Ind. Eng. Chem. Res. 1993,32, 2414-2417
2474
Synthesis of Hydrocarbons from Syngas Using Mixed Zn-Cr Oxides: Amorphous Silica-Alumina Catalysts Ra61 A. Comelli and Nora S . Figoli' Znstituto de Znueetigaciones en Catcilisis y Petroqulmica (ZNCAPE),FZQ, UNL-CONICET, Santiago del Estero 2654, 3000 Santa Fe, Argentina
The influence of operational conditions on the transformation of synthesis gas into hydrocarbons was studied. Mixtures of ZnO-CrzO3 (Zn-Cr) and an amorphous silica-alumina (SA) were used as catalysts. The 1:l Zn-Cr:SA mixture gives a carbon monoxide conversion of 53% at ca. 400 "C; it is similar to that obtained using a Zn-Cr:erionite mixture. The increase of temperature, pressure, and time factor favors CO conversion. Methanol is formed over the Zn-Cr catalyst, and this reaction is the limiting step of the global process. A mechanism is proposed whereby MeOH-DME are the intermediates, which diffuse into the SA where they are converted to hydrocarbons. It can be considered that C1 and C2 species are the hydrocarbon "precursors" during the methanol to hydrocarbons transformation. Introduction Methanol can be obtained at high temperatures and pressures from synthesis gas over mixed oxide catalysts such as ZnO-Cr203 (Natta, 1955; Hiller and Marschner, 1970) and over Cu-ZnO supported on Cr203 or A1203 (Kung, 1980;Mehtaet al., 1979;Burchand Chappell, 1988) at less severe conditions. The conversion of methanol into hydrocarbons on acid catalysts (Chang, 1983;Hayashi and Moffat, 1982),as a subsequent reaction, has increased the attention on the study of the transformation of syngas to hydrocarbons via methanol, in only one step (Fujimoto et al., 1985; Gadalla et al., 1983). The optimal operational conditions for each reaction are quite different; methanol synthesis is carried out at 300-400 "C and 30-35 MPa in the high-pressure process and at 230-210 "C and 5-10 MPa in the low-pressure process (Hiller and Marschner, 1970; Balabrahman and Sunavala, 1980). The hydrocarbon production from methanol requires temperatures of about 350-400 "C (Chang, 1983; Sedran et al., 1984)and pressures no higher than 5 MPa to avoid the formation of undesired products such as poly(methylbenzenes), which are solids at room temperature and atmospheric pressure (Chang et al., 1979). The adequate temperature range to allow the hydrocarbon formation suggests the selection of Zn-Cr as the alcohol synthesis catalyst, due to its higher thermal stability (Yashima et al., 1982). The results obtained when transforming synthesis gas into hydrocarbons in only one step using a mixture of Zn-Cr and an amorphous silica-alumina, which is active in the methanol into hydrocarbon transformation (Comelli and Figoli, 1987,1991),are presented in this paper. The effect of the weight ratio of both catalysts and of operational conditions (temperature, pressure, time factor) on the catalytic activity and selectivity is analyzed. Experimental Section Catalysts. Zn-Cr is a commercial catalyst (TOPSOE) having 50.7% Zn and 17.8% Cr, 106.1m2g-1 BET specific surface area, 0.120 cm3g' pore volume, and 4.5-nm mean pore diameter. The amorphous SA (KETJEN LA-LPV) has a 11.34 si1ica:alumina molar ratio, 559 m2 g1BET specific surface area, 0.633 cm3 g1pore volume, and 4.5nm mean pore diameter. Data about SA acidity, determined by NH3 thermal programmed desorption, were previously published (Comelli and Flgoli, 1991). Zn-Cr: 0888-5885f 9312632-2&i$O4.00/0
