Bio Refinery

 

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RENEWABLE FEEDSTOCKS: TRADING BARRELS FOR BUSHELS Efforts to boost conversion rates and yields and improve separation efficiency are helping, but obstacles remain

Starch based polymers

Current bulk productions

Polyhydroxyalkanoates

Production on pilot scale Research scale

CO2 Starch

C5 and C6 sugars

Ethanol

Sugar beet, sugarcane

Vinyl chloride

Lactic acid 3 HP

Wheat maize potato

Ethylene

Succinic acid

1,3 Propanediol 1,2 Propanediol

Acrylic acid

Acrylic acid

PBS

Poly lactic acid

THF 1,4 Butanediol Glycols

Sorbitol

Isosorbide

Polymer

Isoprene Polyisoproprene C5 and Cellulose/  ith traditional petroleum-derived feedC6 ligno Ethanol stocks facing relentless sugars cellulose economic and environCellulose ethers Levulinic acid MeMbl cellulose esters mental pressures, it’s no surprise and viscose Vegetable that stakeholders throughout Rapeseed, Bio diesel Acrolein fibers oil the chemical process industries soyseed Glycerol Glycerol carbonate (CPI) have been in hot pursuit of Natural oil 1,2 Propanediol alternative routes for producing polyols (NOP) Epoxy resins Epichlorohydrin commodity and specialty chemi- FIGURE 1.  Many platform 1,3 Propanediol Polyurethanes cals and polymers from cheap, and derivative chemicals and polymers can be produced from plentiful renewable feedstocks. a handful of renewable agricultural and forest feedstocks Source: Frost & Sullivan The most promising routes are based on agriculturally derived, starches, sugars, fats, oils, lignocellu- economic impact of using renewable acid, glutamic acid, itaconic acid, lelose, and proteins, and waste streams feedstocks, the integrated biorefiner-  vulinic acid, 3-hydroxbutyrolactone 3-hydroxbutyrolactone,,

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from fruit and vegetable processing ies of the future will need to pursue glycerin, sorbitol and xylitol/arabiplants, pulp-and-paper mills, and a “one-to-many” concept — whereby nitol. According to Frost & Sullivan, other biomass sources (Figure 1). 1 each renewable feedstock will be con- efforts to produce the platform chemiToday, parallel efforts are beginning  verted into any number of basic buildbuild- cals lactic acid, succinic acid, glycerin, to bear fruit. According to market ana- ing block chemicals (so-called “plat- 1,3-propanediol (PDO), levulinic acid, lyst Frost & Sullivan (London; www. form chemicals”), which would then and various cellulose and starch dechemicals.frost.com), the global mar- serve as the interim feedstocks for the rivatives are furthest along on the deket for renewably sourced commodity production of countless downstream,  velopmental continuum continuum today today. Still, challenges remain, because chemicals earned revenues of $1.63  value-added chemicals, chemicals, monomers and billion in 2008, and this figure is pro- polymers, says Joseph J. Bozell, asso- “no two technologies reside within any  jected to reach reach $5.01 $5.01 billion by 2015. 2015. ciate professor, Biomass Chemistry, single company — every company has Many of the most mature processes Forest Products Center, University of perfected its own single technology for producing single target products” says to date tend to be focused on the con- Tennessee (Knoxville).  version of a single renewable renewable feedIn 2004, the U.S. Dept. of Energy Phani Raj Kumar Chinthapalli, senior stock into a single biobased chemical (DOE; Washington, D.C.; www.doe.gov) www.doe.gov) research analyst for Frost & Sullivan, or polymer (a “one-to-one” concept). identified 12 platform chemicals that who is based in Chennai, India. However, to realize the full techno- can be produced from sugars via biological or chemical routes — 1,4-diac- Building blocks 1. A longer version of this article, which conids (succinic, fumaric and malic acids), “After nearly two centuries, petroleum tains additional process details and market information, can be found online at www.che.com. 2,5-furan dicarboxylic acid, 3-hydroxy refineries are able to use proven, optiBrowse the June 2009 issue or search the editopropionic acid, aspartic acid, glucaric mized technologies to produce a specrial archives for this article title to access it. 16 

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Comparison of feedstock prices for the chemical industry 1,400

