Abstrak Penelitian ini dilakukan untuk mengetahui kesalahan konsep pada materi Kimia SMA khususny... more Abstrak Penelitian ini dilakukan untuk mengetahui kesalahan konsep pada materi Kimia SMA khususnya pada pokok bahasan Kesetimbangan Kimia. Metode yang digunakan adalah menyusun 15 soal konsep untuk menguji konsep-konsep pada topik yang terkait. Soal diujikan pada 131 siswa SMA kelas XII IPA. Soal dianalisis menggunakan program Excel yang disebut objective analyzer untuk mengetahui tingkat kesalahan dan dilanjutkan dengan menganalisis jawaban siswa untuk mengetahui penyebab kesalahan konsep. Dari hasil analisis data ditemukan beberapa kesalahan konsep pada pokok bahasan Kesetimbangan Kimia, yaitu (i) keadaan kesetimbangan akan tercapai jika konsentrasi pereaksi sama dengan konsentrasi hasil reaksi, (ii) tidak dapat mengkaitkan nilai K dengan komposisi kimia saat kesetimbangan, (iii) pada suhu tetap penambahan padatan atau cairan murni akan menggeser kesetimbangan heterogen; (iv) tidak dapat menentukan pengaruh dari suatu gangguan terhadap kesetimbangan; (v) penambahan katalis akan me...
ABSTRACT On page 6497, caption to Fig. 1, line 2, 13CO/H2 should read 12CO/H2. On page 6498, capt... more ABSTRACT On page 6497, caption to Fig. 1, line 2, 13CO/H2 should read 12CO/H2. On page 6498, caption to Fig. 2, line 2, 13CO/H2 should read 12CO/H2. On page 6498, caption to Fig. 3, line 2: 13CH313CH=13CH2 should read 13CH313CH=12CH2; 13CH313CH213CH=13CH2 should read 13CH313CH212CH2=12CH2; line 3: 13CH313CH2(13CH2)n13CH=13CH2 should read 13CH313CH2(12CH2)n12CH=12CH2; and line 4: 13CH2 (from 13CO) should read 12CH2 (from 12CO). [on SciFinder (R)]
Steam reforming of methanol (SRM) is known as one of the most favorable catalytic processes for p... more Steam reforming of methanol (SRM) is known as one of the most favorable catalytic processes for producing hydrogen. Current research on zirconia, ZrO2 supported copper catalyst revealed that CuO/ZrO2 as an active catalyst for the SRM. Zircon, ZrSiO4 is available from the by-product of tin mining. In the work presented here, the catalytic properties of CuO/ZrSiO4 with various copper oxide
13C NMR spectroscopy shows that the n-alkene and n-alkane products from the catalytic hydrogenati... more 13C NMR spectroscopy shows that the n-alkene and n-alkane products from the catalytic hydrogenation of CO in the presence of (13)C(2)H(4) probes over Ru/150 degrees C, Co/180 degrees C, Fe/220 degrees C, or Rh/190 degrees C (1 atm, CO:H(2) 1:1, "mild conditions") contain terminal (13)CH(3)(13)CH(2)- units. This is consistent with their formation by a regiospecific polymerization of C(1) species derived from CO and initiated by (13)C(2)H(4). Although the activities toward individual products differed somewhat, similar distributions and similar product labeling patterns were obtained over all the four catalysts. 1-Butene and the higher 1-n-alkenes from all the catalysts were largely (13)CH(3)(13)CH(2)(CH(2))(n)()CH=CH(2) (n = 0-3), propene formed over Ru or Co was (13)CH(3)(13)CH=CH(2), while both (13)CH(3)(13)CH=CH(2) and (13)CH(2)=(13)CHCH(3) were formed over Fe or Rh. Comparison of the conclusions from these probe experiments with those from isotope transient experiments by other workers indicates that the ethene initiator does not significantly modify the course of the CO hydrogenation. The reaction products are largely kinetically determined, and the primary products are mainly linear 1-n-alkenes, while the n-alkanes and 2-n-alkenes largely arise via secondary processes. Since the distribution of products and the labeling in them is so similar, it is concluded that one basic primary mechanism applies over all the four metals. Several different reaction paths involving a polymerization of surface methylene, [CH(2(ad))], have been proposed. Although the predictions based on several of these mechanisms agree with many of the results, the alkenyl + [CH(2(ad))] mechanism, initiated by a surface vinyl [CH(2)=CH((ad))], most