SA mixtures at weight ratios of 1:l and 1:2 (keeping the total weight constant) were used. Pretreatment of the Catalyst. The methanol synthesis catalyst must be reduced in diluted hydrogen flow, slowly increasing the temperature until reaching the reaction temperature (Sofianos and Scurrell, 1991). SA requires an air treatment at more than 450 "C to be active in the methanol transformation (Sedran et al., 1984). At this temperature, the methanol synthesis catalyst surface area decreases by about 40%, but ita activity is not modified. Working with a mixture of Zn-Cr (doped with Pd) and ZSM-5, Inui and Takegami (1982) pretreated the catalyst by oxidizing it for 2 h at 400 "C followed by reduction at 500 "C for 30 min. Using an impregnated Pd/SAPO catalyst, Thomson et al.(1990) calcined in 02 at 400 "C for 3 h, cleaned with He, and then reduced with H2 at 300 "C for 3 h. In this work, the catalyst mixtures were activated overnight under an airflow a t 500 "C, cooled under nitrogen flow to reaction temperature, and finally reduced with hydrogen at the latter temperature for 2 h. Feed. A 1:2:1 molar ratio CO:H2:He mixture was used. CO, H2, and He are from commercial sources, having 98 9% , 99.99 % , and 99.99 % purity, respectively. Helium was added as internal standard. Catalytic Activity and Selectivity Determinations. Experiments were carried out in a stainless steel, fixed bed, continuous flow reactor that can be operated at up to 3.0 MPa of pressure. The feed flow was controlled using a micrometric valve and was measured by means of a microrotameter, before being preheated. The reactor effluent was passed through avalve which reduced pressure to the atmospheric and was operated at high temperature to avoid product condensation; afterward, the gases were sent to a GC with flame ionization detector (FID) via a heated sample valve. The reactor effluent was finally received in a condenser-collector. The noncondensed fraction was divided into two streams: one for feeding a six-port and the other a 10-portsample valve, respectively, from where they were sent to a GC with thermal conductivity detector (TCD). Methanol, methane, and hydrocarbons having more than five C atoms were analyzed in the FID (columns and operational conditions have been previously published (Comelli and Flgoli, 1991)). The gas stream passing through the six-port sample valve was used to analyze He, C02, dimethyl ether (DME),methane, and alkanes and alkenes of CZ-C~(data about that analysis 0 1993 American Chemical Society
Ind. Eng. Chem. Res., Vol. 32, No. 11,1993 2476 Table I. CO Convenion and Selectivities to Hydrocarbons, COS (24-, and Aromatics as a Function of Temperature and
Time Factor.
T (OC)
370 370 390 340 340 190 190 190 xco (%) 26.0 39.1 42.9 42.1 50.5 52.8 52.3 S H C (%) 52.1 49.3 47.1 47.5 sc02 (%) 47.8 su (%) 88.2 80.2 82.1 82.5 4.6 3.0 3.5 SAr (%) 1.9 a Zn-Cr:SA = 1:1,P = 1.1 MPa, time on stream
W/F(ghmol-l)
390 410 340 190 53.1 45.9 52.9 51.6 47.0 48.3 84.5 84.0 2.5 2.6 = 400 min.
Table 11. CO Conversion and Selectivities to Hydrocarbons, COz, C4-, and Aromatics for Different Temwratures. _ _ _ _ _ _ ~ ~ _ _ _ T ("0 340 370 410 xco ( % ) 13.3 21.0 41.5 SHC (%) 49.2 49.8 52.5 scoz (%) 50.6 50.1 47.3 su ( % I 87.3 83.2 89.9 SAr (%) 0.1 1.4 1.2 a Zn-Cr:SA = 1:2,P = 1.1 MPa, WIF = 190 g h mol-', time on stream = 400 min. ~~
were published (Comelli and Flgoli, 1991)). The 10-port sample valve was operated with backflush, and the gas stream passing through it was used to analyze CO and He by means of a Carbosphere column, at room temperature. With the chromatographic data, using He as a link between the two TCD analyses and methane as a link between the FID and TCD analyses, CO total conversion and selectivities to the different hydrocarbons and to oxygenated products were calculated by means of a C atom balance.
