Role of Precious Metal Catalysts

This book provides a broad spectrum of insights into the optical principle, resource, fabrication, nanoscience, and nanotechnology of noble metal. It also looks at the advanced implementation of noble metal in the field of nanoscale materials, catalysts and biosystem. This book is ideal not only for scientific researchers but also as a reference for professionals in material science, engineering, nonascience and plasmonics.


Introduction
Precious metal catalysts have been used in many industries, such as refinery, petrochemicals, polymer, chemicals, pharmaceuticals, and environment, For example, automotive industry utilizes large amounts of precious metal catalysts as a part of auto exhaust gas purifier, because of their high activity and selectivity and stability under various reaction conditions. This article, introduces wide variety of applications on precious metal catalysts. We recognize that precious metal catalysts play very important role in our lives. Not only unique properties of precious metals but also advanced preparation technology allow us to use precious metal catalysts for wide range of applications. Principle of precious metal catalyst preparation is introduced, and various industrial applications of precious metal catalysts follow. Applications of precious metal catalysts were disclosed by some literatures.   (Bartholomew and Farrauto 2006 )

Properties of precious metal catalysts 2.1 High activity and selectivity of precious metals in catalysis
Precious metal catalysts consist of highly dispersed nano-scale precious metal particles on supports with high surface area such as carbon, silica, and alumina. The nano scale metal particles easily adsorb hydrogen and oxygen in the atmosphere. The hydrogen or oxygen is very active due to its dissociative adsorption through d-electron of out of shell of precious metal atoms. Dissociatively adsorbed hydrogen and oxygen readily react with many substitutes at under the mild conditions. Although commercial plants are operated under heated and pressurized conditions, many hydrogenation and oxidation reactions proceed at room temperature. In such case, the product yield is relatively high because byproducts formation can be minimized under milder reaction conditions. For example, in hydrogenation of di-nitrotoluene to di-aminotoluene, reaction conditions of Ni catalyst requires 5 Mpa, 150 C, and solvent such as methanol. However, such reaction with Pd/carbon proceeds under only 0.4 Mpa, and 90 C without solvent. Quantity for Pd/carbon is one tenth of Ni catalyst.
Each precious metal catalyst shows unique characteristics, For instance, olefin hydrogenation can be accomplish with Pd/Al 2 O 3 without hydrogenating aromatic bond at mild condition. In case of hydrogenation of phenol, Pd/Al 2 O 3 gives produces cyclohexanone. Similarly, Pt/Al 2 O 3 is highly selective to cyclohexane formation and Rh or Ru/Al 2 O 3 gives cyclohexanol selectively. Furthermore, preparation technology of precious metal catalyst has been advanced in recent years based upon nano technology. As a result, energy saving, high productivity, production cost reduction were achieved. Precious catalyst is not almighty, low activity for hydrogenolysis of esters, low selectivity for selective oxidation in gas phase. However, many base metal catalysts changed to precious metal catalysts in history.

Stability
Precious metals are stable. They do not easily form oxides by oxidation. The oxides of precious metals are, on the other hand, relatively not stable. Precious metals do not easily dissolve in acid or alkaline solution. Thus for example, Pd/carbon can be used for hydrogenation of maleic acid in water which is acidic condition. However Ni catalyst cannot be used for the same reaction condition due to the leaching. Melting point of precious metals is higher than base metals. It corresponds to resistance to migration and sintering of precious metal catalysts. Because of high thermal stability, precious metal catalyst has been used as automotive exhaust gas purification catalysts.

Control of metal particle size
Catalytic activity and selectivity largely depend upon metal particle size of metals of the catalysts for the some reactions. It is necessary to make sure if the development of reaction is influenced by metal particles size prior to selection of proper catalyst. (Bond 1968) Generally, hydrogenation and hydrogenolysis prefer to small particles, and oxidation prefers to large metal particles. However, there are many exceptions because of different carrier, preparation method and impurity of the catalysts. Smaller metal particles show high tolerance of sulfur poison because of high surface area for adsorption of sulfur. (Okada 1993) The size of metal can be controlled by selection of metal salts, conditions of impregnation and reduction conditions, including metal concentration and reduction temperature.

Metal distribution of catalysts: Ex. eggshell type
Diffusion of reactant to the catalyst surface controls reaction rate at mild condition. Hydrogen and oxygen penetrate into inside of micro pores in the catalysts. However, large molecules are difficult to diffuse into the smaller pores. BASF Catalysts., (Former Engelhard) developed and commercialized highly active hydrogenolysis catalyst which is eggshell type of Pd/carbon as a slurry type catalyst. The catalyst was applied for hydrogenolysis to produce aspartame. DuPont developed eggshell type of vinyl acetate catalyst. This is fixedbed type catalyst, which is prepared by impregnation method using Pd and Au salt and SiO 2 carrier. Preparation of vinyl acetate catalysts consist of, 1) impregnation of metal solution, 2) metal fixation by alkaline, 3) keeping long times, 4) treated with reductive agent, 5) washing, 6) drying, 7) impregnate potassium acetate and 8) dry. Pd and Au deposited outer surface layer of the carrier, which is egg-shell type distribution. On the other hand, in case reduction is immediately employed after impregnation, Pd, and Au deposited more inner layer on the carrier. (DuPont 1977) Eggshell type catalysts have been applied for many other reactions, such as hydrogenation of polymer resin and hydrogenolysis of large molecular, and are expected to be used for other reactions as well. However, there is an example that highly dispersion, not eggshell type metal distribution, shows higher activity www.intechopen.com than eggshell type catalysts in the hydrogenation of benzoic acid under severe condition because of no diffusion control. (Grove 2002)

Unreduced catalysts
The reduced catalysts have been supplied commercially. Unreduced catalysts give higher activity for some hydrogenation reactions. Small particles are formed possibly due to some effect by solvent, which is in-situ reduction before the reaction starts. A combination of eggshell and unreduced catalyst also gives higher activity in hydrogenation at mild condition. But, unreduced catalysts cannot be used for dehydrogenation or oxidation. Unreduced Pd(OH) 2 /carbon, called Pearlman's catalyst, is used widely in pharmaceuticals.

