Propene Oligomerization Research Articles

Catalyst activity comparison of alcohols over zeolites

Alcohol transformation to transportation fuel-range hydrocarbon over HZSM-5 (SiO2/Al2O3 = 30) catalyst was studied at 360 °C and 300 psig. Product distributions and catalyst life were compared between methanol, ethanol, 1-propanol and 1-butanol as a feed. The catalyst life for 1-propanol and 1-butanol was more than double compared with that for methanol and ethanol. For all the alcohols studied, the product distributions (classified to paraffin, olefin, naphthene, aromatic and naphthalene compounds) varied with time on stream (TOS). At 24 h TOS, liquid product from 1-propanol and 1-butanol transformation primarily contains higher olefin compounds. The alcohol transformation process to higher hydrocarbon involves a complex set of reaction pathways such as dehydration, oligomerization, dehydrocyclization and hydrogenation. Compared with ethylene generated from methanol and ethanol, oligomerization of propylene and butylene has a lower activation energy and can readily take place on weaker acidic sites. On the other hand, dehydrocyclization of the oligomerized products of propylene and butylene to form the cyclic compounds requires the sites with stronger acid strength. Combination of the above mentioned reasons are the primary reasons for olefin rich product generated in the later stage of the time on stream and for the extended catalyst life time for 1-propanol and 1-butanol compared with methanol and ethanol conversion over HZSM-5.

Heterogenized nickel catalysts for propene dimerization: Support effects on activity and selectivity

Ni–SiO2 and Ni-[Si]–MCM-41 are synthesized by grafting Ni(MeCN)6(BF4)2 onto SiO2 (nonporous) and MCM-41 (mesoporous). The catalytic properties of the grafted catalysts after activation with Al2Et3Cl3 are compared with the homogeneous equivalent system in propylene oligomerization. The identification of dimers leads to the determination of preferential reaction steps and the corresponding active species. Differences of the insertion modes of propylene are correlated to the textural properties of the support. Supporting the nickel active species reduces the isomerization side reactions and changes the mode of insertion of the first olefin.

Propene oligomerization over Ni-exchanged Na-X zeolites

The oligomerization of propene was investigated over a series of nickel ion-exchanged Na-X zeolites with varying Ni loadings. Catalyst characterization by temperature-programmed reduction, elemental analysis, and XANES indicates that all of the exchanged Ni is present as Ni2+ that charge-compensates two exchange sites. The selectivity to propene oligomers remained greater than 98% for all Ni–Na-X catalysts with dimers being the main product. In contrast, the activity of Ni–Na-X was determined to depend strongly on Ni loading. At low to intermediate Ni loadings, the catalyst activates, reaches a maximum activity, and then deactivates with further time on stream. The rates of activation and deactivation are functions of the Ni content in the zeolite and both increase with increasing Ni loading. Stable activity was achieved for low Ni loadings (<0.6wt%) by rapidly activating and deactivating the catalyst in propene at elevated temperature. The rate of propene dimerization measured under steady state conditions is first order in propene and characterized by an activation energy of 45kJmol−1. Activation of Ni–Na-X is attributed to migration of the Ni2+ cations from hexagonal prisms of the zeolite into the supercage where the cations form a catalytically active Ni2+–olefin complex. Deactivation is proposed to occur via the reaction of two nearby Ni–olefin complexes leading to the deactivation of both sites. A model for the dynamics of activation and deactivation and for the dimerization of propene to hexene is proposed. This model provides a satisfactory description of the effects of propene partial pressure and Ni loading on the rate of propene dimerization as a function of time on stream.

Effects of added phosphorus on conversion of ethanol to propylene over ZSM-5 catalysts

We investigated the effects of added phosphorus on the conversion of ethanol to propylene over ZSM-5 zeolite catalysts. We found that the activity of the catalysts was enhanced by the addition of phosphorus, and we suggest that the added phosphorus suppressed oligomerization of propylene and butene by decreasing the acidity of the active sites of the zeolites. Furthermore, the addition of phosphorus greatly enhanced the hydrothermal stability of the zeolites and thus substantially improved the catalyst durability during ethanol conversion. Carbon deposition, which was the main cause of deactivation of the phosphorus-modified zeolites, was suppressed by H2O produced by dehydration of ethanol.