Results Effect of Temperature and Time Factor. The effect of temperature was studied between 340 and 410 "C. One run for each temperature was carried out for 450 min; reaction products were identified using chromatographic patterns according to previously published procedures (Comelli and Figoli, 1987). Hydrocarbons were alkanes, alkenes, and aromatics, with a maximum of 12 C atoms; the oxygenated compounds were COZ,MeOH, and H2O. Deactivation was not observed during the time of our experiments. Table I shows, using a 1:lZn-Cr:SAmixture as catalyst, total CO conversion (XCO) and selectivities to hydrocarbons (SHC) and to COZ(SCOZ), referred to CO converted, as a function of temperature. There are also given the selectivities to hydrocarbons having four or fewer C atoms (Scp)and toaromatics (SA,), referredto the hydrocarbons produced. The increase in temperature favors Xco,which increases from 26.0% a t 340 "C to 45.9% at 410 "C at a time factor ( WIF,ratio between the weight of catalyst and the molar flow rate of feed) of 190 g h mol-', while selectivities do not change too much. For another WIF = 340 g h mol-', the behavior is qualitatively similar. Table I also compares Xco and selectivities at two different time factors: 190 and 340 g h mol-' at 370 and 390 "C. The behavior is similar for both temperatures. At the highest time factor, Xco is higher (109% higher a t 370 "C and 26 % higher at 390 "C), and the selectivities do not change very much. Table I1 shows, for a 1:2 Zn-Cr:SA mixture, that by increasing the temperature Xco increases from 13.3% a t 340 "C to 41.5% at 410 "C; Sk increases from 0.1 5% at 340 "C to 1.4% at 370 "C. The other selectivitiesdo not change. Effect of Pressure. The effect of pressure on the activity and selectivity was studied between 0.2 and 1.3
Table 111. CO Conversion and Selectivities to Hydrocarbons, Cot, C4-, and Aromatics for Different Pressures Zn-Cr:SA = 1:l ZnCr:SA = 1:2
T ("C)
WIF(ghmo1-1) P (ma)
xco (%) snc (%) scoz ( % ) su (%) SAr (%)
390. 340 0.6 35.4 53.0 46.8 85.0 2.6
390 340 1.1 53.1 52.9 47.0 84.5 2.5
390 340 1.3 56.1 53.9 46.0 82.2 2.5
410 190 0.2 12.0 61.1 38.8 97.1 0.1
410 190 0.6 29.5 50.8 49.0 90.0 1.7
410 190 1.1 41.5 52.5 47.3 89.9 1.2
410 190 1.3 41.0 54.4 45.5 85.5 2.0
MPa, with the results presented in Table 111. By increasing pressure, using a Zn-Cr:SA = 1:lmixture as catalyst, Xco increases from 35.4% a t 0.6 MPa to 56.1% at 1.3 MPa, and there are no significant changes in the selectivities. With the 1:2 Zn-Cr:SA mixture, Xco increases from 12.0% at 0.2 MPa to 41.0% at 1.3 MPa and Scp decreases 14% between 0.2 and 1.3 MPa; SHCdecreases and SA,and Sc02 increase up to 0.6 MPa, and then they remain without significant changes. These results were obtained using 0.2-0.4-mm Zn-Cr and SA particles. The same values were obtained using particles of 0.1-0.2 mm.
