JP5231694B2 - Lubricating oil composition for diesel engine with diesel particulate removal device - Google Patents

Description

Technology to which the invention belongs

  The present invention relates to a lubricating oil composition for a diesel engine with a diesel particulate filter (diesel particulate filter, hereinafter abbreviated as “DPF”), and more specifically, can reduce ash clogging in the filter of the DPF. Improves the flammability of particulate matter (particulate matter, hereinafter abbreviated as “PM”) collected by the DPF filter, and can stably burn the PM at a low temperature, and its removal efficiency It is related with the lubricating oil composition for diesel engines with DPF which can improve DPF and prolong the lifetime of DPF.

Diesel engine vehicles have better fuel efficiency than gasoline engine vehicles, are effective in reducing carbon dioxide, and light oil used as fuel oil has the advantage of lower costs than gasoline. However, in recent years, PM contained in combustion gas discharged from diesel vehicles has been widely taken up due to environmental pollution problems. This PM is a fine burn of fuel oil such as soot, and it is known that when it enters the human body, it adversely affects the respiratory system. Therefore, the reduction of PM in exhaust gas is the biggest issue for diesel vehicles.
Therefore, in Japan, according to the new regulations aimed at achieving in 2005, manufacturers have to reduce PM emissions to 1/3 of the current regulations. In Tokyo, Tokyo is scheduled for 2003. We are considering making DPFs required for running diesel vehicles, and there is a strong possibility that they will spread to other local governments.

Under such circumstances, development of efficient and practical DPF is being actively carried out. At present, several types of DPF, specifically (1) alternating regeneration type DPF, (2) NO ₂ A continuous regeneration type DPF using an oxidation method, (3) a continuous regeneration type DPF using a catalytic oxidation method, and (4) an intermittent regeneration type DPF have been proposed.
The alternating regeneration type DPF of (1) is a switching type that uses two filter units in which both sides of a silicon carbide fiber nonwoven fabric are sandwiched between a wire mesh heater and a protective wire mesh, and alternately performs collection and regeneration. This DPF can also be used with current diesel oil with a high sulfur content, but it requires a large current to burn PM, requires the installation of a dedicated large-capacity generator, and filters due to rapid combustion. It has problems such as possible damage.

The continuous regeneration type DPF by (2) NO ₂ oxidation method uses a porous ceramic made of cordierite having a wall flow honeycomb structure as a filter, and oxidizes NOx to NO ₂ by an oxidation catalyst provided upstream thereof, This is a continuous regenerative device that uses the strong oxidizing power of NO ₂ to combust PM collected by a filter at a low temperature. However, in this method, the sulfur content in the exhaust gas deteriorates the activity of the oxidation catalyst and does not fully function. Therefore, it is necessary to reduce the sulfur content in the fuel oil, which is applicable to the current light oil. There is a problem that it is difficult.
The continuous regeneration type DPF by the catalytic oxidation method of (3) uses a porous ceramic filter made of cordierite having a wall flow honeycomb structure coated with two types of metal catalysts, and does not require a heating device such as a heater. This is a continuous regenerative device that burns PM collected by the filter only by the action of. In this system, the metal catalyst is less susceptible to the sulfur content in the exhaust gas, so it can be applied to the current diesel oil, but it is more susceptible to phosphorus, and the lower the sulfur content, the higher the performance. . Furthermore, since it is necessary to travel at a certain ratio or more when the exhaust temperature is about 300 ° C. or higher, it is difficult to apply to a vehicle or a passenger vehicle that travels at low speed for a long time.
The intermittent regeneration type DPF (4) uses a porous ceramic filter made of silicon carbide having a wall flow honeycomb structure, collects PM, injects fuel during regeneration, raises the exhaust gas temperature, and hydrocarbons by an oxidation catalyst It is a system that burns PM by oxidizing carbon monoxide and raising the temperature further. In this method, a cerium compound is added to the fuel oil to reduce the amount of PM generated. This method is applicable to the current light oil, but requires a power supply facility for regeneration, and there is a problem that cerium oxide remains after combustion of PM, accumulates on the filter, and reduces the life of the DPF.