Effects of Brønsted-acid site proximity on the oligomerization of propene in H-MFI

The oligomerization of propene was investigated over H-MFI zeolites with varying Si/Al ratios. For a constant space time per active site, the conversion of propene as well as the selectivity to products of different carbon number was affected by the density of the sites within the zeolite. In particular, as the Si/Al ratio decreased, corresponding to an increase in site proximity, the rate of oligomerization per site decreased but the selectivity to dimers relative to cracking products increased. These effects were shown to arise from the effects of molecular crowding on the rate coefficient for propene trimer formation and were confirmed by quantum chemical analysis of the energetics of propene oligomerization. It was found that the activation for propene dimerization is unaffected by the presence of oligomers on nearby sites, but the activation energy for propene trimerization relative to desorption of hexene increases by 19kcalmol−1 when two next nearest neighbor sites are occupied by oligomers. In situ IR spectroscopy observations showed the buildup of aromatic species with time-on-stream. The accumulation of these species increases with decreasing Si/Al ratio, suggesting that increasing proximity of Brønsted-acid sites enhances the formation of aromatic species.

In situ FTIR studies of propene adsorption over Ag- and Cu-exchanged Y zeolites

Ag- and Cu-exchanged forms of HY zeolite are prepared by the solid-state ion exchange (SSIE) technique. Samples with different metal loadings ranging from low to high exchange are obtained. Both compositional and structural investigations of the exchanged zeolites are performed by elemental analysis, powder X-ray diffraction (XRD), and nitrogen adsorption porosimetry. The acidity investigation is carried out by using the Fourier transform infrared spectroscopy (FTIR) of pyridine adsorption. Propene adsorption over the Ag- and Cu-exchanged zeolites is studied at room temperature by using in situ FTIR spectroscopy. XRD analysis shows good conservation of the zeolitic structure after ionic exchange even at high exchange degree. Porosity measurements indicate that the increase of Ag and Cu exchange degrees leads to a decrease of the porous volumes and the specific surface areas, which is more pronounced for Ag-exchanged zeolites. The acidity evaluation for both exchanged metals shows an important decrease of Brønsted acidity and a slight increase of Lewis acidity, which are more noticeable at high degree of exchange. Instantaneous oligomerization of propene on HY zeolite at room temperature is favored by the relatively high amount of Brønsted acid sites. The propene molecules interact more strongly with Cu 2+ than with Ag +. The shape of the C C stretching band of the FTIR spectra involves at least two overlapping bands indicating that the propene C C bond may interact with several kinds of Ag +, Cu 2+ and Cu + sites of various propene bonding.

Effects of SiO&lt;sub&gt;2&lt;/sub&gt;/Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Ratio on Physicochemical Properties and Catalytic Performance of the Non-Templated ZSM-5 Zeolite

The ZSM-5 zeolites of various SiO2/Al2O3 ratios were synthesized without using any template agent. X-ray diffraction (XRD), transmission electron microscope (TEM), temperature- programmed desorption of ammonia (NH3-TPD) and Fourier transform infrared spectroscopy (FT-IR) techniques were employed to analyze the natures of the as-synthesized zeolite. The results show that the as-synthesized non-templated ZSM-5 zeolite is very pure. Meanwhile, Lewis acid sites and Bronsted acid sites are all presented in the as-synthesized non-templated HZSM-5 zeolite. The number of acid sites decreases almost linearly with the increasing of SiO2/Al2O3 ratio of the zeolite. In addition, the reaction of propylene oligomerization was carried out over the as-synthesized non-templated HZSM-5 zeolite to evaluate the catalytic properties. The results show that the catalytic activity of propylene oligomerization decreases with the increasing of SiO2/Al2O3 ratio.

Solid-state transformation of hollow silica microspheres into hierarchical ZSM-5 having tunable mesopores

Mesoporous hierarchical ZSM-5 zeolites have been prepared via direct solid-state transformation of hollow silica gel microspheres without changing their spherical geometry. A two-stage hydrothermal method was used where tetrapropylammonium (TPA+) directed the formation of the MFI subunits in the first stage. In the second stage these subunits aggregated around the self-assembled cetyltrimethylammonium micelles and then crystallized by TPA+ templation. The mesoporous structure proved to be tunable in the pore size range of 3.2–4.8 nm by the addition of swelling agent 1,3,5-trimethylbenzene. Catalytic propene oligomerization showed less coke formed over mesoporous than microporous ZSM-5 catalysts.