Modified catalysts: Doping
Modification effectively improves activity and selectivity of catalysts. Addition of alkaline or alkaline earth metal, such as Na, K, Ba, to Pd/carbon leads to high activity towards hydrogenation of aromatic nitro compounds because of electron transfer to Pd. Pd-Pt-Fe/carbon catalyst is commercialized for hydrogenation of di-nitrotoluene. Pd modified with Na is applied for selective hydrogenation of mesityl oxide to produce MIBK. Na prevents hydrogenation of carbonyl. Selective hydrodechlorination can be achieved by Pd/carbon modified Ag or Sn. Pd/Al 2 O 3 modified with heavy metals, such as Pb, and Bi, is applied for hydrogenation of phenyl acetylene in styrene stream. Modification with heavy metals gives leads to high activity for liquid phase oxidation.

Control of migration and sintering
Pd-Au/SiO 2 is used for production of vinyl acetate by acetoxylation of ethylene. In case of Pd/ SiO 2 without Au addition, sintering is observed, which is caused through palladium acetate formation within a few days. Thus, Au addition prevents sintering of Pd by formation of solid solution with Pd. Fluorocarbon substitute, R-134a is introduced from R-114 by hydrodechlorination. Pd/carbon granular shows short life because of sintering in hydrogen chloride. Addition of small amounts of Re or Au to Pd/carbon gives lengthens catalyst life. (Asahi Glass 1989) High thermally stable catalysts have been developed for automotive exhaust catalysts. Precious metal loading amount was needed to be reduced. The technology by interaction with metal oxide such as ZrO 2 , CeO 2 , TiO 2 , enables lower loading of precious metals.

Control of dissolution: Leaching
Although precious metal is stable for migration and/or dissolution, it occurs in acidic or alkaline condition with oxygen atmosphere. Pt ion is leached out from the catalyst a few % www.intechopen.com at reflux condition. Pd/Al 2 O 3 is highly active and selective in hydrogenation of vinyl acetylene to butadiene in order to recover butadiene after extraction of butadiene. However, Pd is dissolved with acetylene by producing acetylide in short time. Pd 4 Te/Al 2 O 3 was developed to prevent leaching by acetylene, and the catalyst life was significantly improved. Pd 4 Te is a chemical compound formed on the alumina carrier. The preparation is, at first Pd/Al 2 O 3 is prepared, and secondary TeCl 4 is impregnated to Pd/Al 2 O 3 . Subsequently, the impregnated catalyst is heated at 500 °C. (JSR 1987) Pd is dissolved in acetoxylation of butadiene producing 1,4-butandiol because of acidic condition and presence of oxygen. Pd 4 Te/carbon is developed by Mitsubishi Chemical and commercialized. (Mitsubishi Chemical 1973) Small particle of Au, less than 5 nm shows excellent oxidation and esterification activity. Methyl glycolate can be produced by ethylene glycol and methanol in slurry bed, of Au/TiO 2 -SiO 2 . This catalyst gives high activity, however Au leached out at oxidation condition. Addition of Pd to Au prevents dissolution. (Nippon Shokubai 2004) 3. History/background of precious metal catalyst development

Sulfuric acid
Industrial revolution started in England in 19th century. Demand of sulfuric acid as basic chemicals, especially producing sodium carbonate for Leblanc process, was increasing for the purpose of bleaching cotton cloth. The first catalytic process is oxidation of sulfur dioxide by Pt/asbestos which was developed by P. Philips in England in 1831. Lead chamber process replaced by catalytic process. That is the beginning of industrial catalysts. Ammonium sulfate for fertilizer production started using sulfuric acid and ammonia from coal distillation plant in the late of 1830s. Production of explosive cellulose nitrate from niter using sulfuric acid has started in Switzer-land in 1845. Novel developed dynamite which is nitro glycerol impregnated clay in 1866. Pt/asbestos had been used until finding V 2 O 5 catalyst by BASF in 1915.

Nitric acid
W. Ostwald found production of nitric acid by oxidation of ammonia with Pt-plate, and the nitric acid plant was commercialized in 1908. He received Novel prize in 1909. Nitric acid is very important to produce explosives. Ammonia was produced in coal furnace at the time. Commercialization of ammonia synthesis using nitrogen in the air by Haber and Boch was in 1913. Nitric acid was produced by

Acetic acid
Cellulose nitrate as fiber was replaced by cellulose acetate for flammability issue. Acetic acid, raw material of cellulose acetate was produced by oxidation of acetaldehyde which was produced hydration of acetylene by HgSO 4 in coal times. Coming petroleum time around after 1960s, acetaldehyde has started to be produced by oxidation of ethylene. The process was developed by Hoechst-Waker which uses PdCl 2 and CuCl 2 in homogeneous reaction. CH 2 =CH 2 + 1/2 O 2 → CH 3 CHO (PdCl 2 -CuCl 2 ) Most of acetic acid is produced by carbonylation of methanol in the world, which was developed by BP (Former Monsant) using Rh carbonyl complex. The product yield is more than 99%. Consumption of Rh is less than 1ppm. CH 3 OH + CO → CH 3 COOH New development, called CATIVA process by BP, uses Ir and Ru carbonyl complex. The precursors are IrI 3 and RuI 3 . Ru complex works as co-catalyst for Ir complex which consumption is said one tenth of Rh complex. In addition, Showa Denko in Japan developed direct acetic acid process from ethylene by gas phase Wacker process. The catalyst is Pd/ H 4 SiW 12 O 40 -SiO 2 . The process was commercialized once. (Showa Denko 1994) Chiyoda Corporation has developed immobilized Rh complex with resin. It was made as fixed bed process producing acetic acid by carbonylation of methanol. The process was licensed to China. (Chiyoda Corporation 1993)

