Abstract: A bearing assembly for an electric motor for a vehicle, having at least one main bearing configured to support a rotational element of the electric motor, and a sacrificial bearing. The main bearing includes at least one inner ring having at least one inner raceway, at least one outer ring having at least one out raceway, and at least one plurality of rolling elements disposed between the raceways. The sacrificial bearing provides an outer ring having an outer raceway, an inner ring having an inner raceway, and a plurality of rolling elements disposed between the outer ring and the inner ring. The sacrificial bearing is provided with an electrically conductive lubricant configured to lubricate the rolling elements of the sacrificial bearing. The main bearing is provided with an isolating lubricant configured to lubricate the rolling elements of the main bearing, wherein the isolating lubricant is electrically isolating.

Abstract: A viscosity index improver comprising a reaction product of (i) an acylated copolymer obtainable by acylating a copolymer of ethylene and one or more C3-C10 alpha-olefins having an Mn of 3,000 to 250,000 g/mol; and (ii) a compound of the formulae (III)-(V): wherein R6, R8, R9, R10, R12 and R15 are independently selected from a hydrogen and an optionally substituted linear or branched alkyl or alkenyl group, and R7, R11, R13, R14, R16, and R17 are independent selected from an optionally substituted linear or branched alkyl or alkenyl group, and a sum of the number of carbon atoms in each compound of the formulae (III)-(V) is from 6 to 31.

Abstract: The present invention aims to provide a viscosity index improver composition and a lubricating oil composition having a low HTHS viscosity at 100° C., an excellent shear stability, and an excellent low temperature viscosity.

Abstract: A quick-release structure includes a shaft and a driving assembly. Two ends of the shaft have a receiving hole and a connecting hole, respectively. The driving assembly includes a rotating handle and a connecting rod. One end of the rotating handle is provided with an end cap. The connecting rod includes a pivoting end and a driving section. The rotating handle is pivotally connected to the pivoting end of the connecting rod so that the rotating handle can be pivoted relative to one side of the connecting rod. When in use, the driving section is engaged in the connecting hole, and the rotating handle can be turned to drive the shaft to rotate; when not in use, the driving assembly is inserted into the receiving hole, and the end cap is pressed against an outer end of the receiving hole to be positioned.

Abstract: A heat treatment oil composition is provided that suppresses the decrease of luster in a heat treatment of a metal material, and is capable of suppressing the increase of the number of second (characteristic number of second) until reaching the temperature where the vapor blanket stage ends with the lapse of time and the decrease of the kinetic viscosity with the lapse of time. The heat treatment oil composition contains (A) a base oil and (B) a vapor blanket breaking agent selected from one or more of a petroleum resin, a terpene resin, rosin, and derivatives thereof.

Abstract: A method for preparing a final grease product comprising steps of: (a) mixing a polymeric thickener, which comprises a polymer of propylene, and a lubricating base oil at a temperature above the melting point of the polymeric thickener, wherein the polymeric thickener is present in an amount of 11.5-15.5 wt %, based on the total weight of the mixture so obtained; (b) cooling the mixture as obtained in step (a); (c) subjecting the cooled mixture as obtained in step (b) to a first mechanical treatment, to obtain an intermediate grease; (d) subjecting the intermediate grease as obtained in step (c) to a second mechanical treatment, carried out at a temperature in the range of from 50-90° C., to obtain the final grease product. The method can be applied to manufacturing of a grease.

Abstract: Disclosed are a device and a method for continuously polymerizing polybutene by removing halogen acid, which is included in a reaction raw material, by adsorbing the halogen acid using an adsorbent and then re-supplying the reaction raw material into a reactor. The device for re-circulating the raw material when manufacturing polybutene comprises a reactor, into which a catalyst and a reaction raw material (diluted with an inactive organic solvent) are supplied and polymerized to produce a reaction product; a neutralizing/washing tank for removing the catalyst from the reaction product and neutralizing the reaction product; a separation tank for separating the reaction product into organic compounds and water; a C4 distillation column for distilling an unreacted raw material and the inactive organic solvent from the organic compounds; and an impurity adsorption column for removing halogen acid from the distilled unreacted raw material and the inactive organic solvent using an adsorbent.

Abstract: The invention is directed to a process for the preparation of high viscosity lubricant base stocks by contacting alphaolefin feedstocks with single-site metallocene catalysts in a mixed flow or continuous stirred tank reactors.

