Ind. Eng. Chem. Res. 2000, 39, 1209-1214
1209
Benzylation of Biphenyl with Benzyl Chloride over Crystalline, Amorphous, and MCM-41 Solid Acid Catalysts Paolo Beltrame* and Giovanni Zuretti Dipartimento di Chimica Fisica ed Elettrochimica, Universita` degli Studi di Milano, Via C. Golgi 19, I-20133 Milano, Italy
Francesco Demartin Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Universita` degli Studi di Milano, Via G. Venezian 21, I-20133 Milano, Italy
The Friedel-Crafts reaction of biphenyl with benzyl chloride in cyclohexane was carried out in a slurry batch reactor, under magnetic stirring, over solid acid catalysts of amorphous or mesoporous MCM-41 aluminosilicates. Mainly benzylbiphenyl isomers (M), but also some dibenzyl derivatives (D), were obtained and determined. The chemically controlled reaction kinetics corresponded to two consecutive reactions. Kinetic models were applied on the basis of an optimization procedure, and the behavior of the amorphous silica-alumina and of the mesoporous aluminosilicates was compared with that of other materials, among which were HY zeolites, previously used as catalysts. Introduction The benzylation of biphenyl by means of benzyl chloride was chosen as a test reaction for a series of solid acid catalysts, to compare their activity, selectivity, and stability, in runs carried out in the liquid phase. The reaction of biphenyl with benzyl chloride over dealuminated HY zeolites1 and over an amorphous silicaalumina,2 has been previously studied. Here other aluminosilicates have been studied, including an amorphous silica-alumina catalyst with a different Si/Al ratio and two mesoporous materials of MCM-41 type. In particular, mesoporous materials could be interesting as catalysts for a process involving molecules of medium-to-large size, as are the products of the reactions observed in the present case:
C6H5-C6H5 + C6H5CH2Cl f (BzCl) (BIP) C6H5-C6H4-CH2C6H5 + HCl (M; three isomers) C6H5-C6H4-CH2C6H5 + C6H5CH2Cl f (BzCl) (M) dibenzyl derivatives + HCl (D; several isomers) Molecular mechanics calculations indicate lengths of 15-20 Å and side dimensions of >10 Å for some of the possible D structures. A few cases of liquid-phase alkylations of aromatics over MCM-41 catalysts have been reported, with olefins,3-6 alcohols,7,8 and, in one case, benzyl chloride9 as alkylating agents. As a consequence of the present experimental study, a comparison of various catalysts of different nature, used for the same reaction in strictly analogous conditions, becomes possible. * To whom correspondence should be addressed. Telephone: +39-0226603250. Fax: +39-0270638129.
The reactions were mainly carried out in solvent cyclohexane. Hydrochloric acid was mostly released as a gas. Experimental Section Materials. Reagents of high purity (g98%, in most cases g99%) were used throughout. Among the solvents used for kinetic runs, cyclohexane was Aldrich “99+%”, while cyclopentane was Aldrich “HPLC grade”. X-ray Diffraction. X-ray powder diffraction data were obtained using a Rigaku DMAX diffractometer with Cu KR radiation, operating at 40 kV and 40 mA, with a 0.05° divergence slit; spectra were recorded in the 2θ range 1-10°. Catalysts. The new catalysts were commercial amorphous silica-alumina with high alumina content (Akzo HA-100-5P), indicated as HA, and two mesoporous materials, indicated as GMS1 and MS9. Catalyst GMS1 was prepared by the synthesis of purely siliceous MCM-41 in an acid environment,10,11 followed by grafting with aluminum.12 Water (154 g), hydrobromic acid (155 g of 48% solution), cetyltrimethylammonium bromide (CTMABr; 4.5 g), and tetraethyl orthosilicate (TEOS; 20.9 g) reacted under stirring at 45 °C for 2 h. The drying temperature was kept at 80 °C, and the calcination temperature slowly reached 540 °C: each porcelain dish contained e1.5 g. Small amounts (ca. 3 g) of the products of four different syntheses were treated with aluminum isopropoxide (1 g) in n-hexane (290 mL) at room temperature for 24 h. Drying and calcination followed, giving materials labeled as AlSiMS10, AlSi-MS11, AlSi-MS12, and AlSi-MS13. They were carefully mixed by dispersing them in n-hexane under stirring. A final calcination gave GMS1. Catalyst MS9 was prepared by direct synthesis in an alkaline environment13 followed by Na/H exchange.14 Water (270 g), sodium hydroxide (2.0 g), CTMABr (7.3 g), TEOS (20.8 g), and Al2(SO4)3‚18H2O (1.67 g) reacted under stirring at room temperature for 2 h and then in a static autoclave at 100 °C for 4 days. Drying was
10.1021/ie990492s CCC: $19.00 © 2000 American Chemical Society Published on Web 04/04/2000
1210
Ind. Eng. Chem. Res., Vol. 39, No. 5, 2000
Table 1. Parameters of the Catalytic Materials Mentioned in This Work Si/Al atomic ratio catalyst HY360 HY330 LA LA HA HA GMS1 MS9 a
nominal value
exptl determn
BET measurements surface area (m2/g)
pore volume (mL/g)
pore size (Å)
7.0a 2.95a 5.7b
6.15
129
0.38
7 7 117c
2.55b
2.68
367
0.60
66c
849 1006
0.73 0.79
34c 31c
19.1 19.1
acid titer (mequiv/g) pKa e -3.7 pKa e 1.5 0.029 0.033 0.032 0.021 0.050 0.042 0.039 0.041
0.328 0.353 0.325 0.214 0.566 0.481 0.445 0.471
activation temp (°C)
ref
220 220 220 150 220 150 150 150
1 1 2 2 this work this work this work this work
Data from Tosoh Corp. b Data from AKZO. c Average value from the pore volume and surface area.
