摘要:

Selectivity of a Heterogeneous Rhodium Catalyst for theCarbonylation of Monohydric AlcoholsBY BJARNE CHRISTENSEN AND MICHAEL S. SCURRELL*Instituttet for Kemiindustri, Technical University of Denmark,2800 Lyngby, DenmarkReceived 22nd April, 1977The carbonylation activity of a heterogeneous rhodium-zeolite catalyst has been examined forthe reactions of methanol, ethanol and propan-2-01. A marked contrast in the behaviour of thesethree alcohols is seen. Selectivity for the carbonylation of methanol is high (>go%) at all tempera-tures, whereas the sole reaction product with propan-2-01 is propene. Ethanol shows intermediatebehaviour, exhibiting high selectivity (approaching 100 %) for carbonylation at low temperatures, butvery poor selectivity at higher temperatures.The results are consistent with the relative ease withwhich dehydration of the reactants occurs on polar catalysts.Recently tremendous interest has arisen concerning the development of hetero-genised forms of rhodium based catalysts for the carbonylation of methanol toacetic acid.The high activity and selectivity of homogeneous catalysts containing rhodium forthis reaction is well known 2-4 and has had a considerable impact on the large-scalemanufacture of acetic acid.4 The catalysts are apparently useful in carbonylatinghigher alcohol^,^ although no detailed studies of this aspect have so far appeared.Catalytically active rhodium complexes have been supported on materials such ascarbon,6* ' alumina,8 modified poly(styrene-divinylbenzene) and molecular sievezeolites lo and the resulting materials are successful heterogeneous versions of thehomogeneous catalysts.Results concern methanol exclusively and there seem to beno readily available reports dealing with the behaviour of these heterogenised cata-lysts with ethanol and other alcohols.Oxide supports such as alumina and zeolites are known to efficiently dehydratealcohols, with ethanol being in general more reactive than methanol and with second-ary alcohols being dehydrated faster than primary alcohols. Methanol shows onlya very slight tendency to produce dimethyl ether as a side product during carbonyla-t i ~ n , ~ ' ~ but it was felt that the effect might be more dramatic for alcohols of highermolecular weight.Accordingly we undertook to investigate the carbonylation ofmethanol, ethanol and propan-2-01 on one supported rhodium catalyst. A zeolitebased catalyst, similar in composition to that employed by other workers lo wasselected. Of the heterogenised rhodium catalysts so far investigated the zeolitebased material has a particularly high activity and selectivity for methanol carbonyla-tion.EXPERIMENTALThe catalyst was prepared using a Linde molecular sieve zeolite Type 13X and rhodiumtrichloride. The zeolite was immersed in an aqueous solution of the rhodium salt and heldat 80°C for 15 h with constant stirring. The solid material after filtration, washing anddrying was compressed into tablets (diameter 13 mm) using a static applied pressure of203B .CHRISTENSEN AND M. S. SCURRELL 2037383 MNm-Z. The tablets were crushed and the fraction of powder with particle size60-100 mesh (140-25Opm) isolated for use by sieving. The rhodium content of the finalcatalyst was - 1 % by weight.Rhodium-oncarbon (Engelhard Industries) contained 5 % rhodium by weight. Particlesize was > 170 mesh (< 88 pm).The rhodium-zeolite catalyst ( - 0.2 g) was placed in a Pyrex glass reactor and activated byheating in a stream of dry air at 723 K for 15 h. Carbon monoxide was passed throughthermostatted saturators containing liquid alcohol and liquid alkyl iodide. The separatestreams were joined and passed over the catalyst at a total pressure of 1 atmosphere. Thetotal flow rate of carbon monoxide was 80 an3 min-l and the molar ratios alochol : carbonmonoxide and alcohol : alkyl iodide varied by adjustment of the relative flow rates of gasthrough the saturators and by the temperature at which saturation took place.Alcohol :CO molar ratios were typically -0.05.Reactant and product streams were analysed using gas chromatographic separation witha column of Chromosorb 101 (Perkin Elmer). Column length was from 1.5 to 5.5 m andthe temperature in the range 418-433 K, depending upon the components present in thesamples. Flame ionization detection (Perkin Elmer F1 1) was utilised with nitrogen carriergas.Further experimental details are given in table 1.TABLE RA RATES AND SELECTIVITIES FOR REACTIONS STUDIEDmolar ratio rate of carbonylationl 'selectivity/ %reactants RI/ROH temperature/K mol ester (gRh)-1 h-10.047 513 0.97 > 90MeOH+ Me1 0.1430.0755134731.010.10>w>900.075 433 0.03 > 900.147 5230.100 473EtOH+ EtI 0.235 4730.282 4330.250 383Pr-2-OH + Pr-2-1 0.1300.130473433EtOH+ EtI 0.360 503(Rh-on-carbon)0.130.070.170.030.02000.036506085>990013] x 100 RCOOR+RCOOH[2R20 + RCOOR + RCOOH + alkene a calculated as molUnder the experimental conditions employed conversion of the product acid to thecorresponding ester took place readily and free acid was not detected.In order to minimisethe number of possible products obtained, it was ensured