Nickel Complexes with Phosphinito-Oxazoline Ligands: Temperature-Controlled Formation of Mono- or Dinuclear Complexes and Catalytic Oligomerization of Ethylene and Propylene

The complex [NiCl2{Ph2POCH2oxMe2}] (Ph2POCH2oxMe2 = 2-((diphenylphosphinooxy) methyl)-4,4-dimethyl-4,5-dihydrooxazole) 14 has been synthesized by reaction of solid [NiCl2(DME)] (DME = 1,2-dimethoxyethane) with a CH2Cl2 solution of the P,N ligand. X-ray diffraction studies on its red crystals established the mononuclear nature of the complex 14a, whose metal center has a distorted tetrahedral coordination geometry. Recrystallization of 14a from a toluene−pentane/CH2Cl2 solution at temperatures below 253 K afforded green crystals of the dinuclear, chloride-bridged, formula isomer complex 14b. Conversion of 14b to 14a was observed as a function of temperature, both in the solid-state and in solution. Together with other Ni(II) complexes containing a chelating P,N ligand of the type phosphino- or phosphinito-oxazoline or phosphino-thiazoline, 14a has been evaluated as precatalyst in the oligomerization of ethylene, with AlEtCl2 or MAO as cocatalyst, or propylene, with MAO as cocatalyst. With AlEtCl2 as activator (6 equiv), the catalytic activities with ethylene were generally modest and [NiCl2{Ph2PCH2ox}] (Ph2PCH2ox = 2-((diphenylphosphinooxy)methyl)-4,5-dihydrooxazole) 1 was the most active, with turnover frequencies (TOF) up to 7.9 × 104 mol of C2H4 (mol Ni × h)−1, whereas 14a, activated with 2 equiv of AlEtCl2, was the most selective for ethylene dimers (up to 96%) and 1-butene (up to 22%). With MAO as cocatalyst, complex 1 was again the most active, with TOF values up to 23 × 104 mol of C2H4 (mol Ni × h)−1. The highest selectivity for butenes was observed with complex [NiCl2{Ph2PCH2thiazMe2}] 3. With propylene, TOFs up to 3.3 × 104 mol of C3H6 (mol Ni × h)−1 were obtained with [NiCl2{Ph2POCH2pyridine}] 8 and selectivities for C6 products higher than 98.5% were observed with precatalysts 3, [NiCl2{t-Bu2POCH2pyridine}] 9, and 14a.

Zirconium and Titanium Complexes Supported by Tridentate LX2 Ligands Having Two Phenolates Linked to Furan, Thiophene, and Pyridine Donors: Precatalysts for Propylene Polymerization and Oligomerization

Zirconium and titanium complexes with tridentate bis(phenolate)−donor (donor = pyridine, furan and thiophene) ligands have been prepared and investigated for applications in propylene polymerization. The ligand framework has two “X-type” phenolates connected to the flat heterocyclic “L-type” donor at the 2,6- or 2,5- positions via direct ring−ring (sp2−sp2) linkages. The zirconium and titanium dibenzyl complexes have been prepared by treatment of the neutral bis(phenol)−donor ligands with M(CH2Ph)4 (M = Ti, Zr) with loss of 2 equiv of toluene. Titanium complexes with bis(phenolate)pyridine and -furan ligands and zirconium complexes with bis(phenolate)pyridine and -thiophene ligands have been characterized by single-crystal X-ray diffraction. The solid-state structures of the bis(benzyl)titanium complexes are roughly C2-symmetric, while the zirconium derivatives display Cs and C1 symmetry. The bis(phenolate)pyridine titanium complexes are structurally affected by the size of the substituents (CMe3 or CEt3) ortho to the oxygens, the larger group leading to a larger C2 distortion. Both titanium and zirconium dibenzyl complexes were found to be catalyst precursors for the polymerization of propylene upon activation with methylaluminoxane (MAO). The activities observed for the zirconium complexes are particularly notable, exceeding 106 g polypropylene/mol Zr·h in some cases. The bis(phenolate)pyridine titanium analogues are about 103 times less active, but generate polymers of higher molecular weight. When activated with MAO, the titanium bis(phenolate)furan and bis(phenolate)thiophene systems were found to promote propylene oligomerization.