Reforming
Due to increasing gasoline demand, reforming process, which produces gasoline with high octane number, was developed by Shell in 1949. The reactions are dehydrogenation of naphthene and isomerization of paraffin. The UOP reforming process is called "Platformer" because the catalyst constituent is Pt. At first, the catalyst life was short due to carbon deposition. In 1967, Chevron developed Pt-Re/Al 2 O 3 bi-metalic catalyst which can be used almost 10 years with several times of regeneration. After that, continuous cyclic regeneration (CCR) process was developed by UOP and IFP. This process can produce gasoline with higher octane number due to higher aromatics yield under much severe condition or under low pressure. The catalyst is spherical Pt-Sn/Al 2 O 3 . More than three hundred plants including semi-regeneration process are running in the world.

Aromatization
To meet the demand of aromatics for in petrochemical industries, aromatization of nhexane process was developed by Chevron. The catalyst for this application is Pt-F/Lzeolite which was improved by Idemitsu Kosan Co., Several plants in the world have been applying this technology.

Removing aromatics
Removing aromatics from diesel fuel is necessary for environmental protection of atmosphere for more severe environmental protection. Many hydrotreating processes are developed, and consist of two series reactors of reactors. First reactor contains Ni-Mo/Al 2 O 3 or Co-Mo /Al 2 O 3 and the second contains Pt/Al 2 O 3 or Pt/SiO 2 -Al 2 O 3 . Bi-metalic catalyst was also developed because hydrogenation by Ni needs high temperature which occurs dehydrogenation to minimize the negative influence by sulfur. Pt-Pd/SiO 2 -Al 2 O 3 shows high activity even containing several tens ppm of sulfur. (Vaarkamp 2000)

Isomerization
Isomerization of butane and pentane is difficult by SiO 2 -Al 2 O 3 . Bi-functional catalyst, Pt/SiO 2 -Al 2 O 3 with halogen can progress isomerization because the reaction occurs through dehydrogenation and hydrogenation by Pt and isomerization by acid. Jet fuel production, for example Hysomer process developed by Shell uses Pt/zeolite under hydrogen pressure. Japan Energy developed Pt-SiO 2 /ZrO 2 -Al 2 O 3 for isomerization of naphtha. Small content of sulfur in naphtha deactivate this catalyst. Hybrid catalyst, consisting of Pt/SiO 2 /ZrO 2 -Al 2 O 3 with addition of Pd/Al 2 O 3 was developed to improve sulfur tolerance. The mechanism of sulfur tolerance is decomposition of sulfur compound by Pd is explained by Watanabe et al. (Watanabe 2005)

Hydrocracking
Gas oil or heavy gas oil is hydrocracked to produce gasoline. The typical cracking catalysts are Co-Mo/Al 2 O 3 or Ni-W/SiO 2 or zeolite. Unicracking process licensed by UOP uses Pd/Y-zeolite producing jet fuel.

FCC additives
Fluid Catalytic Cracking (FCC) processes produce gasoline or diesel fuel from oil from heavier oil. FCC processes are operated in fluid bed with continuous regeneration processes for removal of deposited carbon. The size of catalyst is 70～100 µm  composed SiO 2 -Al 2 O 3 and USY zeolite. Some additives improve stability and propylene yield. Pt/Al 2 O 3 powder is also used to accelerate removal of deposited carbon.

Hydropurification
Ethylene and propylene are important raw materials for many chemicals and polymers. Ethylene and propylene contain acetylene and dienes as impurities from cracker. Acetylenes and dienes are selectively hydrogenated to ethylene and propylene respectively with 0.02-0.2% Pd/Al 2 O 3 in gas phase. These catalysts life is more than several years with carbon removal regeneration. Purification of butadiene in presence of 1-butene and 2-butene is employed under hydrogen by Pd/Al 2 O 3 in liquid phase. Unsaturated C 4 and C 5 molecules are recycled to ethylene cracker after hydrogenation to increase ethylene yield. Small amount of phenyl acetylene as an impurity is removed as polystyrene applying by hydrogenation by Pd/Al 2 O 3 or modified Pd/Al 2 O 3 . (Table-1

Hydrogenation of pyrolysis gasoline
Byproducts in liquid phase of ethylene cracker are aromatics and unsaturated compounds.
In order to blend into gasoline, di-olefins are selectively hydrogenated to mono-olefin by Pd/Al 2 O 3 . Subsequent to the first reactor, Ni-Co/Al 2 O 3 is utilized to remove mono olefins, sulfur, and nitrogen prior to production of benzene, toluene, and xylene before solvent extraction. Catalyst life of Pd/Al 2 O 3 is generally several years with several times of regenerations. Every ethylene cracker equips this hydrogenation process.

Propylene
Propylene demand is increasing due to strong polypropylene market. Dehydrogenation of propane with Pt/Al 2 O 3 is one of commercialized processes. Several plants apply this process.

Cyclohexane
Highly pure cyclohexane is intermediate of Nylon. It is produced by hydrogenation of benzene with Ni or Pt/Al 2 O 3 .

