxylic acid at the reaction temperature, whereas hydrogen was added to depress vaporization and as a reagent for hydrogenative decarboxylation of the substrate. In some runs, a definite amount of water was charged together with aryl carboxylic acid and the catalyst. The autoclave was heated for about 20 min to a desired temperature which was maintained for a predetermined length of time. After the reaction, the autoclave was allowed to cool for 5 min and was then depressurized. The reaction mixture was taken out of the autoclave with ethanol and then separated by centrifugation into ethanol-soluble and an ethanol-insoluble fractions. One portion of ethanol-soluble fraction was methylated with dimethyl sulfate to permit analysis b:7 GC and MS. The ethanol-insoluble residual part was separated by filtration and then weighed after drying. In the reaction mixture the amount of product other than benzene and ethanol-insoluble matter was negligibly small. The gaseous product usually contained an approximately equivalent amount of carbon dioxide to that of benzene or benzene derivatives. The mole percent yield of benzene and weight percent of ethanol-insoluble matter, based on the starting aryl Carboxylic acid, are discussed in a later section. The
Table 11. Decarboxylation Activities of Group I11 Catalystsa cation product yield exchange, benzene, EtOH-insol, cat. % mol % wt % HY H(100) 30.9 10.0 Nd(78)H(22) 75.6 2.3 NdHY Ce(68)H(32) 42.7 13.1 CeHY La(69)H(31) 36.0 8.3 LaHY Materials charged: benzoic acid, 20 mmol; catalyst, 0.5 g; NZ. 1.0 MPa. Calcination temperature of catalysts: 400 "C.
material balances of the reaction were 95-97 % . Materials. Catalysts examined in this study are classified into three groups: as group I, metal oxides supported on alumina, such as W03(20), where the figure in parentheses denotes weight percent of metal oxide in the form of W03: as group 11, alumina-supported nickel and palladium catalysts; and as group 111, Y zeolites, i.e., hydrogen Y type zeolite (HY) and cerium, lanthanum, and neodymium cation-exchanged Y type zeolites (CeHY, LaHY, and NdHY). The group I catalysts were prepared by procedures previously reported (Takemura et al., 1981). Alumina-supported palladium catalyst of group I1 was prepared as follows; 0.11 g of Pd(N03)2was dissolved in 100 mL of water. To this solution was added 0.95 g of granular alumina of 20-60 mesh size, KHA-46, purchased from Nishio Ind., Tokyo. The resulting mixture was stirred thoroughly for 72 h and then dried in air at 110 "C. The catalyst precursor thus prepared was calcined in air at 400 "C for 2 h. In Table I are listed the catalysts of groups I and 11. Among them, nickel and palladium catalysts were reduced by hydrogen before use. The group I11 catalysts, each of which was a pelleted type, were ground to 20-60 mesh size and calcined at 400 "C overnight. They were received in the forms of NH4Y, CeNH,Y, LaNH4Y, and NdNH4Y, respectively. These catalysts precursors were prepared by Research Laboratory, Catalysts and Chemicals Ind., Japan, by standard methods of ion exchange from NaY (Na20 = 13.2 wt% and SiO2/AI2O3 = 4.8) as the starting material. The degree of ion exchange of these catalysts are listed in Table 11. Before use in some runs, CeHY was exposed to the air for about 3 days to allow it to adsorb water and it was heat treated at 110 "C. Benzoic acid, anthranilic acid, and p-hydroxybenzoic acid were commercially available reagents and were used without further purification. Hydrogen and nitrogen of' research grade were used also without purification. Results a n d Discussion Decarboxylation of Benzoic Acid. In the absence of catalysts, an attempt of decarboxylation of benzoic acid for 60 min nominal reaction time gave a trace amount of benzene under nitrogen at 440 "C. The reaction under
Ind. Eng. Chem. Prod. Res. Dev., Vol. 24,
No. 2, 1985 215
Table 111. Decarboxylation Activities of CeHY Catalyst4 product yield run 1 2 3 4' 5 3 6 7 8 9 10
reactant BAb BA BA BA BA BA BA
ABA~ ABA HBA' HBA
reaction temp, OC 370 380 390 370 390 390 390 250 150 250 210
reaction time, min 60 60 60 60 30 60 120 60 60 60 60
EtOH-insol, Ph-H, mol 7'0 8.8 26.0 42.7 86.2 24.3 42.7 48.0
Ph-NH2, mol %
Ph-OH, mol 70
wt%
93.2 26.4
8.3 12.8 13.1 7.3 18.7 13.1 13.7 2.0 0.4 4.7 tr
90.7 26.2
Materials charged: aryl carboxylic acid, 20 mmol; catalyst, 0.5 g, NZ,1.0 MPa. Nominal reaction time: 60 min. bBenzoic acid. Run with moist CeHY. dAnthranilic acid. 'p-Hydroxybenzoic acid.