that the identity of the alkylgroups of the reactant alcohol and alkyl iodide were the same.RESULTS AND DISCUSSIONAll results are summarized in table 1.Methanol was converted to methyl acetateat temperatures in the range 433-513 K. The selectivity for carbonylation wastypically >90 %, even at the highest reaction temperatures. The side product wasdimethyl ether. A slight ( N 10 %) increase in the rate of carbonylation resulted froman increase in the methyl iodide : methanol molar ratio in the reactant stream from0.047 to 0.143. LittIe or no loss of the iodide promoter was seen. In the absenc2038 SELECTIVITY OF A RHODIUM CATALYSTof methyl iodide in the reactant mixture the rate of carbonylation fell rapidly but thedehydration reaction was virtually unaffected.Ethanol carbonylation occurred at 383-523 K and selectivity was determined forthe most part by the choice of temperature.At 523 K the overall conversion ofethanol was slightly greater than for methanol at 513 K but the selectivity was verylow at - 6 %. At lower temperatures the selectivity was higher, reaching a value of99 % at 383 K. Low selectivity was associated with the formation of both ethyleneand diethyl ether, alkene production predominating at temperatures above - 470 K.No significant consumption of ethyl iodide occurred.The carbonylation of propan-2-01 was attempted at temperatures of 433 and 473 K,but the sole product in each case was propene, conversion to the alkene being com-plete at the higher temperature under the experimental conditions employed.The results indicate the striking differences in behaviour of the three alcohols,selectivity for methanol and propan-2-01 approaching 100 and 0 % respectively, andfor ethanol ranging approximately between these limits depending largely on reactiontemperature and to a small extent on the molar ratio of ethyl iodide : ethanol.These observations can be reconciled with the relative ease of dehydration of thealcohols commonly found for reaction on polar cata1ysts.lThe dehydration sites in the rhodium zeolite might be expected to be provided bythe carrier and to be physically distinct from the carbonylation centres, but theresults of a series of experiments using rhodium supported on carbon gave rise todoubts about this conclusion.Thus, at 503 K, ethanol carbonylation took place onthe latter catalyst, but the selectivity was only - 13 %, due to the extensive formationof ethylene.Since high dehydration activity is not normally associated with carbonitself, it may well be that the carbonylation centres provide the catalytic activity forthe elimination reaction. This may also be true at least to some degree for the zeolitebased catalyst, although further experimentation is required for clarification.Since molecular sieve zeolites are known to catalyse the formation of alkenes fromhalogenoalkanes by elimination at temperatures close to those used in this work,l2' l 3it is possible that some ethylene and propene are produced from the respective alkyliodide and not from the alcohol alone. Overall conversion of the iodide would benegligible if the hydrogen halide so produced reacted sufficiently rapidly with thealcohol present, e.g.for ethyl iodideC2H51 -+ C2H,+HIfollowed byHI + CZHSOH + CzHSI + H20.Reaction (2) is also likely to take place readily in the presence of a zeolite catalyst.12A comparison with the data provided by other workers on rhodium zeolite car-bonylation catalysts lo shows that the rate found by us for methanol conversion at513 K [ N 1 mol acetate (gRh)-l h-'1 is higher than theirs [ -0.14 mol acetate (gRh)-'h-l] for reaction under comparable conditions, and is also higher than the ratesreported for other heterogenised rhodium catalysts.'This work confirms that catalysts produced from rhodium trichloride and a zeolitepossess high activity and selectivity for the carbonylation of methanol, but demon-strates that this behaviour is not encountered in the attempts to carbonylate ethanoland propan-2-01.M. S .Scurrell, Platinum Metals Rev., 1977, 21, 92.F. E. Paulik and J. F. Roth, Chem. Comm., 1968, 1578.J. Hjortkjaer and V. W. Jensen, Ind. and Eng. Chem. (Product Res. and Development), 1976,15,46€3. CHRISTENSEN AND M. S . SCURRELL 2039J. F. Roth, J. H. Craddock, A. Hershman and F. E. Paulik, Chem. Tech., 1971, 600.F. E.. Paulik, A. Hershman, J. F. Roth, J. H. Craddock, W. R. Knox and R. G. Schultz,South African Patent 682174 (1968) to Monsanto Co.R. G. Schultz and P. D. Montgomery, Amer. Chem. Soc., Div. Petrol. Chern., Preprints,1972,17, B 13.A. Kryzwicki and G. Pannetier, Bull. SOC. chim. France, 1975, 1093.M. S. Jarrell and B. C. Gates, J. Catalysis, 1975, 40, 225.Nauk. S.S.S.R., Ser. khim., 1976, 582.ti R. G. Schultz and P. D. Montgomery, J. Catalysis, 1969, 13, 105.lo B. K. Nefedov, N. S. Sergeeva, T. V. Zheva, E. M. Shutkina and Ya. T. Eidus, Zzuest. Akad.l 1 H. Noller and W. Kladnig, CataZysis Reu. (-Sci. Eng.), 1976, 13, 149.l2 P. B. Venuto, E. N. Givens, L. A. Hamilton and P. S. Landis, J. Catalysis, 1966,6,253.l3 W. Kladnig and H. Noller, J. Catalysis, 1973, 29, 385.(PAPER 71676