Oxo alcohol
2-Ethylhexanol, a raw material of di-octylphthalate (DOP), is used for vinyl chloride resin plasticizer. 2-Ethylhexanol is derived from n-butyl aldehyde i s p r o d u c e d b y hydroformylation of propylene with hydrogen and carbon monoxide by Rh complex catalyst. RhH(CO)(PPh 3 ) 3 with tri-phenylphosphine produces n and i butylaldehyde. Rh complex generates more than 10 of n/i ratio. (Table-2) In the same reaction, Co complex shows low n/i ratio. n-Butylaldehyde is separated by distillation from the boiling reactor. 2-Ethylhexanol is produced after condensation with NaOH and subsequent hydrogenation by Ni. (Fig. 1 The process called KAAP process is commercialized. Two large plants are under operation in Trinidad and Tobago. Adsorption of nitrogen becomes weak due to electron transfer from Cs to Ru and Ru and from Ru to carbon graphite. The catalyst support, graphite is firstly, produced by thermal treatment of active carbon at 1,500 °C in argon, and in air at around 400 °C followed by subsequent thermal treatment at 1,700 °C in argon. Remaining catalyst preparation takes place as, impregnation of RuCl 3 solution to the graphite, reduction with hydrogen at 450 °C, drying, impregnation of Cs nitrate solution, and drying. (BP 1984)

Hydrogen peroxide
Hydrogen peroxide, H 2 O 2 , has widely been used as bleaching and oxidation agent for food, textile and paper. H 2 O 2 has been producing by oxidation of hydroxyl alkyl anthraquinone after hydrogenation of alkyl anthraquinone by Pd. Small catalyst particles of Pd/Al 2 O 3 or Pd/SiO 2 i s g e n e r a l l y u s e d i n s l u r r y p h a s e , a n d its alkaline modification prevents ring hydrogenation. Kemira process uses Pd black. Some fixed bed processes are commercialized.

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These catalysts form smooth surface because decomposition of hydrogen peroxide occurs by leaked fine catalyst particles after separatio n . C a r b o n m o n o x i d e i n h y d r o g e n s t r e a m i s removed to less than 1 ppm by methanation with Ni or Ru/Al 2 O 3 since small quantity of carbon monoxide poisons Pd catalyst at lower reaction temperature, e.g. 40 °C. (Fig. 2)

Fig. 2. Production of hydrogen peroxide by anthraquinone process
Direct hydrogen peroxide production, which is the process synthesize H 2 O 2 from hydrogen and oxygen was developed by DuPont and commercialized several plants of paper plants in North America. This process uses Pd/carbon. HBr is used stabilizer of peroxide.
Head water has developed direct process at out of explosion range, e.g. H 2 3vol%, O 2 20vol% N 2 77vol% in H 2 SO 4 solution with addition of small amount of NaBr and Pd-Pt/carbon black catalyst. The performance of this process is reported as 33% of the overall hydrogen conversion, 100% H 2 O 2 selectivity with respect to hydrogen and 4.8% of hydrogen peroxide in a final liquid product at 45 C and 10 MPa. (Headwater 2005)

Phenol
Phenol has been used as a raw material of phenol resin, nylon and others. Most phenol process uses cumene process in the world. Cumene is produced by alkylation of benzene with propylene by acid catalyst, such as H 3 PO 4 /Al 2 O 3 or zeolite. Subsequently cumene hydroperoxide is produced by oxidation of cumene and phenol and acetone are converted from cumene hydroperoxide by sulfuric acid. In the step of phenol production, -methyl styrene produced as byproducts is hydrogenated by Pd/Al 2 O 3 . Produced cumene by hydrogenation of -methyl styrene is recycled to the feed. When -methyl styrene demand increases, cumene hydroperoxide is hydrogenated to cumyl alcohol by Pd/Al 2 O 3 and returned to stream to produce -methylstyren more. Off gas treatment, such as oxidation of cumene, takes place by Pt/honeycomb catalyst at 350C.

Aniline
Aniline has been produced by amination of phenol using Lewis acid such as Al 2 O 3 and hydrogenation of nitrobenzene by Ni or Pd/carbon in slurry phase. Pd/carbon or modified Pd/carbon by Pt or Fe is used mainly for highly activity.

Chlorine
Hydrogen chloride is produced as byproducts in TDI process, polycarbonate and other plants. It has to be neutralized by NaOH before disposal. Oxidation process for Cl 2 production was developed using acid resistant RuO 2 /TiO 2 -Al 2 O 3 by Sumitomo Chemical and was commercialized 3 plants. The commercialized Sumitomo fixed bed process is compact compare to Mitsui fluid bed process using Cr catalyst. In the preparation of RuO 2 /TiO 2 -Al 2 O 3 , the carrier is firstly prepared by mixing -Al 2 O 3 and TiO 2 (100%rutile) powder followed by extrusion and calcination at 800 °C, Ru salt is impregnated on the prepared TiO 2 -Al 2 O 3 , and impregnated carrier is calcined. ( (Fig.4) www.intechopen.com Fig. 4. MIBK production from acetone

Oxalic acid
Oxalic acid is used for hydration of starch, and it is a raw material of fertilizer and others. (COOCH 3 ) 2 + 4 H 2 → HOCH 2 CH 2 OH + 2 CH 3 OH

Di-methyl carbonate (DMC)
Di-methyl carbonate is a raw material of resin and others. DMC is expected to replace phosgene in production of polycarbonate and isocyanate. China started to use it diesel fuel additives. DMC is produced from methanol and carbon monoxide. Ube Ind. in Japan developed and commercialized a process applying oxy carbonylation of methanol by PdCl 2 -CuCl 2 /Al 2 O 3 in gas phase. (Fig.6 -butyrolactone (GBL) used as a resin solvent and an intermediate of N-methylpyrrolidone can be produced from maleic anhydride. Maleic anhydride is hydrogenated to GBL by Ru(AcAc) 3 with trioctylphosphine in tetraglyme in homogeneous reaction. This process is commercialized by Mitsubishi Chemical. Reaction rate increases using succinic acid anhydride after hydrogenation by Pd/Al 2 O 3 . Conversion of succinic acid anhydride is 79.2%, Selectivity of GBL is almost 100% at 200 °C, 1.0MPa, 14 h. (Fig.7 )   Fig. 7. Hydrogenation of succinic acid anhydride 7. Polymer