Abstract: An improved process and apparatus for the selective reaction of terpenes (including mono-, sesqui-, di-terpenes, and others in the terpene family), alpha-olefin oligomers (OOA's), and related olefins to their respective dimeric product in high purity using heterogeneous acid catalyst concurrent with full utilization of energy created in the process. Embodiments of the invention carry out a unique and highly efficient dimerization of terpenes, alpha-olefin oligomers (OOA's), and olefins using cost effective catalysts and low cost equipment that are ideally suited for commercialization of jet/turbine and diesel biofuel processes producing fuels with high flashpoints and superb cold flow properties.

Abstract: Processes to produce ethylene copolymers using pyridyldiamido transition metal complexes, a chain transfer agent, and an activator are disclosed.

Abstract: A process for polymerizing or oligomerizing a hydrocarbon includes feeding a liquid hydrocarbon reactant and a liquid evaporative cooling medium into a bulk liquid phase which includes polymeric or oligomeric product admixed with a catalyst, and allowing at least a portion of the liquid hydrocarbon reactant and the liquid evaporative cooling medium to vaporize to form bubbles rising through the bulk liquid phase, with the hydrocarbon reactant polymerizing or oligomerizing to form the polymeric or oligomeric product and with the evaporation of both the liquid hydrocarbon reactant and the liquid evaporative cooling medium effecting heat removal from the bulk liquid phase. Gaseous components are withdrawn from a head space, cooled and separated. Condensed hydrocarbon reactant and condensed cooling medium are recycled to the bulk liquid phase.

Abstract: A lubricating oil composition for an internal combustion engine contains: a base oil including a component (A) of a polyalphaolefin having a kinematic viscosity at 100 degrees C. of 5.5 mm2/s or less, a CCS viscosity at ?35 degrees C. of 3000 mPa·s or less and a NOACK of 12 mass % or less and a component (B) of a mineral oil having a viscosity index of 120 or more; and polyisobutylene having a mass average molecular weight of 500,000 or more. A content of the composition (A) is 25 mass % or more of a total amount of a lubricating oil.

Abstract: A lubricating oil composition for an internal combustion engine contains a component (A) of a polyalphaolefin having a kinematic viscosity at 100 degrees C. of 5.5 mm2/s or less, a CCS viscosity at ?35 degrees C. of 3000 mPA·s or less and a NOACK of 12 mass % or less, and a component (B) of a mineral oil having a viscosity index of 120 or more. The component (A) is contained at a content of 10 mass % or more of a total amount of the composition.

Abstract: A lubricating oil composition for an internal combustion engine contains a component (A) of a polyalphaolefin having a kinematic viscosity at 100 degrees C. of 5.5 mm2/s or less, a CCS viscosity at ?35 degrees C. of 3000 mPA·s or less and a NOACK of 12 mass % or less, and a component (B) of a mineral oil having a viscosity index of 120 or more. The component (A) is contained at a content of 10 mass % or more of a total amount of the composition.

Abstract: A lubricating oil composition for an internal combustion engine contains: a base oil including a component (A) of a polyalphaolefin having a kinematic viscosity at 100 degrees C. of 5.5 mm2/s or less, a CCS viscosity at ?35 degrees C. of 3000 mPa·s or less and a NOACK of 12 mass % or less and a component (B) of a mineral oil having a viscosity index of 120 or more; and polyisobutylene having a mass average molecular weight of 500,000 or more. A content of the composition (A) is 25 mass % or more of a total amount of a lubricating oil.

Abstract: The subject invention pertains to homogeneous liquid low molecular weight ethylene/alpha-olefin polymers having a number average molecular weight (Mn) as determined by gel permeation chromatography, of less than 25,000, a total crystallinity, as measured by DSC, of less than 10%, and a pour point, as measured by ASTM D97, of less than 50° C. The subject invention also pertains to homogeneous gel-like low molecular weight ethylene/alpha-olefin polymers having a number average molecular weight (Mn) as determined by gel permeation chromatography, of less than 25,000, a total crystallinity, as measured by DSC, of less than 50%, and a pour point, as measured by ASTM D97, of less than 90° C.

Abstract: Provided are an ?-olefin copolymer useful as a high-viscosity lubricant oil excellent in viscosity characteristics, low-temperature characteristics and oxidation stability, and a lubricant oil containing the copolymer. The ?-olefin copolymer is a 1-octene/1-decene/1-dodecene ternary copolymer produced by the use of a doubly crosslinked metallocene catalyst.

