Process for the production of alkyltin halides

A process for producing a di-alkyltin oxide-containing catalyst stream comprising:

• (a) contacting a feed stream comprising a di-alkyltin dihalide distillate with an alkylation agent, thereby forming an alkylated mixture comprising R4Sn and optionally R3SnX, R2SnX2, or mixtures thereof, where R is a linear, branched or cyclic C1-C20 alkyl, and X is a halide;
• (b) contacting the alkylated mixture with SnX4, thereby forming an alkyltin halide mixture comprising RSnX3, R2SnX2, and chromophoric impurities, R3SnX or mixtures thereof;
• (c) separating by distillation the alkyltin halide mixture to form a mono-alkyltin halide-rich distillate stream having a boiling point of 150-250° C. at less than 10 mm Hg and a liquid di-alkyltin halide-rich bottoms stream comprising 70.0 to 97.0 wt % R2SnX2, 3.0 to 30.0 wt % RSnX3, chromophoric impurities, and optionally R3SnX;
• (d) separating by distillation the liquid di-alkyltin halide-rich bottoms stream at a temperature of 200-220° C. at less than 5 mm Hg vacuum, thereby forming a separated liquid di-alkyltin dihalide distillate comprising 90.0 to 100.0 wt % R2SnX2, and at most 10.0 wt % RSnX3, having a Gardner color value of 2 or less, and an impurities-rich bottoms stream comprising chromophoric impurities;
• (e) recycling a part, Xrecycle, of the separated liquid di-alkyltin dihalide distillate to step (a), thereby forming a recycled dihalide distillate stream and a non-recycled dihalide distillate stream, where Xrecycle ranges from greater than 10.0% to 90.0% of the separated liquid di-alkyltin dihalide distillate;
• (f) reacting a first portion of the non-recycled liquid di-alkyltin dihalide distillate with iso-octylmercaptoacetate, 2-ethylhexylmercaptoacetate, or n-octylmercaptoacetate, to form the corresponding di-alkyltin bis(thioglycolate ester)-containing stabilizer, wherein the di-alkyltin bis(thioglycolate ester)-containing stabilizer has a Gardner color value of at most 3, and reacting a second portion of the non-recycled liquid di-alkyltin dihalide distillate with water, thereby forming the di-alkyltin oxide-containing catalyst.

A process for producing mono-alkyltin rich and di-alkyltin rich streams comprising:

• (a) contacting a feed stream comprising a liquid di-alkyltin dihalide distillate with a tri-alkyl aluminum compound, thereby forming an alkyltin halide mixture comprising RSnX3, R2SnX2, chromophoric impurities, and optionally R3SnX wherein the alkyltin halide mixture formed in step (a) has a Gardner color value of at most 3;
• (b) separating by distillation the alkyltin halide mixture to form a mono-alkyltin halide-rich distillate stream having a boiling point of 150-250° C. at less than 10 mm Hg and a liquid di-alkyltin-rich bottoms stream comprising 70.0 to 97.0 wt % R2SnX2, 3.0 to 30.0 wt % RSnX3, chromophoric impurities, and optionally R3SnX or mixtures thereof;
• (c) separating by distillation the liquid di-alkyltin halide-rich bottoms stream at a temperature of 200-220° C. at less than 5 mm Hg vacuum, thereby forming a separated liquid di-alkyltin dihalide distillate comprising 90.0 to 100.0 wt % R2SnX2, at most 10.0 wt % RSnX3, and optionally R3SnX;
• and an impurities-rich bottoms stream comprising chromophoric impurities;
• and
• (d) recycling a fraction, Xrecycle, of the separated liquid di-alkyltin dihalide distillate to step (a), thereby forming a recycled liquid di-alkyltin dihalide distillate stream and a non-recycled liquid di-alkyltin dihalide distillate stream, where Xrecycle ranges from greater than 10.0% to 90.0% of the distillate product.