Vinyl chloride
Poly vinyl chloride is used very widely such as pipe, sheet, film, housing material for stability. Vinyl chloride monomer (VCM) is produced by thermal decomposition of ethylene dichloride (EDC) which is produced by oxychlorination with CuCl 2 /Al 2 O 3 . After decomposition of EDC, 2,000-4,000 ppm of acetylene is produced in HCl stream. Acetylene in hydrogen chloride atmospher is removed by hydrogenation with acid resistant catalyst which is Pd/ -Al2O3 or Pd/SiC in order to reduce chlorine consumption in recycled oxychlorination process. (Kaneka 1987)

Methyl methacrylate
Methylmethacrylate (MMA) demand has been increasing in Asia. It is a transparent polymer and is used as glass substitute. A few routes are known to produce MMA. Isobutene process is developed in Japan. MMA is produced by esterification of methacryl acid which is introduced two step oxidation through methacroleine from isobutene. Asahi Kasei Chemicals commercialized direct process from methacroleine and methanol by Pd-Pb/SiO 2 using slurry bed. Oxygen is fed from the bottom of the reactor as very fine bubbles. The catalyst is Pd 3 Pb/SiO 2 . (Asahi Kasei Chemicals 1996) The size of silica carrier containing alumina and magnesia is about 60μm. The catalyst is prepared by starting mixture of HCl solution of PdCl 2 and Pb(NO 3 ), immediately the metal solution mixture is impregnated 1hr and then reduced by hydrazine.

Toluene di-isocyanate
Toluene di-isocyanate (TDI) is used for polyurethane. TDI demand has been increasing due to the applications such as cushion of bed and sheet of car. TDI is produced from diaminotoluene and phosgene. Di-aminotoluene is produced by hydrogenation of dinitrotoluene with Pd/carbon or Pd-Pt-Fe/carbon in slurry bed.

Hydrogenated methaxylene diamine
Methaxylene diamine (MXDA) is used for heat resistant polyamide polymer. It is produced by ammoxidation of o-xylene with Fe catalyst. By Ru/Al 2 O 3 , a p a r t o f M X D A i s hydrogenated to 1,3-di-amino cyclohexane which is highly heat resistant polymer material.

Cyclohexane di-methanol (CHDM)
Cyclohexane di-methyl is used heat resistant polyester resin. It is produced by hydrogenation of di-methylterephthalate. Pd or Ru/Al 2 O 3 is used for hydrogenation of dimethyltrephthalate at first step, hydrogenolysis of cyclohexane di-methyl carboxylate is done by CuCrOx catalyst. (Fig.9 ) www.intechopen.com   Fig. 9. DME synthesis from di-methyl trephthalate

Hydrogenated polymer
Hydrogenation of polymer is important to increase solubility to other polymer and transparency, which is applied such as adhesive for dipper. Hydrogenation of polybutene is conducted by Pd/Al 2 O 3 in fixed bed. C 5 , C 9 and terpentine resin are hydrogenated by Pd/Al 2 O 3 and Pt/Al 2 O 3 . Hydroxypolybutadiene rubber is produced by hydrogenation with Ru/carbon prevention of hydrocracking of hydroxyl group. Nitril rubber and norbornene resin are hydrogenated with Rh complex in homogeneous phase. (Bayer 1980) Separation of catalyst from the system is very difficult. If the catalyst is very highly active, the loading quantity can be very small. Consequently, removal of catalyst is not necessary. (Shinohara 1997) It suggests that reaction system does not need filtration system like polymerization of polyethylene or polypropylene. Many resins are hydrogenated by precious metal catalysts. (Table-3 Fig. 10. Nylon-6 production route by Inventa process

DSM process
Ammonium nitrate is reduced by Pd/carbon or Pd-Pt/carbon in DSM process. Selectivity of Pd/carbon is higher than Pt/carbon. Mixed Pd/carbon and Pd-Pt/carbon gives highly activity and selectivity in H 3 PO 4 aqueous solution with addition of GeO 2 . Reaction temperature is 40-70 C. The process is continuous slurry bed reactor installed swing filter system. Selectivity is effectively increased by small amount of halogen ion. (Fig.11 ) H 3 PO 4 → H + + H 2 PO 4 -NO 3 -+ 2 H + + 3H 2 → NH 3 OH + + 2H 2 O Fig. 11. Cyclohexanone oxime synthesis by DSM process

Snia viscosa process
Firstly toluene is oxidized to benzoic acid by metal acetate such as cobalt acetate in the aqueous phase. Subsequently, benzoic acid is hydrogenated to cyclohexane carboxylic acid by Pd/carbon in slurry bed. Hydrogenation condition is 170 °C, 1.0-1.7 Mpa. The production yield appears to be almost 100%. Cyclohexane carboxylic acid is reacted with NOHSO 4 and produces ε-caprolactam sulfate. (Fig.12) Fig. 12. Hydrogenation of benzoic acid www.intechopen.com

Asahi Kasei process
Asahi Kasei Chemical commercialized selective hydrogenation of benzene to cyclohexene. A 60,000Mton/y plant started to operate in 1990. Selective hydrogenation of benzene to cyclohexene takes place in water with Ru black catalyst. Cyclohexene is hydrated to cyclohexanol by high silica containing MFI. The process was licensed to China. (Fig.13 )   Fig. 13. Cyclohexanone production route by selective hydrogenation of benzene