Abstract: Provided are an ?-olefin copolymer useful as a high-viscosity lubricant oil excellent in viscosity characteristics, low-temperature characteristics and oxidation stability, and a lubricant oil containing the copolymer. The ?-olefin copolymer is a 1-decene/1-dodecene copolymer produced by the use of a doubly bridged metallocene catalyst.

Abstract: The present invention is directed to a method for improving the fuel efficiency of engine oil compositions by reducing the traction coefficient of the oil by formulating the oil using a blend of one or more first base stock(s) selected from Group II base stock, Group III base stock and Group IV base stock and a second base stock selected from polyisobutylene (PIB) and, preferably, additized with a detergent.

Abstract: The present invention is directed to a hydroisomerization process using a new crystalline molecular sieve designated SSZ-81, which is synthesized using a structure directing agent selected from 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dications, 1,5-bis(1,4-diazabicyclo[2.2.2]octane)pentane dications, and mixtures thereof.

Abstract: The invention relates to an aqueous dispersion comprising microcapsules, the capsule wall of which is formed from radically polymerized monomers and the capsule core of which comprises at least one oil, in which the capsule core comprises at least one lipophilic surfactant and the continuous phase of the dispersion comprises at least one agrochemical. In addition, the invention relates to a process for the preparation of an aqueous dispersion by (i) providing an aqueous dispersion comprising microcapsules, the capsule wall of which is formed from radically polymerized monomers and the capsule core of which comprises at least one oil and at least one lipophilic surfactant (microcapsule crude dispersion), and (ii) mixing with at least one agrochemical.

Abstract: This disclosure relates to a liquid syndiotactic polyalphaolefin, sPAO, comprising one or more C4 to C24 monomers, said sPAO having: a) an rr triad content of 5 to 50% as measured by 13C NMR; b) an mr triad content of 25 to 60% as measured by 13C NMR, where the mr to mm triad ratio is at least 1.0; c) a pour point of Z ° C. or less, where Z=0.0648X?51.2, where X=kinematic viscosity at 100° C. as reported in centistokes (cSt); d) a kinematic viscosity at 100° C. of 100 cSt or more (alternatively 200 cSt or more); e) a ratio of mr triads to rr triad (as determined by 13C NMR) of less than 9; f) a ratio of vinylidene to 1,2-disubstituted olefins (as determined by 1H NMR) of less than 8; g) a viscosity index of 120 or more; and h) an Mn of 40,000 or less. This disclosure further relates to processes to make and use sPAOs, including those having any combination of characteristics a) to h).

Abstract: A process for making base oil, comprising: oligomerizing one or more olefins having a boiling point less than 82° C. in the presence of an ionic liquid catalyst to produce the base oil having a kinematic viscosity at 40° C. of 1100 mm2/s or higher. Also, a process, comprising: oligomerizing the olefins in the presence of an ionic liquid catalyst to produce the base oil having a kinematic viscosity at 40° C. of 300 mm2/s or higher and a low cloud point, wherein a wt % yield of products boiling at 482° C.+ (900° F.+) is at least 65 wt % of a total yield of products from the oligomerizing. Additionally, a process, comprising: oligomerizing the olefins in the presence of an ionic liquid catalyst to produce the base oil having a kinematic viscosity at 40° C. greater than 1100 mm2/s and a low cloud point.

Abstract: Provided is an immersion oil for microscope including a liquid olefin polymer (A), a liquid diene polymer (B), a diaryl alkane (C), and an alkyl benzene (D), the immersion oil for microscope being capable of maintaining low fluorescence of its own over a long period of time, having good characteristics required for an immersion oil for microscope, such as good refractive index, Abbe number, viscosity, and resolution, and being particularly suitable as an immersion oil for a fluorescence microscope.

Abstract: A method for improving fuel efficiency in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil having a composition comprising: a lubricating oil base stock; and a viscosity index improver comprising at least one propylene-based polymer. The at least one propylene-based polymer comprises from 60 wt % to 98 wt % propylene derived units and from 2 wt % to 40 wt % units derived from one or more other alpha olefins, a weight average molecular weight (Mw) as measured by GPC of from 100,000 to 500,000, a number average molecular weight (Mn) as measured by GPC of from 100,000 to 400,000, a molecular weight distribution (MWD=Mw/Mn) of from 1 to 2; and a mole ratio of propylene to one or more other alpha olefins from 50:50 to 85:15.