Maize

Wheat

1,200

Sugar

Crude brent

Source: Frost & Sullivan

1,000

lysts to convert plentiful lignin into downstream chemicals. One key to using lignin is the sepa600 ration of biomass into its three main 400 components (lignin, cellulose and hemicellulose). Today, effective up200 front separation remains a huge chal01-03 lenge for any biorefinery. One classic 7-08 1-08 7-07 1-07 7-06 1-06 7-05 1-05 7-04 1-04 7-03 9-08 3-08 9-07 3-07 9-06 3-06 9-05 3-05 9-04 3-04 9-03 3-03 approach (dilute acid pretreatment) 11-08 5-08 11-07 5-07 11-06 5-06 11-05 5-05 11-04 5-04 11-03 5-03 removes a significant portion of the Year hemicellulose, but leaves the remainFIGURE 2.  Three of the most viable renewable feedstocks have enjoyed greater ing two fractions (cellulose and lignin) price stability over the past few years than crude oil, the starting material for convencommingled, and “thus not available tional petrochemical feedstocks in as useful a form,” says Bozell. trum of platform chemicals that serve frequently suffer product inhibition.”  Advances in the use of acid or base as chemical feedstocks for the down- He adds: “Wresting products like alco- treatments, steam treatment and solstream chemical industry,” says Luc hols and acids out of water often re-  vent fractionatio fractionation n “appear to offer good massi ve amounts of energy energ y, and access to the components in biomass Moens, senior scientist, National Re- quires massive newable Energy Laboratory’s National frequently requires steps to overcome and help to reduce the complexity of Bioenergy Center (NREL; Golden, difficulties such as azeotropes.” the heterogeneous starting materials, Colo; www.nrel.gov). For developers  As a result, result, process process developers developers have yielding simpler molecules, carbohyof renewable routes, efforts to take a been pursuing not only advanced en- drates, lignins and plant-based hydro     n      o 800        t        /        $

page fromhave the petrochemical playbook not been as refinery’s straightforward as some might hope. “Many of the classical unit operations from the petrochemical refineries, such as distillation, cracking and conventional thermal processes such as gasification and pyrolysis just don’t work as well for renewable feedstocks,” says Bozell. “The high degree of oxygenation associated with these complex substrates hinders many conventional chemical catalyst systems,” says Moens. “This reduction either comes at the cost of energy (for example, hydrogen

zymes to improve microbial and fermentation processes, but advances that will allow classical chemical process and refinery techniques (such as the use of thermal cracking, and acid or base catalysis using homogeneous and heterogeneous catalysts) to be adapted for renewable feedstocks, as well. “Once perfected, such techniques are expected to offer advantages over purely biological processing methods of biomass,” says Bozell.

and natural gas) or through the loss of carbon as CO2  and solid waste, all of which increase capital requirements and raw materials costs compared to petroleum-based routes,” adds Bob Maughon, Hydrocarbons & Energy R&D director for Dow Chemical Co. (Midland, Mich.; www.dow www.dow.com). .com). Instead of conventional catalysts, many of the most well-developed, biobased chemical production routes in use today, such as fermentation, rely on microbial or enzyme-driven biochemical conversions, which are challenging theselves, “Enzyme-based processes have advantages [for renewable feedstocks], but they also have some disadvantages,” says Maughon. “They tend to be slower than chemical processes, they almost always require water to be present, and they

renewable source of aromatics — an acid, and the mixture is heated at important, high-volume class of com- 140°C for less than one hour. The solpounds,” says Bozell. “The ability to  vent mixture selectively dissolves the carry out direct, efficient conversion lignin and hemicellulose components, of lignin to low-molecular-weight aro- leaving the cellulose as an undissolved matics (including the BTX chemicals solid material that can be washed, fibenzene, toluene and xylenes) is an berized and further purified. attractive goal, but it is particularly The soluble fraction containing both challenging due to the difficulties as- lignin and hemicellulose is treated sociated with separating lignin from with water, resulting in a phase separation into an organic phase conlignocellulosic feedstocks.”  According to DOE, process devel- taining the lignin, and an aqueous opers working with lignin have had solution containing the hemicellulosepromising early success using gasifi- derived sugars (pentosans). More than cation to convert lignin into syngas 95% of the components in the starting (carbon monoxide and hydrogen) and feedstocks can be isolated, says Moen. eventually mixed alcohols, and pyrol- The process normally gives a cellulose ysis to convert lignin into gasoil and yield of about 47–48 wt.%, in compariother pyrolysis oils. These efforts have son to maximum yields of about 40% processes. fueled interest in the development of using conventional pulping processes. The CF process also allows for 99% other processes and improved cata-

Looking at lignin “Lignin is unique among its biomass counterparts, in that it is the only

 

carbons,” says Bozell. process develOne solvent-based oped by NREL, called Clean Fractionation (CF), is able to isolate and purify chemical-grade cellulose from lignocellulosic materials. Designed as a front-end pretreatment step for biorefineries, the process separates the previously commingled lignin/  hemicellulose streams, making both available for chemical production. First, the cellulosic feedstock is treated with a ternary mixture of methyl isobutyl ketone (MIBK), ethanol and water in the presence of a dilute acid promoter such as sulfuric

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Source: Dr. Joseph Bozell, University of Tennessee (Knoxville)

Fuels (convergent) Technology 1

Newsfront

Technology 2 Technology 3

Single product (e.g., EtOH)

etc.