easily accommodates the experimental evidence. An alternative path involving sequential addition of surface methylidyne and hydride either to a growing alkylidene chain (alkylidene + [CH(ad) + H(ad)]) or to an alkyl chain (alkyl + [CH((ad)) + H(ad)]) has recently been proposed by van Santen and Ciobica. The [CH(2(ad))] mechanism offers an easier explanation for the formation of the various alkenes, the distribution of products, and of the initiation, while the [CH(ad) + H(ad)] mechanism can explain any n-alkanes formed as primary products and not derived from alkenes. At higher reaction temperatures over Ru and Co, considerable (13)C(1) incorporation (from natural abundance in the CO and from cleavage of the (13)C(2)H(4) probe) was found in all the hydrocarbons. Thus, at higher temperatures (13)C(1(ad)) in addition to (13)C(2(ad)) species participate in both chain growth and initiation. In summary, adsorbed CO is transformed very easily into surface C(1(ad)), probably [CH(2(ad))] in equilibrium with [CH((ad))+H(ad)], which act as the propagating species.
ABSTRACT On page 6497, caption to Fig. 1, line 2, 13CO/H2 should read 12CO/H2. On page 6498, capt... more ABSTRACT On page 6497, caption to Fig. 1, line 2, 13CO/H2 should read 12CO/H2. On page 6498, caption to Fig. 2, line 2, 13CO/H2 should read 12CO/H2. On page 6498, caption to Fig. 3, line 2: 13CH313CH=13CH2 should read 13CH313CH=12CH2; 13CH313CH213CH=13CH2 should read 13CH313CH212CH2=12CH2; line 3: 13CH313CH2(13CH2)n13CH=13CH2 should read 13CH313CH2(12CH2)n12CH=12CH2; and line 4: 13CH2 (from 13CO) should read 12CH2 (from 12CO). [on SciFinder (R)]
ABSTRACT Zeolites are among the main catalysts in the petroleoum and fine-chemical industry. The ... more ABSTRACT Zeolites are among the main catalysts in the petroleoum and fine-chemical industry. The well-defined channel framework with the acid sites have empowered this kind of material to catalyze many chemical reactions, such as alkylation, isomerization, and hydrocarbon cracking. Controlling the energy consumption towards efficient process in the synthesis of zeolite has been a great interest. In this light, we succesfully show that synthesis of MFI zeolite can be tailored by using high or low temperature heating. Synthesis via high-temperature heating (HTH) at 150 °C, resulted in conventional coffin-type morphology whereas low-temperature heating (LTH) at 90 °C, resulted in a spherical-type morphology. This phenomenon indicates that energy consumption for synthesizing MFI zeolite can be decreased. Moreover, the tetrapropylammonion ion (TPA +) amount as structure-directing agents (SDA) can be lowered, hence reducing the synthesis cost. The obtained samples were charaterized by advanced techniques to compare interesting properties between samples synthesized by HTH and LTH. This concerns on the resulting morphology, textural properties, and Si/Al framework ratio.
Hierarchical zeolites are demanded nowadays to be used as catalyst that can solve problems in pet... more Hierarchical zeolites are demanded nowadays to be used as catalyst that can solve problems in petrochemical and fine chemical industry. These problems normally found in catalytic reaction include molecular diffusion limitation, catalyst deactivation, low product yield and product selectivity. This can be realized since hierarchical zeolites possess additional pore within the mesoscale (>2 nm) despite the presence of micropore (<1 nm) as one of zeolite characteristics itself. Syntheses of hierarchical zeolites have shown independent strategy comprising of soft- and hard-templating route. In this article, synthesis strategy of hierarchical zeolites is reviewed. Addition of mesopore on zeolite crystal may affect changes in morphology, physicochemical properties and catalytic activity. In spite of conventional characterization method such as X-ray diffraction determining the zeolite structure, other characterization techniques to further verify the success of synthesizing hierarch...