Discussion A Zn-Cr:SA ratio of 1:l gives the best result in the transformation of synthesis gas into hydrocarbons (Tables 1-111). The 1:2 mixture has a higher acid sites concentration than the 1:l one, and it was selected in order to know if it was possible to increase the selectivity to hydrocarbons. The change from a 1:l to a 1:2 mixture decreases XCOand does not produce significant changes in the selectivities. CO conversion is a function of the number of the methanol synthesis active sites, and once the alcohol is formed, the other reactions occur rapidly. This is in accordance to Yashima et al. (1982), who suggested that methanol synthesis is the controlling step in the syngas into hydrocarbons transformation, using ZnCr:ZSM-5 as catalyst. On this basis, further examination of temperature, pressure, and time factor effects was carried out. The increase in temperature favors CO conversion (Tables 1-11). Similar results were obtained working with Zn-Cr:ZSM-5 ratios of 1:l and 1:3 (Yashima et al., 1982): CO conversion increased from 139% at 284 "C to 48 % at 344 "C. The same behavior was observed with Zn-Cr: zeolon and Zn-Cr:erionite (Gadalla et al., 1983) and with Zn-Cr(Pd):ZSM-5 (Inui and Takegami, 1982). The temperature increase does not favor the methanol synthesis, due to thermodynamic reasons (Balabrahman and Sunavala, 19801,but it favors the methanol to hydrocarbons transformation (Comelli and Flgoli, 1992a). According to the present results, the global system is favored by increasing temperature. This fact can be interpreted by considering that the acid catalyst converts the alcohol, once formed, and alters the thermodynamic limitations, as has been suggested by other authors (Gadalla e t al., 1983). The pressure increase favors CO conversion (Table 111). Similar results were obtained with Zn-Cr:ZSM-5 (Yashima et al., 1982): at 304 "C, CO conversion increased from 9% at 1.0 MPa to 16% at 4.5 MPa. Experiments made with Cu-Zn:y-A1203 (Fujimoto et al., 1986) between 1.0 and 5.0 MPa produced increments of CO conversion from 60% to 90% . The pressure favors the methanol formation because of thermodynamic effects (Kung, 1980; Balabrahman and
2476 Ind. Eng. Chem. Res., Vol. 32, No. 11, 1993 Table IV. Total Conversion and Hydrocarbon Distributions Obtained in the Transformation of Methanol and of Synthesis Gas feed synthesis gas methanol %-&:SA = 1:l catalyst SA 390 temp (“C) 370 1.1 total pressure ( m a ) 0.1 53.1 total conversion ( % ) 100 HC distribution ((3%) c 1
cz
cs
c4
CS+
9.6 14.1 14.6 24.4 37.3
Table V. Product Distributions in the Syngas to Hydrocarbons Transformation over Mffemnt Catalyst MiXtUreS catalvst mixtures Zn-Cr + Zn-Cr-Al + ZnCr(Pd) + Zn-Cr + Pd/SiOl SAi ZSM-U ZSM-6r erionitd ZSM-P
24.0 20.4 17.3 22.8 15.5
Sunavala, 1980) and also the alcohol into hydrocarbons transformation (Comelli and Flgoli, 1991). There exists a double positive effect of the pressure. Increasing the time factor causes the CO conversion to increase (Table I). Similar results were obtained using Zn-Cr:ZSM-5 (Yashima et al., 1982): when the time factor was increased to 15 g h mol-l, CO conversion increased from 8%to 26%. The same was observed when working with Cu-Zn:y-Al~Oa (Fujimoto et al., 1986). There is a double positive effect over the system when increasing the time factor: both the methanol synthesis and the methanol transformation (Yashima et al., 1982; Fujimoto et al., 1986) are favored. The hydrocarbon distributions obtained from methanol over SA and from synthesis gas over 2n-Cr:SA can be observed and compared in Table IV. The C142 fraction is higher in the syngas transformation, and there are no important changes in the C3-G fraction. An increase in the C1-C2 fraction was also observed by Inui and Takegami (1982)when comparingthe methanol conversion on ZSM-5 and the syngas conversion on Zn-Cr(Pd):ZSM-S. This can be explained by assuming that the C1 