Polyester
Most textile fiber has become polyester. Polyethylene terephthalate is produced ethylene glycol and terephthalic acid. Polyethylene terephthalate is very widely used to make bottles, for examples PET. Terephthalic acid is produced by oxidation of p-xylene introduced by isomerization of mixed xylene with ZSM-5 catalyst. Pt/ZSM-5 is used to convert ethyl benzene to p-xylene in hydrogen atmosphere. 4-carboxybenzaldehyde (4-CBA) is produced as a byproduct in oxidation of p-xylene by Co and Mn acetate in acetic acid solution.
Producing pure terephthalic acid, 4-CBA is needed to remove to less than 25 ppm by hydrogenolysis by Pd/carbon granular in water solvent under severe condition. (Fig.15) www.intechopen.com

Vinyl acetate
Vinylacetate is used for textile, paint, adhesive and others. Acetoxylation of ethylene in gas phase is commercialized developed by Bayer and ND (Millenium) with Pd-Au/SiO 2 or Pd-Au/alumina by multi tube reactor. Allylalcohol also commercialized by acetoxylation of propylene with Pd-Cu/SiO 2 .

City gas
Producing city gas from coke oven gas contains hydrogen and carbon monoxide. Methanation is applied to produce methane by Ru/Al 2 O 3 after removal of tar and sulfur compounds.

Purification of hydrogen
Removal of oxygen in hydrogen is proceeds with Pd/Al 2 O 3 . It is known as DEOXO process, and the catalyst was developed former Engelhard Ind., The technology has been used widely.
The catalyst is applied for purification of He, Ar with addition of hydrogen. CO causes catalyst poisoning for hydrogenation. Thus, methanation using Ru/Al 2 O 3 plays important role to converts CO to non-poisoning CH 4 . Selective oxidation of CO in hydrogen process is also known. It called "Select oxo process" using Pt/Al 2 O 3 modified with Co or Fe developed by former Engelhard. The principle is originated from the facile adsorption of CO on Pt compared to hydrogen. Oxygen addition leads to reaction with CO on the catalyst surface. The catalyst is used for purification of hydrogen for ammonia synthesis and fuel cell.

Purification of nitrogen
Pure nitrogen is essential in fabrication of semiconductor in atmospheric gas. Pure nitrogen gas is generally produced in cryogenic system from the air. But, small content of CO is difficult to remove from N 2 in cryogenic system. Pt or Pd/Al 2 O 3 can oxidize CO to CO 2 at 100-150℃ before cryogenic system.

Carbon dioxide
Carbon dioxide is used for as a coolant and for carbonated drinks. Quality of food grade CO 2 is regulated by government. Hydrocarbons and CO and others are main impurities in off gas of CO 2 from oxidation plant such as ethylene oxide plant. CO 2 is purified to food grade by addition of small amount of oxygen by Pt and Pd/Al 2 O 3 .

Reductive gas
Hydrogen gas is produced by decomposition of NH 3 , a mixed catalyst of Pt/Al 2 O 3 and Rh/Al 2 O 3 is used at 700 C. Transfer of H 2 is difficult, however it is feasible to transport as liquid NH 3 .
Reductive gas for annealing furnace is produced by combustion of butane with Rh/ -Al 2 O 3 at 800 °C.

Dyestuff and organic pigment
Many dyestuffs are produced by hydrogenation of aromatic nitro compounds. Halo nitro compounds are hydrogenated to halo amino compound by Pt/carbon or sulfur modified Pt/carbon. Monochloro acetic acid using as a raw material of dyestuff is produced selective hydrodehalogenation from di-chlrolo and tri-chloro acetic acid with Pd/carbon pellet in fixed bed reactor. The di-and tri-chloro acetic acid are produced by chlorination of acetic acid. p-Methoxy aniline, which is an intermediate of printer ink, is produced from nitrobenzene by Bamberger rearrangement reaction using Pt/carbon in methanol solvent.
Intermediate of an important yellow organic pigment is di-chlorohydrazone (DCH). It is produced from o-chlorobenzene using Pt/carbon.

Rosin
Rosin is gathered or extracted from pine tree. Disproportionated ros i n i s u s e d a s a n emulsion polymerization agent for butadiene rubber. Disproportionation of rosin is www.intechopen.com conducted with Pd/carbon without hydrogen. Hydrogenated rosin is very stable. It is used as pavement paint and used as one of the ingredients of chewing gum. Hydrogenated rosin is produced by hydrogenation using Pd/carbon at severe condition.

Antioxidant
Antioxidant for rubbers has been produced by reductive alkylation of di-phenyl amine with MIBK. Pt/carbon or sulfur modified Pt/carbon has been used for reductive alkylation.

Food industry
Sorbitol, known as a sweetener, is produced by hydrogenation of D-glucose. It is used for a moisturizing agent for ham and bacon, additive in teeth paste and others. Ru/carbon or Ni has been used as hydrogenation catalysts. Continuous process using Ru/carbon granular is developed. Succinic acid is produced by hydrogenation of maleic acid using Pd/carbon in slurry and fixed bed reactor.
Lecithin is hydrogenated to hydrogenated lecithin by Pd/carbon, which is used for food additives and cosmetics.

Fig. 18. Leaf alcohol synthesis by Lindlar's catalysts
Many synthetic perfumes are derivatives of isoprene. Acetylene compound is selectively hydrogenated by Lindlar's catalyst after ethynylation. Linalool is derived from isoprene. (Fig. 19) Many synthetic perfume, such as jasmine, are synthesized by using Lindlar 's catalyst. Fig. 19. Linalool synthesis by Lindlar's catalyst

Cosmetics
Squalene is extracted from liver of shark lives in deep sea. Squalene is hydrogenated with Pd/carbon to squarane which is used basic oil of cosmetics.