2011 2nd International Conference on Instrumentation, Communications, Information Technology, and Biomedical Engineering, 2011
Apatite-type lanthanum silicates are of great interest because of their high ionic conductivity i... more Apatite-type lanthanum silicates are of great interest because of their high ionic conductivity in which it is potential to be used as electrolyte for the solid oxide fuel cell (SOFC) application. In the present work, we report 29Si solid state NMR studies of several doped lanthanum apatite silicates prepared by hydrothermal method. For the undoped apatite La9.33Si6O26 three peaks are
13C NMR spectroscopy shows that the n-alkene and n-alkane products from the catalytic hydrogenati... more 13C NMR spectroscopy shows that the n-alkene and n-alkane products from the catalytic hydrogenation of CO in the presence of (13)C(2)H(4) probes over Ru/150 degrees C, Co/180 degrees C, Fe/220 degrees C, or Rh/190 degrees C (1 atm, CO:H(2) 1:1, &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;mild conditions&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;) contain terminal (13)CH(3)(13)CH(2)- units. This is consistent with their formation by a regiospecific polymerization of C(1) species derived from CO and initiated by (13)C(2)H(4). Although the activities toward individual products differed somewhat, similar distributions and similar product labeling patterns were obtained over all the four catalysts. 1-Butene and the higher 1-n-alkenes from all the catalysts were largely (13)CH(3)(13)CH(2)(CH(2))(n)()CH=CH(2) (n = 0-3), propene formed over Ru or Co was (13)CH(3)(13)CH=CH(2), while both (13)CH(3)(13)CH=CH(2) and (13)CH(2)=(13)CHCH(3) were formed over Fe or Rh. Comparison of the conclusions from these probe experiments with those from isotope transient experiments by other workers indicates that the ethene initiator does not significantly modify the course of the CO hydrogenation. The reaction products are largely kinetically determined, and the primary products are mainly linear 1-n-alkenes, while the n-alkanes and 2-n-alkenes largely arise via secondary processes. Since the distribution of products and the labeling in them is so similar, it is concluded that one basic primary mechanism applies over all the four metals. Several different reaction paths involving a polymerization of surface methylene, [CH(2(ad))], have been proposed. Although the predictions based on several of these mechanisms agree with many of the results, the alkenyl + [CH(2(ad))] mechanism, initiated by a surface vinyl [CH(2)=CH((ad))], most easily accommodates the experimental evidence. An alternative path involving sequential addition of surface methylidyne and hydride either to a growing alkylidene chain (alkylidene + [CH(ad) + H(ad)]) or to an alkyl chain (alkyl + [CH((ad)) + H(ad)]) has recently been proposed by van Santen and Ciobica. The [CH(2(ad))] mechanism offers an easier explanation for the formation of the various alkenes, the distribution of products, and of the initiation, while the [CH(ad) + H(ad)] mechanism can explain any n-alkanes formed as primary products and not derived from alkenes. At higher reaction temperatures over Ru and Co, considerable (13)C(1) incorporation (from natural abundance in the CO and from cleavage of the (13)C(2)H(4) probe) was found in all the hydrocarbons. Thus, at higher temperatures (13)C(1(ad)) in addition to (13)C(2(ad)) species participate in both chain growth and initiation. In summary, adsorbed CO is transformed very easily into surface C(1(ad)), probably [CH(2(ad))] in equilibrium with [CH((ad))+H(ad)], which act as the propagating species.