effected at room temperature; calcination was as in the previous case. The product was exchanged three times with ammonium nitrate (1 mol/L) at 70 °C for 3 h. Drying and calcination, carried out as above, gave a material indicated as MS9. Catalysts were crushed and sieved, employing only particles of GMS1 > HA > LA As to the stability of the various materials, approximate values of the deactivation kinetic coefficient have been calculated for each catalyst (using the mentioned equation, with N ) 2), to compare them with the known values1 for HY zeolites. The results are as follows, for reactions in cyclohexane at 80 °C, in decreasing order of deactivation: HY330, ka ) 0.666 ( 0.085 min-1; HY360, ka ) 0.289 ( 0.063 min-1; MS9, ka = 0.007 min-1; GMS1, ka = 0.006 min-1; HA, ka = 0.005 min-1; LA, ka < 0.004 min-1. The behavior of the last four catalysts can be checked also in the graphical presentation of Figure 1 (this work) and Figure 4 of ref 2. If the para isomer of M is considered as the most interesting product, the para selectivity is an important parameter: in this case the zeolitic catalysts, as a group, have a better behavior, because with one of them (HY330) a para selectivity >70% has been reached. Using HY360 and HA, 64% has been attained; in any other case, values in the range 60-63% have been observed. There is obviously not a case of shape selectivity over amorphous catalysts, but this is apparently true also for MCM-41 materials. Conclusions Amorphous silica-aluminas are stable catalysts for the Friedel-Crafts reaction under examination, but their activity is rather low, particularly when the alumina content and therefore the acid titer are low; para selectivity is in the range 60-64%. Dealuminated HY zeolites deactivate in a fast way; only when fresh do these catalysts have a high catalytic activity; the para selectivity can reach and surpass 70%.
The mesoporous materials of the MCM-41 type are only slightly less stable than amorphous silica-aluminas but are more active than them and about as selective as they are. They seem to be the best catalysts for this reaction, particularly when the pore size of ca. 40 Å extends to the whole sample (catalyst MS9). For the interpretation of the kinetic measurements, the Langmuir-Hinshelwood model has been preferred, for an easy comparison of different catalysts. Acknowledgment This work was supported by Consiglio Nazionale delle Ricerche (CNR, Roma, Italy) within the “Progetto Strategico Tecnologie Chimiche Innovative”. Dr. Ilenia Rossetti is thanked for BET measurements. Nomenclature a ) catalyst activity a0 ) repeat distance in a hexagonal structure, Å Ci ) molar concentration of i, mol/L Ccat ) weight concentration of catalyst, g/L d100 ) distance between adjacent crystallographic planes, Å F ) objective function in the optimization procedure k1, k2 ) rate coefficients in model BIP1X, L1+m/molm‚min‚ g km, kd ) rate coefficients in model BIP3X, L2/mol‚min‚g ka ) deactivation rate coefficient, min-1 KB ) adsorption coefficient, L/mol m ) reaction order (with respect to BzCl) in model BIP1X N ) reaction order in the deactivation rate equation t ) time, min x ) variable employed in the optimization procedure y ) fractional conversion of BzCl Subscript f ) final Superscript ° ) at time zero
Literature Cited (1) Beltrame, P.; Zuretti, G. Benzylation of Biphenyl with Benzyl Chloride over HY zeolites: A Kinetic Model for Reaction and Catalyst Deactivation. Ind. Eng. Chem. Res. 1997, 36, 3427. (2) Beltrame, P.; Zuretti, G. Benzylation of Biphenyl with Benzyl Chloride over Amorphous Silica-Alumina: A Kinetic Study. Ind. Eng. Chem. Res. 1998, 37, 3540. (3) Bellussi, G.; Perego, C.; Carati, A.; Peratello, S.; Previde Massara, E.; Perego, G. Amorphous Mesoporous Silica-Alumina with Controlled Pore Size as Acid Catalysts. Stud. Surf. Sci. Catal. 1994, 84, 85. (4) Reddy, K. M.; Song, C. Synthesis of Mesoporous Molecular Sieves: Influence of Aluminium Source on Al Incorporation in MCM-41. Catal. Lett. 1996, 36, 103. (5) Reddy, K. M.; Song, C. Synthesis of Mesoporous Zeolites and their Application for Catalytic Conversion of Polycyclic Aromatic Hydrocarbons. Catal. Today 1996, 31, 137. (6) Perego, C.; Amarilli, S.; Carati, A.; Flego, C.; Pazzuconi, G.; Rizzo, C.; Bellussi, G.;. Mesoporous Silica-Aluminas as Catalysts for the Alkylation of Aromatic Hydrocarbons with Olefins. Microporous Mesoporous Mater. 1999, 27, 345. (7) Armengol, E.; Cano, M. L.; Corma, A.; Garcia, H.; Navarro, M. T. Mesoporous Aluminosilicate MCM-41 as a Convenient Acid Catalyst for Friedel-Crafts Alkylation of a Bulky Aromatic Compound with Cinnamyl Alcohol. J. Chem. Soc., Chem. Commun. 1995, 519. (8) Armengol, E.; Corma, A.; Garcia, H.; Primo, J. Acid Zeolites as Catalysts in Organic Reactions. tert-Butylation of Anthracene, Naphthalene and Thianthrene. Appl. Catal. A 1997, 149, 411.