Oligomerization of α-olefins by the dimeric nickel bisamido complex [Ni{1-N(PMes 2)-2-N(μ-PMes 2)C 6H 4-κ 3N, N′, P,-κ 1P′}] 2 activated by methylalumoxane (MAO)

The reaction of Li 2[1,2-{N(PMes 2)} 2C 6H 4], formed in situ from n-BuLi and the corresponding amines, with 1 equiv. of [NiBr 2(DME)] gives [Ni{1-N(PMes 2)-2-N(μ-PMes 2)C 6H 4-κ 3 N, N′, P-κ 1 P′}] 2 ( 1). After activation by methylalumoxane (MAO), 1 is a highly active catalyst in the oligomerization and isomerization of α-olefins such as ethene, propene, isobutene, 1-hexene and 1,5-hexadiene. For ethene oligomerization turnover frequencies (TOFs) range from 3000 to 79015 h −1, depending on the reaction conditions. The TOF for propene oligomerization reaches 1 190 730 h −1. To our knowledge, catalyst 1, activated by MAO, is the most active catalyst for the oligomerization of propene and outperforms the best known complexes for this reaction. In the reactions with 1-hexene, 1,5-hexadiene and isobutene dimerization and isomerization products were observed.

Synthetic Jet Fuel Production by Combined Propene Oligomerization and Aromatic Alkylation over Solid Phosphoric Acid

The oligomerization of propene, as well as the alkylation of benzene and toluene with propene, was evaluated at 160−240 °C, 3.8 MPa, and aromatic to olefin ratios of 1:6 to 6:1 using solid phosphoric acid (SPA) as a catalyst. It was found that steric effects were more important than electronic effects in determining alkylation rate and selectivity. Monoalkylation was favored even at the lowest aromatic to olefin ratio, and the isomer distribution of dialkylated aromatics remained constant irrespective of the conversion or operating conditions. No transalkylation or alkylbenzene isomerization activity was observed. It was shown that olefin oligomerization and aromatic alkylation could be combined in a single SPA catalyzed reaction system to produce a synthetic jet fuel that meets Jet A-1 specifications.

Iminopyridine Complexes of 3d Metals for Ethylene Polymerization: Comparative Structural Studies and Ligand Size Controlled Chain Termination

A variety of iron complexes bearing tridentate pyridine based ligands are presented as highly active precatalysts for the oligomerization and polymerization of ethene and propene. The ligands comprise two classes: the first class, where both ketone groups of the 2,6-diacetylpyridine are converted to imines to give symmetrical or unsymmetrical bis(imino)pyridines (NNN ligands; 1−4, 8, and 9), and the second class, where only one keto function of the 2,6-diacetylpyridine is substituted by an imine to give monoiminoacetylpyridines (NNO or MIAP ligands; 5−7). The NNN ligands have been reacted with FeCl2·4H2O to afford the corresponding metal complexes (12−17). These complexes have been activated by modified methylaluminoxane (MMAO) and tested in the oligomerization and polymerization reaction of ethene and propene. Depending on the steric bulk of the ortho substituents at the aryl group of the imines, tunable polymerization products are observed, with molecular weights (Mw) of 102−106. Using the MIAP ligands...

Hafnocene Catalysts for Selective Propylene Oligomerization: Efficient Synthesis of 4-Methyl-1-pentene by β-Methyl Transfer

