# Patent

## Title
Phosphorus-containing catalyst composition and hydroformylation process using the same

## Abstract

Provided are a catalyst composition comprising a bidentate ligand, a monodentate ligand, and a transition metal catalyst and a process of hydroformylation of olefin compounds, comprising reacting the olefin compound with a gas mixture of hydrogen and carbon monoxide while being stirred at elevated pressures and temperatures in the presence of the catalyst composition to produce an aldehyde. The catalytic composition demonstrates the high catalytic activity and option control of selectivity to normal aldehyde or iso aldehyde (N/I selectivity) to a desired value.

## Background
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a phosphorous-containing catalyst composition and a hydroformylation process using the same, and more particularly, to a phosphorous-containing catalyst composition in which a combination of a monodentate phosphorous compound and a bidentate phosphorous compound is used as a ligand to a transition metal catalyst and a process of hydroformylation of olefin compounds comprising reacting the olefin compound with a gas mixture of hydrogen and carbon monoxide while being stirred at elevated pressures and temperatures in the presence of the above catalyst composition to produce aldehyde.
2. Description of the Related Art
The hydroformylation reaction, also known as the oxo reaction, includes reacting an olefin with a synthesis gas (CO/H2) in the presence of a metal catalyst and a ligand to produce a linear (normal) aldehyde and branched (iso) aldehyde which has one more carbon atom than the olefin. The oxo reaction was discovered by Otto Roelen in 1938. In 2001, about 8,400,000 tons of various aldehydes (including its alcohol derivatives) were produced through the oxo reaction worldwide (SRI Report, November 2002, 682. 700A). The various aldehydes synthesized according to the oxo reaction are converted to acids and alcohols through oxidation and reduction reactions. The aldehydes may be subjected to an aldol condensation reaction and then converted to acids and alcohols having a long alkyl chain through oxidation and reduction reactions. The obtained acids and alcohols are used as solvents, additives, raw materials for various plasticizers, and etc.
Cobalt (Co) or rhodium (Rh)-based catalysts are mostly used in the oxo reaction. Depending on the types of ligands and the operating conditions, different N/I (ratio of linear (normal) isomer to branched (iso) isomer) selectivity of aldehyde is obtained. At least 70% of all oxo plants have adopted a low pressure oxo process with a rhodium-based catalyst.
In addition to cobalt (Co) and rhodium (Rh), iridium (Ir), ruthenium (Ru), osmium (Os), planitum (Pt), palladium (Pd), iron (Fe), and nickel (Ni) can be used as a central metal in the catalyst for the oxo reaction. Catalytic activities of these metal complexes can be ordered as follows: Rh>>Co>Ir, Ru>Os>Pt>Pd>Fe>Ni. Therefore, most research and development have been focused on rhodium and cobalt. Examples of ligands in the catalyst may include phosphine (PR3, R═C6H5, n-C4H9), phosphine oxide (O═P(C6H5)3), phosphite, amine, amide, and isonitrile. There rarely exist ligands that are more advantageous in view of catalytic activity, stability, and cost than triphenylphosphine (TPP). Thus, in most oxo reactions, Rh metal is used as a catalyst and TPP and its derivatives are used as ligand. In addition, to increase the stability of a catalytic system, TPP ligand is used in an amount of at least 100 equivalent of the catalyst.
Eastman Kodak Company and Union Carbide Company (merged into Dow) developed a bidentate phosphine ligand having high catalytic activity and high N/I selectivity, respectively (see, U.S. Pat. Nos. 4,694,109 and 4,668,651).
Moloy and coworkers developed N-pyrrolyl phosphine which shows high activity and selectivity (JACS 1995, 117, 7696).
U.S. Pat. No. 5,710,344 describes a process for the preparation of linear aldehydes by hydroformylation using a bidentate ligand which contains at least one P—C or P—N bond.
As the application of iso aldehyde is developed, there is an increasing need for iso aldehyde. However, since the conventional catalyst compositions have high selectivity to normal aldehyde, increase of production of iso aldehyde is limited. Thus, there is a need for a process of producing a normal aldehyde and an iso aldehyde in a desired ratio by controlling N/I selectivity while maintaining a sufficient catalytic activity.
SUMMARY OF THE INVENTION
The present invention provides a hydroformylation catalyst composition comprising a bidentate ligand, a monodentate ligand and a transition metal catalyst which can have very high catalytic activity and is able to control N/I selectivity to a desired value.
The present invention also provides a process of hydroformylation of olefin compounds, comprising reacting the olefin compound with a gas mixture of hydrogen and carbon monoxide while being stirred at elevated pressures and temperatures in the presence of the above catalyst composition to produce aldehyde.
According to an aspect of the present invention, there is provided a catalyst composition comprising a bidentate ligand represented by formula 1, a monodentate ligand represented by formula 2, and a transition metal catalyst represented by formula 3:




wherein
each of R1 and R2 is a substituted or unsubstituted C1-20 alkyl group; a substituted or unsubstituted C1-20 alkoxy group; a substituted or unsubstituted C5-20 cycloalkane or cycloalkene; a substituted or unsubstituted C6-36 aryl group; a substituted or unsubstituted C1-20 heteroalkyl group; a substituted or unsubstituted C4-36 heteroaryl group; or a substituted or unsubstituted C4-36 heterocyclic group,
Ar1-Ar2 is a bisaryl compound, and
X is oxygen (O) or sulfur (S),




wherein
each of R3, R4 and R5 is a substituted or unsubstituted C1-20 alkyl group; a substituted or unsubstituted C1-20 alkoxy group; a substituted or unsubstituted C5-20 cycloalkane or cycloalkene; a substituted or unsubstituted C6-36 aryl group; a substituted or unsubstituted C1-20 heteroalkyl group; a substituted or unsubstituted C4-36 heteroaryl group; or a substituted or unsubstituted C4-36 heterocyclic group, each of R3, R4 and R5 being optionally substituted with nitro (—NO2), fluorine (F), chlorine (Cl), bromine (Br), or a C1-4 alkyl group,

M(L1)l(L2)m(L3)n  (3)

wherein
M is a transition metal,
each of L1, L2 and L3 is hydrogen, CO, acetylacetonato, cyclooctadiene, norbornene, chlorine, or triphenylphosphine, and
each of l, m and n is a number of 0 to 5, provided that all l, m and n are not zero, simultaneously.
According to another aspect of the present invention, there is provided a process of hydroformylation of olefin compounds, comprising reacting the olefin compound with a gas mixture of hydrogen and carbon monoxide while being stirred at elevated pressures and temperatures in the presence of the above catalyst composition to produce an aldehyde.
The olefin compound may be represented by formula 4:




wherein
each of R6 and R7 is hydrogen, a C1-20 alkyl group, fluorine (—F), chlorine (—Cl), bromine (—Br), trifluoromethyl (—CF3), or a C6-20 phenyl group substituted with 0 to 5 substituents selected from the group consisting of nitro (—NO2), fluorine (—F), chlorine (—Cl), bromine (—Br), methyl, ethyl, propyl and butyl.


DETAILED DESCRIPTION OF THE INVENTION
The catalyst composition according to an embodiment of the present invention comprises a bidentate ligand, a monodentate ligand and a transition metal catalyst.
The bidentate ligand represented by formula 1 may be one in which each of R1 and R2 is pyrrole, phenyl, or indole, and the phosphorous is directly linked to a nitrogen atom.
In formula 1, the bisaryl compound Ar1-Ar2 may be represented by either formula 5 or formula 6:




wherein
each of R8, R9, R10, and R11 is hydrogen, a C1-20 alkyl group, a C6-20 aryl group, a triarylsilyl group, a trialkylsilyl group, a carboalkoxy group, a carboaryloxy group, an aryloxy group, an alkoxy group, an alkylcarbonyl group, an arylcarbonyl group, an amide group, a halogen atom, or a nitrile group, the carboalkoxy group being represented by —CO2R (wherein R is a C1-20 alkyl group or a C6-20 aryl group), and preferably, R8 may be methyl, methoxy, or t-butyl group, R9 may be hydrogen, R10 may be methyl, methoxy, or t-butyl, and R11 may be methyl or hydrogen,