ABSTRACT On page 6497, caption to Fig. 1, line 2, 13CO/H2 should read 12CO/H2. On page 6498, capt... more ABSTRACT On page 6497, caption to Fig. 1, line 2, 13CO/H2 should read 12CO/H2. On page 6498, caption to Fig. 2, line 2, 13CO/H2 should read 12CO/H2. On page 6498, caption to Fig. 3, line 2: 13CH313CH=13CH2 should read 13CH313CH=12CH2; 13CH313CH213CH=13CH2 should read 13CH313CH212CH2=12CH2; line 3: 13CH313CH2(13CH2)n13CH=13CH2 should read 13CH313CH2(12CH2)n12CH=12CH2; and line 4: 13CH2 (from 13CO) should read 12CH2 (from 12CO). [on SciFinder (R)]
Abstrak Penelitian ini dilakukan untuk mengetahui kesalahan konsep pada materi Kimia SMA khususny... more Abstrak Penelitian ini dilakukan untuk mengetahui kesalahan konsep pada materi Kimia SMA khususnya pada pokok bahasan Kesetimbangan Kimia. Metode yang digunakan adalah menyusun 15 soal konsep untuk menguji konsep-konsep pada topik yang terkait. Soal diujikan pada 131 siswa SMA kelas XII IPA. Soal dianalisis menggunakan program Excel yang disebut objective analyzer untuk mengetahui tingkat kesalahan dan dilanjutkan dengan menganalisis jawaban siswa untuk mengetahui penyebab kesalahan konsep. Dari hasil analisis data ditemukan beberapa kesalahan konsep pada pokok bahasan Kesetimbangan Kimia, yaitu (i) keadaan kesetimbangan akan tercapai jika konsentrasi pereaksi sama dengan konsentrasi hasil reaksi, (ii) tidak dapat mengkaitkan nilai K dengan komposisi kimia saat kesetimbangan, (iii) pada suhu tetap penambahan padatan atau cairan murni akan menggeser kesetimbangan heterogen; (iv) tidak dapat menentukan pengaruh dari suatu gangguan terhadap kesetimbangan; (v) penambahan katalis akan me...
ABSTRACT On page 6497, caption to Fig. 1, line 2, 13CO/H2 should read 12CO/H2. On page 6498, capt... more ABSTRACT On page 6497, caption to Fig. 1, line 2, 13CO/H2 should read 12CO/H2. On page 6498, caption to Fig. 2, line 2, 13CO/H2 should read 12CO/H2. On page 6498, caption to Fig. 3, line 2: 13CH313CH=13CH2 should read 13CH313CH=12CH2; 13CH313CH213CH=13CH2 should read 13CH313CH212CH2=12CH2; line 3: 13CH313CH2(13CH2)n13CH=13CH2 should read 13CH313CH2(12CH2)n12CH=12CH2; and line 4: 13CH2 (from 13CO) should read 12CH2 (from 12CO). [on SciFinder (R)]
Steam reforming of methanol (SRM) is known as one of the most favorable catalytic processes for p... more Steam reforming of methanol (SRM) is known as one of the most favorable catalytic processes for producing hydrogen. Current research on zirconia, ZrO2 supported copper catalyst revealed that CuO/ZrO2 as an active catalyst for the SRM. Zircon, ZrSiO4 is available from the by-product of tin mining. In the work presented here, the catalytic properties of CuO/ZrSiO4 with various copper oxide
13C NMR spectroscopy shows that the n-alkene and n-alkane products from the catalytic hydrogenati... more 13C NMR spectroscopy shows that the n-alkene and n-alkane products from the catalytic hydrogenation of CO in the presence of (13)C(2)H(4) probes over Ru/150 degrees C, Co/180 degrees C, Fe/220 degrees C, or Rh/190 degrees C (1 atm, CO:H(2) 1:1, &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;mild conditions&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;) contain terminal (13)CH(3)(13)CH(2)- units. This is consistent with their formation by a regiospecific polymerization of C(1) species derived from CO and initiated by (13)C(2)H(4). Although the activities toward individual products differed somewhat, similar distributions and similar product labeling patterns were obtained over all the four catalysts. 1-Butene and the higher 1-n-alkenes from all the catalysts were largely (13)CH(3)(13)CH(2)(CH(2))(n)()CH=CH(2) (n = 0-3), propene formed over Ru or Co was (13)CH(3)(13)CH=CH(2), while both (13)CH(3)(13)CH=CH(2) and (13)CH(2)=(13)CHCH(3) were formed over Fe or Rh. Comparison of the conclusions from these probe experiments with those from isotope transient experiments by other workers indicates that the ethene initiator does not significantly modify the course of the CO hydrogenation. The reaction products are largely kinetically determined, and the primary products are mainly linear 1-n-alkenes, while the n-alkanes and 2-n-alkenes largely arise via secondary processes. Since the distribution of products and the labeling in them is so similar, it is concluded that one basic primary mechanism