As described above, all DPFs currently under development have advantages and disadvantages, and are not necessarily satisfactory.
Industrially, it is important to make the DPF function effectively and to extend its life. To that end, it is necessary to burn PM at as low a temperature as possible and reduce clogging of the filter as much as possible. It is essential. When the filter is clogged, the back pressure increases, which reduces the efficiency of the diesel engine. This clogging of the filter includes PM combustion residue clogging and lubricating oil ash clogging.

Problems to be solved by the invention

  Under such circumstances, the present invention can reduce ash clogging in the DPF filter, improve the flammability of PM collected by the DPF filter, and stably burn the PM at a low temperature. It is an object of the present invention to provide a lubricating oil composition for a DPF-equipped diesel engine that can improve the removal efficiency and extend the life of the DPF.

Means for solving the problem

As a result of intensive studies to develop a lubricating oil composition for a DPF-equipped diesel engine having the above-mentioned preferable properties, the present inventors have found that the sulfated ash content and the sulfur content are not more than a certain value and contain molybdenum. It has been found that a lubricating oil composition whose amount is above a certain value can be adapted to its purpose. The present invention has been completed based on such findings.
Specifically, the present invention provides a lubricating oil composition for a diesel engine with a DPF, characterized by having a sulfated ash content of 1.0% by weight or less, a sulfur content of 0.3% by weight or less, and a molybdenum content of 100 ppm or more. It is.

The lubricating oil composition for a diesel engine with DPF of the present invention (hereinafter sometimes referred to as “the lubricating oil composition of the present invention”) is used as a lubricating oil for a diesel engine equipped with a DPF. As the base oil, mineral oil or synthetic oil is usually used. Although there is no restriction | limiting in particular about the kind of this mineral oil or synthetic oil, etc., Usually, the thing whose kinematic viscosity in 100 degreeC is the range of 1.5-30 mm < ² > / s is used.
Here, examples of the mineral oil include paraffin-based mineral oil, intermediate-based mineral oil, naphthenic-based mineral oil, and the like obtained by ordinary purification methods such as solvent refining and hydrogenation refining.
Synthetic oils include, for example, polybutene, polyolefin [α-olefin (co) polymer], various esters (for example, polyol ester, dibasic acid ester, phosphate ester, etc.), various ethers (for example, poly Phenyl ether), silicone oil, alkylbenzene, alkylnaphthalene and the like.

In the present invention, as the base oil, one kind of the above mineral oil may be used, or two or more kinds may be used in combination. Moreover, the said synthetic oil may be used and it may be used in combination of 2 or more types. Further, one or more mineral oils and one or more synthetic oils may be used in combination.
In the lubricating oil composition of the present invention, the sulfated ash content must be 1.0% by weight or less. This sulfated ash refers to the ash that has been made by adding sulfuric acid to the carbonized residue produced by burning the sample and heating it to make it constant, and is usually used to know the approximate amount of metallic additives in the lubricating oil composition. It is done.
If the sulfate ash content exceeds 1.0% by weight, the amount of ash deposited on the filter of the DPF is large, which causes clogging of the ash content of the filter and shortens the life of the DPF. Further, the effect of improving the PM combustibility by the molybdenum compound described later is hardly exhibited. From these points, the sulfated ash content is preferably 0.9% by weight or less.
Further, the sulfur content needs to be 0.3% by weight or less. When the sulfur content exceeds 0.3% by weight, when a metal catalyst in which sulfur becomes a catalyst poison is used in the DPF, the activity of the catalyst is deteriorated, and the function of the DPF is not sufficiently exhibited. . In this respect, the sulfur content is preferably 0.25% by weight or less.

Furthermore, the molybdenum content needs to be 100 ppm or more. This molybdenum becomes molybdenum oxide or a composite oxide of molybdenum and other elements, and is mixed into the PM collected by the DPF filter. As a result, the PM combustibility is improved, the combustion temperature is lowered by about 40 to 50 ° C., and the life of the DPF is extended. This effect is stably exhibited without being affected by other components in the exhaust gas, such as sulfur compounds and phosphorus compounds.
If the molybdenum content is less than 100 ppm, the above-described effects are not sufficiently exhibited, and the object of the present invention cannot be achieved. In particular, the molybdenum content is preferably 300 ppm or more. In addition, the upper limit of molybdenum content is restrict | limited by the prescription | regulation of the amount of sulfated ash mentioned above.
The molybdenum compound used as the molybdenum source is not particularly limited as long as it can be dispersed or dissolved in the lubricating oil composition of the present invention, and any of inorganic and organic molybdenum compounds can be used. Oil-soluble ones that dissolve in the oil composition are preferred. Examples of oil-soluble molybdenum compounds include molybdenum salts of organic acids such as molybdenum alkyl phosphates and carboxylic acid molybdenum salts, alkylamine salts such as molybdic acid, phosphomolybdic acid and silicomolybdic acid, and thiocarbamate of molybdenum. (MoDTC) and thiophosphate (MoDTP). In addition, when using MoDTC and MoDTP, it is necessary to satisfy | fill the restriction | limiting of the above-mentioned sulfur content. Incidentally, it is preferable that the MoO ₃ or phosphomolybdic acid as a combustion residue.