wherein
each of R12, R13, R14, R15, R16, and R17 is hydrogen, a C1-20 alkyl group, a C6-20 aryl group, a triarylsilyl group, a trialkylsilyl group, a carboalkoxy group, a carboaryloxy group, an aryloxy group, an alkoxy group, an alkylcarbonyl group, an arylcarbonyl group, an amide group, a halogen atom, a nitrile group, the carboalkoxy group being represented by —CO2R (wherein R is a C1-20 alkyl group or a C6-20 aryl group).
The monoidentate ligand represented by formula 2 may be one in which each of R3, R4, and R5 is phenyl, phenyloxy, cyclohexyl, or t-butyl.
In the transition metal catalyst, the transition metal M may be cobalt (Co), rhodium (Rh), or iridium (Ir). Specific examples of the transition metal catalyst may include acetylacetonatodicarbonylrhodium (Rh(AcAc)(CO)2), acetylacetonatocarbonyltriphenylphosphinerhodium (Rh(AcAc)(CO)(TPP)), hydridocarbonyltri(triphenylphosphine)rhodium (HRh(CO)(TPP)3), acetylacetonatodicarbonyliridium (Ir(AcAc)(CO)2), or hydridocarbonyltri(triphenylphosphine)iridium (Hlr(CO)(TPP)3).
In the catalyst composition, the concentration of the transition metal may be 50 to 500 ppm based on the amount of the catalyst composition. If the concentration of the transition metal is less than 50 ppm, the hydroformylation reaction rate can be reduced, which is not economical. If the concentration of the transition metal is more than 500 ppm, it is disadvantageous in view of costs, since the transition metal is very expensive. In addition, the reaction rate is not advantageously increased, even at a concentration of more than 500 ppm.
The molar ratios of the bidentate ligand and the monodentate ligand to the Rh metal are 0.5 to 20 and 0.1 to 50, respectively. Preferably, the molar ratios of the bidentate ligand and the monodentate ligand to the Rh metal are 1 to 10 and 0.5 to 20, respectively. If the molar ratio of the bidentate ligand to the Rh metal is less than 0.5, the catalytic stability could be reduced. If the molar ratio of the bidentate ligand to the Rh metal is more than 20, the N/I selectivity could be increased, however the catalytic activity could be reduced. If the molar ratio of the monodentate ligand to the Rh metal is less than 0.1, the catalytic activity could be increased, but N/I selectivity cannot be controlled. If the molar ratio of the monodentate ligand to the Rh metal is more than 50 the catalytic stability and the activity could be reduced.
According to the embodiment of the present invention, by varying the molar ratio of the monodentate ligand, the N/I selectivity of the aldehyde produced is optionally controlled while maintaining the same catalytic activity as in the case of using a bidentate ligand alone. It appears that this advantage is derived since the monodentate ligand has a tendency to coordinate to a metal center of the catalyst in competition with the bidentate ligand in a catalytic cycle.
If the molar ratio of the bidentate ligand and the monodentate ligand to the Rh metal are 0.5 to 2 and 1 to 10, respectively, then the N/I selectivity is in a range of 2 to 3. If the molar ratio of the bidentate ligand and the monodentate ligand to the Rh metal are 3 to 10 and 1 to 10, respectively, then the N/I selectivity increase upto 15 to 18.
Advantageously, the transition metal catalyst may be acetylacetonatodicarbonylrhodium (Rh(AcAc)(CO)2), the bidentate ligand may be 1,1′-biphenyl-2,2′-diyl-bis(dipyrrolylphosphoramidite) (BPO—P(Pyl)2), and the monodentate ligand may be triphenylphosphine (TPP).
The olefin compound may be a compound selected from the group consisting of ethene, propene, 1-butene, 1-pentene, 1-hexene, 1-octene, and styrene.
The solvent used in the hydroformylation reaction according to the embodiment of the present invention may include aldehydes, such as propane aldehyde, butyraldehyde, and valeraldehyde; ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, and cyclohexanone; aromatics, such as benzene, toluene, and xylene; halogenated aromatics including ortho-dichlorobenzene; ethers, such as tetrahydrofuran, dimethoxy ethane, and dioxane; halogenated paraffins including methylene chloride; paraffinic hydrocarbons such as heptane, preferably various aldehydes and aromatics, such as toluene.
The composition of the synthesis gas CO/H2 used in the hydroformylation reaction according to the embodiment of the present invention can vary within a wide range. The molar ratio of CO/H2 may be generally about 5:95 to 70:30, preferably about 40:60 to 60:40, and especially preferably about 1:1.
The temperature of the hydroformylation reaction may be generally about 20 to 180° C., preferably about 50 to 150° C. The pressure of the hydroformylation reaction may be generally about 1 to 700 bar, preferably 1 to 300 bar.
Hereinafter, the present invention will be in more detail explained with reference to the following examples and not intended to limit the scope of the present invention.
Examples 1 to 9
Hydroformylation of Propene Using Acetylacetonatodicarbonylrhodium (Rh(AcAc)(CO)2) Catalyst, a Bidentate Phosphorous Compound and a Monodentate Phosphorous Compound
10.0 mg (37.8 mmol) of Rh(AcAc)(CO)2 catalyst, 0.2 mL of hexadecane, which is an internal standard of GC analysis, BPO—P(Pyl)2 as a bidentate ligand and ether TPP (triphenylphosphine) or TPPI (triphenylphosphite) as a monodentate ligand were added in toluene so that a total amount of the solution is 100 mL, each ratio of the bidentate ligand and the monodentate ligand to rhodium being listed in Table 1, and charged into a reactor (High Throughput Screening Unit (HTS), manufactured by Auto Clave). A gas mixture of propene:CO:H2 in a molar ratio of 1:1:1 was injected into the reactor to maintain a pressure at 6 bar. Then, the mixture was reacted while being stirred at 85° C. for 2.5 hours.
The applied catalyst and ligands, the molar ratio of each ligand to the catalyst, the reaction temperature, the N/I selectivity, and the catalytic activity were listed in Table 1.
In Table 1, the N/I value represent the relative ratio of normal-butyraldehyde to iso-butyraldehyde produced. Each yield of the aldehyde was obtained by GC analysis based on the amount of the hexadecane added as an internal standard.
To calculate the catalytic activity of the each reaction, the total amount of the produced normal butyraldehyde and iso butyraldehyde was divided by the molecular weight of butyraldehyde, by the concentration of the catalyst, and by the reaction time. The catalytic activity is expressed in mol(BAL)/mol(Rh)/h.














