Heavy-duty NOx/PM catalysts could add 20% to cost of diesel engine - Around The World Of Diesel - nitrogen oxides - Neville Jackson speech
Heavy-Duty NOx/PM Catalysts Could Add 20% To cost of Diesel Engine: According to Ricardo technical director Neville Jackson, the total cost of exhaust gas recirculation (EGR) plus nitrogen oxides (NOx) trap (LNT) plus a diesel particulate filter (DPF) “means 19-20% more cost” for a heavy-duty diesel, while selective catalytic reduction (SCR) plus DPF would add about 8% more cost.
Speaking to Society of Automotive Engineers conference in Pittsburgh last month, Jackson said that a diesel oxidation catalyst (DOC), plus DPF, plus LNG would add about 7% to the cost of a light-duty diesel, although adding a LNT to a gasoline direct-injection (GDI) car also would add more cost. Full variable-valve timing (VVT) would add another 10-20% to improve fuel economy on a gasoline engine, while a downsized, boosted, stratified GDI would add another 40% cost. Even so, the emissions-controlled diesel would be more expensive (although still more fuel-efficient) than the fuel-economy-enhanced gasoline engine, he said. This higher initial cost of diesel means that “I don’t expect diesel [car] share to keep going up and up,” he said. Even with higher fuel economy of diesels and GDIs, “I don’t think European automakers will meet the 140 grams [per kilometer] C[O.sub.2] target” by 2008. “Automakers are trying to get to 140 grams but if customers don’t buy them, then it’s the same issue as in the U.S.–selling smaller cars at a loss to offset the larger vehicles” with poorer fuel economy.
Dynamic duo: two catalysts build valuable carbon chains
By combining the power of two well-known reactions, chemists have devised a way to alter the length of carbon chains. The process might someday convert less-valuable carbon chains into a transportation fuel, the researchers say.
As oil supplies shrink, chemical processes that turn coal or biomass such as corn into liquid hydrocarbons will become more important, says chemist Maurice Brookhart of the University of North Carolina at Chapel Hill. Of particular interest are linear alkanes, chains in which single bonds connect carbon atoms and hydrogen atoms fill out the molecules. Diesel engines, for example, run most efficiently on alkanes with 9 to 20 carbons per molecule.
The reaction that converts coal and biomass to alkanes, however, produces carbon chains of many lengths. Included in the mix are alkanes with four to seven carbons, lengths that can’t be used as fuel, says Brookhart.
Brookhart, Alan S. Goldman of Rutgers University in Piscataway, N.J., and their research teams used two catalysts to promote reactions that together reclaimed the short alkanes. The first reaction removes two hydrogen atoms from an alkane, creating a double bond between two of the molecule’s carbons. The second reaction induces two molecules to exchange chain portions from either side of the double-bonded carbons. Then, the first reaction’s catalyst returns the hydrogen atoms, eliminating the double bond.
The reactions convert a starting short alkane into products with two lengths. For example, two 6-carbon-long alkanes-hexanes-would become a 10-carbon alkane–decane–and a 2-carbon alkane-ethane. “Then, you are in great shape: You’ve got the diesel fuel, and you’ve got the ethane;’ a gas that can be used as heating fuel, says Goldman. The team describes its work in the April 14 Science.
“It’s a spectacularly clever use of those two reactions” says John F. Hartwig of Yale University.
But the process is far from ready for industrial applications, Brookhart notes. For example, the number of reactions that each catalyst molecule can perform before becoming unstable must increase from about 1,000 to several million.
The reactions’ selectivity isn’t optimal either, Brookhart says. The catalysts also convert alkanes of desired lengths into other lengths. “What we would really like is, from hexane, to get only ethane and decane;’ says Brookhart. However, he notes that with the current procedure, chemists could put the unwanted alkanes “back in the pot” to cycle through the reactions again.
A retrofit for Roundy’s: grocery retailer uses own money to retrofit Class 8 fleet vehicles with diesel oxidation catalysts
With the majority of emission retrofit funding directed toward municipalities, transit buses and school buses, most private truck fleets are not volunteering to purchase and install emission technology on their trucks. Roundy’s Supermarkets Inc., a grocery retailer that operates 99 tractor trailers from its distribution centers in the upper Midwest, is using its own money to retrofit more than a quarter of its Class 8 truck fleet with diesel oxidation catalysts (DOC).
“We’re one of the first privately held Class 8 companies in the nation putting these on our trucks” said Russ Weber, corporate director of transportation for Roundy’s, Milwaukee, Wis. “We’re at the forefront of the environmental effort to reduce emissions. And while there is no funding that we’re aware of available statewide, we did it anyway.”