and C2 species produced on the acid sites, which are mainly nonsaturated ones (Itoh et al., 1982; Comelli and Ffgoli, 19881, are hydrogenated on the methanol synthesis catalyst before their growth to larger molecules. The amount of C1 in the hydrocarbon mixture is 2.5 times higher when transforming syngas than when transforming methanol, while C2 increases only 1.4 times. The difference can be attributed to the fact that methane can be produced either by the hydrogenation of the C1 “precursor” species formed on the acid sites or by the methanation reaction on the methanol synthesis catalyst. The CO conversion was only 4% when feeding syngas over Zn-Cr under the same operational conditions indicated in Table IV. Comparison of Zn-CrSA = 1:lto other catalyst mixtures under severaloperationalconditions shows that the current mixture gives a slightly better CO conversion than ZnCr:erionite (a narrow pore, eight-rings zeolite) and a much higher conversion than Zn-Cr-AkZSM5, Pd/SiOz:ZSM5, or Zn-Cr(Pd):ZSM5, as is shown in Table V. The high amount of alkaneg contained in the C4- fraction is generally mentioned, although some differencesexist in the product distributions. The Cs+ nonaromatic fraction is mainly formed by Cs and CS;the aromatica are benzene, trimethyl-, and tetramethylbenzene. The oxygenated compounds are mainly C02 and a very small amount of MeOH; DME is not detected. We have obtained qualitatively similar behavior using an impregnated Pd(4%)/SA catalyst (Comelli and Ffgoli, 1992b). The reactions occurring on the methanol synthesis catalyst and on the SA are shown in Figure 1. A reaction scheme similar to that proposed by Fujimoto et al. (1985) for synthesis gas into hydrocarbons transformation on
390 1.1 340 1:2 53.1 52.9 84.5
343 10
380
427
350
6.1
2.1
1:2 14.w
2.2 66ooo 1:l 21.w
5.w 1:2 49.9
C
C
54.1
98.0
58.3
100.0
10 h 13.3c c 96.1
28.4 24.1 20.5 27.0
7.6 29.4 47.1 15.9
47.7d
43.8 35.5 14.7 6.0
63.7 10.6 23.7 2.0
54.8 19.4 9.7 3.9 5.8 6.4 85.4 0.4 0 14.2
100.0
h h h h h h h h h h
0 0
449
0 0 0 0 0 h h h h
rn
52.3e
Cs+ distribn (C % ) cb
CS c7t
BTX ATP AT10
COn (mol % )
0 0 0 0
75.8
65.18 h
MeOH (mol % ) 5.5 h 4.0 h DME (mol % HzO (mol %) 14.7 h a Space velocity (h-9. WHSV (h-1). Only CO HC. C1+ CZ. e Ca Cb f NonaromaticsCb+. Totalaromatics. * Nonavahble data Thispaper.jChangetal.,1984. InuiandTakegami,1982. Gadalla et al., 1983. Fujimoto et al., 1986. +
+
CO
+ 2 H p e MeOH -1
[ I
.5
OM€
1
Alkones , alkenes
Zn -Cr
SA
Figum 1. Reactions and probable catalyst active sites involved in the SG into HC transformation.
mixed catalyst, is presented. The intermediates between MeOH-DME and hydrocarbons are called hydrocarbon “precursors” (low molecular weight nonsaturated species), as previously done (Comelli and Fsgoli, 1987). Methanol to DME dehydration occurs more rapidly than hydrocarbon formation reactions, as has been demonstrated for methanol to hydrocarbon transformation (Perot et al., 1982). The small amounta of methanol and the absence of DME in the products of the syngaa to hydrocarbons transformation indicate that the conversion of both compounds into hydrocarbon “precursors* occurs easily. The hydrogen pressure as well as the proximity between both types of active sites favors the rapid hydrogenation of hydrocarbon “precursors”to alkanes. This reaction is more favored than their transformation into the producta observed during the methanol conversion on SA (Comelli and Ffgoli, 1991) and on ZSM-5 (Chang, 1983). Conclusions The CO conversion increases when increasing temperature, pressure, and time factor during the syngas into hydrocarbons transformation. Although methanol synthesisis not thermodynamicallyfavored when temperature is increased, the alcohol consumption allows the system to be displaced to the producta. The increase in pressure and time factor favors both the methanol synthesis and the methanol into hydrocarbons transformation.