TABLE 1












Catalytic





Ligand



activity




Ligand 1
2
L1/Rh
L2/Rh

(mol(BAL)/mol(Rh)/



Catalyst
(L1)
(L2)
mol/mol
mol/mol
N/I
h)






















Example
Rh(AcAc)(CO)2
BPO—P(Pyl)2
TPP
1
1
3.2
253.6


1









Example
Rh(AcAc)(CO)2
BPO—P(Pyl)2
TPP
1
3
2.0
192.2


2









Example
Rh(AcAc)(CO)2
BPO—P(Pyl)2
TPP
1
5
2.0
175.0


3









Example
Rh(AcAc)(CO)2
BPO—P(Pyl)2
TPP
1
10
2.2
124.4


4









Example
Rh(AcAc)(CO)2
BPO—P(Pyl)2
TPP
3
1
15.7
204.4


5









Example
Rh(AcAc)(CO)2
BPO—P(Pyl)2
TPP
3
3
17.0
130.3


6









Example
Rh(AcAc)(CO)2
BPO—P(Pyl)2
TPP
5
1
17.2
109.6


7









Example
Rh(AcAc)(CO)2
BPO—P(Pyl)2
TPPI
1
5
2.2
147.7


8









Example
Rh(AcAc)(CO)2
BPO—P(Pyl)2
TPPI
3
1
16.2
135.9


9









Comparative Example 1
Hydroformylation of Propene Using Acetylacetonatodicarbonylrhodium (Rh(AcAc)(CO)2) Catalyst and Triphenylphosphine (TPP)
The experiment for catalytic activity was performed in the same manner as in Example 1 except that TPP was used alone as a ligand and a molar ratio of ligand to rhodium was 100. The results are shown in Table 2.
Comparative Example 2
Hydroformylation of Propene Using Acetylacetonatodicarbonylrhodium (Rh(AcAc)(CO)2) Catalyst and Tripyrrolylphosphine P(Pyl)3)
The experiment for catalytic activity was performed in the same manner as in Comparative Example 1 except that P(Pyl)3 was used instead of TPP as a ligand, and a molar ratio of ligand to rhodium was 50. The results are shown in Table 2.
Comparative Example 3
Hydroformylation of Propene Using Acetylacetonatodicarbonylrhodium (Rh(AcAc)(CO)2) Catalyst and 1,1′-biphenyl-2,2′-diyl-bis(dipyrrolylphosphoramidite) (BPO-P(Pyl)2)
The experiments for catalytic activity were performed in the same manner as in Comparative Example 1 except that BPO—P(Pyl)2 was used instead of TPP as a ligand, and molar ratio of ligand to rhodium was 1. The results are shown in Table 2.