ISSN:0300-9599    

DOI:10.1039/F19777302036

出版商:RSC    

年代:1977

数据来源: RSC

摘要:

Reviews of BooksComprehensive Chemical Kinetics. Vol. 15. Non-Radical Polymerisation. Ed. C. H. BUFORD andC. F. H. TIPPER. (Elsevier, Amsterdam-Oxford-New York, 1976). Pp. 660. Price 649.88/ $99.75.This is the latest volume of the large-scale work on chemical kinetics which was first publishedin 1969. The book contains eight chapters surveying the anionic polymerisation of olehs:homogeneous cationic polymerisation : Ziegler-Natta reactions ; the polymerisation of cyclic ethersand sulphides, of lactams and of aldehydes ; polycondensation reactions ; and the polymerisation ofN-carboxy-a-amino acid anhydrides.The authors achieve a high standard. The plan of giving special attention to particular repre-sentative reactions enhances interest and readability, and should be useful in conveying the “ feel ”of the subject to research workers coming to it for the first time.The book is also, of course, animportant reference work for specialists. The principal theme of kinetic results and their interpre-tation is well interwoven with critical appraisal of characteristic experimental problems, such assensitivity to trace impurities and identification of transient reactive species. There is a noticeableoverlap between chap. 2 and 4, which each include accounts of the polymerisation of tetrahydrofuran ;but the considerable differences in view-point and emphasis make this more instructive than irritating.Although very expensive the book may prove a better bargain than a collection of specialised volumescovering the same region of polymerisation chemistry.The availability, in one volume, of thesereviews of the wide field of non-radical polymerisation kinetics should broaden perspectives and bea stimulus to new investigation. It will be most useful to individuals who can afford it, and shouldcertainly be recommended to libraries.K. E. WEALEReceived 13th September, 1976Phase Transitions and Critical Phenomena. Volume 6. Ed. C. DOMB and M. S. GREEN. (AcademicPress, London, 1976). Pp. xviii+575. Price ;E21.50/$46.75.The sixth volume in the series edited by Domb and Green is entirely devoted to the renormalizationgroup approach to critical phenomena. This departure from the normal format of the series isfitting, however, given the very substantial development that has taken place in the comparativelyshort period since the publication (in 1971) of Kenneth Wilson’s pioneering contributions.As ithappens, the subject is already well served by review articles, and at least two other books arecurrently available which treat the problem in a relatively elementary way. The present work, incontrast, is clearly intended for specialists. The seven major chapters are all written by acknowledgedauthorities in the fieId and for good measure there is a brief introduction by Wilson himself. Standardtopics such as the E (Wallace) and l / n (Ma) expansions are treated at length and a notable featureis the strong effort made to establish the link between renormalization group ideas and the ideas ofquantum field theory: two full chapters (by Di Castro and Jona-Lasinio and by Brezin, Le Guillouand Zinn-Justin) are devoted to this difficult area.There are also two chapters of a more generalnature, by Wegner and Niemeijer and by van Leeuwen (the latter devoted to Ising-like systems),and finally a detailed account of spin anisotropies and long range interactions by Aharony.Multi-authored books have well-known disadvantages, but in this case a real effort has beenmade to cross-link the chapters. The production is excellent and the work as a whole is a fineaddition to a fine series. Everyone active in research into critical phenomena will wish to have thisvolume close at hand.I. R. MCDONALDReceived 27th April, 1977Atmospheric Chemistry. By J. HEICKLEN. (Academic Press, London and New York, 1976).Pp.xivS-406. Price E27.00/$38.50.The sudden growth of interest in atmospheric chemistry will inevitably produce a spate of bookson this topic and the authors and publishers of the ftrst books to appear must be praised for theirrapidity of writing and publication. However, the race is also against inflation in publication costs204REVIEWS OF BOOKS 2041and HeickIen’s book costs twice as much per page as McEwan and Phillips’ “ Chemistry of theAtmosphere ” which appeared the previous year at E9.75.The balance of these two books is quite different. McEwan and Phillips are largely concernedwith the stratosphere and ionosphere and one third of their book is devoted to the airglow and toion-molecule reactions. They provide an interesting discussion of the atmospheres of other planets,but only devote 22 pages to the troposphere and to pollution problems.In contrast, Heicklen’sbook considers only the Earth’s atmosphere and the bulk of the text is related directly or indirectlyto pollution problems. Much of the present volume is an account of those areas of chemical kineticsand photochemistry which are relevant to the atmosphere, but the atmospheric importance of thedifferent reactions discussed is not