Ind. Eng. Chem. Res., Vol. 32, No. 1 1 , 1 9 9 3 2477 The conditions for methanol formation over Zn-Cr, coupled with methanol’s rapid reaction in the SA catalyst to DME (and subsequently MeOH-DME to alkanes and water), result in an attractive overall yield. The low concentration of methanol in the reactor reflects methanol’s slow rate of formation over Zn-Cr and the rapid reaction of methanol and DME to hydrocarbons. Since the methanol and DME concentrations in the SA catalyst are always low, the concentration of DME in the effluent (outside the catalyst) is also low. The low sensitivity of the different selectivities to changes in temperature, pressure, and time factor suggests that the type of active sites and their proximity have the greatest influence in the product distribution. The high selectivity to C1 and CBcan be attributed to the easy hydrogenation of the hydrocarbon “precursors”,produced from MeOH-DME, in the presence of hydrogen on the active sites of the methanol synthesis catalyst. The highest c1-C~fraction obtained in the synthesis gas to hydrocarbons transformation compared to that obtained during the methanol conversion gives value to the assumption that C1and CZspecies are the hydrocarbon “precursors” in the second reaction (Comelli and Flgoli, 1987).
Nomenclature Zn-Cr: ZnO-Cr2Oa S A silica-alumina GC: gas chromatograph WIF: time factor, ratio between the weight of catalyst and the molar flow rate of feed XCO: carbon monoxide conversion SHC: selectivity to hydrocarbons SCO~: selectivity to CO2 SW: selectivity to hydrocarbons with four or fewer C atoms Sh: selectivity to aromatics Literature Cited Balabrahman, P.; Sunavala, P. D. Thermodynamics of Methanol Synthesis. Chem. Eng. World 1980, 15 (10) Sect. 1, 51-59. Burch, R.; Chappell, R. J. Support and Additive Effects in the Synthesis of Methanol over Copper Catalysts. Appl. Catal. 1988, 45, 131-150.
Cham. C. D. Hvdrocarbons from Methanol. Catal. Rev.-Sci. Ena. ig&, 25 (11,i-118. Chang, C. D.; Lang, W. H.; Smith, R. L. The Conversion of Methanol and Other 0-ComDounds to Hvdrocarbons over Zeolite Catalvats. 11. Pressure Effeits. J. Catal.-1979,56, 169-173. Chang, C. D.; Miale, J. N.; Socha, R. F. Syngas Conversion to Ethane over Metal-Zeolite Catalysts. J. Catal. 1984,90,84-87. Comelli, R. A.; Ffgoli, N. S. The Effect of Adding Water to the Feed on the Transformation of Methanol into Hydrocarbons on an Amorphous Silica-Alumina Catalyst. Appl. Catal. 1987,30,325-
Comelli, R. A.; Flgoli, N. S. Hydrocarbons from Methanol over Operational Conditionefor Maximum AmorphousSilica-Al& Ca+Fraction Yields. React. Kinet. Catal. Lett. 1992a, 47 (2), 213219.