Abstract: A lubricating oil composition and methods of operating an internal combustion engine to provide improved engine operation. The lubricating composition includes a major amount of oil of lubricating viscosity and a minor amount of at least one olefin copolymer having a number average molecular weight greater than about 10,000 up to about 300,000. The olefin copolymer is grafted with (A) a vinyl-substituted aromatic compound, and (B) a compound selected from the group consisting of a C5-C30 olefin, a polyalkylene compound, and mixtures thereof. A mole ratio of A/B in the reaction mixture ranges from about 0.25:1 to about 5:1. The lubricating composition optionally includes a minor amount of at least one non-grafted olefin copolymer, styrene-isoprene copolymer, methacrylate copolymer, or styrene butadiene copolymer have number average molecular weight greater than about 50,000 up to about 300,000.

Abstract: The invention relates to industrial lubricant and grease compositions containing high viscosity index polyalphaolefins (HVI-PAO). The use of HVI-PAOs in industrial oils and greases application provides advantages in improved shear stability, wear property, foam property, energy efficiency and improved overall performance.

Abstract: The invention is directed to polyalphaolefins (PAOs) and processes for forming PAOs. In one embodiment, the invention is to a process for forming a PAO comprising polymerizing C8-C12 ?-olefin monomers in the presence of hydrogen, a C8-C12 saturated hydrocarbon, e.g., a C8-C12 saturated straight-chain hydrocarbon, and a catalyst system in a reaction vessel, wherein the C8-C12 saturated straight-chain hydrocarbon has about the same number of carbon atoms as the C8-C12 ?-olefin monomers. The C8-C12 saturated straight-chain hydrocarbon optionally is derived from a crude PAO product formed by the process of the invention. The invention is also directed to reaction systems for performing the processes of the invention, to processes for controlling PAO viscosity based on residence time, and to the removal of spent catalyst using a solid adsorbent particles.

Abstract: The air release rate of lubricating compositions is significantly enhanced when the composition is formulated with one or more vinyl aromatic-olefin block copolymers that forms a micelle-like structure in the oil. Compositions having the specified copolymers retain less than about 2.5% air after 1 min. at 50° C. when tested by ASTM D 3427.

Abstract: The present invention relates to diblock copolymers of the formula A-B which are formed from a polymer block A which is formed essentially from ?-olefin units having from 6 to 22 carbon atoms, and a polymer block B which is formed essentially from isobutene units, to a process for their preparation, to their use in lubricant compositions and to lubricant compositions which comprise such diblock copolymers.

Abstract: A fluid blend suitable for use as a lube basestock comprises two major components: (A) a copolymer made from ethylene with one or more alpha olefins, the copolymer (i) containing not more than 50 wt % ethylene; (ii) having a number average molecular weight of from 400 to 10,000; and (iii) a molecular weight distribution <3; and (B) a polyalphaolefin fluid or a hydroprocessed oil having a VI greater than 80.

Abstract: A method of improving air release is disclosed. The method comprises obtaining a lubricant comprising two base stocks. The first base stock comprises a viscosity greater than 100 cSt, Kv100° C. The second base stock comprises a viscosity less than 10 cSt, Kv100° C. In addition, a lubricant formulation and method of blending a lubricant formulation is also disclosed. The lubricant formulation comprises at least two base stocks. At least 5 percent and no more than 90 percent of a first base stock comprising oil with a viscosity greater than 300 cSt, Kv100° C. At least 5 percent and no more than 90 percent of a second base stock comprising oil with a viscosity less than 10 cSt, Kv100° C.

Abstract: A new P—N—P ligand is useful in ethylene oligomerizations. In combination with i) a source of chromium and ii) an activator such as methylalumoxane; the ligand of this invention may be used to prepare an oligomer product that contains a mixture of hexenes and octenes. The hexenes and octenes produced with this ligand contain very low levels of internal olefins when produced under preferred reaction conditions.

Abstract: Process for the preparation of viscosity index improver (V.I.I.) additives of lubricating oils which comprises a mixing treatment under high shear conditions of a composition comprising: (i) one or more EP(D)M polymers (ii) one or more polyvinylarene/conjugated hydrogenated polydiene/polyvinylarene block copolymers; and (iii) lubricating oil, (ii) being present in a concentration of 1.5 to 20% by weight whereas (iii) is present in a concentration ranging from 1.5 to 45% by weight.

