Abstract
A method to make primary alcohols, carboxylic acids, amines, and other value-added chemicals from plastic waste. The method includes the steps of pyrolyzing plastic waste to yield pyrolysis oil; hydroformylating the pyrolysis oil in the absence of any added co-reactants to yield a mixture comprising aldehydes; and hydrogenating, oxidizing, aminating, or aldolizing the mixture to yield a product comprising primary alcohols, carboxylic acids, amines, or larger (>C10) chemicals with carbonyl function groups.
Claims
1. A method to make primary alcohols, di-alcohols, or esters from plastic waste, the method comprising: (a) providing pyrolysis oil and separating the pyrolysis oil into a light cut having a boiling point less than about 175 C. and a heavy cut having a boiling point greater than about 175 C., where the light cut and the heavy cut comprise olefins, wherein the light cut consists essentially of compounds having less than 11 carbon atoms, and the heavy cut consists essentially of compounds having more than 10 carbon atoms; and then (b) hydroformylating the light cut and/or the heavy cut, independently, at a pressure between about 50 atm and about 70 atm and at a temperature between about 100 C. and 120 C., wherein at least a portion of the olefins in the light cut and/or the heavy cut are converted to aldehydes, to yield corresponding light and/or heavy mixtures comprising aldehydes; (c) separately hydrogenating the light mixture and/or the heavy mixture of step (b) to yield corresponding product mixture(s) comprising a product selected from the group consisting of primary alcohols, di-alcohols, esters, and combinations thereof.
2. The method of claim 1, wherein step (a) comprises providing pyrolysis oil from plastic waste comprising a poly(alkylene).
3. The method of claim 1, wherein step (a) comprises providing pyrolysis oil from plastic waste comprising poly(ethylene).
4. The method of claim 1, wherein step (b) comprises contacting the pyrolysis oil with syngas and a transition metal-containing catalyst.
5. The method of claim 4, wherein the transition metal-containing catalyst comprises cobalt or rhodium.
6. The method of claim 4, wherein the transition metal-containing catalyst comprises HCo(CO).sub.4, Co.sub.2(CO).sub.8, a triphenylphosphine-modified cobalt-containing catalyst, a triphenylphosphine-modified rhodium-containing catalyst, a cobalt-containing salt of triphenylphosphinetrisulfonate, or a rhodium-containing salt of triphenylphosphinetrisulfonate.
7. The method of claim 4, wherein step (c) comprises contacting the mixture of step (b) with hydrogen and a transition metal-containing catalyst, for a time, at a temperature, and at a pressure of hydrogen wherein at least a portion of aldehydes contained in the mixture of step (b) are converted into alcohols.
8. The method of claim 4, wherein when step (c) is performed on the light cut, the product mixture comprises products having from 5 to 13 carbon atoms, and when step (c) is performed on the heavy cut, the product mixture comprises products having from 10 to 30 carbon atoms.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) FIG. 1 depicts the crux of the method disclosed herein. Waste plastics (HDPE is shown as a non-limiting example) is pyrolyzed to yield pyrolysis oil. The 500 C. pyrolysis temperature is also exemplary. Pyrolysis temperatures above and below 500 C. are within the scope of the present disclosure. The pyrolysis oil is then subjected to hydroformylation using syngas (a mixture of carbon dioxide and molecular hydrogen) to yield a product mixture comprising aldehydes. The hydroformylation reaction conditions noted (120 C., for 3 hours, over a CO.sub.2(CO).sub.8 catalyst) are exemplary and non-limiting.
(2) FIG. 2 depicts downstream additional, exemplary processing on the product mixture comprising aldehydes that results from the method depicted in FIG. 1. The exemplary reactions include (but are not limited to) hydrogenation, reductive amination, oxidation, and aldolization.
(3) FIG. 3A is a two-dimensional gas chromatogram (2D-GC) of pyrolysis oil formed as in FIG. 1 and then distilled into a light cut having a boiling point less than about 175 C. (and comprising compounds having less than about 11 carbon atoms, i.e. <C11) and a heavy cut having a boiling point greater than about 175 C. (and comprising compounds having more than about 10 carbon atoms, i.e. >C10); FIG. 3A is the 2D-GC of the light cut.