Figure 1. Doping effect of water on the activity of CeHY catalyst. (benzoic acid charged, 20 mmol; CeHY charged, 0.5 g; N2charged, 1.0 MPa; reaction temperature, 360 OC; nominal reaction time, 60 min.)
hydrogen gave benzene in 0.8 and 7.0% yields a t 400 and 440 OC, respectively, showing that this acid is almost inert against direct decarboxylation. As shown in Table I, catalysts of group I were practically inactive to this reaction under nitrogen; CoO-Mo03 catalyst showed no catalytic activity a t a temperature lower than 400 "C and gave a benzene yield of only 12.3% at 420 OC. On the other hand, Ni (16.4) and Pd (8.8) catalysts exhibited high activities under both hydrogen and nitrogen atmospheres. The high activities under a hydrogen atmosphere confirm the results of Maier et al. (1982). However, the fact that these catalysts facilitate decarboxylation of benzoic acid to a greater extent under nitrogen than under hydrogen has not been shown before. The presence of hydrogen might partially suppress the promotion effect of nickel and palladium by strong and irreversible adsorption of hydrogen on the surface of these metals (Benson and Kwan, 1956). Table I1 shows that at 390 "C HY and a series of REHY exhibit high activities for decarboxylation of benzoic acid under a nitrogen atmosphere. Among them, NdHY shows the highest activity, on which the benzene yields 75.670, and the amount of ethanol-insoluble matter formed is small. The evidence that activities of a series of REHY are higher than that of HY indicates that their decarboxylation activities are due to their acidic character. As shown in Table 111, on CeHY catalyst the yield of benzene increased with increasing temperature and reached 42.7% at 390 OC. Prolonging the nominal reaction time did not bring about significant increases in benzene yield. It was found that the decarboxylation activity of
each zeolite catalyst mentioned above was enhanced by exposing it to air prior to use. The reaction results of run 4 shown in Table I11 are typical of this enhancement. However, the runs at 390 OC using the moist catalysts gave reaction results with poor reproducibility. Nevertheless, a study was made to examine the doping effect of water on the decarboxylation, focussing on the CeHY-H20 catalytic system. Figure 1 shows the relationship between the amount of water initially and externally charged to the autoclave and the benzene yield a t 360 OC at which temperature decarboxylation of benzoic acid is practically nil on the dry CeHY catalyst. The CeHY-H20 catalytic system gave the highest activity when about 0.5 g of water was added. It seems that only a small part of the water added takes part in the decarboxylation reaction. This doping effect of water on the decarboxylation activities of the Y zeolite catalysts, at least that of CeHY, is primarily due to their proton donating character, i.e., Brernsted acidic behavior. The acid strength of the surface of the zeolites should depend on the amount of water, reaching maximum strength a t a certain range of water adsorbed in the catalyst. This leads to a consideration of the mechanism of decarboxylation of aromatic carboxylic acids via protonation (Breslow, 1969). Decarboxylation of Anthranilic Acid and of p Hydroxybenzoic Acid. The reaction results are shown in Table 111. These acids, activated carboxylic acids, were easily decarboxylated at lower temperatures to give corresponding benzene derivatives in high yields. Acknowledgment The authors express their appreciation to Dr. M. A. Sholes, Mining College, Akita University, Japan, for his advice. Registry No. W03, 1314-35-8; Moo3, 1313-27-5; COO, 130796-6; FezOS,1309-37-1; V,05,1314-62-1; CuO, 1317-38-0; Crz03, 1308-38-9; KzCO3, 584-08-7; A1203,1344-28-1; Pd, 7440-05-3; Ni, 7440-02-0; Nd, 7440-00-8; Ce, 7440-45-1; La, 7439-91-0; benzoic acid, 65-85-0; anthranilic acid, 118-92-3; p-hydroxybenzoic acid, 99-96-7.
Literature Cited Benson. J. E.: Kwan, T. J . Phys. Chem. 1958, 60, 1601. Breslow. R. "An Introduction to Organic Reaction Mechanism": W. A. Beniamin Inc.: New York, 1969; p 720. Maier, W. E.; Roth, W.; Thies, I.: Schleyer, R. Chem. Ber. 1982, f15, 808. March, J. "Advanced Organic Chemistry"; McGraw-Hill: New York, 1977; p 514. Mosby, W. I . J . A m . Chem. SOC. 1953, 75, 3600. Orchin, M.; Reggel, 1. J . Am. Chem. SOC. 1951, 73, 436. Takemura, Y.; Itoh, H.; Ouchi, K. Ind. Eng. Chem. Fundam. 1981, 2 0 , 94.
Received f o r review February 2, 1984 Revised manuscript received November 21, 1984 Accepted January 15, 1985