For Roundy’s, the DOC retrofit to its trucks was beneficial to its presence in the community. “By installing the DOCs we eliminated exhaust coming from our trucks” Weber said. “So not only is it good for Roundy’s but it is good for the communities in which our trucks run each day.”
Weber also said that if state or federal funding for retrofits was available, similar to grants that municipalities enjoy for school buses or city-owned vehicles, more privately head companies would be installing DOCs.
Simulation of heterogeneously MgO-catalyzed transesterification for fine-chemical and biodiesel industrial production
A heterogeneous magnesium oxide catalyst is a good alternative for homogeneous catalysts for the transesterification of alkyl esters for the production of fine-chemicals as well as for the production of biodiesel. The transesterification of ethyl acetate with methanol was used as a model reaction to simulate fine-chemical production in a batch slurry reactor at industrial conditions. The transesterification of triolein with methanol to methyl oleate was chosen to simulate continuous production of biodiesel from rapeseed oil. A kinetic model based on a three-step ‘Eley–Rideal’ type of mechanism in the liquid phase was used in both process simulations. The transesterification reaction occurs between methanol adsorbed on a magnesium oxide free basic site and ethyl acetate or the glyceride from the liquid phase. Methanol adsorption is assumed to be rate-determining in both processes. Activity coefficients were required to account for the significant non-ideality of the reaction mixture in the simulations of both processes. The simulations indicate that a production of 500 tonnes methyl acetate per year can be reached at ambient temperature in a batch reactor of 10 m3 containing 5 kg of MgO catalyst, and that a continuous production of 100,000 tonnes of biodiesel per year can be achieved at 323 K in a continuous stirred reactor of 25 m3 containing 5700 kg of MgO catalyst. Although various assumptions and simplifications were made in these explorative simulations the assumptions concerning the reaction kinetics used, the results indicate that for both processes a heterogeneous magnesium oxide catalyst shows promising potential as a viable industrial scale alternative.
Keywords: Transesterification; Solid base catalyst; Magnesium oxide; Reactor modeling; Industrial simulation; Biodiesel; Rapeseed oil; Kinetics
Abbreviations: BuOAc, butyl acetate; BuOH, n-butanol; BuOK, potassium n-butanolate; D, diolein; EtOAc, ethyl acetate; EtOH, ethanol; FAME, fatty acid methyl ester; G, glycerine; M, monoolein; M/E, methanol to ethyl acetate molar ratio; M/T, methanol to triolein molar ratio; MeOAc, methyl acetate; MeOH, methanol; MgO, magnesium oxide; MeOl, methyl oleate; T, triolein
Nomenclature
- ai
- activity of component i (mol m−3)
- aLS
- liquid–solid interfacial area (m2 m−3)
- amn
- group interaction parameter (in calculation activity coefficient)
- A
- pre-exponential factor (m3 kgcat−1 s−1)
- Ci
- concentration of component i (mol m−3)
- d1,2
- Flory–Huggins combinatorial term
- dI
- impeller diameter (m)
- dp
- solid particle diameter (m)
- Di
- liquid diffusion coefficient of component i (m2 s−1)
- Di,eff
- effective diffusion coefficient of component i in the pellet pores (m2 s−1)
- Dim
- bulk diffusivity of component i (m2 s−1)
- binary diffusivity of component B in A (m2 s−1)
- Ea
- activation energy (J mol−1)
- F
- molar flow (mol s−1)
- g
- acceleration of the gravity (m2 s−1)
- kBuOK
- reaction rate coefficient for BuOK catalyzed reaction (m6/mol2Â s)
- kMeOH
- reaction rate coefficient of methanol adsorption step (m3 kgcat−1 s−1)
- kLS,i
- liquid–catalyst mass transfer coefficient for component I (m3 m−2 s−1)
- Keq
- equilibrium constant of the overall reaction
- KA
- equilibrium constant of alcohol adsorption (m3 mol−1)
- li
- volume parameter (in calculation activity coefficient)
- MWi
- molecular weight of component i (kg/mol)
- ni
- number of moles of component i (mol)
- N
- total number of components
- NI
- impeller revolution speed (s−1)
- NP
- impeller power number (=5) (s−1)
- p
- pressure (atm)
- P
- yearly production (tonnes year−1)
- q
- induction parameter
- qi
- molecular surface area parameter (in calculation activity coefficient)
- rBuOK
- BuOK-catalyzed reaction rate (mol m−3 s−1)
- ri
- van der Waals volume parameter (in calculation activity coefficient)
- rMgO
- MgO-catalyzed reaction rate (mol kgcat−1 s−1)
- R
- universal gas constant (J mol−1 K−1)
- Re
- Kolmogoroff Reynolds number =Â
- Sci
- Schmidt number component i = kLS,i dp/Dim (s)
- t
- time (s)
- T
- temperature (K)
- VL
- liquid volume (m3)
- W
- mass of catalyst (kgcat)