A series of hafnocene complexes (eta5-C5Me4R1)(eta5-C5Me4R2)HfCl2 with [R1, R2] = [H, H] (1), [Me, H] (2), [Me, Me] (3), [Et, Me] (4), [(i)Pr, Me] (5), [SiMe(3), Me] (6), [(t)Bu, Me] (7), [(n)Bu, Me] (8), [(i)Bu, Me] (9), [Et, Et] (10), [(n)Bu, (n)Bu] (11), [(i)Bu, (i)Bu] (12) was tested as catalyst precursors for propylene oligomerization. Upon activation with methylaluminoxane or [Ph(3)C][B(C(6)F(5))(4)]/Al(i)Bu(3), complexes 2-4 and 8-12 catalyzed the dimerization of propylene to produce 4-methyl-1-pentene with selectivities ranging from 23.9 to 61.6 wt % in the product mixture. The selectivity was dependent on the nature of the substituents R(1) and R(2), with the highest value found for (eta5-C5Me4(i)Bu)2HfCl2 (12). Rapid deactivation was observed for 5-7, whereas (eta5-C5Me4H)2HfCl2 (1) polymerized propylene. 4-Methyl-1-pentene is proposed to form by repeated 1,2-insertion of propylene into the hafnocene methyl cation, followed by selective beta-methyl elimination. Detailed analysis of the byproduct distribution (isobutene, 1-pentene, 2-methyl-1-pentene, 2,4-dimethyl-1-pentene, 4-methyl-1-heptene, 4,6-dimethyl-1-heptene), determined by gas chromatography, was performed with the aid of a stochastic simulation involving rate constants for the propagation by insertion, beta-hydride elimination, and beta-methyl elimination. The rate of termination is dependent on the structure of the growing chain of the active species as well as on the bulkiness of the cyclopentadienyl ligands. The selectivity highly depends on the reaction conditions (pressure, temperature, concentration of methylaluminoxane). The rates of beta-methyl elimination leading to 4-methyl-1-pentene were proportional to propylene pressure for 2-4 and 8-10 but practically independent from propylene pressure for the sterically bulkier derivatives 11-12.

Structural and Mechanistic Investigation of a Phosphate-Modified HZSM-5 Catalyst for Methanol Conversion

Phosphorus modification of a HZSM-5 (MFI) zeolite by wet impregnation has long been known to decrease aromatic formation in methanol conversion chemistry. We prepared and studied a catalyst modified by introducing trimethylphosphine under reaction conditions followed by oxidation. Magic-angle spinning (MAS) NMR shows that extensive dealumination occurs, resulting in a catalyst with a much higher framework SiO2/Al2O3 ratio, as well as extraframework aluminum and approximately 1.4 equiv of entrained phosphoric acid (under working conditions) per aluminum. Upon dehydration or regeneration, the phosphoric acid is converted, reversibly, to entrained P4O10. The aromatic selectivity of the modified catalyst is significantly lower than that of an unmodified zeolite with a similar, increased framework SiO2/Al2O3 ratio. By comparing the rates of H/D exchange in propene under conditions similar to those in methanol conversion chemistry, we determined that the acid site strength is indistinguishable on modified and unmodified zeolites, and this is consistent with theoretical modeling. On the phosphorus-modified zeolite, the rate of propene oligomerization is greatly suppressed, suggesting that entrained phosphate is an impediment to sterically demanding reactions.

Propylene bulk phase oligomerization with bisiminepyridine iron catalysts: Mechanistic investigation of 1,2-versus 2,1-propylene insertion

Iron(II) complexes were synthesized with bisiminepyridine ligands of different steric demand. Activation with modified MAO (25 mol% isobutyl groups) generated very active catalysts for propylene oligomerization. These oligomerizations were carried out in liquid propylene in a heat flow calorimeter. The oligomers were separated by preparative gas chromatography and the dimers and trimers analyzed using analytical gas chromatography, 1H-NMR-, and 13C NMR-spectroskopy. By means of the knowledge of the dimer and trimer structure, we were able to establish a mechanistic pathway for propylene insertion and obtained knowledge about the iron alkyl species involved. Analysis of the various dimers formed allowed us to determine the percentage of 1,2-versus 2,1-propylene insertions. Considering the same iron alkyl species with ligands of different steric demand, a change in the probabilities for 1,2-versus 2,1-propylene insertions can be observed. With this knowledge, the catalyst behaviour for ligands of varying steric demand can be predicted. The question of how to produce oligomers versus polymers is one of knowing how to control the ratio of the 1.2-and 2.1-insertion. One method is to alter the steric demand in the ortho position of the ligand. The more bulky the ligand, the more often a 2,1-propylene insertion happens and, therefore, the higher the molecular mass of the oligomers, i.e., polymer is formed. Another important observation is that the formation of α-olefines is favored with a higher steric demand of the catalyst.