TABLE 2








L/Rh
Temp.

Catalytic activity



Catalyst
Ligand (L)
(mol/mol)
(° C.)
N/I
(mol(BAL)/mol(RH)/h)





















Comparative
Rh(AcAc)(CO)2
TPP
100
85
3.9
85.4


Example 1








Comparative
Rh(AcAc)(CO)2
P(Pyl)3
50
85
10.1
80.3


Example 2








Comparative
Rh(AcAc)(CO)2
BPO—P(Pyl)2
1
85
8.7
227.3


Example 3









In Comparative Examples 1 and 2, hydroformylation of propene was performed using a monodentate ligand. As described in Table 2, when TPP was used as a ligand (Comparative Example 1), the catalytic activity was 85.4 mol(BAL)/mol(Rh)/h and N/I selectivity was 3.9. When tripyrrolylphosphine (P(Pyl)3) was used as a ligand (Comparative Example 2), the catalytic activity was somewhat lower, but the selectivity to normal-butyraldehyde (N/I selectivity 10.1) was somewhat higher than when TPP was used. Especially, it is known that if the temperature of a hydroformylation reaction is decreased when P(Pyl)3 is used as a ligand, the catalytic activity is somewhat decreased, but the N/I selectivity is rapidly increased.
Referring to Table 1, in Example 1, TPP as a monodentate ligand was added in a ratio of 1 mol per mol of rhodium to the catalyst system using a bidentate ligand alone in Comparative Example 3. In this case, the catalytic activity was increased by about 12% and the selectivity to normal butyraldehyde to iso butyraldehyde was reduced from 8.7 to 3.2, i.e., the selectivity to iso butyraldehyde was increased by at least two folds. In Example 2, TPP was added in a ratio of 3 mol per mol of rhodium to the catalytic system using a bidentate ligand alone in Comparative Example 3. In this case, the N/I selectivity was 2.0.
When BPO—P(Pyl)2 as a bidentate ligand was used in a ratio of 3 mol per mol of rhodium, high N/I selectivity of at least 15 was attained, while maintaining high catalytic activity, which was 240% higher compared with Comparative Example 1 using Rh/TPP. When BPO—P(Pyl)2 as a bidentate ligand was used in a ratio of 5 mol per mol of rhodium, the N/I selectivity was increased up to 17.2.
Examples 8 and 9 using TPPI as a monodentate ligand in addition to the bidentate ligand had similar tendencies to the above case using TPP.
From the above results, it is confirmed that using a catalyst composition comprising acetylacetonatodicarbonylrhodium (Rh(AcAc)(CO)2) as a catalyst and a combination of 1,1′-biphenyl-2,2′-diyl-bis(dipyrrolylphosphoramidite) (BPO—P(Pyl)2) as a bidentate ligand and either TPP or TPPI as a monodentate ligand, it is possible to control yields of normal butylaldehyde and iso butylaldehyde.
A catalyst composition comprising a transition metal catalyst and a combination of a monodentate phosphorous compound and a bidentate phosphorous compound as a ligand according to the present invention can be used in a process of hydroformylation of olefin compounds to produce an aldehyde. In a process of hydroformylation of olefin compounds using the catalyst composition comprising a monodentate phosphorous ligand and a bidentate phosphorous ligand according to the present invention, the catalytic activity is very high, and N/I selectivity can be controlled to a desired value.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.