- xi
- molar fraction of component i
- Xi
- conversion of component i
- Yi
- product yield of component i
- Greek symbols
- α
- acidity parameter
- β
- basicity parameter
- γi
- activity coefficient of component i
- activity coefficient of component i at infinite dilution
- combinatorial contribution to activity coefficient of component i
- residual contribution to activity coefficient of component i
- Φi
- segment fraction (in calculation activity coefficient)
- θi
- area fraction (in calculation activity coefficient)
- Γk
- group residual activity coefficient
- group residual activity coefficient in a reference solution containing only molecules of type i
p- catalyst porosity
- s
- solid fraction in the slurry reactor
- λ
- dispersion parameter
- Λi,j
- Wilson binary parameter of component i in solvent j
- μL
- liquid viscosity (kg m−1 s−1)
- ν
- liquid molar volume at 293 K (cm3 mol−1)
- ξ
- asymmetry parameter due to hydrogen bonding
- ÏL
- liquid density (kg m−3)
- Ïp
- catalyst pellet density (kg m−3)
- Ïp,wet
- density of the catalyst particle filled with liquid (kg m−3)
- Ï„
- polar parameter or catalyst tortuosity
- ψ
- asymmetry parameter due to polarity difference
- ψmn
- group interaction parameter (in calculation activity coefficient)
- Subscripts and superscripts
- 0
- initial condition
- *
- basic site
- cat
- catalyst
- eq
- equilibrium
- i
- component i
- in
- inlet
- I
- impeller
- j
- parameter j
- k
- kth experimental point
- out
- outlet
- p
- catalyst pellet
- R
- reactor
- s
- solvent
- tot
- total
Heavy-duty NOx/PM catalysts could add 20% to cost of diesel engine - Around The World Of Diesel - nitrogen oxides - Neville Jackson speech - Brief Article
Heavy-Duty NOx/PM Catalysts Could Add 20% To cost of Diesel Engine: According to Ricardo technical director Neville Jackson, the total cost of exhaust gas recirculation (EGR) plus nitrogen oxides (NOx) trap (LNT) plus a diesel particulate filter (DPF) “means 19-20% more cost” for a heavy-duty diesel, while selective catalytic reduction (SCR) plus DPF would add about 8% more cost
Speaking to Society of Automotive Engineers conference in Pittsburgh last month, Jackson said that a diesel oxidation catalyst (DOC), plus DPF, plus LNG would add about 7% to the cost of a light-duty diesel, although adding a LNT to a gasoline direct-injection (GDI) car also would add more cost. Full variable-valve timing (VVT) would add another 10-20% to improve fuel economy on a gasoline engine, while a downsized, boosted, stratified GDI would add another 40% cost. Even so, the emissions-controlled diesel would be more expensive (although still more fuel-efficient) than the fuel-economy-enhanced gasoline engine, he said. This higher initial cost of diesel means that “I don’t expect diesel [car] share to keep going up and up,” he said. Even with higher fuel economy of diesels and GDIs, “I don’t think European automakers will meet the 140 grams [per kilometer] C[O.sub.2] target” by 2008. “Automakers are trying to get to 140 grams but if customers don’t buy them, then it’s the same issue as in the U.S.–selling smaller cars at a loss to offset the larger vehicles” with poorer fuel economy.
Thermal shock resistant catalysts for synthesis gas production
Syngas catalyst compositions supported on refractory ceramic textiles and fibrous ceramic composite catalysts are disclosed, together with their methods of making and use for catalyzing syngas production from methane by a net partial oxidation reaction. In certain preferred embodiments the active catalyst material is Rh, Ni, Cr, or combinations thereof. The ceramic textiles may be arranged in a variety of 3-D forms, such as Nextel.TM. or various woven or braided meshes and layers. The ceramic textile is easier to scale up to commercial reactor dimensions than the conventional foams and monoliths comprising ceramics and metals. Tolerance to thermal expansion and thermal heat integration are also improved by the new catalysts. A synthesis gas production process employs a new ceramic composite catalyst in a fixed reaction zone maintained at conversion-promoting conditions effective to produce an effluent stream comprising carbon monoxide and hydrogen in a molar ratio of about 2:1 H.sub.2/CO.
Catalyst Information
A catalyst (Greek: καταλÏτης, catalytÄ“s) is a substance that accelerates the rate (speed) of a chemical reaction (see also catalysis). Chemical catalysts, the focus of this article, participate in reactions but are neither chemical reactants nor chemical products. More generally, one may sometimes call anything which accelerates a reaction without itself being consumed or transformed a catalyst (for example, a “catalyst for political change”).
