Engine lubricants for siloxane deposit control

Abstract

A zinc free or substantially zinc free lubricant having a sulfated ash content of less than about 1.0 percent and including (a) an oil of lubricating viscosity; (b) 0.03 to about 3.0 weight percent of a phosphite compound; (c) an metal containing detergent; (d) a polyisobutylene succinimide dispersant derived from an ethylene polyamine and having a carbonyl to nitrogen ratio equal or greater than 1; (e) at least one other dispersant; (f) a boron containing compound in amount to provide at least 25 ppm boron to the lubricant composition is useful for inhibiting siloxane deposits in a stationary gas engine fueled by natural gas having a high silicon concentration.

Description

BACKGROUND OF THE INVENTION[0001]The disclosed technology relates to a lubricant for a sump-lubricated internal combustion engine, especially such an engine that is fueled by natural gas, and more particularly, engines fueled by natural gasses containing high levels of siloxanes and other silicon containing compounds, such as are commonly found in landfill gases.[0002]Internal combustion engines may be fueled by a variety of liquid or gaseous fuels, including natural gas. While liquefied natural gas or compressed natural gas may sometimes be used to fuel small engines on vehicles, more typically natural gas is used to power large compression ignited or spark ignited “stationary gas” engines that may be fueled by natural gas supplied directly from a gas wellhead. One common application for stationary gas engines is at landfills, where the engines may be fueled by gas emanating from decomposition of refuse at the landfill.[0003]Landfill gasses tend not to be very clean and often have ...

AI Technical Summary

Benefits of technology

This patent describes a new lubricant for gas engines that is zinc-free and has low sulfated ash content. The lubricant composition includes an oil of lubricating viscosity, a phosphite compound, a metal containing detergent, at least two dispersants (including a polyisobutylene succinimide dispersant and at least one other dispersant such as a Mannich dispersant or a polyisobutylene succinic acid ester dispersant), and a boron containing compound. The lubricant composition is effective in providing low-temperature properties, good wear protection, and low-pour points while also reducing emissions and preventing oxidation.

Problems solved by technology

Landfill gasses tend not to be very clean and often have elevated levels of silicon containing compounds and other corrosive materials.

In an engine combusting landfill gas, the silicon containing compounds in the landfill gas will form siloxane macromolecules which will deposit on the engine component surfaces leading to increased wear in the cylinders, valve areas and bearings.

Over time, this wear reduces engine performance, may cause valve seat recession, may increase oil consumption, and may ultimately necessitate refurbishment of the engine.

Scrubbing silicon compounds from landfill gases requires additional equipment that must be maintained and generally complicates the feed stream.

These lubricants are directed to cleaning the engine surface from siloxane deposits and / or providing a sacrificial wear layer, but their efficacy is limited as detergency loses effectiveness and particularly once the siloxane macromolecules have formed.

Accordingly, these lubricant formulations require frequent replenishment / replacement leading to increased lubricant consumption and engine downtime.

Images