The lubricating oil composition of the present invention can contain various additives conventionally used in diesel engine lubricating oils. Examples of the additives include metal detergents, ashless dispersants, antiwear agents, antioxidants, viscosity index improvers, pour point depressants, rust inhibitors, metal corrosion inhibitors, antifoaming agents, and surfactants. Etc.
Here, examples of the metal detergent include Ca-sulfonate, Ca-salicylate, Ca-finate, Mg-sulfonate, Mg-salicylate and the like. The content of these metallic detergents is limited so that the above-mentioned sulfated ash content does not exceed 1.0% by weight. Moreover, when using sulfonate, it is restrict | limited so that sulfur content may not exceed 3 weight% further.
As the ashless dispersant, boron-based imide, bisimide and the like are usually used, and as the antiwear agent, for example, zinc thiophosphate (ZnDTP) -based and sulfur-based ones can be mentioned. When these sulfur-containing antiwear agents are used, it is necessary to satisfy the above-mentioned conditions for the sulfur content. In addition, when using a zinc thiophosphate-based one, it is further necessary to satisfy the conditions for the sulfated ash content.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Reference Example Carbon black (“MA100” manufactured by Mitsubishi Chemical Corporation) was used as PM, and 10 parts by weight of the molybdenum compound and other metal compound powders shown in Table 1 were used as the combustion residue with respect to 100 parts by weight. The mixture was mixed at a rate, and the combustion temperature of the mixture was measured by DT-TGA (differential thermal-thermogravimetric analysis) in air at a temperature rising rate of 10 ° C./min. The combustion temperature of carbon black alone was also measured in the same way. The results are shown in Table 1.

As apparent from Table 1, it can be seen that the presence of a molybdenum compound lowers the combustion temperature of PM.
Examples 1-4 and Comparative Examples 1-7
A lubricating oil composition having the composition shown in Table 2 was prepared, ash was produced according to the following method, the ash was mixed, and the combustion temperature was measured in the same manner as in the reference example. The results are shown in Table 2.
<Production of ash>
Put the lubricating oil in the crucible and heat to a temperature above the flash point and ignite. Waiting for the ignited fire to burn out, the crucible and the crucible were placed in a furnace at 500 ° C. for 3 hours, heat-treated and then allowed to cool.

〔note〕
TBN: Total base number Viscosity index improver: OCP (olefin copolymer)

  As can be seen from Table 2, the PM combustion temperature of the example is lower by about 40 to 50 ° C. than that of the comparative example.

Effect of the invention

  The lubricating oil composition for DPF-equipped diesel engines of the present invention can reduce ash clogging in the DPF filter, and can improve the flammability of PM collected by the DPF filter by the sulfur compounds and phosphorus compounds in the exhaust gas. The PM can be improved without being affected, the PM can be stably burned at a low temperature, the removal efficiency can be improved, and the life of the DPF can be extended.

Claims (4)

Lubricant for diesel engine with diesel particulate removal device for reducing PM combustion temperature, characterized in that sulfate ash content is 0.92 wt% or less, sulfur content is 0.3 wt% or less and molybdenum content is 100 ppm or more Oil composition.
The lubricating oil composition according to claim 1 , comprising an oil-soluble molybdenum compound as a molybdenum source.
Furthermore, the lubricating oil composition of Claim 1 or 2 containing the ashless dispersing agent which consists of a boron-type imide and bisimide.
The lubricating oil composition according to any one of claims 1 to 3 , wherein the sulfur content is 0.25% by weight or less.