Catalysts and reaction energetics
Catalysts enable reactions to occur much faster or at lower temperatures because of changes that they induce in the reactants. Catalysts provide an alternative pathway of lower activation energy, for a reaction to proceed whilst remaining chemically unchanged themselves. This can be observed on a Boltzmann distribution and energy profile diagram. This means that catalysts reduce the amount of energy needed to start a chemical reaction. Molecules that would not have had the energy to react or that have such low energies that they probably would have taken a long time to react are able to react in the presence of a catalyst. Thus, more molecules that need to gain less energy to react will go through the chemical reaction.
Catalysts cannot make energetically unfavorable reactions possible — they have no effect on the chemical equilibrium of a reaction because the rate of both the forward and the reverse reaction are equally affected.
Types of catalysts
Catalysts can be either heterogeneous or homogeneous. Heterogeneous catalysts are present in different phases from the reactants (e.g. a solid catalyst in a liquid reaction mixture), whereas homogeneous catalysts are in the same phase (e.g. a dissolved catalyst in a liquid reaction mixture). A simple model for heterogeneous catalysis involves the catalyst providing a surface on which the reactants (or substrates) temporarily become adsorbed. Bonds in the substrate become weakened sufficiently for new bonds to be created. The bonds between the products and the catalyst are weaker, so the products are released.
For example, in the Haber process to manufacture ammonia, finely divided iron acts as a heterogenous catalyst. The metal uses active sites to allow partial weak bonding to the reactant gases, which are adsorbed onto the metal surface. As a result, the bond within the molecule of a reactant is weakened and the reactant molecules are held in close proximity to each other. In this way the particularly strong triple bond in nitrogen is weakened and the hydrogen and nitrogen molecules are brought closer together than would be the case in the gas phase, so the rate of reaction increases.
Other heterogenous catalysts include vanadium V oxide in the Contact process, nickel in the manufacture of margarine, alumina and silica in the cracking of alkanes and platinum rhodium palladium in catalytic converters.
In car engines, incomplete combustion of the fuel produces carbon monoxide, which is toxic. The electric spark and high temperatures also allow the oxygen and nitrogen to react to form nitrogen monoxide, which is acidic. Catalytic converters reduce such emissions by adsorbing CO and NO onto the catalytic surface, where the gases undergo a redox reaction. Carbon dioxide and nitrogen are desorbed from the surface and emitted as relatively harmless gases:
2CO + 2NO → 2CO(2) + N(2)
Example of homogeneous catalysts are H+(aq) which acts as a catalyst in esterification and chlorine free radicals in the break down of ozone. Chlorine free radicals are formed by the action of ultraviolet radiation on chlorofluorocarbons (CFCs). They react with ozone forming oxygen molecules and regenerating chlorine free radicals:
Cl(.) + O(3) → ClO(.) + O(2)
ClO(.) + O → Cl(.) + O(2)
N.B. Full stops in brackets denote free radicals that should be superscripted. Numbers in brackets should be subscripted
Homogeneous catalysts generally react with one or more reactants to form a chemical intermediate that subsequently reacts to form the final reaction product, in the process regenerating the catalyst. The following is a typical reaction scheme, where C represents the catalyst:
A + C → AC (1)
B + AC → AB + C (2)
Although the catalyst (C) is consumed by reaction 1, it is subsequently produced by reaction 2, so for the overall reaction:
A + B + C → AB + C
the catalyst is neither consumed nor produced. Enzymes are biocatalysts. Use of “catalyst” in a broader cultural sense is in rough analogy to the sense described here. Other biocatalysts are ribozymes and deoxyribozymes.
Poisoning a Catalyst
A catalyst can be poisoned if another compound reacts with it and bonds chemically, but does not release. This effectively destroys the usefulness of the catalyst, as it cannot participate in the reaction with which it was supposed to catalyse, just like Raney nickel catalyst has reduced activity when it is in combination with mild steel. The loss in activity of catalyst can be overcome by having a lining of epoxy or other substances .
Commonly used catalysts
Estimates are that 60% of all commerically produced chemical products involve catalysts at some stage in the process of their manufacture.[1] Some of the most famous catalysts ever developed are the Ziegler-Natta catalysts used to mass produce polyethylene and polypropylene. Probably the best-known catalytic reaction is the Haber process for ammonia synthesis, where ordinary iron is used as a catalyst. Catalytic converters made from platinum and rhodium break down some of the more harmful byproducts of automobile exhaust. The most effective catalysts are usually transition elements.
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