applies over all the four metals. Several different reaction paths involving a polymerization of surface methylene, [CH(2(ad))], have been proposed. Although the predictions based on several of these mechanisms agree with many of the results, the alkenyl + [CH(2(ad))] mechanism, initiated by a surface vinyl [CH(2)=CH((ad))], most easily accommodates the experimental evidence. An alternative path involving sequential addition of surface methylidyne and hydride either to a growing alkylidene chain (alkylidene + [CH(ad) + H(ad)]) or to an alkyl chain (alkyl + [CH((ad)) + H(ad)]) has recently been proposed by van Santen and Ciobica. The [CH(2(ad))] mechanism offers an easier explanation for the formation of the various alkenes, the distribution of products, and of the initiation, while the [CH(ad) + H(ad)] mechanism can explain any n-alkanes formed as primary products and not derived from alkenes. At higher reaction temperatures over Ru and Co, considerable (13)C(1) incorporation (from natural abundance in the CO and from cleavage of the (13)C(2)H(4) probe) was found in all the hydrocarbons. Thus, at higher temperatures (13)C(1(ad)) in addition to (13)C(2(ad)) species participate in both chain growth and initiation. In summary, adsorbed CO is transformed very easily into surface C(1(ad)), probably [CH(2(ad))] in equilibrium with [CH((ad))+H(ad)], which act as the propagating species.
ABSTRACT On page 6497, caption to Fig. 1, line 2, 13CO/H2 should read 12CO/H2. On page 6498, capt... more ABSTRACT On page 6497, caption to Fig. 1, line 2, 13CO/H2 should read 12CO/H2. On page 6498, caption to Fig. 2, line 2, 13CO/H2 should read 12CO/H2. On page 6498, caption to Fig. 3, line 2: 13CH313CH=13CH2 should read 13CH313CH=12CH2; 13CH313CH213CH=13CH2 should read 13CH313CH212CH2=12CH2; line 3: 13CH313CH2(13CH2)n13CH=13CH2 should read 13CH313CH2(12CH2)n12CH=12CH2; and line 4: 13CH2 (from 13CO) should read 12CH2 (from 12CO). [on SciFinder (R)]
ABSTRACT Zeolites are among the main catalysts in the petroleoum and fine-chemical industry. The ... more ABSTRACT Zeolites are among the main catalysts in the petroleoum and fine-chemical industry. The well-defined channel framework with the acid sites have empowered this kind of material to catalyze many chemical reactions, such as alkylation, isomerization, and hydrocarbon cracking. Controlling the energy consumption towards efficient process in the synthesis of zeolite has been a great interest. In this light, we succesfully show that synthesis of MFI zeolite can be tailored by using high or low temperature heating. Synthesis via high-temperature heating (HTH) at 150 °C, resulted in conventional coffin-type morphology whereas low-temperature heating (LTH) at 90 °C, resulted in a spherical-type morphology. This phenomenon indicates that energy consumption for synthesizing MFI zeolite can be decreased. Moreover, the tetrapropylammonion ion (TPA +) amount as structure-directing agents (SDA) can be lowered, hence reducing the synthesis cost. The obtained samples were charaterized by advanced techniques to compare interesting properties between samples synthesized by HTH and LTH. This concerns on the resulting morphology, textural properties, and Si/Al framework ratio.
Hierarchical zeolites are demanded nowadays to be used as catalyst that can solve problems in pet... more Hierarchical zeolites are demanded nowadays to be used as catalyst that can solve problems in petrochemical and fine chemical industry. These problems normally found in catalytic reaction include molecular diffusion limitation, catalyst deactivation, low product yield and product selectivity. This can be realized since hierarchical zeolites possess additional pore within the mesoscale (>2 nm) despite the presence of micropore (<1 nm) as one of zeolite characteristics itself. Syntheses of hierarchical zeolites have shown independent strategy comprising of soft- and hard-templating route. In this article, synthesis strategy of hierarchical zeolites is reviewed. Addition of mesopore on zeolite crystal may affect changes in morphology, physicochemical properties and catalytic activity. In spite of conventional characterization method such as X-ray diffraction determining the zeolite structure, other characterization techniques to further verify the success of synthesizing hierarch...