Vitamin
Lindlar's catalyst was developed for producing vitamin A. (Fig.20

Medicine for pain and fever
Acetaminophen has been widely used as medicine for pain and fever. p-Aminophenol is an intermediate of acetaminophen synthesized from nitrobenzene by hydrogenation in sulfuric acid solution or directly by Bamberger rearrangement reaction with Pt/carbon. Ibuprofen, which shows small side effect, is produced from i -butyl benzene using Pd/carbon and Pd(PPh 3 ) 4 . (Fig.21)

Hemostatic agent
Trans-ternexamic acid, used as a hemostatic agent, is produced by hydrogenation of nitril of p-cyanobenzoic acid with Pd/carbon at 100 C and 5.0 Mpa, in NaOH aqueous solution. Consequently hydrogenation of aromatic conducts by Ru/carbon at the same condition.

Di-hydroxystreptomycin
Streptomycin is hydrogenated to di-hydrostreptomycin which is more stable to alkaline and does not react with other carbonyl compounds. Hydrogenation is conducted by Adams PtO 2 in sulfuric acid solution. (Fig.22 ) www.intechopen.com

Parasiticide
Wilkinson catalyst was discovered by Dr. Wilkinson in 1966. Wilkinson catalyst, RhHCl 2 (PPh 3 ) is used for hydrogenation of avermectin to produce ivermectin for parasiticide. This application is the largest use of Wilkinson catalyst. (Fig.23)

Tetracycline
Tetracycline type antibiotics are synthesized by Pd/carbon and Rh/carbon. Minocycline is produced by hydrodechlorination with Pd/carbon and employed enantio selective hydrogenation of methylene by Rh/carbon or Wilkinson Rh complex. (Fig. 24 ) Doxycycline also produced through hydrodechlorination by Pd/carbon and hydrogenolysis by Rh/carbon.

Carbapenem
Carbapenem antibiotics are produced by chiral Ru complex developed by Dr. Noyori.

L-Dopa
A part of former Monsant developed a drug uses in the treatment of Parkinson's disease.

Indinavir (protease inhibitor)
Piperadine amide is one of the main intermediates of indinavir which is protease inhibitor developed by Merck. There are some synthesis routes to produce piperadineamide. One of synthesis routs is hydrogenation of piperadinecarboxylic acid t-butylamide hydrogenated by Pt/carbon and Ru/carbon and introduced rac-piperadine-2-carboxylic acid.

Anti-hypertensive
Many medicines are producing by Suzuki coupling using tetrakis-tri-phenyl Pd (Pd(PPh 3 ) 4 ) or Pd acetate for anti-hypertensive. ( Table-4 Table 4. Example of anti-hypertensive medicine using Suzuki coupling

Other medicines
Suzuki coupling is applied for many anti-cancer medicines such as Vicenistatin. Negishi coupling is applied to produce anti-depressant. Many alkaloids are produced by the reaction using Pd complex.

Agricultural chemicals
Many agriculture chemicals are produced using Pt or Pd/carbon. Chloro pyridine is used for an intermediate of insecticide. Di-or tri chloropyridine which is over chlorination is hydrogenated to mono-chloro pyridine by Pd/carbon. Poly chloro amine is also hydrogenated to mono or di-chloroaniline by Pd-Sn/carbon. Reductive alkylation is general reaction to produce intermediates of herbicide by Pt/carbon. Heck carbonylation using PdCl 2 is applied for benzanilide type pesticide.

Reduction of Uranium
One of extraction method of Plutonium (Pu) from spent Uranium (U) is conducted using U 4+ . Spent U contains Pu 4+ is reduced to Pu 3+ and separated by U 4+ . U 4+ is produced from U 6+ by hydrogenation with Pt/SiO 2 in PUREX process. U(NO 3 ) 6 + 2 H 2 → U(NO 3 ) 4 + 2HNO 3

Recombiner
Operating nuclear reactors mainly function with boiling water reactor (BWR) and pressurized water reactor (PWR) in the world. In BWR, water (light water) is used as coolant, and moderator is warmed to approx. 200 °C and pressurized to 7 Mpa to make steam in nuclear furnace. Steam is directly sent to gas turbine and recycled after cooled by water. In PWR, operates at approx. 15 MPa, 300 °C of liquid water is produced as the first water which makes steam of the second water for gas turbine. The first water is recycled. Water and nitrogen are decomposed to 3 H, 6 N, 19 O and radioactive Kr, and Xe from fuel rod by neutron. Gas in condenser after gas turbine is separated and introduced to recombiner, which installed Pd or Pt catalyst, after heated. H 2 including T is reacted with O 2 and separated as liquid. Gas components are introduced to gas hold up tower until radioactivity becomes lower. (Fig.27)

Fig. 27. Waste gas treatment in BWR
In PWR, the first water is recycled which is used warming the second water for gas turbine. Gas containing radioactive rare gases and H 2 containing T are purged and treated by recombiner, and treated gas holder as like as BWR (Fig.28

Flammability control system (FCM)
Three Mile Island accident taught us introducing FCM which is countermeasure of accidental coolant loss by breakage of cooling pipe and/or others. When cooling system is out of order, steam and Zr, which is cover metal of fuel rods, react and produces H 2 . And H 2 is potentially generated from fuel rods even after shut down of nuclear furnace. It may hydrogen explosion.
H 2 O + 1/2 Zr → 1/2 ZrO 2 + H 2 FCS is installed recombiner catalyst which is the same catalyst as waste gas treatment system. FCS is fixed outside or inside of the vessel as shown in Fig.30.