Chemicals (divergent) recovery of the organic solProduct 1  vents, and produces no odorous Single technology Product 2 (e.g., selective emissions, says Bozell (who led Product 3 oxidations) the CF process development etc. at NREL for 10 years before moving to the University of Tennessee). “This provides new op- feedstock propylene oxide, PG is used portunities for the use of sugar cane in the manufacture of various plastics bagasse and other lignocellulosic and plasticizers, solvents, hydraulic feedstocks as chemical feedstocks,” fluids and lubricants, heat-transfer adds Moens. fluids, and more. To take advantage of this sudden Levulinic acid availability of excess glycerin supply, Levulinic acid (LA) is a diverse plat- at least a half dozen chemical compaform chemical. This five-carbon com- nies (including Dow Chemical, Huntspound, traditionally produced from man Corp., ADM and others) are maleic anhydride and other petro- working in parallel to build grassroots chemical feedstocks, has historically chemical plants to convert biodieselfound use in the manufacture of ad- derived glycerin into PG. hesives, rubber, plastics, and synthetic synthe tic However, “while near-term crude fiber products. glycerin is in excess, the longterm Today, it can be produced through  view could change, change, as next-generat next-generation ion

the hydrolysis of cellulose acid-catalyzed (using, for instance, sulfuric acid). “Levulinic acid should receive much more attention than it has, because it is such a versatile and reactive molecule, from which numerous derivatives can be synthesized,” says Moens. “When you consider how many chemicals can be made from levulinic acid — including levulinate esters, N-methylpyrrolidone, 1,4-butanediol, succinic acid, pyrrolidine, lactones, acrylic acid, and furans, to name a few — you see the versatile nature of this chemical.  And the ability to produce this cellulose-derived platform chemical from waste materials, such as sugar cane bagasse and other lignocellulosic feedstocks provides a compelling driver for process developers.” Biodiesel’s downstream bounty During the production of biodiesel, the transesterification of feedstock vegetable oils and animal fats produces one pound of glycerin for every nine pounds of diesel (or, stated another way, 1.25 lb of glycerin is produced for every gallon of biodiesel). Swift growth in worldwide biodiesel capacity in recent years has created an abundant supply of byproduct glycerin, which has fueled interest in processes to convert glycerin into propylene glycol (1,2-propanediol; PG; see also CE, Outlets for glycerin, Sept. 2007, pp. 31–37). Traditionally Traditional ly made from fossil 18 

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biodiesel processes make are no glycerin and renewable processes already consuming this surplus,” says Maughon of Dow. He also notes that many of the technologies known today still have competitive cost issues and product quality issues (especially around pharmaceutical grades) that must be reconciled before they can be used more broadly on a commercial basis.

FIGURE 3.  While the ‘single-p ‘single-product’ roduct’ approach has dominated the commercialization of many biobased chemicals and plastics processes to date, many say that the cost-effective biorefinery concept of tomorrow will be predicated on the ability to convert key renewable feedstocks into intermediate ‘platform chemicals,’ which can be further processed to produce a broad slate of value-added chemicals

also reduces wastewater generation by over 90% and consumes 30% less energy compared to the conventional technology. Dow has had a GTE demonstration unit running at its Stade, Germany, site since 2006, and in 2008 announced plans for its first commercial-scale GTE facility in China. Similarly, in April 2007, Solvay Chemicals (Brussels; www.solvay. com) started up a 10,000-m.t./yr plant that produces epichlorohydrin at its Tavaux, France, site, from biodieselderived glycerin, using the company’s patented Epicerol process (for more, see CE, March 2006, p. 14, and April 2006, pp. 27–30).with Theacompany is now moving forward 100,000-metric ton (m.t.)/yr Epicerol production facility in Map Ta Phut, Thailand, with startup slated for 2010.

Epichlorohydrin production Today, several major chemical companies are also developing and commercializing processes to produce epichlorohydrin — a high-volume commodity

PDO and bioplastics Two different renewable routes (based on corn sugar and glycerin) glyceri n) have been commercialized for another widely used propanediol — 1,3-propanediol (PDO), a premium-price intermediate used in the production of polymers, cosmetics, liquid detergents, antifreeze, de-icing and heat transfer fluids and other products. Details about

chemical used largely in the synthesis of epoxy resins — from biodiesel-derived glycerin. The convention conventional al route relies on propylene and chlorine as the primary raw materials, but has particularly low chlorine-atom efficiency, so it produces unwanted byproducts hydrogen chloride or waste chloride anions that are expensive to dispose of, says John Briggs, chemistry and catalysis scientist for Dow. Dow’s two-step glycerin-to-epichlrohydrin (GTE) process provides a  variety of advantages over the multistep incumbent process, including (but not limited to) fewer unit operations, smaller environmental footprint and overall cost, reduced equipment requirements, shorter residence times, fewer reaction byproducts and a purer final product, says Briggs. The process

the corn-sugar-based route from DuPont Tate & Lyle Bio Products LLC (Wilmington, Del.; www.dupont.com), and the glyerin-based route from Metabolic Explorer (Metex; ClermontFerrand, France; metabolic-explorer. com) and Institut Francais du Petrole (IFP; Rueil-Malmaison) can be found in the longer version of this article.1 Several facilities that are already producing plastics from ag-based starting materials are also discussed.  As interest in renewable feedstocks continues to grow, many stakeholders are channeling the spirit of the fairy tale Rapunzel — spinning straw and other low-cost, renewable agricultural and forest products into value-added chemicals that are worth their weight in gold. ■    Suzanne Shelley

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