(4) FIG. 3B is the 2D-GC analysis of the light cut oil analyzed in FIG. 3A after hydroformylation catalyzed by CO.sub.2(CO).sub.8 in a 350 mL stainless steel batch reactor for 3 hours. Conditions: 120 C., 70 Bar Syngas (CO/H.sub.2=1), 900 rpm, 10 wt % CO.sub.2(CO).sub.8 in oil.
(5) FIG. 3C is the 2D-GC analysis of the light cut oil from FIG. 3B after hydrogenation catalyzed by 20% Ni/SiO.sub.2 in a continuous flow reactor for 5 hours. Conditions: 100 C., 78 Bar H.sub.2, WHSV=1 hr.sup.1.
(6) FIG. 4A is the .sup.13C NMR spectrum of the light cut pyrolysis oil from FIG. 3A.
(7) FIG. 4B is the .sup.13C NMR spectrum of the product mix resulting from the light cut oil, post-hydroformylation, whose 2D-GC is shown in FIG. 3B.
(8) FIG. 4C is the .sup.13C NMR spectrum of the product mix resulting from the light cut oil, post-hydrogenation, whose 2D-GC is shown in FIG. 3C.
(9) FIG. 4D shows the .sup.1H-.sup.13C heteronuclear single quantum coherence (HSQC) NMR spectrum of the product mix, post-hydrogenation, whose 2D-GC is shown in FIG. 3C.
(10) FIG. 5A is a process flow diagram for upcycling colored post-consumer waste, high-density polyethylene (HDPE) according to the present method. Here, after distillation into a light cut and a heavy cut (as described above), the two cuts are subjected to hydroformylation followed by hydrogenation to yield a light product mixture comprising alcohols having less than about 13 carbon atoms and a heavy product mixture comprising alcohols having more than about 10 carbon atoms. Exemplary reaction conditions are as stated in the figure.
(11) FIG. 5B is an alternative process flow diagram for upcycling colored post-consumer waste into paraffins, aromatics, alcohols, and/or di-alcohols using the method disclosed herein. Reaction conditions are as stated in the figure.
(12) FIG. 6 is a detailed input-output analysis for upgrading pyrolysis oil made from waste plastics according to the method disclosed herein. The reactant was 100 g of pyrolysis oil, which was then distilled into light and heavy cuts as described previously. Each cut was then subjected to hydroformylation followed by hydrogenation. The light and heavy product mixtures comprised aldehydes, aromatics, paraffins, hemiacetals, esters, mono-alcohols, and di-alcohols in the amounts shown in the figure.
(13) FIG. 7A is a histogram depicting product distributions found in different non-distilled polyolefin pyrolyzed oil (about C5 to about C40) feedstocks. Here, the pyrolysis oil was formed at 500 C. and 20 s residence time. HDPE has the highest yield of olefins and dienes among the plastic types pyrolyzed. With increasing branch density, more paraffins and aromatics are present. Thus, under the same pyrolysis conditions, a HDPE feedstock yields a less-branched pyrolysis oil and favors the formation of olefin and dienes.
(14) FIG. 7B is a histogram depicting product distributions found in non-distilled polyolefin pyrolyzed oil formed at 500 C. and 20 s residence time. The resulting pyrolysis oil contains products distributed from about C7 to C40. Virgin HDPE generates the most linear olefins and linear dienes among the plastics tested. Post-consumer waste HDPE (colored HDPE) oil contained less linear product than the virgin HDPE oil. Impurities or additives in the post-consumer waste HDPE likely caused isomerization of the linear hydrocarbons during the pyrolysis process.
DETAILED DESCRIPTION OF THE INVENTION
(15) Newly developed and disclosed herein is a method of making value-added chemicals, principally primary alcohols, di-alcohols, and esters, from a waste plastic feedstock. The heart of the method is illustrated in FIG. 1. As shown in the figure, post-consumer plastic waste is first subjected to pyrolysis (or other thermal depolymerization processing) to yield pyrolysis oil. The pyrolysis oil is then hydroformylated neat to yield a mixture comprising aldehydes. Surprisingly the aromatics, paraffins, and other impurities in the plastic pyrolysis oil did not cause inhibition of the hydroformylation catalyst. As shown in the figure, the plastic waste feedstock is designated as Post-Consumer HDPE, that is, post-consumer, high-density poly(ethylene). This is an exemplary, non-limiting feedstock for the method. The incoming plastic feedstock may be any waste plastic stream (post-consumer or post-industrial), of any type of polymer or mixtures of polymers, that will yield a pyrolysis oil comprising olefins (i.e., alkenes). Likewise, pyrolysis is an exemplary, non-limiting type of thermal depolymerization that may be used to generate the pyrolysis oil. As noted above, the pyrolysis oil may also be generated by any other type of thermal/chemical/catalytic depolymerization of the incoming plastic feedstock.