VOC abatement
VOC (Volatile Organic Compounds) are removed by catalytic combustion system using Pt/honeycomb at lower than 350 C. A lot of plants, not only chemical plants such as acrylic acid, maleic acid, phenol plants, but also printing, enamel wire, even food plant such as coffee plants, apply VOC removal. In case of high VOC content, heat recovery system equipped with Pt/honeycomb catalysts. The self combustion system after ignition without heating is running in some case. Off gas treatment of PTA plants and phenol plants use Pt/honeycomb, and generated heat during off gas treatment is recovered. In polyester film facilities, Pt/honeycomb reduce falling particle of organic compounds onto the film. Organic chloride compounds are completely oxidized by Pt/mordenite also.

Gas turbine off gas abatement
NOx can be reduced by adding water to fuel gas in gas turbine. NOx concentration can be reduced to 40 ppm from 150 ppm. However, addition of water increases CO from 10 ppm to 400 ppm because of lower flame temperature. In order to solve the problem, Pt/honeycomb is applied to oxidize CO completely. Since Pt/Al 2 O 3 is poisoned by sulfur dioxide producing Al 2 (SO 4 ) 3 , sulfur resistant catalysts, Pt/TiO 2 are developed. Suggested reaction temperature and GHSV are 315-600 °C, and 200,000hr -1 , respectively. (Bartholomew 2006) (Fig.31

Closed type battery
Lead batteries are used as a power source for emergency light, telephone system and traffic light and others. Small amount of water is decomposed as hydrogen and oxygen during charging battery. Waterproof Pd/Al 2 O 3 particles are charged in porous ceramic cage. Hydrogen and oxygen are converted to water and dropped back into battery. Water level can be kept same for the long time.

Ozone decomposition
Aircraft have to take air into the cabin at high altitude where air contains more ozone. This ozone uptake potentially makes from passengers airplane sick. Ozone converter is installed in the every plane now. Ozone is decomposed by Pd/honeycomb catalyst.

Space
Decomposition of hydrazine by Ir/Al 2 O 3 is propulsion power for control of satellite position in the space. Thrusters are fixed at the several sides of satellite wall.

Fuel cell system
Polymer electrolyte fuel (PEFC) is expecting to apply for residential and automotive use for at lower operation temperature. Target amount of Pt use is 0.5-0.7g/unit for residential use, 25-35 g/vehicle. Currently 5-10 times more of Pt is required. Since electric car cannot run long distance, fuel cell car is expected to be commercialized. Infrastructure of hydrogen supply remains as a technical challenge. (Table-7 Table 7. Expecting performance of fuel cell PEFC system for residential use equipped with purification, steam reforming, shift reaction, PROX, electrode and off gas treatment. It still appears to be complicated. (Fig.34)

Reforming and hydrogen purification
City gas can be a fuel for a fuel cell of residential use. Containing small amount of sulfur is removable by Fe or Ag/Al 2 O 3 . Ni or Pt/Al 2 O 3 is used for steam reforming to produce hydrogen. Since containing CO impurity in hydrogen poisons catalyst, CO is needed to remove by shift reaction with Cu-Zn. Remaining 1% of CO is removed by preferential oxidation (PROX) to less than 10 ppm by using Ru, Pt, or Au/TiO 2 . Ni/Al 2 O 3 causes carbon formation in case of kerosene as fuel. Ru/ZrO 2 is developed to overcome the issue.

Electrode
Purified hydrogen is introduced to anode, however small amount of CO (10 ppm) is remain which is catalyst poison, therefore CO resistant Pt-Ru coated carbon is used. Air is fed to Cathode which is Pt coated carbon. Carbon is high temperature treated graphite, however carbon oxidation would not be overcome by produced hydrogen peroxide for long use. Reduction of amount of Pt and Ru loading is the most important target. An example of typical Pt/carbon and Pt-Ru/carbon electrode is shown in

Dry reforming
Dry reforming instead of steam reforming is coming up to reduce CO 2 when syngas is produced from natural gas. Syngas can be used to produce F/T oil and methanol which can be further converted to propylene. Ni/Al 2 O 3 can be used as same as steam forming catalyst, However, Ru/MgO shows stable performance with low carbon deposition. This system is operated in pilot plant scale in Niigata as a national project in Japan. (Chiyoda 2006) CH 4 + CO 2 → 2 CO + 2 H 2

Hydrogen transfer
Electric power generation by utilizing wind power is effective in South America and North islands. Organic hydride is effective material as a hydrogen carrier. For example, toluene is hydrogenated to methyl cyclohexane by Pt/Al 2 O 3 by hydrogen produced electrolysis by wind power. Methyl cyclohexane is transported to consumption area by vessel, and hydrogen is taken from methylcyclohexane by dehydrogenation with Pt/Al 2 O 3 ,. Dehydrogenated toluene is again, transports to strong wind area by vessel and recycled.

Propanediol from glycerol
1,2 -propanediol can be synthesized from glycerol which is expected byproduct of bio-diesel oil production. Mixed catalyst with Ru/carbon and amberlyst gives higher activity than Ru/carbon alon. It presumes that hydroxyacetone is formed as an intermediate with ionexchange resin, and hydrogenation undergoes by Ru/carbon. At last, 1,2-propanediol is formed. (Furizuno 2006)

Hydrogenolysis of glycerol to methanol
Oxford University has disclosed production of methanol from glycerol by hydrogenolysis. Conversion is 50% and selectivity is 80% by Ru/graphite at 2.0 Mpa, and 100 C, 24 hrs. (Fig. 35)

Hydrogen from glycerol
Hydrogen can be produced from diluted glycerol aqueous solution. Hydrogen is generated from 1-10wt% of glycerol at 220 C and 2.9 Mpa by Pt/Al 2 O 3 . Conversion is 90% and selectivity is 90%. Small amount of alkanes are produced by Rh or Ni. (Boonyanuwat 2006)

Acknowledgement
The article could be completed thanks to the kind assistance of Dr. Shigo Watanbe.
He graduated Akita University in Japan and worked in Evonik Degussa as project leader living in USA.