Chain-Length Distributions Obtained over Nickel(II)-Exchanged or Impregnated Silica–Alumina Catalysts for the Oligomerization of Lower Alkenes

In the oligomerization of ethene, the chain-length distributions obtained over heterogeneous nickel catalysts at a low reaction temperature (ca. 110 °C) depend on the acidity of the silica–alumina support, the nickel loading and the olefin feed. Most significantly, ion-exchanged catalysts based on a silica–alumina of high acidity (ca. 0.7 mass% Ni), and those based on a highly-exchanged medium-acidity support (ca. 1.6% Ni), show a distinct superimposed activity for the dimerization of the intermediate butenes. This causes a desirable shift to higher hydrocarbon products, and it is possible to obtain 41 mass% C10+ oligomers, while the corresponding value predicted from Schulz–Flory statistics is only 24 mass%. No such deviation from Schulz–Flory statistics is observed in propene oligomerization.

Solid phosphoric acid oligomerisation: Manipulating diesel selectivity by controlling catalyst hydration

Solid phosphoric acid (SPA) catalyst is traditionally used in crude oil refineries to produce unhydrogenated motor-gasoline by propene and butene oligomerisation. SPA is also used in High-Temperature Fischer–Tropsch refineries (HTFT) to produce synthetic fuels albeit with a different emphasis. The petrol/diesel ratio of an HTFT refinery is very different from crude refining and it is often necessary to shift this ratio depending on market requirements. The influence of hydration was investigated as a means of improving diesel selectivity. This was achieved by studying SPA over a hydration range of 99–110% H 3PO 4, a temperature range of 140–230 °C and using C 3–C 6 model and synthetic FT-derived olefinic feedstocks. A direct correlation was found between the selectivity towards diesel range products and the distribution of the phosphoric acid species viz. H 3PO 4, H 4P 2O 7 and H 5P 3O 10. For various olefinic feedstocks, diesel selectivity increased with decreasing catalyst hydration with a maximum around 108% H 3PO 4 for propene oligomerisation. Commercial tests confirmed the increase in diesel selectivity with lowered catalyst hydration.

Alkylation of toluene with propene over H-MCM-22 zeolite. Location of the main and secondary reactions

Alkylation of toluene with propene was carried out at 200 °C over a H-MCM-22 sample (Si/Al = 15) for which the distribution of protonic acid sites in the three pore systems (supercages, sinusoidal channels, and external hemicages) was estimated by various methods. Different reactions were shown to take place in each of the pore systems. The desired alkylation of toluene into cymenes (and diisopropyltoluenes) occurs only within the external hemicages and without any deactivation. C 4–C 6 alkene production through propene oligomerization cracking was demonstrated to occur essentially within the sinusoidal channels. Mainly nondesorbed products (coke) are formed within the supercages.

Standardization of catalyst preparation using reference catalyst: ion exchange of mordenite type zeolite: 1. Remarkable dealumination accompanying ion exchange

A joint study was organized to establish a standard set of conditions for the ion exchange of zeolite from sodium into proton-form. The sodium-form mordenite with Si/Al 2 = ca. 15 was ion exchanged into an NH 4-form, followed by calcination according to various recipes. Then various advanced techniques for characterization (ICP, TG, XPS, SEM, XRD, N 2 adsorption, 29Si and 27Al NMR, benzene diffusion, IR of OH and adsorbed pyridine and CO, ammonia TPD) were applied, and some test reactions (cracking of cumene, isopropylation of biphenyl, oligomerization of propene and chichibabin condensation of acetaldehyde and ammonia into picoline) were conducted. The ion exchange (removal of sodium) proceeded as expected, but remarkable differences were observed in physicochemical and catalytic properties of the thus-prepared proton-form samples. Exceptionally high temperature (383 K) for the ion exchange resulted in the structural degradation, while most samples exchanged at 333–353 K maintained the crystallinity and pore volume. The use of NH 4Cl slightly changed the crystal morphology. Extra-framework aluminum species was formed on most samples after calcination above 773 K. In contrast, calcination at 673 K maintained the framework aluminum. Therefore, the dealumination is considered to proceed after complete removal of ammonia from the ammonium-form zeolite. However, the proton-form zeolite was stable under dry conditions, so it is speculated that the dealumination was induced by the contact of the proton-form zeolite to atmosphere with humidity. The total and Brønsted acidity decreased with the dealumination, while Lewis acidity increased. On the other hand, rapid heating of the ammonium type zeolite caused narrowing of the micropores. These structural changes seriously affected the catalytic activities for various reactions.