1214
Ind. Eng. Chem. Res., Vol. 39, No. 5, 2000
(9) He, N.; Bao, S.; Xu, Q. Fe-containing Mesoporous Molecular Sieves Materials: very Active Friedel-Crafts Alkylation Catalysts. Appl. Catal. A 1998, 169, 29. (10) Huo, Q.; Margolese, D. I.; Ciesla, U.; Feng, P.; Gler, T. E.; Sieger, P.; Leon, R.; Petroff, P. M.; Schu¨th, F.; Stucky, G. D. Generalized Synthesis of Periodic Surfactant/Inorganic Composite Materials. Nature 1994, 368, 317. (11) Hansen, E. W.; Courivaud, F.; Karlsson, A.; Kolboe, S.; Sto¨cker, M. Effect of Pore Dimension and Pore Surface Hydrophobicity on the Diffusion of n-Hexane Confined in Mesoporous MCM-41 Probed by NMR-a Preliminary Investigation. Microporous Mesoporous Mater. 1998, 22, 309. (12) Mokaya, R.; Jones, W. Postsynthesis Grafting of Al onto MCM-41. J. Chem. Soc., Chem. Commun. 1997, 2185. (13) Yang, R. T.; Pinnavaia, T. J.; Li, W.; Zhang, W. Fe3+ Exchanged Mesoporous Al-HMS and Al-MCM-41 Molecular Sieves for Selective Catalytic Reduction of NO with NH3. J. Catal. 1997, 172, 488. (14) Koch, H.; Bohmer, U.; Klemt, A.; Reschetilowski, W.; Sto¨cker, M. Influence of ion exchange and calcination on pore size and thermal stability of MCM-41 with different Si/Al ratios. J. Chem. Soc., Faraday Trans. 1998, 94, 817. (15) Treadwell, F. P. Chimica Analitica; Vallardi: Milan, Italy, 1962. (16) Bertolacini, R. J. Acidity Distributions in Cracking Cata-
lysts. Anal. Chem. 1963, 35, 599. (17) Branton, P. J.; Hall, P. G.; Sing, K. S. W. Physisorption of Nitrogen and Oxygen by MCM-41, a Model Mesoporous Adsorbent. J. Chem. Soc., Chem. Commun. 1993, 1257. (18) Schu¨th, F. Surface Properties and Catalytic Performance of Novel Mesostructured Oxides. Ber. Bunsen-Ges. Phys. Chem. 1995, 99, 1306. (19) Buzzi Ferraris, G. Automatic Optimum Seeking Method. Ing. Chim. Ital. 1968, 4, 171. (20) Carnahan, B.; Luther, H. A.; Wilkes, J. O. The Approximation of the Solution of Ordinary Differential Equations. Applied Numerical Methods; Wiley: New York, 1969; p 361. (21) Cseri, T.; Be´ka´ssy, S.; Figueras, F.; Cseke, E.; de Menorval, L.-C.; Dutartre, R. Characterization of Clay-based K Catalysts and their Application in Friedel-Crafts Alkylation of Aromatics. Appl. Catal. A 1995, 132, 141. (22) Mravec, D.; Michvocı´k, M.; Hronec, M.; Moreau, P.; Finiels, A.; Geneste, P. Cyclohexylation of Naphthalene over Unmodified HY Zeolite. Catal. Lett. 1996, 38, 267.
Received for review July 9, 1999 Revised manuscript received January 26, 2000 Accepted February 3, 2000 IE990492S