Comelli, R. A.; Ffgoli, N. S. Hydrocarbons from Synthesis Gas over Pd Supported on Silica-Alumina Catalyst, submitted for publication in React. Kinet. Catal. Lett. 1992b. Fujimoto, K.; Saima, H.; Tominaga, H. Synthesis Gas Conversion Utilizing Mixed Catalyst Composed of CO Reducing Catalyst and Solid Acid. IV.Selective Synthesis of CZ,CSand Cd Paraffins from Synthesis Gas. J. Catal. 1985,94,16-23. Fujimoto, K.; Asami, K.; Saima, H.; Shikada, T.; Tominaga, H. TwoStage Reaction System for Synthesis Gas Conversion to Gasoline. Ind. Eng. Chem. Prod. Res. Dev. 1986,26,262-267. Gadalla, A. M.; Chan, T.; Anthony, R. G. Direct Conversion of Synthesis Gasto Light Hydrocarbons on Heterogeneous Catalysts. Int. J. Chem. Kin. 1983,15,759-774. Hayashi, H.; Moffat, J. B. The Properties of Heteropoly Acids and the Conversion of Methanol to Hydrocarbons. J. Catal. 1982,77, 473-484.
Hiller, H.; Marschner, F. Lurgi Makes Low-Pressure Methanol. Hydrocarbon Process. 1970,9, 281-285. Inui, T.; Takegami, Y. Liquid Hydrocarbon Synthesis from Syngas on the CompositeCatalyst of Metal Oxides and Novel Type Zeolite. Proceedings of the Pan-Pacific Synfuel Conference; Japan Petroleum Institute: Tokyo, 1982, Vol. I, pp 146-161. Itoh, H.; Hattori, T.; Murakami, M. Product Distribution in the Conversion of Methanol on Partially Ion-Exchanged Mordenih. Appl. Catal. 1982,2, 19-37. Kung, H. H. Methanol Synthesis. Catal. Rev.-Sci. Eng. 1980,22 (2), 235259.
Mehta, S.; Simmons, G. W.;Klier, K.; Herman, R. G. Catalytic Synthesis of Methanol from CO/Hz. 11.Electron Microecopy (TEM, STEM, Microdiffraction, and Energy Dispersive Analysis) of the CdZnO and Cu/ZnO/CrzOs Catalysts. J. Catal. 1979,57, 339360.
Natta, G. Synthesis of Methanol. Catalysis, Hydrogenation and Dehydrogenation; Reinhold New York, 1956; Vol. 111, Chapter 8. Perot, G.; Cormerais, F.; Guisnet, M. Carbon-13 Tracer Study of the Conversion of Dimethyl Ether into Hydrocarbons on SilicaAlumina and ZSM-5Zeolite. J. Chem. Res. (S)1982,2,58-59. Sedran, U. A.; Comelli, R. A.; Ffgoli, N. S. Coke Deposition in Methanol to Hydrocarbons Reaction over Silica-Aluminas.Appl. Catal. 1984,11,227-234. Sofianca, A. C.; Scurrell, M. S. Conversion of Synthesis Gas to Dimethyl Ether over Bifunctional Catalytic System. Ind. Eng. Chem. Res. 1991,30,2372-2378. Thomson, R.; Montes, C.; Davis, M. E.; Wolf,E. E. Hydrocarbon Synthesis from CO Hydrogenation over Pd Supported on SAPO Molecular Sieves. J. Catal. 1990,124,401-415. Yashima,T.; Ycahimura,A.; Wakuehima,Y.; Namba, S. Hydrocarbon Synthesis from Syngas on Zn-Cr/HZSM-5 Catalyst. Proceedings of the Pan-Pacific Synfuel Conference; Japan Petroleum Institute: Tokyo, 1982, Vol. I, pp 130-136.
Received for review March 4, 1993 Revised manuscript received July 22, 1993 Accepted July 26, 1993.
331.
Comelli, R. A,; Ffgoli, N. S. Transformation of C& Alcohols into Hydrocarbons on an Amorphous Silica-Alumina Catalyst. Appl. Catal. 1988,36,299-306. Comelli, R. A.; Flgoli, N. S. Effect of Pressure on the Transformation of Methanol into Hydrocarbons on an Amorphous Silica-Alumina. Appl. Catal. 1991, 73,185-194.
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Abstract published in Advance ACS Abstracts, October 1,
1993.