Abstract: The invention relates to viscosity modifier polymers, concentrate and lubricant formulations utilizing a diblock polymer having one block A and one block B, block A contributing from 15 to 30% of the total chain length and block B from 70 to 85% of the total chain length, wherein block A comprises at least 93 wt % of ethylene and at least one other alpha-olefin and block B comprises an ethylene content between 40 and 75 wt % and at least one other alpha-olefin and wherein the resulting block copolymer has an average ethylene content of between about 60 wt % to 80 wt % ethylene, a fast Gaussian NMR relaxation signal between 17 and 22% and a slow exponential NMR relaxation signal between 58 and 68% of the total NMR relaxation signal, a SSI of at least 35% and a TE of at least 3.5 in order to obtain improvements in fuel economy.

Abstract: A method comprising: (a) forming a living liquid polymer, wherein said living liquid polymer is anionically initiated and comprises a cation; (b) adding a functional initiator precursor of the formula FI-H, wherein H is hydrogen and FI is a functional group, said H terminates said living liquid polymer resulting in said liquid polymer having a number average molecular weight of about 20,000 (g/mole) to about 100,000 (g/mole), and said FI and said cation form a functional initiator; (c) adding monomer, wherein said functional initiator initiates anionic polymerization of said monomer; and (d) terminating the polymerization reaction initiated in step (c). Steps (a) through (c) may be conducted in a single reactor, allowing a liquid polymer to be dispersed in a functionalized polymer in a single polymerization step. Thus, the liquid polymer does not have to be handled separately and processing efficiency is improved.

Abstract: A traction drive fluid composition which comprises component (A) a base oil for traction drives bearing at least one selected from a quaternary carbon atom or an alicyclic structure in the molecule and component (B) at least one polymer having a weight average molecular weight in the range of 8,000 to 40,000 and which is selected from among (a) hydrocarbon polymers each containing as a constituent at least 10 mole % of a monomer bearing a cyclic structure, (b) hydrocarbon polymers each containing at least 25% of quaternary carbon atoms in the backbone chain, and (c) hydrogenated products from the polymers (a) and (b). The traction drive fluid composition is improved in viscosity index without lowering the traction coefficient to a level lower than that of the base oil and is excellent in shear stability.

Abstract: Higher diamondoid derivatives capable of taking part in polymerization reactions are disclosed as well as intermediates to these derivatives, polymers formed from these derivatives and methods for preparing the polymers.

Abstract: A quenching oil for reduced pressure quenching which comprises a base oil having a kinematic viscosity at 40° C. of 40 mm2/s or more and a vapor blanket breaking agent; and a method for quenching wherein the quenching oil is used and quenching is carried out while adjusting the pressure on the surface of the oil. The method allows the achievement of cooling characteristics over a wide range from those conventionally achieved by a cold oil to those by a hot oil, by the use of a single quenching oil.

Abstract: A viscosity modifier for lubricating oils or an additive composition for lubricating oils, which is excellent in oil-thickening properties and can provide lubricating oil compositions excellent in low-temperature characteristics and handleability at low temperatures; and lubricating oil compositions excellent in low-temperature characteristics and handleability at low temperatures.

Abstract: A synthetic lubricating oil comprising an ?-olefin (co)polymer defined by the features (i) to (v). Also, a lubricating oil composition including the above-mentioned synthetic lubricating oil and a low-viscosity base oil. The synthetic lubricating oil and the lubricating oil composition have high thermal oxidation stability and are excellent in viscosity index, low-temperature viscosity properties and shear stability.

Abstract: The invention is directed to polyalphaolefins (PAOs) and processes for forming PAOs. In one embodiment, the invention is to a process for forming a PAO comprising polymerizing C8-C12 ?-olefin monomers in the presence of hydrogen, a C8-C12 saturated hydrocarbon, e.g., a C8-C12 saturated straight-chain hydrocarbon, and a catalyst system in a reaction vessel, wherein the C8-C12 saturated straight-chain hydrocarbon has about the same number of carbon atoms as the C8-C12 ?-olefin monomers. The C8-C12 saturated straight-chain hydrocarbon optionally is derived from a crude PAO product formed by the process of the invention. The invention is also directed to reaction systems for performing the processes of the invention, to processes for controlling PAO viscosity based on residence time, and to the removal of spent catalyst using a solid adsorbent particles.