(16) The pyrolysis oil is then hydroformylated by contacting it with syngas in the presence of a transition metal-containing catalysts as described herein. As shown in FIG. 1, an exemplary catalyst, Co.sub.2(CO).sub.8, was used. The hydroformylation reaction is carried out under time, temperature, and pressure values that yield a mixture comprising aldehydes. FIG. 1 shows exemplary condition of a reaction at 120 C., for three hours. The pressure, not indicated in FIG. 1, was about 70 bar.
(17) As shown in FIG. 2, the mixture resulting from the hydroformylation reaction is rich in aldehydes. These aldehydes can then be upgraded by any number of subsequent reactions to yield value-added chemicals. Thus, the mixture resulting from hydroformylation can be subjected to hydrogenation to yield alcohols, or reductive amination to yield amines, or oxidized to yield carboxylic acids, or subjected to an aldol reaction to yield new -hydroxy and/or beta-unsaturated carbonyl compounds. Aldolization of the product mixture, post-hydroformylation, thus yields longer-chain polymers.
(18) The hydroformylation reaction can be performed on the bulk pyrolysis oil neatwithout any pre-reaction processing steps. Alternatively, the pyrolysis oil may be separated into light and heavy cuts via distillation (or any other suitable separation means). Thus, for example, the pyrolysis oil may be separated into a light cut that boils at a temperature less than about 175 C. and a heavy cut that boils at a temperature greater than about 175 C. This was done and the heavy and light cuts subjected to 2D-GC. The 2D-GC of an exemplary light cut pyrolysis oil, made from colored post-consumer waste HDPE and having a boiling point of about 175 C. is shown in FIG. 3A. As shown in chromatogram, the light cut includes linear alkanes, alkenes, and alkadienes (top trace), other (non-linear) alkenes (second trace from top), other (non-linear) alkadienes (third trace from top), and various aromatics and cyclic compounds (bottom trace).
(19) The light cut whose 2D-GC is shown in FIG. 3A was then subjected to hydroformylation in a batch reactor at 120 C., for 3 hours, with vigorous stirring (900 rpm) using CO.sub.2(CO).sub.3 as the catalyst, with syngas (CO:H.sub.2=1) at a pressure of about 70 Bar. The 2D-GC of the resulting product mixture is shown in FIG. 3B. As shown in FIG. 3B, the product mixture comprised aldehydes and dialdehydes. That is, at least a portion of the alkenes and alkadienes present in the original pyrolysis oil were converted to aldehydes and dialdehydes.
(20) The mixture whose 2D-GC is shown in FIG. 3B was then subjected to hydrogenation after the removal of Co catalyst. The removal of Co catalysts was carried out in a 125 mL jar. The mixture (e.g., 10 mL) was stirred 6 hours exposed to air with a solution (e.g., 10 mL water, 0.5 g Co(NO.sub.3).sub.26H.sub.2O, and 1 mL acetic acid) under ambient conditions. The hydrogenation was then performed in a continuous flow reactor at 100 C., under 78 Bar of H.sub.2, over 20 wt % Ni/SiO.sub.2, 5 hours time on stream at 1 hr.sup.1 WHSV. For the heavy cut, the mixture was dissolved in hexane before feeding to the continuous flow reactor. The 2D-GC analysis of the result product is shown in FIG. 3C. As shown in the figure, the product mix comprised alcohols and diols.