made c1ea.r enough for someone who is unfamiliar with the topic.For such a reader the treatment of the all-important transport processes is disappointing. Threescale heights are defined, but not discussed and one could be left with the impression that the verticaltransport rate varied exponentially with altitude.The relative importance of transport and chemistryfor different species and at different altitudes are not well brought out, neither are the parameterisationof transport by eddy diffusion coefficients nor the magnitude of the natural sources and sinks ofmany trace components.Nevertheless this book is a useful source of accurate chemical information (apart from out-of-dateradiative lives for singlet molecular oxygen) and its intelligent use of steady state analyses to explainthe balance of chemical processes occurring in the atmosphere will appeal to kineticists. Havingworked their way through the intricacies of hydrocarbon oxidation, smog formation and sulphurdioxide photochemistry and chemistry, it is to be hoped that readers will realise that there is no directrelation between the length of a section and its importance to atmospheric chemistry.It is also tobe hoped that they will not try out Heicklen’s suggestion of releasing diethyl hydroxylamine toinhibit photochemical smog. Only three years ago, CFCIJ and CF2C12 were considered to becompletely inert and innocuous in the atmosphere and, although we are learning rapidly, it will be along time before we understand atmospheric chemistry well enough to contemplate such an experi-men t .B A.THRUSHReceived 27thApri1, 1977Dispersion Forces. By J. MAHANTY and B. W. NINHAM. (Academic Press, London, 1976). Pp. ixf236.Price E9.20/ $20.10.Dispersion forces between molecules or larger bodies result from correlation in the fluctuationsin the charge distributions in the interacting systems.There is much interest in the topic, for itimpinges on many branches of science, including physics , chemistry, crystallography, polymerscience, colloid science, molecular biology and even astronomy. So the appearance of this newbook by two mathematical physicists from the Australian National University is timely. It isintended for “ graduate students and researchers in areas spanning physics, chemistry and biologywhere dispersion forces play a role ”.There are seven chapters, four short appendices and a postscript containing several references topapers published in 1976. The theory of dispersion forces is developed from the field point of viewand emphasis is placed on macroscopic interactions.The last two chapters are on the role ofdispersion forces in adsorption and in polymer solutions, and on the effects of electrolytes andconduction processes.The authors are well known for their original contributions to the theory of long-range forcesbetween macroscopic bodies; their book is clear and concise and it contains much elegant mathe-matics and lively prose. It is a specialised monograph, and is not a text book on intermolecularforces. The reader is not instructed in how to deduce the full interaction potential for even thesimplest atoms. On p. 88 (see also p. 94 and p. 158) it is stated that “the important observationis that the magnitude and selectivity of van der Waals forces acting between macromolecules shouldbe accessible through macroscopic measurements which are model independent ”.This is misleading,for selectivity is associated with short-range forces and hence with the complementarity of theinteracting molecules. Chemistry is not a sub-branch of dielectrics!While most of the text is clear and authoritative, a few blemishes exist. The Kirkwood-Shumaker interaction energy between proteins resulting from fluctuations in their total charge variesas the inverse square of their separation r and not as r-6 (p. 86). On p. 73 it is stated that themeasurements of Israelachvili and Tabor of the force between crossed cylinders of mica “ are inremarkable agreement with the Lifshitz theory ”; but in the postscript (p. 228) we read of discrepanciesbetween theory and that experiment. On p. 129, there is a brief discussion of the relative stabilitiesof the face-centred-cubic and hexagonal close-packed lattices for the solid inert gases. It is state2042 REVIEWS OF BOOKS‘‘ that any difference in energy must arise from the long-range dispersion part. For point moleculesthe dispersion energies turn out to be the same within the limits of computational error ”. Boththese assertions are unjustified, for short-range non-addivity may be an important factor, and the energydifferences between f.c.c. and h.c.p. lattices for a Lennard-Jones potential are accurately known(see T. H. K. Barron and C. Domb, Pruc. Roy. Suc. A, 1955, 227, 447). The symbol n is used forthree different quantities in Chapter 1. S.I. units are not employed.This will be a useful book for the specialist, and colloid scientists in particular will be very gratefulto the authors. The price (4p per page) is reasonable.A. D. BUCKMGHA~VLReceived 1st May, 197

ISSN:0300-9599    

DOI:10.1039/F19777302040

出版商:RSC    

年代:1977

数据来源: RSC