Abstract: A mixture comprising A) a copolymer comprising from about 70 to about 79% by weight of units derived from ethylene, and having (a) Mw measured by gel permeation chromatography employing polystyrene standard ranging from about 50,000 up to less than 130,000 and/or (f) SSI?18; (b) density (D) ranging from about 845 to about 895 kg/m3; (c) Mw/ Mn less than 3; (d) melting point (Tm) measured by differential scanning calorimeter ranging from about 15° C. to about 60° C.; and (e) degree of crystallinity?15%, and B) an amorphous polymer having Mw ranging from about 130,000 to about 1,000,000 having degree of crystallinity?5%. In one embodiment the density and the melting point of the copolymer A) fulfill the expression Tm?1.247 D?1037. In another embodiment, the percentage content (E: % by weight) of repeating units derived from ethylene and melting point (Tm: ° C.) of the copolymer A) fulfill the expression 3.44E?206?Tm.

Abstract: A method for the processing of a polyalphaolefin feedstock having a concentration of organic halide to thereby yield a polyalphaolefin end-product having a low concentration of organic halide. The method includes a hydrogenation step whereby the polyalphaolefin feedstock is contacted under suitable reaction conditions with a specific hydrogenation catalyst composition that is resistant to halide deactivation. The hydrogenation catalyst comprises a noble metal on a support material comprising silica and alumina. The hydrogenated polyalphaolefin feedstock is further processed to remove the hydrogen halide produced during the hydrogenation step to yield the polyalphaolefin end-product.

Abstract: An attrition resistant precipitated bulk iron catalyst is prepared from iron oxide precursor and a binder by spray drying. The catalysts are preferably used in carbon monoxide hydrogenation processes such as Fischer-Tropsch synthesis. These catalysts are suitable for use in fluidized-bed reactors, transport reactors and, especially, slurry bubble column reactors.

Abstract: A process is described for the preparation of viscosity index improver (V.I.I.) additives which includes treatment under high shear conditions of a composition comprising (i) one or more EP(D)M polymers and (ii) one or more polyvinylarene/hydrogenated conjugated diene/polyvinylarene block copolymers, the weight ratio (i)/(ii) ranging from 98:2 to 80:20, preferably from 97:3 to 90:10, the above process being carried out at a temperature ranging from 150° C. to 400° C., preferably from 180° C. to 320° C.

Abstract: A polymer suitable for use as a viscosity index improver for lubricating oil compositions, which is at least one, at least partially hydrogenated linear or star-shaped random copolymer of isoprene and butadiene, in which at least 70 wt. % of the butadiene is incorporated into the polymer as 1,4 units and the weight ratio of isoprene addition product to butadiene addition product in the copolymer is in a range of from about 90:10 to about 70:30.

Abstract: One or more oligomers of an olefin are prepared in the presence of a single-site catalyst. Preferably, the olefin is an ?-olefin, and the oligomers are a poly-alpha-olefin (PAO). The PAO so prepared is completely or substantially free of tertiary hydrogen resulting from isomerization. Consequently, the PAO possesses improved biodegradability, improved oxidation resistance, and/or a relatively higher viscosity index. The PAO has many useful applications, such as a component of a lubricant.

Abstract: A viscosity index (VI) improver concentrate containing at least one VI improver, from 0 to about 5 mass % of lubricating oil flow improver (LOFI) and diluent oil, wherein the diluent oil has a kv100 of at least about 3.0 cSt and a CCS at ?35° C. of less than 3700 cPs, and wherein at least about 98 mass % of the concentrate is composed of VI improver, LOFI and diluent oil.

Abstract: (a) A medium oil wherein a main component is a hydrocarbon, and the number of paraffinic carbon atoms is 70% or more with respect to a total number of carbon atoms, (b) a medium oil wherein a main component is a polybutene, (c) a medium oil wherein a main component is a mixture of hydrocarbons of the formula (1): CH3—C(CH3)2—[—CH2—C(CH3)2—]n—CH2—R ??(1) wherein R is —CH(CH3)2 or —C(CH3)?CH2, and n is 1 to 10, (d) a medium oil wherein a main component is a hydrocarbon prepared by a Fischer-Tropsch synthesis, or (e) a medium oil wherein a main component is a branched paraffinic hydrocarbon prepared by hydrogenolysis of a hydrocarbon prepared by a Fischer-Tropsch synthesis, and a process of producing dimethyl ether using the medium oil, are disclosed.