## Claims

1. A catalyst composition for hydroformylating an alpha-olefin compound comprising a bidentate ligand represented by formula 1, a monodentate ligand represented by formula 2, and a transition metal catalyst represented by formula 3:



wherein
each of R1 and R2 is a substituted or unsubstituted C4-36 heteroaryl group,
Ar1-Ar2 is a bisaryl compound, and
X is oxygen (O),
wherein the bisaryl compound Ar1-Ar2 is represented by either formula 5 or formula 6:






wherein
each of R8, R9, R10, and R11 is hydrogen, a C1-20 alkyl group, a C6-20 aryl group, a triarylsilyl group, a trialkylsilyl group, a carboalkoxy group, a carboaryloxy group, an aryloxy group, an alkoxy group, an alkylcarbonyl group, an arylcarbonyl group, an amide group, a halogen atom, or a nitrile group, the carboalkoxy group being represented by —CO2R (wherein R is a C1-20 alkyl group or a C6-20 aryl group),






wherein
each of R12, R13, R14, R15, R16, and R17 is hydrogen, a C1-20 alkyl group, a C6-20 aryl group, a triarylsilyl group, a trialkylsilyl group, a carboalkoxy group, a carboaryloxy group, an aryloxy group, an alkoxy group, an alkylcarbonyl group, an arylcarbonyl group, an amide group, a halogen atom, or a nitrile group, the carboalkoxy group being represented by —CO2R (wherein R is a C1-20 alkyl group or a C6-20 aryl group),






wherein
each of R3, R4 and R5 is a substituted or unsubstituted C1-20 alkoxy group; a phenoxy group; a substituted or unsubstituted C4-36 heteroaryl group; or a substituted or unsubstituted C4-36 heterocyclic group, each of R3, R4 and R5 being optionally substituted with nitro (—NO2), fluorine (F), chlorine (Cl), bromine (Br), or a C1-4 alkyl group,


M(L1)l(L2)m(L3)n  (3)


wherein
M is rhodium,
each of L1, L2 and L3 is hydrogen, CO, acetylacetonato, cyclooctadiene, norbornene, chlorine, or triphenylphosphine, and
each of l, m and n is a number of 0 to 5, provided that all l, m and n are not zero simultaneously; and

wherein the concentration of rhodium is 50 to 500 ppm based on the amount of the catalyst composition, and per mole of the rhodium, the concentration of the monodentate ligand is 0.1 to 10 mol and the concentration of the bidentate ligand is 0.5 to 2 moles to give a N/I selectivity of 2 to 3, or 3 to 10 moles to give a N/I selectivity of 15 to 18.

2. The catalyst composition of claim 1, wherein in formula 1, each of R1 and R2 is pyrrole or indole, and the phosphorous is directly linked to a nitrogen atom.

3. The catalyst composition of 1, wherein in formula 5, R8 is methyl, methoxy, or t-butyl group, R9 is hydrogen, R10 is methyl, methoxy, or t-butyl, and R11 is methyl or hydrogen.

4. The catalyst composition of claim 1, wherein the transition metal catalyst is acetylacetonatodicarbonylrhodium (Rh)(CO)2), acetylacetonatocarbonyltriphenylphosphinerhodium (Rh)(CO)(TPP)), hydridocarbonyltri(triphenylphosphine)rhodium (HRh(CO)(TPP)3).

5. The catalyst composition of claim 1, wherein the transition metal catalyst is acetylacetonatodicarbonylrhodium (Rh(AcAc)(CO)2), the bidentate ligand is 1,1′-biphenyl-2,2′-diyl-bis(dipyrrolylphosphoramidite) (BPO—P(Pyl)2), and the monodentate ligand is triphenylphosphite (TPPI).

6. A process of hydroformylating an olefin compound, comprising reacting the olefin compound with a gas mixture of hydrogen and carbon monoxide while being stirred at elevated pressures and temperatures in the presence of the catalyst composition of claim 1 to produce an aldehyde.

7. The process of claim 6, wherein the olefin compound is represented by formula 4:



wherein

each of R6 and R7 is hydrogen, a C1-20 alkyl group, fluorine (—F), chlorine (—Cl), bromine (—Br), trifluoromethyl (—CF3), or a C6-20 phenyl group substituted with 0 to 5 substituents selected from the group consisting of nitro (—NO2), fluorine (—F), chlorine (—Cl), bromine (—Br), methyl, ethyl, propyl and butyl.

8. The process of claim 6, wherein the olefin compound is a compound selected from the group consisting of ethene, propene, 1-butene, 1-pentene, 1-hexene, 1-octene, and styrene.