(21) FIG. 4A presents the .sup.13C NMR spectrum of the light cut pyrolysis oil from FIG. 3A. As shown, the light cut pyiolysis oil prior to further manipulation contained a very strong signal for aromatic compounds, but no detectable signal for carbonyl-containing compounds nor primary alcohols. FIG. 4B is the .sup.13C NMR spectrum of the same product mix, post-hydroformylation. (The corresponding 2D-GC is shown in FIG. 3B.) The comparison to FIG. 4A is immediately apparent. Whereas FIG. 4A has no signal for carbonyl compounds or alcohols, the .sup.13C NMR spectrum shown in FIG. 4B has very pronounced signals indicating the presence of aldehydes, and a less-pronounced, but still easily detectable set of signals indicated a small presence of alcohols. FIG. 4C is the .sup.13C NMR spectrum of the product mix resulting from the light cut oil, post-hydrogenation. (The corresponding 2D-GC is shown in FIG. 3C.). Here, the spectrum clearly shows that a very substantial portion of the aldehydes present in the mixture resulting from hydroformylation have been converted to alcohols. See the right-hand portion of FIG. 4C. FIG. 4D shows the .sup.1H-.sup.13C heteronuclear single quantum coherence (HSQC) NMR spectrum of the product mix, post-hydrogenation, whose 2D-GC is shown in FIG. 3C. Signal assigned to secondary alcohols were labeled and the rest of the .sup.1H/.sup.13C correlation signals belong to primary alcohols. This confirms the abundance of the primary alcohols.
(22) FIG. 5 shows an illustrative (exemplary) implementation of the method disclosed herein. Starting from the top of the figure, a feed stock of waste plastic, in this case colored post-consumer waste HDPE is subjected to pyrolysis to yield pyrolysis oil. 120 grams of the HDPE were introduced to a pyrolysis chamber set at 500 C. at a rate of 2 g/min (1 hour total feed time). The pyrolysis yielded 83.8 grams (70 wt %) of pyrolysis oil. The pyrolysis oil was then distilled into two fractions: a light fraction having a boiling point of less than about 175 C. (73 wt %) and a heavy fraction having a boiling point of more than about 175 C. (27 wt %). The light fraction was comprised mainly of compounds having about 11 carbon atoms or less. The heavy fraction was comprised mainly of compounds having more than 10 carbon atoms.
(23) The light fraction was subjected to hydroformylation in a batch reactor under 70 Bar syngas (1:1; H.sub.2:CO), for 3 hours, at 120 C. with vigorous stirring, and with Co.sub.2(CO).sub.8 as the catalyst. The catalyst was loaded at a 1:10 wt ratio catalyst-to-pyrolysis oil. The resulting mixture was then subjected to hydrogenation. This was done in a continuous flow reactor at 78 Bar H.sub.2. The reaction was performed using 20 wt % Ni/SiO.sub.2 at 100 C., for 5 hours, at a WHSV of 1 hr.sup.1. The resulting product mix comprised alcohols having about 13 carbon atoms or less.
(24) In an analogous fashion, the heavy fraction was subjected to hydroformylation in a batch reactor under 70 bar syngas (1:1; H.sub.2:CO), for 3 hours, at 120 C. with vigorous stirring, and with CO.sub.2(CO).sub.8 as the catalyst. The catalyst was loaded at a 1:12 wt ratio catalyst-to-pyrolysis oil. The resulting mixture was then subjected to hydrogenation. This was done in a continuous flow reactor at 78 Bar H.sub.2. The reaction was performed using 20 wt % Ni/SiO.sub.2, at 100 C., for 5 hours, at a WHSV of 1 hr.sup.1. The resulting product mix comprised alcohols having about 10 carbon atoms or more.
(25) FIG. 6 is a detailed input-output analysis for the reaction shown in FIG. 5 and described above. The reaction conditions were the same as those described in FIG. 5. The reactant was 100 g of pyrolysis oil, which was then distilled into light and heavy cuts as described previously. Each cut was then subjected to hydroformylation followed by hydrogenation as described previously. The light and heavy product mixtures both yielded final product mixtures (post-hydroformylation and post-hydrogenation) that comprised aldehydes, aromatics, paraffins, esters, mono-alcohols, and di-alcohols.
(26) The ultimate product mix from the light cut, post-hydroformylation and post-hydrogenation, contained 1.1 g aldehydes, 35.9 g aromatics and paraffins, 1.3 g hemiacetals, 56.3 g alcohols, and 15.2 g di-alcohols. The hydroformylation reaction consumed 34.5 g of syngas. The hydrogenation reaction consumed 2.3 grams of hydrogen.
(27) The ultimate product mix from the heavy cut, post-hydroformylation and post-hydrogenation, contained 0.8 g aldehydes, 12.2 g aromatics, olefins, and paraffins, 1.1 g hemiacetals and esters, 13.1 g alcohols, and 3.5 g di-alcohols. The hydroformylation reaction consumed 3.4 g of syngas. The hydrogenation reaction consumed 0.3 grams of hydrogen.