2011 2nd International Conference on Instrumentation, Communications, Information Technology, and Biomedical Engineering, 2011
Apatite-type lanthanum silicates are of great interest because of their high ionic conductivity i... more Apatite-type lanthanum silicates are of great interest because of their high ionic conductivity in which it is potential to be used as electrolyte for the solid oxide fuel cell (SOFC) application. In the present work, we report 29Si solid state NMR studies of several doped lanthanum apatite silicates prepared by hydrothermal method. For the undoped apatite La9.33Si6O26 three peaks are
13C NMR spectroscopy shows that the n-alkene and n-alkane products from the catalytic hydrogenati... more 13C NMR spectroscopy shows that the n-alkene and n-alkane products from the catalytic hydrogenation of CO in the presence of (13)C(2)H(4) probes over Ru/150 degrees C, Co/180 degrees C, Fe/220 degrees C, or Rh/190 degrees C (1 atm, CO:H(2) 1:1, &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;mild conditions&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;) contain terminal (13)CH(3)(13)CH(2)- units. This is consistent with their formation by a regiospecific polymerization of C(1) species derived from CO and initiated by (13)C(2)H(4). Although the activities toward individual products differed somewhat, similar distributions and similar product labeling patterns were obtained over all the four catalysts. 1-Butene and the higher 1-n-alkenes from all the catalysts were largely (13)CH(3)(13)CH(2)(CH(2))(n)()CH=CH(2) (n = 0-3), propene formed over Ru or Co was (13)CH(3)(13)CH=CH(2), while both (13)CH(3)(13)CH=CH(2) and (13)CH(2)=(13)CHCH(3) were formed over Fe or Rh. Comparison of the conclusions from these probe experiments with those from isotope transient experiments by other workers indicates that the ethene initiator does not significantly modify the course of the CO hydrogenation. The reaction products are largely kinetically determined, and the primary products are mainly linear 1-n-alkenes, while the n-alkanes and 2-n-alkenes largely arise via secondary processes. Since the distribution of products and the labeling in them is so similar, it is concluded that one basic primary mechanism applies over all the four metals. Several different reaction paths involving a polymerization of surface methylene, [CH(2(ad))], have been proposed. Although the predictions based on several of these mechanisms agree with many of the results, the alkenyl + [CH(2(ad))] mechanism, initiated by a surface vinyl [CH(2)=CH((ad))], most easily accommodates the experimental evidence. An alternative path involving sequential addition of surface methylidyne and hydride either to a growing alkylidene chain (alkylidene + [CH(ad) + H(ad)]) or to an alkyl chain (alkyl + [CH((ad)) + H(ad)]) has recently been proposed by van Santen and Ciobica. The [CH(2(ad))] mechanism offers an easier explanation for the formation of the various alkenes, the distribution of products, and of the initiation, while the [CH(ad) + H(ad)] mechanism can explain any n-alkanes formed as primary products and not derived from alkenes. At higher reaction temperatures over Ru and Co, considerable (13)C(1) incorporation (from natural abundance in the CO and from cleavage of the (13)C(2)H(4) probe) was found in all the hydrocarbons. Thus, at higher temperatures (13)C(1(ad)) in addition to (13)C(2(ad)) species participate in both chain growth and initiation. In summary, adsorbed CO is transformed very easily into surface C(1(ad)), probably [CH(2(ad))] in equilibrium with [CH((ad))+H(ad)], which act as the propagating species.
ABSTRACT On page 6497, caption to Fig. 1, line 2, 13CO/H2 should read 12CO/H2. On page 6498, capt... more ABSTRACT On page 6497, caption to Fig. 1, line 2, 13CO/H2 should read 12CO/H2. On page 6498, caption to Fig. 2, line 2, 13CO/H2 should read 12CO/H2. On page 6498, caption to Fig. 3, line 2: 13CH313CH=13CH2 should read 13CH313CH=12CH2; 13CH313CH213CH=13CH2 should read 13CH313CH212CH2=12CH2; line 3: 13CH313CH2(13CH2)n13CH=13CH2 should read 13CH313CH2(12CH2)n12CH=12CH2; and line 4: 13CH2 (from 13CO) should read 12CH2 (from 12CO). [on SciFinder (R)]
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